(a) Presentation of Group BF restored with a composite resin (C= Composite resin). The thickness of the lingual and buccal walls of the cavity was 2.5 mm; the gingival wall of the cavity was 1.5 mm from the coronal aspect to the cemento-enamel junction. (b) Presentation of Group PRF1 restored with a polyethylene reinforced fiber under composite resin (PRF=. polyethylene reinforced fiber). (c) Presentation of Group PRF2 restored with an additional polyethylene reinforced fiber. (d) A compressive force was applied with a stainless-steel ball parallel to the long axis of the teeth.