C

The chief factor weakening endodontically treated posterior teeth is the removal of coronal dentin (marginal ridges, pulp chamber roof) during access and caries/restorative procedures; this loss markedly decreases fracture resistance, whereas changes in moisture content or the presence of a “hollow” canal have minimal effect [Sorensen & Engelman, 1990, PMID 2187080; Ng et al., 2006, PMID 16616126].