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

Two subject groups had their mandibular positions determined, using an electrognathograph, at the clinical rest position (CRP) and at the closest speaking position (CSP). They were classified into a toothwear (largely of attritional origin) group (n=30) and a non-toothwear, or normal, group (n=60). 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 intercuspal position (IP) and approximately in the midline. The CSP, in two dimensions, 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 the normal group but CSP was significantly reduced in comparison to CRP for the toothwear group. The most forward component of CSP was significantly more anteriorly placed than was that of CRP. Although there was a pronounced inter-individual variation the results suggest toothwear, of long acting aetiology, has less affect on CRP than on CSP.