Pienkos Todd E, Morris W Jack, Gronet Peter M, Cameron Stephen M, Looney Stephen W
US Army Prosthodontic Residency program, Fort Gordon, Ga., USA.
J Prosthet Dent. 2007 May;97(5):299-304. doi: 10.1016/j.prosdent.2007.04.001.
The design of a removable dental prosthesis (RDP) must balance functional strength, comfort to the patient, and the health of the tissue. While research has been conducted to enhance the strength of major connectors, little has been done to determine if the dimensions of major connectors can be reduced in order to enhance patient comfort and tissue health.
The purpose of this study was to determine the minimum major connector dimensions of 1 mandibular and 2 maxillary major connectors that would provide adequate functional strength.
Sixty chromium-cobalt alloy (Vitallium) RDP frameworks were fabricated. The major connector designs were: a mandibular lingual bar, a maxillary palatal strap, and a maxillary anterior-posterior (A-P) palatal strap. Four groups of 5 frameworks with diminishing dimensions were fabricated for each major connector design. The lingual bar was tested at 4, 3, 2.5, and 2 mm in height, occlusogingivally, and 1.6 mm in thickness; the palatal strap at 8, 6, 4, and 2 mm, anteroposteriorly; and the A-P palatal strap at 10 x 6, 8 x 4, 6 x 2.5, and 4 x 2 mm, anteroposteriorly. All maxillary frameworks were 0.65 mm in thickness. The frameworks were of a Kennedy Class II Mod I design with 3 widely separated vertical reference points to measure deformation. Two tests were conducted to evaluate the functional strength for each framework. The first test was masticatory simulation, or torsional force. The second test was a drop test from a height of 3 feet. Permanent deformation was then determined after each test. The Cochran-Armitage test (alpha=.05) was used for both the torsion test and the drop test.
A statistically significant difference in permanent deformation was found for the palatal strap design among the 4 different dimensions for the compressive test (P=.015) and the drop test (P=.044).
It is safe to reduce the dimensions of some major connectors under normal loads. The reduced size of the connectors places the removable partial denture at increased risk for deformation when dropped from a height.
可摘局部义齿（RDP）的设计必须在功能强度、患者舒适度和组织健康之间取得平衡。虽然已经开展了研究以增强大连接体的强度，但对于是否可以减小大连接体的尺寸以提高患者舒适度和组织健康，却几乎没有进行过相关研究。
本研究的目的是确定1种下颌和2种上颌大连接体能够提供足够功能强度的最小尺寸。
制作了60个铬钴合金（维他灵）RDP支架。大连接体设计包括：下颌舌杆、上颌腭板和上颌前后腭板。每种大连接体设计制作4组，每组5个尺寸逐渐减小的支架。舌杆在垂直方向上测试高度分别为4、3、2.5和2mm，厚度为1.6mm；腭板在前后方向上测试尺寸分别为8、6、4和2mm；前后腭板在前后方向上测试尺寸分别为10×6、8×4、6×2.5和4×2mm。所有上颌支架厚度均为0.65mm。支架为Kennedy II类I型设计，有3个广泛分开的垂直参考点以测量变形。对每个支架进行两项测试以评估功能强度。第一项测试是咀嚼模拟，即扭力测试。第二项测试是从3英尺高度进行跌落测试。然后在每次测试后确定永久变形。扭力测试和跌落测试均采用 Cochr an-Armitage检验（α = 0.05）。
在压缩测试（P = 0.015）和跌落测试（P = 0.044）中，腭板设计在4种不同尺寸之间的永久变形存在统计学显著差异。
在正常负荷下减小某些大连接体的尺寸是安全的。连接体尺寸减小会使可摘局部义齿从高处跌落时变形风险增加。
