Determination of Caries Lesion Activity: Reflection and Roughness for Characterization of Caries Progression

Used by permission. © Operative Dentistry, Inc. Transmission or reproduction of protected items beyond that allowed by fair use requires the written permission of Operative Dentistry, Inc.Caries lesion progression is difficult to determine with visual and tactile examinations. The hypothesis of this study was that reflection and roughness measurements could determine caries progression. Ground/polished sound human enamel specimens were analyzed at baseline (sound) and after two four-day demineralization periods for reflection using optical reflectometry (ORef) and for roughness using optical surface profilometry (SPro). Specimens were demineralized using a microbial–Streptococcus mutans aries model. Comparisons among the periods for ORef and SPro were performed using repeated measures analysis of variance. Two-sample t-tests were used for differences in transverse microradiography. The integrated mineral loss and depth of the four-day demineralization period were significantly smaller than those for the eight-day demineralization period (p<0.01). With increased demineralization time, reflection was significantly decreased and roughness was significantly increased (p<0.01). Correlation between ORef and SPro was moderate (r=−0.63). Both reflection and roughness can be characterized for nondestructive longitudinal assessment of caries lesion progression

A study of the evaporation of organic liquids and mixtures of organic liquids

The purpose of this thesis is to make a study of the evaporation of organic solvents. The relative rates of evaporation of the single substances and binary and ternary mixtures are to be considered. A study of the changes in composition of binary and ternary mixtures that occur on evaporation are to be made. Information on the evaporation of organic liquids is important in relation to lacquers, and for that reason the solvents used in this work are liquids commonly used in making lacquers --Introduction, page 2

Preliminary Performance of the Advanced Dental Admission Test (ADAT): Association Between ADAT Scores and Other Variables for Applicants to Residency Programs at a U.S. Dental School

Historically, dental residency programs have used numerical assessment criteria to evaluate and identify qualified candidates for admission. Recent elimination of such assessment tools has undermined many programs’ holistic evaluation process. The Advanced Dental Admission Test (ADAT) was developed and recently piloted in hopes of addressing this issue. The aim of this study was to evaluate the preliminary performance and validity of the ADAT by exploring the association between ADAT scores and other variables for a sample of applicants to residency programs. The WebAdMIT admissions database was used to identify the test scores and educational and demographic information of 92 individuals who completed the pilot ADAT and were seeking a 2017 postgraduate specialty position at Indiana University School of Dentistry. The results showed that the ADAT had strong to weak correlations with certain applicant variables (p<0.05). No significant differences were found for age, race, school location, or country of origin. However, males performed better than females (p<0.05), and non-Hispanics performed better than Hispanics (p<0.01). ADAT component scores were also higher for individuals with a history of research activity (p<0.05). This study found that significant associations existed between the ADAT and indices typically associated with competitive applicants. These findings suggest that the ADAT may serve as a useful numerical assessment instrument, with the potential to identify high-performing candidates. Furthermore, the ADAT seemed to be a plausible option for programs seeking to incorporate a quantitative assessment instrument as part of a holistic candidate selection process

A CLINICAL AND HISTOMORPHOMETRIC STUDY OF CALCIUM SULFATE (DENTOGEN®), COMPARED TO FREEZE DRIED BONE ALLOGRAFT (FDBA) FOR ALVEOLAR RIDGE PRESERVATION

poster abstractThere is significant ridge resorption following tooth extraction. Freeze dried bone allograft (FDBA) is most widely used for ridge preservation and calcium sulfate has begun to show popularity. The objective of this study is to evaluate if DentoGen® (calcium sulfate) is as effective in preserving post extraction ridge dimensions compared to FDBA. Thirty consecutive single rooted extraction sites were selected that met the inclusion criteria for the study. Post extraction clinical measurements were made with a pre-fabricated stent and dental calipers. The sites were then divided randomly into the test group (calcium sulfate) or the control group (FDBA). Patients were recalled after 3 months, sites were reentered and clinical measurements were again made. A trephine bone core was harvested and sent for histomorphometric analysis. A total of 21 subjects with 41 potential sites were recruited to this study (IRB approval # 1003-56). Following extraction, 29 sites met the inclusion criteria. To date, no significant change in vertical ridge height pre to post surgery was noted within the test and control groups (0.53 + 1.63mm, 0.35 ± 1.13mm, respectively). There was a significant decrease in buccal-lingual ridge width within both groups, (-1.23 + 1.14mm test group. 0.93 + 0.94mm control group) There was no significant difference in the preservation performance between the two treatment groups for both ridge width and vertical height. Histological samples are currently being analyzed. Results suggest no statically significant differences between the use of calcium sulfate versus FDBA in preserving post extraction ridge dimensions

The roles of wedging and friction in the mechanics of dental occlusal contacts

Objective: The primary aim of this project is to elucidate the basic mechanical engineering principles that govern and explain unexpected and counter-intuitive occlusal contact force measurements. Methods: Forces were measured on matched pairs of first molar denture, ceramic and stainless steel crowns during occlusion and disclusion, with human saliva and dry (control). The weighted maxillary assembly, guided by a precision slide, was lowered onto, and raised from, the mandibular crown. The forces experienced by the mandibular tooth were continuously measured by the load cell that supported it. Statistical analyses included LOESS smoothing splines and generalized additive models. Principles of basic statics and classic friction were applied to explain and validate the results. Results: It was determined that within the span of a single chomp, the in-occlusal plane force component (Flateral) on the tooth is highly variable in direction and/or magnitude. The most salient observations were that Flateral was higher in disclusion than in occlusion, and the largest Flateral did not necessarily occur when the bite force was maximum. Furthermore, saliva significantly affected the results. Conclusions: The results demonstrated that contacting teeth experience complex transient mechanical environments that can be readily explained with elementary engineering principles involving wedging and friction at the occlusal contacts

Comparative Effectiveness of Structural versus Regulatory Protein Gene Transfer on Articular Chondrocyte Matrix Gene Expression

OBJECTIVE: The production of extracellular matrix is a necessary component of articular cartilage repair. Gene transfer is a promising method to improve matrix biosynthesis by articular chondrocytes. Gene transfer may employ transgenes encoding regulatory factors that stimulate the production of matrix proteins, or may employ transgenes that encode the proteins themselves. The objective of this study was to determine which of these 2 approaches would be the better choice for further development. We compared these 2 approaches using the transgenes encoding the structural matrix proteins, aggrecan or type II collagen, and the transgene encoding the anabolic factor, insulin-like growth factor I (IGF-I). METHODS: We transfected adult bovine articular chondrocytes with constructs encoding type II collagen, aggrecan, or IGF-I, and measured the expression of type II collagen ( COL2A1) and aggrecan ( ACAN) from their native genes and from their transgenes. RESULTS: IGF-I gene ( IGF1) transfer increased the expression of the native chondrocyte COL2A1 and ACAN genes 2.4 and 2.9 times control, respectively. COL2A1 gene transfer did not significantly increase COL2A1 transcripts, even when the transgene included the genomic COL2A1 regulatory sequences stimulated by chondrogenic growth factors. In contrast, ACAN gene transfer increased ACAN transcripts up to 3.4 times control levels. IGF1, but not ACAN, gene transfer increased aggrecan protein production. CONCLUSION: Taken together, these results suggest that the type II collagen and aggrecan production required for articular cartilage repair will be more effectively achieved by genes that encode anabolic regulatory factors than by genes that encode the matrix molecules themselves