TYPES OF BRIDGES A fixed partial denture is

TYPES OF BRIDGES

A fixed partial denture is defined as “A partial denture that is cemented to natural teeth or roots which furnish the primary support to the prosthesis”also known as bridges. Types of bridges : CONVENTIONAL FIXED PARTIAL DENTURES They are the most commonly used type of fixed partial dentures. The design involves fabrication of a fixed partial denture, which takes support from abutments on either side of the edentulous space. The design may vary according to the condition of the abutments but the abutments on either side should be able to support the fixed partial denture

CANTILEVER FIXED PARTIAL DENTURES cantilever fixed partial denture is used when support can be obtained only from one side of the edentulous space. These dentures have compromised support. The abutment teeth on the supporting side should be strong enough to withstand the additional torsional forces. Support can be obtained from more than one tooth on the same side of the edentulous space

• SPRING CANTILEVER FIXED PARTIAL DENTURES This is a special cantilever bridge exclusively designed for replacing maxillary incisors but these dentures can support only a single pontic. Support is obtained from posterior abutments (usually a single molar or a pair of splinted premolars).

FIXED PARTIAL DENTURES The term denotes fixed partial dentures with rigid connectors. The design of these dentures is more conventional. Since the connectors are rigid, there can be no movement between the connected components. These are the most commonly used fixed partial denture designs

FIXED MOVABLE PARTIAL DENTURES It is defined as, A fixed partial denture having one or more non-rigid connectors. { GPT } Here, a non rigid connector is used/ fabricated to connect the components of the fixed partial denture. Commonly used non rigid connectors include Tenon Mortis connectors (TMC), loop connectors, split pontic connectors and cross pin and wing connectors

FIXED REMOVABLE PARTIAL DENTURESI REMOVABLE BRIDGES One of the major disadvantages of long span fixed partial dentures is that if one abutment fails, the entire prosthesis has to be sacrificed. To overcome this disadvantage, fixed removable bridges were introduced. These dentures cannot be removed by the patient but can be easily removed by the dentist.

MODIFIED FIXED REMOVABLE PARTIAL DENTURES They were developed by Andrew, hence they are also known as Andrew's bridge systems. These dentures are indicated for edentulous ridges with severe vertical deficit. The prosthesis consists of a fixed component and a removable component.

ALL METAL FIXED PARTIAL DENTURES These dentures are fabricated using only meta. L Characteristics. They are indicated for replacing maxillary and mandibular posterior teeth. They are not aesthetic. They have the maximum strength and durability.

METAL-CERAMIC FIXED PARTIAL DENTURES Here, metal is used to fabricate the core of the prosthesis. The external surface is fabricated using ceramic. The metal is bonded to ceramic chemically, mechanically and ionically. Metal ceramic fixed partial dentures can be of two types. In the first type, the metal is surrounded by porcelain on all the surfaces. In the second type the lingual and occlusal surface is formed by metal and the labial and gingival surface is alone formed by porcelain. These restorations are also termed as porcelain facings or porcelain veneers.

Advantages Aesthetically pleasing. Stronger metal substructure. Characterization possible with use of internal and external stains. Disadvantages. Significant tooth preparation necessary. To achieve better aesthetics, the facial margin of an anterior restoration is often placed subgingivally, this increases the potential for gingival destruction. Brittle fracture can occur due to failure at the metal ceramic junction. More expensive.

ALL CERAMIC FIXED PARTIAL DENTURES All ceramic partial dentures are fabricated using only ceramic. All ceramics are less fracture resistant, hence, they do not render as good retainers. However, alumina reinforced porcelains (inceram) have sufficient strength to be used as good retainers. Advantages. Superior aesthetics. Excellent translucency. Requires slightly more preparation of the facial surface. The appearance can be influenced and modified by selecting different colors of luting agent.

Disadvantages. Reduced strength due to lack of reinforcement with metal. It is very difficult to obtain a well finished margin because the ceramic edges tend to chip easily. These crowns cannot be used on extensively damaged teeth because they cannot support these restorations. Due to porcelain's brittle nature, large connectors have to be used, which usually leads to impingement of the inter dental papilla. This increases the potential for periodontal disease. . Wear of opposing natural teeth.

ALL ACRYLIC FIXED PARTIAL DENTURES Characteristics. Only indicated for long term temporary or interim prostheses. Can be used for making fixed periodontal splints. Poor wear resistance. Easy to fabricate and adjust. Aesthetically pleasing.

VENEERS Veneer is a layer of restoration placed over the labial surface of a tooth. They are primarily used as aesthetic adjuncts to discolored or fractured teeth. Type of Veneers Ceramic It is the most ideal veneering material when used with metal substructure or in all ceramic restorations. Acrylic Tooth colored acrylic can be used with metallic restorations as a veneer. They are not considered as a permanent material due to poor wear resistance. Recent advances include use of indirect composite resins as veneer materials.

SHORT SPAN BRIDGES These are simple fixed partial dentures, which replace one or two teeth, and the teeth on either side are ideal abutments. These dentures are considered ideal because they have minimal torquing forces. For example First molar replacement.

LONG SPAN BRIDGES Long span bridge denotes a condition where two or more teeth have to be replaced and more than one abutment has to be taken for support on either side. Long span bridges have the potential for producing more torquing forces on the bridge and the weaker abutment. (especially weak abutments are adversely affected) PERMANENT OR DEFINITIVE PROSTHESIS This term denotes all conventional fixed partial dentures inserted as definitive or final treatment. Most fixed partial dentures made of metal ceramic, all metal or all ceramic are considered permanent restorations. They are placed at the final phase of a rehabilitative procedure.

LONGTERM TEMPORARY BRIDGES These dentures are usually made of acrylic resin. They are designed to be used for a few weeks to months. Indications: These restorations may be given for the following conditions: During the interim period of treatment when the patient is undergoing extensive occlusal rehabilitation. (E. g. Intruding a supra erupted tooth). . In patients undergoing periodontal therapy these restorations may be inserted to act as splints.

FIBRE REINFORCED COMPOSITE RESIN BRIDGES These are basically bridges, which are reinforced by a bar of glass fibers over which indirect posterior composites are built. Classification Fibre reinforced composites can be classified into: Pre impregnated (e. g. Fibrekor, Splint it): The manufacturer impregnates them with the resin. Impregnation required (e. g. Ribbond, Cpost): fibre impregnation has to be done by the dentist. Contra indications It cannot be used when fluid control is not possible. Cannot be used for long span bridges It should be avoided in patients with para functional habits It should not be used opposing unglazed porcelain teeth.

TYPES OF ADHESIVE BRIDGES • This classification of resin bonded bridges is based on the finishing technique of the metal framework. According to this these are of following types: • Rochette bridge • Maryland bridge • Cast mesh FPD • Virginia bridge

ROCHETTE BRIDGE: • The first use of wing like retainers, with funnel shaped perforations through them to enhance resin retention is attributed to Rochette in 1973. He combined mechanical retention with a silane coupling agent to produce adhesion to metal. • The perforated retainer became a standard design for several years for both anterior and posterior FPD’s.

MARYLAND BRIDGE • Livaditis and thomson postulated that the retentive resin rivets extruding through the perforated framework were exposed to increased stresses as well as abrasion and leakage that diminished their longitivity. • They adapted electrochemical pit corroding technique that had been used by Dunn and Reisbick.

• Livaditis and Thompson used a 3. 5% solution of nitric acid with a current of 250 m. A/sqcm for five minutes, followed by immersion in 18% hydrochloric acid solution in an ultrasonic cleaner for 10 minutes to etch the internal surfaces of solid base metal retainers for resin bonded fixed partial dentures. This type of etched metal prosthesis is called Maryland Bridge.

CAST MESH FIXED PARTIAL DENTURE • Techniques that produce roughness before the alloy is cast or use a non etching method after casting, have also been employed. • A net like nylon mesh can be placed over the lingual surfaces of abutment teeth on the working cast. It is then covered by and incorporated into the retainer wax pattern with the undersurface of the retainer becoming a mesh like surface when the retainer is cast. It eliminates the need for etching and permits the use of base metal alloys.

VIRGINIA BRIDGE Moons and Hudgins e tal produced particle roughened retainers by incorporating salt crystals into the retainer patterns to produce roughness on the inner surfaces. In this method also known as lost salt technique for producing virginia bridges the framework is outlined on the die with a wax pencil, and the area to be bonded

and the area to be bonded is coated first with model spray and then with lubricant. Sieved salt crystals ranging in size from 149 to 250µm are sprinkled over the outlined area. The retainer patterns are fabricated from resin, leaving a 0. 5 to 1. 0 mm wide crystal free margins around the outlined area. • When the resins are polymerized, the patterns are removed from the cast,

cleaned with a solvent, and then placed in water in an ultrasonic cleaner to dissolve the salt crystals. This leaves cubic voids in the surface that are reproduced in the cast retainers, producing retention for the fixed partial denture. Subsequent investigation showed that retainers fabricated by this technique could be 30 to 150% more retentive than retainers prepared by the electrochemical technique, depending on the resin used.

• Air abrasion with aluminium oxide has been used as a sole means of surface treatment, as well as the precursor for other treatments. • Tanaka et al used 50µ aluminium oxide air abrasion to prepare cobalt chromium castings for bonding with 4 META resin.

INDICATIONS • Retainers for FPD for abutments with sufficient enamel to etch for retention • Resin bonded retainers can be used to replace one or two mandibular incisors when the abutment teeth are unblemished. • They can be used to replace maxillary incisors if they are in open bite, end to end bite or moderate overbite situation. • Indicated for splinting of periodontally compromised teeth. but if a resin bonded prosthesis is to be used as a splint, attention must be paid to the resistance features on

the abutment preparation. • Stabilizing dentitions after orthodontics. • Prolonged placement of interim prosthesis to augment surgical procedures that is craniofacial anamolies. • Medically compromised, indigent and adolescents patients. • For replacing single missing posterior teeth if they are opposed by RPD.

CONTRAINDICATIONS • Patients with acknowledged sensitivity to base metal alloys. • When facial esthetics of the abutments require improvement. • Insufficient occlusal clearance to provide 2 to 3 mm vertical retention eg abraded teeth.

• Inadequate enamel surfaces to bond, eg caries, existing restorations. • Incisors with extremely thin faciolingual dimension. • Exceptionally demanding esthetics for adults.

ADVANTAGES • Noninvasive to dentin with lingual and proximal tooth preparation including occlusal rest. • Conservative with undeniable patient appeal. • Tissue tolerant because of supragingival margins without pulpal irritation.

• Unaltered casts without removable dies. • Reduced cost with less chair time. • No anesthetic needed.

DISADVANTAGES • Uncertain longitivity is one of the drawbacks. • No space correction is possible. If the mesiodistal width of the edentulous span is greater then that cannot be corrected beyond a certain limit. • It is impossible to correct the alignment problems with these restorations as not much is done on facial, proximal and incisal areas of abutment teeth.

• Temporization is difficult, as a provisional fixed partial denture cannot be fabricated, if a missing tooth is to be replaced then a while fixed restoration is being made temporization is accomplished muco adhesion temporary removable partial denture. • Heavy dependence on laboratory for competent treatment of cast metals and selective waxing to ovoid overcontouring.

• Patients expectations of esthetics are high but the results are only fair. • Usually restricted to one tooth replacement. • “Graying out” of teeth that are thin labiolingually at the incisal surfaces.

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