The Orthodontics Professors
the latest in contemporary & evidence-based orthodontics
BY TATE H. JACKSON
A group from Belgium has published results of a Randomized Controlled Trial to evaluate the effect of flapless corticotomies on tooth movement.
24 consecutively-treated adult patients were randomized to 2 groups: 1) a control group treated with non-extraction alignment or 2) an intervention group treated with non-extraction alignment and piezocision one week after brackets were bonded. All participants had similar malocclusions with only mild – moderate crowding.
Both groups were treated using self-ligating brackets (Damon) and a standardized archwire sequence with a 2 week recall interval. A single blinded orthodontist validated readiness for appliance removal – or gave guidance for further adjustments to be made – based on an evaluation of dental casts and “5 criteria”.
For the intervention group, piezocision was accomplished using a 5mm x 3mm piezoelectric device apical to each interdental papilla. An incision was created before the corticotomy, but no sutures were used. Where root proximity might be a concern, corticotomy was avoided.
For the piezocision group, treatment was 43% faster. That means that the total treatment time was about 7 months less (about 11 months of total treatment time vs. 18 months in the control group). As treatment proceeded, the difference decreased between the two groups in terms of time spent in each archwire, suggesting a decreasing effect of the corticotomies over time.
No adverse outcomes in terms of periodontal health or root resorption were reported – nor were there any apparent differences (increase or decreases) in alveolar bone support or thickness, as assessed by CBCT. 50% of patients experienced some degree of scarring.
WHAT THE PROFESSOR THINKS
Despite some minor drawbacks, this study is one that provides some useful information to clinicians with a patient population who demand accelerated treatment. A description of the randomization process and the “5 criteria” used to determine if treatment was complete would be very helpful.
Nonetheless, using a single blinded examiner who evaluated casts and used objective criteria to determine when treatment was complete for both the piezocision and the control groups was a clever design. Using total treatment time as the outcome, rather than just the time to initial alignment, makes the study results more relevant to practicing clinicians.
As in previous reports, the acceleratory phenomenon was limited to a period of time early in treatment (the authors suggest about 4 months). For non-extraction patients with mild-moderate crowding, a single procedure was enough to yield a clinically-relevant reduction in treatment time of 7 months. It is imperative to note that the reported recall rate during treatment was 2 weeks. That means treatment is accelerated, but it is no more efficient for the patient or the orthodontist – since an increased number of office visits would be required.
The findings presented in this study suggest that less-invasive piezocision may carry with it a low risk of adverse outcomes. No participants experienced a loss of root structure or bony support, as judged using CBCT. Interestingly however, half of the piezocision participants did experience scarring of the gingiva, an outcome that could have very negative effects on a patient with a high esthetic demand.
For the practicing orthodontist, this study carries with it some helpful information to guide patients when they ask for quicker treatment:
Will treatment time be shorter? Yes.
By how much? About 7 months.
Are there risks? Yes – and we still do not know the full extent of those risks, including the esthetic risk of scarred gingiva.
Will it be more convenient? No. (Remember, the reported recall interval in this study was 2 weeks.)
Article Reviewed: Charavet C, et al. Localized Piezoelectric Alveolar Decortication for Orthodontic Treatment in Adults: A Randomized Controlled Trial. J Dent Res. April 2016.
BY LORNE D. KOROLUK
A recent study in the AJO-DO summarized findings from a Cochrane Review that re-investigated evidence regarding orthodontic treatment for prominent maxillary incisors and Class II malocclusion in children. The authors identified three randomized clinical trials (Florida, North Carolina, and United Kingdom) that compared outcomes of two-phase treatment in the mixed dentition and permanent dentition versus single phase treatment in the permanent dentition.
Data from all three clinical trials showed no statistically significant difference between final overjet, final ANB, final PAR score and self-concept score. Early functional appliance therapy, however, was shown to reduce the risk of incisor trauma which was reported as a number needed to treat (NNT=10). This suggests an orthodontist must treat 10 such patients in order to prevent 1 incidence of new incisal trauma. Analysis of early headgear treatment in the North Carolina and Florida studies showed a significant reduction in the risk for new incisor trauma that prevented 1 incidence of new trauma for every 6 patients treated. No differences were found between early functional appliance and headgear treatment for all variables, including incidence of trauma.
In the discussion the authors raise some very salient issues and advise caution interpreting the results. The authors conclude that there are no advantages in providing 2-phase treatment compared to single-phase treatment in early adolescence, except for a potential reduction in risk for new incisor trauma.
WHAT THE PROFESSOR THINKS
The authors have used systematic review and meta-analysis to combine data from three groups of randomized clinical trials to increase the power of the statistical analysis. In the analysis, trauma is very simplistically defined as new incisor trauma versus no new incisor trauma. Incisor trauma consists of a very wide continuum ranging from minor craze lines and enamel fractures to very serious fractures, luxations and avulsion.
The Florida and North Carolina studies used the Ellis and NHANES III classifications respectively to identify the severity of new trauma. The United Kingdom study did not rate the severity of trauma, but instead simply coded trauma as yes or no. Readers must very carefully apply these findings to individual patients. The yes / no definition of new incisor trauma over-simplifies the clinical implications of the findings.
Further, there was wide variability associated with the NNT statistics reported. Careful scrutiny of the statistical analysis shows that risk reduction with the functional appliance could range from 2% to 54% and from 13% to 61% for headgear. Similarly, the confidence intervals for the measure of treatment impact as NNT are quite large: 5 to 175 for functional appliance and 3 to 23 for headgear.
The most important sentence in this article is, “the prevention of trauma should not be the only reason for routinely providing treatment for Class II malocclusion. The decision should be taken as part of a risk evaluation….”
The existing literature, without question, has shown that increased overjet is a significant risk factor for traumatic dental injuries and incisor trauma. Logically, one can infer that reducing overjet should reduce future trauma. Overjet, however, is not the sole risk factor. Dental factors such as overjet, lip incompetence, maxillary protrusion, Class II relationship, and past history of dental trauma are important risk factors. Psychosocial, environmental, and behavioral factors also determine an individual’s future risk. Behavioral and psychosocial factors may be even more important that dental factors, since they place the individual and their teeth in the at-risk situations in the first place.
Clinicians must compare the cost of potentially lengthy orthodontic treatment to reduce risk of incisor trauma to the cost of treating incisor trauma and its potential future sequelae.
One of the North Carolina studies(1) showed that the expected-cost of new incisor trauma was significantly less than the cost of orthodontic intervention to reduce future risk.
Hopefully clinicians (and organized orthodontics) don’t ignore the numerous cautionary warnings by the authors. A narrow interpretation of the results to justify early orthodontic treatment as a necessity for all children in the mixed dentition with increased overjet is certainly not an evidence-based conclusion.
Article Reviewed: Thiruvenkatachari B, Harrison J, Worthington H, O'Brien K. Early orthodontic treatment for Class II malocclusion reduces the chance of incisal trauma: Results of a Cochrane systematic review. Am J Orthod Dentofacial Orthop 2015;148:47-59
BY TATE H. JACKSON
A recent study published in the Angle Orthodontist compared two cohorts of children in Finland in terms of the timing of eruption of permanent teeth. The historic group of children born from 1976-1980 included more than 1,500 children from rural parts of the country. The more recent group, born from 1999-2002, included 483 children who lived in a less rural environment and were followed longitudinally.
Permanent tooth eruption was observed clinically and graded using consistent criteria for both groups. Two age ranges were the focus of the study: 1) age 6-9 years, to include the early mixed-dentition transition and 2) age 9-12 years, to include the late transition to permanent dentition.
Compared to the 1980 group, the 2000 group showed more advanced permanent tooth eruption during the first age range (6-9 years). There was no difference, however, in permanent tooth eruption between the 1980 and 2000 groups when considering the second age range (9-12 years). So, although teeth began to erupt earlier in the 2000 group, the full transition to permanent dentition was completed no quicker than the group observed 20 years earlier.
Effectively, the 2000 group had a longer transitional phase from primary to permanent dentition.
WHAT THE PROFESSOR THINKS
The authors compared cross-sectional observations of eruption stage for a historic group to a modern group who were followed longitudinally. To help account for one of the evident drawbacks of this design, the statistical analysis appropriately accounted for differences in age distribution between the groups. Further, few studies include any good longitudinal data of this sort.
This report of a secular trend – that the emergence of permanent teeth is occurring at an earlier age compared to many years ago – is worth consideration by clinicians. Especially since this finding means that the transitional dentition phase is effectively longer.
Put in a clinical context, this study implies that the orthodontist who begins comprehensive treatment for children in the mixed dentition because they appear to be advanced dentally may find that they also have longer treatment times. Why? Because all of the permanent teeth did not finish erupting on the apparently accelerated pace that was initially observed.
It is unfortunate that the magnitude of the secular trend effect was not reported in a meaningful way in this study. So how should clinicians use these data?
These data find utility when combined with individual clinical experience. For the orthodontist who suspects that he or she is waiting on the eruption of permanent teeth longer today than a few years ago, this study provides some evidence to trust their clinical judgement – and not rush to start patients younger and thereby sacrifice treatment efficiency.
Article Reviewed: Eskeli, Losonen et al. Secular trends affect timing of emergence of permanent teeth. Angle Orthod. 86:53-58. 2016 (Jan.)
BY HENRY W. FIELDS
Several factors affect the expression of the third order (torque) configuration of archwires upon teeth. These include the bracket slot size, wire dimension, and the bevel of the edge of square and rectangular wires. These variables have been examined in the past, but this recent study combined all three aspects for 43 archwires of different wire sizes and types using a digital gauge and micrographs measured with digital image software. The wires came from six manufacturers. Each wire was examined using 3 samples.
The results demonstrated that there is substantial variation within each wire for each manufacturer. Wire width and height were both under and over-sized—many significantly so. Some manufacturers displayed sizing tendencies, but all had significant differences from the ideal nominal sizes. Corner radiuses were present (not 90 degrees) in all of the samples, and often there were four different radii for one wire (each corner was a different shape).
The wire material affected sizing as well. Coated wires were the most true to size, followed by NiTi and TMA. Steel and tempered steel were the most undersized.
WHAT THE PROFESSOR THINKS
These results, along with the knowledge that most bracket slots are oversized, leads to more problems than expected in expressing torque in tooth movement. The undersized wires and corner bevels lead to a considerable amount of play (rotation before expressing a moment) between the bracket and rectangular wire. This difference can be considerably larger than ideal and up to 3 times what is expected.
Unfortunately, since the cross-sectional size and shape of commercially-available wires are highly variable, straightwire clinicians are likely to encounter difficulty in torquing unexpectedly. . . and more frequently than desired.
For the clinician who wants more ideal torque, the options are 1) to increase the wire size, which is perhaps a better option when using TMA wires so that harsh forces are not produced 2) purchase high torque brackets for potential problem cases or 3) consider torquing auxiliaries or archwire bends.
Article Reviewed: Lombardo L, Arreghini A, Bratti E et al. Comparative analysis of real and ideal wire-slot play in square and rectangular archwires. Angle Orthod 85: 848-58, 2015 (Sept).
BY TUNG T. NGUYEN
This study, published in the January 2016 issue of the AJODO, followed 43 Class I patients treated with 4 bicuspid extractions for 5 years during retention. The mean age of the subjects was 13.6 +/- 1.4 at the start of treatment and 16.1 +/- 2.0 at the end of treatment. All subjects had maxillary Hawley retainers and mandibular 3-3 fixed retainers. Crowding, spacing, intercanine distance, and incisor angulation, along with multiple dental measurements were made for initial, final, 1-year and 5-year retention records.
30% of the patients had at least one extraction space reopen, with the majority occurring within the first year of retention. Extraction space tended to reopen more in the maxilla (2.5 to 1 ratio) than the mandible and often times only in 1 quadrant. In addition, the reopened extraction space tended to close at the 5-year retention point.
WHAT THE PROFESSOR THINKS
The extraction debate continues to be a source of controversy in our profession. We make decisions between expansion and extraction based on our practice philosophy / training, esthetic preferences, the degree of crowding, and of course, stability. Proponents of extraction will cite the stability of tooth movement as a major advantage. However, it may be the magnitude of tooth movement that has more to do with stability – not simply whether one extracts or expands.
The authors found that the larger degree of incisor retraction and smaller the initial crowding, the more likely premolar extraction space were to reopen; ie: the farther you move teeth, the more likely they are to return to their original anterior-posterior (A-P) position. It is interesting to note that when the initial crowding was at least 11.63mm, none of these subjects showed space opening. When the initial crowding was only 8.39mm, these subjects had 2.6mm of incisor retraction and tended to show space opening. Could 2-3mm of AP movement of the incisor be the threshold for relapse? Unfortunately, the sample size is too small to make that assumption.
The authors should have reported the size of the extraction space opening. 0.25-0.5mm is often clinically insignificant, whereas 1-2mm of space opening is often a source for interdental food impaction.
It is important to note that extraction spaces tended to decrease at the 5-year retention mark. Was that due to late mandibular growth? Bjork’s studies have already hinted at that point, but we need more data.
The Bottom Line: Regardless of whether you extract or not, careful consideration of retention strategy is needed, especially when teeth are moved greater distances. That is true for both growing and non-growing patients.
Article Reviewed:Garib D, Bressane L, Janson G, Gribel B. Stability of extraction space closure. Am J Orthod Dentofacial Orthop 2016;149:24-30.