Advantages, Disadvantages, Indications, Contraindications And Preparation Steps Of Resin-Bonded Bridges

Classify adhesive bridges/resin-bonded bridges. Cite the advantages, disadvantages, indications, contraindications and preparation steps. Add a note on types of bonding to metal and tooth.

Resin-Bonded Bridges Definition

Resin-bonded bridges are fixed partial dentures, which are cemented onto the abutments using special resins.

First described by Rochette in 1973 (to splint mandibular anterior teethusing cast gold bar).1

Read And Learn More: Fixed Partial Denture Short Essay Question And Answers

Introduction Of Adhesive bridges/resin-bonded bridges

• Howe and Denehy introduced the first form of resin-bonded FPD (RBFPD)2
• Livaditis proposed preparation of proximal and lingual surfaces to create a path of insertion, along with occlusal rest seat preparation3
• Livaditis and Thompson later introduced the concept of electrolytically etched non precious metal4
• Other developments happened in regard to bonding techniques and etching which in turn depended on factors, such as type of casting alloy, type, time and concentration of acid etchant, acid and electrical current density
• Silicoating improved the longevity and bonding of metal. This involves the fusion of a 0.5μ thin layer of silica to the metal fitting surface which bonds with a silane coupling agent.

Resin-Bonded Bridges Classification

• Rochette bridge.
• Maryland bridge.
• Virginia bridge.
• Cast-mesh fixed partial dentures.

Advantages Of Adhesive Bridges

• Minimal tooth reduction—Conservation of tooth structure
• Preparation is confined to enamel
• No pulpal trauma
• Anesthesia not required
• More biocompatible
• Supragingival margin placement
• Less periodontal trauma
• Less chair side time
• Does not require cast alterations or removable die preparation
• Reduced cost.

Disadvantages Of Adhesive Bridges

• Good patient selection is a must
• Technique sensitive
• Laboratory errors cannot be corrected easily
• Chances of over contouring leads to plaque accumulation
• Over contouring can result in patient discomfort
• Can only replace one tooth
• Cannot be prepared on thin tooth
• Debonding can occur due to faulty preparation or improper luting technique
• Difficulty in isolation during bonding procedures
• Cannot be done on tooth with small clinical crowns.

Indications Of Adhesive Bridges

• For abutments with sufficient enamel
• Splinting periodontally compromised teeth
• For medically compromised patients
• As a temporary restoration
• Young patient
• Large pulp chambers
• Post ortho-retention.

Contraindications Of Adhesive Bridges

• Sensitivity to base-metal alloys
• Insufficient occlusal clearance
• Deep vertical overbite
• Thin teeth
• Loss of tooth structure
• Parafunctional habits
• Short clinical crowns
• Narrow embrasures
• Mobile tooth
• Defective enamel
• In extensive restorations.

Rochette Bridge (1973)

• It is a wing-like retainer with six perforations to provide mechanical undercuts for resin cement
• Etched retainers are coated with pyrolized silane and bonded with resin cements.

Rochette Bridge Disadvantage

• The resin is exposed to oral fluids and external stress, which leads to abrasion and marginal leakage.

Variation

Nonperforated retainers can be used.

Maryland Bridge

(Livaditis and Thompson from University of Maryland School of Dentistry)

Here a nonperforated retainer was etched for mechanical retention to form microporosities present and was bonded by resin cement.

Virginia Bridges

• Use particle-roughened retainers
• The retainer wax patterns are sprinkled with salt crystals prior to resin fabrication
• The salt crystals get incorporated onto the tissue surface of the resin pattern
• During dewaxing the salt crystals dissolve leaving voids in the resin pattern for mechanical retention
• Air abrasion with aluminium oxide improves retention.

Virginia Bridges Advantages

• Surface treatment of the retainer is not necessary
• Noble metal alloys also can be used as retainers.

Cast-mesh Fixed Partial Denture

• A nylon mesh is placed on the tissue surface of the retainer wax pattern before fabricating the wax pattern.

Fixed Partial Denture Disadvantages

• The nylon mesh adaptation to the cast is not good
• The wax may flow in between the mesh locking all the undercuts.

Steps in the Fabrication/Preparation of A Resin-bonded Fixed Partial Denture

• Preparation of abutment teeth.
• Fabricating the provisional restoration.
• Design of the restoration.
• Bonding.

Preparation of abutment teeth

• Single path of insertion
• The incisal finish line is kept 2 mm short of the incisal edge to avoid any esthetic impairment of incisal edge translucency
• A reduction of 0.5 mm palatally is ensured for adequate metal thickness
• The gingival finish line ends 1 mm supragingivally for optimal gingival health
• Proximal undercuts must be removed
• Interproximally, the finish line ends at the centre of the contact area or proximal grooves are given for maximum wrap effect
• Rest seats as cingulum rest should provide good resistance form and is prepared with flat-ended tapered diamond bur
• Definite and distinct margins should be present.

Design of Anterior Resin-bonded Fixed Partial Dentures

• A single path of insertion in the incisogingival direction along the proximal surface of the abutment
• Lingual clearance (0.8 mm–1.0 mm) should be provided
• Cingulum rest seat should be prepared to act as a vertical stop
• A supragingival finish line (1 mm above the crest of tissue)
• An additional retention in proximal facial extensions.

Cantilever Anterior Designs

Canine is used as abutment to replace the lateral incisor.

Design of Posterior Resin-bonded Fixed Partial Dentures

The occlusal rest (for resistance to gingival displacement)

The retentive surface (for resistance to occlusal displacement)

The proximal wrap (for resistance to torquing forces).

Occlusal Rest Seat

• Should be spoon-shaped and placed on the proximal marginal ridge of the abutment adjacent to the edentulous area.

Retentive Surface

• Proximal and lingual axial walls should be reduced to about 1 mm above the gingival margin.

Proximal wrap:

• The alloy framework should be designed to engage at least 180° of tooth structure with a knife-edge margin (1 mm supragingivally).

Types of material used

• Gold alloy earlier
• Presently Ni–Cr alloy
• Zirconium
• Fiber-reinforced composites.

Types of bonding to provide retention

• Mechanical
• Chemical.

Mechanical Bonding

Subtypes

Macroscopic retention

By mechanical locks as in Rochette’s (six perforations in metal), mesh and water-soluble salt crystal.

Microscopic retention

By electrolytic etching (Maryland bridge).

Chemical bonding

Chemical bonding of resin:

• Chemical etching.
• Tin-plating.

Mechanical etching techniques

Electrochemical etching

Results in microscopic porosity.

Non-beryllium Nickel–chromium alloys

Two stages:

• Retainer is immersed in 35% nitric acid under a current of 250 milliamps per square centimeter for 5 minutes.
• Retainer is cleaned by immersing in 18% HCl in an ultrasonic cleaner for 10 minutes.

Beryllium-containing Nickel–chromium alloys

• Retainer is immersed in 10% H2SO4 under a current of 300 milliamps per square centimeter.
• Retainer is cleaned by immersing in 18% HCl in an ultrasonic cleaner for 10 minutes.

Other technique (Mc Laughlin technique)

• Retainer is etched with a mixture of HCl and H2SO4 in a beaker.
• The beaker with the retainer is directly placed in an ultrasonic cleanser for 99 seconds under an electrical field.

Nonelectrochemical

Roughening by aluminium oxide-air abrasion.

Chemical Bonding of Resin

Chemical etching

• A gel consisting of nitric and hydrochloric acids is applied to the internal surface of the metal framework for approximately 25 minutes.

Tin plating

• Precious alloys can be plated with tin and used as retainers to increase adhesiveness of resins thereby increasing bond strengths.

Adhesive Bridges Conclusion

• Ketabi et al. observed a survival of 69% after 13 years of 74 RBFPDs. The fifteen failures were due to loss of retention, caries and fracture of porcelain5
• Djemal et al. studied 832 RBFPDs and found survival of seven years and 10 months
• RBFPDs still debond frequently but showed an increase in survival rate after five years as 87.7%.