The International journal of prosthodontics最新文献

Purpose: This clinical study aimed to compare one-year survival rates of zirconia single-retainer resin-bonded fixed partial denture (RBFPD) on upper canines versus upper central incisors.

Materials and methods: Fifty-four multilayered, ultra-translucent zirconia single-retainer RBFPDs were placed in 50 patients, divided equally into two groups: an intervention group with a distal retainer (D-retainer) on the upper canine and a control group with a mesial retainer (M-retainer) on the upper central incisor. Patients were followed for one year. Survival was assessed by debonding, fracture, and abutment mobility using modified USPHS criteria. Patient satisfaction was measured via the visual analog scale (VAS). Fisher's exact test was used for comparisons, and survival analysis was performed with the Kaplan-Meier method (significance set at p ≤ 0.05).

Results: The D-retainer group showed an 81% survival rate, with five cases experiencing two debondings. The M-retainer group had an 86% survival rate, with three cases debonded twice. Both groups showed high patient satisfaction and stable abutment mobility.

Conclusions: Within the limitations of this study, no difference was found between canine and central incisor abutments. Both designs showed excellent fracture resistance, stable mobility, and high satisfaction. Debonding was the only failure mode. This study was registered at ClinicalTrials.gov (NCT05812066).

Purpose: To investigate the resistance, retention, and prosthetic adaptability of an abutment prosthetic support interface (APSI) for single and splinted implant restorations.

Materials and method: Twenty-five 3 mm hexagonal-tapered hybrid abutments were subjected to fatigue testing to evaluate resistance of cemented metal crowns, applied on-axis and off-axis. Crowns of three different heights, 10 mm, 12 mm, and 14 mm were assessed. Retention was evaluated via dislodgement force testing for two configurations, single crowns (n=5) cemented on five 3 mm-high hybrid abutments and five 6 mm-high 8° tapered abutments; and splinted two-unit prostheses (n=10) cemented on two 3 mm-high hybrid abutments and two 3 mm-high 8° tapered abutments, both arranged in converging implant configurations.

Results: All resistance specimens subjected to axial loading survived 1 million cycles. Off-axis loading resulted in implant body fractures in all specimens for 12 mm and 14 mm crown heights. Mean number of cycles to failure was 320,117 ± 114,230 for the 12 mm group and 137,375 ± 144,420 for the 14 mm group. Mean dislodgment forces of single crowns cemented on 3 mm-high hybrid abutments compared to 6 mm-high 8° tapered abutments were significantly different (p<0.05). Splinted prostheses on 3 mm-high hybrid abutments compared to 3 mm-high 8° tapered abutments were significantly different (p<0.001).

Conclusion: The APSI (hybrid abutment) concept demonstrated: (1) a cemented crown-abutment interface strength exceeding the inherent strength of the titanium implant material; (2) significantly greater cemented crown retention compared to tapered abutments; and (3) rotational adaptability, enabling optimized insertion paths for splinted restorations.

Purpose: The effect of ambient lighting on intraoral scanner accuracy has mostly been evaluated for single-arch scans, leaving limited evidence regarding its comparative influence on maxillary and mandibular arches. The purpose of this study was to compare intraoral scanner accuracy for maxillary and mandibular arches under varying ambient lighting conditions.

Material and methods: A maxillary and a mandibular typodont model was digitized using a laboratory scanner (3Shape E4) to obtain reference STL files. Two different intraoral scanners (iTero Element 5D and TRIOS 3) were evaluated under five different lighting conditions: zero light, daylight, room light, low intensity chair light and high intensity chair light. 10 digital scans per each group and a total of 200 scans were performed (n=10). The digital scans and the reference STL files were superimposed using Geomagic Design X software to analyze accuracy.

Results: Statistically significant differences were found among scanners, arches, and ambient lighting conditions (p<0.001). The mandibular arch showed greater accuracy than the maxillary arch (p<0.001). Zero light yielded the lowest trueness values while room light provided the most accurate results (p<0.001). Scanner performance varied under different lighting conditions, with iTero Element 5D consistently outperforming TRIOS 3.

Conclusions: Ambient lighting significantly affects intraoral scanner accuracy, with room light providing the most reliable results. Optimizing lighting conditions is crucial for improving digital impression accuracy in clinical and laboratory settings.

Purpose: This study evaluated the bond strength of flowable and packable composites to sandblasted dentin using different adhesive systems.

Materials and methods: A total of 160 extracted premolars were sectioned at the upper-middle third and allocated into 16 groups (n=10) based on composite type, surface treatment, and adhesive system. In sandblasted groups, dentin was air-abraded with 50 µm aluminum oxide for 10 s. Composite cylinders (3 mm × 3 mm; 7.065 mm²) were bonded using Single Bond 2, Palfique Bond, or Single Bond Universal. Shear bond strength (SBS, MPa) and failure modes were recorded, and bonding interfaces were examined by scanning electron microscopy (SEM). Data were analyzed using three-way ANOVA with Tukey's HSD, Kruskal-Wallis with Bonferroni correction, and Weibull analysis.

Results: Flowable composites, sandblasting, and the two-step application of Single Bond Universal each significantly improved bond strength. A three-way interaction was observed (F=5.12, p=0.01). Groups 1, 8, and 13 showed the highest bond strengths (11.47 ± 6.44, 15.88 ± 5.39, and 12.90 ± 4.98 MPa; p<0.05), with Groups 8 and 13 demonstrating superior Weibull modulus (m) and characteristic strength (σ₀). SEM analysis revealed these groups exhibited the most intimate adhesive-dentin contact with minimal interfacial defects. Failure mode assessment showed predominantly cohesive and mixed failures in Groups 1, 8, and 13.

Conclusions: Sandblasting, flowable composites, and two-step Single Bond Universal enhance dentin bond strength. The most effective combinations were sandblasted dentin with flowable composite and Single Bond Universal (one-step), and non-sandblasted dentin with packable composite and Single Bond Universal (two-step).

Purpose: To evaluate the trueness and precision of alignment protocols across three dental CAD platforms for spatially aligning virtually altered digital dental models to their original position.

Materials and methods: A digital cast of the lower dentition served as the basis for generating a digital model, which was morphologically altered through base trimming, virtual extractions, crown modifications, orthodontic tooth movements, surface adjustments, and mesh density reduction. The altered model was then displaced and aligned to the original cast using five alignment protocols across three software platforms: BlueSky Plan (landmark-based), Exocad (landmark-based and landmark-based with best-fit optimization), and Blender for Dental (B4D) (landmark-based with generalized ICP and reference-based with localized ICP). Each protocol was repeated ten times. Alignment accuracy was quantified against the reference standard using root mean square (RMS) error, average and maximum absolute 3D deviation, and linear landmark deviation. Data were analyzed using descriptive statistics, coefficient of variation (CV%), and Welch's ANOVA with Games-Howell post hoc tests (α = 0.05).

Results: Alignment accuracy differed significantly between methods (P<.001). Exocad's landmark-based with best-fit optimization achieved 12 μm RMS error (CV: 1.17%). B4D's reference-based with localized ICP achieved 47 μm (CV: 14.82%). Landmark-based methods performed poorly: BlueSky 250 μm, Exocad 160 μm, and B4D with generalized ICP 152 μm, with high variability (CV: 20.1-25.3%).

Conclusion: Alignment method selection critically affects accuracy when processing altered dental digital models. Landmark-based alignment combined with optimized best-fit algorithms and reference-based alignment with localized ICP achieved clinically acceptable accuracy, while landmark-based methods alone produced unacceptable errors unsuitable for precision digital workflows.

Purpose: To evaluate the impact of different resin injection guides (RIGs) on the surface roughness (Ra), microhardness (MH), and conversion degree (CD) of direct composite resin restorations.

Materials and methods: Disc-shaped specimens (diameter: 4.5 mm, thickness: 2 mm) were fabricated using five molding methods (n = 16 per group): freehand filling (FH), transparent polyester strip (PS), transparent polyvinyl siloxane guide (PVS), flexible resin guide with rigid shell (FR), and rigid resin guide (RG). Surface topography was analyzed using a multi-functional tribometer, and Ra values were calculated. MH was measured with a microhardness tester. CD was determined via Fourier transform infrared spectroscopy. Data were analyzed with ANOVA and post hoc tests.

Results: Significant differences in Ra were found (P < .05), in the order of PS < FH < PVS < FR < RG. The PS, FR, and RG groups showed no significant differences in MH or CD (P > .05), but these values were significantly greater than those in the FH and PVS groups (P < .05). The PVS group had higher MH and CD than the FH group (P < .05).

Conclusions: The use of guides prevents formation of the oxygen inhibition layer, increasing MH and CD by up to 22% compared to the freehand technique. Although all guides increased Ra compared to the polyester strip, the PVS guide produced the smoothest surfaces among the RIGs, albeit with lower MH and CD than the 3D-printed guides (FR, RG).

Purpose: This in vitro study evaluated the influence of digital cement space thickness (80 μm, 100 μm, 120 μm) on the marginal discrepancy of monolithic zirconia crowns fabricated using CAD/CAM technology.

Materials and methods: Seventy-five monolithic zirconia crowns were digitally designed and milled with cement space thicknesses of 80, 100, and 120 μm (n = 25 per group). Marginal discrepancies were assessed at eight predetermined points using scanning electron microscopy at ×100 magnification. The measurement points-mesial (M), mesiobuccal (MB), buccal (B), distobuccal (DB), distal (D), distolingual (DL), lingual (L), and mesiolingual (ML)-were precisely marked on each crown using a custom-made PMMA mold with pre-formed positioning holes to ensure consistent localization. Statistical analysis included one-way ANOVA and Tukey's post hoc tests.

Results: The mean marginal discrepancy at the 80 μm cement space was 33.35 μm, at the 100 μm cement space 31.36 μm, and 28.37 μm at 120 μm cement space. No statistically significant difference was found between groups. However, significant localized differences were found at the D and ML points between the 80 μm and 120 μm cement space groups (P = .035). All measured discrepancies were within the commonly accepted range (<120 μm).

Conclusion: Within the limits of this in vitro study, variations in cement space thickness between 80 μm and 120 μm did not significantly influence marginal discrepancy. Digital cement space settings within this range produced accurate and consistent fits.

Purpose: To evaluate five-year survival rates of metal-ceramic, veneered all-ceramic, and monolithic all-ceramic tooth-supported single crowns (SCs) and assess biological and technical complications.

Materials and methods: A systematic search of Medline (PubMed), Embase, and CENTRAL (2014-2024) identified clinical studies on tooth-supported fixed dental prostheses (≥3 years mean follow-up). Manual screening and 30 studies from previous reviews were added. Sixty-four studies met inclusion, reporting on 3,509 metal-ceramic and 8,051 all-ceramic SCs. Robust Poisson regression models were used to estimate pooled five-year survival rates.

Results: Twelve studies investigated metal-ceramic crowns, 49 all-ceramic crowns, and three both. Five-year survival rates were: 98.5% for monolithic lithium-disilicate reinforced glass-ceramic, 97.3% for veneered densely-sintered zirconia, 97.1% for metal-ceramic, 96.8% for monolithic densely-sintered zirconia, 95.7% for veneered leucite/lithium-disilicate reinforced glass-ceramic, 94.5% for densely-sintered alumina, 94.3% for glass-infiltrated alumina, 90.4% for feldspathic/silica-based ceramic. Survival rates of feldspathic/silica-based ceramic (p<0.0001), glass-infiltrated alumina (p=0.019), densely sintered alumina (p=0.002), and veneered leucite/lithium-disilicate reinforced glass-ceramic (p=0.021) were significantly lower than monolithic lithium-disilicate SCs. Except for feldspathic/silica-based ceramic and metal-ceramic crowns, material/design types performed similarly in anterior and posterior regions. Monolithic lithium-disilicate and monolithic zirconia crowns showed significantly fewer ceramic fractures and chipping compared to veneered alternatives.

Conclusions: Lithium-disilicate and zirconia-based all-ceramic SCs achieve five-year survival rates comparable to metal-ceramic crowns. Monolithic designs reduce fracture and chipping risk, improving long-term clinical outcomes.

Purpose: To evaluate the effect of one crown one time (1C1T) protocol, in comparison with soft tissue conditioning involving multiple abutment disconnections, on the esthetic outcomes of single implant-supported restorations in healed implant sites.

Materials and methods: Twenty-nine patients over the age of 25, each receiving a single implant in the anterior or premolar regions, participated in this study. Half of the submerged implants were restored immediately after uncovering using a final screw-retained zirconia crown, luted to a titanium base. The remaining submerged implants initially received a healing abutment, followed by soft tissue conditioning phase with provisional restorations prior the delivery of the definitive crowns. All patients were followed for 12 months. Esthetic outcomes were assessed using Pink Esthetic Score (PES), analysis of peri-implant soft tissue volumetric alterations, and patient-reported outcome measures (PROMs).

Results: The CG and 1C1T group exhibited mean PES of 8.9±2.6 and 10.5±1.6, respectively, at baseline (p >0.05) and of 10.8±2.2 and 11.1±1.2 at 1-year follow-up (p>0.05). Regarding volumetric soft tissue alterations, the CG presented a higher root mean square (RMS) discrepancy (median:336) compared to the 1C1T group (median:192 µm) (P<0.05). The CG exhibited a median linear gain of 329μm, while the test group showed a slight median reduction on -19μm. PROMs remained consistently high in both groups over time, with no statistically significant differences in median values at baseline (p>0.05), as well as in 12-months follow-up (P>0.05).

Conclusions: When appropriate surgical and prosthetic protocols are followed, omission of the provisional phase does not compromise the short-term esthetic outcomes of single implant restorations, rendering the one-crown one-time concept a viable treatment alternative.

Purpose: To evaluate the marginal and internal fit of anterior monolithic zirconia crowns fabricated over preparations with different TOC angles with and without a rounded incisal design.

Materials and methods: Crown preparations of fourteen maxillary central incisors were digitally designed and fabricated using photosensitive resin. The axial wall inclinations were -8°, -4°, 0°, 8°, 12°, 16°, 22° with and without rounded incisal corners and a 1-mm-wide chamfer-type finish line. Monolithic zirconia crowns (n=10) were milled and assessed for fit using the dual-scan technique using an intraoral scanner. The STL files were analyzed in Geomagic Control X, measuring fit at 100, 150, and 175 points on the incisal, axial and marginal areas, respectively. Data normality was tested (Shapiro-Wilk), and TOC angle groups were compared using One-way ANOVA, Levene's test, Tukey HSD, and Independent Samples T-tests (p<0.05).

Results: TOC angle groups showed statistically significantly differences (p<0.001). The 22° preparation had the lowest marginal discrepancies (36±5 μm rounded, 61±5 μm non-rounded), while -8° had the highest (117±9 μm rounded, 147±30 μm non-rounded). Axial discrepancies were lowest at 22° (77±14 μm) and highest at -8° (208±52 μm) in non-rounded samples (p<0.001). The smallest incisal discrepancy was found in 22° (95 ± 13 μm); while the largest (163 ± 31μm) was at -4° in the non-rounded groups (p<0.001).

Conclusions: TOC angle and rounded preparations have a significant impact on the fit of CAD/CAM milled monolithic zirconia crowns. Rounded incisal corners and preparations with higher TOC angles increased marginal and internal adaptation of the crowns.