Journal of prosthodontic research最新文献

Purpose: To investigate whether depth-gauge burs in veneer preparations influence preparation depth in a randomized, controlled, single-blinded trial and whether inexperienced operators can perform adequate veneer preparations.

Methods: Participants were 20 undergraduate dental students with no prior veneer preparation experience. The instruments used were the "Laminate Veneer System" (LVS), "Keramik-Veneers. de" (KVD), and a "Freehand" group (FH) for reference. All participants prepared three educational acrylic resin maxillae and three mandibular central incisors mounted in typodonts in patient simulators. The objectives were to achieve a preparation depth of 0.6 mm (tooth 11) and 0.4 mm (tooth 31). The sequences of the instruments used and prepared teeth were randomized. The measurements were performed using a laser triangulation coordinate-measuring machine. The data were stratified according to tooth location.

Results: The preparation depths of both depth-gauge-instrument-groups LVS and KVD achieved the objectives significantly better than did the instruments from the "Freehand" group (P < 0.001). The differences between the depth gauge groups were insignificant, although the maximum preparation depths were smaller in the KVD group. Regarding the prepared teeth, the preparation depths in the mandibular incisors were lower, and the differences were smaller.

Conclusions: The use of special depth-gauge burs for initial veneer preparation leads to significantly lower preparation depths than "Freehand" preparations. The tapered instruments resulted in a lower incidence of extreme preparation depths. The inexperienced operators performed veneer preparation remarkably well.

Purpose: Individuals with impaired masticatory function tend to prefer soft foods, which results in decreased masticatory muscle activity. This study examined the association between the oral condition (number of teeth, occlusal force, and occlusal contact area) and dietary hardness using a daily dietary questionnaire.

Methods: This cross-sectional study evaluated 1841 participants aged 69-71 and 79-81 years. Registered dentists examined the number of teeth, occlusal force, and occlusal contact area. Dietary hardness was defined as the estimated masticatory muscle activity required for a habitual diet. Habitual diet during the preceding month was assessed using a brief self-administered diet history questionnaire. Confounding factors, such as age, sex, socioeconomic status, smoking habits, history of chronic diseases (hypertension, hyperlipidemia, and diabetes), and cognitive function were also evaluated. Multivariate linear regression analyses were performed to assess the association between dietary hardness and each oral condition.

Results: Occlusal force (standardized regression coefficients [β]=0.08, P < 0.01) and occlusal contact area (β=0.06, P < 0.01) were significantly associated with dietary hardness after adjusting for the confounding factors. Number of teeth was not significantly associated with dietary hardness. In addition, the associations between dietary hardness, sex, and a history of diabetes were stronger than those between dietary hardness and oral factors.

Conclusions: Occlusal force and contact area were significantly associated with dietary hardness as estimated from the masticatory muscle activity using a daily diet questionnaire.

Purpose: This study aimed to investigate the effect of collagen cross-link deficiency on collagen fiber formation around an implant and its effect on the osseointegration process.

Methods: Wistar rats were fed 0.1% beta-aminopropionitrile (BAPN) dissolved in water to induce collagen cross-link deficiency. Custom-made mini-implants with machined surfaces were placed proximal to the tibia. At 1, 2, and 4 weeks postoperatively, the bone area around the implant, bone-implant contact ratio, osteoclast/osteocyte activity, and osseointegration strength were evaluated using histological and immunohistochemical analyses and biomechanical tests.

Results: Long-term disturbance of collagen cross-link formation in the BAPN group resulted in faster collagen fiber maturation than that in controls, with a defective collagen structure, low bone formation quantity, and low bone-implant contact values. Deficiency of collagen cross-links resulted in increased bone resorption and decreased osteocyte activity.

Conclusions: Collagen cross-linking is important for the formation of the collagen matrix, and their deficiency may impair bone activity around implants, affecting the osseointegration process.

Purpose: Laughter is expected to have health-protective effects, but the potential link between tooth loss and laughter remains unclear. Therefore, this study aimed to examine the association between tooth loss and a low frequency of laughter among older adults in Japan, to elucidate whether this association could be mitigated by dental prostheses, and to evaluate the magnitude of the association mediated by poor oral function.

Methods: We used cross-sectional data from 157,708 functionally independent participants aged ≥65 years (46.3% male) from the Japan Gerontological Evaluation Study. A modified Poisson regression model was applied to examine the association between the number of remaining teeth (≥20/10-19/0-9), dental prostheses use, and infrequent laughter (i.e., laughing never or almost never). Causal mediation analysis was performed to assess whether the association was mediated by difficulties in eating hard foods, choking, or dry mouth.

Results: Among the participants, 9,129 reported infrequent laughter. Participants with ≤9 and 10-19 teeth who did not use dental prostheses had a 1.29 and 1.14 times higher likelihood of infrequent laughter than those with ≥20 teeth, respectively. Furthermore, difficulty eating hard foods, choking, and dry mouth mediated 22.8%, 0.4%, and 4.3% of the association between fewer remaining teeth and infrequent laughter, respectively. Meanwhile, we did not find evidence for the differences in infrequent laughter between participants with ≤19 teeth using dental prostheses and those with ≥20 teeth.

Conclusions: Tooth loss among individuals without dental prostheses was associated with infrequent laughter, and this association was mediated by poor oral function.

Purpose: Fixed restorations and dental enamel have different structures that produce different wear on opposing teeth, resulting in clinical problems. Therefore, it is necessary to determine the type of restoration that causes less wear on naturally opposing teeth to make recommendations. The objective of this study was to systematically analyze the evidence from observational studies and clinical trials on enamel wear in different ceramic restorations.

Study selection: The designs of the included studies were randomized clinical trials (RTCs), non-randomized clinical trials (non-RTCs), and observational studies (OS). The studies must answer the research question, be available in full text, be written in English or Spanish, and have had at least six months of follow-up. Protocol number: CRD42023397759.

Results: After screening 499 records, 20 RTCs were subjected to data extraction, 10 were excluded, 10 were included in the systematic review, and only 5 were included in the network meta-analysis. The risk of bias assessment reported moderate to high risk of bias, quality, and certainty of evidence was evaluated and rated as moderate. Network meta-analysis showed higher enamel wear was observed in natural dental enamel against metal-ceramic antagonists.

Conclusions: Enamel wear occurs in all teeth, even when the antagonist is a natural tooth. The wear is larger on surfaces with the ceramic crown antagonists studied (metal-ceramic, glazed zirconia, and polished zirconia). It is necessary to conduct additional clinical trials with larger follow-up periods and sample sizes.

Titanium implants have revolutionized restorative and reconstructive therapy, yet achieving optimal osseointegration and ensuring long-term implant success remain persistent challenges. In this review, we explore a cutting-edge approach to enhancing implant properties: ultraviolet (UV) photofunctionalization. By harnessing UV energy, photofunctionalization rejuvenates aging implants, leveraging and often surpassing the intrinsic potential of titanium materials. The primary aim of this narrative review is to offer an updated perspective on the advancements made in the field, providing a comprehensive overview of recent findings and exploring the relationship between UV-induced physicochemical alterations and cellular responses. There is now compelling evidence of significant transformations in titanium surface chemistry induced by photofunctionalization, transitioning from hydrocarbon-rich to carbon pellicle-free surfaces, generating superhydrophilic surfaces, and modulating the electrostatic properties. These changes are closely associated with improved cellular attachment, spreading, proliferation, differentiation, and, ultimately, osseointegration. Additionally, we discuss clinical studies demonstrating the efficacy of UV photofunctionalization in accelerating and enhancing the osseointegration of dental implants. Furthermore, we delve into recent advancements, including the development of one-minute vacuum UV (VUV) photofunctionalization, which addresses the limitations of conventional UV methods as well as the newly discovered functions of photofunctionalization in modulating soft tissue and bacterial interfaces. By elucidating the intricate relationship between surface science and biology, this body of research lays the groundwork for innovative strategies aimed at enhancing the clinical performance of titanium implants, marking a new era in implantology.

Purpose: This observational retrospective clinical study aimed to investigate the survival and success rates of partial indirect lithium disilicate restorations with margins extending above or beyond the cementoenamel junction (CEJ).

Methods: The study included patients who underwent partial indirect lithium disilicate restorations with immediate dentin sealing (IDS) between January 2008 and October 2018. All the restorations were placed in a single general dental practice following a standardized protocol. The impact of various predictive variables on the survival rates was assessed. Moreover, modified United States Public Health Service (USPHS) criteria were used to evaluate the survival quality.

Results: Totally 1146 partial indirect lithium disilicate restorations in 260 patients were evaluated over an average period of 7.5 years. The cumulative survival and success rates were 97.3% and 95.3%, respectively. Margins extending beyond the cemento-enamel junction did not increase the risk of success or survival failure (P > 0.05). Patients with a high risk of caries, male sex, or non-vital teeth had a significantly higher risk of restoration failure (P < 0.05). Restorations with longer clinical service times exhibited marginally lower clinical quality (P < 0.001).

Conclusions: Partial indirect glass-ceramic restorations demonstrated survival and success rates of 97.3% and 95.3%, respectively, over an extended period. However, a higher risk of restoration failure existed in patients with a high caries risk for (pre)molars that had undergone endodontic treatment and in males. In terms of the risk of success or survival failure, comparable results were obtained for the positions of the restoration margin in relation to the cemento-enamel junction.

Purpose: This study investigated the fracture resistance of 0.5-mm-thick restorations for minimally invasive therapy. Anterior partial-coverage crowns composed of three-dimensional (3D)-printed 3-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP; Lithacon 3Y210, Lithoz) and 3D-printed composite (Varseo Smile Crown plus, Bego) were compared with a control group made from milled 3Y-TZP (Cercon ht, DentsplySirona).

Methods: Three groups each with 27 restorations were produced. For milled 3Y-TZP partial-coverage crowns, drill compensation was needed so the milling bur could access the inner surface at the incisal edge. Restoration fit was verified by cross-sectioning 12 specimens in each group. The remaining 15 restorations were sandblasted (Al2O3, 0.1 MPa) and adhesively cemented (Panavia SA, Kuraray) onto CoCr teeth. Static load-to-failure tests were performed. The load was induced on the incisal edge. The forces needed to fracture the specimens were analyzed using the Welch analysis of variance and post hoc Dunnet-T3 tests. The Weibull parameters were also calculated.

Results: Drill compensation increased cement thickness at the loading area by 200 µm in milled 3Y-TZP restorations compared with the 3D-printed partial-coverage crowns. Fracture resistance was the highest in 3D-printed 3Y-TZP restorations (1570±661N) followed by milled 3Y-TZP (886±164N) and 3D-printed composite partial-coverage crowns (570±233 N). Milled 3Y-TZP was associated with a substantially higher Weibull modulus (m=6) than the 3D-printed materials (m=2), suggesting greater reliability.

Conclusions: Fracture resistance increased with tighter fit, demonstrating the benefit of the geometric freedom associated with 3D-printing. Future research should focus on making 3D-printed 3Y-TZP more reliable to increase its safety in clinical use.

Purpose: Based on a self-controlled case, this study evaluated the finite element analysis (FEA) results of a single missing molar with wide mesiodistal length (MDL) restored by a single or double implant-supported crown.

Methods: A case of a missing bilateral mandibular first molar with wide MDL was restored using a single or double implant-supported crown. The implant survival and peri-implant bone were compared. FEA was conducted in coordination with the case using eight models with different MDLs (12, 13, 14, and 15 mm). Von Mises stress was calculated in the FEA to evaluate the biomechanical responses of the implants under increasing vertical and lateral loading, including the stress values of the implant, abutment, screw, crown, and cortical bone.

Results: The restorations on the left and right sides supported by double implants have been used for 6 and 12 years, respectively, and so far have shown excellent osseointegration radiographically.

The von Mises stress calculated in the FEA showed that when the MDL was >14 mm, both the bone and prosthetic components bore more stress in the single implant-supported strategy. The strength was 188.62–201.37 MPa and 201.85–215.9 MPa when the MDL was 14 mm and 15 mm, respectively, which significantly exceeded the allowable yield stress (180 MPa).

Conclusions: Compared with the single implant-supported crown, the double implant-supported crown reduced peri-implant bone stress and produced a more appropriate stress transfer model at the implant-bone interface when the MDL of the single missing molar was ≥14 mm.

Purpose: The purpose of this study is to compare the shear bond strength of ultraviolet (UV)-polymerized resin to 3D-printed denture materials, both with and without post-polymerization. Moreover, the effects of surface treatment and thermocycling on shear bond strength after post-polymerization were investigated.

Methods: Cylindrical 3D-printed denture bases and teeth specimens were prepared. The specimens are subjected to two tests. For Test 1, the specimens were bonded without any surface treatment or thermal stress for comparison with and without post-polymerization. In Test 2, specimens underwent five surface treatments: untreated (CON), ethyl acetate (EA), airborne particle abrasion (APA) with 50 μm (50-APA) and 110 μm alumina (110-APA), and tribochemical silica coating (TSC). A UV-polymerized resin was used for bonding. Half of the Test 2 specimens were thermocycled for 10,000 cycles. Shear bond strength was measured and analyzed using Kruskal-Wallis and Steel-Dwass tests (n = 8).

Results: In Test 1, post-polymerization significantly reduced shear bond strength of both 3D-printed denture materials (P < 0.05). No notable difference was observed between the denture teeth and the bases (P > 0.05). In Test 2, before thermocycling, the CON and EA groups exhibited low bond strengths, while the 50-APA, 110-APA, and TSC groups exhibited higher bond strengths. Thermocycling did not reduce bond strength in the latter groups, but significantly reduced bond strength in the EA group (P < 0.001).

Conclusions: Post-polymerization can significantly reduce the shear bond strength of 3D-printed denture materials. Surface treatments, particularly APA and TSC, maintained bond strength even after thermocycling.