Protocols for Initial Caries Lesion and Enamel Acid Etching for Treatment with Experimental Resin Infiltrants

• Grant number: 24/20006-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2025
• End date: May 31, 2026
• Field of knowledge: Health Sciences - Dentistry - Dental Clinics
• Principal Investigator: Giselle Maria Marchi
• Grantee: Maria Luiza Vieira Guidi
• Host Institution: Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil

Abstract

The aim of this study will be to establish a protocol for the induction of initial carious lesions in bovine and human teeth and to define an acid-etching protocol for an experimental infiltrant. The study will be divided into two parts: the first focusing on the lesion protocol and the second on the acid-conditioning protocol. Enamel blocks measuring 5x2 mm will be obtained from bovine incisors. These blocks will be divided into two groups (n=12): DES and DES-RE. For the DES group, blocks will be immersed in a demineralizing solution for 16 hours and then rinsed with purified water to ensure complete removal of the solution. For the DES-RE group, which involves demineralizing and remineralizing solutions with an 8-day cycling process (4 hours in the demineralizing solution and 20 hours in the remineralizing solution), the solutions will be replaced on the fourth day, and on the eighth day, the samples will remain in the remineralizing solution for 24 hours. For human teeth, two protocols will also be selected (n=12): DES and DES-RE. Enamel blocks measuring 4x2 mm will be prepared from sound third molars. Following polishing, the DES protocol will involve immersing the blocks in a demineralizing solution for 32 hours. For the DES-RE protocol, the blocks will be individually immersed in the demineralizing solution for 4 hours and in the remineralizing solution for 20 hours daily, with the cycle repeated over 5 days at 37°C. Surface microhardness will be assessed before and after the carious lesion induction using a Knoop microhardness tester, with a 50 kgf load for 5 seconds. The samples will then be sectioned to perform transverse microhardness measurements using a 25 kgf load for 5 seconds, with 30 readings per sample, followed by the calculation of mineral loss. Transverse microradiography will also be conducted, with the remaining halves polished manually. Based on these results, one bovine and one human protocol will be selected for further study. New bovine and human enamel blocks will be prepared, cut, and polished. The selected blocks will undergo carious lesion induction. Surface microhardness will be measured before and after lesion induction. The specimens will then be conditioned according to four groups (n=25): hydrochloric acid for 1 minute (H60), hydrochloric acid for 2 minutes (H120), phosphoric acid for 1 minute (F60), and phosphoric acid for 2 minutes (F120). After conditioning, the experimental infiltrant will be applied for 3 minutes, followed by excess removal and light curing for 40 seconds, with a second 1-minute application similarly performed. Transverse microhardness (n=12), confocal laser scanning microscopy (n=3) to measure the infiltrant penetration depth and lesion depth, and contact profilometry (n=10) will be conducted on these blocks. Data will be tabulated and analyzed for homogeneity to determine the appropriate parametric or non-parametric statistical analysis, with a significance level of 5%.