POLYETHYLENE FIBER–REINFORCED STRESS-REDUCED COMPOSITE RESIN RESTORATION ON EXTENSIVE CARIOUS LESION: A CASE REPORT

The purpose of this article about the use of polyethylene fibers and resin composite to treat large carious tooth providing a high strength restoration within one appointment. Polyethylene fibers decrease the polymerisation shrinkage and increase the fracture resistance of the teeth. The polyethylene fibers, besides offering the proper strength to the mastication forces, as well reduce the risk of fractures, voids and micro-filtration.

The purpose of this article about the use of polyethylene fibers and resin composite to treat large carious tooth providing a high strength restoration within one appointment. Polyethylene fibers decrease the polymerisation shrinkage and increase the fracture resistance of the teeth. The polyethylene fibers, besides offering the proper strength to the mastication forces, as well reduce the risk of fractures, voids and micro-filtration.

…………………………………………………………………………………………………….... Introduction:-
Composite resin has been the material of choice for restoring teeth as it provides excellent aesthetics and mechanical properties. Main concern has been present in bonding of composite resin during and after cure as polymerization shrinkage occur which forms gap between them and which in turn decrease the bond strength of composite restoration with different substrates. [1] When bonding composite with substrate other than sound dentine, polymerization shrinkage would be to a greater extent as compared to sound dentine. [2] In conservative cavity preparation for composite restoration after removal of infected-carious dentin, large portion of cavity preparation is of affected -carious dentin. Therefore, in clinical situation bonding substrate is commonly caries affected dentin ra ther than normal dentin. Various studies have stated that caries aff ected dentine (CAD), with more sclerosed intertubular dentine, is more acid resistant and is less permeable to bonding agents. Which will undermine dentine hybridization and reduce tag formation in caries aff ected dentine (CAD). [3] [4] [5] Various methods have been advocated to reduce polymerization shrinkage and those methods are including curing techniques, incremental build up, addition of reinforced glass or polyethylene fibre. The reinforced polyethylene fibre is also supposed to limit the polymerization shrinkage and provide reinforcement in material while setting. [6] ISSN: 2320-5407 Int. J. Adv. Res. 9(11), 789-796 790 The main advantage of Polyethene fiber is that it is colourless and pliable material which easily adapts to the tooth substrate. Polyethene fiber are translucent so they can be used in aesthetic restoration and they can be cured with light-cured composite. [7] Case Report A 25-year-old male patient presented to Department of Conservative dentistry and Endodontics complaining about intermittent pain during meals in the mandibular posterior area on the left side. An initial clinical examination revealed that caries extended along the central fissure on the occlusal surface of tooth 37. Extensive Class I caries with ICDAS 6on the occlusal surface was visualized. Informed consent was obtained before the treatment of the patient. No institutional approval was required to publish this case report.
A rubber dam (GDC) was placed for the isolation of the working field with a 202-clamp fixed on tooth 37. The excavation of caries-infected dentine was first performed using a # 2 and #4round diamond bur in a high-speed handpiece. In a very conservative manner cavity prepared, removing only the decayed dental tissue and preserving the remaining sound tooth structure according to the basic guidelines for direct adhesive preparations.
After washing and drying the prepared cavity, place a drop of caries detecting dye on a disposable brush and apply on to the cavity. Rinsed after 10 seconds of application.
After washing, stained nonmineralized and denatured dental tissues were removed using round carbide bur in a slow-speed handpiece to an ideal caries removal end point that creates a highly bondable peripheral seal zone (PSZ). Bevels were not placed on neither the occlusal nor the gingival margins. Main goal of this step wereto avoid any sharp line angles on either the prepared enamel or dentin and to preserve the peripheral rim. 37% Phosphoric acid etchant was applied for 30 seconds andwashed for 10 seconds and dried gently with a weak stream of air until water puddles disappeared from the line angles but the surfaces remained moist and then Bonding agent (3M ESPE) was applied using disposable micro-brush. Single thin coat of adhesive was applied thoroughly andcured for 20 seconds.
Small pieces of Polyethylenefibers are required for placed in the cavity. So, the long Fiber are cut using scissors into small pieces. Cutting of Polyethylene fiber is done careful as the small fiber pieces may spring away. Small pieces of fibers are the wetted using unfilled bonding adhesive. Wetted Polyethylene fibers is placed over the floor of the cavity. A very thin layer of tacky flowable composite is applied over it and light-cured for 20 seconds. Same procedure is done for the further second small wetted Polyethylene fibers placement in the cavity and are light cured for 20 seconds. Being bondable reinforcement fibers, they could be closely attached to the residual tooth structure. The fibers' tight adaptation to tooth structure was the key to decreasing the composite volume between the tooth structure and the fiber which prevents the stress from polymerization shrinkage on the residual weakened walls. Stratification of dentin was started by placing a 1-to 1.5-mm even layer of A3.5 flowable composite on the dentin floor, which was followed by the application of dentin wedge-shaped increments strategically placed to only two bonded surfaces, decreasing the cavity configuration or C-factor ratio. Each cusp was cured separately, achieving the final primary and secondary occlusal morphology. Finishing and polishing of the restoration is done.    It is advised to cut the fiber directly with package using scissor. Also a special scissor named Ribbond Scissor is available for cutting of these fiber.

Discussion:-
Various modifications in dental composite resins have now allowed for their use in stress-bearing areas of the mouth so they have been widely used in restoring extensive carious lesion. But the major drawback of composite is its longevity as there is volumetric dimensional change during the polymerization of monomers which is 1% to 5%. [8] Polyethylene fiber is biocompatible, bondable, aesthetic, translucent material. Because of its broad range of these properties, it can be used in various applications in clinical dentistry. Various clinical applications of Polyethylene fiber are they can be used as endodontic posts and cores, space maintainers, as fixed partial dentures with a natural tooth pontic, and splint materials. [9] When bonding of composite restoration to a dentin substrate, there is the volumetric shrinkage and this leads to the development of stresses at the restoration-tooth interface. And stresses exceed the adhesive strength of the bonding system, and this leads to marginal gaps at the interface, leading to marginal leakage and ultimately bond failure. If these stresses are less than the adhesive bond strength, so these stresses will be transmitted to the tooth structure, causing cuspal deflection and postoperative sensitivity. [1] 796 The polyethylene fibre in between the composite material can decreases the volumetric contraction of composites. It also provides fracture resistance to deformation during the subsequent loading. [1] Embedding a Polyethylene fiber into a bed of tacky flowable composite resin under an extensive composite restoration increases fracture strength in root canal treated tooth and microtensile bond strength to dentin. Also, they decrease microleakage in cavities that have high c-factor. [1] Conclusion:-By using this approach, Polyethylene fiber-reinforced stress-reduced direct composite restorations can be used to restore structurally compromised vital and nonvital teeth.