Pull-out strength of unloaded orthodontic mini-screws at different healing periods. In vivo study in Beagle dogs

Com o objetivo de avaliar a influência do processo de cicatrização óssea sobre o desempenho biomecânico de mini-parafusos utilizados como ancoragem em ortodontia, foram inseridos 60 mini-parafusos (1,6 x 6mm) auto-rosqueantes (Tomas® Dentaurum / Germany) na maxila e na mandíbula de 5 cães adultos da Raça Beagle. Os pré-molares (P1, P2, P3, P4) superiores e inferiores foram extraídos três meses antes da inserção vertical dos mini-parafusos. Os cães foram sacrificados nos dias 0, 2, 7, 15 e 30 após a instalação dos mini-parafusos. Os maxilares foram dissecados e os corpos de provas contendo os mini-parafusos foram preparados para avaliação da resistência à tração na Máquina de Ensaios Universal EMIC® 2000, utilizando uma garra desenvolvida especificamente para este estudo. Os valores e gráficos correspondentes ao desempenho mecânico foram imediatamente gerados e registrados pelo programa de aquisição Tesc 3.01®. As possíveis diferenças entre os períodos de cicatrização foram avaliadas pela análise de variância (ANOVA) e pelo teste de comparações múltiplas de Bonferroni. Os resultados demonstraram um índice de sucesso de 100% dos mini-parafusos inseridos. Após a dissecação dos segmentos ósseos, verificou-se que em alguns casos a superfície da rosca ficou parcialmente exposta, razão pela qual o cálculo da resistência à tração (média na maxila de: 141,76 ± 92,82 Ncm a 237,02 ± 78,34 Ncm e média na mandíbula de: 156,86 ± 75,55 Ncm a 328,76 ± 82,17 Ncm) foi feito em relação à área real de inserção (maxila: 24,01 ± 6,09mm2 e mandíbula: 22,88 ± 5,31mm2), observando-se um valor médio por mm2 significativamente maior na mandíbula (11,60 ± 5,22 Ncm) quando comparado à maxila (8,22 ± 5,04 Ncm). A relação entre a intensidade da força de tração (Ncm), superfície inserida (mm2) e períodos de cicatrização não apresentaram diferenças significantes (p= 0,126). Com base nestes resultados podemos concluir que os mini-parafusos avaliados demonstraram excelente desempenho biomecânico nos diferentes períodos de cicatrização analisados, apresentando maior resistência à tração no osso mandibular.With the purpose of evaluating the influence of bone healing process on the biomechanical performance of mini-screws used as anchorage in orthodontics, 60 self-tapping (Tomas® - Dentaurum / Germany) mini-screws were inserted (1.6 x 6 mm) in the maxilla and in the mandible of 5 adult Beagle dogs. Upper and lower premolars (P1, P2, P3, P4) were extracted three months before the vertical insertion of mini-screws. The dogs were sacrified on days 0, 2, 7, 15 and 30 after the insertion of mini-screws. The jaws were dissected and the bone blocks, containing the miniscrews, were prepared to the axial pull-out strength in the Universal Testing Machine EMIC ® 2000, using a device developed specifically for this study. The values and graphics for the mechanical performance were immediately generated and recorded by the acquisition program. The clinical success rate of mini-screws was 100%. The possible differences between the healing periods were analyzed by Bonferroni´s multiple test comparisons and variance analysis (ANOVA). After the dissection of the bone segments, it was found that in some cases, the mini-screw thread was not fully inserted into the bone, reason why the pull-out strength (average of the maxilla: 141.76 ± 92.82 Ncm to 237.02 ± 78.34 Ncm and average in the mandible of 156.86 ± 75.55 Ncm to 328.76 ± 82.17 Ncm) was evaluated in relation to the real area of insertion (maxilla: 24.01 ± 6.09 mm2 and mandible: 22.88 ± 5.31 mm2). Mean value/mm2 were significantly higher in the mandible (11.60 ± 5.22 Ncm/mm2) than the maxilla (8.22 ± 5.04 Ncm/mm2). There was no statistically significant difference (p = 0126) between pull-out strength (Ncm), surface inserted (mm2) and the observed healing periods. Based on these results it can be concluded that mini-screws evaluated in this study demonstrated an excellent biomechanical behavior in all different periods of healing, showing more resistance to traction in the mandibular bone

Apicotomy as Treatment for Failure of Orthodontic Traction

Objective. The purpose of this study was to present a case report that demonstrated primary failure in a tooth traction that was subsequently treated with apicotomy technique. Case Report. A 10-year-old girl had an impacted upper right canine with increased pericoronal space, which was apparent on a radiographic image. The right maxillary sinus showed an opacity suggesting sinusitis. The presumptive diagnosis was dentigerous cyst associated with maxillary sinus infection. The plan for treatment included treatment of the sinus infection and cystic lesion and orthodontic traction of the canine after surgical exposure and bonding of an orthodontic appliance. The surgical procedure, canine position, root dilaceration, and probably apical ankylosis acted in the primary failure of the orthodontic traction. Surgical apical cut of the displaced teeth was performed, and tooth position in the dental arch was possible, with a positive response to the pulp vitality test. Conclusion. Apicotomy is an effective technique to treat severe canine displacement and primary orthodontic traction failure of palatally displaced canines

Enamel Roughness Changes after Removal of Orthodontic Adhesive

The aim of this study was to evaluate enamel roughness, quality of the enamel surfaces and time duration comparing different orthodontic adhesive removal protocols. Premolars were used to test three adhesive removal methods (n = 20): five-blade carbide bur, 30-blade carbide bur, and ultrasonic diamond bur. Bracket was bonded using TransbondTM XT adhesive. Roughness with different parameters was measured before bracket bonding and after adhesive remnants removal. Micromorphological analysis of enamel surface (n = 5) was performed by SEM images and categorized in enamel damage index—“perfect”; “satisfying”; “imperfect”; and “unacceptable”. Time was measured in seconds. All removal methods caused increased roughness in relation to Ra, Rq, and Rz parameters (X axis) comparing to healthy enamel surface. Enamel surface resulted from removal using five-blade burs was scored as satisfactory. Carbide bur groups decreased the roughness values of Ra, Rq, and Rz parameters on the Y axis and enamel surface was considered unacceptable. The 30-blade group increased symmetry (Rsk) and flattening (Rku) parameters of roughness and surface was scored as unsatisfactory. Diamond bur removed adhesive in 54.8 s, faster than five-blade carbide bur. The five-blade bur group resulted in less enamel roughness than the 30-blade and diamond groups