Histological Evaluation of Root Repair after Damage due to Intentional Contact with Orthodontic Micro-Screw Implants: An in vivo Study

Abstract

Introduction: Orthodontic Micro-Screw Implants (MSIs) are modern orthodontic aids generally used for conditions where orthodontic procedures like mass movement of teeth, rectification of severe overbite, retraction of anterior teeth without compromising the anchorage, molar intrusion for treatment of open bites etc., are required. However, the use of MSIs can lead to complications such as peri-implant mucositis, mucosal ulcerations, root injury of the teeth adjacent to the implants and fracture of the implant. Among these complications, root injury and its squeal may be the most deleterious effect for the patient's oral health. This is the most likely reason why orthodontists are apprehensive about the placement procedures of these MSIs. Aim: To evaluate the root repair after damage due to intentional damage with orthodontic MSIs in humans using a histological method. Materials and Methods: Cases indicated for premolar extraction for orthodontic treatment were selected. Intentional damage using MSIs was made to the roots of four premolars, selected from 10 patients, followed by extraction at time intervals of one day, three weeks, six weeks and 12 weeks. Forty extracted teeth were then demineralised and processed for paraffin embedded sectioning. Haematoxylin and Eosin (H&E) stained sections were analysed using compound light microscope and thickness of newly formed cementum was measured using image-analysing software. Comparison of mean healing cementum thickness in each group was done using ANOVA and unpaired t-test. Results: The stained decalcified sections of all the damaged teeth showed break in the continuity of cementum after one day. Cementum formation began at early third week, and the thickness gradually increased by the end of 12 weeks. Progressive increase in the thickness of newly formed cementum filled the notch completely at the end of 12 weeks. The average mean thickness of cementum was 8.49 µm at the end of three weeks, 69.05 µm at the end of six weeks and 192.40 µm at the end of 12 weeks. The root repair was nearly complete at the end of 12 weeks suggesting that a minimum period of 12 weeks is required for root healing during which further tooth movement should be avoided. Conclusion: The average mean thickness of cementum was 8.49 µm at the end of three weeks, 69.05 µm at the end of six weeks and 192.40 µm at the end of 12 weeks. The root repair was nearly complete at the end of 12 weeks suggesting that a minimum period of 12 weeks is required for root healing during which further tooth movement should be avoided.

Keywords

• cemental repair
• cemental thickness
• orthodontic root resorption