Expansion with Damon appliances results in buccal bone loss?
The wheels of the extraction/non-extraction debate continue to spin. This study highlights a problem with non-extraction expansion treatment.i
Since the early days of orthodontic treatment, we have been debating the need to extract teeth. This has resulted in confusion, lengthy discussion and changing extraction patterns over time. Recently, orthodontists have been extracting less teeth. This has been a result of by non-evidenced based discussion, social media driven orthodontics and extreme claims made for the harm that extractions cause. For example, it has been claimed that extractions harm the airway, cause bed wetting, damage the profile and we are removing perfectly good body parts.
The only true theme that surrounds this situation is the lack of evidence that supports these claims. When we look at research, there does not seem to be any harmful effects of extractions as part of a well planned and executed orthodontic treatment. Nevertheless, the wheel of this debate was given another spin by the claims made by the promoters of non extraction self ligation appliances. This was that the use of self ligating brackets, to expand arches, resulted in expansion with the development of new bone.
A team from Brazil and Denmark did this study. The Angle Orthodontist published the paper.
A cone beam computed tomographic study
Juliana F. Morais et al
Angle Orthodontist: On line. DOI: 10.2319/101117-686.1
They set out to ask this question:
“What were the changes in the maxillary alveolar bone during the alignment phase of non extraction treatment with a self ligating appliance”?
What did they do?
They did a prospective cohort study. The PICO was:
Participants: Twenty two orthodontic patients aged 11-17 years old with more than 4 mm of crowding.
Intervention: Non extraction treatment with Damon3MX brackets with a standard “Damon” arch wire sequence.
Outcome: Analysis of buccal bone using CBCT scans that were taken at the start of treatment and 4 weeks after the insertion of the final 19×25 ss archwires.
They analysed the CBCT scans to measure the following:
- Buccal bone thickness at 3 and 6mm from the CEJ
- The buccal bone area
- Buccal bone height, this was defined as the distance from the CEJ to the alveolar crest.
They also measure, expansion, rotations of teeth and amount of tip of the teeth.
Finally, they did some simple univariate statistics across the variables. They also looked at associations between initial bone morphology, amount of tipping and initial crowding on the buccal bone data.
What did they find?
All the patients completed the study. The mean age of the patients was 14.7 years and the mean Little’s index of the maxillary teeth was 11.3 (SD=5.2). When they looked at the buccal bone measurements they found the following:
There was a decrease in both the buccal bone thickness of 0.2mm (23%) and bone area of -1.2 mm (13%) for the incisors. There were similar losses for the molars. They also showed that there was significant apical migration of marginal bone at the incisors (0.4mm) and molars (0.3mm). Finally, more that 20% of the patients had bone recession measuring greater than 1mm related to one tooth or more. We need to decide ourselves whether these are clinically significant effects.
The maxillary arch widths increased and this was associated with significant buccal tipping. There was also incisor proclination of 2.1mm.
They concluded that the crowding was alleviated by maxillary tooth tipping and that the teeth “moved through the bone” and did not “remain centred in the bone” with development of the alveolar bone. That is the appliances did not make the bone grow.
What did I think?
I thought that this was an interesting small study that provided us with useful information. However, we need to take care with the interpretation of this data. This is because there was no comparison group. The ideal study would be a trial in which patients were randomised to treatment with with expansion/self ligation brackets or extraction and conventional brackets. As a result, we cannot conclude that expansion with self-ligating brackets results in loss of alveolar bone any more than conventional extraction treatment. Indeed, there are studies that show bone loss with extraction treatment. Nevertheless, I feel that we can conclude that there is absence of evidence that non-extraction expansion treatment with Damon brackets, or any other bracket, develops the alveolar bone. The Damon and non-extraction story continues….
Emeritus Professor of Orthodontics, University of Manchester, UK.