Statement of problem

Increasing occlusal vertical dimension (OVD) is often indicated in complex prosthodontic rehabilitations to gain restorative space and improve the occlusal relationship and esthetics. The effect of increasing occlusal vertical dimension on lower facial height (distance from subnasale to soft-tissue menton) and perceived facial esthetics is not well understood.

Purpose

The purpose of this clinical study was to investigate the effect of incremental increases in the occlusal vertical dimension on lower facial height and perceived facial esthetics by using a digital approach.

Material and methods

Twenty-five participants with Class I jaw relationship and no loss of OVD participated in the study. Custom mandibular devices were digitally designed and 3-dimensionally printed to increase the OVD by 3, 6, and 9 mm in each participant. Three-dimensional facial scans and frontal photographs were made with the participants wearing a specific device to achieve the desired OVD increase. The lower facial height, total facial height (distance between nasion to soft-tissue menton), nasolabial angle, lip width, and lip height were digitally measured on facial scans. All measurements were recorded in a computer-aided design (CAD) software program and were repeated 3 times. Subsequently, frontal photographs of 10 participants were randomly selected for survey. Three groups each of 10 prosthodontists, general dentists, or laypersons participated in the survey and were asked to detect OVD difference in 2 photographs of the same participant and to rank facial esthetics at varying OVDs. One-way repeated measures ANOVA (α=.05) for the facial measurements and descriptive statistics for the survey results were used.

Results

Lower facial height, the ratio of lower facial height to total facial height, lip height, and nasolabial angle increased with an OVD increase, whereas lip width decreased (P<.001). Bonferroni corrected paired t tests revealed all groups of OVD increase to be significantly different from each other (P<.001) except for an OVD increase to 6 mm versus 9 mm in lip height (P=.540) and lip width (P=.019), respectively. Prosthodontists, general dentists, and laypersons could detect a +3 mm OVD increase 63.9%, 62.5%, and 56.5% of the time, respectively. The participants’ original OVD was considered the most esthetic (60.0%, 45.0%, and 68.0%) by prosthodontists, general dentists, and laypersons, respectively.

Conclusions

Increased OVD increases lower facial height, the ratio of lower facial height to total facial height, lip height, and nasolabial angle but decreases lip width. Prosthodontists are more sensitive to a smaller increase in OVD, closely followed by general dentists and then laypersons. In case of no loss of OVD, a vertical increase as small as 3 mm can be detected by both dentists and the general public and perceived as less esthetic. The larger the increase in OVD, the more detectable the difference and the less the faces are perceived as esthetic.

中文翻译：

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增加咬合垂直尺寸对下面部形状和感知面部美学的影响：数字评估

问题陈述

增加咬合垂直尺寸 (OVD) 通常用于复杂的修复修复，以获得修复空间并改善咬合关系和美学。增加咬合垂直尺寸对较低的面部高度（从鼻下到软组织的距离）和感知的面部美学的影响尚不清楚。

目的

本临床研究的目的是通过使用数字方法研究咬合垂直尺寸的增量增加对较低的面部高度和感知的面部美学的影响。

材料与方法

25 名具有 I 类颌骨关系且 OVD 未丧失的参与者参与了该研究。定制的下颌装置经过数字化设计和 3 维打印，使每位参与者的 OVD 增加 3、6 和 9 毫米。参与者佩戴特定设备进行 3D 面部扫描和正面照片，以实现所需的 OVD 增加。下面部高度、面部总高度（鼻根与软组织之间的距离）、鼻唇角、唇宽和唇高在面部扫描中进行数字测量。所有测量均记录在计算机辅助设计 (CAD) 软件程序中并重复 3 次。随后，随机选取 10 名参与者的正面照片进行调查。三组，每组 10 名修复牙医、普通牙医、或非专业人士参与了调查，并被要求检测同一参与者的 2 张照片中的 OVD 差异，并对不同 OVD 的面部美学进行排名。使用了面部测量的单向重复测量方差分析 (α=.05) 和调查结果的描述性统计。

结果

较低的面部高度、较低的面部高度与总面部高度的比率、唇高和鼻唇角随着 OVD 的增加而增加，而唇宽则减少（P <.001）。Bonferroni 校正配对t检验显示所有组的 OVD 增加彼此显着不同（P <.001），除了 OVD 增加到 6 mm 与唇高（P = .540）和唇宽（P = 9 mm ）.019），分别。修复医生、普通牙医和外行可以分别检测到 OVD 增加 63.9%、62.5% 和 56.5%。参与者的原始 OVD 分别被修复医生、普通牙医和外行认为最美观（60.0%、45.0% 和 68.0%）。

结论

OVD 增加会增加下面部高度、下面部高度与总面部高度、唇高和鼻唇角的比率，但会降低唇宽。修复医生对 OVD 的较小增加更敏感，紧随其后的是普通牙医，然后是外行。在没有损失 OVD 的情况下，牙医和公众都可以检测到小至 3 毫米的垂直增加，并认为不美观。OVD 的增加越大，差异越容易被检测到，面部被认为是美学的就越少。