Compomer, a term evidently created by Dentsply and adopted by the rest of the industry, is a polyacid-modified composite that incorporates some of the attributes of resin ionomer, such as being relatively self-adhesive and having fluoride release. The self-adhesive property of both resin ionomers and compomers is presumably due to their both undergoing an acid-base reaction. This reaction requires the presence of water, which is present in the resin ionomer liquid. As soon as the powder and liquid are mixed, resin ionomers undergo the acid-base reaction. But being anhydrous, compomers need external moisture to initiate their acid-base reaction. This occurs after a compomer is light-cured and exposed to moisture in the mouth. This acid-base reaction presumably allows compomers to bond to tooth structure without etching.

Etching vs. No Etching REALITY RESEARCH LAB (RRL) results found significantly higher bond strengths to etched enamel compared to unetched enamel. We did not find a significant difference in bond strength between etched and unetched dentin. When this information is coupled with our clinical experience that shows better enamel margins with etching, we advise using a bonding agent (etch & rinse or self-etch) when compomers are placed as definitive restorations or core build-ups in primary and permanent teeth.

+ More fluoride release
- Less shades and worse surface finish
- Lower strength

+ Superior esthetics
+ No-mix formula
+ Better handling
+ More polishable
- Cannot alter consistency by mixing thinner or thicker
- Light-cured-only, while resin ionomers are dual-cured (for the most part)
- Does not release as much fluoride
- Requires bonding agent

Microleakage Reduction A wide-ranging RRL study of microleakage in Class II and V restorations found compomers either had a similar leakage pattern or less leakage than the packable (Class II) and hybrid composite (Class V) controls. In addition, Dyractflow had significantly less leakage than a number of other flowables when applied to the gingival walls of Class II preparations.

+ Class V lesions, especially carious
+ Gingival wall of proximal box in Class II preparations
+ Blocking out undercuts in inlay/onlay/crown preparations
+ All types of restorations in primary teeth
- Restorations in highly visible areas
- High stress areas


Translucency/Opacity Discs of several body shades in 1.0mm thicknesses and incisal shades (if available) in 0.5mm thicknesses were measured in a spectrophotometer. The scale was 0 - 100, with 0 being totally clear and 100 being totally opaque. Our findings are in each product's commentary.

Shade Shift after Curing This test shows how much color change there is after light curing the material. This is only important if you want to do a shade check without bothering to light cure the mockup. If the material does not have a shade shift , you could do a mockup without light curing. However, removing uncured material from a tooth can be messy, so light curing is a good idea in any event. This shift, if any, was measured using the spectrophotometer.

Porosity This test shows how well the material has been vacuum mixed by the manufacturer to remove air from the final product. The higher the percentage of porosity, the higher the probability you will have voids present on the surface when you finish and polish the material. These voids are an annoyance and repairing them can be time-consuming as well as being an esthetic challenge.

Fluorescence Many venues use black light for its special effects. If a restorative material does not exhibit fluorescence similar to tooth structure, it could create an embarrassing situation for a patient. This test shows how the material appears in vivo under black light. Materials exhibiting fluorescence that do not match that of natural teeth would not be a good choice in the mouth of patients with high esthetic needs.

Curing Time for Gingival Wall Increment This test will tell you if the increment of the products marketed for posterior use placed on the gingival wall of the proximal box has achieved the benchmark 80% hardness value of the occlusal surface. The test is done in simulated Class II preparations with the depth of the gingival wall 6mm from the tip of the light. The gingival increment is placed no thicker than 2mm.

Working Time under Dental Unit Light This test will tell you when the material will start to cure under the dental unit light, if the light is at high power and positioned at a typical working distance (30in/76.2cm) from the preparation.

Finishing and Polishing Restorations were polished with three standardized instruments for 30 seconds and then were compared to a natural extracted tooth with a typical enamel glossy surface.

Radiopacity We took a digital x-ray with the flowable product in the proximal box of the Class II preparation. This x-ray can be seen in its commentary.

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