ciinicai Communication Restoration of a cracked tooth with a bonded amalgam Richard Trushkowsky* The diagnosis and treatment of the cracked tooth can present difficulties. The causes of the cracked tooth include masticatory accident, radical preparation and overuse of di- reet restorative materials, trauma from occlusion, and torque on abutment teeth. Place- ment ofa cast restoration eovering the cusp is mually suggested. However, bonded res- torations are effective in restoring the strength of teeth weakened bv cavity prepara- tion. A material that bonds amalgam to dentin may pre.'sent a more conservative and less expensive restoration of the cracked toolh. (Quintessence Int 1991:22:397-400.) Introduction The cracked tooth syndrome in posterior teeth is oc- curring with increasing frequency.' The diagnosis and treatment of the cracked tooth can present difficulties to the dentist,- The cracked tooth syndrome is also known as the incomplete fraeture of the posterior teeth. Various other terms have been used, including incom- plete erown root fraeture, coronal fracture, simple and complicated fractures, hairline fracture, split root, split tooth, ßssurat fracture, crazing, and enamel eracks.^ Symptoms A patient with cracked tooth syndrome classically complains of pain during biting and from cold.'' Other symptoms that may accompany this syndrome are pain on release of pressure, pain when fibrous foods are eaten, or a history of unrelieved discomfort.' Pa- tients may also experience sensitivity to extreme heat or to sweet foods. Patients may not be able to localize the pain to the exact tooth or correct quadrant. Any force applied to a cracked tooth may cause separation along the line of the crack in the crown. Stalen Island University Hospital, 483 JelTerson Boulevard, Sta- ten Island, New York 10312. The acute pain during mastication is probably due to stretching and rupturing of the odontoblastic pro- cesses. Pain is also probably dtie to movement of fluid through the dentinai tubules, stimulating receptor mechanisms in the pulp.^ Any force that widens the crack will result in pain.* Causes and prevention The most common cause of fracture is the masticatory accident: biting on a hard rigid object, such as a bone, during crushing biting movement. Radieal preparation and overuse of direct restora- tive materials are frequent factors in iatrogenic frac- ture. The preparations weaken the buccal and lingual cusps, while the restoration wedges the weakened seg- ments apart.' The tooth is weakened by the prepara- tion and receives no protection from the restoration. An amalgam restoration contaminated by moisture will expand, possibly causing future complications. Composite resin not plaeed inerementally causes con- traction stresses, which may result in cuspal fracture. Deep carving may also cause problems. Wedging of cusp-fossa relationships could result from prolonged excessive interocclusal contact. Overcarving alters the natural cusp-fossa relationship and contributes to the fracture of the nonfunctional cusp. Binding internal walls of an inlay can cause a wedging effect. The inlay should fit passively. Castings should protect and sup- port weakened tooth structure. Trauma from occlusion can also lead to fracture. Quintessence internationai Volume 22, Number 5/1991 397