Disadvantage of replacing missing teeth

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1 Fixed partial denture /bridges/ as preventive and treatment measures. Classification of FPD, parts of FPD, types of pontics, advantages and disadvantages. Biomechanical considerations,abutment selection. Indications and contraindications Fix appliance Fix appliance replacing one or more teeth that cannot be removed by the patient. Substantial tooth preparation is necessary for a conventional restoration. The appliance usually occupies no more space than the original dentition. Fixed partial denture A fixed prosthesis is defined as, A restoration or replacement which is attached by a cementing medium to natural teeth,roots, implants. - These dentures are often termed as Bridges. Indication for FPD A fixed partial denture is preferred for the following siruations: -Short span edentulous arches. -Presence of sound teeth that can offer sufficient support adjacent to the edentulous space. -Cases with ridge resorption where a removable partial denture cannot be stable or retentive. -Patient s preference. -Mentally compromised and physically handicaped patients who cannot maintain the removable prosthesis. Contraindication for FPD Fixed partial dentures are generally avoided in the following conditions: -Large amount of bone loss as in trauma. -Very young patients where teeth have large pulp chambers. -Presence of periodontally compromised abutments -Long span edentulous spaces -Bilateral edentulous spaces,which require cross arch stabilization. -Congenitally malformed teeth, which do not have adequate tooth structure to offer support. -Mentally sensitive patient who cannot cooperate with invasive treatment procedures. -Medically compromised patients( e.g. leukemia, hypertension). -Very old patient. Advantage of replacing missing teeth Appearance Ability to eat Speech Periodontal splinting A feeling of completeness Orthodontic retention Restoring occlusal vertical dimension Disadvantage of replacing missing teeth Damage to tooth and pulp Secondary caries Failures Effects on the periodontium Cost and discomfort.

2 The srtucture of FPD Abutment An abutment is a tooth, root or implant to which a bridge is attached. Retainer A retainer is a crown or other restoration that is cemented (screwed) to the abutmen. Pontic A pontic is an artificial tooth as a part of a bridge. Pontics are attached to retainers. All forces acting on the pontic are transferred to the abutment through the retainer. A unit, when applied to bridgework, means either a retainer or a pontic. A connector connects a pontic to a retainer or two retainers to each other. Types of retainer Retainers in fixed partial dentures can be broadly classified as: Based on tooth coverage: -Full veneer crowns -Partial veneer crowns -Conservative(minimal prerparation) retainers Based on the material being used: -All metal retainers -Metal ceramic retainers -All ceramic retainers All acrylic retainers All retainers except conservative retainers require the abutment tooth to be prepared(reduced) to accept them. the amount of required tooth preparation varies according to the type of retainer. Full veneer crowns These retainers cover all the five surfaces of the abutment. They are fabricated like a cap and are usually indicated for extensively damaged teeth. They are most retentive and ideal retainers because their design can resist masticatory forces in all directions. Partial veneer crowns They are preferred over full veneer crowns because they require less tooth reduction. But, they are less retentive compared to full veneer crowns. pins can be fabricated to fit pin holes created on tooth for additional retention. Conservative retainers

3 They require minimal tooth reduction /preparation, e.g. acid etching. These dentures cannot accept heavy occlusal load and are primarily indicated for anterior teeth. They have small metallic extensions, which are designed to be luted directly onto the lingual surface of the abutment teeth / All Metal retainers They can either be partial or full veneer crowns. These retainers require minimal tooth reduction. They are strong even in thin sections. Metal ceramic retainers They can be fabricated over an entire full veneer crown or they can be fabricated as a facing over the labial/buccal surface of the full veneer crown, or they can be fabricated over a partial veneer crown. They require more tooth reduction. All ceramic retainers They may also be fabricated as a partial veneer or full veneer crown. They require maximum tooth reduction because porcelain requires sufficient bulk for adequate strength. All acrilic retainers They are used for long-term temporary fixed partial dentures. They are not indicated for permanent restorations. Pontic A pontic is a suspended member of a FPD that replaces the lost natural tooth, restors function and occupies the space of the missing tooth. Ideal requirements of a pontic A pontic should fulfil the following ideal requirements. -It should be restore the function of the tooth it replaces. -It should provide good aesthetics. -It should be comfortable to the patient It should be biocompatible. It should not impinge on the tissues or produce any kind of tissue reaction. It should permit effective oral hygiene. It should be easy to clean and easy to maintain. It should preserve underlying mucosa and bone. It should not produce resorption of the residual alveolar ridge. Pontic design. The success of a fixed partial denture depends on the proper design of the pontic. there are three important factors that control the design of the pontic. Factors affecting the design of a pontic. -Space available for the placement of the pontic. -The contour of residual alveolar ridge. -Amount of occlusal load that is anticipated for that patient. Edetulous space. The space created due to the loss of a tooth is usually sufficient for the fabrication of a good pontic. But in many cases, due to a long period of edentulousness the adjacent teeth tend to be tilted or drifted towards this space. In such cases a proper pontic cannot be placed and the design of the pontic should be compromised. Residual alveolar ridge contour. During treatment planning the diagnostic cast should be thoroughly examined. The contour should be observed during intra-oral examination.

4 A smooth rounded ridge is best for the placement of a pontic. In cases with overhanging hyperplastic tissues, surgical excision of these tisuues should be carried out. Occlusal load on the pontic. The basic requirement of a pontic is that it should be able to restore proper function.the amount of occlusal load determines the selection of material as well as the design of the FPD.To restore proper function, the pontic should contain the same occlusal pattern as the remaining dentition. General design consideration for a pontic As mentioned before, each surface should be designed to fulfil their requirements. Design of each surface of the pontic contributes to the success of the partial denture. We shall see the design consideration to be followed for each surface of the pontic. Gingival surface. The gingival surface is the most interesting aspect of the pontic design. Highly glazed porcelain is the material of choice for this surface. Tissue contact is very important for a pontic. The pontic should not be designed to pressurize the alveolar mucosa, as it may ulcerate. Tissue contact should be minimal. Based on the amount of mucosal contact pontics can be classified as. -Saddle pontic -Ridge lap pontic -Hygienic or sanitary pontic. Saddle pontic. A pontic with a concave gingival surface that overlaps the ridge buccally and lingually is called a saddle. These pontics are generally avoided because they are very difficult to maintain and it is impossible to avoid accumulation of food debris. Ridge lap pontic. This pontic resembles a natural tooth. They do not overlap the ridge on either sides like saddle pontics instead the tissue contact is limited to the buccal surface of the ridge crest. Hygienic or sanitary pontic. These pontics have zero tissue contact. Though they are easy to maintain, they are highly unaesthetic. Occlusal surface. The following factors should be considered while designing the occlusal surface. -The size of the occlusal table can be reduced to decrease the amount of force centred on the abutment. -The functional cusps of the occlusal surface of the pontic should not be reduced, to preserved a stable vertical dimention -In the maxillary teeth the buccal cusps provide aesthetics. In the lower teeth the lingual cusps aid to protect the tongue. Buccal and lingual surfaces. They are designed based on the aesthetic, functional and hygienic requirements. Proximal surface. Vertical clearance should be sufficient to permit physiologic contour of the pontic and allow space for interproximal tissues. Biomechanical consideration The design of a fixed partial denture is determined by the physical factors affecting the prosthesis. The major biomechanical factors which affect the design of an FPD are: -Length of the edentulous span -Occlusogingival height of the pontic -Arch curvature -The direction of forces acting on the FPD. Length of the edentulous span and occlusogingival height of the pontic

5 A long span fixed partial denture transfers excessive load to the abutment and also tends to flex to a greater extent. Longer the span, more is the flexion of the FPD. The flexion of an FPD varies as follows: (Length of teh fixed partial denture)³ Flexion= (Occlusogingival height of the Pontic)³ For example a span of two pontics will flex eight times more than a single pontic FPD. Hence, the flexion of a long span fixed partial denture can be decreased by increasing the occlusogingival height of the pontic or by using high strength alloys like nickel chromium. Abutment selection The most important factor to be considered in the design of a fixed prosthesis is the location and the characteristics of the abutment. The choice of a suitable abutment is important because the abutment has to withstand both the forces acting on it, and the forces acting on the pontic. Teeth, with the following characteristics are preferred abutments: -Teeth adjacent to edentulous spaces. -Teeth with grossly decayed crowns that can be restored with full veneer crown.(note: the periodontal support should be uncompromised) -Modifications like dowel core may be needed to restore crown morphology in grossly destructed teeth. Vital teeth are preferred, though endodontically treated teeth can also be used. Root Cofiguration The forces acting on a tooth are transferred to the supporting bone through the root. The shape of the root determines the ability of the abutment to transfer the masticatory load to the supporting bone. Some facts to be remembered regarding the configuration of an abutment root are: -roots with greater labiolingual widths are preferred. -roots with longer roots serve as better abutment. Crown Root Ratio The ratio between the length of the crown and the length of the root should always be less than one. The length of the crown indicates the length of the tooth structure above the crest of the alveolar bone. Teeth with alveolar defects are considered to have very long crowns. Ideally the crown root ratio should be 2:3. Ratios up to 1:1 are acceptable. Ratios above one are unacceptable. Root Support The supporting alveolar bone should be healthy. It should show no signs of bone defects or bone loss. Intraoral radiographs should be used to evaluate the bone architecture. The alveolar bone support is one of the most important factors that aid to evaluate an abutment.

6 Full- metal FPD clinical-laboratory procedures Construction of the full metal crown. Clinical and Laboratory steps 1.Anesthesia 2.Tooth preparation 3.Gingival retraction 4. Impression taking 5. Temporary crown making 6. Gypsum cast fabrication (Dies and working casts) 7.Wax pattern fabrication 8.Casting 9.Correction of ready crown on the cast model 10.Try in oral cavity and cementation For gold alloy restorations, we need about 1.5 mm of clearance on the functional cusps and about 1.0 mm on the nonfunctional ones. For nongold alloy crowns, we need correlatively 1.0 mm and 0.6 mm. Gingival retraction permits completion of the preparation and cementation of the restorations and helps the operator to make a complete impression of the preparation. The techniques used for gingival retraction can be classified: Mechanical Chemico - mechanical Surgical Mechanical methods include the use of copper band, retraction cord, rubber dam. Chemico - mechanical methods include the use of gingival retraction cords. Surgical methods include rotary curettage and electrosurgery. Chemico - mechanical methods of gingival retraction is a method of combining a chemical with pressure packing, which leads to enlargement of the gingival sulcus as well as control of fluids seeping from the sulcus. We know that a gingival retraction cord soaked in a chemical (which promotes gingival contraction) will provide better gingival retraction compared to a plane retraction cord. The following chemicals are generally local vasoconstrictors which produce transient gingival shrinkage. 8 per cent Racemic epinephrine Aluminium chloride Aluminium potassum sulphate Aluminium sulphate Ferric sulphate Ideal requirements for chemicals used with gingival retraction cords.

7 It should produce effective gingival displacement and haemostasis. It should not produce any irreversible damage to the gingival. It should not have any systemic side effects. Impression An impression for a cast restoration should meet the following requirements: 1. It should be an exact duplication of the prepared tooth, including all of the preparation and enough uncut tooth surface beyond the preparation to allow the dentist and technician to be certain of the location and configuration of the finishing line. 2. Other teeth and tissue adjacent to the prepared tooth must be accurately reproduced to permit proper articulation of the cast and contouring of the restoration. 3. It must be free of bubbles, especially in the area of the finish line and occlusal surfaces of the other teeth in the arch. Impression technique Double mix Single mix Closed Bite Double Arch Method or triple tray technique. Double mix technique A suitable stock tray is selected. Tray adhesive is applied uniformly into the tray. Putty impression material is mixed and made into a rope and loaded onto the tray. Making and removing the impression. The impression is additionally relieved by scraping the areas, which recovered the tooth preparation. The light body material is then syringed over the putty impression and also over the tooth preparation. The final impression will contain the accurate details recorded by the light body materials. Single mix technique In this procedure both the materials (light body and putty) are used simultaneously. The putty material is loaded into the stock tray. The light body material is syringed around the tooth preparation. A full mouth impression is made using the loaded stock tray. Closed Bite Double Arch Method or triple tray technique. The syringe material is injected into the area to be recorded. The high viscosity material is mixed and placed in excess on both the arches. The tray is placed in between the arches. Patient is asked to inter- digitate (bite) slowly. As the patient opens his mouth, the tray will adhere to one arch.

8 Bilateral pressure (right and left) should be applied to remove the tray as it helps to minimize distortion. Gypsum cast fabrication A die is a positive replica of the individual prepared tooth on which the margins of the wax patterns are finished. These are individual tooth replicas prepared for easier handling during wax pattern fabrication and finishing of inaccessible areas of the cast. Ideal requirements of a die system The die should be easy to remove and replace in its original position. The die must be stable when placed in the cast. Working cast with a removable die system In this system a special type of working cast is prepared and the dies are carefully sectioned so that the individual dies can be removed and replaced in their original position in the cast. Wax pattern fabrication Apply to die compensation varnish for: Compensation the alloys shrinkage during metal framework casting Provision space for cement. To prevent the wax from sticking to the die stone, coat the die thoroughly with die lubricant and allow it to soak in for several minutes. Wax pattern fabrication involves three major steps namely fabrication of the retainer, pontic connector. Casting. The various steps in a casting procedure are: preparing the wax pattern for casting spruing the wax pattern attaching the sprue to the crucible former investing the pattern in a casting ring burnout of the wax pattern casting recovery finishing and polishing Correction of ready crown on the cast model by the technician. Try in oral cavity and cementation.

9 During try in the following features are checked in the cast restoration proximal contact marginal integrity stability occlusion Checking for proximal contacts the proximal contact between the crown and natural tooth should allow the passage of floss. Ideally the contacts should be stable and easy to maintain. Checking for marginal integrity Margin adaptation with a gap around 30 μm is clinically acceptable. Testing whether the casting binds to the tooth surface, is helpful to determine the marginal integrity. This can be done using the following material: pressure indicating paste, powdered sprays, and elastomeric detection paste. Marginal integrity can be assessed by moving a sharp explorer from the restoration to the tooth and from the tooth the restoration. Checking for stability The restoration should not rock or rotate when a force is applied Instability produced by a small positive nodule on the fitting surface can be corrected by trimming. Checking for occlusion Occlusal discrepancies are one of the most common errors that occur during the fabrication of a fixed partial denture. Occlusal adjustment during eccentric movements (clinical correction) is necessary. Cementation is the process by which the restoration is cemented to the tooth using a suitable luting agent. Preparing the casting: the casting should be cleaned by sandblasting with 50μm alumina or by steam, followed by ultrasonic or organic cleaning. Next the operatory side is isolated with cotton rolls. The cement should be mixed to a luting consistency. A thin coat of cement should be applied on the internal surface of the casting. The tooth surface is dried and the prosthesis is inserted with a firm, rocking dynamic seating force. A static load will lead to fracture. Next the margins of the retainers are examined to verify the fit of the prosthesis. Excess cement should be removed with an explorer. Floss can be used to remove the excess cement in the inter-proximal surface. Occlusion should be checked with articulating paper. The patient should be advised to avoid loading for the first 24 hours.

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11 Metal ceramic FPD. Clinical and Laboratory steps Construction of the metal ceramic crown. Clinical and Laboratory steps 1. Anesthesia 2. Tooth preparation 3. Gingival retraction 4. Impression taking 5.Temporary restoration fabrication 6.Gypsum cast fabrication 7.Wax pattern fabrication 8. Casting metal framework 9.Correction of ready metal framework on the cast model 10.Try in oral cavity and shade selection 11. Ceramic material is veneered (sintered) onto a metal frame in several firing processes 12.Correction of ready crown on the cast model 13.Try in oral cavity 14.Glazing 15.Try in oral cavity and cementation The amount of tooth reduction necessary for the metal-ceramic crown depends on the metal and ceramic thickness. The necessary thickness of the metal is mm for gold alloy and for simple alloy mm. The minimal ceramic thickness is 1,0-1,5 mm The ceramic layer has to be at least mm in the gingival part. Therefore, the tooth reduction is approximately 1,5-2,0 mm. Shade selection Use the shade guide that matches the porcelain your technician is using. Every porcelain is different, and best results are obtained if you use the same guide the manufacturer used in designating the colors of the product. The shade should always be matched prior to preparation of the tooth to be restored. Ask the patient to remove all distractions before attempting to match a shade. Lipstick in particular should be removed. Large, bright items, such as earrings or glasses, can also distract the eye from the intended focus of attention on the teeth. Heavy facial makeup, such as rouge, could also interfere with an accurate match and would need to be removed or masked. Be sure that the teeth are clean and unstained before attempting to match a shade. Perform a quick rubber cup and paste prophylaxis in the area of the mouth where the shade is to be matched. Rinse the area thoroughly to remove any traces of the prophy paste. Seat the patient in an upright position with the mouth at the operator`s eye level. Position yourself between the patient and the light source. Ceramic material is veneered (sintered) onto a metal frame in several firing processes Any remaining investment or abrasive particles embedded in the surface of the casting could oxidize and release gases during firing. Oils from the skin left during handing of the casting are

12 another serious form of contamination. «Live steam» is effective in removing residual contamination caused by surface deposits of abrasive particles. The coping is ready for the oxidation cycle. Metal surface treatments are unique for each porcelain alloy combination, and manufacturer`s recommendation should be followed. Bond strength varies with the surface treatment. Typically, a coping is placed in a furnace at a relatively low temperature and the temperature is raised 300 to 400 ºC at a designated rate of climb. The atmosphere (air or vacuum) during this heating process, as well as the length of time at temperature, is dictated by the alloy. Heat treatment of noble metal alloys causes the trace quantities of tin, gallium, indium, and zinc in the alloy to form oxides that enhance bonding with the porcelain. Base metal alloys, on the other hand, readily oxidize, so oxide formation must be carefully controlled. Following oxidation, most alloys require air abrasion with 50 μm aluminium oxide to reduce the layer of oxide, as excess oxide weakens the porcelain-to-metal bond. Oxidation is only one of the functions of the initial firing. During casting, hydrogen gas is incorporated into the molten alloy. This gas, if left in the coping, can weaken the bond between porcelain and metal, causing the formation of bubbles in the porcelain. The hydrogen is released during the oxidation cycle, degassing the alloy as well as forming the important oxide layer. The casting is now ready for the actual placement of porcelain. Opaque porcelain is applied first to mask the metal, to give the restoration its basic shade, and to initiate the porcelain - metal bond. The prepared coping is painted with a thin coating of distilled water or the specially formulated liquid, forming a thin wash which is applied with a brush. No attempt should be made to toughly mask the metal with this initial application. It is intended to completely wet the metal and penetrate the striations created by finishing. The coping is dried and fired under vacuum to a specific temperature. The vacuum is broken and the coping held at the temperature under air for 1 minute. The second application of opaque porcelain should mask the metal. The powder and liquid are mixed to a creamy consistency and applied to the coping with a brush a vibrating motion. The opaque layer should be applied as thinly as possible to still mask the metal. The coping is gently vibrated to condense the porcelain, and excess water is removed with a dry tissue. The second layer of opaque is fired using the same firing cycle. The opaque layer of porcelain should be approximately 0,3mm thick. Between the metal and porcelain exists mechano-chemical bonding. After opaque dentin and enamel porcelain application, this is fired as per the manufacturer s instructions. Correction of ready crown on the cast model. Try in oral cavity. During the try-in of a porcelain restoration, the following factors should be examined. Checking for proximal contact and marginal fit in ceramic restoration. They are examined as explained in cast metal restorations. Checking for occlusal discrepancies in ceramic restoration.

13 Evaluation of aesthetics in ceramic restorations. The contour of the gingival embrasure space and the placement of the incisal edge are important factors to be considered during anterior try-in. Some mild discrepancies can be incorporated into the restoration to produce a natural appearance (enamel cracks, stained crack lines, exposed occlusal dentin, fracture lines areas of discoloration). After trying glaze porcelain is added and fired as usual. Try in oral cavity and cementation. Metal-acrylic FPD 1. Anesthesia 2. Tooth preparation 3. Gingival retraction 4. Impression taking 5.Temporary restoration fabrication 6.Gypsum cast fabrication 7.Wax pattern fabrication 8. Casting metal framework 9.Correction of ready metal framework on the cast model 10.Try in oral cavity and shade selection 11. Acrylic veneering 12.Correction of ready crown on the cast model 13.Try in oral cavity 14. Finishing and polishing 15.Try in oral cavity and cementation The procedure is similar to ceramic veneering except for a few differences. One of the major differences is that only mechanical bonding exists between the metal and resin. Hence, the bond strength is considerably less. The steps to be followed for resin veneering are: Mechanical undercuts (for retention) should be made over the entire metal surface to be veneered. Mechanical undercuts can be created by sprinkling plastic retentive pearls over the wax pattern before casting. The surface if the cast metal can be roughened using Al203 air abrasive unit. A small quantity opaque resin is added onto the metal surface. Body shade resin is added over the opaque resin and contoured using a modeling instrument. The resin should be polymerized under pressure in a warm water bath. Light cure resins are also available.

14 The resin core should be carved to remove excess material. Space should be provided to accommodate incisal resin. Finally incisal shade resin is added and contoured using a modeling instrument. After polymerization of the incisal resin, the restoration is finished and polished.

15 Fixed partial dentures A fixed partial denture is A partial denture that is cemented to natural teeth or roots which furnish the primary support to the prosthesis. A fixed prosthesis is A restoration or replacement which is attached by a cementing medium to natural teeth, roots, implants. These dentures are often termed as BRIDGES. Fixed partial dentures are fabricates in a complex manner. The prosthesis is cemented to the supporting teeth and cannot be removed by the patient. Common terms used in fixed prosthodontic Crown Laminate veneers or facial veneers Inlay Onlay Abutment Pontic Connectors Crown is a cemented extracoronal restoration that covers or veneers the outer surface of the clinical crown. The primary function of a crown is to protect the underlying tooth structure and restore the function, form and aesthetics. We know three types of the crowns 1. clinical crowns depicts the intraorally visible tooth structure 2. anatomical crowns depicts the area of the tooth covered by enamel 3. artificial crowns. If the prosthetic crown covers all five surfaces of the clinical crown it is referred to as a Full veneer crown (FVC). If the prosthetic crown does not cover the entire clinical crown, it is referred to as a Partial veneer crown (PVC). A crown that is used as a part of the fixed partial denture for retention and support from the abutment tooth is called as a Retainer. Abutment It is any tooth, root or implant which gives attachment and support to the fixed partial denture Pontic The artificial tooth that replaces a missing tooth in a fixed partial denture is called a pontic. Pontics are attached to the retainers. All forces acting on the pontic are transferred to the abutment through the retainers. Connectors It is the connection that exists between the pontic and retainer. They may be rigid or non-rigid. Rigid connectors are immovable attachments between the pontic and retainer. Ex. Solder joints. Non-rigid connectors are movable attachments with a key-keyway mechanism. Ex precision attachments.

16 Classification of partial adentia. External clinical features Lips retraction, especially upper lip Buccal retraction, in case of masticatory tooth absence The lowering of the vertical dimension of the face, in loss of mastication teeth of both jaws. Angular cheilitis development Big amplitude of vertical movement of the lower jaw during swallowing Complaints If the defect is located in frontal part of dental arch. Esthetical dissatisfaction Diction impairment Saliva sprinkle during speech Impossibility to bite off If the defect is located in lateral part of dental arch. Mastication impairment Damage of the gum mucous and pain Esthetical dissatisfaction in case of premolars absence Anamnestic data Causes of the tooth loss Dates of the tooth loss If the patient has had prosthodontic prosthesis and the type of construction Patient s examination Type of defect Extension of defect Availability of antogonists pair. Condition of periodont and hard tissues of the preserved teeth Occlusal curve Additional methods of examination Palpation Soundation Determination of the tooth agility X-Ray examination of all probable abutment teeth Results of tooth partial loss Impairment of continuity of dental arch and defect formation Development of 2 group of teeth: functional, and non-functional Functional overloading of some tooth groups Dental arch deformation Mastication, speech and esthetic impairment TMJ and masticator muscles functional impairment Defects can be Limited or involved Unlimited or terminal Several classifications of partially edentulous arches have been proposed. This variety has leаd to some confusion and disagreement concerning which classification best describes all possible configurations and should be adopted. The Kennedy method of classification is probably the most widely accepted classification of partially edentulous arches today. Kennedy classification

17 The Kennedy method of classification was originally proposed by Dr. Edward KENNEDY in It attempts to classify the partially edentulous arch in a manner suggests certain principles of design for a given situation. Kennedy divided all partially edentulous arches into four basic classes. Edentulous areas other than those determining the basic classes were designated as modification spaces. The following is the Kennedy classification. Class I Bilateral terminal adention (edentulous areas located posterior to the natural teeth) Class II a unilateral terminal adention (edentulous areas located posterior to the remaining natural teeth) Class III a unilateral involved adention (edentulous areas with natural teeth remaining both anterior and posterior to it). Class IV - invovlved adention in frontal part of dental arch. (it is single, but bilateral (crossing the midline), edentulous area located anterior to the remaining teeth). Classification defects by size minor in absence of 1-3- adjacent teeth moderate - in absence of 4-6 adjacent teeth large - in absence of adjacent teeth Reserved force of periodont Perioodnt ability for increased functional adaptation Causes of functional overloading Bite s anomaly, common deep bite Partial absence of teeth mixed function of frontal teeth pathological dental abrasion mistakes in preparing prosthesis increase of bite, wrong clasp system etc. bruxizm acute and chronic apical periodontitis Functional overloading can be different by influence force value by direction by duration combined Clinical features of functional overloading increased enamel and dentin abrasion, which are in traumatic occlusal condition dislodgement(displacement) of teeth in different directions pathological movements of teeth development of periodontal pockets gingivitis By X-ray exam enlargement (deformation) of periodontal slit atrophy of dental alveoli osseos pocket formation on the side of inclination Traumatic occlusion primary secondary For primary traumatic occlusion is typical Local character of pathological process No purelent discharge from pathological pockets

18 Hyperemic gingival edge not detached from the tooth Radially dystrophy of periodont is noted only in the region of functional overloading