Stability of Mini-Screws Invading the Dental Roots and Their Impact on the Paradental Tissues in Beagles

Abstract

Objective: To examine the stability of mini-screws that invade a dental root by measuring the retention period/failure rate, and to illustrate their effects on paradental tissues. Materials and Methods: Three adult male beagle dogs received 48 orthodontic mini-screws. Half of the mini-screws were implanted to invade the roots, and the rest were placed in the middle of the alveolar bone. Half of the mini-screws were loaded immediately. The retention period of the mini-screws was documented. The dogs were euthanized after 8 weeks, and tissue samples were examined histologically. Results:The failure rate of the mini-screws that invaded the roots was 79.2%, and that of the mini-screws in the middle of the alveolar bone was 8.3%. The application of force had little effect on the failed mini-screws. Moderately injured roots were repaired with osteoid and/or cementoid tissues with normal periodontal ligaments, followed by recovery of the original configuration.

Root and Bone Response to the Proximity of a Mini-Implant under Orthodontic Loading

“…15 There may also be direct root contact, which can affect the stability of the mini-implant. 16 The damaged root might be influenced by the periodontal ligament (PDL), the cementoid calcified tissue, or the bone to heal. [16][17][18] Ankylosis can occur on the resorbed root.…”

“…16 The damaged root might be influenced by the periodontal ligament (PDL), the cementoid calcified tissue, or the bone to heal. [16][17][18] Ankylosis can occur on the resorbed root. 16 However, there are few studies reporting the histological evaluation of root proximity, PDL contact, root contact, or root perforation by a mini-implant or the distance required to induce a histological reaction of the root.…”

“…[16][17][18] Ankylosis can occur on the resorbed root. 16 However, there are few studies reporting the histological evaluation of root proximity, PDL contact, root contact, or root perforation by a mini-implant or the distance required to induce a histological reaction of the root. Therefore, this study was designed to evaluate the histological reaction of the root, PDL, and bone tissue at various root proximities of the miniimplant and the distance needed to stimulate a histological reaction in the beagle.…”

Estudo in vitro da perfuração radicular por diferentes diâmetros de mini-implantes

“…Outros parâmetros clínicos que podem ser utilizados para evitar ou minimizar estas lesões indesejadas seriam o torque e a carga axial de inserção do mini-implante. Estudos experimentais em animais demonstraram que os torques de inserção dos miniimplantes ao tocarem as raízes dentárias foram maiores do que aqueles onde não havia o contato com os dentes, ou seja, apenas com o osso alveolar (BRISCENO et al, 2009;WILMES et al, 2008b Além disso, quanto maior o diâmetro, maior o torque de inserção e de fratura (BARROS et al, 2011;JOLLEY;HWANG, 2008 (CHENG et al, 2004;KANG et al, 2009;POGGIO et al, 2006 KAVANAGH, 2012;MIYAWAKI et al, 2003). Verificaram que o torque de inserção alcançou valores duas vezes maiores quando os mini-implantes contactaram as raízes dentárias comparados aos sem contato radicular.…”

“…Os resultados destas análises corroboram com a afirmação de Kang et al (2009) de que os mini-implantes não conseguem perfurar facilmente a raiz dentária e, assim, deslizam sobre a superfície radicular lesionando os tecidos adjacentes.…”