Computer Aided Indirect Bonding: A new direction for improved efficiency?

This interesting new study looks at computer-aided indirect bonding.  Padhraig Fleming provides his interpretation of this study in this post. 

Dentistry has witnessed a digital revolution of sorts in recent decades with plain radiographic films largely superseded, three-dimensional imaging gaining increasing traction, and 3D printing now commonplace. Orthodontics has been at the vanguard of these changes. For example, we have seen full customisation of fixed appliances, removable appliances and archwires.  Digital workflows have become integral to practice. Practitioners are increasingly judged based on the adoption of technology- what we use, rather than what we know or produce. Terms such as ‘digital orthodontist’, ‘Invisalign dentist’ and ‘Damon doctor’ have been spawned and, given the direction of travel, may increasingly come to define us. Of course, this trend is essential if industry and orthodontic companies are to thrive. The effect on our treatment outcomes and processes is less clear-cut.

Investigators have investigated these digital and other technological advances. Much of the most rigorous investigation into this newer technology has produced underwhelming results. However, before these more recent technologies are discredited, a holistic assessment must be carried out. Importantly, these developments could conceivably produce a range of benefits. These may not just concern treatment outcome or efficiency but also patient experiences of treatment. In addition to, prompting practical and economic benefit for practitioners.

This study attempted to evaluate the potential benefit of indirect bonding procedures holistically. A team from Aarhus did this study. I was fortunate to spend some time there in 2018. The European Journal of Orthodontics published this trial.

What did they do?

They conducted a split-mouth randomised controlled trial with a 1:1 allocation

Participants:

They included extraction and non-extraction cases with at least four permanent teeth (except molars) bonded in each of the four quadrants with all teeth fully erupted. In addition, they excluded patients with significant rotations impeding proper bracket positioning.

Interventions:

Ten orthodontic residents performed the procedures using metal brackets bonded to incisors, canines, and premolars. The residents had each bonded a single case indirectly before trial commencement. The randomisation allocated participants to having indirect bonding on either the upper left and lower right or upper right and lower left quadrants. They did the indirect bonding procedures after alginate impressions, fabrication of digital models (O3DM) and digital placement of the brackets using DDP-Ortho software. They used two 3D-printed bonding trays were used to facilitate indirect bonding. The indirectly bonded attachments were placed first followed by direct bonding.

They used a standard conventional etch-based technique using TransBond XT adhesive and LED light-curing for 10 seconds per attachment for both interventions.  Occlusal interferences were removed using bite blocks as required.

Primary outcome: Time required to bond attachments

Secondary outcomes: Immediate bracket failure rate and analysis of costs.

Their sample size calculation revealed that they needed ten participants per group (20 in total) to demonstrate a difference of 5 minutes between the bonding techniques. Overall, however, thirty-seven participants were randomly allocated to the intervention. Of these, twenty-seven completed the study.

What did they find?

They found that less clinical chair time was needed to bond brackets using the indirect (CAD-CAM) technique with a mean saving of 3 minutes 55 seconds per half-arch. However, the time required for non-clinical preparation for indirect bonding meant that the total time needed for the indirect bonding technique was actually significantly longer (by 11 minutes 26 seconds). The indirect approach was also associated with immediate debonding relatively often (14 attachments; 5.1%), while this did not happen at all with the direct method. It is unclear how these fractured brackets were subsequently rebonded; however, it is likely that these debonds led to an increase in chairside time. Importantly, the costs were marginally higher for indirect bonding based on two possible scenarios- allowing either 2 or 5 minutes of the orthodontist’s time to check the digital placement of the brackets.

What did I think?

I thought that this was an interesting study on an important topic. In fact, I was surprised that there had not been previous randomised trials on this relatively established clinical technique. The authors are, therefore, to be commended for their work. The paper is very well written. I really like the use of various outcomes with the economic analysis critical as the introduction of these bonding systems can be an ‘office management decision’ rather than a purely clinical one. They also present a comprehensive rationale for the study and a thorough, candid description of the limitations. The latter, I think, is particularly refreshing.

They conducted the study well and reported it in line with accepted standards. They did undertake a sample size calculation with the projected required sample small. I am not sure why they allowed for such a high drop-out rate; however, the slightly larger sample does help to increase the credibility of the findings.

Generalisability of findings.

A key question here (as with any clinical trial) is whether the findings can be applied to other (and ideally our) clinical setting(s). Again, the authors were candid in this regard and included a detailed section around generalizability. Postgraduates with limited experience of indirect bonding (in particular) undertook all of the clinical procedures. The authors acknowledge that there is a learning curve associated with indirect bonding and suggest that this might help to explain the lack of benefit found with indirect techniques. The study was undertaken within a university setting; as such, the economic analysis might yield different results in a practice setting where auxiliaries may carry out indirect bonding releasing an orthodontist to perform other treatments simultaneously. While the involvement of postgraduates in a university setting might affect the generalizability of the findings, it is essential to highlight that a large majority of orthodontic trials are performed in university settings, and a large proportion of these also involve trainees. There have been efforts to ingrain independent prospective clinical research within clinical practices. This type of comparison might well be amenable to research within a practice-based setting.

Operator factors

The high number of early failures with the indirect approach is interesting and important. This might again relate somewhat to the inexperience of the operators; however, a higher initial failure rate is not unsurprising given the added steps involved in indirect bonding. One-third of the bracket failures were also attributed to processing errors with the indirect trays.

I have referred to inexperience on more than one occasion in this summary. This has made me think a little more about how we respond to, adopt or indeed ignore technology. Ultimately, as informed practitioners, we must be aware of newer technologies. We must then decide whether we should incorporate these into our practices. Ideally, this decision should be informed by high-quality evidence. I do wonder, however, how early, ‘teething’ problems (possibly related to inexperience) may shape our decision to embrace and persevere with new technologies.

What can we conclude?

 Based on a relatively small sample, indirect bonding procedures seem to lead to a minimal clinical time saving but increased overall time commitment among inexperienced operators. The costs associated with indirect bonding were also higher in university settings. ‘Digital orthodontics’ is here to stay. The authors have provided us with an excellent roadmap for its evaluation.