title: Comparative Evaluation of the Etching Pattern of Er,Cr:YSGG & Acid Etching on Extracted Human Teeth-An ESEM Analysis.
abstract: BACKGROUND
  Etching of enamel and dentin surfaces increases the surface area of the substrate for better bonding of the tooth colored restorative materials. Acid etching is the most commonly used method. Recently, hard tissue lasers have been used for this purpose.
  
  
  OBJECTIVE
  The aim of the present study was to evaluate and compare the etching pattern of Er,Cr:YSGG and conventional etching on extracted human enamel and dentin specimens.
  
  
  METHODS
  Total 40 extracted non-diseased teeth were selected, 20 anterior and 20 posterior teeth each for enamel and dentin specimens respectively. The sectioned samples were polished by 400 grit Silicon Carbide (SiC) paper to a thickness of 1.0 ± 0.5 mm. The enamel and dentin specimens were grouped as: GrE1 & GrD1 as control specimens, GrE2 & GrD2 were acid etched and GrE3 & GrD3 were lased. Acid etching was done using Conditioner 36 (37 % phosphoric acid) according to manufacturer instructions. Laser etching was done using Er,Cr:YSGG (Erbium, Chromium : Ytrium Scandium Gallium Garnet) at power settings of 3W, air 70% and water 20%. After surface treatment with assigned agents the specimens were analyzed under ESEM (Environmental Scanning Electron Microscope) at X1000 and X5000 magnification.
  
  
  RESULTS
  Chi Square and Student "t" statistical analysis was used to compare smear layer removal and etching patterns between GrE2-GrE3. GrD2 and GrD3 were compared for smear layer removal and diameter of dentinal tubule opening using the same statistical analysis. Chi-square test for removal of smear layer in any of the treated surfaces i.e., GrE2-E3 and GrD2-D3 did not differ significantly (p>0.05). While GrE2 showed predominantly type I etching pattern (Chi-square=2.78, 0.05<p>0.10) and GrE3 showed type III etching (Chi-square=4.50, p<0.05). The tubule diameters were measured using GSA (Gesellschaft fur Softwareentwicklung und Analytik, Germany) image analyzer and the 't' value of student 't' test was 18.10 which was a highly significant result (p<.001). GrD2 had a mean dentinal tubule diameter of 2.78μm and GrD3 of 1.09μm.
  
  
  CONCLUSIONS
  The present study revealed type I etching pattern after acid etching, while type III etching pattern in enamel after laser etching. The lased dentin showed preferential removal of intertubular dentin while acid etching had more effect on the peritubular dentin. No significant differences was observed in removal of smear layer between the acid etched and lased groups. Although diameter of the exposed dentinal tubules was lesser after lased treatment in comparison to acid etching, further long term in vivo studies are needed with different parameters to establish the usage of Er,Cr:YSGG as a sole etching agent.
authors.affiliation: Reader, Department of Conservative Dentistry & Endodontics, Buddha Institute of Dental Sciences and Hospital , Patna, Bihar, India .
authors.forename: Rashmi
authors.initials: R
authors.lastname: Issar
authors.affiliation: Professor, Department of Conservative Dentistry & Endodontics, R. Ahmed Dental College and Hospital , Kolkata, West Bengal, India .
authors.forename: Dibyendu
authors.initials: D
authors.lastname: Mazumdar
authors.affiliation: Reader, Department of Oral & Maxillofacial Pathology, Buddha Institute of Dental Sciences and Hospital , Patna, Bihar, India .
authors.forename: Shashi
authors.initials: S
authors.lastname: Ranjan
authors.affiliation: Professor, Department of Orthodontics, KGF College of Dental Sciences , Karnataka, India .
authors.forename: Naveen Kumar
authors.initials: NK
authors.lastname: Krishna
authors.affiliation: Senior Lecturer, Department of Conservative Dentistry and Endodontics, Bharati Vidyapeeth Deemed University , Sangli, Maharashtra, India .
authors.forename: Ravindra
authors.initials: R
authors.lastname: Kole
authors.affiliation: Senior Resident, Department of Oral Surgery, Indira Gandhi Institute of Medical Sciences , Patna, India .
authors.forename: Priyankar
authors.initials: P
authors.lastname: Singh
authors.affiliation: Senior Lecturer, Department of Conservative Dentistry and Endodontics, Dental College , Azamgarh (UP), India .
authors.forename: Deirimika
authors.initials: D
authors.lastname: Lakiang
authors.affiliation: Senior Lecturer, Department of Pedodontics and Preventive Dentistry, Himachal Pradesh Govt. Dental College , Shimla, India .
authors.forename: Chiranjeevi
authors.initials: C
authors.lastname: Jayam
keywords: Power density; Smear layer; Target tissues; Wavelength