An In Vitro Comparison Study of the Use of a Drill or a Saw in the Hunsuck-Dal Pont Modification of the Obwegeser Sagittal Split Osteotomy in Pig Mandibles.

PURPOSE: Fracture lines in unfavorable locations are referred to as "bad splits" in a mandibular sagittal split osteotomy (SSO). Several modifications of the technique by Obwegeser have been introduced to minimize this risk. This in vitro study was performed to determine whether the shape of the osteotomy cut affects the torque and the fracture pattern of an SSO in pig mandibles. MATERIALS AND METHODS: In a split-mouth model, 16 mandibles were split according to the Hunsuck-Dal Pont modification of the Obwegeser technique. Using an oscillating saw, sharp-edged osteotomies were created on one side of the mandible and round-edged osteotomies were created on the contralateral side using a Lindemann bur. Torque forces were measured during the splitting, and the lingual fracture pattern of each split was classified. RESULTS: Torque forces were significantly (P < .05 by paired t test) decreased by 0.77 N-m (15.6%) when a saw was used for the osteotomy. In the 2 groups, fractures were produced along the mandibular canal. The mandible was more often completely fractured, including the lower mandibular border, when the fracture was created with an oscillating saw (P = .06 by Pearson χ2 test). No correlation was found between the torque used and the fracture pattern. CONCLUSION: Compared with round-edged osteotomies, sharp-edged osteotomies in pig mandibles facilitated the Hunsuck-Dal Pont modification of the Obwegeser sagittal splitting procedure and produced predictable results with decreased torque.

Radiological changes with magnetic resonance imaging and computed tomography after irradiating minipig mandibles: The role of T2-SPIR mixed signal intensities in the detection of osteoradionecrosis.

PURPOSE: Radiotherapy in the head and neck can induce several radiologically detectable changes in bone, osteoradionecrosis (ORN) among them. The purpose is to investigate radiological changes in mandibular bone after irradiation with various doses with and without surgery and to determine imaging characteristics of radiotherapy and ORN in an animal model. MATERIALS AND METHODS: Sixteen Göttingen minipigs were divided into groups and were irradiated with two fractions with equivalent doses of 0, 25, 50 and 70 Gray. Thirteen weeks after irradiation, left mandibular teeth were removed and dental implants were placed. CT-scans and MR-imaging were made before irradiation and twenty-six weeks after. Alterations in the bony structures were recorded on CT-scan and MR-imaging and scored by two head-neck radiologists. RESULTS: Increased signal changes on MR-imaging were associated with higher radiation doses. Two animals developed ORN clinically. Radiologically mixed signal intensities on T2-SPIR were seen. On CT-scans cortical destruction was found in three animals. Based on imaging, three animals were diagnosed with ORN. CONCLUSION: Irradiation of minipig mandibles with various doses induced damages of the mandibular bone. Imaging with CT-scan and MR-imaging showed signal and structural changes that can be interpreted as prolonged and insufficient repair of radiation induced bone damages.

The histological and histomorphometric changes in the mandible after radiotherapy: An animal model.

PURPOSE: Approximately 5% of irradiated head and neck cancer patients develop osteoradionecrosis of the mandible. The current non-surgical treatment options for osteoradionecrosis have limited effects and are based on a small number of studies. Therefore, we aimed to enhance the understanding of the pathophysiology of osteoradionecrosis by investigating changes induced by external irradiation in mini-pigs. METHODS: Sixteen Göttingen mini-pigs were divided into four groups for the application in two fractions with total equivalent radiation dosages of 25, 50, 70 Gray, and one group served as control. Thirteen weeks after irradiation, the left lateral teeth the mandible were removed and implants were placed. The pigs were sacrificed twenty-six weeks after irradiation, and the bone samples were stained with Masson's trichrome. RESULTS: The amount of fibrosis, resorption lacunae, necrosis, and the woven/lamellar bone ratios were increased after higher radiation dosages. The diameter of the lumen of the inferior alveolar artery was reduced depending on the irradiation dosages. The rate of bone remodeling decreased after irradiation. CONCLUSION: Both surgery and increasing irradiation dosages cause architectural bone changes and damage the vascularization. This might result in a chronic hypoxic state of the mandibular bone. In general, the bone formation rate was markedly decreased after radiotherapy.

In vitro comparison of the sagittal split osteotomy with and without inferior border osteotomy.

PURPOSE: By adding an osteotomy of the inferior border of the mandibular body to the classic sagittal split osteotomy, the authors expected to prevent unfavorable splits and damage to the inferior alveolar nerve. MATERIALS AND METHODS: Thirty-five human mandibles were used to perform 70 sagittal split osteotomies as an in vitro study. Conducted as a split-mouth model, each mandible was split at the midline. One side of the mandible was split using the traditional Obwegeser-Dal Pont technique, and the other side was split in the same manner with an additional osteotomy of the inferior mandible border. The torque used to split the mandible was measured, and the fracture line of the mandible was recorded. RESULTS: The average torque associated with the original technique was 1.38 Nm (standard deviation, 0.60 Nm), with a fracture line along the mandibular canal. The average torque required to split the hemimandible with the modified technique was 1.02 Nm (standard deviation, 0.50 Nm), a significant (P < .001) difference, with a fracture line parallel to the posterior ramus of the mandible. The fracture pattern depended significantly on the technique used (P < .001), but not on the applied torque force. CONCLUSION: By adding an osteotomy of the inferior mandibular border to the sagittal split osteotomy, less torque was needed to split the mandible. The fracture line was more predictable, even when all the surgical manipulations were performed at a safe distance from the inferior alveolar nerve.

Assessment of local blood flow with laser Doppler flowmetry in irradiated mandibular and frontal bone, an experiment in Göttingen minipigs.

PURPOSE: The aim of this study was to investigate local blood flow changes in the mandibular bone compared to the os frontale after irradiation in various doses. MATERIALS AND METHODS: This study used an animal experiment with 16 female Göttingen minipigs. Three groups of four animals were irradiated with equivalent doses of 25, 50 or 70 Gray on the mandible and os frontale and four animals served as control. Three months after irradiation laser Doppler flowmetry (LDF) was used to record local blood flow on the left mandible and in the irradiated area on the os frontale. At 6 months measurements were repeated. Descriptive and univariate analyses were conducted and p-values lower than 0.05 were considered statistically significant. RESULTS: Local blood flow measurements in the mandible were significantly higher compared to the os frontale. In the os frontale and mandible there was no significant change in the measurements with increasing irradiation dose. CONCLUSION: We found a non-significant decrease in LDF values with an increase in radiation dose in the mandible and non-significant changes in the os frontale at 3 and 6 months. We consider this to represent the process of on-going fibrosis affecting the local blood flow in the mandible.

Does a change in bone mineral density occur in the mandible of Göttingen minipigs after irradiation in correlation with radiation dose and implant surgery?

PURPOSE: To date, studies have not agreed on the effects of irradiation on bone mineral density. The aim of our study was to investigate the changes in mandibular bone mineral density after irradiation at various doses with and without surgery. MATERIALS AND METHODS: We implemented a descriptive animal experiment. The sample included 16 female Göttingen Minipigs, randomly assigned to 4 groups and irradiated with equivalent doses of 0, 25, 50, and 70 Gy to the mandibular region. At 3 months after irradiation, the mandibular left premolars and molars were removed, and dental implants were placed. Computed tomography scans were taken before and 6 months after irradiation. The measured bone density was related to a bone phantom to calculate the bone mineral density quotient (BMDQ). The outcome variable was the BMDQ. Other study variables were the radiation dose and surgery. Descriptive and univariate analyses were computed, and significance was set at P ≤ .05. RESULTS: In the left hemimandible, compared with the control group, a significant decrease in BMDQ was observed: 0.01 at 0 Gy, -0.01 at 25 Gy, -0.06 at 50 Gy, and -0.11 at 70 Gy (P = .023). The right hemimandible compared with the control group also showed a significant decrease in BMDQ: -0.02 at 0 Gy, -0.08 at 25 Gy, -0.09 at 50 Gy, and -0.11 at 70 Gy (P = .007). CONCLUSIONS: The present study used a large animal model to simulate the tissue reactions induced by various radiation doses in the mandible. We found a significant decrease in the BMDQ after irradiation, but no significant correlation could be found between the irradiation dose and a decrease in the BMDQ.

The modifications of the sagittal ramus split osteotomy: a literature review.

BACKGROUND: In 1953, the sagittal ramus split osteotomy was introduced by Obwegeser. For many years, and in some countries still, this technique has defined the term oral and maxillofacial surgery. METHODS: The basic design of the sagittal ramus split surgical procedure evolved very quickly. The original operation technique by Obwegeser was shortly after improved by Dal Pont's modification. The second major improvement of the basic technique was added by Hunsuck in 1967. Since then, the technical and biological procedure has been well defined. Resolution of the problems many surgeons encountered has, however, taken longer. Some of these problems, such as the unfavorable split or the damage of the inferior alveolar nerve, have not been satisfactorily resolved. RESULTS: Further modifications, with or without the application of new instruments, have been introduced by Epker and Wolford, whose modification was recently elaborated by Böckmann. The addition of a fourth osteotomy at the inferior mandibular border in an in vitro experiment led to a significant reduction of the torque forces required for the mandibular split. CONCLUSIONS: The literature was reviewed, and the last modifications of the successful traditional splitting procedure are presented narrowly. It indicates the better the split is preformatted by osteotomies, the less torque force is needed while splitting, giving more controle, a better predictability of the lingual fracture and maybe less neurosensory disturbances of the inferior alveolar nerve.

Prosthetic rehabilitation of head and neck cancer patients focusing on mandibular dentures in irradiated patients.

PURPOSE: This retrospective study assessed treatment outcomes and patient satisfaction of irradiated head and neck cancer patients treated with mandibular implant overdentures (IODs) or conventional dentures (CDs). MATERIALS AND METHODS: Fifty-one irradiated head and neck cancer patients, out of a total of 158 patients included, completed the standardized questionnaire and underwent a clinical assessment. Nineteen patients were treated with removable CDs and 32 patients received IODs between January 2006 and January 2011. The mean follow-up of patients was 5.75 years (range: 1 to 23 years). RESULTS: A total of 45 (88.3%) mandibular dentures were in function at the time of assessment. The overall denture satisfaction was 7.3 (range: 1 to 10, SD: 2.14). Patients being treated with adjuvant concepts, including surgical tumor ablation, scored worse than patients after radiation therapy alone. Edentulous patients seem to benefit from implants, especially with respect to prosthesis retention. Men take more benefit from IODs compared with women. CONCLUSIONS: The results are comparable to other studies of head and neck cancer patients and also of healthy individuals. Surgical interventions in adjuvant therapy concepts lead to reduced denture satisfaction. The concept of prosthetic rehabilitation as part of oncologic treatment can be judged as successful.

A bilateral cervical swelling and it is not a malignancy.

BACKGROUND: This case report is about a patient with 2 synchronous bilateral cervical schwannomas. PATIENTS AND METHODS: A 59-year-old white man presented a 6-month history of painless bilateral cervical swelling. Magnetic resonance imaging revealed 2 tumors in the carotid sheath. Both tumors, which derived from the cervical sympathetic chain, were surgically removed. RESULTS: Histopathologically, both tumors were diagnosed as schwannomas. CONCLUSIONS: Commonly, a bilateral cervical swelling is not caused by 2 schwannomas. It is unusual for 2 schwannomas to appear in a patient synchronously without any evidence of neurofibromatosis or schwannomatosis. Differential diagnosis of a bilateral cervical swelling includes malignancy, carotid body tumor, and chronic infection.

Additive manufacturing for microvascular reconstruction of the mandible in 20 patients.

OBJECTIVES: The aim of this study was to evaluate the use of model mandibles made preoperatively by additive manufacturing, which were used to prebend reconstruction plates prior to mandibular resection and reconstruction with microvascular bony flaps. MATERIALS AND METHODS: Computer Tomography (CT) or Cone Beam Tomography (CBT) scans acquired preoperatively were used to obtain DICOM data sets to produce a model of the mandible using rapid prototyping. This model was used as a template to prebend and then sterilize a 2.3 or 2.7 reconstruction plate, which was used to reconstruct the mandible with a microvascular bony flap. This technique was used in 20 consecutive patients who required mandibular resection and reconstruction because of a tumour or osteoradionecrosis. RESULTS: The prebent plate was used in all patients intraoperatively without the need for any further bending. The average time to bend a plate on a nonsterile model was 0.42 h (range 0.25-0.68 h). This is felt to represent the minimum amount of time saved during the operation. Additive manufacture of the mandible prior to resection and reconstruction with a microvascular flap is a useful technique which reduces the operating time.

Pilot study of modification of the bilateral sagittal split osteotomy (BSSO) in pig mandibles.

OBJECTIVE: This study investigated a new technique for the bilateral sagittal split osteotomy (BSSO) by adding a new osteotomy line at the inferior border of the mandible in the Obwegeser-Dal Pont operation. MATERIAL AND METHODS: For this purpose a test system was designed and 100 pig mandibles were split to assess the test's reliability, to compare the torque necessary to split the mandible in both techniques and to record the fracture lines. The splitting technique was standardized, avoiding any contact with the inferior alveolar nerve. All outcomes were statistically examined by paired t-tests. RESULTS: By using the new technique, we demonstrated a decrease in the torque force required to split the mandible of 29.7% (t(69)=-12.68; p<0.05, paired t-test) compared to the Obwegeser-Dal Pont technique. The fracture lines were close to ideal. CONCLUSION: The additional osteotomy facilitates the BSSO technique and it reduces the likelihood of bad splits and damage to the inferior alveolar nerve in pig mandibles.

The anterolateral thigh as a universal donor site for soft tissue reconstruction in maxillofacial surgery.

OBJECTIVE: The experience with 191 flaps from the anterolateral thigh is described with special regard to variations of vascular anatomy and possible flap designs. PATIENTS: Since 1992, 191 flaps from the anterolateral thigh donor site were used in 187 patients. The size of the defects varied from 3 x 5 cm to 21 x 10 cm, being located in nearly all areas of the head and neck region including the skull base. METHODS: The functional and aesthetic outcome was routinely evaluated during follow-up of the patients. All complications and secondary procedures were documented during the whole follow-up period ranging from 4 weeks to 11.2 years. RESULTS: Six different patterns of variations were observed concerning the flap pedicle, but none of these resulted in failure of flap raising except for two patients, in whom no perforators could be found. Poor functional results were observed in 17 patients, and debulking procedures or scar revisions were carried out in 58 of the 187 patients. Nine flap types reaching from voluminous and large myocutaneous flaps to ultra-thin cutaneous perforator flaps were used, enabling closure of virtually any type of soft tissue defect. Twelve flaps were lost, resulting in a success rate of 93.7%. CONCLUSION: Due to the combined advantages of minimal donor site morbidity, the option of simultaneous flaps and the satisfying results, the anterolateral thigh can be considered a universal donor site which is ideally suited for soft tissue reconstruction in cranio-maxillofacial surgery.

Bilateral synchronous submandibular lumps in a patient with gastric carcinoma.

This case report deals with a patient who was readmitted with a bilateral submandibular swelling after having received primary surgery due to gastric adenocarcinoma 6 months before. After bilateral submandibulectomy both glands were diagnosed histopathologically as metastasis of adenocarcinoma. This is the rare case of a submandibular gland metastasis and the first case of a bilateral synchronous submandibular gland metastasis from gastric carcinoma.

Degradable injectable bone cement in maxillofacial surgery: indications and clinical experience in 27 patients.

BACKGROUND: A carbonated apatite cement (NORIAN SRS) was used as a bone mineral substitute for the calvaria or viscerocranium in 27 patients. It has the consistency of a paste and hardens at physiologic pH and body temperature due to dahllite crystallization, which has the stoichiometric formula Ca(8.8)(HPO(4))(0.7)(PO(4))(4.5)(CO(3))(0.7)(OH)(1.3). MATERIAL AND METHODS: The cement was used for posttraumatic bone defects in the orbital, periorbital or malar regions (nine patients), posttraumatic deformities of the frontal bone (six patients), tumour-dependent bony defects of the calvaria (two patients) and posttraumatic or cystic defects of the mandible (five patients). In another five patients, the material was used to augment the atrophic anterior mandible in combination with the insertion of dental implants. Follow-up varied between 6 and 40 months (mean: 29 months). RESULTS: There was no inflammatory reaction surrounding the implanted material. There was no sign of infection in any of the patients and only one case of partial wound dehiscence with superficially exposed material. The defect fillings and augmentations were successful in all patients. None of the 19 dental implants which were inserted in combination with the material showed any sign of infection or loosening. Also, there was no loosening of the implants after loading (mean follow-up: 15 months). From the check-up radiographs, the material could be seen as a dense, radio-opaque structure. There were no material fractures or dislocations. Radiologically, the material seemed to be completely replaced by bony tissue after 30 months. CONCLUSION: Our 5-year clinical experience suggests that the material is a suitable bone mineral substitute for cranio-maxillofacial surgery especially for moderate-sized defects of the calvaria and forehead bone. It has advantages over preformed, solid bone substitute materials, and, due to its initial plasticity and eventual great compressive strength, it can also stabilize dental endosseous implants in the atrophic mandible.

Follow-up in patients with oral cancer.

PURPOSE: To provide standardized follow-up of patients who underwent oral cancer treatment, the German-Austrian-Swiss Cooperative Group on Tumors of the Maxillofacial Region (DOSAK) established a schedule of check-up examinations for a 5-year period. MATERIALS AND METHODS: On the basis of a questionnaire, we investigated oncologic follow-up in respect to early detection of recurrences, cost and outcome efficiencies, and physician and patient judgment in the development of impairments. RESULTS: Only 11% of all operated patients participated regularly in the follow-up program within the first 3 years. Ultrasound was the most effective imaging for the detection of recurrences. Swallowing, speaking, tongue mobility, and facial appearance were the most common problems. Troubles with swallowing were mainly induced by poorly fitted dentures, discontinuity of the mandible, osteomyelitis, and xerostomia. Outer appearance was mostly impaired by scars, missing facial muscle function, and edema. The problem of chronic pain remained unsolved. CONCLUSION: Due to the sequelae of treatment, this study shows the need for close medical and psychological follow-up.