Effect of a calibration aid and the intraoral scanner on the registration of a partially edentulous maxilla: An in vitro study.

STATEMENT OF PROBLEM: Precise data are a prerequisite for accurately fitting restorations. Therefore, intraoral scanners have to be reliable. Data on differences between the same model of intraoral scanning systems are lacking. PURPOSE: This in vitro study evaluated differences in the scanning accuracy of a partially edentulous maxilla between combinations of new intraoral scanners of a single model from the same manufacturer (Primescan; Dentsply Sirona) and several calibration aids. MATERIAL AND METHODS: The in vitro reference model simulated a maxilla with 6 prepared teeth for a complete arch fixed partial denture. Five precision ceramic balls were used to detect dimensional deviation between the reference model and the scan. Distances were divided into 4 categories, from short distances between 2 neighboring precision balls to the cross-arch distance with the scan path comprising all 5 balls. For each combination of 4 new intraoral scanners and their respective calibration aids, 12 model registrations were generated. The data were statistically analyzed using ANOVA (α=.05). RESULTS: Distance deviations increased with increasing scan path length and were significantly affected by the covariates "scanner" (P≤.023) and, for 3 of 4 distance categories, the "calibration aid" (short, medium, and long distances: P≤.013). For short and medium distances, acceptable scanning results were achieved for all test groups. The largest deviation was 539 µm for the cross-arch distance. CONCLUSIONS: Scanning accuracy depends on the scanner and the calibration aid used, in particular, for spans exceeding a single quadrant.

Influence of artificial landmarks on the accuracy of complete arch scans in the partially edentulous maxilla: An in vitro study.

STATEMENT OF PROBLEM: Scan path length and the presence of edentulous alveolar ridge sections have a negative influence on scanning accuracy. How different artificial landmarks combined with an adapted scanning method affect accuracy is unclear. PURPOSE: The purpose of this in vitro study was to determine the influence of 2 different artificial landmarks combined with an adapted scanning method on the scanning accuracy of a partially edentulous maxillary model. MATERIAL AND METHODS: The model simulated a maxilla with 6 prepared teeth to accommodate a complete arch fixed partial denture. Five ceramic precision balls (ball center P1-P5), distributed buccally to the dental arch, were used to detect the dimensional and angular changes between the reference model and the intraoral scans. One intraoral scanner (Primescan) was used to make 30 scans each with either the scanning strategy recommended by the manufacturer (M) or with an adapted scanning strategy and the use of a bar (B) or 4 plates (P) as artificial landmarks in the dorsal palate. Data were statistically analyzed using a generalized least squares regression model (α=.05). RESULTS: Scanning with artificial landmarks reduced the maximum absolute distance deviations (M: 249 µm, B: 190 µm, P: 238 µm) and the maximum angle deviations (M: 0.31 degrees, B: 0.28 degrees, P: 0.26 degrees). Vertical distance deviations were improved by 10 to 50% with the use of artificial landmarks. Absolute mean distance deviations were significantly lower for group M (P<.001). In contrast, with artificial landmarks, mean angle (P<.001) and mean vertical distance deviations (P<.014) improved significantly. CONCLUSIONS: Scanning with artificial landmarks in the dorsal palate combined with an adapted scanning method improved the scanning accuracy and reliability of vertical distance deviations.

In vitro accuracy of digital and conventional impressions in the partially edentulous maxilla.

OBJECTIVES: This in vitro study compared the dimensional accuracy of conventional impressions (CI) with that of digital impressions (DI) in a partially edentulous maxilla. DIs were made by two intraoral scanners, Omnicam (OC) and Primescan (PS). MATERIALS AND METHODS: CI and both intraoral scanners were used to take 30 impressions of two identical reference models. CIs were poured with type 4 gypsum and the saw-cut models were digitized. The reference models simulated a maxilla with six prepared teeth that accommodated a cross-arch fixed partial denture. Center points of five precision balls and center points at the margin level of each prepared tooth were used to detect changes in dimensions and tooth axis between the reference model and the scans. RESULTS: For DI, the largest deviations (176 µm for OC and 122 µm for PS) occurred over the cross-arch. For CI, the largest deviation (118 µm) occurred over the anterior segment. For shorter distances up to a quadrant, DI was superior to CI. For longer scan distances, DI was comparable (2 sextant and anterior segment) or inferior (cross-arch) to CI. Vertical and tooth axis deviations were significantly smaller for CI than for DI (p < 0.001). CONCLUSIONS: The impression method affected the impression accuracy of a partially edentulous maxilla with prepared teeth. DI is recommended for scans up to a quadrant. Larger scan volumes are not yet suitable for fabricating a fixed partial denture because of the high scatter of accuracy values. CLINICAL RELEVANCE: In contrast to conventional impressions, digital impressions lead to comparable or better results concerning scans up to a quadrant. Consequently, for larger scan volumes, several smaller scans should be performed or, if restoration-related not possible, it is recommended to take conventional impressions.

Effect of scan-path length on the scanning accuracy of completely dentate and partially edentulous maxillae.

STATEMENT OF PROBLEM: The accuracy of fit of fixed partial dentures is directly dependent on the accuracy of a digital scan. However, the influence of scan-path length on scanning accuracy is unclear. PURPOSE: The purpose of this in vitro study was to evaluate how scan-path length influenced the scanning accuracy of a completely dentate or partially edentulous maxilla captured by 3 intraoral scanners: Omnicam AC (OC), TRIOS 4 (TR), and Primescan (PS). MATERIAL AND METHODS: Each intraoral scanner was used to make 30 scans each of the 2 clinical scenarios (completely dentate and partially edentulous) simulated with a reference model. The partially edentulous model simulated a maxilla with 6 prepared teeth to support a complete arch fixed partial denture. The missing teeth were then added to create a completely dentate model. The prepared teeth were later used to determine distance, angular, and tooth-axis deviations between the reference model (digitized with high precision before the tests) and the intraoral scans. Data were statistically analyzed by using a linear model or, if not applicable, a type II ANOVA (α=.05). RESULTS: Distance deviations increased linearly as the scan-path length increased. In contrast, angular and tooth-axis deviations did not increase linearly. All types of deviation differed depending on the scanning system used. Regarding the 90% quantile values, total distance deviations related to scan-path length amounted to 1.31 µm/mm (OC), 1.00 µm/mm (PS), and 1.45 µm/mm (TR) for the completely dentate maxilla and 1.10 µm/mm (OC), 1.46 µm/mm (PS), and 1.40 µm/mm (TR) for the partially edentulous maxilla. CONCLUSIONS: Distance deviations became larger as the scan-path length increased.

Five-year clinical performance of monolithic and partially veneered zirconia single crowns-a prospective observational study.

PURPOSE: The purpose of this study was to prospectively evaluate the medium-term clinical performance and esthetics of monolithic and partially (i.e., facially) veneered zirconia single crowns (MZ-SC and PZ-SC, respectively). METHODS: Between September 2011 and June 2013, 68 participants received 90 MZ-SC and 72 PZ-SC. Clinical study documentation was performed at crown cementation (baseline), at 6-month follow-up, and then yearly thereafter using standardized report forms. Three participants with four MZ-SC dropped out during clinical follow-up. Thus, 65 participants (n = 31, 47.7% men) fitted with 158 restorations (86 MZ-SC, 72 PZ-SC) were evaluated. The mean observation period of the restorations was 5.8 ±2.5 years; 6.3 ±2.2 for MZ-SC and 5.2 ±2.6 for PZ-SC. RESULTS: The 5-year rate of complication-free survival (success) was 87.0% for MZ-SC and 95.8% for PZ-SC (log-rank test, p = 0.026). The 5-year failure-free survival rate was 93.1% for MZ-SC and 96.2% for PZ-SC (log-rank test, p = 0.111), and the 5-year ceramic fracture-free survival rate was 100% for MZ-SC and 98.6% for PZ-SC (log-rank test, p = 0.274). Crowns of both designs were awarded excellent scores for esthetics by participants and dentists. CONCLUSION: Monolithic and partially veneered zirconia crowns can be used clinically with high medium-term survival and success and uncompromised esthetic results.

In-vitro accuracy of complete arch scans of the fully dentate and the partially edentulous maxilla.

PURPOSE: This in-vitro study aimed to compare the accuracy of complete arch scans (CAS) of a fully dentate (FD) and a partially edentulous (PE) maxillary model. Three intraoral scanning systems were used: Omnicam AC (OC), TRIOS 4 (TR), and Primescan (PS). METHODS: Each intraoral scanner was used to take 30 scans each of two clinical scenarios (FD and PE) simulated by a reference model. The PE model simulated a maxilla with six prepared teeth to accommodate a jaw-spanning fixed partial denture (FPD). The missing teeth were then added to create an FD model. Five ceramic precision balls (ball centers P1-P5) mounted on metal pins were welded to the metal base on the buccal side of the dental arch. These were later used to determine dimensional (given by each 2 ball centers) and angular changes (given by each 3 or 4 ball centers) between the reference model (digitized with high precision before the tests) and the intraoral scans. Data were statistically analyzed using a type II ANOVA. RESULTS: The maximum mean absolute distance deviations were as follows. OC: 147 µm (FD) and 139 µm (PE). TR: 133 µm (FD) and 136 µm (PE). PS: 87 µm (FD) and 80 µm (PE). The scanning system used had a significant effect on distance deviations (p < 0.027) and CAS scanning time (p < 0.001). Dental status had no clear effect on distance deviations but did significantly affect angular changes (p < 0.001) and scanning time (p < 0.001). CONCLUSION: The manufacture of jaw-spanning FPDs based on a CAS cannot yet be recommended.

Ceramic Crowns and Sleep Bruxism: First Results from a Randomized Trial.

Background: This randomized clinical trial was conducted to assess whether sleep bruxism (SB) is associated with an increased rate of technical complications (ceramic defects) in lithium disilicate (LiDi) or zirconia (Z) molar single crowns (SCs). Methods: Adult patients were classified as affected or unaffected by SB based on structured questionnaires, clinical signs, and overnight portable electromyography (BruxOff) and block randomized into four groups according to SB status and crown material (LiDi or Z): LiDi-SB (n = 29), LiDi-no SB (n = 24), Z-SB (n = 23), and Z-no SB (n = 27). Differences in technical complications (main outcome) and survival and success rates (secondary outcomes) one year after crown cementation were assessed using Fisher's exact test with significance level α = 0.05. Results: No technical complications occurred. Restoration survival rates were 100% in the LiDi-SB and LiDi-no SB groups, 95.7% in the Z-SB group, and 96.3% in the Z-no SB group (p > 0.999). Success rates were 96.6% in the LiDi-SB group, 95.8% in the LiDi-no SB group (p > 0.999), 91.3% in the Z-SB group, and 96.3% in the Z-no SB group (p ≥ 0.588). Conclusions: With a limited observation time and sample size, no effect of SB on technical complication, survival, and success rates of molar LiDi and Z SCs was detected.

Effects of Training on the Execution of Complete-Arch Scans. Part 1: Scanning Time.

PURPOSE: To investigate the effect of training on scanning times of complete-arch scans (CAS) performed by first-time users, with a distinction made between specific training (repeated practice of CAS) and nonspecific training (simple use of an intraoral scanner for a sextant scan in the context of a student CAD/CAM course). METHODS: Thirty-six students with no experience in intraoral scanning were randomized into three groups (n = 12 per group) according to the number of specific CAS training sessions: three sessions (3S), two sessions (2S), and one session (1S). Each student performed 10 CAS per scanning session. These sessions were scheduled at baseline (T0), T1 (2 weeks after T0), and T2 (4 weeks after T0) for group 3S; at T0 and T2 for group 2S; and at T2 for group 1S. Before the final scanning session in each group (ie, the first scanning session in group 1S), the students participated in a CAD/CAM course (3 weeks after T0) in which a monolithic crown was fabricated in a fully digital chairside workflow. The scanning time was measured as the time between the activation and termination of the scanning mode of the intraoral device. Data were analyzed using SPSS Statistics 25 (IBM). The level of significance was set to α = .05. RESULTS: A continual decrease in scanning time was observed for all groups as experience in intraoral scanning increased. The mean scanning times were as follows: for group 3S, 305 seconds at T0, 246 seconds at T1, and 233 seconds at T2; for group 2S, 380 seconds at T0 and 303 seconds at T2; and for group 1S, 355 seconds at T2. When compared to group 1S after it had received nonspecific training only, the effect of a single specific training session in groups 3S and 2S was not significant (P = .4428). However, two specific training sessions had a significant effect on scanning time compared to nonspecific training only (P = .0005). CONCLUSION: Training does affect the scanning time required for CAS. To perform such scans in a time-efficient manner, dental practitioners should undertake training that comprises at least 12 CAS.

Effects of Training on the Execution of Complete-Arch Scans. Part 2: Scanning Accuracy.

PURPOSE: To investigate the effect of training on scanning accuracy of complete arch scans (CAS) performed by first-time users, with a distinction made between specific training (repeated performance of CAS) and nonspecific training (simple use of an intraoral optical scanner for a sextant scan in the context of a CAD/CAM teaching module). MATERIALS AND METHODS: A total of 36 students with no experience in intraoral scanning were randomized into three groups (n = 12 per group) according to the number of CAS sessions: three sessions (3S), two sessions (2S), and one session (1S). Each student had to perform 10 CAS per scanning session. Sessions were scheduled at T0, T1, and T2 for group 3S; at T0 and T2 for group 2S; and at T2 for group 1S. Before the final scanning session in each group (ie, the first scanning session in group 1S), the students completed a CAD/CAM teaching module, which included fabrication of a monolithic crown in a fully digital chairside workflow. RESULTS: In all groups, repeated CAS resulted in improved scanning accuracy. Participation in the CAD/CAM module had a positive effect on initial accuracy for CAS. Mean absolute deviations in cross-arch distance were 84 µm (T0), 68 µm (T1), and 63 µm (T2) for group 3S; 79 µm (T0) and 61 µm (T2) for group 2S; and 67 µm (T2) for group 1S. CONCLUSION: To perform CAS with the best possible accuracy, specific training is highly recommended. In addition, nonspecific training leads to an improvement in initial scanning accuracy.

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.

Accuracy of complete-arch intraoral scans based on confocal microscopy versus optical triangulation: A comparative in vitro study.

STATEMENT OF PROBLEM: Fully digital dentistry is contingent on an accurate digital scan of the complete arch; however, the dimensional accuracy of different scanners for digitizing a complete arch is unclear. PURPOSE: The purpose of this in vitro study was to compare the accuracy of 2 intraoral scanners, TRIOS 3 (TR) and CEREC Omnicam (OC). Accuracy was assessed from changes to reference distances defined along the complete arch of a reference cast including 3 precision balls and 3 prepared teeth. The local accuracy (trueness and precision) of the scanned surface of each prepared tooth was also assessed. MATERIAL AND METHODS: Each intraoral scanner was used to scan a metal mandibular reference cast 20 times in a randomized sequence. The complete dental arch of a mandible in which the second left premolar was missing contained 2 prepared teeth, the first left premolar (LP) and the first left molar (LM) to accommodate a fixed partial denture (FPD) with complete crowns. The arch also contained an inlay preparation on the right second premolar (RP). Stainless-steel precision balls (ball centers P1, P2, and P3), which were welded onto the left second molar (P1), the incisal contact point of the central incisors (P3), and the right first molar (P2), were used to determine dimensional changes over the complete arch. Powder (CEREC Optispray) was applied to the reference cast to reduce reflections. Deviations between the reference cast (digitized with high precision before the tests) and the intraoral scans were calculated using Matlab R2015a and Geomagic Design X. To evaluate dimensional changes, the centers of the balls were determined, and their absolute changes in distance (ΔP1P2, ΔP1P3, and ΔP2P3) were calculated. To calculate accuracy (trueness and precision) in relation to the prepared teeth, the mesh deviation between the intraoral scans and the superimposed reference teeth was determined. The data were statistically analyzed by using a nonparametric rank-based 2-way repeated-measures ANOVA, and differences in least square means for pairwise comparisons were calculated (α=.05). RESULTS: The following mean absolute changes in distance were determined: ΔP1P2, TR: 74.4 µm, OC: 119.6 µm; ΔP1P3, TR: 24.7 µm, OC: 17.2 µm; ΔP2P3, TR: 68.6 µm, OC: 41.2 µm. The scanner did not have a statistically significant effect (P=.118) for distance, and the different distances differed significantly from each other (P<.001). Both scanners provided results acceptable for the fabrication of inlays and short-span FPDs. A complete-crown scan was more accurate than an inlay scan (P<.001). Accuracy and precision were better for TR than for OC (P<.001). CONCLUSIONS: With maximum discrepancies of 192.5 to 294.6 µm across the dental arch, complete-arch scans cannot yet be recommended for the fabrication of long-span FPDs.

Correlations between Sleep Bruxism and Temporomandibular Disorders.

The aim of this study was to identify correlations between sleep bruxism (SB) and temporomandibular disorders (TMD) as diagnosed by means of the research diagnostic criteria for temporomandibular disorders (RDC/TMD). Sleep bruxism was diagnosed on the basis of I) validated questionnaires, II) clinical symptoms, and III) electromyographic/electrocardiographic data. A total of 110 subjects were included in the study. Fifty-eight patients were identified as bruxers and 52 as nonbruxers. A psychosocial assessment was also performed. An RDC/TMD group-I diagnosis (myofascial pain) was made for 10 out of 58 bruxers, whereas none of the nonbruxers received a diagnosis of this type. No significant differences were found between bruxers and nonbruxers with regard to RDC/TMD group-II (disc displacement) and group-III (arthralgia, arthritis, arthrosis) diagnoses. Somatization was significantly more common among bruxers than nonbruxers. Multivariate logistic regression analysis revealed that somatization was the only factor significantly correlated with the diagnosis of myofascial pain. The results of this study indicate a correlation between myofascial pain, as diagnosed using the RDC/TMD, and somatization. It seems that somatization is a stronger predictor of an RDC/TMD diagnosis of myofascial pain than sleep bruxism is.

Three-year clinical performance of monolithic and partially veneered zirconia ceramic fixed partial dentures.

OBJECTIVE: To compare the 3-year survival and success rates of monolithic (M) and partially veneered (PV) zirconia-fixed partial dentures (FPDs). MATERIALS AND METHODS: Sixty-seven FPDs (n = 33 M-FPDs; n = 34 PV-FPDs) were placed in 51 patients (n = 23 males; mean age 61.5 years) and clinically followed up 1 week, 6 months, and then yearly after placement. One hundred per cent (100%) of M-FPDs and 70% of PV-FPDs were located in the posterior region. Ninety-two per cent (92%) of M-FPDs had three units, whereas 50% of PV-FPDs had more than three units. A facial veneer was present in 73% of the PV-FPDs units. Survival and success were calculated using the Kaplan-Meier method and compared using the log-rank test (α = .05). RESULTS: The mean observation period was 3.5 years for M-FPDs and 3.1 years for PV-FPDs. Most complications associated with FPDs were biological in nature. Ceramic defects occurred exclusively among PV-FPDs. Three-year survival was 96.7% for M-FPDs and 93.8% for PV-FPDs (P = .064). Three-year success was 93.8% for M-FPDs and 81.7% for PV-FPDs (P = .039). CONCLUSIONS: The use of both M-FPDs and PV-FPDs yielded clinically successful results over a mean period of 3 years. CLINICAL SIGNIFICANCE: By using monolithic or facially veneered zirconia, ceramic FPDs could be fabricated which showed only a minimum of technical complications over the period of investigation without sacrificing adequate esthetics.

Fully digital fabrication of an occlusal device using an intraoral scanner and 3D printing: A dental technique.

This dental technique describes a fully digital method for fabricating occlusal devices using a complete-arch intraoral scan and 3D printing. The maxillary and mandibular arches of a healthy, fully dentate volunteer were digitized using an intraoral scanner. A second scan and modified recording of the centric relation enabled a virtual arrangement of the maxillary and mandibular arches, both in centric relation and in the desired vertical dimension of occlusion. An occlusal device was subsequently designed virtually and fabricated from a light-polymerizing acrylic resin using a 3D printer. The occlusal device was tested for fit, occlusion, and patient-friendly handling. As only minor occlusal corrections were required, the fully digital procedure described is suitable for the fabrication of occlusal devices.

Tooth substance removal for ceramic single crown materials-an in vitro comparison.

OBJECTIVES: The aim of this in vitro study was to compare the tooth structure removal required for currently available ceramic crown materials. MATERIAL AND METHODS: Ninety typodont teeth (60 incisors, 30 molars) were assigned to nine study groups. The teeth were digitized, weighed with a high-precision balance, and fixed in carriers in identical alignment. Full-crown restorations were prepared according to material-specific guidelines for monolithic zirconia (MZ), polymer-infiltrated ceramics (PIC), buccally veneered zirconia (BVZ), feldspathic ceramics (FC), fully veneered zirconia (FVZ), and lithium disilicate (LD). Tooth structure removal was assessed by weighing the teeth before and after preparation. Coronal volume loss was analyzed statistically by use of one-way ANOVA and post-hoc Tukey HSD tests with α = 0.05. RESULTS: Mean tooth structure removal for incisors was 42% (SD 2%) for MZ, 46% (SD 1%) for PIC, 50% (SD 2%) for BVZ, 57% (SD 1%) for FC, 57% (SD 2%) for FVZ, and 59% (SD 2%) for LD. Mean tooth structure removal for molars was 21% (SD 2%) for MZ, 31% (SD 1%) for PIC, and 35% (SD 1%) for LD. Inter-group differences were statistically significant, except for between FC and FVZ. CONCLUSIONS: Preparation of full ceramic crowns for restoration-free teeth is an invasive procedure. Selecting the ceramic material can, however, reduce loss of tooth structure substantially. CLINICAL RELEVANCE: Monolithic zirconia is the least invasive material for the preparation of incisor and molar ceramic single crowns. Prescribing buccally veneered instead of fully veneered zirconia reduces preparation invasiveness significantly.

In vitro comparison of the load-bearing capacity of ceramic and metal-ceramic resin-bonded fixed dental prostheses in the posterior region.

STATEMENT OF PROBLEM: The clinical use of ceramic resin-bonded fixed dental prostheses (RBFDPs) in the posterior region is desirable for esthetic and biological reasons but has been associated with many technical problems, including fractures or chipping of the veneer. Although these problems may be overcome by using monolithic zirconia, information is lacking about the load-bearing capacity of resin-bonded monolithic zirconia restorations for replacing a molar. PURPOSE: The purpose of this in vitro study was to compare the load-bearing capacity (Fu), the load at initial damage (F1d), and the failure pattern of posterior RBFDPs fabricated from monolithic zirconia (MZr), veneered zirconia (VZr), and veneered cobalt-chromium (VCo). MATERIAL AND METHODS: For the replacement of a maxillary first molar, 4 groups (n=8) of RBFDPs differing in prosthesis material and retainer design (MZr-IR-RBFDPs, VZr-IR-RBFDPs, MZr-WR-RBFDPs, and VCo-WR-RBFDPs; IR, inlay-retained; WR, adhesive wing-retained) were fabricated with anatomic congruence of the FDP-abutment complex. The RBFDPs were subjected to thermocycling (10000×6.5°C/60°C) and mastication simulation (30-degree oblique loading on the pontic; 1200000×108 N) and then loaded until failure in a universal testing machine (0.5 mm/minute). Test forces correlating with Fu and F1d were recorded. Statistical analysis was performed by using 2-way analysis of variance (ANOVA), 2-way repeated measures ANOVA, and the Tukey honest significant differences post hoc test (2-sided α=.05). RESULTS: Fu was significantly affected by retainer design (P<.001) and F1d by both retainer design (P<.001) and prosthesis material (P<.001). Fu was more than 2000 N for WR-RBFDPs and more than 1000 N for IR-RBFDPs (Tukey test ranking: MZr-WR-RBFDPs = VCo-WR-RBFDPs > MZr-IR-RBFDPs = VZr-IR-RBFDPs). Ceramic RBFDPs failed by complete fracture in the connector region, whereas failure of VCo-WR-RBFDPs was limited to the ceramic veneer. F1d was significantly lower (P≤.004) than Fu for veneered specimens only; F1d started at test forces below 500 N and coincided with veneer cracking. CONCLUSIONS: Load-bearing capacity suitable for the definitive restoration of a molar was observed for all groups. Veneered resin-bonded fixed dental prostheses, however, were susceptible to cracking of the veneer.