Several reports revealed that the cracked-tooth syndrome is a common problem in dental practice, which often results in extraction of the affected incompletely fractured teeth. Predominantly restored teeth suffer from these incomplete fractures. Therefore, it is of outstanding importance to stabilize teeth weakened due to cavity preparation. Besides full cuspal coverage by partial or full crowns, bonded restorations have been proposed for internal splinting of restored teeth. Although contradictory data have been published, there is evidence that bonded amalgam or resin-based composite restorations (RBC) do not increase fracture resistance of teeth with wide occlusal-proximal cavities to values similar to sound, unrestored controls. Indirectly fabricated RBC inlays and various ceramic inlays, however, increased fracture strength to levels as high as those of sound caries-free teeth. Therefore, it is recommended that weakened teeth with wide cavities be strengthened by full cuspal coverage with cast or ceramic restorations, by bonded ceramic inlays, or by indirectly-fabricated bonded RBC composite inlays.