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

Infraoccluded primary molars are a relatively common dental abnormality, however, it is rare for them to cause significant problems. This paper will discuss a case in which a patient's infraoccluded upper deciduous second molars led to associated pathology.

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