The International Journal of Prosthodontics, 04/2024

Purpose: To evaluate the masticatory efficiency of dentate and rehabilitated complete denture patients in various facial forms. Materials and Methods: A total of 60 subjects were selected for the study; 30 subjects belonged to the dentate group (D Group) and 30 subjects belonged to the completely edentulous group rehabilitated with conventional complete dentures (CECD Group). All patients were divided into a subgroup (brachyfacial, mesofacial, and dolichofacial facial forms) using facial index measurement and cephalometric analysis. After the subjects were divided into groups, masticatory efficiency testing was performed with spectrophotometric analysis using diluted expectorate of chewed natural beetroot test food (10, 15, and 20 strokes). The mean absorbance value was considered as the mean masticatory efficiency from which the average masticatory efficiency percentage was determined using a masticatory efficiency percentage equation and considered as the masticatory efficiency of that particular subject. Results: Statistical analysis revealed that in the D Group, brachyfacial subjects exhibited the highest masticatory efficiency (70.9 ± 12.64%), followed by mesofacial (60.6% ± 10.66%) and dolichofacial (34.3% ± 10.81%) subjects. In the CECD groups, the results for brachyfacial were highest (52.7% ± 8.11%), followed by the mesofacial (42.3% ± 6.52%), and dolichofacial (29.3% ± 7.76%) subjects. Conclusions: Along with other determinant factors, facial form plays an influential role on masticatory efficiency. Brachyfacial subjects exhibited the highest masticatory efficiency, followed by mesofacial and dolichofacial subjects in both study groups.

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 evaluate the clinical survival and impact on oral health–related quality of life (OHRQoL) of immediate loading of implant-supported full-arch CAD/CAM–milled PMMA interim restorations. Materials and Methods: This was a practice-based prospective cohort study performed in a Portuguese dental clinic. Eleven patients received a total of 17 CAD/CAM fully implant-supported, screw-retained, full-arch restorations with milled PMMA and were followed up for 1 year. The primary outcome was prosthesis survival, determined with a modification of the California Dental Association score and a Kaplan-Meier survival function analysis. The secondary outcome was the patient quality of life, as defined by application of the OHIP-14-PT questionnaire and standardized effect size variation between two visits. Significance was set at 5%. Results: Survival probability at 12 months was 76%, complete fracture of the prosthesis occurred in 17.6% of the cases, and small fractures without lab involvement occurred in 5.9% of cases. There was a significant improvement in OHRQoL between visit 1 and visit 4. The mean difference and effect size for total OHIP-14-PT score were –32.91 ± 3.68 and 3.66 (95% CI –1.83 to –5.80) respectively (P < .001* Wilcoxon matched paired rank test). Conclusions: Fullarch implant-supported CAD/CAM—milled PMMA interim prosthesis seem to be a viable approach with good survival rate and great impact on patient OHRQoL.

Purpose: To examine the long-term performance of bonded all-ceramic restorations, specifically veneers, in patients with amelogenesis imperfecta (AI). There are few studies of long-term outcomes using a minimally invasive procedure in these patients. This aspect is essential when treating young patients. All-ceramic restorations, especially veneers, offer a more tissue-preserving treatment but rely on successful bonding. However, due to the defect enamel in AI patients, the bond strength is lower. Materials and Methods: A retrospective evaluation of 40 subjects with AI (26 women, 14 men) was provided with a total of 360 bonded restorations (282 veneers, 78 crowns). The restorations were evaluated according to complications, survival, and success rate. Results: The patients were observed up to 25.3 years (mean 15.4 ± 4.3 years). The mean age when receiving the restorations was 18.5 ± 4.2 years. In total, 59 (16.4%) restorations with prosthetic complications were made, 29 of which (8.1%) were remade (6 due to esthetic reasons, all in one patient) and 30 (8.3%) were recemented (60% caused by trauma). We found 11 teeth with caries and 3 with endodontic complications. The overall survival rate was 91.9%, and the overall success rate was 83.6%. Conclusions: Bonded all-ceramic restorations with no active retention in AI patients have excellent performance. The most common complications were debonding and fractures. The treatment should be based on individual indications and be preceded by a multidisciplinary approach.

Purpose: To assess the clinical performance of CAD/CAM laminate veneers placed by a single operator and systematically evaluated for up to 10 years. Materials and Methods: A total of 197 laminate veneers fabricated using either feldspathic ceramics (VMII) or lithium disilicate ceramics (EmaxCAD) were followed up to 10 years in 32 patients. Technical, esthetic, and biologic findings of each restoration were evaluated using modified United States Public Health Service criteria. The survival and complication rates were assessed using Kaplan-Meier survival analysis and compared using log-rank test. Statistical significance was set at P < .05. Results: The estimated Kaplan-Meier survival rate was 91.9% after the mean observation period. According to the ceramic system used, the estimated Kaplan-Meier survival rate amounted to 92.7% for EmaxCAD and 89.1% for VMII. Survival rates were significantly affected by the location of veneer according to log-rank test (P < .05). A range of survival rates between 83.3% and 98.6% were observed based on the location of veneer. Conclusions: CAD/CAM laminate veneers milled from feldspathic or lithium disilicate ceramics have comparable long-term survival rates. Oral positioning affects the survival of veneers. Veneers of incisors have higher survival rates than the veneers of maxillary canines and premolars.

Purpose: To propose and evaluate standardized polishing protocols for in vitro experiments using a custommade apparatus under controlled force to create consistent surface roughness on titanium and zirconia discs. Materials and Methods: A total of 160 discs were manufactured with a diameter of 10 mm, 80 titanium (Ti) and 80 zirconium oxide (Zr). Specimens were categorized into two groups: controlled force (CF) and without controlled force (WCF). Specimens in the CF group were polished with a custom apparatus incorporating a tension gauge on the Ti and Zr disc surfaces to achieve consistent roughness. The WCF group was polished without the use of a tension gauge. Each group had four subgroups (n = 10): control/machined with no polishing (C), rough (R), smooth (S), and very smooth (VS). The subgroups were processed using a sequence of diamond-impregnated polishing burs and polishing paste. Results: The CF group showed consistent surface roughness and a gradual decrease in surface roughness. Control in Ti (Ra = 6.5 ± 0.03 μm) and in Zr (Ra = 5.4 ± 0.04 μm); R in Ti (Ra = 3.5 ± 0.06 μm) and in Zr (Ra = 3.2 ± 0.07 μm); S in Ti (Ra = 1.5 ± 0.04 μm) and in Zr (Ra = 1.1 ± 0.06 μm); and VS in Ti (Ra = 0.05 ± 0.002 μm) and in Zr (Ra = 0.02 ± 0.005 μm). There were significant differences for R, S, and SV under CF and WCF in Ti and Zr surfaces. Conclusions: The specimens polished under control force produced significantly more uniform surface roughness than those polished without controlled force and were produced with a higher degree of consistency.

Purpose: To evaluate changes in color and translucency of stained and glazed monolithic lithium disilicates and zirconia after toothbrushing with conventional or whitening dentifrices followed by thermocycling. Materials and Methods: Samples (n = 20/material) from CAD/CAM (IPS e.max CAD [EC]) and pressable (IPS e.max Press [EP]) lithium disilicates and 5Y-PSZ zirconia (Prettau 4 Anterior [PA]) were prepared and received staining and glazing procedures. Aging was performed by toothbrushing with conventional (n = 10) or whitening (n = 10) dentifrices, followed by thermocycling simulating 5, 10, and 15 years. Color coordinates L*, a*, b*, , and C* and hº values were assessed with a spectrophotometer at baseline and after each aging period to calculate color changes (ΔE₀₀), lightness (ΔL*), and translucency parameter (TP). Data were analyzed using three-way repeated measures ANOVA's followed by Sidak post-hoc test (α = .05). Results: When comparing the dentifrices, EC and EP produced the greatest ΔE₀₀ after 15 years with the whitening dentifrice (P < .05). Regardless of the dentifrice, PA showed greater ΔE₀₀ than EC after 10 years (P < .05). When comparing the aging periods, EC and PA did not show differences in ΔE₀₀ for both dentifrices (P ≥ .05). EC and EP produced an increased ΔL* after 15 years in the whitening group (P < .05). In the whitening groups, the ΔL* values of PA differ (P < .005) from those of lithium disilicates. Regardless of the experimental group, the TP values followed the inequality: PA < EC < EP (P < .05). Conclusions: Overall, the color of stained and glazed monolithic lithium disilicates and zirconia changed under aging with greater effects for whitening dentifrice. Aging did not influence translucency.

Purpose: To assess whether a health education video increased prosthodontic treatment demand for replacing missing teeth compared to a traditional health education (IEC) leaflet among patients visiting a university dental care center in Saudi Arabia. Materials and Methods: A nonrandomized educational intervention was conducted among patients with missing teeth. A total of 350 participants were divided equally into two health-education intervention groups: leaflet group and video group. Two major variants were ascertained: demand for prosthodontic dental care and awareness (knowledge) about the importance of replacing missing teeth. These two variants were studied for the difference in the scores between base line and at the end of the program (after 3 months). Bivariate analysis was done with chi-square test, McNemar chi-square test, and Wilcoxon matched-pairs tests, and finally binary logistic regression analysis was done. Results: The final analysis included 324 participants. There was improvement in both knowledge and demand for prosthodontic care in both the groups after health education, but a statistically significant improvement in demand for dental care was observed in the video group compared to the leaflet group (42.9% vs 63.2%). Logistic regression analysis identified that missing teeth in the anterior region and being in the video group were two significant factors associated with increased demand for care. Conclusions: The health education video method was found to be a more effective method compared to leaflets in improving knowledge and demand for replacing missing teeth.

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 (R_a), mean square height (R_q), and maximum roughness (R_z) 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 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 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 published literature on tooth–tissue supported removable partial dentures (RPDs) and determine the attachment system that provides the best clinical outcome. Materials and Methods: A comprehensive search of studies published up to November 2021 was performed in the PubMed/MEDLINE, Web of Science, and Cochrane Library databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The study protocol was approved and was registered in the International Prospective Register of Systematic Reviews (PROSPERO: CRD42021268449). The PICO question was, “What is the best attachment system used in Kennedy class I and II removable partial dentures?” Results: The search identified 871 articles, of which 21 met the inclusion criteria. The evaluation period in the studies ranged from 3 to 282 months. A total of 1,357 patients were included, of which 526 used prostheses with attachments. The mini SG attachment (extracoronal) was the most commonly used attachment, and the survival rate ranged from 37% to 98.1% in 10 studies, with no significant differences between the systems. Among the 10 studies selected for quantitative analysis, the meta-analysis revealed an overall failure rate of 16.6% (95% CI: 10.4% to 25.4%) and heterogeneity of I² = 65.725 (q value: 26.258, P = .002). Conclusions: Clinical studies comparing different attachment systems for rehabilitation are lacking. Our findings suggest that attachment-retained RPDs have good retention and better esthetics than conventional RPDs, and the extracoronal attachment system is the most viable choice for treatment at the free end.

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. Keywords: accuracy, natural smile, posed smile, surface-based matching, three-dimensional facial scan

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 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 investigate the resistance of an implant crown telescopically engaged to a geometrically defined hexagonal abutment with and without cement under compressive dynamic cyclic fatigue loading. Materials and Methods: 40 crowns, 9 mm in height, were cast from prefabricated plastic copings, each telescopically engaged to a 3-mm-high machined hexagonal abutment. 20 crowns were retained with zinc phosphate cement, and 20 crowns were retained with a screw. A vertical load of 15 kg was applied to all samples under oscilla)on. A Periotest was used to measure the mobility of the implant crown in Periotest values (PTV). Test endpoints were defined by the following: fatigue cycles ≥ 20 million; crown PTV > 10; or if samples became visibly loose or component fracture. Results: Cement-retained crowns failed on average at 2.60 x 10⁶ cycles ± 2.27, while screw-retained crown samples failed at 2.17 x 10⁶ cycles ± 1.27 with no significant difference (P > .05). Implant and abutment screw fractures were the most prevalent mode of failure in the cement-retained group, while in the screw-retained group, failures were caused by the loosening of one or both screw joints. The rate of increase in PTV was higher in the screw-retained group than in the cement-retained group. Conclusions: Under the experimental conditions, an implant crown telescopically engaged vertically to a 3-mm-tall hexagonal abutment, under compressive dynamic cyclic fatigue loading with or without cement, demonstrated no differences in resistance or failure outcomes. A cement-retained implant crown with telescopic engagement to the abutment is more rigid, resulting in more implant and abutment screw fractures than loosening. Keywords: Screw vs Cement Retention, Telescopic Engagement, Set Screw, Dynamic Cyclic Fatigue Loading, Implant Crown, Emergence Profile