Influence of retainer design and number of inlay boxes on the biomechanical behavior of zirconia cantilever resin bonded fixed dental prosthesis.

OBJECTIVES: The development of dental adhesives with enhanced bond strength has assisted minimally invasive dentistry. The aim of this study was to evaluate the fracture load and stress distribution pattern of two retainer designs for posterior cantilever resin bonded fixed dental protheses (RBFDPs). MATERIALS AND METHODS: Forty human mandibular molars were divided into two groups according to the retainer design; lingual coverage (LC) and occlusal coverage (OC) retainers. Each main group was then divided according to the number of inlay boxes (n = 10); one inlay and two inlay boxes. High translucency (3Y) zirconia was used to manufacture all restorations, and a dual-polymerizing adhesive resin cement was used for bonding. All specimens underwent 10,000 cycles of thermocycling (5-55°C), 240,000 cycles of dynamic loading (50 N, descending speed v = 30 mm/second, frequency = 1.6 Hz), and failure load test. Both one-way and two-way ANOVA tests were used to analyze the data. The four models included in the in-vitro study are part of the finite element analysis (FEA). When the restorations failed, maximal principal stress values on restorations, enamel, dentin, and luting resin were investigated. RESULTS: A statistically significant (p = 0.018) higher failure load was recorded for OC1 (627.00 ± 153.4 N) than the other groups; (548.0 ± 75.6 N, 521.20 ± 11.3 N, and 509.20 ± 14.9 N for LC1, LC2, and OC2, respectively). With regard to failure mode, one inlay box designs showed more favorable failure pattern than those of two inlay boxes. FEA showed higher stress magnitude transmitted to the tooth structure in models LC2 and OC2. CONCLUSIONS: Lingual coverage and occlusal coverage retainers are promising designs capable to withstand the normal occlusal force for cantilever RBFDP in premolar area. The use of two inlay boxes decreased the fracture load of the two retainer designs and increased the stress transmitted to the tooth and resulted in high incidence of catastrophic failure. CLINICAL SIGNIFICANCE: Monolithic high translucent zirconia RBFDP could be considered as a viable treatment option to substitute missing posterior tooth, with improved esthetics and biocompatibility.

Evaluation of different designs for posterior cantilever zirconia inlay-retained fixed dental prostheses in missing tooth replacement: Stage one results with 18-month follow-up assessment.

OBJECTIVES: This clinical study aimed to investigate the outcomes and survival rates of different variations of inlay-retained fixed dental prostheses (IR-FDPs) composed of monolithic zirconia ceramic. The IR-FDPs with a single-retainer design were used for replacing missing mandibular second premolars. The research evaluated the effectiveness and longevity of these prostheses in clinical settings. METHODS: A total of 30 IR-FDPs (n = 30) were placed for 27 female patients who presented with missing mandibular second premolar teeth. For this study, the mandibular first molar was chosen as a retainer for the cantilever IR-FDPs and the study involved a random assignment of participants into three distinct groups, each comprising 10 individuals (n = 10). The criterion for the grouping was the retainer design: inlay ring (IR), lingual coverage (LC), and occlusal coverage (OC). The three groups included mesial inlay box with the same dimensions (3 mm height, 3 mm width and 2 mm depth). All IR-FDPs were manufactured using monolithic high translucent 3Y zirconia and the connector area to the cantilever pontic was adjusted to dimensions of 3 × 3 mm for all designs. The restorations were bonded using adhesive resin cement. The clinical and radiographic evaluations of the restorations were conducted for a duration of 18 months, following the modified FDI (World Dental Federation) criteria. RESULTS: The restorations were observed in stage one for a period of 18 months. Only one restoration in group LC was debonded after 10 months and re-bonded. The clinical quality of all crowns and the patient's satisfaction were high. No adverse soft tissue reactions around the crowns were observed and only one abutment in group IR was endodontically treated after 12 months. CONCLUSIONS: Zirconia cantilever IR-FDPs offer a viable short-term treatment option for replacing missing posterior teeth, providing esthetic and functional benefits while minimizing invasiveness. Over an 18-month observation period, these prostheses have demonstrated a remarkable survival rate of 100% and a success rate of 96.6%. These findings suggest the effectiveness and reliability of zirconia cantilever IR-FDPs as a short-term solution for replacing missing posterior teeth. CLINICAL SIGNIFICANCE: Zirconia cantilever IR-FDPs could present a practical solution for addressing posterior tooth loss, especially in cases where implant placement is not recommended and conventional fixed dental prostheses entail excessive invasiveness.

Cantilever resin-bonded fixed dental prosthesis to substitute a single premolar: Impact of retainer design and ceramic material after dynamic loading.

PURPOSE: To evaluate the influence of retainer design and ceramic materials on the durability of minimally invasive cantilever resin-bonded fixed dental prostheses (RBFDPs) after artificial aging. METHODS: One hundred caries-free human mandibular molars were prepared as abutments for all-ceramic cantilevered fixed dental prostheses using the following retainer designs: One wing (OW), Two wings (TW), Inlay ring (IR), Lingual coverage (LC), and Occlusal coverage (OC). Two ceramic materials were used: monolithic high translucent zirconia(z) and zirconia-reinforced lithium disilicate (ZLS2) (n=10). All restorations were adhesively bonded with resin cement. The thermocycling of the specimens were performed between 5°C and 55°C for 10,000 cycles and then exposed to 240.000 cycles of dynamic loading on a chewing simulator. All surviving specimens were loaded onto the pontic until failure using a universal testing machine. RESULTS: The mean failure load ranged from 124.00 to 627.00 N for the zirconia groups and from 133.30 to 230.00 N for the ZLS2 groups. Regarding the materials, a significantly higher failure load was recorded in the zirconia groups than in the ZLS2 groups (P<0.001), except for OW (P=0.748). Regarding the retainer designs, a significant different failure load was recorded between the different designs except for IR and LC in the zirconia groups, IR and OC, OW and TW, and TW and LC in the ZLS2 groups (P<0.001). CONCLUSIONS: Zirconia IR, LC, and OC can be used as cantilever RBFDP in the premolar region. The fracture resistance of the ZLS2 design was below the normal bite force and should not be recommended as the first option.

Biomechanical behavior of posterior metal-free cantilever fixed dental prostheses: effect of material and retainer design.

OBJECTIVE: To study the fracture resistance and stress distribution pattern of translucent zirconia and fiber-reinforced composite cantilever resin-bonded fixed dental prostheses (RPFDPs) with two retainer designs. MATERIALS AND METHODS: Forty human mandibular molars were divided into two groups according to the retainer design. The restorations included a premolar pontic and 2 retainer designs: (D1) inlay ring retainer and (D2) lingual coverage retainer. Each main group was then divided according to the material used (n = 10): zirconia (Z) or fiber-reinforced composite (FRC) (F). Restorations were cemented using dual polymerizing adhesive luting resin. All specimens were thermo-cycled (5-55 °C for 10,000 cycles), then subjected to dynamic loading (50 N, 240,000, and 1.6 Hz) and fracture resistance test. The finite element analysis includes the two models of retainer designs used in the in vitro test. Modified von Mises stress values on enamel, dentin, luting resin, and restorations were examined when the restorations failed. RESULTS: A significantly higher failure load was recorded for zirconia groups (505.00 ± 61.50 and 548.00 ± 75.63 N for D1Z and D2Z, respectively) than for FRC groups (345.00 ± 42.33 and 375.10 ± 53.62 N for D1F and D2F, respectively) (P = 0.001). With regard to failure mode, D2 showed a more favorable failure pattern than D1. Model D2 resulted in lower stresses in tooth structure than model D1, and zirconia transmitted more stresses to the tooth structure than FRC. CONCLUSIONS: The lingual coverage retainer (D2) enhanced the biomechanical performance of the restoration/tooth complex. Considering the failure mode and tooth stress, FRC is a promising treatment option when constructing a cantilever RPFDP. CLINICAL RELEVANCE: Dentists should be aware of the biomechanical behavior during the selection of the material and for the replacement of a single missing mandibular premolar tooth with minimally invasive RBFDP.

Effect of different designs of minimally invasive cantilever resin-bonded fixed dental prostheses replacing mandibular premolar: Long-term fracture load and 3D finite element analysis.

PURPOSE: To evaluate the fracture load and stress magnitude of different retainer designs of minimally invasive cantilever resin-bonded fixed dental prostheses (RBFDPs) after artificial aging. MATERIALS AND METHODS: Fifty caries-free human mandibular molars were prepared as abutments for cantilever fixed dental prostheses using different retainer designs: one wing (OW), two wings (TW), inlay ring (IR), lingual coverage (LC), and occlusal coverage (OC). Computer-aided design and computer-aided manufacturing were used for milling the RBFDPs using fiber-reinforced composite (FRC), and the restorations were adhesively bonded. The specimens were then subjected to thermomechanical aging and loaded until failure. The 3D finite element analysis (FEA) was performed with five models of retainer designs similar to the in vitro test. Modified von Mises stress values on enamel, dentine, luting resin, and restorations were examined. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests (p < 0.001). RESULTS: A statistically significant difference (p < 0.001) was found between all groups except between IR and LC and between OW and TW designs, with the highest mean failure load detected for OC (534.70 N) and the lowest detected for OW (129.80 N). With regard to failure mode, OW, TW, and LC showed more incidences of favorable failure patterns than IR and OC designs. FEA showed that FRC transmitted low stresses in tooth structure and high stresses to the luting resin. CONCLUSIONS: LC and OC designs can be used to design cantilever RBFDPs in premolar area. IR design transmitted more stresses to the tooth structure and resulted in 30% catastrophic failure. OW and TW were below the normal occlusal force and should be carefully used.

Ten-Year Clinical Survival of Anterior Cantilever Resin-Bonded Fixed Dental Prostheses: A Retrospective Study.

PURPOSE: To assess the 10-year clinical retention and survival rates of metal-ceramic (MC) and all-ceramic (AC) cantilever resin-bonded fixed dental prostheses (CRBFDPs). MATERIALS AND METHODS: Forty CRBFDPs constructed from either cobalt-chromium ceramic (MC group; n = 20) or glass-infiltrated alumina ceramic (AC group; n = 20) were placed in 40 patients between August 2007 and December 2009. After baseline recordings, the patients were followed up using modified United States Public Health Services (USPHS) criteria after 6 months and thereafter annually for 10 years. Data were statistically analyzed using Kaplan-Meier estimation with log-rank (Mantel-Cox) test. RESULTS: The 10-year clinical retention rate was 95.0% in the MC group and 70% in the AC group. The difference was statistically significant (P = .02, log-rank test). Three all-ceramic CRBFDPs fractured at 6, 12, and 84 months after insertion. No statistically significant difference in survival rate was observed between the MC and AC groups over the 10 years of clinical observation (MC: 100%; AC: 85%; P = .075) (Kaplan-Meier method, confidence interval = 92.5% to 97.5%). CONCLUSION: Although glass-infiltrated alumina ceramic anterior CRBFDPs exhibited a lower clinical retention rate compared to metal-ceramic CRBFDPs, the debonded prostheses were recemented and continued in function over the observation period. Additionally, an acceptable 10-year clinical longevity was recorded.

Clinical survival of anterior metal-ceramic and all-ceramic cantilever resin-bonded fixed dental prostheses over a period of 60 months.

PURPOSE: To evaluate the survival of maxillary anterior cantilever resin-bonded metalceramic (MC) and all-ceramic (AC) fixed dental prostheses (RBFDPs). MATERIALS AND METHODS: Between August 2007 and December 2009, 40 patients received 40 RBFDPs made of either cobalt-chromium-ceramic (n = 20) or glass-infiltrated alumina (In-Ceram, Vident; n = 20) and were followed up until December 2012. Restorations were adhesively cemented (Panavia 21, Kuraray). RESULTS: Two fractures were observed with AC. No debondings were observed with MC (n = 0) but were observed with AC (n = 3). The difference in survival rates of MC and AC was not significant (MC: 100%; AC: 90%; P = .15) (Kaplan-Meier method, confidence interval = 95%). CONCLUSIONS: Cantilever AC RBFDPs could be a promising alternative to MC RBFDPs for replacement of missing anterior incisors, provided that no mechanical complications were experienced with the latter.

Immediate and delayed micro-tensile bond strength of different luting resin cements to different regional dentin.

We sought to evaluate immediate and delayed micro-tensile bond strength of Panavia F2.0 and Multilink Sprint resin cement to superficial, deep and cervical dentin. Thirty-six freshly extracted non-carious human molars were sectioned in the mesiodistal direction to expose three different dentin regions including superficial dentin (1 mm below the dentine-enamel junction), deep dentin (1 mm above the highest pulp horn) and cervical dentin (0.5 mm above the cemento-enamel junction and 0.5 mm below the dentine-enamel junction). Resin cements were applied on dentin surfaces and composite blocks were luted under constant seating pressure. Each group was divided into three subgroups according to time intervals. Specimens were sectioned to obtain sticks of 1 mm(2) in diameter and subjected to microtensile bond strength testing at a cross head speed of 1 mm/min. Both resin cements showed higher micro-tensile bond strength to superficial dentin than that to deep or cervical dentin (P < 0.001). Micro-tensile bond strengths of Panavia F2.0 were higher than those of Multilink Sprint at different dentin regions (P < 0.001). Immediate micro-tensile bond strengths were higher than those of delayed micro-tensile bond strengths for both resin cements (P < 0.001). It was concluded that resin cements with different chemical formulations and applications yield significantly different micro-tensile bond strengths to different dentin regions.