IADR Abstract Archives

Standard- versus low-dose CBCT in decision-making for impacted third molars

Objectives: To investigate whether there were significant differences in the diagnostic variables and treatment decisions for impacted mandibular third molars (M3M) between paired standard- and low-dose cone-beam computed tomography (CBCT) as evaluated by dental practitioners with different qualifications.
Methods: A randomised non-inferiority clinical study was conducted involving patients with an impacted M3M indicated for removal and panoramic radiograph showing ≤2mm between the mandibular canal (MC) and an M3M. The patients’ M3Ms were randomly assigned to three groups for two small field-of-view CBCT scans performed using one standard-dose (333mGy×cm²) and one of the three low-dose (78-131mGy×cm²) protocols, with doses equivalent to panoramic radiography. Diagnostic variables (MC visibility on four-point scale and the risk of inferior alveolar nerve injury) and treatment decisions (surgical approach between full removal and coronectomy, referral to an oral-maxillofacial surgeon (OMFS), and the need for M3M crown/root sectioning) were assessed on both paired low- and standard-dose CBCT images by four blinded general practitioners and OMFSs. The differences in all variables between paired low- and standard-dose CBCTs were evaluated using Wilcoxon signed-ranks or McNemar test.
Results: A total of 154 paired CBCTs were obtained from 90 patients. Standard-dose CBCTs were deemed diagnostically acceptable in 85-99% of cases, with a visibility score of ≥3 across four observers. Inferior MC visibility was found in 2-31% of low-dose CBCTs compared to paired standard-dose images. No significant differences were found in all treatment decisions regarding surgical approach (p=0.453-1.000), referral (p=0.250-1.000), the need for crown (p=0.125-1.000)/root (p=0.07-1.000) sectioning between paired standard- and low-dose CBCTs for all three groups.
Conclusions: The three low-dose CBCT protocols were clinically acceptable for M3M management without significant changes in treatment decisions, regardless of the observer’s qualification, when compared to paired standard-dose scans. The implementation of low-dose CBCT protocols, with doses equivalent to panoramic radiography, would not significantly affect clinical decision-making in M3M management.

Division:
Meeting: 2023 South East Asian Division Meeting (Singapore)
Location: Singapore
Year: 2023
Final Presentation ID: 052
Abstract Category|Abstract Category(s): Diagnostic Sciences

Authors

Hung, Kuo Feng ( Faculty of Dentistry, The University of Hong Kong , Hong Kong , Hong Kong ; Faculty of Dentistry, The University of Hong Kong , Hong Kong , Hong Kong )

Yeung, Andy Wai Kan ( Faculty of Dentistry, The University of Hong Kong , Hong Kong , Hong Kong )

Wan, Joan Chi-ching ( Faculty of Dentistry, The University of Hong Kong , Hong Kong , Hong Kong )

Wang, Rui ( Faculty of Dentistry, The University of Hong Kong , Hong Kong , Hong Kong )

Wai, Tak Shun Dustin ( Restorative Dental Sciences, Faculty of Dentistry, The University of Hong Kong , Hong Kong , Hong Kong )

Hon, Ki Adrian ( Restorative Dental Sciences, Faculty of Dentistry, The University of Hong Kong , Hong Kong , Hong Kong )

Leung, Yiu Yan ( Faculty of Dentistry, The University of Hong Kong , Hong Kong , Hong Kong )

Financial Interest Disclosure: NONE

SESSION INFORMATION

Oral Session
Oral Session-7: IOHS Award
Friday, 11/24/2023 , 09:00AM - 10:50AM

TABLES

Comparisons of the diagnostic variables and treatment decisions between paired standard- and low-dose CBCT, as evaluated by different observers

MC Visibility

IAN injury risk

Surgical approach

Referral to an OMFS

Crown sectioning

Root sectioning

Proportion of LD scans with inferior MC visibility compared to paired SD scans

p value

Proportion of LD scans with increased IAN injury risk assessed compared to paired SD scans

p value

Proportion of LD scans with the decision made for M3M coronectomy while full removal decided on paired SD scans

p value

Proportion of LD scans with referral decision made while non-referral decided on paired SD scans

p value

Proportion of LD scans with M3M crown sectioning considered necessary, while not deemed necessary on paired SD scans

p value

Proportion of LD scans with M3M root sectioning considered necessary, while not deemed necessary on paired SD scans

p value

Standard-dose CBCT (normal-resolution) vs. Low-dose CBCT (low-resolution without ULD mode)

OMFS1

1.000*

7.8%

0.366*

1.000#

7.8%

0.125#

5.9%

1.000#

OMFS2

19.6%

0.046*

3.9%

0.655*

1.000#

7.8%

1.000#

GP1

25.5%

0.029*

5.9%

0.206*

3.9%

0.688#

3.9%

0.289#

3.1%

1.000#

12.5%

0.375#

GP2

11.8%

0.564*

9.8%

0.275*

3.9%

0.688#

5.9%

0.250#

1.000#

Standard-dose CBCT (normal-resolution) vs. Low-dose CBCT (high-resolution with ULD mode)

OMFS1

9.6%

0.317*

5.8%

0.02*

1.000#

0.5#

OMFS2

7.7%

0.134*

7.7%

0.705*

1.9%

1.000#

1.9%

1.000#

GP1

30.8%

0.05*

9.6%

0.564*

7.7%

0.754#

9.6%

1.000#

10.7%

0.625#

GP2

7.7%

0.222*

11.5%

0.527*

3.8%

0.453#

1.9%

1.000#

11.1%

0.688#

13.9%

0.453#

Standard-dose CBCT (normal-resolution) vs. Low-dose CBCT (normal-resolution with ULD mode)

OMFS1

7.8%

0.414*

21.6%

0.225*

1.000#

0.07#

OMFS2

13.7%

0.564*

11.8%

0.157*

1.000#

10.2%

1.000#

GP1

15.7%

0.371*

19.6%

0.317*

5.9%

1.000#

9.8%

0.727#

1.000#

5.9%

1.000#

GP2

19.6%

0.003*

11.8%

0.317*

7.8%

1.000#

2.6%

0.219#

CBCT, cone-beam computed tomography; MC, mandibular canal; ULD, ultra-low dose; OMFS, oral-maxillofacial surgeon; GP, general practitioner; vs., versus; SD, standard-dose; LD, low-dose; IAN, inferior alveolar nerve, M3M, mandibular third molar; NA, not applicable *Wilcoxon Signed Ranks test and #McNemar test were performed for the paired comparisons
The low- and standard-dose protocols assessed

Imaging protocol	M3M group	Pre-set imaging setting	ULD mode	FOV (D in cm × H in cm)	Tube voltage (kV)	Tube current (mA)	Exposure time (s)	Voxel size (mm)	Dose in DAP (mGy×cm2)	Dose in CTDI (mGy)
Low-dose CBCT	1	Low resolution	N	4 × 5	90	5.6	6	0.4	131	2.1
	2	Normal resolution	Y	4 × 5	90	5.6	4	0.2	78	1.3
	3	High resolution	N	4 × 5	90	7.1	5	0.15	123	2
Standard-dose CBCT	1, 2, 3	Normal resolution	Y	4 × 5	90	8	12	0.2	322	5.8

CBCT, cone-beam computed tomography; CTDI, computed tomography dose index; DAP, dose-area product; FOV, field-of-view; M3M, mandibular third molar; ULD, ultra-low dose; D, diameter; H, height; N, no; Y, yes

IMAGES

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