Selective caries removal using Er:YAG laser and dentin biomodification with chitosan

Author(s)

Fabiana Almeida Curylofo Zotti

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC)
• Defense date: 2018-02-08

Examining board members

Silmara Aparecida Milori Corona; Danielle Cristine Furtado Messias; Alessandra Nara de Souza Rastelli; Fernanda de Carvalho Panzeri Pires de Souza

• Advisor: Silmara Aparecida Milori Corona

Abstract

The aim of this study was to evaluate the effect of Er:YAG laser for selective removal of carious lesion, followed by biomodification with chitosan. The specific objectives were: 1) To evaluate the chemical elements and the morphology of the dentin surface, as well as, the subsurface microhardness (Experiment 1). 2) To evaluate the microtensile bond strength (TBS) and adhesive interface after 24h, 6 and 12 months of water storage, the dry mass loss and dentin collagen degradation (Experiment 2). Dentinal caries lesions were created in 208 bovine specimens by pH-cycling method (14 days). Specimens were divided according to the carious removal method: bur (low-speed handpiece) or Er:YAG laser (250 mJ/4Hz). Specimens were treated with 35% phosphoric acid and were subdivided according to dentin biomodification: without chitosan (control) and 2.5% chitosan. For the experiment 1, specimens were submitted to Energy Dispersive X-Ray Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) and subsurface microhardness of the dentin. For the experiment 2, specimens were submitted to microtensile bond strength and SEM analysis of the adhesive interface after 24h, 6 and 12 months of storage in water, evaluation of dry mass loss and hydroxyproline release (HYP). Data were analyzed by parametric and non-parametric tests (=0.05). The selective caries removal with Er:YAG laser increased the microhardness value of caries-affected dentin (p=0.03) and reduced the amounts of Ca (0<0.0001) and P (0<0.0001). The biomodification with chitosan did not influence the microhardness (0.0796) and atomic percentage of Ca (p=0.2269) and P (p=0.8842) of residual dentin. SEM analysis showed morphological changes on dentin surface (p>0.05). After 24h, the highest bond strength values were found for bur compared to Er:YAG laser (p<0.001). After 6 months, methods were similar (p=0.432) and after 12 months, the highest bond strength values were found for Er:YAG laser-irradiated dentin (p=0.025). Biomodification with chitosan significantly increased bond strength to dentin after 6 (p=0.011) and 12 months (p<0.001). SEM analysis showed that the biomodification with chitosan preserved the adhesive interface after 12-month storage. The dry mass loss (p>0.664; p>0.263) and HYP release (p>0.6347; p>0.4274) were not influenced, respectively, by the carious removal method or by dentin biomodification. The selective removal of carious dentin with Er:YAG laser increased microhardness of residual caries-affected dentin changing its surface morphology and chemical composition. The biomodification with chitosan did not influence the structural and chemical composition of residual dentin. After 24 hours of water storage, the composite resin bond strength to dentin was affected by Er:YAG laser. However, the bond strength to irradiated-dentin was maintained, while the bur-treated dentin showed a continuous reduction. Biomodification with chitosan, regardless of removal method used, preserved the bond strength and adhesive interface over 12 months. The dry mass and the hydroxyproline release were not influenced (AU)

• FAPESP's process: 14/23654-9 - Selective caries removal using Er:YAG laser and rewetting dentin with chitosan solution
• Grantee: Fabiana Almeida Curylofo Zotti
• Support Opportunities: Scholarships in Brazil - Doctorate