Interrupted orthodontic force results in less root resorption than continuous force in human premolars as measured by microcomputed tomography

Abstract

Introduction. Root resorption is an undesirable but very frequently occurring sequel of orthodontic treatment. The aim of this study was to compare root resorption caused by either continuous (CF) or interrupted (IF) orthodontic force. Material and methods. The study was performed on human subjects on 30 first upper and lower premolars scheduled for extraction for orthodontic reasons. During four weeks before extraction 12 teeth were subjected to either CF or IF. The force was generated by a segmental titanium-molybdenum alloy cantilever spring that was activated in buccal direction. Initially a force of 60 CentiNewton was used in both CF and IF groups, the force in the former, however, was reactivated every week for 4 weeks. There was no reactivation of force in the IF group after initial application. A morphometric analysis of root resorption was performed by microcomputed tomography and the extent of tooth movement was measured on stone casts. Furthermore, a Tartarate-Resistant Acidic Phosphatase activity (TRAP), the marker enzyme of osteoclasts and cementoclasts, was determined by histochemical method. The Mann-Whitney U test was used to compare the difference in measured parameters between treatment and control tooth groups. Results. The number of resorption craters was significantly higher and their average volume almost twice as large in the CF compared to the IF group (p < 0.05). However, the distance of tooth displacement was similar for both groups. Cementoclasts were detected with the TRAP technique on the surface of two teeth only; both were subjected to continuous force. Conclusions. The use of IF leads to less destruction of root structure as opposed to continuous force while the same tooth movement was achieved.

Apical External Root Resorption and Repair in Orthodontic Tooth Movement: Biological Events

“…Cementum resorption and subsequent repair by cellular cementum (cementum turnover), which according to some researchers can be regarded as a physiological remodelling process, occurs throughout life in response to metabolic changes in the periodontal ligament mediated by forces of mastication, by continual tooth eruption and drifting, and possibly by parafunctional gnathic activities [ 10 , 32 – 34 ]. On the other hand, other researchers are of the opinion that, unlike bone, cementum does not undergo such physiological remodelling but increases in thickness throughout life [ 30 , 35 ].…”

“…It is caused by orthodontic load-induced sterile inflammation that brings about resorption of the superficial root cementum, or it can become more severe with eventual resorption of the underlying dentin [ 10 ]. Apical external root resorption is ultimately repaired by cellular cementum but nevertheless may result in permanent loss of root length.…”

Apical Resorption of Upper Incisors and Canines During Orthodontic Treatment in Class III Orthognathic Surgery Patients – a Longitudinal Cone Beam Computer Tomography Study

“…Other precise imaging methods are described in other studies. Sawicka et al (2014) (18) research shows that computed micro-tomography is more precise that CBCT, but it is only applicable to extracted teeth. Although CBCT images are 3D, only linear changes in the root were detected in this study; 3D reconstruction of the root surface was not performed.…”

Root resorption in orthodontic treatment with clear aligners: A systematic review and meta‐analysis

“…Clear aligners create intermittent forces due to occasional removal during food consumption and hygiene maintenance. Sawicka et al assessed variations of ERR during orthodontic treatment using continuous and interrupted forces, describing less ERR with interrupted forces . However, there is no further evidence on comparing the effect on ERR induced by these two different types of forces in comprehensive orthodontic treatment.…”