Effects of Er:YAG and Diode Laser Irradiation on Dental Pulp Cells and Tissues

Abstract

Vital pulp therapy (VPT) is to preserve the nerve and maintain healthy dental pulp tissue. Laser irradiation (LI) is beneficial for VPT. Understanding how LI affects dental pulp cells and tissues is necessary to elucidate the mechanism of reparative dentin and dentin regeneration. Here, we show how Er:YAG-LI and diode-LI modulated cell proliferation, apoptosis, gene expression, protease activation, and mineralization induction in dental pulp cells and tissues using cell culture, immunohistochemical, genetic, and protein analysis techniques. Both LIs promoted proliferation in porcine dental pulp-derived cell lines (PPU-7), although the cell growth rate between the LIs was different. In addition to proliferation, both LIs also caused apoptosis; however, the apoptotic index for Er:YAG-LI was higher than that for diode-LI. The mRNA level of odontoblastic gene markers—two dentin sialophosphoprotein splicing variants and matrix metalloprotease (MMP)20 were enhanced by diode-LI, whereas MMP2 was increased by Er:YAG-LI. Both LIs enhanced alkaline phosphatase activity, suggesting that they may help induce PPU-7 differentiation into odontoblast-like cells. In terms of mineralization induction, the LIs were not significantly different, although their cell reactivity was likely different. Both LIs activated four MMPs in porcine dental pulp tissues. We helped elucidate how reparative dentin is formed during laser treatments.

Pulpal and periapical tissue response after direct pulp capping with endosequence root repair material and low-level laser application

“…Similar results were obtained using different laser types in other studies [ 17 , 18 ]. LLLT application on the pulp–dentine interface after conservative cavity preparation without pulp exposure leads to more aggregated organized collagen fibrils and odontoblast process [ 19 ].…”

Efficacy of Er:YAG laser‐assisted direct pulp capping in permanent teeth with cariously exposed pulp: A pilot study

“…Kinds of laser have been applied for direct pulp capping therapy in vitro and in vivo . Yamakawa showed that Er:YAG and diode laser irradiation could promote cell proliferation, induce dentin proteins genes expression, and stimulate pulp cell differentiation into functional odontoblasts by activating TGF‐β cell signal pathway (14). Animal experiments showed that the CO 2 laser aid procedures not only enhancing the success rate of vital pulp preservation, but also improving the thickness of reparative dentin bridges (15).…”

“…But, inadequate or excessive irradiation can also cause injury. Er:YAG laser may induce cell shrinkage or even apoptosis (14). When lasers are set at high output power, the accumulated heat can cause pulpal damage.…”

Characterization of Living Dental Pulp Cells in Direct Contact with Mineral Trioxide Aggregate

“…Since pigs are relatively close to humans physiologically and anatomically, they are expected to be used as a model for future regenerative medicine. We previously established the PPU7 cell line from porcine dental pulp cells [ 26 ] and used it for dentin-regeneration research [ 27 , 28 ]. Hence, we used PPU7 cells for basic research to investigate the cell dynamics on the MTA disk.…”

“…The immortalized porcine dental pulp cell line (PPU7) was established [ 26 ] and has been used for endodontic research associated with laser irradiation [ 27 ]. PPU7 cells can express alkaline phosphatase (ALP) and odontoblastic marker genes that form precipitated nodules when cultured in a medium containing β-glycerophosphate and ascorbic acid.…”