Sang E. Park

Clinical performance of a newly developed spectrophotometric system on tooth color reproduction

STATEMENT OF PROBLEM Matching a natural maxillary central incisor to a metal ceramic crown is one of the most difficult challenges in clinical dentistry due to the limitations of dental shade guides and the subjectivity of perceptual evaluation. PURPOSE The purpose of this study was to assess the clinical effectiveness of a spectrophotometric shade-matching system on tooth color reproduction. MATERIAL AND METHODS Two metal ceramic crowns were fabricated for a maxillary central incisor for 36 patients using 2 shade-matching techniques. The first technique was conventional visual matching using 3 shade guide systems, and the second was an instrument-based color-matching technique using a new spectrophotometric system. Color difference (DeltaE) values between the contralateral natural tooth and each of the 2 crowns were calculated in the cervical, middle, and incisal regions. The DeltaE values were compared using a Students t test (alpha=.05). Three calibrated examiners evaluated the color match by ranking it from 1 to 10 (10 = perfect match; 1 = no match; < or =8, accepted; > or =7, rejected). McNemars test was used to calculate the odds ratio of accepting restorations fabricated using a spectrophotometric system to conventional methods. RESULTS Results revealed that the mean DeltaE values of crowns matched with the spectrophotometer were significantly lower than those using a conventional technique (P<.001). The odds ratio of 12.5 was calculated, indicating that conventionally matched crowns were more likely to be rejected than those matched using the spectrophotometer (P<.001). CONCLUSIONS In this clinical study, crowns fabricated using a dedicated spectrophotometer had a significantly better color match and a lower rate of rejection due to shade mismatch compared to crowns fabricated with a conventional shade-matching method.

Candida albicans adherence to surface-modified denture resin surfaces.

PURPOSE The purpose of this study was to investigate two innovative methods in reducing adhesion of Candida albicans to denture base resins through modification of the surface characteristics of denture resin by incorporation of surface charge and application of a self-bonding polymer on denture resins. MATERIALS AND METHODS Three groups were tested [Group 1: control, pure poly(methyl methacrylate) (PMMA); Group 2: modified PMMA (mPMMA) with 16% methacrylic acid; Group 3: pure PMMA coated with self-bonding polymer (SBP)]. Twenty resin specimens for each group were polymerized, and four experimental subgroups for each surface type were devised, consisting of 2, 4, 6, and 12 days of incubation in C. albicans suspension. The surface area of adherent C. albicans stained with Grams crystal violet was examined under a light microscope at 400x magnification. Four areas were photographed on each block, one on each quadrant. The images were analyzed using Scion Image 1.63 software to calculate the percent surface area containing adherent C. albicans. Kruskal-Wallis test and Tukeys honest significant difference (HSD) procedure were used to compare the groups. RESULTS At day 2, the modified resin had statistically significantly lower levels of Candida than both the control group and the SBP group (p<or= 0.036). Both the mPMMA group and SBP group had statistically significantly lower levels of Candida accumulation at days 4, 6, and 12, compared to the control. CONCLUSIONS The amount of C. albicans adhering to the resin surfaces reduced significantly with modification of surface charge and application of self-bonding polymer. Modification of surface characteristics of polymeric biomaterials is an effective method in reducing adhesion of C. albicans to PMMA surfaces.

Can Noncognitive Components of Admissions Data Predict Dental Student Performance and Postdoctoral Program Placement

The aim of this retrospective cohort study was to evaluate whether the noncognitive factors of the dental student application, including undergraduate major and interview score, predicted success in the predoctoral program and placement in postdoctoral programs. The study population consisted of 169 students in the Harvard School of Dental Medicine DMD graduating Classes of 2012 through 2016. Noncognitive factors in the dental application, including letters of recommendation, extracurricular activities, undergraduate major, and dental school admission interview performance, were collected for the study population. Groups were analyzed for differences among undergraduate majors and any association between postgraduate placement and dental school performance. Dental school performance measures were grades obtained in the third and fourth years in a combination of preclinical and clinical course assessments. The results showed that neither interview score nor undergraduate major was significantly associated with dental school performance or postdoctoral program placement. There was a non-significant association between interview score and performance in the course Treatment of Active Disease. These results suggest that noncognitive factors of the dental school application offered low yield to predicting predoctoral student performance and residency placements, with interview performance possibly outweighing undergraduate major in selection of successful predoctoral candidates.