Cytotoxicity of Common Local Anesthetics on Odontoblast-like Cells in Vitro

Objectives: Odontoblasts, one of the major cellular components of dental pulp, play an important role in maintaining pulpal homeostasis. Ideally, odontoblasts respond to various dental treatments, activating pulpal healing and mineralizing a dentin bridge at the site of pulp exposure. We investigated and compared the cytotoxicity of commonly used local anesthetics on odontoblast-like cells in vitro.

Methods: Procaine, lidocaine, mepivacaine, articaine, prilocaine, and bupivacaine were tested on the odontoblast cell line MDPC-23. Concentration- and time-dependent cytotoxic effects were measured by methyl tetrazolium (MTT) assay. The mechanism of cytotoxicity was investigated using microscopic observation of morphological changes and flow cytometric analysis of annexin V and propodium iodide (PI) staining.

Results: Of the local anesthetics tested, only bupivacaine significantly induced cell death in a concentration- and time-dependent manner (LC₅₀ = 1200 µM; 18 hr). Annexin V and PI staining results, as well as morphologic findings, showed that the proportion of apoptotic cells gradually increased as concentration and incubation time increased.

Conclusions: Unlike other local anesthetics, bupivacaine was cytotoxic to odontoblasts, and this cytotoxicity was closely associated with apoptosis. Since odontoblasts are responsible for the majority of oral hard tissue homeostasis, this means that the use of bupivacaine might have an adverse effect during or after dental treatments performed under otherwise uneventful local anesthesia.