The International journal of prosthodontics最新文献

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.

Purpose: To investigate the effect of titanium surface treatment and heat-cured acrylic resin (AR) thickness on color differences (ΔE00) in AR.

Materials and methods: Thirty AR specimens were divided into three groups: 1.0, 2.0, and 3.0 mm (n = 10 each). Each AR thickness group underwent testing over six titanium surface treatments (n = 10): untreated titanium (T), gleaming titanium (PT), 50 V anodization (G), polished gold-anodized (PG), 70 V anodization (P), and polished pink-anodized titanium (PP). All specimens from the 18 experimental groups were examined using a spectrophotometer and compared with the control group (10.0 mm AR, n = 5) to establish the color difference (ΔE00). ΔE00 < 4.08 was considered 50% clinically acceptable (50%AT), whereas ΔE00 < 1.72 denoted 50% clinically perceptibility (50%PT). The data collected were statistically analyzed using analysis of variance and post-hoc tests (P =.05).

Results: The AR thickness and type of titanium surface treatment significantly affected the observed ΔE00 (P <.05). When using a 1.0-mm AR over P- and PP-treated titanium, the mean ΔE00 was below 50%AT. When using a 2.0-mm AR over the P and PP, the 95% CIs of ΔE00 were < 50%PT.

Conclusions: The use of a 1.0-mm AR over pink-anodized titanium potentially results in acceptable color matching with 95% CIs.

Purpose: This study evaluated the marginal and internal adaptation, fabrication trueness, and retention of endocrowns made from additively manufactured (AM) glass-filler-reinforced resin composite and zirconia, and subtractively manufactured (SM) advanced lithium disilicate (ALD).

Materials and methods: A resin typodont model was scanned to design endocrowns. Sixty restorations (n=20/group) were fabricated using AM composite (Group C), AM zirconia (Group ZrO2), or SM lithium disilicate (Group ALD). All restorations were scanned with the same intraoral scanner; adaptation (marginal and internal gaps) was quantified with cross-sectional measurements, and trueness was analyzed as RMS deviations. Endocrowns were cemented on resin dies, thermomechanically aged, and tested for pull-out forces. One-way ANOVA (α = .05) was used for statistical analysis.

Results: ALD showed the lowest marginal (30.81 ±2.45 μm) and internal (33.41 ±2.62 μm) discrepancies, followed by ZrO2 (40.45 ±2.80 μm; 46.23 ±2.20 μm), and C (63.92 ±4.30 μm; 60.34 ±3.30 μm). Significant differences were observed between C and ALD (p=.003; p=.009) and between C and ZrO2 (p=.007; p=.012), but not between ALD and ZrO2 (p=.386; p=.115). Trueness was highest in ALD (38.72 ±3.91 μm), followed by ZrO2 (43.55 ±4.16 μm) and C (51.08 ±4.84 μm), with significant differences between ALD and C (p<.001) and ZrO2 and C (p=.004). ZrO2 showed the highest retention (754 ±211 N), significantly greater than ALD (709 ±208 N; p=.014) and C (634 ± 363 N; p=.002).

Conclusions: ALD and ZrO2 endocrowns showed superior adaptation and trueness compared to AM composite. ZrO2 exhibited the highest retention. Within the study's limitations, AM-zirconia appears to be a viable alternative to SM lithium disilicate for endocrown fabrication.

Objective: To compare the effectiveness of four intermaxillary relation recording methods for guiding the virtual adjustment of all-ceramic restorations.

Materials and methods: Twelve participants underwent buccal intermaxillary relation recording using traditional methods (Control group), 3Shape TRIOS3 dynamic scans (SD group), Zebris mandibular motion trajectories (ZT group), and Zebris articulator parameters (ZP group). Virtual adjustments were performed for four restoration types: single anterior/posterior crowns, two posterior crowns, and three-unit fixed bridge. Three-dimensional (3D) occlusal surface deviations between the natural teeth and restorations were measured.

Results: All three digital intermaxillary relation recording methods met clinical requirements. The Zebris trajectory group demonstrated significantly smaller 3D deviations compared with the 3Shape dynamic scan group (P<0.05), exhibiting superior performance in eliminating occlusal interferences of restorations. Notably, the Zebris trajectory group showed significantly reduced 3D deviations only in the single anterior tooth subgroup compared with the Zebris articulator parameter group (P<0.05), indicating better efficacy in removing restorative occlusal interferences.

Conclusions: The three digital techniques matched or exceeded traditional methods in eliminating occlusal interferences, with the Zebris mandibular motion trajectory recording technique demonstrating superiority over the 3Shape dynamic recording method.

Clinical significance: Application of the mandibular motion trajectory recorded by the Zebris mandibular motion analysis system to guide restorative fictive adjustment outperformed the utilization of 3Shape dynamic occlusion.

The study was aimed to retrospectively evaluate differences in marginal bone loss (MBL) between bone level (BL) implants, with (LMS) and without (noLMS) laser-microtextured collar surface, restored with screwed single crowns with different emergence profiles (EP) and emergence angles (EA). Materials and methods: A retrospective evaluation of records and radiographs of 90 patients scheduled for single implant therapy at the molar region over a period of up to 10 years after prosthetic restoration was performed. The radiographic MBL and clinical parameters were measured over time and statistically analyzed. Results: LMS implants presented a statistically significant higher cumulative success rate (97.7 % vs. 91.1%. p<.05) and lower mean MBL compared to noLMS (0.8mm vs. 1.7 mm, p<.05). Around noLMS BL implants an EA.