OBJECTIVES This study aimed to evaluate the effect of different materials and undercut on the removal force and stress distribution in the supporting tooth and in the circumferential clasp used in removable partial prosthesis. METHODS Upper molars prepared for Akers circumferential clasp with retention and opposing arm were modeled, scanned, elaborated with CAD software and the geometries imported in FEA and analyzed. Six different materials were selected for the clasp (Polyamide, Polyoxymethylene, Polyetheretherketone - PEEK, Gold alloy, Titanium and CoCr) and 3 different undercuts (0.25, 0.50 and 0.75mm), totaling 18 groups. RESULTS The clasps presented greater stress in their structure and potentially greater damage to the dental enamel when made with rigid materials and with more undercut; however, they presented greater ability to remain in position. SIGNIFICANCE Polyamide with a higher undercut is an esthetic alternative to rigid metallic clasps. It showed promising behavior because it strongly reduces the damage to the enamel, and even with an undercut of 0.75, the retention is lower than for CoCr with a 0.25 undercut, and this retention might still be sufficient. Polyoxymethylene and Polyetheretherketone (PEEK) are not suitable materials for the clasps, because the maximum stress occurring during removal with higher undercuts is higher than the material strength.

中文翻译：

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在可移动局部义齿中直接保持作用期间，不同材料和底切对周向扣的去除力和应力分布的影响。

目的本研究旨在评估不同材料和底切对可摘局部假体所使用的支撑齿和周向扣的去除力和应力分布的影响。方法建模，扫描，用CAD软件制作为带有固定和相对臂的Akers环扣准备的上颌磨牙，并在FEA中导入几何形状并进行分析。为表扣选择了六种不同的材料（聚酰胺，聚甲醛，聚醚醚酮-PEEK，金合金，钛和CoCr）和3种不同的咬边（0.25、0.50和0.75mm），共18组。结果当用刚性材料和更多的底切制成时，扣具在结构上施加更大的应力，并可能对牙釉质造成更大的损坏。然而，他们表现出更大的保持位置的能力。意义高底切的聚酰胺是刚性金属搭扣的美学替代品。它显示出令人鼓舞的行为，因为它极大地减少了对瓷釉的损害，即使底切为0.75，固位率也比底切为0.25的CoCr低，并且这种固位可能仍然足够。聚甲醛和聚醚醚酮（PEEK）不适合用作表扣，因为在带有较高咬边的去除过程中出现的最大应力高于材料强度。25个底切，并且此保留量可能仍然足够。聚甲醛和聚醚醚酮（PEEK）不适合用作表扣，因为在带有较高咬边的去除过程中出现的最大应力高于材料强度。25个底切，并且此保留量可能仍然足够。聚甲醛和聚醚醚酮（PEEK）不适合用作表扣，因为在带有较高咬边的去除过程中出现的最大应力高于材料强度。