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Is there a justification for cone beam computed tomography for assessment of proximity of mandibular first and second molars to the inferior alveolar canal: A systematic review

December 7, 2017 / Categories: Digital Dentistry, Implant Dentistry

Khijmatgar-Shahnawaz

Khijmatgar, Shahnawaz

Chowdhury-Chitta

Chowdhury, Chitta

Rao-Kumuda

Rao, Kumuda

Thankappan-Swarnadhai-Sanal

Swarnadhai, Sanal Thankappan

Nayak-Krishna

Krishna, Nayak

The objective of this review was to determine the distance from the apices of mandibular first and second molars to the inferior alveolar canal (IAC) using cone beam computed tomography (CBCT).

Introduction

The inferior alveolar canal (IAC) runs in an S-shaped pattern in the mandible. Factors like age, race, sex and the anatomy of the mandible influence its location.

The IAC contains a nerve that, along with the inferior alveolar artery and vein, innervates the posterior teeth through the IAC before splitting into incisive and mental components that innervate the mandibular anterior teeth, lower lip and gingiva. All of these factors have clinical significance with reference to the distance from the first and second molars to the IAC, more so than the distance from the third mandibular molar. These facts are well documented with regard to the proximity of the IAC to the apices of the mandibular first molars. The inferior alveolar nerve (IAN) is the most commonly injured nerve—about 64.4% of injuries occur from trauma due to implant placement.1Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4.
While evaluating the benefits and outcomes of dental treatment, the dentist should be aware of the position of the IAN/IAC with respect to the apices of the mandibular molars.2Chong BS, Quinn A, Pawar RR, Makdissi J, Sidhu SK. The anatomical relationship between the roots of mandibular second molars and the inferior alveolar nerve.
→ Int Endod J. 2015 Jun; 48(6):549–55.

Injuries to the IAC are mostly iatrogenic.3Burstein J, Mastin C, Le B. Avoiding injury to the inferior alveolar nerve by routine use of intraoperative radiographs during implant placement.
→ J Oral Implantol. 2008 Feb;34(1):34–8.
Dental clinical procedures such as endodontics, tooth extraction, implant placement and other surgical procedures in the area of the first and second molars are the major causes of iatrogenic injury to the branches of the trigeminal nerve within the IAC.4Renton T. Prevention of iatrogenic inferior alveolar nerve injuries in relation to dental procedures.
→ Dental Update. 2010 Jul–Aug;37(6):350–2, 354–6, 358–60 passim.
In 40% of the cases, injury is due to dental implants,5Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4.
followed by 1–10% due to endodontic procedures (Fig. 1). Other types of injury to the IAN occur through mechanical trauma caused by overinstrumentation, extrusion of chemical agents such as irrigants, intracanal medicaments, root filling materials, the presence of foreign material or thermal injury during endodontic procedures.6Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4.
7Escoda-Francoli J, Canalda-Sahli C, Soler A, Figueiredo R, Gay-Escoda C. Inferior alveolar nerve damage because of overextended endodontic material: a problem of sealer cement biocompatibility?
→ J Endod. 2007 Dec;33(12):1484–9.
The consequence of injury to the nerve is postoperative paresthesia or anesthesia that may be transient or permanent. The mandibular second molar apices have been reported to be the closest to the IAN compared with the premolars and first molar8Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4.
and hence more prone to injury.

In order to interpret these problems, clinicians rely on various methods of radiographic examination. Information regarding teeth and their associated anatomy, including root canal morphology, is commonly obtained from conventional imaging modalities such as intraoral radiographs, cephalograms, dental panoramic tomograms and cone beam computed tomography (CBCT). The conventional signs of proximity of the IAN to molars include root narrowing, root deflection and bifid apices, as well as root canals that show diversion, narrowing or loss of lamina dura.9Renton T. Prevention of iatrogenic inferior alveolar nerve injuries in relation to dental procedures.
→ Dental Update. 2010 Jul–Aug;37(6):350–2, 354–6, 358–60 passim.
Hence, the newer method of 3-D imaging is considered to be the most reliable aid in assessing the relationship of roots to the IAN because of its accuracy, efficiency and effectiveness.10Escoda-Francoli J, Canalda-Sahli C, Soler A, Figueiredo R, Gay-Escoda C. Inferior alveolar nerve damage because of overextended endodontic material: a problem of sealer cement biocompatibility?
→ J Endod. 2007 Dec;33(12):1484–9.

The objective of this review was to determine the proximity of mandibular first and second molar apices to the IAC and to determine the justification of the use of CBCT of mandibular first and second molars to assess treatment outcome. The results of this review will enable clinicians to estimate the distance between the IAN/IAC and the apices of mandibular first and second molars on the basis of various published studies. The information obtained can be applied during various dental procedures to estimate the potential risk of any injury to the IAN/IAC due to varying dental procedures in the mandibular posterior areas.

Materials and methods

We used secondary data and included studies that considered mandibular first and second molar apices in determining proximity to the IAC using 3-D imaging. We did not include the studies for analysis from 2-D imaging, but considered them to determine the difference between 3-D and 2-D imaging in distances recorded.

Search methods and identification and selection of studies

We carried out a search of the literature using the PubMed, Web of Science and Scopus databases. A total of three independent searches were carried out. The study used reports of CBCT scans from 1986 to 2016 that included first and second mandibular molars and their distance to the IAC in different populations and considering age, sex and various other factors. The key terms used for extracting the relevant articles were “cone beam computed tomography” or “cbct” or “CBCT dental” or “cone beam CT dental” or “cone beam dental” and “inferior alveolar canal” or “IAN canal” or “IAN” and “lower molar” or “lower first molar” or “lower second molar” or “mandibular molar”. The process of article inclusion and exclusion was according to the PRISMA protocol (Fig. 2).

Fig. 1

Fig. 1
Prevalence of causes of inferior alveolar nerve injury.

The initial search of all three databases yielded 94 articles. Later, after reviewing the titles and abstracts, 74 articles found to be duplicates and not to meet the criteria were eliminated. Ten articles were included for full-text reading and one study was eliminated. The 3-D studies Hiremath et al.,11Hiremath H, Agarwal R, Hiremath V, Phulambrikar T. Evaluation of proximity of mandibular molars and second premolar to inferior alveolar nerve canal among central Indians: a cone-beam computed tomographic retrospective study.
→ Indian J Dent Res. 2016 May–Jun;27(3):312–6.
Kawashima et al.,12Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4
Chong et al.,13Chong BS, Quinn A, Pawar RR, Makdissi J, Sidhu SK. The anatomical relationship between the roots of mandibular second molars and the inferior alveolar nerve.
→ Int Endod J. 2015 Jun; 48(6):549–55.
Bürklein et al.,14Bürklein S, Grund C, Schäfer E. Relationship between root apices and the mandibular canal: a cone-beam computed tomographic analysis in a German population.
→ J Endod. 2015 Oct;41(10):1696–700.
Adigüzel et al.15Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8.
and Simonton et al.16Simonton JD, Azevedo B, Schindler WG, Hargreaves KM. Age- and gender-related differences in the position of the inferior alveolar nerve by using cone beam computed tomography.
→ J Endod. 2009 Jul;35(7):944–9.
were included for further data analysis. The 2-D studies Tilotta-Yasukawa et al.17Tilotta-Yasukawa F, Millot S, El Haddioui A, Bravetti P, Gaudy JF. Labiomandibular paresthesia caused by endodontic treatment: an anatomic and clinical study.
→ Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006 Oct;102(4):e47–59.
and Littner et al.11 were included for the sake of comparison. A summary of the included articles found in the search of the databases is provided in Table 1.

Data collection and analysis

The data were the year of publication, author, country of study, type of imaging modality, model of CBCT machine, technical specifi cations and the distances in millimeters measured from the apices of mandibular first and second molars to the IAC. Meta-analyses were planned only when suff icient similarities were found among the included studies with regard to the side of mandible, that is, right or left; mesial or distal root; first or second molar; male or female. Subgroup analyses were conducted for diff erent quadrants of the mandible, sex and tooth. Mean diff erences and standard deviations were used to summarize the data in the studies with continuous outcomes. Heterogeneity was assessed using the I2 statistic. A forest plot was constructed using Review Manager (Version 5.3, Nordic Cochrane Centre, Cochrane Collaboration, Copenhagen, Denmark).

Assessment of risk of bias in included studies

Based on the design and content of the selected studies, their quality was evaluated independently by two reviewers (SK and STS). The risk of bias assessment was not possible owing to nonavailability of clinical trials and the nature of the study. It was only possible to extract data from secondary data.

Results

Among 94 articles, the authors selected 9 articles, including 7studies that used a 3-D imaging modality, for further analysis. Since the review made use of secondary data, it was not possible to comment on risk of bias. The sample size ranged from 216 to 999 adults. This review identifi ed an average mean distance of 7.3 mm (range: 0.00–14.71 mm) from the apices of mandibular first and second molars to the IAC. The mean diff erence (IV, fi xed, 95% CI) on both sides of the mandible for first molars in women was 0.29 (95% CI: 0.11, 0.48) and for second molars was 0.50 (95% CI: -0.00, 1.01) compared with 0.31 (95% CI: 0.08, 0.54) for first molars in men and 0.23 (95% CI: -0.51, 0.98) for second molars. The proportion of women to men whose first or second molars were closely located to the IAC was 3 to 1. According to some studies, the distance was smaller in young individuals. The meta-analysis of the articles that had similar characteristics and data is illustrated in Figures 3 to 11.

a6fig2

Fig. 2
Schematic representation of the article selection process.

Discussion

According to the studies in Table 1, the distance of the IAN from the apices of first and second molars ranged from 0.00 to 14.71 mm. The average mean distance was found to be 7.3 mm. These findings were from both 2-D and 3-D imaging techniques (Fig. 12). The distance varied according to factors such as sex, age and race (Table 2).

Sex

Recent studies Hiremath et al. and Adigüzel et al. considered sex as one of the factors in their studies that may infl uence proximity of the IAN to the apices of first and second molars.18Hiremath H, Agarwal R, Hiremath V, Phulambrikar T. Evaluation of proximity of mandibular molars and second premolar to inferior alveolar nerve canal among central Indians: a cone-beam computed tomographic retrospective study.
→ Indian J Dent Res. 2016 May–Jun;27(3):312–6.
19Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8.
These studies found that the distance from the IAN to the apices of first and second molars was smaller in women than in men.20Hiremath H, Agarwal R, Hiremath V, Phulambrikar T. Evaluation of proximity of mandibular molars and second premolar to inferior alveolar nerve canal among central Indians: a cone-beam computed tomographic retrospective study.
→ Indian J Dent Res. 2016 May–Jun;27(3):312–6.
21Bürklein S, Grund C, Schäfer E. Relationship between root apices and the mandibular canal: a cone-beam computed tomographic analysis in a German population.
→ J Endod. 2015 Oct;41(10):1696–700.
Studying an Indian population, Hiremath et al. found that the distance of the mesial apices of first molars from the IAN was 1.46–13.2 mm in men and 0.93–8.03 mm in women, and for second molar, the average distance was 1.31–14.71 mm in men and 0.00–6.90 mm in women.22Hiremath H, Agarwal R, Hiremath V, Phulambrikar T. Evaluation of proximity of mandibular molars and second premolar to inferior alveolar nerve canal among central Indians: a cone-beam computed tomographic retrospective study.
→ Indian J Dent Res. 2016 May–Jun;27(3):312–6.
A study by Adigüzel et al. on a Turkish population found that the distance from the IAN to first molars in men was 5.1 mm mesially and 4.8 mm distally and for women was 4.4 mm mesially and approximately 4.1 mm distally.23Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8
The difference in distance between men and women may be due to men generally having a larger bone structure and consequently a greater distance between apices and first and second molars.24Bürklein S, Grund C, Schäfer E. Relationship between root apices and the mandibular canal: a cone-beam computed tomographic analysis in a German population.
→ J Endod. 2015 Oct;41(10):1696–700.
Hence, clinically, there will be a greater possibility of iatrogenic nerve damage in women compared with men.25Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4.

Age

Bürklein et al. and Adigüzel et al. considered age also as a factor in their studies to determine proximity of the IAN to the apices of first, second and third molars.26Bürklein S, Grund C, Schäfer E. Relationship between root apices and the mandibular canal: a cone-beam computed tomographic analysis in a German population.
→ J Endod. 2015 Oct;41(10):1696–700.
27Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8.
In a study conducted on a German population, Bürklein et al. sought to determine the proximity of the IAN to the apices of mandibular first and second molars.28Bürklein S, Grund C, Schäfer E. Relationship between root apices and the mandibular canal: a cone-beam computed tomographic analysis in a German population.
→ J Endod. 2015 Oct;41(10):1696–700.
They found that the distance from the IAN to the mandibular first, second and third molars was smaller in patients younger than 35 years when compared with older age groups. Adigüzel et al. concluded that the distance was smaller in the groups aged 16–25 years and 56–65 years compared with other age groups.29Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8.
Previous studies have confirmed that the distance between the apices and the mandibular canal increased with eruption of mandibular teeth.30Littner MM, Kaffe I, Tamse A, Dicapua P. Relationship between the apices of the lower molars and mandibular canal— a radiographic study.
→ Oral Surg Oral Med Oral Pathol. 1986 Nov;62(5):595–602.
Kawashima et al. showed that there was increased bone growth after eruption of teeth and/or inferior migration of the IAC with age in both sexes.31Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4.

Table 1

Table 1
Summary of the articles that were included in the review.

Fig. 3

Fig. 3
Forest plot for the comparison of the distance of the inferior alveolar canal from the apices of first molars in men.

Fig. 4

Fig. 4
Forest plot for the comparison of the distance from the apices of first molars in women.

Fig. 5

Fig. 5
Forest plot for the comparison of the distance of the inferior alveolar canal from the apices of left first molars in men and women.

Fig. 6

Fig. 6
Forest plot for the comparison of the distance of the inferior alveolar canal from the apices of right first molars in men and women.

Fig. 7

Fig. 7
Forest plot for the comparison of the distance of the inferior alveolar canal from the apices of second molars in men.

Fig. 8

Fig. 8
Forest plot for the comparison of the distance of the inferior alveolar canal from the apices of second molars in women.

Fig. 9

Fig. 9
Forest plot for right and left side.

Fig. 10

Fig. 10
Forest plot for second molar distal root.

Fig. 11

Fig. 11
Forest plot for comparison of differences in the distance of the inferior alveolar canal from second molars in relation to sex.

Fig. 12

Fig. 12
Schematic representation of differences in distance estimated with the respective 2-D and 3-D imaging modality.

Race

Levine studied an American population and found that white patients on average had a lower distance between the buccal aspect of the canal and the outer buccal and superior cortical plates of the mandible.32Levine MH, Goddard AL, Dodson TB. Inferior alveolar nerve canal position: a clinical and radiographic study.
→ J Oral Maxillofac Surg. 2007 Mar;65(3):470–4.
They concluded that, in order to minimize the risk of IAN injury, these variables should be considered when planning mandibular osteotomies or using monocortical plates.

Hiremath et al. found that the distance from the IAN to the apices of first and second molars ranged from 0.00 to 14.71 mm in general,33Hiremath H, Agarwal R, Hiremath V, Phulambrikar T. Evaluation of proximity of mandibular molars and second premolar to inferior alveolar nerve canal among central Indians: a cone-beam computed tomographic retrospective study.
→ Indian J Dent Res. 2016 May–Jun;27(3):312–6.
and Adigüzel et al. found it to be 4.1–5.1 mm.34Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8.
Chrcanovic found the distance from the IAN to first and second molars to be less than 6 mm.35Chrcanovic BR, de Carvalho Machado V, Gjelvold B. Immediate implant placement in the posterior mandible: a cone beam computed tomography study.
→ Quintessence Int. 2016 May;47(6):505–14.
Bürklein et al. showed that the distance from the IAN to first molars to be 4.9 mm, to second molars to be 3.1 mm and to third molars to be 2.6 mm.36Bürklein S, Grund C, Schäfer E. Relationship between root apices and the mandibular canal: a cone-beam computed tomographic analysis in a German population.
→ J Endod. 2015 Oct;41(10):1696–700.
Chong et al. demonstrated that the distance between the anatomical apex and the IAN was less than 3 mm.37Chong BS, Quinn A, Pawar RR, Makdissi J, Sidhu SK. The anatomical relationship between the roots of mandibular second molars and the inferior alveolar nerve.
→ Int Endod J. 2015 Jun; 48(6):549–55.
Al-Jandan et al. showed that the horizontal distance at the level of the apex and the IAC area at the second molar was 4 mm greater than at the first molar.38Al-Jandan BA, Al-Sulaiman AA, Marei HF, Syed FA, Almana M. Thickness of buccal bone in the mandible and its clinical significance in mono-cortical screws placement. A CBCT analysis.
→ Int J Oral Maxillofac Surg. 2013 Jan;42(1):77–81.
Alves et al. found that the distance of second and third molars from the mandibular canal was less than 1 mm.39Alves FR, Coutinho MS, Gonçalves LS. Endodontic-related facial paresthesia: systematic review.
→ J Can Dent Assoc. 2014;80:e13.
Littner et al. suggested that the mandibular canal was located 3.5–5.4 mm.40Littner MM, Kaffe I, Tamse A, Dicapua P. Relationship between the apices of the lower molars and mandibular canal— a radiographic study.
→ Oral Surg Oral Med Oral Pathol. 1986 Nov;62(5):595–602.
Denio et al.’s study of dry mandibles concluded that the distance from second molars to the IAN was 3.7 mm and from first molars was 6.9 mm on 2-D radiographs.41Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8.
42Sharma U, Narain S. Unusual facial pain secondary to inferior alveolar nerve compression caused by impacted mandibular second molar.
→ J Indian Soc Pedod Prev Dent. 2014 Apr–Jun;32(2):164–7.
43Umar G, Bryant C, Obisesan O, Rood JP. Correlation of the radiological predictive factors of inferior alveolar nerve injury with cone beam computed tomography findings.
→ Oral Surgery. 2010 Aug;3(3):72–82.

Basically, there are three important processes that influence the development of the craniofacial bones: size increase, remodeling and displacement. The first two processes occur simultaneously by a combination of bone resorption and displacement. The last one results in the displacement of all the bones away from each other to undergo a size increase. The remodeling and displacement processes change and vary according to age, sex and race. These changes will have impact on the location of the IAC/IAN with respect to the apices of mandibular first and second molars.

Quality of evidence

The data in the first instance were derived from secondary data and the studies used varying methodologies to estimate the distance from the apices of the mandibular first and second molars to the IAC. Hence, the results obtained should be interpreted with caution.

a6table2

Table 2
Overview of the distance between the apices of mandibular first and second molars (data considered for meta-analysis).

Agreements and disagreements between studies included in there view

Adigüzel et al. and Simonton et al. used a similar methodology in determining the distance between the apices of mandibular first and second molars and the IAC.44Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8.
45Simonton JD, Azevedo B, Schindler WG, Hargreaves KM. Age- and gender-related differences in the position of the inferior alveolar nerve by using cone beam computed tomography.
→ J Endod. 2009 Jul;35(7):944–9.
These two studies used sagittal scans and intervariability tests and considered various factors that influence IAC location with respect to first and second molars. Bürklein et al. stated the inclusion and exclusion criteria.46Bürklein S, Grund C, Schäfer E. Relationship between root apices and the mandibular canal: a cone-beam computed tomographic analysis in a German population.
→ J Endod. 2015 Oct;41(10):1696–700.
The above-mentioned studies lack a scientific approach in determining the distance and hence, this might be a source of potential bias. Chong et al. tried to follow the principle of the Pythagoras theorem to determine the distance, which is the scientific method of determining the distance between two points.47Chong BS, Quinn A, Pawar RR, Makdissi J, Sidhu SK. The anatomical relationship between the roots of mandibular second molars and the inferior alveolar nerve.
→ Int Endod J. 2015 Jun; 48(6):549–55.
The investigators should have considered an interobserver reliability between two dental radiologists. The study should also have considered sex and age as factors in determining the distance.

Conclusion

We can conclude that the average mean distance between the IAC and the apices of mandibular molars is approximately 7.3 mm. In addition to this, certain factors, such as age, sex, race, position of tooth and bone thickness, play a key role in determining the distance between the IAC and the apex. The values found are mean values and the clinical decision should be made on a caseby- case basis and the type of imaging modality used. There is significant application of CBCT in clinical outcome while treatment planning in the first and second mandibular molar region.

Acknowledgment

We would like to thank Drs. Namitha Thomas, Natasha Shetty and Neethu for their initial participation in the review.

Competing interests

The authors declare that they have no conflict of interest regarding the materials used in the present study. No funding was given to conduct this review.

Interview

with Shahnawaz Khijmatgar

Why did you conduct the research reported on in this paper?

The prevalence of inferior alveolar canal (IAC) injury due to implant placement in the first and second mandibular molar region is 40%. Similarly, 10% of these injuries are due to endodontic procedures and 2.5% to extractions. These problems are due to insufficient information being available to clinicians regarding the approximate distance from the apices of the first and second mandibular molars to the IAC. Hence, clinicians tend to overinstrument, causing damage to the IAC. Therefore, there was a need for evidence in the form of a systematic review and meta-analysis that addresses the gap in the knowledge available.

For what reasons could others cite your paper?

There are no recent systematic reviews or meta-analyses available that aimed at determining the approximate distance between the apices of the first and second mandibular molars to the IAC. Since, this specific review critically analyzed all of the published articles that aimed at determining the distance between the apices of the first and second mandibular molars to the IAC, it gives an overview regarding the approximate distance, flaws in the methods, recommendations for future research required and the importance of CBCT in the outcome as compared with 2-D. It will provide a road map for clinicians and researchers to conduct further studies and research that can easily be translated into clinical practice.

How could your study’s findings have an impact on dentistry?

Since 40% of IAC injuries are due to implant placement, followed by 10% due to endodontic procedures by the clinicians, use of CBCT during treatment planning in the region of the first and second mandibular molars could avoid injury to the IAC. It helps clinicians to make informed decisions and improve patients’ clinical outcomes.

What is the relevance of your study’s findings to the daily practice of a dentist?

Our review results show that the distance varies between sex and age. Future studies should consider uniform age ranges to confirm that age can influence the distance between the IAC and the tooth apices. There was no significant difference between the right and left sides of the mandible. Clinicians can use this information to make informed decisions during treatment planning and when choosing the mode of imaging, that is, 2-D or 3-D.

What are your recommendations for further investigation of the topic of your article?

Future research should be conducted using secondary data of CBCT scans by using the most scientific way of determining the distance between 2 points and employing uniform factors and methods. This will enable the generation of conclusive evidence and hence translate into clinical practice with ease.

References   [ + ]

1, 5, 6, 8, 25, 31. Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4.
2, 13, 37, 47. Chong BS, Quinn A, Pawar RR, Makdissi J, Sidhu SK. The anatomical relationship between the roots of mandibular second molars and the inferior alveolar nerve.
→ Int Endod J. 2015 Jun; 48(6):549–55.
3. Burstein J, Mastin C, Le B. Avoiding injury to the inferior alveolar nerve by routine use of intraoperative radiographs during implant placement.
→ J Oral Implantol. 2008 Feb;34(1):34–8.
4, 9. Renton T. Prevention of iatrogenic inferior alveolar nerve injuries in relation to dental procedures.
→ Dental Update. 2010 Jul–Aug;37(6):350–2, 354–6, 358–60 passim.
7, 10. Escoda-Francoli J, Canalda-Sahli C, Soler A, Figueiredo R, Gay-Escoda C. Inferior alveolar nerve damage because of overextended endodontic material: a problem of sealer cement biocompatibility?
→ J Endod. 2007 Dec;33(12):1484–9.
11, 18, 20, 22, 33. Hiremath H, Agarwal R, Hiremath V, Phulambrikar T. Evaluation of proximity of mandibular molars and second premolar to inferior alveolar nerve canal among central Indians: a cone-beam computed tomographic retrospective study.
→ Indian J Dent Res. 2016 May–Jun;27(3):312–6.
12. Kawashima Y, Sakai O, Shosho D, Kaneda T, Gohel A. Proximity of the mandibular canal to teeth and cortical bone.
→ J Endod. 2016 Feb 29;42(2):221–4
14, 21, 24, 26, 28, 36, 46. Bürklein S, Grund C, Schäfer E. Relationship between root apices and the mandibular canal: a cone-beam computed tomographic analysis in a German population.
→ J Endod. 2015 Oct;41(10):1696–700.
15, 19, 27, 29, 34, 41, 44. Adigüzel Ö, Yiğit-Özer S, Kaya S, Akkuş Z. Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.
→ Med Oral Patol Oral Cir Bucal. 2012 Nov 1;17(6):e1103–8.
16, 45. Simonton JD, Azevedo B, Schindler WG, Hargreaves KM. Age- and gender-related differences in the position of the inferior alveolar nerve by using cone beam computed tomography.
→ J Endod. 2009 Jul;35(7):944–9.
17. Tilotta-Yasukawa F, Millot S, El Haddioui A, Bravetti P, Gaudy JF. Labiomandibular paresthesia caused by endodontic treatment: an anatomic and clinical study.
→ Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006 Oct;102(4):e47–59.
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