Moris Izabela Cristina Maurício, Faria Adriana Cláudia Lapria, Ribeiro Ricardo Faria, Rodrigues Renata Cristina Silveira
Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
Clin Oral Implants Res. 2017 Apr;28(4):432-436. doi: 10.1111/clr.12816. Epub 2016 Feb 29.
The aim of this study was to analyze failure modes and misfit of abutments with reduced diameter for both cement and screw retentions after cyclic loading.
Forty morse-taper abutment/implant sets of titanium were divided into four groups (N = 10): G4.8S-4.8 abutment with screw-retained crown; G4.8C-4.8 abutment with cemented crown; G3.8S-3.8 abutment with screw-retained crown; and G3.8C-3.8 abutment with cemented crown. Copings were waxed on castable cylinders and cast by oxygen gas flame and injected by centrifugation. After, esthetic veneering ceramic was pressed on these copings for obtaining metalloceramic crowns of upper canine. Cemented crowns were cemented on abutments with provisional cement (Temp Bond NE), and screw-retained crowns were tightened to their abutments with torque recommended by manufacturer (10 N cm). The misfit was measured using a stereomicroscope in a 10× magnification before and after cyclic loading (300,000 cycles). Tests were visually monitored, and failures (decementation, screw loosening and fractures) were registered. Misfit was analyzed by mixed linear model while failure modes by chi-square test (α = 0.05).
Cyclic loading affected misfit of 3.8C (P ≤ 0.0001), 3.8S (P = 0.0055) and 4.8C (P = 0.0318), but not of 4.8S (P = 0.1243). No differences were noted between 3.8S with 4.8S before (P = 0.1550) and after (P = 0.9861) cyclic loading, but 3.8C was different from 4.8C only after (P = 0.0015) loading. Comparing different types of retentions at the same diameter abutment, significant difference was noted before and after cyclic loading for 3.8 and 4.8 abutments. Analyzing failure modes, retrievable failures were present at 3.8S and 3.8C groups, while irretrievable were only present at 3.8S.
The cyclic loading decreased misfit of cemented and screw-retained crowns on reduced diameter abutments, and misfit of cemented crowns is greater than screw-retained ones. Abutments of reduced diameter failed more than conventional.
本研究旨在分析循环加载后用于粘结和螺丝固位的直径减小的基台的失败模式及不匹配情况。
四十套钛制莫氏锥度基台/种植体分为四组（每组n = 10）：G4.8S - 4.8基台搭配螺丝固位冠；G4.8C - 4.8基台搭配粘结冠；G3.8S - 3.8基台搭配螺丝固位冠；以及G3.8C - 3.8基台搭配粘结冠。在可铸型圆柱体上用蜡制作帽状冠，通过氧气火焰铸造并用离心法注入。之后，在这些帽状冠上压制美观的饰面陶瓷以获得上颌尖牙的金属烤瓷冠。粘结冠用临时粘结剂（Temp Bond NE）粘结在基台上，螺丝固位冠按照制造商推荐的扭矩（10 N·cm）拧紧到基台上。在循环加载（300,000次循环）前后，使用放大10倍的体视显微镜测量不匹配情况。对测试进行视觉监测，并记录失败情况（粘结失败、螺丝松动和骨折）。不匹配情况通过混合线性模型分析，而失败模式通过卡方检验分析（α = 0.05）。
循环加载影响3.8C（P≤0.0001）、3.8S（P = 0.0055）和4.8C（P = 0.0318）的不匹配情况，但不影响4.8S（P = 0.1243）。在循环加载前（P = 0.1550）和后（P = 0.9861），3.8S和4.8S之间未发现差异，但仅在加载后（P = 0.0015），3.8C与4.8C不同。在相同直径基台比较不同类型的固位方式时，对于3.8和4.8基台，循环加载前后存在显著差异。分析失败模式，3.8S和3.8C组出现可修复的失败情况，而不可修复的失败情况仅出现在3.8S组。
循环加载降低了直径减小的基台上粘结和螺丝固位冠的不匹配情况，且粘结冠的不匹配情况大于螺丝固位冠。直径减小的基台比传统基台更容易失败。
