Research Progress on Dental Age Estimation Based on MRI Technology.

Dental age estimation is a crucial aspect and one of the ways to accomplish forensic age estimation, and imaging technology is an important technique for dental age estimation. In recent years, some studies have preliminarily confirmed the feasibility of magnetic resonance imaging (MRI) in evaluating dental development, providing a new perspective and possibility for the evaluation of dental development, suggesting that MRI is expected to be a safer and more accurate tool for dental age estimation. However, further research is essential to verify its accuracy and feasibility. This article reviews the current state, challenges and limitations of MRI in dental development and age estimation, offering reference for the research of dental age assessment based on MRI technology.

Computer-aided superimposition of the frontal sinus via 3D reconstruction for comparative forensic identification.

The anatomical uniqueness of the frontal sinus morphology has been widely used for comparative forensic identification using various techniques, mostly including 2D X-rays or one fixed slice of an axial computed tomography (CT) scan image. However, computer-aided 3D automatic graphical comparison techniques can provide accurate comparisons between two 3D models that allow users to comply with even the strictest deviation standards, avoiding error-prone identification of frontal sinuses with similar morphologies. The study proposes the use of a computer-aided comparative paradigm based on the 3D-3D frontal sinus model superimposition process and further assesses the anatomical uniqueness of frontal sinuses using a large Chinese Han sample. Three hundred thirty-six patients older than 20 years with two multi-slice CT scans were collected. Frontal sinus 3D models were semi-automatically segmented through Dolphin Imaging software. Automatic pairwise comparisons of 336 matched pairs from the same person and 340 mismatched pairs from different individuals with an analysis of average root mean square (RMS) point-to-point distance were performed using Geomagic Studio Qualify software. RMS ranged between 0.005 and 1.032 (mean RMS 0.390 ± 0.25 mm) in the group of matches and between 1.107 and 19.363 (mean RMS 4.49 ± 2.69 mm) in the group of mismatches. On average, the RMS value was over ten-fold greater in mismatches than in matches. Statistically significant differences in RMS between the group of matches and mismatches were assessed using the Mann-Whitney U test (p < 0.05). This study supports the value of the frontal sinus with a 3D computer-aided superimposition method for human identification with large samples when DNA, fingerprints, and dental materials are not accessible.

[Establish Assessment Model of 18 Years of Age in Chinese Han Population by Mandibular Third Molar].

OBJECTIVE: To explore the value of estimating chronologic age based on the grades of mandibular third molar development. To evaluate whether mandibular third molar could be used as an indicator for estimating the age under or over 18 years. METHODS: The mineralization status of mandibular third molar of 1 845 individuals aged 10 - 30 was graded and marked based on Demirjian's classification of grades reformed by Orhan. Gender difference was examined by t-test. A cubic regression model was established to analyze the correlation between third molar and chronologic age. Each grade of age cumulative distribution diagram and ROC curve was respectively performed to evaluate the relationship between third molar and the age of 18. Using Bayes discriminant analysis, an equation was established for estimating the age of 18. RESULTS: The inner-rater reliability was 0.903. Statistical analysis showed a moderate correlation between age and grade. Significant differences of both genders were found only in grade D and H (P < 0.05). Males at the grades from 1 to D and females at the grades from 1 to C were under 18 years old, and both males and females at grade H were over 18 years old. The area under the ROC curve was 0.797 (P < 0.05). CONCLUSION: Third molar development shows a high correlation with age, and combined with other indicators, it can be used to estimate the age of 18.

[Indexes of forensic identification by the digital orthopantomogram of the normal teeth].

OBJECTIVE: To explore more concise and unified forensic identification indexes for people with none dental disease in digital orthopantomogram. METHODS: To select randomly 170 digital orthopantomogram with none dental disease. Then to select indexes for full dentition patterns and dental alignment patterns according to the dental physiological variations and the characters of dental alignment respectively. Finally diversity of the indexes would be evaluated by statistical analysis. RESULTS: The group with none dental disease had 74 kinds of full dentition pattern in 170 samples, thus its diversity was 43.53%. The group had 129 kinds of dental alignment pattern, thus its diversity was 75.88%. The group had 150 kinds of full dentition/dental alignment pattern, thus its diversity was 88.24%. CONCLUSION: The diversity of the full dentition pattern was not very good. So the full dentition coding was not very effective when it was used solely. The diversity of dental alignment pattern was good. So the method of dental alignment coding could be used in the maxillofacial forensic identification. If the group was coded by the full dentition and dental alignment pattern at the same time, its diversity was better than any single pattern. So the method would be valuable in forensic identification.

[Study on the indexes of forensic identification by the occlusal-facial digital radiology].

OBJECTIVE: To discuss the coding of full dentition with 32 locations and measure the characteristics of some bony indexes in occlusal-facial digital radiology (DR). METHODS: To select randomly three hundred DR orthopantomogram and code the full dentition, then analyze the diversity of dental patterns. To select randomly one hundred DR lateral cephalogram and measure six indexes (N-S,N-Me,Cd-Gn,Cd-Go,NP-SN,MP-SN) separately by one odontologist and one trained forensic graduate student, then calculate the coefficient variation (CV) of every index and take a correlation analysis for the consistency between two measurements. RESULTS: (1) The total diversity of 300 dental patterns was 75%.It was a very high value. (2)All six quantitative variables had comparatively high CV value.(3) After the linear correlation analysis between two measurements, all six coefficient correlations were close to 1. This indicated that the measurements were stable and consistent. CONCLUSION: The method of coding full dentition in DR orthopantomogram and measuring six bony indexes in DR lateral cephalogram can be used to forensic identification.