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Enamel Deproteinization After Acid Etching - Is It Worth The Effort?

Ramakrishna Y*,Bhoomika A,Harleen N,Munshi AK

Objectives: This study was undertaken to observe the topographical features of enamel surface deproteinized with 5.25% sodium hypochlorite(NaOCl) after phosphoric acid (H3PO4) etching using Scanning Electron Microscope (SEM) analysis and also the effect of enamel deproteinization after acid etching on the shear bond strength (SBS) of AdperTM Single Bond 2 adhesive and FiltekTM Z- 350 XT composite resin.
Study Design: SEM Observation: 10 enamel blocks of 1mm2 from 10 human sound permanent molar teeth were obtained and treated with 37% H3PO4 gel for 15 seconds followed by treatment with 5.25% NaOCl for 60 seconds. All the 10 samples were subjected to SEM analysis and 5 microphotographs of each sample were obtained at 500X magnification and evaluated for the occurrence of Type I – II etching pattern in percentage (%) using Auto – CAD 2007 software. SBS Evaluation: A 5X4 mm window of the enamel surface was etched with 37% H3PO4 gel for 15 seconds, washed with distilled water and air dried. The etched enamel surface was then treated with 5.25% NaOCl for 60 seconds, washed with distilled water and air dried. A single coat of Adper™ Single Bond 2 adhesive was applied and photo polymerized for 20 seconds and Filtek™ Z- 350 XT composite resin block of length 5mm, width 4mm and height 5mm respectively was built and photo polymerized in increments for 20 seconds each. The shear bond strength of all the 20 test samples (permanent molar teeth) were measured (in MPa) on Instron Mechanical Testing Machine.
Results: The mean value of Type I – II etching pattern of all the test samples was observed to be 40.68 + 26.38 % and the mean SBS value for all the test samples was observed to be 17.35 + 7.25 MPa.
Conclusions: No significant enhancive effect of enamel deproteinization after acid etching with respect to the occurrence of Type I-II etching patterns as well as on the SBS of adhesive resin and composite resin complex to the enamel surface was observed in this study. The use of 37% phosphoric acid alone for 15 seconds still remains the best method for pretreatment of the enamel.