Assessment of Root Apex Position of Mandibular Molars and Premolars Linear to Inferior Alveolar Canal Among a Sample of Egyptian Population Using CBCT: A Cross Sectional Study
Conditions: Linear Measurement Between Roots of Mandibular Premolars & Molar & IAC
Sponsor: Cairo University

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Assessment of Root Apex Position of Mandibular 
Molars and Premolars linear to Inferior Alveolar 
Canal among a sample of Egyptian Population 
Using CBCT: A Cross sectional study 
 
Protocol 
submitted to Faculty of Dentistry, Cairo University for partial 
fulfillment of the requirements for Master Degree in Oral and 
Maxillofacial Radiology 
Research code :Rad 2:5:1 
05/09/2018 
 
Presented by 
Menna Tallah Mosaad El-said 
Resident at Oral and Maxillofacial Radiology Department 
B.D.S. 2012 
Faculty of Dentistry  
Cairo University 
2018 
 

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Supervisors 
 
 
Dr. Farid Medhat  
Assistant professor of Oral and Maxillofacial Radiology  
 
Faculty of Dentistry 
 
Cairo University 
 
Dr. Alaa Nawwar  
Lecturer of Oral and Maxillofacial Radiology  
 
Faculty of Dentistry 
 
Cairo University 
 
 

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Introduction 
 The inferior alveolar nerve (IAN) position is important in avoiding nerve 
damage during invasive dental procedures. The inferior alveolar bundle is located in 
the mandibular canal, which runs obliquely through the ramus of the mandible and 
horizontally through the mandible. The components of the inferior alveolar 
neurovascular bundle, which is the major supplier of both sensation and blood to the 
mandible, are arranged consecutively from the superior to inferior positions as 
follows: vein, artery, and nerve (Yu, Lee, Jeon, Chung, & Kim et al 2016). The 
IAN, which is a branch of the mandibular nerve ( the third branch of trigmenial 
nerve(,is prone to injury due to trauma, tumors , and a variety of surgical treatments. 
The IAN provides innervation to the mandibular molars and premolars and their 
gingiva. The incisive branch, an extension of the IAN, supplies the anterior teeth 
(Juodzbalys, Wang, & Sabalys et al 2011).  
The dental procedures posterior to the mental foramen increases the risk for 
injuring the IAN as a result of its proximity to the root apices of mandibular 
premolars and molars (Pogrel et al 2007;Valmaseda et al 2001).The dental 
procedures may be endodontic procedures (Pogrel et al 2007;Escoda et al 2007), 
implant placements (Burstein et al 2008;kraut et al 2002), or extraction of 
mandibular third molar (Valmaseda et al 2001) can cause injury to IAN, or implant 
placement ,resulting in neuropathic pain or partial or complete numbness in the chin 
area(Microsc et al 2017) . 
Endodontic therapy might also damage the IAN. Several mechanisms have 
been proposed, including (1) neurotoxic effect from root canal filling material 
penetrating the IAN (Pogrel et al 2007;Valmaseda et al 2001); (2) mechanical 
pressure on the nerve caused by overextension of filling material or over 

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instrumentation with hand or rotary files (Pogrel et al 2007;Valmaseda et al 2001); 
IAN damage has been suggested to occur in 1% of mandibular premolars that receive 
root canal treatment (Escoda et al 2007). 
There is an incidence for nerve injury during dental implant placement, 
resulting from the poor assessment of bone length or excessive length of implant 
bodies. Therefore to avoid damage of inferior alveolar nerve, it is important to assess 
the mandibular canal location in the mandible and edentulous space that represent 
the missing tooth.( Jui-Ting Hsu et al 2013) 
The nerve injury is unfavorable consequences for the patient (Escoda et al 
2007;Burstein et al 2008). If an intimate relation exists, this may have clinical 
relevance and risk of nerve injury implications in relation to root canal treatment and 
dental placement of mandibular premolars and molars 
Rational of the Study 
 
The linear relation between mandibular premolar and mandibular molars to 
inferior alveolar canal is not correlated; this study may help to reduce IAN injury 
during dental and surgical procedures. 
Statement of the Problem 
 
Direct nerve damage may be caused by placement of implants, or surgical extraction, 
or endodontic treatment. All of these may cause temporary or permanent damage to 
the IAN (poveda et al 2006; Lvovsky et al 2018). These procedure are invasive, and 
the nerve may be close to the root apex of the posterior teeth. So the clinical relation 
between inferior alveolar canal and apices of roots of mandibular premolar and molar 
is important to avoid nerve damage. 

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Review of literature 
 
List of main databases used in search: 
- Pubmed  
- Google Scholar 
 Keywords: 
- Cone-beam computed tomography- Inferior Alveolar Nerve-Mandibular 
Premolars- Mandibular Molars -Nerve Injury. 
Various dental procedures distal to mental foramen pose a potential iatrogenic cause 
of inferior alveolar nerve injury  (Escoda et al 2007), The dental procedures include 
the surgical and non-surgical procedural, they include the endodontic treatment, 
implant placement, or extraction of third mandibular molar (kovisto et al 2011). 
In endodontic treatment obturation,  gutta percha is traditionally considered 
an inert root-filling material, the parasthesia’s cases involving gutta percha results 
from overfill of thermoplastic gutta-percha. If the sealers are excluded from the 
apices in the mandibular canal space, it can cause nerve injury (Hiremath et al 
2016). 
Injury to the IAN has also been shown with extraction of mandibular third 
molars (frequency of 1.3%), suggesting that teeth are often close to the nerve. In 
patients with mental nerve injury, extraction and implant placement have been 
implicated in 63% of cases with problems (Kalladka et al 2008). Hidenobu et al 
reported the relation of third mandibular molar and position of the inferior alveolar 
nerve without reporting the root apices relation to the nerve.  
One of the dentists’ objectives is to retain the nature tooth, but if loss of tooth 
structure, periodontal disease, or trauma is severe, the tooth might be un-restorable. 
To replace a lost tooth, the treatment option is placement of dental implant to replace 
the extracted tooth. Immediate implant placement, with apical penetration of the 

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implant 4–5 mm beyond the previous position of the tooth root into bone for 
stabilization, can cause injury to the nerve. If the IAN is in close proximity to the 
root apex of the tooth extracted, implant placement 4–5 mm below the apex of the 
socket of extracted tooth might cause injury to the nerve. Nerve damage has been 
reported in 17% of implant cases (Kubilius et al 2004). Paresthesia can be as high 
as 13% in the posterior mandible from implants (Burstein et al 2008). Neurosensory 
problems can be as high as 52% in patients who have received a dental implant 
(Kovisto et al 2011).Although IAN damage is infrequent and the prevalence is not 
well-defined, it is a serious situation that has unfavorable complication for the 
patient. Before going procedures with potential for IAN injury, it is critical to 
determine the location of the inferior alveolar canal with respect to the surrounding 
structures to avoid injury of anatomical structure (Burstein et al 2008).  
Jerjes et al 2005 has reported also that the parasthesia of inferior alveolar 
nerve may result from infection as inflammatory cyst in correspondence with first 
and second mandibular premolars, while in the mandibular molars, the distance 
between the root apex and inferior alveolar canal should be in consideration. In the 
study by Tilotta-Yasukawa et al 2006, the distance of root apex of first mandibular 
molars from the inferior alveolar nerve varies from 1 and 4 mm and it is less than 
1 mm with the second and third mandibular molars. For this reason, the spread of 
infectious cases to the inferior alveolar nerve that originates from apices of first or 
second mandibular molar may be quickly involved the nerve even if the periapical 
lesion size is small(Rachele et al 2016). 
In infectious cases, the paresthesia can be the result of a combination of the 
following mechanisms.(1) Mechanical Pressure: In particular, the expanding 
infectious process can cause pressure on the nerve fibers. The pressure induces the 
paresthesia. (2) Microbial Products: in which the products of certain microbes (gram 

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negative bacteria) can puncture the perineurium with resultant nerve bundle 
impairment and soiled the conduction. 
In view of these potential complications, several studies were conducted to 
assess the distances between inferior alveolar canal and the root apices of mandibular 
premolars and molars. However, most studies included only a limited number of 
specimens (Kim et al 2010) or were based on orthogonal and eccentric periapical 
radiographs or on panoramic radiographs. The value of such analyses is limited 
because of superimpositions of surrounding structures or distortions (Bürklein et al 
2015).Although there is too many studies correlate the relation of  third molars to 
inferior alveolar canal ,and also too many studies correlate the relation of molars to 
the buccal-lingual cortical bone. There is no relation of root apices of the mandibular 
premolars and molars to the inferior alveolar nerve in a sample of Egyptian 
population. 
Cone-beam computed tomographic (CBCT) imaging provides 3-dimensional (3D) 
images with a moderate radiation dose (Patel et al 2014), and numerous studies 
have reported its value in diagnosing spatial relationships between anatomic 
structures (Temple et al 2016; Tahmasbi et al 2017). So spatial proximity of vital 
structures such as the inferior alveolar nerve, the incisive canal, and the mental 
foramen can be accurately assessed and measured (Benavides et al 2012).CBCT 
can overcome the limitations of radiographs by providing an accurate and 3D 
image of teeth and surrounding structures. CBCT scans were found to have an 
error less than that 0.6 % when measuring mandibular anatomy(Ludlow et al 
2007).The advantages of CBCT are the weaknesses of 2D intraoral periapical and 
panoramic radiographic representations. The ability to visualize the area of interest 
and avoid superimposition permits accurate radiographic interpretation. So it is 
useful to assess the position of root apex of first and second premolar and 
mandibular molars to IAN. In other conventional radiographic techniques, there 

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are distortion and magnification of the anatomic structures ranging from 3.4% for 
periapical radiographs to more than 14% for panoramic radiographs (Lazzerini et 
al 1996). 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Aim of the Study 
The aim of the study is to assess the linear position  between the roots of 
mandibular premolars and molars and the superior border of inferior alveolar 
canal. 
Population: Adults, male and female from Egyptian population  
Outcome Variable: Linear measurement of the distance between root apices of 
mandibular premolars and molars to the superior border of 
IAN. 
 
 
Outcome 
Measured 
Measuring Device Measuring Unit 
 
Primary Outcome 
Distance between 
root apices of 
mandibular 
premolars and 
molars to inferior 
alveolar canal 
 
CBCT software 
Romexis® 
 
Millimeters  
 
 
Research question: 
Among the mandibular premolars and molars, which roots are the closest to the 
inferior alveolar canal, in sample of Egyptian Population? 

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Materials and Methods 
 
Study Design: Cross-sectional Study 
Setting and Location:  
1- The data collection will be obtained from the data base available at Oral & 
Maxillofacial Radiology department at faculty of Dentistry, Cairo University. 
2- CBCT images will be obtained from Egyptian patients who had CBCT 
examination as part of their dental examination, diagnosis or treatment 
planning during the years 2018. 
Participants: 
A total of 162 CBCT scans of mandibular permanent premolars and molars 
belonging to Egyptian individuals are selected according to the following: 
Inclusion criteria: 
 First and second mandibular permanent premolars and molars of Egyptian 
patients starting from 18 years, males or females. 
 Intact roots without fractures or cracks. 
 Posterior teeth are present and their adjacent and opposing teeth. 
 Absence of radiological evidence of dental malocclusion that could have 
altered the position of premolars or molars. 
 CBCT scans of mandibular first and second premolars and molars using     20 
x 10 cm FOV, 0.4mm voxel resolution. 
 

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Exclusion criteria: 
 Evidence of apicectomy or periapical surgery. 
 Odontogenic or non-odontogenic pathology. 
 Congenital deformity of the mandible.  
 External Root resorption. 
 Previous history of fracture of the mandible. 
 Tomographic images of poor quality or artifacts interfering with the detection 
of mandibular canal and apical morphology of the teeth. 
Variables:  
1. The crowding and overlapping of the mandibular posterior teeth . 
2. Extraction of the adjacent or the opposing tooth may cause tilting of the tooth 
or over eruption of the opposing tooth. 
3. Attrition of the teeth may cause over eruption of the teeth. 
4. The presence of dental anamolies may influence the position of the tooth to 
the inferior alveolar canal. 
Data Sources / Measurements: 
Retrospective Data Analysis will be performed after the CBCT images are 
pooled from the computer database by convenient sampling technique. 
CBCT images will be obtained from patients who required CBCT 
examination as part of their dental examination, diagnosis or treatment planning 
without exposing them to unnecessary radiation dose for the research purpose. 
All the CBCT examinations are scanned  by Planmeca Promax 3D®, 20 x 10 
cm FOV, 0.4 mm voxel resolution, 90 kVp, 8 mA and 13.5 seconds exposure 
time. 

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To assess the shortest distance from the root apices to the border of the inferior 
alveolar canal, the multiplanar reconstruction view of the manufacturer’s software 
viewer (Planmeca Romexis) with its axial, sagittal and coronal plane will be used, 
and the cross-sectional images through the mandible will be also used. 
 Cross sectional images will be oriented parallel to the long axis of the tooth, 
then the shortest distance from the deepest point of root apices and superior border 
of the inferior alveolar canal will be obtained to be examined (Umut et al 2017). 
CBCT images will be interpreted by two oral radiologists independently; 
blinded from demographic data of the patients and from the results of each other. 
All measurements will be assessed, once by the first investigator and then 
another time two weeks later for intra-observer reliability. The second investigator 
will assess the measurements once for inter-observer reliability. 
Then inter-observational and intra-observational variability between the 
observers will be evaluated. 
Bias:  
No source of bias. 
Study Size: 
The aim of the study is to assess the relationship between the roots of 
mandibular premolars and molars and the superior border of inferior alveolar canal 
in Egyptian population. Based on the previous paper by San Chong,et al,2017,the 
prevalence of alveolar nerve 78%.Using a precision of 5, a design effect set at 1 with 
95%CI(confidence interval), a total sample size of 162 will be sufficient. The sample 
size was calculated by Epi info. 

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Sampling Strategy: The sample will be collected by convenient sampling 
technique. 
Statistical Methods: 
Data will be analyzed using IBM SPSS advanced statistics ( Statisitcal 
Package for Social Sciences), version 24 (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 percantages. Comparsions between male and 
females for normally distributed numeric variables will be done using Student’s t-
test while for non-normally distributed numeric variables will be done by Mann-
Whitney test. Comparisons between categorical variables will be performed using 
the chi square test, A p-value less than or equal to 0.05 will be considered statistically 
significant. All tests will be tailed. 
 
 
 
 
 
 
 
 

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