Survey of Orthodontists' Attitudes and Experiences Regarding Miniscrew Implants

Each certified network orthodontist was e-mailed a secure link to a web-based survey. This recollection- and opinion-based questionnaire was divided into six sections: practice characteristics, treatment planning, practice management, miniscrew placement, miniscrew complications and failures, and miniscrew removal.

Blinded, annotated data were extracted for statistical analysis. Cross-tabulations were performed as appropriate, and the significance of observed differences was assessed by means of the Wilcoxon rank-sum, chi-square, or Fisher exact test as appropriate. A "p" value of .05 or less was considered statistically significant.

Results

Practice Characteristics

In all, 47 of 59 eligible orthodontists completed the survey, for an 80% response rate. Respondents were distributed geographically among all five network states, and the 47 practitioners were graduates of 28 different residency programs. Most respondents (57%) had been in practice more than 10 years; only three had been out of residency for less than two years.

Molar protraction was the most commonly reported treatment indication (64%), followed by indirect anchorage for space closure (55%) and intrusion of supererupted teeth (52%; Table 1). A panoramic radiograph was the most requested or readily available diagnostic tool used to guide miniscrew placement. For pain management, most respondents (69%) reported using a combination of topical and local anesthetics; 38% said they administered only a strong topical agent, while 10% used a full nerve block.

The three preferred miniscrew systems were those manufactured by 3M Unitek^*, Dentaurum^**, and Ormco^***, while 10 other systems were used by far fewer doctors. The 1.4mm- and 1.6mm- diamater miniscrews were most popular, in lengths of 8-10mm. Regardless of the system used, 28 of 29 respondents reported always or frequently loading the implants with force immediately after placement.

A cross-tabulation of practice variables with miniscrew placement experience (in-office vs. referred) is shows in Table 2. No variables tested were statistically significant.

Miniscrew Complications

The most commonly reported biological, mechanical, or iatrogenic complications of miniscrew treatment (Fig. 1) were screw loosening (76%), soft-tissue overgrowth/irritation (69%), and irritation caused by auxiliary springs(67%). There were no reported cases of tooth ankylosis, sinus perforation, or subcutaneous emphysema.

The most commonly cited side effect of miniscrew usage was excessive torquing/tipping of teeth, with 32% of the respondents reporting at least one occurrence. Much less commonly reported side effects were excessive extrusion/intrusion of teeth (7%) and root resorption (7%).

Most respondents (82%) were satisfied with the performance of miniscrews in their practices. Only one respondent who had personally placed miniscrews reported being dissatisfied enough to stop using the devices. Of the 23 practitioners who had referred miniscrew placement, six were dissatisfied. Reasons cited for dissatisfaction were that the procedure was not well tolerated by patients and that tooth movement was not as effective as hoped.

Discussion

Although miniscrew usage has been less common within the United States than in other parts of the world,¹⁰orthodontists practicing in the five Northwest PRECEDENT states appear to be adopting this technique rapidly.

Results of our study are comparable with those of two larger-scale published surveys of orthodontists' experiences with miniscrews.^9,10 Our study had a higher response rate, but the potential number of participants was limited, whereas JCO invited all orthodontists in the United States⁹ and the AAO surveyed all its U.S. and international members.¹⁰ The proportion of respondents placing miniscrews personally in our study (43%) was identical to that reported in the JCO survey⁹ and somewhat lower than that in the AAO member survey (55%).¹⁰ Referral to oral surgeons over periodontists was preferred consistently across all three studies.

Our network respondents and the AAO respondents¹⁰ agreed regarding the use of diagnostic tools, anesthesia protocols, and the timing of force loading. A panoramic radiograph was the primary placement guide in both surveys, and near-equal percentages reported using a combination of topical and local anesthetics rather than topical agents alone. Immediate loading within two weeks after miniscrew placement was performed by about 80% of both samples, in agreement with the 2007 Cochrane Review's recommendations on the appropriateness of early loading.⁸ These results suggest an evolving consensus regarding certain aspects of miniscrew treatment--a trend noted by Baumgaertel and colleagues.¹¹

The most common miniscrew treatment indications differed slightly among our network members, AAO members, and JCO survey respondents. Although space closure and bodily movement were the most commonly reported indications in both the PRECEDENT and AAO groups,¹⁰ respondents to the JCO survey were more likely to use miniscrews for molar intrusion⁹--an application that has been linked to higher failure rates in two studies.^3,12 By comparison, the most common indication for miniscrew placement in previous studies has been maxillary anterior retraction, followed by molar protraction and posterior intrusion, with other types of treatment in a clear minority.^3,4,13,14

Two recent systematic reviews have suggested that implant diameters of less than 1.3mm or greater than 2mm, as well as lengths of less than 8mm, are more susceptible to failure.^15,16 Our network respondents' preferred miniscrew diameters of 1.4mm or 1.6mm and lengths of 8-10mm agreed with these guidelines.