Does combining laser therapy and piezoelectric surgery accelerate overjet reduction?

We are still seeking methods to accelerate the speed of orthodontic tooth movement.  Recent research shows that no method has been found to provide a clinically meaningful reduction in orthodontic treatment time.

I have decided not to review all studies that evaluate these efforts, unless the study adds to our knowledge. This new study provides insight into the effect of combining interventions on the rate of tooth movement.

A team from Damascus and Amman did this trial. The EJO published the paper.

What did they ask?

They did this study to ask

“What is the effect of combining flapless piezocision and low-level laser light therapy on orthodontic tooth movement in patients requiring anterior tooth retraction”?

What did they do?

The team carried out a single-centre, three-arm, parallel group RCT.  The PICO was

Participants

Adult patients between 17 and 28 years with Class II Division 1 malocclusion requiring the extraction of upper first premolars to reduce their overjet.

Interventions

The operator reduced the overjet with en masse retraction from TADs with

Outcomes

Rate of tooth movement in mm/month

The team conducted a clear sample size calculation. They utilised a pre-prepared randomisation, and concealment was performed using sealed envelopes. The operator was not blinded to the treatment allocation. This is a common characteristic of most orthodontic studies. It is impossible to blind the operators.

The piezocision involved 18 incisions and bone cuts 3mm deep between the teeth, performed once. In the laser group, this procedure was applied 6 weeks after the piezocision and repeated 3, 7, and 14 days later.

The teeth were retracted with a 250g per side and checked and reapplied, if necessary, every two weeks.

After levelling and alignment, once the patients had been in 019×025 wire for two weeks, they began mass retraction with the three interventions.  They took study casts at the start of retraction, then every month, with a final impression when they achieved a Class I incisal relationship.

They photographed the sequential models. They measured from the incisors to the medial ends of the third palatal raphe. This method was employed in several previous studies.

They took several measures of tooth movement, and I will only examine the en-masse reduction.

What did they find?

The most important outcome was the rate of en-masse retraction from the start to end of retraction. Their data analysis revealed the following.

The rate of en-mass retraction for the Piezocision and LLLT group was 1.32 (SD = 0.19) mm/month. For the Piezocision-only group, the rate was 1.09 mm/month (SD = 0.13), and for the conventional group with no additional intervention, it was 0.73 mm/month (SD = 0.06). They reported that this was statistically significant; however, according to their table, the p-value was 0.84, which left me confused.

When they looked at the differences between the groups, they found that 

• Conventional – Piezocision difference = -0.33 (95% CI -0.42 to -0.25) mm/month
• Conventional – Piezocision plus laser light = -0.57 (95% CI -0.66 to -0.47) mm/month
• Piezocison –  Piezocision plus laser light = -0.24 (95% CI -0.32 to -0.15) mm/month

These were all statistically significant.

Their conclusion was

“Maxillary anterior en-masse retraction, enhanced by either piezocision alone or with low-level laser therapy, can expedite orthodontic tooth movement and shorten the retraction time compared to the conventional method”.

What did I think?

This was a valuable small trial that examined a clinically significant question. This team has conducted numerous trials and adhered to standard trial methodology. In their paper, they clearly outlined their perceptions of the study’s shortcomings. They noted that the operator was not blinded, which is common in most orthodontic studies. Importantly, they mentioned that they did not perform a 3D analysis of the models. However, they employed a reliable method to measure the amount of retraction.

I was concerned that they reported the percentage difference in outcomes. For example, they stated that combining piezocision with laser therapy significantly boosts upper anterior tooth retraction by 43.8% compared to conventional retraction. This form of reporting is unclear, as 43.8% may seem large, but this translates to only 0.57 mm/month, which does not sound as impressive.  

This brings me to the long-standing debate between statistical and clinical significance. In this study, the differences were statistically significant. However, let’s examine the effect size and confidence intervals. The 95% confidence intervals indicate the range within which the true value from the population is likely to fall. 

If we examine this data, the mean difference between the combined laser light and piezoelectric intervention and no intervention was -0.57 mm/month, with a 95% Confidence Interval of -0.66 to -0.47. This shows us that the effect size is small and can be as low as 0-.47 mm/month. 

These values are not particularly impressive. I certainly would not recommend this to my patients, considering the additional trauma of piezocision.

This conclusion is similar to those reached in other studies examining this potentially traumatic technique, and it adds to the evidence that we should not be doing it!

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