Department of Orthodontics and Pediatric Dentistry, Faculty of Dentistry, Chiang Mai University, Suthep Road, Muang, Chiang Mai, 50200, Thailand.
Department of Mechanical Engineering, Faculty of Engineering, Chiang Mai University, Chiang Mai, Thailand.
Clin Oral Investig. 2022 Oct;26(10):6177-6186. doi: 10.1007/s00784-022-04567-x. Epub 2022 May 31.
To compare the center of resistance (Cres) of the maxillary central incisor in models with and without the pulp cavity and to evaluate the association of pulp cavity/tooth volume ratio and difference in Cres position between the two models.
CBCT images of the right maxillary central incisor were collected from 18 subjects. Pulp cavity/tooth volume ratio was measured, and finite element models of teeth and periodontal structures were generated. Cres location was presented as a percentage of root length measured from the root apex. Differences in Cres positions between models were compared using the paired t-test, while the correlation between pulp cavity/tooth volume ratio and a difference in Cres was evaluated by Pearson's correlation coefficient.
For the pulp cavity model, the average location of the Cres measured from the apex of the root was 58.8% ± 3.0%, which resulted in a difference of 4.1% ± 1.1% (0.5 mm) apically, when compared with the model without pulp cavity. Differences in Cres between the models were statistically significant (P < 0.01), while the correlation between pulp cavity/tooth volume ratio and a difference in Cres between models was significantly positive (r = 0.709, P = 0.001).
In the pulp cavity model, the Cres was located in a more apical position. The difference in Cres between models increased as the pulp cavity/tooth volume ratio increased.
The line of force must be applied more apically in the pulp cavity model to achieve the desired orthodontic tooth movement.
比较有髓腔和无髓腔模型中上颌中切牙的阻力中心（Cres）的位置，并评估髓腔/牙体体积比和两种模型之间 Cres 位置差异的相关性。
从 18 名受试者的右侧上颌中切牙采集 CBCT 图像。测量髓腔/牙体体积比，并生成牙齿和牙周结构的有限元模型。 Cres 位置表示为从根尖测量的根长的百分比。使用配对 t 检验比较模型之间 Cres 位置的差异，而 Pearson 相关系数评估髓腔/牙体体积比与 Cres 位置差异之间的相关性。
对于有髓腔模型，从根尖测量的 Cres 的平均位置为 58.8%±3.0%，与无髓腔模型相比，根尖方向相差 4.1%±1.1%（0.5 毫米）。模型之间 Cres 的差异具有统计学意义（P<0.01），而髓腔/牙体体积比与模型之间 Cres 位置差异之间的相关性呈显著正相关（r=0.709，P=0.001）。
在有髓腔模型中，Cres 位于更根尖的位置。随着髓腔/牙体体积比的增加，模型之间 Cres 位置的差异增大。
为了达到预期的正畸牙齿移动，必须在髓腔模型中将力线更根尖地施加。
