The purpose of this study was to evaluate the abrasion resistance of surface penetrating sealant which was applied on a composite resin restoration and to provide proper time to reapply sealant on composite resin surface. Two hundred rectangular specimens, sized 8 x 3 x 2 mm, were made of Micronew (Bisco, Inc., Schaumburg, IL, U.S.A) and divided into two groups; F group (n = 10) was finished with coarse and medium grit of Sof-Lex discs and BisCoverwas applied B group (n = 190) after finishing with discs. B group was again subdivided into nineteen subgroups. From B-1 group to B-18 group were subjected to toothbrush abrasion test using a distilled water-dentifrice slurry and toothbrush heads. B-IM group was not subjected to toothbrush abrasion test. Average surface roughness (Ra) of each group was calculated using a surface roughness tester (Surfcorder MSE-1700: Kosaka Laboratory Ltd., Tokyo, Japan). A representative specimen of each group was examined by FE-SEM (S-4700: Hitachi High Technologies Co., Tokyo, Japan). The data were analysed using cluster analysis, paired t-test, and repeated measure ANOVA. The results of this study were as follows; 1. Ra of F group was 0.898 +/- 0.145 microm and B-IM group was 0.289 +/- 0.142 microm. Ra became higher from B-1 group (0.299 +/- 0.48 microm) to B-18 group (0.642 +/- 0.313 microm). 2. Final cluster center of Ra was 0.361 microm in cluster 1 (B-IM ~ B-7), 0.511 microm in cluster 2 (B-8 ~ B-14) and 0.624 microm in cluster 3 (B-15 ~ B-18). There were significant difference among Ra of three clusters. 3. Ra of B-IM group was decreased 210.72% than Ra of F group. Ra of B-8 group and B-15 group was increased 35.49% and 51.35% respectively than Ra of B-IM group. 4. On FE-SEM, B-IM group showed the smoothest resin surface. B-8 group and B-15 group showed vertically shallow scratches, and wide and irregular vertical scratches on composite resin surface respectively. Within a limitation of this study, finished resin surface will be again smooth and glazy if BisCover would be reapplied within 8 to 14 months after applying to resin surface.
Head

The purpose of this study was to evaluate the abrasion resistance of surface penetrating sealant which was applied on a composite resin restoration and to provide proper time to reapply sealant on composite resin surface. Two hundred rectangular specimens, sized 8 x 3 x 2 mm, were made of Micronew (Bisco, Inc., Schaumburg, IL, U.S.A) and divided into two groups; F group (n = 10) was finished with coarse and medium grit of Sof-Lex discs and BisCoverwas applied B group (n = 190) after finishing with discs. B group was again subdivided into nineteen subgroups. From B-1 group to B-18 group were subjected to toothbrush abrasion test using a distilled water-dentifrice slurry and toothbrush heads. B-IM group was not subjected to toothbrush abrasion test. Average surface roughness (Ra) of each group was calculated using a surface roughness tester (Surfcorder MSE-1700: Kosaka Laboratory Ltd., Tokyo, Japan). A representative specimen of each group was examined by FE-SEM (S-4700: Hitachi High Technologies Co., Tokyo, Japan). The data were analysed using cluster analysis, paired t-test, and repeated measure ANOVA. The results of this study were as follows; 1. Ra of F group was 0.898 +/- 0.145 microm and B-IM group was 0.289 +/- 0.142 microm. Ra became higher from B-1 group (0.299 +/- 0.48 microm) to B-18 group (0.642 +/- 0.313 microm). 2. Final cluster center of Ra was 0.361 microm in cluster 1 (B-IM ~ B-7), 0.511 microm in cluster 2 (B-8 ~ B-14) and 0.624 microm in cluster 3 (B-15 ~ B-18). There were significant difference among Ra of three clusters. 3. Ra of B-IM group was decreased 210.72% than Ra of F group. Ra of B-8 group and B-15 group was increased 35.49% and 51.35% respectively than Ra of B-IM group. 4. On FE-SEM, B-IM group showed the smoothest resin surface. B-8 group and B-15 group showed vertically shallow scratches, and wide and irregular vertical scratches on composite resin surface respectively. Within a limitation of this study, finished resin surface will be again smooth and glazy if BisCover would be reapplied within 8 to 14 months after applying to resin surface.
Head

Correct alignment of pedicle screws is imperative in multilevel instrumentation. However, there has been no report addressing the technical aspects of this subject. If the head diameter of a pedicle screw is D, the head height is H, and the convergence angle of the screw being inserted is alpha, then the distance between the extension line of the medial borders of the inserted screw heads and the insertion point of the adjacent screw (A) is described by the following formula: A = 1/2Dcos alpha- Hsin alpha If an L3 pedicle screw (D=13 mm, H=15 mm) is to be inserted with a convergence angle of 14 degrees after the insertion of L4 and L5 screws, its insertion point should be 3.6 mm medial to the extension line of the centers of the L4 and L5 screws and 2.7 mm lateral to the extension line of their medial borders for all screw heads, so it can be aligned in the coronal plane. In order to achieve the best alignment, a pedicle screw is inserted between the extended line of the centers and that of the medial borders of the inserted adjacent screw heads. For the routine range of convergence angles, it is essential to move the entry point medially toward the extended line connecting the medial borders of the inserted adjacent screw heads.
Head

No abstract available.
Head*

No abstract available.
Head

No abstract available.
Head*

No abstract available.
Head and Neck Neoplasms* ; Head*

No abstract available.
Head and Neck Neoplasms* ; Head*

No abstract available.
Head Impulse Test* ; Head*

The purpose of this paper is to develop an efficient method for the quick determination of multiple isocenters plans to provide optimal dose distribution in stereotactic radiosurgery. A Spherical dose model was developed through the use of fit to the exact dose data calculated in a 18cm diameter of spherical head phantom. It computes dose quickly for each spherical part and is useful to estimate dose distribution for multiple isocenter. An automatic computer search algorithm was developed using the relationship between the isocenter move and the change of dose shape, and adapted with a spherical dose model to determine isocenter separation and collimator sizes quickly and automatically. A spherical dose model shows a comparable isodose distribution with exact dose data and permits rapid calculation of 3-D isodoses. The computer search can provide reasonable isocenter settings more quickly than trial and error types of plans, while producing steep dose gradient around target boundary. A spherical dose model can be used for the quick determination of the multiple isocenter plans with a computer automatic search. Our guideline is useful to determine the initial multiple isocenter plans.
Head ; Radiosurgery*