The permanent maxillary right canine is the single-rooted anterior tooth situated in the upper right quadrant of the dental arch, between the maxillary right lateral incisor and the maxillary right first premolar. Designated as tooth #6 in the Universal Numbering System and UR3 in FDI notation, it is commonly called the upper right cuspid or eye tooth.
Anatomical Features
The permanent maxillary right canine is defined by several characteristics that distinguish it from all other anterior teeth:
- Single prominent cusp: One sharp cusp tip gives the tooth its pointed form and the alternative name “cuspid,” enabling it to pierce and tear food during mastication.
- Longest root in the dentition: Its root exceeds that of any other permanent tooth, anchoring it deeply in the alveolar bone and contributing to its remarkable longevity.
- Thick labial enamel: A robust enamel layer on the facial surface resists wear and supports the tooth’s durability over decades of function.
- Canine eminence: The bony ridge overlying the root on the facial aspect of the maxilla supports the corner of the upper lip and influences facial soft-tissue contour.
- Mesial and distal ridges: Two prominent vertical ridges on the labial surface converge at the cusp tip, a hallmark feature used in dental identification and morphology study.
Clinical Significance
In function, the permanent maxillary right canine serves as a guide for jaw movement. During lateral excursions of the mandible, it commonly bears the occlusal load and disengages posterior teeth — a mechanism called canine-protected occlusion, or canine guidance. This protective role reduces potentially damaging lateral forces transmitted through the periodontal ligament and supporting bone of the posterior segments.
Aesthetically, the maxillary canines define the transition between the anterior smile zone and the posterior arch, acting as cornerstones of smile design. Their position, angulation, and color profoundly affect perceived smile width and facial harmony.
Impaction is one of the most clinically significant concerns associated with this tooth. The maxillary canine is the second most frequently impacted tooth in the permanent dentition, surpassed only by the mandibular third molar. Early radiographic screening during the mixed dentition stage — typically between ages 10 and 13 — allows for timely orthodontic or surgical intervention before extensive root resorption of adjacent teeth occurs.
Because of its unique combination of structural, functional, and esthetic contributions, every effort is made to retain the permanent maxillary right canine throughout a patient’s lifetime rather than extract it.