A challenging problem of restorative dentistry is the diagnosis and treatment of distal surface caries on a second mandibular molar, resulting from chronic food impaction between the second molar and a mesio-angular impacted mandibular third molar located distal to the second molar. Decay removal is difficult due to compromised access, visibility and lighting. Placing a matrix band around the second molar class II preparation may be difficult since the proximal box may be located on undercut, sub-gingival or concave root structure. Due to access, lighting and visibility challenges, it is suggested that dentists use a surgical operating microscope, or binocular surgical telescopic loupes of 6-8x magnification or greater, combined with co-axial illumination, when treating these lesions, instead of using unaided vision and overhead lighting. As part of the treatment plan, the dentist should decide whether or not to extract the third molar, based on the potential future use of the third molar as a fixed or removable partial denture abutment, the potential food impaction, caries and periodontal risks of retaining the third molar, the prognosis of the second molar given the size of the distal decay, and the difficulties of restoring the second molar due to the presence of the third molar.