Post-adolescence Growth8.1 Behrents RG (1985, 1989)219,220

Behrents studied post-adolescence growth by obtaining data from the Bolton Growth Studies. It was a longitudinal study on subjects between 17-83 years old. He investigated 163 cases (113 from untreated original, 40 years later) with 524 lateral cephalograms (this is possible because the magnification in the x-rays was known precisely).

Behrents found that facial growth continued throughout adult life. All of the facial dimensions had increased but size and shape of the craniofacial complex altered with time. Vertical changes in adult life were more prominent than A-P changes, width changes were least continuation of the patterns seen during maturation. Change in magnitude per year is small but overall is quite significant. A 2-10% increase was the rule: the bones of the cranial base, altering least, the facial bones a moderate amount, frontal sinus more and soft tissue most. Females had an apparent deceleration of growth in late teens follow by a resumption of growth in the 20s (child bearing age). Vertical change was more characteristic of female.

Rotation of both jaws continued into adult life, coinciding with the vertical changes and eruption of teeth. Male showed a net rotation of the jaws in a forward direction, slightly decreasing the MPA. Females had a tendency towards backward rotation with increase in MPA. Chin continues to be displaced in an anterior direction in all ages more so in male. Tendency for the Female mandible to appear more retruded with age even though the chin is coming forward. Compensatory changes were noted in the dentition so that occlusal relationships were largely maintained.

Figure 1 Superimposition: untreated male and female. Dashed lines indicate the initial tracing

Little changes were detected in the region of pterygomaxillary fissure. Palatal structures continue to relocates posteriorly and inferiorly (inferior change is greater in males). Anterior palate moves inferior and anteriorly. Nasal region continues to develop anteriorly so the position of the nasion and the tip of the nasal bone relocated anteriorly. Female has the tendency for the tip of the nasal bone to elevate. Orbit cavity increased in size in all direction.

Figure 2 Maxillary positional change and maxillary dimensional change based on palatal superimposition

Chin is displaced anteriorly but much greater extent in male. Mandibular forward rotation in males and backward in females were detected. Gonion move anterior and inferiorly in males, posterior and inferiorly in females. Anterior border of the ramus continues to relocate posteriorly with time. Posterior border of the ramus moves anteriorly in males and remain stationary in females. Female’s chin moves forward, the mandible is in effect rotating backward increasing the anterior vertical dimension of the face with no relative movement of the chin.

Figure 3 Mandibular dimension changes and positional changes

Maxillary anterior teeth become more vertically upright but the lower anterior teeth appear quite stable in their orientation with the tendency for proclination only in females. Posterior teeth change their inclination in response to the altered positive of the mandible. Axis of the molars shows a significant uprighting in Males and a tendency for being more distally inclined in Females. Overbite increase with age but compensated by attrition in most cases. Occlusal plane showed a decrease in angulation in males and stable in females. Occlusal plane changes toward a flatter plane. Continued increase in alveolar height with time in both arches

Figure 4 The direction of dental and mandibular plane movements and the resultant dental changes

Figure 5 Male occlusal plane changes

Soft tissue over nasal region, midface and the chin all move anteriorly. Nose grows a great deal in size, become broader and the tip becomes more angular and downturned, increase size of dorsal hump especially females. The height of the upper lip follows a similar course and lengthens to the same extent that the nose grows. Lips increase in length though they also flatten leading to more retruded position with time. Mamandras (1988) showed that maximal lip thickness is reached in female by age of 14 and in male at age 16 and beyond this time there is a gradual thinning of these tissues. Together with the growth of the nose and the anterior movement of the chin, the teeth appear less prominent, lip area flattened and lips located more inferiorly almost completely covering the upper incisors. Overall, there is a straightening and elongation of profile

Figure 6 Soft tissue outlines for composite males and females

The clivis angle of the cranial base decreases in Class II and increases in Class III individuals. Condyle tends to be more distant from sella in Class IIs and the reverse for Class IIIs. Class II females may be prone to relapse after treatment than class II males. Class III males would be prone to relapse than treated Class III females. Class II correction in males depended more on an apical base change (growth) whereas in female depended more on mesial movement of the lower molar along with a small apical base change. (i.e. growth of male accomplishes the correction whereas females, tooth movement is necessary). Correction of Class III is difficult in male and relapse is likely. Because of the clockwise rotation of mandibles in females, treatment would be aided by growth and relapse would tend to favour the maintenance of correction

Figure 7 Class II Treatment changes for male and females

8.2 Forsberg (1979)221

Growth changes in adult face were recorded form 24-34 years of age. There were 25 males and 24 females in the study with lateral cephalogram taken initially and 10 years after. 27 skeletal and 6 soft tissue variables were used and Frankfurt horizontal is the reference base.

The significant changes in the vertical direction included an increased lower facial height (ANS-Gn) of 0.39mm in female and 0.66mm in male. The angle SN:MP increased in both sex but no changes in gonial angle was evident. The increased in SN:MP was due to posterior rotation of mandible. The decreased in the incisor:SN are necessary to maintain normal contact relationship between the teeth. There was a continue forward movement of the apex of the nose and retrusion of both lips. A posterior movement of soft tissue pogonion is also detected in females.

8.3 Sarnas & Solow (1980)222

Sarnas and Solow reviewed a sample of 50 Swedish females and 101 Swedish male dental students using cephalometry. Examinations were carried out at the age of 21 years and 26 years old.

They found that: N point moved downward and forward 0.33mm S point moved downward and backward 0.33mm Total AFH ↑1.5mm with the LFH ↑ being larger Upper and lower dentoalveolar heights ↑0.5mm No change in upper and lower incisal angulations or interincisal angle Vertical OB ↑0.5mm

Length of nose ↑0.75-1 mm in both sexes Height of the upper lip showed an increase of 0.5mm in both male and females Males lip thickness is reduced Tip of the nose was displaced forwards and downwards in relation to the ACB in

both sex

8.4 Bondevik (1995)223

Bondevik (1995) carried out a longitudinal examination of a large group of males and females from beginning of 3rd to 4th decade. Cephalograms of all 3rd year Norwegian dental students from 1972to 1983 (22years 3 months). 74 females and 90 males were followed up 10years 9 months after. These subjects had no previous orthodontic treatment.

Results showed that SN increased linearly in 36.5% females. The length of the mandible increased in both sexes. PNS-ANS increased in 39.3% female and 42.2% males. Vertically, the total face height has increased mainly in the lower facial height. Anterior facial height increased more than posterior facial height in females and opposite for males. The mandibular prognathism decreased in females. SN:MP increased more than 10 in females and no change in males. There was no change in the occlusal plane. Upper incisors and lower incisors were retroclined in both genders. Thickness of lower lip and chin increased in males. The inferior part of the upper lip become thinner and superior part become thinner only in females. There are no change in the nose depth.

8.5 Nanda & Gosh (1995)224

Nanda and Gosh examined 17 males and 23 females from the Child Research Council (Denver). The age ranged from 7-18 years and 6 or more x-rays were taken. They discovered that the vertical dimension of the nose increased until 18 years. 80% of the upper nose height is completed for both sexes at age of 7 years. Lower nose height at age 7 is 90% complete in females and 67% in males. Males show a larger increment of growth of the lower nose at 17 years. The nose projection is 70% completed at age 7 in females and 63% in males. There is a significant increased at age 17 years in males. Skeletal base to the nose measurement is completed by 17 years. Average upper and lower lip length in males is twice the females. 6.9mm for males and 2.7mm for females. Short lip at age 7 will continue to have a short lip even at age 18 years. Point A & B increased more than at the vermilion borders. The lower lip thickness at vermilion border increased very little for females. Lips of males increased 7mm in length and therefore can accommodate more protrusion of incisors than the lips of females.

Adult DentitionArch length decrease form 14-18 years minimal intercanine decreases.227 Arch length will continue to decrease at a declining rate after the age of 15 years (male and female). This may contribute to relapse of incisor crowding.228 Permanent teeth move and wear, resulting in shortening of the dental arches. Vego (1962) found that there is greater (0.8mm) arch perimeter loss in cases with 8s and more crowding develops in presence of 8s.229 All subjects (with or without 8s) had arch perimeter loss. Sinclar & Little (1983, 1985) investigated the maturation of untreated normal occlusions and

found a decrease in the arch length and intercanine width.230,231 The intermolar width is relatively stable. This is concurrent with the study by Carter & McNamara (1998) that showed a decrease in arch width, length and perimeter throughout adulthood.232 The mean decrement in any one dimension was less than 3mm. Mandibular incisor irregularity increased but not in all subjects regardless of orthodontic treatment. The maxillary intermolar width, overbite, overjet and curve of Spee are stable during adulthood

Post-eruptive movement

Teeth continue to move in three planes of space after their full eruption at an

approximate rate of 0.4mm per annum. There is many reasons for post eruptive

movement including compensation for occlusal and proximal wear as well as

accommodation for growth. The latter occurs to accommodate the final growth of the

jaws and usually complete by the late teens. Observing the effects of an ankylosed

tooth best sees the amount of growth occurs after eruption.