Assessment of the Anterior Loop of the Inferior Alveolar Nerve in a Sample of Egyptian Population Using CBCT: An Observational Cross-Sectional Study
Conditions: Mandibular Nerve
Sponsor: Cairo University

 
I
 
 
Assessment of the anterior loop of the inferior alveolar nerve 
in a Sample of Egyptian Population using CBCT: An Observational 
Cross-Sectional Study 
Submitted for partial fulfillment of the PHD requirements in Oral and Maxillofacial                
Radiology department, Faculty of Dentistry, Cairo University 
By 
Yomna Mohamed Gamal El-Din Saadi 
B.D.S 2012 
Assistant Lecturer, School of Dentistry, New Giza University  
2019 
Research Code: ORAD 7.1.1 
NCT ID not yet assigned 
Date of Document: 23/06/2020 
 
Supervisors’ signature 
 
            Head of department’s signature 
 1-Dr. Hossam Kandil 
Professor of Oral and 
Maxillofacial Radiology 
Faculty of Dentistry 
Cairo University 
 
2-Dr. Farid Medhat 
Assistant Professor of Oral and 
Maxillofacial Radiology
 
Faculty of Dentistry
 
Cairo University
 
 
                Dr.Mohamed El-Sorougy 

 
II
 
 
 
Protocol Checklist 
Section and topic
 
Item 
No. 
Checked item 
Reported 
on page 
No. 
Reviewer’s 
check 
 
I. Administrative Information
 
 
1
 
Title: PECOS elements included
 
1
 
 
2
 
Protocol Registration
 
1
 
 
3
 
Protocol Version
 
1
 
 
4
 
Funding
 
1
 
 
5
 
Roles and Responsibilities of the 
Authors 
1,2
 
 
 
Introduction
II. 
 
 
6a
 
Scientific Background
 
2,3
 
 
 
6b
 
Review of Literature
 
      4,5 
 
 
6c
 
Statement of the Problem
 
5,6 
 
 
Methods
III. 
 
A) Study Design 
and Settings
7 
Study Design
 
6
 
 
8 
Settings
 
6
 
 
B) Participants
9a 
Eligibility Criteria
 
6,7 
 
9b 
Methods of selection or case/control 
ascertainment
 
-
 
 
9c 
Methods of follow up for cohort 
studies and rationale for choosing 
cases and controls for case control 
-
 
 

 
III
 
 
studies
 
10 
Matched cohort study—matching 
criteria and allocation ratio (exposed: 
non-exposed)
 
Matched case-control study— 
matching criteria and allocation ratio 
(case: control)
 
7
 
 
C) Variables
11 
Clearly define all variables including 
outcomes and exposures
 
7
 
 
12 
For each variable of interest, give data 
sources/ measurement
 
7,8,9 
 
13 
Addressing potential sources of bias
 
9
 
 
D) Study Size
    14       
Study size
 
9
 
 
E) Quantitative 
Variables
15 
Handling of quantitative variables in 
the analyses
 
9
 
 
F) Statistical 
methods
16 
Statistical methods used to control for 
confounders
 
9
 
 
 
 
 
 
 
and Dissemination
Ethics 
-
IV
 
 
 
17a 
Research ethics approval
 
10
 
 
17b 
Protocol amendments
 
10
 
 
17c 
Access to Data
 
10
 
 
17d 
Dissemination Policy
 
10
 
 
 
References
 -
V
 
 
References by reference manager
 
10,11
 
 
 

 
IV
 
 
Evidence Based Committee (Reviewers)
 
Name
 
Signature
 
Date
 
1.
 
 
2.
 
 
 
Research Plan Committee
 
Name
 
Signature
 
Date
 
1. 
2. 

 
1
 
 
 
I-Administrative Information 
1-Title: Assessment of the anterior loop of inferior alveolar nerve in a sample of Egyptian 
Population using CBCT: An Observational Cross-Sectional Study. 
 
2-Protocol Registration: 
Registered at www.clinicaltrials.gov 
ID: ………………… 
 
3-Protocol Version: 2nd version 
 
4-Funding: self-funding 
 
5-Roles and responsibilities of the authors: 
Principal Investigator: Yomna Mohamed Gamal El-Din Saadi 
          Masters degree in Oral and Maxillofacial radiology 
          Department of Oral and Maxillofacial Radiology 
          Faculty of Dentistry, Cairo University 
Roles of the investigator: 
 Preparing the technical proposal  
 Assuring that the design is appropriate to the proposed question. 
 Identifying the need for sub-recipient agreements. 
 Ensuring that the used procedures are consistent with sound research design and do not unnecessarily 
expose subjects to risk/harm. 
 Being responsible for all required actions to manage and complete the scientific and programmatic 
aspects of the project (including data collection and assessment). 
 Ensuring the integrity and safeguarding of notebooks and scientific data. Ensuring the completion, 
accuracy and timeliness of programmatic (technical) reports. 
Chief Supervisor: Dr. Hossam Kandil 
Professor 
Department of Oral and Maxillofacial Radiology 
Faculty of Dentistry, Cairo University 
Roles of Chief Supervisor: 
 Assisting the candidate -in association with the co-supervisor -to prepare a full research plan that can 
be completed and written up within the prescribed period of study, and to seek approval for that 
proposal. 
 Establishing a research plan with the investigator, in which the work is completed. 
 Discussing the work done through meetings or exchanging email messages if the candidate is in a 
remote location, at least once per month.Assisting the candidate by regularly checking the records of 
data and observations and suggesting improvements where appropriate. 

 
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 Providing constructive criticism and advice on submitted written drafts within agreed time frames. 
 Supporting the candidate in the preparation for thesis defense. 
 Facilitating timely completion of the candidate's study and ultimate completion of the thesis. 
 
Assistant Supervisor:  Dr. Farid Medhat 
                       Assistant Professor 
                       Department of Oral and Maxillofacial Radiology  
                       Faculty of Dentistry, Cairo University 
Roles of Assistant Supervisor: 
 Monitoring the progress of the student’s research through regular formal supervisory meetings and 
ensuring that the research student keeps an agreed record of these meetings. 
 Being accessible at mutually convenient times when the research student may need advice. 
 Performing the blind assessment during the data collection stage. 
 Giving detailed advice on the necessary completion dates of successive stages of the work so that the 
thesis can be submitted within the relevant maximum registration period. 
 Reading and commenting on the whole of the final draft of the thesis, provided that this is presented 
within a reasonable and agreed time frame, and ensuring that the research student is aware that the 
thesis must comply with all relevant regulations, including those on word length, format, and binding. 
II-Introduction  
6. a. Scientific Background: The proper knowledge of anatomical structures and their precise position is 
of a paramount importance for different dental specialties. The inferior alveolar nerve (IAN) canal is one 
of the most important anatomical landmarks in the mandible Shaban et al., 2017. By definition the 
inferior alveolar nerve (IAN) is a terminal division of the mandibular branch of the trigeminal nerve, it is 
confined within the mandibular canal and innervates all the mandibular teeth. The IAN initiates from the 
mandibular foramen and goes obliquely downward and forward in the ramus, and then horizontally within 
the body of the mandible. The IAN gives off the mental nerve, which exits the mandible through the 
mental foramen, supplying sensory branches to the chin, lower lip, mucous membranes and the gingiva; 
from the midline to about the second premolar region. It then continues its path anteriorly and turn into 
the mandibular incisive nerve, which innervates the mandibular canines and incisors Siddiqui et al. 2018. 
Before leaving the mental foramen and branching into the incisive nerve, the IAN may continue anteriorly 
and form an anterior loop (Al). This anterior loop is the part where the IAN directs mesially and 
occlusally before reversing direction and coursing distally towards the mental foramen Ragu et al., 2019. 
During implant planning and other surgical procedures knowing the presence of the anterior loop and its 
length is very crucial to avoid its injury. Specially concerning implantology where the location of the 
mental foramen and anterior loop determines the most distal point for implant placement in the 

 
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interforaminal area; in order to avoid any injury resulting in sensory disturbances in this area 
Panjnoush et al., 2016 
Recently, several studies have been published discussing the prevalence and length measurement 
of the anterior loop in many populations. However, no published researches were done on the 
Egyptian population. Therefore, this study is designed to assess the presence of the anterior loop 
and its length in a sample of Egyptian population using CBCT. 
 
PO question   
P: mandible quadrants in Adult Egyptian Population. 
O: Presence of the anterior loop of the inferior alveolar nerve; and its length in the mandibles of 
adult Egyptian population 
* MPR: Multiplanar Reformatting 
** DVR: Direct Volume Rendering 
Research question: 
How frequent is the anterior loop and how long its mesial extension is in a sample of Egyptian 
population? 
                                                                                                         
 
Outcome Measured 
Measuring Device 
Measuring Unit 
 
Primary Outcome 
 
Prevalence of the 
anterior loop 
CBCT axial cuts (Ondemand 
3D software) 
Categorical 
nominal data 
Percentage (%) 
Secondary Outcomes 
length of the anterior 
loop 
Built in measuring tools 
(axial cuts) in Ondemand 3D 
software “MPR* module” 
mm 
 
Mesial extension of 
the anterior loop 
Cross-sectional cuts on 
Ondemand 3D software 
“DVR** module” 
mm 

 
4
 
 
 
6b. Review of literature 
List of main databases used in search: 
 Pubmed  
 Google Scholar 
Keywords: 
Anterior Loop, Mandibular Canal, Mental Foramen, CBCT, Maxillofacial Anatomy, Dental 
Implants. 
In 1994 Solar et al classified the mental nerve path of the IAN canal into three types; where type 
I is defined as a Y-shaped anatomy of the incisive branch & the mental branch with absence of 
the anterior loop, while type II is a T-shaped anatomy with the incisive branch being 
perpendicular to the mental branch still with the anterior loop’s absence, and finally type III is 
defined as a Y-shaped anatomy with the presence of the anterior loop (Figure 1). 
 
Figure 1: IAN Types (Demir et al 2015) 
 According to Bavitz et al. 1993 & Misch 1999 the IAN’s anterior loop is defined as the structure 
where the mental neurovascular bundle passes inferior and anterior to the mental foramen then 
loops backwards to exit the mental foramen (Figure 2). 

 
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Figure 2:  Schematic diagram showing key image of anterior loop of IAN (Siddiqui, et al 2018) 
 
Different methods were used to assess the anterior loop including cadavers, dry skulls, 
panoramic radiographs, medical CT and CBCT; which is the reason behind the considerable 
variation of the prevalence and average length of the anterior loop mentioned in the literature 
where the mean length ranges between 0.1 mm & 6.92 mm Patterson 2015. In addition to the 
effect of different races, age and gender. Ngeow et al 2009 stated that several authors have 
suggested the limitation of panoramic radiograph regarding the visualization of the anterior 
loop for the purpose of implant planning due to the high percentage of false-positive and 
negative findings compared to cadaveric dissection data owing to its limitation as a two 
dimensional radiographic method. Bringing us to the fact that three dimensional imaging 
techniques such as medical CT, Magnetic Resonance Imaging (MRI) and Cone beam CT evade 
this draw back Ngeow et al 2009 & Nair at al 2013. 
Nair et al 2013 stated that CBCT surpasses medical CT in its significantly lower dose with 
producing high resolution, superimposition and magnification free undistorted 3D images of 
the maxillofacial anatomy. 
Therefore it is the method of choice for assessment of the anterior loop before surgical 
intervention as mentioned by Demir et al 2015, Moghddam et al 2017 & Siddiqui et al. 2018. 
 6c. Statement of the Problem  
A high percentage of iatrogenic damage to the mental nerve occurs due to the unawareness of 
dental clinicians with the presence of an IAN’s anterior loop in the interforaminal area during 
implant placement or other surgical procedures such as tumor or tooth impaction removal; 
leading to its injury. Therefore, dental clinicians should know the prevalence of the anterior loop 
in different populations in addition to having a proper case examination and planning using 
CBCT. 

 
6
 
 
Specific Objectives: 
To detect the prevalence of anterior loop and measure its length in relation to gender effect in a 
sample of the Egyptian population.  
Hypothesis: null                                                                                                                           
III -Methods  
A) Study design and setting 
7- Study Design: An observational Cross-sectional Study 
8- Setting and Location:  
The CBCT data of this study will be obtained from the CBCT data base available at a private 
radiographic centre “ORASCAN Oral & Maxillofacial Imaging Centre” located in Cairo, Egypt. 
Being a retrospective study, CBCT images of Egyptian patients who have already been subjected 
to CBCT examination as part of their dental diagnosis and/or treatment planning during the years 
2018-till present will be included according to the proposed eligibility criteria. 
B) Participants: 
Based on sample size calculation, a sample of 192 CBCT images of mandible quadrants 
belonging to Egyptian individuals will be examined. The selection of the scans to be included 
will be based on the following eligibility criteria. 
9- Eligibility criteria and selection method: 
 Inclusion criteria: 
 CBCT scans of adult Egyptian patients, males and females. 
 CBCT scans with unilateral or bilateral anterior mandibles; with minimum 2 mm length distal 
to the mental foramen (mental foramen & anterior mandible are clearly delineated) 
Moghddam et al, 2017. 
 Exclusion criteria 
 CBCT images of poor quality or artifacts interfering with the assessment of the anterior loop 
of IAN. 
 Scans showing any pathosis in the interforaminal area (tumor or impaction). 
10- Matching criteria and allocation ratio: 

 
7
 
 
Not applicable in the study 
 
C) Variables:  
11- Details about variable 
1. Length of anterior loop’s mesial extension if present. 
2. Sex of the patient will be identified and addressed as the prevalence of the anterior loop 
of the IAN and its length may show sex predilection. 
12- Data Sources / Measurements: 
 Retrospective Data Analysis will be performed after the CBCT images are pooled from the 
computer database. 
 Exposure parameters of the scans were as following; scanned using Cranex® 3DX 
SOREDEX, 0.2 voxel resolution, 8 × 6 cm FOV, 90 kVp, 10 mA and 6 seconds exposure 
time 
 CBCT images will be analysed using OnDemand3D ® App (Cybermed, Seoul, Korea); using 
the 3D module, reference lines are modified to confine with the buccolingual orientation of 
the inferior alveolar loop, to obtain a modified axial cut showing the inferior alveolar loop and 
mental foramen opening on the same plane. 
In scans with an anterior loop, on the corrected axial cut the distance between the most mesial 
point of the mental foramen and the maximum mesial extension of the anterior loop will be 
measured Von Arx et al 2013 (Figure 3). 
 

 
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Figure 3: the distance between the most mesial point of the mental foramen and the 
maximum mesial extension of the anterior loop will be measured Von Arx et al 2013 
 Using the DVR module; an arch line will be drawn on the axial plane to obtain a reformatted 
panorama; then the mesial extension of the AL will be detected and its length will be 
measured by counting the number of the consecutive adjacent vertical cuts on cross-sectional 
view between the slice showing the anterior border of the mental foramen and the anterior 
border of the loop using slice interval of 1mm Apostolakis et al 2012 (Figure 4). 
 
Figure 4: Cross-sectional reconstructions showing the AL Apostolakis et al 2012 

 
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 CBCT images will be interpreted by two oral radiologists independently; blinded from 
demographic data of the patients and from the results of each other.  
 Each radiologist will evaluate the images for detection of the anterior loop and measuring its 
length. Then one of them will re-evaluate the images with two weeks interval between the two 
reading sessions. 
 Intra-observer and inter-observer and variability between the observers will be evaluated. 
13- Addressing potential sources of bias:  
No source of bias. CBCT images will be interpreted by two oral and maxillofacial radiologists 
independently blinded from demographic data of the patients and from the results of each other.                           
D) Study Size: 
14- Study Size: 
The aim of this study is to detect the prevalence and length of the anterior loop among a sample 
of Egyptian population. Based upon the results of Shariati et al 2017, the prevalence of the 
anterior loop= 24.3%. Using alpha (α) level of (5%), acceptable margin of error = 6%, the 
minimum estimated sample size was 192 subjects. Sample size calculation was performed using 
Epi Info 7.2.2.2  
E) Quantitative variables 
15- Handling of quantitative variables in analyses: 
The number of CBCT scans of Egyptian individuals with an anterior loop of the IAN will be 
counted and its length will be measured to estimate the variations in the Egyptian population. 
The length of the anterior loop will be handled as mean and standard deviation. 
F) Statistical methods: 
16- Statistical methods: 
Data will be analyzed using IBM SPSS advanced statistics (Statistical Package for Social 
Scienceaszxs), version 21 (SPSS Inc., Chicago, IL). Numerical data will be described as mean 
and standard deviation or median and range. Categorical data will be described as numbers and 
percentages. A p-value less than or equal to 0.05 will be considered statistically significant. All 
tests will be two tailed.  

 
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IV. Ethics and dissemination  
17a. Research ethics approval: The Study protocol will be submitted to the Ethics commute in 
Faculty of Dentistry- Cairo University for approval  . 
17b. Protocol amendments: Any amendments in the protocol will be reported to the main and 
co-supervisor. 
17c. Access to Data: Investigator, Co-supervisor and main supervisor will have access to the 
final trial data set . 
17d.Dissemination Policy: The Investigator will communicate her results with other participants 
and healthcare providers through publication of the protocol and the research final results and 
recommendations. This will be done through publication websites and journals concerned Oral 
and Maxillofacial Radiology specialty, For Sharing the recommended clinical application 
obtained from the final results of the research. 
V) References 
 Apostolakis D, Brown JE. The anterior loop of the inferior alveolar nerve: prevalence, 
measurement of its length and a recommendation for interforaminal implant installation 
based on cone beam CT imaging. Clinical oral implants research. 2012 Sep;23(9):1022-
30. 
 Bavitz JB, Harn SD, Hansen CA, Lang M. An anatomical study of mental neurovascular 
bundle - implant relationship. Int J Oral Maxillofac Implants 1993;8:563-7.  
 Demir A, Izgi E, Pekiner FN. Anterior loop of the mental foramen in a Turkish 
subpopulation with dentate patients: a cone beam computed tomography study. Clinical 
and Experimental Health Sciences. 2015 Oct 1;5(4):231. 
 Misch CE. Root form surgery in the edentulous mandible: Stage I implant insertion. In: 
Misch CE, ed. Implant Dentistry. 2nd ed. St. Louis: The CV Mosby Company; 1999. pp 
347-70 
 Moghddam MR, Davoudmanesh Z, Azizi N, Rakhshan V, Shariati M. Prevalence and 
length of the anterior loop of the inferior alveolar nerve in Iranians. Journal of Oral 
Implantology. 2017 Oct;43(5):333-6. 

 
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 Nair UP, Yazdi MH, Nayar GM, Parry H, Katkar RA, Nair MK. Configuration of the 
inferior alveolar canal as detected by cone beam computed tomography. Journal of 
conservative dentistry: JCD. 2013 Nov;16(6):518. 
 Ngeow WC, Dionysius DD, Ishak H, Nambiar P. A radiographic study on the 
visualization of the anterior loop in dentate subjects of different age groups. Journal of 
oral science. 2009;51(2):231-7. 
 Panjnoush M, Rabiee ZS, Kheirandish Y. Assessment of location and anatomical 
characteristics of mental foramen, anterior loop and mandibular incisive canal using cone 
beam computed tomography. Journal of Dentistry (Tehran, Iran). 2016 Mar;13(2):126. 
 Patterson GO. The anterior loop of the inferior alveolar nerve: prevalence and 
measurement using reformatted medical computed tomographic imaging (Doctoral 
dissertation, University of Pretoria).2015. 
 Raju N, Zhang W, Jadhav A, Ioannou A, Eswaran S, Weltman R. Cone beam computed 
tomography analysis of the prevalence, length, and passage of the anterior loop of the 
mandibular canal. Journal of Oral Implantology. 2019 Sep 19. 
 Shaban B, Khajavi A, Khaki N, Mohiti Y, Mehri T, Kermani H. Assessment of the 
anterior loop of the inferior alveolar nerve via cone-beam computed tomography. Journal 
of the Korean Association of Oral and Maxillofacial Surgeons. 2017 Dec 1;43(6):395-
400. 
 Siddiqui Z, Rai S, Ranjan V. Efficacy and evaluation of cone beam computed 
tomography in determining the prevalence and length of anterior loop of inferior alveolar 
nerve in North Indian population. Journal of Indian Academy of Oral Medicine and 
Radiology. 2018 Jan 1;30(1):32. 
 Solar P, Ulm C, Frey G, Matejka M. A Classification of the Intraosseous Paths of the 
Mental Nerve. International Journal of Oral & Maxillofacial Implants. 1994 May 1;9(3). 
 Von Arx T, Friedli M, Sendi P, Lozanoff S, Bornstein MM. Location and dimensions of 
the mental foramen: a radiographic analysis by using cone-beam computed tomography. 
Journal of endodontics. 2013 Dec 1;39(12):1522-8