Wearing complete dental prostheses - Effects on perioral morphology

Background To adequately perform rehabilitation of edentulous patients by a complete removable dental prosthesis (CRDP) is from basic interest to dentists to understand the morphologic changes caused by re-establishment of a physiologic jaw relationship. Anthropometric analyses of standardized frontal view and profile photographs may help elucidate such changes. Material and Methods Photographs of 31 edentulous patients were compared in relaxed lip closure and after insertion of a CRDP in stable occlusion. 2232 anthropometric distances were raised. Eighteen anthropometric indices reflecting the perioral morphology and its integration in the vertical facial harmony were investigated. Results The intercanthal – mouth width index (p<.001), medial - lateral cutaneous upper lip height index (p=.007), lower vermilion contour index (p=.022), vermilion - total upper lip height index (p=.018), cutaneous - total upper lip height index (p=.023), upper lip - nose height index (p=.001), nose - upper face height index (p=.002), chin - mandible height index (p=.013), upper lip - mandible height index (p=.045), nose - lower face height index (p=.018), and nose - face height index (p=.029) showed significant pre- to post-treatment changes. Conclusions The investigated anthropometric indices presented reproducible results related to an increase in occlusal vertical dimension. Their application may be helpful in assessment, planning, and explanation of morphologic effects of CRDPs on the perioral and overall facial morphology, which may helps to improve the aesthetic outcome. Key words:Dentures, removable dentures, anthropometry, perioral morphology.


Introduction
Worldwide, conventional complete removable dental prostheses are the most established form of treatment of edentulous jaws (1). Most patients treated with CRDPs are satisfied with the increase in quality of life achieved. The perception of gain of quality of life maybe considered as the most established indicator for a successful therapy (2)(3)(4)(5). Today, patients exhibit an increased awareness not only of the functional but also of the aesthetic quality of their artificial dentition. To ensure an adequate aesthetic appearance of CRDPs, there are established clinical methods to perform e.g. an aesthetic anterior tooth arrangement or selection of tooth colour (6,7). Beside these techniques to improve the oral appearance of CRDPs it is beyond dispute, that CRDPs have also an immense influence on patients´ overall facial appearance. Despite this knowlegde, there is no established objective and reproducible procedure to evaluate the influence of CRDPs on the perioral and facial morphology. Anthropometric indices described by Leslie G. Farkas provide objective and relative information about relationships between at least two anthropometric distances (8)(9)(10). They have proven useful to objectively quantify changes in the facial morphology by reconstructive (11), traumatologic (12) and orthognathic (13) surgery. Furthermore, they are used in the description of perioral aging as well as of planning facial changes e.g. in orthodontics (14)(15)(16). In the present study the effect of CRDPs on anatomic landmarks and perioral relationships on standardized frontal view and profile photographs in edentulous patients was investigated. Results of photo-assisted anthropometric measurements of edentulous patients without CRDP in relaxed lip closure and with their CRDP in situ were compared.

Material and Methods
Before the study was initiated, the local ethic committee gave its approval. All patients willing to participate signed consent before being enrolled. Patients exhibiting specific or general diagnoses potentially influencing the perioral architecture, like e.g. earlier facial operations, were excluded. All patients were edentulous and received a conventional CRDP at the Dental Clinic in a standardized manner (17). At the time the photographs were taken all patients exhibited a stable occlusion in all quadrants, when CRDP was inserted.
-Objective Rating Scheme Coloured frontal view and profile photographs with open eyes were taken of the patient's by a professional photographer (Nikon D 80 camera; objective: Nikon AF Micro Nikkor 105 mm 1: 2.8 D; aperture: f13; Nikon Corp, Tokyo, Japan). Photographs were made after the CRDP were inserted, stable, and with lips in a relaxed position. Only photographs showing patients´ faces clearly at rest and in which the interpupillary axis was at the same level as the camera lens were selected to avoid photographic distortion (18). Photographic analysis was performed using Adobe Photoshop CS2 (Adobe Inc, San Jose, CA) software measurement tool. On the basis of predefined landmarks (Table 1) and data (Table 2), the following anthropometric indices based on the work of Farkas and Munro (9,10) were investigated (see also Fig. 1): (1) Intercanthal-mouth width index, representing the intercanthal width (IW, en-en), as a percentage of the mouth width (MW, ch-ch) (2); Upper lip height mouth width index, representing the upper lip height, the vertical distance between the subnasale and the stomion (ULH, sn-sto) as a percentage of the mouth width (MW, ch-ch) (       especially. Due to loss in the alveolar ridge height patients show a tendency towards a Class III relationship of the jaws, reduction of the vertical relationships between lower and upper face, and an increased prominence of the chin (6,(19)(20)(21)(22). Also the upper and lower vermilion present a collapsed aspect in edentulous patients, as the former inner dental support of the lips is absent (6). Due to this morphologic changes the physiologic rest position seems to undergo a subtle process of neuromuscular adaptation which leads to a decreased vertical relation of the jaws (20). Knowledge and a complete understanding of facial changes achievable by CRDPs are fundamental to perform a successful functional and aesthetic rehabilitation of edentulous patients (23,24). Given patients´ increased demand on an aesthetic appearance it seems occasionally to be more important to achieve an adequate endorsement by the patient of the perioral soft tissues than to focus on the appearance of the teeth themselves (25)(26)(27). Thus, the correct determination of the vertical relation is of greatest importance (28). It serves to determine the correct relation and redefine the physiological level of occlusion. Despite this key role, there is no established method to reproducibly and objectively determine the vertical relation of the jaws in edentulous patients. (19,28). In this context, anthropometric measurements may help to approximate the correct vertical relation. A deeper understanding of the morphology of the facial soft tissues, together with established intraoral measurements, may be particularly helpful to younger colleagues to explain the impact of CRDPs on the perioral morphology and to successfully plan CRDPs as well as to discuss with the patient the expected outcome. Multiple anthropometric and anatomic relations of the perioral region are available. The selected anthropometric indices by Farkas were found useful in earlier studies investigating the effect of orthognathic and reconstructive surgery or aging on the perioral soft tissues (16,29,30), and in the present study were adequate to investigate the complex aesthetic interactions in the aesthetic units of upper and lower lips and their subunits. All anthropometric landmarks were easily and reproducibly identifiable on the standardized photographs.
Intercanthal -mouth width index describes the relationship of the perioral region to the upper central face.
It gives a direct reflection of the aspect of the mouth width, which often seems to be decreased in patients with a collapsed vertical relation (9). The presented photo-assisted anthropometric measurements may help to understand the direction and extent of morphological changes in the rehabilitation not only of edentulous jaws but also of the edentulous face.

Conclusions
The evaluation of the effects of conventional CRDPs on the facial morphology of edentulous patients by using anthropometric data extracted from standardized photographs helps to accurately analyze and quantify treatment related changes. The vertical height of the upper and lower lip and the upper vermilion show a significant increase meanwhile upper lip´s lateral portion decreases in height. Support of the soft tissues surrounding the mouth opening leads to a decreased aspect of the mouth width.