International Journal of Prosthodontics最新文献

Purpose: To analyze the influence of pristine matrix and O-ring dimensions on retention force and reproducibility in single one-piece mini dental implants (MDIs) with ball patrices under in vitro conditions.

Materials and methods: Three different matrix and O-ring combinations (MH1-MH3) were evaluated (n = 50 per group) on 1.8-mm-diameter implants. The matrices were manually mounted on the implants and were subsequently removed in a vertical linear manner using a metal pin with two strain gauges, recording the maximum force during disconnection. After five disconnections, the O-rings were exchanged, and the mean retention force was calculated, resulting in 50 values for each matrix and O-ring combination. Mean retention forces, SDs, and 95% CI were calculated. Analysis of variance was used to test the global differences, and post hoc pairwise comparisons were subsequently applied. The level of significance was set to P < .05.

Results: ANOVA (global P < .0001) and pairwise comparisons (all P < .0001) demonstrated statistically significant differences among the three different matrix and O-ring combinations, with mean values of 5.18 N (MH 1), 6.73 (MH 2), and 9.08 (MH 3). Within each combination, retention force variations of > 1 N could not be demonstrated; ie, by exchanging O-rings, a similar retention force can be reestablished.

Conclusion: Matrix and O-ring dimensions have a significant influence on retention forces in one-piece MDIs. Pristine O-rings demonstrated highly reproducible initial retention forces in all matrices.

Purpose: To provide a 1-year assessment of friction-retention abutments (Acuris, Dentsply Sirona) used to retain a single lithium disilicate (LS₂) monolithic restoration.

Materials and methods: A total of 522 implants were placed to treat single-tooth premolar and molar edentulous sites in the mandible or maxilla. Three types of implants were used. The tested abutments were connected 3 months after implant placement. A single pressed LS₂ monolithic restoration was cemented to a dedicated titanium cap and engaged to the abutment without the use of screws or cement. Any complications affecting the restoration or the opposing dentition, soft tissue dimensional changes, the distance between the implant platform and the bone peak, and pocket probing depths were recorded at the time of restoration placement (T0), after 6 months of function (T1), and after 1 year of function (T2). Esthetic, functional, and biologic parameters were recorded at T0 and T2.

Results: A total of 507 patients (284 women and 223 men) received a restoration (T0), and 504 of them reached the T2 1-year follow-up. One restoration fractured after 10 months in function. No statistically significant difference was assessed in the soft tissue measurements or in the measurements of the distance between the supporting implant platform and the bone peak. None of the restorations detached during the observation period.

Conclusion: The friction retention abutment is a viable option to retain an implant-supported monolithic LS₂ glass-ceramic restoration in cases of premolar or molar single-tooth edentulism.

Purpose: To evaluate the minimal ceramic thickness needed to increase the lightness by one value by means of glass-ceramic restorations perceived by dental technicians, dentists, and laypersons.

Material and methods: A total of 15 assessment pairs (reference and test samples) were formed using glass-ceramic blocks in four different colors. Each assessment pair was comprised of two underground blocks differing in one value of lightness. On top of the underground blocks, glass-ceramic platelets were cemented in five different thicknesses (0.1 to 0.5 mm) and in the same color as the reference. Dental technicians, dentists, and laypersons (n = 41/group) were asked to determine the presence of a color difference between the two samples under standardized lighting conditions. The threshold ceramic thickness was defined as the thickness at which ≥ 50% of the evaluators were not able to perceive a difference within an assessment pair. The thresholds were analyzed, and groups were compared by applying chi-square test (P < .05).

Results: The majority of dentists and dental technicians (> 50%) detected a lightness difference between the test and reference samples up to a ceramic thickness of 0.5 mm. The majority of laypersons (≥ 50%) did not perceive a lightness difference with ceramic thickness of 0.5 mm. If separated by the different color changes, the threshold ceramic thickness started at 0.4 mm and varied within the groups of evaluators and by the lightness of the assessed color.

Conclusion: A considerable number of evaluators perceived a lightness difference when minimally invasive ceramic restorations of 0.5-mm thickness were applied. The threshold ceramic thickness, however, was reduced when the lightness of the substrate was lower.

Purpose: To measure the validity and reliability of two gingival shade guides to represent in vivo gingival color using a Caucasian population sample.

Materials and methods: CIELab color space was used to study three gingival reference areas (the free gingival margin, the keratinized gingival body, and the upper part of the keratinized gingiva) in a sample of 259 Caucasian individuals. The color coordinates on the HeraCeram and on the IPS d.SIGN physical gingival shade guides were collected to compare with the color coordinates taken in vivo. The coverage errors of the two shade guides evaluated were calculated using CIELab, and CIEDE 2000 formula and each area of the gingiva was compared with the 50:50% acceptability threshold for ΔE* = 4.6 and ΔE00* = 4.1. The spectroshade spectrophotometer was used.

Results: The IPS d.SIGN guide has similar coverage errors in all three areas and, in all cases, surpasses the 50:50% acceptability threshold. In contrast, the HeraCeram Gingiva guide has a lower coverage error in the free gingival margin than in the other two areas, and the coverage error remains below the 50:50% acceptability threshold only for δE00*. The HeraCeram gingiva shade guide has overall coverage errors (ΔE* = 7.9 and ΔE00* = 5.6) significantly lower than the coverage errors obtained for the IPS d.SIGN gingival shade guide (ΔE* = 9.2 and ΔE00* = 6.8).

Conclusion: Statistically significant differences were found in the coverage errors of both guides, both at the level of the three reference areas and at the global level. For both guides and in both sexes, the global coverage errors calculated with the CIELab and CIEDE2000 formulas were below the literature data on 50:50 acceptability thresholds.

Purpose: To assess the influence of two preparation techniques on the microleakage, marginal fit, and cement thickness of lithium disilicate veneers.

Materials and methods: A total of 24 human maxillary central incisors were divided randomly into two groups according to preparation technique (n = 12): minimally invasive preparation with butt-joint design (0.3-mm depth) and a chamfer finish line (group MP); and no preparation (NP). All teeth were restored with lithium disilicate veneers cemented with photopolymerizable resin cement. Specimens were aged thermally (6,000 cycles of 5°C to 55°C) and mechanically (100,000 cycles at 100 N, 4 Hz). Specimens were immersed in fuchsin for 24 hours employing a standard dye penetration technique, then sectioned and evaluated under a stereomicroscope (x20). Data were analyzed by ANOVA and Kruskal-Wallis tests (P < .05).

Results: There was significant microleakage (P = .0163) at the cervical area compared to the proximal area. The marginal fit was similar, with no statistical difference (P = .212) between groups MP (153 ± 81 μm) and NP (111 ± 74 μm). Group MP showed a significantly (P = .006) reduced cement thickness at the cervical area (87 ± 27 μm) compared to group NP (210 ± 89 μm).

Conclusion: Although the preparation technique was shown to influence the cement thickness, it did not show any influence on microleakage or marginal fit.

Purpose: To compare patient adaptation to and satisfaction with new complete dentures fabricated with a duplication construction protocol (DCP) using two different occlusal schemes, bilateral balanced (BBO) and lingualized (LO).

Materials and methods: Twenty complete denture wearers who received replacement DCP dentures participated in this study. Ten participants received complete dentures with a BBO scheme, and the other 10 received DCP dentures with an LO scheme. All of them evaluated their prostheses subjectively through the Oral Health Impact Profile-20 (OHIP-20) and the Complete Denture Satisfaction (CDS) questionnaires before treatment and at 3- and 6-month posttreatment intervals. The new prostheses were also normatively evaluated by recording the location and number of sore spots present at the scheduled early adjustment visits. Data were analyzed with nonparametric tests to identify differences in patient responses between groups and within each group at each evaluation interval point (α = .05).

Results: The within-group comparisons revealed statistically significant improvement for both denture groups (P < .05), while the between-group comparisons did not record statistically significant differences at the overall evaluation period (P > .05). Significant within-group differences were recorded in the pain, functional limitation, and psychologic disability domains of the OHIP-20 questionnaire and the comfort, esthetics, and stability domains of the CDS questionnaire.

Conclusion: The patients' adaptation to and satisfaction with newly constructed DCP dentures improved significantly for both BBO and LO denture groups throughout the evaluation period. The mean number of early adjustment visits was equal for both the BBO and LO denture groups.

Purpose: To evaluate the effect of different treatments applied to titanium implant abutment surfaces on the retention of implant-supported cement-retained crowns using resin cement.

Materials and methods: A total of 72 titanium implant abutments were divided into six groups (n = 12 each) based on the selected surface treatments: (1) untreated; (2) airborne particle abrasion; (3) hydrogen peroxide etching; (4) atmospheric plasma; (5) chemical mechanical polishing; and (6) titanium dioxide (TiO₂) nano coating. After the surface treatments, scanning electron microscopy analyses and surface roughness measurements of the abutment surfaces were performed. Seventy-two metal copings were fabricated and cemented on the abutments with dual-curing resin cement. After a thermal cycling process, crown retention was measured using a universal testing machine. The experimental results were statistically evaluated with one-way analysis of variance, Tukey honest significant difference, and Tamhane's T2 tests.

Results: The highest surface roughness values were obtained with the airborne-particle abrasion group (1.44 μm), which also resulted in the highest retention values (828.5 N), followed by the hydrogen peroxide-etching group (490.7 N), the atmospheric plasma group (466.5 N), the chemical mechanical polishing group (410.8 N), and the control group (382.6 N).

Conclusion: It was determined that airborne particle abrasion, hydrogen peroxide etching, and atmospheric plasma treatments significantly increased the crown retention and that all alternative treatments, except for TiO₂ nano coating, worked better than the untreated control.

This case report describes a new digital workflow for computer-assisted implant surgery in an edentulous patient using transitional implants to support a fixed surgical template and interim prosthesis. The accuracy of the final implant position using the described protocol was evaluated and compared to the outcomes obtained using other types of surgical templates. This novel digital approach appears to enhance the accuracy of implant positioning for edentulous patients and seems to be comparable to a tooth-supported surgical template.

Purpose: To compare the marginal gap and internal fit of fixed dental prostheses (FDPs) fabricated using intraoral vs extraoral scanning methods.

Materials and methods: MEDLINE/PubMed and the Cochrane database were searched. The focused PICO question was: For the fabrication of FDPs, does an intraoral scanning technique result in a different marginal gap than an extraoral scanning technique? The secondary outcome assessed was internal fit. Studies were selected based on the inclusion criteria, and a meta-analysis was performed.

Results: A total of 14 studies (10 in vitro and 4 in vivo) were included in the meta-analysis. Marginal gap in single crowns was evaluated in 5 studies, copings for single crowns in 5 studies, three-unit FDPs in 3 studies, and both single-crown and three-unit FDPs in 1 study. Significantly lower marginal gap was found with intraoral scanning compared to impression scanning (P < .001) and cast scanning (P < .001), and for impression scanning compared to cast scanning (P = .037). Internal fit was superior with intraoral scanning compared to impression scanning, and this difference was significant (P < .001). No significant differences were found in internal fit with cast scanning compared to intraoral or impression scanning. The mean marginal gap/internal fit was 188.3 μm/146.2 μm with intraoral scanning, 116.29 μm/168.2 μm with impression scanning, and 195.1 μm/229.1 μm with cast scanning.

Conclusion: Marginal gap was lower with intraoral scanning than with impression scanning and cast scanning. Impression scanning showed less marginal gap than cast scanning. Internal fit with intraoral scanning was superior to impression scanning, but when compared to cast scanning, no difference was found.

Purpose: To evaluate the effects of acidic solutions on the surface roughness (SR) and surface microhardness (SMH) of indirect restorative materials by analyzing in vivo and in vitro studies.

Materials and methods: Studies comparing the SR and SMH of indirect restorative materials after erosion were included in the meta-analysis. Meta-analyses were conducted with a random-effects model at a significance level of P < .05 using Review Manager software (Cochrane Collaboration). The literature search was conducted using Web of Science, MEDLINE (PubMed), and the Cochrane Library, with no limitations on publication year.

Results: Of the 1,097 potentially relevant studies, 32 full-text articles were assessed for eligibility. A total of 16 articles were included in the systematic review, and 15 were included in the meta-analyses. The kappa score between the two reviewers was 0.80. The effects of erosion on ceramics, indirect composites, and hybrid ceramics were evaluated by immersion in or rinsing with acidic solutions (eg, hydrochloric acid [HCl], cola drinks, and juices). An increase in the SR (Ra values) (P < .00001; mean difference [MD] = -0.04; 95% CI = -0.06 to -0.03) and a decrease in the SMH (Vickers microhardness) (P < .00001; MD = 13.94; 95% CI = 12.33 to 15.55) were found after erosion. Subgroup analyses revealed that in vitro erosion led to significantly higher Ra values and lower VHN values than in vivo erosion; cola drinks and juices led to more surface degradation than HCl; and the SR and SMH of polymer-infiltrated ceramic network (PICN) materials remained unchanged after erosion.

Conclusion: After acidic challenges, a significantly rougher and softened surface was found for indirect restorative materials. Among all the indirect restorative materials, PICN showed the best acid resistance. Nevertheless, the changes in the SR and SMH of indirect restorative materials after erosion detected in the present study were minor and may not have any clinical significance.