A patient with treated, stable periodontitis has 3 mm of generalised gingival recession and horizontal bone loss. A Class II restoration is placed on tooth #29. It is technically well executed with correct contour, contacts and occlusion. At the follow-up visit the patient reports sensitivity in tooth #28, which was not treated. What is the MOST likely explanation?

Correct answer: B. Dentin hypersensitivity from root surfaces exposed by the recession

• A. Referred pain is a real phenomenon in pulpal disease, but it requires a symptomatic pulpitis in the source tooth. The stem specifies the restoration on #29 was well executed, with no indication of pulpal involvement — and referred dental pain more typically crosses arches or moves to a distant site rather than settling neatly on the immediate neighbour.
• B. CORRECT. Tooth #28 was not touched. Its sensitivity must have an independent cause, and this patient's periodontal history supplies it: 3 mm of RECESSION exposes root surfaces where cementum is thin and readily abraded away, opening dentinal tubules to the oral environment. By Brännström's hydrodynamic theory, thermal, osmotic and evaporative stimuli move fluid within those tubules and excite A-delta fibres, producing the classic short, sharp pain of DENTIN HYPERSENSITIVITY. The patient most likely had it before the appointment and became aware of it once attention was drawn to the area.
• C. A properly performed adjacent restoration does not inflame the pulp of the neighbouring tooth. Post-operative sensitivity from a restoration is confined to the RESTORED tooth and arises from causes such as inadequate cure, deep unlined preparations, or lack of a proper seal.
• D. Occlusal trauma from a high restoration produces pain on biting in the restored tooth and would have been detected when the occlusion was verified. It also does not produce the thermal sensitivity pattern described here, and the stem states the occlusion was correct.

Note: Managing dentin hypersensitivity, least to most invasive: first correct the cause — abrasive brushing technique, a hard brush, acidic diet, or an undiagnosed parafunctional habit. Then home desensitisers: 5% potassium nitrate (which blocks nerve depolarisation) or stannous fluoride and arginine-calcium carbonate (which occlude tubules). Then in-office agents: fluoride varnish, oxalates, glutaraldehyde-HEMA, or a bonding agent sealing the exposed dentin. Only then consider a restoration or a root coverage graft. Important caveat: dentin hypersensitivity is a DIAGNOSIS OF EXCLUSION — always rule out caries, a cracked tooth, a defective restoration, and reversible pulpitis before settling on it.