An in vitro study of a few crystal growth solutions on the bracket shear bond strength / 대한치과교정학회지

The purpose of this study was to compare bracket shear bond strengths of th crystal growth solutions wi those of the 37% phosphoric acid etch technique. The 4 crystal growth solutions were made experimentally in th lab, that is (1)30% polyacrylic acid solution containing 0.3 M sulfuric acid (ES 1), (2)30% polyacrylic acid solution containing 0.6 M solution acid (ES 2), (3)30% polyacrylic acid solution containing 0.3 M solution acid and 0.6M lithium sulfate(ES 3), (4)30% polyacrylic acid solution containing 0.3 M solution acid and 5% phosphoric acid (ES 4). The 37% phosphoric acid solution used as a control. Bovine lower incisor tooth enamel was treated by the above solutions for 60 sec, washed out for 20 sec with slow water stream, and bonded lower anterior edgewise bracket with the light curing orthodontic composit resin adhesives. The teeth bonded brackets were stored in the distilled water at room temperature for 24h, and followed to test the bracket shear bond strength. The acid etch technique showed 177.6kg/cm(2) of mean shear bond strength which was the highest among the enamel treatment solutions. ES 1 shown 58.4 kg/cm(2) of mead shear bond strength and the of ES 4 showed 66.5 kg/cm(2). There was no significant difference between the two(p>0.05). Es 2 showed 110.6kg/cm(2) of mean shear bond strength which was 62.3% of that of acid etch technique. ES 3 showed 131.3kg/cm(2) of mead shear bond strength which was the highest among experimental crystal growth solution and which was 74% of that of acid etch technique. The shear bond strengths of the crystal growth solutions and were significantly lower that that of acid etch technique(p<0.05). The results suggest that bracket shear bond strength of 30% polyacrylic acid solution containing 0.3M sulfuric acid and 0.6M lithium sulfate were showed the highest, it is low for the clinical application of this solution.

The cephalometric study of facial types in Class II division 1 malocclusion / 대한치과교정학회지

This study was focused on the distribution of different facial types of the Class II division 1 malocclusion groups and skeletal characteristics of the each group and those that anteropsterior relationship of the maxilla and mandible calculated from the analysis of ANB angle and Wits appraisal was quite different from each other, as well. Cephalometric headplates of 140 persons of Class II division 1 malocclusion whose mean age was 11.2 years and 69 persons of normal occlusion whose mean age was 12.2 years were utilized as materials. Measurements were recorded, tabulated and statistically analyzed employing the tracings of the lateral cephalograms, then Class II division 1 malocclusion group was divided into 9 Types according to the angle of SNA and SNB for the anteroposterior relationship of the maxilla and mandible, another 9 Types according to the FH-NPog and SN-MP for the horizontal and vertical relationship, and the other 9 Types according to the ANB and Wits appraisal for intermaxillary relationship as well, with which was based on Mean+/- 1SD of those of normal occlusion. The result allowed the following conclusion: 1. 37.1 % of population demonstrated maxilla within normal range and retrognathic mandible to the cranial base, 30% for both maxilla and mandible within normal range, 20% for retrognathic maxilla and mandible and 12.9 % of the rest were arranged in Class II division 1 malocclusion groups. 2. Retrognathic mandible and hyperdivergent face accounted for 30.7 %, mesognathic mandible and neutrodivergent face for 29.3 %, mesognathic mandible and hyperdivergent face for 16.4 %, retrognathic mandible and neutrodivergent face for 13.6 %, mesognathic mandible and hypodivergent face for 10% of population were computed in Class II division 1 malocclusion groups. 3. It was suggested that skeletal Class II malocclusion might be due to anomaly in size and shape of cranial base, underdevelopment of mandible, retropositioning of mandible, underdevelopment of posterior face against anterior face, or any combination of these factors. 4. Population with underdevelopment and/or retropositioning of the mandible showed hyperdivergent tendency of facial profile. 5. The ANB angle and Wits appraisal did not coincide the severity of anteroposterior dysplasia in 35.7% of Class II division 1 malocclusion group each other, and this inconsistency was suggested to be related with mandibular rotation, inclination of cranial base, and anteroposterior position of the maxilla.