Influence of interdental spaces and the palate on the accuracy of maxillary scans acquired using different intraoral scanners.

PURPOSE: To assess the influence of interdental spaces and scanning the palate on the accuracy of maxillary scans acquired using three intraoral scanners (IOSs). MATERIALS AND METHODS: A virtual completely dentate maxillary cast without interdental spaces was obtained and modified to create 1, 2, and 3 mm of interdental spacing between the anterior teeth. These three files (reference standard tessellation language files) were used to print three reference casts. The reference casts were scanned using three IOSs: TRIOS4, iTero Element 5D, and Aoralscan2. Three groups were created based on the interdental spaces: 0, 1, 2, and 3 mm (n = 10). The groups were subdivided into two subgroups: no palate (NP subgroup) and palate (P subgroup). The reference STL files were used to measure the discrepancy with the experimental scans by calculating the root mean square (RMS) error. Three-way analysis of variance (ANOVA) and post hoc Tukey pairwise comparison tests were used to analyze trueness. The Levene test was used to analyze precision (α = 0.05). RESULTS: Trueness ranged from 91 to 139 µm and precision ranged from 5 to 23 µm among the subgroups tested. A significant correlation was found between IOS*group (p<0.001) and IOS*subgroup ( p<0.001). Tukey test showed significant trueness differences among the interdental spaces tested (p<0.001). The 1- and 2-mm groups obtained better trueness than the 0- and 3-mm groups (p<0.001). An 11 µm mean trueness discrepancy was measured among the different interdental space groups tested. The P subgroups demonstrated significantly higher trueness when compared to the NP subgroups (p<0.001). The discrepancy between the maxillary scans with and without the palate was 4 µm. Significant precision discrepancies were found (p = 0.008), with the iTero group showing the lowest precision. CONCLUSION: Interdental spaces and incorporation of the palate on maxillary intraoral scans influenced trueness and precision of the three IOSs tested. However, the scanning discrepancy measured may be of no clinical relevance.

Profile of prosthodontics program directors in North America.

PURPOSE: To develop a current profile of prosthodontics program directors (PPDs) in United States dental schools and describe the current challenges and responsibilities of those serving in the position and assess the professional needs of the program directors (PDs) to better support them in their roles. MATERIALS AND METHODS: A survey was sent to 51 participants who were identified as PPDs in North America via Qualtrics in 2019 to assess the professional needs of PDs to better support their roles. The survey consisted of 29 items organized into six sections: (1) demographic information; (2) hours and time spent in various areas of the job; (3) greatest challenges; (4) perceived importance of specific competencies; (5) opinions on the greatest rewards of the position; (6) their needs for support from the American College of Prosthodontists and advice for the future PD. RESULTS: The response rate for this survey was 88.3%. Of the 45 respondents, the majority were white/non-Hispanic, followed by Asian/Pacific Islanders. The two largest and equal numbers of participants who worked for more than 10 years and between 1 and 3 years were observed with approximately 29% each, and PDs who worked less than a year occupied the least amount. Overall, 34% of PDs are on the tenure track and 80% of those are tenured. Teaching and clinical services took away the greatest time with approximately 42% and 22.1%, respectively. Thirty-five (78%) PDs listed the greatest challenge they encountered was the workload of the role. Skills listed in leadership and personnel competencies were all rated more important than most of the skills listed in management. CONCLUSIONS: There is a wide gender gap and a lack of racial diversity among the PPDs. The biggest challenge faced by them is the amount of workload followed by budget and fiscal constraints. And for their improved efficiency, they gave emphasis on learning time management and continuous clinical training of newer advances.

Viscoelastic Properties of Human Facial Skin and Comparisons with Facial Prosthetic Elastomers.

Prosthesis discomfort and a lack of skin-like quality is a source of patient dissatisfaction with facial prostheses. To engineer skin-like replacements, knowledge of the differences between facial skin properties and those for prosthetic materials is essential. This project measured six viscoelastic properties (percent laxity, stiffness, elastic deformation, creep, absorbed energy, and percent elasticity) at six facial locations with a suction device in a human adult population equally stratified for age, sex, and race. The same properties were measured for eight facial prosthetic elastomers currently available for clinical usage. The results showed that the prosthetic materials were 1.8 to 6.4 times higher in stiffness, 2 to 4 times lower in absorbed energy, and 2.75 to 9 times lower in viscous creep than facial skin (p < 0.001). Clustering analyses determined that facial skin properties fell into three groups-those associated with body of ear, cheek, and remaining locations. This provides baseline information for designing future replacements for missing facial tissues.

Color and translucency of enamel in vital maxillary central incisors.

STATEMENT OF PROBLEM: Limited data, especially in vivo data, exist regarding translucency parameter (TP) values for vital anterior nonrestored dentition. Additionally, published information on the CIELab values of vital enamel at a theoretical infinite thickness is lacking. Obtaining TP and CIELab values in a population that varies in terms of ethnicity, age, and sex would be useful to inform the development and placement of esthetic dental restorations that more accurately capture the complex optical qualities of enamel. PURPOSE: The purpose of this clinical study was to investigate in vivo the TP and CIELab values of vital anterior incisor enamel at a theoretical infinite thickness in a diverse pool of participants who varied in age, ethnicity, and sex. MATERIAL AND METHODS: Spectral reflectance measurements (380 to 780 nm at 2-nm intervals) of the mid-incisal region of vital, unrestored maxillary anterior teeth were made in 120 participants, equally divided into 2 sexes, 4 racial or ethnic groups, and 5 age ranges. Instruments were oriented to achieve 0-degree observation and 45-degree illumination, and spectral measurements were made with white and black silicone backgrounds. Reflectance spectra of the incisal enamel from both the black and white silicone backing were used to fit to the Kubelka-Munk (K-M) reflectance theory. The CIEDE2000 color difference formula was used to determine TP, and data were compared among participant demographics. CIELab color coordinate values for enamel at an infinite thickness were calculated by using a D65 illumination and CIE standard human (2-degree) observer. To determine value ranges and significant differences among participant groups, CIELab values were analyzed with a 4-way ANOVA, and TP values were analyzed with a generalized linear mixed model. Pairwise comparisons of interest were evaluated with Bonferroni-corrected Student t tests. RESULTS: For maxillary central incisor enamel, the average TP was 10.1 ±3.6, and the average CIELab color coordinates were L∗=73.5 ±7.6, a∗=2.2 ±1.8, b∗=11.9 ±8.4. TP values of incisal enamel significantly differed among specific age and ethnic groups, with general significant interactions of age and sex (P=.009), as well as ethnicity and age (P=.042). CIE color coordinates of enamel at an infinite thickness were found in the L∗ coordinate among different age groups with the same sex and ethnicity, specifically when comparing CIELab direction with the population characteristics of age (P=.011) and the interaction between age, sex, and ethnicity (P=.035). CONCLUSIONS: In vivo L∗ values and TP values of incisal enamel differed significantly among groups determined by ethnicity, age, and sex.

Effect of Nano Ceramic Coating on Color Perceptibility and Acceptability of Polymethylmethacrylate: In Vitro and Clinical Study.

The effect of a novel nano-ceramic coating (TiO2) using an atomic layer deposition (ALD) technique on the surface of polymethyl methacrylate (PMMA) material was investigated. The patients' and clinicians' perception and acceptance of the PMMA color with TiO2 coating were also examined. In vitro color measurement was performed on thirty specimens (light, original, and dark pink) before and after TiO2 coating. Patients' and clinicians' perception and acceptance of color changes on PMMA were measured and compared. Descriptive and analytic statistics were analyzed (a = 0.05). TiO2 films were successfully deposited on the PMMA specimen by the ALD technique. Color changes after TiO2 coating were observed on all three PMMA shades, significantly higher than the established 50:50% perceptibility threshold, but below the established 50:50% acceptability threshold. The percentage of patients that perceived a color difference after TiO2 coating were 83.3%, 63.9%, and 77.8% for light, original, and dark pink, respectively. The percentages of clinicians that were satisfied with the color difference were 96.4%, 80%, and 69.2% for light, original, and dark pink, respectively. Color changes after TiO2 coating were observed, but below the acceptable threshold. The clinical survey demonstrated that a color difference was perceived but was clinically acceptable. In general, laypeople have lower perception and higher acceptance of changes in PMMA color than clinicians.

The Effect of Smoking and Brushing on the Color Stability and Stainability of Different CAD/CAM Restorative Materials.

This study aimed to investigate and compare the color stability and stainability of computer-aided design/computer-aided manufacturing (CAD/CAM) restorative materials in their glazed (G) and polished (P) state when exposed to cigarette smoke, as well as after brushing. Three CAD/CAM restorative materials were investigated: lithium disilicate CAD (LD), zirconia (Zr), and Telio PMMA CAD (PMMA), according to their surface finishing and assignment to cigarette smoking exposure or soaking in the saliva (control) group. The color change (∆E) was calculated before and after the intervention performed for all specimens, using the L*a*b values to quantitatively assess the shade differences. Statistical analysis was performed using one-way repeated measures ANOVA and Bonferroni multiple comparison analysis (α = 0.05). The surface finishing did not influence the materials' stainability. Color change was noted after smoking, LD and Zr-G and Zr-P had a comparable color change (p > 0.05), while PMMA presented lower ∆E values (p < 0.05). After brushing, all specimens had a significant color change that was high for LD-G and LD-P, and Zr-G, compared with Zr-P and PMMA (p < 0.05). In conclusion, the exposure to cigarette smoke showed that LD, Zr, and PMMA are all susceptible to staining, but brushing decreases surface staining.

Validation of two clinical color measuring instruments for use in dental research.

OBJECTIVE: There are several shade matching instruments developed for clinical use, but the validity of their use in dental research has not been thoroughly investigated. The objective of this study is to evaluate the accuracy of using two clinical color measuring instruments, VitaEasyshade and Spectroshade, against a referent laboratory color measuring instrument (Spectroradiometer PR670). METHODS AND MATERIALS: The validity and repeatability of the referent laboratory color measuring instrument was assessed using standard color patches with certified CIE L*a*b* values. 10% of the 240 color patches were randomly selected and measured ten times in a random order to test for repeatability. 16 metal ceramic specimens, fabricated from base metal alloy veneered with porcelain of different Vita Classic shades, were measured for L*a*b* values using the PR670, Vita EasyShade and the Spectroshade. The CIE L*a*b* values obtained from the three color measuring instruments were compared using repeated measures ANOVA and post hoc using the Bonferroni test. The color difference, CIEDE2000 (∆E00), between the gold standard (PR670) and the two color measuring instruments were also determined and compared against the known perceptible color difference. RESULTS: L*a*b* values varied significantly between the three instruments. When comparing the mean ΔE00, the differences in values between PR670 and Spectroshade were not clinically significantly. However, the mean ΔE00 values between PR670 and Vita Easyshade were both clinically and statistically significant. CONCLUSION: The lack of clinical significance in values obtained from the SpectroShade when compared to those obtained by the PR670 suggests that the SpectroShade may be recommended for use in dental color research. CLINICAL SIGNIFICANCE: The SpectroShade instrument and PR670 spectroradiometer provided values that lacked clinical significance, suggesting that its use may be highly beneficial for clinical shade matching as well as color research.

Mathematical Tooth Proportions: A Systematic Review.

PURPOSE: The aim of this systematic review was to evaluate and compare three commonly used proportions that include the golden proportion, golden percentage, and Recurring Esthetic Dental (RED) proportion to identify which of the mathematical formulas, if any, can be used to provide predictable and repeatable esthetic clinical outcomes. METHODS: A comprehensive search of electronic databases that included EBSCO, ProQuest, SCOPUS, Science Direct, Wiley, Google Scholar and PubMed was conducted using the terms: "golden proportion," "golden percentage," and "Recurring Esthetic Dental (RED) proportions" alone or in concurrence with one or both ensuing terms: "tooth proportions" and "esthetic tooth proportions." In addition, the following journals were hand searched for relevant articles: Journal of Prosthodontics, Journal of Prosthetic Dentistry and Journal of Esthetic and Restorative Dentistry. Related citations were also considered. RESULTS: Tooth proportions varied substantially in the natural dentition. No studies revealed findings that supported the use of one mathematical formula to predict esthetic success. The golden proportion is present between the central to lateral incisor in some cases, but rarely between the lateral incisor and the canine. When compared to the other proportions, the golden percentage provided better starting points for tooth shape and size, but only when values were adjusted to consider other factors such as ethnicity and/or facial proportions. CONCLUSION: Mathematical formulas did not provide consistent results that would allow for their use as a standardized guide for esthetically pleasing smiles. Although the golden percentage may be a good starting point if the percentages are adjusted on a case-by-case basis, generalized esthetic ideals cannot be determined by a mathematical formula and are open to interpretation by both the clinician and the patient.

Management of intraoral stents for radiotherapy during COVID-19 pandemic.

Radiotherapy is being performed in many situations as a curative approach for head and neck cancer instead of surgery due to the current novel coronavirus disease (COVID-19) pandemic. A recent publication reported that even hypofractionation was being conducted in order to reduce the daily exposure of both patients and the medical staff involved in cancer therapies. As a result, dental teams may be requested more frequently than usual to fabricate intraoral stents (IOS). Given that IOS may be a potential source of COVID-19 contagion, the main purpose of the present correspondence is to offer a guide on how health professionals may be safely presented in the room, on the management of the IOS and also how to sanitize the stents.

Three-Dimensional Accuracy of Conventional Versus Digital Complete Arch Implant Impressions.

PURPOSE: The accuracy of digital impressions is still controversial for complete arch implant cases. The aim of this study is to compare the accuracy of different intraoral scanners with the conventional technique in terms of trueness and precision in a complete arch implant model. MATERIAL AND METHODS: Eight implants were inserted asymmetrically in a polyurethane edentulous mandibular model with different angulations. A 3-dimensional (3D) reference model was obtained by scanning this polyurethane model with an optical scanner. First, digital impressions were made by using 3 different intraoral scanners: Carestream 3500 (DC), Cerec Omnicam (DO) and 3Shape Trios 3 (DT). Subsequently, a nonsplinted open tray impression technique was used for conventional impression group (C) and then the master casts were digitalized with a lab scanner. Each 10 STL files belonging to 4 different impression groups were imported to a reverse engineering program, to measure distance and angle deviations from the reference model. All statistical analyses were performed after taking absolute values of the data. After comparing the impression groups with one-way ANOVA, the trueness and precision values were analyzed by Tukey post hoc test and 0.05 was used as the level of significance. RESULTS: The mean trueness of distance was 123.06 ± 89.83 µm for DC, 229.72 ± 121.34 µm for DO, 209.75 ± 47.07 µm for DT, and 345.32 ± 75.12 µm for C group (p < 0.0001). While DC showed significantly lower deviation compared to DO and C, no significant difference was found between DC and DT. C showed the highest distance deviation significantly in all groups; and no significant difference was found between DO and DT groups. In angle measurements; the trueness was 0.26° ± 0.07° for DC, 0.53° ± 0.42° for DO, 0.33° ± 0.30° for DT, and 0.74° ± 0.65° for C group. There was no significant difference between the groups in terms of angular trueness (p = 0.074). In terms of the precision for distance, the results of DC 80.43 ± 29.69 µm, DO 94.06 ± 69.96 µm, DT 35.55 ± 28.46 µm and C 66.97 ± 36.69 µm were determined (p = 0.036). The significant difference was found only between DT and DO among all groups. Finally, angular precision was determined to be 0.19° ± 0.11° for DC, 0.30° ± 0.28° for DO, 0.22° ± 0.19° for DT, and 0.50° ± 0.38° for Group C. No significant difference was found between the groups, in terms of angular precision (p = 0.053). CONCLUSIONS: All digital impression groups yielded superior data compared to conventional technique in terms of trueness. DC formed the impression group with the highest trueness in both distance and angular measurements. The results of this in vitro study suggest the use of intraoral scanners compared to the conventional impression techniques in complete arch implant cases with high angulations.

Status of Sleep Apnea and Snoring Disorder Curriculum in U.S. Advanced Education Prosthodontic Programs.

PURPOSE: To assess the management of sleep apnea and snoring disorders in Advanced Education Programs in Prosthodontics (AEPP) in the United States. MATERIALS AND METHODS: A 51 item, online survey was sent to program directors at 48 AEPPs in the United States in 2015. Data results were analyzed descriptively. RESULTS: Thirty-five program directors responded to the survey. Twenty-four (68.6%, N = 35) programs report not having a dedicated course for the treatment of sleep apnea and snoring disorders. The majority (94.3%) of programs chose to treat sleep disordered breathing with oral appliance therapy and 80.0% (N = 35) of programs utilize customized sleep apnea oral devices. However, only 48.6% (N = 35) and 51.4% (N = 35) of programs regularly address sleep apnea and snoring disorders at initial examination during the comprehensive exam and medical history questionnaire, respectively. CONCLUSIONS: The confidence interval for this survey is 8.71 at a confidence level of 95% due to a response rate of 72.9%. This confidence interval suggests there is responder bias in the survey results. Therefore, the results of this survey provide a suggestion of how sleep disorders are managed in AEPPs. Programs appear to be consistent among each other with regards to treatment modalities for sleep disordered breathing. The results suggest that patients are not screened enough to receive treatment addressing sleep disorders.

Prosthodontic Resident Selection by Postdoctoral Dental Matching Program: A National Survey by Participating Program Director.

PURPOSE: The purpose of this study was to obtain information about the resident selection and Match process that occurred for the Commission on Dental Accreditation (CODA)-accredited Advanced Education in Prosthodontics program in North America from the program directors' perspective, after the first year of implementation. MATERIALS AND METHODS: The list of Advanced Education in Prosthodontics program in CODA-accredited North American institutions was obtained from the ACP central office, and the directors of each program were identified. The surveys were distributed to 48 program directors online and results were compiled. RESULTS: Out of 48 programs, 43 directors responded to and completed the survey (90.0%), where 35 programs participated in the Match process, 5 did not, and 3 were omitted due to incomplete surveys. While the majority of programs did not see any changes in their applicant pool or their quality, 10 programs (25.0%) observed a number of increases in the application and 13 programs (32.5%) observed an increase in the quality of the applications. Among the 35 programs that participated in the Match process, the main reasons for their participation were "fairness" (48.2%), "did not want to keep moving up interview dates" (23.2%), and "have applicants come to interview as planned" (21.4%). Thirty-three programs reported that 75% to 100% of the invited applicants came to the interview (76.7%). The majority of programs that participated in Match expressed satisfaction with the process (29/33, 80.6%). Sixteen programs (45.7%) reported that they matched with 100% of their first selections. CONCLUSION: Overall response of reintroduction of the Match process for advanced prosthodontic resident selection was very positive for majority of the program directors.

Accuracy of complete-arch implant impression made with occlusal registration material.

STATEMENT OF PROBLEM: Which impression material, impression tray type, and implant impression technique combination produces the most accurate complete-arch impression is unclear. PURPOSE: The purpose of this in vitro study was to compare the implant impression accuracy of a completely edentulous arch made with addition silicone occlusal registration material and an open tray with the implant impression accuracy of other conventional impression techniques. MATERIAL AND METHODS: A master cast was fabricated from Type IV gypsum with four 3.8-mm diameter implants with internal hexagon located in the area of mandibular canines and first molars. Impressions (N=60) were made from the master cast using the 6 techniques investigated: group B-OC-N with occlusal registration impression material (B), open custom tray (OC), and nonsplinted impression pins (N); group B-OS-N with occlusal registration impression material (B), open plastic perforated stock tray (OS), and nonsplinted impression pins (N); group PE-OC-N with polyether medium-body impression material (PE), open custom tray (OC), and nonsplinted impression pins (N); group PE-OC-S with polyether medium-body impression material (PE), open custom tray (OC), and impression pins splinted (S) with autopolymerizing resin cut after 17 minutes and reconnected; group PE-CC-N with polyether medium-body impression material (PE), closed custom tray (CC), and nonsplinted impression pins (N); group PVS-CS-N with simultaneous double-mix polyvinyl siloxane impression material (PVS), closed stock perforated metal tray (CS), and nonsplinted impression pins (N). Type IV gypsum casts were fabricated 24 hours after making the impressions. A computerized numerical control 3D coordinate measuring machine was used to measure the absolute differences of the distances between the centroids of the 4 implants among the casts produced and the distances measured at the master cast. The Kruskal-Wallis test was used to determine differences among the experimental groups (α=.05). The Mann-Whitney U post hoc analysis was used for all group combinations. RESULTS: No significant differences were found between the test groups B-OC-N and PE-OC-S, which were more accurate than the other groups. Group B-OS-N resulted in the least accurate impressions of all experimental groups. Group PE-OC-S resulted in more accurate impressions than the PE-OC-N group. No statistically significant differences were found between groups PE-OC-N and PE-CC-N or between groups PVS-CS-N and PE-CC-N. CONCLUSIONS: For complete edentulism, the use of silicone occlusal registration material with an open custom tray and nonsplinted impression pins resulted in impressions as accurate as those produced with PE open custom tray with splinted impression pins. These 2 techniques resulted in more accurate impressions than the other 4 techniques studied.

Long-term stainability of interim prosthetic materials in acidic/staining solutions.

OBJECTIVE: To evaluate the long-term color stainability, translucency, and contrast ratio (CR) of different resins used to fabricate interim prostheses after immersion in acidic/staining solutions. MATERIALS AND METHODS: A total of 160 specimens were divided into 16 groups (n = 10) according to the material (heat-polymerized acrylic resin [HPAR], auto-polymerized acrylic resin [APR], nanoparticulated bis-acrylic resin [BR], and prefabricated poly(methyl methacrylate) block for CAD/CAM [CADR]) and immersion solutions (artificial saliva, cola beverage, coffee, and red wine). A spectrophotometer was used before and after each immersion period (7, 14, 28, 90, and 180 days). Color differences (CIEDE2000 and CIELab) were calculated. A three-way repeated-measures analysis of variance and Bonferroni test (α = .05) were used. RESULTS: After 180 days, the APR presented the highest value for coffee and the CADR presented the smallest value for the cola (P < .001). For the CR, the highest values were obtained at 180 days for BR in coffee (1.35) and wine (1.18) (P < .001). Higher translucency parameters were obtained in the BR and CADR in the initial, 14, 28, and 90 days (P < .001). CONCLUSIONS: From the greatest to the smallest staining potential, the solutions were classified as: wine > coffee > cola beverage > saliva, while for the materials as: APR > BR > HPAR > CADR. CLINICAL SIGNIFICANCE: The knowledge of the long-term optical behavior of interim prosthetic materials is important for clinicians to decide which material to use to match the dietary intake of their patients and their esthetic demands. Prefabricated blocks for CAD/CAM systems have been shown to maintaining their optical characteristics even after a long period of immersion in acidic/staining solutions.

Predoctoral Dental Education in Tooth Prognosis and Treatment Complexity: A Survey of U.S. Dental Schools.

The aim of this study was to determine the educational methods and tools used to teach tooth prognosis and treatment complexity determination in U.S. predoctoral dental programs. In 2018, an online survey was emailed to the academic deans of all 66 accredited U.S. dental schools. Of these, 42 schools responded (63.6%), and 36 schools completed the entire survey (54.5%). The methods reported for teaching tooth prognosis and case complexity determination varied widely among the participating schools. Among the respondents, 25% reported using the American Association of Endodontists' Endodontic Case Difficulty Assessment, while 10% reported having no specific method for teaching prognosis. The most common method for teaching overall treatment complexity was the Prosthodontic Diagnostic Index, which was used by 24% of the respondents. However, another 24% reported that their school did not have a specific method for teaching treatment complexity. Large percentages of the respondents reported that students sometimes or often made wrong tooth prognosis and case complexity determination (90% and 92%, respectively). The most prominent feedback provided by the respondents based on their experience was the importance of faculty standardization, the understanding of students' inexperience, and the need for an interdisciplinary approach. The majority of these respondents reported that their schools had specific methods of teaching prognosis and case complexity determination. However, there was a wide range of teaching practices related to the contents and levels of evidence.

Retrospective Evaluation of the Status of Advanced Dental Education in Prosthodontics from 2006 to 2016.

The aim of this study was to analyze information about advanced education programs in prosthodontics (AEPPs) collected in American Dental Association (ADA) surveys on advanced dental education from 2006-07 to 2016-17. Data recorded included number of AEPPs and information on program directors, applicants, and enrollees in AEPPs. The results showed that, from 2006 to 2016, there was an increase in the number of AEPPs and enrollment of prosthodontic residents, and the number of applicants per program more than doubled. Despite these increases, steps are needed to increase the number of underrepresented minority residents in prosthodontics. Also, a periodic survey of prosthodontic residents to identify their goals, experiences during training, and career plans could benefit the specialty by providing more insight into the future prosthodontic workforce.

Qualifications and Characteristics North American Dental Deans Seek in Department Chairpersons.

The aim of this study was to determine whether deans of North American dental schools perceived that one category of department chairperson skills (leadership or management) was more important than the other for their chairpersons to be successful. A secondary purpose was to determine the professional qualifications and personal characteristics these deans perceived contributed most to the success of department chairpersons and whether those differed by the research emphasis of the school. An email survey was sent in 2016 to all 75 deans of U.S. and Canadian dental schools with graduating classes. Section one of the survey was an open response section asking deans to list the five most essential characteristics of a successful department chairperson. Section two asked deans to rank the importance of eight listed professional qualifications, and the last section asked deans to rate the importance of four leadership and four management traits that could contribute to the success of their chairpersons. Questions about characteristics of the deans and the schools were also included. A response rate of 46.7% was obtained. The most frequent characteristics listed in the open response section were in the categories of vision, academic expertise, and integrity. The three most highly ranked professional qualifications were previous teaching experience, previous administrative experience, and history of external research funding. Four of the eight professional qualifications were ranked differently by deans of high compared to moderate research-intensive schools (p<0.05). Overall, the respondents rated leadership skills more highly than management skills (p=0.002) as important for departmental chairpersons.

Wear Characteristics and Volume Loss of CAD/CAM Ceramic Materials.

PURPOSE: In the field of prosthodontics, patients often require complex and extensive restorative care. This can involve the use of dental restorations to restore teeth on both the maxillary and mandibular arch. Current literature has evaluated the wear properties of different dental ceramics against enamel, but studies regarding dental ceramics opposing one another are limited. The purpose of this study was to assess the wear potential and wear behavior of CAD/CAM zirconia (ZR) and lithium disilicate (LD) materials against a similar ceramic material, and how the surface finish of these dental ceramics might affect patterns of wear. MATERIALS AND METHODS: Using a sphere-on-plate tribometer system, different surface finishes (glazed-G and glazed then polished-GP) of ZR and LD were evaluated following wear simulation. Artificial saliva of physiologic pH was used as a lubricant during wear simulation at 37°C. The coefficient of friction (COF) was calculated during the wear simulation. After wear simulation was complete, volume loss, surface roughness, and surface characterization of the specimens were analyzed using white-light interferometry and scanning electron microscopy (SEM). Statistical significance between materials and surface finish was established with two-way ANOVA and Bonferroni post hoc test (α = 0.05). RESULTS: Based on the 2-way ANOVA, material (p = 0.002) significantly affected the COF. LD showed a higher COF (p = 0.002) than ZR. Material (p < 0.001) and surface finish (p = 0.004) significantly affected the surface roughness inside the scar. ZR had significantly lower surface roughness compared to LD (p < 0.001). For outside scar, surface finish (p < 0.001) significantly affected the surface roughness. Polished specimens showed significantly higher roughness compared to glazed specimens for both inside (p = 0.004) and outside scar (p < 0.001). For volume loss, material (p < 0.001) and the interaction between material and surface finish (p < 0.001) were statistically significant. LD had higher volume loss than ZR (p < 0.001). For both glazed and polished finished, LD-G and LD-GP had significantly higher volume loss than ZR-G (p = 0.028), and ZR-GP (p < 0.001), respectively. SEM analysis indicated particle build-up and a grooving mechanism of wear for the LD-GP specimens. This suggested a three-body wear phenomenon occurring for LD-GP specimens, which was not visible in SEM imaging for other specimen types. CONCLUSIONS: This study demonstrated the resistance to wear and low abrasiveness of ZR when compared to LD in a simulated masticatory environment. This can be best explained by the increased strength of ZR, and the introduction of three-body wear to LD specimens from the accumulation of embedded wear debris onto its surface. Wear data and comparison of SEM images following wear simulation confirmed this interpretation.

Color stability of maxillofacial prosthetic silicone functionalized with oxide nanocoating.

STATEMENT OF PROBLEM: Maxillofacial prostheses made of silicone elastomers undergo undesirable color degradation over time. How this color change can be prevented is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the ability of an oxide nanocoating to prevent color degradation of maxillofacial silicone elastomers after artificial accelerated aging. MATERIAL AND METHODS: A silicone elastomer with functional intrinsic pigment was tested. Specimens (N=20) were fabricated, and half of them were coated with a nanolayer of titanium dioxide (TiO2) using atomic layer deposition. Both coated and noncoated specimens (control) were exposed to artificial aging at 450 kJ/m2 of total energy. Changes in the color of all the specimens with and without TiO2 nanocoating were measured before and after the atomic layer deposition coating and before and after aging. The obtained color data were analyzed by using independent t tests and the 1-sample t test (α=.05). RESULTS: Color change (ΔE1=3.4 ±1.4) was observed for the silicone elastomers after the specimens were surface coated with TiO2 nanofilm, although this change was not statistically significant (P=.369) compared with the acceptability threshold (ΔE=3.0). Upon exposure to artificial aging, the noncoated control specimens underwent color change (ΔE2=2.5 ±0.7, P=.083 compared with the acceptability threshold). The specimens with TiO2 nanocoated surface experienced the least color change (ΔE3=1.4 ±0.6) when subjected to artificial aging, and this change was significantly lower (P<.001) than the established acceptability threshold of ΔE=3.0. In addition, the chemical analyses confirmed that the TiO2 nanocoating remained on the surface after exposure to artificial aging. CONCLUSIONS: TiO2 nanocoating was shown to be effective in reducing color degradation of the silicone elastomer exposed to artificial aging for 120 hours with 450 kJ/m2 of total energy.