Award for Research in Prosthodontics

¹ Ohio State University College of Dentistry, Columbus, Ohio

Periodic clinical examinations, cephalometric radiographs, and laboratory measurements on 52 patients and their dentures over a period of as long as 5 years have shown that:

1. A closure of the vertical relation of occlusion as determined by nation to mention distances, with their dentures held in centric occlusion, occurred for all patients and only 9 percent of the loss was due to occlusal abrasion of porcelain posterior teeth.

2. The amount of this centric occlusion closure over several years varied widely between individual patients, but was less on the average for one group of 18 patients who had anatomic posterior occlusal schemes on their dentures. The anterior-upward movement of mention was also less for the anatomic occlusal group when compared with two other similar-sized groups of patients wearing dentures with nonanatomic and with semianatomically shaped posterior teeth.

3. Less postinsertion denture adjustments were necessary for the group of patients with the anatomic posterior occlusion, and the most alterations were required for the patients with nonanatomic (flat-cusped) teeth.

4. In previous studies by Hickey, Allison, and Woelfel, using the same three posterior occlusal schemes interchangeably on one denture base, better denture stability was found and 12 percent less closing muscle activity required to masticate weighed portions of test foods using the anatomic occlusion compared to the other two occlusions. It is possible that this greater combined chewing efficiency and denture stability with anatomic posterior teeth could account in part over the years for the less rapid and less total bone resorption that occurred in the group of patients with the anatomic posterior occlusion.

5. Using two observers and an electro-myograph (oscilloscope for visual monitoring and a high fidelity amplifer and speaker for aural monitoring, with simultaneous pen recordings) to determine mandibular physiologic rest position, very little closure, if any, could be found in the resting height of the mandible over 5 years even though a considerable loss in the occluding vertical dimension occurred. Consequently, an increase of the interocclusal distances from year to year occurred and was most noteworthy the first year.

6. No correlation was found between the amount of interocclusal distance built into the dentures and the rate or amount of resorption or loss in vertical dimension that took place subsequently. In fact, the nonanatomic occlusal group had on the average, 0.6 mm. more interocclusal distance at insertion than the other two groups, yet these patients had the most vertical occlusal closure in the ensuing 5 years.

7. Patients are not usually able to ascertain the amount of change or loss in fit and occlusion of their dentures. Therefore, since changes do take place, it is important that all patients who wear complete dentures be recalled periodically so that the conditions can be evaluated and corrections instituted as deemed necessary by the dentist.