Comparisons of the effects of systemic administration of L-thyroxine and doxycycline on orthodontically induced root resorption in rats

Abstract

The aim of this study was to histologically evaluate and compare the effects of the systemic administration of L-thyroxine (TX) and doxycycline (DX) on orthodontically induced root resorption, Twenty-eight male 50- to 60-day-old Wistar rats were used. Seven rats served as the baseline control. Seven animals received TX (20 μg/kg bodyweight/day) and seven DX (1.2 mg/kg bodyweight/day), by means of a mini-osmotic pump implanted subcutaneously. Seven rats were separated as a sham, in order to evaluate the pure effect of the surgical procedure on the animals' health. Tooth movement (TM) was achieved with a continuous force of 50 g by placing Elgiloy coil springs between the right maxillary first molar and incisors for 14 days. The animals were sacrificed and specimens containing the appliance and maxillary tooth-bearing segments were processed for light microscopy. The surface area of root resorption lacunae was measured histomorphometrically using digital photomicrographs. To evaluate the resorptive changes on the molar root surface of each group, scanning electron microscopy (SEM) examinations were also carried out. Statistical evaluation of root resorption percentages was performed using Kruskal-Wallis analysis of variance test. Multiple comparisons were determined by the Student-Newman-Keuls method. The level of significance was set at P < 0.05. Histomorphometric analysis of root resorption, expressed as a percentage, showed that the average relative root resorption affecting the maxillary molars on the TM side was 0.32 ± 0.25 in the TX and 0.26 ± 0.06 in the DX groups and 2.19 ± 0.86 in the control. Statistically significant inhibition of root resorption was determined both in the TX and DX groups (P < 0.001) on the TM side. There was no statistically significant difference in relative root resorption between the TX and DX groups. Systemic administration of TX and DX demonstrated similar effects on root resorption in rats and may have inhibitory effects on orthodontically induced resorptive activity.

The effects of low-level laser therapy on orthodontically induced root resorption

“…Furthermore, a significant reduction in root length may cause an unfavorable crown/root ratio of the affected teeth with increased mobility and periodontal destruction inducing vulnerability to occlusal forces [16]. Up to the present, several pharmacological agents have been tested to inhibit orthodontically induced root resorption (OIIRR) [4][5][6][7]. However, none of them get into clinical use due to their possible systemic effects or adverse effects on orthodontic tooth movement.…”

“…Among treated adolescents, some form of orthodontically induced inflammatory root resorption (OIIRR) incidence is reported as 93 % while 10-20 % of the cases had severe resorption of >3 mm [2,3]. Several chemicals/pharmacological agents (PGE 2 , calcium gluconate, doxycycline, L-thyroxin, bisphosphonates, tetracycline, fluoride) have been tested to prevent or to repair this pathological condition [4][5][6][7]. Although most of them were found effective, they did not get into clinical use due to their possible systemic or adverse effects on orthodontic tooth movement.…”

An Extensive Review of Literature: Considering Bone Reaction To Different Agents In Orthodontically Induced Root And Alveolar Resorption

“…37 However, it was demonstrated in a study that although the level of parathyroid hormone in serum plays an important role in the regulation of the resorptive activity in bone, a change in serum calcium level is a determining factor for root resorption. 38 In addition to parathyroid hormone, bone resorptive activity is also regulated by L-thyroxine. 39,40 Thyroid hormone plays a crucial role in normal growth and development of vertebrate bones.…”

Effect of Low-Level Laser Therapy on Orthodontic Induced Inflamatory Root Resorption in Rats

“…In order to minimize and/or repair the OIIRR; several chemicals and methods have been tested on human and animal study models. Some of these chemicals are fluoride (12), steroidal and nonsteroidal drugs (4,13), calcitonin (14), human growth hormone (15), clodronate (16), Icariin (17), and tetracycline (5,18). Other non-invasive and clinically suitable potential methods to prevent and repair the OIIRR are low-intensity pulsed ultrasound (LIPUS) (19) and low-level laser therapy (LLLT) (1,4,5).…”