Shear bond strength of orthodontic bonding resins to porcelain; an in vitro study / 대한치과교정학회지

Bonding orthodontic adhesive resins to glazed porcelain surface is not attainable. The aim of this investigation was to examine, in vitro, the effect of three methods of porcelain surface pretreatment on the shear bond strength of orthodontic adhesives, and to compare the shear strength of orthodontic bracket bonding to porcelain surface by the best results that to human enamel. Porcelain disks (Ceramco((TM)) and Vita((TM))) baked in the laboratory were roughened by sandpapers, #320, #600, #800, #1000 and #1200, and were pretreated with silane and dried at the various temperatures, room temperature, 50degreesC, 70degreesC and 90degreesC, and were etched by 3% hydrofluoric acid solution for 1, 3, 5, 7, and 9 minutes, orthodontic adhesives (System 1 +((TM)) and Unite((TM))) were applied on them, and shear bond strengths were measured by Instron. The best results of pretreatment of each method were determined by the shear bond strengths. Again, porcelain disks were pretreated by the determined best results and human enamel were etched by 37% hydrofluoric acid solution, orthodontic brackets were bonded on them by the orthodontic adhesives, and the shear bond strengths were measured and compared between them. 1. Roughening porcelain surfaces with coarse sandpaper (#300) showed higher shear bond strength than that with finer sandpapers, but it (22.44 Kgf/cm2) was distinguishably low compared to that from etched human enamel (144.11 Kgf/cm2). 2. There were disparities in shear bond strengths upon the orthodontic resins, which was presumably related to the contents of fillers in orthodontic adhesive resins. Also there were disparities in shear bond strength upon the porcelains which had different composition. 3. Silane enhanced the shear bond strength of orthodontic resins to porcelain surfaces (25.20 Kgf/cm2 at 50degreesC), which was markedly low compared to that from etched human enamel. 4. Etched porcelain surface with 3% hydrofluoric acid solution for 1 to 9 minutes showed no difference in shear bonding strength of orthodontic adhesive resins. Shear bond strength from etched porcelain (97.43-120.72 Kgf/cm2) were as high as clinically available, but low compared to that from etched human enamel. 5. Roughening with #300 sandpaper and etching by 3% hydrofluoric acid followed silane application on porcelain surface showed lower shear bond strength than etched human enamel, but were as high as clinically useful. 6. The results suggest that etching porcelain surface by 3% hydrofluoric acid solution might provide comparatively high shear bond strength as much as clinically favorable.

Occlusal variations in the posterior and anterior segments of the teeth / 대한치과교정학회지

The purpose of this study was(1) to determine the prevalence of some causes by which dental occlusion might be affected, (2) to determine the prevalence of malocclusion, and types of molar, vertical incisor and horisontal incisor frlationships, and (3) to examine the sex difference in the prevalence ratios, and (4) to determint the between-examiner differences in asseassing types of dental occlusion. The material consisted of 1281 males and 811 females, total 2091 persons, aged 17 to 21 years. Tow examiners who were graduate students in the orthodontic course, examined independently dental occlusion of the material. Before calculating the statistics, the subjects consisted of 156 males and 164 females, total 320 persons, having any one or more causes suspected to affect dental occlusion, was eliminated. Than the remained subjects, 1124 males and 647 females, total 1771 persons, were assessed. The results were as follows 1. The prevalence of some causes by which dental occlusion might be affected was 15.32 per cent. The missing rate of any one or more first molars was 8.85 percent, that of any one or more teeth positioned anterior to the first molar was 3.83 per cent. The prevalence of crossbite of the first molat 0.48 per cent, that of retained primary teeth was 0.77 percent, and that of orthodontic treatment was 0.43 per cent. 2. The rate of between-examiner difference was 12.35 per cent in assessing the types of molar relationship, 18.86 percent in assessing the types of horziontal incisor relationship, and 26.37 percent in assessing the types of horizontal incisor relationship. 3. There was no sex difference in the prevalence ratios of the types of molar relationship . The pervalence of Class I molar relationship was 80.91 percert, that of Class II was 5.03, that of Class II subdivision was 4.01, percent, that of Class III was 5.99 percent and that of Class III subdivision was 4.07 percent. 4. In the prevalence of the types of horizontal incisor felationship, there were no sex differences except that of Class II division 2. The prevalence of Class I horizontal incisor relationship was 73.12 percent, that of Class II division 1 was 12.03 percent, that of Class II division 2 was 6.58 percent in male and 4.33 percent in female, and that of Class III was 9.09 percent. 5. In the pervalence of the types of vertical incisor relationship, there were no sex difference except that of deep bite. the prevalence of open bite was 2.20 per cent, that of edge-to-edge bite was 9.15 percent, that of normal bite was 76.34 percent, and that of deep bite was 14.15 percent in male and 9.12 percent in female. 6. There was no sex difference in the prevalence of malocclusion the prevalence of maloccusion was 82.67 percent and that of normal occlusion was 17.33 percent. 7. There was a tendedcy that when Class I molar relationship vhanged to Class II, incisor-ships were to be larger overjet or upright upper incisors and deep bite, but when that changed to Class III molar relationship, these were to be cross bite and openbite.