Canine impaction is a sign of abnormal dental development with potentially far-reaching consequences (such as significant root resorption and loss of lateral incisors. This compromises both aesthetics and function of the teeth, making the prediction of canine tooth impaction increasingly important. Interceptive orthodontic measures, such as extraction of deciduous canines or molars or maxillary expansion aim to create extra space in the dental arch, allowing the canines to position themselves better and normalizing their eruption pattern.

This study corresponds to the second phase of an RCT, based on the results of the first phase, published in July 2023 (S59030) (Willems G, Butaye C, Raes M, Zong C, Begnoni G, Cadenas de Llano-Pérula M. Early prevention of maxillary canine impaction: a randomized clinical trial. Eur J Orthod. 31;45(4):359-369). The first phase compared the effect of 3 interceptive strategies (expansion, extraction and no intervention) on the position of impacted maxillary canines, finding that maxillary expansion provides the most improvement on impacted canine position. In second phase, 8-year-old patients without posterior crossbite and lack of space in the dental arch are randomized to treatment with 'slow maxillary expansion with removable plates' or 'no treatment'. These groups are additionally compared with patients with a crossbite and lack of space, which always receive expansion treatment. All selected patients will be followed up for at least 18 months. The primary endpoint is to investigate the effect of maxillary expansion with removable plates on the position of maxillary canines prone to impaction during early mixed dentition, assessed on panoramic X-rays. The secondary endpoint is the assessment of the need for additional orthodontic treatment.

Inclusion Criteria:

General inclusion criteria:

• Female or male patients between 7.5 and 9.5 years-old coming to the department of Orthodontics of UZ Leuven (or one of the participating centres) seeking for orthodontic advice.
• Presenting with one or two impacted maxillary permanent canines, defined by 3¨ML between 15 and 45 degrees (If bilateral impaction occurs, categorization into the different protocol groups will be based on the canine showing the worst position).
• Presenting with one or two maxillary permanent canines showing no more than ¾ root formation, persisting deciduous canines and molars and lack of space in the maxillary arch, defined by ALD>0 mm
• Any race Inclusion criteria Group A: posterior crossbite Inclusion criteria Groups B and C: no posterior crossbite

Exclusion Criteria:

• Fully erupted permanent canines
• Previous orthodontic treatment.
• Canines with completed root formation
• Evidence of root resorption of adjacent teeth or root malformation of the canines that would obligate to extract any adjacent teeth or the canine(s).
• Craniofacial syndromes
• Systemic disease that would impede orthodontic treatment/surgery
• Recent exposure to radiotherapy.