ACID ETCHING IN COMPOSITE RESTORATIONS

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.

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