Cephalometric evaluation of different methods for recording denture position

In the follow up studies, it was recommended to use cephalometric X-ray technique to study the changes of denture position. It was advised, according to the results, to follow the light contact condition technique in keeping the upper denture in place during successive exposures

study on the effect of lower denture weight on the action potential of masseter and temporalis muscles

To study the effect of increasing the weight of the lower denture on the action potential of the masseter and temporalis muscles, 10 complete denture wearers were selected complaining of unstable lower denture. Electromyographic recording in different functional situations were done for each patient with their original denture. The weight of the lower denture was doubled and delivered to the patient to use it for three weeks. Another electromyographic recordings in the same functional situations were recorded with modified denture. From the obtained results it was concluded that, increasing weight of the lower denture affects the action potential of the masseter and temporalis muscles. Besides, increasing weight of lower denture increases muscular activity of temporalis and masseter muscles. Finally, increasing weight of the lower denture improves denture service and patient's comfort

Effect of polymerization under pressure on dimensional changes of acrylic resin maxillary dentures

The aim of this study was to investigate the effect of increased curing pressure on the dimensional changes of acrylic maxillary denture. Twelve reference guides were used to measure the changes in the horizontal lateral, horizontal anteroposterior and vertical direction between the waxed and the processed dentures with each technique. The results showed a change in the lateral direction of 0.5%, 0.14%, in the anteroposterior direction of 0.53%, 0.26%, in the vertical direction of 0.098%, 0.25% for the conventional and pressure processing techniques, respectively. From this study, it could be concluded that the pressure polymerization techniques reduce the dimensional changes of acrylic resins significantly in all the measured directions

Influence of reinforcement on the creep behaviour of polymeric denture base

Acrylic resin, the widely used material for denture bases, creeps under protracted load, this endangers the clinical performance of the dentures as well as their supporting tissues. Therefore creep is an important property but it has not been evaluated to date in the standard dental materials testing. This study characterizes the viscoelastic behavior of three types of polymer based denture base material and eight volume fractions of Aramid fibers reinforced acrylic resin. The instant deformation, primary creep, secondary creep, elastic recovery, time dependent deformation, and the permanent set have been shown. The creep rate, creep compliance have been computed for every material tested. The effect of the magnitude of stress on the creep behavior was also tested. The results given were the mean of four specimens tested in each group of material i.e. 56 specimens were tested. The following conclusions are drawn; 1. The High impact material showed; a permanent set twice that of the heat cure acryl while their creep rates were similar. 2. The light cure material showed higher deformations, a lower value for the permanent set and a similar creep rate compared to the heat cured acryl. 3. The reinforced specimens showed a general improvement in the creep behavior, particularly with the higher volume fraction concentrations 14.5, 15.8, 16 percent. An average decrease in the instant deformation to about half, the permanent set to about 20 times and the creep rate by about 3 times compared to the heat cured acrylic resin. 4. Complete recovery was reached with one group of reinforced specimen 14.0 percent. Therefore Aramid fibers reinforcement can be used with the heat cured acrylic dentures to decrease their creep effect and consequently offer a better clinical service. 5. To obtain efficiency with the fibers reinforcement, the fibers should be uniform, continuous, firmly gripped by the matrix, unidirectional and their direction should be parallel to the direction of the induced stresses in the composite. 6. To obtain reproducibility of the composite properties, effort should be done to apply pressure on the dough without disrupting the fibers arrangement, as occurred with the 10 percent volume fraction specimens. 7. The creep test requires simple instruments, and provides important characterization about the mechanical behavior in service

Clinical evaluation of polyvinyl siloxane for complete and partial denture impressions

The addition silicones impression material can be used for complete and partial denture, and can be stored over 15 days and still give satisfactory results. All the impression used in this study experienced a negative dimensional change. Changes in anteroposterior directions was more than that of the lateral direction in both complete and partial impressions. Partial dentures impression experienced more shrinkage than the compete dentures impressions in all measured directions through out the study period