Abstract
Statement of problem
Mandibular second molars have variable root, pulp chamber floor, and radicular groove
morphologies, potentially affecting residual dentin thickness and post placement suitability.
However, an identification of the danger zones is lacking.
Purpose
The purpose of this in vitro study was to investigate the residual dentin thickness
in the danger zone of mandibular second molars after virtual fiber post placement
by using a simulation method based on microcomputed tomography (μCT).
Material and methods
A total of 84 extracted mandibular second molars were scanned using μCT and classified
according to root morphology (separate or fused) and pulp chamber floor morphologies
(C-shaped, non-C-shaped, or no pulp chamber floor). Fused-root mandibular second molars
were further classified based on the radicular groove type (V-, U-, or Ω-shaped).
All specimens were accessed, instrumented, and rescanned with μCT. Two types of commercial
fiber posts were also scanned. Clinical fiber post placement was simulated in all
prepared canals by using a multifunctional software program. The minimum residual
dentin thickness of each root canal was measured and analyzed by using nonparametric
tests to identify the danger zone. Perforation rates were calculated and recorded.
Results
Larger fiber posts decreased minimum residual dentin thickness (P<.05) and increased perforation rate. In regard to mandibular second molars with separate
roots, the distal root canal exhibited a significantly higher minimum residual dentin
thickness than the mesiobuccal and mesiolingual root canals (P<.05). However, no significant difference in minimum residual dentin thickness was
found between the different canals in fused-root mandibular second molars with C-shaped
pulp chamber floors (P<.05). Fused-root mandibular second molars with Ω-shaped radicular grooves had a lower
minimum residual dentin thickness than those with V-shaped radicular grooves (P<.05) and demonstrated the highest perforation rate.
Conclusions
The morphologies of the root, pulp chamber floor, and radicular groove were correlated
with residual dentin thickness distribution in mandibular second molars after fiber
post placement. A comprehensive understanding of mandibular second molar morphology
is essential for determining the suitability of post-and-core crown restorations after
endodontic treatment.
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Article info
Publication history
Published online: May 18, 2023
Publication stage
In Press Corrected ProofFootnotes
Funding: Supported by the National Natural Science Foundation of China [grant 62171193] and the Key Research and Development Program of Sichuan Province [grant 2021YFS0031].
Identification
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© 2023 by the Editorial Council for The Journal of Prosthetic Dentistry.
