|Year : 2021 | Volume
| Issue : 6 | Page : 601-609
Measurements of mandibular radiomorphometric indices in Egyptian population at different ages using cone beam computed tomography: A cross-sectional study
Hanaa S Mansy, Reham M Hamdy, Sahar H El Dessouky, Yara R Helaly
Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Cairo University, Cairo, Egypt
|Date of Submission||14-Aug-2021|
|Date of Decision||08-Oct-2021|
|Date of Acceptance||11-Oct-2021|
|Date of Web Publication||30-Nov-2021|
Dr. Hanaa S Mansy
Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Cairo University, 11 Saraya Street, El Manial, Cairo.
Source of Support: None, Conflict of Interest: None
Aim: This research was conducted to correlate the mandibular radiomophometric indices with age in a sample of Egyptian population using cone beam computed tomography (CBCT). Materials and Methods: A total number of 318 CBCT scans of the Egyptian population were assigned to six age groups (53 per group) in a cross-sectional study using the simple random sampling method. Mandibular radiomophometric indices were assessed for each side and for each age group. Four quantitative indices were measured. The quantitative indices were mental index (MI), panoramic mandibular index superior (PMIS), panoramic mandibular index inferior (PMII), and panoramic mandibular index average (PMIA), which were measured on the CBCT cross-sectional cuts. Post hoc pairwise comparisons between the groups and both sides were done. Association and correlation between the indices and age were done. Results: There was a positive weak correlation between the indices and age. There was a statistically significant difference between panoramic mandibular indices. Conclusions: Age affects the mandibular radiomophometric indices. The mental index and panoramic mandibular indices increase with age.
Keywords: Age, Estimation, Index, Mandible, Mental Foramen
|How to cite this article:|
Mansy HS, Hamdy RM, El Dessouky SH, Helaly YR. Measurements of mandibular radiomorphometric indices in Egyptian population at different ages using cone beam computed tomography: A cross-sectional study. J Int Oral Health 2021;13:601-9
|How to cite this URL:|
Mansy HS, Hamdy RM, El Dessouky SH, Helaly YR. Measurements of mandibular radiomorphometric indices in Egyptian population at different ages using cone beam computed tomography: A cross-sectional study. J Int Oral Health [serial online] 2021 [cited 2022 Jan 26];13:601-9. Available from: https://www.jioh.org/text.asp?2021/13/6/601/331604
| Introduction|| |
Bone remodeling is a continuous process affecting one of the hardest tissues in the body throughout life. This turnover ensures the continuous replacement of old bone tissue, which affects bone adaptation to various mechanical forces exerted on the skeleton. In the course of life, the mandible undergoes morphological and dimensional changes. Mandibular stimuli are present from the development stage to adulthood and can change the growth of the mandible, along with its bone remodeling. The mandible is subjected to remodeling and morphological changes in several of its parts, such as the gonial, antegonial, condylar, and ramus regions.
Panoramic radiographs were used for several years to assess the mandibular age-related changes through linear and angular measurements. There are panoramic radiomorphometric indices measured on the two-dimensional (2D) panoramic radiograph, with its limitation. These indices were used to assess the thickness and shape of the inferior border (IB) of the mandible, such as: mental index (MI), panoramic mandibular index (PMI), gonial index (GI), antigonial index (AI), and mandibular cortical index (MCI). Several studies assessed the role of these indices in the detection of patients with osteoporosis.,
With the advancement of the three-dimensional (3D) imaging modalities, CBCT was used for forensic purposes, such as age and sex estimation. Research was conducted on CBCT for forensic purposes that were focused on the dimensional changes on the ramus and condyle. There were limited studies conducted to assess the effect of age on the mandibular radiomorphometric indices regarding the IB of the mandible., Also, there were limited studies that assessed these indices using CBCT images with its advantages over the panoramic radiograph.,,
There was a controversy in the literature on the effect of age and its correlation with the mandibular radiomorphometric indices. A study conducted by Goyushov et al. reported that the mandibular indices increase with age. However, studies conducted by Yüzügüllü et al., Bozdag and Sener, and Sghaireen et al. reported a decrease in indice values with age. With different populations and different age groups, the results were deceiving and the answer of the effect of age on these indices is still unclear. The aim of the current study was to correlate the mandibular indices with age in a sample of Egyptian population using CBCT assuming the null hypothesis that there is no correlation between age and the aforementioned indices.
| Materials and Methods|| |
A cross-sectional study was performed on 318 CBCT scans of Egyptian patients seeking dental treatment obtained from the Oral and Maxillofacial Radiology Department, Faculty of Dentistry, Cairo University, Egypt.
Sample size calculation
In their study, Mostafa et al. (2011) divided their study population into six age groups with the maximum difference between the six age groups being (0.3714–0.3293) = 0.0422 and standard deviation (SD) = 0.069. Assuming the α error 0.05 and the power 80%, the required sample size was a total of 318 cases (53 per group). The sample size calculation was approved by the Medical Biostatistics Unit, Faculty of Dentistry, Cairo University on October 22, 2018.
Sampling and addressing potential sources of bias
- -The sample was collected prospectively and assessed from November 2018 to January 2021.
- -3000 CBCT scans were explored and filtered to 750 scans based on the inclusion and exclusion criteria for sampling and randomization. Using the simple random sampling method, 318 scans were coded and recruited in the study.
- -The key of coding was done by one of the authors (SHD) and concealed from the two observers who assessed and did measurements.
- -Also, the age, name, and gender of all scans were concealed from the observers by one of the authors (SHD) prior to the interpretation of scans.
Inclusion criteria of the participants’ CBCT scans
Medically free Egyptian females and males with an age range of 10–70 years were included in the study.
Exclusion criteria of the participants’ CBCT scans
The CBCT scans for individuals with any evident radiographic abnormality suggestive of systemic disease predisposing to osteoporosis were excluded. The mandibular areas intended for measurements with a large pathological lesion, bone asymmetry, deformity, surgical defect healing, fracture, mandibular reconstruction, and severely resorbed mandibular alveolar bone were also excluded from the study.
Data sources and management
The following data were collected from the included participants:
- A.Clinical data
- Individual’s demographic data: Name, Age, and Sex.
- Individual’s medical history, including any systemic condition that can possibly affect the bone.
- B.Radiographic data
Radiographic examination was performed at the Oral and Maxillofacial Radiology Department, Faculty of Dentistry, Cairo University, Egypt.
The CBCT Planmeca Promax 3D MID (Proface) machine (Asentajankatu, Helsinki, Finland) was used to scan the mandibles of the patients using 90 kVp, 10 mA, 14 s, and 200 × 60 mm field of view with a 0.2 or 0.4 mm voxel size.
The scans of the study population were prospectively collected and then allocated into equal six age groups following the age grouping of Mostafa et al. and Moradi et al.:
Group 1: 10–19 years.
Group 2: 20–29 years.
Group 3: 30–39 years.
Group 4: 40–49 years.
Group 5: 50–59 years.
Group 6: 60–70 years.
- A.Four mandibular radiomorphometric indices were assessed by the cross-sectional images;
- Mental index.
- Panoramic mandibular indices (panoramic mandibular index superior [PMIS], panoramic mandibular index inferior [PMII], and panoramic mandibular index average [PMIA]).
- B.These indices were assessed on the right and left sides for each scan to find whether there is a significant difference between both sides or not.
- C.All measured indices were assessed to find whether there is an association with sex or not.
For standardization and reproducibility of the MI and PMI linear measurements, the following steps were taken:
- -The volume was first viewed in the explorer module to ensure that the participant was indicated for enrollment in this study.
- -The implant module was selected for measuring the MI and PMIs.
- -The axial cut was selected for drawing the panoramic curve.
- -The thickness of reformatted panoramic image was selected to accommodate the mandibular width with an average thickness of 20–25 mm.
- -The cross-sectional cuts were selected to be 1 mm in thickness.
- -The distance between consecutive cross-sectional cuts was selected to be 1 mm.
- -The three cross-sectional cuts in the middle of the mental foramen (MF) were selected subjectively.
- -The cut of the largest height of the mental foramen was selected for the measurements.
- -To facilitate and standardize the linear measurements, the square tool for area measurement was selected.
- -All indices were measured for both sides (right and left) of each individual.
Measurement of the indices
For measurements of MI, a square was drawn between the most convex point on upper and lower margins of the inferior border of the mandible, with the distance between them representing the height of the square [Figure 1]A.
|Figure 1: A cross-sectional image showing the measurement of: (A) MI, (B) PMIS, (C) PMII, and (D) PMIA|
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Panoramic mandibular index
The PMI was calculated as the ratio between two distances in three different ways[13 as follows:
- -PMIS: A ratio between the MI and the height of a square drawn between the superior margin of the mental foramen and the inferior mandibular cortex [Figure 1B].
- -PMII: A ratio between the MI and the height of a square drawn between the inferior margin of the mental foramen and the inferior mandibular cortex [Figure 1C].
- -PMIA: A ratio between the MI and the average of heights of both squares [Figure 1D].
Measurements and observers’ calibration
- -For calibration of the observers’ measurements, 30 randomly selected CBCT images were interpreted independently by two observers (HSM and RMH) with experience ranging from 10 to 20 years in the field of Oral and Maxillofacial Radiology.
- -Each observer evaluated the images separately twice, with a period of two weeks between the two reading sessions.
- -The two observers were blinded from the results of each other. Then, interobservational and intraobservational variability between the observers was evaluated.
- -After the agreement between the two observers’ readings, the whole sample was measured and assessed by both of them.
Numerical data were presented as mean and SD values and were explored for normality and variance homogeneity using Shapiro–Wilk and Levene’s tests. Data showed parametric distribution and variance homogeneity, so they were analyzed using one-way analysis of variance followed by Tukey’s post hoc test. Inter- and intraobserver reliability was analyzed using intraclass correlation coefficient (ICC). Correlations between age and different numeric indices were analyzed using Spearman’s rank order correlation coefficient. The significance level was set at P ≤ 0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.0.3 for Windows (R Core Team (2021). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. (URL https://www.R-project.org/).
| Results|| |
The study population included 118 (37.1%) males and 200 (62.9%) females. There was no significant difference between the values measured on the right and left sides (P > 0.05), and there was an excellent inter- and intrarater agreement between different observations (ICC = 0.925).
Descriptive statistics for numerical indices (mm) are presented in [Table 1].
Comparison between panoramic mandibular indices
There was a significant difference between values of different panoramic mandibular indices (P < 0.001). The highest value was found in PMII, followed by PMIA whereas the lowest value was found in PMIS [Table 2] and [Table 3]. Post hoc pairwise comparisons showed the values of different indices to be significantly different from each other (P < 0.001).
|Table 2: Intergroup comparison of different panoramic mandibular indices (mm)|
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|Table 3: Pairwise comparisons of different panoramic mandibular indices (mm)|
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Association with age
Mean and SD values for the numerical indices (mm) in different age groups are presented in [Table 4] and [Table 5].
|Table 4: Intergroup comparisons of numerical indices (mm) in different age groups|
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|Table 5: Pairwise comparisons of numerical indices (mm) in different age groups|
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MI: There was a significant difference between the values of different age groups (P < 0.001). The highest value was found in the 60–70 age group, whereas the lowest value was found in the 10–19 age group. Post hoc pairwise comparisons showed the value of the 10–19 age group to be significantly lower than that of the 40–70 age group (P < 0.001).
PMIS: There was a significant difference between the values of different age groups (P < 0.001). The highest value was found in the 50–59 age group, whereas the lowest was found in the 10–19 age group. Post hoc pairwise comparisons showed the value of the 10–19 age group to be significantly lower than that of the 20–70 age group (P < 0.001).
PMII: There was a significant difference between the values of different age groups (P < 0.001). The highest value was found in the 50–59 age group, whereas the lowest was found in the 10–19 age group. Post hoc pairwise comparisons showed the value of the 10–19 age group to be significantly lower than that of the 50–70 age group (P < 0.001).
PMIA: There was a significant difference between the values of different age groups (P < 0.001). The highest value was found in the 50–59 age group, whereas the lowest was found in the 10–19 age group. Post hoc pairwise comparisons showed the value of the 10–19 age group to be significantly lower than that of the 50–59 age group (P < 0.001).
Correlation with age
There was a significant positive weak correlation between age and different indices (P < 0.001) [Table 6].
Association with sex
Mean and SD values for the numerical indices (mm) in both sexes are presented in [Table 7].
|Table 7: Mean ± standard deviation (SD) of numerical indices (mm) in both sexes|
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MI:There was no significant difference between the values of different sexes (P = 0.491).
PMIA:The value of females was significantly higher than that of males (P = 0.007).
PMII:The value of females was significantly higher than that of males (P = 0.040).
PMIS:The value of females was significantly higher than that of males (P = 0.007).
| Discussion|| |
The current observational cross-sectional study aimed at assessing the correlation between the mandibular radiomorphometric indices (MI, PMII, PMIS, and PMIA) and different ages in the Egyptian population. The sample comprised 318 CBCT scans of Egyptian individuals grouped into six age groups (53 individuals per group). The indices of the right and left sides were assessed to find whether there was a significant difference between both sides or not.
The CBCT offers a 3D examination of the object and allows sub-millimetric measurements owing to its isotropic voxel with equal dimensions, thus providing accurate linear, angular, and volumetric measurements. Several studies in a systematic review conducted by Fokas et al. assessed the accuracy of CBCT in linear and angular measurements and concluded that the measurements of CBCT were highly accurate and reliable. The voxel sizes used in the current study were 0.2 or 0.4 as it was reported in the literature that there is no significant difference between the different voxel sizes in the accuracy of linear measurements by CBCT.
In the current study, the study sample was divided into six age groups: The youngest was 10–19 years old, whereas the oldest was 60–70 years old. It was found that there was a significant weak positive correlation between the numerical indices (MI, PMII, PMIS, and PMIA) and different ages. Both right and left sides were assessed and compared, with no significant difference between the values measured at both sides (P > 0.05). This result was consistent with the results of the previous studies conducted by Ledgerton et al. and Dagistan and Bilge, who reported that there was no significant difference between the right and left mandibular radiomorphometric indices assessed in their studies.
In terms of the correlation between the MI and age, the mean value of the mental index for the six groups was 4.04 mm. The highest value was found in the 60–70 age group, whereas the lowest was found in the 10–19 age group. The remaining age groups of 20–59 had close values. The current study results can be explained by the theory of Ulm et al., which indicated that the thickness of the cortical borders increases with age, especially in males. They also related the increased thickness to the functional adaptation to occlusal forces stresses on the mandible that maintains jaw stability. This theory was supported by Isman et al., who conducted their study assessing the effect of excessive occlusal forces by bruxism on the MI and reported that cortical thickening in the mental index mandible was observed. They explained that the bone thickening was a secondary response to microfracture and vascularization caused by excessive bite force with the muscle tension.
In agreement with the current study results were those of Goyushov et al., who reported that the values of MI in the 18–30 age group were lower than older ages till 71 years old and older. Their study was conducted on CBCT scans of the Turkish population. The positive correlation between MI and age in the current study was attributed to the normal bone remodeling process affected by masticatory forces and growing potential of the bone with cortical thickening to accommodate and compensate the functional forces on the jaw bone.
The study was conducted on the same population by Mostafa et al., who studied the effect of age on the MI of five age groups (20–70) using 2D panoramic radiographs. They reported in their study that there was an increase in the mean values of the MI with age up to age 49 years followed by a statistically significant decrease to 60–70 years. They clarified this decrease by the age-related mandibular bone loss that may cause general thinning and increased porosity of the mandibular cortex. They stated that the bone mineral density of the skeleton decreases after the age of 40 years and by the age of 65 years, about one-third of the bone minerals are lost. Decreased physical activity, lowered secretion of estrogen, diet, race, and heredity may all play a role in age-related bone loss in the elderly.
There were two major differences between our study and the study of Mostafa et al. The first difference is that the measurements in the current study were obtained from 3D CBCT scans whereas their measurements were taken from 2D panoramic radiographs. The second difference is that the youngest age group in the current study included participants 10–19 years old whereas their youngest age group was 20–29 years old. The lowest value in the first group in the current study was expected due to the skeletal growing stage with thin cortical boundaries that increase by age. However, the highest value in the sixth group was different as the suspected hypothesis was the dramatic decrease in the mandibular cortical thickness starting from the age of 49 years old as mentioned by Mostafa et al.
In contrast to the current study results, Yüzügüllü et al., Pal and Amrutesh, Bozdag and Sener, and Sghaireen et al. reported that with the increase of age, MI values decreased. Other studies conducted by Musa et al. and Rachmadiani et al. concluded that there was no statistically significant correlation between the MI value and aging. These results were different from those of the current study and were attributed to the different populations and different sample age distributions.
Regarding the PMI’s measurements, the PMI is a ratio between two distances (a/b) as previously mentioned. In the current study, the PMI was expressed in three different ways: PMIS, PMII, and PMIA. The first distance (a) was the same in the three methods of measurement (MI), whereas the second distance (b) differed between them. The mean values of PMIS, PMII, and PMIA were 0.25, 0.31, and 0.27, respectively. The highest values of PMII, PMIA, and PMIS were found in the 50–59 age group, whereas the lowest was found in the 10–19 age group. There was a significant difference between the three ratios. The highest value was found in PMII, followed by PMIA whereas the lowest value was found in PMIS.
The distance between the inferior border of the MF and the IB of the mandible was easily defined and measured, whereas the distance between the superior border of the mental foramen and the IB of the mandible was sometimes ill-defined due to the flared upper end of the MF in addition to the effect alveolar bone loss due to teeth extraction. There was controversy in literature about which ratio is best used for the assessment of the PMI. Yüzügüllü et al. and Bozdag and Sener reported that sometimes the upper border of the MF may not be correctly identified. For this reason, they recommended the use of the lower border of the mental foramen. Consequently, the results of PMII were considered more reliable than PMIS and PMIA, which may be affected by the unclear upper border of the MF.
In terms of the correlation between the PMI and age, the results of the current study were in agreement with those of Mudda et al., Mostafa et al., and Govindraju and Chandra since they reported a gradual increase till the age of 59 years and a decline till the age of 70 years. They mentioned that there was a controversy in the literature regarding the pattern of change in mean PMI with age. On the contrary, Ledgerton et al., Bozdag and Sener, and Sghaireen et al. reported that there was a gradual reduction with an increase in age. However, Yüzügüllü et al. and Moradi et al. reported no significant difference in PMI among their age groups. These different patterns might result from the difference in the ethnic origin and the difference in the size of the study sample. Mostafa et al. explained the positive correlation between age and PMI by the compensatory increase in the cortical bone for functional adaptation to preserve the bone stability, as mentioned earlier.
Regarding the association between sex and all indices, the sample included 118 (37.1%) males and 200 (62.9%) females. There was no significant difference for both the MI values of the two sexes, whereas the PMII, PMIS, and PMIA values of females were significantly higher than those of males. The results of the current study are contrary to the conclusion of the previous studies conducted by Mostafa et al., Bathla et al., Bozdag and Sener, and Sghaireen et al. as they reported that the mean values of all indices were higher in males than in females at different ages and concluded that the effect of gender was more potent on MI than PMI. They explained these results by the stronger masticatory effect in males than females, in addition to the hormonal changes in females.
The studies conducted by Mostafa et al. and Sghaireen et al. reported that sex had a significant effect on the MI whereas it did not affect the PMI. Bozdag and Sener reported that gender had a statistically significant effect on MI and PMI. Bathla et al. reported that there was a significant difference in the PMI values between males and females, as males showed higher values than females.
The current study results were in agreement with the results conducted by Moradi et al., who concluded that there was no effect of the sex on the MI, and the values of the PMI in females were higher than males. The difference between studies was attributed to the differences in ethnic origin, sample size, distribution, different age groups, inclusion criteria, and dental status. The reason behind the current study results could be attributed to the unequal distribution of males and females within the different sample groups due to the limited number of males, as the study focused on the primary outcome to investigate the correlation between the indices and age.
From the results of this study, it could be concluded that: age has a weak effect on the mandibular radiomorphometric indices (MI, PMII, and PMIA), as the indices values increase with age, whereas there is no effect of age on PMIS. Anatomic variation between the right and left mandibular sides has no effect on the three radiomorphometric indices. The PMII values are more reliable than the values of PMIS and PMIA.
| Recommendations|| |
- It is recommended to assess the panoramic mandibular index using the inferior border of the mental foramen rather than the superior one.
- Further studies with an equal distribution of males and females are recommended to investigate the association of gender with the mandibular radiomorphometric indices.
- Further studies with an equal distribution of the dental status are recommended to investigate the effect of the dental status on the mandibular radiomorphometric indices.
The authors would like to thank Dr. Bassam Ahmed Abulnoor for his statistical guidance.
Financial support and sponsorship
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Conflicts of interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.
HSM: Conceived and designed the study, sample collection, data entry, interpretation of data, drafting the article, and approval of the final article. RMH: Contributed to study design, data interpretation, revising the drafted article, and approval of the final article. SHE: Coding the data, contributed to data analysis, revising the drafted article, and approval of the final article. YRH: Sample collection, data analysis, drafting the article, and approval of the final article.
Ethical policy and institutional review board statement
The current study was approved by the ethical committee of the Faculty of Dentistry, Cairo University, Egypt (approval number 18-10-42) (approval date 30/10/2018) and it complies with the Declaration of Helsinki (2013). The trial is registered on clinicaltrials.gov under identifier: NCT03714035 (https://clinicaltrials.gov/ct2/show/NCT03714035).
Patient declaration of consent
Patient declaration of consent was obtained in a Helsinki declaration consent form in their native language (Arabic). Provided is the English version of said form and a signed Arabic one by one of the study participant.
Data availability statement
The data that support the findings of this study are available from the corresponding author, [HSM], upon reasonable request.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]