Dental bridges.

Partial and full removable dentures.

Dental bridges

INDICATIONS:

1.  Absence from 1-4 teeth before the frontal section.

2.  Absence of the 2 molars  with of distal support.

3.  Absence of the 3rd lateral teeth through one with the presence of distal support.

4. Absence of the 3rd next confronting teeth the presence of distal support (to consider the standing of supporting teeth and antagonists)

CONTRA-EVIDENCE:

1. Included defects with in 4-5 teeth.

2. Mobility of the teeth (atrophy of bone hole down 1/2 and more).

3 Deformations of a bite and dental numbers with the partial loss of teeth.

4. Production of cantilever prothesis in the region of molars.

CLINICAL STAGES

First visit:Preparation of supporting teeth under selected construction of supporting parts crowns, half-crown’s, pin teeth and so forth the removal of the anatomical of vises.

Second visit:Adjustment of crowns (or other supporting elements) the determination of central occlusion, the removal of occlusion impression.

Third visit:Adjustment (fitting of bridge-shaped prosthesis. Identification of the color of plastic for the facets.

Fourth visit:Fitting and the fixation of bridge-shaped prosthesis by hanging-fop- cement.

LABORATORY STAGES

 1.  Obtaining model, making of supporting parts.

2.  Casting of models to articulator (or casting occlusion impression), modeling of the intermediate part of the bridge-shaped prosthesis from wax, casting. Soldering immediate part to supporting crowns.

3.  Polishing, chromium-plating, the simulation of facets from wax, the replacement of wax down the plastic.

 

Dental bridges are false teeth, which are anchored onto neighbouring teeth in order to replace one or more missing teeth. The false tooth is known as a pontic and is fused in between two crowns that serve as anchors by attaching to the teeth on each side of the false tooth, thereby bridging them together.

What are the parts of a typical dental bridge (fixed)?

A dental bridge essentially consists of:

§     A pontic or false tooth used to replace the missing tooth, which is made from gold, alloys, porcelain or a combination of these materials.

§     Two crowns – serving to anchor the false tooth in place.

 

When are dental bridges needed?

Bridges are recommended when there are one or more teeth missing that affect:

§     Your smile and appearance.

§     Your bite, as a result of adjacent teeth leaning into the space and altering the way the upper and lower teeth bite together.

§     Your speech.

§     The shape of your face.

§     The rates of gum disease and tooth decay as a result of food accumulated in the gap.

Must missing teeth be replaced?

Yes, missing teeth must be replaced for many reasons:

§     To improve your appearance.

§     To reduce the strain on the teeth at either side of the missing tooth.

§     To prevent the neighbouring teeth from leaning into the resulting gap and altering the bite.

§     To prevent gum disease and tooth decay due to accumulation of food in the gap.

There are three main types of dental bridges:

1. Traditional fixed bridge This is the most commonly used type of bridge and consists of a pontic fused between two porcelain crowns that are anchored on neighbouring teeth or implants. The pontic is usually made of either porcelain fused to metal or ceramics. These are fixed and cannot be removed.

2. Resin-bonded bridges or Maryland-bonded bridges These are chosen when the gap to be filled is in between the front teeth, or when the teeth on either side of the missing tooth are strong and healthy without large fillings. The false tooth is made of plastic and is fused to metal bands that are bonded to the adjacent teeth using resin that is hidden from view.

3. Cantilever bridges These are opted for in areas such as the front teeth that are susceptible to lower stress. Cantilever bridges are used when there are teeth present on only one side of the space, where the false tooth is anchored to one or more adjacent teeth on one side.

What are bridges made of?

Bridges may be made of

§     Porcelain.

§     Porcelain bonded to precious metal.

§     All-metal dental bridges (gold).

How are dental bridges fitted?

At the first appointment:

§     The dentist will numb the area with a mild anaesthetic.

§     The teeth on either side of the space are prepared by trimming away a small area in order to accommodate the new crown over them.

§     The dentist then uses dental putty to make an impression of the teeth, which will be used to make the bridge and crown in the laboratory.

§     A temporary bridge is fitted in to protect the exposed gums and teeth.

§     A Vita shade guide may be used to determine the right shade for the dental bridge, by selecting a shade that resembles natural colour variations in your teeth, as well as suits your complexion, hair colour, the colour of your natural teeth and even your eye colour.

At the second appointment:

§     The temporary bridge is removed and the custom-made bridge is fitted, checked for its fit and bite, and adjusted accordingly. It is then cemented into place

§     Multiple visits are often required to check and adjust the fit.

§     In case of permanent or fixed bridges, the bridge is temporarily cemented for a couple of weeks and checked for its fit. It is permanently cemented only after several weeks.

How long will dental bridges last?

Dental bridges can last 10-15 years, provided that you maintain good dental hygiene and eating habits.

How to take care of your dental bridges?

Practise good dental hygiene:

§     Clean the dental bridge every day to prevent tooth decay, bad breath and gum disease.

§     Clean under the false tooth every day.

§     Keep the remaining teeth healthy, as these serve as the foundation for the dental bridge.

Brushing and flossing:

§     Brush twice and floss daily.

§     To floss, use a bridge floss threader, which is a flexible piece of plastic with a loop at one end to thread the floss.

§     Thread one end of a 14-to-18-inch piece of dental floss through the loop, making sure to leave one side about half as long as the other.

§     Insert the end of the flosser without the hole between the bridge and the gumline.

§     Hold onto the longer piece of floss, gently bring it up and pull the pointed end all the way through.

§     Floss using both hands, moving the floss back and forth under the bridge.

§     Floss the bridge completely from one end to the other.

Diet and eating habits:

§     Eat soft foods or food cut into small pieces until you get accustomed to the dental bridge.

§     Eat a balanced and nutritious diet for good general and dental health.

What are the advantages of dental bridges?

§     They are natural in appearance.

§     They generally require only two appointments with the dentist.

§     They have a good life period, lasting for 10-15 years, providing you maintain good dental hygiene.

§     They improve your appearance, bite issues and speech problems occurring as a result of missing teeth.

What are the disadvantages of dental bridges?

§     Teeth become mildly sensitive to extreme temperatures for a few weeks.

§     They require healthy tooth tissue from neighboring teeth to be prepared.

§     Your teeth and gums are vulnerable to infection as a result of accumulation of bacteria due to the food acids (if proper hygiene is not maintained).

§      

Dental Bridges is The Best Arternative for Your Artificial teeth

The face is one of the most important aspects of people and gear is the most valuable, when it comes to the structure of the jaw faces. Dental Bridge is protesis, associated with teeth that help in bridging the gap created by one or more teeth are missing chelyustta.Ima many reasons to go to dentalcare cosmetics, have healthy teeth and shine. You may need for any individual who has problems such as toothache, dental problems between the teeth, mouth, teeth, tooth decay and other dental-related illnesses. Dental Bridge is one of the options for missing teeth. Gigi is very important for people like us talk well with a combination of tongue and teeth, we chew properly because the teeth are healthy and most important is to help convince usmihvashe.Ne certain age to go for dental bridges protesis. But if all the individual tooth is fully developed, it is better to go during this protesis. This is very important to choose a dentist who is experienced and professional, so you do not have to worry about the success of three types protesis protesis.Sashtestvuvat dental bridges: Traditional bridges, cantilever bridges and Maryland bridges connected. Depending on the problems faced by the patient, type of bridge izbrana.Stomatolog process is required if the person is missing teeth and do not have good oral hygiene practices, he should discuss this with his dentist. If there are empty, they can cause the surrounding teeth drift out of position. In addition, the interval of the missing tooth can cause other teeth and gums become more susceptible to caries and previous parodontoza.Po dentistfordental accessed to find the bridge had to do a lot of market research that the cost of what the dentist, but thanks to the World Wide Web, the practice of all lesno. Ponyakoga protesis to get a dental bridge is cheaper than a dentist, one loses the ability to have good dental care protesis by experienced dentists, as usual, they are expected to cost quite high. But do not worry, there are some experts who have left their spirit and serve the people with a nominal fee, so that this procedure can be accessed by people from different strata of society.

Restorative and Reconstructive Bridgework Dentistry

Dental bridges are a popular treatment choice for replacing one, a few or all teeth on a given jaw structure. Bridgework is available for the maxilla as well as the mandible.

The most common examples are those used to replace one or two teeth that are either missing or need to be extracted. These types of bridges are usually cemented to adjacent, healthy tooth structures, which serve as an abutment. In other instances, they may be supported by dental implants.

Cemented bridges pose the threat of becoming loose, and, in extreme cases, cause failure of the anchoring teeth. Implant supported bridges overcome this limitation. Each replacement tooth, or pontic, is attached to the crowns that cover the abutments or anchor ends of the bridge. As the span of a bridge increases (replaces 2-3-4 or more teeth) additional pontics are used to create the desired cosmetic result.

Metallic and Ceramic (Porcelain) Bridges

The infrastructure of the bridge will vary, depending on the length of the span. Most bridge substructures are either metallic or ceramic. Where the bridge is to be used plays a determining role in how the bridge is designed. The Lava Bridge has become a well known and popular choice for attractive cosmetic outcomes since the entire structure is porcelain. Some dentists, nonetheless, may recommend a metallic bridge in areas of the jaw where biting and physical forces are significant For some patients, unnatural lateral forces arising from disturbed occlusal factors may be better suited for metallic bridgework. These same lateral forces can cause common bridgework to fail due to bonding leakages occuring at the anchor points of the bridge. As bacteria seep into and accumulate between the bonding surfaces, decay begins and makes eventual bridge replacement almost inevitable. Treatment of missing teeth is normally recommended for all patients. Wisdom teeth are rarely treated… but may be required for some patients. Open gaps between teeth can cause teeth to shift and rotate. Occlusion can become disrupted. Severe movements and rotations of teeth can lead to tooth breakage if left untreated. Going a step further, it is not uncommon for patients with malaligned or shifted teeth to develop disorders of the tmjoints. In extreme cases jaw positioning and jaw movement becomes affected which can create additional symptoms for one side or both sides of the jaw. Missing teeth can also accelerate bone loss in the immediate area. Bone stimulation is required for maintaining healthy jawbone. When a tooth is removed, bone tissue in the extraction site typically begins to deteriorate eventually. The opposing tooth will typically super erupt, simulataneously causing the threat of bone and tooth loss issues for the opposing tooth.

Maryland Bridge

A popular bridge used primarily for cosmetic reasons. A pontic (restorative tooth replacement) is fabricated to replace a missing tooth yet is configured to use a cementation process that attaches to the lingual surfaces of adjacent teeth. Maryland Bridges are frequently used to bridge a missing tooth gap with an attractive tooth that nearly defies detection while underlying tissues are healing from bone and tissue graft surgeries. As new bone (tooth extraction site is filled with bone matrix or a graft plug) becomes regenerated and stable, the bridge is replaced with a traditional dental implant, thereby recreating properties of bone stimulation that were lost when the tooth was extracted (avulsed, damaged, traumatized, etc.)  Because of intrinsic design and methods of cementation – attachment to anchor teeth, a bridge of this type is not particularly suited for areas of the jaw where occlusal forces are significant, as in chewing.

Articulation Analysis and Diagnostic Waxups

With good attention to detail and thorough articulation studies, bridgework can be fabricated to produce excellent aesthetics and dental function. Sizing and color shading requires close scrutiny. The use of temporary crowns and bridges can provide the ability to make adjustments in color shading. Patients undergoing bridge and crown work are advised to view temporaries and final color shading selections under different light sources. Office lighting (fluorescent, incadescent) creates different effects, compared to sunlight or daylight. Endurance levels for bridgework are highly varied and are affected by life style, eating habits, occlusal factors, oral health habits and the frequency of maintaining regular dental check ups. Bridgework has been known to fail in 2-3 years … but has also been known to last 25 years and more. Anchor teeth for a non implant supported bridge are prepared to be fitted with crowns, to which the missing teeth are attached. The anchor teeth are reduced in size and prepared with specialized bonding compounds. Implant supported bridgework is the preferred treatment of choice for some, although cost can be a factor. For large spans or the entire length of the jawbone, fixed bridges are popular, but are serviced typically by the dentist. Immediate Function or one day implant surgery enable some patients to have a full arch reconstruction started and completed in one treatment session. Watch this graphic video showcasing a Maxillary Arch reconstructive surgery involving extractions, grafting and implant placements… all completed in one office visit. As with cemented bridgework, fixed bridges are subject to the same bacteria and decay issues. Thorough cleaning and inspection is usually performed by the dentist.

A newly developed fixed bridge, called the Marius Bridge, is reportedly designed to make a fixed bridge servicable by the patient.

 A porcelain dental bridge is recommended when either a tooth is lost or missing. It is very important to fill the “gap” of the missing tooth so that the chewing system is not compromised. Porcelain dental bridges typically are considered “3 units,” meaning each tooth adjacent to the missing tooth serve as anchors for the bridge. The tooth between the anchors is called the “pontic.”

 

Listed below are some of the benefits of a fixed porcelain dental bridge:

• Maintaining a properly functioning chewing system

• Preventing teeth from shifting out of position

• Keeping the biting forces even

• Restoring your smile and shape of your face

• Decreasing your risk of periodontal disease

 Dental bridge

Dental bridge

A dental bridge is partial denture for your mouth, usually implanted on a permanent basis. Two teeth are used for anchoring the bridge, these are called abutment teeth, then the false one or ones are placed in between the two of these anchors. The bridge can be made from a variety of different materials, gold, porcelain, and even alloy metals, and they can also be a combination of things. The most common of course is porcelain, because they more closely match the color of your real teeth.

The dental bridge has a long history, and has been recorded in some cases as far back as 2,600 years ago when the Etruscan first created them. They were master gold workers, and created bridges so women could brag about how rich they were. Some of these women would even have their incisor teeth removed, just so they could be fitted with gold replacements. How is that for vanity?

There are a number of reasons why people end up with missing teeth. Having kids breaks down tooth enamel, and can cause some women to loose teeth. Excessive drug use can also cause your teeth to fall out, and there are accidents, and certain sports activities like hockey where you can lose one of more. Having missing teeth can not only be embarrassing, but can also cause problems. Speech impediments, higher risks of periodontal disease, and shifting of your teeth are just a few of these problems.

Unlike conventional dentures, a dental bridge is a permanent implant. There are three, common types of bridges, fixed bridges, resin-bonded, and cantilever. Conventional and Cantilever bridges usually need shaping of the existing teeth on either side of the gap. A Crown is then placed over the teeth, and then attached to the pontic, or artificial tooth. Resin bonded bridges are used to replace mostly front teeth and require less preparation, as long the the front gums are healthy, and there are no extensive fillings in the surrounding teeth.

When you first go in for a dental bridge, your doctor will find out if you are a good candidate for the procedure. Not everyone can get an implant. There are some requirements before you get one,. A patient should have good healthy gums and teeth, and enough bone to place the implant in the jaw. You also shouldn’t get an implant if you are pregnant, a heavy smoker, or have received a high radiation dose to the head or neck area. Younger kids, under eighteen shouldn’t get a bridge because their bones are not yet developed.

The cost of a dental bridge depends on different things. You may need to have more work done on surrounding teeth, like a root canal, or fillings. It also depends on the dentist or lab technicians way they make the bridge, as well as where the dentist is located. It also depends on the number of teeth the bridge covers, the material, and how much preparation is involved. Depending on your insurance coverage, a dental bridge can cost one, to three thousand dollars per tooth. The pros are that it will restore your smile, and the cons can be jaw pain, extended healing time, and a difference in color between your real teeth and the implant.

Clinical and laboratory stages of making dental bridges

1 st laboratory step

Production of metal skeleton is very hard process, its better to see one time, that  ten times read.

 

 

Any construction starts with the model. This time with sectional model

 

 

The working surface is covered by the compensation varnish, which serves to compensate for the space under the cement and partial shrinkage of the metal after casting. The varnish is covered to the whole teeth but leave 1 mm near the border preparation to better clossing of metal edge

 

 

The gypsum stamps is covered with isolated fluid.

 

We put the intermediate part  of the prosthesis on the model

 

 

 

We put wax on the thin parts of the stamp. We need to do that on the model, especially if we are doing the correction of the shape

 

 

A view of the finished element

 

 

The carcass after the casting cuts from the casting system.

 

 

2 laboratory step

 

The finished carcass. The surface should not have sharp edges or wedges

Before putting ceramics on it, we  wash with oxide aluminum oxide with 150-250 microns, and with pressure 4-6 Bar.

 

 

 

Then with the dentine color we form the midle platen. He helps to see the height of the teeth and direction of the teeth. The  prosthesis controls in the articulator in the position of central and lateral occlusion

The view after the burning

 

 

 

We do the first separation with rough disc

 

we polish the chewing surface with balls from baked diamond  and carbide burs

We control the bridge in the articulator.

3 laboratory step

 

 

We need to put the glaze with the thin layer on the teeth

 

The Treatment RPD (flippers)

 

FlipperAffectionately known in dentistry as a “flipper”, this is the least expensive of all the removable partial dentures.  The one pictured on the left replaces 4 missing upper teeth, leaving spaces for 7 natural teeth.  Two  of the natural teeth are clasped with wrought wire clasps which are cured into the structure of the denture base.  

When a flipper is intended for temporary use while replacing one or more front teeth, it is often termed a “stayplate”. Most frequently, these are intended to be used only for several months while awaiting healing during the various phases of implant placement.

stayplate

The pink plastic of the denture base is brittle acrylic, the same material used to make standard full dentures.  The largest single advantage to this type of RPD (aside from the cost) is that new teeth and new denture base can easily be added to an existing treatment RPD.  These are frequently fabricated even if the remaining teeth have existing decay or periodontal disease and their prognosis is doubtful.  If later in the course of treatment some of the existing natural teeth are extracted for any reason, new false teeth can be added quickly to the partial, maintaining the patient’s appearance.  In spite of the fact that they are considered a temporary solution, many people keep this type of appliance for many, many years, because as long as they are properly maintained, they look outwardly as good as the more expensive permanent appliances described below.

One of the neatest tricks that a flipper can do is to act as an “immediate partial denture”.  This means that the appliance can be made before the teeth are removed, and inserted immediately after the extraction of the offending teeth.  If the patient is presently wearing one of these inexpensive appliances, and needs to have an existing natural tooth extracted, an impression can be taken with the flipper in place.  The impression with the flipper embedded in it is sent to the lab and a new denture tooth put in place of the one to be extracted.  This can be done in the course of a single day, so a patient can come in with a bad tooth and walk out with a good false tooth in its position. 

Flippers do have a number of disadvantages, however. 

    The acrylic denture base is somewhat brittle, and due to their irregular shape, these partials tend to break frequently, especially those made for the lower arch.  (Full dentures are more regular in shape and tend to be fairly strong as a result.)

    In order to counteract their tendency to break, the acrylic is usually built fairly thick which can take some “getting used to”. 

    The denture base rests only on the gums, and even though they are much more stable than full dentures, they are much less stable than the more permanent RPD’s which are “tooth born”

    As the gums resorb, The false teeth tend to sink below their original level making it necessary to reline them frequently, and sometimes even to reset the teeth which adds to their expense.

    Flippers are most frequently retained with wire clasps (shown in image above).  These are frequently unsightly due to the limitations that pertain to their placement (they can’t interfere with the way you bite).

Cast Metal RPD’s

Cast metal framework RPD    Metal Framework Partial

Removable Partial Dentures with cast metal frameworks are probably one of the oldest forms of dentistry.  Originally, the frameworks (an example seen on the right) were made out of wrought (hammered) silver.  One of the most famous American dentists was Paul Revere who was a silversmith when he wasn’t fighting redcoats.

This type of partial denture offers numerous advantages over the treatment partial described above.  A close look at the pictures above will show you that these frameworks are cast to fit the teeth. Since they sit on the teeth, as well as being attached to them, they are extremely stable and retentive.  The teeth have been altered slightly beforehand in order that the partial denture can rest upon them without interfering with the way the patient bites the teeth together. 

Metal framework on model. The metal framework does not contact the gums.  Thus, as the gums resorb, this type of partial does not sink with them and rarely requires relines.  Because the teeth are altered by the dentist beforehand, there are fewer limitations in the placement of clasps, and they are less likely to be seen than the wrought wire clasps of the treatment partial. Modern frameworks are cast from an extremely strong alloy called chrome cobalt which can be cast very thin and are much less likely to break than the all plastic variety.  They are also much less noticeable to the tongue.

The largest single advantage that cast metal framework partial dentures have over the newer flexible framework partials (covered below) is that sore spots are almost never an issue since neither the framework, nor the plastic extensions contact the soft oral tissues with any force!  Patients who exhibit the symptoms of TMJ, or who are known bruxers are much better off with cast metal partials than with flexible framework partials. 

The flexible framework RPD’s

ValPlast Partial DentureThe most recent advance in dental materials has been the application of nylon-like materials to the fabrication of dental appliances.  Nylon generally replaces the metal, and the pink acrylic denture material used to build the framework for standard removable partial dentures. Nylon  is similar to the material used to build those fluorescent orange traffic cones you sometimes see on highways. It is nearly unbreakable, is colored pink like the gums, can be built quite thin, and can form not only the denture base, but the clasps as well.  Since the clasps are built to curl around the necks of the teeth, they are practically indistinguishable from the gums that normally surround the teeth.  Brands of this type are: Luciton FRS, Sunflex, TCS, Duraflex, Valplast, and Flexstar.

 

A second type of flexible partial denture base uses a vinyl composite instead of nylon.  The most commonly sold brand is Flexite.  A second brand  Is Ultraflex.  These materials are also flexible and can be built with tooth or gum colored clasps.  Ultraflex even comes in a clear variety.  Unlike nylon partial dentures, they are much easier for the dentist to adjust making them a much more “user friendly” denture base.

Even though this type of denture does not rest on the natural teeth like the metal framework variety, the clasps rest on the gums surrounding the natural teeth.   This tissue, unlike the gums over extraction sites, is stable and changes very little over time which keeps these RPD’s stable and unchanging similar to the cast metal variety.  The clasps can be seen (if you look hard) on the image on the right below just under my thumb and index fingers. This type of partial denture is extremely stable and retentive, and the elasticity of the flexible plastic clasps keeps them that way indefinitely.

Valplast Try-in    ValPlast Partial

A lower Nylon based partial denture

ValPlast before     Valplast insert

ValPlast on Model

The Vitallium/Nylon Partial denture

 

Vitallium/Valplast         Vitallium/Valplast

A good alternative to the all-nylon partial denture is one made with a combination cast metal framework with nylon clasps.  This has the advantage of being tooth supported (like the cast metal framework partial denture discussed above) and also having gum colored plastic clasps like the nylon partial.

This combination of metal framework and plastic clasp eliminates most of the difficulty of recurrent sore spots, since the framework resists movement and pressure from the clasps, while having the benefit of nearly invisible clasps.

The Nesbit RPD

NesbitThe flexible framework RPD can replace any number of teeth in a dental arch, similar to the flipper and cast metal RPD.  There is, however, one type of removable tooth replacement device that can (legally) be built ONLY out of the flexible framework variety of material.  This is the single tooth RPD that we refer to as a NESBIT.

Dentists used to build Nesbits for their patients all the time.  They were composed of a single denture tooth (usually a back tooth) between two cast metal clasps which attached onto the teeth on either side of the missing one.  They looked a little like spiders when out of the mouth.  Patients tended to like them, but they came to an abrupt end in the 1970’s.  Prior to that time, in the rare event that a patient swallowed his appliance, he either waited for it to pass, or sought medical help on his own assuming that the accident was his own fault. Nesbit In rare instances, the metal clasps were sharp enough to cause damage to the digestive system.  After that time, tort lawyers discovered that it was a law suit made in Heaven, (or Hell depending on your point of view) and it didn’t take the dental profession long to abandon this service.

The design of the new flexible plastic framework takes the danger out of an accidental swallowing of the appliance.  In the event that someone did swallow one, it is unlikely that any damage could be done to the lining of the digestive system.  This is a series of pictures that show the form and function of a nylon.

Full Removable Dentures

 Full dentures are still the most common restoration used today for edentulous (no teeth present) patients. The only other alternative to the complete dentures is implants. Full dentures are plastic plates custom-made to fit each individual. It is made from pink acrylic simulating gum tissue and plastic or porcelain teeth, custom set for each patient. The name full denture or complete denture this restoration gets from it’s function: it substitutes the full dentition on the patient’s jaw

How full dentures are done?

It is usually takes five appointments to make standard full dentures.

1.     At the first visit, the doctor will take a first impression with the standard trays and send it to the lab, where these impressions are poured with plaster to form accurate models of the patient’s mouth. The technician will make the custom trays (trays that fit the patient) and send it back to the doctor

Preliminary alginate impression

2.     On the second visit, the doctor will take second functional impression with custom trays. This impression is more precise and records more details of the gums. The success of the full denture depends on its borders, which are determined by this impression. The impression is sent back to the lab, new models are poured and the base is fitted with wax rims for bite determination.

Custom Upper tray is ready for final impression

3.     Using wax rims the doctor will determine the size of the desired teeth, the relation of upper and lower teeth and jaws, the height of occlusion, direction of smile, fullness of cheeks and lips. Doctor will make several marks on the wax rims allowing technician to set the teeth correctly. In the lab, the technician will set the teeth according to doctor’s marks and prescription and send it back for the try in.

Bite rims with doctor’s marks

4.     The next appointment is called “wax try-in”. The wax try-in looks like the final dentures, except it fits loosely in the mouth and there is wax instead of plastic. At this time, we check how the teeth are set up, how they look, and patient comfort when biting. The bases fit loosely so we cannot check how tight the denture will stay, but all the rest is checked and necessary corrections are done. The wax-up is sent to the lab and final dentures are processed there.

5.   After minor adjustments and correction of pressure spots dentures are inserted in and patient walks out of the office with new full dentures.

 6.     It may take few more appointments for minor adjustments and removal of pressure spots.

Full Upper Denture completed

Full Lower Denture Completed

Inside view of Full Upper Denture

Inside view of Full Lower Denture

The view of the work after glazing

As most edentulous patients are elderly, the examination must be carried out not only with regard to the condition of the oral cavity, but in relation to their general health. However, sometimes dentists with less clinical experience may reach for an impression tray and start making the impression as soon as the patient sits in the dental chair without a definite treatment plan. If we want to make a successful denture, we must first conduct a thorough extra and intraoral examination of the mouth including the condition of the existing denture, denture-supporting areas, the condition of the temporoman­dibular joint and the appearance. The intraoral examination, in particular, should be done not only by glancing at, but also by closely observing and palpating the alveolar ridge. For example, if the bone resorption is severe, the alveolar ridges are flattened and moreover the mylohyoid ridge is sharpened on the lingual side and the covering mucosa is very thin. These points can be determined by palpating the areas. If such areas are found, we should think about using relief and a soft lining material.

First we must look at, carefully observe and then palpate the alveolar ridge.

1. Surgical treatment

 

Certain oral conditions require surgical treatment to im­prove the environment for denture construction. If there is redness or an ulcer over the area where the denture impinges, we can eliminate it by adjusting the denture. If there is wide­spread inflammation over the denture-bearing mucosa, it will recover quickly by removal of the denture for 2-3 days or by use of a tissue conditioning material. However, surgical treat­ment is still necessary for the denture-bearing tissues of some edentulous patients. Other cases may only require rehabilita­tion by prosthodontic means, but surgical modification is sometimes advantageous to improve the retention and stability of the denture.

The wearing of an ill-fitting denture for a long time causes

In the case of severe alveolar bone resorption, palpation is inevitable. If spiny ridges and thin covering mucosa are felt, we have to think about re­lief and soft liners.

 

repeated irritation to the mucosa during chewing, and conse­quently fibrous growth of the tissue will occur as a defense re­sponse. Soft tissue hyperplasia occurs under or around a com­plete denture and is referred to as so-called flabby gums or denture fibroma.

As flabby gums, which are seen in the anterior residual ridge of the maxilla and mandible, are highly compressible and displaceable, it is difficult to make an impression in the usual way. When this is not excessive, a good result may be possible by proper prosthodontic treat­ment, but a severe case may need surgical intervention. Elder­ly people may have difficulty in cleaning their dentures and mouth sufficiently and thus the prolonged wearing of an ill-fit­ting denture might lead to a stomatitis like papillomatosis. In mild cases, healing may occur after resting the tissues which can be achieved by removal of the dentures and im­provement of oral hygiene.

 

In certain cases, it is impossible to make impressions with­out any surgical treatment. shows a so-called de­nture fibroma. A massive roll of hyperplastic tissue which ex­tends from the anterior residual ridge to the oral vestibule in the maxilla is referred to as epulis fissuratum and needs to be excised surgically before making a new denture. However, when we eliminate a wide area as in this case, if we try to eli­minate all the pathological tissue, it may leave a scar in the area which is essential for denture retention and consequently, the subsequent prosthodontic treatment will become harder. So, we must decide the area of elimination by careful treat­ment planning which will be favorable for further procedures.

Some cases have large undercuts in the region of the tuber­osity or anterior residual ridges. If the flanges in these areas are extended deep into the sulci for the peripheral seal, these undercuts might interfere with denture insertion and removal. When there is an undercut on only one side, the insertion of the denture is possible by rotating it into position and this undercut may even enhance denture retention. However, when there are undercuts on both sides, surgical elimination or easing of the denture border must be per­formed. In the case of surgical treatment, it is important that the amount of bone removed should be as minimal as possi­ble because many undercuts are covered by compressible mu­cosa and are not as large as we expect.

The other indications for pre-prosthetic surgery are a pen­dulous maxillary tuberosity, prominent maxillary torus and mandibular tori, excessive undercuts, spiny ridges, etc. In cases with severe alveolar bone resorption where the denture-supporting tissues are limited, surgical procedures such as tibuloplasty or ridge augmentation may be carried out.

 

 

 

Although surgical treatments may be necessary for a good result, for elderly patients, the physical and mental trauma might effect their general health and therefore surgical treat­ment is sometimes better avoided. Even if they can withstand the surgery, in advanced age, the healing processes are delayed and post-operative conditions of the oral cavity may be more severe.

In any case, the indiscriminate use of surgery just for pros-thodontic convenience should be avoided. Surgery should be avoided if at all possible and the denture should be improved by various prosthodontic techniques such as varying the im­pression technique and providing appropriate relief over the affected area.

 

 Correcting the occlusion

 

It is important to examine whether any problems of the temporomandibular joint may be present and also the occlusion of the existing dentures. A patient wearing ill-fitting de­ntures for a long time tends to occlude in a position far away from the centric occlusal position as a result of the functional adaptation in which one masticates in a position comfortable to him/herself. This is the so-called “habitual bite” and will cause a decrease in masticatory efficiency and moreover lead to mandibular dysfunction.

The habitual eccentric occlusion should be treated before making new dentures. However, because the muscles of mas­tication have learned the habitual eccentric jaw position for a long time, sudden correction is not easy. Generally, the habi-

The flattened occlusal surface eliminates the intercuspation of the artificial teeth in the habitual eccentric jaw position and therefore can relieve the stiffness in the muscles and joints. Without the limitation of the cusps, the jaw can gradually return to its centric occlusal position.

tual eccentric occlusion may be corrected by wearing treat­ment dentures for a relatively long period of time. The patient will also be satisfied with the recovery of the occlusion by treatment dentures and further recording of the maxilloman-dibular relationship will be smooth and accurate.

3. Flow of saliva

Through aging, salivary flow decreases and its contents change. As saliva enhances denture retention by intervening between the denture and the mucosa, a patient with scanty saliva will have poor denture retention. Also in a dry oral cavity, the mucosa lying beneath the denture base may be easily-traumatized and therefore the impression surface of the de­nture must be polished more smoothly. The diminution in salivary flow will not moisten the oral mucosa and will inter­fere with the functions of mastication, swallowing and phonetics. In some cases, the use of artificial saliva or medications promoting salivary secretion should be recommended.

4. Patient’s requests and desires

There is one more important step in the examination. At the patient’s first visit to the clinic, we must quickly and pre­cisely gather what (s)he requests mostly from his/her complaints about the existing dentures. Their requests might be confined to mastication, esthetics or phonetics.

It once happened that a patient repeatedly came to my clinic and complained of pain, even though the dentures were thought to be perfect and no ulcers or inflammation could be found on the mucosa. Finally, it was proved that the patient’s complaint was not pain, but the appearance of the arrangement of the anterior teeth. If the patient is satisfied with the appearance, (s)he would definitely wear the denture even with a little bit of pain or a poor fit. Complaints related to esthetics are difficult to find as the patient is sometimes too embarrassed to talk about them and sometimes it is even an underlying complaint which the patient is not conscious of. Therefore a careful examination which involves gathering the patient’s requests is recommended.

In any case, the denture is a piece of work constructed by the dentist, but the patient becomes its owner after insertion. We can be no more proud of, or satisfied with, our dentures as wonderful products by ourselves alone. It is important to make the denture suit the patient so that the new dentures can truly become his/her own. For this, we must make a denture that contains the patient’s “heart”. The denture should

never be a “stranger” to the patient. In other words, only when the patient’s requests have been included in the den­ture, will it then become his/her own denture. The complaints of the patient are often unclear, misunderstood and confused; however, I believe that they have expressed their honest feel­ings and I have therefore tried to listen to their words careful’y

Making the impressions

In a favorable denture case where alveolar bone resorption is minimal and the cross section of the alveolar ridge resembles a U-shaped outline, border molding during impression making is easy. A proper impression is made possible just by reproducing the contour of the sulcus onto the impression as it is seen. However, in an unfavorable case with severe alveolar bone resorption due to severe periodontitis or prolonged wearing of an ill-fitting denture, some dentists might be puzzled how to take the impression and how to extend the denture borders correctly. In these unfavorable cases, if the denture border is placed at the junction of immovable gingivae and movable mucosa only by passive hand manipulations, it will result in the so-called cord-like denture, leading to poor denture retention, especially in the mandible.

As is generally known, the wider the denture base area, the better the denture retention will be. Therefore the impression making — not impression taking — should be performed actively according to our objectives so that the denture base area can be enlarged as much as possible. However, it is not appropriate to extend the denture border at random. The denture border should be appropriately extended in the areas where it is possible to extend it and the border should be limited where extention is not required. In order to perform this, initially it is important to understand what form the denture base should take and then the impression making is car­ried out in accordance with that mental image.

When the condition of the alveolar ridge is unfavorable, some dentists may say, “Only after impression taking can the situation of the alveolar ridge be grasped or the denture border can be shaped”. HoweveT, if we are not convinced of the contour of the impression before impression making, we will never obtain a successful denture. It is like admitting defeat before beginning the battle.

1. Landmarks for the mandibular impression

 

Buccal flange area

In Ihc poor situation where the ridges are flat and the movable mucosa reaches up to the crest of the alveolar ridges, the sole area of resistance to occlusal forces would be the buccal shelf which is situated on the buccal side of the area of the posterior teeth. The buccal shelf is covered with dense cortical bone and is also a wide area lying perpendicular to the direction of the occlusal forces. Therefore, it is an appropriate area for denture support. Thus, in severely resorbed ridges, there must be no doubt in using the buccal shelf as the denture support. The buccal shelf must be recorded during the impression procedure, otherwise a satisfactory impression will not result.

Outside the buccal shelf, a bony ridge runs anteroposterior-ly which is called the external oblique ridge and is used as a landmark for the denture border. The denture border can be extended 1-2 mm beyond the external oblique ridge and therefore the ridge must be recorded by making the imprcss-ion.

 

 

 

 

However, if the denture border is extended beyond the external oblique ridge, the denture base will be widened over the buccinator muscle attachment and thus located on the buccinator muscle fibers

On the buccal shelf, the buccinator muscle fibers run close to the bone, and are thin, tendinous and thus inactive. In addition, the lower muscle bundles of the buccinator are not tense and slacken laterally from the external oblique ridge

area. The muscle fibers run anteroposteriorly, paralleling the denture border and function in a horizontal direction.

 

 

 

Therefore, the force dislodging the denture during mastication is small and thus it is possible to extend the denture border into this area.

 

 

 

If the denture border is underextended in this area, it is dif­ficult to mould the convex buccal flange correctly, leading to food accumulation in the buccal sulcus and under the denture base.

 

Mylohyoid ridge area

If the denture border is short of the mylohyoid ridge, it will dig into the residual ridge and cause pain.

The border is shor­tened to remove this pain, but shortly after, the shortened border again impinges upon the residual ridge. Finally this re­petition will make the denture into a cord-like denture which has poorer retention and stability.

 

 

 

Border molding of the mylohyoid ridge area should be per­formed to cover the ridge 4-6 mm beyond it. At the insertion appointment, the impression surface of the denture on the mylohyoid ridge is relieved so that pain during mastication will be diminished.

 

 

In addition, when the lingual denture border is extended properly as mentioned above, the lingual polished surface can be shaped into a concave form(the concave shelf, which is important for the retention and stability of the de-nture.

In a serious case where the residual ridge is poor, the mem­branous attachment of the floor of the mouth appears high in the mylohyoid area. This appearance may lead dentists to assume that the muscles are strained parallel to the floor of

A denture border short of the mylohyoid ridge digs into the residual ridge and causes pain. If shortened, the denture border will impinge again upon the ridge.

the mouth during contraction which might cause pain or de­nture dislodgment and therefore the denture borders tend to be mistakenly shortened. However, as the muscle fibers run anteroinferiorly even during maximum muscle contraction, it is possible to extend the denture border beyond the mylohy­oid ridge to which the mylohyoid muscle attaches. Moreover, in the case of the elderly, the contraction of the mylohyoid muscle is not so strong. The muscle tension can be evaluated by palpating the floor of the mouth with a finger or a mouth mirrorf.

 

 

 

When making an impression of this region, some think that the movement of the mylohyoid muscle would be recorded by moving the tip of tongue toward the opposite side. However, tongue movement is due to the action of the gcnioglossus musclc. The mylohyoid muscle contracts during swallowing. By this tongue movement, instead of the move­ment of the mylohyoid muscle, the movement of the floor of the mouth which might be strained by the tongue will be recorded. This movement of the tongue can be considered to be exaggerated.

 

As exaggerated tongue movements during impression making will be the cause of underextended borders, excessive movements should be avoided. If the tongue is protruded over the dental arch, the lingual sulcus will become shallow and an extremely shortened border will be obtained. During ordinary functions like mastication, the tongue is never protruded outside the dental arch, like a child’s playful gesture of sticking out his/her tongue. If protruded, it might be bitten during mastication. A functional situation is, in other words, not a state of exaggerated movements. Furthermore, even if the dentist understands the tongue movements, during impression taking, it is impossible to expect an elderly patient to follow such a complicated instruction. Impression making should be performed only by the dentist him/herself. U should never be a task requiring assistance from the patient.

As the denture is used in a closed mouth, the tongue should not be moved around too much during impression making. The author never invites tongue movement during impression making. The patient is asked only to relax the tongue comfortably. The impression is then made 4-6 mm below the landmark, the mylohyoid ridge, and thus the extent of the denture border is decided at the mylohyoid ridge area. Even though the case may be favorable for more inferior extension of the border, the border is limited only to this length by trimming the extended border. Of course, denture reten­tion and stability may be better with the lengthened border.

However, some patients will complain of tightness at the base of the tongue in lengthened cases. Therefore the denture bor­der should be extended only as far as necessary.

 

Retromolar pad area

The denture must cover more than half of the retromolar pad. Histologically, the retromolar pad is composed of a firm fibrous connective tissue papilla in its anterior half and soft tissue containing molar glands in the posterior half. These two parts are named separately as the anterior “pear-shaped pad” and the posterior “retromolar pad”. However, in edentulous cases, it is hard to distinguish them with the naked eye and thus clinically the two parts should be regarded together as the retromolar pad.

The posterior peripheral seal can be obtained by placing the denture border over this resilient glandular tissue. Anywhere is possible on the glandular tissue, but if the den­ture border is placed too far posteriorly, some patients will complain of tightness at the base of the tongue and therefore it is best to cover 2/3 of the retromolar pad.

As the temporalis muscle fibers attach to the distal portion of the retromolar pad, stimulation from this muscle prevents the pad from resorbing. So, the retromolar pad is also used as a landmark for orientation of the occlusal plane. There­fore the retromolar pad must be included in the impres­sion.

Even though the mandibular molar region is thought to be the most difficult area for impression making, the outline of the denture base can be determined easily and automatically by using these indexes. It is just necessary to connect the index lines, namely lines placed 1 mm beyond the external obli­que ridge, 2/3 of the way from the anterior border of the retromolar pad and 4 to 6 mm below the mylohyoid ridge.

 

 

 

 

However, pain may occur on the buccal side of the re­tromolar pad region during mastication even though the de­nture is designed in the above mentioned ways. This is due to the masseter muscle, a strong elevator, which is lateral to the retromolar pad and covers the buccinator muscle. When the masseter muscle contracts, its enlargement presses the denture border with the cramped buccinator muscle. As the denture occludes, it caot move during function of the elevators. So, when the distobuccal border of the denture base is extended into the functioning area of the masseter muscle, the mucosa will be pressed against the denture base leading to pain .

In order to avoid such a situation, the movement of the

masseter muscle is recorded in the impression by creating its reactive contraction through pushing the tray during the bor­der molding procedure. The tension of the masseter muscle will make a concavity in the distobuccal outline of the im­pression. Another way is to reduce the ovcrlengthened border through observing the redness or displacement of the denture after insertion of the new denture made by connecting the in­dex lines. This method is easier for those who are not familiar with the previous one.

 

 

Retromylohyoid fossa

The posterior border of the lingual flange can be the curve obtained by connecting the index lines placed 4-6 mm lower than the mylohyoid ridge and on the retromolar pad. However, it is generally assumed that the denture border lengthened posteroinferiorly into the retromylohyoid fossa can promote retention and stability of the denture. The author has occasionally lengthened the border for those cases with severe bone resorption. However, it has caused the complaint of tightness at the base of the tongue. Therefore retention and stability have been obtained by other mcansfP. 103) rather than a lengthened border in the majority of cases.

Actually it is very difficult to make a definitive border, namely to make an appropriate impression, in this area. If the denture border is lengthened inappropriately, this will be the worst possible situation and will result in the opposite effect of the aim such as the dislodgment of the denture or an ulcer occurring along the overextended border. The posterior border established by connecting the index lines, as mentioned before, is just enough in cases where retention and stability can be obtained by other means. In almost all cases, the bor­der obtained by this method will be usable. Simplicity is best.

Although the above method is recommended, one may make use of the retromylohyoid fossa.

The space distal to the mylohyoid muscle is referred to as the retromylohyoid fossa. It is bounded by the mylohyoid muscle anteriorly, the retromolar pad laterally, the superior constrictor muscle posterolaterally, the palatoglossus muscle posteromedially, and the tongue medially. There is no struc­ture and so it is possible to lengthen the denture border into this space. During border molding, the border in this area is pushed into the retromylohyoid fossa by the strong intrinsic and extrinsic tongue muscles, and thus it will show the so-called S-curve as viewed from the impression surface. At this time, the posterior limit of the lingual border is defined by the palatoglossus muscle and the lingual slip of the superior constrictor muscle. This is called the retromylohyoid

curtain. When the tongue is protruded, the curtain also moves anteriorly. In some cases, the retromylohyoid fos­sa becomes greatly shortened and it seems impossible to ex­tend the denture border. The extension of the denture border can be determined by examining the tightness of the fossa with a mouth mirror when the patient is instructed to make moderate tongue movements such as touching the maxillary anterior ridge with the tip of the tongue. Usually the space is wideT than expcctcd.

By extending the denture flange into this region, a peripheral seal can be obtained continuously from the re-tromolar pad region to the anterior lingual sulcus. In addition, this extended lingual flange can be shaped accordingly for guiding tongue placement onto the polished surface of the lingual flange. Moreover, the projected posterior border will literally serve as a flange(the projecting edge of a train wheel) by physical means, leading to an improved denture.

 

Sublingual gland area        

The sublingual gland lies above the mylohyoid muscle. The gland is raised when the mylohyoid muscle contracts during swallowing.

 

The position of the mucosa of the floor of the mouth may be recorded higher through impression making by excessively moving the tip of the tongue. However, the lingual flange extension is decreased and a space is created between the denture border and the mucosa of the floor of the mouth whilst the mylohyoid muscle is at rest, leading to impairment of the peripheral seal.

Similar to impression making in the mylohyoid ridge area, the patient is never instructed to perform any movements of the tongue, but asked only to relax the tongue comfortably. The mouth is nearly closed and the tongue lies on the floor of the mouth completely. This is the “impression position” of the tonguef.

 

 

 

 

 

Through border molding, the depth of the lingual vestibule is recorded in this situation and this will in turn be used as the length of the lingual flange in the sublin­gual gland area, so that the lingual border seal can be estab­lished effectivelyf.

Is this length all right when the sublingual gland is raised by the contracted mylohyoid muscle or not?

The lower denture will not be lifted up, even though the sublingual gland is raised, as the upper and lower teeth are in contact when swallowing. On the other hand, the sublingual gland serves as a cushion due to its soft and resilient nature and therefore it will neither lift the denture nor will its cover­ing mucosa be traumatized by the denture.

 

 

 

 

This length is quite enough for normal functional movements.

Retruded tongue position

 

The retruded tongue position is seen in a slightly opened mouth. This is found in 25% of people. It is hard to maintain the lingual peripheral seal, and thus air or food easily enter beneath the lingual borders.

In a slightly opened mouth, the tongue appears relaxed and completely covers the floor of the mouth with the tip of the tongue lightly contacting the lingual surfaces of the lower anterior teeth and the lateral border of the tongue covering the occlusal surfaces of the posterior teeth. This is the normal position of the tongue”. This tongue position is quite favorable for maintaining the lingual peripheral seal which improves retention and stability of the denture.

However, such a normal tongue position is missing in some people. Wright et al. found that about 75% of people had a normal tongue position, but the re­maining had a retruded tongue position. In these cases, it is hard to obtain a peripheral seal as air or food can easily enter beneath the lingual borders. Even the “concave shelf”, as mentioned later, can not work effectively.

It is thought that the retruded tongue position can be improved by training the tongue. Levin reported that the following method proved successful for many patients⁷‘.

A small “training groove” about 10 mm long, 2 mm wide, and 2 mm deep is made just below the central incisorsf. The patient is instructed to place the tongue on the groove at all times except when eating and speaking. The edges of the groove are slightly ta­pered and smooth so as not to irritate the tongue. He reported that most patients could learn to keep the tongue on this correct position within a few weeks. Finally, the training groove is filled with auto-polymerizing acrylic resin.

However, it must be noted not to insert the tray carelessly because the patient might open his/her mouth widely and roll up the tongue.

 

Some dentists are not satisfied unless tongue movements are used to record the movement of the floor of the mouth. The movements should be carried out by pressing the anterior portion of the tongue with the forefinger of the operator’s other hand during impression making. Only such an degree of tongue movement is recommended. Exaggerated tongue movements will cause an underextended denture border.

Labial flange area

The orbicularis oris is the major muscle in this region. As its muscle fibers run horizontally, care must be takeot to overextend the impression border in cases with weak muscle tension in this region.

The mentalis muscle is one of the muscles constituting the lower lip. Its muscle fibers are vertical and the origin attaches high on the mandibular alveolar process, therefore the labial vestibule becomes shallow when this muscle contracts. However, if the lip is pulled too much as a result of being over conscious about this contraction during border molding, the vestibule will become too shallow because the attachment of the muscle is higher than the base of the labial vestibulc.

In patients exhibiting strong muscle tension of these muscles in this region, this causes the lower lip to fall inwards and the impression border becomes thin and short. As a result, the completed denture might have an insufficient peripheral seal. In general, the instruction is given to bite the operator’s fin­gers which are placed between the tray and the maxillary ridge. As the masticatory muscles become tense and the lower lip becomes loose as a reflex, the impression is then made in this situation.

Usually it is recommended that the patient is instructed to close the mouth slightly with relaxed lips and the lower lip is pulled lightly outwards and the depth of the vestibule is re­corded as it is seen. However, with this method a portion of the mentalis muscle will be covered by the denture base. So care should be takeot to apply excessive pressure with the insufficiently softened compound during border molding and moreover, the impression surface of the com­pleted denture should be carefully adjusted using pressure-indicating paste. In the case of severe ridge resorption, it may be difficult to recognize the inferior labial frenum even though the lower lip is pulled outwards. It need not be recorded foreibly, but if the frenum is irritated by the completed denture, relief should be provided.

Anterior lingual flange area

The border of the impression in this area is mainly influ­enced by the lingual frenum and the genioglossus muscle. Sometimes the lingual frenum is broad. The strong genioglossus muscle lies just beneath the lingual frenum and its action is mainly to raise and protrude the tongue.

The genial tubercles, which are the origins of both the genioglossus muscle and the geniohyoid muscle, are hardly involved in the process of alveolar bone resorption. Thus in the case of severe bone resorption, the genial tubercles project higher than the crest of the residual ridge. The projection is extremely prominent in some cases.

The denture flange covering the genial tubercles may be widely eliminated in many dentures for fear that the tubercles would be irritated by settling of the denture due to occlusal forces. However, if the denture border ends on the hard tissues, no peripheral seal will be possible. The denture border must be extended over the genial tubercles in favor of improving the peripheral seal.

 

The genioglossus muscle and the lingual frenum which lies over the muscle move actively and are easily traumatized, therefore their movements and tension must be recorded exactly during border molding. Thus the patient must be instructed to make appropriate tongue movements in order to record the exact depth and width of the notch made by the lingual frenum. To provide adequate clearance in this area, the patient is instructed to make some overactive movements such as licking the lower lip by moving the tip of the tongue from side to side. Inadequate clearance may result in pain or

inflammation. Tongue movement is never requested during impression making. However, this is the only area where functional movement of the tongue is necessary. But this procedure may require great skill. If the clearance is too wide, the denture will loose its seal, which is important for retention. Finally the denture should be trimmed little by little by properly examining the denture after it has been inserted.

 

The internal surface of the denture covering the genial tubercles should be adjusted carefully using pressure-indicating paste at the time of denture insertion. Therefore appropriate relief on the impression, or fitting surface of the denture base is provided, which compensates for the amount of tissueward movement of the denture resulting from occlusal forces.

2. Landmarks for the maxillary impression

Maxillary border molding is easier than that for the mandible except for those cases with a flat ridge and little or no vestibular space. The length of the border will be adequate if the sulcus is recorded as deeply as it is observed. Even if the length of the border is inadequate, it is thought that good retention is possible by the so-called ‘facial seal’ which is created by the drape of the lips and cheeks’. Thus, the only areas where care is needed in impression making for the maxillary denture are the frenal, buccal vestibular, and posterior border areas.

Frenal area

The maxillary labial frenum is a fold of mucous membrane mainly consisting of fibrous connective tissue. It tenses between the labial gingiva and the upper lip mucosa when the upper lip is raised. A labial notch is formed in the denture border due to the movement of this frenum.

The lip movement near the maxillary labial frenum is vertical and thus the notch becomes long and narrow. If the frenum is pulled too far laterally during border molding, the notch will become too wide and the peripheral seal will be lost, therefore care is needed so as not to manipulate the lip excessively .

In some cases, depressions are recorded beside the labial frenum notch due to muscle bands consisting of the origins of the nasal septal depressor muscle and the orbicularis oris’. In these cases, the denture must be adequately relieved so as not to disturb the function of these muscles.

On the other hand, the muscle movements around the buccal frenum arc both vertical and horizontal, thus a wider.

notch should be formed compared with the labial frenum. It will become a V-shaped notch. Generally the frenum runs obliquely and posteriorly, therefore its anterior movement should be recorded by pursing the lips such as when whistling, during border molding.

Buccal vestibular area

The vestibule which extends posteriorly from the buccal frenum, the so-called the buccal space, should be recorded just as it is seen. Even though it appears rather wide, the impression should be made as it is seen. If this space is inadequately formed, the denture will lose its peripheral seal because of the ingress of air under the denture base due to the opening up of the buccal vestibule when the patient laughs and opens the mouth widely. In addition, it may not lead to an appropriate arrangement of artificial teeth and a proper polished surface.n the rare case when it is hard to determine the width ofthe vestibule and thus the width of the denture border, due to severe alveolar ridge resorption, the appropriate width of the vestibule can be estimated by using the remnants of the lingual gingival margin as a guide.

Watt measured the buccolingual breadth of the dentate alveolar ridge(the horizontal breadth of the alveolar process from the lingual gingival margin to the maximal projection of the buccal surface of the ridge) and found that this measure­ment for every tooth position was remarkably constant. Therefore he has suggested that when the remnants of the lingual gingival margin can be located in the edentulous mouth, the cheek position can also deduced by using it as a landmark

 

 

 

 the average measurement of the buccolingual breadth in the dentate molar region is 10-12 mm. However, afteT extraction of the teeth, the remnants move outward 3-4 mm from the position in the dentate mouth, so the width of the vestibule should be esti­mated by deducting this value from the mean buccolingual breadth of dentate patients.

As mentioned by Watt, this estimation caot be applied to all cases: however, it can be used as an approximate guide to determine the width of the denture border.

 

In addition, he staled that a slight overestimation of sulcus breadth is preferable to an underestimation.

In other words, the additional breadth in the molar region can be accepted because in the dentate patient contact between the cheek and alveolar process may not be present in the molar region. Moreover, the buccinator can act more effectively against a slightly over-molded bulge, leading to an improved buccal seal.

In cases where one is worried that the border may have been molded too thickly, when the thickness is transferred to the denture border, the coronoid process of the mandible may come into contact with the border during function. This should be confirmed by asking the patient to move the jaw laterally after softening the compound on the distobuccal border. If there is any contact, a shallow concavity will be cre­ated on the outer surface of the buccal border.

Posterior border area

The hamular(pterygomaxillary) notch is situated between the maxillary tuberosity and the hamulus of the medial pterygoid plate. It is a favorable landmark for placing the posterior border, which is the most important part for retention of the upper denturc. If a mouth mirror or a T-burnisher is slid posteriorly along the crest of the alveolar ridge, its edge will drop into a displaceablc depression, the hamular notch-. II can be satisfactorily recorded as there is no muscle or ligament in this notch. If the denture is extended inadequately, the posterior border will be situated on the maxillary tuberosity and a peripheral seal caot be expected from this nonrcsiliciu tissue.

The vibrating line(ah-line) runs from one hamular notch to the other across the palate, on which the distal end of the upper denture should be placed. When the patient says “ah” the soft palate rises up and returns to its original position when the patient relaxes. By repeating this movement, the junction of the hard and soft palatesfvibrating line) can be recognized as a fold. The hard and soft palates described here mean the clinical ones. See “Clinical junction of the hard and soft palates and its relation to ah-line”). However, the bound­ary line of movement is not well-defined and is an area rather than a line.

Strictly speaking, the vibrating line is situated slightly posterior to the junction of the hard and soft palates, that is, on the soft palate, thus if the posterior border is placed on this line, the peripheral seal will be established due to the cushion-

The “clinical” junction of the hard and soft palates and its relation to the vibrating line(ah-line)

In anatomy, the hard and soft palates are distin­guished by the existence of bony support. Thus the junction of these two palates is on the distal end of the bony palate. In general, the vibrating line which is used as a posterior guide for the upper denture is con­sidered to coincide with, or he situated somewhat pos­terior to, this anatomical junction.

The foveae palatinae situated near this junction are also used as a landmark for determining the posterior border of the denture. In anatomy, the foveae palatinae are situated on the distal end of the bony palate or somewhat anterior to it. Various reports have described the relation between the foveae palatinae and the vibrating line, perhaps depending upon the various methods of determining the vibrating line. Among the reports, Chen stated that “No foveae palatinae are situated anterior to the vibrating line”‘”. Thus, if the vibrating line is thought as the junction between the movable and immovable portions of the palate, when the patient says “ah”, it would be guessed that the vibrating line is located on the anatomical hard palate which is situated anterior to the end of the bony palate.

the hard palate possesses a portion made up of a 4-5 mm thickness of subtnucosa which contains muscle insertions as well as glandular tissue. liven though the hard palate is supported by bone, it is effected by the levator and tensor muscles of the velum palatini and so it is considered to be movable.

Clinically, from only inspection and palpation, it is difficult to determine whether the palate is supported by bone or not. So, the term, “clinical” hard and soft palates, should be advocated. The hard palate has a firm attachment to the underlying bone, and thus it is hard and immovable on palpation. It is covered by keratinized epithelium, the masticatory mucosa. The soft palate does not lie directly on bone and is soft and movable on palpation. It is covered by non-keratinized epithelium and filled with blood vessels which make it appear red in color. The further it extends posteriorly, the greater the movement is effected by the muscles in the submucosa. The clinical junction of the palates is entirely anterior to the anatomical junction as. A similar idea is demonstrated in Pendleton’s figure in Boucher’s textbook, but it does not mention a distinction between the anatomical and clinical junctions and the junction in the textbook seems to be somewhat anterior to the clinical junction mentioned above.

ing effect of the soft palate⁹‘. Moreover, as mentioned later, if the posterior border is slightly pressed into the mucosa along this line, the valve seal will be improved. This junction can also be located by blowing out through the nose with the nos­trils closed in which case the soft palate will expand down-wards, nose-blowing method).

Usually the vibrating line passes slightly anterior to the foveae palatinac, thus the posterior border can be determined by using the fovea as a landmark”^,.

 

In the posterior part of the submucosa of the palate, the palatine glands extend anteriorly from the soft palate to the first molar region, taking the shape of a mountain on cither side of the midline. The thickness is 4-6 mm in the soft palate and 2-3 mm even in the anterior part on the hard palatc. Thus there is no need to be anxious regarding how far the posterior border can be extended. If the border is placed only on these palatine glands which possess a cushioning effect, this would be adequate for retention, even if it is placed slightly anteriorly. A little more extension may not lead to much better retention. If it is overdone, the situation will be worse than that of under extension and will lead to a gag reflex and irritation of the movable mucosa. Therefore it is recommended that the posterior border is determined by carefully avoiding the portion moving around the vibrating line whilst saying “ah”.

Some clinicians might extend the posterior border posterior­ly so as to cover the foveae palatinae by considering the ana­tomical junction of the two palates, but this concept is not recommended.

 

a: The palatine glands extend anteriorly from the soft palate to the first molar region taking the shape of a mountain on either side of the midline(From Kamijo. Y.). b: The thickness is 4-6 mm in the soft pa­late and 2-3 mm in the anterior regionfCross section in the region of the maxillary molars, by courtesy of Hiroyuki Uchida).

In addition, during border molding, one layer of compound is added on the tissue side of the posterior border of the im­pression tray and then the tray is seated in the mouth so that additional pressure is applied to this area. In other words, the distal end of the denture will be pressed into the mucosa lead­ing to a better peripheral seal.

3. Preliminary Impression

When making the preliminary impression using a stock tray, a rough but maximally extended impression should be made so as to obtain all the anatomical landmarks. Alginate impression material should be used for the preliminary impres­sion because its manipulation is simple and the setting time is fast, making it a little more pleasant for the patient. In addition, it will not distort the soft tissues because of its soft con­sistency. However, it is necessary to push away the surrounding tissues to a certain extent in order to capture the anato­mical form of the alveolar ridge. For this purpose, the consistency of alginate must be stiff or thick by reducing the amount of water compared with a normal mix.

When the impression material is to be alginate, an edentulous stock tray for alginate is usually used, but it may be preferable to use the Britannia metal edentulous tray for model­ing compound(Nakazawa’s tray, Sankin). This type of tray can be adjusted to some degree by cutting and bending even for complicated alveolar ridges. Moreover it is strong and easy to clean. Any deficient tray border should be corrected by adding utility wax.

In the case of a severely resorbed ridge with quite a complicated contour, a rough impression is frequently made with im-a   b

: The inner impression surface of the compound impression is reduced 1-2 mm. b: The alginate impression is made using this compound tray(a).

 

 

pression compound and then the inner surface of the impression is reduced to a depth of l-2mm. This will serve as a pre­liminary impression tray for alginate.