Nelson Neha, K S Jyothi, Sunny Kiran
Coorg Institute of Dental Sciences, Virajpet, affiliated to Rajiv Gandhi University of Health Sciences, Bangalore.
Eur J Prosthodont Restor Dent. 2017 Mar;25(1):20-25. doi: 10.1922/EJPRD_01611Nelson06.
The margins of copings for crowns and retainers of fixed partial dentures affect the progress of microleakage and dental caries. Failures occur due to altered fit which is also influenced by the method of fabrication. An in-vitro study was conducted to determine among the cast base metal, copy milled zirconia, computer aided designing computer aided machining/manufacturing zirconia and direct metal laser sintered copings which showed best marginal accuracy and internal fit. Forty extracted maxillary premolars were mounted on an acrylic model and reduced occlusally using a milling machine up to a final tooth height of 4 mm from the cementoenamel junction. Axial reduction was accomplished on a surveyor and a chamfer finish line was given. The impressions and dies were made for fabrication of copings which were luted on the prepared teeth under standardized loading, embedded in self-cure acrylic resin, sectioned and observed using scanning electron microscope for internal gap and marginal accuracy. The copings fabricated using direct metal laser sintering technique exhibited best marginal accuracy and internal fit. Comparison of mean between the four groups by ANOVA and post-hoc Tukey HSD tests showed a statistically significant difference between all the groups (p⟨0.05). It was concluded that the copings fabricated using direct metal laser sintering technique exhibited best marginal accuracy and internal fit. Additive digital technologies such as direct metal laser sintering could be cost-effective for the clinician, minimize failures related to fit and increase longevity of teeth and prostheses.
固定局部义齿冠和固位体的边缘影响微渗漏和龋齿的进展。由于制作方法也会影响适配性的改变，从而导致失败。进行了一项体外研究，以确定铸造金属基、复制铣削氧化锆、计算机辅助设计计算机辅助加工/制造氧化锆和直接金属激光烧结固位体中，哪种显示出最佳的边缘精度和内部适配性。将40颗拔除的上颌前磨牙安装在丙烯酸模型上，使用铣床进行咬合面降低，直至距牙釉质牙骨质界的最终牙冠高度为4毫米。在观测仪上完成轴向降低，并给出一个倒角终结线。制作印模和模型以制作固位体，在标准化负荷下将其粘结在预备好的牙齿上，嵌入自凝丙烯酸树脂中，切片并使用扫描电子显微镜观察内部间隙和边缘精度。使用直接金属激光烧结技术制作的固位体显示出最佳的边缘精度和内部适配性。通过方差分析和事后Tukey HSD检验对四组之间的均值进行比较，结果显示所有组之间存在统计学上的显著差异（p＜0.05）。得出的结论是，使用直接金属激光烧结技术制作的固位体显示出最佳的边缘精度和内部适配性。直接金属激光烧结等增材数字技术对临床医生来说可能具有成本效益，可将与适配性相关的失败降至最低，并提高牙齿和假体的使用寿命。
