Influence of beverage type and ingestion time on tooth corrosion / 대한치과재료학회지

This study was conducted to analyze the effects of beverages on tooth corrosion by selecting drinks that are enjoyed by modern people. Drinks were selected for carbonated beverages (Coca Cola), energy drinks (Red Bull), orange juice, beer (Hite) and water (Evian). Bovine tooth was immersed for 1 hour, 24 hours and 48 hours. The root mean square (RMS) values were obtained by scanning the bovine tooth at pre-immersion and immersion time after impression making. Two-way ANOVA, one-way ANOVA, and Tukey-test were used to compare differences between groups (α=0.05). The RMS value tended to increase with longer immersion times in all beverages, and there was a significant difference (p < 0.05) between before immersion-1hr and before immersion-48 hr. The mean of RMS according to the type of beverage was significantly different and there was a significant difference according to the change of immersion time (p < 0.05). In order to prevent tooth corrosion, it is necessary to change the method of ingestion or to reduce the time of ingestion.

A STUDY ON THE FACTORS AFFECTING TO TOOTH WEAR / 대한치과보철학회지

This study was performed to investigate the factors related to tooth wear. For this study, 78 patients with temporomandibular disorders and 76 dental students without any signs and symptoms of temporomandibular disorders were selected as the patients group and as the normal group, respectively. Preferred chewing side, Angle's classification, lateral guidance pattern, head and shoulder posture wee observed clinically. Electromyographic activity of anterior temporalis and masseter muscle were recorded with BioEMG and occlusal status were recorded with T-Scan . Wear facet area of each tooth was measured from working model of upper arch corresponding to the occlusal status from T-Scan, Wear facet area were measured with planimeter in mm2. Total area were divided into incisal, canine, posterior tooth area. Anterior wearfacet area was incisor area plus canine area, and unilateral area was anterior area plus posterior area. The data collected were analyzed by SAS statistical program and the results of this study were as follows: 1. There was no significant difference between the two groups in total werafacet area, and male subjects showed tendency to have larger area in the normal group but female subjects showed tendency vice versa. 2. There was no significant difference related to preferred chewing side and Angle's classification, however, some difference was observed by lateral guidance pattern. Anterior wear facet area in subjects of canine guidance was the largest in the three subgroups. 3. Subjects with head tilting to right side had larger posterior and total area, and subjects with higher shoulder in right side had larger canine and anterior area than any other subgrous. 4. Electromyographic activity of masseter muscle was more correlated with wear facet area than anterior temporalis muscle, and tooth contact number and force were significantly correlated with wear facet area, but the most important factor affecting tooth attrition was age.

A STUDY ON THE PRESSING ACCURACY OF THE REUSED IPS-EMPRESS INGOT / 대한치과보철학회지

IPS-empress system is one of widely used all ceramic system. The purpose of this study was to determine the pressing accuracy of refused IPS%Empress ingot. 10 specimens were made using new ingot first, and using the rests of the specimen the another group of specimens were made next. Finally, the third group of specimens were made with same procedure mentioned above. The results obtained in this study were as follows ; 1. The pressing accuracy of the first group of specimen was 96.1%, that of the second group was 95.4%, and that of the third group was 95.4%. There was no statistical signifcance among them, that is, the reuse of the IPS-Empress ingot did not influence on the pressing accuracy. 2. the common site of the defect in pressed ingot was central area at the margin opposite of sprue hole.