Characterization of the acquired pellicle formed in situ over human enamel and dentin before and after mechanical and chemical salivary flow stimulation: proteomic study

• Grant number: 12/10137-0
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: September 27, 2012
• End date: January 26, 2013
• Field of knowledge: Health Sciences - Dentistry
• Principal Investigator: Marília Afonso Rabelo Buzalaf
• Grantee: Flávia Zaidan Cardoso dos Santos
• Supervisor: Walter Luiz Siqueira
• Host Institution: Faculdade de Odontologia de Bauru (FOB). Universidade de São Paulo (USP). Bauru , SP, Brazil
• Institution abroad: Western University , Canada
• Associated to the scholarship: 11/03112-9 - Determination of the composition of the acquired pellicle formed on enamel and dentin and its modification after chemical and mechanic stimulation of salivary flow: proteomic study, BP.MS

Abstract

All solid surfaces exposed to the oral cavity are covered by a closely adherent protein film termed the acquired pellicle. It is an organic film, bacteria free, that overlies the hard dental tissues and is basically composed by glycoproteins and proteins. Recently, many studies have focused on the protector impact of the acquired pellicle formed in situ over the enamel surface; while for the dentin, the information about the role of the acquired pellicle on the erosion prevention is quite limited. The aim of the present study was to compare the protein profile of acquired pellicles formed in situ over the human enamel and dentin surfaces in resting condition and also analyze the protein profile of the pellicles formed after mechanical and chemical salivary flow stimulation. For each of the three studied groups, 60 blocks of human enamel (3x3mm) and 60 blocks of human dentin (3x3mm) were used. The experimental phases were performed for 3 consecutive days in a crossed design. On each day, the volunteers (n=10) wore a mandibular appliance containing 6 blocks of enamel and 6 blocks of dentin. On the first day, after wearing the appliance for 10 and 120 minutes the blocks were removed and the acquired pellicle was harvested with an electrode wick filter soaked in 3% citric acid. On the second day, directly after inserting the appliance in their oral cavity, the volunteers were instructed to chew a piece of paraffin wax during the initial 10 minutes and, as in the first day, the pellicle formed over the blocks was collected after 10 and 120 minutes. On the third day, the same procedures described for the first day will be conducted, but the salivary flow will be stimulated during the initial 10 minutes by dropping a certain amount of 2% citric acid on both sides of their tongue. For each group a "pool" will be done with the wick filters obtained from all volunteers, for each type of substrate and time of harvesting. After the protein extraction, they will be subjected to fractioning by ion exchange chromatography. The fractions will be concentrated and then subjected to liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). MS/MS spectral data were searched against human protein databases (Swiss Prot and TrEMBL, Swiss Institute of Bioinformatics, Geneva, Switzerland, http://expasy.org/sprot) by SEQUEST (Bioworks Browser 3.2, Thermo-Finnigan, San Jose, CA, USA). (AU)