Functional appliances play a crucial role in the correction of skeletal and dental discrepancies during growth, particularly in Class II malocclusions. However, the success of these appliances heavily relies on patient compliance, especially the number of hours they are worn each day.

Andresen believed that wearing his activator appliance only at home in the evenings and during sleep was sufficient for effective treatment

Teuscher recommended that his combination of activator and headgear be worn for at least 12 hours a day to achieve optimal results.

both Fränkel and Clark advocated for full-time wear of their functional appliances.

However, it’s worth noting that these varying recommendations were mainly guided by clinical experience, with limited support from strong scientific research.

It might seem logical that the more you wear it , the more effective it would be , but is there any evidence for this ?

in a study "Effectiveness of part-time vs full-time wear protocols of Twin-block appliance on dental and skeletal changes: A randomized controlled trial"(Parekh et al 2018) this was investigated.

and the conclusion of the study is that, There was no difference in either dental or skeletal changes achieved with Part Time or Full Time wear of a Twin-block appliance over 12 months. Less burdensome PT wear regimens may therefore be a viable alternative to FT wear of removable functional appliance

However it is wise to always ask patients to wear them full time as patients will invariably wear a removable appliance for less time than prescribed (Al-Moghrabi et al, 2017).

References:

1. Effectiveness of part-time vs full-time wear protocols of Twin-block appliance on dental and skeletal changes: A randomized controlled trial (Jeet Parekh , Kate Counihan , Padhraig S Fleming , Nikolaos Pandis , Pratik K Sharma )

2. Compliance with removable orthodontic appliances and adjuncts: A systematic review and meta-analysis (Dalya Al-Moghrabi , Fiorella Colonio Salazar , Nikolaos Pandis , Padhraig S Fleming )

3. Handbook of orthodontics(Martyn Cobourn & Andrew Dibiase)

4. Twin Blocks designed for 24-hour wear ( W.J Clark)

5. Part-time vs full-time wear of Twin-block appliance: Can we rejoice? (Elbe Peter ∙ J. Monisha ∙ R.M. Baiju ∙ Vivek Narayan ∙ Suja Ani)

In a Letter to the Editor (2019)

Dr, W. J Clark the originator of the appliance had another opinion about Parekh et al study

Dr. Clark mentioned:

"Twin Blocks designed for 24-hour wear"

• "In my opinion, Parekh et al did not follow a reliable protocol for successful cooperation with the use of removable Twin Blocks "

• "A previous multicenter RCT in the U.K. led by O'Brien and Sandler had a failure rate of 33.6%. The high failure rate was attributed to excessively thick occlusal blocks, which represented a departure from the original design and protocol for the Twin Block technique. This compares to a failure rate in my original D.D.Sc. thesis of 6.7% for 148 consecutively treated patients"

• "I strongly recommend that the findings of this RCT should be rejected in favor of temporary fixation of Twin Blocks to establish full-time wear as the treatment of choice. This protocol has been tried and tested for 4 decades and is the most effective approach to maximize cooperation for mandibular advancement in Twin Block therapy."

  His intention in making this criticism is to avoid a potential increase in the failure rate if part-time wear is adopted in preference to full-time wear

Another letter by Peter et al "Part-time vs full-time wear of Twin-block appliance: Can we rejoice?

Mentioned that it was still too early to rejoice these findings by Parekh et al study for the following reasons:

• Since the average wear time in the Full-Time group was only 12.38 ± 5.89 hours, it does not meet the criteria for full-time wear. The results might have been different if the participants had adhered to the recommended wear schedule

• The investigators assessed skeletal response solely based on the ANB angle. Although the linear mandibular length (Ar-Gn) was documented at baseline, changes following treatment were not reported regarding the Ar-Gn

• Although no differences were observed between the two groups, the study fails to provide a biological explanation for this similarity in outcomes, especially considering Dr. Clark's claim that only full-time wear can elicit the required pterygoid response

• What justified their consideration of a 2-mm overjet reduction as clinically significant in Class II, Division 1 malocclusion? Given a pretreatment overjet exceeding 10 mm, such a minimal reduction seems highly inadequate.

• Although it is rightly mentioned that the external validity could be doubtful owing to a hospital based sample, we believed that it could still be diluted because of “contamination between intervention groups.”This is because all subjects were of the same peer group, receiving different instructions for the same appliance. There is no evidence in the article regarding any precautions against a contamination bias.

  
  

Also Check Out Our Products!