Evaluation of transverse and tensile bond strength of repaired nylon denture base material by heat, cold and visible light cure acrylic resin

Abstract

Background: Denture fracture is one of the most common problems encountered by the patients andprosthodontists. The objective of present study was to evaluate the transverse strength of nylon denture base resinrepaired by using conventional heat polymerized, autopolymerized and visible light cure {VLC} resins, surfacetreatment that used for repair and adjustment of insufficient nylon denture bases and in case of addition of artificialteeth. As these corrective procedures are common chair side procedures in dental clinic.Materials and methods: One hundred twenty nylon specimens were prepared by using metal patterns withdimension of (65x10x2.5 mm) length, width, and thickness respectively for transverse strength test while for tensilebond strength a dumbbell-shaped with measurement (65x12.5x25mm) length, width, and thickness respectively wereflasked with stone. The nylon specimens were molded by reflasked with dental stone that used as an index for thesespecimens in the repair procedure and repaired with 45 degree bevel joint by using metal holding device. The twoparts of nylon specimen to be repaired were realigned in its repair index and adhere with special adhesive materialto stabilize the combination during repair procedure. The dough of heat and cold cure resin was packed into thejoint and then cured. The specimen repaired with cold cure resin was placed in the Ivomat containing water at(40°C) and pressure (30IB/inch²) for 15 minutes. The specimen repaired with {VLC} was placed in the light cure unit for4 minutes following manufacturer’s instruction. The fractured nylon specimens were divided according to the type ofrepaired materials into (40) specimens received heat cure acrylic and the (40) specimens received cold cure acrylicand the other 40 specimens received {VLCR}. Each 40 specimens were subdivided according to the type of surfacetreatment received into 20 specimens were treated with coarse stone bur (control), 20 specimens were treated withcombination of coarse stone bur and monomer of the heat cure acrylic. After that the specimens were subjected totransverse {Tr} and tensile bond {TB} strength tests. For each test 10 specimens.Results and conclusions: This study showed that specimens treated with combination of coarse stone bur andmonomer of the acrylic (heat, cold or VL cure) had the highest transverse and tensile strength values, followed bythe specimens treated with coarse stone bur. The results showed that the specimens repaired with heat cure acrylichad transverse and tensile strength values higher than the specimens repaired with cold and VL cure acrylic whencompared between subgroups of heat, cold and VL cure acrylic that received the same treatments