Accuracy of Linear Measurements of Ultra-low Dose Cone Beam Computed Tomography and Digital Panoramic Radiography Performed on Mandibular Anaesthetic Landmarks Versus Real Mandibular Measurements
Phase: NA
Conditions: Cone Beam Computed Tomography
Sponsor: Cairo University

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I. Administrative information: 
Title:  
Accuracy of linear measurements of ultra-low dose Cone Beam Computed Tomography and 
Digital Panoramic Radiography Performed on mandibular anaesthetic landmarks Versus Real 
mandibular measurements (Diagnostic Accuracy Study) 
 
II. Introduction: 
Background: 
One of the important mandibular anatomical landmarks is the inferior alveolar Nerve which 
can be damaged during surgical procedures such as third molar extraction, management of 
trauma and surgical removal of tumors. Therefore the dentist must be able to localize it prior 
to any dental procedure (Patil et al 2015).  
The mandibular foramen represents the entrance of the inferior alveolar nerve, which passes 
through the mandibular canal throughout the body of the mandible till it reaches the mental 
foramen where it divides into mental nerve and incisive nerve (Salinas et al 2016). 
In the past, the anterior region of the mandible was regarded as a safe area for implant surgery 
due to the absence of neurovascular structures. However, recent studies have shown 
haemorrhage and hematoma formation in the floor of the mouth due to injury to the vessels of 
the mandibular lingual foramen (Rosano et al 2009). 
Panoramic radiography is simple, inexpensive, and widely used, in addition to offering low 
radiation exposure to the patient. Kaffe et al 1994 found panoramic radiographs to be beneficial 
in locating mandibular foramen. In another study performed by Kositbowornchai et al 2007 it 
was found that there is a high accuracy between the distances measured  on panoramic 
radiographs and real measurements on dry mandibles (Kaffe et al 1994) and (Kositbowornchai 
et al 2007). 
Ultra-Low Dose CBCT technology is a recommended option for clinicians due to the decrease 
in radiation exposure to patients. Patients must not be exposed to a higher dosage than needed 
to acquire images of sufficient diagnostic quality (Kusnoto et al 2015) 
 
Review of literature: 
Resources: PubMed, Science direct. 
In a study performed on dry mandibles the comparison of linear measurements made with 
digital caliper and CBCT showed no significant differences for 95% of the distances measured. 
The 5% discrepancy is considered acceptable (Kamburoglu et al 2011) and (Sanjana et al 
2017). 

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A study was performed to evaluate the accuracy of panoramic radiographs in the localization 
of mandibular foramen on dry mandibles, where the position of mandibular foramen in relation 
to the ramus width and height was noticed. The results showed that there were statistically 
significant differences between distances measured on dry mandibles and radiographs except 
for the upper anterior ramus height (Kositbowornchai et al 2007) and (Patil et al 2015).  
 Another study was conducted on dry mandibles for the localization of the mental foramen. 
Measuring the distances from the crest of the ridge to the center of the mental foramen and 
from the inferior border of the mandible to the center of the mental foramen in addition to the 
location of the mental foramen relative to its’ alignment with  mandibular teeth.  For mental 
foramen measurement from crest of the ridge till its’ center did not show a significant 
difference for laterality, while the distance from the inferior border of the mandible till the 
center of the mental foramen the results showed a significant difference. Studies have shown 
that the most common location of the mental foramen is aligned with the second premolar, 
followed by between the first and the second mandibular premolar (Lopes et al 2010). 
A study was performed for the localization of the lingual foramen using CBCT. Linear 
measurements were made including their diameter, the distance between the lingual foramen 
and the crest of the ridge and the distance from the inferior border of the mandible to the lingual 
foramen. Lingual foramina were classified according to their location into midline type, Para 
median type or posterior type. (He et al 2016).  
CBCT and panoramic radiographs have been used to detect and measure lingual foramina. It 
has been proposed that CBCT provides highly accurate data of the mandibular anatomy 
(Ludlow et al 2007) and (Stratemann et al 2008). 
 
 
 
 
 
 
 
 
 
 
 
 
 

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III. Methods: 
A. The pre-analytical phase: Mandibular anaesthetic landmarks will be identified on each dry 
mandible and will be marked using gutta percha. 
B. The analytical phase, The ten human dry mandibles will be submitted for: 
1-Digital Panoramic Radiography. 
Panoramic radiographs will be obtained using the SOREDEX CRANEX™ 3Dx unit. The 
exposure parameters will be 8Ma, 63kVp and 16.4 sec exposure time. 
2-Cone Beam Computed Tomography (CBCT). 
SOREDEX CRANEX™ 3Dx unit will be used in this study. Images will be acquired at a single 
rotation.  SOREDEX® MiniDose parameters will be used. The exposure parameters will be 
3.2 Ma, 90kVp and 2.3 sec exposure time to take the advantage of 3D data in dose sensitive 
cases like children, or reduce the radiation dose for the patient. 
The real linear measurements will be measured in millimeter on dry mandibles using digital 
caliper and will be compared with measurements obtained from both techniques.  
 
C. The post analytical phase, Images will be evaluated by two experienced radiologists of ten 
years of experience. Each one will evaluate the images separately twice with a period of two 
weeks in-between the two reading sessions. The researcher will measure out the real linear 
measurements on the dry mandibles using digital caliper. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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D) Statistical analysis 
Sample size calculation and how it was determined  
Sample size calculation was done using R statistical package, version 3.3.1 (21-06-2016).  
Copyright (C) 2016.  The R Foundation for Statistical Computing. 
One-way analysis of variance power calculation for more than two groups was used to detect 
the proper sample size.  Means and standard deviations were determined according to Patil et. 
al (2015) based on the difference in distances measured on dry mandibles between different 
radiographic techniques. 
The results showed that, at a power of 80% and a two-sided significance level of 5%; a total 
sample size of 10 dry mandibles will be adequate to reject the null hypothesis that the group 
means are equal; i.e there’s no difference between radiographic techniques.   
 
Sample Size Calculation statistical output 
Name of the test:  One-way analysis of variance (ANOVA) power calculation for more 
than two groups. 
Source use for calculation**: Patil et. al, 2015 
Output: 
> m1=15.27 
> sd1=1.57 
> m2=16.93 
> sd2=1.54 
> n1=n2=25 
> k=2 
> within.var=(sd1^2+sd2^2)/2                                                   
> m=((n1*m1)+(n2*m2))/(n1+n2)                                             
>  between.var=(((m-m1)^2)+((m-m2)^2))/(k-1)                      
> 
power.anova.test(groups 
= 
3, 
between.var 
= 
between.var, 
within.var 
= 
within.var,power=0.80, sig.level=0.05)  
 
     Balanced one-way analysis of variance power calculation  
 
         groups = 3 
              n = 9.52841 
    between.var = 1.3778 
     within.var = 2.41825 
      sig.level = 0.05 
          power = 0.8 
NOTE: n is number in each group 

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