ASSESSMENT OF BONE ALTERATIONS IN HYPERCHOLESTEROLEMIC RATS UNDERGOING EXPERIMENTAL ORTHODONTIC MOVEMENT

Abstract: Objectives: To analyze the effects of experimental orthodontics (EO) on the alveolar bone tissue of hypercholesterolemic rats. Methods: Eighteen weaned Wistar rats (60±5g) were divided into two groups of n=9, Group 1 (G1) received a control diet (CD); Group 2 (G2) received a high-cholesterol diet (HCD). After five weeks, extraction of the left lower second molar and installation of an orthodontic device on the first molar (1M) with a force of 17 grams towards the post-extraction alveolus were performed. Following the installation, administration of CD and HCD continued for two more weeks. At seven weeks, the rats were euthanized. Blood was collected via cardiac puncture to study the lipid profile. Microtomography was performed to study tooth movement (TM), interradicular bone (IB) and bucal cortical (BC) and lingual cortical (LC). The following morphometric points were measured: M1(mesial 1M), D1(distal 1M), M3(mesial of third molar); D3(distal of third molar), Point F (spix spine). Also, a qualitative analysis was performed to measure bone mineral density(BMD) and cortical mineral density (CMD) and a quantitative analysis to know %BV/TV, Trabecular thickness (Tb.Th), number of trabeculae (Tb.N) and trabecular separation (Tb.Sp). Statistical analysis was performed with Student's t-test and Mann-Whitney U test (p<0.05). Results: All results were expressed as mean±SD except Tb.N, Tb.Sp, BMD and CMD which were expressed as median(Q1/Q3). Serum TC was higher in G2 (61±7.73mg/dl vs.168.7±39.92 mg/dl; p<0.0001). TM did not show significant variations between groups. For bone tissue the results were: BV/TV%: IB(G1:10.65±0.75 vs G2:3.14±0.45); BC(G1:10. 74±0.67 vs G2:2.08±0.49); LC(G1:9.78±0.46, vs G2:1.63±0.55);Tb.Th(mm):G1:5.09±0.37 vs G2:1.39±0.55;Tb.N(1/mm):G1:2.19(2.11/2.22) vs G2:0.99(0.76/1.35);Tb.Sp(mm):G1:3,09 (3,01/3,12) vs G2:4,83 (4,53/5,24);BMD(gr/cm3)for IB: G1:2,36(1,96/2,52) vs G2: 1.44(1.39/1.53);CMD(gr/cm3):for BC G1: 2.10 (2.07/2.15) vs G2:0.75(0.63/1.00); for LC G1:1.70(1.61/1.72) vs G2:0.46(0.34/0.50). All these were statistically significant (p<0.05). Conclusions: EO produces a significant deterioration of alveolar bone tissue in hypercholesterolemic rats. The results would condition orthodontic therapies in patients with high cholesterol levels.