Technol Health Care. 2021;29(4):781-795. doi: 10.3233/THC-202736.
Fabrication of complete dentures by computer-aided designing and computer-aided manufacturing (CAD-CAM) techniques are now common. Subtractive and Additive are the two principal CAD-CAM techniques used for this purpose. However, studies that evaluated the occlusal forces by CDs manufactured by these techniques are lacking.
To compare the occlusal forces in complete dentures fabricated by additive, subtractive and conventional techniques with different occlusal schemes, using computerized occlusal force analysis system [Tech-Scan III (T-Scan III)].
Three groups (Gr) were made on the basis of techniques of fabrication of CDs: Conventional CDs (CCD), Subtractive CDs (SCD), and Additive CDs (ACD). Each group CDs were further divided into three sub groups based on occlusion schemes: bilateral balanced occlusion (BBO), lingualized occlusion (LO) and mono plane occlusion (MO). A total of 45 CDs were made: 15 in each group with 5 CDs of each occlusal scheme. For all samples, occlusal force analysis (percentage of occlusal force applied on the right and left sides of the arch, centralization of forces and percentage of maximum occlusal force) was done using computerized occlusal analysis system: T-Scan III. Univariate regression analysis and logistic regression analysis were used to find the effects of the technique of fabrication and occlusion scheme over the occlusal forces (p< 0.05).
The intergroup comparison revealed statistically significant differences (p< 0.01) in right-left side force difference, maximum bite force in CDs fabricated by various techniques and with different occlusion schemes. Though the effect of occlusion scheme was more than the technique of fabrication (according to effect size estimation). The maximum force difference between right-left side was observed in combination of CCD technique and MO scheme (36.88 ± 2.82 N). Furthermore, the maximum bite force was observed for SCD technique (89.14 ± 6.08 N) and LO scheme (92.17 ± 3.22 N). In comparison to ACD, the chances of centre of force out of ellipse was 2.53 time more in CCS and 0.75 times less in SCD techniques and in comparison to MO, the chances of out of ellipse was 0.298 times less in BBO and 0.396 times less in LO schemes, though these chances were not statistically significant (p> 0.05).
The digital CDs fabricated by subtractive technique were proved to be superior to additive technique in terms of occlusal force analysis on tested parameters. However, further research is needed on patients to determine the exact superiority of one technique over the other.
计算机辅助设计和计算机辅助制造（CAD-CAM）技术制作全口义齿现在已经很常见。用于此目的的两种主要 CAD-CAM 技术是减法和加法。然而，缺乏评估这些技术制作的义齿的咬合力量的研究。
使用计算机化咬合分析系统 [Tech-Scan III（T-Scan III）]，比较通过加法、减法和常规技术制造的全口义齿的咬合力量，这些技术具有不同的咬合方案。
根据义齿制作技术，将三组（Gr）分组：常规义齿（CCD）、减法义齿（SCD）和加法义齿（ACD）。每组义齿进一步根据咬合方案分为三组：双侧平衡咬合（BBO）、舌侧化咬合（LO）和单平面咬合（MO）。共制作了 45 个义齿：每组 15 个，每个咬合方案 5 个。对于所有样本，使用计算机化咬合分析系统：T-Scan III 进行咬合力分析（咬合力在弓的左右两侧的应用百分比、力的集中和最大咬合力的百分比）。使用单变量回归分析和逻辑回归分析来发现制作技术和咬合方案对咬合力的影响（p<0.05）。
组间比较显示，各种技术和不同咬合方案制作的义齿的左右侧力差异、最大咬合力均有统计学意义（p<0.01）。尽管咬合方案的影响大于制作技术（根据效应大小估计）。在 CCD 技术和 MO 方案的组合中观察到左右侧最大力差异最大（36.88 ± 2.82 N）。此外，SCD 技术的最大咬合力为 89.14 ± 6.08 N，LO 方案为 92.17 ± 3.22 N。与 ACD 相比，在 CCS 中力中心出椭圆的几率是 2.53 倍，在 SCD 技术中是 0.75 倍，而在 MO 中，出椭圆的几率是 0.298 倍，在 LO 方案中是 0.396 倍，尽管这些几率没有统计学意义（p>0.05）。
在测试参数方面，减法技术制作的数字义齿在咬合力分析方面被证明优于加法技术。然而，需要对患者进行进一步研究，以确定一种技术相对于另一种技术的的确切优势。
