The document discusses acid etching techniques in dentistry. It describes how etchants such as phosphoric acid are used to remove the smear layer and expose collagen fibers to allow resin infiltration. 37% phosphoric acid gel is commonly used for 15 seconds to etch enamel, creating a frosted appearance. This increases surface area and micromechanical bonding between tooth and restoration. Care must be taken when using etchants due to their acidic properties.

3. ,

5.  Introduction
 Compositions
 Etching pattern
 Concentration time
 Effect of Etchant on Enamel and Dentin

6. :
Etchants are the organic acids which is used to remove the smear
layer and it also exposes the microporous collagen network into
which resin monomer penetrates .
Examples :
37.5%- Phosphoric acid gel
Maleic acid
Citric acid
EDTA etc.
(a) Prepared tooth
surface prior to acid
etchant placement

7. (b) Acid etchant placement c) Chalky white/frosted
appearance on enamel

8. :
 37.5% Phosphoric acid
solution Available in:
• Liquid solution (rarely
used)
• Gel (tends to be easier)
• Syringes or bottles etc.

9. When seen microscopically three types of enamel etching patterns
are seen .
Type I:
Demineralization of enamel prism core leaving the prism peripheries
intact .
Type II:
Preferential demineralization of inter prismatic enamel leaving prism
cores intact .

10. Type III:
Combination of above two less distinct type .
NOTE: There was concept of total etch up to Fifth Generation
and from Sixth Generation onwards , concept of self etch is
introduced.

11. • Scanning electron
micrograph (SEM) of
enamel etched with
35% phosphoric acid
for 15 seconds

12. A. Scanning electron micrograph
of enamel etched with
35%phosphoric acid for 15
seconds ,denoting a type I
etching pattern .
B. Scanning electron micrograph
of enamel etched with 35%
phosphoric acid for 15 seconds
,denoting type lll etching pattern

13. As measured in the laboratory shear bond strengths of composite to
phosphoric acid - etched enamel unusually exceed 20 megapascals
(Mpa)depending on the test method used .
Such bond strength provide adequate retention for broad variety of
procedures and prevent leakage around enamel margins of
restorations rations.

14. Begining with Buonocore’s use of 85% phosphoric acid ,various
concentration of phosphoric acid have been used to etch enamel .
Most current phosphoric acid gels have concentration of 30-40%
,with 37% phosphoric acid being most common .

15. Currently an etching time 15 seconds is recommended An etching
time of 60 seconds originally was recommended for permanent
enamel using 30-40% phosphoric acid .
15 seconds etch resulted in a similar surface roughness as that
provided by a 60 seconds etch .
Other in vitro studies have shown bond strength and leakage for
etching times of 15 and 60 seconds .
The enamel was etched for a total of 30 seconds .
The dentin was etched for 15 seconds .

16. Teeth is clean and washed
Apply acid etchant in the form of gel to 10-15 seconds 37%-
phosphoric acid .
Washed the etchant continuously for 10-15 seconds .
Frosty white appearance on drying indicates properly etched surface
.

17. Removes 10 microns of surface and creates microporous layer .
Three etching patterns
Type I- Core etching
Type II- Periphery etching
Type II- Mixed patterns
Resins tags
Macrotags
Microtags

18. Chemical alteration of dentine.
Objective is to remove the smear layer .
Demineralizing the dentine to exposed a microporous scaffold of
collagen fibrils (Hybrid layer ).

19. Kerr's distinctive purple-colored 37.5% phosphoric acid gel is
designed for maximum etching efficiency.
Its perfect viscosity allows the material to stay where it is placed, yet
can be rinsed off easily.

20. Moisture sensitive .
Best practice is to use a rubber dam when using acid etch .
Prior to use, the surface must be clean (use pumice and brush – do
not use prophylaxis paste as the fluoride and other constituents may
leave residue and interfere with bonding properties).

21. Creates a surface roughness of enamel that aids in increasing the
wettability of enamel, which allows for the micromechanical
bond between the restorative material and enamel.

22. Care must be taken to protect eyes, skin and intra-oral soft tissues
when using acid etch due to its acidic properties.
The dental team should always wear appropriate personal protective
equipment, as well as ensuring the patient wears protective eye
wear .
Technique sensitive .

23. In areas where a micromechanical bond is desired,
such as sealant placement, resin composite restorations,
 directly bonded orthodontic brackets
 veneers and resin-bonded crowns and bridges .
During pit and fissure sealing .

24. Dentine
Demineralizes dentine
surface
Opens dentinal tubules
Exposes collagen
Condition dentine for
better wetting of the
primer
Enamel
Selective demineralization
Increases surface area
Increases life of composite
Decreases marginal staining
Decreases secondary caries
Decreases post –operative sensitivity
Permits efficient wetting by
hydrophobic resin
Tag formation in microporosities

26. • Short Notes:
a) Etchant (4) [27th NOV, 2016]
b) Acid etch technique (4) [30th Dec ,2015]

27. Q. What is acid etch technique?[30 Dec, 2015]
Ans:-
Acid etching is the use of an acidic substance to prepare the
tooth's natural enamel for the application of an adhesive.

The acid roughens the surface microscopically, increasing
retention of resin sealant. Etching of dental enamel
with acid removes the smear layer and opens enamel tubules.

28. The most frequently used etchant is 37% phosphoric acid .
The acid in concentrations greater than 50% results in the formation
of monocalcium phosphate monohydrate that reduces further
dissolution .
It may be supplied as clear or colored gel or liquid .
Brushes are used to apply or the acid is supplied in a syringe for
direct application on to the enamel .

29. The etchant are acidic in nature .
They may be grouped as
Mineral (eg. Phosphoric acid , Nitric acid ,)
Organic(eg. Maleic acid ,citric acid ,Ethylene diamine –tetracetic acid
(EDTA),etc ).
Polymeric (eg. Polyacrylic acid).

30. • Sturtevant's Art and Science of OPERTAIVE DENTISTRY : A
South Asian Edition .