Heinz-Theo Lübbers

Precision and accuracy of the 3dMD photogrammetric system in craniomaxillofacial application.

Background: In modern anthropometry of such complex structures as the face, three-dimensional scanning techniques have become more and more common. Before establishing them as a criterion standard, however, meticulous evaluation of their precision and accuracy under both ideal and clinical circumstances is essential. Potential sources of error need to be identified and addressed. Materials and Methods: Under ideal circumstances, a phantom is used to examine the precision and accuracy of the 3dMD system. A clinical setting is simulated by varying different parameters such as angle, distance, and system reregistration, as well as data evaluation under different levels of magnification. Results: The handling of the system was unproblematic in matters of data acquisition and data analysis. It was very reliable, with a mean global error of 0.2 mm (range, 0.1-0.5 mm) for mannequin head measurements. Neither the position of the head nor that of the camera influenced these parameters. New referencing of the system did not influence precision and accuracy. Conclusions: The precision and accuracy of the tested system are more than sufficient for clinical needs and greater than those of other methods, such as direct anthropometry and two-dimensional photography. The evaluated system can be recommended for evaluation and documentation of the facial surface and could offer new opportunities in reconstructive, orthognathic, and craniofacial surgery.

Classification of potential risk factors for trigeminocardiac reflex in craniomaxillofacial surgery.

PURPOSE Trigeminocardiac reflex (TCR) in craniomaxillofacial surgery can lead to severely life-threatening situations. At least mild forms are probably much more common than the existing surgical literature suggests. Therefore, the aim of this presentation of cases and literature review was to evaluate the predisposing factors leading to a classification of risk factors for potential TCR and to give information concerning preventive measures and management procedures. PATIENTS AND METHODS All surgery reports from the Department of Cranio-Maxillofacial and Oral Surgery in the University Hospital in Zurich between 2003 and 2008 were searched for severe intraoperative cardiovascular complications, and a literature review was performed for publications concerning asystole or bradycardia during maxillofacial surgical procedures. RESULTS Three incidents were revealed in which severe bradycardia--in 2 cases followed by asystole--had occurred. All incidents were successfully managed. CONCLUSION All craniomaxillofacial surgeons involved in orbital surgery in general and in the treatment of midface fractures, eyelid surgery, and orthognathic procedures in particular should be aware of the possibility of the TCR and should be familiar with its prevention and therapy.

Surgical Navigation in Craniomaxillofacial Surgery: Expensive Toy or Useful Tool? A Classification of Different Indications

The complex 3-dimensional (3D) anatomy and geometry of the human skull and face combined with the need for precise symmetry poses challenges for reconstructive surgery of the region. Therefore, and with the technical improvements during the past 10 years or so, surgical navigation has become an established technique in craniomaxillofacial surgery. 1-4 Many technical problems have been solved, and the accuracy of multiple strategies of imaging and registration has been proved. 5 However, the procedure of preparing a patient for navigation is still linked to extra effort for the patient and surgeon. Even noninvasive registration procedures, such as a splint fixed to the upper jaw, as described by Schramm et al, 6 require dental impressions and additional imaging with the splint in situ. Insecurity surrounds surgical navigation of the lower jaw with different techniques available, such as mounting a dynamic reference frame to the mandible 7-9 or retaining the mandible in a defined position against the maxilla. 7,10-15 Thus, the state of surgical navigation of the mandible has been deemed unsatisfactory to date. 16 The aim of the present study was to evaluate the feasibility and limitations of surgical navigation. In addition, we determined the time and effort of the surgical team in relation to the benefit.

Point-to-point registration with mandibulo-maxillary splint in open and closed jaw position. Evaluation of registration accuracy for computer-aided surgery of the mandible

INTRODUCTION Computer navigation plays an increasingly important role in craniomaxillofacial surgery. The difficulties in computer navigation at the craniomaxillofacial site lie in the accurate transmission of the dataset to the operating room. This study investigates the accuracy of the dental-splint registration method for the skull, midface, and mandible. MATERIAL AND METHODS A synthetic human skull model was prepared with landmarks and scanned with cone beam computer tomography (CBCT). Two registration splints fixed the mandible against the viscerocranium in two different positions (closed vs. open). The target registration error was computed in all 278 landmarks spread over the entire skull and mandible in 10 repeated measurements using the VectorVision(2) (BrainLAB Inc., Feldkirchen, Germany) navigation system. RESULTS If registered in the closed position an average precision of 2.07 mm with a standard deviation (SD) of 0.78 mm was computed for all landmarks distributed over the whole skull. Registration in the open position resulted in an average precision of 1.53 mm (SD=0.55 mm). For single landmarks the precision decreases linearly with distance from the reference markers. The longer the three-dimensional distance between the registration points, the more precise the computer navigation is, mainly in the most posterior area of the cranium. CONCLUSION Our findings in the cranium are comparable with those of other studies. Artificial fixation of the lower jaw via splint seems to introduce no additional error. The registration points should be as far apart from each other as possible during navigation with the splint.

3-Dimensional Imaging for Lower Third Molars: Is There an Implication for Surgical Removal?

PURPOSE Surgical removal of impacted third molars may be the most frequent procedure in oral surgery. Damage to the inferior alveolar nerve (IAN) is a typical complication of the procedure, with incidence rates reported at 1% to 22%. The aim of this study was to identify factors that lead to a higher risk of IAN impairment after surgery. MATERIALS AND METHODS In total 515 surgical third molar removals with 3-dimensional (3D) imaging before surgical removal were retrospectively evaluated for IAN impairment, in addition to 3D imaging signs that were supposed predictors for postoperative IAN disturbance. Influence of each predictor was evaluated in univariate and multivariate analyses and reported as odds ratio (OR) and 95% confidence interval (CI). RESULTS The overall IAN impairment rate in this study was 9.4%. Univariate analysis showed narrowing of the IAN canal (OR, 4.95; P < .0001), direct contact between the IAN and the root (OR, 5.05; P = .0008), fully formed roots (OR, 4.36; P = .045), an IAN lingual course with (OR, 6.64; P = .0013) and without (OR, 2.72; P = .007) perforation of the cortical plate, and an intraroot (OR, 9.96; P = .003) position of the IAN as predictors of postoperative IAN impairment. Multivariate analysis showed narrowing of the IAN canal (adjusted OR, 3.69; 95% CI, 1.88 to 7.22; P = .0001) and direct contact (adjusted OR, 3.10; 95% CI, 1.15 to 8.33; P = .025) to be the strongest independent predictors. CONCLUSION Three-dimensional imaging is useful for predicting the risk of postoperative IAN impairment before surgical removal of impacted lower third molars. The low IAN impairment rate seen in this study-compared with similar selected study groups in the literature of the era before 3D imaging-indicates that the availability of 3D information is actually decreasing the risk for IAN impairment after lower third molar removal.

Cephalometric and three-dimensional assessment of the posterior airway space and imaging software reliability analysis before and after orthognathic surgery.

PURPOSE This study aimed to compare the reliability of three different imaging software programs for measuring the PAS and concurrently to investigate the morphological changes in oropharyngeal structures in mandibular prognathic patients before and after orthognathic surgery by using 2D and 3D analyzing technique. MATERIAL AND METHODS The study consists of 11 randomly chosen patients (8 females and 3 males) who underwent maxillomandibular treatment for correction of Class III anteroposterior mandibular prognathism at the University Hospital in Zurich. A set of standardized LCR and CBCT-scans were obtained from each subject preoperatively (T0), 3 months after surgery (T1) and 3 months to 2 years postoperatively (T2). Morphological changes in the posterior airway space (PAS) were evaluated longitudinally by two different observers with three different imaging software programs (OsiriX(®) 64-bit, Switzerland; Mimics(®), Belgium; BrainLab(®), Germany) and manually by analyzing cephalometric X-rays. RESULTS A significant increase in the upper airway dimensions before and after surgery occurred in all measured cases. All other cephalometric distances showed no statistically significant alterations. Measuring the volume of the PAS showed no significant changes in all cases. All three software programs showed similar outputs in both cephalometric analysis and 3D measuring technique. CONCLUSION A 3D design of the posterior airway seems to be far more reliable and precise phrasing of a statement of postoperative gradients than conventional radiography and is additionally higher compared to the corresponding manual method. In case of Class III mandibular prognathism treatment with bilateral split osteotomy of the mandible and simultaneous maxillary advancement, the negative effects of PAS volume decrease may be reduced and might prevent a developing OSAS.

Anatomy of impacted lower third molars evaluated by computerized tomography: is there an indication for 3-dimensional imaging?

OBJECTIVE Surgical removal of impacted third molar is one of the most frequent procedures in oral surgery. Today 3-dimensional (3D) imaging is occasionally used. The aim of this study was to describe and estimate the frequencies of anatomic variations of lower third molars in patients with panoramic findings at high risk for inferior alveolar nerve (IAN) injury. STUDY DESIGN The investigators designed and implemented a retrospective cases series study with a study population composed of patients presenting with an impacted lower third molar with projection of the tooth over the full width of the IAN in panoramic radiograph and, therefore, 3D imaging before a planned surgical removal. Spatial relationship to the IAN, type of angulation, root configuration and maturation were primary study variables. Descriptive statistics were computed for all variables. RESULTS A total of 707 wisdom teeth in 472 patients (54% female, 46% male) were evaluated. A close relationship to the IAN was seen in 69.7%, and in 45.1% the diameter of the mandibular canal was reduced. In 52.8% the IAN was vestibular and in 37.3% lingual to the roots; there were 9.9% with an inter- or intraroot course. Most teeth had 1 or 2 roots (86.7%), but 13.3% had ≥3 roots. Mesial angulation was the main type (40.2%), followed by vertical (29%), horizontal (13.9%), distal (10.2%), and transverse (6.8%) positions. CONCLUSION Based on the range of variations in the course of the nerve and the number of roots the authors recommend 3D imaging before surgical removal of a lower third molar that shows signs of a close relationship to the IAN.

The inferior alveolar nerve's loop at the mental foramen and its implications for surgery

BACKGROUND In this study, the authors aimed to identify and measure the anterior extension of the alveolar loop (aAL) and the caudal extension of the alveolar loop (cAL) of the inferior alveolar nerve by using cone-beam computed tomography (CBCT). They also aimed to provide recommendations for surgery in the anterior mandible. METHODS In this retrospective case study of the frequency and extension of aAL and cAL, the authors evaluated 1,384 mandibular sites in 694 CBCT scans of dentate and partly edentulous patients, performed mainly for further diagnosis before removal of the mandibular third molars between January 2009 and February 2013, by using multiplanar reconstructions. RESULTS The frequency of aAL was 69.73 percent and of cAL was 100 percent. The mean value for aAL was 1.16 millimeters, with a range of 0.3 to 5.6 mm; the mean value for cAL was 4.11 mm, with a range of 0.25 to 8.87 mm. For aAL, 95.81 percent of the sites showed values of 0 to 3 mm; for cAL, 93.78 percent of the sites showed values of 0.25 to 6 mm. Dentate patients showed statistically significantly higher values for cAL than did partly edentulous patients (P = .043). CBCT resolution had a statistically significant impact on cAL measurements (P = .001), with higher values at higher resolution. CONCLUSIONS This study showed a high frequency of and large variations in aAL and cAL. In contrast to panoramic radiography, CBCT has been shown to be a reliable tool for identifying and measuring the AL. Therefore, preoperative diagnosis with CBCT is recommended for planning three-dimensional tasks such as implant placement in the vicinity of the mental foramen. PRACTICAL IMPLICATIONS Owing to the variability of aAL and cAL measurements, it is difficult to recommend reliable safety margins for surgical procedures such as implant placement, bone harvesting or genioplasty Depending on the indication, the clinician should consider preoperative diagnosis by means of CBCT.

A Simple and Flexible Concept for Computer-Navigated Surgery of the Mandible

Computer navigation is a common tool in the daily routine of craniomaxillofacial surgery, particularly for the mid-face region, but experience in mandible application is still limited. Materials and methods Three cases are presented with navigation of the mandible: two cases of removal of a wisdom tooth fragment and one case of resection of an ameloblastoma. Results The described method is simple and time-saving. In all three patients the surgical technique was easy to perform. No typical complications followed, like damage of the lingual nerve or a hematoma of the mouth floor, which can appear when the surgeon intensely looks for a tooth fragment. Conclusions Computer navigation of the mandible is a promising tool, in particular for removal of foreign bodies, tooth fragments, and cystic or tumor lesion with clear margins. Advantages are 3D presentation of the lesion, evaluation of nerve location, and possible preoperative evaluation of graft size. Further applications could be orthognathic surgery, including distraction planning, bony tumor surgery, cyst removal, and planning for bony reconstructions.

Is mandibular reconstruction using vascularized fibula flaps and dental implants a reasonable treatment

PURPOSE this study retrospectively analyzed the rate of screwed implant insertion and risk factors in patients undergoing mandibular reconstruction with microsurgical revascularized fibula flaps. METHODS This study retrospectively analyzed all patients with microvascularized fibula grafts between 1997 and 2005. Collected data included general data and risk factors (e.g., smoking, alcohol use), and irradiation was the main predictor variable. The number of patients rehabilitated with dental implants and the implant success rate were evaluated, possible influencing factors were identified, and the results were compared with previously published data. RESULTS The sample included 33 patients (17 men, 16 women; mean age: 52 years); 76% were smokers, 42% drank alcohol regularly, and 73% had undergone mandible irradiation. Twenty-three patients received 140 screw-retained implants for dental rehabilitation. Twenty-three implants were lost. Overall 1- and 5-year implant survival rates were 94% and 83%, respectively. Implant survival rates were 86% in non-irradiated mandibular bone, 86% in non-irradiated grafted fibular bone, 82% in irradiated mandibular bone, and 38% in irradiated grafted fibular bone. CONCLUSION This study showed that the use of dental implants in patients with fibula flaps is an appropriate and successful option for dental rehabilitation, even in those with risk factors such as smoking, alcohol use, and irradiation. Implant placement in irradiated grafted bone seems to be a high-risk procedure.