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In vitro and in situ assessment of the CO2 laser effects on dentin and enamel demineralization

Grant number: 08/02813-0
Support Opportunities:Regular Research Grants
Duration: October 01, 2008 - December 31, 2010
Field of knowledge:Health Sciences - Dentistry - Pediatric Dentistry
Principal Investigator:Marines Nobre dos Santos Uchôa
Grantee:Marines Nobre dos Santos Uchôa
Host Institution: Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil


Even though there have been a significant caries experience reduction in the world and in Brazil, groups of population still present a high dental caries incidence. Thus, there is a need to improve the caries preventive methods used and also to introduce inovative and effective techniques in the prevention of enamel and dentin caries. A number of studies have already demonstrated that CO2 laser application in enamel and dentin result in increase in acid demineralization resistance and in inhibition of carious lesion progression. Besides that, it´s known that, when associated with fluoride, the CO2 laser effects are potencialized. However, there are no studies aiming at evaluating in vitro the CO2 laser effects: 1. In the demineralization around orthodontic brackets and adhesive resistance in bonding materials; 2. Associated with fluoride in root caries reduction, and aiming at assessing, in situ, the CO2 laser effects: 3. Combined with fluoride in the demineralization reduction in enamel adjacent to composite resin restoration; 4. Associated with fluoride in the oclusal surface caries development. The first study will use a microbiological model to produce caries in enamel in vitro. CO2 laser irradiation will be performed on the enamel slabs and then the brackets will be bonded. Bacteria colonies present in the biofilm formed around the brackets will be counted. Water insoluble polyssacaride analysis and mineral content through longitudinal enamel sectioned microhardness will also be performed. The second study will, initially, develop an in vitro standardized microbiological model to produce dentin caries, using a media that will simulate the de- and remineralizing conditions as those that occur in the oral cavity. After the exposition of the dentin slabs to this model, the biofilm formed will be collected and submitted to biochemical and microbiological analysis, besides microbiological and microhardness analysis of the carious dentin. In a second phase, new dentin slabs will be submitted to this previously established microbiological model which will enable the assessment of the interaction of the CO2 laser and acidulated phosphate fluoride. After the results collection, biochemical analysis of the formed biofilm will be performed (fluoride, calcium, phosphorus and water insoluble polyssacaride concentrations) and microhardness of the carious dentin will be evaluated to quantify the mineral content. The third study will use an in situ model and enamel slabs will be prepared with diamond bur and will be irradiated with CO2 laser in the cavosurface angle associated with fluoride by dentifrice use by 14 volunteers who will wear the palatal appliances in two phases of 14 days. In order to promote a high carious challenge, the volunteers will drip onto the slabs a 20% sucrose solution, 8 times a day. At the end of each phase, the levels of F, Ca, Pi and water insoluble polyssacaride will be evaluated in the collected biofilm. The mineral loss, around the restorations, will be quantified by the microhardness analysis. The fourth study will also use an in situ model with 2 phases of 14 days each, in which 16 volunteers will wear a palatine intra-oral appliance with 2 enamel slabs including the oclusal surface, associated with the use of dentifrices by the volunteers. In order to promote a high carious challenge, the volunteers will drip onto the slabs a 20% sucrose solution, 8 times a day. In the 14° day of each phase, the slabs will be collected, longitudinally sectioned and submitted to microharness analysis to quantify the mineral loss. All data will be statistically analyzed, accordingly to the most appropriated test to each experimental phase with a significant level of 5%. (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
DE SOUZA-E-SILVA, CINTIA MARIA; PARISOTTO, THAIS MANZANO; STEINER-OLIVEIRA, CAROLINA; KAMIYA, REGIANNE UMEKO; AZEVEDO RODRIGUES, LIDIANY KARLA; NOBRE-DOS-SANTOS, MARINES. Carbon dioxide laser and bonding materials reduce enamel demineralization around orthodontic brackets. Lasers in Medical Science, v. 28, n. 1, p. 111-118, . (08/02813-0)

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