title: Influence of high expansion dental stone used as investing medium on the changes in occlusal vertical dimension of complete dentures.
abstract: OBJECTIVE
  Despite advances in materials and techniques, complete dentures made of acrylic resin experience an increase in the occlusal vertical dimension (OVD) during processing. Many factors that affect the OVD of complete dentures are known. However, no study has examined the effect of using high-expansion dental stone (type V) as an investing material on the OVD.
  
  
  OBJECTIVE
  This study investigated the effects of using a high-expansion dental stone as an investing material on changes in the OVD of complete dentures.
  
  
  METHODS
  Twenty sets of simulated upper and lower dentures were processed by the compression molding technique. Specimens were equally divided into 2 groups. In the dental stone type III (DST III) group, the lower, middle, and upper parts of a flask were filled with DST III. In the dental stone type V (DST V) group, the procedure was the same as in the DST III group, except that the middle layer was made of high-expansion DST V. Changes in the OVD were measured before and after denture processing. Collected data were analyzed with t-test statistics. Differences were considered statistically significant at the 95% confidence level.
  
  
  RESULTS
  Both groups showed a small increase in the OVD as a result of processing, but the OVD increase was significantly less in the DST V group compared to the DST III group.
  
  
  CONCLUSIONS
  High-expansion DST V can be recommended as an investing material to reduce the increase in the OVD that may occur while processing complete dentures.
authors.affiliation: Department of Removable Prosthodontics, Faculty of Dental Medicine, Damascus University, Damascus, Syria.
authors.forename: Alaa'a M
authors.initials: AM
authors.lastname: Salloum
keywords: Acrylic resin; Complete denture; Denture base; High expansion dental stone; Investing; Occlusal vertical dimension