Graduate student, Department of Prosthodontics, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
Professor, Department of Prosthodontics, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
J Prosthet Dent. 2022 Apr;127(4):585-592. doi: 10.1016/j.prosdent.2020.09.047. Epub 2020 Dec 30.
Different designs of posterior minimally invasive fixed partial dentures (MIFPDs) still require additional tooth preparation for guide planes, occlusal rest seats, and grooves and/or slots to increase retention and resistance forms. Whether a design with less tooth reduction can be successful is unclear.
This in vitro study compared the long-term survival and retention after cyclic loading of a conventional MIFPD and a posterior MIFPD that was designed for less tooth reduction and improved esthetics.
Previously frozen extracted human premolars and molars were embedded in polymethylmethacrylate resin blocks to simulate the loss of a first molar. The block specimens were divided into 3 groups (n=10) according to prosthesis design: control, a conventional posterior MIFPD with partial-coverage retainers; A2S, a 2-part posterior MIFPD with a semiprecision attachment; and A3, a 3-part posterior MIFPD. The prostheses were cemented onto the abutments with 4-methacryloxyethyl trimellitate anhydride/methylmethacrylate-tri-n-butylborane (4-META/MMA-TBB) resin. The specimens were subjected to 2 500 000 cyclic loading cycles with a compressive force of 50 to 800 N in a universal testing machine. After cyclic loading, the intact prosthesis was removed by using tensile force at a crosshead speed of 1 mm/min until failure. The mode of failure and bonding interface were evaluated by using stereomicroscopy and scanning electron microscopy. The retention data were analyzed by using 1-way ANOVA and the Tukey honestly significant difference (HSD) test (α=.05).
No prosthesis detached during cyclic loading. The mean ±standard deviation retentive forces among the control (396.7 ±73.2 N), A2S (228.3 ±52.5 N), and A3 (529.9 ±86.2 N) groups were significantly different (P<.05). The hybridized enamel layer of the abutments had a consistent thickness after immersion in 6 mol/L hydrochloric acid.
The results suggest that the 2- and 3-part posterior MIFPDs should have a high long-term survival rate in the oral cavity.
不同设计的后牙微创固定修复体（MIFPD）仍然需要额外的牙体预备来制作导平面、咬合支托和凹口/槽，以增加固位和抗力形。减少牙体预备的设计是否能成功尚不清楚。
本体外研究比较了常规 MIFPD 和后牙微创固定修复体的长期存活率和循环加载后的保留率，后者的设计减少了牙体预备量并改善了美观。
将先前冷冻的人前磨牙和磨牙嵌入聚甲基丙烯酸甲酯树脂块中，以模拟第一磨牙的缺失。根据修复体设计，将块状标本分为 3 组（n=10）：对照组，带有部分覆盖式固位体的常规后牙 MIFPD；A2S 组，带有半精密附着体的 2 部分后牙 MIFPD；A3 组，带有 3 部分后牙 MIFPD。用 4-甲基丙烯酰氧基乙基偏苯三酸酐/甲基丙烯酸甲酯-三正丁基硼烷（4-META/MMA-TBB）树脂将修复体粘接到基牙上。在万能试验机上用 50 至 800 N 的压缩力对标本进行 250 万次循环加载。循环加载后，以 1mm/min 的十字头速度用拉伸力将完整的修复体移除，直至失效。用体视显微镜和扫描电子显微镜评估失效模式和结合界面。用单向方差分析和 Tukey Honestly 显著差异（HSD）检验（α=.05）分析保留数据。
在循环加载过程中，没有修复体脱落。对照组（396.7±73.2 N）、A2S 组（228.3±52.5 N）和 A3 组（529.9±86.2 N）的平均保留力有显著差异（P<.05）。浸入 6mol/L 盐酸后，基牙的混合釉质层具有一致的厚度。
结果表明，2 部分和 3 部分后牙 MIFPD 在口腔中应有较高的长期存活率。
