Statement of problem

Milling is a well-established method for manufacturing prosthetic frameworks. However, information about the influence of ceramic veneer and spark erosion on the accuracy of the all-on-six complete-arch fixed frameworks manufactured from different materials is lacking.

Purpose

The purpose of this in vitro study was to compare the accuracy of milled complete-arch fixed frameworks with zirconia, cobalt-chromium, and titanium at different steps of their manufacturing process and the influence of mechanical cycling.

Material and methods

Fifteen milled complete-arch fixed frameworks, supported by 6 implants, were made in zirconia, cobalt-chromium, and titanium (n=5). The fit was measured by the single-screw test protocol. Stress was measured by photoelastic analysis. The loosening torque was evaluated by tightening the screws, retightening them after 10 minutes, and then evaluating the loosening torque 24 hours later. Thereafter, all frameworks received ceramic veneer, and the previous tests were repeated. Cobalt-chromium and titanium frameworks received spark erosion after ceramic veneer, and all analyses were repeated. Before and after mechanical cycling, loosening torque was evaluated. The results were subjected to 2-way repeated-measures ANOVA and the Bonferroni test (α=.05).

Results

Titanium presented higher fit values than zirconia (P=.037) and similar to cobalt-chromium frameworks (P>.05) at baseline. After ceramic veneer, higher fit levels were observed for zirconia (P=.001) and cobalt-chromium (P=.008). Titanium showed higher stress values (P<.05) regardless of time. Baseline for all materials presented lower stress values (P<.05). Higher loosening torque values were found for the titanium group at baseline (P<.001) and after ceramic veneer (P<.001). Spark erosion improved fit and loosening torque values only for cobalt-chromium (P<.05). Mechanical cycling did not influence the loosening torque (P>.05).

Conclusions

Titanium milled complete-arch fixed frameworks presented poorer fit values than zirconia, although the loosening torque at baseline was higher. Ceramic veneer increased the fit levels for zirconia and cobalt-chromium, decreased the loosening torque values for cobalt-chromium, and enhanced stress levels. Spark erosion can be a reliable technique to improve fit and loosening torque for cobalt-chromium frameworks. Mechanical cycling did not decrease loosening torque.

中文翻译：

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陶瓷贴面电火花腐蚀和机械循环是否会影响由 6 个种植体支撑的铣削完整牙弓框架的准确性？

问题说明

铣削是一种成熟的制造假肢框架的方法。然而，关于陶瓷贴面和电火花腐蚀对由不同材料制成的全六个完整拱形固定框架精度影响的信息缺乏。

目的

这项体外研究的目的是比较在其制造过程的不同步骤中使用氧化锆、钴铬和钛的铣削完整拱形固定框架的准确性以及机械循环的影响。

材料与方法

由 6 个种植体支撑的 15 个铣削完整牙弓固定框架由氧化锆、钴铬合金和钛制成 (n=5)。通过单螺杆测试协议测量拟合。通过光弹性分析测量应力。通过拧紧螺钉，10 分钟后重新拧紧，然后在 24 小时后评估松开扭矩来评估松动扭矩。此后，所有框架都接受了陶瓷贴面，并重复了之前的测试。钴铬合金和钛框架在陶瓷贴面后受到电火花腐蚀，并重复所有分析。在机械循环之前和之后，评估松动扭矩。结果经过 2 向重复测量方差分析和 Bonferroni 检验 (α=.05)。

结果

钛的拟合值高于氧化锆 ( P = .037) 并且与基线的钴铬框架 ( P > .05)相似。陶瓷贴面后，观察到氧化锆 ( P =.001) 和钴铬 ( P =.008) 的贴合度更高。无论时间如何，钛都显示出更高的应力值 ( P <.05)。所有材料的基线呈现较低的应力值 ( P <.05)。钛组在基线 ( P <.001) 和陶瓷贴面后 ( P <.001) 的松动扭矩值更高。仅针对钴铬合金 ( P<.05）。机械循环不影响松动扭矩 ( P >.05)。

结论

钛铣削的完整足弓固定框架的拟合值比氧化锆差，尽管基线的松动扭矩更高。陶瓷贴面提高了氧化锆和钴铬合金的贴合度，降低了钴铬合金的松动扭矩值，并增强了应力水平。火花腐蚀是一种可靠的技术，可以提高钴铬框架的配合和松动扭矩。机械循环不会降低松动扭矩。