The primary maxillary right second molar is the most posteriorly positioned deciduous tooth in the upper right quadrant, designated as tooth A in the Universal Numbering System and tooth 55 in the FDI World Dental Federation notation. It is one of the longest-serving primary teeth, remaining in function for roughly a decade after eruption.

Anatomy and Development

This tooth typically erupts between 25 and 33 months of age and is not shed until approximately 10 to 12 years. Its crown morphology closely resembles the permanent maxillary first molar, featuring four to five cusps, including a pronounced mesiopalatal cusp that may display a tubercle of Carabelli. The enamel layer is thinner and more translucent than in permanent teeth, and the pulp chamber is proportionally large relative to crown size—two features that directly influence treatment planning when caries is present.

The tooth has three roots—mesiobuccal, distobuccal, and palatal—that diverge widely to accommodate the developing bud of the permanent second premolar below. This flaring root configuration is a hallmark of primary posterior teeth and must be respected during extractions to avoid disturbing the underlying successor.

Clinical Significance

Because the primary maxillary right second molar is eventually replaced by the permanent second premolar, it plays a critical space-maintenance role throughout the mixed dentition period. Premature loss due to caries, trauma, or infection allows adjacent teeth to drift mesially, reducing arch length and contributing to malocclusion and crowding of the permanent dentition.

• Serves as a natural space maintainer for the erupting permanent second premolar
• Helps establish the terminal plane relationship that guides permanent first molar positioning
• Supports vertical dimension and occlusal function during childhood
• Thin enamel increases susceptibility to early childhood caries
• Proportionally large pulp horns place the pulp at elevated risk when decay progresses rapidly

Treatment Considerations

Restorative options range from tooth-colored or amalgam restorations for small lesions to stainless steel crowns, which are preferred when decay is extensive given the tooth’s long functional lifespan. When pulpal involvement is confirmed, pulpotomy—removal of the coronal pulp tissue while preserving the radicular pulp—is the standard vital pulp therapy, maintaining the periodontal ligament and root integrity to prevent premature exfoliation. If extraction is unavoidable, a fixed or removable space maintainer should be placed promptly to prevent arch-length loss before the permanent second premolar is ready to erupt.

Vigilant monitoring of this tooth at every preventive visit is essential, because its early loss creates downstream consequences for permanent tooth alignment and long-term occlusal health.