2D and 3D CT reconstructions of the facial skeleton: an unnecessary option or a diagnostic pearl?

Multifunctional Templates for Minimized Osteotomy, Implantation, and Palatal Distraction with a Mini-Screw-Assisted Expander in Schizodontism and Maxillary Deficit

Purpose

Schizodontism is complete separation of a dental germ. It results in a twin tooth and supernumerary teeth. The treatment of transverse constriction in combination with supernumerary dental germs and impacted central incisors can pose a challenge, especially in young patients, when the number of permanent teeth is not adequate to ensure secure anchorage. The use of navigation templates based on three-dimensional X-ray images allows for precise insertion of temporary mini-implants for the acquisition of palatal distractors. In addition, templates allow for minimally invasive biopsies and osteotomies.

Methods

The treatment of schizodontism, dentitio tarda, and transverse constriction is to be assessed as an interdisciplinary method by using mini-screw-assisted devices. Minimized osteotomy of impacted supernumerary teeth or dental implantation can be carried out in a one-step-procedure based on digital preplanning and prefabrication of orthodontic devices.

Results

Multifunctional templates allow for early planning, preoperative fabrication, and intraoral fixation of orthodontic appliances. In the case of an adolescent patient, a sustainable, interdisciplinary treatment concept could be demonstrated that shows age-appropriate gnathological development and stable growth conditions over a follow-up period of 10 years.

Conclusion

One can likely assume that multifunctional templates allow for minimally invasive one-step surgeries as an interdisciplinary tool between orofacial surgery and modern orthodontics.

Accuracy and precision of manual segmentation of the maxillary sinus in MR images-a method study

OBJECTIVE

To assess the accuracy and precision of segmentation of the maxillary sinus in MR images to evaluate the potential usefulness of this modality in longitudinal studies of sinus development.

METHODS

A total of 15 healthy subjects who had been both craniofacial CT and MR scanned were included and the 30 maxillary sinus volumes were evaluated using segmentation. Two of the authors did segmentation of MRI and one of these authors did double segmentation. Agreement in results between CT and MRI as well as inter- and intraexaminer errors were evaluated by statistical and three-dimensional analysis.

RESULTS

The intraclass correlation coefficient for volume measurements for both method error, inter- and intraexaminer agreement were > 0.9 [maximal 95% confidence interval of 0.989-0.997, p < 0.001] and the limit of agreement for all parameters were < 5.1%. Segmentation errors were quantified in terms of overlap [Dice Coefficient (DICE) > 0.9 = excellent agreement] and border distance [95% percentile Hausdorff Distance (HD) < 2 mm = acceptable agreement]. The results were replicable and not influenced by systematic errors.

CONCLUSION

We found a high accuracy and precision of manual segmentation of the maxillary sinus in MR images. The largest mean errors were found close to the orbit and the teeth. Advances in knowledge: MRI can be used for 3D models of the paranasal sinuses with equally good results as CT and allows longitudinal follow-up of sinus development.

Generation and evaluation of 3D digital casts of maxillary defects based on multisource data registration: A pilot clinical study

STATEMENT OF PROBLEM

Digital techniques are not clinically applied for 1-piece maxillary prostheses containing an obturator and removable partial denture retained by the remaining teeth because of the difficulty in obtaining sufficiently accurate 3-dimensional (3D) images.

PURPOSE

The purpose of this pilot clinical study was to generate 3D digital casts of maxillary defects, including the defective region and the maxillary dentition, based on multisource data registration and to evaluate their effectiveness.

MATERIAL AND METHODS

Twelve participants with maxillary defects were selected. The maxillofacial region was scanned with spiral computer tomography (CT), and the maxillary arch and palate were scanned using an intraoral optical scanner. The 3D images from the CT and intraoral scanner were registered and merged to form a 3D digital cast of the maxillary defect containing the anatomic structures needed for the maxillary prosthesis. This included the defect cavity, maxillary dentition, and palate. Traditional silicone impressions were also made, and stone casts were poured. The accuracy of the digital cast in comparison with that of the stone cast was evaluated by measuring the distance between 4 anatomic landmarks. Differences and consistencies were assessed using paired Student t tests and the intraclass correlation coefficient (ICC). In 3 participants, physical resin casts were produced by rapid prototyping from digital casts. Based on the resin casts, maxillary prostheses were fabricated by using conventional methods and then evaluated in the participants to assess the clinical applicability of the digital casts.

RESULTS

Digital casts of the maxillary defects were generated and contained all the anatomic details needed for the maxillary prosthesis. Comparing the digital and stone casts, a paired Student t test indicated that differences in the linear distances between landmarks were not statistically significant (P>.05). High ICC values (0.977 to 0.998) for the interlandmark distances further indicated the high degree of consistency between the digital and stone casts. The maxillary prostheses showed good clinical effectiveness, indicating that the corresponding digital casts met the requirements for clinical application.

CONCLUSIONS

Based on multisource data from spiral CT and the intraoral scanner, 3D digital casts of maxillary defects were generated using the registration technique. These casts were consistent with conventional stone casts in terms of accuracy and were suitable for clinical use.

The use of 3D planning in facial surgery: preliminary observations

Three-dimensional (3D) planning is becoming a more commonly used tool in maxillofacial surgery. At first used only virtually, 3D planning now also enables the creation of useful intraoperative aids such as cutting guides, which decrease the operative difficulty. In our center, we have used 3D planning in various domains of facial surgery and have investigated the advantages of this technique. We have also addressed the difficulties associated with its use. 3D planning increases the accuracy of reconstructive surgery, decreases operating time, whilst maintaining excellent esthetic results. However, its use is restricted to osseous reconstruction at this stage and once planning has been undertaken, it cannot be reversed or altered intraoperatively. Despite the attractive nature of this new tool, its uses and practicalities must be further evaluated. In particular, cost-effectiveness, hospital stay, and patient perceived benefits must be assessed.

Optic nerve monitoring

Orbital and anterior skull base surgery is generally performed close to the prechiasmatic visual pathway, and clear strategies for detecting and handling visual pathway damage are essential. To overcome the common problem of a missed clinical examination because of an uncooperative or unresponsive patient, flash visual evoked potentials and electroretinograms should be used. These electrophysiologic examination techniques can provide evidence of intact, pathologic, or absent conductivity of the visual pathway when clinical assessment is not feasible. Visual evoked potentials and electroretinograms are thus essential diagnostic procedures not only for primary diagnosis but also for intraoperative evaluation. A decision for or against treatment of a visual pathway injury has to be made as fast as possible due to the enormous importance of the time elapsed with such injuries; this can be achieved additionally using multislice spiral computed tomography. The first-line conservative treatment of choice for such injuries is megadose methylprednisolone therapy. Surgery is used to decompress the orbital compartment by exposure of the intracanalicular part of the optic nerve in the case of optic canal compression. Modern craniomaxillofacial surgery requires detailed consideration of the diagnosis and treatment of traumatic visual pathway damage with the ultimate goal of preserving visual acuity.

The role of three-dimensional computed tomography in the evaluation of temporomandibular joint ankylosis

Aims:

The aim of the study was to evaluate the role of three-dimensional computed tomography (3D-CT) in the assessment of temporomandibular joint (TMJ) ankylosis and its importance in treatment planning. The objectives of study were to measure and assess the mediolateral extent of ankylosis mass in 3D-CT and to compare the extent with intraoperative assessment. The study was also aimed to measure the coronoid process elongation in 3D-CT and its significance in treatment planning.

Materials and Methods:

This prospective study included 3D-CT evaluation of 11 patients with TMJ ankylosis during the period of February 2006–October 2007.

Results:

The 3D-CT assessment provided the length of the coronoid process and the relation of vital structures including maxillary artery to the ankylosed mass. Measurement of ankylosed mass also aids in preoperative measurement of the graft required to reconstruct the defect following removal of the ankylosed mass.

Conclusion:

Our study concludes that 3D-CT is a useful tool in the diagnosis and treatment planning of TMJ ankylosis.

Alveolar ridge augmentation for implant fixation: status review

This literature review was performed to illustrate and compare different alveolar ridge augmentation procedures before dental implant placement. The review was based on clinical and research studies listed in Pubmed. There is not enough evidence to support any single method as gold standard for any given condition, and choice seemed to be based on personal preferences. There is a lack of long-term survival data or success rates of grafting materials regarding donor and recipient sites. Although ridge splitting and distraction osteogenesis techniques eliminate donor site morbidity, circumvent the use of grafting materials, and reduce the operation time, some disadvantages and limitations should be considered. More studies are needed to compare the fate and characteristics of new bone obtained by these different procedures, as well as subsequent implant survival rates.

Position of the mental foramen on panoramic radiographs and its relation to the horizontal course of the mandibular canal: a computed tomographic analysis

AIM

The purposes of this study were (1) to investigate the bucco-lingual course of the mandibular canal in the bony structure and (2) to figure out the relationship between the position of mental foramen on panoramic radiographs and the horizontal course of the mandibular canal.

MATERIALS AND METHODS

A database of panoramic radiography and spiral computed tomography (CT) scans was searched and 100 subjects were selected based on the criteria. Mental foramina were classified into four groups according to its antero-posterior position. Three measurements were made on each slice of coronal CT scans at three different points: (1) apex of second premolar; (2) median point of two root apexes of first molar; and (3) median point of two root apexes of second molar. The bucco-lingual ratios were calculated to access the relative bucco-lingual position of the mandibular canal.

RESULTS

The distribution of subjects according to the type of mental foramen was: (1) type 3, 67%; (2) type 2, 26%; (3) type 4, 5%; and (4) type 1, 2%. The overall horizontal course of the mandibular canal was relatively constant from the second molar to first molar, whereas much significant directional change was found on the remaining course. Between types 2 and 3, no statistically significant differences were found at the level of the second molar and first molar (P = 0.461 and 0.965, respectively). Only below the second premolar, significant differences were found (P = 0.001).

CONCLUSIONS

Based on the findings of our computed tomographic image analysis, the position of mental foramen on panoramic radiographs was affected by its horizontal course of inferior alveolar nerve. The significant horizontal direction change of the course was found after the canal passing below the mandibular first molar regardless of the antero-posterior position of mental foramen.

Customized titanium reconstruction of post-traumatic orbital wall defects: a review of 22 cases

The authors present the clinical results of their method of customized reconstruction of orbital wall defects using titanium mesh or sheet. High resolution computed tomography (CT) data are imported and processed to create a three-dimensional (3D) image which is used to reconstruct the orbital defect. Mirror imaging of the air in the contralateral maxillary sinus is used to overcome artefact defects in the floor. A stereolithographic model is constructed, from which titanium mesh or sheet is shaped and sized to the required contours for implantation. Twenty-two patients were treated using this technique from 2003 to 2008. Postoperatively 10 patients reported early resolution of their diplopia. Six patients noticed significant improvement of their symptoms with mild residual diplopia in one direction only and at the extremes of gaze at final review. One patient required ocular muscle surgery. Enophthalmos resolved in eight of the nine cases. No patients developed enophthalmos or diplopia as a postoperative complication. The use of titanium mesh for orbital floor reconstruction has been shown to be safe and effective. Customized titanium implants accurately reproduce orbital contours thus restoring orbital volume. This reduces operative time and improves the functional and aesthetic outcomes of post-traumatic orbital reconstruction.

The role of three-dimensional CT in the evaluation of nasal structures and anomalies

Traditionally, computed tomography (CT) is the primary radiographic method to analyze the morphology of the craniofacial bones: Because of the many overlapping anatomical structures, it is difficult and sometimes impossible to evaluate craniofacial bones three-dimensionally (3D) with these images. For this reason, the aim of this paper has been to evaluate and demonstrate the importance of CT scans integrated by three-dimensional reconstructions (3D-CT) volume rendering imaging for the accurate understanding of the nasal pyramid morphology in the evaluation of patients submitted to secondary rhinoseptoplasty. Twenty patients enrolled for a secondary rhinoseptoplasty, underwent a preoperative evaluation through 3D-CT volume rendering imaging. This technique allowed a prefect reconstruction of the nasal structures at the level of the valve, as well as the medial and lateral walls of the nasal fossa in all of its components (bone and cartilage). In our experience, the 3D-CT volume rendering imaging studies improve the preoperative evaluation of structures and anomalies which are hard to evaluate by the anterior rhinoscopy and/or nasal endoscopy: alar and lateral cartilages, interdomal distance, tip morphology, valvular configuration, loss of bone-cartilaginous substance, etc. All of these points are important during the preoperative planning of secondary rhinoseptoplasty.

Computed tomography imaging strategies and perspectives in orbital fractures

Objective:

The objective of this study was to demonstrate the sensitivity and specificity of multislice computed tomography (CT) for diagnosis of orbital fractures following different protocols, using an independent workstation.

Materials and methods:

CT images of 36 patients with maxillofacial fractures (symptomatic to orbit region) who were submitted to multislice CT scanning were analyzed, retrospectively. The images were interpreted based on 5 protocols, using an independent workstation: 1) axial (original images); 2) multiplanar reconstruction (MPR); 3) 3D images; 4) association of axial/MPR/3D images and 5) coronal images. The evaluated anatomical sites were divided according to the orbital walls: lateral (with or without zygomatic frontal process fracture); medial; superior (roof) and inferior (anterior, medial). The collected data were analyzed statistically using a validity test (Youden's J index; p<0.05). The clinical and/or surgical findings (medical records) were considered as the gold standard to corroborate the diagnosis of the anatomical localization of the orbital fracture.

Results:

3D-CT scanning presented sensitivity of 78.9%, which was not superior to that of MPR (84.0%), axial/MPR/3D (90.5%) and coronal images (86.1%). On the other hand, the diagnostic value of axial images was considered limited for orbital fractures region, with sensitivity of 44.2%.

Conclusions:

Except for the axial images, which presented a low sensitivity, all methods evaluated in this study showed high specificity and sensitivity for the diagnosis of orbital fractures according to the proposed methodology. This protocol can add valuable information to the diagnosis of fractures using the association of axial/MPR/3D with multislice CT.

The diagnostic value of the sagittal multiplanar reconstruction CT images for nasal bone fractures

AIM

To compare the diagnostic performance of sagittal multiplanar reconstruction (MPR) images and axial images for the detection of a nasal bone fracture.

MATERIALS AND METHODS

This prospective study included 533 consecutive patients who underwent three-dimensional images with 64-section multidetector-row CT for the evaluation of a facial bone fracture between June 2007 and May 2008 (366 males; 167 females; mean age +/- standard deviation 31.1+/-21.2 years; age range 1-92 years). Two observers independently scored the possibility of a nasal bone fracture on axial and sagittal images. Receiver operating characteristic (ROC) curve analysis was performed.

RESULTS

The Az values of the sagittal images were higher than those of the axial images for both observers (p=0.002 and 0.010, respectively) with higher accuracy (p<0.001 and 0.016, respectively). The sensitivities of sagittal images were superior to those of axial images, especially for type 1simple nasal bone fractures with no or minimal displacement (observer 1, 98.6 versus 72.8%; observer 2, 84.9 versus 71%).

CONCLUSION

Sagittal MPR facial bone CT images provided superior diagnostic performance, and their addition to axial images is useful for the evaluation of nasal bone fractures.

Subtle pathology detection with multidetector row coronal and sagittal CT reformations in acute head trauma

We sought to analyze retrospectively the advantages of coronal and sagittal reformations obtained with multidetector row computed tomography (CT) in patients with acute head trauma. Multidetector 16-section CT was performed in 200 patients (110 male and 90 female; age range, 3-87 years; mean age, 45 years) with acute head trauma. Scans were performed sequentially, and axial 5-mm-thick slices were obtained from base of skull to vertex. The source data set was reformatted in coronal and sagittal planes, with 2-mm-thick sections at 2-mm intervals. Images were analyzed retrospectively by two independent, blinded readers. The final diagnosis was determined by clinical follow-up. CT imaging abnormalities were detected in 55 out of 200 patients who were scanned for head trauma. Acute traumatic intracranial abnormality was detected on axial scans in 45 patients. Subtle findings were confirmed on coronal and sagittal CT reformations in ten cases, and these were undetected initially on axial CT. Coronal and sagittal reformations confirmed subtle findings in 18.2% (10/55) of the cases (P = 0.001). Indeterminate neuroimaging findings confirmed by coronal and sagittal CT head reformations include tentorial and interhemispheric fissure subdural hemorrhage, subarachnoid hemorrhage, and inferior frontal and temporal lobe contusions. Coronal and sagittal CT head reformations improve the sensitivity and diagnostic confidence in the clinical setting of acute trauma. Overall, coronal and sagittal reformations improved diagnostic confidence and interobserver agreement over axial images alone for visualization of normal structures and in the diagnosis of acute abnormality.

Application of computed tomography for supernumerary teeth location in pediatric dentistry

Conventional radiographs provide bi-dimensional images of three-dimensional structures limiting optimal treatment planning. To overcome this deficiency, Computed Tomography (CT) has been used as a diagnostic method in Medicine and Dentistry. CT allows for supernumerary teeth location, the establishment of positional relations with other teeth, and the assessment of surrounding bone thickness; thus, facilitating surgical access and technique choice while reducing the procedure time, of great importance in pediatric dental care. The aim of this study was to present the possibility of applying CT for supernumerary teeth location, through the case report of a five-year-old female patient presenting two supernumerary teeth in the anterior palatal area. In conclusion, CT appears to be an excellent image diagnostic method for locating unerupted supernumerary teeth, providing precise information for planning and performing the surgical approach, while reducing operatory time and post-operatory complications; factors of extreme importance when treating young children.

Mandibular muscle morphology in children with different vertical facial patterns: A 3-dimensional computed tomography study

INTRODUCTION

This study was undertaken to assess whether 3-dimensional computed tomography (CT) can be used to evaluate the relationships between the mandibular muscles and craniofacial morphology in children with different underlying vertical facial patterns.

METHODS

Twenty children (mean age, 11.9 +/- 1.6 years) underwent cranial CT examination. Three-dimensional CT images were reconstructed for the evaluation of the cross-sectional size, volume, and spatial orientation of the masseter, medial pterygoid, and lateral pterygoid muscles. These muscle factors were also assessed in relation to vertical and transverse craniofacial form.

RESULTS

Positive correlations were found between the muscles' cross-sectional area and volume, and between muscle size and transverse facial width. Despite the limited sample size, differences were also found in the orientation of the masseter and medial pterygoid muscles in growing patients with different underlying vertical facial patterns.

CONCLUSIONS

Three-dimensional CT can be used for the assessment of soft- and hard-tissue dentofacial forms. Clinicians should note the potential differences in muscle cross-sectional area, volume, and orientation in subjects with different underlying vertical facial patterns.

Individual preformed titanium meshes for orbital fractures

OBJECTIVES

The aim of this investigation was to develop and test the accuracy of a procedure for fabricating individual preformed titanium meshes for orbital fractures.

STUDY DESIGN

Preoperative CT datasets from five patients with orbital fractures were used for 3D reconstruction by mirroring the unaffected side onto the defective one, resulting in a new sub-volume. A template for adaptation of the titanium mesh was produced by applying these sub-volumes. Navigation-aided procedures guaranteed the exact placement of the preformed mesh during the operation.

RESULTS

The accuracy of the reconstructed orbital floor was determined to be approximately 1 mm, which lies within the technical limit of detection.

CONCLUSION

These results indicate a further application or navigation-aided reconstruction, which will serve as a pilot project for further investigations. Clustered databases of patients will be used to produce various template sets, reflecting ideal skeletons, according to age, sex, and other patient variables. These could be used for manufacturing preformed osteosynthesis templates.

Use of stereolithographic templates for surgical and prosthodontic implant planning and placement. Part I. The concept

Surgical and prosthodontic implant complications are often an inadvertent sequelae of improper diagnosis, planning, and placement. These complications pose a significant challenge in implant dentistry. Presented in this article is a technique using a highly advanced software program along with a rapid prototyping technology called stereolithography. It permits graphic and complex 3D implant simulation and the fabrication of computer-generated surgical templates. These templates seat directly on the bone and are preprogrammed with the individual depth, angulation, and mesio-distal and bucco-lingual positioning of individual implants as planned during the 3D computer simulation.

Computer-assisted reconstruction of orbital floor based on cone beam tomography

We used a navigation system for computer-assisted preoperative planning based on cone beam tomography with virtual reconstruction to obtain symmetry of the orbit and intraoperative control of virtual contours. In operations for reconstruction of the orbital floor this technique offers a reliable intraoperative control in an area of limited exposure and visibility. There was no significant difference in visualisation of anatomical structures between the cone beam tomographic digital imaging and communication (DICOM) data and computed tomographic data. Cone beam tomography seems to be suitable for computer-assisted planning in the management of orbital trauma with reduced costs and less radiation.

Imaging of maxillofacial trauma: Evolutions and emerging revolutions

The aim of diagnostic imaging for maxillofacial trauma is to provide additional information that can positively influence medical or surgical patient management. Current advances in diagnostic imaging have come from the confluence of 3 driving forces: (1) the demand from clinicians to enhance and expand their diagnostic abilities; (2) the development of new theoretical concepts by basic scientists; and (3) the application of concepts by engineers and manufacturers to provide increasingly sophisticated imaging capabilities. The role of imaging within the health care environment is, however, also buffeted by the complex, sometimes competing, interactions of external social, political, economic, and technological pressures at the national, regional, and local levels. The purposes of this review are to provide a perspective on current imaging modalities used for maxillofacial trauma and to provide an insight into the influences, both technologic and external, on future developments and applications.

Isolierte Orbitabodenfrakturen

BACKGROUND

The goal of this retrospective study was quantitative calculation of area and volume of isolated orbital floor fractures from computed tomography (CT) and correlation of these data with post-traumatic ophthalmologic findings.

PATIENTS AND METHODS

A total of 76 patients with isolated orbital floor fractures were evaluated radiologically and clinically. CT scanning was performed in coronal sections (1.5-mm to 3.0-mm slice thickness) with contiguous table feed. Orbital floor and fracture area as well as volume of displaced tissue were measured and calculated from the CT dataset. The relation of quantitative CT data to ophthalmologic findings (motility, diplopia, and globe position) was assessed statistically.

RESULTS

Calculation of the CT dataset revealed a mean orbital floor area of 6.33+/-1.05 cm(2), a mean fracture area of 2.60+/-1.14 cm(2), and a mean volume of displaced tissue of 1.16+/-0.80 cm(3). Volume of displaced tissue correlated significantly with ophthalmologic findings (p< or =0.01). Fracture area correlated significantly with globe position (p< or =0.01) and was less associated with diplopia and motility disturbances (p<0.10).

CONCLUSION

Efficient evaluation of two-dimensional CT data enables quantitative assessment of orbital floor fractures. Position and function of the globe are mainly affected by the volume of displaced periorbital tissue.

Validity of multislice computerized tomography for diagnosis of maxillofacial fractures using an independent workstation

OBJECTIVE

The purpose of this study was to demonstrate the sensitivity and specificity of multislice computerized tomography (CT) for diagnosis of maxillofacial fractures following specific protocols using an independent workstation.

STUDY DESIGN

The study population consisted of 56 patients with maxillofacial fractures who were submitted to a multislice CT. The original data were transferred to an independent workstation using volumetric imaging software to generate axial images and simultaneous multiplanar (MPR) and 3-dimensional (3D-CT) volume rendering reconstructed images. The images were then processed and interpreted by 2 examiners using the following protocols independently of each other: axial, MPR/axial, 3D-CT images, and the association of axial/MPR/3D images. The clinical/surgical findings were considered the gold standard corroborating the diagnosis of the fractures and their anatomic localization. The statistical analysis was carried out using validity and chi-squared tests.

RESULTS

The association of axial/MPR/3D images indicated a higher sensitivity (range 95.8%) and specificity (range 99%) than the other methods regarding the analysis of all regions.

CONCLUSION

CT imaging demonstrated high specificity and sensitivity for maxillofacial fractures. The association of axial/MPR/3D-CT images added important information in relationship to other CT protocols.

Reconstruction of skull bone defects using the hydroxyapatite cement with calvarial split transplants

PURPOSE

We sought to present a new method for primary reconstruction of traumatic or tumor calvarial defects.

PATIENTS AND METHODS

Forty-one patients underwent reconstruction of calvarial bone defects between October 1998 and December 2001. Among them were 19 patients who needed reconstruction of the calvaria due to traumatic bone loss. Five of these trauma cases had insufficient primary reconstruction of the calvaria. Tumor resection caused calvarial defects in 22 patients. For primary reconstruction of the skull bone defects, calvarial split grafts were used to cover the defect as accurately as possible. The monocortical layers of the calvaria were fixed with titanium miniplates. Irregular defects surrounding the transplanted regions were filled with hydroxyapatite cement. In one case of posttraumatic bone loss, hydroxyapatite cement alone was sufficient to reconstruct the defect.

RESULTS

The follow-up of each patient was at least 6 months; the longest period was 38 months. Evaluated clinical and radiologic results are stable, showing no measurable side effects.

CONCLUSION

Hydroxyapatite cement alone or in combination with calvarial split grafts gave clinically and aesthetically stable results in the reconstruction of skull bone defects. The cement can be used for many reconstruction possibilities in craniofacial surgery.

Imaging technique selection for the preoperative planning of oral implants: a review of the literature

BACKGROUND

As the use of oral implants for the treatment of partially as well as fully edentulous patients has increased the past two decades, more specialized radiographic techniques have become available for the preoperative planning of oral implant placement.

PURPOSE

The goal of this article was to enable clinicians to select the appropriate imaging techniques when planning for oral implants.

MATERIALS AND METHODS

This artide reviews the available literature about various imaging techniques and their indication for the preoperative planning of oral implants. The advantages and drawbacks of each technique are described. A dosimetric overview is given relative to different radiologic techniques used in various clinical situations.

RESULTS

For preoperative planning of implant placement, advantages and drawbacks of the available imaging techniques have been considered, which allows guidelines for image technique selection to be formulated based on the clinical situation provided, considering the diagnostic yield of each technique and the radiation doses involved.

CONCLUSIONS

From the available literature, it can be stated that many clinical situations demand the use of cross-sectional imaging techniques for optimal preoperative planning of implant placement. Nevertheless, such techniques are not required in cases in which the clinical examination reveals sufficient bone width and where standard radiographic examinations, such as intraoral and panoramic radiography, reveal adequate bone height and space for implant placement.

A comprehensive classification of craniofacial fractures: postmortem and clinical studies with two- and three-dimensional computed tomography

A comprehensive classification of midfacial/craniofacial fractures, based on two- and three-dimensional computed tomography (2D and 3D-CT) is presented. We performed a postmortem analysis of 24 patients who had died from trauma with signs of craniofacial fractures, based on 2D and 3D-CT studies with pathoanatomical findings. In addition, CT findings for 100 patients with craniofacial injuries requiring an emergency CT were correlated with surgical findings and follow-up results. On the basis of the analysis of a total of 377 fractures a classification system is proposed. The system is based on the use of the AO/ASIF (Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation) scheme, defining three types (A, B, C), three groups within each type (e.g. A1, A2, A3) and three subgroups within each group (e.g. A1.1, A1.2, A1.3) with increasing severity from A1.1 (lowest) to C3.3 (highest). The craniofacial region is divided into three units: the lower midface (I), the upper midface (II) and the craniobasal-facial unit (III). Lateral and central fractures are also distinguished. Type A fractures are non-displaced fractures, type B are displaced fractures and type C are complex/defect fractures. Groups A1, B1 and C1 comprise fractures of an isolated unit; groups A2, B2 and C2, combined fractures without involvement of the skull base; and groups A3, B3 and C3 are those combined fractures with involvement of the skull base. A correlation between the severity of the fracture and (i). the number of posttraumatic functional limitations (Spearman rank test, correlation coefficient r=0.42), (ii). the need for bone grafting or dural plastic (r=0.39) and (iii). facial asymmetry (r=0.37), was observed. The proposed classification system allows standardised documentation of midfacial and craniofacial fractures, including those not precisely defined by the Le Fort classification scheme.

3D volume rendering using multislice CT for dental implants

OBJECTIVES

To determine the precision and accuracy of three-dimensional (3D) volume rendering spiral multislice computed tomography (CT)-based linear measurements of the mental foramen for dental implants, in vitro, and their precision, in vivo.

METHODS

Five cadaver heads were imaged by multislice spiral CT (Toshiba Aquilion) with 0.5 mm thick axial slices (0.5 mm/0.5 s of table feed) at 0.5 mm interval reconstructions. The image data sets were transferred to a networked computer workstation. Using computer graphics the data were analysed with a 3D volume rendering technique using Vitrea software. Two oral and maxillofacial radiologists, independently, made electronic linear measurements from the superior border of the mental foramen to the crest of the alveolar process. The soft tissues were removed and physical measurements made using a 3 Space (Polhemus, Colchester, VT, USA) electromagnetic digitizer with a personal computer running Windows 98. The same linear measurements of 15 patients using the same imaging methodology were performed and the precision was analysed.

RESULTS

The findings showed no statistically significant inter- or intra-observer differences in vitro and in vivo, or between imaging and physical measurements in vitro (P>0.05).

CONCLUSIONS

3D multislice spiral CT imaging allows highly accurate measurements for dental implant placement in proximity to the mental foramen. Computer graphics software, using volume rendering is suitable for implant planning.

2D- and 3D-based measurements of orbital floor fractures from CT scans

OBJECTIVE

Two methods for area and volume calculation of the orbit were evaluated following blow-out fractures of the orbital floor using computed tomography (CT) scans.

MATERIAL AND METHODS

Isolated blow-out fractures of the orbital floor in human cadavers were simulated by fracturing the orbital floor and placing a defined volume of silicone within each defect. The area of fracture and the volume of silicone simulating herniated periorbital tissue were evaluated in 16 orbits by the use of a three-dimensional (3D) CT-based software package (Analyze((R)); Mayo Clinic, Rochester, MN, USA) and software based on two-dimensional (2D) coronal CT scans. Both methods were compared with direct anatomical measurements and evaluated with Lin's concordance coefficient (rho(c)).

RESULTS

Between-method concordance of area and volume calculation were rho(c)=0.962, and 0.872 for the 3D-CT-based method, and 0.981 and 0.952 for the 2D-CT method, respectively. The time allocated for measurement was significantly longer for the 3D-CT than for the 2D-CT method (p<0.001).

CONCLUSION

Calculations of blow-out fractures of the orbital floor by 3D-CT and 2D-CT method are accurate for assessing the area of fracture and the volume of herniated tissue. Lesser processing time and simple usage favour the 2D-CT-based calculation method.

Development of a protocol for coronal reconstruction of the maxillofacial region from axial helical CT data

Using a fresh frozen cadaver head, a series of axial helical CT scans were obtained using varying imaging parameters both before and after traumatizing the head. The appearance of reformatted coronal images was optimized for the lowest radiation dose. A protocol for imaging the maxillofacial region was developed that produced diagnostic coronal reconstructed images from the axial helical CT data.

Diagnostic maxillofacial coronal images reformatted from helically acquired thin-section axial CT data

OBJECTIVE

This study was undertaken to determine the sensitivity and specificity of coronal images reformatted from helical thin-section axial CT data obtained for the evaluation of maxillofacial fractures.

MATERIALS AND METHODS

Multiple fractures were created in nine cadaver heads by blunt trauma and were then evaluated using a late-generation helical CT scanner. Two neuroradiologists then independently evaluated the axial and reformatted coronal maxillofacial images. Subsequently, they reviewed the axial and direct coronal CT images, which were considered the criterion standard.

RESULTS

A total of 87 fractures were identified. An experienced neuroradiologist failed to identify one displaced fracture and two nondisplaced fractures when evaluating the reformatted coronal and direct axial images for an overall sensitivity of 97%. A less experienced neuroradiologist failed to identify a total of five minimally displaced or nondisplaced fractures for an overall sensitivity of 94%. For each radiologist, no significant difference in the time required to interpret the direct versus the reformatted coronal images was seen.

CONCLUSION

Interpretation of axial and reformatted coronal images resulted in accurate identification of displaced maxillofacial fractures in cadavers. This study suggests that the added cost and radiation exposure associated with incremental direct coronal CT may not be necessary for detection of clinically significant maxillofacial fractures and that further evaluation of this protocol in live trauma patients is warranted. However, because nondisplaced fractures were not routinely detected using reformatted coronal images, physical examination and clinical suspicion will still also remain necessary to determine the need for further imaging.

The validation of 3D spiral CT-based measurements of simulated maxillofacial neoplasms

OBJECTIVE

The purpose of this study was to determine the precision and accuracy of 3-dimensional spiral computed tomography-based linear measurements of neoplasms associated with the mandible.

STUDY DESIGN

Four cadaver heads, each with 2 simulated tumors made of clay, containing contrast medium, and positioned medial to the mandible, were examined by means of a subsecond spiral computed tomography unit. The computed tomography data were transferred to a computer workstation and analyzed through use of 3-dimensional reconstructed images. Linear measurements of the length, width, and depth of the simulated tumors were made by 2 observers, twice each. The soft tissues were then removed and the same measurements made by means of calipers.

RESULTS

There were no statistically significant differences between the 3-dimensional computed tomography and physical measurements (P >.05). The mean difference was found to be less than 0.4 mm.

CONCLUSIONS

Spiral computed tomography imaging allows for precise and accurate 3-dimensional computed tomography-based measurements for neoplastic lesions in the mandible.

Accuracy and precision of spiral CT in the assessment of neoplastic lesions associated with the mandible

RATIONALE AND OBJECTIVES

The purpose of this study was to determine the accuracy (validity) and precision (reliability) of spiral computed tomographic (CT) images by using film- and computer graphics-based measurements of simulated neoplastic lesions associated with the mandible.

MATERIALS AND METHODS

Four cadaver heads, each with two simulated tumors containing contrast medium positioned medial to the mandibles, were examined by using a subsecond spiral CT scanner. Data were transferred to film and to a computer workstation. With computer graphics, data were analyzed by using multiplanar reconstructed images. Linear measurements of the length, width, and depth of simulated tumors were made by two observers, twice each, on the film scans by using manual calipers and on the multiplanar reconstructed images by using computerized measurements. The soft tissues were then removed from the cadavers and the same measurements made by using the same calipers.

RESULTS

No statistically significant differences between computer graphics- or film-based measurements and physical measurements (P > .05) or between inter- and intraobserver measurements (P > .05) were found.

CONCLUSION

The authors found high reproducibility of measurements for all dimensions. Spiral CT allows accurate computer graphics- and film-based measurements of neoplastic lesions associated with the mandible.

Hemifacial microsomia and treatment options for auricular replacement: A review of the literature

STATEMENT OF PROBLEM

Although surgical reconstruction is the treatment of choice for auricular deformities that result from hemifacial microsomia, the implant-retained auricular prosthesis must be considered when surgical reconstruction is not possible. The competent and successful practitioner should be knowledgeable of the nature of this congenital disease.

PURPOSE

This article reviewed the first and second branchial syndrome, treatment approaches, and potential advances in surgical and prosthetic rehabilitation for patients with hemifacial microsomia.

CONCLUSION

Advantages and disadvantages of autogenous and alloplastic ear reconstructions are discussed. New research initiatives, such as tissue engineering and fabrication of auricular prosthesis by CAD/CAM, offer the potential for improved treatment for the future treatment of hemifacial microsomia.

Three-dimensional computed tomography landmark measurement in craniofacial surgical planning: experimental validation in vitro

PURPOSE

This study evaluated the measurement accuracy of three-dimensional (3D) volumetric images from spiral computed tomography (CT) in vitro.

MATERIALS AND METHODS

The study sample consisted of nine cadaver heads that were submitted to an impact force by a special device to promote blunt traumatic craniofacial fractures. The heads were subsequently scanned by a spiral CT scanner (Toshiba Xpress S/X). The archived CT data were transferred to networked computer workstations (Sun Microsystems with Cemax VIP version 1.4 software) to generate 3D volumetric images. The visualization software was used to make interactive linear measurements on the 3D images. Measurements were made on the images twice by two observers, based on conventional craniofacial anatomic landmarks. The soft tissues were subsequently removed, and the same measurements were repeated on the cadaver heads with an electromagnetic digitizer (3 Space, Polhemus, Colchester, VT).

RESULTS

The results showed no statistically significant differences between the 3D-CT and the physical measurements, with P>.05 for all measurements. The mean difference between the image and real measurements was less than 2 mm in all instances.

CONCLUSIONS

It is concluded that measurement of the skull and facial bone landmarks by 3D reconstruction is quantitatively accurate for surgical planning and treatment evaluation of craniofacial fractures.

Facial imaging in an urban emergency department

To describe the facial imaging practice pattern in our an emergency department and to assess the implications of this practice, a retrospective review was conducted of patients with blunt facial trauma requiring facial imaging over a 2-month period. Patients were compared based on their initial imaging study, either facial x-rays (primary FXR) or spiral computed tomography (primary FSCT). Of 211 patients imaged, 148 (70%) received primary FXR and 63 (30%) primary FSCT. A greater proportion of primary FSCT patients had at least one fracture detected (57% v. 26%; odds ratio 3.9, confidence interval 2.0-7.5). Of patients with a fracture on FXR, 29% underwent secondary FSCT. The average facial imaging charges per case detected (patient with a fracture) were $978 for primary FXR and $2,048 for primary FSCT. Physicians made avid use of FSCT. Additional studies are needed to determine the appropriateness of this practice and to improve clinical selection of patients requiring FSCT.

2-D and 3-D reconstructions of spiral computed tomography in localization of the inferior alveolar canal for dental implants

OBJECTIVE

The purpose of this study was to compare and validate the accuracy of measurements on 2-dimensional and 3-dimensional reconstructions from spiral computed tomography in localization of the inferior alveolar canal.

STUDY DESIGN

Four edentulous human cadaver heads with intact mandibles were imaged in a spiral computed tomography scanner. The data were transferred to a networked computer workstation to generate 2-dimensional orthoradially reformatted and 3-dimensional volumetric images. Linear measurements of the images were made from the superior border of the inferior alveolar canal to the alveolar crest. The specimens were then dissected at corresponding locations, and physical measurements were made.

RESULTS

There were no statistically significant differences between the 2-dimensional computed tomography measurements and the physical measurements or between the 3-dimensional computed tomography measurements and the physical measurements. However, we did find a statistically significant difference between the 2-dimensional and 3-dimensional computed tomography measurements.

CONCLUSIONS

2-dimensional and 3-dimensional computed tomography images allow accurate measurements for localization of the inferior alveolar canal.

Unravelling the helix--a physician's guide to spiral computed tomography

The introduction of spiral technology to computed tomography (CT) scanners in the late 1980s has revolutionised the field of CT. Spiral CT offers definite practical benefits over conventional scanners and has expanded the role of CT through the development of new scanning techniques. CT scanning now rivals magnetic resonance imaging in many areas of investigation, and for some situations is the clear investigation of choice. This review is aimed at those clinicians who have access to spiral scanning services but wish to have a greater understanding of the technique and its clinical applications. The concept of spiral CT, and the differences between spiral and conventional scanning are discussed. The various clinical applications of the technique are illustrated.