What is the best method of correcting increased overbite: Turbos or arch wires?
We use several methods to correct increased overbites. The most common practice is using archwires. However, recently bite turbos have become popular. These investigators did an excellent trial to look at the effectiveness of archwires and bite turbos in correcting increased overbites.
When we consider methods of overbite correction, it appears that the most likely tooth movement is extrusion of the mandibular premolars and molars with a small degree of lower incisor intrusion. Although, it is usual to have some degree of lower incisor proclination. This new study looked carefully at these tooth movements.
A team from Irbid, Jordan, did the study. The Angle Orthodontist published the paper. As usual, for the Angle, the article is open access.
Ekram M. Al-Zoubi and Kazem Al-Nimri. Angle Orthodontist DOI: 10.2319/020921-117.1
What did they ask?
They did the study to:
“Compare the effects of 16×22 NiTi wires and anterior bite turbos in treatment increased overbites”.
What did they do?
The authors did a two-arm parallel-sided RCT with a 1:1 allocation. They did the study at one site at a dental school. The PICO was:
Participants: Orthodontic patients with an increased overbite (more than half of the lower incisors) treated non-extraction.
Intervention: Fixed metal anterior bite turbos bonded to the middle of the palatal surface of the upper incisors.
Comparator: Lower 016×022 NiTi archwires that they cinched back distal to the lower second molars.
Outcomes: A lot of cephalometric measurements. The primary outcomes were the AP and vertical changes of the lower teeth. The cephalograms were taken at the post alignment and post-levelling stage of treatment.
The sample size calculation showed that they needed to enrol 48 participants in the study. They used pre-prepared randomisation using blocks and concealed the allocation using sealed envelopes. It was not possible to blind the clinician or patient during treatment. However, they recorded the data blind. Finally, they used simple univariate statistics to measure any differences between the interventions.
What did they find?
The authors enrolled 48 participants into the study. Notably, they excluded six patients; this was because they corrected the overbite during the alignment stage.
There was no difference between the groups at the start of treatment.
The mean overbite change for the archwire group was 4.07 mm (SD=0.69), and for the turbos group, this was 3.87 (SD=0.72). This difference was not clinically or statistically significant.
When they looked at the tooth movements, it appears that in the archwire group, there was greater lower incisor proclination than in the turbo group (mean difference 0.69mm). There was also more lower molar extrusion in the turbo group than in the archwire group (mean difference 1.04mm). Nevertheless, I found it challenging to interpret the details of their cephalometric measurements. However, this may also reflect my difficulty in understanding most cephalometric analyses.
When they looked at the time taken to reduce the overbite, the authors found that for the turbo group, this was 4.85 months (SD=1.56) and 3.15 months (SD=0.93) for the archwire group. This amount was statistically and clinically significant.
Their overall conclusion was
“Archwires result in lower incisor proclination with distal tipping of the lower molars, while bite turbos result in lower posterior tooth extrusion”.
What did I think?
Firstly, I thought it was great to see that they did this study as part of a Master’s project. This was an outstanding achievement, and I would like to congratulate the team.
I thought that they did this study nicely. However, as with all trials, we need to look at it closely as part of critical appraisal. I had the following concerns that we need to consider when we look at the findings. These were:
The investigators only looked at the effect of a NiTi wire on overbite depression. I would have liked to see the impact of stainless steel wires with a reverse curve. This impression may be subjective, but I always felt that overbites reduced well in SS wires. This method would be accepted treatment mechanics.
The operator was not blinded. This issue is important in this study because it appears that the operator decided on when the OB was corrected. This step means that the investigation is at high risk of bias.
While the investigators found a reduction in the duration of OB depression treatment, it would have been far more relevant to see if the interventions had any effect on total treatment time. Furthermore, we also need to consider that any impact on tooth position at the end of OB depression are likely to be modified by the mechanics that they used to complete treatment.
Suppose I consider these potential shortcomings. My feeling is that this study does add to our knowledge, to a degree. The findings are undoubtedly logical, and they tend to reinforce our understanding. However, I am not sure that the results of this paper would persuade me to change my practice. This paper is, perhaps, an example of a study that shows us that everything works in orthodontics?