Infraocclusion level and root resorption of the primary molar in second premolar agenesis: A retrospective cross-sectional study in the Portuguese population.

BACKGROUND

Mandibular second premolar (M2P) agenesis results in the second primary molar (2pm) retention, infraocclusion, a reduced alveolar height and width, the supraeruption of antagonists, or the movement of the adjacent teeth. Infraocclusion affects the survival of the retained 2pm to a greater extent than root resorption.

OBJECTIVES

The aim of the study was to evaluate the lifespan of the primary molar as a substitute, with root quality and occlusal adaptation, in cases of M2P agenesis in a low-income population to determine if the attitude of just vigilance could be the best clinical option whenever other clinical problems are absent.

MATERIAL AND METHODS

A total of 12,949 orthopantomograms were analyzed. Sixty-one patients (25 males and 36 females aged 7–36 years) were divided into group 1 (the first permanent molar in occlusion) and group 2 (the second permanent molar also in occlusion). Vertical positioning to the occlusal plane, root condition and the movement of the adjacent teeth were evaluated.

RESULTS

Despite the study having a cross-sectional design, root resorption, infraocclusion, the distance between the first permanent molar and the first primary molar or the first permanent premolar, and the width of the 2pm were correlated with age. The 2pm root resorption increased with age, which was more pronounced when the second permanent molar was also in occlusion. The mesial movement of the adjacent teeth was absent in all groups. The 2pm was often occluded, but infraocclusion increased with age. Age periods of 11–15 years and 21–25 years were critical for the primary tooth loss.

CONCLUSIONS

The second primary molar remains functional in the mandibular arch for up to 25 years. A well-documented no-intervention attitude based on clinical and radiographic data must be weighed in cases without orthodontic issues or with financial constraints.