Periodontal tissue reaction during orthodontic relapse in rat molars

Abstract

Relapse after orthodontic tooth movement (OTM) is an undesirable outcome that involves a number of factors. This study investigated the remodelling of the alveolar bone and related periodontal structures during orthodontic relapse in rat molars. The maxillary right first molars of 35 Wistar rats were moved mesially by a fixed orthodontic appliance for 10 days and the contralateral molars served as controls. The appliances were removed and six animals killed. The molars were allowed to relapse, and the remaining animals were sacrificed at 1, 3, 5, 7, 14, and 21 days. The jaws were sectioned and stained with haematoxylin and eosin and tartrate-resistant acid phosphatase (TRAP). One day after appliance removal, the molars relapsed to a mean 62.5 per cent of the achieved OTM and then steadily relapsed to 86.1 per cent at 21 days. The number of osteoclasts situated along the alveolar bone of the first molars was highest at the end of active treatment and significantly decreased during the relapse period. In the OTM group, osteoclasts were most numerous in the pressure side of the periodontal ligament (PDL). As the molars relapsed over time, the osteoclast distribution shifted, and after 7 days of relapse, TRAP-positive cells were registered in previous pressure and tension sides of the first molars. After 21 days, these cells were concentrated in the distal parts of the PDL of all three maxillary right molars. These results indicate that orthodontic relapse in the rat model occurs rapidly and remodelling of the alveolar bone and PDL plays a central role in the relapse processes of both actively moved and adjacent teeth.

Alkaline phosphatase expression during relapse after orthodontic tooth movement

“…Thus, it can be said that alveolar bone can be considered as an important element in the process of relapse. 5 It is also known that alkaline phosphatase activities are usually higher in the periodontal ligament than those in the other connective tissue.…”

“…4 Relapse in orthodontic treatment can occur quickly, so it is important to provide immediate retention appliance. 5 Bone remodeling that occurs during orthodontic tooth movement is a biological process that involves an acute inflammatory response in periodontal tissue. 6 In the initial phase of orthodontic tooth movement, an acute inflammatory response is involved together with periodontal vasodilatation and leukocyte migration out of the blood vessels of periodontal ligament.…”

“…This indicates that alveolar bone is an important element in relapse process. 5 In other words, relapse is affected by occlusal instability, increased mechanical tension influenced by transepted fibers and alveolar bone resorption caused by osteoclasts. Thus, relapse will occur if there is bone resorption caused by osteoclasts.…”

O efeito da tetraciclina modificada e sinvastatina na recidiva da movimentação dentária no ligamento periodontal de ratos

“…Foi descoberto que a maior parte da recidiva dentária ocorre nas primeiras horas após a remoção da força ortodôntica (FRANZEN et al, 2013). O que leva a crer no papel fundamental da remodelação óssea no mecanismo da recidiva dentária, e relegue a um papel secundário, as fibras gengivais no mecanismo etiológico das recidivas ortodônticas.…”

“…Para alguns autores, a remodelação do osso alveolar e do ligamento periodontal são os maiores responsáveis pela recidiva dentária (FRANZEN et al, 2013), e são dependentes de um A família das metaloproteínases é composta por 25 enzimas proteolíticas que contribuem para a degradação da matriz extracelular do tecido ósseo, sendo produzidas por diversas linhagens celulares como os polimorfonucleares, fibroblastos gengivais, células ósseas e certo tipo de macrófagos (INGMAN et al, 2005), e provavelmente são também responsáveis pelo fenômeno de remodelação óssea presente na recidiva dentária.…”