The face is one of the most diverse parts of the human body. The distinction between race, ethnic origin, sex and age is reflected in the faces of everybody. In today's society, which is dictated by the general social acceptance and the associated aesthetics, the appearance of the face has an important role. On the other hand the influence of tooth loss on facial appearance is still very poor explained. Recognizing the characteristics of an older adults’ face and being able to differentiate between the changes as a result of an ageing face or as a result of tooth loss have a large impact on treatment planning. 3D facial analysis is not involved in the standard diagnostic procedures for the dental treatment. However, diagnostics of the whole face is possible with a 3D scan of the facial surface. The cephalometric analysis of a 3D scans is a well-established and proven method nowadays.
Our study involved 18 cephalometric parameters on the basis of 39 facial landmarks of the older and young adults. The inclusion criterion was 65 years and older, since this is the definition of an older adult. At the same time, the main skeleton changes happen before that age, between the 4th and 5th decades (17). Males and females were examined separately, due to the sexual dimorphism (18). Since the participants have been edentulous for more than 2 decades, the major part of alveolar bone loss due to atrophy has already occurred.
When comparing the older and younger adults we have to take into account the difference in body mass index; older adults had significantly higher BMIs than younger ones, but there were no obese subjects among them. There were no differences in BMI between our subgroups of old adults and there were no differences regarding the sex in the old adults group. Also, it is known that, for example, high BMI conditioned changes of the face are ethnically and racially conditioned (19). So we have to state that in our study all the participants were Slovenian with Caucasian ancestry.
Different studies have proven that the face is getting wider with age (20). Facial width was larger in both sexes compared to the control group. The difference in the male group was statistically significant (p = 0.001) and close to statistical significance (p = 0.071) in the female group. Wider, older adults’ faces could also be a consequence of the higher BMI in the older adults’ group, because the influence of BMI on transverse facial dimensions has been proven (21). We assumed that the loss of teeth had no great impact on the facial width, but surprisingly our study proved narrower faces in the completely edentulous participants, most probably as the consequence of cheek soft-tissue ptosis.
Among the facial heights we excluded the parameter known as the upper facial height, because of large variability in the position of the trichion point, especially in the male group. Some studies have found that total facial height increases with age and the same was proved in our study, but some studies have proved the consistency in facial height in spite of tooth loss (22). Older adults had longer faces than the control group, statistically significant (p = 0.000) in the male group. We assumed that posterior rotation of the mandible (23), the increase in the dentoalveolar height with age (24), the effect of gravity on the soft tissues, the loosening of muscle tonus and the ageing of the chin’s soft tissues (13) are the main causes. Older adults had a longer middle facial height in comparison to the control group, statistically significant only in the male group (p = 0.010). The position of the glabella point on a facial scan does not change with years (25), so we assume the prolongation to be a result of the clockwise rotation of the maxilla (26) and the changed position of the spina nasalis anterior and the subnasale point. Older adults have a larger lower facial height than the controls. Shimizu et. al. have found shorter upper facial height and longer lower facial height comparing older adults with younger (27).
Facial height and lower facial height were significantly smaller in the completely edentulous subgroup than in the toothed subgroup for both sexes. Barlett et al. have studied skull differences in the toothed and edentulous older adults and discovered a shortening in the facial height, because of a shortening of the lower facial height as a result of teeth loosening and atrophy in both jaws (20). When comparing different older adults’ subgroups with each other, we observed the trend of reducing the size of the middle facial height with the loss of teeth, which is statistically significant among the female subgroups and close to statistical significance among the male subgroups.
Apart from the eyes, the most recognizable part of every face is the mouth. Ageing has no impact on mouth width, but the tooth loss does. The completely edentulous participants of both sexes had statistically significant narrower mouths than the toothed. Sex dimorphism is observed for this parameter, with men having wider mouths than women (28). The upper lip height was longer in the older adults’ group, and close to statistical significance in the male group (p = 0.072). Some studies have already proven it to be a result of gravity (11), but not a decrease in soft-tissue volume (29). The height was the longest for the toothed, and the shortest in the completely edentulous subgroup. The teeth in the intercanine sector are preventing the lip from curling inwards. Upper and lower lip rednesses were statistically significantly narrower for the older adults’ group in both sexes, as has been already described (11). The completely edentulous subgroup had the most narrow rednesses, which has not been described yet.
The nose is a very significant part of the face and has his own characteristics. In our study we have proven nose prolongation with age, no matter the shape and the size of the nose. Older men had statistically significant longer noses than the young adults, but no statistical significance was found in the female group (p = 0.084). The prolongation of the nose is a consequence of the intrinsic loosening of the lower lateral alar cartilages and the supporting ligaments (30). We discovered longer noses in the toothed than the completely edentulous adults. No such study comparing edentulism and nose length has been conducted before.
In the profile view of the scan we investigated the distance between the upper and lower lip and the aesthetic line (E-line). Ageing and tooth loss have an important influence on these two parameters. Older adults, especially the completely and partially edentulous, had statistically significant longer distances between the upper and lower lip and the E-line that means they have worse facial aesthetics.
The angles that we studied were the facial angle, the soft-tissue ANB angle, the angle of the lower facial height and the nasolabial angle. Older adults have a statistically significant (p = 0.000) larger facial angle than the young adults, which means a more flat profile. The largest facial angle is found for the completely edentulous participants, and this is statistically significant in the females.
In our study we placed the soft-tissue points a, n, b corresponding to the bone points in skeletal angle ANB. In a systematic review of the existing literature we did not find any study about the soft-tissue ANB angle changes in connection with dentition. The soft-tissue ANB angle was significantly (p = 0.000) smaller in the older adults’ group in comparison with the control group. This is a result of a narrowing of the upper lip and changing the a point position. The change was larger in the female group, because of the more voluminous upper lip. The soft-tissue ANB decreases with tooth loss as a result of maxilla and mandibular atrophy. After loosening of the teeth, especially in the upper jaw, the upper lip is retruded. The statistically significant differences were just in the female subgroups, which means that it is a sex-dependent parameter.
The lower facial height angle was significantly greater in the older adults’ group and shows the retrusion of the perioral tissues. With tooth loss there was a tendency to increase the angle. Studies have shown that the skeletal angle ANB, the inclination of the incisors and canines – supporting the upper lip and ptosis of tip of the nose – have the main impact on the nasolabial angle (31). We have proven a smaller angle in the older adults’ group, but it is not statistically significant. A smaller angle is especially significant in toothed and partially edentoulous participants, but the edentoulous groups of both sexes have significantly greater nasolabial angle, which means that tooth loss greatly affects it.
We wanted to simplify the ageing facial changes with facial ratios, which did not prove to be a good indicator. For the ratio between the facial height and the width there were no statistically significant differences, because of the changes in both directions.