Correction to Effective dose of dental CBCT--a meta analysis of published data and additional data for nine CBCT units

Radiographic assessment of the peri-implant site

While peri-implant mucositis relies solely on clinical parameters, radiological assessment becomes indispensable for diagnosing peri-implantitis. Intraoral radiography, with its simplicity of application, low radiation exposure, and adequate representation of peri-implant structures, stands out as the standard of care for both immediate and follow-up assessments. Standardization by custom-made radiologic splints allows for excellent comparability with previous images and allows for the determination of even small changes in contour and density of the peri-implant bone. Furthermore, other radiographic modalities like panoramic radiography and cone beam computed tomography (CBCT) may provide useful features for specific patients and clinical cases while also showing innate limitations. Beyond the assessment of the marginal peri-implant bone level as the crucial parameter of clinical relevance, radiologic assessment may reveal various other findings related to the prosthetic restoration itself, the precision of its fit to the implant, and the peri-implant soft and hard tissues. Since such findings can be crucial for the assessment of peri-implant health and the implants' prognosis, a systematic diagnostic evaluation pathway for a thorough assessment is recommended to extract all relevant information from radiologic imaging. This article also provides an overview of the clinical and chronological indications for different imaging modalities in peri-implant issues.

The effect of optimum, indication-specific imaging fields on the radiation exposure from CBCT examinations of impacted maxillary canines and mandibular third molars

OBJECTIVE

Indication-specific optimum field-of-views (FOVs) have been assessed for CBCT scans of impacted maxillary canines and mandibular third molars, as 40∅ × 35 mm and 35∅ × 35 mm, respectively. The objective was to investigate possible changes in absorbed organs and effective doses, for these two imaging indications, performing CBCT examinations with optimum FOV sizes instead of commonly used FOVs. Additionally, radiation exposure-induced cancer risk was calculated for both imaging indications with optimum FOVs.

METHODS

An adult female head phantom (ATOM 702-D, CIRS, Norfolk, VA, USA) was scanned using Planmeca Viso G7 CBCT-device (Planmeca, Helsinki, Finland). Scanning factors, different FOV sizes, dose-area product (DAP) values and anatomical FOV locations were used for Monte Carlo PCXMC-simulation and ImpactMC software. In the PCXMC- simulation, 10-year-old child and 30-year-old adult phantoms were used to estimating effective and absorbed organ doses.

RESULTS

The effective dose varied from 58 µSv to 284 µSv for impacted maxillary canines, and from 38 µSv to 122 µSv for mandibular third molars, the lowest dose value for each corresponding to optimum FOV. Effective dose reduction between the optimum FOV and the smallest common FOV of 50∅ × 50 mm, maintaining other scanning factors constant, was 33% for impacted maxillary canines, and 45% for mandibular third molars. At all examinations, the highest absorbed organ doses were in salivary glands or in oral mucosa.

CONCLUSIONS

Optimum FOVs, 40∅ × 35 mm for impacted maxillary canine and 35∅ × 35 mm for mandibular third molar, could decrease effective doses received by young patients, and improve radiation safety in these common CBCT imaging procedures.

[A prevalence survey of cone-beam computed tomography use among endodontic practitioners]

OBJECTIVE

To investigate the clinical application of cone-beam computed tomography (CBCT) among endodontic practitioners, and to analyze the indications and reasonability of CBCT in the diagnosis and treatment of pulpal and periapical diseases.

METHODS

The clinical data were collected from patients who visited the Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology and underwent CBCT examination from January to December, 2021. The data with their complete clinical information (including clinical records, radiology request forms/reports, two-dimensional and three-dimensional imaging data) were included. Those who underwent CBCT examination for orthodontic or prosthodontics were excluded. The experience and training background of the endodontic specialists, the number of patients treated in the whole year, the objective and region of interest (ROI) of CBCT examination, technical parameters, such as machine type, field of view (FoV) and radiographic reports were collected and analyzed to evaluate the impact on diagnosis. Wilcoxon and Mann-Whitney tests were used to compare the distribution of CBCT ROI. Chi-squared test and pairwise comparison were used to compare the application of CBCT by endodontic specialists with different clinical experience (senior, middle and junior).

RESULTS

In 2021, a total of 3 308 CBCT scans were prescribed by 61 endodontic specialists who treated 34 952 patients throughout the year. 3 218 patients (male ∶female about 1 ∶2) amounting for 10% of the patients treated in the whole year who received CBCT scans with an median age of 35 years (28, 49). Around 98% CBCT examinations were performed after clinical examination and two-dimensional periapical radiographs were taken. The FoV of CBCT scanning less than 10 cm×10 cm accounted for 96% of the total number of the images. Among the 3 308 CBCT scans, 83% of the ROI were in posterior teeth, with a higher number of anterior teeth (Z=-2.278, P < 0.05). Maxillary and mandibular first molars accounted for 35% of the examined teeth. The objectives of CBCT scanning included three aspects: clarifying clinical diagnosis, guiding surgical and non-surgical endodontic treatment (including management of endodontic complications), and outcome assessment, accounting for 1 111 (34%), 1 745 (54%), 311 (10%), respectively. and the others 2%. In the diagnosis process, CBCT was mainly used for the diagnosis of chronic periapical periodontitis, root fracture, root resorption and dental trauma. In the study, 353 CBCT were used in the diagnosis of root fracture, with a positive diagnosis rate of 35% (125/353). 846 CBCT used to reveal the anatomy of the root canal system, of which 297 cases were used to find missed/extra canals after treatment failure, and 58% (171/297) were used to confirm the missed/extra canals. In the management of complications or errors, CBCT was mainly used to assist the diagnosis of perforation and to locate the separated instruments. In the study, 311 CBCT scans were used for outcome assessment, including 240 cases related to non-surgical treatment and 71 cases related to surgical endodontic treatment for follow-up or presence of clinical symptoms, and persistent lesions on 2D films. Among the 61 endodontic specialists who used CBCT, 23 (45%) were with senior experience, 15 (30%) with middle experience, and 23 (25%) with junior experience. The proportion of senior or junior experience prescribing CBCT examination was 10%, higher than that of middle experience (8%, χ12=39.4, χ22=29.1, P < 0.001). The application rate of chief endodontists was 18%, which was higher than that of associate chief endodontists (9%, χ12=139.4, P < 0.001). 31% (1 109/3 308) cases of diagnosis or treatment plans were changed after CBCT was taken.

CONCLUSION

Use of CBCT in endodontic practice could provide more clinical information, which is helpful for diagnosis, accurate treatment and prognosis evaluation.

Minimum size and positioning of imaging field for CBCT-scans of impacted lower third molars: a retrospective study

Background

Cone-beam Computed Tomography (CBCT) is widely used for preoperative 3D imaging of lower third molars. Hence, for this imaging indication, the present study aimed to define the minimum field-of-view (FOV) size and its optimum placement, to decrease radiation exposure, and highlight the need of computer-assisted FOV centering technique for dental CBCT devices. To facilitate proper placement of image field, lower second molar was chosen as reference.

Methods

The retrospective study included 50 CBCT-scans of 46 patients with mean age of 34 years. Based on the lower second molar, a three-dimensional coordinate was formed and the location of mandibular canal (MC) and the dimensions and locations of the lower third molars, and possible associated pathological findings were assessed. Accordingly, the FOV size and position for third-molar imaging were optimized, while ensuring encompassment of all relevant structures.

Results

The minimum cylindrical volume, covering lower third molars and MC, was 32.1 (diameter) × 31.6 (height) mm, placed in relation to the second molar crown, top 2.2 mm above cusp tips, anterior edge 6.7 mm in the front of the most distal point of the crown, and lingual edge 7.9 mm on the medial side of the lingual wall.

Conclusions

The optimized FOV for lower third molars was smaller than common standard small FOVs. We recommend using FOV volume 3.5∅ × 3.5 cm for third molars without associated pathology. Accurate FOV protocols are essential for development of new CBCT-devices with computer-assisted and indication-specific FOV placement.

Non-surgical correction of gummy smile using temporary skeletal mini-screw anchorage devices: A systematic review

Background

There are no studies that have systematically reviewed randomized control trials and/or prospective cohort studies that have assessed the significance of temporary skeletal mini-screw anchorage devices (TSAD) for the correction of gummy-smile. The aim of the present systematic review was to assess the significance of non-surgical correction of gummy smile using TSAD.

Material and Methods

The addressed focused question was “Are temporary skeletal mini-screw anchorage devices effective for the correction of gummy smile?” Indexed databases were searched up to and including May 2020. Different combinations of the following key-indexing terms were used: anchorage; gummy smile, mini-screw; orthodontic; and vertical maxillary excess. The literature search was performed without time and language barriers. Randomized clinical trials and prospective cohort studies that addressed the focused questions were included. Risk of bias was assessed using the Downs and Black and Cochran collaboration tools. Letters to the Editor, commentaries, case-reports/series and articles published in non-indexed databases were excluded.

Results

The initial search yielded 2118 studies out of which, four studies met the inclusion criteria and were processed for data extraction. All studies had a prospective research design. One study was a clinical trial and 3 had a non-randomized design. Results of the clinical trial showed no statistically significant difference in the extent of intrusion between the test- and control-groups. The non-randomized studies showed that TSAD are useful in reducing deep overbite. All studies had a high risk of bias.

Conclusions

The TSAD are an effective and practical option in facilitating reduction of excessive gingival display or gummy-smile. However, further long-term follow-up, well-designed and power-adjusted clinical trials are warranted in this regard.

Key words:Anchorage, Excessive gingival display, Gummy-smile, Mini-screw.

A meta-review of effective doses in dental and maxillofacial cone beam CT using the ROBIS tool

OBJECTIVES

To apply the ROBIS tool for assessment of risk of bias (RoB) in systematic reviews (SRs) in a meta-review on effective doses (EDs) in dental and maxillofacial cone beam CT.

METHODS

Three electronic databases and reference lists of included SRs were searched. Eligible SRs were classified as having low, high or unclear RoB. Findings of SRs were synthesised and data from primary studies combined to relate ED to field of view (FOV) and operating potential (kV).

RESULTS

Seven SRs were included: three displayed low RoB, three high and one had unclear RoB. Only one SR related ED to image quality. Deficiencies in reporting of eligibility criteria, study selection and synthesis of results in SRs were identified. FOV height had a significant relationship with ED, explaining 27.2% of its variability. Median ED for three FOV categories differed significantly. Operating potential had a weak relationship with ED, with no significant difference in median ED between three operating potential groups.

CONCLUSION

The ROBIS tool should have a role for meta-reviews of different aspects of radiology. The disappointing results for RoB might be remedied by developing standards to improve the quality of reporting of primary dosimetry studies and of SRs. Future dosimetry studies should always relate ED to image quality or diagnostic accuracy.

ADVANCES IN KNOWLEDGE

This meta-review is the first to implement ROBIS for SRs of ED and identified that trustworthiness of some SRs is questionable. The percentage change in average ED per cm increase in FOV height could be calculated, emphasizing the importance of FOV as a determinant of ED in CBCT.

Outcomes of different radioprotective precautions in children undergoing dental radiography: a systematic review

PURPOSE

To evaluate the effectiveness of all radioprotective measures in underage patients who undergo a dental radiodiagnostic examination.

METHODS

A systematic review was performed including randomised controlled trials (RCTs), or cluster trials, cohort studies, cross-sectional studies, case-control studies and comparative in vitro research. These studies examined the healthy underage human population (below 18 years) undergoing a dental radiodiagnostic examination. All radioprotective measures were included except for justification as an intervention. The primary outcomes were in vivo mortality and morbidity. Some surrogate or indirect outcomes such as in vitro effective dose and organ absorbed doses were also accepted. Secondary outcomes with regards to image quality and therapeutic value were also analysed.

RESULTS

Eighteen papers were eligible for implementation. Fifteen studies underwent narrative synthesis. Regression analysis was performed on three studies.

CONCLUSION

The following radioprotective measures can reduce the exposure dose. For lateral cephalometry: collimation, filtration, the fastest receptor type and circumstantial thyroid shielding. For oblique lateral radiographs: the shortest exposure time, a smaller horizontal angulation, a longer focus to skin distance. For intraoral radiography: rectangular collimation, the fastest image receptor speed and thyroid shielding when the thyroid gland is in line of or very close to the primary beam. For panoramic radiographs: collimation, the fastest receptor type and the use of automatic exposure control (AEC) or manual adjustment of intensity. For cone-beam computed tomography: collimation, the largest voxels size in relation to the treatment need, change in image settings such as ultra-low dose settings, shorter exposure time, a lower amount of projections, lower beam intensity, reduction of the potential, use of a thyroid shield except in two situations and the use of AEC. All of the changes in exposure parameters should be performed while maintaining a sufficient therapeutic value on an individual and indication-based level.

Detection accuracy of maxillary sinus floor septa in panoramic radiographs using CBCT as gold standard: a multi-observer receiver operating characteristic (ROC) study

OBJECTIVES

To investigate diagnostic accuracy of panoramic radiography in detecting maxillary sinus floor septa by means of a multi-observer receiver operating characteristic (ROC) analysis and a standardized protocol for reporting (STARD protocol; Clin Chem 49(1):1-6, 2003).

MATERIAL AND METHODS

From our database, 25 cone beam computed tomographies (CBCTs) were selected with one maxillary sinus floor septum (height ≥ 2.5 mm). For the same patient, a recent panoramic radiograph (PAN) had to be available in the database. As controls, 28 CBCTs plus corresponding PANs without evidence of a sinus septum were selected. Using the CBCTs as ground truth, 17 observers from our dental school on a five-point confidence scale rated both sinuses in all 53 PANs with respect to presence/absence of a sinus septum. Areas beneath ROC curves (Az-values), sensitivity/specificity (SNT/SPF), positive/negative predictive values (PPV, NPV), and positive/negative likelihood ratios (LR+, LR-) were computed for each observer and pooled over all observers. Inter-rater reproducibility was assessed by means of the intraclass coefficient (ICC) using a two-way random effects model.

RESULTS

A pooled Az-value of 0.839 was observed (SNT 84.6%, SPF 73.5%). PPV ranged between 0.492 and 0.824 (median 0.627) and NPV between 0.838 and 0.976 (median 0.917). A median LR+ of 3.567 was computed (LR- median 0.193). Inter-rater reliability revealed an ICC of 0.55 (95% confidence interval 0.48 to 0.62).

CONCLUSIONS

Our results indicate that PAN is a moderately accurate method for sinus elevation planning for the purpose of septum detection. Ruling out a septum by PAN seems to work more accurately than ruling in.

CLINICAL RELEVANCE

For the purpose of maxillary sinus floor septa detection, panoramic radiography can be relatively safely advocated, particularly for judgment of a septum-free sinus.