Clinical rest and closest speech positions in the determination of occlusal vertical dimension

Two subject groups had their mandibular positions determined, using an elec trognathograph, at the clinical rest position (CRP) and at the closest spea king position (CSP). They were classified into a toothwear (largely of attr itional origin) group (n = 30) and a non-toothwear, or normal, group (n = 6 0). The mean CRP deduced for the groups was similar in all three dimensions and found to be just less than 2 mm open from and 0.6 mm posterior to inte rcuspal position (IP) and approximately in the midline. The CSP, in two dim ensions, of the toothwear group was significantly closer to IP than that of the normal group. The vertical component of CRP and CSP was similar for th e normal group but CSP was significantly reduced in comparison to CRP for t he toothwear group. The most forward component of CSP was significantly mor e anteriorly placed than was that of CRP. Although there was a pronounced i nter-individual variation the results suggest toothwear, of long acting aet iology, has less affect on CRP than on CSP.