Vitamin D signaling regulates oral keratinocyte proliferation in vitro and in vivo.

The secosteroidal hormone 1,25-dihyroxyvitamin D [1,25(OH)(2)D(3)] and its receptor, the vitamin D receptor (VDR), are crucial regulators of epidermal proliferation and differentiation. However, the effects of 1,25(OH)(2)D(3)-directed signaling on oral keratinocyte pathophysiology have not been well studied. We examined the role of 1,25(OH)(2)D(3) in regulating proliferation and differentiation in cultured oral keratinocytes and on the oral epithelium in vivo. Using lentiviral-mediated shRNA to silence VDR, we generated an oral keratinocyte cell line with stable knockdown of VDR expression. VDR knockdown significantly enhanced proliferation and disrupted calcium- and 1,25(OH)(2)D(3)-induced oral keratinocyte differentiation, emphasizing the anti-proliferative and pro-differentiation effects of 1,25(OH)(2)D(3) in oral keratinocytes. Using vitamin D(3)-deficient diets, we induced chronic vitamin D deficiency in mice as evidenced by decreased serum 25-hydroxyvitamin D (25OHD) concentrations. The vitamin D-deficient mice manifested increased proliferation of the tongue epithelium, but did not develop any morphological or histological abnormalities in the oral epithelium, suggesting that vitamin D deficiency alone is insufficient to alter oral epithelial homeostasis and provoke carcinogenesis. Immunohistochemical analyses of human and murine oral squamous cell carcinomas showed increased VDR expression. Overall, our results provide strong support for a crucial role for vitamin D signaling in oral keratinocyte pathophysiology.

Characterization of an optically stimulated dosimeter for dentomaxillofacial dosimetry.

OBJECTIVE: The objective of this study was to examine the suitability of optically stimulated luminescent dosimeters (OSLD) for point dosimetry of maxillofacial radiographic examinations. STUDY DESIGN: The dose response of OSLD nanoDot dosimeters was evaluated over the range of 10 µGy to 4900 µGy x-radiation. The angular dependence of the OSLD nanoDots was examined and compared with that of thermoluminescent dosimeter (TLD) chips. The concordance between OSDL- and TLD-measured absorbed doses at selected anatomic sites in an anthropomorphometric phantom was examined. RESULTS: OSLD-measured doses were not significantly different from the actual delivered dose, as determined by an ionization chamber. The dose response is linear over the dose response over the examined dose range. Angular variation of OSLD dosimeters ranged from 88% to 109%; however, the magnitude of this variation was not significantly different from that of TLDs. There was a good concordance between OSLD- and TLD-measured absorbed doses. CONCLUSIONS: The OSLD nanoDots dosimeter system performs as well as currently used TLD systems and effective dose estimates using this new system did not differ significantly from current TLD-based dose estimates.

Cone-beam computed tomography to detect erosions of the temporomandibular joint: Effect of field of view and voxel size on diagnostic efficacy and effective dose.

INTRODUCTION: In this study, we examined the influence of field of view (FOV) and voxel size on the diagnostic efficacy of cone-beam computed tomography (CBCT) scans to detect erosions in the temporomandibular joint (TMJ). METHODS: The sample consisted of 16 TMJs containing natural or artificially created erosions and 16 normal TMJs. CBCT scans were obtained with 3 imaging protocols differing in the FOV and the size of the reconstructed voxels. Two oral and maxillofacial radiologists scored the scans for the presence or absence of erosions. Diagnostic efficacies of the 3 imaging protocols were compared by using receiver operating curve analysis. For each TMJ imaging protocol, we used thermoluminescent dosimetry chips to measure the absorbed dose at specific organ and tissue sites. Effective doses for each examination were calculated. RESULTS: Areas under the receiver operating characteristic curves were 0.77 ± 0.05 for the 6-in FOV, 0.70 ± 0.08 for the 9-in FOV, and 0.66 ± 0.05 for the 12-in FOV. The diagnostic efficacy of the 6-in FOV, determined by the area under the curve, was significantly higher than that of the 12-in FOV (P ≤0.05). Effective doses for bilateral TMJ evaluation were 558 µSv for the 6-in FOV, 548 µSv for the 9-in FOV, and 916 µSv for the 12-in FOV. CONCLUSIONS: The diagnostic efficacy of CBCT scans for the evaluation of erosive changes in the TMJ is highest for the 6-in FOV and lowest for the 12-in FOV.

Multilevel analysis of group-randomized trials with binary outcomes.

OBJECTIVES: Many dental studies have assessed the effectiveness of community- or group-based interventions such as community water fluoridation. These cluster trials, of which group-randomized trials (GRTs) are one type, have design and analysis considerations not found in studies with randomization of treatments to individuals (randomized controlled trials, RCTs). The purpose of this paper is to review analytic methods used for the analysis of binary outcomes from cluster trials and to illustrate these concepts and analytical methods using a school-based GRT. METHODS: We examine characteristics of GRTs including intra-class correlation (ICC), their most distinctive feature, and review analytical methods for GRTs including group-level analysis, adjusted chi-square test and multivariable analysis (mixed effect models and generalized estimating equations) for correlated binary data. We consider two- and three-level modeling of data from a cross-sectional cluster design. We apply the concepts reviewed using a GRT designed to determine the effect of incentives on response rates in a school-based dental study. We compare the results of analyses using methods for correlated binary data with those from traditional methods that do not account for ICC. RESULTS: Application of traditional analytic methods to the dental GRT used as an example for this paper led to a substantial overstatement of the effectiveness of the intervention. CONCLUSIONS: Ignoring the ICC among members of the same group in the analysis of public health intervention studies can lead to erroneous conclusions where groups are the unit of assignment. Special consideration is needed in the analysis of data from these cluster trials. Randomization of treatments to groups also should receive more consideration in the design of cluster trials in dental public health.