Relation of soluble RANKL and osteoprotegerin levels in blood and gingival crevicular fluid to the degree of root resorption after orthodontic tooth movement.

The aim of the present study was the determination of the levels of osteoprotegerin and soluble RANKL in blood serum and in gingival crevicular fluid relative to the degree of orthodontic root resorption in a rat model. Blood samples and gingival crevicular fluid were collected from fourteen 6-month-old male Wistar rats weighing 350-500 g. A 25-g closed orthodontic coil spring was inserted between each upper right first molar and the upper incisors. After 21 days of loading, both upper first molars (treated and control) were extracted and studied under microcomputed tomography scanning. Statistical analysis demonstrated a positive linear correlation between the initial concentration of RANKL in blood serum and the degree of root resorption. The ratio of the initial concentrations of osteoprotegerin to RANKL in blood serum proved to be an independent prognostic factor of the degree of root resorption. The initial concentration of RANKL in gingival crevicular fluid showed a negative correlation to the initial concentration of RANKL in blood serum and for a finite range of initial concentrations of osteoprotegerin in gingival crevicular fluid, the dental root seemed protected against extreme external root resorption. Finally, the concentration of osteoprotegerin in blood serum decreased significantly in cases of severe root resorption.

Evaluation of root resorption associated with orthodontic movement in stressed rats.

AIM: The aim of this study was to investigate the effects of acute and chronic systemic stress response on orthodontically induced root resorption. METHODS: Male Wistar rats were restrained during 1 hour a day by stress models of short (3 days) and long duration (40 days), while control group was not submitted to restraint (N.=10/group). The upper left first molars of all rats were moved mesially by a fixed orthodontic appliance exerting 50 g force upon insertion during the last 14 days of the experiment. Then, animals were killed for blood collection and mensuration of plasmatic corticosterone by radioimmunoassay; the tissues around mesial root of the first molar were processed for histological and histochemical techniques with tartrate-resistant acid phosphatase. The degree of root resorption and the number of odontoclasts were evaluated, being the contralateral side of each animal serving as its control (split-mouth design). RESULTS: The results revealed that the plasmatic levels of corticosterone were significantly higher in both the stressed groups than in the control one. There were no significant differences in the degree of root resorption and in the number of odontoclasts on the root between the 3 groups studied. CONCLUSIONS: These results indicate that systemic stress alone can not be considered a risk factor for root resorption induced by orthodontic tooth movement.

Humoral immune response of patients with dental trauma and consequent replacement resorption.

Replacement dental resorption may be a consequence of trauma and may cause dental transplants or reimplants to fail. Previously, we demonstrated the participation of the immunopathological response in inflammatory dental resorption. The induction mechanisms of the two types of dental resorption are well known to be different. The aim of the present study was to observe the immune response of patients who suffered dental trauma with subsequent replacement dental resorption. Four patients with replacement radicular resorption and four healthy individuals with no evidence of radicular resorption participated in the study. The results of ELISA demonstrated that serum from patients with replacement dental resorption contained larger amounts of IgG and smaller amounts of IgM anti-total human-dentin extract and anti-fractions of extract than did serum from control individuals. These results signal the hypothesis that dentin is immunogenic and the serological profile of patients with replacement dental resorption may be identified through biochemical analysis of their blood. Precise screening by this method may allow early diagnosis of dental resorption before it becomes visible radiographically.