Effects of different types of tooth movement and force magnitudes on the amount of tooth movement and root resorption in rats

Abstract

Objective: To investigate differences in the amount of tooth movement and root resorption that occurred after tipping and bodily movement of the maxillary first molar in rats. Materials and Methods: Ten-week-old female Wistar rats were divided into two groups according to type of tooth movement and subdivided into four subgroups according to the magnitude of applied force. Nickel-titanium closed-coil springs exerting forces of 10, 25, 50, or 100 g were applied to the maxillary left first molars to induce mesial tooth movement. We designed a novel orthodontic appliance for bodily tooth movement. Tooth movement distance and root resorption were measured using microcomputed tomography and scanning electron and scanning laser microscopy. Results: The amount of tooth movement in the bodily tooth movement group was less than half that in the tipping tooth movement group. The greatest amount of tooth movement occurred in the 10-g tipping and 50-g bodily tooth movement subgroups, and the amount of tooth movement decreased with the application of an excessive magnitude of force. Conversely, root resorption increased when the heavier orthodontic force was applied in both groups. Root resorption in the tipping tooth movement group was approximately twice that in the bodily tooth movement group. Conclusions: Root resorption in the tipping tooth movement group was more pronounced than that in the bodily tooth movement group. Although the amount of tooth movement decreased when extremely heavy forces were applied, root resorption increased in both the tipping and bodily tooth movement groups in rats.

Saturation of the biological response to orthodontic forces and its effect on the rate of tooth movement

“…If application of higher forces does not increase the activity of inflammatory markers and the cascade of molecular and cellular events that follows, application of higher forces cannot increase the rate of tooth movement and can only expose the tooth to increased risk of side effects such as root resorption. Indeed, the experimental group that received 100 cN showed larger areas of root resorption in comparison with other groups (data not shown) in agreement with previous observations .…”

Prevalence and severity of apical root resorption during orthodontic treatment with clear aligners and fixed appliances: a cone beam computed tomography study

“…Many factors have been found to influence the orthodontic root resorption, including genetics [28], ethnicity [19], systemic diseases and allergic constitution [29], gender and age [7,30], treatment time [31], as well as the type (continuous or intermittent) and magnitude of orthodontic forces [32]. It has been found that heavy force used is associated with the prevalence of ARR [20], and an increase of force used is associated with the severity of ARR [33,34]. Intermittent force resulted in less ARR than continuous force [32,35] because the intermittent force provided cementum with the time to heal [36].…”

Types of tooth movement, bodily or tipping, do not affect the displacement of the tooth's center of resistance but do affect the alveolar bone resorption

“…The orthodontic appliances used in this study were designed as described previously. 13 Orthodontic anchor miniscrews of 1.4 mm in diameter and 6 mm in length (Dual-top, Anchor Screw; Jeil Medical, Seoul, Republic of Korea) were placed into the anterior palatal bone with a hand screwdriver. Then, a 0.016-inchdiameter, round, cobalt-chromium wire (Elgiloy; Rocky Mountain Morita, Tokyo, Japan) was fixed over the occlusal surfaces of the left second and third molars, all right molars, and the orthodontic anchor screws with a self-curing resin (Super-Bond; Sun Medical, Shiga, Japan).…”