The International journal of prosthodontics最新文献

Purpose: To investigate the influence of milling parameters on the durability and fracture force of resinbased composite crowns during in vitro aging simulation.

Materials and methods: Identical molar crowns (n = 8 per group) were milled from resin-based composite crowns (Grandio, VOCO Dental) with different processing speeds (soft, normal, fast) or levels of detail (very high, high, low) from 98-mm disks. One group was milled wet to investigate the influence of cooling. The influence of polishing was tested in two groups. All crowns were adhesively bonded on standardized resin-based composite molars. Aging was performed with thermal cycling and mechanical loading (2 × 3,000 × 5°C/55°C, 2 minutes, H20 dist., 1.2 × 106 force at 50 N). Fracture forces were determined (v = 1 mm/minute, Z010, Zwick Roell).

Results: For statistical analysis, Pearson correlation, one-way ANOVA, and Bonferroni post hoc tests were used (α = .05). All crowns survived thermal cycling and mechanical loading (TCML) without any failures. The fracture values varied between 1,237.3 ± 326.7 N and 3,308.6 ± 655.8 N. Significant (P < .001) differences between the individual manufacturing approaches were detected. Failure was categorized as a fracture of the crown and partial loosening of the crown. No different failure pattern was observed between the tested systems.

Conclusions: A medium level of detail seems to be ideal to achieve the highest fracture forces. No relationship existed between machine speed and fracture force. Fracture force was not affected by wet grinding. In individual cases, polishing reduced crown fracture values due to reduced wall thickness.

The aim of this short communication is to present a technique to rehabilitate severely discolored teeth with computer-aided designed and computer-aided manufactured (CAD-CAM) zirconia crowns. After confirming the absence of periapical lesions and sufficient crown structure, any caries or fractured restorations can be removed and replaced by an interim composite restoration. A shoulder subgingival preparation is performed and scanned with an intraoral scanner to design a CAD-CAM zirconia crown using a monolithic zirconia material. This crown is highly polished using a specific polishing kit, but not glazed. This technique is suggested to be useful in cases of dark discolored teeth due to staining endodontic materials such as resorcinol-formaldehyde resin.

This study aimed to investigate the efficiency of different cements for luting implant restorations. Standard restorations were bonded with different cements, including a zincoxide-based temporary cement (ZOE), a resin-modified glass ionomer cement (GIC) and a resin-based, eugenol-free cement (RBEFC). The restorations were stored under moist conditions and were subsequently subjected to thermal cycling and mechanical loading (TCML). Retention forces were determined with an axial tensile test and removabilty of the restorations was analyzed with a pneumatic crown remover. GIC provided significantly higher retention forces than RBEFC, which provided significantly higher values than ZOE. After storage, retention forces were significantly higher than after TCML. With regard to removability, no significant differences were identified between ZOE and RBEFC, but a significantly higher number of applications was required to remove restorations luted with RBEFC. All cements provided sufficient retention forces, yet removal of restoration might be more demanding if luted with RBEFC.

This retrospective study evaluated the clinical long-term survival of 1405 double-crown retained removable partial dentures (DRPDs) over 30 years of follow-up. Kaplan Meier survival rate for DRPDs was 96.6% after 5 years, 88.2% after 10 years, 61.7% after 20 years, and 38.3% after 30 years. Survival rates of abutment teeth were 94.3% after 5 years, 80.2% after 10 years, 51% after 20 years, and 27% after 30 years. Key failure risk factors of DRPDs were age, ≤ 3 abutment teeth, and complete denture in opposing jaw. Abutment teeth failure risk factors included age, anterior abutment teeth, punctual support, and non-vital teeth.

Purpose: Evaluate the influence of different Co-Cr framework manufacturing techniques on the bond strength between metal and two types of veneering ceramic with and without a metal primer.

Materials and methods: 72 metal specimens were fabricated using the same Co-Cr alloy (Keramit NP; Nobil Metal) with three different techniques: ingots for casting (Keramit NP); disks for CAD/CAM milling (Synergy Drive Keramit NP); and powder for SLM (Keramit NP-S). Each of the 24-specimen groups, was divided into two subgroups, according to the application, or not, of Nobil Metal Bonding (NMB) (Nobil Metal). Two different veneering ceramic systems were used: Ceramco iC (Dentsply) and Noritake super porcelain EX-3 (Noritake). The bond strength of the metal-ceramic system was evaluated using the three-point bending test and the modality of failure with SEM analysis. Three-way Anova with interactions was used to evaluate the influence of the metal production process, the presence or absence of the bonding agent and the type of veneering ceramic on ceramic-metal adhesion.

Results: All specimens exceeded the minimum bond strength of 25 MPa required by ISO Standard 9693 - 1:2012. The highest values of adhesion were registered for specimens manufactured with casted metal/Noritake veneering ceramic (40.59 ± 7.30 MPa). The lowest values were registered for specimens manufactured with CAD/CAM metal/NMB/Ceramco iC veneering ceramic (29.47 ± 3.38 MPa).

Conclusions: The fabrication method and the type of veneering ceramic had a significant influence on the mean bond strength. The application of the NMB did not show an influence on bond strength.

Purpose: The aim of this prospective clinical study was to evaluate the 12 and 24-month clinical results of overlay and one-piece endodontic crown restorations applied with additively manufactured 3D printed permanent ceramic-filled resin (PCR) according to the Modified US Public Health Service (USPHS) criteria.

Materials and methods: A total of 33 indirect restorations (16 overlay, 17 endocrown) (4 premolar, 29 molar) produced using PCR (Formlabs) were applied to 30 patients by a single dentist. The restorations were evaluated according to the modified USPHS criteria at baseline (7 days), 12 and 24 months times by two independent evaluators. The study registration number is NCT05168852. In the comparisons of the dependent criteria scores, the Related Samples Cochran Q test was used, and in post-hoc paired comparisons, the Bonferroni test. The Fisher-Freeman-Halton test was applied in the comparisons of categorical variables according to the restoration type groups (α = 0.05).

Results: No statistically significant difference was determined between the evaluation criteria scores at baseline, 12 months, and 24 months for the marginal adaptation (P=0.05), retention (P=1), interproximal contact (P=0.368), color match (P=1), surface texture (P=1), and patient satisfaction (P=1). The only score criteria that showed a statistically significant difference between baseline and 24 months (P=0.001) among all other criteria was marginal discoloration. This criteria's score change was from 100% A score to 69.7% A score.

Conclusion: In the 2-year follow-up of indirect single-tooth restorations produced with 3D-printed PCR, all restorations showed acceptable clinical performance. (≥99.5%A+B score at 2 years).

Purpose: The objective of this clinical study was to evaluate comfort, satisfaction, chewing ability and complications with digital complete dentures (DCD) and conventional complete dentures (CCD).

Materials and methods: For 16 edentulous patients, two sets of upper and lower dentures were fabricated by students in a university dental clinic. The impression for the DCD was done using indirect scanning of the cast. When the patients were pain free, each set of dentures was worn for four weeks. OHIP-14 and a DSI (Denture Satisfaction Index)were used to measure patient satisfaction and chewing ability respectively. Both questionnaires were administered before fabrication and after wearing each set. Adjustments made during the follow up period were included. At the end of the study, patients could express which set of dentures they preferred. The 25 dental students involved in fabricating the dentures, were questioned in terms of discomfort, preference and future use for both techniques.

Results: OHIP-14 showed significantly higher scores for the DCD for the domain concerning psychological discomfort. DSI showed no significant difference for both sets of dentures. In terms of complications, a significant difference was found for occlusion. The DCD required more occlusal adjustments. A minority of the patients (37.5%) chose the DCD as their favourite set. The students preferred the wax try-in and workflow of the CCD.

Conclusions: The CCD and DCD showed differences in patient satisfaction. Chewing ability was comparable for both sets of dentures. More occlusal complications were seen in the DCD. Both students and patients preferred the CCD.

Purpose: To evaluate the mechanical properties of the 3D printed provisional restoration material that was repaired using different materials.

Material and methods: The bar specimens have been manufactured using three-dimensional printing technology in accordance with the ISO 10477:2020 standards and divided into 5 groups randomly. For repair material application and replacement on the standardized silicone mold, the test specimens were ground at the center by 1x2x2 mm. No grinding was done on the control group specimens. Flowable composite, bis-acrylic composite resin, polymethyl methacrylate resin, and temporary 3D printing resin are utilized as repair materials (n=16). The specimens underwent a three-point-bending (3PB) test, with a cross-head speed of 1mm/min, in order to assess their flexural strength (FS) and flexural modulus (FM). The data received statistical analysis with one-way ANOVA and Tukey test. A Weibull analysis was performed, and the Weibull modulus of specimens was calculated.

Results: Control group specimens were showed the highest FS (142±12.6 MPa) and FM (4497±1205 MPa) values. Among the test groups, the utilization of temporary 3D printing resin as a repair material exhibited the greatest FS (67±33.3 MPa) values and showed statistical significance when compared to all other groups.

Conclusion: Repairing 3D-printed provisional resin material weakens its mechanical properties. However, utilizing the own resin made of 3D-printed provisional resin material can be an effective choice for implementing minor modifications and additions.

Purpose: The study aims at evaluating the impact of a full digital workflow on the restoration of masticatory function and aesthetic features in subjects rehabilitated with fixed prosthesis.

Materials and methods: The study involved 12 adult participants in need of complex rehabilitation due to masticatory dysfunction. They underwent a comprehensive diagnostic examination involving intraoral scan, facial 3D-photos, jaw kinematics recording, and Cone Beam Computed Tomography extended to temporo-mandibular joint. The subjects were consecutively treated with fixed prosthesis following surgical and implant therapy using a full-digital individualized workflow. Three different study moments were set: diagnostic phase (T0), one week after the delivery of the prototype (T1) and one week after the delivery of the final prosthetic solution (T2).

Results: Jaw kinematics recording showed a widening of movements at T2 compared to T0. Sagittal movements increased by 5.7±6.4 mm (95%CI from 1.7 to 9.8, P = 0.010), frontal movements increased by 7.2±5.6 mm (95%CI from 3.6 to 10.8, P = 0.001), and horizontal movements increased by 1.7±4.5 mm (95%CI from -1.1 to 4.6, P = 0.210). Occlusal adjustment timing at T1 was 350±175 seconds, while at T2 was 677±286. At T2 functional VAS was 9.4±0.4 while aesthetic VAS was 9.3±0.4.

Conclusions: The rehabilitation process using the full digital workflow showed a widening of the sagittal and frontal masticatory movements with short occlusal adjustment time and with functional and aesthetic satisfaction by all the subjects.

This study examined changes in facial geometry while playing wind instruments. Nine musicians participated (6 men, 3 women, mean age 52 years) in part 1 of the study, and 3 musicians participated (3 women, mean age 41 years) in part 2. In part 1, the high and low notes of each instrument were selected as test sounds. Facial geometry data were recorded using a 3D scanner. In part 2, facial geometry data were recorded using a 4D scanner while a melody was played. Data were superimposed and analyzed using 3D analysis software. Numerical values and color maps of deviations were obtained. The results of part 1 revealed that the median 3D deviation was 1.1 mm (range 0.42-1.45 mm), indicating that facial geometry while playing high and low notes was varied. The results of part 2 showed that the stable part was the frontal region and dorsal part of the nose. The approach used in this study has potential applications for evaluating facial geometry during musical instrument performances.