Hypothetical mortality risk associated with spiral tomography of the maxilla and mandible prior to endosseous implant treatment

Correlation between gray values of cone-beam computed tomograms and Hounsfield units of computed tomograms: A systematic review and meta-analysis

Purpose

The aim of this review was to systematically analyze the available literature on the correlation between the gray values (GVs) of cone-beam computed tomography (CBCT) and the Hounsfield units (HUs) of computed tomography (CT) for assessing bone mineral density.

Materials and Methods

A literature search was carried out in PubMed, Cochrane Library, Google Scholar, Scopus, and LILACS for studies published through September 2021. In vitro, in vivo, and animal studies that analyzed the correlations GVs of CBCT and HUs of CT were included in this review. The review was prepared according to the PRISMA checklist for systematic reviews, and the risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool. A quantitative analysis was performed using a fixed-effects model.

Results

The literature search identified a total of 5,955 studies, of which 14 studies were included for the qualitative analysis and 2 studies for the quantitative analysis. A positive correlation was observed between the GVs of CBCT and HUs of CT. Out of the 14 studies, 100% had low risks of bias for the domains of patient selection, index test, and reference standards, while 95% of studies had a low risk of bias for the domain of flow and timing. The fixed-effects meta-analysis performed for Pearson correlation coefficients between CBCT and CT showed a moderate positive correlation (r=0.669; 95% CI, 0.388 to 0.836; P<0.05).

Conclusion

The available evidence showed a positive correlation between the GVs of CBCT and HUs of CT.

Cone-beam computed tomography evaluation of the pterygomaxillary fissure and pterygopalatine fossa using 3D rendering programs

PURPOSE

The aim of this study was to investigate the detailed anatomy of the pterygomaxillary fissure (PMF) and pterygopalatine fossa (PPF) and variations therein using three-dimensional (3D) cone-beam computed tomography (CBCT) software.

METHODS

This study was based on a retrospective evaluation of CBCT scans. A total of 825 CBCT images of patients (448 females, 377 males) who met the inclusion criteria were analyzed. PMF shapes were classified, and morphometric measurements (PMF area and PPF volume) were performed according to age, right/left side, and gender using 3D rendering programs. Maxillary and sphenoid sinus pathologies were also classified to reveal possible correlations between morphometric measurements. Analysis of variance was used for comparisons. Multiple comparisons were assessed using the Bonferroni test. Pearson's test was used to assess correlations between parameters. A p value < 0.05 was considered to indicate statistical significance.

RESULTS

Six types of PMF shapes were defined. There were no significant differences in types according to gender, age or sinus pathology. Males had a significantly larger PMF area than females (p < 0.001). Left/right comparison of the PMF area revealed that the mean PMF coronal, axial, and sagittal area dimensions were significantly higher on the right side in all patients. Our results also indicated that the PMF area and PPF volume increased significantly after 40 years of age.

CONCLUSION

Various PMF shapes were defined and classified. PMF and PPF dimensions increased with age. Knowledge of these anatomical variations will allow surgeons to avoid damage to the neurovascular structures passing through the area.

Effect of patient anxiety on image motion artefacts in CBCT

BACKGROUND

Artefacts in images related to patient movement decrease image quality, potentially necessitating re-scanning, which leads to an extra radiation dose for the patient. Thus, avoiding patient motion reduces patient exposure to radiation. The aim of this study was to analyse image motion artefacts (MAs) and how they are affected by patient anxiety during cone beam computed tomography (CBCT) examination.

METHODS

A total of 100 patients undergoing CBCT examination were investigated. The State Trait Anxiety Inventory (STAI-S and STAI-T) form was used to measure patient anxiety. Patient's age, gender, dental anxiety score, diagnostic reason for CBCT examination, field of view (FOV), acquisition time, anatomical area, and presence of motion artefacts on images were recorded. Comparisons of the parameters were evaluated using Pearson's correlation, the chi-square test, the Mann-Whitney U test, the Kruskal-Wallis test and t-tests. The significance level was set at 0.05.

RESULTS

The mean values of the scores for the total population were 37.2 for the STAI-S and 41.6 for the STAI-T. Women exhibited higher anxiety levels than men. The patients' anxiety scores were significantly correlated with dental fear. The prevalence of patients showing motion artefacts was 6%. The mean age of patients with motion artefacts on their images (56.83) was higher than that of patients without (39.14). There was no relationship between motion artefact presence and patient gender, anxiety score, diagnostic reason for CBCT examination, FOV, acquisition time, or anatomical area. Patients showing motion artefacts on their images had higher STAI scores than those with no motion artefacts (non-significant).

CONCLUSIONS

The population in this study experienced anxiety before CBCT scanning. Excessive anxiety did not clearly affect whether image motion artefacts were generated during CBCT examination, although a non-significant increase in STAI scores was noticed in patients with motion artefacts on their images.

A comparison of computed tomography scans and digital periapical radiographs ridge height measurements

To investigate the agreement between computerized tomography scans (CT) and intraoral periapical digital radiographs (PA) alveolar ridge height measurements in maxillary and mandibular posterior regions. We reviewed 100 implant patient radiographic records and identified 27 mandibular sites in 19 patients and 23 maxillary sites in 13 patients with available CT scans and matching PA radiographs. The distance from the crest of the ridge to the floor of the maxillary sinus or to the superior border of the inferior alveolar canal was measured. PAs were measured with Dexis software v. 8.0 and CTs were measured with Simplant software v. 11.02. Two examiners (RJ and MM) recorded the measurements separately; each examiner recorded two readings. The average of the 4 readings was used for data analysis. Absolute agreement: Paired t test comparing ridge-height measurements between the two imaging methods showed no differences for maxillary sites (P > 0.2) and significant differences for the mandibular sites (CT > PA, P = 0.0009). Relative agreement: Kendall rank correlation analysis of ridge-height measurements between the 2 imaging methods showed a high positive correlation for maxillary sites (Kendall's tau = 0.76, P = 0.0001) and moderate correlation for the mandibular sites (Kendall's tau = 0.46, P = 0.001). Maxillary PAs tend to approximate CT ridge-height measurements. By contrast mandibular PAs tend to underestimate the distance from the crest of the ridge to the inferior alveolar canal.

Denta Scan

DentaScan is a unique new computer software program which provides computed tomographic (CT) imaging of the mandible and maxilla in three planes of reference: axial, panoramic, and oblique sagittal (or cross-sectional). The clarity and identical scale between the various views permits uniformity of measurements and cross-referencing of anatomic structures through all three planes. Unlike previous imaging techniques, the oblique sagittal view permits the evaluation of distinct buccal and lingual cortical bone margins, as well as clear visualization of internal structures, such as the incisive and inferior alveolar canals.

Individualised, micro CT-based finite element modelling as a tool for biomechanical analysis related to tissue engineering of bone

Load-bearing tissues, like bone, can be replaced by engineered tissues or tissue constructs. For the success of this treatment, a profound understanding is needed of the mechanical properties of both the native bone tissue and the construct. Also, the interaction between mechanical loading and bone regeneration and adaptation should be well understood. This paper demonstrates that microfocus computer tomography (microCT) based finite element modelling (FEM) can have an important contribution to the field of functional bone engineering as a biomechanical analysis tool to quantify the stress and strain state in native bone tissue and in tissue constructs. Its value is illustrated by two cases: (1) in vivo microCT-based FEM for the analysis of peri-implant bone adaptation and (2) design of biomechanically optimised bone scaffolds. The first case involves a combined animal experimental and numerical study, in which the peri-implant bone adaptive response is monitored by means of in vivo microCT scanning. In the second case microCT-based finite element models were created of native trabecular bone and bone scaffolds and a mechanical analysis of both structures was performed. Procedures to optimise the mechanical properties of bone scaffolds, in relation to those of native trabecular bone are discussed.

Study on the necessity for cross-section imaging of the posterior mandible for treatment planning of standard cases in implant dentistry

OBJECTIVE

To investigate whether cross-section imaging influences the planning and therapy of standard implant cases in the posterior mandible.

MATERIAL AND METHODS

In a prospective study conducted over 16 months, the planned treatment (standard implant therapy without bone augmentation procedures in the premolar and molar regions of the mandible) was compared with the postoperative result in 50 randomly selected patients. Clinical examinations and panoramic radiographs were performed pre- and postoperatively, whereas cross-sectional tomography was performed only preoperatively.

RESULTS

The vertical magnification factor in the panoramic radiographs was very constant pre- and postoperatively with 1 : 1.27 and in the spiral tomograms with 1 : 1.52. In 11 of 77 implant sites, the mandibular canal could not be evaluated in the spiral tomograms. The additional information from cross-sectional spiral tomography did not influence the original planning in 74 of 77 (96.1%) implant sites. Based on the postoperative panoramic radiograph, the average distance from the tip of the implants to the mandibular canal was 3.04+/-2.06 mm. In two cases (2.6%), transient postoperative altered tactile sensation of the mental nerve was found.

CONCLUSION

The information from preoperative cross-sectional spiral tomography has minor impact on treatment planning in standard implant cases in mandibular premolar and molar regions. The clinical examination provides sufficient information for selecting implant diameter and the panoramic radiograph provides sufficient information for implant length selection.

Quality of digital pre-implant tomography: comparison of film–screen images with storage phosphor images at normal and low dose

OBJECTIVES

The aim of this pilot study was to compare the image quality of a storage phosphor system with that of conventional film-screen in pre-implant conventional tomography, and to test the influence of radiation dose on image quality in the storage phosphor system.

METHODS

Cross-sectional conventional tomographic images (Scanora) technique) were obtained on 11 patients with film-screen and with storage phosphor image plates (Digora) PCT) at normal and low doses. Ten observers graded the visibility of anatomical structures of importance for implant planning. A three-step rating scale was used, where -1 =worse, 0=equal and 1=better than the reference image.

RESULTS

Although image quality was graded as equally good in the majority (59%) of images, the storage phosphor system scored significantly lower than film-screen (-0.37 vs 0.00, respectively) for all the images. Low dose storage phosphor images were rated significantly lower (-0.21) than normal dose images (0.00).

CONCLUSIONS

In the majority of patients, anatomic structures of importance for implant planning are visualized equally well on storage phosphor and film-screen images. However, where differences do exist, storage phosphor images score lower than film-screen images. Dose reduction in the storage phosphor system had a negative influence on image quality.

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.

Advanced imaging: Magnetic resonance imaging in implant dentistry

For accurate and safe placement of dental implants, and planning of associated surgery, a full assessment of the surgical anatomy of the site is necessary. Thus, it is highly desirable to have tomographic, sectional information available, to permit the implant to be aligned correctly. In recent years, X-ray computed tomography (CT) has become accepted as the gold standard in assessment, but the exposure to ionising radiation can be substantial. Artefacts due to dental restorations can also be significant, and some doubts may exist over the accuracy of reformatted CT. Magnetic resonance imaging (MRI) entails no exposure to ionising radiation, and allows direct acquisition of tomographic information in any desired plane. Sequential studies may be safely performed, allowing us a valuable insight into bone graft behaviour. Other than in a small number of cases, MRI may be safely used for presurgical assessments. Artefacts are few and in most cases localised. The surgical confidence from the sectional information gained is a significant step forward in the safe placement of dental implants.

Absorbed doses from spiral CT and conventional spiral tomography: a phantom vs. cadaver study

For several radiological examinations, a clinician can select between conventional and spiral computed tomography. Using both techniques, this study aimed at evaluating the difference in absorbed doses when examining a single lateral jaw segment in a human cadaver head and Rando phantom. The present study involved the placement of thermoluminescent dosimeter (TLD) chips (GR-200) in the thyroid gland, and bilaterally, in the parotid and submandibular glands and the lenses of the eyes in both a human cadaver and a Rando phantom at corresponding locations. Consecutive conventional spiral tomographic examinations were carried out in both the left upper and lower premolar area, using a Cranex TOME multifunctional unit. Each examination consisted of 4 slices with a 2 mm slice thickness and exposure parameters of 57 kV, 56 seconds and 1.6-2.0 mA. Regarding spiral computed tomography (CT), a Somatom Plus S scanner (Siemens, Erlangen, Germany), with a slice thickness of 1 mm with settings at 120 kV and 165 mA, was used on both phantoms and separately in the upper and lower jaw. With conventional tomography, the findings of the present study showed that the parotid and submandibular glands on the side near the X-ray tube received the highest dose, both for the cadaver head (doses ranging from 0.5 to 1.3 mGy) and the phantom (doses ranging from 0.6 to 2.6 mGy). For CT of the upper jaw, the highest doses were delivered to the parotid glands with an average absorbed dose of 9.2 and 10.6 mGy for the cadaver head and phantom, respectively. The submandibular glands received the highest doses during CT examination of the lower jaw with an average of 7.8 and 12.9 mGy for the cadaver head and phantom, respectively. It appears from the present investigation that if small edentulous regions are examined, radiation doses during conventional tomography remain much lower than during CT imaging. However, when multiple tomographic cuts are required, a spiral CT examination can replace a series of conventional examinations, especially in cases such as the rehabilitation of an edentulous upper jaw or a more complex surgery.

Comparative dose measurements by spiral tomography for preimplant diagnosis: the Scanora machine versus the Cranex Tome radiography unit

Objective. The purpose of this study was to determine the dose profile of the Cranex Tome radiography unit and compare it with that of the Scanora machine. Study design. The radiation dose delivered by the Cranex Tome radiography unit during the cross-sectional mode was determined. Single tooth gaps in regions 3 (16) and 30 (46) were simulated. Dosimetry was carried out with 2 phantoms, a head and neck phantom and a full-body phantom loaded with 142 thermoluminescent dosimeters (TLD) and 280 TLD, respectively; all locations corresponded to radiosensitive organs or tissues. The recorded local mean organ doses were compared with those measured in another study evaluating the Scanora machine.Results. Generally, dose values from the Cranex Tome radiography unit reached only 50% to 60% of the values measured for the Scanora machine. The effective dose was calculated as 0.061 mSv and 0.04 mSv for tooth regions 3 (16) and 30 (46), respectively. Corresponding values for the Scanora machine were 0.117 mSv and 0.084 mSv.Conclusion. Cross-sectional imaging in the molar region of the upper and the lower jaw can be performed with the Cranex Tome unit, which delivers only approximately half of the dose that the Scanora machine delivers.

Organ radiation dose assessment for conventional spiral tomography: a human cadaver study

The head of a human cadaver was positioned in a Cranex TOME multifunctional unit (Orion Corporation Soredex, Helsinki, Finland) to measure the organ radiation doses after tomographic examinations of the upper and lower edentulous jaw bone. Five consecutive examinations were carried out in the upper and lower anterior jaw regions to cover the entire frontal area, 2 in the upper and lower left premolar regions, and 3 and 4 in the upper and lower left molar regions, respectively. Each examination consisted of 4 slices with a 2 mm slice thickness. Thermoluminescent dosimeter chips were placed in the thyroid gland and bilaterally in the parotid and submandibular glands. Dosimetric measurements were repeated for the different tomographic examinations mentioned above. For spiral tomography in the maxilla, organ doses for both parotid glands were most elevated, while those for the thyroid glands were the lowest. Average doses per examination reached levels of 0.27 mGy for the right (OS) parotid gland with frontal tomography, and 3.89 mGy and 1.67 mGy for the parotid gland at tube-side (TS) for premolar and molar tomography. For the thyroid gland, a minimal dose of < or = 0.004 mGy was noticed for all examinations. For spiral tomography of the frontal area in the mandible, the OS parotid gland received the highest dose (0.77 mGy), while for an analysis of the premolar and molar areas, doses were more elevated for the TS parotid gland (1.22 mGy and 1.72 mGy, respectively). For the TS submandibular gland, organ doses were also raised, with values of 0.39 mGy for frontal, 1.31 mGy for premolar and 1.61 mGy for molar tomography. This study thus indicates that for conventional spiral tomographic examinations in the maxilla and the mandible, radiation doses for the TS submandibular and parotid glands were significantly more elevated than those to the thyroid gland. These values remain however below the organ doses previously reported for spiral CT involving both a full upper or lower jaw.