Resin bonded fpd/ academy general dentistry

RESIN BONDED FIXED

PARTIAL DENTURE

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.com

INTRODUCTION


Definition

Resin bonded prosthesis

A prosthesis that is luted to tooth structure, primarily enamel, which has been etched to provide mechanical retention for the resin cement. -GPT-7



BONDED PONTICS CAST PERFORATED RESIN RETAINED FPD (MECHANICAL RETENTION) ETCHED CAST RESIN RETAINED FPD (MICROMECHANICAL RETENTION ) MACROSCOPIC MECHANICAL RETENTION

RESIN RETAINED FPD’S (VIRGINA BRIDGE) CHEMICAL BONDING RESIN RETAINED FPD’S (ADHESION BRIDGES)

DEVELOPMENT OF RESIN RETAINED FIXED PARTIAL

DENTURE


Natural teeth and acrylic teeth used as pontics Composite resin connectors were brittle and

required supporting wire or a stainless steel mesh framework

Limited lifetime Limited to short anterior Spans

BONDED PONTICS


Cast perforated resin retained FPD In 1973, Rochette introduced the

concept of bonding metal to teeth using flared perforations of the metal casting to provide mechanical retention. He used the technique principally for periodontal splinting but also included pontics in his design.

Howe and Denehy recognized the metal frame work's improved retention (as compared to bonded pontics) and began using FPDs with cast‑perforated metal retainers bonded to abutment teeth and metal‑ceramic pontics to replace missing anterior teeth


Their design recommendation, extending the framework to cover a maximum area of the lingual surface, suggested little or no tooth preparation. Patient selection limited these FPDs to mandibular teeth or situations with an open occlusal relation ship. The restorations were bonded with a heavily

filled composite resin as a luting medium. This concept was expanded to replacement of posterior teeth.

Perforated retainers were used to increase resistance and retention." The castings were extended interproximally into the edentulous areas and onto occlusal surfaces. The design included a defined occlusogingival path of insertion by tooth modification, which involved lowering the proximal and lingual height of contour of the enamel on the abutment teeth.


Limitations Weakening of the metal retainer by the perforationsExposure to wear of the resin at the perforations Limited adhesion of the metal provided by the perforations


Etched cast resin retained FPD

Based on the work of Tanaka et al on pitting corrosion for retaining acrylic resin facings and the metal etching studies of Dunn and Reisbick, Thompson and Livaditis at the University of Mary land developed a technique for the electrolytic etching of Ni‑Cr and Cr‑Co alloys.

Etched cast retainers have definite advantages over the cast perforated restorations:


Retention is improved because the resin‑to etched metal bond can be substantially stronger than the resin‑to‑etched enamel.

The retainers can be thinner and still resist flexing.

The oral surface of the cast retainers is highly polished and resists plaque accumulation.


Several methods have been developed to provide visible macroscopic mechanical undercuts on the inner surface of FPD.

The first was developed at the Virginia Commonwealth University School of Dentistry and is known as the "Virginia Bridge”.

It involves a "lost salt crystal” technique . On the working cast, the abutments are coated with a model spray, and a lubricant is then applied.

Macroscopic mechanical retention resin retained FPD’S


Within the outlines of the retainers, specially sized salt crystals(150 to 250 µm) are sprinkled over the surface in a uniform monolayer, leaving a 0.5 mm border without crystals at the periphery of the pattern. This is followed by application of a resin pattern. After pattern investment, the salt crystals are dissolved from the surface of the pattern.

Adequate bond strengths are possible with this method, but the thickness of the casting mustbe increased to allow for the undercut thickness.


An alternative technique for macroscopic retention is the use of a cast mesh pattern on the internal surface of the retainers. The mesh, usually made of nylon, should be adapted to the lingual and proximal surfaces of the abutments.

The mesh is then covered by wax or resin; this must be done carefully to prevent occluding the mesh with the pattern material. Investing and casting then follow.


This method is technique sensitive but can provide adequate retention with a resulting thick lingual casting.

The cast mesh and the lost salt crystal method have been supplanted by direct adhesion with resin, which is possible for most casting alloys if the correct surface treatment is provided.


Chemical bonding resin retained FPD’S (Adhesion bridges)

While etched castings were the method of choice for retention of resin‑retained FPDs during the 1980s and early 1990s, extensive research was underway to develop adhesive systems for direct bonding of metal for this application.

The first of these resin systems is Super‑Bond which has the highest initial bond strengths of any adhesive resin system.

Advantages Lower elastic modulus and higher fracture toughness

when compared to BISGMA‑based resin cements


A BISGMA‑based composite resin luting cement that is modified with the adhesion promoter MDP .

Panavia has shown excellent bonds to air abraded Ni‑Cr and Cr‑Co alloys" as well as tin plated gold and gold palladium‑based alloys.

Panavia has a tensile bond to etched enamel (10 to 15 MPa) comparable to the traditional BISGMA low‑film thickness composites. The combination of metal electrolytic etching, followed by application of an adhesive such as Panavia, does not improve the tensile bond to the alloy and is actually slightly lower than the bond of Panavia to airborne‑particle‑abraded (sandblasted) base metal alloys."


Recent version of Panavia, Panavia F, is a dual cure system (chemical and visible light) that releases fluoride. It also incorporates a self‑etching primer system (ED Primer) for bonding to enamel and dentin.

Particle abrasion. of the alloy surface with 50 µm alumina before bonding or tin‑ plating not only creates a roughened, higher surface area substrate for bonding, but it also creates a molecular coating of alumina .

The alumina on the surface aids in oxide bonding of the phosphate‑based adhesive systems (e.g., Panavia to alloy surfaces). Studies of this bonding mechanism are also reinforced. by laboratory data on bonding to alumina and zirconia surfaces .

This simplifies the laboratory and clinical procedures for placement of resin‑retained FPDs


Laboratory systems for adhesive bonding,resin to metal have been developed.

Methods The flame application of a silica‑carbon layer to the

metal surface. This treated metal is then silane‑coated, which provides a surface to which composite resin will bond. The system marketed to the dental laboratory industry as the Silicoater.

It has since evolved to an oven method to bake the silica‑carbon layer to the alloy surface and is now called the Silicoater MD system.


Another laboratory method for resin bonding is the Rocatec System. In this method, the metal sur face is initially particle‑abraded with 120 µm alumina. This is followed by abrasion with a special silicate particle‑containing alumina. This second particle abrasion step deposits a molecular coating of silica and alumina on the alloy surface. Silane is then applied to the surface, making it adhesive to composite resin.


Careful laboratory technique and are generally confined to bonding composite resin veneers to alloy castings because of the con cern that the silane‑treated surface may become contaminated before or during the clinical bonding procedures.

Changing the method of attachment of the resin to the metal framework does not change the design of the framework itself, because the limiting factor, in the system is still the bond of resin to enamel.

There is a need for mechanical retention of the framework to limit the stress on the bond interfaces (resin‑to‑metal and resin‑to‑enamel) and in the composite resin, which can become fatigued with time


Minimal removal of tooth structure Minimal potential for pulpal trauma Anaesthesia not usually required Supragingival preparation Easy impression making Provisional not usually required Reduced chair time Reduced patient expense Rebond possible.

Advantages


Disadvantages

Reduced restoration longevity Enamel modifications are required. Space correction is difficult Good alignment of abutment teeth is required. Esthetics is compromised on posterior teeth.


Indications

Replacement of missing anterior teeth in children and adolscents.

Short span. Unrestored abutments. Single posteior tooth. Significant crown length. Excellent moisture control.


Contraindications

Parafunctional habits. long edentulous spans. Restored or damaged abutments. Compromised enamel. Deep vertical overlap. Nickel allergy.


Fabrication

In the fabrication of resin‑retained FPDs, following three phases is necessary for predictable success:

1. Preparation of the abutment teeth

2. Design of the restoration

3. Bonding


Preparation of the abutment teeth

Common principles dictate tooth preparation design. A distinct path of insertion must exist, proximal

undercuts must be removed to provide "planes of metal" on the lingual and proximal surfaces,

occlusal rest seats and proximal groove slots must provide resistance form, and a definite and distinct margin gingival margin should be established wherever possible.


The tooth preparation includes axial reduction and

guide planes on the proximal surfaces with a slight extension onto the facial surface to achieve a faciolingual lock.

should encompass at least 180 degrees of the tooth to enhance the resistance

extended as far as possible to provide maximum bonding area

should be a finish line which is placed about 1.0 mm supragingivally.


Occlusal clearance is needed on very few teeth: 0.5 mm is needed on maxillary incisors

Vertical stops are placed on all the preparations consisting of two or three flat countersinks on the lingual surface of an incisor, a cingulum rest on a canine or an occlusal rest seat on a premolar or molar .

Wilkes found rests to be the dominant feature in a preparation, contributing to both resistance and rigidi ty.98 The occlusal rest directs the applied force frorn the pontic to the abutments.

Barrack strongly recommends the use of two rests.


The resistance features used in a tooth preparation for an acid etched resin‑bonded retainer will normally be grooves

31% to 77% in study by saad etal and 81% in study by burgess et al found grooves were found to increase resistance to displacement on anterior preparations

If there is an existing amalgam, all of the amalgam, or at least all of its surface, is removed so that the box form can be utilized

BARRACK et al in his study proposed that the entire occlusal outline of the existing amalgam restoration is included within the outline of the retainer's occlusal rest.

HEMBREE et al in his study stated if the retainer margins cross over an amalgam‑enamel margin, there is a high probability of leakage occurring around that margin.


Preparation of anterior teeth

Centric occlusal contacts are marked with articulating paper. occlusal clearance and lingual reduction of 0.5 mm is done with small wheel diamond.end this reduction 1.5 -2.0 mm from the incisal edge or just incisal to the incisal most occlusal contact whichever is closer to the incisal edge


Counter sinks are placed Proximal reduction done in facial segment and

lingual segment.www.indiandentalacademy.co

m

Lingual axial reduction is done. Proximal groove and cingulum groove is placed


Preparation for a mandibular incisor and for maxillary canine


Preparation of posterior tooth The basic framework for the posterior resin

retained FPD consists of three major components: occlusal rest (for resistance to gingival displace

ment), retentive surface (for resistance to occlusal

displacement), and proximal wrap and proximal slots (for resistance to torquing forces


A spoon‑shaped occlusal rest seat is placed in the proximal marginal ridge area of the abutments adjacent to the edentulous space. An additional rest seat may be placed on the opposite side of the tooth .

Proximal and lingual axial surfaces are reduced to lower their height of contour to approximately 1 mm. from the crest of the free gingiva.

Proximal surfaces are prepared so that parallelism results Occlusally, the framework should be extended high on the

cuspal slope, well beyond the actual area of enamel recontouring

A single path of insertion should exist. The alloy framework should be designed to engage at least 180 degrees of tooth structure when viewed from the occlusal .


This proximal wrap enables the restoration to resist lateral loading by engaging the underlying tooth structure and is assisted in this re gard by grooves in the proximal just lingual to the buccal line angle. Distal to the edentulous space, the retainer resistance is augmented by a groove at the lingual proximal line angle.

Moving a properly designed resin‑bonded FPD in any direction except parallel to its path of insertion should,,not be possible, nor should it be possible to displace any tooth to the buccal from the framework


Preparation differs between maxillary and mandibular molar teeth only on the lingual sur faces. The lingual wall of the mandibular tooth may be prepared in a single plane. The lingual surface of the maxillary molars requires a two‑plane reduction due to occlusal function and the taper of these functional cusps in the occlusal two thirds.

Lingually inclined mandibular molars (this may require a two plane modification)


Preparation for maxillary premolar

Preparation for mandibular 2 premolar

Preparation for mandibular 1 premolar. Placement of rest seat would leave very little area in the lingual cusp of premolar lingual cusp coverage when it does not interfere in occlusion is an excellent means of incerasing surface area and reinforcing the retainer


Preparation for maxillary molar

Preparation for mandibular molar


Posterior resin bonded fixed partial denture framework configurations. Standard

2 grooves one near the facioproximal angle adjacent to the edentulous space and one at the opposite linguoproximal corner, with 180° of axial wall convergence.


Two rests : this variation suggested by barrack, has axial coverage on both proximal walls and teo rest seats located near the cetral groove at the mesioocclusal and distoocclusal. They resist displacement by occlusal forces


Loops : these features are formed by occlusal inlays being joined to a groove on a lingual or proximal surface. They brace the arms


Lingual cusp coverage: lingual cusps of mandibular molars and premolars can be covered to bolster the retainer againist deformation.

Tilted molars: mesial and particularly mesiolingual tipped molars are out of occlusion can be covered to improve occlusion and remove sublingual food traps.


Other design concepts Occasionally, a combination restoration can be used. This type of

FPD includes a resin‑bonded re tainer on one of the abutment teeth and a conven tional cast restoration on the other

Periodontal splinting is the most demanding of the restoration designs; splints and splint‑FPD combinations require care in designing adequate mechanical retention

The posterior FPD splint uses multiple rests and distinct mechanical retention of the abutment in the retainer, which can be important when the abutment is the most distal tooth in the arch

The anterior splint must engage as much enamel as possible to aid in retention and is more demand ing in tooth alignment and preparation design.


FRAME WORK FABRICATION

MASTER CAST DUPLICATION RESIN COPING FABRICATION WAX PATTERN INVESTING AND CASTING


MASTER CAST DUPLICATION


RESIN COPING FABRICATION



WAX PATTERN




INVESTING AND CASTING


Bonding Isolation of abutment teeth by

rubber dam

Tooth facing surfaces of retainers are air abraded using 30-50µm aluminium oxide. Wash the casting in running water for 1 min and place in dish washing detergent for 2 min in ultrasonic unit and then rinse. If noble alloys are used they must be tin plated.


Abutments are cleaned with pumice and rubber cup.

Etchant is applied to the teeth for 1 min and then rinsed of with water and the abutment teeth are dried.


Primer is applied onto the teeth leave it for 60 sec .

Resin pastes are dispensed and mixed over a wide area for 25 sec .


FPD is held in place for 60 sec. use a small brush to clean excess resin

Thin layer of mixed resin is applied to the retainers

OxyguardII is applied to protect the resin from exposure to oxygen


Post operative care Should be scrutinized at the regular recall examinations Early diagnosis and treatment of a partially debonded

prosthesis can prevent significant caries. Debonding is most commonly associated with biting or

chewing hard food. patients should be warned about this danger.

Attention to periodontal health is critical, because this retainer design has the potential to accumulate excess plaque as a result of lingual over contouring and the gingival extent of the margins

Calculus removal with hand instruments is recommended over ultrasonic scalers to reduce the chance of debonding.


Causes of failure1. Inappropriate patient selection Alignment of teeth results in a poor path of

insertion. Insufficient vertical length of abutment

teeth. Inadequate enamel for bonding. History of metal sensitivity. Labiolingual dimensions of abutments.


2.Incomplete tooth preparation. Insufficient proximal and lingual

surface reduction. Incomplete or less than 180°extension of

wraprounds.Lack of accomodation to mandibular

excursive movement (protrusive)3.Bonding Contamination Prolonged mixing. Inappropriate luting agent.


REVIEW OF TECHNIQUE Patient selection is generally limited to sound abutments with

minimal or no restorations. Occlusion must be stable. Tooth preparations consist of creating a large lingual bonding

area with proximal wrap; a definite, single path of insertion; occlusal , incisal or cingulam rest seats; and proximal grooves/ slots.

An accurate elastomeric impression material should be used. Careful laboratory technique is necessary to ensure a well

fitting and esthetic casting. Specially formulated resin luting agents that are capable of

adhering to metal should be used to bond the prosthesis.


SUMMARY Basic principles of tooth preparation is

conservation of tooth structure. This is the primary advantage of the resin

retained fixed partial dentures. A long lasting prosthesis can be provided if

restoration is carefully planned and fabricated. Careful patient selection is an important factor

in predetermining clinical successwww.indiandentalacademy.co

m


Date post:	01-Jul-2015
Category:	Education
Upload:	indian-dental-academy
View:	644 times
Download:	48 times

Resin bonded fpd/ academy general dentistry

Education