Temporal dynamics of headache for incident TMD cases and TMD-free controls in the OPPERA nested case-control study (n=439). (2A) Distribution of headache types at follow-up visit in TMD cases and controls. Denominator for percentages of TMD cases is n=248 subjects who developed TMD between baseline and follow-up. Denominator for percentages of controls is n=191 subjects who remained TMD-free at baseline and follow-up. (2B) The same data from 2A with patterns of change between baseline and follow-up collapsed to signify worsening, no change, or improvement in headache types. Abbreviations: TMD = temporomandibular disorder, C = TMD-free controls, HA = headache, MIG = migraine, TTH = tension-type headache, Prob. = probable.