Assessing bone volume for orthodontic miniplate fixation below the maxillary frontal process

The maxillary bone below the frontal process is used for orthodontic anchorage; indications have included skeletally anchored protraction of the maxilla for treating Class III malocclusions or the intrusion of teeth in patients with a deep bite. This study was conducted to assess the condition of bone before cortically implanting miniplates in that area of the maxilla. A total of 51 thin-sliced computed tomography scans of 51 fully-dentate adult patients (mean age 24.0 +/- 8.1 years; 27 men and 24 women) obtained prior to third-molar osteotomy were evaluated. Study parameters included total bone thickness, thickness of the facial cortical plate, and width of the nasal maxillary buttress. All these parameters were measured at different vertical levels. The bone volume adjacent to the piriform aperture was most pronounced at the basal level and decreased progressively toward more cranial levels. The basal bone structure had a mean total thickness of 7.8 mm, facial cortical plate thickness of 1.9 mm, and nasal maxillary buttress width of 9.2 mm. At 16 mm cranial to the aperture base, these values fell to 5.6 mm, 1.3 mm, and 5.8 mm, respectively. These bone measurements suggest that screws 7 mm in length can be inserted at the base level of the piriform aperture and screws 5 mm long at the cranial end of the bone

Bone condition of the maxillary zygomatic process prior to orthodontic anchorage plate fixation

The clinical success of orthodontic miniplates depends on the stability of the miniscrews used for fixation. For good stability, it is essential that the application site provides enough bone of good quality. This study was performed to analyze the amount of bone available for orthodontic miniplates in the zygomatic process of the maxilla. We examined 51 dental CT scans (Somatom Plus 4; Siemens, Erlangen, Germany) obtained from 51 fully dentate adult patients (mean age 24.0 +/- 8.1 years; 27 male and 24 female) prior to third molar surgery. The amount of bone in the zygomatic process region at the level of the first molar root tips and at several other cranial levels as far as 15 mm from the root tips was measured Bone thickness at the root tip level averaged 4.1 +/- 1.0 mm; the lowest value measured at this level in any of the patients was 2.7 mm. Bone thickness averaged 8.3 +/- 1.0 mm at 15 mm cranial to the root tips; 6.9 mm was the lowest value. The zygomatic process appears to provide sufficient bone to accommodate screws for miniplate fixation. While some patients may possess a borderline amount of bone at more caudal levels, lack of volume is not a problem near the zygomatic bone

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 surgeon's 3-dimensional perception. Sixteen adult class III patients were treated with by bimaxillary osteotomy. Seven hard tissue variables were chosen to compare (Delta T-1-T-0) the virtual maxillary planning (T-0) with the postoperative result (T-1) 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 degrees), 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. (C) 2013 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved

Quantitative Analyse der anterioren Spaltregion mit der digitalen Volumentomografie

Kurzfassung der Dissertationsschrift Quantitative Analyse der anterioren Spaltregion mit der digitalen Volumentomografie von Isabell Wend aus der Poliklinik für Kieferorthopädie des Zentums für Zahn-, Mund- und Kieferheilkunde der Universität zu Köln Direktor: Universitätsprofessor Dr. med. Bert Braumann Ein Mittel zur quantitativen und qualitativen Analyse von LKGS-Spalten zur effektiven Behandlungsplanung stellt neben der Erstellung des klinischen und des Modellbefunds die röntgenologische Diagnostik dar. Sie liefert unter anderem Informationen über das Ausmaß des knöchernen Defizits im Bereich der anterioren Spaltregion sowie Anlage, Morphologie und Lokalisation der spaltbenachbarten Zähne. Mit der konventionellen zweidimensionalen Röntgendiagnostik ist die präzise Ermittlung des knöchernen Defizits bzw. die Erfolgskontrolle nach sekundärer Osteoplastik nicht durchführbar. Die vorliegende Untersuchung präsentiert eine Analyse der dreidimensionalen Darstellung des Alveolarfortsatzdefektes mittels DVT-Technologie (DVT-Prototyp Galileos® Sirona Dental Systems, Bensheim). Bei 33 Patienten mit einseitigen oder doppelseitigen LK(GS)-Spalten wurden zur Planung der kieferorthopädischen/kieferchirurgischen Behandlung DVT-Aufnahmen angefertigt. In jeder axialen Schicht innerhalb der anterioren Spaltregion wurden durch mehrere Befunder die Spaltränder identifiziert, der Defekt markiert und das Volumen durch Summation der einzelnen Schichten visualisiert und berechnet. Mit der Durchführung von drei Untersuchungsteilen wurde die Messmethode validiert und die Messgenauigkeit der volumetrischen Messungen bestimmt. Der mittlere prozentuale Messfehler lag zwischen 1,48 % und 5,68 % und hat keine klinische Relevanz. Die Ergebnisse der vorliegenden Pilotuntersuchung zeigen, dass mit Hilfe der angewandten Messmethode das Volumen des Spaltbereichs reproduzierbar und verlässlich bestimmt werden kann. Der knöcherne Defekt im anterioren Spaltbereich läss