推荐理由

When it comes to discussing the clinical value of an RCT with some of our readers, I often hear this comment; “The RCT designed in a University setting does not resemble real world orthodontic treatment. Most clinicians don’t treat an entire group of patients to a specific protocol for comparison with another group. Whether its randomized or not, I treat one patient at a time, making decisions at every appointment to achieve the best treatment result.” If you are one to keep an open mind, I believe your will like this study, and yes…it’s a randomized controlled trial of 64 patients with Class I or II malocclusions and maximum anchorage requirements. All subjects were assigned to one of the two treatment regimens. All had maxillary extractions, either first or second premolars depending on the patient’s need, most used the most appropriate extraoral anchorage device and some, but not all needed a transpalatal arch for a boost in anchorage. In other words, the clinicians did what was most appropriate for each patient while undergoing treatment. The primary purpose of the study was to test whether there were statistically significant between-treatment differences in mesial displacement of the maxillary first molar when maximum anchorage patients were randomized to 2 kinds of treatment; 1) closing spaces in two-steps -retracting canines first, then remaining anterior teeth until full closure of the extraction spaces or 2) the alternative approach of retracting all anterior teeth as a single unit, or the “en masse retraction” approach. Was there a difference in anchorage loss between these approaches?

This is an important paper for two reasons: first because it is one of the few bona fide RCTs in orthodontics that deals with a real clinical question, and second, because it represents a unique collaborative effort among three groups --- a leading-edge statistician at NIH, a group of experienced clinical investigators at the Craniofacial Research Instrumentation Laboratory of the Arthur A Dugoni School of Dentistry, University of the Pacific, and a serious and up-and-coming group of clinical orthodontists at the leading university in mainland China.

Prior to the start of patient selection, a power calculation was conducted to determine the appropriate sample size and inclusion / exclusion criteria for all subjects were stated and adhered to. The subsamples were also well balances for sex, Angle class, starting age, and pretreatment crowding. With the start of treatment, latitude in making all treatment decisions for each individual patient was delegated to the treating clinician because these decisions were considered to be part of the clinician’s unique treatment plan for that individual patient. For more details, be sure to look up the online version of this study.

Take home points:

• The findings demonstrate fairly conclusively that there was no statistically significant difference in mesial displacement of the maxillary first molar between the two samples under examination.
• When the en masse and two-step treatment groups were pooled, mean mesial displacement of the upper molar for all boys in the study was significantly greater than mean mesial displacement for all girls.
• Patients of both genders who started treatment before age 13 had significantly more mesial displacement of the upper first molar than patients who started treatment at ages greater than 13.