Infraoccluded upper deciduous second molars leading to caries in the permanent dentition

Background

The term dental infraocclusion refers to a tooth which ‘fails to maintain vertical height with the adjacent teeth, hence appearing to submerge below occlusal level’.1 A tooth is considered to be infraoccluded if its intact marginal ridge is greater than 0.5 mm below the intact marginal ridge of the adjacent tooth.2

The prevalence of infraocclusion has been reported to range from 1.3–38.5%.3^,4 This phenomenon has been shown to affect children as young as 3 years old, although peak prevalence ranges from 8–9 years.5

At present, the aetiology is unknown, although there are a number of theories that have been suggested. The most commonly cited cause is ankylosis of the deciduous molar.6^,7 Ankylosis describes the union of cementum and alveolar bone and occurs when there is a break in the continuity of the periodontal membrane and osteoclasts can act directly on the root cementum.8 Deciduous molars have the highest incidence of anklyosis, ranging from 1.5–9.9%.9 Mandibular first deciduous molars appear to be the most frequently affected, followed by the second mandibular deciduous molars.10 A review by Messer and Cline found that, when this phenomenon presents bilaterally, it tends to affect symmetrical teeth.11

It has been shown that there may be a genetic predisposition to infraocclusion. A familial tendency was recognized by Via, who reported a general incidence of 1.3%, and an incidence of 44% in their siblings when looking at a sample of the general population.3

Other suggested theories include disturbed local metabolism, gaps in the periodontal membrane, local mechanical trauma and local infection.12 Chemical or thermal irritation, local failure of bone growth, abnormal pressure from the tongue and disturbance in interaction between normal resorption and hard tissue repair have also been suggested as causes.12

Developmentally absent premolars have been associated with infraocclusion of the deciduous predecessor, along with other dental abnormalities.13 A study of 1032 patients reported 65.7% of children with missing permanent teeth had infraoccluded primary teeth compared to 1.5% of control children.14 Bjerklin et al reported, however, that 90% of healthy second deciduous molars with adequate root length and mild infraocclusion had good long-term prognosis.15

Infraocclusion of deciduous molars can have a detrimental effect on the developing dentition. Examples of this include tipping of adjacent teeth, periodontal problems and restriction of bone growth leading to alveolar ridge defects. Other consequences include space loss, delay or displacement of developing successor teeth, overeruption of teeth in the opposing arch, caries and gingival hyperplasia.16

Brearley's system is commonly used for classifying the extent of infraocclusion as follows:10

Severe infraocclusion only affects 2.5–8.3% of all affected deciduous molars and is specifically related to the absence of a permanent successor.17

Case presentation

MC, a 12-year-old female, presented to the Accident and Emergency department of Pinderfields Hospital with left-sided facial swelling. The patient had visited the dentist previously, where she was prescribed a five-day course of amoxicillin 500 mg and was advised to attend the hospital.

The patient complained of toothache in the upper left quadrant, starting two weeks previously and a two-day history of facial swelling. The patient was medically fit and well with no known drug allergies. She also revealed that she was an irregular dental attender.

On examination the patient was awake, alert, apyrexial and able to maintain her own airway. Mild oedema was noted around the left eye and erythema was observed at the left angle of the mandible. Intra-oral examination revealed that there was a large swelling in the upper left buccal sulcus. Despite this, the patient had good mouth-opening with minimal trismus. UL6 was tender to percussion and it was noted that ULE was severely infraoccluded.

At presentation the case had lateral open bites bilaterally, mesial tipping of the upper first permanent molars and over-eruption of the upper second molars (Figure 1). An orthopantomogram was taken and showed that both upper Es were severely infraoccluded with associated caries in UR6 and UR5 (Figure 2). After incision and drainage of the buccal space abscess under local anaesthetic, the patient was referred for a joint orthodontic/oral surgery opinion.

The orthodontic assessment revealed the following findings:

A periapical radiograph revealed UL6 was affected by gross caries extending into the pulp below the alveolar crest (Figure 3).

After discussion with the oral surgeon, the patient and her mother, a decision was made to remove UR5, URE, ULE and UL6 surgically then treat the malocclusion with fixed appliances.

Discussion

When managing the developing dentition, knowledge of normal eruption allows abnormalities to be identified early. There are many adverse outcomes if infraoccluded teeth are inappropriately managed. Figure 4 gives a timeline of how to manage infraoccluded primary molars. Treatment of these cases depends upon the degree of infraocclusion, the presence of a successor, the time of onset and the degree of tilting of adjacent teeth. The main aims of treatment should be to allow normal eruption of permanent successors and maintain alveolar ridge height so that restoration of functional units, if required, is possible.

Infraoccluded primary molars with absent permanent successor must be handled with care.

Extraction of the infraoccluded tooth would be indicated if there were obvious signs that this anomaly was impacting upon the health of the neighbouring dentition. Generally, the extraction would be carried out early to allow mesial drift of the first permanent molar. This phase should be carefully monitored; over-eruption of the opposing teeth can become problematic and may restrict mesial drift.

Restoration of occlusal height is another option for treating infraoccluded teeth to prevent undesirable effects occurring. This can be done by using composite resin, stainless steel crowns or cast crowns.18 Owing to progressive infraocclusion with facial growth, further intervention may be required to maintain occlusal height. For this treatment option to be viable, there must be substantial periodontal support and regular monitoring.

In cases where there is a permanent successor, there are further options, such as monitoring of infraoccluded teeth or early extraction and space maintenance.

Conclusion

As a general practitioner, one should be aware of the complications associated with long-term monitoring of infraoccluded teeth. They can have a tendency to cause problems in the developing dentition which could be avoided if interceptive orthodontics is carried out. Figure 4 shows the most reasonable options for treatment of these cases.