LEARNING OBJECTIVES: 1. That students understand the correlation between intensity of injurious force and the extent and severity of tissue damage, including serious, occult systemic injuries.
2. To familiarize the students with normal bone healing.
3. That students are able to apply the principles of patient management AND normal bone healing to the management of various dental, dento-alveolar or jaw injuries.
A. INJURIES 1. Tissue Damage: Acute application of excessive force to the tissues of the face results in tissue damage. This damage is related to the magnitude of the force and to the site of force application.
2. The magnitude of force application can usually be correlated to the nature of the circumstances surrounding the injury. The following injuries roughly correlate with tissue damage in increasing order:
3. Site of the injury: the tissues that may be damaged in an injury include:
Skull / brain and vertebral column / spinal cord
Larynx and trachea
chest wall and lungs
heart and great vessels
liver, spleen, GI tract
pelvis, kidneys, bladder
long bones: femur, humerus, etc
soft tissues of the face: scalp, skin, muscle, nerve, mucosa, etc
4. In the area of the jaws …
Soft tissue injuries include: abrasions, contusions or lacerations.
Bone injuries include: dental avulsions, single tooth alveolar fractures, segmental alveolar fractures, body fractures or ramus / condyle fractures. As far as bone injuries are concerned, not all sites in the facial skeleton are created equal. The condylar neck is quite slender and weak. In contrast, the mandibular symphysis is very dense and strong. The greater the force of the injury, the more extensive will be the damage with respect to distribution (multiple fractures) and severity ( comminution ).
Dental injuries include: cracks, enamel chips, fractures through enamel and dentin, pulp exposures or root fractures.
All of the above may be combined in any given patient. Combinations are more likely as the force of the injury increases.
B. NORMAL BONE HEALING: The initial event in normal bone healing following fracture is bleeding followed by the formation of a blood clot in the fracture site and the initiation of inflammation. The clot forms in and around the ends of the fractured bone, torn periosteum and displaced soft tissues ( such as muscle ). The clot forms the matrix or scaffold for future bone healing.
Inflammation with the transudation of fluid, increased in blood flow and release of various mediators ( such as prostaglandins, bradykinins, etc.), result in the swelling, redness, heat pain and loss of function associated with injury. These inflammatory effects are demonstrable in the jaws as swelling, pain and trismus. Within days, endothelial in-growth along with macrophages and fibroblasts results in elimination of the original clot and replacement with granulation tissue rich in blood vessels and collagen. This new collagen network forms the matrix for initial bone deposition and the formation of a woven bone primary callus.
By four to six weeks, this callus reaches a level of “ strength” of approximately 30 to 40% of the ultimate strength of the fully healed bone ( which occurs by six to twelve months ). With time, the bone remodels in response to physiological stressed ( exerted by muscles ) and resumes the normal configuration of periosteum, cortex and trebecular bone.
Stability relates to normal bone healing during the fixation period. The main consideration in stability is resistance is forces generated by muscles. If fixation is inadequate, muscle forces can distract the segments and result in malpositioning of segments. This can lead to either localized sepsis, malunion or non-union. During the six weeks of fixation, the wires hold the bones in position while initial callus formation occurs. By six weeks, the bones usually have enough strength to resist muscle forces on their own and the wires can be released.
C. HISTORY, EXAMINATION, RADIOGRAPHS AND DIAGNOSIS: 1. History
Airway / Breathing / Circulation / Disability: maintenance of an intact airway, control of serious bleeding and prevention or management of cranial or neck injuries are obviously the first priorities on an emergency basis. Having managed these problems or determined that these are not issues, management can now proceed to the jaw problems.
Tetanus status: must be determined and tended to either through active (tetanus booster) or passive (tetanus immune globulin) immunization
Restoration of function: 3 main principles of fracture management
i. reduction: return of a displaced part to its original anatomical location
ii. fixation: ligation of the displaced part to adjacent non-fractured structures
iii. immobilization: stabilization of displaced parts to prevent movement during healing
1. Informed consent: regarding options with respect to treatment (for example extraction versus splint, endo, post and core and crown), includes duration of treatment, costs, sequelae and complications as well as patient expectations (maintenance of a soft diet, avoidance of sports, etc)
2. Intra-operative pain control: local vs. sedation vs. general anaesthesia
3. Prevention of sepsis: pre- and post-op antibiotics, wound prep solutions, debridement of foreign debris and necrotic tissue. OHI
3. Reduction, fixation and immobilization of injuries in sequence: reduce and fix dental injuries, reduce and fix bone injuries and then repair soft tissue injuries last so to avoid damage to sutures while manipulating teeth and bones. By the selective application of the principles of reduction, fixation, and immobilization, normal bone healing is guided by the clinician. The clinician’s aim is to restore the fractured parts to their original form and function. Understanding of the processes of bone healing allow the clinician to understand the need for minimal movement when bone to bone healing is required. In contrast, management of the dental avulsion is dictated by the need to prevent ankylosis from occurring. From this point of view, the avulsed tooth needs to be removed from fixation at approximately two weeks in order to allow for “physiological stimulation” and the formation of a fibrous union only in the area of the PDL.