Influence of lower third molar anatomic position on postoperative inflammatory complications.

PURPOSE: Postoperative inflammatory conditions, including alveolar osteitis, surgical site infections, and abscess, are frequent complications after surgical removal of impacted mandibular third molars and multiple associated risk factors have been identified. However, few studies have evaluated the influence of extraction difficulty according to anatomic variables on postoperative inflammatory complications. PATIENTS AND METHODS: A retrospective study was performed of 585 surgically removed lower third molars. All molars were classified by a difficulty score (range 3 to 10) according to the anatomic parameters. RESULTS: For 109 third molars (19%), the extraction difficulty was rated noncomplex (score 3 to 4); for 341 (58%), moderate (score 5 to 7); and for 135 (23%), difficult (score 8 to 10). Molars rated as moderate or difficult for extraction were more often accompanied by postoperative infection than molars rated noncomplex (odds ratio 5.3 and 3.9, respectively, P < .0001). CONCLUSIONS: The results from the present study revealed a highly significant correlation between the level of difficulty for surgical removal of lower third molars (predicted by the anatomic variables) and postoperative inflammatory complications.

Occurrence of cervical lymph node metastasis of maxillary squamous cell carcinoma - A monocentric study of 171 patients.

INTRODUCTION: Fewer than 5% of oral squamous cell carcinomas (SCC) are presented in the maxilla. The absence of cervical lymph node metastasis (LNM) is one of the main positive prognostic factors. This single-centre study analysed the cervical lymph node metastasis behaviour in patients with oral SCC of the upper jaw and serves as a basis for a cervical lymph node treatment suggestion. MATERIAL AND METHODS: The retrospective study includes 171 patients with isolated SCC of the maxilla. In addition to tumour resection, 83% of the patients underwent a selective neck dissection (ND). The data of cervical metastasis, TNM-status, tumour grade, tumour location as well as nicotine and alcohol behaviour were statistically analysed. RESULTS: The average rate of cervical metastasis was 44% in total. Tumour stage significantly affected risk for cervical metastasis (T1 = 6%, T2 = 41%, T3 = 60% and T4 = 60%) (p < 0.01). Development of cervical LNM was seemingly influenced by male gender. DISCUSSION: This study postulates a high rate of cervical metastasis of maxillary SCC. Risk for metastasis is mainly determined by the tumour stage. Alcohol and nicotine abuse have a negative impact on cervical LNM. CONCLUSION: Reviewing recent literature underlined by the illustrated data, we put up for discussion the treatment of SCC of the maxilla as similar to therapy protocols for SCC of the oral cavity. This would include an ipsilateral ND even in low tumour stage and in T4 staged tumours on both sides. However, prospective multicentre studies are needed to verify and recommend these therapy assumptions.

A system for context-aware intraoperative augmented reality in dental implant surgery.

PURPOSE: Large volumes of information in the OR are ignored by surgeons when the amount outpaces human mental processing abilities. We developed an augmented reality (AR) system for dental implant surgery that acts as an automatic information filter, selectively displaying only relevant information. The purpose is to reduce information overflow and offer intuitive image guidance. The system was evaluated in a pig cadaver experiment. METHODS: Information filtering is implemented via rule-based situation interpretation with description logics. The interpretation is based on intraoperative distances measurement between anatomical structures and the dental drill with optical tracking. For AR, a head-mounted display is used, which was calibrated with a novel method based on SPAAM. To adapt to surgeon specific preferences, we offer two alternative display formats: one with static and another with contact analog AR. RESULTS: The system made the surgery easier and showed ergonomical benefits, as assessed by a questionnaire. All relevant phases were recognized reliably. The new calibration showed significant improvements, while the deviation of the realized implants was <2.5 mm. CONCLUSION: The system allowed the surgeon to fully concentrate on the surgery itself. It offered greater flexibility since the surgeon received all relevant information, but was free to deviate from it. Accuracy of the realized implants remains an open issue and part of future work.

The value of ultrasound-assisted pinned resorbable osteosynthesis for cranial vault remodelling in craniosynostosis.

Resorbable osteosynthesis is a widespread tool in craniofacial surgery, however only a limited number of studies have focused on ultrasound-assisted pinned resorbable systems in the treatment of craniosynostosis. Thirty-eight children with various types of craniosynostosis including scaphocephaly, trigonocephaly, anterior and posterior plagiocephaly were treated using the Sonic Welding resorbable osteosynthesis system. All patients were evaluated for operation time, stability of the surgical results, rate of local infections and visibility or palpability of the osteosynthesis material in the follow-up ranging from 15 to 21 month. Mean operation time was not significantly higher compared to conventional osteosynthesis material and all remodelled cranial vaults showed immediate stability. Only one patient showed signs of an inflammatory skin reaction, which recovered spontaneously. The number of palpable or visible plates, respectively, increased during the first months with a maximum at 12 months (34 (89%) plates palpable, 26 (68%) plates visible). After this time point, the number decreased continuously until the end of the follow-up period at 21 months when 3 (20%) plates were palpable, 0 (0%) plates were visible). Ultrasound-assisted pinned resorbable systems seem to be a promising tool in craniofacial surgery providing a timesaving and stable osteosynthesis. An initial swelling of the plates during the first 12 months before the complete degradation might result in a palpable and visible bulge.

Proximal segment positioning with high oblique sagittal split osteotomy: indications and limits of intraoperative mobile cone-beam computerized tomography.

OBJECTIVE: The purpose of this study was to evaluate the indications and limits for intraoperative proximal segment positioning control by mobile cone-beam computerized tomography (CBCT). STUDY DESIGN: For mandible osteotomy in orthognathic surgery, the high oblique sagittal split osteotomy (HSSO) is our standard procedure. In 22 patients, positioning control of the proximal segment was performed during and after surgery to check this alternative osteotomy technique. RESULTS: The mean intercondylar distance increased 0.31 mm in all patients. No significant change of the condyle positions was found in the axial and coronal planes. In the sagittal plane a significant change was found. In 1 case, revision was required because of a lateral shifting of the condyles. CONCLUSIONS: Intraoperative positioning control with CBCT is an effective and reliable method to avoid condyle malpositions. Only minor position changes occur when using HSSO in orthognathic surgery, without compromising temporomandibular joint function postoperatively.

Neurosensory alterations and function of the temporomandibular joint after high oblique sagittal split osteotomy: an alternative technique in orthognathic surgery.

The current most common technique for repositioning of the mandible, bilateral sagittal split osteotomy (BSSO), was first described by Obwegeser and Dal Pont in the early1960s, and has since been modified several times. However, there is always a risk of damaging the inferior alveolar nerve. We have studied 50 consecutive patients who had high oblique sagittal split osteotomy (HSSO) as an alternative to avoid damage to the nerve. The patients were evaluated for sensory alterations and function of the temporomandibular joint (TMJ). Healing of both wound and bone were complete and uneventful in all 50 patients. Mean (SD) sagittal movement of the mandible was 6.6 (2.9)mm and length of the osteotomy line was 11.0 (3.1)mm. No patient had either temporary or permanent alteration in sensitivity. Pinprick tests showed no significant changes between the preoperative and postoperative readings (p>0.16) or in the chronological results (p>0.23). No disorders of the TMJ developed. Mean (SD) mouth opening 6months postoperatively was 41.6 (8.6)mm. The lateral excursion increased postoperatively by 1.86mm to the left and by 0.76mm to the right. Protrusion increased by 0.66mm. HSSO is therefore a suitable alternative to BSSO as it avoids injury to the inferior alveolar nerve without compromising the TMJ. Ossification was uneventful though bony attachment was less than with the classic BSSO.

Accuracy assessment for navigated maxillo-facial surgery using an electromagnetic tracking device.

PURPOSE: To evaluate the accuracy and the usability of an electromagnetic tracking device in maxillo-facial surgery through testing on a phantom skull under operating room (OR) conditions. MATERIAL AND METHODS: A standard plastic skull phantom was equipped with a custom made model of the maxilla and with target markers and dental brackets. Imaging was performed with a computed tomography (CT) scanner. The extent and robustness of the electromagnetic tracking system's target registration error (TRE) was evaluated under various conditions. RESULTS: For each measurement a total of 243 registrations were performed with 5 point registration and 4374 registrations with 6 point registration. The average target registration error for the 5 point registration under OR conditions was 2.1 mm (SD 0.86) and 1.03 (SD 0.53) for the 6 point registration. Metallic instruments applied to the skull increased the TRE significantly in both registration methods. CONCLUSION: The electromagnetic tracking device showed a high accuracy and performed stable in both registration methods. Electromagnetic interference due to metallic instruments was significant but the extent of TRE was still acceptable in comparison to optical navigation devices. A benefit of EM tracking is the absence of line-of-sight hindrance. The test setting simulating OR conditions has proven suitable for further studies.

Condylar metastasis from prostatic carcinoma mimicking temporomandibular disorder: a case report.

BACKGROUND: Although metastatic carcinoma is the most common malignant tumor of the bone, less than 1% of all metastatic bone lesions are presented in the maxillofacial area. As the mandibular body is the most frequent localization, metastasis to the mandibular condyle is extremely rare. CASE REPORT: This report describes a rare case of prostate carcinoma metastatic to the mandibular condyle in a 75-year old man, who was referred because of persistent pain in the temporomandibular joint (TMJ) region and a limitation of opening, initially misdiagnosed and treated as temporomandibular disorder (TMD). Histopathological examination confirmed the suspected metastasis of prostate carcinoma and local radiation therapy was performed. DISCUSSION: TMD represent a diagnostic challenge and sometimes an interdisciplinary approach is required to prevent a delay of the correct treatment. Metastatic cancer should be included in the differential diagnosis of TMD, especially in patients with a malignant disease.

Image quality of two different mobile cone beam computed tomographs for maxillofacial surgery.

PURPOSE: We evaluated two mobile cone beam computed tomographs (mCBCT) comparing image quality with respect to radiation dosage. Image quality was analyzed by using different scanning modes. MATERIALS AND METHODS: The skulls of three human cadavers were scanned by use of conventional Computed Tomography (CT) as well as with two mobile cone beam computed tomographs (Siemens Arcadis Orbic 3D and Ziehm Vision Vario 3D). Six different acquisition modes with different radiation dosages were used. The axial views of all scans were evaluated by five medical doctors regarding image quality by identifying predefined anatomical structures of the skull. A five-point ranking scale was used. The inter-rater reliability was statistically depicted by Cohen's Kappa coefficient. A Wilcoxon signed rank test was used to evaluate the rater's results. For evaluating the signal-to-noise ratio (SNR) a Catphan 600 reference body with two different inlays was used. RESULTS: Comparing the mCBCTs, the image quality of the Siemens Arcadis Orbic 3D in high-dosage mode received the best score (median: 2.27). The inter-rater reliability was fair (Kappa=-0.030 to 0.328). The Wilcoxon test showed significant (p<0.05) different median rating values in 18 out of 21 imaging modes. The SNR was higher (better) in the high-dosage modes. CONCLUSION: Intra-operative 3D imaging by using mCBCT for maxillofacial surgery in low-dose mode acquisition is adequate in terms of signal-to-noise ratio and image quality. The image quality does not correlate in a linear manner with a higher radiation dosage. Surgeons using this technique should gather their own experience with the different acquisition modes.