Utility of injectable bisphosphonates in enhancing orthodontic retention in a goat model: A split-mouth study

Abstract

Objective: The aim of this study was to evaluate the utility of bisphosphonates in reducing relapse after orthodontic tooth movement when injected intra-periodontally in a goat model.

Methods: Right and left second incisors of four goats were extracted and the first and third incisors were approximated orthodontically and retained. A bisphosphonate gel was injected into the mesial and distal periodontal spaces of first and third incisors on one side, while the first and third incisors of the other side received normal saline as a control. After 12 weeks of retention, the orthodontic appliance was removed and teeth were relieved from any active force. Following 6 weeks from appliance removal, millimetric measurements were performed to calculate the amount of relapse of orthodontically moved incisors. Histological and microcomputed tomographic examination was performed to assess the periodontal space and surrounding alveolar bone of the study and control incisors.

Results: The millimetric measurements and microcomputed tomographic scanning revealed that the orthodontically moved incisors in the side of bisphosphonate injection had significantly less relapse (p ≤ 0.05) and significantly narrower periodontal ligament width (p ≤ 0.05) than in the control side, respectively. Histologically, newly formed bone projecting into the periodontal ligament was observed in the side of bisphosphonate injection with newly formed cementum overlying areas of resorbed cementum.

Conclusion: The results suggest that bisphosphonate injection has the potential to enhance post-orthodontic stability and repair of root resorption following orthodontic treatment.

Keywords: Bisphosphonates; Orthodontic tooth movement; Periodontal ligament; Relapse; Root resorption.

Fig. 1

Photographs of the anterior region of animal’s mandible showing: (A) After 2nd incisor extraction and healing. (B) Space closure between 1st and 3rd incisors on each side with an elastomeric chain. (c) Complete space closure btween 1st and 3rd incisors on each side.

Fig. 2

Micro-CT image showing the midpoint reference for measurement of PDL width between the alveolar crest and root apex (A).

Fig. 3

(A) A photomicrograph showing islands of bone formation in the PDL of BPG, (B) Higher magnification of framed area in (A) showing clusters of osteoblasts and osteoclasts in a bony-like formation.

Fig. 4

Photomicrographs of the apical region showing: (A) cementoid formation in BPG, (B) active cementum resorption in CG.