Growth changes of the mandibular body with eruption of mandibular third molars: analysis of anatomical morphometry and quantitative bone mineral content by using radiography

Tomographic analysis of relationship of mandibular morphology and third molars eruption

BACKGROUND

Lower third molars (L3M) are the last teeth to erupt in the oral cavity. Uneruption of these teeth still raises questions about its causes, in the literature (1) genetic factors, (2) dental lamina activity and, mainly, (3) insufficient growth and development of the bone bases are included. While the lack of space theory influenced by mandibular morphology and size of L3M was argued to be the main reason for L3M impaction, there is a limitation in the literature in examining such association using more accurate tomographic analysis obtained from CBCT. This work aimed to evaluate the relationship between mandibular morphology and the eruption of L3M.

METHODS

In this regard, 85 Cone Beam Computed Tomographies (CBCT), with 147 L3M, were selected from the archives of the Department of Surgery, Stomatology, Pathology and Radiology, Bauru School of Dentistry, obtained using an Accuitomo® Morita device and using the Dolphin Imaging 11.9 software. L3M eruption was related to linear measurements of jaw length (Co-Gn), retromolar space dimension (D2R), mesiodistal width of the L3M crowns, mandibular first molars (L1M) and mandibular canines (LC) and the angle mandibular (Ar-Go-Me). Independent samples t-test, chi-square tests and logistic regression were performed adopting a significance level of 5%.

RESULTS

The average mandible length of 116.446 mm + 6.415 mm, retromolar space of 11.634 mm + 2.385 mm, mesiodistal size of the L3M of 10.054 mm + 0.941 mm, sum of the mesiodistal widths of the L1M and LC of 15.564 mm + 1.218 mm and mandibular angle of 127.23° + 6.109. There was no statistically significant association between these factors and the eruption.

CONCLUSION

With the results obtained in this study, we conclude that the length and angle of the mandible, teeth size and dimension of the retromolar space are not associated with the L3M eruption.

Morphology of the antegonial notch and its utility in the determination of sex on skeletal materials

A number of criteria for the assessment of biological sex, which are applied to living or recently deceased individuals, have been developed, such as genetic, chromosomal, gonadal, hormonal, and phenotypic criteria. Features of a metric and descriptive nature are used to assess the sex of skeletal materials. The diagnostic features of the skull are concentrated in the craniofacial region and around the eye sockets. The mandible is a diagnostically important part of the skull, on which a complex of features is visible. These features develop up to the third decade of life. The goal of the research was to assess the suitability of the parameters of the preangular notch, in other words, the length, height, and surface area for sex prediction applied to skeletal materials. The study included computed tomography images of the masticatory system of 194 patients, consisting of 83 females and 111 males, aged from 16 to 93 years. The three straight lines which correspond to the sides of the triangle representing the notch, in addition to its height, were determined and measured digitally. The receiver operating characteristic method was used to assess the usefulness of the studied features for the purposes of sex prediction. The sensitivity of the test ranged from 51.4% to 67% for the parameters of the preangular notch on the right-hand side, and from 44.4% to 80.2% on the left-hand side. The most reliable predictive models were obtained for two features (shown in the graphical abstract). However, when taking into account, the specificity and sensitivity of the tests presented here, only the length of side AB (a basal length of the notch) can be regarded as a feature that supports the assessment of sex on the basis of other diagnostic features of the mandible. The size and shape of the preangular notch should be treated as auxiliary features in the assessment of sex. For this reason, it is recommended that they should be applied simultaneously to the set of features described in the section on anthropological standards.

Correlation between symphyseal morphology and mandibular growth

Background:

This study sought to assess symphyseal morphology in adolescents with different mandibular growth patterns (MGPs) in order to see if a relation exists.

Materials and Methods:

In this study the symphyseal parameters (height, depth, and ratio) of normal subjects were compared with four groups with malocclusion (cl III vertical, cl II vertical, cl III horizontal, and cl II horizontal). These groups (15 samples each) were matched (for sex and cervical maturation stage [CVMS]) based on their cephalograms and patient charts. Growth patterns were differentiated by seven vertical parameters and the Wylie analysis. After confirmation of normality of the groups and similarity of their variances the two-way analysis of variance (ANOVA) was used for analysis of data assessed by adjusted chi-square (P < 0.001). The comparison of cases with the normal group was performed by the Dunnett method. Intraclass Correlation Coefficient (ICC) was used for evaluation of intraobserver reliability.

Results:

We found the symphyseal ratio to have a significant correlation with the MGP (P < 0.001). The symphyseal ratio (Height/Depth) was small in a mandible with vertical growth pattern Cl II or Cl III. Conversely, a horizontal growth pattern of a Cl II or Cl III mandible was associated with a larger ratio of the symphysis in comparison with the normal group. The symphyseal ratio was also found to be greater in females.

Conclusion:

The symphyseal ratio was found to be strongly associated with the MGP.

Association of gonial angle with morphology and bone mineral content of the body of the adult human mandible with complete permanent dentition

We investigated the differences between 2 gonial angle (GA) size groups with respect to the morphometry and quantitative bone mineral content (QBMC) of mandibles with all teeth erupted and normal occlusion. We used 19 dried mandibles that were obtained from an Indian population and stored in our department. These mandibles were at Hellman's developmental dental stage VA and were divided into low gonial angle (LGA) (GA ≤ 120°; 8 specimens; 16 sides) and high gonial angle (HGA) (GA ≥ 125°; 11 specimens; 22 sides) groups. After lateral radiography of the mandibles using a titanium step wedge, linear measurements and the QBMC were determined, on hard copies and digital images, respectively. The age and sex of the cadavers to which the specimens belonged were unknown. The mandibular cortical width (MCW) and the antegonial notch depth of the LGA group were significantly larger than those of the HGA group. No significant difference was found in the distribution of the 3 categories of mandibular cortical index (MCI) or in cortical and trabecular bone mineral contents (CBMC and TBMC). The GA size was negatively and moderately associated with the MCW and the mandibular cortical width on the point AG (MCWAG), but was not significantly associated with either variable for CBMC and TBMC. These results suggested that the GA size of these stage-VA mandibles influenced changes in the width of inferior cortex and morphology of antegonial notch. The GA size did not influence QBMC under the mental foramen of the mandible and had negative associations with the MCW and MCWAG.