Factors related to the clinical application of orthodontic mini-implants

Orthodontic mini-implants use has been increased. The purpose of this review was to analyze the factors related to the clinical application of orthodontic mini-implants. For the present study, the electronic databases PubMed, MEDLINE, Cochrane, and Google Scholar were searched for available data. The literature search was performed on the articles published from 2003 up to 2017. International peer-reviewed journal articles related to factors which are associated with the clinical application of orthodontic mini-implants were searched. Successful application of mini-implants depends on proper selection of insertion site, proper selection of mini-implant (length, diameter, tapering), proper insertion (site, predrilling, angle, primary stability, injury, and absence of adjacent anatomic structures), absence of inflammation, and proper orthodontic loading. Insertion site and mini-implant characteristics are selected based mainly on cortical bone thickness, bone density, available bone, adjacent anatomic structures, and soft-tissue thickness. Sites of high cortical bone thickness, high cancellous bone density, sufficient available bone, and thin attached gingiva are ideal for mini-implant insertion. Extremely thick cortical bone requires attention. In thick cortical bone, shorter mini-implants can be selected. For sites of low cortical bone thickness and low cancellous bone density, longer and wider mini-implants are indicated. Very thin cortical bone and very low cancellous bone density negatively affect the prognosis of mini-implants. Very narrow implants entail fracture risk. Predrilling is preferred at high bone quality sites, whereas it is used with caution or even be avoided at low bone quality sites. Angled placement might be considered to increase bone-to-implant contact and reduce root injury risk. Loading time depends on insertion torque. Successful application of mini-implants is based on proper insertion site and mini-implant characteristics selection, proper insertion, absence of inflammation, and proper orthodontic loading. Careful assessment of all the factors that might compromise mini-implant success is important for their clinical application.