Comparison of mandibular index values determined from standard panoramic versus cone beam computed tomography reconstructed images

Evaluation of sex dimorphism of the mandible with geometric morphometric analysis: conventional and reconstructed panoramic radiography study

PURPOSE

The purpose of the study was to investigate the mandible shape dimorphism between males and females both on conventional panoramic radiographs (cPR) and reconstructed panoramic radiographs obtained from cone beam computed tomography (rPR) with geometric morphometric method.

METHODS

Panoramic radiographs and cone beam computed tomography scans were performed on 33 males and 35 females with median age 23.0 (13.0-57.0) years old. The mandibular shape comparisons between genders were examined with Procrustes analysis, mandible shape classification analysis was made with principal component analysis and shape deformations were concluded from thin plate spline (TPS) analysis.

RESULTS

Age had no statistically significant difference between gender (p = 0.580). For the shape of mandible on cPR and rPR, there were statistically significant differences between males and females (p = 0.002, p = 0.032, respectively). The shape variabilities of mandible on cPR for females were 0.054 and for males 0.053. The shape variabilities of mandible on rPR for females were 0.051 and for males 0.049. Both on cPR and rPR, the shape variability of the females' mandible was similar within their group, the shape variability of the males' mandible was similar within their group. In the examination of mandibular dimorphism in cPR, maximal deformations were seen in the region between the mandibular notch, posterior ramus, anterior ramus, gonion, in both sides, in TPS graphs. On the other hand, a high level of deformations was observed in all landmarks that define the mandibular shape on rPR.

CONCLUSIONS

The mandible dimorphism can be detected in the examination performed with geometric morphometric methods on cPR and rPR. While mandible shape differences according to gender are seen most in the ramus region in cPR, differences can be detected in all landmarks in rRP.

Evaluation of mandibular indices and cephalometric parameters in adolescents with impacted maxillary canines

Objectives:

Maxillary impacted canines have an important place in orthodontics for the reason of being a common anomaly and its treatment is time consuming and difficult. The aim of this study was to investigate the mandibular indexes and cephalometric parameters in adolescents with impacted maxillary canines.

Materials and Methods:

The radiographs of 4026 patients aged 12–19 years old were scanned and a total of 155 patients were included in the study. Subjects were divided into three groups according to the permanent maxillary canines: Bilateral impacted canine (BIC) (52 subjects; mean age 15.02 ± 1.74 years), unilaterally impacted canine (UIC) (51 subjects; mean age 14.89 ± 1.39 years), and the control (52 subjects; mean age 14.84 ± 1.65 years) groups. Skeletal, soft tissue and dental measurements were performed on cephalometric radiographs. Mandibular index analyzes including the panoramic mandibular index (PMI), mental index (MI), antegonial index (AI), and gonial index (GI) measurements and also angular measurements of impacted maxillary canines were performed on panoramic radiographs. Data were analyzed statistically and P < 0.05 was considered significant.

Results:

Maxillary skeletal and dental measurements showed retrusive positioned maxillary dental arch in the sagittal direction in the impacted canine groups (P < 0.05). PMI and MI values were greater in the BIC and UIC groups than in control group (P < 0.05). There was no statistically significant difference in AI value among groups (P < 0.05). GI value of BIC group was found statistically lower than other groups (P < 0.05).

Conclusion:

Individuals with impacted maxillary canines have more retrusive maxillary dental arch and soft-tissue components. Furthermore, mandibular cortex was thicker in subjects with impacted maxillary canine than individuals with not and clinicians should keep in mind this when examine the panoramic radiographs in terms of early diagnosis of impacted maxillary canine teeth.

Automatic measurement of mandibular cortical bone width on cone-beam computed tomography images

OBJECTIVE

The computed tomography cortical index (CTCI), computed tomography mandibular index (CTMI), and computed tomography index (inferior) [CTI(I)] are indexes obtained from cone-beam computed tomography images for the assessment of the mandibular cortex quality for implant planning or osteoporosis. However, cross-sectional image reconstruction for the measurements is labor-intensive. This study aimed to develop and evaluate a method to automatically reconstruct cross-sectional images and measure the cortex width in all areas inferior to the mental foramen (MF).

METHODS

Seventy-one women (mean age: 52.4 years; range: 20-78 years) were enrolled. They were divided into four age and CTCI groups, including females younger (FY) and females older (FO) than 50 years (C1: normal, C2: mild/moderate erosion, and C3: severe porosity). Automatic and manual measurements of CTMI and CTI(I) were compared, and the inter- and intraobserver agreements were assessed using the intraclass correlation coefficient (ICC). The relationships between CTMI or CTI(I) and CTCI were also assessed.

RESULTS

The mean processing times for reconstruction and measurements were 31.9 s and 1.22 s, respectively. ICCs for the comparison of automatic and manual measurements were 0.932 and 0.993 in the C1 and C2/C3 groups, respectively. Significant differences in CTMI and CTI(I) were observed between the FY or the FO-C1 and FO-C3 groups (p < 0.05).

CONCLUSION

The automatic and manual measurements showed a strong agreement. The new method could drastically reduce routine clinical workload. Additionally, our method enables the measurement of the cortex width in all the mandibular bones inferior to the MF.

Mandibular cortical indices and their relation to gender and age in the cone-beam computed tomography

OBJECTIVES

The purpose of this study is to evaluate normal ranges of cortical bone Hounsfield units indices through cone beam CT images, and to investigate their relationships with age and sex.

METHODS

700 adult human cone beam CT images were evaluated retrospectively, and divided into 4 age groups. Six different cortical bone Hounsfield unit measurements were applied bilaterally, where gender and age were recorded. Collected data were subjected to statistical analysis and ANOVA tests were used for various comparisons.

RESULTS

The cortical bone measurements between female and male patients were significantly different (p<0.05). Cortical bone thickness indices showed greater values in male patients compare to female patients (p<0.05). Quantitative mandibular indices were significantly lower in first age group (18-30 years) than other three older age groups (p<0.01).

CONCLUSION

The results of this study seems to propose a persistent alteration in the mandibular cortical bone with age and that this influced by sex. Further studies with larger patient groups are needed to clarify and understand these mandibular indices.

Relationship between mandibular condyle and articular eminence cortication with mandibular cortical index on cone-beam CT

PURPOSE

Mandibular condyle development can be evaluated with radiographic evaluation of subchondral cortical bone. The aim of this study is to investigate mandibular condyle cortication (MCC), articular eminence cortication (AEC) and mandibular cortical index (MCI) according to age and gender on CBCT, and relationship between each other.

METHODS

CBCT scans of 520 patients (312 male and 208 female, age range 7-84) were retrospectively investigated to evaluate MCC, AEC and MCI. MCC and AEC were examined in sagittal section and MCI in panoramic reformatted image. MCC and AEC were classified as Type I, Type II and Type III according to density difference between the cortical bone enclosing condyle and articular eminence. Categorical variables were tested by Chi square.

RESULTS

When MCC, AEC and MCI were compared, a significant relationship was detected (p < 0.05). According to age, there was a significant difference between MCC, MCI and AEC types with each other (p < 0.05). No significant discrepancy was found between gender and MCC, AEC and MCI (p > 0.05).

CONCLUSIONS

This study evaluated the distribution of MCC, AEC, MCI according to age and gender and detected that these cortications were correlated. This result may be caused by anatomical proximity bone components and functional stimuli. Knowledge of these cortications can be important for accurate diagnosis of TMJ disorders and may also be helpful for prediction of osteoporotic changes.