Healing of fractures takes place by inflammatory and regeneration processes leading to reparation of bony tissue. Healing of bones is dependent on activity of osteoblasts, similarly to bone growth at young individuals or bone reconstruction at adults. The sources of osteoblasts are probably non-differentiated perivascular cells, capillary endothelia, monocytes and most likely also reticulous cells of bone marrow. A healing process begins with formation of hematoma at a breakage crevice and around it from broken vessels. Blood coagulum is the first bandage that joins a fracture. It is followed by formation of fibrin fibers network that is a basis for leading of growing bands of granulous tissue from the periosteum and the bone marrow, as well as Haver’s canals. A fracture provokes an aseptic inflammation of surrounding tissues accompanied by an edema and accumulation of cell elements. The amount of granulous tissue gradually increases which replaces hematoma between fragments. A capillary network is formed and growing fibroblasts create bands of ligamentous tissue strengthened by collagen fibers thus creating a primary fixing ligamentous callus.
According to course of healing process, two types of bone healing may be distinguished:
Primary bone healing
If bone fragments are left still and osteosynthesis is stable, bones heal by a contact way or by slit means, if a slit is present. It is a direct healing with absence of ligamentous callus. A fixation callus function is replaced by a rigid fixation by a splint. Contact healing takes place upon a close contact of both fragments which prevents growth of blood vessels from nearby areas, necrotic ends of fragments do not get resorbed and elimination and formation of a new bone take part simultaneously. Bone regeneration is provided by osteons growing at the rate of 0.1 mm per day thus making a bridge across a fracture line. At the osteon’s tip, osteoclasts form a resorption canal with a blood vessel, around which a bone is formed by osteoblasts.
Secondary bone healing
An indirect, secondary bone healing is typical for conservative therapy and surgical adaptive osteosuture that holds fragments together. Healing proceeds in two phases:
first, the above described primary fixation callus is formed which ensures a mechanical rest for healing
the callus is reconstructed and remodeled at the second phase: osteoblasts form an osteoid along blood vessels at the callus; this osteoid is gradually calcified and ligamentous fibers are built up at the bone.
Remodeling is the last phase of healing, during which periosteal and endosteal calluses are resorbed and bone marrow is remade.
A tooth present at a fracture line.
With regards to healing of fractures of the jawbones, a question of teeth presence at a fracture line is often discussed. At those parts of jawbones which contain teeth, a fracture line runs always across the alveolus of one of the teeth. The teeth itself may get damaged during an injury at the same time (subluxations, fractures of roots). As a rule, teeth that had been proven as devitalized or with a peri-apical finding before an injury has happened, should be removed from fracture lines. Retained or semi-retained teeth should be removed as well, providing that fragments moved or a gingival cover integrity was damaged thus increasing risk of infection. Damaged teeth are extracted from a fracture line, unless they can be treated according to rules for therapy of damaged teeth. Teeth germs in cases of fractures at children should be approached as retained teeth during a surgical treatment. They are usually removed from a fracture line.
Occurrence of a mock joint is one of the most serious complications of healing. It is a state during which fragments are not joined firmly by a bony callus. A fracture heals only by a primary ligamentous callus and pathological movability remains at the broken site. This kind of complication may happen at fractures of the lower jawbones. There are three types of pseudoarthrosis:
syndesmosis (the bones are joined by a ligamentous tissue)
synchondrosis (fragments fused by a cartilage)
neoarthrosis (a mock joint is formed together with a joint slit)
These healing complications require surgical ways of treatment, often even transfer of a bone transplant (commonly from ala ilii or a rib) and a long-term fixation.
Ankylosis appears most frequently at an injured mandibular joint, fractures of a joint head, fractures of comminuted character, overlooked fractures at children or newborn babies. Ankylosis may also result from inflammatory complications (osteomyelitis) at the mandibular joint area. The basis for ankylosis is elimination of a joint slit and bony consolidation from the movable lower jaw onto the skull’s base or zygomatic arches that results in immobility of the lower jaw and inability to open the mouth. Therapy is always surgical - wide interruption of pathologically fused bones and insertion of a material (fascia, muscle) between edges of formed breakage in order to prevent coalescence. An intense rehabilitation of the mouth opening is necessary.
An inflammatory complication at the site of fracture can spread onto a surrounding bony tissue, causing osteitis or osteomyelitis. The causative agent is most often Staphylococcus aureus or a mixed non-specific infection. Specific actinomycotic osteomyelitis of the lower jawbone have been described, resulting from a bone injury. Therapy is analogous to that of inflammatory non-traumatic states, it is a long-term one, and an affected bone deformation may persist.
10.7 Injuries of the Teeth
Either an individual tooth or the whole groups of teeth may be subject to an injury. The frontal teeth of the upper jaw are affected in most cases due to their prominence at the upper jaw. Teeth damage is often associated with injuries of bones and soft tissues.
Subluxation appears as a result of damage to supporting apparatus of a tooth causing a tooth to move at its alveolus, but without leaving it. A fracture of the alveolus may occur at the same time. Clinically, a tooth protrudes out, it is sensitive to percussion and loose to a various degree. The vicinity of marginal gingiva is usually bruised and sometimes even torn. Therapy requires a good anesthesia that enables for pushing a tooth back to its bed and for fixing it at this position by a resin splint made by molding at a prosthetic laboratory according to an impression, or more often, from a free hand made of a fast polymerizing resin. Wire fixtures or splints do not provide for good results since they rather pull a tooth out from its socket by wire loops. Required period of fixation is usually 3-4 weeks, eating soft foods and increased oral hygiene are a must. An antibiotic therapy is not necessary at isolated injuries of the teeth.
Luxation results from breakage of the supporting apparatus of a tooth, that leaves its socket completely. The alveolus edge does not have to be necessarily damaged. Especially teeth with incomplete root development are prone to luxation. It is necessary to replant a tooth as soon as possible (only at young individuals providing the bony tooth socket is not damaged). A tooth should be kept at moist environment before replanting. Excochleation and rinsing of the tooth socket should be performed under a local anesthesia followed by replanting of a tooth washed at sterile physiological solution (remnants of the periodontium at the root must not be removed). Fixation is the same as in case of subluxation, duration of fixation should be longer - 4 to 5 weeks. It is desirable to use an antibiotic screen. After a fixture is removed, a tooth vitality should be followed, and an eventual resorption assessed on X-ray images.
Fractures of the Teeth
Teeth breakages can affect their crowns (treatment described at the chapter on restorative stomatology), or its root. In case of a longitudinal root fracture, extraction of such a damaged tooth is unequivocally indicated. In case of a fracture across a root at its half, such breakage can be treated by intra-dental fixation (by a titanium pin inserted through the fracture line and the apex into the peri-apical bone, so called trans-dental implant). A degree of the root’s development is crucial for this kind of treatment since it is necessary to dress and close hermetically the root canal. A dental splint (resin or metal molded) is left at place for at least 5 to 8 weeks. If the root development is incomplete, it is possible to use a conservative approach, i.e. to fix a tooth by a splint for a long period of time, thus allowing for formation of a ligamentous fusing band on the root, or rarely joining by the secondary cement and dentine. If a root is broken at its apical part, removal of the split apex has to be made followed by filling the root canal, excochleation and egalization of the root fragment. Fixation is not needed.