Root Canal Anatomy of Maxillary and Mandibular Teeth

It is a common knowledge that a comprehensive understanding of the complexity of the internal anatomy of teeth is imperative to ensure successful root canal treatment. The significance of canal anatomy has been emphasized by studies demonstrating that variations in canal geometry before cleaning, shaping, and obturation procedures had a greater effect on the outcome than the techniques themselves. In recent years, significant technological advances for imaging teeth, such as CBCT and micro-CT, respectively, have been introduced. Their noninvasive nature allows to perform in vivo anatomical studies using large populations to address the influence of several variables such as ethnicity, aging, gender, and others, on the root canal anatomy, as well as to evaluate, quantitatively and/or qualitatively, specific and fine anatomical features of a tooth group. The purpose of this chapter is to summarize the morphological aspects of the root canal anatomy published in the literature of all groups of teeth and illustrate with three-dimensional images acquired from micro-CT technology.info:eu-repo/semantics/publishedVersio

Ultrastructure of smear layer-covered intraradicular dentin after irrigation with BioPure MTAD

The structure of mechanically instrumented intraradicular dentin after irrigation with NaOCl as the initial rinse and BioPure MTAD as the final rinse were examined from the coronal, middle, and apical parts of root canal walls using transmission electron microscopy. Sterile distilled water and EDTA as final rinses were employed as the respective positive and negative controls under the same experimental conditions. There were 2 to 5 μm thick smear layers produced on mechanically instrumented root canal walls that were completely removed by EDTA and BioPure MTAD under agitation. Both irrigants created a zone of demineralized collagen matrices in eroded dentin and around the dentinal tubules, with the mildly acidic BioPure MTAD being more aggressive than EDTA. These demineralized dentin zones create the opportunity for dentin hybridization by infiltration of hydrophilic adhesives/sealers. However, the potential consequences of compaction of hydrophobic sealers against air-dried, collapsed collagen matrices, and hydrolytic degradation of incompletely infiltrated matrices remain unresolved. Copyright © 2006 by the American Association of Endodontists.link_to_subscribed_fulltex

Does Hybridization of Intraradicular Dentin Really Improve Fiber Post Retention in Endodontically Treated Teeth?

This study tested the hypothesis that hybridization of intraradicular dentin eliminates interfacial gaps, thereby improving the coronal seal and retention of teeth restored with fiber posts. Post spaces were bonded with two types of fiber posts, using the corresponding etch-and-rinse adhesives and dual-cured resin cements. Longitudinal sections of the interfaces were examined for dentin hybridization in the coronal- and middle-thirds of the root canals. Resin replicas of these sections were evaluated for interfacial gap formation. Although intraradicular dentin hybridization was not compromised irrespective of whether the adhesives were light-cured before cementation, the universal occurrence of interfacial gaps along the hybrid layer surface or the post-cement interface reflects the challenge in bonding to post spaces with low compliance and high C-factors. The clinical success associated with bonded fiber posts is probably due predominantly to frictional retention

Bondability of Resilon to a Methacrylate-Based Root Canal Sealer

Resilon broadens the dimensions of endodontic adhesion by introducing the possibility of creating monoblocs between root canal filling materials and intraradicular dentin by using methacrylate-based sealers. The adhesive strength of Resilon to RealSeal, a methacrylate-based root canal sealer, was evaluated using a modified microshear bond testing design. Flat Resilon surfaces with different roughness were created for bonding to the sealer and compared to a composite control. The composite control exhibited mean shear strength 7.3 to 26.9 times higher than those of the Resilon groups. Shear strength differences among the Resilon groups of different surface roughness highlighted the contribution of micromechanical versus chemical coupling in sealer retention. Ultrastructural evidence of phase separation of polymeric components in Resilon suggested that the amount of dimethacrylate incorporated into this filled, thermoplastic composite may not yet be optimized for effective chemical coupling to methacrylate-based sealers

HYBRYD ROOT SEAL (METASEAL)CREATES HYBRID LAYERS IN RADICULAR DENTIN ONLY WHEN EDTA IS USED AS A FINAL RINSE

ABSTRACT: Purpose: To test if the hybrid layer formation by Hybrid Root SEAL (Sun Medical Co.), a 4-METAcontaining auto-adhesive self-etching root canal sealer, is affected by the sequence of irrigants employed for removing canal wall smear layers during root canal treatment. Methods: Single-rooted teeth were shaped and irrigated with EDTA as initial rinse/NaOCl as active final rinse (Group 1), or NaOCl as initial rinse/EDTA as active final rinse (Group 2). All canals were obturated with Hybrid Root SEAL using a single-cone technique. Root slices derived from the coronal, middle and apical thirds of the roots were processed for transmission electron microscopy after removing the gutta-percha, leaving the sealer intact. Additional filled canals from the two groups were evaluated for fluid leakage. Results: Hybrid layer was absent in Group 1 and was present only when a collagen matrix was produced by EDTA demineralization (Group 2). Significantly more leakage (4.03 ± 1.94 μLmin-1 vs. 1.50 ± 0.42 μLmin-1; P< 0.05) was observed in the absence of dentin hybridization. (Am J Dent 2009;22:299-303)

Effectiveness of resin-coated gutta-percha cones and a dual-cured, hydrophilic methacrylate resin-based sealer in obturating root canals.

The introduction of a polybutadiene-diisocyanate-methacylate resin-coating of gutta-percha enables the polyisoprene to be chemically coupled to methacrylate-based resin root canal sealers. This study examined the effectiveness of using passively fitting cones of this type of gutta-percha with a dual-cured version of EncloREZ sealer in obturating cleaned and shaped root canals. The hydrophilic nature of the sealer enabled the creation of an extensive network of 800 to 1200 mu m long sealer resin tags after removal of the encloclontic smear layer. Although no adhesive was employed, thin hybrid layers in root dentin were observed when EDTA was used as the final rinse, Nevertheless, interfacial gaps and silver leakage could be,observed along the sealer-dentin interfaces that might be attributed predominantly to polymerization shrinkage of the sealer. Gaps and silver leakage were also identified between the gutta-percha resin-coating and the sealer

Susceptibility of a polycaprolactone-based root canal filling material to degradation. III. Turbdimetric evaluation of enzymatic hydrolysis

The susceptibility of Resilon (Pentron Clinical Technologies, Wallingford, CT) to biotic biodegradation by two hydrolases, lipase PS and cholesterol esterase, was investigated with a turbidimetric approach by measuring the optical density reductions in aqueous emulsions containing dissolved, filtered, surfactant-stabilized polymeric components of Resilon. Polycaprolactone, the major polymeric component of Resilon, was also examined in a similar manner using equivalent or a four-fold increase in enzyme concentration. Optical density time plots were characterized by an initially linear steep reduction in optical density, from which the reaction rates were derived. For both enzymes, the rates of hydrolysis for Resilon were much faster than those of polycaprolactone at 1x or even 4x enzyme concentration. Field-emission scanning electron microscopy of air-dried Resilon and polycaprolactone emulsions revealed the presence of spherical polymer droplets that appeared deformed, pitted, or much reduced in dimensions after enzymatic hydrolysis