IADR Abstract Archives
A novel methodology for direct measurements of intra-canal circumferential strains in teeth restored with cast post/core and crown
Objectives: Endodontically treated teeth with severe substance loss are restored by cast post-core -crown. The purpose of the current study was to measure directly the circumferential strains in the intra-canal post
Methods: Six central incisors bovine teeth were horizontally sectioned 5mm coronal to the CEJ. The root canals were prepared with K files to #140. The axial surfaces of the teeth were prepared to receive a full coverage metal crown with 2 mm ferrule. Cast post and cores were constructed using burnout plastic posts in Ni-Cr alloy. The buccal and lingual surfaces of the intra-canal cast post were reduced by 0.4mm to enable bonding of miniature strain gauges. Four miniature strain gauges (EA-06-031DE-350) were bonded on the buccal and lingual surfaces of the post and the root dentin. Electric wires connected the strain gauges to computerized data acquisition system (System 2100, Measurement Group) by passing along the root canal and through the apex of the root. Cementation of the cast post and core was done by ZPC. The teeth embedded in epoxy cylinders were inserted to an adjustable loading apparatus and the cemented crown was loaded at angulations of 0°, 15°, 30° and 45° till 100N. .
Results: The buccal and lingual aspects of the post and root were characterized by negative (compression) and positive (tension) strains. The strains linearly grow with increased load (r>0.94, p<0.01). Higher angulation of load is characterized by higher absolute values of strain. The strains at the root dentin were ±100µs, ±250µs, ±420µs and ±600µs at 0°, 15°, 30° and 45° respectively. The strains at the intra canal post were ±50µs, ±90µs, ±210µs and ±300µs at 0°, 15°, 30° and 45° respectively. .
Conclusions: Avoiding excursive movements in cast post-core-crown resulted in less intra canal stresses induced by the post, probably reducing the risk of vertical root fracture.
Methods: Six central incisors bovine teeth were horizontally sectioned 5mm coronal to the CEJ. The root canals were prepared with K files to #140. The axial surfaces of the teeth were prepared to receive a full coverage metal crown with 2 mm ferrule. Cast post and cores were constructed using burnout plastic posts in Ni-Cr alloy. The buccal and lingual surfaces of the intra-canal cast post were reduced by 0.4mm to enable bonding of miniature strain gauges. Four miniature strain gauges (EA-06-031DE-350) were bonded on the buccal and lingual surfaces of the post and the root dentin. Electric wires connected the strain gauges to computerized data acquisition system (System 2100, Measurement Group) by passing along the root canal and through the apex of the root. Cementation of the cast post and core was done by ZPC. The teeth embedded in epoxy cylinders were inserted to an adjustable loading apparatus and the cemented crown was loaded at angulations of 0°, 15°, 30° and 45° till 100N. .
Results: The buccal and lingual aspects of the post and root were characterized by negative (compression) and positive (tension) strains. The strains linearly grow with increased load (r>0.94, p<0.01). Higher angulation of load is characterized by higher absolute values of strain. The strains at the root dentin were ±100µs, ±250µs, ±420µs and ±600µs at 0°, 15°, 30° and 45° respectively. The strains at the intra canal post were ±50µs, ±90µs, ±210µs and ±300µs at 0°, 15°, 30° and 45° respectively. .
Conclusions: Avoiding excursive movements in cast post-core-crown resulted in less intra canal stresses induced by the post, probably reducing the risk of vertical root fracture.