Clear aligners: Study examines anchorage loss during maxillary molar distalisation

Dental Tribune International

Fri. 31 March 2023

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ROME, Italy: Seeking to address a gap in the literature, researchers have analysed premolar and canine anchorage loss occurring during maxillary molar distalisation in patients receiving clear aligner therapy for Class II malocclusion. They found that the treatment was effective in obtaining molar distalisation movement but observed an anchorage loss at the level of the upper canines at the end of the first maxillary molar distalisation movement.

The researchers, from two universities in Rome and a university in Tirana in Albania, said that only a few studies had analysed anchorage loss obtained during upper molar distalisation movement using clear aligner therapy, particularly at the level of upper premolars and canines. Their retrospective study included 49 patients who had received clear aligner therapy at the University of Rome Tor Vergata during a 12-month period beginning in January 2021. All patients underwent the same non-extractive molar distalisation protocol using Invisalign clear aligner trays with attachments and Class II elastics as auxiliaries and showed either good (44) or moderate (5) compliance.

Comparing 3D digital casts that were taken prior to the treatment and at the end of the first maxillary molar distalisation movement, the researchers observed a statistically significant distalisation of the maxillary first permanent molars (2.5 mm) and a slight, non-significant anchorage loss of the first and second premolars. A statistically significant mesial movement of the upper canines (1.33 mm) was highlighted.

The researchers wrote: “Upper-molar distalisation achieved with clear aligner therapy allows the correction of Class II relationship due to maxillary dentoalveolar protrusion or moderate skeletal discrepancies. However, during the distal movement of the upper molars, side effects on the anchorage teeth were present; in particular, a significant mesial movement of the upper canines was noticed.”

Discussing the results, the researchers pointed out that the significant loss of anchorage was detected in patients who had shown poor compliance with the use of Class II elastics. “This indicates that the use of Class 2 full-time elastics was able to generate an equal and opposite force to the reaction force in the anterior sector, supporting the distalisation movement, strengthening the anterior anchorage, and counteracting the unwanted side effects,” they said.

The study, titled “Anchorage loss evaluation during maxillary molars distalization performed by clear aligners: A retrospective study on 3D digital casts”, was published online in Applied Sciences on 13 March 2023, ahead of inclusion in an issue.