Evaluating the accuracy of resection planes in mandibular surgery using a preoperative,intraoperative, and postoperative approach

In mandibular surgery, three-dimensionally printed patient-specific cutting guides are used to translate the preoperative virtually planned resection planes to the operating room. This study was performed to determine whether cutting guides are positioned according to the virtual plan and to compare the intraoperative position of the cutting guide with the resection performed. Nine patients were included. The exact positions of the resection planes were planned virtually and a patient-specific cutting guide was designed and printed. After surgical placement of the cutting guide, intraoperative cone beam computed tomography (CBCT) was performed. Postoperative CT was used to obtain the final resection planes. Distances and yaw and pitch angles between the preoperative, intraoperative, and postoperative resection planes were calculated. Cutting guides were positioned on the mandible with millimetre accuracy. Anterior osteotomies were performed more accurately than posterior osteotomies (intraoperatively positioned and final resection planes differed by 1.2 ± 1.0 mm, 4.9 ± 6.6°, and 1.8 ± 1.5°, respectively, and by 2.2 ± 0.9 mm, 9.3 ± 9°, and 8.3 ± 6.5° respectively). Differences between intraoperatively planned and final resection planes imply a directional freedom of the saw through the saw slots. Since cutting guides are positioned with millimetre accuracy compared to the virtual plan, the design of the saw slots in the cutting guides needs improvement to allow more accurate resections.     

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??Objective??To measure and compare the discrepancy of Collum angle of incisors among different types of Angle malocclusion using CBCT??and to provide guidance for the prevention of alveolar bone fenestration and dehiscence in anterior region. Methods??The cases of malocclusion were chosen in the Xi'an Jiao Tong University Hospital of Stomatology from 2014 to 2016??and four types of malocclusion were obtained class ??30 cases????class ??1 ??29 cases????class ??2??27 cases????class ??30 cases????according to the clinical occlusion. Sagittal sections of right upper and lower incisors were obtained by three-dimensional CBCT images using Invivo 5 software?? and Auto CAD 2007 software was used to measure the angle formed by the long axis of crown and root??Collum angle????and then analyzing the differences among groups were analyzed by single factor variance and compared by Scheffe method. Results??There were significant differences in the size of Collum angle among different types of malocclusion??P??0.05??. The Collum angle of upper incisor in class ??2 was ??7.02 ± 1.83??°??which was significantly larger than that of other groups. The Collum angle of lower incisor in Class ??1 was??-2.25 ± 4.76??°??which meaned that the crown could be lip side compared to the root??and there was significant difference compared with the other groups. The Collum angle of the lower incisor in class ?? was??8.15 ± 2.50??°??which was also significantly larger than other groups. Conclusion??There are significant differences in the Collum angle of the upper and lower incisors among different types of malocclusion. The crown of upper incisor in Class ?? 2 and lower incisor in Class ?? can be lingual side to the root??and the crown of lower incisor in Class II1 can be lip side compared to the root??which should be taken into consideration when the incisor is pulled backward or inclined to lip to avoid the root cutting through bone cortex.     

La risoluzione delle complessità nei ritrattamenti

ObjectivesThe aim of this study is to describe the main causes and prevalence of endodontic therapy failures, to promote a diagnostic and prognostic work-up suited to the relevant pathology evolution degree and to suggest appropriate clinical strategies to achieve the expected results.Materials and methodsThrough an extensive review of recent literature, combined with an accurate analysis of clinical cases and epidemiological investigation, it was possible to gather and evaluate the necessary information and data for providing clinical dictates on the solution of endodontic retreatment problems.ResultsThe success percentage of endodontic retreatments is quite variable, ranging from 60% to 85% of treated cases. Such percentage is strongly dependent on two critical variables: the preoperative condition of periapical tissues and the previously provided treatment. A chronic apical periodontitis subjected to inadequate therapy leading to the structural alteration of dental elements, is indeed a crucial factor affecting the retreatment prognosis.ConclusionsAll retreatment procedures should be preceded by an accurate case analysis. Adverse anatomical conditions and periapical bone lesions may predict an unfavorable prognosis and should be taken into great consideration. However, in all other clinical conditions, high success rates can be achieved, ensuring a long-term survival of dental elements.     

Guided biopsy of osseous pathologies in the jaw bone using a 3D-printed,tooth-supported drilling template

Suspicious radiological findings in the jaw bone require histopathological examination for the confirmation of a diagnosis. As pathologies in this region are difficult to reach or are in close proximity to relevant anatomical structures, e.g. tooth roots or nerves, they often represent a challenge. Such factors may adversely affect the predictability of the surgical outcome of a biopsy of the osseous tissues. This technical note introduces a novel method for performing a digitally planned, guided biopsy. For this purpose, a cone beam computed tomography scan and an intraoral scan are superimposed using specific planning software. The resulting three-dimensionally printed, tooth-supported drilling template is designed for a trephine biopsy. It allows a precise, minimally invasive approach, with an exact three-dimensional determination of the biopsy location prior to surgery. The risk of devitalization of the neighbouring teeth or possible damage to the nerve structures can be minimized. Furthermore, a small access flap can be sufficient. In summary, the method of bone biopsy presented here allows high precision and greater predictability for biopsy sampling and is minimally invasive for the patient.     

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??Canted occlusal plane is the main feature of mandibular deviation. The causes of occlusal plane canting are very complicated and inconclusive. A large number of studies have shown that it is related to bite force??bite contact area??chewing movement and even head or neck position. CBCT is the best diagnostic method for assessing occlusal plane canting at present. Canted occlusal plane and mandibular deviation are mainly ipsilateral??and a small number reveals contralateral. It can also have adverse effects on temporomandibular joint and mastication??and it has been difficult to be corrected with non-surgical methods. Based on the existing literature??we summarized the canted occlusal plane features??adverse effects and the commonly used non-surgical treatment methods.     

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

PurposeThis 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 methodsThe 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.ResultsA 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.ConclusionA 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.     

Three-dimensional reconstruction of the temporal bone: Comparison of in situ,CT, and CBCT measurements

ObjectiveTo evaluate the accuracy of three-dimensional (3D) Cone Beam Computed Tomography (CBCT) and Computed Tomography (CT) reconstructions of human temporal bones compared with in situ measurements.Material and methodsExperimental anatomical study of 10 human temporal bones. Wilcoxon's test was used to compare 8 distances on each temporal bone measured in situ and then on 3D CT and CBCT reconstructions. Six landmarks were used: external auditory canal (EAC), tip of the mastoid process, tip of the occiput, zygoma, a point situated 1 cm above the tip of the mastoid process (T0) (open technique: lower limit of the mastoidectomy), head of stapes.ResultsNo significant difference was observed between the 3 measuring techniques for any of the distances studied (P > 0.05).DiscussionThis study demonstrates the equivalence of CBCT and CT for temporal bone measurements.ConclusionCBCT is a new imaging modality providing 3D reconstructions of the temporal bone that are as reliable as those obtained by CT. As a result of better spatial resolution compared to CT, CBCT is associated with a significantly lower radiation dose. This technique constitutes a morphological progress, as CBCT is comparable to CT, allowing investigation of pathological ears with a lower radiation dose.     

Head posture and pharyngeal airway volume changes after bimaxillary surgery for mandibular prognathism

PurposeThe purpose of this study was to evaluate head posture and the pharyngeal airway volume changes using 3D imaging after bimaxillary surgery in mandibular prognathism patients by null hypothesis.Materials and methodsCone-beam computed tomography (CBCT) scans were obtained for 25 mandibular prognathism patients before bimaxillary surgery (T1) and 6 months after surgery (T2). The head posture of each patient was assessed by measuring cranio-cervical angle on a midsagittal plane passing through the anterior nasal spine at T1 and T2. Additionally, the volume of each subject's pharyngeal airway was measured using InVivoDental 3D imaging software.ResultsThe cranio-cervical angle increased significantly 6 months after bimaxillary surgery (p < 0.01). The total volume of the pharyngeal airway slightly decreased (p > 0.05) at the same timepoints, while naso- and oro-pharyngeal airway volume decreased significantly (p < 0.05, p < 0.05). There was significant relationship between the changes of head posture and those of total airway volume (p < 0.05).ConclusionThe null hypothesis was rejected. Bimaxillary surgery resulted in significant head flexion and a slight decrease in total pharyngeal airway volume.