The invention is directed to lenses having thin walls and a generally conical shape for use with dental light-curing devices. The conical or otherwise tapered shape enables the apex of the lenses to be inserted at least partially within a dental preparation (e.g., a Class II dental preparation). The thin walls allow the light emitted from the light-curing device to pass through the lens and apex without being undesirably refracted, thereby enabling light to be emitted directly in front of the apex with sufficient intensity to cure light-curable compounds within the dental preparation.