Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany.
Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany; Department of Dental Prosthetics, Propaedeutics and Materials Science, Dental School, University Hospital Bonn, Bonn, Germany.
J Dent. 2022 Oct;125:104276. doi: 10.1016/j.jdent.2022.104276. Epub 2022 Aug 30.
To investigate how the stress distribution and forces transmitted from orthodontic aligners to the tooth surface are affected by the geometry and extension of the trimming line.
Thirty-six aligners were thermoformed from Zendura FLX sheets (0.75 mm thick) and divided into four groups based on the design of the trimming line: Scalloped, Scalloped extended, Straight and Straight extended. Fuji pressure-sensitive films were used for pressure measurement. The pressurized films were scanned and evaluated. Pressures and forces were measured over the entire facial surface of an upper right central incisor (Tooth 11) and at 7 different locations [cervical, middle, incisal, mesio-incisal, mesio-cervical, disto-incisal, and disto-cervical]. In addition, the thickness of the aligners at these 7 sites was measured with a digital caliper.
The active force ranged from (2.2 to 6.9) N, and the average pressure was (1.6-2.7) MPa. The highest values were recorded for the (straight extended) design, while the lowest values were recorded for the scalloped design. The forces and stresses were not uniformly distributed over the surface. When the values in each area were compared separately, significant differences were found between the different designs in the cervical area, with the scalloped design transmitting the lowest cervical forces. Aligner thickness was drastically reduced (60-75% thinning) over the entire tooth surface after thermoforming.
The straight extended design of aligner's trimming line exhibited more uniform force transfer and stress distribution across the surface than the other designs.
The trimming line design could have a significant impact on the clinical outcome of orthodontic aligner treatment.
研究正畸矫治器的切痕线的几何形状和延伸对牙面的力分布和传递的影响。
用 Zendura FLX 片（0.75 毫米厚）热成型了 36 个矫治器，并根据切痕线的设计将其分为四组：锯齿形、锯齿形延伸、直形和直形延伸。使用富士压敏胶片进行压力测量。对加压胶片进行扫描和评估。在上颌右中切牙（牙 11）整个唇面和 7 个不同位置[颈、中、切、近中切、近中颈、远中切、远中颈]测量压力和力。此外，还使用数字卡尺测量了这 7 个位置的矫治器厚度。
主动力范围为（2.2 至 6.9）N，平均压力为（1.6-2.7）MPa。（直延伸）设计的数值最高，而（锯齿形）设计的数值最低。力和应力在表面上不均匀分布。当单独比较每个区域的值时，不同设计在颈区的力有显著差异，锯齿形设计传递的颈区力最低。热成型后，整个牙面的矫治器厚度急剧减少（变薄 60-75%）。
直延伸设计的矫治器切痕线在表面上表现出更均匀的力传递和更均匀的应力分布。
切痕线设计可能对正畸矫治器治疗的临床效果有重大影响。
