INTRODUCTION

• Acid etching is a process by which naturally smooth tooth surface is roughend to create micromechanical interlocking of surfaces.
• the end point of etching is creation of irregular tooth surface that appears frosty white due to light refraction.
• recommended etching time to prepare the enamel surface for bonding is 15-20 sec.
  • primary teeth-60 sec.
  • teeth effected by fluorosis-60-120 sec.

• 37% phosphoric acid is ideal concentration for the purpose.

Types

• liquids
• gels

LIQUIDS- useful when-

• larger surface area is to be etched as they flow easily.
• surfaces have deep grooves or fissures as it easily penetrates the irregularities.
• applied using-
  • small cotton pellets
  • foam sponges
  • micro sponges
  • special applicator tips

GELS-

• They were developed by adding small amount of micro fillers or cellulose as thickening agents.
• they show less flow and higher viscosity.
• useful when controlled applications are required such as preparation walls, bevels and margins.
• applied using-
  • brushes
  • paper points
  • syringe applicators.