Effect of ascorbic acid, ethanol and acetone on adhesion between the treated fiber posts and...

Effect of ascorbic acid, ethanol and acetone on adhesion between the treated fiber posts and composite resin cores

2012 Nov;4(4):187-91. doi: 10.4047/jap.2012.4.4.187. Epub 2012 Nov 29.

Reza Talebian ALS, DDS, CCRD

Contact with the author:.


. Cosmetic & Reconstructive Dentist at Dental Private Practice

. wWw.QueenDent.cO.uK.

. email: wWw.QueenDent.cO.uK @gmail.com

INTRODUCTION...


Nowadays, fiber posts are routinely used for adequate retention of core when significant coronal part of the tooth has been lost during root canal therapy.

Factors which can participate in long term success of a post/core restoration include build up material which is used, type of post and quality of adhesion between post and core.

Surface treatments of posts are recommended in order to improve the retention between structures


Mechanical treatment techniques such as air abrasion with silica or sandblasting can increase bond strength between fiber post and resin composite material, but decrease in post fitness within root canal, due to modification of post shape.

Chemical treatments lead to greater mechanical retention by roughening the post surface. Some of chemical solutions used for post surface treatments are potassium permanganate, Hydrofluoric acid, silane and hydrogen peroxide.


Dissolution of the resin matrix, breaking epoxy resin bonds and exposing the fibers is the main function of hydrogen peroxide, which can provide stronger adhesion between post surface and resin composite.

The most important problem with use of hydrogen peroxide is oxygen free radicals accumulation within post surface micro porosities, due to hydrogen peroxide degradation. New born oxygens interact with post to core adhesion procedure. So use of agents which can neutralize the effect of these oxygen free radicals is recommended.


Some of these agents can neutralize oxygen effect by removing and evaporating it from the surface, such as ethanol and acetone while some of those have direct antioxidant properties as reducing agents like ascorbic acid.

The aim of this study was to evaluate and compare the effect of ascorbic acid, ethanol and acetone on bond strength between hydrogen peroxide pre-treated fiber post to composite resin core.


Materials and Methods…


24 white quartz fiber posts (RTD) with ,maximum 1.8 mm diameter were selected.

Immersion in 24% hydrogen peroxide solution for 10 minutes at room temperature and then rinsed under running water for two minutes and gently air-dried.

Group-1 : control group (no any surface treatment). Group-2 : treatment with ascorbic acid 10% for 5 minutes.Group-3 : treatment with ethanol 70% for 5 minutes.Group-4 : treatment with acetone 70% for 5 minutes.

Rinsing under running water for 2 minuets and then gently air-dried.


Core build up was then performed using a light cured flowable composite. Each post was positioned upright on a glass slab and fixed with a drop of sticky wax. A cylindrical matrix was made with 10 mm in diameter and the length was equal to the non-tapered portion of the post (6 mm). It was placed around the post and adjusted so that the post was positioned exactly in the center.


Flowable composite was applied on the post in one-millimeter thickness increments and each layer was cured separately using a halogen light curing unit then were stored in dionized water at 37°C for 24 hours.


first two sections parallel to the long axis of the post and then sections perpendicular to the long axis of the post were done, resulting in sections containing the post in the center and composite cores on both ends. The final sections had 1±0.1mm diameter measured by a digital caliper.


Each stick was glued to the two free sliding components of a jig mounted on the microtensile tester. This set-up was designed to apply pure tensile forces.


The specimens were loaded at a crosshead speed of 0.5 mm/min until failure. Bond strength was expressed in MPa, by dividing the load at failure point (N) to the bonding surface area (mm2).


Failure modes of the samples were assessed using a stereomicroscope at 20x magnification and recorded as

Cohesive failure (failure in post or core

material), Adhesive failure (failure at the interface of post

and core material),

Mixed failure (adhesive-cohesive failure).


Two randomly selected fractured sticks of each group were sputter-coated with gold- palladium and assessed with Scanning electron microscope at different magnifications.


Tukey HSD & One-way ANOVA were used for statistical analysis.


Results…


According to statistical analysis; Highest value of bond strength values in G4 and the lowest in G1.

A higher bond strength values was seen in G3 than G2. There were honestly meaningful statistical difference among all of groups (P<0.001).

Under stereomicroscope, all of the failures were adhesive, between post and core.

SEM assessment was confirmed these results.


Discussion…


Results of The present study demonstrated that bond strength in groups 2, 3, 4 has significant difference with control group.

Ascorbic acid plays role as a reducing agent. Electron transfer from ascorbate to oxygen free radicals -derived from hydrogen peroxide degradation- can result in formation of semi-dehydroascorbate, a more stable material.

Ascorbic acid + 2O2¯→ H2O + semi-dehydroascorbate (DHA)


Higher amount of bond strength in group-3, 4 than other two groups is probably attributed to higher surface wetting compared to their effects on removing surface oxygen free radicals.

The results show that acetone can increase bond strength even more than ethanol; it can be due to more evaporating power of acetone in comparison to other materials used.

Stereomicroscopy and SEM evaluations, both of them, showed that Adhesive area is the weakest area in adhesion of fiber post to resin composite core. Although, presence of more epoxy resin on fiber posts surfaces in Group4 than control Group after adhesive failure indicated higher bond strength.


It seems that flowable composites, due to their low viscosity, are the choice for core build up since they provide a more homogenous available surface and without void for bonding.

For more similarities to the oral conditions, it is recommended to perform fatigue test in combination with use of antioxidants. Also, in this study, one type of fiber post and resin composite material evaluated, future studies on other types of fiber post and resin composite materials are recommended. Clinical trials and evaluation of aging effect on bond strength is yet to be evaluated.


CONCOLUSION…


Within the limits of this study, it can be concluded that:

Application of ascorbic acid, ethanol and acetone can increase microtensile bond strength of hydrogen peroxide pre-treated fiber posts to resin composite core.

Use of acetone demonstrated higher increase in bond strength than the other materials.


FINISHReza Talebian ALS, DDS, CCRD

Effect of ascorbic acid, ethanol and acetone on adhesion between the treated fiber posts and...

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