Chong-Myeong Kim1, So-Ri Kim1, Ji-Hwan Kim2, Hae-Young Kim3, Woong-Chul Kim4. 1. Doctoral student, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea. 2. Professor, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea. 3. Associate Professor, Department of Dental Laboratory Science and Engineering, College of Health Science and Department of Public Health Sciences, Graduate School and BK21+ Program in Public Health Sciences, Korea University, Seoul, South Korea. 4. Professor, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea. Electronic address: kuc2842@korea.ac.kr.
Abstract
STATEMENT OF PROBLEM: Making a computer-aided design/computer-aided manufacturing (CAD/CAM) prosthesis with a milling machine often requires 2 (2- and 1-mm diameter) or 3 (2-, 1-, and 0.6-mm diameter) burs; however, using 3 burs can reduce time effectiveness and increase cost. Studies evaluating the trueness of prostheses made with 2 and 3 burs are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the 3-dimensional trueness of crown prostheses made using 2 and 3 ball-end mill burs in the milling process. MATERIAL AND METHODS: The abutment die of the maxillary right first molar for ceramic crowns was designed with computer-aided design software. After the crown prosthesis design was completed, polyurethane blocks were milled using 2 and 3 burs with a 5-axis milling machine. The outer and inner surfaces of the milled crown prostheses were scanned with a dental scanner. The inner part was separated into a marginal part and an internal part using 3-dimensional evaluation software. The 3-dimensional trueness of the prostheses milled with 2 or 3 burs was compared. RESULTS: No significant differences in trueness were found for the inner or internal parts of the prosthesis (P>.05). However, the outer and marginal parts of the prosthesis did show significant differences in trueness (P<.05). CONCLUSIONS: Milling the marginal part of the inner prosthesis was better with 2 burs, whereas milling the outer part was better with 3 burs.
STATEMENT OF PROBLEM: Making a computer-aided design/computer-aided manufacturing (CAD/CAM) prosthesis with a milling machine often requires 2 (2- and 1-mm diameter) or 3 (2-, 1-, and 0.6-mm diameter) burs; however, using 3 burs can reduce time effectiveness and increase cost. Studies evaluating the trueness of prostheses made with 2 and 3 burs are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the 3-dimensional trueness of crown prostheses made using 2 and 3 ball-end mill burs in the milling process. MATERIAL AND METHODS: The abutment die of the maxillary right first molar for ceramic crowns was designed with computer-aided design software. After the crown prosthesis design was completed, polyurethane blocks were milled using 2 and 3 burs with a 5-axis milling machine. The outer and inner surfaces of the milled crown prostheses were scanned with a dental scanner. The inner part was separated into a marginal part and an internal part using 3-dimensional evaluation software. The 3-dimensional trueness of the prostheses milled with 2 or 3 burs was compared. RESULTS: No significant differences in trueness were found for the inner or internal parts of the prosthesis (P>.05). However, the outer and marginal parts of the prosthesis did show significant differences in trueness (P<.05). CONCLUSIONS: Milling the marginal part of the inner prosthesis was better with 2 burs, whereas milling the outer part was better with 3 burs.