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Effect of Endocrown Pulp Chamber Extension Depth on Molar Fracture Resistance.
Oper Dent. 2017 May/Jun; 42(3):327-334.OD

Abstract

PURPOSE

The purpose of this study was to evaluate the effect of endocrown pulp chamber extension on mandibular molar fracture resistance.

METHODS AND MATERIALS

A total of 36 recently extracted mandibular third molars of approximate equal size were sectioned at the facial lingual height of contour followed by endodontic access into the pulp chamber. The specimens were then randomly divided into three groups (n=12) and pulpal and root canal contents removed. Pulp chamber floors were established at 2, 3, and 4 mm from the occlusal table using a three-step etch-and-rinse adhesive and a flowable resin composite. The prepared specimens were then embedded in auto-polymerizing denture base resin with surface area available for adhesive bonding determined using a digital recording microscope. Specimens were restored using a standardized template with a chairside computer-aided design/computer-aided manufacturing unit with the endocrown milled from a lithium disilicate glass-ceramic material. Restoration parameters of occlusal table anatomy and thickness were standardized with the only parameter difference being the pulp chamber extension depth. The endocrown restorations were luted with a self-adhesive resin luting agent and tested to failure after 24 hours on a universal testing machine, with force applied to the facial cusps at a 45° angle to the long axis of the tooth. The failure load was converted into stress for each specimen using the available surface area for bonding. Mean failure load and stress among the three groups was first subjected to the Shapiro-Wilk and Bartlett tests and then analyzed with an analysis of variance with the Tukey post hoc test at a 95% confidence level (p=0.05).

RESULTS

The 2- and 4-mm chamber extension groups demonstrated the highest fracture resistance stress, with the 3-mm group similar to the 2-mm group. The 3- and 4-mm chamber extension group specimens demonstrated nearly universal catastrophic tooth fracture, whereas half the 2-mm chamber extension group displayed nonrestorable root fractures.

CONCLUSIONS

Under the conditions of this study, mandibular molars restored with the endocrown technique with 2- and 4-mm pulp chamber extensions displayed greater tooth fracture resistance force as well as stress. All groups demonstrated a high number of catastrophic fractures, but these results may not be clinically significant because the fracture force results are higher than normal reported values of masticatory function.

Authors

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Pub Type(s)

Journal Article

Language

eng

PubMed ID

28467258

Citation

Hayes, A, et al. "Effect of Endocrown Pulp Chamber Extension Depth On Molar Fracture Resistance." Operative Dentistry, vol. 42, no. 3, 2017, pp. 327-334.
Hayes A, Duvall N, Wajdowicz M, et al. Effect of Endocrown Pulp Chamber Extension Depth on Molar Fracture Resistance. Oper Dent. 2017;42(3):327-334.
Hayes, A., Duvall, N., Wajdowicz, M., & Roberts, H. (2017). Effect of Endocrown Pulp Chamber Extension Depth on Molar Fracture Resistance. Operative Dentistry, 42(3), 327-334. https://doi.org/10.2341/16-097-L
Hayes A, et al. Effect of Endocrown Pulp Chamber Extension Depth On Molar Fracture Resistance. Oper Dent. 2017 May/Jun;42(3):327-334. PubMed PMID: 28467258.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of Endocrown Pulp Chamber Extension Depth on Molar Fracture Resistance. AU - Hayes,A, AU - Duvall,N, AU - Wajdowicz,M, AU - Roberts,H, PY - 2017/5/4/entrez PY - 2017/5/4/pubmed PY - 2018/4/18/medline SP - 327 EP - 334 JF - Operative dentistry JO - Oper Dent VL - 42 IS - 3 N2 - PURPOSE: The purpose of this study was to evaluate the effect of endocrown pulp chamber extension on mandibular molar fracture resistance. METHODS AND MATERIALS: A total of 36 recently extracted mandibular third molars of approximate equal size were sectioned at the facial lingual height of contour followed by endodontic access into the pulp chamber. The specimens were then randomly divided into three groups (n=12) and pulpal and root canal contents removed. Pulp chamber floors were established at 2, 3, and 4 mm from the occlusal table using a three-step etch-and-rinse adhesive and a flowable resin composite. The prepared specimens were then embedded in auto-polymerizing denture base resin with surface area available for adhesive bonding determined using a digital recording microscope. Specimens were restored using a standardized template with a chairside computer-aided design/computer-aided manufacturing unit with the endocrown milled from a lithium disilicate glass-ceramic material. Restoration parameters of occlusal table anatomy and thickness were standardized with the only parameter difference being the pulp chamber extension depth. The endocrown restorations were luted with a self-adhesive resin luting agent and tested to failure after 24 hours on a universal testing machine, with force applied to the facial cusps at a 45° angle to the long axis of the tooth. The failure load was converted into stress for each specimen using the available surface area for bonding. Mean failure load and stress among the three groups was first subjected to the Shapiro-Wilk and Bartlett tests and then analyzed with an analysis of variance with the Tukey post hoc test at a 95% confidence level (p=0.05). RESULTS: The 2- and 4-mm chamber extension groups demonstrated the highest fracture resistance stress, with the 3-mm group similar to the 2-mm group. The 3- and 4-mm chamber extension group specimens demonstrated nearly universal catastrophic tooth fracture, whereas half the 2-mm chamber extension group displayed nonrestorable root fractures. CONCLUSIONS: Under the conditions of this study, mandibular molars restored with the endocrown technique with 2- and 4-mm pulp chamber extensions displayed greater tooth fracture resistance force as well as stress. All groups demonstrated a high number of catastrophic fractures, but these results may not be clinically significant because the fracture force results are higher than normal reported values of masticatory function. SN - 1559-2863 UR - https://www.unboundmedicine.com/medline/citation/28467258/Effect_of_Endocrown_Pulp_Chamber_Extension_Depth_on_Molar_Fracture_Resistance_ L2 - https://meridian.allenpress.com/operative-dentistry/article-lookup/doi/10.2341/16-097-L DB - PRIME DP - Unbound Medicine ER -