Orthodontic TADs, including miniscrews, mini-implants and miniplates, are commonly used in clinical practice to offer absolute anchorage for orthodontic or orthopedic purposes.(7, 20) Since the introduction of orthodontic TADs into orthodontic residency programs in 2005,(17) more and more orthodontists have been using orthodontic TADs in their practice to facilitate orthodontic tooth movement. A recent survey revealed that early attending courses on orthodontic TADs may improve students’ clinical problem-solving skills.(21) In 2008, we initiated clinical courses on orthodontic TADs where students learned how to insert and use TADs for orthodontic purposes at the Department of Orthodontics, West China Hospital of Stomatology, Sichuan University. However, a systematic course on orthodontic TADs was not available until 2018 when a systematic TADs course was incorporated into orthodontic graduate didactic education program. The “FACCI” TADs course included four didactic sessions and one hands-on session. Specifically, the didactic sessions included fundamentals of orthodontic TADs, available anatomic sites for TADs, clinical applications of TADs and complications associated with TAD. Moreover, in the hands-on session, the insertion techniques of TADs at different anatomic sites were demonstrated to the students and the students practiced these skills on skull models.
Before the TADs course, about 67.2% graduate students reported that they used TADs in their practice. This proportion (67.2%) is similar to that for private practitioners (69%) in US while smaller than that for orthodontic residents (83%).(17) In contrast, after the course, 98.4% of the students reported that they would use TADs in their practice. Moreover, only a small proportion (16.4%) of students placed orthodontic TADs by themselves, with a majority (75.4%) of students having their patients’ TADs placed by their clinical supervisors. In contrast, after the course, about one half of students (47.5%) would insert TADs by themselves. These findings could be attributed to the phenomenon that lack of education and training is a major cause for not using orthodontic TADs in clinical practice.(16) In effect, we found that the students were more familiar with the insertion techniques of orthodontic TADs after the course (Fig. 3).
With the development of orthodontic materials and advances in orthodontic techniques, clear aligner appeals to orthodontic patients for its comfort and ease of oral hygiene care.(22, 23) A recent treatment-difficulty evaluation system on clear aligner revealed that clear aligner had its distinct biochemical system and different types of difficult tooth movements as compared to fixed appliances,(24) suggesting that clear aligner may require more additional anchorage than fixed appliances. A recent finite-element study revealed that an anterior inter-radicular miniscrew between central incisors was effective for incisor intrusion and palatal torquing during anterior retraction.(25) However, we found that the percentage of orthodontic patients was similar between aligner patients (23.2%) and fixed patients (25.8%).
It was reported that the most frequently use of TADs was for anterior en-masse retraction and the augmentation of posterior anchorage.(17) In addition to anterior en-masse retraction, TADs are commonly used for molar distalization.(5) Consistently, in the present study, we found that TADs were most frequently used for anterior en-masse retraction and molar distalization. For anterior en-masse retraction, TADs are often placed at maxillary posterior interradicular regions (for sagittal control) and maxillary anterior interradicular region (for vertical control of incisors). This could explain the phenomenon that the students were most familiar with the insertion technique of TADs at maxillary posterior interradicular region and maxillary anterior interradicular region. Moreover, the two aforementioned regions are easier to place TADs due to ease of operation and good surgical view as compared to the two least familiar anatomic sites, i.e., anterior nasal spine and mandibular ramus. The insertion of TADs at anterior nasal spine is indicated for patients who require large-scale incisor intrusion with limited interradicular space. For the insertion of TADs at anterior nasal spine, flap reflection is required to expose the anterior nasal spine and extension hooks may be needed for the ease of force application, which is more difficult and technique-sensitive than placing TADs at interradicular regions. The insertion of TADs at mandibular ramus is often indicated for orthodontic patients with impacted mandibular molars.(4, 7) The procedures of placing TADs at the ramus region is very difficult. It requires tough flap reflection and pre-drilling due to medial pterygoid muscle lying on the ramus region and thick and high-density cortex. Despite the difficult insertion technique associated with these regions, through the hands-on module, students were significantly more familiar with the insertion technique at all the anatomic sites especially the anterior nasal spine and the mandibular ramus region.
We found that TADs were least frequently used for molar protraction and temporary prosthesis in clinical practice among the students. This may be attributed to the fact that fewer patients require molar protraction or temporary prosthesis as compared to other types of orthodontic tooth movement. Moreover, molar protraction with the aid of TADs requires meticulous biomechanical design and prolonged treatment duration,(11, 26) rendering patients to choose implant prosthesis instead of molar protraction for missing molar space.
We found that the scales of need of TADs for different tooth movements were high for both before (range: 3.0-4.2) and after (range: 3.3–4.1) the course, suggesting that TADs are important adjuncts for efficient orthodontic tooth movements in orthodontic practice. Interestingly, the scales of need of TADs for different tooth movements were similar between before and after the course, except for molar protraction. Since TADs were least frequently used for molar protraction before the course, the need of TADs for molar protraction was not high. Demonstration of clinical cases of successful molar protraction in this course fostered students to develop confidence on protracting molars with TADs, resulting in higher scale of need of TADs for molar protraction after the course.
Despite the clinical effectiveness of TADs, orthodontic TADs are still associated with several complications or adverse effects, e.g., root contact, facture of TADs, soft tissue inflammation and loosening.(27, 28) The incidence of these complications was low in clinical practice, especially fracture of TADs, which could explain why students were not familiar with the skills of addressing complications associated with TADs. Moreover, root contact or perforation by orthodontic TADs requires multidisciplinary treatments,(29) which is beyond the skills mastered by the graduate students. Thus, learning the skills of addressing these complications was highly needed before the course. After the course, the students reported that they were more familiar with the skills of addressing complications associated with TADs, indicating that objectives of the course on TADs was achieved.