Eastman Institute of Oral Health, University of Rochester, New York, USA.
Studio Poggio, Private Practice, Milan, Italy.
J Esthet Restor Dent. 2024 Jan;36(1):231-238. doi: 10.1111/jerd.13186. Epub 2023 Dec 18.
In many esthetic treatments, clinicians may consider the option to modify the maxillo mandibular position. A raise of the vertical dimension of occlusion (VDO) may help restore esthetics, increase the space for dental materials, and reduce the invasiveness of dental procedures. Traditionally, VDO increases are done by using the centric relation (CR) position. Despite a long history of use, the neuromuscular effects of different maxillo mandibular relations are not fully studied. The aim of this study was to investigate the effect of alterations of maxillo-mandibular relation from maximal intercuspal position (MIP) to a raised VDO CR position on jaw-elevator muscle activity.
Fifteen healthy individuals were asked to carry out maximal voluntary clenching (MVC) in MIP and in CR on individual splints. Electromyographic (EMG) activity of the masseter and anterior temporalis muscles was assessed in μV as the root mean square of the amplitude. Specific indexes and ratios were also computed. Data analyzed in MIP and CR were compared by paired student's t-tests.
MVC levels were not negatively affected by a VDO increase in CR position. On the contrary masseter muscles showed a statistically significant increase (p < 0.005). No significant effect on the anterior temporalis was observed.
These results suggest that no immediate negative effect on maximum voluntary clenching was induced by a VDO increase in CR position. A slight increase observed in EMG clenching levels could be explained by the increase in VDO when clenching on the splint.
The results of this study support the use of CR position as a pragmatic reference position due to the absence of relevant or negative changes in neuromuscular function.
在许多美容治疗中，临床医生可能会考虑改变上下颌位置的选择。咬合垂直距离（VDO）的升高可以帮助恢复美观，为牙体材料增加空间，并减少牙体治疗的侵袭性。传统上，通过使用正中关系（CR）位置来增加 VDO。尽管已经使用了很长时间，但不同上下颌关系的神经肌肉影响尚未得到充分研究。本研究旨在探讨从最大牙尖交错位（MIP）到升高的 VDO CR 位改变上下颌关系对咀嚼肌活动的影响。
要求 15 名健康个体在个体夹板上的 MIP 和 CR 中进行最大自主咬合（MVC）。以振幅均方根的形式评估咀嚼肌和前颞肌的肌电图（EMG）活动，以 μV 为单位。还计算了特定的指标和比率。通过配对学生 t 检验比较 MIP 和 CR 中的数据。
CR 位置的 VDO 增加并未对 MVC 水平产生负面影响。相反，咀嚼肌显示出统计学上的显著增加（p<0.005）。前颞肌没有观察到显著影响。
这些结果表明，CR 位置的 VDO 增加不会立即对最大自主咬合产生负面影响。在夹板上咬合时 VDO 增加而观察到的 EMG 咬合水平略有增加，可以解释为 CR 位置。
由于神经肌肉功能没有明显或负面变化，本研究的结果支持将 CR 位置用作实用参考位置。
