Post Graduation Department, School of Dentistry, University Center of Maranhão-UniCeuma, São Luís, MA, Brazil.
J Prosthet Dent. 2011 Sep;106(3):184-90. doi: 10.1016/S0022-3913(11)60119-4.
The oval-shaped palatal roots of maxillary molars usually have smaller cross-sectional diameter in the buccolingual direction. However, the effect of parallel-sided post preparation on the remaining dentin thickness of root canal walls is unknown.
The purpose of this study was to investigate, in vitro, the residual dentin thickness (RDT) of palatal roots in maxillary molars after various intracanal procedures for post placement, and to determine the risk of root canal perforation or weakening on different root canal walls at 2 levels, coronal and apical.
Fifteen extracted first maxillary molars exhibiting radiographic mesiodistal root canal widths ranging from 3.8 to 4.2 mm, measured at 5 mm from the apex, were selected from a pool of teeth. The teeth were horizontally sectioned at 2 levels, coronal and apical, after being embedded in acrylic resin with the aid of a metal index, allowing identical repositioning of the sectioned parts throughout the study. Each sectioned surface was photographed with a digital camera coupled to a microscope. The palatal roots were subsequently prepared for post placement as follows: endodontic preparation up to file K50, Largo 3 and 4 drills, and ParaPost 4.5 and 5.0. Cross-sections were rephotographed after each step. Image J software was used to measure the RDT of each root wall at both levels, and data were further analyzed with a 3-way ANOVA/General Linear Model (GLM) for repeated measures. The post-hoc Tukey's range test was used to calculate differences in RDT among the 4 root walls at each root level (α=.05).
A significant difference was observed among the intracanal procedures (P<.001). At the apical level, RDT was significantly lower after ParaPost preparation than at the coronal level (P=.009). Buccal and palatal walls displayed significantly lower RDT than the mesial and distal walls at both levels (P=.004).
Intracanal preparation up to ParaPost 5.0 increased the risk of perforation or weakening of the buccal and palatal walls, especially at the apical level.
上颌磨牙的腭侧根在颊舌向的横截面直径通常较小。然而，平行根管预备对根管壁剩余牙本质厚度的影响尚不清楚。
本研究旨在体外研究不同根管内后牙预备对上颌磨牙腭侧根管的剩余牙本质厚度（RDT）的影响，并确定在冠根和根尖 2 个水平不同根管壁穿孔或弱化的风险。
从一组牙齿中选择了 15 颗具有从根尖 5 毫米处测量的 3.8 至 4.2 毫米的近远中根管宽度的第一上颌磨牙。在借助金属指数将牙齿嵌入丙烯酸树脂后，将牙齿在冠根和根尖 2 个水平上水平分段，使分段部分在整个研究中能够重新定位。将每个分段表面用数字相机与显微镜耦合进行拍照。随后按照以下步骤对上腭根进行后牙预备：根管预备至 K50 、Largo 3 和 4 锉，ParaPost 4.5 和 5.0。每个步骤后都重新拍摄横截面照片。使用 Image J 软件测量每个根管壁在两个水平的 RDT，并使用 3 因素方差分析/广义线性模型（GLM）进行重复测量的数据分析。在每个根水平的 4 个根管壁之间，使用 Tukey 范围检验进行 RDT 差异的后测（α=.05）。
在根管内程序之间观察到显著差异（P<.001）。在根尖水平，ParaPost 预备后 RDT 明显低于冠根水平（P=.009）。在两个水平上，颊侧和腭侧壁的 RDT 明显低于近中和远中壁（P=.004）。
根管预备至 ParaPost 5.0 增加了颊侧和腭侧壁穿孔或弱化的风险，尤其是在根尖水平。
