The effect of varying cone beam computed tomography image resolution and field-of-view centralization on effective radiation dose

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.

Alveolar bone loss and root resorption in mesialized second molars in mandibular first molar extraction cases as compared to contralateral non-extraction side in young adults: A retrospective cross-sectional study

INTRODUCTION

The alveolar bone loss (ABL) and external apical root resorption (EARR) depict the safety of mesialization of mandibular second molars into the extraction space of mandibular first molars. The aim of this study was to evaluate the ABL and EARR after closure of mandibular first molar extraction space by mesialization of second molar on extraction side (ES) as compared to the contralateral non-extraction side (NES).

MATERIAL AND METHODS

A retrospective cross-sectional study was carried out using the pre and posttreatment orthodontic records of young adults with complete set of permanent dentitions treated with extraction of unilateral mandibular first molar and non-extraction treatment on the contralateral side. All patients underwent mini-implant supported mesialization of second molar on ES. The ABL and EARR of second molar on ES and contralateral NES were measured on digital orthopantomograms. The ABL and EARR of second molars on ES and contralateral NES were compared using independent sample t-test.

RESULTS

A total of 36 subjects (14 males and 22 females) were included in the study. The mean treatment duration for molar mesialization was 28.75±8.05months. The mean crown and root movements of mandibular second molar on ES were 10.94±1.25mm and 9.04mm±1.14mm, as compared to 0.91±1.01mm and 0.77±0.83mm on contralateral NES, respectively. The mean ABL and EARR at mandibular second molar were found to be significantly greater on the ES than the contralateral NES (P<0.001 and<0.05, respectively). A total of seven patients (19.4%) experienced ABL≥1mm on ES as compared to none in the contralateral NES. EARR of>2mm of at least one root was found in seven patients (19.4%) in ES as compared to four (11%) in contralateral NES.

CONCLUSION

There was small but statistically significant difference in the ABL and EARR of mesialized mandibular second molar at first molar ES as compared to the contralateral NES. For majority of patients this difference was small but few isolated cases experienced severe ABL and EARR.

Impact of radiographic field-of-view volume on alignment accuracy during virtual implant planning: A noninterventional retrospective pilot study

OBJECTIVE

To evaluate the impact of reducing the radiographic field-of-view (FOV) on the trueness and precision of the alignment between cone beam computed tomography (CBCT) and intraoral scanning data for implant planning.

MATERIALS AND METHODS

Fifteen participants presenting with one of three clinical scenarios: single tooth loss (ST, n=5), multiple missing teeth (MT, n=5), and presence of radiographic artifacts (AR, n=5) were included. CBCT volumes covering the full arch (FA) were reduced to the quadrant (Q) or the adjacent tooth/teeth (A). Two operators, an expert (exp) in virtual implant planning and an inexperienced clinician, performed multiple superimpositions, with FA-exp serving as a reference. The deviations were calculated at the implant apex and shoulder levels. Thereafter, linear mixed models were adapted to investigate the influence of FOV on discrepancies.

RESULTS

Evaluation of trueness compared to FA-exp resulted in the largest mean (AR-A: 0.10 ± 0.33 mm) and single maximum discrepancy (AR-Q: 1.44 mm) in the presence of artifacts. Furthermore, for the ST group, the largest mean error (-0.06 ± 0.2 mm, shoulder) was calculated with the FA-FOV, while for MT, with the intermediate volume (-0.07 ± 0.24 mm, Q). In terms of precision, the mean SD intervals were ≤0.25 mm (A-exp). Precision was influenced by FOV volume (FA<Q<A) but not by operator expertise.

CONCLUSIONS

For single posterior missing teeth, an extended FOV does not improve registration accuracy. However, in the presence of artifacts or multiple missing posterior teeth, caution is recommended when reducing FOV.

CBCT in Advanced Dental Education: A Survey of U.S. Postdoctoral Periodontics Programs

Historically, predoctoral and advanced dental education programs used two-dimensional panoramic and periapical radiographs for implant planning. Three-dimensional (3D) Cone Beam Computed Tomography (CBCT) imaging has improved visualization of anatomic structures that can positively influence implant planning and surgical implant placement. The aim of this study was to assess how U.S. postdoctoral periodontics programs have incorporated CBCT technology into their curricula. A ten-question survey was sent to all 57 U.S. postdoctoral periodontics programs in November-December 2018. Thirty-seven responses were received, for a 65% response rate. All participating programs reported providing residents access to CBCT machines, and most of their residents received some training in the acquisition and interpretation of CBCT images. Nearly all (95%) participating programs provided training to apply implant planning software. Among the participating programs, 14% reported using a surgical guide fabricated with a CBCT scan 76-100% of the time, and 60% reported obtaining a CBCT scan for implant cases 76-100% of the time. These results suggest that, while residents are receiving training in CBCT and implant planning, it is not used often. There may be merit in adopting the American Academy of Oral and Maxillofacial Radiology's recommendation to use 3D imaging for all implant planning, with CBCT as the imaging modality of choice.

Single-step surgical treatment of odontogenic maxillary sinusitis: A retrospective study of 98 cases

PURPOSE

The aim of this study was to review clinical and radiological presentation, surgery, and results of treatment in patients with chronic odontogenic maxillary sinusitis (OMS) treated with a single surgical procedure, including endoscopic sinus surgery (ESS) and oral surgical approaches to treat the odontogenic source of infection.

MATERIALS AND METHODS

A retrospective case series analysis of 98 patients was performed. All the patients received ESS. 88 patients required oral surgical approaches.

RESULTS

Nasal symptoms were present in 58 patients (59.2%). Nasal endoscopy was positive in 65 patients (66.3%). A positive nasal endoscopy was significantly associated with nasal symptoms (p < 0.05). 60 patients (61.2%) had OMS of iatrogenic origin. Total opacification of the maxillary sinus was the most common radiological presentation (74.5%) and was significantly associated with nasal symptoms (p < 0.05). 91 patients (92.9%) had complete clinical and radiological resolution of the OMS.

CONCLUSIONS

Iatrogenic origin, sinonasal symptoms and positive clinical endoscopy are common in patients with OMS. Nasal symptoms were significantly associated with total maxillary sinus opacification and positive endoscopic clinical examination. Combining treatment of the odontogenic source of infection via an oral surgical approach and of the sinus inflammation by ESS appears to be sufficient for successfully treating patients with OMS.