However they may give rise to various symptoms and pathologies such as pain, pericoronitis, distal caries of 2nd molar, swelling, periodontal problems, resorption of adjacent teeth and their roots, odontogenic cysts and tumors.4,5
The second most common pathology found in association with MIMTM was distal caries of the second molar (23.4%) while caries of the third molar itself was found in 11% cases while for other angulations the 3rd molar caries were seen in 20.4% and 2nd molar caries in 6.5% of all associated pathologies.
The mesial angulation of 3rd molar allows space between 2nd and 3rd molar for accumulation of plaque and calculus with sequelae of distal caries in 2nd molars.
Incidence of distal caries in mandibular second molars due to impacted third molars: Nonintervention strategy of asymptomatic third molars causes harm?
 found that the presence of distal caries in second primary molars increased the risk of developing mesial surface caries in the proximal first permanent molars.
The authors concluded that caries developing on the mesial surface of mandibular first permanent molars is primarily due to distal caries in second primary molars, whereas in the maxillary teeth, other factors together with distal caries in the second primary molars, should be considered.
A quadrant was excluded if the radiograph was of poor quality, or the FMP or the primary second molar was missing, or if there was distal caries in the primary molar.
Conversely, the exclusion of patients with missing second primary molars or distal caries may have actually resulted in under reporting.