Fluid Mechanics in Dentinal Microtubules Provides Mechanistic Insights into the Difference between Hot and Cold Dental Pain

Dental thermal pain is a significant health problem in daily life and dentistry. There is a long-standing question regarding the phenomenon that cold stimulation evokes sharper and more shooting pain sensations than hot stimulation. This phenomenon, however, outlives the well-known hydrodynamic theory used to explain dental thermal pain mechanism. Here, we present a mathematical model based on the hypothesis that hot or cold stimulation-induced different directions of dentinal fluid flow and the corresponding odontoblast movements in dentinal microtubules contribute to different dental pain responses. We coupled a computational fluid dynamics model, describing the fluid mechanics in dentinal microtubules, with a modified Hodgkin-Huxley model, describing the discharge behavior of intradental neuron. The simulated results agreed well with existing experimental measurements. We thence demonstrated theoretically that intradental mechano-sensitive nociceptors are not “equally sensitive” to inward (into the pulp) and outward (away from the pulp) fluid flows, providing mechanistic insights into the difference between hot and cold dental pain. The model developed here could enable better diagnosis in endodontics which requires an understanding of pulpal histology, neurology and physiology, as well as their dynamic response to the thermal stimulation used in dental practices

Chewing side, bite force symmetry, and occlusal contact area of subjects with different facial vertical patterns

Craniofacial dimensions influence oral functions; however, it is not known whether they are associated with function asymmetry. The objective of this study was to evaluate chewing side preference and lateral asymmetry of occlusal contact area and bite force of individuals with different craniofacial patterns. Seventy-eight dentate subjects were divided into 3 groups according to the VERT index as follows: (1) mesofacial, (2) brachyfacial and (3) dolichofacial. Chewing side preference was evaluated using jaw tracking equipment, occlusal contact area was measured by silicon registration of posterior teeth, and bite force was measured unilaterally on molar regions using 2.25 mm-thick sensors. Statistical analysis was performed using ANOVA on Ranks, Student's t-test, and Mann-Whitney tests at a 5% significance level. Mesofacial, brachyfacial, and dolichofacial subjects presented more occlusal contact area on the left side. Only dolichofacial subjects showed lateral asymmetry for bite force, presenting higher force on the left side. No statistically significant differences were found for chewing side preference among all groups. Within the limitations of this study, it can be concluded that craniofacial dimensions play a role in asymmetry of bite force. ClinicalTrials.gov ID: NCT01286363

Regenerative approaches in endodontic therapies of immature teeth

Regenerative therapies in endodontics have recently gained momentum in clinical dentistry primarily due to the availability of effective root canal disinfection protocols, biocompatible materials with enhanced marginal seal, and discovery of mesenchymal stem cells (MSCs) in the dental pulp. These constitute the “triad” of tissue engineering required for pulp regeneration, assembled to meet the unique needs of the pulp-dentin microenvironment. Endodontic regeneration may be offered to patients at varying levels, including direct and indirect pulp capping, partial and complete pulpotomy, apexogenesis, apexification, and revascularization procedures, all of which require the triad of pulp tissue preservation or engineering. Successful outcomes in revascularization, for example, depend on root canal disinfection employing irrigation and medicaments using biocompatible calcium silicate-based cements (CSCs) paired with adhesion-based restorations that ultimately promote recruitment of MSCs from the apical papillae. These regenerative procedures yield high success rates in treatment outcome, although they are not routinely performed in the day-to-day practice of dentistry. In this chapter, we discuss the rationale for endodontic regeneration procedures in the era of markedly successful conventional therapies, and we outline the procedural aspects of available regenerative endodontic therapies