International Journal of Prosthodontics最新文献

Purpose: To investigate the influence of finishing, polishing, and glazing on the roughness, flexural strength, and microstructure of lithium disilicate glass-ceramics.

Materials and methods: LD CAD/CAM blocks were cut into 96 discs (1.2 × 12 mm). After crystallization, a layer of glaze was applied to the discs' surfaces. The specimens were randomly divided into eight groupsn = 12) for different surface treatments (glaze [G], diamond abrasion [D], find diamond abrasion [F], and polishing [P]): G(glaze, control), GD, GDG, GDP, GF GFG, GFP, and GDFP. Mean roughness (Ra), mean square height (Rq), and maximum roughness (Rz) were measured. The biaxial flexural strength test was performed in a universal testing machine at 0.5 mm/minute. Microstructural analysis was performed using x-ray diffraction patterns (XRD). Differences on the roughness obtained in distinct groups was analyzed with Kruskal-Wallis and Bonferroni tests (α = .05). The flexural strength tests were compared with one-way ANOVA.

Results: Glazed groups (G, GDG, and GFG) presented the lowest surface roughness, lower crystallinity, and higher flexural strength than the other groups. Although polishing and glaze presented similar surface roughness, polishing protocol decreased the flexural strength compared to the control group G.

Conclusions: Clinically adjusted LD glass-ceramic restorations should be reglazed whenever possible to improve strength.

Purpose: To investigate the aging and fracture resistance of screw-retained implant-supported single crowns (iSCs) fabricated from lithium disilicate containing virgilite (VLD).

Materials and methods: iSCs were fabricated from VLD (CEREC Tessera, Dentsply Sirona) and lithium disilicate (control, n = 8; IPS e.max CAD, Ivoclar) and bonded to a Ti-base abutment. VLD crowns were luted either with (VLDc, n = 8) or without (VLDw, n = 8) a coupling agent. iSCs were cleaned, sterilized, and screw-retained on implants. Fracture force was determined after thermal cycling and mechanical loading (TCML).

Results: All crowns survived TCML. No significant differences in mean fracture forces were identified between VLDc (1,583 N), VLDw (1,694 N), and control (1,797 N; P = .639 ANOVA, P = 1.000 Bonferroni).

Conclusions: Screw-retained iSCs fabricated from VLD provide acceptable stability, which is independent on the usage of a coupling agent for bonding to Ti-base abutments and sterilization.

Purpose: To clarify the influence of clenching strength on interocclusal registration using an intraoral scanner (IOS).

Materials and methods: The study includes eight volunteers as subjects, and the two experimental conditions were light clenching (LC) and 40% maximum voluntary clenching (MVC). Conventional silicone bite registration and an IOS were used for comparison. Occlusal contact areas (OCAs) for different clenching strengths were compared, along with variation of measured values (VMVs) between recording methods.

Results: Significant differences were observed between conditions on OCA and between methods on VMV.

Conclusions: Clenching strength influenced interocclusal registration using IOS.

Purpose: To evaluate the reliability of various reference areas for digital alignment between 3D resting and smiling facial models.

Materials and methods: 3D posed and natural smiling faces of 33 adults were registered to the respective neutral faces, using six matching strategies with different reference matching surfaces: nose (N), nose + central forehead (NFc), nose + whole forehead (NFw), nose + chin (NC), nose + central forehead + chin (NFcC), and nose + whole forehead + chin (NFwC). The positional discrepancies of the registered images were measured at the left and right pupil centers.

Results: Two-way ANOVA and post hoc multiple pairwise t test with Bonferroni correction (α = .05) were used to evaluate the measurements. As a result, the use of larger reference areas increases the trueness of image-matching, whereas there was no statistically significant difference between the matching strategies within the same smiling type. Meanwhile, the image registration of posed smiles resulted in fewer positional disparities than the natural smiles with significant differences observed for the registration using the NC and NFcC surface-based matching areas at the right pupil (P = .030 and .026, respectively).

Conclusions: The findings of this study suggest that the reference surface areas and smiling types have some impact on the accuracy of 3D smiling facial image alignments. Large and evenly distributed matching surfaces are recommended for posed smiles, whereas caution should be taken when using the chin area as a reference surface for matching natural smile facial images.

Purpose: To compare abutment screw loosening in 24-degree angulation-correcting and straight implants subjected to nonaxial cyclic loading.

Materials and methods: Seven external connection 24-degree angulation-correcting implants (AI) and seven external connection straight implants (SI) were embedded in acrylic resin within a brass housing. A hemispherical titanium fatigue abutment was secured to each implant using a titanium abutment screw tightened to 32 Ncm. Each implant-abutment complex was positioned within a tooth wear machine and subjected to 1,000,000 cycles of 50-Ncm nonaxial loading to simulate 1 year of function. The abutment screw removal torque values were measured before and after cyclic loading, and the differences were statistically analyzed using two-way ANOVA and post hoc pairwise Dunn tests. Scanning electron microscopy and finite element analyses were performed to assess the wear of the abutment screws.

Results: The mean torque loss for the AI group was 21.44% (P < .001) compared to 24.56% (P < .001) for the SI group. There was a statistically significant difference between the AI and SI groups (P = .006).

Conclusions: Both groups exhibited significant abutment screw loosening. Within the limitations of this study, 24-degree angulation-correcting implants resisted screw loosening significantly more than straight implants.

Purpose: To establish the interrelationships between temporomandibular disorders (TMDs), pain, and otologic and psychologic comorbidities in Asian youths.

Materials and methods: Youths from a local polytechnic, aged 17 to 24 years old, were enrolled and an electronic survey encompassing demographic variables-the DC/TMD TMD pain screener (TPS), Short- form Fonseca Anamnestic Index (SFAI), modified Maciel's Otologic/Pain Symptom Inventory, and Patient Health Questionnaire-4-was administered. Par.cipants were subsequently categorized into groups: no TMD pain (NP), with TMD pain (WP), no TMDs (NT), and with any TMDs (WT). Data were evaluated with chi-square test, nonparametric, and logistic regression analyses (α = .05).

Results: Among the 198 participants (mean age 18.8 ± 1.7 years), 11.1% had painful TMDs and 18.2% experienced TMD pain or dysfunction. Significant differences in total-otologic symptoms (total-OS), vertigo, and dizziness plus otalgia, tinnitus, and hearing loss scores were observed between the WP-NP and WT-NT groups correspondingly. While total-comorbid pain (total-CP) and psychologic distress (total-PD) scores varied substanally between the WT-NT group, only a significant difference in total-PD scores was discerned between the WP-NP group. Total-OS scores were moderately correlated to TPS/SFAI, total-CP, and total-PD scores, and psychologic distress was a risk factor for painful TMDs.

Conclusions: Otologic and pain comorbidities were prevalent among Asian youths with TMDs and appear to be interrelated. The complex interaction of TMDs with pain, otologic, and psychologic comorbidities must be considered when caring for youths with multiple somatic complaints.

Purpose: To assess satisfaction and preference among rugby union players for custom mouthguards with and without labial reinforcement, and to assess discomfort and perceived protection.

Materials and methods: This prospective RCT used a crossover design of four 1-week periods to compare conventional (Type A) and labial reinforced (Type B) customized mouthguards for rugby union players from February to May 2022. Type B mouthguards included a 0.75-mm insert of polyethylene terephthalate glycol (Duran) in the anterior labial region. We ensured intraoral occlusion accommodation for both mouthguards. Players wore each mouthguard type when training and in competitive matches for 2 weeks according to one of two randomized sequences. After each session, they rated the mouthguard on 10-point scales regarding discomfort, functional interference, protection, and general satisfaction. After 4 weeks, we asked participants to nominate their preferred mouthguard.

Results: In total, 22 of the 24 invited players (16 men and 6 women) were included. We observed no significant differences in discomfort, functional interference, protection, or general satisfaction by mouthguard type (P > .05, Wilcoxon test). Ultimately, 12 players (55%) preferred the Type A mouthguard and 10 (45%) preferred the Type B mouthguard (P = .832; one-sample binomial test). No serious adverse events occurred.

Conclusions: Labial reinforcement does not affect satisfaction, perceived comfort and protection, or mouthguard preference among rugby union players.

Purpose: To develop the most compatible cementation protocol for ensuring minimal residual cement and optimal retention of cement-retained implant-supported fixed dental prostheses.

Materials and methods: A total of 30 custom implant abutments and zirconia crowns with bilateral wings were prepared. Three cement types were used for cementation: noneugenol resin cement (Premier Implant Cement; Group IC), dual-polymerizing self-adhesive resin cement (SmartCem2; Group SC), and zinc oxide eugenol cement (Temp-Bond; Group TB; n = 30 per group). Three cementation methods were applied for each cement type, and the samples were divided into subgroups: (1) cement was injected using a graduated syringe (ICN, SC-N, and TB-N); (2) a cementa/on jig made with a silicone impression material and temporary resin material was used (IC-CJ, SC-CJ, and TB-CJ); (3) 3D-printed abutments were used as replicas for cementation (IC-3DP, SC-3DP, and TB-3DP). The amount of cement injected, surface area of the residual cement, and retentive strength were measured. Kruskal- Wallis and post-hoc Mann-Whitney tests were used for statistical analyses.

Results: Excess cement was not observed when cementa/on jig or 3D-printed replicas were used. For IC and SC subgroups, non-use of these auxiliary tools resulted in significantly higher amounts of injected cement. The retentive strength differed significantly among the IC subgroups but not among the SC subgroups. The retentive strength of subgroups TB-N and TB-CJ was significantly higher than that of subgroup TB-3DP.

Conclusions: To prolong the main purpose of each cement type, a cementation jig or 3D-printed replica is highly recommended regardless of the cement type.

Purpose: To perform a bibliometric study in the literature about the increasing number of global studies on dental esthetics in recent years.

Materials and methods: Articles on dental esthetics published between 1980 and 2021 were pulled from the Web of Science (WoS) database. In this comprehensive bibliometric study on dental esthetics, a summary of 2,858 articles published in the last 41 years was shared. Network visualization maps were used to identify citation analyses and trending topics. Spearman correlation coefficient was used for correlation studies. The exponential smoothing estimator was used to estimate the number of articles to be published in the coming years.

Results: Of the 3,666 publications, 2,858 (77.9%) were articles. The top three contributing countries to the literature were the USA (816, 28.5%), Brazil (286, 10%), and Italy (246, 8.6%). The most active institution was the University of Bern (n = 55). The journal with the highest number of articles was Journal of Prosthetic Dentistry (n = 178). According to the average number of citations per article, the most influential journal was Journal of Periodontology (citations: 55.6).

Conclusions: Keywords of the trending topics related to dental esthetics are perception, bleaching, cleft lip, connective tissue graft, smile esthetics, adolescent, esthetic region, soft tissue augmentation, and clinical studies. In regard to the global output in dental esthetics, this article is a useful resource for clinicians, scientists, and dental students.

Purpose: To evaluate the effect of restoration design on fracture resistance and stress distribu0on of veneered and monolithic three-unit zirconia fixed partial dentures (FDPs) using finite element analysis (FEA).

Materials and methods: Identical epoxy resin replicas of mandibular second premolars and second molars (to serve as abutments for the three-unit bridges) were divided into four groups (n = 10): monolithic zirconia (MZ) restorations; conventional layering veneering technique (ZL); heat pressed-on technique (ZP); or CAD/CAM lithium-disilicate glass-ceramics (CAD-on). Specimens were subjected to compressive cyclic loading on the mesio-buccal cusp of the pontic (load range 50 to 600 N; aqueous environment; 500,000 cycles) in a universal testing machine. Data were statistically analyzed at 5% significance level with Fisher exact test and Kaplan-Meier survival analysis. 3D models were constructed in accordance with experimental groups. The stress distribution in each model was analyzed and evaluated according to the location and magnitude of the maximum principal stresses (MPSs) using ANSYS soware.

Results: Specimens from ZL and ZP groups failed at different stages of the 500,000 cycles fatigue, while CAD-on and MZ restorations survived the fatigue test. Statistically, there was a significant difference between the groups (P < .001). The MPS were located under the mesial connector in both monolithic and bilayered three-unit zirconia FDPs. These stresses were found to be higher in monolithic geometries compared to bilayered zirconia FDPs.

Conclusions: Monolithic threeunit zirconia and CAD-on zirconia frameworks resulted in superior fracture resistance. Restora0on design significantly affected the stress distribu0on of three-unit zirconia FDPs.