The optimal insertion torque (IT) for orthodontic anchoring screws (OASs) was hypothesized to vary with OAS features and insertion methods. This review examines the indexed English literature, to determine the appropriate IT range for OAS success based on area of insertion and OAS features. Eleven original articles with OAS placement in humans including IT and success rate were selected and were used to evaluate the relationships among IT, success rates, screw design, and placement methods at different sites. The ITs and success rates ranged from 6.0 ± 3.2 to 15.7 ± 2.3 Ncm and from 62.5 to 100.0% in the upper and lower buccal alveolar areas, respectively. For the mid-palatal area, the range was 14.5 ± 1.6 to 25.6 ± 5.5 Ncm and 83.0 to 100.0%, respectively. ITs of 5–12 and 6–14 Ncm were found to be optimal for the commonly used φ1.5–1.7 mm OASs in the upper and lower interproximal areas, respectively. In the mid-palatal suture area, ITs of 11–16 and 20–25 Ncm were considered suitable for tapered φ1.5 mm and φ2.0 mm OASs, respectively. Although identified optimal IT ranges deserve the recommendations, care must be taken to monitor the IT during placement constantly.

This study used finite element (FE) analysis to investigate the stability of miniscrews (screws) placed at the median palate. FE models with variable suture maturity and screw-suture distances were used to examine the relationship with screw stability. Four groups were classified by extent of maturation of the midpalatal suture (0%, 60%, 75%, and 100%). The placement position was set at the center of the suture (0.0 mm), or 0.5, 1.0, and 1.5 mm to the side of the suture, and von Mises stress values in bone and screw displacement were compared among models. The stress value for the unsutured model, in which the screw was placed at the center of the suture, was greater than 30 MPa. Stress values for models in which screws were placed to the side (0.5-1.5 mm) were less than 28 MPa. Maximum screw displacement was greater in the 0.0-mm incomplete suture model than at other placement positions. Because bone conditions vary among patients, placement position and suture maturation should be examined on cone beam-computed tomography images, to ensure screw stability.

This study was performed to investigate the influence of pre-etching area and functional monomers in orthodontic adhesive pastes on enamel bond strength. Bovine enamel was partially pre-etched with phosphoric acid for 30 s over areas with a diameter of 1.0, 2.0 or 3.0 mm, and metal brackets were then bonded with or without functional monomers in the orthodontic adhesive paste. For the baseline groups, the whole adherent area was pre-etched. The shear bond strength (SBS) and adhesive remnant index (ARI) were determined. The adhesive paste/enamel interfaces were observed by scanning electron microscopy (SEM). Although the adhesive paste with functional monomers showed higher SBS than the functional monomer-free adhesive paste in all groups, there were no significant differences in SBS between them regardless of the pre-etched area. The SBS increased with increasing pre-etched area in both orthodontic adhesive pastes. In SEM images of adhesive paste/enamel interfaces, although adhesive with functional monomers showed excellent adaptation, the functional monomer-free adhesive paste showed gap formation at the interface. These findings suggested that the pre-etching area greatly influenced bond strength, regardless of the presence or absence of the functional monomer in the orthodontic adhesive paste.