Does Micro-osteoperforation speed up tooth movement?
We would all like to make teeth move faster. This systematic review looked at whether Micro-osteoperforation (MOP) increases the rate of tooth movement.
Many new developments are intended to increase the rate of orthodontic tooth movement. One of these is micro-osteoperforation. The theory behind this technique is that local trauma to the alveolar bone results in an increase in inflammatory mediators. This then increases bone metabolism and resorption. As a result, the rate of tooth movement increases.
There have been several trials done on this technique, and the results are unequivocal. I was, therefore, very interested to see this new systematic review. The EJO published the paper. A team from Iran did the review.
Mostafa Shahabee et al
European Journal of Orthodontics, 2019, 1–11 doi:10.1093/ejo/cjz049
What did they ask?
They did the review to ask:
“What are the effects of MOP on the rate of orthodontic tooth movement”?
What did they do?
They did a standard systematic review based on the Cochrane methodology. They registered the review before they started their work. This is important because it reduces the possibility that it can be biased.
The PICO was
Participants: Any patient having orthodontic treatment.
Control:Treatment as usual or no intervention.
Outcome: The rate of canine retraction over four weeks.
They did an electronic and hand search and only included RCTs.
When they found relevant papers, they evaluated the risk of bias using the Cochrane Risk of Bias tool. Finally, they measured the strength of their findings using the GRADE approach.
What did they find?
The obtained an initial sample of 635 studies and then after applying strict inclusion criteria; they included six studies in their analysis.
All these studies were RCTs. Four had a split-mouth design, and two had parallel arm designs. Most of the studies compared the rate of canine retraction over four weeks. In all the trials the canine was retracted using sliding mechanics. The MOPs were made distal to the canine teeth.
Importantly, no two studies used the same measurement technique for the amount of canine retraction.
When they looked at the risk of bias, they reported that five out of the six studies were of unclear risk of bias.
The meta-analysis showed that MOPs increased the rate of tooth movement by 0.45mm/4 weeks with a 95% CI of 0.17-0.74.
When they looked at heterogeneity, this was 99%. I will discuss the effect of this later.
Their overall conclusion was
“MOPs increased the rate of canine retraction over four weeks. However, clinically, this effect was not substantial”.
What did I think?
I thought that they did a nice systematic review using Cochrane methodology. Their search was extensive, and they appeared to find the relevant papers.
The authors drew attention to the significant variation in the methods of applying the MOP. In two studies, the investigators used the PROPEL device; all the others used mini-screws to deliver the trauma. They also mentioned that no two trials used the same method of measuring the amount of tooth movement. This may have led to the very high level of heterogeneity in this review. Heterogeneity is a measurement of the variation in the data. When this is high, we are less sure about the results of an analysis. This is the case for these results and we need to interpret them with caution.
This is a good explanation of heterogeneity from the excellent students4bestevidence. Investigators may address this using different methods of meta-analysis. However, this does not entirely remove the uncertainty in the data.
We also need to look at the effect size. This was 0.45mm/4 weeks. The rate of movement of the MOPs teeth was 1.04mm/month and for the control teeth this was 0.76mm/month. If we consider that the average width of a first premolar is 7.1, then this equates to a reduction in the duration of space closure of 2 months (assuming that all the space closure is due to distal movement of the canine). We then need to consider whether this is clinically significant and whether this difference is worth the additional treatment with MOP.
Finally, all the studies have looked at individual tooth movement. As a result, they have all evaluated a “proximal” outcome measure. This may bear no relationship to the overall treatment time and we have no idea whether the use of MOPs reduces the overall duration of treatment. We need trials that evaluate the effect of MOP on total treatment time before we can say that they are effective or not.
My feeling was that this was a useful review. However, high levels of uncertainty in the data and small effect size cast doubt on the effectiveness of this procedure. We may need to think carefully about using this invasive procedure that may not provide a clinically meaningful effect in the long term.