Research

The Role Of Monitors In The Visualization And Assessment Of The Inferior Alveolar Canal

Sindhura Anamali,B.D.S, M.S, Assistant Professor, The University of Iowa College of Dentistry
sindhura-anamali@uiowa.edu   phone: 319-335-9656   fax: 319-335-7351
Contribution: Conception of the idea of the work, analysis and interpretation of the data, evaluator, revising and editing drafts, and approving final manuscript..
Joshua J Orgill,DDS, Oral and Maxillofacial Radiology Resident, The University of Iowa College of Dentistry
joshua-orgill@uiowa.edu  
Contribution: Evaluator, analysis, and interpretation of the data; drafting, editing and approving final manuscript..
Suvendra Vijayan,BDS, MS, MPH, Assistant Professor, University of Pittsburgh School of Dental Medicine
suvendrav@gmail.com   phone: 319-335-9656   fax: 319-335-7351
Contribution: Data collection, organizing study, design, analysis, verification of data analysis, drafting, editing, and approval of final draft..
Veeratrishul Allareddy,BDS, MS, Professor, The University of Iowa College of Dentistry
veeratrishul-allareddy@uiowa.edu   phone: 319-335-9656   fax: 319-335-7351
Contribution: Evaluator and design of the work, acquisition, analysis, and interpretation of the data. Drafting, revising, editing, and approval of final draft..

Address for correspondence

Joshua J Orgill, DDS
Email : joshua-orgill@uiowa.edu
Address : The University of Iowa College of Dentistry 801 Newton Road Iowa City, IA 52242-1010

Published on : 24 Jan 2019

INTRODUCTION:

The inferior alveolar nerve and its canal are familiar landmarks of the mandible for dentists and plays an important role in nearly all aspects of dentistry from locating the mandibular foramen for a mandibular block to tracing the pathway of the canal through the body of the mandible at the time of extraction of mandibular third molars or prior to placing implants in the posterior regions of the mandible.

Clear visualization of the inferior alveolar canal and its relationship with developing or impacted mandibular third molars is especially important for the surgical planning of third molar extractions. The risk of injury to the inferior alveolar nerve during extraction of third molars is a major concern and has been reported as being the most common reason for damage to this nerve [1] . Once damage and altered sensation occurs, reports have shown that 35% to 40% of those patients will continue to experience altered sensation for 2 years or more [2, 3] .

Prior to Cone Beam Computed Tomography (CBCT) use in dentistry, dentists and oral surgeons relied upon the two-dimensional panoramic images along with selected periapicals. Though used for many years, there are shortcomings of the two dimensional imaging in identifying the true relationship between the inferior alveolar canal and the roots of the mandibular third molars [4] . CBCT has the ability to provide a 3-dimensional image for evaluation of this relationship [5] . A study conducted by Matzen et. al. showed the clinical importance of having the information provided by CBCT. They showed that 12% of 3 rd molar extraction treatment plans changed from the original treatment plan established with a pantomograph after evaluating the same case with CBCT [6] . These studies, and other similar ones have shown, CBCT as an important aid to the surgeon in pre-surgery planning and for optimizing the success while minimizing complications during and after surgery. For example, when an intimate relationship between the roots of the third molars and the nerve is observed the surgeon may decide to perform a coronectomy rather than extraction as this treatment has been shown to be particularly successful in such situations [7, 8] .

The benefits and uses of CBCT in this and other clinical scenarios continue to be studied, such as the study done by Nakayama et. al. which assessed the ability of CBCT to predict the exposure and injury of the inferior alveolar canal and showed that there may be some validity. [9] These and other studies are important to further refine the pre-treatment and in-treatment process for even better patient care.

We have found that there are no studies at this time which show if the quality of the monitor has any effect on assessing the accuracy of the impacted third molar-nerve relationship. Many studies have already looked at the ability to visualize caries [10-12] , detection of anatomical and pathological structures on consumer, tablet and medical grade displays [13-16] . The aim of this study is to determine if there is a difference in the ability to appropriately assess the third molar- canal relationship between three different monitor types.

MATERIALS AND METHODS:

The CBCT scans were retrieved from archived cases in the University of Iowa College of Dentistry and Dental Clinics Oral and Maxillofacial Radiology department. The cases were received between 2015 and 2017. Out of the 4719 cases, a search was conducted to determine eligible cases. The search was conducted for unique term within reports that were evaluating inferior alveolar canals. A total of 493 cases were collected out of which 186 cases were deemed eligible for this research study as these were the cases where the teeth were impacted and an evaluation of the inferior alveolar canal in relation to the impacted tooth was assessed. IRB approval was obtained prior to the selection of the cases

The reports and the corresponding datasets were collected. The gold standard for the position of the canal was established by the two board certified oral and maxillofacial radiologists (VA and SA) and one oral and maxillofacial radiology resident (JO) looking at the datasets after the evaluation was completed and reaching a consensus on the location of the canal. A list of random numbers were generated in Excel 2016 using the RANDBETWEEN function. The list was copied and pasted as values to a new column and sorted from smallest to largest. Using the conditional formatting function, duplicate records were found and eliminated. The new list was used to allot random filenames to the datasets and corresponding report. A master key file was created by an oral and maxillofacial radiology resident who was not an observer. Patients’ age and sex was also entered in the master file. All data entered in master file was verified by a board certified oral and maxillofacial radiologist (SA).

The monitors were evaluated in a dimly lit area. The luminance and ambient light were measured using a light meter. All three monitors were placed in the same position for the evaluators and were adjusted such that the luminance was the same.

Two evaluators, one board certified oral and maxillofacial radiologist (VA) and one oral and maxillofacial radiology resident (JO) evaluated the cases. Six cases were randomly selected for calibrating the two evaluators. Another 105 cases were randomly selected from the initial database for conducting the research. All cases were randomized and anonymized. The evaluators were masked to the type of cases being evaluated and were also masked on the age and sex of the patients. The datasets were all anonymized with a single date of birth and no sex assigned at the time of anonymization. The two evaluators evaluated all the cases on three different monitors, a BARCO Nio Color 3MP DE medical grade monitor, a BARCO Nio Color 2MP DE monitor (a prototype at the time of the study), and a DELL UltraSharp 2MP monitor. The monitors when used for the study were connected to the same display graphics card in the same display port to keep other factors similar. The computer was restarted prior to evaluation of the datasets for each type of display and all the local cache was cleared to make sure the speed of the computer was not compromised and consistent for all the evaluations across all the monitors. The datasets were all placed in one folder and the computer was configured to open the datasets default in invivo (Anatomage, CA) software 5.4 version. The evaluators took 5 minutes break for every 30 minutes of evaluation. Each monitor was evaluated on a separate day to avoid fatigue. The observers noted the number of cases completed in 30 minutes and their fatigue levels. The fatigue levels were completely subjective. Fatigue levels were ranked for 1 to 10 where 1 was least fatigue and 10 was most fatigued.

The position of the inferior alveolar nerve canal (IAN) was evaluated and coded (see Table 1). A spreadsheet with prepopulated random case names was prepared by VS. The IAN was evaluated and based on location was categorized to be located into one of the following positions 1.facial, 2.lingual, 3.inferior, 4.in between, 5.facial inferior, and 6.lingual inferior.

STATISTICAL ANALYSIS:

As a measure for diagnostic accuracy the percentage of correct answers reached on the different displays was calculated. The percentage correct for both observers was calculated for each monitor by comparing the indicated location of the canal with the actual location. For each observer Cochran Q tests (α = 5%) were performed to statistically compare the correctness of the answers on the different displays. Tests were also were also split up per gender (male / female) and age category (under and over 21 years old) of the selected subjects. The interrater reliability or extent of agreement among both observers for each monitor was determined by calculating percentage of agreement and by means of Cohen’s kappa statistics.

RESULTS:

Interrater reliability

The percentage of agreement in answers among the two observers has been calculated per monitor and the results are displayed in Table 1. The Barco medical 3MP monitor scores best for this measure of interrater reliability with a percent agreement of 87%. Cohen’s kappa statistics were also performed on the data to take into account that the observers could have guessed when the location was not clear. The Barco 3MP medical monitor shows a strong level of agreement by means of this measure with a Kappa value of 0.83 (see Table 2).

Accuracy

The reached accuracy for indicating the actual location of the inferior alveolar nerve canal has been calculated as the number of correct answers given when working on each of the monitors. Overall results for both observers can be found in Figure 1. The accuracy of the Barco medical 3MP is respectively 11.9% and 8.3% higher than the consumer display for observer A and observer J. These results are statistically significant. An average increase in accuracy of 10.1% was thus reached by use of the Barco medical 3MP display compared to the consumer display. For observer A, a statistically significant higher accuracy (7.2%) was also obtained for the Barco medical 3MP in comparison with the medical 2MP. No other statistically significant results were evident, but the overall numbers though not statistically significant clearly showed that the medical grade displays had better accuracy levels when compared to the consumer grade displays.

The difference in accuracy between the Barco medical 3MP and the other displays is more pronounced in males than in females with an average increase of 13.1% and 11.9% compared with respectively the consumer and the medical 2MP monitor. The results are statistically significant for both observers. The reached accuracy for the female cases is overall also higher for the medical 3MP monitor and for one of the observers the result is even significant in comparison with the consumer display (see Figure 2).

The data has further been divided in the age categories: 11 till 21 and over 21 years old. Results are presented in Figure 3. For the last category the medical 3MP ensured a higher accuracy than the consumer monitor with statistically significant results for both observers. An average accuracy increase of 10.9% was reached. The accuracy reached with the medical 3MP for the 11 till 21 age category was only significantly better than both other monitors for observer A.

DISCUSSION:

Radiographic examination initially panoramic and intraoral radiography if necessary are often staples in localization of the inferior alveolar canal prior to extraction of impacted mandibular third molars. The ability to accurately visualize the inferior alveolar canal is arduous and when in close proximity to the roots of an impacted third molar is often inconclusive on traditional panoramic radiographs supplemented with intra oral radiographs, in such cases CBCT is an invaluable tool in determining the relationship of the inferior alveolar canal and localizing how the canal and its contents are in relation to the roots of the impacted mandibular third molars. In this study, we found that location of the inferior alveolar canal can be well visualized and with a higher degree of accuracy on Medical grade displays (3MP) monitor compared to a consumer display. With the 2MP monitor, though it showed a higher degree of accuracy compared with a consumer grade monitor, the results were not statistically significant. These results are similar to other studies evaluating the efficacy of medical grade monitors and how they compared to tablets and consumer grade monitors [12, 17-20] for the consumer grade and 2MP monitors but was statistically significant for the 3MP medical grade display. The accuracy and intraobserver reliability and interobserver reliability was significantly higher for the 3MP monitor compared to the 2MP and consumer grade monitors especially in males compared to females. The 3MP monitor showed a markedly better accuracy and a statistically significant difference especially in individuals older than 21 years while for those individuals who were 21 years or younger only one observer visualized statistically significant difference in accuracy on the 3MP monitor compared to the 2MP and consumer grade displays.

Table 3 summarizes that from the observers’ perspective it was felt that more information was available for viewing on the medical grade displays compared to the consumer display and the fatigue levels were higher while using the consumer grade display. Additionally the amount of time spent on cases on different displays was not statistically significant and there was a variance in times between the observers. It was clear that the observer who first used the medical grade display (3MP followed by 2MP followed by the consumer display) spent less time as he had become used to on what display parameters to use to exactly visualize the canals, the reverse order was true with the other observer who used the consumer display first, followed by the 2MP monitor followed by the 3MP monitor.

This study is unique in that this is the first of its kind which studies the efficacy of medical grade displays using CBCT scans and in particular the inferior alveolar canal and how it relates to the roots of the mandibular impacted third molars. All the other studies were on conventional intraoral and extraoral radiographs. Most of the other studies evaluating dental disease and landmarks also did not comment on fatigue levels by users while evaluating images on different types of displays.

Medical grade displays are often not used by dentists for evaluation of radiographs mostly due to the cost factor involved in purchasing a display, while this was true in the past with the awareness of multiple display manufacturing companies significantly more at this time this cost factor has dramatically reduced and the displays are more affordable. To date, a new consumer grade monitor can be purchased from $100 to over $2,500 depending on the brand, manufacturer and several other factors including monitor size, pixel size, brightness, etc,. The current price for medical grade displays varies from $850 to over $36,000; which also depends on the brand, manufacturer and other factors. The cost of medical grade displays now has some overlap with the higher end consumer grade monitors. This, coupled with the factor that critical landmarks like the inferior alveolar canal can be visualized with a greater degree of accuracy on such displays, the status quo is expected to change with publication of more studies which potentially could show the benefits of using medical grade displays in optimal conditions.

References

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Table 1

Summary of the location of the inferior alveolar canal in the subjects

Table 2

Percent agreement amongst both observers and Cohen's kappa values (with confidence intervals of 95%) as measures of interrater reliability for each monitor.

Figure 1

Overall percentages correct calculated for each monitor per observer. Differences on the 5% significance level compared to the consumer display are indicated with stars (*), while those compared to the medical 2MP display are highlighted with circles (°).

Figure 2

Percentages correct calculated per gender (male / female) for each monitor and each observer (A and J). Differences on the 5% significance level compared to the consumer display are indicated with stars (*), while those compared to the medical 2MP display are highlighted with circles (°).

Figure 3

Percentages correct calculated per age category (under and over 21 years old) for each monitor and each observer (A and J). Differences on the 5% significance level compared to the consumer display are indicated with stars (*), while those compared to the medical 2MP display are highlighted with circles (°).

Table 3

Summary of Cases evaluated by two observers on different monitors including time and fatigue levels

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