COMPARISON OF NASOLABIAL ANGLE IN YOUNG ADULTS AND MIDDLE AGED DENTATE AND ELDERLY EDENTULOUS SUBJECTS.
Objective: To compare the mean value of nasolabial angle in dentate and edentulous subjects in young adults, middle aged dentate (having normal occlusion) and elderly edentulous subjects. Study Design: Cross-sectional comparative study Place and Duration of Study: The study was conducted in the Department of Prosthodontics, Armed Forces Institute of Dentistry, and Army Medical College, Rawalpindi from September 2007 to November 2008. Patients and Methods: A total of 250 subjects were divided in three age groups. Group 1: 100 Subjects 20-30 years , Group 2: 100 subjects 35-45 years and Group 3: 50 edentulous subjects >50 years. The subjects with Intact maxillary and mandibular arches and Angle's Class-I molars, canine and incisor relationship were included. Standard lateral cephalometric radiographs of the heads were traced and nasolabial angle was measured. Results: The mean values of nasolabial angle in dentate and edentulous were 96.79deg+-2.6 and 111.40o+-2.51respectively.
The mean values of nasolabial angle in young adults (20-30 years), middle aged (35-45 years) and old edentulous (>50 years) subjects were 97.39o+-2.94, 96.19o+-2.58 and 111.40o+-2.51respectively. The difference in mean values of nasolabial angle among three groups, was statistically significant (p<0.001). Conclusions: Nasolabial angle in middle aged subjects is greater than younger subjects and even greater in elderly edentulous subjects. Sexual dimorphism exists as males have greater nasolabial angle in younger age. While fabricating dental prosthesis nasolabial angle may be restored near to the dentate subjects.
INTRODUCTION The lower one-third of the face has major impact on facial appearance and profile, which seems to be adversely affected in edentulous subjects as maxillary lip is no more supported by teeth1. This situation is even verse if the residual arches are excessively resorbed.2 When complete dentures are fabricated, it remains a challenge to re-establish lip support and restore the facial profile2. In prosthesis fabrication, anterior artificial dental arch, denture flange and appropriate occlusal vertical dimension are important factors in successfully restoring the esthetic objective3. The presence and position of anterior artificial dental arches affect not only the lip contour but also the lower half of the nose. The nasolabial angle and lip position are useful indices for examining lip support in denture wearers4
The nasolabial angle is a clinical and cephalometric parameter for the determination of soft tissue profile,4 which is representative of maxillary inclination, increased angle reflects a maxillary retrusion, and decreased amount shows a maxillary protrusion5. Owen6 reported its arbitrary value to be in the range of 90deg to 110deg (considered as the standard) McNamara Jr.7 reported a value of 102deg+- 8 in cephalometric evaluations. However, study on Brazilian black showed a mean value of 88.14o and 104deg +- 11.5deg 9 and 114deg +- 10deg in young white adults, suggesting ethnic variations8. Different ethnic groups demonstrate variations in their skeletal, dental and facial profiles and a better treatment plan can be formulated if these racial variations are considered in the diagnosis9. Individuals from our population present craniofacial characteristics which differ from those of other races, especially the white race, whose cephalometric analyses and norms are usually considered as the standard.
Our study was conducted to establish the norm of our population by assessing the mean values of nasolabial angle in young adults, middle aged and edentulous subjects, and to assess the effects of age on nasolabial angle along with sexual dimorphism. PATIENTS AND METHODS This cross-sectional comparative study was conducted in Department of Prosthodontics, Armed Forces Institute of Dentistry, and Army Medical College, Rawalpindi from September 2007 to November 2008. 250 subjects were divided in three age groups. 100 dentate subjects with 20-30 years were included in Group 1. In Group 2, 100 subjects with 35-45 years were included and Group 3 consisted of 50 edentulous subjects above 50 years. The subjects with Intact maxillary and mandibular arches and Angle's Class-I molars, canine and incisor relationship were included in the study while the subjects with history of orthodontic treatment or maxilomandibular defect were excluded from the study.
Standard lateral cephalometric radiographs of the heads were obtained using standard cephalostat. The cephalograms were divided in two groups according to gender (male and female). In a dark room, a single operator traced all the cephalograms by using a transparency viewer. Templates were used for comparison. Intra operator accuracy was improved by repeating measurements after 10 days. The nasolabial angle was measured as the angle between the line tangent from the Subnasale (Sn) to the lower border of the nose and the line from the Sn to maxillary lip (Fig) Data had been analyzed using SPSS Version 15. Descriptive statistics were used to describe the data. Analysis of variance (ANOVA) was used to compare nasolabial angle between the groups. p-values 0.05) (Table-1).
The mean values of nasolabial angle in dentate and edentulous were 96.79deg+-2.6 and 111.40deg+-2.51 respectively. The difference was statistically significant (P<0.001). The mean values of nasolabial angle in group 1, group 2 and group 3 were 97.39deg +- 2.94, 96.19deg+-2.58 and 111.40deg+-2.51 respectively. ANOVA showed statistically significant difference in the mean values of nasolabial angle among three groups (p0.001), group 1 and group 3 (p<0.001) and group 2 and group 3 (p<0.001). Amongst each group male and female showed sexual dimorphism. In group 1 mean nasolabial angle was 98.48+-2.51in males while in female it was 96.10+-2.90. In group2 mean nasolabial angle was 95.92+-2.43 in males while in females it was96.46+-2.71.
In group3 mean nasolabial angle was 112.83+-2.09 in males while in female it was110.07+-2.13. p-values of gender comparisons between the groups has been shown in Table 2 DISCUSSION Owen6 reported racial differences of the nasolabial angle in the facial appearances of dentate subjects, ranging in age from 18 to 41 years, from six racial groups, including Japanese. They evaluated that Japanese had a smaller nasolabial angle (97o+-1) than did Caucasians (109o+-5) and Hispanics (105o +-1), but a larger angle than did Koreans (92o +-9), Chinese (92o+-5) and African Americans (90o). According to our study the dentate subjects between 20 to 45 years showed mean nasolabial angle of 96.790 with standard deviation+-2.6, this value is very close to that of Japanese. The related literature indicates that the value of the nasolabial angle in harmonious faces varies considerably. Among the cited values are 114.08deg +- 9.58deg; 102deg; 105deg +- 8deg; 111.04deg; 104deg +- 11.5deg and from 108.76deg to 114.40deg.9
Kamashita et al3 conducted a study using waxed dental rims at different angles, representing anterior dental arch. He concluded that recovery of lip support with dentures could reduce the larger nasolabial angle that results from the loss of lip support owing to missing teeth to the level of that in dentate groups. Watt and MacGregor10 stated that the nasolabial angle for adequate lip support is approximately 90o in fabricating complete dentures. Brunton and McCord11 have reported that the nasolabial angle of Caucasian dentate subjects is approximately 110o and edentulous patients should be given an obtuse nasolabial angle exceeding 90o as a prosthodontic guideline.
We found similar results in our study that optimal aesthetic results from a prosthesis may be achieved if nasolabial angle be restored near to the dentate i.e. 96.79deg +-2.6 According to Hwan WJ12 the average nasolabial angle was 78.5o in young Korean males and 126o in young Korean females showing sexual dimorphism, we also found sexual dimorphism in our study in younger groups as males are more prognathic than females but in middle age groups the females are slightly more prognathic than males which is in accordance with another study conducted by Sheikh and Alvi13 according to whom females showed more dental protrusion. Silva Filho et al4 found an angle of 104deg +- 11 in white individuals with normal occlusion, without sexual dimorphism. The nasolabial angle presented variation according to gender; in females it was significantly smaller, confirming the existence of sexual dimorphism.
This result differs from those of Silva Filho et al.4 and Fitzgerald et al.14 who found that black individuals showed similar angular and linear measurements in both groups, males and females. According to Prahl-Andersen et al.15 the tendency of the nasolabial angle is, to decrease with age, specially until adolescence, when the growth of nose, chin and lips is expressed more intensely9. Silva Filho et al4 observed that craniofacial growth did not alter the nasolabial angle significantly. Prahl-Andersen et al15 observed a small decrease in the value of the nasolabial angle with age, but with subsequent stabilization of this value in adolescence. Siqueira et al16 studied the changes of the nasolabial angle as a result of deviations in the upper incisors position induced by craniofacial growth. It was concluded that facial and dental alterations that occurred during the craniofacial growth in Brazilian white youths did not influence the nasolabial angle significantly9.
Nanda et al17 reported that the nasolabial angle decreased slightly from 7 to 18 years of age in both genders with means at 7 years , 107.8 o +- 9.4 for boys and 114.7 o +- 9.5 for girls. At 18 years, the means were 105.8 o +- 9.0 for males and 110.7 o +- 10.9 o for females. Lo and Hunter18 found no significant changes in nasolabial angle because of growth. Scheideman et al19 and Fitzgerald et al14 conducted longitudinal studies and reported a normal mean nasolabial angle at 111.4deg with a small decrease in this angle expected with age, primarily because of the downward growth of the nose. In our study we found slight acute nasolabial angle in middle aged subjects as compared to the young ones suggesting decrease in nasolabial angle with age. It may be because of proclination of maxillary anterior teeth or the continued nasal growth. CONCLUSIONS Nasolabial angle in middle aged subjects is greater than younger subjects and even greater in elderly edentulous subjects.
Sexual dimorphism exists as males have greater nasolabial angle in younger age. While fabricating dental prosthesis nasolabial angle may be restored near to the dentate subjects ACKNOWLEDGEMENTS This study project was completed with financial grant of Higher education commission, RandD Department and National University of sciences and technology, RandD department, Islamabad.
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|Publication:||Pakistan Armed Forces Medical Journal|
|Date:||Sep 30, 2010|
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