When we use the total-etch dentin adhesive system for composite resin restorations, gel or liquid acid etchant such as 37% phosphoric acid is commonly used. Thirty seven percentage phosphoric acid is very powerful erosive agent, and can cause severe harmful effects when it contacts with an oral mucosa and facial skin.

This case describes iatrogenic chemical burn on facial skin caused by phosphoric acid which was happened during composite resin restorative procedure.

Chemical burn by acid etchant can be evoked by careless handling of remnant and syringe. In order to prevent these iatrogenic injuries, we should check the complete removal of the etching agent both in intra and extra-oral environments after etching and rinsing procedure and it is necessary to use of the rubber dam or isolation instruments.

If accidental burn were occurred, immediate wash with copious water. And bring the patient to the dermatologist as soon as possible.

Recently, self-etching adhesive system has been introduced to simplify the clinical bonding procedures. It is less acidic compared to the phosphoric acid, thus there is doubt whether this system has enough bond strength to enamel. The purpose of this study was to investigate the influence of additional etching on the adhesion of resin composite to enamel.

Ninety extracted bovine permanent anterior teeth were used. The labial surfaces of the crown were ground with 600-grit abrasive paper under wet condition. The teeth were randomly divided into six groups of 15 teeth each. Clearfil SE Bond®, Adper™ Prompt L-Pop and Tyrian SPE™ were used as self-etching primers. Each self-etching primers were applied in both enamel specimens with and without additional etching. For additional etching groups, enamel surface was pretreated with 32% phosphoric acid (UNI-ETCH, Bisco, Inc., Schaumburg, IL, USA). Hybrid resin composite Clearfil AP-X, (Kuraray Co., Ltd., Osaka, Japan) was packed into the mold and light-cured for 40 seconds. Twenty-four hours after storage, the specimens were tested in shear bond strength. The data for each group were subjected to independent t - test at p < 0.01 to make comparisons among the groups.

In Clearfil SE Bond®, shear bond strength of additional etching group was higher than no additional etching group (p < 0.01). In Adper™ Prompt L-Pop and Tyrian SPE, there were no significant difference between additional etching and non-etching groups (p > 0.01).

In conclusion, self-etching adhesive system with weak acid seems to have higher bond strength to enamel with additional etching, while self-etching adhesive system with strong acid seems not.

The purpose of this study is to evaluate the effect of additional enamel etching with phosphoric acid on the microleakage of the adhesion of self-etching primer system.

Class V cavity(4 mm×3 mm×1.5 mm) preparations with all margins in enamel were prepared on buccal surface of 42 extracted human upper central incisor teeth. Prepared teeth were randomly divided into 3 groups.

Group 1 : no additional pretreatment with 37% phosphoric acid (NE).

Group 2 : additional pretreatment with 37% phosphoric acid for 10 seconds (E10s).

Group 3 : additional pretreatment with 37% phosphoric acid for 20 seconds (E20s).

The adhesives(Clearfil SE Bond®, Kuraray, Osaka, Japan) and composite resins(Clearfil AP-X®, Osaka, Kuraray, Japan) were applied following the manufacturer's instructions. All the specimens were finished with the polishing disc(3M dental product, St Paul, MN, USA), thermocycled for 500 cycles between 5℃ and 55℃ and resected apical 3-mm root. 0.028 stainless steel wire was inserted apically into the pulp chamber of each tooth and sealed into position with sticky wax. Surrounding tooth surface was covered with a nail varnish 2 times except areas 1 mm far from all the margins. After drying for one day, soaked the samples in the distilled water. Microleakage was assessed by electrochemical method(System 6514, Electrometer®, Keithley, USA) in the distilled water.

In this study, the microleakage was the lowest in group 1(NE) and the highest in group 3(E20s)(NE<E10s<E20s). But no statistically significant differences were found(p=0.5).

On the basis of findings from this experiment, it can be concluded that additional enamel etching has no influence on the microleakage of the adhesion of self-etching primer system.