Predictability of resin bonded bridges – a systematic review

Autotransplantation of Premolars to the Anterior Maxilla: A Long-Term Retrospective Cohort Study of Survival, Success, Esthetic, and Patient-Reported Outcome With up to 38-Year Follow-Up

BACKGROUND/AIM

Autotransplantation is a well-documented procedure for replacing missing teeth in the anterior maxilla. This retrospective study aims to evaluate long-term survival rate, success rate as well as esthetics and patient-reported outcome of premolars autotransplanted to the anterior maxilla and secondarily to identify potential prognostic factors for survival, success, esthetic, and biological complications.

MATERIAL AND METHODS

One hundred and twenty-two patients with 153 transplants were assessed on survival rate and potential prognostic factors, while 50 patients with 61 autotransplanted premolars underwent clinical, radiographic, and esthetic assessment. Clinical and radiographic parameters were recorded. Esthetic outcomes were evaluated using a comprehensive score system comparing transplanted teeth to neighboring tooth. All patients filled in a questionnaire about the esthetic outcome of the treatment.

RESULTS

The survival rate of transplants after 16-38 years was 76%, with the majority showing no periodontal complications (95%). Radiographically, 46% of transplanted premolars showed no signs of pathosis. Ankylosis and inflammatory resorption were observed in 19% and 16%, respectively. Prognostic factors such as donor tooth type and root stage did not significantly affect transplant survival. Premolars transplanted at an immature stage had a significant lower risk of ankylosis, compared to more mature transplants. Esthetically, 72% of the transplants matched their neighboring teeth, and taking the biological success into consideration an overall success rate was 57.3%. In total, 71% of all patients were esthetically satisfied with their autotransplant, 18% were fairly satisfied, and 11% were dissatisfied.

CONCLUSIONS

The transplants demonstrated high survival rate, albeit with biological complications such as ankylosis and inflammatory root resorption. Developmental stage of the root at the time of transplantation had a significant influence on ankylosis of transplanted teeth. Esthetic outcomes were generally satisfactory, although challenges were noted with certain restoration types and donor tooth selections. Overall, the majority of patients expressed satisfaction with their autotransplanted teeth.

Corrections of Dental Anomalies in the Maxillary Incisors and Their Influence on Perceived Smile Esthetics: A Systematic Review

INTRODUCTION

Dental anomalies present a significant challenge to clinicians due to their impact on both dental function and esthetics. The correction of these anomalies plays a critical role in improving the quality of life of our patients, highlighting the importance of this restorative work.

OBJECTIVE

The purpose of this systematic review is to assess the techniques used to restore various dental anomalies, and their subsequent esthetic impact on the overall dentition.

METHODS

Inclusion criteria consisted of restorative rehabilitations of the permanent dentition in non-syndromic patients with dental anomalies of morphology, structure, size, and number in the maxillary incisors. Exclusion criteria included surgical rehabilitation techniques, endodontic treatments, and anomalies of the primary dentition. The medical literature was systematically searched (Pubmed, PMC, Embase, Cochrane Central Register of Controlled Clinical trials, Scopus and Google Scholar) to identify all relevant articles reporting data regarding the chosen anomalies. ROBINS-I was used to assess the risk of bias tool, and the results were tabulate due to data heterogeneity.

RESULTS

Of the 1821 analyzed articles, 46 articles met the inclusion criteria, and were chosen to go through the final review procedure. Of the selected articles, 3 investigated amelogenesis imperfecta and dentinogenesis imperfecta, 1 analyzed conoid teeth, 1 considered hypodontia (other than MLIA), 3 concerned microdontia (excluding peg laterals and conoid teeth), 10 evaluated peg-shaped laterals, 2 investigated talon cusps and geminated teeth, 15 were regarding maxillary lateral incisor agenesis, and 11 papers were related to the perception of anomalies.

CONCLUSIONS

Pre-visualization using Digital Smile Design, a treatment plan encompassing minimally invasive restorations, and using a multidisciplinary approach among practitioners helps the anomalous patient achieve the best possible esthetic result.

Long-term complications and management of dental trauma in the adult patient - Part 2: discoloured, displaced and missing teeth

The second paper in this two-part review series aims to outline the long-term complications of dental trauma in the adult patient in relation to discoloured, displaced or missing teeth. A brief overview of the cause of discolouration is outlined, followed by assessment and management options. These can include bleaching, veneers, or crown restorations to mask the discolouration. Displacement of teeth from the socket can occur due to luxation injuries. Management can include simple digital manipulation, surgical repositioning, or orthodontic extrusion based on the severity of extrusion and the time from injury. Teeth can be lost early or in the long-term following dental trauma and associated hard and soft tissues deficiencies may also ensue. Replacement options can include a removable partial prosthesis, resin-retained bridge or dental implants. Often, hard and soft tissue augmentation procedures may be required to address any defects and rebuild lost anatomical contours. A thorough assessment followed by the development of a sound management plan which takes patients' general and local factors into account can ensure a predictable and successful treatment outcome. This would end in an aesthetically pleasing and a functionally stable result for the patient.

Shear Bond Strength of Simulated Single-Retainer Resin-Bonded Bridges Made of Four CAD/CAM Materials for Maxillary Lateral Incisor Agenesis Rehabilitation

OBJECTIVES

 Maxillary lateral incisor agenesis (MLIA), treated orthodontically by space opening, requires complimentary aesthetic rehabilitation. Resin-bonded bridges (RBBs) can be equated as interim rehabilitation until skeletal maturity is achieved to place an implant-supported crown or as definitive rehabilitation in case of financial restrictions or implant contraindications. Scientific evidence of the best material must be confirmed in specific clinical situations. Computer-aided design and computer-aided manufacturing (CAD/CAM) materials are promising versatile restorative options. This study aimed to identify a straightforward material to deliver interim or definitive RBBs for nonprepared tooth replacement in MLIA.

MATERIALS AND METHODS

 Single-retainer RBB made from CAD/CAM ceramic blocks (Vita Enamic [ENA], Suprinity [SUP], and zirconia [Y-ZPT]) and a three-dimensional (3D) printed material (acrylonitrile butadiene styrene [ABS]) were evaluated by shear bond strength (SBS) and mode of failure, after adherence to an artificial tooth with RelyX Ultimate used in a three-step adhesive strategy.

STATISTICAL ANALYSIS

 The load to fracture (N) was recorded, and the mean shear stress (MPa) was calculated with standard deviations (SD) for each group and compared between materials using boxplot graphics. One-way analysis of variance (ANOVA) followed by the Tukey-Kramer post hoc test was used to compare the differences (α = 0.05). A meta-analysis focusing on CAD/CAM materials evaluated the magnitude of the difference between groups based on differences in means and effect sizes (α = 0.05; 95% confidence interval [CI]; Z-value = 1.96). Failure mode was determined by microscopic observation and correlated with the maximum load to fracture of the specimen.

RESULTS

 The mean ± SD SBS values were ENA (24.24 ± 9.05 MPa) < ABS (24.01 ± 1.94 MPa) < SUP (29.17 ± 4.78 MPa) < Y-ZPT (37.43 ± 12.20 MPa). The failure modes were mainly adhesive for Y-ZPT, cohesive for SUP and ENA, and cohesive with plastic deformation for ABS.

CONCLUSION

 Vita Enamic, Suprinity, Y-ZPT zirconia, and 3D-printed ABS RBBs are optional materials for rehabilitating MLIA. The option for each material is conditioned to estimate the time of use and necessity of removal for orthodontic or surgical techniques.

Creating space for a resin-bonded fixed partial denture retainer by using the Dahl concept

A technique is presented for creating interocclusal space for a resin-bonded fixed partial denture retainer by applying the Dahl concept. A missing mandibular first molar was replaced with a cantilevered resin-bonded fixed partial denture and had been successfully retained at the 9-year clinical review.

Biomechanical reinforcement by CAD-CAM materials affects stress distributions of posterior composite bridges: 3D finite element analysis

OBJECTIVES

This 3D finite element analysis study aimed to investigate the effect of reinforcing CAD-CAM bars on stress distribution in various components of a posterior composite bridge.

METHODS

A virtual model mimicking the absence of an upper second premolar was created, featuring class II cavity preparations on the proximal surfaces of the adjacent abutment teeth surrounding the edentulous space. Five distinct finite element analysis (FEA) models were generated, each representing a CAD-CAM reinforcing bar material: 3-YTZP (IPS. emax ZirCAD MO; Zr), lithium disilicate (IPS e.max CAD; EX), nano-hybrid resin composite (Grandio Blocs; GB), Fibre-reinforced composite (Trilor; Tri), and polyetheretherketone (PEEK). A veneering resin composite was employed to simulate the replacement of the missing premolar (pontic). In the FEA, an axial force of 600 N and a transverse load of 20 N were applied at the center of the pontic. Subsequently, maximum von Mises (mvM) and maximum principal stresses (σmax) were computed across various components of the generated models. Additionally, shear stresses at the interface between the CAD-CAM bars and the veneering resin composite were determined.

RESULTS

CAD-CAM materials with high modulus of elasticity, such as Zr and EX, exhibited the highest mvM stresses and shear stresses while transferring the lowest stress to the veneering resin composite in comparison to other materials. Conversely, PEEK demonstrated the lowest mvM stresses but produced the highest stresses within the veneering resin composite. There was a uniform distribution of mvM stresses in the remaining tooth structure among all groups, except for a noticeable elevation in the molar region of Zr and EX groups.

SIGNIFICANCE

Reinforcing CAD-CAM bar materials with a high modulus of elasticity, such as Zr and EX, may result in debonding failures at the connector sites of posterior composite bridges. Conversely, GB, PEEK, and Tri have the potential to cause fracture failures at the connectors rather than debonding.

Effect of a novel mesh design and the sandblasting technique on the bond strength of computer-designed and three-dimension laser printed resin bonded bridges: an in vitro study

Resin-bonded bridges (RBBs) are a minimally invasive and aesthetically pleasing treatment modality. However, their frequent failure has posed challenges for both dental professionals and patients. This necessitates the exploration of innovative strategies to enhance the longevity of RBBs. This study aimed to assess the bond strength of a mesh bridge fabricated using computer-aided design and three-dimensional (3D) printing technology in comparison to the traditional aluminum oxide sandblasting method. A total of 48 lower incisors were embedded in acrylic bases according to a standardized computer-generated model to receive 24 metal RBBs. The two groups underwent distinct metal surface treatments: the 3D mesh novel design and sandblasting with aluminum oxide particles sized at 250.00 µm. The bond strength of the bridges was evaluated, and statistical analysis was performed using the independent samples t-test with a significance level set at α = 0.05. The findings revealed a significant difference between the two methods (p < 0.001). The 3D mesh design exhibited a mean bond strength of 387.89 ± 24.15 N, while the sandblasting technique yielded a mean value of 161.46 ± 31.25 N. In summary, the 3D mesh design substantially enhanced the bond strength of RBBs compared to the traditional sandblasting technique.

Rehabilitation of Congenitally Missing Bilateral Incisors With the Maryland Bridge: A Case Report

Congenital partial hypodontia is a commonly encountered disorder, presenting a challenge for adolescents seeking treatment, as existing options often come with drawbacks. Among these options, the Maryland Bridge stands out for its accessibility and notable benefits in terms of both strength and aesthetics. This article explores the merits of this treatment modality, supported by a detailed case study demonstrating its successful application. An 18-year-old patient was referred to our hospital with a complaint of missing bilateral maxillary incisors. Upon clinical examination, it became apparent that the orthodontic treatment was done and exhibited the absence of bilateral incisors in the upper arch. Subsequent diagnosis confirmed congenital partial hypodontia. To address the missing teeth, a treatment plan centered around the use of a Maryland Bridge was devised. One of the persistent challenges faced by restorative dentists is devising solutions for congenitally missing lateral incisors. Despite the availability of numerous therapeutic alternatives, none are without their limitations. However, the outcome of the rehabilitation in this case proved to be notably aesthetically pleasing, effectively fulfilling the intended purpose. As a result, this article advocates for the Maryland Bridge as a viable option for patients facing similar dental challenges.

Resin-bonded fixed dental prosthesis versus implant-supported single crowns in the anterior region

BACKGROUND

Different treatment options exist for replacement of an anterior tooth, and as implant-supported single crowns (ISSC) and resin-bonded fixed dental prosthesis (RBFDPs) both are widespread treatment options, it is of clinical relevance to know which treatment modality can be considered superior.

PURPOSE

The purpose of this comparative study was to evaluate the 3- and 5-year survival and failure rate of tooth-supported resin-bonded fixed dental prosthesis compared to implant-supported single crowns. The null hypothesis was that there was no significant difference in survival rate, occurrence of complications or patient-reported outcome between RBFDPs and ISSCs.

MATERIALS AND METHODS

A total of 45 resin-bonded FDPs were inserted in 27 young patients (test group) with tooth agenesis in the anterior part of the maxilla or mandible and a control group of 28 patients also with tooth agenesis in the anterior region but treated with 40 implant-supported single crowns were included in this study. All patients and treatments were followed with a baseline and a 3- or 5-year examination. All patients had to fill out an Oral Health Impact Profile (OHIP-49) questionnaire at baseline and at the 3- or 5-year examination. The restorations were evaluated according to the Copenhagen Index Score (CIS).

RESULTS

For the RBFDP (test) group there was an 82% survival rate and 18% failure rate, that is, four RBFDPs were not in situ after 3 years and four RBFDPs were not in situ after 5 years. Correspondingly, the ISSC showed a survival rate of 98% and a failure rate of 2%, that is, only one failure (ceramic fracture) after 3 and none after 5 years. Of the 82% RBFDPs in situ, there were no complications in 78% of the cases, whereas 22% had complications after 3 (4 complications) and 5 years (4 complications). There were 92% of the ISSCs without any complications and 8% (ie, 3 ISSCs) with complications after 3 or 5 years. In general, there was a significant reduction in the OHIP-49 scores, for example, an improved oral health quality of life for both treatment options.

CONCLUSION

The results of this study indicate that ISSCs have lower complication and failure rates than RBFDPs. In general, the OHIP-scores were significantly reduced regardless of whether RBFDPs or ISSC were used.

Restorative dentistry clinical decision-making for hypodontia: peg and missing lateral incisor teeth

Peg-shaped and missing lateral incisor teeth are common features for patients affected by hypodontia. While improvements in dental appearance may be a strong motivating factor for these patients, providing dental treatment to improve the clinical condition and achieve an acceptable and stable outcome can be complex and lengthy.For patients affected by hypodontia, discussion and consideration of various approaches to their individual treatment are best achieved in a multidisciplinary team environment. This allows debate of options and joint agreement between at least orthodontic and restorative dentistry specialist colleagues, based largely on clinical factors, towards a treatment plan that is acceptable to the patient. As most patients with this lateral incisor form of hypodontia are initially treated as teenagers and young adults, there is also an understanding that treatment outcomes will have lifelong maintenance and resource implications to consider.This paper identifies and discusses the key clinical features that influence the treatment planning process for a patient with either missing or peg lateral incisor teeth. These will often involve consideration of whether to open or close the lateral incisor spaces and whether to restore or replace a peg lateral incisor tooth. The process should be patient-centred, evidence-based, and aim to minimise the lifelong treatment burden, retaining options for future maintenance and retreatment.

Designing anterior cantilever resin-bonded fixed dental prostheses based on finite element analysis

PURPOSE

A resin-bonded bridge (RBB) is a minimally invasive prosthetic treatment option for intact adjacent teeth. However, it is contentious as to whether the mesial or distal adjacent tooth should be used as an abutment. This study aimed to investigate the potential of finite element analysis (FEA) for the selection of abutment teeth and the determination of the optimal design for anterior cantilever RBBs.

METHODS

Three types of RBBs were designed to simulate loss of the maxillary left lateral incisor. The fixed-fixed RBB (FF-RBB) had one retainer each for the left central incisor and canine. Distal- and mesial-cantilever RBBs (D-CRBB and M-CRBB) had a single retainer on the central incisor and canine, respectively. Three-dimensional models for FEA were generated from computed tomography slices and dental casts. FEA was performed for each RBB to evaluate stresses in the intercuspal, protrusive, and lateral mandibular positions.

RESULTS

The maximum principal stresses on the bridges in the intercuspal position were 141.9 MPa, 93.6 MPa, and 45.7 MPa, for the FF-RBB, D-CRBB, and M-CRBB, respectively. The stress in the D-CRBB position was greater than in the M-CRBB position in the intercuspal, protrusive, and lateral mandibular positions.

CONCLUSIONS

Based on the results, M-CRBB on the canine had a higher clinical performance than D-CRBB on the central incisor. FEA was useful for determining the optimal design of RBB for each patient.

Structural Integrity of Anterior Ceramic Resin-Bonded Fixed Partial Denture: A Finite Element Analysis Study

This study was conducted as a means to evaluate the stress distribution patterns of anterior ceramic resin-bonded fixed partial dentures derived from different materials and numerous connector designs that had various loading conditions imposed onto them through the utilization of the finite element method. A finite element model was established on the basis of the cone beam computed tomography image of a cantilevered resin-bonded fixed partial denture with a central incisor as an abutment and a lateral incisor as a pontic. Sixteen finite element models representing different conditions were simulated with lithium disilicate and zirconia. Connector height, width, and shape were set as the geometric parameters. Static loads of 100 N, 150 N, and 200 N were applied at 45 degrees to the pontic. The maximum equivalent stress values obtained for all finite element models were compared with the ultimate strengths of their materials. Higher load exhibited greater maximum equivalent stress in both materials, regardless of the connector width and shape. Loadings of 200 N and 150 N that were correspondingly simulated on lithium disilicate prostheses of all shapes and dimensions resulted in connector fractures. On the contrary, loadings of 200 N, 150 N, and 100 N with rectangular-shaped connectors correspondingly simulated on zirconia were able to withstand the loads. However, two of the trapezoidal-shaped zirconia connectors were unable to withstand the loads and resulted in fractures. It can be deduced that material type, shape, and connector dimensions concurrently influenced the integrity of the bridge.

A Digital Way for Fabricating a Resin-Bonded Fixed Partial Denture Combined with Periodontal Splint in the Mandibular Anterior Region

Teeth loosening are caused by insufficient supporting tissue, inflammation of periodontal tissue, or occlusal trauma, which is one of the main clinical symptoms of periodontitis. A digital technique for fabricating resin-bonded splinting fixed partial dentures (S-FPDs) is presented. It restores the missing mandible anterior teeth and splints the adjacent periodontally mobile teeth of the patient at the same time. The S-FPDs is designed and fabricated by computer-aided design and computer-aided manufacturing (CAD/CAM) technology with flexible PMMA material. The workflow is straightforward, convenient, and accurate. Meanwhile, the restoration can meet the esthetic requirements and help with the stability of adjacent loosening natural teeth spontaneously. It could be considered a medium-term provisional restorative treatment option, but further controlled investigations still be needed.

Comparison of Tensile Bond Strength of Fixed-Fixed Versus Cantilever Single- and Double-Abutted Resin-Bonded Bridges Dental Prosthesis

Resin-bonded fixed dental prostheses (RBFDP) are minimally invasive alternatives to traditional full-coverage fixed partial dentures as they rely on resin cements for retention. This study compared and evaluated the tensile bond strength of three different resin-bonded bridge designs, namely, three-unit fixed-fixed, two-unit cantilever single abutment, and three-unit cantilever double-abutted resin-bonded bridge. Furthermore, the study attempted to compare the tensile bond strengths of the Maryland and Rochette types of resin-bonded bridges. Based on the inclusion and exclusion criteria, a total of seventy-five extracted maxillary incisors were collected and later were mounted on the acrylic blocks. Three distinct resin-bonded metal frameworks were designed: three-unit fixed-fixed (n = 30), two-unit cantilever single abutment (n = 30), and a three-unit cantilever double abutment (n = 30). The main groups were further divided into two subgroups based on the retainer design such as Rochette and Maryland. The different prosthesis designs were cemented to the prepared teeth. Later, abutment preparations were made on all specimens keeping the preparation as minimally invasive and esthetic oriented. Impression of the preparations were made using polyvinyl siloxane impression material, followed by pouring cast using die stone. A U-shaped handle of 1.5 mm diameter sprue wax with a 3 mm hole in between was attached to the occlusal surface of each pattern. The wax patterns were sprued and cast in a cobalt-chromium alloy. The castings were cleaned by sandblasting, followed by finishing and polishing. Lastly, based on the study group, specimens for Rochette bridge were perforated to provide mechanical retention between resin cement and metal, whereas the remaining 15 specimens were sandblasted on the palatal side to provide mechanical retention (Maryland bridge). In order to evaluate the tensile bond strength, the specimens were subjected to tensile forces on a universal testing machine with a uniform crosshead speed. The fixed-fixed partial prosthesis proved superior to both cantilever designs, whereas the single abutment cantilever design showed the lowest tensile bond strength. Maryland bridges uniformly showed higher bond strengths across all framework designs. Within the limitations of this study, the three-unit fixed-fixed design and Maryland bridges had greater bond strengths, implying that they may demonstrate lower clinical failure than cantilever designs and Rochette bridges.

A retrospective comparison of the survival of vital teeth adjacent to single, bounded edentulous spaces rehabilitated using implant-supported, resin-bonded, and conventional fixed dental prostheses

OBJECTIVES

In this study, we aimed to compare the long-term survival of vital teeth adjacent to bounded edentulous spaces rehabilitated using an implant-supported prosthesis (ISP), a resin-bonded fixed partial denture (RBFPD), or a conventional fixed partial denture (CFPD). The risk factors for complications in teeth adjacent to the edentulous space (TAES) were also investigated.

METHODS

We followed-up a consecutive series of 514 patients who underwent rehabilitation of a single bounded edentulous space with vital TAES (ISP: 103; RBFPD: 216; and CFPD: 195) from 2008 to 2017. Cumulative survival rates of prosthesis and TAES, and complication-free rates of TAES, were evaluated using the Kaplan-Meier analysis and log-rank test. Risk factors were evaluated using a Cox proportional hazards model.

RESULTS

Cumulative complication-free rates of TAES showed no significant differences among the three groups. The cumulative survival rate of TAES in CFPD was significantly lower than that of ISP (p = 0.037); no significant differences were observed between ISP and RBFPD (p = 0.513), and RBFPD and CFPD (p = 0.076). Older age (p = 0.027) was the only independent significant risk factor for complications in TAES. Installation of CFPD (p = 0.019), ceramic prosthesis in edentulous space (p = 0.026), and deeper periodontal probing depth (p = 0.018) of TAES were significant risk factors for non-surviving TAES.

CONCLUSIONS

Rehabilitating a single bounded edentulous space with CFPD could increase the risk for TAES loss compared with ISP. Risk of TAES loss remained similar between ISP and RBFPD, which can minimize the loss of coronal tooth structure during tooth preparation.

CLINICAL SIGNIFICANCE

Teeth adjacent to edentulous space show equivalent longevity when rehabilitating a single bounded edentulous space with resin-bonded fixed partial dentures or single standing implant-supported prosthesis, at least 10 years post-installation.

Prosthetic rehabilitation of maxillary lateral incisors agenesis using dental mini-implants: a multicenter 10-year follow-up

Objectives

Implants are used to replace congenitally missing lateral incisors but often the space across the alveolar crest is too narrow to permit their use. This multicenter study (Dental Clinic of the University of Foggia, Odontostomatology Clinic of the University of L’Aquila) evaluated the efficacy of mini-implants in cases of maxillary lateral incisor agenesis with severe osseous atrophy in 10-year follow-up.

Materials and methods

Forty-seven mini-implants have been inserted in 35 patients affected by lateral incisors agenesis (23 single and 12 bilateral ageneses). All patients underwent orthodontic opening of the space of the upper lateral incisors. After the insertion of the implants, the immediate, non-functional loading, positioning of crowns, presence of pain during percussion and mini-implant function, horizontal and vertical movement when a force of 5 N was applied, ridge loss, and plaque index have been evaluated 1 month after loading, 1 year after loading, and then every 5 years in the following 10 years. Little’s test was used to evaluate the assumption that data of loss to follow-up implants are missing completely at random (MCAR) and that a complete-case scenario could be adopted. Wilcoxon test was carried out to look statistically significant differences between the various parameters resulting in the complete-case scenario and those assumed for the worst scenario. The software R (v. 3.6.1, 2019) was employed to perform the statistical analysis.

Results

The results obtained over 10 years range from 89% of success rate in a worst-case scenario to the 100% using a complete-case analysis with satisfactory values of marginal bone resorption and good conditions of the peri-implant tissue. Ten-year follow-up using complete-case analysis shows survival rates of 100% for implants with no signs of peri-implantitis, stability of the marginal bone levels and soft tissue around the dental implants.

Conclusions

The data collected show very good implant stability, absence of progressive peri-implantitis, and satisfactory aesthetical results in time (no signs of infraocclusion).

Clinical relevance

Mini-implants can be considered a valid and stable over time solution in the restorative treatment of maxillary lateral incisors agenesis.

Establishment of optimal variable elastic modulus distribution in the design of full-crown restorations by finite element analysis

To establish optimal elastic modulus distribution throughout the entire all-ceramic crown, aiming at improvement of the mechanical properties of the restoration as well as the adhesive interface, seven 3D models of mandibular first premolars of zirconia monolithic and bilayer crowns and lithium disilicate monolithic and bilayer crowns were constructed. The elastic modulus distribution of 8-layer crown A referred to human enamel, B was calculated by a genetic algorithm (GA) to minimize the principle stresses on the crown, and C minimized the shear stresses at the cementing lines. After applying a static load of 600 N, the maximum principle stresses were calculated and analyzed by finite element analysis (FEA). Group C were found to have the lowest peak shear stress at the cementing line and moderate peak tensile stress in the crown. Introduction of the modified elastic modulus distribution from human enamel into the entire all-ceramic crown reinforces the mechanical properties of the whole restoration as well as the adhesive interface against chipping and debonding.

Critical review about two myths in fixed dental prostheses: Full-Coverage vs. Resin-Bonded, non-Cantilever vs. Cantilever

The purpose of this review was to assess the literature regarding four types of fixed dental prostheses (FDPs)/resin-bonded FDPs (RBFDPs) to provide clinicians with a comparative overview of two myths: “RBFDPs are easy to debond in patients’ mouths” and “cantilever RBFDPs still have some clinical problems, especially in terms of overloading the abutment teeth and being easy to debond”. A total of 782 papers were identified, 753 of which were judged unsuitable and thus excluded, leaving a total of 29 articles for inclusion in this review. The results indicated that 1) Two-retainer RBFDPs achieve clinical results comparable to full-coverage three-unit FDPs; 2) Cantilever RBFDPs show excellent long-term clinical outcomes (especially in incisor teeth) compared with other FDPs; 3) RBFDPs typically show less catastrophic failure than conventional FDPs, rebonding should be considered when debonding occurs; and 4) Cantilever RBFDPs can be recommended as defect replacement prostheses for maxillary lateral incisors and mandibular incisor teeth.

Scientific field: Prosthodontics, Adhesive dentistry, Esthetic dentistry

Occlusal force and occlusal contact reestablishment with resin-bonded fixed partial dental prostheses using the Dahl concept: A clinical study

STATEMENT OF PROBLEM

Space creation for a metal retainer of the resin-bonded fixed partial dental prostheses (RBFPDPs) with the Dahl concept remains controversial because of the lack of clinical studies.

PURPOSE

The purpose of this clinical study was to investigate the occlusal force and occlusal contact reestablishment of RBFPDPs cemented at an increased occlusal vertical dimension (the Dahl concept) and to evaluate the factors affecting them.

MATERIAL AND METHODS

A prospective clinical study was carried out on 28 participants receiving cantilevered RBFPDPs at an increased occlusal vertical dimension at the Faculty of Dentistry, University Teknologi MARA. Maximum occlusal forces were recorded at precementation, postcementation, and 12-week review visit by using pressure indicating film, while occlusal contact reestablishment was assessed at the precementation stage and 12-week review visit by using shim stock foils. The Wilcoxon signed-rank and chi-squared tests were used for statistical analysis (α=.05).

RESULTS

Significant differences were found for maximum occlusal force between the precementation and the postcementation and between the postcementation and the 12-week review of RBFPDPs (P<.05 for both) in all 28 participants. However, no significant difference was found between the precementation and the 12-week review (P=.085). The occlusal force reestablishment concerning sex, age, location, and arch of the prosthesis was found to be similar. Most of the participants (89.3%) achieved complete occlusal contact reestablishment and 10.7% partial occlusal reestablishment. The demographic and prosthesis factors were not significantly related to the occlusal reestablishment (P>.05).

CONCLUSIONS

Overall, occlusal force was reestablished after 12 weeks, and occlusal contact was completely reestablished in most participants after placement of RBFPDPs at an increased occlusal vertical dimension.

Occlusal re-establishment and clinical complications of resin-bonded fixed partial dental prostheses cemented at an increased occlusal vertical dimension: A retrospective study

STATEMENT OF PROBLEM

Resin-bonded fixed partial dental prostheses (RBFPDPs) cemented at an increased occlusal vertical dimension (OVD) (the Dahl concept) to create space for a metal retainer remain controversial because of the lack of reported clinical studies. This study evaluated RBFPDPs by applying the Dahl concept.

PURPOSE

The purpose of this retrospective study was to investigate the clinical factors affecting the occlusal re-establishment and short-term complications of RBFPDPs cemented at an increased OVD.

MATERIAL AND METHODS

Occlusal re-establishment and clinical complications were reviewed in 109 participants (155 RBFPDPs) treated at the Faculty of Dentistry, Universiti Teknologi MARA from January 2013 to May 2018. Types of complications and risk factors were assessed from clinical data. Demographic factors, clinical factors, and prosthesis factors were distinguished and their association with occlusal re-establishment analyzed by using multiple regression analysis.

RESULTS

A total of 155 RBFPDPs (42 anterior, 113 posterior) were placed in 109 participants. All achieved occlusal re-establishment, 89.9% complete occlusal re-establishment and 10.1% partial occlusal re-establishment, a minimum of 4 months after the RBFPDPs had been placed at an increased OVD. The design of the metal retainer coverage was found to be a significant factor affecting occlusal re-establishment and decementation (P<.05). Widening of the periodontal ligament space was the most common complication (29.2%).

CONCLUSIONS

RBFPDPs cemented at an increased OVD can be clinically recommended. The design of the retainer coverage was a significant factor influencing occlusal re-establishment and clinical complications.

Clinical Performance of Posterior Inlay-Retained and Wing-Retained Monolithic Zirconia Resin-Bonded Fixed Partial Dentures: Stage One Results of a Randomized Controlled Trial

PURPOSE

To prospectively compare the clinical performance of posterior inlay-retained and wing-retained monolithic zirconia fixed partial dentures (FPDs).

MATERIALS AND METHODS

After simple randomization, 30 participants received either one inlay-retained (n = 15; mean age: 56.38 ± 12.70 years; 10 men [66.7%]) or one wing-retained (n = 15; mean age: 45.90 ±13.24 years; 7 men [46.7%]) FPD. The restorations, which predominantly replaced first molars, were fabricated from translucent, 3 mol% yttria-stabilized zirconia and attached with self-etching resin cement. Restorations and abutment teeth were clinically followed up for complications one week and 3, 6, and 12 months after cementation. Plaque and gingival scores, probing pocket depths, and attachment levels were recorded for the abutment and contralateral reference teeth both before treatment and during follow-up examinations. The restorations were also assessed in accordance with FDI World Dental Federation criteria. Statistical analyses were conducted with R (α = 0.05). An adaptive, 2-stage study design based on the incidence of failure-free survival in the groups after 12 months (stage 1) was implemented. Predefined decision rules were used to determine whether further recruitment (stage 2) would enable the detection of a statistically significant difference between the restoration designs with sufficient power.

RESULTS

During 12 months, only one wing retainer debonded which required removal of the FPD. Failure-free survival was thus 93.3% for wing-retained and 100% for inlay-retained FPDs (log-rank test, p = 0.317). Moderate aftercare resulted in intervention-free rates of 78.8% and 86.7% for inlay-retained and wing-retained restorations, respectively (log-rank test, p = 0.605). Based on FDI World Dental Federation criteria, all restorations were acceptable at the 12-month follow-up (Fisher-Boschloo test, p = 0.161). Plaque, gingival, and periodontal scores remained practically unchanged from before treatment to the 12-month follow-up. Recruitment was stopped after stage 1 because, based on the small difference in the incidence of failure-free survival in the groups, it was accepted that it would not be possible to recruit the necessary number of participants to show a statistically significant difference between the retainer designs.

CONCLUSIONS

Both inlay-retained and wing-retained monolithic zirconia resin-bonded FPDs performed well for the 12-month, short-term follow-up period.

Fracture strength of lithium disilicate cantilever resin bonded fixed dental prosthesis

OBJECTIVES

Metal and Zirconia cantilever resin bonded fixed dental prosthesis (RBFDPs) are extensively used when missing anterior teeth. Lithium disilicate is not used a lot as it is not indicated by the manufacturers. The aim of this in vitro study was to investigate the fracture strength of lithium disilicate cantilever RBFDPs with different configurations and compare them to metal and zirconium RBFDPs.

METHODS

Sound extracted human canines (N = 60) were divided into six groups, to be restored with a cantilever RBFDP. Specimen were randomly divided over 6 groups (n = 10): Full crown of lithium disilicate (FCL); Veneer wing of lithium disilicate (VL); Connector of lithium disilicate (CL); Palatal wing of lithium disilicate (PL); Palatal wing of zirconia (PZ) and Palatal wing of metal ceramic (PM). All bridges were bonded with an adhesive system. After thermalcyclic ageing (20 × 10³x, 5-55 °C) all samples were loaded until fracture occurred. Failure types were classified and representative SEM done.

RESULTS

The mean fracture strength results per group were: 588N (FCL) 588N (PM), 550N (CL), 534N (PL), 465N (VL), 38N (PZ). A significant (p = 0.001) difference was found between the groups, all groups had a higher fracture strength than the zirconia RBFDPs. Failure type analysis showed some trends among the groups. Irrepairable fractures of the root were only seen in samples restored with lithium disilicate. Metal and zirconia RBFDPs predominantly failed on the adhesive interface, where 60% of the zirconia samples had pretest debondings.

SIGNIFICANCE

No differences in fracture strength were found between cantilever RBFDPs made from metal or lithium disilicate. Metal (0% pre-test failures) and zirconium (60% pretest failures) RBFDPs failed predominantly on the adhesive interface whereas the lithium disilicate (0% pre-test failures) samples showed fractures in the contact area. The least invasive connector (CL) and Metal (PM) RBFDP obtained a high fracture strength and optimal fracture pattern.

Effects of 10-MDP Based Primer on Shear Bond Strength between Zirconia and New Experimental Resin Cement

To date, numerous materials in the dental field are marketed to ensure stable adhesive cementation of zirconia ceramics (Y-TZP). The aims of this study were to assess the shear bond strength of the new experimental cement Surgi Dual Flo' Zr to Y-TZP compared to Panavia V5 cement, and to evaluate the effect of 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate) containing primer on their bond strength. Twenty composite cylinders and Y-TZP disks were adhesively luted and divided into four groups based on cement type used and application or not of 10-MDP. The groups (n = 5 each) were S 10MDP (Surgi Dual Flo' Zr with 10-MDP); S no 10MDP (Surgi Dual Flo' Zr without 10-MDP); P 10MDP (Panavia V5 with 10-MDP); P no 10MDP (Panavia V5 without 10-MDP). Maximum load resistance (ML) and shear bond strength (SBS) were tested and mode of failure qualitative documented via scanning electron microscopy. The data were analyzed with one-way ANOVA, Holm-Sidak method, and Bayesian analysis. ML and SBS were significantly higher in S 10MDP than in S no 10MDP; and in P 10MDP than in P no 10MDP (p < 0.05). No significant differences were found between S 10MDP and P 10MDP; S no 10MDP and P no 10MDP (p > 0.05). Cohesive, adhesive, and mixed failure occurred among the groups. Bond strength between the experimental resin-based cement and Y-TZP was adequate for clinical application when 10-MDP was added. 10-MDP containing primer was effective improving the bond strength to Y-TZP more than the different type of resinous cement.

Short communication: Influence of retainer configuration and loading direction on the stress distribution of lithium disilicate resin-bonded fixed dental prostheses: 3D finite element analysis

The present study elucidates the mechanical performance of different designs of resin-bonded fixed dental prostheses made of lithium disilicate simulating masticatory loads of anterior or canine guidance. A three-dimensional model of maxilla was constructed containing central incisor and canine teeth, with edentulous space of the lateral incisor. Three designs of prosthesis were created: retained in central incisor (1-I), retained in canine (1-C) and fixed in both teeth (2-IC). The computational analysis was performed for load in canine and central incisor separately (100N, 45°). The tensile and shear stresses were calculated for the resin-bonded fixed dental prosthesis, bonding surface of each retainer and cement layer using 3D finite element analysis. The 20 highest stress values were analyzed using two-way ANOVA and post-hoc Tukey test, all with α = 5%. The computational analysis showed that 2-retainer resin-bonded fixed dental prosthesis presented the worst prognosis regardless of the mandibular movement. ANOVA showed that Mandibular movement*Retainer interaction influenced on the tensile and shear stresses values (p < 0.01). Higher stresses were observed in the connector region for all groups (13-82.2 MPa; 11-70.2 MPa). In order to reduce the stress concentration in the resin-bonded fixed dental prosthesis and the retainer made of lithium disilicate, the occlusion may serve as the selection criteria of the unitary abutment for better sustainability.

[All-ceramic premolar guiding plate retains resin-bonded fixed partial dentures]

OBJECTIVE

This study aims to investigate the fracture resistance and short-term restorative effects of resin-bonded fixed partial dentures (RBFPDs) made from heat-pressed lithium-disilicate-based glass-ceramic (IPS e.max press) and zirconia ceramic (WIELAND) and retained by all-ceramic guiding plates when used to restore missing mandibular second premolars.

METHODS

A total of 64 human mandibular first premolars and first molars were prepared as abutments, then were randomly divided into 4 groups (n=8): E0, heat-pressed ceramic RBFPDs, no cyclic loading; E1, heat-pressed ceramic RBFPDs exposed to 300 000 cycles of dynamic loading; W0, zirconia ceramic RBFPDs, no cyclic loading; and W1, zirconia ceramic RBFPDs exposed to 300 000 cycles of dynamic loading. Fracture strength was tested in a universal testing machine.

RESULTS

The medians of fracture strength were 1 242.85 N±260.11 N (E0), 1 650.85 N±206.77 N (W0), 1 062.60 N±179.98 N (E1), and 1 167.61 N±265.50 N (W1). Statistical analysis showed that all the groups exhibited significantly higher fracture strength compared with the maximum bite force in the premolar region (360 N; P<0.001). The W0 group had significantly higher fracture strength than the E0 group (P<0.05). Meanwhile, no significant difference in fracture strength was observed between the E1 and W1 groups (P>0.05). Significant statistical differences were found between the zirconia ceramic groups (W0 and W1, P<0.05) but not between the glassceramic groups (E0 and E1, P>0.05) after dynamic loading.

CONCLUSIONS

The RBFPDs retained by all-ceramic guiding plates exhibited promising fracture properties and optimal short-term restorative effects when used to restore missing mandibular second premolars.

Short communication: Influence of restorative material and cement on the stress distribution of posterior resin-bonded fixed dental prostheses: 3D finite element analysis

The goal of this study was to compare the mechanical response of resin-bonded fixed dental prosthesis (RBFDP) made in zirconia, metal, lithium disilicate and composite resin cemented using resin cements with different elastic modulus. For the finite element analysis, a three-dimensional model of partial right maxilla was used to create a model with edentulous space in the second premolar and the cavity's preparation on the first pre-molar and first molar to receive a RBFDP. The model was imported to the analysis software in which they were divided into mesh composed by nodes (371,101) and tetrahedral elements (213,673). Each material was considered isotropic, elastic and homogeneous. No-separation contacts were considered between restoration/resin cement and resin cement/tooth. For all other structures the contacts were considered ideal. The model fixation occurred at the base of the bone and an axial load of 300 N was applied on the pontic occlusal surface. To simulate polymerization shrinkage effects on the cement, the thermal expansion approach was used. The displacement and maximum principal stress (in MPa) were selected as failure criteria. The prosthesis made in composite resin showed higher displacement, while in zirconia showed higher stress concentration. Tensile stress between restoration/cement, cement and cement/cavity was directly proportional to the restorative material's elastic modulus. The more rigid cement increases the tensile zones in the cement layer but decreases the stress between prosthesis and cement. The molar cavity showed higher stress concentration between restoration/cement than the preparation in the pre-molar tooth. The use of composite resin for the manufacturing of RBFDP increases the displacement of the set during the loading. However, it reduces the amount of stress concentration at the adhesive interface in comparison with the other materials.

Effect of Fixed Metallic Oral Appliances on Oral Health

There is a substantial proportion of the population using fixed metallic oral appliances, such as crowns and bridges, which are composed of various dental alloys. These restorations may be associated with a number of effects on oral health with variable degrees of severity, to review potential effects of using fixed metallic oral appliances, fabricated from various alloys. The MEDLINE/PubMed database was searched using certain combinations of keywords related to the topic. The search revealed that burning mouth syndrome, oral pigmentation, hypersensitivity and lichenoid reactions, and genotoxic and cytotoxic effects are the major potential oral health changes associated with fixed prosthodontic appliances. Certain oral disorders are associated with the use of fixed metallic oral appliances. Patch test is the most reliable method that can be applied for identifying metal allergy, and the simultaneous use of different alloys in the mouth is discouraged.