Evaluate the Effectiveness of an Experimental Urethane Dimethacrylate Resin Based Dental Composite Material

Inclusion Criteria:• must have given written consent to participate in the trial * must be in need of at least two restorations in natural tooth * replacement restorations with or without caries are acceptable * must be available for the required post-operative follow-up visits * restorations to be in bicuspids, 1st or 2nd molars * restorations to be in contact with opposing natural or crowned teeth * class II restorations must have at least one proximal contact * restorations must have a buccal to lingual/palatal width equal to or greater than 1/3 the distance from buccal to lingual/palatal cusp tips * 75% of the restorations must be Class II * all restorations must have at least one occlusal contact in habitual closure Exclusion Criteria: * have severe medical complications (organ transplants, long term antibiotic or steroid treatment, cancer or immunocompromised) or disabilities who may not be able to tolerate the time required to complete the restorations or to provide adequate oral hygiene * have xerostomia either by taking medications known to produce xerostomia or those with radiation induced or Sjogren's syndrome patients * have chronic periodontitis, rampant caries or poor oral hygiene which may require extraction of the teeth to be restored * have a history of chronic bruxism and those unavailable for long term recall * can not tolerate the rubber dam required for tooth isolation during preparation and restoration. * do not meet all inclusion criteria * present with any systemic or local disorders that contra-indicate the dental procedures included in this study * have an unstable occlusion * have severe bruxing or clenching or need of TMJ related therapy * have teeth with periapical pathology or expected pulp exposures * have teeth that are non-vital or that exhibit signs of pulpal pathology * Pregnancy * Known sensitivity to methacrylates and/or acrylates