# Effect of the Increasing Operator's Experience on the Miniscrew Survival Rate
## 4 Discussion
However, according to the results of the logistic regression analysis, the chance of a successful procedure did not depend on the doctor (their academical or clinical experience) but only on the number of procedures performed when learning a new technique. Although increasing the probability of the miniscrew success by 1.016 times with each procedure may not seem like much, with any learning curve consistency is the key. The role of growing experience, remarkably contributing to the higher success rate of TADs, was also confirmed by the study of [PERSON] et al. [10], which investigated the success rate of the miniscrews serving as anchorage for premolar distalization and molar uprighting, mesialization, distalization, or intrusion. In this study, 11 out of 36 miniscrews failed before the end of treatment, corresponding to a high failure rate of 30%. Again, the failure rate tended to decline with the time duration of the study and with increasing operator's experience or the ascending learning curve. It is natural to expect that clinicians inexperienced in TAD placement are likely to have more potential failures since they are learning a new technique. [PERSON] et al. [3] reported that practitioners who inserted more than 20 self-drilling miniscrews obtained approximately a 3.6-fold higher rate of initial stability compared to TADs implanted by less experienced clinicians. The authors considered \"wobbling\" or an inadequate miniscrew angle as the two major factors responsible for failure caused by an inexperienced operator. At this point, it is worth noting that although [PERSON] et al. [3] achieved a high overall success rate of 93.1% (379/407), they assessed stability only one week after placement, while most miniscrews usually fail several weeks or months after placement [11; 12]. In our study, a period of observation lasted 16 (\(\pm\)5) months; therefore, we avoided bias resulting from reporting \"success\" prematurely. Still raising the issue of comparison of experience and its lack, in the study by [PERSON] et al. [6] there was no significant difference in the failure rates between an oral surgeon and an orthodontist who were both introduced to a new mini-implant system. They both exhibited the same learning curve regardless of the fact that the oral surgeon had inserted hundreds of pre-drilling miniscrews in the past. However, the novel technique, namely, the self-drilling type of miniscrews, ensured the oral surgeon encounter had a high failure rate, and again, such a result confirms the necessity of the gradually progressing learning curve in order to obtain excellence in any orthodontic or dental field. Furthermore, the same oral surgeon [13] lost 17.4% of TADs as a novice in inserting pre-drilling miniscrews, and then--three years later--reduced that number to 9.5% [6]. A lack of experience with TAD placement may possibly result in TAD insertion in the proximity of dental roots, which is recognized as a major factor for TAD loss [14; 15; 16]. In a study by [PERSON] et al. [17], experienced and inexperienced dentists drilled 192 and 240 holes in phantoms, respectively. It turned out that novice operators generated a statistically significant higher occurrence of root contacts (21.3%) than their advanced colleagues (13.5%). Similar results were reported in the in vitro study by [PERSON] et al. [18], where an orthodontist student without experience inserted stainless steel alloy orthodontic miniscrews less accurately than an orthodontist with 10 years of experience, which resulted in more intraoperative complications (root perforations). Therefore, it is no wonder that even fear of complications is a psychological factor restraining inexperienced doctors from performing new surgical procedures [19]. [PERSON] et al. [15] evaluated this issue in a group of 35 orthodontists placing miniscrews for the first time in typodonts with the gingival part covered with an opaque tape. The fear level was measured before and after the experiment and ranked on a 10-point visual scale.