INTRODUCTION
Traditionally, root canal-treated teeth are restored using porcelain-fused-to-metal (PFM) crowns or full-ceramic crowns. Although these restorative procedures are widely accepted, they are often invasive to both the crown and root structure of the tooth. In cases of treatment failure, the extensive removal of dental tissue may limit the possibility of retreatment due to insufficient remaining tooth structure. Furthermore, such invasive procedures may increase the risk of irreversible tooth fractures.¹
The development of advanced restorative materials has encouraged clinicians to move away from mandatory full-crown coverage toward more conservative approaches for restoring endodontically treated teeth. Modern adhesive restorative materials and techniques have provided alternative methods that preserve tooth structure while maintaining satisfactory functional and esthetic outcomes.² Among these materials, direct composite resin restorations have demonstrated superior intracoronal reinforcement and improved resistance to tooth fracture compared with several conventional restorative options.³
One of the major factors influencing the success of large composite restorations is polymerization shrinkage. During polymerization, composite resins undergo volumetric contraction, generating stresses that may compromise the bond between the restoration and tooth structure. To minimize these effects, the use of a low-viscosity intermediate resin layer has been proposed as an “elastic buffer” between the adhesive system and composite resin.?
Previous studies have shown that the use of flowable resin alone in root-filled molars with mesio-occluso-distal cavities does not significantly increase fracture resistance.? However, when Leno Weave Ultra High Modulus (LWUHM) polyethylene fibers were incorporated into the flowable resin layer, a significant improvement in fracture strength was observed. Fiber reinforcement is therefore recommended to strengthen weakened cavity walls and reduce restoration failure in endodontically treated teeth.
Recent developments in restorative dentistry suggest that fiber reinforcement can reduce cusp deflection, improve fracture resistance, decrease polymerization stress, and enhance micro-tensile bond strength.? The “wallpapering technique,” in which fibers are placed circumferentially along the cavity walls, allows lateral forces generated during occlusal loading to be distributed more effectively. This technique may reduce catastrophic failures and improve the reparability of restorations if failure occurs.
Studies have shown that cavity walls thinner than 2 mm are associated with a higher risk of catastrophic fracture.? To minimize polymerization shrinkage stress, conventional resin-based composite restorations should be placed incrementally in layers not exceeding 2 mm in thickness, allowing adequate polymerization of each increment.? However, restoring large endodontic cavities requires multiple increments, making the procedure time-consuming and increasing the risk of contamination and void formation between layers.?
Titanium mesh has gained popularity in oral and maxillofacial applications because of its excellent mechanical properties, including high stiffness, low density, corrosion resistance, biocompatibility, and non-toxic nature. Additionally, its flexibility allows it to be shaped according to clinical requirements. Titanium particles have been reported to have no significant adverse effect on human cellular growth.?
The average occlusal force generated in the molar region of an adult male ranges from 45 to 68 kg, corresponding to approximately 441.3–666.8 MPa. In comparison, titanium mesh exhibits a maximum flexural strength ranging from 503 to 900 MPa, making it a potentially suitable reinforcement material for posterior restorations.¹?
Ribbond (Ribbond, Seattle, WA, USA) is a leno-woven, ultra-high-molecular-weight polyethylene fiber reinforcement material. Its woven structure facilitates effective resin impregnation and enhances bonding between the fiber and restorative materials. Polyethylene fiber networks have been shown to modify stress distribution at the enamel-composite interface and improve force transmission throughout the restoration.¹¹
Therefore, this in vitro study was undertaken to evaluate whether titanium mesh and fiber reinforcement incorporated within composite resin restorations can improve fracture resistance and potentially eliminate the need for full-crown coverage in root canal-treated posterior teeth with Class I cavities.