Anatomical and physiological peculiarities of masticatory apparatus with the loss of teeth. Functional impressions during complete absence of teeth. Occlusion and articulation. Defining the central value of the jaws.
The increased course of preclinical training in orthopedic dentistry is aimed not only at studying anatomy and physiology of the organs of the dentomaxillary systems, but also at deeper mastering of the practical skills, and thus at general improvement of training quality of dental students.
Orthopedic treatment of patients is given for final restoration of the maxillodental system, reconstructions of the lost form of some organs of this system, their functional interrelations.
The maxillodental system is organs and tissues interconnected functionally by anatomy, performing various but co-ordinated functions. It contains the hard tissues – bones of the facial skeleton, including the maxilla and mandible, masticatory and mimic muscles, salivary glands, temporomandibular joint – a paired organ – mobile connection of the mandible with the temporal bone of the skull.
In the correctly formed maxillodental system the structure of each organ is precisely coordinated with its function. The compensatory process that is compensation of the impaired function due to activity of the intact organs begins to develop in the damaged maxillodental system, for example, influence of the environmental factors on an organism: physical, chemical, biological, social, with genetic defect or under the effect of local factors. But the compensatory process has a limit which is followed by rather steady deviation from the norm, having biologically negative meaning for an organism, resulting in development of a disease.
Each disease is characterized by certain signs or a group of symptoms. There are subjective and objective symptoms.
Subjective symptoms are symptoms revealed while questioning the patient, the unusual sensations which the patient began to experience. For example, difficulty in chewing food, pain, itching in the gums, dryness in the mouth, retention of food between the teeth, etc.
Objective symptoms are found by the dentist during examination: inspection, palpation, instrumental and apparatus investigation.
Sometimes it is necessary to apply functional methods of investigation to find out the function of the maxillodental apparatus: chewing tests, graphic records of movements of the mandible, investigations of the muscle biocurrents, etc.
A disease can be manifested by one or several objective symptoms, one of which is characteristic only of the given kind of the disease, and others may be observed in other diseases. Examination of the patient is also aimed at making clear the symptoms, etiology and pathogenesis, course of the disease, his physical and mental condition, function of themaxillodental apparatus. Careful and thorough clinical examination of the patient will promote correct diagnosis, purposeful orthopedic treatment.
While examining the patient, the dentist should know precisely significance of physiological norms, possible variants of the structure and functioning of separate organs of the maxillodental system, topography and functional interrelations. Thus he should not only detect the signs, but also be able to interpret them logically, determine the leading symptoms, basing on the examination of the patient. So the dentist should know well all sections of dentistry, a clinical picture of every nosologic form of the maxillodental system.
Examination of the patient is made consistently under a certain plan and includes: the anamnesis (questioning of the patient), external survey, survey and examination of organs of the oral cavity; examination of the temporomandibular joint; examination of the muscles of the head and neck, laboratory and instrumental methods of investigation.
SUBJECTIVE METHODS OF INVESTIGATION
Taking the anamnesis is the first investigation phase of the patient. The anamnesis consists of the following sections: 1) complaints and subjective condition of the patient; 2) anamnesis of this disease; 3) anamnesis of life of the patient.
During the first visit of the patient the dentist listens attentively to the story of the patient about unusual sensations (complaints) which he began to experience. It is important to find out the earliest manifestations of the disease, character and peculiarities of its course, to know the cause of unusual sensations in patient’s opinion. In one case the anamnesis may be very brief and there is no necessity to go into detailed history of the patient’s life, in other cases, for example, when the patient has a feeling of burning in the mucous membrane of the oral cavity under the denture , the anamnesis and all investigations will be detailed with the use of apparatus and laboratory methods with participation of doctors of other specialities.
It is necessary to listen to the patient attentively and patiently, at the same time concentrating his attention to the main, from his point of view, sensations, correctly specifying some moments by purposefully asked questions. All this can determine questions which are required for statement of the diagnosis, special or additional methods of investigation.
While listening to the complaints of the patient it is necessary to pay attention to response of the patient in statement of complaints. It will help to get idea about the type of his nervous activity that is of great importance in choice of construction of a denture and the subsequent adaptation to wearing it, to faster establishment of mutual contact between the dentist and patients.
During inspection it is important to obtain data about the onset of the disease, the cause of its development, its course before referring to the dentist, what treatment was applied, if it was, it is necessary to find out a kind and scope of the treatment.
In some diseases it is difficult to establish the cause of their development. So, for example, pain, burning in the mucous membrane of the oral cavity under the denture can be caused by a badly made denture, a mechanical trauma or allergic reaction to the basic material. The same character of pain are observed in glossalgia, impairment of heat exchange in the tissues of the orthopedic bed, diseases of the gastrointestinal tract. Hence, pain may be caused by various causes, the mechanism of its development is also different.
Sometimes during questioning it is possible to establish that deterioration of a condition of the maxillodental system occurred during some general disease or after it. Then there is a question, whether the revealed disease is independent nosologic form or is one of symptoms of other diseases (stomach ulcer, gastritis, diabetes, etc.). Therefore it is important to assess the general condition of the patient.
The anamnesis of life. The anamnesis of life is a“the medical biography” of the patient. It is of great significant for understanding the causes, conditions of development of the present disease. For example, data about feeding (formula feeding, the use of the soft grated food during formation of milk and replaceable bite) can presumably specify the cause of abnormal development of the maxillodental system.
The birthplace, peculiarities of the environment (lack or excess of fluorine in water) may be the cause of noncarious affection of the teeth in some people.
Harmful working conditions, such as work connected with manufacture of acids, alkalis, coal-mining industry can promote development of pathological abrasion of the teeth.
It is important to find out the sustained illnesses and presence of general somatic diseases at the moment of inspection as they also can promote development of pathological changes in the maxillodental system. The knowledge of their course peculiarities will also help the dentist to choose correct tactics in orthopedic treatment. So, in diseases of the cardiovascular system (myocardial infarction, stenocardia, insult) such injuring factor to this system as preparation of the teeth should be eliminated and it is better to recommend prosthesis by removable dentures. In presence of bronchial asthma, it is impossible to apply the materials having smell for taking inpressions (repin, thyodent, dentafol). They also should not be made relocation of the denture directly in the oral cavity. Otherwise it may cause an attack of asthma. Thus, on the basis of the anamnesis and subjective data of the patient, the dentist makes a presumable conclusion about the character and form of the disease. It is a working diagnostic hypothesis, which will promote the further purposeful investigation to specify the assumptions.
OBJECTIVE METHODS OF INVESTIGATION
Detailed inspection of all organs of the maxillodental system is made for specification of the assumption of the disease and for better understanding of the disease. Data of the objective inspection reject or increase reliability of the assumptions of the disease. The objective inspection includes: external survey, survey and examination of organs of the oral cavity, radiological and laboratory (the analysis of blood, urine, saliva, smears and biopsy material, myography, rheography, etc.) methods of investigation.
The objective methods of investigation are used, while going on questioning the patient as it is important to know subjective sensations. For example, whether the patient feels pain in probing, percussion, etc.
External survey of the patient. After questioning survey of the face is started which is made imperceptibly for the patient. By the end of formation of the facial and brain skull, the face of the person gets individual features. The type of the face is influenced by development of the brain skull, respiratory apparatus, masticatory apparatus or musculoskeletal system. Four types of the face are distinguished accordingly: cerebral, respiratory, digestive and muscular .
The cerebral type is characterized by strong development of the brain and skull. The high and wide frontal part of the face sharply predominates other parts therefore the face gets the pyramidal form with the basis directed up.
The respiratory type is characterized by prevailing development of the middle part of the face, therefore the facial part of the head, neck and trunk get a number of prominent features. Cavities of the nose and its sinuses are strongly developed, maxillary sinuses are great, cheekbones protrude a little. The face is diamond-shaped, the nose is strongly developed in length, its back is quite often convex.
The digestive type is characterized by prevailing development of the lower part of the face. The maxilla and mandible are excessively developed. The distance between angles of the mandible is great. The ramus of the mandible is very wide, massive, its coronoid process is short and wide, chewing muscles are strongly developed. The mouth is bordered by thick lips. The chin is wide and high. Due to strong development of the lower part of the face in relative narrowness of the frontal part sometimes the face gets the characteristic form of a trapeze.
The muscular type: the upper and lower parts of the face are approximately equal, hair border is usually direct, the face of the square form .
It should be also noted that the face of the person is disproportional: there is asymmetry in the structure of the left and right side. It is accounted for the fact that the left half of the brain skull is bigger than the right one, and the left half of the face is longer, the back of the nose does not coincide with the midline, the tip of the nose is shifted aside, with distance between the external corner of the eye and the corner of the mouth is not equal on both sides of the face, the right zygomatic bone and the lower half of the maxilla are shifted to the right, the right canine fossa is deeper and narrower, the teeth of the maxilla and the lower part of the nose septum are shifted to the right.
Division of the face into three parts is widely used in clinic of orthopedic dentistry: the upper, middle and lower thirds. The upper third of the face is located between scalp border on the forehead and a line connecting eyebrows. Borders of the middle part of the face are the line connecting eyebrows, and the basis of the nose septum. The lower third of the face is a part of the face from the basis of the nose septum up to the lower point of the chin.
Division of the face into three parts is conditional as position of the points during life varies. For example, the scalp border of the head in different people is located unequally and moves with the years. The height of the lower third of the face also is changeable and depends on the kind closing and amount of the teeth preserved. Only the middle part of the face has rather stable points. Absence of constant anatomic reference points and strict functional division of various parts is of little value of the offered division of the face for regenerative orthopedics.
Anatomic formations of the lower third of the face are of greater practical value
Expressiveness of the mental folds allows to assume presence of deep bite, distal displacement of the mandible with reduction of the vertical size of the lower third of face due to loss of the lateral teeth or their pathological abrasion. Decrease in the lower third of face is frequently accompanied by formation of perleches in corners of the mouth. Thus they become wet and have hyperemic look. Retraction of the lips speaks about absence of the frontal group of the teeth and if there is expressiveness of the nasolabial folds it is possible to draw a conclusion about complete loss of the teeth.
The establishment of such deviations on survey is evidence of sharp reduction of the interalveolar height in the lower third of the face which are interrelated with absence of teeth-antagonists.
It is important to distinguish two heights of the lower part of the face for the orthopedic purposes: height of relative rest and occlusionheight. The dentitions are not closed in height of relative rest, there is an opening between them from 1 up to 8 millimeters, depending on depth of incisal overlappings, the muscles of the face are in the condition of physiological rest. Occlusion height is characterized by tight closing of thedentitions under the condition of central occlusion, the muscles are in the contracted condition. Knowledge of these characteristics is important in construction of removable dentures.
Survey of the face also allows to establish diseases the patient had before or concomitant general somatic diseases. For example, presence of cicatrices in the area of the upper lip is evidence of operative interventions for creft. Dryness of the skin integuments, presence of the skin folds pulled together in the area of the upper and lower lip with reduction of size of the oral fissure surmises the diagnosis of systemic scleroderma. Presence of cicatrices speaks about consequences of chemical or thermal burns. The face has a characteristic form in a number of endocrine diseases, e.g. acromegaly. Presence of moustaches and beard in women is characteristic of the disease of Ischenko –Cushing.
A close survey of the face accompanied by purposeful questioning of the patient will promote a correct diagnosis both the basic and concomitant.
Inspection of organs of the oral cavity. Inspection of organs of the oral cavity is one of the basic moments as detection of local manifestations of the disease determines further tactics of orthopedic treatment.
Inspection is made in the following sequence: survey of the oral cavity, estimation of the teeth, estimation of the dentitions, presence of defects in them, interrelation of the dentitions, estimation of the mucous membrane of the oral cavity, estimation of the maxillary bones.
First of all, pay attention to a degree of opening of the mouth. Restriction of opening of the mouth is probable iarrowing of the oral aperture as a result of muscular or articular contraction and will prevent carrying out of many manipulations in prosthesis (introduction of trays for taking impressions, imposing of denture, preparation of the teeth).
Inspection of the teeth. Inspection of the teeth is made by a probe, mirror and tweezers. For convenience survey of the teeth is started with the right side of the mandible, then left with transition to the maxilla, continuing survey from the left to the right. On examination the mirror is held in the left hand, and a probe or tweezers – in the right one. The mirror enables to examine the tooth from different directions. Attention is paid to the position of the tooth, its shape, colour, condition of the hard tissues (affection by caries, fluorosis, hypoplasia, etc.), Stability of the tooth, a ratio of its extraalveolar and intraalveolar parts, position in relation to occlusion planes, presence of a filling, crown, their condition. The probe determines integrity of the crown parts, sensitivity of the tooth, depth of the gingival pocket. Simultaneously colour of the tooth is evaluated (reduction or absence of enamel shine, presence of chalk-like or brown spots, sulci). In depulpated teeth enamel has no characteristic shine, it is of a grayish-yellowish shade. The enamel happens to change in smoking, in workers connected with manufacture of acids, alkalis. The form of the teeth also changes in a number of diseases.
The important point in survey of the teeth is determinationof mobility of the tooth. There are physiological and pathologicalmobility of the teeth. The former is natural and is imperceptible to the eye. Its existence is proved by abrasion of contact points andformation of contact areas. Pathological mobilityis characterized by appreciable displacement of the tooth in small effort.
Mobility of the teeth is a sensitive indicator of the parodont condition, its supporting apparatus, that is of great importance for making the diagnosis, estimation of results of treatment or prognosis.
There are four degrees of pathological mobility of the teeth (by Entin). In the first degree displacement is in the vestribulo-oraldirection. In pathological mobility of the seconddegree the tooth is displaced in vestibulo-oral and mesiodistal directions. In the third degree the tooth, plunges in the socket on pressure and then comes back in the initial positionbesides displacement ina vertical direction. In the fourth degreeof pathological mobility the tooth has not only visiblemobility in three specified directions, but also can rotate.
Pathological mobility is always accompanied by presenceof pathological gingival pockets. Presence and their depth are determined by the probe.
Pathological mobility of the teeth is often accompanied by the expressedatrophy of the alveolar process thereforethe extraalveolar part of the tooth prevails over intraalveolar one. This is most typical of single-standing teeth. The increase in the external lever causes a functional overload of the tooth. A special preparationis requiredto use such teeth for prosthesis consisting of shortening of the crown part of the tooth.
The restored dental defect by a filling or cupping (crown) is carefully examined, paying attention to undamaged state of the filling, conformityof the artificial crown to requirements (dense adjacency of edges of the crown to the neck of the tooth, its integrity, change of colour, etc.).
Results of survey of the teeth are written down in the dental formula.Deciduous teeth are designated by Roman figures,permanent – Arabian.
Methods of percussion, probing and palpationare widelyusedwhile inspecting the teeth and making the clinical diagnosis.
Percussionis made by the handle of tweezers or dental surgery probe,slightly tapping on various surfaces of the tooth. On percussion of a healthy tooth the clear loud sound is heard and the patient does not react. In changes of the pulp, parodont there are painfulsensations of different intensity. Percussion is made cautiously, and pain in weak impact does not demand further increase in impact force.The teeth with the lost pulp, depulpated with the filled upcanals give an empty sound. Make percussion of the adjacent teethfor comparison. In extension of the periodontal fissures a muffled sound is audible. Dullness of the sound results from disorder of blood circulation in the periodont, development of edema. Edematious tissues as though absorb the sound. In the pathological process at the topof the root there is marked dullness of the sound on percussion.
Probing is applied to determine depth of the carious cavity, character of the softened tissue as well as to study the conditionof the parodont. The concept of the parodont includes a complex of the formations having genetic and functional unity: the tooth, tissues of the periodont, bone tissue and periosteum, gum. At the neck of the tooth in the gum there is a circular ligament attaching the gum to the tooth and protecting the periodont from external damages. Impaired integrity of this formation leads to inflammation, various formations along the depth of pathological gingival pockets. An angular probe with blunt end is used for determination of the pocket depth, there are millimetric divisions on its surface. The probe is introduced ingingival sulci without effort from different directions of the tooth. If the probeplunges by 1-2 millimeters it is evidence of absence of the pocket or it is called a physiological gingival pocket. In immersing of the probe fromthe anatomic neck by half of the vertical size of the crown part of the tooth or more, we speak about a degree of atrophy of the alveolus.
Presence of the pathological gingival pocket should be differentiated with false gingival pocket which is formed in inflammation and significant edema of the marginal parodont tissues and in hypertrophic gingivitis. In appropriate treatment the mucous membrane of the gums comes to norm and the pocket disappears.
In a number of diseases there is a reduction of the gingival space therefore it is at the certain levelin relation to the tooth root. In this case we speak about clinical neck of the tooth.
Palpation is applied for determination of mobility of the tooth. Mobilityof the tooth is a symptom of many diseases: parodontitis,periodontitis, acute and chronic trauma arising due to inflammatory processes and edema of the surrounding tissues.
During survey and instrumental inspection absence of the teeth is also established. Thus by questioning we find out whether the tooth was extracted orprimary edentia takes place.
Assessment of the condition of dentitions. Inspection of the dentition is made separately. We determine: 1) number of the remained teeth; 2) presence and topography of the defect; 3) replacement of defects by dentures and theirkind; 4) character of contacts with the adjacent teeth; 5) form of the dentalarches; 6) a level and position of each tooth in relation to occlusion planes; 7) a kind of bite.
In the correctly formed maxillodental systemthe dentitions representa single whole both morphologically andfunctionally. The unity of the dentitions is provided with interdentalcontacts, alveolar process and parodont.
Interdental contact points in the frontal teeth are located near the cutting edge, and in the lateral – near the chewingsurface from the approximal sides. There are triangularspaces under them turned by the basis to the alveolar process which are filled in with gingival pupillae. Thus they are protected from damage by food. Besides, the pressure falling on the teeth,is distributed not only to the root of the tooth, but also to the adjacent teeth by interdental contacts, providing unity of the dentition.
With the years contact points are obliterated and contact platforms are formed instead of them. Their abrasion is a proofof physiological mobility of the teeth. A mesial shift of the teeth takes place causing shortening of the dentition up to 1cm.There is no impairment of continuity of the dental arch.
While examining the dentitions we revealabsenceof a tooth (teeth), the cause of its loss. The tooth caot erupt because of absence of the permanentdental germ, then we speak about primary or congenital adentia.If loss of the tooth has occurred after eruption, we speak about secondaryor acquired adentia.
There is a lot of variants of edentulous defects.There was offerred a classification of dentition defects formed as a result of loss of the teeth.The most widespread classification in our country and abroad is that offered by Kennedy which takes into consideration position of defect in the dental arch and its extent. Defects of the dental arches are divided into 4 classes.
The dental archeswith bilateralend defectswhich have formedas a result of lossof chewing teethare related to the first class.
The second class is madeby the dental arches havingunilateralend defect.
The dental arches with intermediatedefectin the lateral part on one side are related to the third class.
In the fourth class only frontal teeth are absent.
If there are some defects of various classesin the dental arch, the dental arch is related to a smaller order class. For example, in the dental formula
0004300 0004560
There is a defect of the fourth and first class, in this case dentalarches are related to the first class.
In physiological norm each tooth has a certainpositionin relation to occlusion planes.Occlusion planeis a plane drawn from the cutting edge of the central incisor of the mandible to the top of the distal buccal tubercle of the second (third) molar. In orthognatic bitethe teeth are located in relation to occlusion surfaces in a certain order: cutting edges of the incisors, canines and distal buccal tubercle of the thirdmolar touch a plane, the first and the second premolars and molars are located below this plane. The central incisors and canines of the maxilla are by 2/3 mm (depth of the incisiveoverlappings) belowthe occlusion plane. Such arrangement of the teeth providescurvatureof the dental arch in anterior-posterior and lateral directions.
Defects of the dentitions not onlybreak morphologicalunity of the dentitions but also leadto its complex reorganizationin the area of the defect at first, and then extends to alldentition.This reorganization is manifested by an inclination of the teeth asidedefect, vertical moving of the teeth deprived of antagonists,turning around the axis and other impairments which result in deformation of the occlusion surface.
There are primary and secondary moving of the teeth.Primarymovingbegins with eruption of the teeth and comes to an endwith formation of the dental arches. It is acceptedto consider change of the positionof the teethafter their eruption andformations of dentitions as secondary movingdue to defectsof the dental arches or as result of parodontitis, tumours of the jaw,traumatic occlusion
Most often there issecondary movingof the teeth which is made in variousdirections.
The following kinds of secondarymovingare most widespread.
The first group.
1. Verticalmovingof the upper teeth unilaterallyor bilaterally.
2. Verticalmovingof the upper and lower teeth unilaterallyor bilaterally.
3. Mutualvertical displacement of the upper and lower teeth unilaterally orbilaterally.
The second group.
1. Distal or mesial displacement of the upper teeth unilaterallyor bilaterally.
2. Distal or mesial displacement of the lower teeth unilaterallyor bilaterally.
The third group.
1. Inclination of the upper teeth to the palatal or buccal side.
2. Inclination of the lower teeth to the palatal or buccal side.
The fourth group.
Turn of the tooth around of the longitudinal axis.
The fifth group.
Combined moving of the teeth.
Secondary movings of the teeth sometimes are brought to the forefront,determining character of all clinical picture, and determinerelativetypicalness of the therapeutic measures in different kindsof secondarymovings. Hence it is important to reveal them during clinical inspection of the patient.
Estimation of the condition of the mucous membrane of the mouth.The healthymucous membraneis pale pink colour in the area of the gums and pinkin other sites. In the pathological processes colour of the mucous membrane varies, there are various elements of affection on it. The most widespread of them: erosion – superficialdefect, aphtae- small sites of ulceration of yellow-grey colourwith bright red rim of inflammation, ulcers – a primary morphological element in the form of defect with rough and undermined edges and the bottom covered with grey coating.
The patient complains of reddening of the mucous membrane, bleeding, edema and burning of the orthopedic bed mucous membrane.
The cause of the specified symptoms can be:a mechanical trauma, disorder of heat exchange of the mucous membranedue tobad heat conductivity of the plastic denture,toxico-chemical influence of plastic components, allergic responseto plastics, systemic diseases (avitaminosises, endocrine diseases, diseases of the gastrointestinal tract, mycosises, etc).
During inspection it is important to establish character of affection of the mucous membrane, the cause which has caused this affection, stages of the disease(aggravation, remission). All these factors are of great value fora choice of the method of treatment and the material of whichdentures will be made as well asdetermination of term of the beginning of prosthesis. For example,in presence of erosion, ulcers of the traumatic character, prosthesisis made after their complete cure. On detection of manifestations of lichen rubor planus, leucoplakia and other chronic diseasesinthe oral cavity, prosthesis is made during remission.
On detection of the above-stated affections of the mucous membrane of the oral cavity, it is necessary to carry out additional investigations (the analysis of blood, cytology), consult with the dentist – therapist and specialist on skin and veneral diseases if necessary for differentiation. For example, traumatic ulcers should be differentiated from cancer and tubercular ulcerations, syphilitic ulcers.
The long-term trauma may lead to hypertrophyof the mucous membrane and formation of fibromas, papillomas.
Inspection of the maxillary bones.Formations of the bone bed are simultaneously investigatedduring surveyof the mucous membraneof the oral cavity and palpation. Attention should be paid to expressivenessof the alveolar process, the arch of the hard palate, maxillar tubers.The zone of the median suture for determination of the torus is necessarily investigated.
The sharp bone ledges are sometimes determinedin the area of edentulous alveolar process which have formed as a result of incompleteobliteration of sockets of the tooth and protruded interdental septum. Theseledges are painful, as the mucous membrane covering them is thinned; it is not expedient to make prosthesis without special surgical preparation of these sites.
In some cases it is possible to establish presence of boneledges (exostoses) on the mandible on the lingual sides on the right and the lefthalf of the jaw, their significant expressiveness demands specialpreparation before prosthesis by removable denture.
Inspection of the temporomandibular joint.The interalveolar distance decreases, positionof the mandible is changed causing changed position of the articular heads and all ratios of elements of the jointin formation of defects of the dentitions due to loss of masticatory teeth, pathologicalabrasion of the remained group of the teeth, diseases of the parodont. All thisleadsto disease of the joint.
Synchronism of displacement of the articular head in relation tothe articulardisk and articular fossa in movements of the mandiblecanbe disturbed in diseases of the muscles, especially external pterygoid muscles, central nervous system, diseases of the joint (arthritis, arthrosis). Therefore during inspection it is important to reveal the original cause of the disease of the joint as the techniqueof prosthesis and character of therapeutic treatmentdepends on it.
The most frequent complaints are pains inthe joint: swelling in the joint region, difficulty in opening orclosing of the mouth, pain, clicking, headache, burningof the tongue, dryness in the mouth. A method of palpationis used to examine the joints. For this purpose the index fingers of the hands are placed at the anterior surface of the tragus of the ear and the patientis askedto openthe mouthslowly. By palpation we determine the surface of the articularhead and a the posterior zone of the articular fissure. Moving fingers forward and pressing on the projection of the articular fissure and articular head, we determine painful points. Palpation is made in the closed denttition, at the moment of opening and in widely open mouth.
Sound of friction, crepitation in the joint may be associated with impaired release of the synovial fluid. A click or a crackle at the momentof opening of the mouth is more likely caused by reduction in height of bite and distal displacement of the mandible, and, hence, articular heads.Crepitation, crackle and click is also possible to determine by the methodof auscultation by means of phonendoscope. In pains in the joint, click and crackle, it is necessary to carry out additional investigations (roentgenography, rheography, arthography).
LABORATORY AND INSTRUMENTAL METHODS OF INVESTIGATION
Laboratory-instrumental methods of investigation are consideredadditional as they are not always used. The purpose of theseinvestigations – establishment and confirmation of the exact diagnosis.
Radiological examination is based on taking andperusalof the X-ray pictures. Varioustechniquesare used for this purpose:
- Intra- and extraoral roentgenography;
- Tomography;
- Panoramicroentgenography
Roentgenographyis the most widespread andaccessiblemethod of radiological investigation of the teeth, alveolar processes, jaws, bones of the facial skeleton and skull.
Roentgenography gives valuable data of the condition of hard tissues of the crown and root, the size and peculiarities of the pulp chamber,root canals, width and character of the periodontal fissure , a conditionof a wall socket an alveolar process. With its help it is possibleto study alsoa structure jaws, mutual relation of elementsof the temporomaxillary joint and to reveal thus presence of pathological processes in the areas inaccessible to external examination, deformation of bones of the maxillofacial area.
In the X-ray picture the image is negative: the bone tissue has light shades, soft tissues, air spaces -dark. The enamel has a ligher tone than cement and dentin.Carious cavities have darkshades. The cavity of the tooth,periodontal fissures look as darklinesof various configuration.
The intraoral roentgenogramallows to determine carious cavities, retention teeth,topographyof the pulp, patency of canals, presence of denticles, condition of the periapical tissues, hanging edges of the crowns, a degree of atrophyof the bone tissue of the alveolus.
Tomography.The radiologicalresearch convenientin studying structuralchangesof the alveolar process and jaws, has appeared insufficient in examination of the temporomandibular joint asit has a difficult structure and is located near the basisof the skull. Therefore it is almost impossible.to receive the X-ray imageof the temporomandibular joint by means of usual methodsof roentgenography
Usual roentgenography of the jointgives pictures only aboutrough changes in the joint(fractures, sharp deformationsof the articular surfaces in inflammatoryand degenerateprocesses). It is impossible to reveal thin changes at the initial stages of the disease by this methodand the joint looks normal on the roentgenogram.
All this has induced search for new, more perfect ways of radiological investigation of the joint.Tomography is related to such methods. It allows to receive the X-rayimage of the certain layer of the bone located at this or thatdepth. This method enables to study interrelationof elements of the temporo-maxillary joint at certain depth. It is also possible to reveal fine structural changes in the jointboneswith its help, caused both by general and local (dysfunction, trauma) diseases.
Panoramic roentgenography (panography).Panoramicroentgenography was offered by Blackman. It allows to receive a fullpicture of all teeth in the form of a panoramic picture of sufficient sharpnesswith 2 times magnification and considerably smaller irradiation than in usual picture. The survey is made during movement of the object and cassette, and the X-ray tube remains without movement.Only those layers of the object which are taken with identicalspeed with a filmare determined. These layers are shown with greater sharpness, andthe others are greased. The X-ray tube is placed behind,below the occiput. In making a picture the armchair with a patientrotates clockwise, and the cartridge with an X-ray film- in the opposite direction.As a result a developed image of the jaws is obtained.Availability of a radiologicalmethod generated a notion of its harmlessness in some dentists. It has led to unreasonable indications to roentgenography of the teeth and alveolar process. Meanwhilethe X-ray irradiation is not harmless for an organism and it is necessary to rememberit.
On inspection of the patient before prosthesis it is necessary to make roentgenography of the teeth with affected parodontous membrane, teethwith fissures, teeth – abutments of bridge dentures, clasps, covered by crowns, teeth with pathological abrasion andteeth changed in colour, etc.
X-ray visiography.Lately there have been devised the devicescombiningX-ray installation and a videocamera, the so-called X-ray visiograph. They enable to receive the image of tissues of the tooth and soft tissues magnified 27 times onthe screen by means of a videocamera. Besides by means ofX-ray visiograph it is possible to receive a photoof the imagereceived on the screen.It distinguishes it from the usual X-raydevice as time is not required for development of the film.The image in the photois more precisethan on the X-rayfilm. X-ray visiographis placeddirectlyin the dentist’s room.
Methods of determinationof masticatory pressure.Absolute forceof chewing muscles.The chewingmusclesare related to force muscles, i.e. developing preferred force unlikeother muscles which can develop preferred velocity.
Absolute muscular force is determined by number of the tissues which are a part of the given muscle, i.e. the area of the physiologicaldiameter. The more fibers in the muscle, the moreis the areaof the physiological diameter,the greater forcethe given musclecan develop. Weber considers that “force of the muscle is proportionalto its transversal section under equal conditions”.
By Weber, a muscle with a diameter of 1 cm2develops the force equal of 10 kg.The muscles lifting the mandible have the followingdiameters of section: the temporal muscle – 8 cm2, chewing muscle – 7.5 cm2,external pterygoid muscle – 4 cm2. Proceeding from data of transversal section, absolute force of the temporal muscle is equal to 80 kg, chewingmuscles – 75 kg, external pterygoid – 40 kg, i.e. the general absoluteforce of muscles of one side is equal to 195 kg. The general absolute forceof chewingmuscles of the right and left sides makes 290 kg (195×2).
The absolute force of muscles established theoretically byaddition of indices of physiological diameters of the chewing muscles,lifting themandible, and multiplication of the received sum by possible development of force in each square centimeterof the transversal sectionsection of the muscle, naturally,does not represent the facts. In concomitant work the chewing muscles cannotdevelop the force equal to 290 kg. Absolute force both of chewing andother muscles, develops only at the moment of danger and mental shock, and in the ordinary life the person does not have necessity to develop such force in chewing food. Therefore researchersare interested in pressure which develops onthe certain site for nibbling and chewing food of definite consistence (meat, bread, crackers, etc.). It is also important to know endurance of the parodont of certain teeth to chewing pressure. It would allow to be guided in permissible load in prosthesis with bridge and other dentures.
Endurance of the parodont is measured by special devices –gnatodynamometers. A gnatodynamometer was offered for the first time in 1893by Bleck. Then other devices have been designed, based onthe same principle. The device is supplied by a platform for the teeth. In closing of the mouth the teeth transmit certain pressure tothe springthrough the platform which is registered by the scale inkg. Last years new designsof gnatodynamometry were offeredwith strain sensores.
The method of gnatodynamometry proved to be insufficiently exact asthese devices measure endurance of the parodont to the pressure havingonly one direction (vertical or lateral). In actionof force on the tooth the pressure expands and effects the abutment and adjacent teeth.
Static methods of determination of chewingefficiency.For determination of endurance of the parodont and role of eachtooth in chewing special tables are offered which receivedthe name of statistical systems of accounting of chewing efficiency. A degree of participation of each tooth in the act of chewing is determined by a constantvalue expressed in percentage.
While drawing up the specified tables the role of each tooth is determined by size of the chewing and cutting surface, amount of roots, size of their surface, distance at which they are movedfrom the jaw angle. Some tables are offered constructed bythe sameprinciple (Dushange, Vustrov, Mamlok, etc.).The static system of accounting of the chewing efficiency developed by N.I.Agapov is widely used in ourcountry (Table 1).
Table 1Chewing coeeficients of the teeth by N.I.Agapov
|
Teeth |
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
Total |
|
Chewing factors, % |
The maxilla |
2 |
1 |
3 |
4 |
4 |
6 |
5 |
– |
25 |
|
The mandible |
1 |
2 |
3 |
4 |
5 |
6 |
5 |
– |
25 |
N.I.Agapov has accepted chewing efficiency of all dentalapparatus for 100 %, and for unit of chewing ability andenduranceof the parodont – a small incisor, comparing all other teeth with it. Thus, each tooth has constantchewing coefficient in his table .
N.I.Agapov’s has made the amendment in this table, recommending to take into consideration teeth-antagonistsin calculationof chewing efficiency of the remaining dention. For example, in the dentalformula
654001 1 100345
654001 100345
Chewing efficiency is equal to 58 %, and in the dental formula
654001 100345
000000 I 000000
it is equal to zero as there is no pair of antagonists.
As it is already noted, in Agapov’s system value of each toothis constantand does not depend on condition of its parodont. For example, the roleof the canine in chewing is always determined by the same factorirrespective of, whether it is steady or has a pathologicalmobility. It is serious lack of the offered system.
V.Yu.Kurljandsky offered a static system of the accounting of the conditionof the basic apparatus of the teeth, named a parodontogram by him.The parodontogram is received by recording data about eachtooth in the special table.
A conditional coefficient is given toeachtooth with healthy parodont in the parodontogram like in other static schemes. Thesecoefficients are made on the basis of proportional ratioof endurance parodont of different teeth to loading thatwas determined by gnatodynamometry in unaffected parodont.The coefficient of endurance of the parodont to loadingis accordingly loweredat different degrees of socket atrophy in different teeth.In atrophy of IV degree the parodont does not possessendurance to loading(the tooth is subject to extraction).
It is assumed in practice that the parodont of the tooth is able to indure twice more loading than loading in processing food.
FUNCTIONAL METHODS OF INVESTIGATION
Functional chewing tests.Static methods appearedto be poorly acceptable to determination of a disorder degree of chewing efficiency not only because theyinsufficiently preciselydetermine a role of each tooth in chewing and perception of chewingpressure but also because they do not consider a kind of bite, intensityof chewing, force of chewing pressure, influence of saliva on grinding of food, a role of the tongue in the mechanism of formation of food bolus. Therefore, there were offered functional (chewing) tests allowingto receive more correct concept about dysfunction of chewing.
Chewing force of the muscles.In physiology it is force which can be developed by all chewing muscles lifting the mandible. According to Weber’s data it is equal on an average to 390 – 400 kg (the physiological diameter of all three pairs of muscles-elevatorsof the mandible is equal to 39 cm2, and 1 cm2 of the area of the physiological diameter of the muscle can develop force of 10 kg). Hence all chewing muscles can develop force of 390-400 kg. The physiological diameter of the internal pterygoid muscle is equal to 4.0 cm2, proper chewing – 8 cm2, temporal -7.5 cm2, i.e. the internal pterygoid muscle can develop force of 40 kg, proper chewing -75, and temporal-80 kg, all in all 195 kg on one side, and 390 kg – on both.
Chewing pressure is force realized by chewing muscles on one side of food grinding. There is vertical and horizontal chewing pressure. It is measured by kgs by means of gnatodynamometer.
Chewing efficiencyis a degree of crushing food by the teeth. Chewing efficiency is measured by percentage in comparison with the intact maxillodental system which chewing efficiency is accepted to be 100 %.
Chewing test by Christiansen is thefirst of techniques for determination of chewing efficiency. He investigated a degree of crushing of certain food – a hazelnut or a coconut. 5 g of a nut were taken for the test, after 50 chewing movements the patient spat out masticated mass on a small sieve with a diameter of 2.4 mm. The mass was sifted, the leftovers were weighed. The leftovers divided by 5 g and multiplied by 100 % – made the factor of Christiansen.
Chewing test by Gelmanis a modified technique of Christiansen offered for estimation of the functional condition of the maxillodental system and determination of chewing efficiency. The test is based on the author’s supervision that the intact dentomaxillary system crushs 5 g of almond for 50 sec. till the size of the particles siftedthrougha 2.4 mm sieve. In presence of dentition defects – for 50 sec. but the almond is not completely crushed, and its part remains on the sieve.
Technique: 5 g of almond is weighed and given the patient to put in the mouth and to start chewing after a signal “begin”. The beginning of chewing is marked by a stop-watch. In 50 sec. the examined stops chewing on the signal “stop”, spits out the chewed mass in the cup, rinses his mouth and spits out water in the same cup. 5-8 drops of 5 %solution ofmercuric chloride are added for disinfection. The ontents of the cup is filtered through gauze and evaporated in water bath. Then the mass is carefully sifted through the sieve, often stirring, it is better to use a wooden stick. The part of the mass which have remained on the sieve is accurately poured onto the watch glass, and weighing is made. A percent of chewing disorder is calculated by the following formula. Suppose there was a mass of 2.62 gon the sieve, then:
5 : 2.82 = 100:X, where X-percent of chewing disorder
х: 2.82 = 100 : 5
х= 2.82х100 282:5 = 56.4 %.
Chewing efficiency makes 100 %– 5б.4 % = 43.6 %.
Chewing test by I.S.Rubinov
Itis offered for estimation of the functional condition of the maxillodental system. Various products with different physical properties are applied (a nut, a cracker, fresh bread, etc.). On the basis of the chewing test it is revealed that in deterioration of conditions of the dental system time of chewing in processing firm food substances (nut) before swallowing is extended and despite it food particles of rather big size are swallowed. It is known that in adults with a high-grade chewing apparatus duration of chewing of a nut kernel before swallowing on the average makes 14sec and the leftovers are equal to zero (by the method of Christansen), and in absence of 2-3 teeth time of chewing is equal to 23sec, and a part of the kernel remains insufficiently crushed. In cases of the intactand damaged dental system time of chewing soft food differs a little. I.S.Rubinov uses a nut kernel for test instead of 5 g almonds. It enables to judge about functional condition of separate groups of the teeth. Processing of the data received of the kernel chewing is made by S.E.Gelman’s technique.
Graphic methods of studying of themandiblechewing movements.Various diseases of the oral cavity and chewingmuscles impair biomechanics of themandible. In process ofrecoveryof the patient movements of the mandible can be normalized. Normal movements of the mandible, their impairment and dynamics of restorationcan be studied by means of a graphic method.Nowrecord of chewing movements of the mandible can be made by various devices: cymograph, oscillograph, etc.
I.S.Rubinov has been detailed record of chewingmovements of the mandible (masticationagraphy)and value of each of components of the graphic record is deciphered.
Investigation of function of the masticatory muscles.
The function of the masticatory muscles changes not only duringvariousmovings of the mandible but also due to pathologicalconditions of the chewing apparatus: loss of the teeth, diseaseof the joint, change of bite height. Therefore it is desirable to obtain data of the functional condition of chewing muscles bymyotonometryandelectromyographyfor full characteristic of the clinical picture accompanying this or that diseaseof the chewingapparatus.
The tone of the chewingmusclesis measured by means ofmyotonometry. The devices applied for this purpose refer to as myotonometres. A degree of tension (density) of the muscles we may judge of the supplied force with which a probe of the device is plunged into the selected depth. Arrows of the dial show a degree of muscle tension in grams.
Electromyography.Electromyography is measurementof biopotentials of the muscles in general and on chewing in particular. There arecurrents of actionin themduringcontraction of the muscles. These currents of actioncan be strengthened by special devices and write them down on photographic paper of the oscillograph in the form of a curve. Such methodof research is referred to as myography.
Thermodiagnosis.Detection of the tooth response to temperaturestimuli (warmth or cold) – thermodiagnosis- is one of the simplest methods of investigation of the pulp condition of the tooth. The teethwhich have nochanges in the hard tissues and pulp respond to the thermalfactorabove +50°C, to cold below +10°C. In pulpitis irrigation of the tooth by hot water of +50°C, sometimes below, or applying the tampon moistened with hot waterto the toothcauses sharp, long-termpain, and in deep caries pain is quickly over. The teeth respond to cold and hot substances after preparation, in exposure of the neck, in wedge-shaped defects.
A special device, athermoodontochronometeris used for determination of the tooth response. By means of the device the selected temperatureinfluences a certain site of the tooth. The devicesensor enables to receive temperature from 0 up to +70°C and can smoothly adjust it. The device fixes time of the response.
Diagnosis is one of the most difficult sectionsof clinicalmedicine in general and orthopedic dentisty in particular.Correct diagnosis is possible if resultsof the various investigations confirm reliability of symptoms, andthere is a clear etiology, pathogenesis of the disease,clinical course and pathological anatomy.
The dentist collects the separatefacts (symptoms) in a certain sequence, analyzes them to carry out synthesis of the factscollected.
