Advisory Committee Chair
John O Burgess
Advisory Committee Members
Mark Litaker
Richard Gray
Document Type
Thesis
Date of Award
2007
Degree Name by School
Master of Science in Biomedical Engineering (MSBME) School of Engineering
Abstract
Impression materials make a record of tooth structure and provide a critical step in many dental applications. The mechanical properties of the impression material determine its clinical viability. Purpose: This thesis examines three novel methods for measuring mechanical properties of elastomeric impression materials including: (1) flow, (2) tear strength, and (3) elastic recovery. Methods: Flow of 8 impression materials (6 silicone, 1 polyether, 1 hybrid) was measured using a shark fin testing device. The shark fin height of each material (n = 5) was collected at 30 second intervals beginning 30 seconds after mix and ending when material ceased to flow. Shark fin heights at each interval were compared among material groups. Tear strength specimens of 6 materials (4 silicone, 1polyether, 1 hybrid material) were prepared using a ―thin film‖ tear strength mold. Specimens were divided into four groups (n=5). Group 1 and 2 were immediately loaded in tension until failure. Groups 3 and 4 were tested 24 hours after fabrication. Groups 1 and 3 were tested at 1mm/min and groups 2 and 4 were tested at 500mm/min tearing rate. Elastic recovery specimens of 6 materials (5 silicone, 1 hybrid) were prepared using an ASTM D412 (dumbbell) mold modified by the addition of notches delineating a 20mm span. The specimens (n=5) were stretched by 50%, 100%, and 150% of their original length at 300mm/min. After one hour, the distance between the two notches was measured and used to calculate the percent elongation. The elastic recovery of the same materials were tested using the ISO Specification 4823.9.7. Statistical iv analysis of all testing methods was performed with an ANOVA and Tukey’s Test (α = 0.05). Results Polyether materials demonstrated significantly greater flow than hybrid and silicone materials. Silicone materials provided significantly higher tear strength values than polyethers and hybrid materials. Faster tearing rates and longer setting time improved tear strength. The hybrid material provided the second lowest amount of elastic recovery. Conclusion The novel testing methods presented in this manuscript can be used to differentiate materials based on their mechanical properties. Properties vary among composition groups and should be considered when selecting a material.
Recommended Citation
Lawson, Nathaniel C., "Mechanical Properties Of Dental Impression Materials" (2007). All ETDs from UAB. 3601.
https://digitalcommons.library.uab.edu/etd-collection/3601
