| Co-Investigator(Kenkyū-buntansha) |
SHINKAI Koichi The Nippon Dental University, School of Life Dentistry at Niigata, Associate Professor, 新潟生命歯学部, 助教授 (90147843)
EBIHARA Takashi The Nippon Dental University, School of Life Dentistry at Niigata, Lecturer, 新潟生命歯学部, 講師 (40287777)
SUZUKI Masaya The Nippon Dental University, School of Life Dentistry at Niigata, Assistant, 新潟生命歯学部, 助手 (10409237)
SHIRONO Manabu The Nippon Dental University, School of Life Dentistry at Niigata, Lecturer, 新潟生命歯学部, 講師 (40339453)
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| Research Abstract |
As reparative dentin-promoting agents, four types of calcium phosphates: hydroxyl-calcium phosphate (HAP), dicalcium phosphate dehydrate (brushite : DCPD), beta-tricalcium phosphate (whitrokite : β-TCP) and octacalcium phosphate (OCT), were mixed with experimental monomer liquid to create materials for experimentally developed direct pulp capping agents and bonding agents of dental substrates. After polymerization, dispersion, shape and composition of calcium phosphates were analyzed by using SEM, EPMA and ICP Atomic Emission Spectrometry.
Results obtained were as follows :
1) The powder of calcium phosphates in polymerized monomer liquid scattered like dispersed fillers in composite resin. The dispersion of the powder was highly influenced by vibration and trituration during the mixing preparation of the materials.
2) Ca showed a relatively high concentration in relation to P. But Mg was present only in a trace amount and was detected only when using line analysis.
3) Each calcium phospha
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te showed different elutions of Ca and P. The amount of elutions was affected by the solubility product (Ksp) of each calcium phosphate.
4) It was suggested that when the materials were used as direct pulp capping agents, reparative dentin formation was particularly promoted and reliability of wound healing was expected to increase, especially improvement of wound healing in the first stage after capping.
5) Calcium phosphates in polymerized pulp capping and bonding agents were found in the vicinity of the exposed pulp. Reparative dentin formation was effectively promoted under the following conditions: calcification promoting effect by direct contact, ionic effect of Ca and P eluted from calcium phosphates and environmental change of the surface of the exposed pulp through the effect of the change in pH.
In total twelve types of bonding agents were prepared at a fixed amount of calcium phosphates. The exposed pulp in rats were directly capped with combined use of experimental primers and twelve types of bonding agents. After direct capping of exposed pulp, the rats were sacrificed at the experimental periods of 1, 3, 7, 14 and 28 days. Inflammatory and reparative pulpal changes were examined immunohistochemically and histopathologically under an optical microscope.
Results could be summarized as follows :
1) After day one, mild inflammatory changes were observed in all groups but they decreased over time (3, 7 days).
2) In the groups which used no calcium phosphates, almost no reparative dentin formation was observed on day 14 but a little was observed on day28.
3) In the groups which used calcium phosphates, reparative dentin formation was already recognized on day 14 and increased over time up to day 28.
4) Reparative dentin formation was clearly affected by the types and concentrations of calcium phosphates. In addition, differences were also observed between the primers.
5) In the groups containing calcium phosphates, relatively more reparative dentin formation was observed in the following groups: MB5 (β-TCP 5wt%), MB9 (HAP 5wt%, β-TCP 5wt%), MB1 (HAP 5wt%), MB2 (HAP 1Owt%) and MB3 (β-TCP 5wt%). In general, the groups containing β-TCP showed more advanced reparative dentin formation.
6) In experimentally developed primer, MP3 (MB primer containing 5-NMSA 2wt%) showed less inflammatory change than another experimental primer (ABP) containing the antibacterial monomer MDPB. The combination use of MB1 and MP3 showed the least inflammatory change and the most advanced reparative dentin in orthodentin. It was suggested that the combination use of MB1 and MP3 was the most reliable for wound healing in the first stage after direct capping.
In the CO_2 laser irradiation groups, Opelaser^<【○!R】> 03 S II SP (Yoshida Dental Mfg Co) was used. After carbonization, the pulpal surface was directly capped with MB.
Results could be summarized as follows:
1) After day one, slightly stronger inflammatory changes were observed. But they disappeared over time.
2) No reparative dentin formation was observed, even after day 14.
3) Almost no reparative dentin formation was observed, even after day 28. Instead large amounts of irritative dentin formation was observed on the pulpal wall.
4) An irregular type of dentin matrix formation was recognized under the layer of pulpal carbonization.
5) The irradiated area of the dentin wall showed the following layers : a carbonization layer, a necrotic layer dyed well with hematoxylin, and a protein denaturation layer dyed well with eosin.
6) Carbonization and necrotic layers induced by laser irradiation obstructed reparative dentin formation and delayed wound healing of the pulp. Neither layer worked as an isolation layer from outside stimulation nor as a protective layer of the pulp.
7) Irradiation conditions employed were as follows: mild, moderate with an LLLT effect and strong levels. Four types of experimentally developed direct pulp capping agents and bonding agents containing calcium phosphates (MB8, MB9, MB11 and MB12) and an experimentally developed primer (MP) were examined with and without irradiation using a CO_2 laser. There were no significant differences between the groups, and it was confirmed that a mild level of irradiation showed fast would healing properties of the pulp and formed a relatively better quality of reparative dentin.
8) By a masking effect at a moderate level of irradiation, an LLLT effect of the CO_2 laser was not clearly confirmed. Regarding the irradiation conditions using the CO_2 laser, more studies are required in the future. Less
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