According to Angle's Classification, what relationship is demonstrated on the patient's right side?

• A. Class II, Division 1
• B. Class II, Division 2
• C. Class I
• D. Class III

Answer: (C)

In Angle’s system, the main reference is how the upper and lower first molars relate to each other. A normal, or Class I, molar relationship occurs when the mesiobuccal cusp of the upper first molar sits in the buccal groove of the lower first molar. If you observe this exact alignment on the patient’s right side, it means the right-side molar relationship is Class I.

This contrasts with other classes: in Class II the upper molar sits ahead of the lower molar (the cusp occludes mesial to the lower groove), and in Class III the lower molar sits ahead of the upper molar (the cusp occludes distal to the lower groove). Division 1 vs Division 2 refers to the orientation of the upper front teeth, not the molar relationship itself, which is why the right-side observation aligns with Class I even when incisors vary.

So, seeing a normal maxillary-to-mandibular molar relationship on the right side is why the correct label is Class I.