Robert A. Mischkowski

Computer-assisted orthognathic surgery: feasibility study using multiple CAD/CAM surgical splints

OBJECTIVE We present a virtual planning protocol incorporating a patented 3-surgical splint technique for orthognathic surgery. The purpose of this investigation was to demonstrate the feasibility and validity of the method in vivo. MATERIALS AND METHODS The protocol consisted of (1) computed tomography (CT) or cone-beam computed tomography (CBCT) maxillofacial imaging, optical scan of articulated dental study models, segmentation, and fusion; (2) diagnosis and virtual treatment planning; (3) computed-assisted design and manufacture (CAD/CAM) of the surgical splints; and (4) intraoperative surgical transfer. Validation of the accuracy of the technique was investigated by applying the protocol to 8 adult class III patients treated with bimaxillary osteotomies. The virtual plan was compared with the postoperative surgical result using image fusion of CT/CBCT dataset by analysis of measurements between hard and soft tissue landmarks relative to reference planes. RESULTS The virtual planning approach showed clinically acceptable precision for the position of the maxilla (<0.23 mm) and condyle (<0.19 mm), marginal precision for the mandible (<0.33 mm), and low precision for the soft tissue (<2.52 mm). CONCLUSIONS Virtual diagnosis, planning, and use of a patented CAD/CAM surgical splint technique provides a reliable method that may offer an alternate approach to the use of arbitrary splints and 2-dimensional planning.

Comparison of cone-beam volumetric imaging and combined plain radiographs for localization of the mandibular canal before removal of impacted lower third molars

OBJECTIVE The removal of third molars requires information about the relative position of the root tips and the mandibular nerve. The diagnostic value of conventional radiologic procedures using a panoramic radiograph and symmetrical PA cephalometric radiograph (PAN&PA) was compared with that of a cone-beam volumetric imaging (CBVI) device (Galileos; Sirona, Bensheim, Germany). STUDY DESIGN Six observers evaluated 30 PAN&PA and 30 CBVI for the position of root tips. Diagnostic information was rated from 1 to 5 (excellent to poor). RESULTS With PAN&PA, 3 times more scans showed nondetectable information for horizontal position compared with CBVI. The diagnostic information in the vertical dimension received a median rating of 2 (good) for CBVI and for PAN & PA; for the horizontal dimension, CBVI received a median rating of 2 (good), compared with a significantly worse median rating of 3 (sufficient) for PAN & PA (P = .000). The variance was highest for the horizontal dimension with PAN & PA (1.27). CONCLUSION These findings indicate that cone-beam technology improves the localization of third molar for presurgical planning.

MRI examination of the TMJ and functional results after conservative and surgical treatment of mandibular condyle fractures

Thirty patients with healed condylar fractures were included in this study. Ten patients were conservatively treated while in 20 patients the fractures were treated surgically. All patients were assessed using: magnetic resonance imaging of both temporomandibular joints (TMJs) to evaluate the disc position and morphology; radiographs to evaluate the alignment of the bony fragments after consolidation; and clinical examination including the stomatognathic functional status and mechanical axiography. The study shows that anatomical reduction of a low, displaced or dislocated condylar fracture by surgical approach may be of benefit for the functional recovery of the TMJ.

Prevalence of pathologic findings in the maxillary sinus in cone-beam computerized tomography

OBJECTIVE The aim of this study was to assess the prevalence of pathologic findings in the maxillary sinus by using cone-beam computerized tomography (CBCT). STUDY DESIGN One thousand twenty-nine consecutive CBCT scans were retrospectively inspected for pathologic findings in the maxillary sinus by 3 observers. Findings were differentiated by mucosal thickening, partial opacification with liquid accumulation, total opacification, and polypoidal mucosal thickening. Position and diameter of the maxillary sinus ostium were assessed. Correlations for pathologic findings and the factors of age and gender were calculated. Patients with clinical manifestations of sinusitis or total opacification in either sinus were reevaluated. RESULTS A total prevalence for pathologies in the maxillary sinus of 56.3% was found in this study. The most frequent pathology was mucosal thickening. Patients >60 years of age showed significantly more pathologies in the maxillary sinus (P = .02), and male patients showed significantly more pathologies than female patients (P = .01). Clinical signs of sinusitis could be confirmed on CBCT images for all patients. CONCLUSIONS Pathologies in the maxillary sinus are frequently found in CBCT imaging and have to be treated or followed-up accordingly. CBCT is applicable for diagnosis and treatment planning of clinically present sinusitis.

Accuracy of a newly developed integrated system for dental implant planning

OBJECTIVES To evaluate the accuracy of the first integrated system for cone-beam CT (CBCT) imaging, dental implant planning and surgical template-aided implant placement. MATERIALS AND METHODS On the basis of CBCT scans, a total of 54 implant positions were planned for 10 partially edentulous anatomical patient-equivalent models. Surgical guides were ordered from the manufacturer (SICAT). Two different types of guidance were assessed: for assessment of the SICAT system inherent accuracy vendors titanium sleeves of 2 mm internal diameter and 5 mm length were utilized for pilot drills. The guide sleeves of the NobelGuide system were implemented for fully guided surgery and implant insertion. Deviations perpendicular to the implant axes at the crestal and apical end, as well as the angle deviations between the virtual planning data and the surgical results, were measured utilizing a follow-up CBCT investigation and referential marker-based registration. RESULTS The SICAT system inherent mean deviation rates for the drilled pilot osteotomies were determined to be smaller than 500 mum even at the apical end. Mean angle deviations of 1.18 degrees were determined. Utilizing the NobelGuide sleeve-in-sleeve system for fully guided implant insertion in combination with the investigated template technology enabled to insert dental implants with the same accuracy. Crestal deviations, in general, were significantly lower than the apical deviations. CONCLUSION Although hardly comparable due to different study designs and measurement strategies, the investigated SICAT systems inherent accuracy corresponds to the most favourable results for computer-aided surgery systems published so far. In combination with the NobelGuide surgical set for fully guided insertion, the same accuracy level could be maintained for implant positioning.

Computer-assisted orthognathic surgery: waferless maxillary positioning, versatility, and accuracy of an image-guided visualisation display

There may well be a shift towards 3-dimensional orthognathic surgery when virtual surgical planning can be applied clinically. We present a computer-assisted protocol that uses surgical navigation supplemented by an interactive image-guided visualisation display (IGVD) to transfer virtual maxillary planning precisely. The aim of this study was to analyse its accuracy and versatility in vivo. The protocol consists of maxillofacial imaging, diagnosis, planning of virtual treatment, and intraoperative surgical transfer using an IGV display. The advantage of the interactive IGV display is that the virtually planned maxilla and its real position can be completely superimposed during operation through a video graphics array (VGA) camera, thereby augmenting the surgeons 3-dimensional perception. Sixteen adult class III patients were treated with by bimaxillary osteotomy. Seven hard tissue variables were chosen to compare (ΔT1-T0) the virtual maxillary planning (T0) with the postoperative result (T1) using 3-dimensional cephalometry. Clinically acceptable precision for the surgical planning transfer of the maxilla (<0.35 mm) was seen in the anteroposterior and mediolateral angles, and in relation to the skull base (<0.35°), and marginal precision was seen in the orthogonal dimension (<0.64 mm). An interactive IGV display complemented surgical navigation, augmented virtual and real-time reality, and provided a precise technique of waferless stereotactic maxillary positioning, which may offer an alternative approach to the use of arbitrary splints and 2-dimensional orthognathic planning.

Biomechanical properties of orthodontic miniscrews. An in-vitro study.

Objective:Comparing five commercially-available miniscrew types for skeletal anchorage with regard to the biomechanical properties influencing their primary stability.Material and Methods:Included in this study was a total of 196 self-tapping and self-drilling miniscrews having a diameter of 2 mm (or the largest possible diameter of the manufacturer in question), a thread shaft length of 10 mm, or the longest miniscrew supplied by the manufacturers. The screw types tested were the FAMI 2, Orlus mini-implant, T.I.T.A.N. Pin, tomas®-pin and Vector TAS™. Insertion and loosening torque measurements, and pullout tests in axial (0°), 20° and 40° directions, as well as test series with and without pilot hole drilling were performed. Bovine femoral heads having the same bone mineral density (BMD) were used as bone-testing material.Results:Higher insertion torques were found for the cylindrical FAMI 2 screw, the conical Orlus mini-implant and the Vector TAS™ screw (with mean values of 39.2 Ncm, 32.1 Ncm and 49.5 Ncm) than for the cylindrical T.I.T.A.N. pin and tomas®-pin. Insertion without predrilling led the insertion torques of all five screws to rise significantly. We noted statistically significant differences among the five screws in the pullout tests. Those highly significant differences at axial (0°) and 20°angles were not apparent at the 40° pullout angle. Compared with the pullout forces (load) in the axial direction, the cylindrical screws’ load values decreased markedly according to the angle (by up to –46.6%). The reduction in pullout force in conjunction with an increasing angle was much less pronounced in the conical screws (–0.8% to –29.0%). The tomas®-pin demonstrated the highest pullout force and stiffness values throughout the tests. A total of five tomas®-pins, two Orlus mini-implants and one FAMI 2 screw fractured during the pullout tests.Conclusions:Results from our insertion torque measurements suggest that a conical screw design will provide greater primary stability than cylindrical screw types. The cylindrical screw design’s superiority was evident in the pullout tests. All the miniscrews’ primary stability rose after drill-free insertion. The tomas ®-pin screws, although biomechanically superior to the other screws, were most prone to fracture.ZusammenfassungZiel:Ziel dieser Studie war der Vergleich fünf handelsüblicher Minischraubentypen zur skelettalen Verankerung hinsichtlich ihrer die Primärstabilität beeinflussenden biomechanischen Eigenschaften.Material und Methodik:Insgesamt wurden 196 zugleich selbstschneidende und selbstbohrende Minischrauben mit einem Durchmesser von 2 mm oder mit dem größtmöglichen Durchmesser des jeweiligen Fabrikats und einer Gewindeschaftlänge von 10 mm oder die längste von den Herstellern angebotene Minischraube, darunter die Schraubentypen FAMI 2, Orlus Mini- Implant, T.I.T.A.N. Pin, tomas®-pin und Vector TAS™, untersucht. Es wurden Eindrehmoment-, Lösemomentmessungen und Ausreißversuche in axialer (0°) sowie in 20°- und 40°-Zugrichtung durchgeführt sowie Testreihen mit und ohne Pilotbohrung vorgenommen. Als Knochentestmaterial wurden bovine Femurköpfe mit der gleichen Knochendichte (BMD) verwendet.Ergebnisse:Im Vergleich zu dem zylindrischen T.I.T.A.N. Pin und tomas®-pin waren die Eindrehmomente für die zylindrische FAMI-2-Schraube, das konische Orlus Mini-Implant und die Vector- TAS™-Schraube (mit Durchschnittswerten von 39,2 Ncm, 32,1 Ncm und 49,5 Ncm) höher. Bei der Insertion ohne Vorbohrung konnten die Eindrehmomente aller fünf Schraubentypen statistisch signifikant erhöht werden. In den Ausreißversuchen ergaben sich statistisch signifikante Unterschiede zwischen den fünf Schraubentypen. Die hochsignifikanten Unterschiede, die zwischen den fünf Schrauben für die Ausreißkräfte in axialer (0°) und 20°-Zugrichtung festgestellt wurden, waren für die Werte in 40°-Zugrichtung nicht ersichtlich. Verglichen mit den Ausreißkräften in axialer Zugrichtung, verringerten sich die Ausreißkräfte bei den zylindrischen Schrauben mit dem Winkel deutlich (um bis zu –46,6%). Bei den konischen Schrauben war die Abnahme der Ausreißkräfte mit steigendem Winkel deutlich geringer (–0,8% bis –29,0%). Der tomas®-pin erreichte in allen Testungen die höchsten Werte für Ausreißkraft und Steifigkeit. Insgesamt fünf tomas®-pins, zwei Orlus Mini-Implants und eine FAMI-2- Schraube frakturierten in den Ausreißversuchen.Schlussfolgerung:Der konische Schraubentyp weist bei den Eindrehmomentmessungen im Gegensatz zu den zylindrischen Schraubentypen eine höhere Primärstabilität auf. In den Ausreißversuchen war eine Überlegenheit der zylindrischen Schraubentypen zu erkennen. Durch die Insertion ohne Vorbohrung konnte die Primärstabilität bei allen Minipins gesteigert werden. Der tomas®-pin war trotz biomechanischer Überlegenheit gegenüber den anderen Schraubentypen am frakturanfälligsten.

The influence of body mass index, age, implants, and dental restorations on image quality of cone beam computed tomography

OBJECTIVE The aim was to determine the influence of patient age, gender, body mass index (BMI), amount of dental restorations, and implants on image quality of cone-beam computerized tomography (CBCT). METHODS Fifty CBCT scans of a preretail version of Galileos (Sirona, Germany) were investigated retrospectively by 4 observers regarding image quality of 6 anatomic structures, pathologic findings detection, subjective exposure quality, and artifacts. Patient age, BMI, gender, amount of dental restorations, and implants were recorded and statistically tested for correlations to image quality. RESULTS A negative effect on image quality was found statistically significantly correlated with age and the amount of dental restorations. None of the investigated image features were garbled by any of the investigated influence factors. CONCLUSIONS Age and the amount of dental restorations appear to have a negative impact on CBCT image quality, whereas gender and BMI do not. Image quality of mental foramen, mandibular canal, and nasal floor are affected negatively by age but not by the amount of dental restorations. Further studies are required to elucidate influence factors on CBCT image quality.

Biomechanical comparison of four different miniscrew types for skeletal anchorage in the mandibulo-maxillary area

This study compared four miniscrew types for skeletal anchorage (Aarhus, FAMI, Dual Top and Spider) regarding their biomechanical properties contributing to primary stability. Insertion torque measurements and pull-out tests in axial (0 degrees ) as well as in the 20 degrees and 40 degrees direction were performed. Stiffness of the screw-bone construct was calculated from the load-displacement curve. Conic FAMI and Dual Top screws had higher insertion torques. Insertion torques were raised by drill-free insertion of FAMI and Dual Top screws. Statistically significant differences were found between the 4 screw types in pull-out tests. The highly significant differences between the four screws for peak load in the axial (0 degrees ) and 20 degrees direction were not apparent in 40 degrees angular loads. For the conical screws, peak load values increased in angular compared with axial load. The Dual Top screw achieved the highest values for peak load and stiffness. 12 Dual Top and 1 Spider screw heads fractured in the pull-out tests. A conical drill-free screw design achieves higher primary stability compared with cylindrical self-tapping screws. This effect was more obvious in insertion torque estimations rather than in pull-out tests. The Dual Top screws, although biomechanically superior to other screw types, were most prone to fractures.

Salivary calculus diagnosis with 3-dimensional cone-beam computed tomography

OBJECTIVE The objective of this study was to evaluate cone-beam CT (CBCT) diagnoses of sialoliths in the major salivary glands. STUDY DESIGN Twenty-nine CBCT images containing salivary calculi were retrospectively evaluated for image quality and artifact influence. Additionally, the reproducibility of calculus measurement and the differences between CBCT measurements and ultrasonography (US) and histomorphometry (HM) measurements were determined. Diagnostic sensitivity and specificity calculations were based on the observations of 3 masked clinicians, who reviewed a total of 58 CBCT volumes. RESULTS Salivary calculi were sufficiently visualized in all patients. Metal artifacts were detected in images of 7 patients, and movement artifacts in 2. CBCT calculi measurements were highly reproducible, with mean differences of less than 350 microm. Mean CBCT measurements of calculi diameters differed from mean US measurements by approximately 500 microm and differed from mean HM measurements by approximately 1 mm. For calculus diagnoses, the mean sensitivity and specificity were both 98.85%. CONCLUSION Although poor image qualities and artifacts can reduce diagnostic information, salivary calculi can be evaluated adequately with CBCT. CBCT measurements of calculi are highly reproducible and differ little from measurements made with US and HM. Diagnostic sensitivity and specificity levels with CBCT are as high as or higher than those obtained with other diagnostic methods. Because of its high diagnostic-information-to-radiation-dose ratio, CBCT is the preferable imaging modality for salivary calculus diagnosis.