The Journal of Indian Prosthodontic Society最新文献

Aim: To evaluate the effect of print orientation (0°, 45°, and 90°) on the dimensional accuracy, precision, and production parameters of three-dimensional (3D) printed complete denture models fabricated using VAT photopolymerization and fused deposition modeling (FDM) technologies.

Settings and design: An in-vitro experimental comparative study was conducted to analyze orientation-dependent variations in dimensional trueness and precision among denture models fabricated with two additive manufacturing systems.

Materials and methods: A complete denture prosthesis STL file was fabricated in 60 samples using VAT photopolymerization and FDM technologies across three orientations (0°, 45°, and 90°). Printed models underwent postprocessing, followed by digital superimposition to evaluate trueness and precision.

Statistical analysis used: Statistical analyses were performed using one-way ANOVA with post hoc Tukey's honestly significant difference tests and independent t-tests for intertechnology comparison.

Results: VAT prints demonstrated higher average accuracy (mean deviation: 0.1106 mm) but greater variability (standard deviation [SD] =0.2448 mm) than FDM (mean deviation: 0.0316 mm, SD = 0.1558 mm). Across both technologies, the 0° orientation showed the least deviation (VAT: 0.1106 mm and FDM: 0.0316 mm). ANOVA indicated no significant differences among orientations (P = 0.109), whereas t-tests revealed substantial differences between technologies (t = 16.46, P < 0.00001). FDM at 90° exhibited the lowest variability (SD = 0.1163 mm), suggesting a trend toward improved consistency, though this did not reach statistical significance.

Conclusion: Print orientation influenced dimensional accuracy trends, but only technology type showed statistically significant differences. VAT photopolymerization is suitable for high-precision applications.

Aim: The aim of this study was to evaluate and compare the fracture strength of ceramic veneers bonded to natural teeth using different light-cure resin cements.

Settings and design: An ex vivo study.

Materials and methods: Thirty extracted human maxillary anterior teeth were collected and prepared to receive lithium disilicate ceramic veneers, which were allocated into two groups based on the type of resin cement employed for bonding to natural teeth. The specimens were randomly divided into two groups. One group was bonded with Variolink NLC (Ivoclar), whereas the other was bonded with RelyX cement (3M ESPE). Fracture strength was evaluated using a universal testing machine (UTM), with the maximum load required to induce fracture recorded. The tests were conducted under a controlled crosshead speed of 1 mm/min using the UTM, and the maximum load required to cause fracture was recorded for each specimen.

Statistical analysis used: The Shapiro-Wilk and Kolmogorov-Smirnov tests were employed to assess the data's normality. The variables between the groups were compared using the independent t-test. If P < 0.05, all results were deemed statistically significant.

Results: The mean fracture strength of lithium disilicate veneers differed significantly between the two groups. The mean fracture resistance for RelyX was 0.237 ± 0.083 kN, whereas Variolink demonstrated a higher mean of 0.363 ± 0.109 kN.

Conclusion: Within the limitation of the study, it was concluded that veneers bonded with Variolink NLC cement exhibited higher fracture strength compared to those bonded with RelyX veneer cement.

Aim: To evaluate and compare the mechanical and physical properties of provisional crown and bridge materials fabricated using milling, three-dimensional (3D) printing, and conventional methods.

Settings and design: This was a comparative in vitro study.

Materials and methods: Six different provisional resin materials, with two commercial brands representing each fabrication technique (milled resins including Sagemax and Ruthinium, 3D printed resins including Dionavi and Ackudent, and conventionally fabricated cold-cure resins including Dental Products of India (DPI) and Cool Temp) were tested. A total of 210 samples were prepared, 35 from each material, using their respective fabrication methods. Based on the properties to be evaluated, the 35 samples were further divided into 5 subgroups, each with 7 samples (n = 7). The cylindrical-shaped samples (4 mm × 6 mm) were subjected to tests for compressive strength (CS) and diametral tensile strength (DTS). Rectangular samples (25 mm × 2 mm × 2 mm) were used to assess the flexural strength (FS) and the microhardness (MH). Additionally, disc-shaped samples (10 mm × 2 mm) were examined for physical properties, surface roughness (SR).

Statistical analysis used: One-way analysis of variance and post hoc Tukey's tests were used.

Results: Both milled and 3D printed resin groups demonstrated significantly higher CS and FS (P = 0.001) except with 3D Ackudent. Significantly higher DTS and MH (P = 0.001) were found with both the milling and control groups compared to the 3D-printed resin groups. Control groups exhibited the highest SR (P = 0.022) compared to both milling and 3D printed groups.

Conclusion: Milled provisional resins showed superior mechanical properties, with Sagemax showing the highest FS and MH, Ruthinium with the highest DTS. Both 3D printed resins exhibited the lowest DTS and MH, though 3D Dionavi showed higher CS compared to milled and conventional resins. The conventional resins showed lower FS than milled resins and 3D Dionavi but higher than 3D Ackudent. Both 3D printed and milled resins showed smoother surfaces than those of conventional provisional resins.

Aims: To evaluate the impact of implant collar design on peri implant inflammatory biomarkers and crestal bone levels over a 6-month period.

Settings and design: This pragmatic, randomized, parallel-group clinical trial was conducted at the Department of Prosthodontics and Crown and Bridge, Manav Rachna Dental College, between May 2023 and May 2024.

Materials and methods: The study included 30 systemically healthy patients aged 20-60 years with a single missing tooth in the mandibular molar region. Patients were randomly assigned to two groups based on the implant collar design - smooth or microthreaded. Implants were placed following a standardized two stage surgical protocol. Peri-implant crevicular fluid was collected at the time of implant placement, 3 months, and 6 months postplacement to assess inflammatory biomarkers (interleukin-1 [IL-1β] and tumor necrosis factor alpha [TNF-α]) using ELISA. Peri-implant crestal bone levels were measured radiographically at the same intervals.

Statistical analysis used: Statistical analysis was performed using the SPSS (version 21.0). The data were analyzed using appropriate statistical tests. P < 0.05 was considered statistically significant.

Results: IL-1β and TNF-α increased in both groups at the 3-month follow-up, reflecting a typical postsurgical inflammatory response and subsequently decreased at 6 months. The changes in cytokine levels were not significantly different (P > 0.05) between groups, suggesting a similar inflammatory response regardless of collar design. Crestal bone levels in implants with microthreaded collar design exhibited significantly lower loss (0.44 mm) compared to smooth collar implants (0.94 mm), with a statistically significant mean difference of 0.5 mm (P = 0.019). Correlation analysis revealed no statistically significant relationships between crestal bone levels and inflammatory markers at any time point.

Conclusion: Although both collar designs had a limited influence on the early peri-implant inflammatory response, but microthreaded collars were more effective in preserving crestal bone.

Aim: To evaluate and compare the effects of different thread lockers on implant abutment screw loosening.

Settings and design: An in-vitro study.

Materials and methods: Thirty implant-abutment assemblies were divided into 3 groups: Control group (without threadlocker), dimethacrylate group, and methacrylate group. Each group was subdivided into static and dynamic groups. The specimens were torqued to 35 Ncm, and detorque values were measured after 1 month in static conditions and after cyclic loading. The cyclic loading protocol involved 240,000 cycles at a velocity of 16 mm/s over a 48-h period in a moist environment, simulating 1 year of clinical function.

Statistical analysis used: Two-way ANOVA tests were applied to assess intergroup comparisons of detorque values (Ncm) under static and dynamic conditions.

Results: Results were assessed using one-way, two-way ANOVA and multiple pairwise comparisons with a significance level of P ≤ 0.05. The methacrylate group demonstrated the highest detorque values (static: 36.46 ± 0.95 Ncm, dynamic: 33.22 ± 0.34 Ncm), followed by the dimethacrylate group (static: 32.84 ± 1.12 Ncm, dynamic: 29.98 ± 1.05 Ncm). The control group exhibited the lowest detorque values (static: 28.80 ± 0.96 Ncm, dynamic: 25.84 ± 0.63 Ncm). Detorque values were consistently higher in the static condition (32.40 ± 3.37 Ncm) compared to the dynamic condition across all groups (29.68 ± 3.20 Ncm), with statistically significant differences observed (P = 0.000).

Conclusion: Within the limitations of the study, application of threadlockers significantly improved abutment screw retention, with methacrylate exhibiting superior performance over dimethacrylate. The reduction in detorque values under cyclic loading highlights the need for enhanced retention strategies in implant prosthetics. Incorporating methacrylate-based threadlockers in clinical practice may mitigate screw loosening and enhance the long-term success of implant-supported prostheses.

Aim: The aim of this study was to evaluate the effect of the number of intraoral scan bodies (ISBs) on the accuracy of digital impressions and the resulting master casts in full-arch maxillary implant rehabilitations in "all-on-4" and "all-on-6" situations.

Settings and design: This was an in vitro comparative study.

Materials and methods: Forty-two digital impressions were obtained for all-on-4 (Group A) and all-on-6 (Group B) implant situations. Group A had three scan situations-1, 2, and 3-using 1, 2, and 4 scan bodies, respectively. Group B had four scan situations-1, 2, 3, and 4-employing 1, 2, 4, and 6 scan bodies, respectively, with six scans per situation. Linear and angular measurements were digitally evaluated by superimposing STL files onto reference models using Geomagic Control X. One master cast was fabricated for each scan situation, and verification jigs were assessed for passivity and fit.

Statistical analysis used: Data were analyzed using the Shapiro-Wilk test to confirm normal distribution, followed by one-sample t-test for comparison of linear and angular deviations between scan and reference models (p < 0.05).

Results: In Group A, regardless of the scan situation, the differences in the measurements between the scan and reference model were statistically significant. In Group B, the study showed that scan situation 4 yielded the most accurate measurements when compared with reference model (P = 0.136). In both Groups A and B, master models fabricated using four and six scan bodies, respectively, exhibited the best passive fit of the verification jig.

Conclusion: Within the limitations of this study, scan body quantity significantly influenced digital impression accuracy in full-arch implant prosthodontics. All-on-4 achieved reliable results with two ISBs but benefited from four for angular accuracy, while all-on-6 required six ISBs for optimal trueness and passive fit, underscoring their importance in complex rehabilitations.

Aim: To compare infra-sinus residual ridge height measured preoperatively using Cone-Beam Computed Tomography (CBCT) with intraoperative measurements recorded during indirect sinus lift osteotomy using the Crestal Approach Sinus (CAS) kit, and to evaluate the reliability of CBCT in posterior maxillary implant planning.

Settings and design: This prospective observational clinical study was conducted on participants requiring implant rehabilitation in the posterior maxilla.

Materials and methods: Fifty participants indicated for implant placement in the posterior maxilla were included. Infra-sinus residual ridge height was measured preoperatively on CBCT scans using Planmeca Romexis® software. Intraoperative measurements were recorded during indirect sinus lift osteotomy using a depth gauge from the CAS kit. Preoperative CBCT measurements were compared with intraoperative findings.

Statistical analysis used: Statistical analysis was performed using Jamovi version 2.3.28 software. The Shapiro-Wilk test was applied to assess the normality of numerical variables. As the data were non-normally distributed, the Wilcoxon signed-rank test was used to determine the significance of differences between CBCT and intraoperative measurements. A p-value <0.05 was considered statistically significant.

Results: The mean infra-sinus residual ridge height measured on CBCT was 4.66 ± 0.798 mm, while the mean intraoperative measurement was 6.50 ± 1.074 mm. The difference between the two measurement methods was statistically significant (p < 0.001), indicating a consistent underestimation of ridge height by CBCT.

Conclusion: CBCT consistently underestimates infra-sinus residual ridge height by approximately 1.86 mm when compared with intraoperative measurements. Although CBCT remains indispensable for pre-surgical planning, reliance on CBCT alone may be insufficient for sinus lift procedures, particularly in borderline cases. A dual-modality approach combining CBCT evaluation with intraoperative verification improves accuracy and safety, thereby supporting evidence-based and precise clinical decision-making.

Aim: Verification jigs play a vital role in ensuring the passive fit of implant-supported prostheses by accurately transferring implant positions to the working cast. This in vitro study aimed to compare the dimensional accuracy of verification jigs fabricated using chemically polymerized (self-cure) and photopolymerized acrylic resin.

Settings and design: In-vitro study design.

Materials and methods: Sixteen three-dimensional-printed mandibular edentulous models with embedded implant analogs were used and divided into two groups (n = 8). Group A jigs were fabricated using self-cure resin (Pattern Resin™ LS, GC America), while Group B used light-cured resin (Resinlay®, TDV Dental, Brazil). All jigs were sectioned and relined to compensate for polymerization shrinkage before pouring the final working casts. The casts were scanned using a desktop optical scanner, and standard tessellation language (STL) files were superimposed onto a reference model using Geomagic Control X software. Root mean square (RMS) deviation, linear inter-implant distance deviation, and angular deviation were calculated.

Statistical analysis used: Statistical comparisons were made using an independent t-test.

Results: Group A and Group B demonstrated comparable RMS deviation (0.057 ± 0.003 mm vs. 0.060 ± 0.003 mm; P = 0.170), linear deviation (0.084 ± 0.003 mm vs. 0.090 ± 0.002 mm; P = 0.270), and angular deviation (1.855° ± 0.023° vs. 1.965° ± 0.061°; P = 0.148). None of the differences were statistically significant.

Conclusion: Both groups provide clinically acceptable dimensional accuracy in verification jig fabrication. Resinlay, with its superior handling and reduced working time, may serve as an efficient alternative in clinical settings.

Aim: To assess the association between mock-up technique (chairside bis-acryl vs digitally fabricated 3D-printed) and shade-matching protocol (chairside visual vs laboratory-assisted/digital) with patient-initiated esthetic dissatisfaction resulting in refund or retreatment within 12 months of veneer delivery.

Settings and design: Single-center, 1:1 matched case-control study (23 pairs; n = 46) in a private prosthodontic practice.

Materials and methods: Exposures were chairside bis-acryl versus digitally fabricated 3D-printed mock-ups and chairside visual versus laboratory-assisted/digital shade matching. The primary outcome was patient-initiated esthetic dissatisfaction within 12 months resulting in refund or retreatment; refund-only and retreatment-only outcomes were prespecified as exploratory.

Statistical analysis used: Primary analysis used exact conditional methods for matched pairs (McNemar) with exact 95% confidence intervals; in the presence of separation, the exact lower confidence bound was reported without continuity corrections. A supportive multivariable unconditional logistic regression adjusted for age, sex, exact number of units, arch, and cost tier, and E-values were calculated to assess robustness to unmeasured confounding.

Results: Chairside mock-ups and chairside-only shade selection were more frequent in cases than controls. The matched odds ratio (OR) for chairside versus digitally fabricated mock-ups was ∞ (exact lower 95% confidence interval ≥2.51; P = 0.0010), and for chairside versus laboratory-assisted/digital shade matching was 6.00 (95% confidence interval 1.34-55.20; P = 0.0129). In the supportive adjusted model, the ORs were 5.87 (95% confidence interval 1.59-21.66; P = 0.008) for mock-up technique and 4.41 (1.26-15.42; P = 0.021) for shade protocol; corresponding E-values were 11.48, 11.22, and 8.29, respectively.

Conclusion: Within the limitations of a retrospective, single-center design and modest sample size, chairside bis-acryl mock-ups and chairside-only shade matching were associated with higher odds of early esthetic dissatisfaction leading to refund or retreatment. Adoption of standardized digital workflows with digitally designed/3D-printed mock-ups and calibrated shade protocols is recommended as a clinical quality-assurance measure to mitigate this risk.