Novel low-dose protocols using cone beam computed tomography in dental medicine: a review focusing on indications,limitations, and future possibilities

Objectives

A narrative review on the potential use of low-dose protocols for cone beam computed tomography (CBCT) was conducted to identify indications and their relevance for various dental disciplines.

Materials and methods

Google Scholar was searched using the words “low-dose CBCT”. Reviews, consensus papers, clinical studies, and experimental studies were eligible for the initial screening process, but for data extraction only original articles were selected. Similar search procedures were then performed with the additional search words “pedo,” “ortho,” “endo,” “implant,” “perio,” and “oral surgery.” Furthermore, references of included articles were examined to identify further relevant articles.

Results

After screening, 27 publications remained for the data extraction process. Low-dose protocols have been reported for specialties such as pediatric dentistry (evaluating orofacial clefts, periapical lesions, impacted teeth, and autotransplantation), orthodontics (cephalometric analysis and interim assessment of treatment results), endodontics (detecting root fractures, resorptions and periapical bone loss), implant dentistry (planning implant insertion, evaluating peri-implant fenestration and dehiscence), periodontology (assessing periodontal structures), and oral and maxillofacial surgery (assessing mandibular third molars and TMJs). Nevertheless, most of the literature available is related to non-clinical studies. Furthermore, there is a lack of position statements or guidelines from authoritative bodies regarding the use of low-dose protocols in dental medicine.

Conclusions

Low-dose protocols for CBCT imaging seem to have potential in various disciplines in dental medicine ranging from pediatric dentistry to oral and maxillofacial surgery. Dose reduction is usually achieved by mAs reduction, use of partial rotations, reduced number of projections, and larger voxel sizes, but seldom by kV reduction.

Clinical relevance

Albeit low-dose protocols have potential to result in a reduction of dose exposure for 3D imaging due to dental indications, there is a need to more clearly specify indications and limitations to avoid indiscriminate use of standard and high-dose CBCT scans in the future on the lines of ALARA/ALADA principles.

     

Abrasivity of toothpastes: An in vitro study of toothpastes marketed in Norway

Abstract

Objectives. Cone beam computed tomography (CBCT) was introduced to Norwegian dental clinics in 2007. The aim of the study was to investigate how dental clinics use this imaging modality, including factors related to workflow and image quality, and to evaluate dentists’ opinions on and experiences of using it. Materials and methods. A web-based 59-item questionnaire regarding the clinical use of CBCT was sent to all 39 CBCT clinics in Norway. Results. Twenty-nine clinics (74%) responded. Most respondents (93%) were from clinics with more than one dentist and 83% had at least one specialist. All clinics had digital intraoral x-ray receptors and all but one had panoramic imaging. The most common indications for CBCT were implant treatment planning (34% of all clinics) and localization of impacted teeth (43% of specialist clinics). Seventy-two per cent of clinics reported an average of four or fewer CBCT examinations each week and 83% of respondents were subjectively satisfied with the image quality. The most commonly used enhancement functions were contrast (97%), brightness (90%) and zoom (86%). Conclusions. The Norwegian CBCT clinics surveyed were fully digitized and had multiple dentists. Periodontists and oral and maxillofacial surgeons were the most frequent specialties represented in the clinics. Clinics with only dental specialists performed more CBCT examinations/week than clinics with general practitioners or both general practitioners and specialists. The most common indications for CBCT examinations were related to treatment planning. This study found some challenges related to image quality and communication within the radiological team.     

Registration accuracy of three-dimensional surface and cone beam computed tomography data for virtual implant planning

Objective: Virtual wax‐ups based on three‐dimensional (3D) surface models can be matched (i.e. registered) to cone beam computed tomography (CBCT) data of the same patient for dental implant planning. Thereby, implant planning software can visualize anatomical and prosthetic information simultaneously. The aim of this study is to assess the accuracy of a newly developed registration process. Material and methods: Data pairs of CBCT and 3D surface data of 16 patients for dental implant planning were registered and the discrepancy between the visualized 3D surface data and the corresponding CBCT data were measured on 64 teeth at seven points by two investigators in two iterations with a total of 1792 measurements. Results: All data pairs were matched successfully and mean distances between CBCT and 3D surface data were between 0.03(±0.33) and 0.14(±0.18) mm. At two of seven measuring points, statistically significant correlations were determined between the measured error and the presence and type of restorations. Registration errors in maxilla and mandible were not statistically significantly different. Conclusion: According to the results of this study, registration of 3D surface data and CBCT data works reliably and is sufficiently accurate for dental implant planning. Thereby, barium‐sulfate scanning templates can be avoided and dental implant planning can be accomplished fully virtual. To cite this article:
Ritter L, Reiz SD, Rothamel D, Dreiseidler T, Karapetian V, Scheer M, Zöller JE. Registration accuracy of three‐dimensional surface and cone beam computed tomography data for virtual implant planning.
Clin. Oral Impl. Res. 23 , 2012 447–452.
doi: 10.1111/j.1600‐0501.2011.02159.x     

Panoramic imaging may detect morphologically abnormal temporomandibular joints in children with juvenile idiopathic arthritis

ObjectiveTo investigate the reliability of panoramic imaging (PAN) with cone beam computed tomography (CBCT) as gold standard to distinguish between normal and abnormal temporomandibular joint (TMJ) morphology in a sample of children with juvenile idiopathic arthritis (JIA).Material and methodIn this prospective cohort study, 106 PAN and 108 CBCT examinations from 54 children were obtained. A classification system with reference images was developed and used to discriminate between normal and abnormal TMJ morphology. The severity of abnormality and additional findings were registered. Three experienced and calibrated maxillofacial radiologists evaluated the images and intra- and inter-reader agreement was calculated.ResultsConsensus diagnosis of abnormal TMJ morphology on PAN and on CBCT was registered in 27.6% and 28.1% of the joints, respectively. There were differences between the two imaging modalities regarding severity grading of abnormality and registration of additional findings. With CBCT abnormal TMJ morphology was frequently graded as more severe and additional findings such as erosions and osteophytes more frequently found.ConclusionWith trained readers, PAN was found to distinguish between morphologically normal and abnormal TMJs equally often as CBCT. Thus, the method seems valuable for assessing TMJ involvement in children with JIA. However, CBCT was found to be superior for assessing severity of abnormality and additional diagnostic information.     

3D CBCT morphometric assessment of mental foramen in Arabic population and global comparison: imperative for invasive and non-invasive procedures in mandible

Background: Recent advancements in clinical dentistry have increased the possibilities of surgical procedures in the mental region. A detailed knowledge of mental foramen (MF) morphometry is significant to preserve integrity of the mental nerve trunk in surgical interventions such as orthognathic surgery, implant placement and anaesthetic block.

Objective: The aim of this study was to determine the most accurate position of the mental foramen by using new assessment approach in a sample of dental patients presenting to the specialist dental clinic, College of Dentistry, Al Jouf University, Saudi Arabia.

Study design: A retrospective study was performed using cone beam computed tomography (CBCT) of 600 patients (40.1?±?11.78 years old). Following inclusion and exclusion criteria, 395 CBCT were finally obtained and analyzed for the most accurate position of the mental foramen (MF) by OnDemand 3D software (Seoul, Korea). Prevalence of shape of MF and accessory MF were also assessed. Pearson chi-square test was employed to test significant differences between genders and races.

Results: The most common horizontal and vertical position of the mental foramen was in line with the long axis of 2nd premolar (41.3%) and below the root apex level (93.2%), respectively. The most common shape of MF was round type (72.66%). The prevalence of accessory 2MF and 3MF was 2.28% and 0.25%, respectively.

Conclusion: New information about MF presented in this article can help anatomists, prosthodontists, orthodontists, surgeons, forensic odontologists and paleoanthropologists to predict the position of the MF and perform safer surgeries.     

The B.S.S.O. M.Orth. Prize of the Royal College of Surgeons of England 1998

Abstract

Aim: To determine the relationship between treatment need assessment scores of orthodontists, general practitioners, and pediatric dentists.

Study design: Observational.

Sample: Ten general dental practitioners, 18 orthodontists and 15 pediatric dentists reviewed 137 dental casts and recorded their opinion on whether orthodontic treatment was needed.

Results: We found a high level of agreement between pediatric dentists, orthodontists and general practitioners (Kappa range 0.86–0.95). Between the groups, the amount of agreement was lower.

Conclusions: Orthodontists, general dental practitioners, and pediatric dentists in this sample exhibit high levels of agreement on orthodontic treatment need.     

A rater agreement study on measurements in cross-sectional CBCT images exploring the association between alveolar bone morphology and craniofacial height

Objectives

To investigate rater agreement regarding measurements of height and width of the maxilla and mandible using cross-sectional images from CBCT examinations. Furthermore, to explore the association between vertical craniofacial height and alveolar bone morphology.

Methods

Pre-treatment CBCT scans from 450 patients referred for treatment to a private clinic for orthodontics and oral surgery in Scandinavia were available and of these, 180 were selected. Lateral head images were generated from the CBCT volumes to categorise subjects into three groups based on their craniofacial height. Cross-sectional images of the maxillary and mandibular bodies at three locations in the maxilla and mandible, respectively, were obtained and measured at one height and two width recordings by five raters. One-way analysis of variance with a Tukey post hoc test was performed. A significance level of 5% was used.

Results

Rater agreement was mostly excellent or good when measuring height and width of the maxilla and mandible in cross-sectional CBCT images. For height (of the alveolar bone/bodies), there were statistically significant differences between the low- and the high-angle groups for all the observers when measuring in the premolar and midline regions, both in the maxilla and in the mandible.

Conclusion

The high agreement found ensures a reliable measurement technique and confirms the relation between craniofacial height and alveolar bone height and width.

     

Diagnosis of vertical root fracture in teeth close and distant to implant: an in vitro study to assess the influence of artifacts produced in cone beam computed tomography

Objectives

To evaluate the influence of artifacts produced by zirconium implant on the diagnosis of vertical root fracture (VRF) in teeth close and distant to the implant in cone beam computed tomography (CBCT) images. We also determined if kilovoltage (kVp) and metal artifact reduction (MAR) tool could influence this diagnosis.

Materials and methods

Twenty single-root teeth were divided in control and fractured groups (n = 10). The teeth were randomly positioned in the first and second and right and left pre-molar alveoli of a dry human mandible. CBCT exams were acquired using a ProMax 3D unit with varying kVp (70, 80, or 90 kVp), with or without MAR, and with and without a zirconium implant placed in the alveolus of first right molar. The images were evaluated by five observers. The area under the receiver operating characteristic curve (ROC), sensitivity, and specificity were calculated and compared by analysis of variance with a significance level of 5%.

Results

In general, ROC and sensitivity were not affected by the factors studied (p > 0.05). The main effects occurred in specificity; when implant was used without MAR, the values were lower for tooth 45 for all kVps (p = 0.0001).

Conclusions

Artifacts produced in the vicinity of teeth with suspected VRF impair the diagnosis by decreasing the specificity, because they can mimic the VRF line generating false positives. However, MAR improves the specificity, being its use recommended when metallic objects are present near teeth with suspected VRF.

Clinical Relevance

Since nowadays, many patients who undergo CBCT show implants and they definitively produce artifacts, it is important to evaluate the influence of such artifacts in the diagnosis of teeth that are close to the generator-artifact object.

     

Influence of cone-beam computed tomography image artifacts on the determination of dental arch measurements

Objective:To compare dental plaster model (DPM) and cone-beam computed tomography (CBCT) in the measurement of the dental arches, and investigate whether CBCT image artifacts compromise the reliability of such measurements.Materials and Methods:Twenty patients were divided into two groups based on the presence or absence of metallic restorations in the posterior teeth. Both dental arches of the patients were scanned with the CBCT unit i-CAT, and DPMs were obtained. Two examiners obtained eight arch measurements on the CBCT images and DPMs and repeated this procedure 15 days later. The arch measurements of each patient group were compared separately by the Wilcoxon rank sum (Mann-Whitney U) test, with a significance level of 5% (α  =  .05). Intraclass correlation measured the level of intraobserver agreement.Results:Patients with healthy teeth showed no significant difference between all DPM and CBCT arch measurements (P > .05). Patients with metallic restoration showed significant difference between DPM and CBCT for the majority of the arch measurements (P > .05). The two examiners showed excellent intraobserver agreement for both measuring methods with intraclass correlation coefficient higher than 0.95.Conclusion:CBCT provided the same accuracy as DPM in the measurement of the dental arches, and was negatively influenced by the presence of image artifacts.     

Dental implant primary stability in different regions of the Jawbone: CBCT-based 3D finite element analysis

AimThis study aimed to analyze the primary stability of dental implant in maxillary and mandibular anterior and posterior regions using a finite element analysis.Materials and methodsCBCT images of maxillary and mandibular regions were collected from patients’ radiographic data and transformed to 3D models. A Straumann Dental implant was inserted in each bone model and then pulled-out, where amount von-Mises stress was obtained and analyzed for each. A comparison between the insertion and the pull-out was evaluated.ResultsTwenty-four images were randomly selected for analysis from 122 scans. In both the insertion and the pull-out of the dental implant, von-Mises stress was high in cortical as compared to the cancellous bone (p < 0.0001). Maxillary posterior region had a low von-Mises stress (p < 0.001). Bone plastic deformation was higher in cancellous than the cortical bone in all bone regions and was the lowest in maxillary posterior region (p < 0.001). Bone displacement decreased from Type I to type IV bone.ConclusionEvaluation of von-Mises stress showed different measurements in maxillary and mandibular regions. Bone deformation was low in the maxillary posterior region.     

Radiographic assessment of the mandibular retromolar canal using cone-beam computed tomography

Abstract

Objective. The ‘retromolar’ nerve is a collateral branch of the inferior alveolar nerve. Cone-beam computed tomography (CBCT) provides higher resolution images. This CBCT study reports the frequency of the retromolar nerve. Materials and methods. From 2007–2010 the CBCT study of 233 hemi-mandibles have been examined. The CBCT study was obtained from an investigation of the posterior mandibular region in 187 patients suffering from different pathologies and it was aimed at detecting in patients the presence of a retromolar canal and foramen. Results. Thirty-four retromolar canals with a foramen were detected on 233 CBCT (14.6%) in 30 out of 187 patients (16%). In the 46 patients who underwent CBCT bilaterally, the retromolar canal was found in nine subjects (19.6%) and was present bilaterally in four subjects, for an incidence of 8.7%. Conclusions. The results suggest that the radiological frequency of the retromolar nerve is notable, with a possible relevance in the surgical approach of the mandibular retromolar area. The presence of a retromolar canal, well detected with CBCT, may warn clinicians about the possibility of inadequate pre-surgical anaesthesia, local intra-operative bleeding and post-operative alterations of the sensation in the third molar area.     

Nervo alveolare inferiore bifido: revisione della letteratura e presentazione di un caso clinico

ObjectivesThe aim of this study is to describe a case of bifid Inferior Alveolar Nerve (IAN) identified using tomographic radiology.This finding motivated an extensive review of the literature to establish how frequently this anatomical variation occurs.Materials and methodsA case of a female patient is reported who was a candidate for implant rehabilitation and was subjected to a pre-surgical CT exam showing a duplication of the right inferior alveolar canal.ResultsFrequency studies of bifid IAN with panoramic radiographs report an incidence ranging from 0.08% to 8.3%. These results are discordant with those obtained by more recent studies conducted with the aid of three-dimensional radiology (CT and CBCT); in this case, frequency rates increase significantly (30%).ConclusionsThere is a large inter-individual variability in the course of bifid IAN and literature doesn’t provide reliable information about the frequency with which such anomaly occurs. This underlines the value of CT radiology as a routine examination for the planning of surgical procedures involving the posterior region of the mandible.     

Reliability and accuracy of automatic segmentation of mandibular 3D models on linear measurements

Objective

Evaluate if automatic segmentation of mandibular three-dimensional (3D) models is reliable and accurate.

Materials and methods

Eight dry mandibles with eight silica markers were scanned in the i-CAT Classic device (Imaging Sciences International). Automatic segmentation was performed using nine standard preset thresholds in the Dolphin software (Dolphin Imaging & Management Solutions). Three observers individually made twice eight linear measurements on the mandibular 3D models. Another observer made physical measurements, twice as well, on the dry mandibles. Reliability and accuracy were evaluated with intraclass correlation coefficients (ICCs), Dahlberg’s formula, Bland-Altman analyses, and changing bias with regression analyses.

Results

Inter-observer and intra-observer ICCs and Dahlberg’s error were ≥ 0.75 and ≤ 1.0 mm, respectively, for all measurements. Inter-observer agreement between mandibular 3D models and physical measurements ranged from −0.37 to 0.91 mm.

Conclusions

Linear measurements made on mandibular 3D models obtained using standard preset thresholds are reliable and accurate. However, additional studies are necessary to confirm this hypothesis for clinical applications.

Clinical relevance

Since the 3D models are useful for diagnostics and surgical planning, it is necessary to determinate whether the linear measurements made on 3D models obtained by automatic segmentation are sufficiently reliable and accurate.

     

Comparison of orthodontic measurements on dental plaster casts and 3D scans

Background and objectives

Over recent years, we have witnessed a growing trend in orthodontics toward the use of three-dimensional (3D) techniques for diagnostic purposes, treatment planning, and fabricating appliances. This study was undertaken to compare the traditional manual technique of using vernier calipers to take orthodontic measurements on plaster dental casts versus an all-digital measuring technique based on virtual 3D scans of casts. In this study, we focused on the quantitative agreement between and time requirements of both methods.

Materials and methods

Plaster casts obtained from the jaws of 55 fully dentate patients who had not previously undergone orthodontic treatment underwent 3D scanning using a white-light scanner (d-Station ^3D; Breuckmann, Meersburg, Germany). Once the casts had been blinded by an independent individual, three examiners with different degrees of expertise in dentistry and orthodontics measured the mesiodistal widths of teeth 6–6 in each jaw. A randomized sequence was used when taking the measurements three times using OnyxCeph^3TM analysis software (Image Instruments, Chemnitz, Germany) and a dental vernier caliper. Bland-Altman plots were used to illustrate the level of agreement between the two methods, standard deviations of repeated measurements were calculated to assess their reproducibility, and the Wilcoxon’s signed-rank test was employed to compare their time requirements.

Results

The Bland-Altman analysis of all single values revealed no statistically significant difference between the software-based and caliper-based measurements of mesiodistal tooth width. Assuming the presence of normal distribution, the limits of agreement disclosed a 95% probability for the software values to range between +0.499 and ?0.545 mm of the same value measured with the caliper. The standard deviations of repeated measurements were 0.33 mm with the software and 0.21 mm with the caliper. The digital method required significantly less time (p<0.01); however, differences were observed to be associated with operator experience.

Conclusion

Inexperienced examiners, in particular, take measurements of mesiodistal tooth dimensions faster using a software-based method than when using a dental vernier caliper. Similar values were obtained with both methods.     

Piccole lesioni osteolitiche: l’utilizzo della Tomografia Computerizzata Cone Beam (TCCB) per la diagnostica prechirurgica in endodonzia

ObjectivesTo describe the use of Cone Beam Computed Tomography (CBCT) in endodontic patients when first-level diagnostic techniques (intra-oral and panoramic X-rays) are inconclusive.Materials and methodsA cone beam volumetric CT scanner was used. Using multiplanar tomographic cuts (with particular emphasis on transverse cuts), we were able to detect fine osteolytic alterations and identify their topographic features with greater precision.Results and conclusionsThe cases presented show that CBCT is being increasingly recognized as a valid diagnostic aid in the field of endodontics, particularly for pre-surgical work-ups, because the radiation exposure it involves is marginal in relation to the cost/ benefit advantages it offers.     

The use of 3D models to improve sinus augmentation outcomes – A case report

Sinus augmentation is a predictable procedure that is often required when restoring the posterior maxilla with dental implants. Even with high success rates, careful pre-surgical planning is crucial. A 3D model is a valuable aid for the clinician as it allows for pre-operative simulation, which can reduce surgical time, reduce the risk of intra-operative complications and decrease the potential for error. The aim of this case report is to focus on how such a model is useful when undertaking a sinus augmentation procedure with simultaneous implant placement.     

Dental implants in the functionally impaired: experience from the patients' perspective

Abstract

Objective. Edentulousness has a great impact on the individual. Extensive tooth loss is more common among functionally impaired individuals. Such groups may have difficulties with removable prostheses. The aim of this qualitative study was to explore functionally impaired patients' experience of receiving and living with dental implants. Materials and methods. Seventeen patients with several types of functional impairment who had undergone treatment with dental implants were interviewed. Analysis of the open-ended questions was inspired by grounded theory methodology and began at the first interview, proceeding in parallel until no further relevant information could be obtained. Results. ‘The implant treatment is a process of normalization' was identified as the core category. It was related to four other categories: ‘The functionally impaired are also entitled to dental care', ‘Edentulousness is a burden for functionally impaired individuals', ‘There is interaction between implant treatment and other aspects of life' and ‘It is important to understand the implications of implant treatment'. Conclusions. Normalization was the motivation for implant treatment. Edentulousness had enhanced the feeling of being different and treatment with dental implants was important for well-being. The experience of the treatment process was linked to circumstances of life. Information about procedure, alternative prosthetic constructions and hygiene routines was crucial to the experience and the outcome of the treatment.     

Cone beam CT for pre-surgical assessment of implant sites

The pre-surgical assessment of proposed implant sites requires very specific and accurate data. Imaging has always been used to assist with the implant site assessment but until the recent introduction of cone beam CT scanners, the available imaging had a low value when considering the ratio between diagnostic potential, cost of study, and risk to the patient. CBCT scanners are nearing the end of their first-generation dedicated maxillofacial imaging modalities and have proven to be an extremely useful imaging tool for pre-surgical assessment of implant sites. CBCT scanners are easy to use and produce a 3-D image volume that can be reformatted using software for customized visualization of the anatomy. Protocols have been developed that optimize the visualization of image for implant site assessment.