S.J. Donegan

Tooth Loss, Apolipoprotein E, and Decline in Delayed Word Recall

Our previous research suggests an association between a low number of teeth and increased risk of dementia. The aim of the present study was to determine if a low number of teeth is specifically related to memory decline as evidenced by low Delayed Word Recall scores. In addition, we examined the combined effect of a low number of teeth and the apolipoprotein E ϵ4 allele on Delayed Word Recall scores. We hypothesized that the scores of those who had the allele and a low number of teeth (0-9) would decline more rapidly over time than those participants with a greater number of teeth who lacked the allele. We found that individuals with both risk factors (the allele and fewer teeth) had lower Delayed Word Recall scores at the first examination and declined more quickly compared with participants with neither of these risk factors or with either risk factor alone.

Accuracy of impression materials for complete-arch fixed partial dentures

The accuracy of 12 impression materials of six different types were studied by using complete-arch FPD impressions. Sixty impressions were made of a Columbia dentoform maxillary model with complete cast crown abutment preparations on the canines and the second molars. A one-piece casting was constructed by connecting the four individual castings made for the four abutment teeth. The master prosthesis was seated on the stone casts produced from the impressions. The marginal adaptation on the four abutments was then evaluated with a travelling microscope. The individual marginal adaptation of the four castings on the abutments was also examined after sectioning the four joints. The following conclusions were drawn. 1. The polyethers produced the most accurate complete-arch replicas. The second most accurate were the vinyl polysiloxanes, followed by the polysulfides and the irreversible-reversible hydrocolloids. The least accurate were the reversible hydrocolloids and the irreversible hydrocolloids. 2. The polyether impression materials exhibited the most consistent accuracy for a master cast to fabricate a complete-arch FPD.

Canine tooth guidance and temporomandibular joint sounds in non-patients and patients.

In 46 non-patients and 46 patients, the authors examined the presence (+) and absence (-) of canine tooth guidance (CG), i.e. dynamic dental articulation events in contrast to static dental occlusion events. During a right and a left laterotrusion of the mandible, the number of simple, mutually exclusive and exhaustive tooth guidance events (possibilities) was four. In addition, the authors examined the associations between temporomandibular joint (TMJ) sounds and canine guidance events. In non-patients, CG+ was relatively infrequent (30%), and CG- was relatively frequent (70%). In patients, CG+ was relatively infrequent (22%), and CG- was relatively frequent (78%). In both non-patients and patients, bilateral CG+ was rather infrequent (15%). In both non-patients and patients with the presence of TMJ sounds, CG+ was relatively infrequent (38%) while CG- was relatively frequent (61%). In non-patients as well as patients, no evidence was found that distal CG+ (putative lateral retrusive guidance) was associated with ipsilateral TMJ sounds (relative risk = 0%), nor that the association between mesial CG+ (putative lateral protrusive guidance) and ipsilateral TMJ sounds was beyond that of mere chance (relative risk = 50%).