No abstract available.
Bicuspid*

The aim of this study was to measure the cusp deflection during composite restoration for MOD cavity in premolar and to examine the influence of cavity dimension, C-factor and restoration method on the cusp deflection. Thirty extracted maxillary premolar were prepared to four different sizes of MOD cavity and divided into six groups. The width and depth of the cavity were as follows. Group 1; 1.5 x 1 mm, Group 2; 1.5 x 2 mm, Group 3; 3 x 1 mm, and Group 4-6; 3 x 2 mm respectively. Group 1-4 were restored using bulk filling method with Z-250 composite. However, Group 5 was restored incrementally, and Group 6 was restored with an indirect resin inlay. The cusp deflection was recorded at the buccal and lingual cusp tips using LVDT probe for 10,000 seconds. The measured cusp deflections were compared between groups, and the relationship between the cube of the length of cavity wall/the cube of the thickness of cavity wall (L3 / T3), C-factor and cusp deflection or %flexure (100 x cuspal deflection / cavity width) was analyzed. The cusp deflection of Group 1-4 were 12.1 microm, 17.2 microm, 16.2 microm and 26.4 microm respectively. The C-factor was related to the %flexure rather than the cusp deflection. There was a strong positive correlationship between the L3 / T3 and the cusp deflection. The cusp deflection of Group 5 and 6 were 17.4 microm and 17.9 microm respectively, which are much lower value than that of Group 4.
Bicuspid ; Inlays

No abstract available.
Bicuspid* ; Molar*

STATEMENT OF PROBLEM: when using resin for class II restoration, micoleakage by instrumentation can be regarded as the primary negative characteristic. A review of the available literature suggests that using flowable resin as liner to decreased microleakage. PURPOSE: The aim of this study was to determine the influence of the nanofilled flowable resin lining on marginal microleakage after load cycling in class II composite restoration fillings using nanofiller resin. MATERIAL AND METHODS: 24 extracted premolars were prepared with class II cavity. F group was restored the nanofilled resin with the nanofilled flowable resin as liner. NF group was restored the nanofilled resin only. After restoration, an experiment was performed on 2 groups using a 300N load at 104, 105 and 106 cycles. Prior to and before each load cycling, it was gauged length on total marginal microleakage, axial marginal microleakage and buccal, gingival, lingual marginal microleakage. Data were analyzed with the Mann-Whitney test & Kruskal-Wallis test. RESULTS: There were statistically significant differences between 2 groups and between individual groups. (P < .05) The result showed less microleakage in teeth restored by the nanofilled resin, which was lined by the nanofilled flowable resin. CONCLUSION: There was significant reduction in microleakage when the nanofilled flowable resin lining was placed underneath the nanofilled resin in class II composite restoration fillings.
Bicuspid ; Tooth

No abstract available.
Bicuspid* ; Echocardiography*

The purpose of this study was to photoelastically visualize the distribution of forces transmitted to the alveolus and surrounding structures using three different types of headgear for the distal movement of the upper molars. A photoelastic maxillary model was made and three different directional forces applied, which were high-pull, straight- pull, and cervical-pull. Stress distribution was recorded through circular polariscope, and two-dimensional photoelastic stress analysis was performed according to isochromatic fringe characteristics. The results were as follows: 1. In the case of high-pull headgear, bodily movement occurred in the medium-length outer bow, stress distribution in the apical region was 1st molar, 2nd premolar, 1st premolar in sequence and there was no apparent difference. 2. In the case of straight-pull headgear, bodily movement occurred in the long outer bow and stress distribution in the apical region was heavy in the 1st molar, 2nd premolar, 1st premolar in sequence. But, there were no apparent differences according to the length of the outer bow. 3. In the case of cervical-pull headgear, bodily movement also occurred in the long outer bow, and apical stress of the premolar region was heaviest among other cases and apical stress of the 2nd premolar was heaviest in the short outer bow. In clinical situations, to achieve bodily movement of the upper 1st molars without modifying outer bow height, applying an outer bow length as long as the inner bow length in high-pull headgear and applying an outer bow length longer than the inner bow length in straight-pull, cervical-pull headgear are recommended.
Bicuspid ; Molar*

PURPOSE: This study aimed to evaluate the accuracy of digitizing dental impressions of abutment teeth using a white light scanner and to compare the findings among teeth types. MATERIALS AND METHODS: To assess precision, impressions of the canine, premolar, and molar prepared to receive all-ceramic crowns were repeatedly scanned to obtain five sets of 3-D data (STL files). Point clouds were compared and error sizes were measured (n=10 per type). Next, to evaluate trueness, impressions of teeth were rotated by 10degrees-20degrees and scanned. The obtained data were compared with the first set of data for precision assessment, and the error sizes were measured (n=5 per type). The Kruskal-Wallis test was performed to evaluate precision and trueness among three teeth types, and post-hoc comparisons were performed using the Mann-Whitney U test with Bonferroni correction (alpha=.05). RESULTS: Precision discrepancies for the canine, premolar, and molar were 3.7 microm, 3.2 microm, and 7.3 microm, respectively, indicating the poorest precision for the molar (P<.001). Trueness discrepancies for teeth types were 6.2 microm, 11.2 microm, and 21.8 microm, respectively, indicating the poorest trueness for the molar (P=.007). CONCLUSION: In respect to accuracy the molar showed the largest discrepancies compared with the canine and premolar. Digitizing of dental impressions of abutment teeth using a white light scanner was assessed to be a highly accurate method and provided discrepancy values in a clinically acceptable range. Further study is needed to improve digitizing performance of white light scanning in axial wall.
Bicuspid ; Crowns ; Molar ; Tooth*

The purpose of this study was to evaluate the accuracy and the consistency of four different electronic apex locators in an in vitro model. Fourty extracted premolars were used for the study. Four electronic apex locators (EAL) were Root ZX, SmarPex, Elements Diagnostic Unit (EDU), and E-Magic Finder Deluxe (EMF). After access preparation, the teeth were embedded in an alginate model and the length measurements were carried out at "0.5"and "Apex"mark using four EALs. The file was cemented at the location of the manufacturers'instruction (Root ZX, EDU, EMF: 0.5 mark, SmarPex: Apex mark). The apical 4mm of the apex was exposed and the distance from the file tip to the major foramen was measured by Image ProPlus (x 100). The distance from the file tip to the major foramen was calculated at 0.5 and Apex mark and the consistency of 0.5 and Apex mark was compared by SD and Quartile of Box plots. In this study, Root ZX and EMF located the apical constriction accurately within +/- 0.5 mm in 100%, whereas SmarPex and EDU located in 90% and in 70% respectively. For Root ZX and EMF, there was no significant difference between the consistency of 0.5 and Apex mark. However, for the EDU and SmarPex, Apex mark was more consistent than 0.5 mark. From the evaluation of the consistency in this study, for Root ZX and EMF, both 0.5 and Apex mark can be used as a standard mark. And for EDU and SmarPex, the Apex mark can be recommended to be used as a standard mark.
Bicuspid ; Constriction ; Tooth

The purpose of this study was to compare the retentive force of cast half round circumferential clasps, cast round circumferential clasps and wrought wire clasps on three different depths of undercut(10G,20G,30G), and to determine the proper amount of undercut for cast round circumferential clasp. Three different lower second premolar crowns were cast and each of clasp was made. Each of clasp affixed to the different types of clasp. Their retentive forces were measured with universal testing machine. The results were as follows: 1. When the depth of undercut was same, the greatest retentive force was exerted by cast half round circumferential clasp, followed by cast round - 33 - circumferential clasp and wrought wire clasp. 2. The degree of variation amount of retentive force according to depth of undercut was greatest for cast round circumferential clasp. 3. Not only elastic deformation but also permanent deformation of the retentive arm was observed after insertion and removal of the clasp. The results of this study show that the retentive force of cast round circumferential clasp falls between those of cast half round circumferential clasp and wrought wire clasp, and suggest that a 20G undercut is suitable for ensuring an appropriate degree of the retentive force.
Arm ; Bicuspid ; Crowns

STATEMENT OF PROBLEM: Loss of the marginal bone to the first thread have been accepted but continuous effort have been made to reduce this bone loss by varying implant design and surface texture. PURPOSE: This animal study has examined the histomorphometric variations between implants with micro-thread, micro-grooved and turned surfaced neck designs. MATERIAL AND METHODS: Four mongrel dogs have been used the premolars removed and left to heal for three months. One of each implant systems with turned neck, micro-thread and micro-grooved were placed according to the manufacturers' protocol and left submerged for 8 and 12 weeks. These were then harvested for histological examination. RESULTS: The histologically all samples were successfully ossointegrated and active bone remodelling adjacent to implants. With the micro-grooved implants 0.40 mm and 0.26 mm of the marginal bone level changes were observed at 8 and 12 weeks respectively. The micro-threaded implants had changes of 0.79 mm and 0.56 mm at 8 and 12 weeks respectably. The turned neck designed implants had marginal bone level changes of 1.61 mm and 1.63 mm in 8 and 12 weeks specimens. A complex soft tissue arrangement could be observed against micro-threaded and micro-grooved implant surfaces. CONCLUSION: Within the limitations of this study, it could be concluded that implants with micro-grooved had the least and the turned neck designed implants had the most changes in the marginal bone level. The textured implant surfaces affect soft tissue responses.
Animals ; Bicuspid ; Dogs ; Neck