Effects of groove placement on retention/resistance of maxillary anterior resin-bonded retainers

Terminology focused on design and retention methods used for anterior resin-bonded fixed partial dentures in English literature: A scoping review

Purpose

Novel terms describing several designs of resin-bonded fixed partial dentures (RBFPDs) continue to appear. Indeed, a variety of terms are used in the English scientific literature The use of a standard terminology is important for a fair and efficient understanding. This study aimed to investigate if the terminology used to describe designs and retention methods for anterior RBFPDs is standard.

Methods

An electronic search in the English literature was conducted in PubMed/Medline to identify all publications reporting RBFPDs in the anterior region until August 2022. This search was completed by hand searching. Terms indicating different designs of RBFPDs were listed and then classified. Percentages of their use were calculated to determine the commonly used terms. Analysis of the use of these terms was performed based on the standards determined by the latest edition of the Glossary of Prosthodontic Terms (GPT). The impacts of the MeSH Thesaurus and GPT on the nomenclature used for RBFPDs was assessed.

Results

A total of 125 articles were eligible for this review. In the retained articles, 86 terms were found. Among them, thirty-nine terms were classified into three groups. Only six terms were defined in the latest edition of GPT (GPT-9). Several classified terms that are commonly used were not identified in the GPT-9. Conversely to the GPT-9 which impact was insignificant, the MeSH Thesaurus had an important impact on the nomenclature used for RBFPDs.

Conclusion

The terminology used to describe designs and retention methods for anterior RBFPDs was non-standard. The GPT-9, constituting an important reference, defined a limited number of terms related to RBFPDs and had no significant impact on the standardization of the terminology used for RBFPDs. Efforts should therefore be continued to standardize the terminology. A specialized mini-glossary grouping and defining all the terms found in this study will helpful in clarifying the terminology used for the anterior RBFPDs.

Comparative Evaluation of Stress Acting on Abutment, Bone, and Connector of Different Designs of Acid-Etched Resin-Bonded Fixed Partial Dentures: Finite Element Analysis

Background: Finite element analysis (FEA) is one of the best methods for evaluating the stress distribution of restorations, such as fixed partial dentures. The development of resin cement has transformed prosthesis bonding and retention properties. Resin-bonded fixed partial dentures (RBFPD) have been considered minimally invasive treatment options for the prosthetic rehabilitation of single missing teeth.

Objectives: The aim of this study was to evaluate the stress load and distribution in four different designs of acid-etched RBFPDs using FEA.

Materials and Methods: The designs included standard tooth preparation principles and additional features. The first premolar and first molar abutments replaced the missing second premolar. Designs 1, 2, 3, and 4 included (1) lingual wings and occlusal rests; (2) wings and proximal slices; (3) wings, rests, and grooves; and (4) wings, rests, grooves, and occlusal coverage. The prepared models were restored with RBFPDs. A load of 100 N was applied to the central groove of the pontic to simulate occlusal forces. The materials used in the models were considered to be isotropic, homogeneous, and linearly elastic. FEA was used to reveal stresses acting on the abutment, bone, and connector in all prosthesis designs.

Results: The stresses transmitted to the abutment and bones were lowest for design 3, using wings, rests, and grooves. The stresses acting on the connector were the weakest in design 2. The stresses transmitted to the abutment and bone were highest in designs 1 and 4. The stresses transmitted to the connector were highest in design 3.

Conclusion: The wings, rests, and grooves design is possibly the ideal and conservative tooth preparation design to receive a posterior RBFPD. This design transmits less stress to the abutments and less bone resorption in the FEA. It is most likely to be successful in the clinical provision and ensures the longevity of the prosthesis.

Increased Stress Concentration in Prosthesis, Adhesive Cement, and Periodontal Tissue with Zirconia RBFDPs by the Reduced Alveolar Bone Height

PURPOSE

To investigate the risk of debonding of resin-bonded fixed dental prosthesis frameworks and the effects on the periodontal tissue in patients with reduced alveolar bone levels.

MATERIALS AND METHODS

The abutment teeth were the upper central incisor and the canine. Resin-bonded fixed dental prosthesis framework fabricated using zirconia was set to models with five different alveolar bone levels. A 200-N load (the maximum clenching force of the anterior teeth) was applied to the center of the pontic to analyze the internal stress on the framework, adhesive cement, and periodontal tissue using finite element analysis.

RESULTS

The mean maximum principal stress generated in the framework was 25.33 and 29.35 MPa in the models with the normal and the lowest alveolar bone level, respectively. Regarding shear stress on the adhesive cement, stress concentration was observed on the connector side in all models, and it increased on the cervical side of the central incisor as the alveolar bone level decreased. In addition, the mean maximum and minimum principal strains generated on the periodontal ligament of the central incisor and canine tended to increase as alveolar bone loss progressed. Furthermore, the mean maximum principal stress on the cortical bone was the greatest in the model with the most significant bone loss at 5.10 MPa.

CONCLUSIONS

This study suggested that the risk of debonding and periodontal tissue damage might be higher when resin-bonded fixed dental prosthesis frameworks were used in patients with reduced alveolar bone levels compared to those in a healthy state.

Strain analysis of anterior resin-bonded fixed dental prostheses with different thicknesses of high translucent zirconia

Background/purpose

High translucent zirconia has been used as a new monolithic zirconia prosthesis, which has the potential to make anterior resin-bonded fixed dental prostheses (RBFDPs) without veneering porcelain. However, it is unclear whether the RBFDPs retainer can be thinned as much as conventional zirconia RBFDPs. The aim of this study was to assess the usability of high translucent zirconia RBFDPs with a thin retainer thickness by evaluating differences in retainer thickness on the surface strain.

Materials and methods

A model with a missing upper lateral incisor was used. The abutment teeth were upper central incisor and canine. Three types of RBFDPs were fabricated as follows: metal RBFDPs with a retainer thickness of 0.8 mm (0.8M), and high translucent zirconia RBFDPs with a retainer thicknesses of 0.8 and 0.5 mm (0.8Z, 0.5Z) (n = 10). The fitness of the margins was evaluated by the silicone replica technique. The surface strain of each retainer under static loading was measured and statistically analyzed using a t-test with Bonferroni correction.

Results

The marginal fitness of all RBFDPs was under 76.1 μm, which was clinically acceptable. Each strain of the 0.8Z and 0.5Z groups was significantly lower than that of the 0.8M (p < 0.05). There was no difference in strain of the zirconia RBFDPs even if the retainer thickness was changed.

Conclusion

Our results suggest that the high translucent zirconia RBFDPs can be manufactured with a retainer thickness of 0.5 mm, which reduces the amount of tooth preparation compared to the metal RBFDPs.

Functionally Orientated Tooth Replacement for Older Patients

Across the globe the population is ageing. In addition, older patients are retaining increasing numbers of natural teeth into old age. Therefore, clinicians are faced with the challenges of managing chronic dental diseases, including caries and periodontal disease, alongside replacing missing units. A number of treatment options are available to replace missing teeth for such patients with large numbers currently receiving removable partial dentures. Alternative approaches to treatment should be considered for this population group, including functionally orientated tooth replacement according to the principles of the shortened dental arch concept. In correctly chosen cases, this approach can provide patients with an acceptable, functional and aesthetic reduced dentition. Additionally, evidence suggests that such an approach can significantly reduce the maintenance burden for patients and clinicians which can ultimately deliver a more cost effective solution compared to removable alternatives.

Biomechanical behavior of adhesive cement layer and periodontal tissues on the restored teeth with zirconia RBFDPs using three-kinds of framework design: 3D FEA study

PURPOSE

To investigate stress and strain concentrations on resin-bonded fixed dental prostheses (RBFDPs) frameworks of different design using finite element analysis.

METHODS

A human dry skull was scanned and models were produced using three-dimensional printer. After abutment preparation, three frameworks, including a three-unit RBFDP, and two-unit cantilevered RBFDPs using #21 and #23 for the abutment tooth, were fabricated. Scanned data were subtracted to define boundary of each structure. Occlusal force (200N) was loaded at 45° to long axis of the pontic. The distributions of shear stress and principal strain in the RBFDP models were measured to evaluate the risk for framework-debonding from the abutment teeth and the impact on periodontal tissue.

RESULTS

The percentage voxels with shear stress >11MPa in adhesive cement layer of three-unit RBFDP using #21 and #23 were 4.16% and 2.25%, respectively; in two-unit cantilevered RBFDPs, it was 19.25% using #21, and 23.4% using #23. The maximum principal strain on periodontal ligaments in two-unit cantilevered RBFDPs using #21 was the largest, and smallest in the three-unit RBFDP. The maximum principal strain in framework was largest in the two-unit cantilevered RBFDP using #23, and smallest in the three-unit RBFDP.

CONCLUSIONS

The risk for framework-debonding in three-unit RBFDPs was substantially lower than that in two-unit RBFDPs. In difficult cases with indication for three-unit RBFDPs, two-unit cantilever design using the canine would be more advantageous for preservation of periodontal tissue, while for risk of framework-debonding, the design using the central incisor would be more advantageous.

Modified PEEK resin-bonded fixed dental prosthesis as an interim restoration after implant placement

A polyetheretherketone (PEEK) (BioHPP) framework veneered with composite resin was used as an alternative material for the fabrication of an interim 3-pontic resin-bonded fixed dental prosthesis (RBFDP) after implant placement. The low modulus of elasticity (4 GPa) of PEEK combined with the use of indirect light-polymerized resin as a veneering material used for a RBFDP provided an advantage over metal ceramics or ceramics in dampening the occlusal forces and reducing debonding rates. Further long-term clinical evidence is required before recommending the application as a substitute material.

Resin-Bonded Bridges--Can We Cement Them 'High'?

Controversy exists surrounding resin-bonded bridges (RBBs), particularly with regards to abutment preparation. Should the abutments be prepared? If the abutments are prepared what design should be adopted? If there is to be no preparation, will there be space for the restoration? Many factors need consideration when planning for this treatment. This article aims to explore the effect of abutment preparation. In this regard, a literature review was conducted to present the latest available evidence. CPD/Clinical Relevance: Minimal intervention is key in modern dentistry, so clinicians must be able to make confident decisions in the provision of minimally invasive treatments like the RBB and be aware of the latest evidence.

Restoring Congenitally Missing Maxillary Lateral Incisors Using Zirconia-Based Resin Bonded Prostheses

OBJECTIVE

This clinical report describes an alternative treatment modality for the replacement of congenitally missing maxillary lateral incisors in a 17-year-old patient.

CLINICAL CONSIDERATIONS

Zirconia-based resin-bonded fixed partial dentures (RBFPDs) were selected as a viable and conservative treatment option in a young individual with highly aesthetic expectations. Fabrication of all-ceramic RBFPDs followed specific preparation design and features to accommodate two retainers. The zirconia frameworks with bilateral wings were digitally designed and then milled by a computer-aided design and computer-aided manufacturing (CAD/CAM)-controlled milling machine. Zirconia surface was treated with a two-step chairside tribochemical silica-coating/silane coupling surface treatment protocol, and adhesive resin luting cement was used to achieve micromechanical and chemical bonding. Completion of the treatment resulted in a functional and aesthetic successful outcome and a 17-month follow-up presented uneventful.

CONCLUSION

Contemporary adhesive techniques involving resin-bonded zirconia-based prostheses can be utilized successfully and predictably in young patients with single missing teeth when implant therapy is currently not a treatment of choice and a less invasive approach is desired.

CLINICAL SIGNIFICANCE

The zirconia-based resin-bonded prosthesis constitutes a viable and conservative treatment modality for the replacement of missing teeth either congenitally or from another etiology in young patients in which implant therapy and a fixed partial denture are currently contraindicated.

The use of newer high translucency zirconia in aesthetic zone

Loss of anterior tooth causes aesthetic and functional disharmony. Although no restorative material can approach the appearance of intact tooth enamel, glass ceramic, at the increased risk of brittle fracture, can mimic original tooth color better than the other restorative options. The newest zirconia material comes with unparalleled individualization in aesthetics and optimal physical properties. One of the basic principles of tooth preparation is conservation of tooth structure. This clinical report describes the replacement of maxillary and mandibular incisor with latest generation zirconia adhesive fixed partial denture. The authors have achieved unmatched aesthetics with newer high translucency zirconia.

Evaluation of shear bond strength of composite resin bonded to alloy treated with sandblasting and electrolytic etching

Conservation of natural tooth structure precipitated the emergence of resin-retained fixed partial dentures. The weakest link in this modality is the bond between resin cement and alloy of the retainer. Various alloy surface treatment have been recommended to improve alloy-resin bond. This in vitro study was carried out to observe changes in the Nickel-Chromium alloy (Wiron 99, Bego) surface following sandblasting or electrolytic etching treatment by scanning electron microscope (SEM) and to evaluate the shear bond strength of a resin luting cement bonded to the surface treated alloy. 80 alloy blocks were cast and divided into four groups of 20 each. In groups-A & B, the test surfaces were treated by sandblasting with 50 and 250 μm sized aluminium oxide particles respectively. In groups-C & D, the test surfaces were first treated by sandblasting with 50 and 250 μm sized aluminium oxide particles respectively followed by electrolytic etching. Test surfaces were observed under SEM at 1,000× magnification. Two alloy blocks of each group were luted together by a resin luting cement (Rely X, 3M) and their shear bond strength was tested. The mean shear bond strength in MPa of groups-A to D were 6.44 (±0.74), 8.18 (±0.51), 14.45 (±0.59) and 17.43 (±1.20) respectively. Group-D showed bond strength that is more than clinically acceptable bond strength. It is recommended that before luting resin-retained fixed partial dentures, the fitting surface of the retainer should be electrolytically etched to achieve adequate micromechanical retention.

Effect of framework design on the surface strain of zirconia fixed partial dentures

The purpose of this study was to evaluate the design of resin-bonded fixed partial dentures (RBFPDs) with zirconia frameworks. The abutment teeth were the upper central incisor and the canine. Three types of frameworks were fabricated as follows: 0.5-mm- and 0.8-mm-thick zirconia frameworks with grooves and holes (0.5ZrG, 0.8ZrG) and 0.5-mm-thick zirconia frameworks without grooves and holes (0.5Zr). The control group was designed as a 0.8-mm-thick metal framework with grooves and holes (0.8MG). Static loading was applied and the surface strain of the retainers was measured with strain gages. The magnitude of the principal strain of the 0.5ZrG framework was significantly lower than that of the 0.8MG and the 0.5Zr frameworks. This result suggests that the zirconia and retention form had a significant effect on decreasing the framework deformation, indicating that the RBFPDs that use a 0.5-mm thick zirconia framework are effective for replacing a single anterior missing tooth.

Comparative evaluation of retentive properties of acid etched resin bonded fixed partial dentures

BACKGROUND

Little consensus exist in suitable tooth preparation design and alloy pre-treatment methods for improving the retention of resin bonded fixed partial dentures (RBFPDs).

METHODS

An in-vitro experiment was done with four designs. Group A: standard form, B: wings and proximal slices, C: wings, proximal slice and grooves, D: wings, proximal slice, grooves and occlusal coverage. Alloys were subjected to pre-treatment procedures like Group I: control, II: sand blasting, III: electro etching, IV: tin plating. Debonding forces of the castings were recorded in a universal testing machine and results were analyzed by student's 't' test.

RESULTS

Group B, C and D showed higher debonding forces compared to A. However, there were no significant differences in mean force values among Groups B, C and D. Group II, III and IV with different alloy pre-treatment methods demonstrated higher values against control. Inter group variations among Group II, III and IV were not significant.

CONCLUSION

Tooth preparation with adequate surface extensions and pre-treatment procedures of casting alloys are two parameters that play important role in determining the retentive features of RBFPDs. Different types of tooth preparation designs and alloy pre-treatment methods exert almost similar influence in increasing the retention of acid etched RBFPDs.

NUMERICAL INVESTIGATION OF SPAN LENGTHS AFFECTING MECHANICAL RESPONSES IN ANTERIOR RESIN-BONDED FIXED PARTIAL DENTURE

The geometric shape and mechanical structure of RBFPD compared to conventional FPD are relatively complex and unstable. The low retention rate between the retainer and abutment affects the prosthesis/abutment interface de-bonding, and closely relates to the design of the prosthesis and varied occlusion status. This study used reverse engineering (RE) and computer-assisted design (CAD) to construct two solid models of anterior RBFPD with different span lengths. After mesh generation, biomechanical interactions of span length in RB prosthesis with two loading conditions (axial and lateral) were performed by FE analysis. The simulated results indicated that lateral occlusal force increased significantly 2-3 times maximum stress than that of axial occlusal force. For different span lengths simulation, the analysis on static movement finds that longer pontic would lead to high stress to the prosthesis. Thus, the length of the pontic has significant effect on the overall intensity of the prosthesis under static clenching loading, and the effect of lateral loading exceeds that of axial loading.

Evaluation of the effects of different groove length and thickness of the retainers on the retention of maxillary anterior base metal resin bonded retainers-an in vitro study

Objectives: The resin-bonded fixed partial dentures have gained immense popularity in recent years as they are more conservative, esthetic, economic and easily fabricated. However debonding is considered the most common cause of failure of resin bonded prosthesis. The objective of the study were to compare the effects of different groove lengths and thickness of retainers on retention of maxillary anterior base metal resin bonded retainers. Study Design: Twenty five metal dies of maxillary central incisor duplicated from pure typhodont teeth (maxillary left central incisors) prepared to receive retainer for resin bonded fixed partial denture having different test designs were made. Five test groups were made with each group having five specimens. Two groups were having preparation depth of 0.5mm and retention groove lengths of 3mm and 5mm. Two groups had preparation depths of 0.3 and 0.7mm with no groove preparation with retainer thickness of 0.3 and 0.7mm respectively. Fifth group with no groove preparation and preparation depth of 0.5mm was kept as control for all the groups. All the specimens were cemented using calibra (Dentsply) resin cement. Each specimen was subjected to tensile loading in vertical direction on universal testing machine (Instron 5569) at a crosshead speed of 1mm/min. \ Results: Groups with 5mm and 3mm groove length recorded higher mean vertical forces when compared to the group with no groove preparation. Group with 5mm groove length showed highest mean vertical forces. The group with 0.7mm retainer recorded higher mean vertical force values when compared to groups with 0.5mm and 0.3mm retainer thickness. Group with 0.3mm retainer thickness recorded the least mean vertical force value. Conclusion: Placement of the grooves increased the retention values almost 2 ½ times than the grooveless preparation and as the thickness of the retainers increased retention values also increased. Retention value was directly proportional to the groove length and retainer thickness.

Key words:Groove length, retainer thickness, resin bonded bridges.

Improved retention of anterior cantilever resin-bonded prostheses by design alteration: an experimental and finite element study

STATEMENT OF PROBLEM

Anterior cantilever resin-bonded prostheses fail as a result of a labio-lingual peeling action, which creates a stress concentration within the adhesive layer.

PURPOSE

The purpose of this study was to identify the factors that determine the retention of an anterior resin-bonded prosthesis and to seek to eliminate the stress concentration within the adhesive layer by fundamentally altering the prosthesis design.

MATERIAL AND METHODS

The first experiment involved 40 Ni/Cr (Wiron 99) beams with a width of 5 mm, thickness of 0.5 mm, and lengths ranging from to 13 to 22 mm. The beams were cemented onto a block of the same material using an adhesive resin luting agent (Panavia 21). The length of the beam that was bonded ranged from 1 to 10 mm, resulting in a bonded area ranging from 5 to 50 mm(2). A load was applied onto the cantilevered portion of the beam 2 mm from the end, causing a peeling action. The force (N) required to debond these beams was measured using a pull-to-fracture test. Subsequently, a second experiment was undertaken, and 7 beams with an altered point of attachment (new design) were tested. The new design had the point of attachment of the cantilevered portion located centrally on the bonded area of the beam. Implementing this new design clinically would result in a cantilevered resin-bonded fixed partial denture that would have the connector arm attached more centrally on the retainer wing. The data were analyzed using a 1-way analysis of variance (alpha = .05), and a Tukey pairwise comparison test was used when the results was statistically significant. Two finite element analysis (FEA) models, one simulating the first experimental design and the other simulating the new design, were created. A load was then applied on the cantilevered portion of the beams similar to the experimental models, and the stress patterns were examined. The numerical values of these resultant stresses were plotted graphically.

RESULTS

The direction of load application, which may be transferred to a clinical setting as labio-lingual forces, was identified as the dominant force responsible for debonding. The new design, which addressed this problem, showed a significant increase (P < .001) in retention. The FEA models identified the stress concentrations within the adhesive layer of the traditional design, which were eliminated when the new design was tested.

CONCLUSIONS

For the in vitro model, loads that may be interpreted clinically as labio-lingual forces resulted in the lowest forces required to cause debonding, and these forces were independent of the surface area of bonding. Altering the point of attachment of the cantilevered portion onto the retainer caused a significant increase in the forces needed to cause debonding.

Replacement of two mandibular central incisors using a zirconium resin-bonded fixed partial denture: A clinical report

Maxillary and mandibular anterior tooth loss may cause esthetic and functional problems. Successful treatment for these situations may necessitate a minimally invasive technique to preserve sound remaining abutment tooth structure. This article describes the use of zirconium resin-bonded fixed partial denture as a conservative treatment option for the replacement of 2 mandibular central incisors.

Multi-factorial retainer design analysis of posterior resin-bonded fixed partial dentures: a finite element study

OBJECTIVES

Biomechanical aspects related to prosthesis design of RBFPD have been proposed as the predominant contributor to unpredictable clinical retention. The aim of this study was to investigate the biomechanics of multiple posterior retainer designs and their interactions using three-dimensional finite element analysis.

METHODS

To understand the interactions among the retainer design factors, three values of retainer thicknesses (1.2, 0.8 and 0.4mm), heights (100, 75 and 50% of the distance from 2mm above the CEJ to the occlusal surface) and angle of the axial surface extensions (150, 180 and 210 degrees ) were selected as the design parameters. Twenty-seven RBFPD FE models with three retainer-design parameters were created by image processing, contour stacking, and mapping mesh procedures. The maximum principal and von Mises stresses in remaining tooth and prosthesis, respectively, were recorded in 54 FE analyses (27 FE models with axial and lateral occlusal loadings).

RESULTS

The simulated results showed that the averaged stress values of the remaining tooth and prosthesis decreased with greater retainer thickness and height as a result of increasing prosthesis stiffness and maximizing of the bonding area between the enamel and the retainer, respectively. However, no significant stress differences were found according to the angle of the retainer extension because stress transmission was concentrated at the connectors.

CONCLUSIONS

The stress elevation rate (termed as VSR-stress elevation by decreasing one unit volume of the remaining tooth) addresses that the height was the most influential factor for the remaining tooth structure, followed by retainer thickness and extension angle.

Effect of groove placement on the retention/resistance of resin-bonded retainers for maxillary and mandibular second molars

STATEMENT OF PROBLEM

Lack of retention/resistance form in the clinical preparation of teeth for resin-bonded retainers may lead to clinical failure.

PURPOSE

This study investigated the effect of proximal grooves on the retention/resistance of cast resin-bonded retainers for maxillary and mandibular second molar teeth.

MATERIAL AND METHODS

Two ivorine teeth (a maxillary and a mandibular second molar) were prepared for resin-bonded retainers. Twenty metal replicas of the prepared teeth were made (10 for each tooth morphotype). Resin-bonded retainers 0.5 mm thick were made for the 40 replicas and luted with Panavia EX cement. Forces for dislodgment of the retainers were applied along the long axes of the teeth. Forces recorded at the time of dislodgment were analyzed with 2-way analysis of variance and the post hoc Scheffé test.

RESULTS

Grooves resulted in substantial increases in debonding forces for maxillary molars (P<.001). The effect of grooves on mandibular second molars was not significant (P=.13).

CONCLUSION

Grooves placed in tooth preparations of maxillary molar teeth for resin-bonded retainers had a significant effect on retention/resistance. The effect of grooves on mandibular second molars was less pronounced.

Management of missing maxillary lateral incisors

BACKGROUND

Missing maxillary lateral incisors create an esthetic problem with specific orthodontic and prosthetic considerations. The purpose of this article is to describe treatment protocols and problems encountered in the management of this disorder.

CASE DESCRIPTION

The two common treatment options are orthodontic space opening for future restorations or orthodontic space closure using canines to replace the missing maxillary lateral incisors. The required amount of space opening and the various prosthetic options are discussed. The methods for reshaping canines in orthodontic space closure and building them up to simulate lateral incisors also are described. The indications, advantages and disadvantages of both treatment modalities are outlined to help clinicians make decisions in borderline situations.

CLINICAL IMPLICATIONS

Teamwork between the orthodontist, general practitioner and restorative dentist is important when analyzing factors related to individual patients and establishing overall treatment plans. This also will allow treatment modalities and the various options for replacing missing maxillary lateral incisors in space opening to be discussed between team members and the patient.

Bond strengths of maxillary anterior base metal resin-bonded retainers with different thicknesses

PURPOSE

This study evaluated the effect of three different thicknesses of base metal resin-bonded retainers on retention/resistance.

MATERIAL AND METHODS

Three ivorine teeth, a central incisor, lateral incisor, and canine, were prepared to receive resin bonded retainers. Fifteen metal replicas of prepared teeth were made (five for each tooth morphotype). A total of 45 metal retainers were cast in three different thicknesses, 0.3, 0.5, and 0.7 mm, with 15 for each thickness. Retainers were cemented to metal die replicas with Panavia EX luting agent. After 24 hours, forces to dislodge the retainers were applied at 45 degrees to the vertical mesiodistal plane at the proximolingual line angle.

RESULTS

An increase in thicknesses resulted in elevation of dislodging forces that were almost linear for the three thicknesses of canine retainers. The central incisor exhibited the greatest increase in resistance to dislodgment between retainers that were 0.3 and 0.5 mm thick, whereas increased thickness for the lateral incisor retainer resulted in minimal or no benefit.

Resin-bonded fixed partial dentures: a review of three decades of progress

The resin-bonded fixed partial denture has undergone significant changes in design, materials and tooth preparation since its development in 1973. The selection of resin cement and micromechanical retention have closely paralleled alloy-resin-bonding research. Despite impressive in vitro research results, only 74 percent of the prostheses are still functional at the end of four years. Understanding the limitations, indications and design of resin-bonded fixed partial dentures will result in improved longevity and patient satisfaction.