Cephalometric changes during aging in subjects with normal occlusion

Abstract Objective To assess craniofacial changes from early adulthood to the seventh decade of life in individuals with normal occlusion. Methodology The sample comprised lateral cephalograms of 21 subjects with normal occlusion (11 male, 10 female), taken at 17 (T1) and 61 years of age (T2). Anteroposterior and vertical maxillomandibular relationships, and dentoalveolar and soft tissue changes were analyzed. Interphase comparisons were performed using paired t-tests. Differences between sexes, and subgroups with and without tooth loss were evaluated using t-tests (p<0.05). Results Maxillary and mandibular anterior displacement, and facial and ramus height increased from T1 to T2. Maxillary molars showed significant mesial angulation. Maxillary and mandibular molars, and mandibular incisors developed vertically during the evaluation period. Soft tissue changes included a decrease of the nasolabial angle, upper and lower lip retrusion, decrease of upper lip thickness and increase of the lower lip and soft chin thickness. Maxillary incisor exposure by the upper lip decreased 3.6 mm in 40 years. Males presented counterclockwise rotation of the mandible, whereas females showed mandibular clockwise rotation and backward displacement of the chin. The group with tooth loss showed a greater increase of the posterior facial height and ramus height. Conclusion We observed aging changes in dentoskeletal structures and soft tissue, as well as sexual differences for craniofacial changes during the maturational process. Subjects with multiple tooth losses showed a greater increase in mandibular ramus height.


Introduction
Life expectancy remarkably increased in the last century. Craniofacial growth and development are continuous processes, and maturational changes can occur during aging. 1,2 The number of adults who seek orthodontic treatment for functional or esthetic improvement has increased, and understanding the natural changes that occur throughout life in the craniofacial complex is extremely important. Most previous longitudinal studies evaluated changes in the first two decades of life. [3][4][5][6] Previous studies show that growth continues during adulthood, 1,2,7-15 rather than immediately stopping after puberty. 14 Behrents 1 (1984) showed that craniofacial growth is a continuous process during human aging. In his  years (SD=1.61). The enrollment process is shown in Figure 1. In our sample, up to one tooth loss without prosthetic rehabilitation was observed in nine out of 21 subjects, who were placed in the subgroup without tooth losses. Two or more tooth losses without prosthetic rehabilitation were observed in the other 12 individuals, who were placed in the subgroup with tooth losses. Active periodontal disease was not observed in on clinical examination, considered as bleeding on probing. 17 All T1 cephalograms were scanned and all cephalograms were analyzed with the Dolphin Imaging ® 11.5 software (Dolphin Imaging, Chatsworth, Calif., USA). Correction of 11% and 10% magnification factors for T1 and T2 were performed, respectively. In total, 39 cephalometric variables were evaluated (Table 1). Variables were grouped in Table   1  Interphase changes from T1 to T2 were evaluated using paired t-tests. Differences between males and females, and between subgroups with and without tooth losses were also investigated with t-tests.
A 5% significance level was considered. Holm-Bonferroni correction for multiple comparisons was applied. 19 For the error study, 50% of the sample was randomly remeasured by the same examiner (G.M.N) after a minimum 30-day interval. Random errors were estimated using Dahlberg`s formula 18 , and systematic errors were estimated with dependent t-tests, at a 5% significance level. Statistical analyses were performed using the Statistica © software (Statistica for Windows, StatSoft Inc., Tulsa, USA).

Results
Random errors ranged from 0.21mm to 1.82mm for linear variables (overjet and Co-Go, respectively), and from 0.32° to 1.61° for the angular measurements (SNB and Mx1.Md1, respectively). We found no significant systematic error. The achieved power was 0.99, considering a mean change of 6mm in the CoGn

Interphase changes
From 17 to 61 years of age, we observed a significant increase of 2.74 mm (p<0.001) in the anterior cranial base. The maxillary and mandibular lengths increased 5.40 mm and 6.60mm (p<0.001), respectively. We also observed maxillary and mandibular anterior displacements of 1.47 mm (p<0.001) and 2.42 mm (p<0.001), respectively ( Figure 2a, Table 2). The measurements showed a significant increase of the upper and lower facial height (0.74 mm and 2.44 mm, respectively), of the posterior facial height (3.38 mm), and of the ramus height (5.36 mm). Maxillary molars showed a significant mesial angulation of 3.50° (p<0.001), and a vertical development of 2.74 mm (p<0.001).

Variables
Male (

Influence of tooth losses
The subgroup with tooth loss showed a greater increase of the posterior facial height (4.25 mm; p<0.035) and ramus height (7.01 mm; p<0.001) compared to the group without multiple tooth loss (  maturational changes of the craniofacial complex in untreated individuals. 1,2,8,10,14,15,20 One of the limitations of longitudinal studies is the difficulty in collecting data, which restricts the sample size. 14,15,21,22 The difficulty in recalling the sample after 47 years were relevant considering the subjects had changed phone numbers and addresses. Additionally, women had adopted marital names. After trying to reach all the 82 subjects from the initial sample group, 24 were reached, of which 21 accepted to participate. which confirms a nasal downward movement over time. 14 Other studies also reported similar findings of downward movement of the nose with ageing. 1,10,15,20,28 Lips became more retruded, specially the upper lip. Considering the inexistence of significant changes for maxillary and mandibular incisor protrusion with aging, lip retrusion is probably mostly related to forward movement of the nose and chin, and to an actual decrease of upper lip thickness. Similar findings were reported in previous studies in untreated subjects. 1,10,14 Reduction of upper lip thickness observed in our study might be related to the natural aging process of the skin which becomes less consistent and inelastic over time. 1,10,14,29 In contrast to the upper lip, the lower lip showed a slight thickness increase of 1.28 mm. On the contrary, six out of 10 female subjects showed stage CS6 at T1. These differences in sexual skeletal maturation at T1 could explain the greater changes observed in men between 17 and 61 years of age. The sexual differences in soft tissue changes consisted in greater retrusion of the upper and lower lips in males that might be related to the greater increase of nose and soft chin dimensions. These findings corroborate previous studies. 1,2,15,36 Soft chin thickness increased more in males than in females in a 3:1 ratio (Figure 2b and c). These results support previous studies showing similar findings. 1,14,29,33 The subgroup with tooth loss showed greater increase of the posterior facial height and ramus height than the subgroup without multiple tooth loss (Table   4). These results might be due to a counterclockwise rotation of the mandibular plane that occurs in subjects with posterior tooth losses, decreasing the vertical occlusal dimension. Our findings corroborate a previous study that compared mandibular size of edentulous, old dentate and young dentate individuals and showed significant greater ramus length in edentulous individuals, compared to young and old dentate individuals. 37 Hutchinson, Farella and Kramer (2015) found edentulous mandible with greater ramus height compared to dentate and partially edentulous mandibles. Differences between subgroups should be interpreted with caution due to the reduced sample power -a limitation of our study. Despite this limitation, this is the first cephalometric study following subjects with untreated normal occlusion until 70 years of age.
In short, this study has provided further evidence that the craniofacial complex continues to change from early to mature adulthood, probably due to terminal growth and bone remodeling processes throughout life.¹ Several changes in the dentoskeletal and soft tissues might be expected with aging in subjects with normal occlusion. As clinical considerations, orthodontists should be very careful when suggesting procedures that reduce lip protrusion, straighten the facial profile, and decrease maxillary incisor display, to avoid accelerating facial aging.

Conclusions
Between 17 and 61 years of age, normal occlusion subjects present anterior displacement of the maxilla and mandible, and increases in facial heights; maxillary molars showed mesial angulation and extrusion. The mandibular incisors and molars also extruded with aging. They also showed closure of the nasolabial angle, retrusion of the lips, increase of the soft-tissue chin, and reduction of the maxillary incisor exposure occurred during aging. These subjects also showed sexual differences in the craniofacial changes from J Appl Oral Sci. 2021;29:e20210199 10/11 early to mature adulthood. Finally, subjects with multiple tooth losses presented a greater increase in mandibular ramus height.