The effect of additional enamel etching on microleakage of the adhesion of self-etching primer system / 대한치과보존학회지

The purpose of this study is to evaluate the effect of additional enamel etching with phosphoric acid on the microleakage of the adhesion of self-etching primer system. Class V cavity(4 mmx3 mmx1.5 mm) preparations with all margins in enamel were prepared on buccal surface of 42 extracted human upper central incisor teeth. Prepared teeth were randomly divided into 3 groups. Group 1 : no additional pretreatment with 37% phosphoric acid (NE). Group 2 : additional pretreatment with 37% phosphoric acid for 10 seconds (E10s). Group 3 : additional pretreatment with 37% phosphoric acid for 20 seconds (E20s). The adhesives(Clearfil SE Bond(R), Kuraray, Osaka, Japan) and composite resins(Clearfil AP-X(R), Osaka, Kuraray, Japan) were applied following the manufacturer's instructions. All the specimens were finished with the polishing disc(3M dental product, St Paul, MN, USA), thermocycled for 500 cycles between 5degrees C and 55degrees C and resected apical 3-mm root. 0.028 stainless steel wire was inserted apically into the pulp chamber of each tooth and sealed into position with sticky wax. Surrounding tooth surface was covered with a nail varnish 2 times except areas 1 mm far from all the margins. After drying for one day, soaked the samples in the distilled water. Microleakage was assessed by electrochemical method(System 6514, Electrometer(R), Keithley, USA) in the distilled water. In this study, the microleakage was the lowest in group 1(NE) and the highest in group 3(E20s)(NE

A study of the shear bond strength of metal brackets and ceramic brackets and the condition after debonding / 대한치과교정학회지

Metal brackets and ceramic brackets were bonded to natural teeth, porcelain crowns and gold crowns. After stored in artificial saliva solution for 72 hours at 37degreesC, the shear bond strengths were measured by Instron and compared with them, the bonding sites and bracket bases were examined by scanning electron microscope and light optical stereomicroscope. The results were as follows: 1. The shear bond strengths of the group which metal brackets were bonded to natural teeth and the groups which ceramic brackets were bonded to natural teeth and porcelain crowns were comparable to each other, the shear bond strength of the group which metal brackets were bonded to gold crowns was significantly low. 2. The bond failed predominantly at the bracket base/adhesive interface with the bulk of adhesive remaining on enamel in the group which metal brackets were bonded to natural teeth. 3. The bond failed consistently at the crown/adhesive interface with all of adhesive remaining on the bracket bases in the group which metal brackets were bonded to gold crowns. 4. The bond failed at the enamel or crown/adhesive interface with the bulk of adhesive remaining on the bracket bases in the groups which cramic brackets were bonded to natural teeth and porcelain crowns. 5. The shear bond strengths of the groups which ceramic brackets were bonded to porcelain crowns were not affected by etching time.

A study of the crown angulation in normal occlusion / 대한치과교정학회지

The purpose of this study was to collect the information of the straight-wire appliance and to determine the amount of second-order bends in clinical orthodontics. The author analysed the study model of 50 individuals with normal occlusion and results were obtained as follows 1. The crown angulation was 4 degree in upper central incisor, 7 degree in upper lateral incisor, and 0 degree in lower central incisor and lateral incisor. 2. The crown angulation was 8 degree in upper cuspid and 2 degree in lower cuspid. 3. The crown angulations were 4 degree in upper first bicuspid, upper second bicuspid and lower second bicuspid and 1 degree m lower first bicuspid. 4. The crown angulation was 3 degree in upper first molar, 0 degree in upper second molar, 5 degree in lower first molar and 8 degree in lower second molar. 5. The crown angulations in lower arch were progressively increased from first premolar to second molar. 6. In upper arch, as the crown angulation of one tooth was increased, those of adjacent teeth were increased, too. 7. In the case of lower arch, the crown angulation of cuspid was increased as that of lateral incisor was increased, the crown angulation of second premolar was increased as that of first premolar was increased, and similarity the crown angulation of second molar was increased as that of first molar was increased.