Medical Radiation Engineering Department, Science and Research Branch, Islamic Azad University, Daneshgah Blvd., Simon Bolivar Blvd., P.O. Box: 14515-775, Tehran, Iran.
Radiation Biology Research Center, Iran University of Medical Sciences, Shahid Hemmat Highway, P.O. Box: 14665-354, Tehran, Iran.
Int J Implant Dent. 2021 Sep 6;7(1):90. doi: 10.1186/s40729-021-00372-5.
Materials with high atomic numbers are part of the composition of dental implant systems. In radiotherapy of oral cavity cancers, an implant can cause dose perturbations that affect target definition, dose calculation, and dose distribution. In consequence, this may result in poor tumor control and higher complications. In this study, we evaluated dose homogeneity when a dental implant replaced a normal tooth. We also aimed to evaluate the concordance of dose calculations with dose measurements.
In this study, 2 sets of planning CT scans of a phantom with a normal tooth and the same phantom with the tooth replaced by a Z1 TBR dental implant system were used. The implant system was composed of a porcelain-fused-to-metal crown and titanium with a zirconium collar. Three radiotherapy plans were designed when the density of the implant material was corrected to match their elements, or when all were set to the density of water, or when using the default density conversion. Gafchromic EBT-3 films at the level of isocenter and crowns were used for measurements.
At the level of crowns, upstream and downstream dose calculations were reduced when metal kernels were applied (M-plan). Moreover, relatively measured dose distribution patterns were most similar to M-plan. At this level, relative to the non-implanted phantom, mean doses values were higher with the implant (215.93 vs. 192.25), also, new high-dose areas appeared around a low-dose streak forward to the implant (119% vs. 95%).
Implants can cause a high dose to the oral cavity in radiotherapy because of extra scattered radiation. Knowledge of the implant dimensions and defining their material enhances the accuracy of calculations.
高原子序数的材料是牙科植入系统组成的一部分。在口腔癌的放射治疗中，植入物会导致剂量分布的变化，从而影响靶区的定义、剂量计算和剂量分布。因此，这可能导致肿瘤控制效果不佳和更高的并发症发生率。在本研究中，我们评估了当一颗牙齿被植入物取代时的剂量均匀性。我们还旨在评估剂量计算与剂量测量的一致性。
本研究使用了一个带有正常牙齿的体模和一个带有 Z1 TBR 牙科植入系统的相同体模的两套计划 CT 扫描。植入系统由烤瓷熔附金属冠和带有氧化锆环的钛组成。当植入物材料的密度被校正以匹配其元素时，或者当所有密度都被设置为水的密度时，或者当使用默认的密度转换时，设计了三种放射治疗计划。在等中心和冠部水平使用 Gafchromic EBT-3 胶片进行测量。
在冠部水平，当应用金属内核时（M 计划），上游和下游剂量计算减少。此外，相对测量的剂量分布模式与 M 计划最为相似。在这个水平上，与未植入的体模相比，植入物的平均剂量值更高（215.93 比 192.25），并且在植入物周围出现了新的高剂量区域，向前延伸到植入物的低剂量条纹（119%比 95%）。
由于额外的散射辐射，植入物会在放射治疗中对口腔造成高剂量。了解植入物的尺寸和定义其材料可以提高计算的准确性。
