Evaluation of Dypirone activity on bone remodeling by orthodontic tooth movement in rats

The orthodontic tooth movement (OTM) is an inflammatory process,that combines pathologic and physiologic answers to forces applied to teeth. One of the main mediators responsible by OTM is prostaglandin, which is also related to pain events. Paracetamol (PAR) and Sodium Dypirone (DYP) are analgesic drugs that do not interfere significantly in peripheral inflammatory mediators. Knowning that PAR does not interfere on bone remodeling process during OTM, it seems reasonable to evaluate the DYP effect on bone remodeling process. So, the aim of this study was to evaluate the DYP effect on bone remodeling process using OTM model in male Wistar rats, distributed in groups: Saline (SAL=2 ml/kg), Paracetamol (PAR 200 mg/kg) and Sodium Dypirone, which was divided in 3 subgroup (DIP 25; 75 or 225 mg/kg), given by oral gavage, daily 30 min before installation of orthodontic device between 1st left superior molar and incisive during 4 days, when, then, they were sacrificed and the following parameters were evaluated. 1) microscopic analyses of periodontium through: a) semi-quantitative histological study, morphometric study and immunohistochemical staining to TRAP; b) analyses of mieloperoxidase (MPO) activity in gingiva; 2) Serum dosage of Bone-specific Alkaline Phosphatase (BALP); and 3) Systemic evaluation through: a) leukogram; b) serum dosage of TGO and TGP and c) body mass weight variation. The animals submitted to 4 days of OTM presented large hyalin areas, reduced periodontal ligament thickness and irregular frontal bone tissue [Median: 3 (2-3)], when compared to Normal group (p<0.05). The treatment with PAR [3 (0-3)] was histologically similar to SAL. DYP did not reverse the histological findings [DYP 25=3 (0-3); DYP 75=3 (3-3); DYP 225=3 (2-3)] when compared to controls SAL and PAR. The SAL group presented percentual of hyalin area by 12.5±0.9%, different from Normal group (0%) (p<0.05), but it was similar to groups treated with PAR (12.2±1.2%) and DYP (25=10.7±0.7%; 75=11.0±0.8%; 225=10.8±1.0%). All experimental groups presented positive immunostaining to TRAP. DYP did not prevent the raise of MPO activity when compared to Normal group (p<0.05), however it caused significant reduction of MPO, DYP (25=48.9%; 75=43.1%; 225=43.5%) when compared to SAL or PAR (p<0.05). All groups presented significant reduction of BALP serum levels, SAL=54.3%; PAR=62.4%; DYP (25=59.7%; 75=76.1%; 225=71.2%). The hematological study showed leukocytosis on 4th day on animals of SAL group (23.8±2.1) and PAR (22.3±2.1), marked by neutrophilia ([7.5±1.2] and [5.7±0.9]). DYP reversed leukocytosis DYP (25=16.1±2.2; 75=16.7±1.4; 225=15.4±2.4) reducing the number of neutrophils (p<0.05) DYP (25=2.4±0.6; 75=3.1±0.6; 225=2.8±0.2). There was no significant difference on TGO or TGP serum levels between the groups. DYP did not reversed the initial loss of body weight seen on groups SAL and PAR, however there was a tendency on following the weight curve of normal animals from the 3rd day on. In this way, the results of this study revealed that DYP did not affect the inflammatory response and bone resorption in rats submitted to OTM. Besides, the treatment with DYP did not caused either neutropenia, or alterations in TGO and TGP, and it did not affect significantly the body mass weight, when compared to animals from SAL and PAR groups. Therefore, it is suggested that DYP can be an important pharmacological tool to pain control after orthodontic activation without interfere on tooth movement, or induce systemic risks.Movimentação dentária induzida (MDI) é um processo inflamatório, que combina respostas patológicas e fisiológicas a forças aplicadas aos dentes. Um dos principais mediadores responsáveis pela MDI é a Prostaglandina que também relaciona-se à eventos álgicos. Paracetamol (PAR) e Dipirona Sódica (DIP) são fármacos analgésicos que não interferem significantemente em mediadores inflamatórios periféricos. Sabendo que o PAR não interfere no processo de remodelação óssea durante a MDI, parece-nos razoável avaliar o efeito da DIP no processo de remodelação óssea. Assim o objetivo desse trabalho foi avaliar o efeito da DIP na remodelação óssea utilizando o modelo de MDI em ratos Wistar machos distribuídos em grupos: Salina (SAL=2 ml/kg), Paracetamol (PAR 200 mg/kg) e Dipirona sódica dividido em 3 subgrupos (DIP 25; 75 ou 225 mg/kg), administrados por via oral, diariamente 30 min antes da instalação do dispositivo ortodôntico entre o 1º molar superior esquerdo e os incisivos durante 4 dias, quando, então, foram sacrificados e os seguintes parâmetros avaliados: 1) Análises microscópicas do periodonto através de: a) estudos histológico semi-quantitativo, morfométrico e marcação imunohistoquímica para TRAP; b) análises da atividade da mieloperoxidase (MPO) gengival; 2) Dosagem sérica de Fosfatase Alcalina Óssea (FAO); e 3) Avaliação sistêmica através de: a) leucograma; b) dosagens séricas de TGO e TGP e c) variação de massa corpórea. Os animais submetidos a 4 dias de MDI apresentaram áreas hialinas extensas, espessura de ligamento periodontal diminuída e tecido ósseo frontal irregular [Mediana: 3 (2-3)], quando comparado ao grupo Normal [0 (0-0)] (p<0,05). O tratamento com PAR [3 (0-3)] foi histologicamente semelhante a SAL. DIP não reverteu os achados histológicos [DIP 25=3 (0-3); DIP 75=3 (3-3); DIP 225=3 (2-3)] quando comparados aos controles SAL e PAR. O grupo SAL apresentou percentual de áreas hialínicas de 12,5±0,9%, diferente do grupo Normal (0%) (p<0,05), porém semelhante aos grupos tratados com PAR (12,2±1,2%) e DIP (25=10,7±0,7%; 75=11,0±0,8%; 225=10,8±1,0%). Todos os grupos experimentais apresentaram imunomarcação positiva para TRAP. DIP não impediu o aumento da atividade de MPO quando comparado ao grupo Normal (p<0,05), contudo causou redução significante de MPO DIP (25=48,9%; 75=43,1%; 225=43,5%) quando comparada à SAL ou PAR (p<0,05). Todos os grupos apresentaram redução significante dos níveis de FAO, SAL=54,3%; PAR=62,4%; DIP (25=59,7%; 75=76,1%; 225=71,2%). O estudo hematológico mostrou leucocitose no 4ºd nos animais dos grupos SAL (23,8±2,1) e PAR (22,3±2,1), marcado por neutrofilia ([7,5±1,2] e [5,7±0,9]). DIP reverteu a leucocitose DIP (25=16,1±2,2; 75=16,7±1,4; 225=15,4±2,4) reduzindo o número de neutrófilos (p