In a case where a patient shows a normal reaction to cold testing, has no percussion sensitivity, but shows caries on x-ray, what is the likely diagnosis?

The diagnosis of reversible pulpitis is consistent with a scenario where the patient exhibits a normal reaction to cold testing and no percussion sensitivity. In cases of reversible pulpitis, the pulp is still vital and responsive to stimuli, which explains the normal cold test response. The absence of percussion sensitivity further supports that there is no significant inflammation or infection affecting the pulp.

The presence of caries on x-ray indicates that there may be some degree of irritation to the pulp due to the decay, but since the pulp remains healthy and the physiological responses are normal, it suggests that the inflammation is mild and potentially reversible. If the pulp had been more significantly affected, the patient would likely present with painful symptoms upon percussion or a different reaction to cold stimulus, indicative of a more severe pulp condition such as irreversible pulpitis or pulp necrosis.

Thus, given the clinical findings and x-ray evidence of caries, reversible pulpitis is indeed the most likely diagnosis in this situation.