# Effect of the Increasing Operator's Experience on the Miniscrew Survival Rate
###### Abstract  
The aim of our study was to determine the learning curve of orthodontic miniscrew insertion in novices, unsupervised and supervised by experts. Three inexperienced orthodontists, two unsupervised (JA-S, MS) and one supervised (JL) by the experts, inserted 404 AbsoAnchor(r) miniscrews (Dentos, SH131208) into 202 patients for en masse retraction or distalization purposes. Miniscrews were inserted symmetrically on both sides of the maxilla between the 2 nd bicuspid and the 1 st molar. Then, the miniscrew survival rate and the orthodontists' learning curves were estimated. After first 40 insertions JA-S, MS, and JL achieved 73, 70, and 83% of stable miniscrews, respectively. The overall outcome showed that after 74 and 118 insertions, the miniscrew survival rate reached 80% and 85%, respectively, and from that point the learning curve still presented an ascending trend. The success rate increased significantly: by 1.016 times with every procedure (odds ratio = 1.016, \(p\) = 0.006). Since the success rate significantly increased after each miniscrew insertion in the buccal maxillary area, this finding might encourage hesitating clinicians to introduce the miniscrews to the daily practices. Obtained data could also help to plan an effective training system for novice orthodontists. skeletal anchorage; miniscrews; orthodontic treatment +
Footnote †: journal: Medical  
to implanting TADs, were analyzed and--seven years later--compared with an analogous chart obtained by the third clinician [PERSON], a postgraduate student trained and supervised by [PERSON] and [PERSON]. The analyzed study material comprised 202 generally healthy patients (both genders) aged from 20 to 50 years, without symptoms of oral diseases and with good oral hygiene, treated at the Department of Dentofacial Orthopedics and Orthodontics, Wroclaw Medical University. All patients presented with skeletal Class II, with either a hypodivergent or normal angle between the maxillary and mandibular planes, with excellent oral hygiene determined by the Simplified Oral Hygiene Index (OHI-S), which was rated as good (0.0-1.2). Records also showed that the patients with massive frenula, which could potentially irritate the TAD's heads while chewing or during facial muscles activity, were disqualified as the recipients of skeletal anchorage reinforcement. In total, patients received 404 TADs. Within first six months [PERSON] and [PERSON] inserted 160 TADs each, whilst [PERSON] implanted 84 TADs within an analogous period. Miniscrews came from one manufacturer, AbsoAnchor\({}^{\circledR}\) (Dentos, Daegu, South Korea), and served as an anchorage for symmetrical dental movements: either distalization of the maxillary dentition or en masse retraction of six anterior maxillary teeth after extraction of first premolars. Eight-millimeter long, made of titanium alloy (Ti-6 Al-4V), tapered (diameter of 1.3 mm at the neck and 1.2 mm at the apex) miniscrews SH1312-08 were inserted on both sides of the maxilla between the 2 nd bicuspid and the 1 st molar, in a high position (nonkeratinized mucosa) for en masse retraction or in a low position (keratinized mucosa) for distalization purposes.