Leave it or treat it? Orthodontic issues in the early mixed dentition

This article was first published in the ADA's News Bulletin, December 2022.

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Even though we expect the dentition to develop in a certain way, we know it almost never does as perfectly as we would like. There are lots of orthodontic issues to look out for in the early mixed dentition, many of which present without warning. Certain things can be left to manage later in life, but others require early intervention, and managing them in a young child can be challenging. Following are some of the common orthodontic issues seen in children during the transition from the primary to the early mixed dentition, with a brief overview of the treatment options available.

Oral habits

Thumb or digit sucking and dummy use are an almost normal part of early childhood. Children develop these habits from a very early stage as a comforting behaviour. There is evidence that some babies will suck their thumbs in the womb! From an occlusion perspective, these habits can, over time, lead to an anterior open bite, narrow maxilla, proclined incisors and dental crowding (1). Fortunately, these consequences have the tendency to self-correct as long as the habit stops by approximately four to five years of age. Some children, particularly those who persist with an oral habit beyond this age, will develop irreversible ‘damage’ to their developing occlusion. Therefore, it is important to educate parents of those children who are at risk of this.

Various methods can be implemented to help curb the habit such as positive encouragement, reward systems, nail-biting deterrent polish, taping or covering the offending finger or hand, and cutting off the tip of the dummy. A dental practitioner may also construct an anti-habit appliance such as a palatal crib to help curb the habit. As with any habit, helping a child stop this habit takes time, persistence and consistency.

Space loss

Tooth extraction is the typical treatment of choice for primary teeth with infection, significant tooth decay or after severe dental trauma. Attempting to salvage a primary tooth with a hopeless prognosis is a recipe for disaster, and is usually best extracted despite the inevitable consequence of space loss. Fortunately, extraction of primary incisors rarely causes space loss, and the permanent successors usually still erupt without issue. Early loss of a primary molar, however, can cause space loss which, without appropriate management, can create spacing issues for the permanent successor (2). The decision to place a space maintainer depends on a large number of factors, including:

- the severity of space loss expected. This is largely tooth and age dependant;

- patient factors, including medical history, caries risk, cooperation and finances; and

- the presence of other orthodontic issues whereby if the child is likely to require comprehensive orthodontic treatment in the future, then space maintenance at a younger age may not be entirely necessary.

Space maintainers come in various forms, with band and loop spacers being ideal for a single tooth extraction and a lingual or transpalatal arch being used when multiple teeth in an arch are extracted. It is important to remember that a child must be able to keep these appliances clean, avoid sticky foods and attend for regular maintenance visits.

Otherwise commonly referred to as ‘shark teeth’, lower anterior crowding is a very common issue seen in the early mixed dentition. Often parents attend a dental practice worried that a primary tooth has not exfoliated despite its permanent successor erupting lingually to it. Even though this may appear abnormal, this situation very rarely needs any intervention from a dental practitioner. In more than 90% of cases, the primary tooth will eventually exfoliate, and the permanent tooth still erupt fully into the arch and migrate forward with tongue pressure (3). Removing the primary tooth is only of benefit if:

- the tooth is not mobile at all despite the permanent successor being fully erupted;

- enough time (usually six to 12 months) has been given beyond the normal stage of development the tooth is expected to exfoliate by;

- there is evidence the permanent successor will not erupt and become impacted or erupt severely ectopically without this extraction; and/or

- the primary tooth is significantly impacting normal hygiene and dietary practices.

It is important to not proceed with extraction of a primary tooth unless it is absolutely necessary as this is often the child’s first exposure to a dental procedure. For them to have to sit through local anaesthetic and a tooth extraction as their first ever dental experience may lead to a negative experience and may induce dental anxiety. Lower anterior crowding indicates a developing malocclusion and is better managed orthodontically, typically in the mid to late mixed dentition.

Crossbites

Anterior and posterior crossbites are caused by dental or skeletal discrepancies, or a combination of the two. A dental crossbite usually involves one or two teeth whereas a skeletal crossbite generally involves multiple teeth. Other factors such as a high palatal vault, mouth breathing, cleft palate and skeletal malocclusions (class II or class III) more commonly have skeletal crossbites (4).

Crossbites in the primary dentition usually do not need early correction unless the crossbite is causing a functional shift or it has been indicated by a medical specialist, usually an ENT specialist or sleep physician, for obstructive sleep apnoea. In the early mixed dentition, correction of any crossbite is typically done once the first permanent molars and permanent incisors have erupted so that it is easier to maintain the correction and any incisor irregularities can be corrected at the same time. In general, single tooth crossbites do not need early correction unless there is evidence of trauma to teeth or gingival recession occurring.

Posterior crossbites are generally corrected with the use of a maxillary expander. In the early mixed dentition either a removable appliance with an expansion screw or a fixed maxillary expander can be used with a similar level of effcacy as the palatal suture has not yet started to interdigitate. Anterior crossbites are generally corrected at this stage using a removable appliance with a Z-spring or partial fixed appliances.

Ectopic first permanent molars

Ectopic first permanent molars are identified when these teeth do not erupt or remain partially erupted and are found to have part of its crown stuck behind the second primary molar. They have a prevalence of approximately 4% in the general population, are more common in the maxilla, and fortunately approximately 70% of the time they self-resolve (5). Any external resorption that occurs on the second primary molar tends to remain of radiographic significance only, and thankfully these teeth usually do not require extraction. In fact, these teeth tend to serve a full life expectancy without issue.

In severe cases, the resorptive defect may extend through to the pulp of the primary molar, with some eventually becoming infected and needing extraction. Given that the majority self-resolve, clinical intervention is usually not required. For moderate to severe cases or when enough time has been given to allow for natural correction and the first permanent molar remains impacted, then some form of treatment becomes necessary. 

This could be as simple as placing an elastomeric separator between both teeth for mild cases or orthodontically distalising the first permanent molar with either a removable or fixed appliance. Extraction of the second primary molar is reserved for severe cases, when the tooth becomes infected or is heavily mobile. In this scenario a space maintainer may be required once the first permanent molar has been appropriately distalised to prevent space loss from occurring. Prior to treatment it is also important to consider other factors such as the presence of a second premolar, any skeletal or dental malocclusion and the patient’s behaviour.

References

1. Silva M, Manton D. Oral Habits – Part 1: The dental effects and management of nutritive and non-nutritive sucking. Journal of Dentistry for Children, 2014;81(3):133-139.

2. Rock WP, British Society of Paediatric Dentistry. UK National Clinical Guidelines in Paediatric Dentistry. Extraction of primary teeth – balance and compensation. International Journal of Paediatric Dentistry / The British Paedodontic Society [and] the International Association of Dentistry for Children. 2002;12(2):151-153.

3. Thilander B. Dentoalveolar development in subjects with normal occlusion. A longitudinal study between the ages of 5 and 31 years. European Journal of Orthodontics. 2009;31(2):109-20.

4. Kutin G, Hawes R. Posterior cross-bites in the deciduous and mixed dentitions. American Journal of Orthodontics. 1969;56(5):491-504.

5. Barberia-Leache, Suarez-Clúa MC, Saavedra-Ontiveros D. Ectopic eruption of the maxillary first permanent molar: characteristics and occurrence in growing children. The Angle Orthodontist. 2005;75(4):610-615.

Go to the ADA's CPD Portal to watch a presentation on this topic.