**4. Etiologies related with bone grafting complications**

#### **4.1. Technique associated**

Precautions have to be taken while harvesting bone from the ramus when the inferior cut is below the inferior alveolar canal. Elevation of the bone graft should be avoided unless assured that the nerve is not attached to the inside surface of the bone graft. As the thickest area of the ramus is 12.23 mm and the thinnest area is 2.35mm, the thickness of bone graft will not be homogenous. About 60% of the inferor alveolar canals were reported to be notched to the inner surface of the mandibular cortical plate or the third molar root surface. Thus it is recommended that whie performing the osteotomy, after 2 mm of penetration great care be taken with the surgical bur short before reaching cancellous bone to avoid damaging the inferior alveolar nerve. The mean thickness of the lateral cortical wall of the maxillary sinus has been reported to be 0.91±0.43 mm. Cautious removal of the bone with surgical bur while performing the sinus lift procedure is crucial in preservation of sinus membrane integrity. A recently developed piezoelectric ultrasonic surgical device(piezotome, Acteon, Bordeaux, France) presents an alternative way to safely remove hard tissue keeping the soft tissue intact,is an effective tool for sinus lift procedures as well as harvesting autogenous bone from the ramus. Attaching an onlay bone graft to the host site can affect revascularization of a graft. A loose graft may develop nonunion and become compressed and encapsulated. To ensure close adaptation, the fixation screws should be tightened. Contamination is usually an outcome of poor infection control during the surgery. Rinsing with chlorhexidine before surgery is recommended before the surgery on order to reduce the risk of infection. A study showed that infections were more prevalent when using nonresorbable membranes for GBR comparing with the use of bioab‐ sorbable membranes over a bovine bone xenograft. A suitable membrane and proper mem‐ brane removal timing may be effective in reduction of the risk of infection. To prevent exposure of membrane or fixation microscrews, tension free flap is mandatory.

#### **4.2. Anatomy related**

#### **Ramus**

Complications with regard to harvesting bone from the ramus may include damage to the nerve, opening of the incision line, fracture of the mandible and trismus. The prevalence of nerve damage caused by harvesting autogenous bone from the ramus is far less comparing to that of the mandibular symphysis. Buccal nerve damage followed by incision along the external oblique ridge is expectable. Nevertheless rarely are any reports present with regard to the incidence of buccal mucosa sensory loss and patients do not often pay attention to the change. On the contrary in this procedure, the potential of injuring the inferior alveolar nerve is of great consideration. A great understanding of the local normal anatomy is required to prevent such complications. Trismus may also be experienced by the patient underwent bone harvesting from the ramus area because of the masseter muscle retraction. But the symptom is not permanent. Furthermore, other complications related to ramus harvesting procedure may consist of third molar involvement and mandibular fracture ; though not reported.

#### **Mandibular symphysis**

**4. Etiologies related with bone grafting complications**

572 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

of membrane or fixation microscrews, tension free flap is mandatory.

Complications with regard to harvesting bone from the ramus may include damage to the nerve, opening of the incision line, fracture of the mandible and trismus. The prevalence of nerve damage caused by harvesting autogenous bone from the ramus is far less comparing to that of the mandibular symphysis. Buccal nerve damage followed by incision along the external oblique ridge is expectable. Nevertheless rarely are any reports present with regard to the incidence of buccal mucosa sensory loss and patients do not often pay attention to the change. On the contrary in this procedure, the potential of injuring the inferior alveolar nerve is of great consideration. A great understanding of the local normal anatomy is required to prevent such complications. Trismus may also be experienced by the patient underwent bone harvesting from the ramus area because of the masseter muscle retraction. But the symptom is not permanent. Furthermore, other complications related to ramus harvesting procedure may consist of third molar involvement and mandibular fracture ; though not reported.

Precautions have to be taken while harvesting bone from the ramus when the inferior cut is below the inferior alveolar canal. Elevation of the bone graft should be avoided unless assured that the nerve is not attached to the inside surface of the bone graft. As the thickest area of the ramus is 12.23 mm and the thinnest area is 2.35mm, the thickness of bone graft will not be homogenous. About 60% of the inferor alveolar canals were reported to be notched to the inner surface of the mandibular cortical plate or the third molar root surface. Thus it is recommended that whie performing the osteotomy, after 2 mm of penetration great care be taken with the surgical bur short before reaching cancellous bone to avoid damaging the inferior alveolar nerve. The mean thickness of the lateral cortical wall of the maxillary sinus has been reported to be 0.91±0.43 mm. Cautious removal of the bone with surgical bur while performing the sinus lift procedure is crucial in preservation of sinus membrane integrity. A recently developed piezoelectric ultrasonic surgical device(piezotome, Acteon, Bordeaux, France) presents an alternative way to safely remove hard tissue keeping the soft tissue intact,is an effective tool for sinus lift procedures as well as harvesting autogenous bone from the ramus. Attaching an onlay bone graft to the host site can affect revascularization of a graft. A loose graft may develop nonunion and become compressed and encapsulated. To ensure close adaptation, the fixation screws should be tightened. Contamination is usually an outcome of poor infection control during the surgery. Rinsing with chlorhexidine before surgery is recommended before the surgery on order to reduce the risk of infection. A study showed that infections were more prevalent when using nonresorbable membranes for GBR comparing with the use of bioab‐ sorbable membranes over a bovine bone xenograft. A suitable membrane and proper mem‐ brane removal timing may be effective in reduction of the risk of infection. To prevent exposure

**4.1. Technique associated**

**4.2. Anatomy related**

**Ramus**

Associated with mandibular symphysis/chin graft, complications such as insufficient bone regeneration, altered sensation, nerve damage, pulp necrosis, vascular damage, opening of the incision line and bone fracture may occur. Incomplete bone regeneration was found more prevalent in old patients. Nevertheless, it was reported that the change in profile was not obvious. Change in sensation of mandibular anterior incisors after loss of support of the mentalis muscle was reported. The manifestation of dullness usually resolved within 6 months. A high incidence of anterior mandibular incisors pulp necrosis was reported. Negative pulpal reaction and canal obliteration may be caused by damage to pulp vasculature. There have been reports on prevalence of nonvital teeth after genioplasty or subapical osteotomy. An effective preventive way is to keep about 4 to 5 mm clearance from the root apices and avoidance of harvesting bone close to them. Patients should also be informed about possible disturbances that may occur in the function of the inferior alveolar nerve which may last longer than 12 months. Damage to incisal branch of the inferior alveolar nerve is expectable if the graft is harvested too deep into the cancellous bone. Similarly mental nerve damage may occur if the graft is harvested too distally. Fracture and posterior displacement of the lingual cortical plate of the anterior mandible was reported as a specific complication which occurred during the healing phase but not at the time of surgery. On the whole, careful measurement and assess‐ ment before the surgery are required to avoid facing most of the complications.

#### **Maxillary tuberosity**

Precaution has to be taken with regard to the adjacent anatomical elements such as the maxillary sinus, pterygoid plates, proximal teeth and the greater palatine canal when using the maxillary tuberosity as harvesting site. Although rare, oral-antral communication may occur when harvesting bone which can be closed using the buccal fat flap as coverage, antibiotics and decongestants. Bleeding and tethering of the lateral and medial pterygoid muscles has been reported to be a potential complication when the tuberosity was fractured.

#### **4.3. Patient related**

Systemic issues affecting bone grafting include smoking, diabetes, alcoholism, radiation, osteoporosis and medication.

#### *4.3.1. Bisphosphonates*

An inorganic analog of pyrophosphate, Bisphosphonate has recently been used to treat osteoporosis or bone metastatic malignancies by reduction of osteoclastic differentiation and induction of osteoclastic apoptosis. Bisphosphonate lets remodeling spaces be filled with new bone by its anti-osteoclastic effect and as a result, abates the prevalence of fractures and also increases the bone strength. Nevertheless, it was also found that not only does the bisphosph‐ onate suppress bone turnover but also interacts with micro-damage repair mechanism of bone. The accumulation of the micro-damage reduces the strength of the bone resistance against traumas. Furthermore, another drawback of the bisphophonate is that it decreases vascularity in regenerative connective tissue. It was found that IV use of bisphosphonate in metastatic malignancies may contribute to osteonecrosis of the jaw. However the relationship between osteonecrosis and use of bisphosphonate has not yet been recognized. Bisphosphonate related osteonecrosis appears to be multifactorial. The susceptibility of osteonecrosis in patients underwent IV bisphosphonate therapy for cancer was four times more than others. For patients who receive IV bisphosphonate, aggressive dental procedures should be avoided due to risk of jaw osteonecrosis. With insufficient research documents, guided regeneration and bone grafts should be applied with great caution (see Dental management of patients receiving oral bisphosphonate therapy, expert panel recommendations, report of the council on scientific affairs, ADA, June 2006)as reduced integrity of the bone and decreased vascularity may have negative drawbacks on grafted site. The incidence of osteonecrosis caused by oral adminis‐ tration of bisphosphonate is considered to be very low among the most common alendronates prescribed. Thus, patients underwent IV bisphophonate therapy are contraindicated for advanced surgical operations. This includes but not limited to implant placement, dental extraction and periodontal procedures. Latterly, suggested that dentist should discuss the risks, benefits and alternative treatments with the patients underwent bisphosphonate therapy before any surgical procedures. Before starting the treatment, the discussion and the patient informed approval should be documented.

#### *4.3.2. Smoking*

Almost 75% of the patients referred to periodontists were either current tobacco users or claimed previous use of tobacco. It was reported that smoking has negative effects on revas‐ cularization of the bone regenerative treatments such as bone grafting, majorly because of its vasoconstriction effect on arteries. Retardation of graft integration is caused as a consequent of decreased blood supply. The rate of infection caused by smoking-induced change in oral flora is 2 to 3 times more in smokers contributing to negative effects on complications of periodontal procedures, including bone grafting. Levin and Schwartz-Arad reported that nicotine, carbon monoxide and hydrogen cynide from smoking are possible risk factors that result in weakened wound healing. This consequently threatens the success of bone grafting and implant surgeries. Notwithstanding the cigarettes smoked, a patient with a smoking history, presented higher rate of failure of implants placed in grafted maxillary sinus. Smoking has negative influences on onlay grafts. While nonsmokers presented only 23.1% rate of complications in monocortical onlay grafts,smokers had a 50% rate. Nevertheless no relations were found in this article between sinus lift procedure complications and smoking tendency. Surprisingly failure rate in maxillary bone was 1.6 times more than that of mandible under‐ going the same periodontal procedure showing that the maxilla was more prone to negative reactions of tobacco. Furthermore bone grafting procedures are negatively affected by use of tobacco with bone loss of 4 times as much as in nonsmokers. Such bone loss was majorly a consequent of estrogens suppression caused by over expression of interleukin-1, interleukin-6 and tumor necrotising factor(TNF)-α. Quitting smoking has been shown to decrease the progression of periodontal diseases and contribute the healing process of the bone graft.

#### *4.3.3. Diabetes*

Diabetes is able to enhance expression of TNF-α which has been blamed to be responsible for apoptosis of osteoblasts and their precursors. This enhanced apoptosis is considered to be influential to the bone healing process. cellular malfunctions such as prolonged infiltration of inflammatory cells, decreased production of growth factors and cell synthesis and increased proteolytic activities are all assumed to be blamed for delayed healing and failure of bone grafts. Osteopenia and delayed bone healing are both characteristics of diabetic bone disease. Moreover, recurrent nonenzymatic protein glycation contributes to formation of advanced glycation end product(AGE) that can be accumulated in different tissues such as bone. Further alveolar bone loss can occur followed by accumulation of AGE.

#### *4.3.4. Radiation*

malignancies may contribute to osteonecrosis of the jaw. However the relationship between osteonecrosis and use of bisphosphonate has not yet been recognized. Bisphosphonate related osteonecrosis appears to be multifactorial. The susceptibility of osteonecrosis in patients underwent IV bisphosphonate therapy for cancer was four times more than others. For patients who receive IV bisphosphonate, aggressive dental procedures should be avoided due to risk of jaw osteonecrosis. With insufficient research documents, guided regeneration and bone grafts should be applied with great caution (see Dental management of patients receiving oral bisphosphonate therapy, expert panel recommendations, report of the council on scientific affairs, ADA, June 2006)as reduced integrity of the bone and decreased vascularity may have negative drawbacks on grafted site. The incidence of osteonecrosis caused by oral adminis‐ tration of bisphosphonate is considered to be very low among the most common alendronates prescribed. Thus, patients underwent IV bisphophonate therapy are contraindicated for advanced surgical operations. This includes but not limited to implant placement, dental extraction and periodontal procedures. Latterly, suggested that dentist should discuss the risks, benefits and alternative treatments with the patients underwent bisphosphonate therapy before any surgical procedures. Before starting the treatment, the discussion and the patient

Almost 75% of the patients referred to periodontists were either current tobacco users or claimed previous use of tobacco. It was reported that smoking has negative effects on revas‐ cularization of the bone regenerative treatments such as bone grafting, majorly because of its vasoconstriction effect on arteries. Retardation of graft integration is caused as a consequent of decreased blood supply. The rate of infection caused by smoking-induced change in oral flora is 2 to 3 times more in smokers contributing to negative effects on complications of periodontal procedures, including bone grafting. Levin and Schwartz-Arad reported that nicotine, carbon monoxide and hydrogen cynide from smoking are possible risk factors that result in weakened wound healing. This consequently threatens the success of bone grafting and implant surgeries. Notwithstanding the cigarettes smoked, a patient with a smoking history, presented higher rate of failure of implants placed in grafted maxillary sinus. Smoking has negative influences on onlay grafts. While nonsmokers presented only 23.1% rate of complications in monocortical onlay grafts,smokers had a 50% rate. Nevertheless no relations were found in this article between sinus lift procedure complications and smoking tendency. Surprisingly failure rate in maxillary bone was 1.6 times more than that of mandible under‐ going the same periodontal procedure showing that the maxilla was more prone to negative reactions of tobacco. Furthermore bone grafting procedures are negatively affected by use of tobacco with bone loss of 4 times as much as in nonsmokers. Such bone loss was majorly a consequent of estrogens suppression caused by over expression of interleukin-1, interleukin-6 and tumor necrotising factor(TNF)-α. Quitting smoking has been shown to decrease the progression of periodontal diseases and contribute the healing process of the bone graft.

Diabetes is able to enhance expression of TNF-α which has been blamed to be responsible for apoptosis of osteoblasts and their precursors. This enhanced apoptosis is considered to be

informed approval should be documented.

574 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

*4.3.2. Smoking*

*4.3.3. Diabetes*

Osteopenia may be experienced, after one yearin mature patients underwent head and neck radiotherapy. Osteoblasts activities may be diminished by radiation and results in decrease of bone matrix. Moreover, following long-term vascular damage caused by radiotherapy, osteonecrosis might happen. Due to poor blood supply and superficial location of mandible, most cases of head and neck radionecrosis were found in that area. Weakened areas of the bone are more susceptible to fracture. However, Despite the drawbacks mentioned above, one study reported that bone grafting in radiated bone tissues showed a survival rate of 89%. Another study reported that the prevalence of post-radiotherapy operative complications was 42%, while bone grafting procedures in nonirradiated sites had a 28% complication rate.

### *4.3.5. Alcoholism*

The use of alcohol is shown to have adverse impact on intraoral bone grafting operations by increasing osteoclast activities and weakening oseoblast proliferation. An animal study reported that alcoholic beverages caused considerable delay in reparative process of alveolus. Another study demonstrated that use of ethanol led to suppression of bone turnover and provoked bone resorption. Other negative effects on bone grafting procedures attributed to the use of alcohol may be ascribed to possible direct toxic effect of ethanol in periodontal structures and other elements in oropharynx. Even a higher rate of complication in surgical procedures of the mandible was presented by patients consuming large amounts of alcohol when combined with other predisposing factors such as poor nutrition. Thus, it has been suggested that quitting ethanol consumption should be applied a few weeks before aggressive dental operations to minimize complications.
