Edentulism

Clinical anatomy of the edentulous mouth. Making individual spoons for the upper and lower jaw.

Edentulism is the condition of being toothless to at least some degree; it is the result of tooth loss. Loss of some teeth results in partial edentulism, while loss of all teeth results in complete edentulism.

Organisms that never possessed teeth can also be described as edentulous, such as members of the former zoological classification order of Edentata, which included anteaters, sloths and armadillos, all of which possess no anterior teeth and either no or poorly developed posterior teeth.

Signs and symptoms

For people, the relevance and functionality of teeth can be easily taken for granted, but a closer examination of their considerable significance will demonstrate how they are actually very important. Among other things, teeth serve to:

• support the lips and cheeks, providing for a fuller, more aesthetically pleasing appearance

• maintain an individual’s vertical dimension of occlusion

• along with the tongue and lips, allow for the proper pronunciation of various sounds

• preserve and maintain the height of the alveolar ridge

• cut, grind, and otherwise chew food

Facial support and aesthetics

When an individual’s mouth is at rest, the teeth in the opposing jaws are nearly touching; there is what is referred to as a freeway space of roughly 2–3 mm. However, this distance is partially maintained as a result of the teeth limiting any further closure past the point of maximum intercuspation. When there are no teeth present in the mouth, the natural vertical dimension of occlusion is lost and the mouth has a tendency to overclose. This causes the cheeks to exhibit a “sunken-in” appearance and wrinkle lines to form at the commisures. Additionally, the anterior teeth, when present, serve to properly support the lips and provide for certain aesthetic features, such as an acute nasiolabial angle. Loss of muscle tone and skin elasticity due to old age, when most individuals begin to experience edentulism, tend to further exacerbate this condition.

The tongue, which consists of a very dynamic group of muscles, tends to fill the space it is allowed, and in the absence of teeth, will broaden out. This makes it initially difficult to fabricate both complete dentures and removable partial dentures for patients exhibiting complete and partial edentulism, respectively; however, once the space is “taken back” by the prosthetic teeth, the tongue will return to a narrower body.

Vertical dimension of occlusion

As stated, the position of maximal closure in the presence of teeth is referred to as maximum intercuspation, and the vertical jaw relationship in this position is referred to as the vertical dimension of occlusion. With the loss of teeth, there is a decrease in this vertical dimension, as the mouth is allowed to overclose when there are no teeth present to block further upward movement of the mandible towards the maxilla. This may contribute, as explained above, to a sunken-in appearance of the cheeks, because there is now “too much” cheek than is needed to extend from the maxilla to the mandible when in an overclosed position. If this situation is left untreated for a many years, the muscles and tendons of the mandible and the TMJ may manifest with altered tone and elasticity.

Pronunciation

The teeth play a major role in speech. Some letter sounds require the lips and/or tongue to make contact with teeth for proper pronunciation of the sound, and lack of teeth will obviously affect the way in which an edentulous individual can pronounce these sounds.

For example, the fricative consonant sounds of the English language s, z, x, d, n, l, j, t, th, ch and sh are achieved with tongue-to-tooth contact, and the fricative f and v are achieved through lip-to-tooth contact. These sounds are very difficult to properly enunciate for the edentulous individual.

Preservation of alveolar ridge height

The green line indicates the faciolingual dimensions of a newly edentulous ridge, while the blue line indicates these dimensions after the occurrence of very severe resorption.

The alveolar ridges are columns of bone that surround and anchor the teeth and run the entire length, mesiodistally, of both the maxillary and mandibular dental arches. The alveolar bone is unique in that it exists for the sake of the teeth that it retains; when the teeth are absent, the bone slowly resorbs. The maxilla resorbs in a superioposterior direction, and the mandible resorbs in an inferioanterior direction, thus eventually converting an individual’s occlusal scheme from a Class I to a Class III. Loss of teeth alters the form of the alveolar bone in 91% of cases.

In addition to this resorption of bone in the vertical and anterioposterior dimensions, the alveolus also resorbs faciolingually, thus diminishing the width of the ridge. What initially began as a sort of tall, broad, bell curve-shaped ridge (in the faciolingual dimension) eventually becomes a short, narrow, stumpy sort of what doesn’t even appear to be a ridge. Resorption is exacerbated by pressure on the bone; thus, long-term complete denture wearers will experience more drastic reductions to their ridges that non-denture wearers. Those individuals who do wear dentures can decrease the amount of bone loss by retaining some tooth roots in the form of overdenture abutments or have implants placed. Note that the depiction above shows a very excessive change and that this many take many years of denture wear to achieve.

Ridge resorption may also alter the form of the ridges to less predictable shapes, such as bulbous ridges with undercuts or even sharp, thin, knife-edged ridges, depending of which of many possible factors influenced the resorption.

Bone loss with missing teeth, partials and complete dentures is progressive. According to Wolff’s law, bone is stimulated, strengthened and continually renewed directly by a tooth or an implant. Teeth and implants provide this direct stimulation which develops stronger bone around them.

A 1970 research study of 1012 patients by Jozewicz showed denture wearers had a significantly higher rate of bone loss. Tallgren’s 25-year study in 1972 also showed denture wearers have continued bone loss over the years. The biting force on the gum tissue irritates the bone and it melts away with a decrease in volume and density. Carlsson’s 1967 study showed a dramatic bone loss during the first year after a tooth extraction which continues over the years, even without a denture or partial on it.

The longer people are missing teeth, wear dentures or partials, the less bone they have in their jaws. This may result in decreased ability to chew food well, a decreased quality of life, social insecurity and decreasing esthetics because of a collapsing of the lower third of their face.

The bone loss also results in a significant decrease in chewing force, prompting many denture and partial wearers to avoid certain kinds of food. Food collecting under the appliance takes their enjoyment out of eating so they make their grocery and restaurant choices by what they can eat. There are several reports that correlate the quality and length of peoples lives with their ability to chew.

Dental implant studies from 1977 by Branemark and countless others show dental implants stop this progressive loss and stabilize the bone over the long term. Implanted teeth provide a stable, effective tooth replacement that feels natural. They also provide an improved ability to chew comfortably and for those missing many teeth an improved sense of well being. Dental implants have become the standard for replacing missing teeth in dentistry.

Masticatory efficiency

Physiologically, teeth provide for greater chewing ability. They allow us to masticate food thoroughly, increasing the surface area necessary to allow for the enzymes present in the saliva, as well as in the stomach and intestines, to digest our food. Chewing also allows food to be prepared into small boli that are more readily swallowed than haphazard chunks of considerable size. For those who are even partially endentulous, it may become extremely difficult to chew food efficiently enough to swallow comfortably, although this is entirely dependent upon which teeth are lost. When an individual loses enough posterior teeth to make it difficult to chew, he or she may need to cut their food into very small pieces and learn how to make use of their anterior teeth to chew. If enough posterior teeth are missing, this will not only affect their chewing abilities, but also their occlusion; posterior teeth, in a mutually protected occlusion, help to protect the anterior teeth and the vertical dimension of occlusion and, when missing, the anterior teeth begin to bear a greater amount of force for which they are structurally prepared. Thus, loss of posterior teeth will cause the anterior teeth to splay. This can be prevented by obtaining dental prostheses, such as removable partial dentures, bridges or implant-supported crowns. In addition to reestablishing a protected occlusion, these prostheses can greatly improve one’s chewing abilities.

As a consequence of a lack of certaiutrition due to altered eating habits, various health problems can occur, from the mild to the extreme. Lack of certain vitamins (A, E and C) and low levels of riboflavin and thiamin can produce a variety of conditions, ranging from constipation, weight loss, arthritis and rheumatism. There are more serious conditions such as heart disease and Parkinson’s disease and even to the extreme, certain types of Cancer. Treatments include changing approaches to eating such as cutting food in advance to make eating easier and less likely to avoid as well as consumer health products such as multivitamins and multi-minerals specifically designed to support the nutritional issues experienced by denture wearers.

Numerous studies linking edentulism with instances of disease and medical conditions have been reported. In a cross-sectional study, Hamasha and others found significant differences between edentulous and dentate individuals with respect to rates of atherosclerotic vascular disease, heart failure, ischemic heart disease and joint disease.

Cause

The etiology, or cause of edentulism, can be multifaceted. While the extraction of non-restorable or non-strategic teeth by a dentist does contribute to edentulism, the predominant cause of tooth loss in developed countries is periodontal disease. While the teeth may remain completely decay-free, the bone surrounding and providing support to the teeth may reabsorb and disappear, giving rise to tooth mobility and eventual tooth loss. In the photo at right, tooth #21 (the lower left first premolar, to the right of #22, the lower left canine) exhibits 50% bone loss, presenting with a distal horizontal defect and a mesial vertical defect. Tooth #22 exhibits roughly 30% bone loss.

Individual spoon manufacturing from standard basis plates.

 

Manufactured by the laboratory method the individual spoon.

 

One-moment individual spoon by CITO methodic /from wax/.

For upper jaw.

        

 

                                                               

For lowerjaw.

 

It is having a methodic of individual wax spoon manufacturing by Vasylenko Z.S. It’s differing by shortly margins manufacturing /lower thaeutral zone/, strengthening in the middle by a small portion of plaster.

 

Nowadays the most widespread is basis individual spoon manufacturing from the self-hardening plastics («Protacryll», «Reodont» etc.).

 

 

 

For the lower jaw.

 

 

Having dentures made starts out with impressions of both the upper and lower arches. These preliminary impressions are used to make custom trays that take an even more precise impression of the upper and lower arches. Because dentures are precision fitting prosthetic appliances, only a licensed dental professional should take final impressions with a custom tray. A dental auxiliary can take the preliminary impressions for the custom tray.

 

Selection of Impression Trays

The patient’s old dentures may be used in selecting impression trays. A slightly oversized tray is needed to cover all of the anatomic landmarks to be registered in the impression. Do not use trays intended for patients with teeth to make edentulous preliminary impressions unless faculty indicate this is appropriate for your patient.

Mandibular tray selection

a. With the patient seated upright, stand to the right and in front of the patient. (Please note this would be reversed for a left-handed student.) Hold the tray in your right hand. Retract the right corner of the mouth with a mouth mirror held in your left hand. Insert the left side of the tray in the mouth rotating the tray to center it over the ridge.

b. When you insert the tray into the mouth, lift the handle superiorly and position the tray so that the posterior portion covers the retromolar pads.

c. Lower the tray anteriorly and observe the adaptation of the tray to the anterior alveolar ridge. 3-5 mm of clearance should exist between the tray and ridge to allow space for the impression material.

Maxillary tray selection

a. With the patient seated upright, stand to the right and slightly in front of the patient. Hold the maxillary tray in your right hand. With a mouth mirror, retract the right corner of the mouth. rotate the impression tray into the mouth. The right side of the tray enters first and as the tray rotates, the outside of the right flange exerts tension against the corner of the mouth allowing gentle tray placement.

b. Move the tray handle inferiorly and place the posterior edge of the tray in the pterygomaxillary notches.

c. move the anterior edge of the tray toward the ridge. you should observe 3-5 mm of clearance between the tray and anterior ridge.

Impression Materials Used for the Preliminary Impression

1. Impression compound (Modeling compound)

2. Irreversible hydrocolloid (Alginate)

Modeling compound: Impression compound is relatively simple to use, has a minimal danger of aspiration, and can be stored for a longer period of time without distortion than alginate. Most importantly, compound impressions can be corrected by additions of small amounts of compound. Alginate cannot be corrected. This allows you to fix small errors in the impression avoiding subjecting your patient to multiple impressions.

The material used for edentulous preliminary impressions in the prescribed procedures is red impression compound supplied in cake form. The softening temperature is 132 degrees F. The water bath is maintained at 140 degrees F. The material should not stay in the water at this temperature any longer than is necessary to make the impression.

Irreversible hydrocolloid. Alginate is used by many dentists for making preliminary impressions. It has greater accuracy of surface detail than impression compound. Edentulous impression trays are available which are designed specifically for use with alginate. The major advantages of alginate are related to its flow properties when easily displaceable tissues are present. It is the material of choice when extreme undercuts exist.

Making the Preliminary Impression

After data collection and treatment plan presentation to your clinical instructor, you will be making preliminary impressions.

This impression will then be used to form a preliminary (diagnostic) cast upon which a final impression tray is made.

Definitions

Anatomic Landmarks Recorded by the Preliminary Impressions

The dentist must be able to identify the anatomic landmarks recorded in the impression. Either the maxillary or mandibular impression may be made first. The mandibular impression is made first if the patient has a tendency to gag.

Steps in Making the Maxillary Preliminary Impression using impression compound

1. Place 1& 1/2 cakes of red impression compound wrapped in a paper towel in the water bath set at 140 degrees F, 5 to 10 minutes prior to impression making.

2. Seat the patient and be sure the patient’s clothing is protected with a napkin.

3. Remove the softened impression compound from the water bath, kneed it, and roll it into a rounded triangular shape. Place it in the previously selected tray and mold the compound with your fingers to the approximate size and shape of the patient’s mouth. Create a grove fro the maxillary residual ridge with your fingers. Be certain to cover the borders of the tray with compound to retain the impression in the tray once the material hardens.

4. Flame the compound surface by passing over it quickly with a torch several times until it is glossy and smooth. this softens the surface layer of the compound and will ensure the accurate reproduction of the tissue surface. Temper the compound in the water bath after flaming to avoid burning the patient. This is accomplished by briefly about 10 seconds) immersing the tray in the 140 degree F water bath.

5. Stand slightly in front of and to the right of the patient. Rotate the tray against the right corner of the mouth. The left corner is reflected with a mouth mirror.

6. Center the tray over the residual ridge so that the tray handle is in alignment with the median line of the face.

7. Apply pressure, using the index finger of one hand, in an upward and backward motion to the middle of the palatal portion of the tray.

8. Discontinue the seating pressure when the impression material has reached the vestibular border.

9. Hold the impression in position with the index finger of one hand in the palate and grasp the cheek with the index finger and base of the thumb of the other hand. Gently pull the cheek outward and downward.

10. Change hands and manipulate the other cheek in a similar manner.

11. Lift the lip outward and downward. Gently massage the outside of the lips with both thumbs to shape the impression in this area. The impression is held until firm (about 30 seconds).

12. raise the cheeks to break the seal and gently push downward on the flange of the impression in the first molar region. It might be necessary to apply a downward and forward pull on the handle of the tray simultaneously. If unsuccessful, ask the patient to close his or her lips and blow air to inflate the cheeks. This will also break the border seal and cause the impression to dislodge.

13. Inspect the impression to determine if it is acceptable. Correct any deficiencies present with the green or brown stick compound.

14. Chill in ice water.

Oral tissue must be in an optimal state of health prior to impression making. To prevent any distortion of the oral tissue by the patient’s dentures, tell the patient to leave the dentures out of the mouth for 24-48 hours prior to the next appointment.

15. Disinfect the impression by placing it into a plastic bag and spraying into the bag with the current surface disinfectant in use in the clinic. Seal the bag for 10 minutes prior to pouring the impression

Steps in Making the Mandibular Preliminary Impression using Impression Compound

Generally, the mandibular impression procedure is more easily tolerated by the patient. It is often accomplished first to gain the patient’s confidence, especially if the mandibular ridge is parallel to the floor when the mouth is open.

1. Place 1 & 1/2 cakes of red impression compound wrapped in a paper towel in the water bath heated to 140 degrees F, 5 to 10 minutes prior to impression making.

2. Have the patient seated upright.

3. Remove the softened impression compound from the water bath, kneed it, and roll it into a sausage shape. Mold the compound with your fingers to the approximate shape and size of the previously selected tray. make a grove in it with your finger s approximately where the crest of the alveolar ridge will be located. Allow a small amount of compound to cover the tray borders to retain the impression in the tray when the compound hardens.

4. Flame the compound surface by passing over it quickly with a torch several times until it is smooth and glossy. Temper the compound by immersing it in the 140 degree F water bath to avoid burning the patient.

5. Stand in front of the patient and place the tray at the left corner of the mouth. The right corner of the mouth is reflected with a mouth mirror.

6. Rotate the tray into the mouth and carefully center it over the residual ridge.

7. Apply pressure to seat the tray by placing your index fingers over the premolar areas on both sides. Place the thumbs outside the mouth under the mandible for support.

8. As you seat the tray, distend the cheeks in the molar area to make certain they are not trapped beneath the impression material. Use an even downward pressure until the compound has reached the depth of the vestibule.

9. Hold the tray firmly in position and border mold on the right in the area of the buccal frenum by pulling the cheeks upward, inward, anteriorly and posteriorly while the compound is still soft.

10. Change hands and manipulate the left cheek in a similar manner.

11. Now have the patient lick the upper lip from one corner of the mouth to the other corner of the mouth. The impression is held until firm.

12. Loosen the impression after the compound has set by placing the index fingers along the border in the buccal shelf area and gently lift by rotating the fingers along the border.

13. Inspect the impression to determine if it is acceptable. If minor defects or small voids are present, they can be corrected using stick compound.

14. Chill in ice water.

15. Disinfect the impression using current recommended surface disinfectant for 10 minutes in a sealed bag prior to proceeding to the labs.

Oral tissues must be in their optimal state of health prior to impression making. To prevent any distortion of the oral tissues by the patient’s dentures, tell the patient to leave the dentures out of the mouth for 24-48 hours prior to the next appointment.

Steps in Making the Maxillary Preliminary Impression using Irreversible Hydrocolloid (alginate)

1. Seat the patient and be sure the patient’s clothing is protected with a napkin.

2. Select stock try that will cover all the landmarks indicating the denture bearing area. Also check the impression try and make sure it covers the hamular notches posteriorly.

3. The tray should be lifted in the front. You should observe 3-5 mm of clearance between the tray and anterior ridge.

4. Deficient tray borders should be corrected by adding utility wax.

5. Utility wax can be added to the central portion of the try to act as a guiding stop to seat the tray in place without displacing the mucosa.

6. Mark the hamular notches and the vibrating line (AH line) using the indelible sticks.

7. The alginate is mixed following the manufacturer instructions then loaded into the stock tray. Stand in front of the patient and place the tray at the left corner of the mouth. The right corner of the mouth is reflected with a mouth mirror.

8.The loaded tray should be seated posteriorly first then pushed slowly to the front so that the alginate flows anteriorly. Center the tray over the residual ridge so that the tray handle is in alignment with the median line of the face. At this time the upper lip is elevated so that the alginate flows into the labial sulcus.

9. The seating pressure is stopped and border molding is performed so that the impression is not overextended. The tray is held in place until the alginate has completely set.

10. Remove the impression from the mouth. Inspect the impression to determine if it is acceptable.

11.Disinfect the impression using current recommended surface disinfectant for 10 minutes in a sealed bag prior to proceeding to the labs.

12. Alginate impressions tend to be overextended so the denture outline should be drawn on the impression with an indelible stick. This outline will be transferred onto the cast and will be helpful to fabricate the custom tray.

Steps in Making the Mandibular Preliminary Impression using Irreversible Hydrocolloid (alginate)

1. Select stock try that will cover all the landmarks indicating the denture bearing area. Also check the impression try and make sure it covers the retromolar pads, external oblique ridge and Mylohyoid ridge.

2. The retromolar pad area should be marked using indelible stick before making the impression.

3. Any deficient area should be corrected by utility wax. The wax should be used on the entire lingual border and retromolar pad to carry the alginate into the lingual sulcus.

4. The alginate is mixed following the manufacturer instructions then loaded into the stock tray. Stand in front of the patient and place the tray at the left corner of the mouth. The right corner of the mouth is reflected with a mouth mirror.

5.Center the tray over the residual ridge so that the tray handle is in alignment with the median line of the face. At this time the upper lip is elevated so that the alginate flows into the labial sulcus.

6.The seating pressure is stopped and border molding is performed so that the impression is not overextended. The tray is held in place until the alginate has completely set.

7. Remove the impression from the mouth. Inspect the impression to determine if it is acceptable.

8. Disinfect the impression using current recommended surface disinfectant for 10 minutes in a sealed bag prior to proceeding to the labs.

9. Alginate impressions tend to be overextended so the denture outline should be drawn on the impression with an indelible stick. This outline will be transferred onto the cast and will be helpful to fabricate the custom tray.

 

A dimensionally accurate impression is one of the primary determinants for a precise fitting indirect restoration. The clinical success of the indirect restoration requires a precise working model and thus depends upon the accuracy of the final impression. The use of custom fabricated trays with elastomeric impression materials can improve the accuracy of the working model. There are a myriad of materials and techniques available for custom tray fabrication, including autopolymerizing and heat-activated acrylic resins, thermoplastic resins, and visible light-cured resins. The techniques for custom tray fabrication also vary and range from direct intraoral techniques to indirect laboratory procedures on a primary model.

 

The design and use of the custom tray offers distinct clinical advantages compared to the stock tray. First, dimensional changes that occur during the polymerization of elastomeric impression materials are proportional to the thickness of the material.3 Custom tray design can provide dimensional accuracy and stability by providing a uniform thickness of material throughout the tray. Utilization of stock trays can result in variations in thickness of the material and the potential for dimensional changes and inaccuracies in the model. Second, the custom tray rigidity reduces the potential for distortion of the impression in comparison to the flexible stock trays. Flexible trays can increase the potential for the impression material to pull away from the adhesive during polymerization of the material and removal from the oral cavity. Reports also indicate that tray flexure can contribute to impression and cast distortion. Finally, the custom tray design controls the size and conserves the volume of material required for the impression, reducing the cost of the impression material used for each impression. A streamlined design can reduce discomfort to the patient during the impression procedure because of the smaller design size and reduced volume of material. Furthermore, reducing the volume of elastomeric material utilized can minimize the polymerization-induced shrinkage while offsetting the additional economical costs of the tray fabrication.

CONSIDERATION FACTORS FOR FABRICATION AND UTILIZATION OF THE CUSTOM IMPRESSION TRAY

Visible light-cured resins exhibit dimensional stability immediately after curing, thus allowing immediate clinical use after fabrication. Research indicates that autopolymerizing acrylic resins should be fabricated 24 hours before the impression procedure. The dimensional stability of elastomeric impression materials is considered to depend on the bulk of material which is the distance from the inner surface of the tray to the surface of the impression. Elastomeric impression materials are considered most stable when they have a uniform thickness of 2 to 4 mm. Incorporating dental and/or tissue stops can provide a uniform impression material thickness of approximately 2 to 4 mm.

 Evaluate the stone model for potential undercuts and design the form and dimension of the tray. Diagram with a margin liner pencil the boundaries of the wax spacer (red), borders of the custom tray (blue) and the occlusal stops (blue).

 

 

 

 

 

Adapting the visible light-cured resin material directly over the wax spacer may leave a wax residue remaining in the tray. This residue contamination can interfere with adhesion of elastomeric impression materials to the impression tray. Even a small release of the impression material can cause a distortion in the impression, so this is critical. Surface cleaning of the tray using boiling water, pressurized steam and/or a wax remover is suggested. Another recommended method involves burnishing tin foil over the wax spacer.

 

 

 

 

 

It is essential that the impression material be securely attached to the tray, especially during removal of the set material from the oral cavity. Surface preparation of the custom tray can significantly affect the retention of the impression material and can improve adhesion between impression material and tray. Methods for improving retention/adhesion include: perforating or roughening of the custom tray surface with tungsten carbide burs and application of adhesive solutions.

 

Adhesive drying times of less than 15 minutes reduced the bond strength values of the elastomeric impression materials to the custom tray. To obtain durable and stable adhesion between elastomeric impression material and tray, the drying time after application of adhesive should be at least 15 minutes. Also, it is important to remember that each adhesive is specific to the impression material (ie, a polysulfide adhesive caot be used with an addition silicone impression material).

FABRICATION AND UTILIZATION OF THE VISIBLE LIGHT-CURED CUSTOM IMPRESSION TRAY

The main objective in tray construction is to provide a rigid tray for retention of the impression material. The aforementioned consideration factors can provide insight into the optimal fabrication and utilization of the custom tray. A visible light-cured resin material (Palatray XL [Heraeus Kulzer]) was selected for its rigidity, high dimensional stability, ease of manipulation, and unrestricted working time. Also, this material provides the ability to be ideally contoured prior to curing, thus eliminating prolonged finishing times. Other visible light-cured resins include Individo Lux (VOCO), Triad (DENTSPLY International), and Fastray LC (Bosworth Products).

 

Fabricating an indirect custom impression tray requires planning, a diagnostic model, and laboratory procedural time. Figures 1 to 10c illustrate the laboratory fabrication and clinical utilization of the visible light-cured custom impression tray that can be used to obtain a precise and predictable final impression.

Getting functional impression of the upper and lower jaws.

The doctor must  fit an individual spoon, made by a technician,(to adjust, make its surface and edges as much as possible close to the prosthetic bed). Fitting lays in that the orthopedist achieves the maximum stability (a spoon keeps on a jaw) it, “does not fall off” at movements of tongue and cheeks, the spoon edges do not come on a movable mucous membrane. A number of tests of Gerbst (see corresponding methodical recommendations and workbooks) are used for this purpose .

After fitting spoon it is necessary to edge edges with thermoplastic mass (Dentafol) and again to repeat tests of Gerbst. This stage is called registration of borders of an individual spoon.

Further an impression material is selected. The choice of an impression material depends on degree of an atrophy of an alveolar process, its form and the main thing of character of a mucous membrane of an orthopedic field, its degree of a pliability (softness). According to height of edges functional impressions are divided into:

Actually functional

Functional-adhering

According to degree of pliability — into:

compressive

differentiated

decompressive

There is not a single method of obtaining an impression, shown in all cases. A technique  of taking compression  functional impression is the most common. Such impressions are necessary to be removed with rigid impression masses – “Dentafol”, plaster, “Ortokor”, “Dentaflex”, “Stomaflex”, etc. The given technique is recommended for a normal or very pliable mucous membrane.

Pressure upon a mucous membrane at removing impression can be carried out either with a hand of the doctor, or chewing muscles of the patient. In the first case an individual spoon is adjusted with the issued borders and filled with impression  mass. Then the doctor enters into an oral cavity and presses a spoon with the mass to an alveolar process, keeping a spoon until the mass hardens. Pressure in each case turns out a miscellaneous and fluctuates even throughout removal impression.

     More uniform load and distinctive for the given patient can be reached as follows. It is necessary to make on a rigid spoon bite platens, fit a spoon, and to define to a toothless patient central occlusion, having lowered bite height a little. To fill a spoon impression with mass and to enter mass with a spoon into an oral cavity. To allow the patient with his own chewing pressure under bite control to keep a spoon in an oral cavity. Pressure will be uniform. It is the best technique.

Under some clinical conditions there is a necessity, on the contrary, to unload a mucous membrane. Such impressions will be decompressive, unloading. They are removed with liquid impression masses – liquid plaster, “Repin”, but an indispensable condition is the punched individual spoon. For this purpose in laboratory to the made spoon the doctor does necessary quantity of apertures by means of a spherical-shaped dental drill.

Decompressive impressions are recommended at very thin atrophied mucous or at the big atrophy of alveolar processes and thickening, easily movable mucous membrane covering an orthopedic field.

The technique of removal differentiated functional impression is known. For this purpose with an individual spoon preliminary impression is removed, then in places, where it is necessary to unload mucous (thickening, a small pliability)  impression mass is removed with a  spatula, or a by-pass channel is made. Liquid impression mass is mixed and again  removal of functional impression is repeated.

Methods of  forming functional impression edges.

 

 

 

The most common is the mixed method.

 

FOR AN UPPER JAW. Individual spoon with impression mass is entered into an oral cavity, grasping maxillary tuberosities (the patient with a half-closed mouth), the spoon is pressed to the palate and an alveolar process with one hand, the second hand the doctor shapes  impression edges from the vestibular side at a half-closed mouth of the patient. Cheeks at lateral teeth are pulled forward and downwards, and at foreteeth the lip is pulled downwards or it is done by the patient. For shaping of edge at the line “A”  the patient is asked to say sounds “A” and “K” at which the soft palate rises upwards. When mass stiffens, the doctor lifts an upper lip, pulling it upwards and simultaneously presses a spoon from top to down at foreteeth then impression is removed from an oral cavity.

FOR A LOWER JAW. A spoon with impression mass is entered and  the patient is suggested to hold covered mouth longer whenever possible . The doctor processes outer side, pulling his cheeks to the field of lateral teeth upwards and forward and a lip in the field of foreteeth – upwards. Processing at tongue side  is made by an active method: the patient is suggested to put out his tongue, with a tongue tip at a half-closed mouth the patient touches cheeks. Impression  is removed this way. The patient is suggested to put out his tongue and simultaneously a lower lip is pulled upwards. Impression is risen and  it is carefully removed.

 IMPRESSION QUALITY ASSESSMENT. Impression on the internal surface must not have  sunken places, the edges at vestibular and tongue sides should be of uniform thickness, all places of prosthetic field, which are important for retention (buccal-alveolar space for the upper jaw and the retroalveolar area for the lower jaw), must be accurately taken down, a neutral zone should be precisely outlined. Impression must be clean, free from saliva.

The casts dividing on anatomical and physiological at fully removable prosthetics. The cast, putted off by standard casting spoons without using functional probes for processing margins in calmness, is anatomical. They are dividing on the worker and additional. By the worker manufacturing denture, additional putting off from opposite side for corrects teeth statement. Booth casts will be workers, if prosthetics booth jaws.

Functional cast putting off by individual spoons with functional probes using. They are dividing on functional and functional-suction by the margins height. By mucosa pushing off degree – on compression and uploading.

Can use plaster and alginate materials for anatomical casts. Methodic of pushing off consist in spoon choosing, mix casting mass, putting on the mass on spoon, mixing in enough quality for margins forming. Should to grease selected sites by casting mass by spatula at the expressed upper jaw tubers and high connecting palatum before introduction a spoon in oral cavity. Then by dento-medical mirror delaying a right angle of patient mouth, and casting spoon with mass injecting in right mouth angle pushing backward under sight control against block in front palatum arches and grasping upper jaw tubers. Forcing out remains forward, press down the spoon to palatum by medial and index fingers. Moving its up and backward by left hand forming a vestibular side of cast, soft buccal tissues and upper lip – to forward and down. Asking a patient to repeat this movements. After hardening the casting mass putting off the spoon and estimating a cast from the elastic mass, then should to mould the model. It’s using for individual spoon manufacturing.

Casting methodic from lower jaw differing, because it is injected at first a spoon, down in front part and moving at once in retromolar space; asking a patient to up the end of tongue to palatum, and then put out forward and spend on the border of upper lip by tongue. The margin was process from vestibular side active /by patient/ and passive /by doctor/. Additional cast putted off only if denture manufacturing in one jaw at fully prosthetics.

The individual impression tray, prepared with any method, in the cavity of mouth they compulsorily fit. For this, as a rule, are used the Herbst tests.

FORMING OF THE MARGINS OF THE INDIVIDUAL TRAY IN THE MOUTH OF PATIENTS WHILE USING FUNCTIONAL HERBST TESTS

For the upper jaw:

For the lower jaw.

 

 

Today’s dentists are exposed to a multitude of dental materials, with each manufacturer claiming the benefits and superiorities of its respective products. Sometimes, I feel that the “prehistoric” techniques that we learned in dental school years ago display more benefits than what is in vogue today. This is especially true for crown and bridge impression materials and techniques. One has to only look back and visualize copper band impressions taken with dental compound, and picture the definition, accuracy, margin detail, and meticulous dies that these impressions provided. Eveow, we are still seeing the results of the “copper band masters” decades after the restoratons were placed. I sometimes wonder if the restorations fabricated from today’s materials are as accurate, or will last as long?

The MixStar-eMotion (DMG America).

     We all know that a meticulous impression is paramount for a precision fit of the permanent indirect restoration. Unfortunately, for many clinicians, taking a crown and bridge impression is one of the most stressful procedures in restorative dentistry. The good news is that taking great impressions can be simple if a dentist chooses the correct impression tray, achieves adequate retraction with controlled bleeding, and uses a rigid impression material with a light body wash to clearly capture every detail of the preparation.

     The purpose of this article is to share material choice rationale and technique protocols that we use in our office for taking consistently accurate impressions.

IMPRESSION MATERIALS

Throughout the last 2 centuries, different types of impression materials have been developed for use in dentistry. The nonelastic materials include: plaster, dental compound, and zinc oxide eugenol pastes. The elastic materials include: alginate (irreversible hydrocolloid), agar (reversible hydrocolloid), polysulfide, condensation silicone, addition silicone (polyvinyl siloxane [PVS]), and polyether.

 The rigid Honigum Putty (DMG America) keeps implant transfers firmly in place to ensure accuracy for the work to be done by our dental laboratory team.

      When evaluating an impression material, dentists tend to focus mainly on 3 factors:hydrophilicity, setting time, and cost. However, there are physical and mechanical characteristics which are far more critical to consider such as: detail reproduction, dimensional stability, ease of removal, gypsum (die and model stone) compatibility, elastic recovery/strain in compression, tear resistance, viscosity, complete conversion to an elastic solid, acceptable odor and taste, shelf life, and having the capability to be poured multiple times while still maintaining accuracy. Dental marketing seems to be focused on the concepts of hydrophilicity as if it were the only standard on which to judge the product.

     It is also paramount for the dentist to understand that not all impression materials and impression situations are the same. As a result, one should choose an impression material accordingly. The dentist must evaluate what type of impression is being taken (whole arch, sectional, multiple, or single tooth) and chose an appropriate impression tray, method of tissue retraction, and impression material.

     In my opinion, when taking sectional-arch impressions, or when picking up implant impression transfers; a thick consistency putty-like material is preferable, since its rigidity offers greater support. The putty material is a kneadable material that is used as a base material. After a low viscosity material is injected around the tooth, the impression tray filled with putty is then placed over the teeth, displacing the light body (low viscosity), into the crevices surrounding the preparation. After setting, the impression tray is removed, yielding an extremely accurate reproduction.

 Metal nonflexing impression trays are the first step to success.

     The choice of impression materials, coupled with the appropriate impression-taking techniques, is critical to success. In my opinion, it seems that we have traded accuracy for convenience. Most dentists are using disposable plastic trays, as opposed to metal (rigid) ones. Then, the flexible plastic trays are filled with impression materials that flow, rather than with a stiff material that would provide less chance for distortion. This is, in part, due to the manufacturers’ need to have a flowable impression material with a viscosity that works with automix delivery systems (where the base and catalyst are combined and mixed in a small mixing tip). These flowable impression materials lack the rigidity of the previous generation of putty systems that had to be hand mixed.

      Despite the introduction of dynamic mixing devices (cartridges or automated), many dentists still value the consistency of the previous generation of putties and continue to mix their materials manually. Manual mixing putty systems such as Silagum (DMG America), Aquasil Putty (DENTSPLY Caulk), Express Penta Putty (3M ESPE), Flextime and Provil (Heraeus Kulzer), Panasil Putty (Kettenbach LP), and President and Affinis Putty (Coltène/Whaledent) have continued to be manufactured.

      Until recently, I have not experienced an automix impression system displaying the benefits of the copper band technique or the putty systems where the dentist would mix 2 balls of catalyst and base together. (This stiff material, when placed in an impression tray, would displace a light body wash material injected into the sulcus surounding the preparation, resulting in an impression with sharp definable margins.) For clinicians like me, who value a thick consistency, an innovative putty (Honigum-MixStar Putty  has been recently introduced in an automix cartridge that is mixed in an automix machine (MixStar-eMotion) .

     Since I have been using this material in my own practice, I feel that the definition and sharpness of my margins have improved. I do not need to retake impressions as frequently since the stiff putty displaces the light body material easily into the preparation sulcus. As a result, I have now been able to return to my “old school” roots with the benefit of modern convenience. Furthermore, I also find that this putty material, which has neither an unpleasant smell nor taste for the patient, is easier to remove from the mouth than regular heavy body materials. We have found that it maintains excellent dimensional stability and does not distort over time, making it unnecessary for it to be poured immediately. In addition, since dental implants have become a major part of our restorative practice, accurate impressions are vital to the success of these procedures. A firm putty impression system captures the implant transfer postion very accurately. In the dental laboratory, the rigidity provided by the putty allows the transfers to be precisely poured into an analog model.

IMPRESSION TRAYS

When a dentist places an impression material in the patient’s mouth, using many of the commercially available plastic impression trays, any flexing of the plastic tray causes the impression to be distorted. It is the lack of tray rigidity that leads to flexure, resulting in incaccurate dies in the buccal-lingual and occlusal dimension. Although the impression may look perfect, even the most minute bending of the tray on placement will create inaccuracies in the final restoration, causing adjustment to be necessary when placed in the patient’s mouth.

 Patient practices biting into maximum habitual intercuspation (centric occlusion).

      Dentists often receive cases back from their dental laboratory team that appear to be perfect. The occlusion looks accurate, the marginal ridges line up, and the contacts are tight. However, when tried in the patient’s mouth, the case has to be adjusted significantly. Sometimes a new impression must be taken and the case totally remade. There are many possible reasons for these inaccuracies.

 Bite registration paste (O-Bite [DMG America]) is placed on the contralateral opposing arch (nonprep side) to create a lock bite that will ensure that an accurate restorative bite is taken

 Perhaps the stone used to create the model was not poured according to the manufacturer’s instructions and specified proportions, causing too much expansion, yielding a totally inacurate model. Perhaps the stone dies were not properly prepared, preventing the restorations to fully seat in the mouth. There are many factors that can affect the fit of our restorations, so we must eliminate inaccuracies and distortions right from the beginning of the process. Using rigid impression trays is the first step to accuracy in your impressions.

 Capturing the centric occlusion lock bite.

 Occlusal lock-bite registration left in place to act as bite jig.

 Practicing accurate placement of the tray.

 

 The doctor injects the light-bodied (Honigum [DMG America]) impression material.

 Simultaneuosly, while the doctor injects the light-bodied impression material, the assistant is dispensing the putty (Honigum Putty [DMG America]) from the MixStar-eMotion.

 Closing into the putty using the bite jig, which serves to guide the teeth into the proper predetermined bite relationship.

 Precise details, using the impression technique protocol as outlined, were easily attained.

 

 Gingival retraction paste  was used in this case for tissue and fluid control, instead of packing retraction cord.

Full-Arch Impression Trays

Full-arch metal impression trays are the “gold standard.” When accurate full-arch impressions are taken of the opposing arches and poured and prepared in a consistent and precise manner, many sources of inaccuracy are eliminated resulting in restorations that should require minimal adjustment intraorally.

     Rigid protocols are essential for reliability and consistency in dental procedures. All full-arch impressions in our practice (PVS, alginate) are taken with Rim-Lock Impression Trays (DENTSPLY Caulk). When I place and remove these trays from the patient’s mouth, I am confident that these trays are not flexing, thus eliminating the first source of error from the impression-taking process. It is then up to the dental laboratory team to follow the remainder of the protocol and to produce consistent restorations requiring minimal adjustment.

 A beautiful and accurate impression was achieved on a multiple unit full-arch impression using the putty-wash technique protocol and materials as described in this article.

Dual-Arch Impression Trays

Dual-arch impressions continue to be very popular and, if done properly, will produce single-unit restorations requiring minimal or no adjustment. Dual-arch trays have several advantages: only one tray is needed for the impression of both of the opposing arches; the bite is registered simultaneously in the impression; it provides improved patient comfort versus full-arch trays; less impression material is used, resulting in lower cost; and, because 3 procedures (2 impressions, bite registration) are performed simultaeously, it takes less time, further reducing the costs associated with impression taking.

     However, one must keep in mind that the dual-arch impression procedure is very technique sensitive and should only be used when the following criteria are met:

• It should be used with an intact dentition (Braley Class I) and the single prepared unit should have intact teeth adjacent to it.

• The occlusal surfaces opposing the prepared teeth should be ideal.

• The patient should be able to close down into maxiumum intercuspation without interference.

     In my opinion, plastic impression trays should never be used because they flex, creating inaccuracies. Instead, a metal dual-arch impression tray should be chosen. It should fit passively and the operator must ensure that it does not rub against any tooth/anatomic structures to avoid any potential interferences when the patient bites together. If passive fit of the tray cannot be achieved, then conventional full-arch impressions should be taken. In our practice, we use the Quad Tray Plus (CLINICIAN’S CHOICE). It is designed in its shape and dimensions to accommodate most patients’ dental arches. Its rigidity creates extremely accurate impressions when used with compatible rigid impression materials.

DUAL-ARCH IMPRESSION TECHNIQUE

After selecting the appropriate dual-arch impression tray, the dentist should practice inserting the tray into position in the patient’s mouth. Also, the patient should practice biting into maximum intercuspation . After several practice runs of placing the tray and having the patient bite down, place some O-Bite (DMG America) bite registration material on the opposing arch  on the contralateral arch (the nonprepped side of the patient’s mouth). Then, have the patient bite together to capture this contraleteral bite; this bite will serve as a “lock” to ensure that the patient is biting consistently into maximum intercuspation . Leaving this bite registration in place , the clinician once again practices accurate placement of the dual-arch impression tray . Next, light body Honigum (DMG America) is injected into the sulcus of the preparation by the doctor , while the dental assistant simultaneously dispenses the Honigum Putty from the MixStar-eMotion . The dual-arch tray loaded with putty is placed in the manner that was previously practiced. The bite registration will serve as a guide to ensure that the patient is in complete habitual centric occlusion closure . Using this impression technique protocol will allow the dentist to easily achieve consistently accurate impressions with precise detail .

RETRACTION TECHNIQUE

In order to take consistently accurate impressions, we must be able to visualize the margins of our preparations clearly. If our margins are placed supragingivally, capturing them is relatively simple. However, much of the time, the margins are placed subgingivally beyond the presence of existing large restorations, or for aesthetic reasons. Dentists sometimes proceed to take subgingival impressions without being 100% able to visualize the prepared margins, “hoping” that the impression will succeed. If they miss the first impression, they often take it again, while still not being able to totally visualize their margins. They are basically again “hoping for a miracle.” They blame the lack of hydrophilicity of the material (or some other reason?) for their own fundamental errors.

      Hydrophilicity is not an issue if there is no bleeding and the dentist can totally visualize the margin of the preparation. Dentists are obsessed with hydrophilicity. However, there is really no such thing as a hydrophilic PVS impression material. A clear field, free of blood and other oral fluids/contamination, is the most important factor in capturing a good impression. All PVS materials have the same weakness: they are unable to consistently make an impression in the presence of blood/fluids. Since 2 materials cannot occupy the same space at the same time, sulcular bleeding must be controlled prior to taking the impression. Adequate retraction must be accomplished in all subgingival areas to guarantee that the impression material will flow under the margin. Several different methods of retraction are in vogue today, the most popular of which are: retraction cords, laser or electrosurgery techniques, and paste systems.