The age-related effects on orthodontic tooth movement and the surrounding periodontal environment

Abstract

Orthodontic treatment in adults is often related to longer treatment time as well as higher periodontal risks compared to adolescents. The aim of this review is to explore the influence of age-related chages on orthodontic tooth movement (OTM) from macro and micro perspectives. Adults tend to show slower tooth movement speed compared to adolescence, especially during the early phase. Under orthodontic forces, the biological responses of the periodontal ligament (PDL) and alveolar bone is different between adult and adolescents. The adult PDL shows extended disorganization time, increased cell senescence, less cell signaling and a more inflammatory microenvironment than the adolescent PDL. In addition, the blood vessel surface area is reduced during the late movement phase, and fiber elasticity decreases. At the same time, adult alveolar bone shows a higher density, as well as a reduced osteoblast and osteoclast activation, under orthodontic forces. The local cytokine expression also differs between adults and adolescents. Side-effects, such as excessive root resorption, greater orthodontic pain, and reduced pulpal blood flow, also occur more frequently in adults than in adolescents.

Keywords: age-related changes; aging; alveolar bone; orthodontic tooth movement; periodontal ligament; tooth movement speed.

FIGURE 1

Age-related effects in orthodontic tooth movement. Age-related changes occurs during orthodontic treatment, reducing tooth movement speed. The internal reason can be explained by alterations of biological responses in the PDL and alveolar bone. Meanwhile, side effects such as orthodontic pain, pulpal reaction, root resorption can be aggrevated. Created with BioRender.com.

FIGURE 2

Age-related changes in the biological response of PDL under orthodontic force. (A) Young PDLC under orthodontic force; (B) aged PDLC under orthodontic force. Differences between the Young and Aged PDLC was shown: a) Slower biological reaction and recovery with increased disorganization time; b) Cell senescence; c) More inflammatory microenvironment; d) Fewer extensions in cells leading to deteriorated signaling activity; e) More complex and irregular oxytalan fibers with loss of elasticity; f) Reduced blood vessel surface area during late phase, with solely proliferation of small blood vessels instead of large blood vessel. Among the above differences, a only occurs on the compression side, while b, c, d, e, f occurs on both the compression side and the tension side. Created with BioRender.com.

FIGURE 3

Age-related changes related to the alveolar bone under orthodontic force. (A) Young alveolar bone remodeling under orthodontic force; (B) aged alveolar bone remodeling under orthodontic force. Differences shown above: a) Higher bone density; b) Slower osteoclast activation and decreased cell sensitivity; c) Reduced osteoblast differentiation and formation; d) Hindered bone turnover. Among the above differences, b only occurs on the compression side, while a, c, d occurs on both the compression side and the tension side. Created with BioRender.com.