Elizabeth Kao

Comparison of bracket debonding force between two conventional resin adhesives and a resin-reinforced glass ionomer cement: An in vitro and in vivo study

The purpose of this study was to compare the debonding force of orthodontic brackets bonded with two conventional resin adhesives (Resilience L3 and Light Bond) and a resin-reinforced glass ionomer cement (Fuji Ortho LC). For the in vitro part of the study, 80 extracted premolars were randomly divided into four groups. In groups A and B, brackets were bonded to unetched enamel using Fuji Ortho LC cement in wet and dry conditions, respectively. In groups C and D, brackets were bonded to etched enamel using Resilience L3 and Light Bond, respectively. Debonding force was determined using a servohydraulic testing machine at a crosshead speed of 1 mm/min. Data was analyzed using the ANOVA and Tukey-Kramer multiple comparison test at p<0.05. A significant difference was found in debonding force between unetched Fuji Ortho LC and the two conventional resins. There was no significant difference between the two conventional resins or between unetched resin-reinforced glass ionomer in the wet and dry conditions. For the in vivo part of the study, 30 patients were randomly assigned to one of the three bonding material groups. Bracket survival rates and distributions were obtained by following these patients for 1.2 years. Data was analyzed using the Kaplan-Meier product-limit estimates of survivorship function. Bond failure interface was determined using a modified adhesive remnant index (ARI). These results showed no significant difference between survival rates and distributions among the three bonding materials with respect to the type of malocclusion, type of orthodontic treatment, or location of bracket. There were significant differences between survival distributions of males and females in the unetched Fuji Ortho LC group and among type of teeth in the conventional resin groups. The predominant mode of bracket failure for the unetched Fuji Ortho LC cement was at the enamel-adhesive interface, and for conventional resins, the enamel-adhesive interface and the bracket-adhesive interface. These results suggest that resin-reinforced glass ionomer cement can withstand occlusal and orthodontic forces despite having a bond strength lower than that of conventional resin adhesives.

Preparation of glass ionomer cement using N-acryloyl-substituted amino acid monomers — Evaluation of physical properties

OBJECTIVES The objectives of this study were (1) to develop polyacid formulations through the incorporation of amino acid-derived monomers with carboxylic acid groups at various distances away from the polymer backbone to allow for greater flexibility, less rigid ionic cluster formation and improved solubility, and (2) to test selected physical and handling properties of experimental ionomers with a conventional glass ionomer as a control. METHODS The polycarboxylic acids prepared and used in glass ionomer formulation in this study included N-acryloylglutamic acid (AGA) and N-acryloyl-6-aminocaproic acid (AACA)- modified acrylic acid- ++itaconic acid copolymers, where the acrylic acid:itaconic acid:amino acid monomers were combined in different proportions. The characterization and purity of the monomers were determined by FTIR and their melting points. The characterization of synthesized polymers included molecular weight and relative viscosity determinations. The compressive strengths, diametral tensile strengths, flexural strengths and fracture toughness of the experimental ionomers and a commercially available ionomer (control) were measured after storage in water, at 37 degrees C for 1 h or 7 d. The working times and setting times of the experimental ionomers were compared to the control specimens. Separate analysis of variance and Tukeys tests were used to study the statistical significance of the physical strength parameters as a function of materials and storage times. RESULTS Significant increases (p< 0.001) in diametral tensile, compressive, flexural strengths and fracture toughness were observed in the AGA co-polymers, while significant increases were observed in diametral and flexural strengths in the AACA co-polymers compared to the control Fuji II. The working and setting times of all except one experimental ionomer studied were comparable to the controls. SIGNIFICANCE The use of amino acid-modified acrylic monomers to produce water soluble copolymers of acrylic-itaconic acid offers a new route of discovery to produce chemical-cured glass ionomers with improved physical properties. The spacer chain length, the hydrophobicity of the chains, the molecular weight and viscosity of the polymer all played important roles in determining the physical properties of the material.

Tooth Whitening Effects on Bracket Bond Strength In Vivo

OBJECTIVE To test the hypothesis that there is no difference between the bracket survival rate of brackets bonded to bleached and unbleached teeth. MATERIALS AND METHODS Thirty-eight patients who required comprehensive orthodontic treatment were included in the study. A split mouth technique was used with one arch exposed to in-office whitening gel containing 38% hydrogen peroxide for 30 minutes, while the unbleached arch served as the control. Patients were divided into two groups: Brackets bonded within 24 hours after bleaching and brackets bonded 2-3 weeks after bleaching. The bracket survival rate was computed using the log-rank test (Kaplan-Meier Analysis). RESULTS A significantly higher rate of bracket failure was found with bleached teeth (16.6%) compared with unbleached teeth (1.8%) after 180 days. Brackets bonded within 24 hours of bleaching resulted in significantly higher clinical failure (14.5%) compared with those bonded after 3 weeks (2.1%). Adhesive Remnant Index scores of failed brackets revealed that the majority of failure in bleached teeth occurred in the enamel/resin interface. CONCLUSIONS The hypothesis was rejected. Brackets bonded within 24 hours after bleaching have a significantly higher risk for bond failure. Orthodontic bonding should be delayed for 2-3 weeks if patients have a history of in-office bleaching with 38% hydrogen peroxide.

Wire-bending test as a predictor of preclinical performance by dental students

Traditional Dental Aptitude Test and academic grade point average have been shown to be poor predictors of clinical performance by dental students. To refine predictors of psychomotor skills, a wire-bending test was given to 105 freshmen at the beginning of their dental education. Grades from seven restorative preclinical courses in their freshman and sophomore years were compared to scores on wire bending and the three traditional predictors: GPA, academic aptitude, and perceptual aptitude scores. Wire-bending scores correlated significantly with six out of seven preclinical restorative courses. The predictive power for preclinical performance was doubled when wire bending was added to traditional predictors in stepwise multiple regression analysis. Wire-bending scores identified students of low performance. These preliminary results suggest that the wire-bending test shows some potential as a screening test for identifying students who may have psychomotor difficulties, early in their dental education.

Depression and Rural Environment Are Associated With Poor Oral Health Among Pregnant Women in Northern Appalachia

Both oral health problems and depression among pregnant women contribute to maternal–infant health outcomes. Little is known, however, about the potential effects of clinically significant depression on the oral health status of pregnant women. The purpose of the present study was to determine the influence of clinically significant depression and rural- or urban-dwelling status on oral health outcomes among pregnant women. Pregnant women (N = 685) in rural (i.e., West Virginia) and urban (i.e., Pittsburgh, PA) areas of northern Appalachia were assessed by calibrated examiners regarding gingivitis, oral hygiene, and DMFT (decayed, missing, and filled teeth), completed the Center for Epidemiologic Studies–Depression Scale (CES-D) and provided demographics. Participants were categorized based on clinically significant depressive symptoms (CES-D ≥ 16) and rural/urban domicile. Women with depression and those living in rural areas had worse oral health on all three indices than their non-depressed and urban counterparts. Depression, particularly among women in rural areas, affects certain oral health indices and represents a modifiable target for intervention. Moreover, treatments designed specifically for rural populations may be of particular utility. Women who are pregnant or planning to become pregnant may benefit from regular depression screenings from their dental and medical health care providers.

Comparison of computer-generated, enhanced and conventional 2-dimensional radiographic imaging

INTRODUCTION Technological advances have attempted to improve the standard of traditional x-ray imaging. ImageIQ software (LumenIQ, Bellingham, Wash) enhances conventional radiography by producing a computer-generated, enhanced 2-dimensional (2D) image, adding depth and detail. The software converts the scales of gray to topographic height values, which are easier for the eye to see. The purpose of this study was to determine whether the enhanced 2D renderings are as sensitive as traditional 2D radiographs for detecting periodontal defects in cadaver mandibles. METHODS Periodontal defects were located and classified on 20 cadaver mandibles. These defects were radiographed, and computer-generated, enhanced 2D topographic renderings were made with ImageIQ software. A panel of evaluators was shown the 2D radiographs and the enhanced 2D renderings in random order. The evaluators classified the defects from these images. RESULTS Significantly better agreement by the evaluators with the intrasurgical classification was found with the enhanced 2D rendering to view periodontal defects vs the traditional 2D x-ray. Enhanced 2D renderings improved the accuracy of radiographic periodontal defect classification by 14.3% over traditional 2D radiographs. CONCLUSIONS Computer generated, enhanced 2D renderings of conventional radiographs might provide a reliable diagnostic alternative to conventional 2D radiographs when attempting to classify periodontal defects.