The International Journal of Prosthodontics, 04/2014

This invited commentary describes the development of dental standards activity, how it functions within ISO, and the challenges it faces. George A Zarb Editor-in-Chief

Purpose: This study aimed to assess the efficacy of palatal brushing in the treatment of denture stomatitis. Materials and Methods: After screening 143 individuals with a potential diagnosis of denture stomatitis, 48 patients (mean age: 66.0 ± 11.2 years) were enrolled in a two-center phase 1 clinical trial with a one-group pretest/posttest design. The intervention of interest was manual palatal brushing after each meal and before bedtime. Clinical and microbiologic examinations were performed at baseline and 1 and 3 months after treatment. Additional data were obtained using a validated questionnaire. The primary and secondary outcomes were the remission of denture stomatitis and diminution of Candida colony-forming units (CFUs), respectively. Descriptive and nonparametric statistical tests were conducted to analyze the data. Results: At the 3-month follow-up, denture stomatitis was completely cured in 10.4% of the participants, and 70.8% of denture wearers showed improvement in the clinical signs of denture stomatitis. There was a significant reduction in the area and severity of the palatal inflammation (P .0001). The effect size ranged from medium to large (0.34 to 0.54) depending on the classification used for the diagnosis of denture stomatitis. A significant reduction in the number of Candida CFUs isolated from the palatal mucosa and dentures (P ≤ .05) was observed. Conclusions: The results of this study suggest that palatal brushing is an effective treatment of denture stomatitis.

Purpose: This study aimed to develop a classification of edentulous jaws for use as a diagnostic tool during implant-prosthodontic treatment planning. Materials and Methods: The morphology of 200 fully edentulous alveolar ridges (100 maxillae, 100 mandibles) was assessed with cone beam computed tomography. Generic implants (length: 8 mm; diameter: 4.1 mm) were used. To develop the classification system, the feasibility of virtually placing the implants without vertical ridge augmentation was considered. Potential implant sites were evaluated in terms of ridge width and described as either type A (no horizontal augmentation required) or type B (horizontal augmentation required). A descriptive statistical analysis of subjects' age, sex, and arch classification was performed. Results: In total, 880 implants were virtually planned. Based on alveolar ridge height, four arch patterns were identified (C1 to C4), providing a basis for prosthodontic planning with either removable or fixed implant-supported restorations. The frequencies of each category were as follows: C3 (n = 62, 62%), C4 (n = 16, 16%), C2 (n = 12, 12%), and C1 (n = 10, 10%) for the maxilla and C3 (n = 36, 36%), C4 (n = 31, 31%), C1 (n = 24, 24%), and C2 (n = 9, 9%) for the mandible. Conclusion: The proposed classification of the edentulous arch represents a useful tool for communication between clinicians when planning implantsupported rehabilitations.

The aim of this study was to examine the contribution of the palate to denture base support. Four subjects with tooth- or implant-supported maxillary overdentures were enrolled. Recordings (strain values converted to load values) were performed using miniature strain gauges and force transducers for the following conditions: metal framework only (A), denture base with full palatal coverage (B), and denture base without palatal coverage (C). The palatal-supporting ratio (PSR) was calculated using the equation PSR = (B - C) / A. The PSR values were less than 10% in all subjects, suggesting that the palate plays a minimal role in denture base support.

Purpose: The aim of this in vivo study was to evaluate the accuracy of metal-ceramic crowns fabricated using computer-aided design/computer-assisted manufacturing (CAD/CAM) in conjunction with intraoral digital impressions. Materials and Methods: Fifty patients in a general practice participated in the study. Patients were provided with crowns fabricated from digital impressions taken with an intraoral chairside scanner. Prior to crown insertion, the marginal integrity, esthetics, and occlusal and articulation contacts were evaluated using California Dental Association (CDA) criteria. The precementation space of the crowns was evaluated with the replica technique. Results: No adjustments were needed for any of the interproximal contact points. Adjustments of occlusion and articulation contacts were needed in 20% of the restorations. Clinical evaluation of the marginal integrity showed satisfactory results according to the CDA criteria. The 50 silicone replicas showed a median precementation space of 46 μm at the marginal measurement location, 94 μm at the midaxial location, and 185 μm at the centro-occlusal location. Conclusions: The precementation spaces of the crowns were within the acceptable range for CAD/CAM restorations.

Purpose: This study investigated changes in oral health-related quality of life (OHRQoL) in partially edentulous patients treated with removable dental prostheses (RDPs), fixed dental prostheses (FDPs), fixed-removable (combined) restorations (COMBs), and implant-supported fixed prostheses (ISFPs). Materials and Methods: A total of 200 patients (30 to 50 years old) were enrolled: 45 received RDPs, 32 received FDPs, 66 received COMBs, and 57 received ISFPs. OHRQoL was measured using the shortened version of the Oral Health Impact Profile (OHIP-14) before treatment and 6 weeks and 6 months after treatment. Treatment groups were sex-neutral; however, significant differences were found relative to age and Kennedy classification. A general linear model was used to explore the interaction of age and Kennedy classification with treatment modality. Results: Pretreatment analysis revealed that the psychologic discomfort domain showed the greatest negative impact on OHRQoL, while functional limitation had the smallest effect. Within-group comparison revealed a significant decrease in OHIP scores throughout the study in all groups except the younger age group treated with RDPs after 6 weeks. Between-group comparison revealed significant differences among the treatment groups. The least amount of OHRQoL improvement was recorded for RDPs for both age groups at 6 weeks and for the younger age group at 6 months. There were no significant differences between FDPs and ISFPs. Conclusions: All treatments produced significant improvement in OHRQoL. The least amount of improvement was observed in patients with RDPs. OHRQoL changes in patients treated with FDPs and ISFPs were comparable. The same treatment can have different impacts on the OHRQoL of partially edentulous individuals depending on their age and Kennedy classification.

Purpose: The study aimed to investigate the personality judgments made by observers of elderly individuals with different dental appearances. Materials and Methods: A random sample of 120 elderly (57 men, 63 women; third age: n = 51, mean age: 68.6 ± 5.0 years; fourth age: n = 69, mean age: 85.8 ± 3.0 years) and 120 young (54 men, 66 women; mean age: 24.9 ± 3.5 years) subjects were included. Decayed, natural, and ideal dental appearances were simulated on photographs of an elderly man and woman. Participants were asked to judge the personality traits of two randomly selected photographs. Univariate and multivariate analyses were performed. Results: Both groups judged the photographs similarly by attributing a higher social class to the individuals with an ideal dental appearance (elderly group: P = .0295 for the male subject, P = .0420 for the female subject; young group: P = .0003 for the male subject, P = .0042 for the female subject). This difference was less obvious when only the third-age participants were analyzed; they attributed a higher social class to the photograph of the man with a natural dental appearance than to the man with decayed and ideal appearances (P = .0322 and P = .0092, respectively) and lower intellectual capacities to the woman with a decayed appearance (P = .0351). The fourth-age subgroup made no such distinction. Conclusions: Personality judgments made by young and elderly persons are influenced by dental appearance. However, in the very old subgroup, no such influence could be verified. Dental esthetics should not be neglected in dental care for elderly patients.

The aim of this prospective clinical study was to investigate the long-term performance of all-ceramic veneers with overlap (OV) and full veneer (FV) preparation designs. Twenty-five patients were restored using 42 OV restorations (incisal/palatal butt-joint margin) and 24 FV restorations (palatal rounded shoulder margin). All restorations were leucite-reinforced glass-ceramic anterior veneers. The 7-year Kaplan-Meier survival rate was 100% for FV restorations and 97.6% for OV restorations. The all-ceramic veneers revealed significant deterioration over time according to United States Public Health Service criteria, irrespective of the preparation design. Based on the 7-year results of this study, both preparation designs can be considered reliable treatment options for anterior teeth with extended deficits.

Purpose: This study aimed to evaluate the survival probability of four narrow-diameter implant systems when subjected to fatigue loading. Materials and Methods: Seventytwo narrow-diameter implants to be restored with single-unit crowns were divided into four groups (n = 18): Astra Tech (3.5-mm diameter), with a standard connection (ASC); BioHorizon (3.4-mm diameter), with a standard connection (BSC); Intra-Lock (3.4-mm diameter), with a standard multilobular connection (ISC); and Intra-Lock (3.4-diameter), with a modified square connection (IMC). The corresponding abutments were screwed onto the implants, and standardized metal crowns (maxillary central incisors) were cemented and subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and reliability for 100,000 cycles at 150 and 200 N (90% two-sided confidence intervals) were calculated. Polarized light and scanning electron microscopes were used to access the failure modes. Results: The calculated survival probability for 100,000 cycles at 150 N was approximately 93% in group ASC, 98% in group BSC, 94% in group ISC, and 99% in group IMC. At 200 N, the survival rate was estimated to be approximately 0.1% for ASC, 77% for BSC, 34% for ISC, and 93% for IMC. Abutment screw fracture was the main failure mode for all groups. Conclusions: Although the probability of survival was not significantly different among systems at a load of 150 N, a significant decrease was observed at 200 N for all groups except IMC.

This study aimed to evaluate whether chlorhexidine mixed with irreversible hydrocolloid powder decreases microbial contamination during impression taking without affecting the resulting casts. Twenty volunteers were randomly divided into two groups (n = 10) according to the liquid used for impression taking in conjunction with irreversible hydrocolloid: 0.12% chlorhexidine or water. Surface roughness and dimensional stability of the casts were evaluated. Chlorhexidine mixed with irreversible hydrocolloid decreased the percentage of microorganisms when compared with water (P .001) but did not affect the surface quality or dimensional stability of the casts. Mixing chlorhexidine with irreversible hydrocolloid powder is an alternative method to prevent contamination without sacrificing impression quality.

Purpose: Fast-setting impression materials may be prone to inaccuracies due to accidental divergence from the recommended mixing protocol. This prospective randomized clinical trial aimed to assess three-dimensional (3D) deviations in the reproduction of subgingival tooth surfaces and to determine the effect of either following or purposely diverging from the recommended mixing procedure for a fast-setting addition-curing silicone (AS) and fast-setting polyether (PE). Materials and Methods: After three impressions each were taken from 96 participants, sawcut gypsum casts were fabricated with a standardized procedure and then optically digitized. Data were assessed with a computer-aided 3D analysis. Results: For AS impressions, multivariate analysis of variance revealed a significant influence of the individual tooth and the degree to which the recommended mixing protocol was violated. For PE impressions, the ambient air temperature and individual tooth showed significant effects, while divergence from the recommended mixing protocol was not of significance. Conclusions: The fast-setting PE material was not affected by changes in the recommended mixing protocol. For the two fastsetting materials examined, no divergences from the recommended mixing protocol of less than 2 minutes led to failures in the reproduction of the subgingival tooth surfaces.

Purpose: Although the VITA 3D-Master (3D) shade guide offers improved shadematching performance, many dental materials are only available in VITA Classical (VC) shades. This study aimed to clarify whether it is possible to convert 3D shades determined by observers into VC shades (indirect method) without adding a clinically significant error in comparison with direct shade determination using the VC shade guide. Materials and Methods: Forty ceramic specimens were fabricated. L*a*b* values were recorded using a spectroradiometer. Sixty participants (35 dentists, 15 technicians, and 10 students) were recruited and asked to determine the shades of specimens using the VC and 3D shade guides under standardized conditions. Conversion tables were constructed by allocating the closest VC shade tab to every matched 3D shade and by use of an optimization algorithm (indirect methods). Differences between ΔE values for VC matches and for the indirect methods were evaluated using t tests. Results: A mean ΔE (SD) of 4.34 (2.00) for VC and 4.22 (2.21) for 3D was observed (P = .040). Compared with direct shade matching using VC, the indirect method with the optimized tables resulted in a mean ΔE of 4.32 (1.96), which was not significantly different (P = .586). Conclusions: Within the limitations of this study, the conversion tables were suitable for the determination of tooth color using the 3D shade guide followed by conversion into VC shades without adding a clinically significant error.

Purpose: The purpose of this study was to examine, on the basis of masticatory performance (MP), total muscle work (TMW), and range of movement (RoM), whether reduction of the profile of the cusps results in loss of the biomechanical effectiveness of chewing by healthy dentate patients. Methods: Twenty healthy patients (10 female, mean age: 24.1 ± 1.2 years) chewed standardized silicone particles, performing 15 masticatory cycles. Three experimental conditions were investigated: chewing on (1) the natural dentition (ND), (2) splints with structured occlusal profiles simulating the patient's natural dentition (SS), and (3) splints with a plane surface (PS). The expectorated particles were analyzed by a validated scanning procedure. The size distribution of the particles was calculated with the Rosin-Rammler function and the mean particle sizes (X50) were determined for each experimental condition. The target variables of the experimental conditions were compared by repeated measures analysis of variance. Results: X50 values calculated for MP differed significantly (P .002) between PS and SS, and between ND and SS. Conversely, no significant differences (P > .05) were observed between SS and ND. Regarding muscle work the EMG activity of the masseter differed significantly (P .001) between the left and right sides, with higher values for the right (chewing) side. No significant differences (P > .05) were observed for TMW and RoM under the three test conditions. Conclusions: The results confirm the biomechanical significance of structured occlusal surfaces during chewing of brittle test food by young dentate subjects.