Deep learning for 3D cephalometric landmarking with heterogeneous multi-center CBCT dataset.

Cephalometric analysis is critically important and common procedure prior to orthodontic treatment and orthognathic surgery. Recently, deep learning approaches have been proposed for automatic 3D cephalometric analysis based on landmarking from CBCT scans. However, these approaches have relied on uniform datasets from a single center or imaging device but without considering patient ethnicity. In addition, previous works have considered a limited number of clinically relevant cephalometric landmarks and the approaches were computationally infeasible, both impairing integration into clinical workflow. Here our aim is to analyze the clinical applicability of a light-weight deep learning neural network for fast localization of 46 clinically significant cephalometric landmarks with multi-center, multi-ethnic, and multi-device data consisting of 309 CBCT scans from Finnish and Thai patients. The localization performance of our approach resulted in the mean distance of 1.99 ± 1.55 mm for the Finnish cohort and 1.96 ± 1.25 mm for the Thai cohort. This performance turned out to be clinically significant i.e., ≤ 2 mm with 61.7% and 64.3% of the landmarks with Finnish and Thai cohorts, respectively. Furthermore, the estimated landmarks were used to measure cephalometric characteristics successfully i.e., with ≤ 2 mm or ≤ 2° error, on 85.9% of the Finnish and 74.4% of the Thai cases. Between the two patient cohorts, 33 of the landmarks and all cephalometric characteristics had no statistically significant difference (p < 0.05) measured by the Mann-Whitney U test with Benjamini-Hochberg correction. Moreover, our method is found to be computationally light, i.e., providing the predictions with the mean duration of 0.77 s and 2.27 s with single machine GPU and CPU computing, respectively. Our findings advocate for the inclusion of this method into clinical settings based on its technical feasibility and robustness across varied clinical datasets.

Comparison of subjective image analysis and effective dose between low-dose cone-beam computed tomography machines.

OBJECTIVES: To compare the cone-beam computed tomography (CBCT) image quality and effective dose between low-dose scanning and standard manufacturer-recommended protocols among different CBCT units. METHODS: Three human-equivalent phantoms were scanned using the ultra-low-dose (ULD), low dose (LD), and standard dose (STD) modes of ProMax 3D Mid (Planmeca Oy, Helsinki, Finland) and Orthophos SL (Sirona, Bensheim, German) for the CBCT images. The quality of the dental anatomical images was assessed by four experienced oral and maxillofacial radiologists using a 5-point Likert scale. OnDemand3D (Cybermed Co., Seoul, Korea) was used as the third-party software for viewing. The percentage of absolute agreement was calculated to determine intra- and interrater agreements among the observers. The effective doses for all CBCT scanning protocols were also calculated. RESULTS: The STD protocol yielded a higher image quality than did the ULD and LD protocols in both ProMax 3D Mid and Orthophos SL. The ULD and LD protocols demonstrated an "acceptable-to-good" sense of visual perception of the CBCT images. The visibility scores significantly differed between the ULD and LD and the STD protocols in ProMax 3D Mid and Orthophos SL, except for the 120-kVp setting in ProMax 3D Mid. The average intra- and interrater agreement scores ranged from 0.63 to 0.89 and from 0.44 to 0.76, respectively. The ULD and LD protocols reduced the radiation dose sixfold compared with the STD protocol. CONCLUSIONS: High-tube-voltage protocols could remarkably reduce the imaging dose without degrading the image quality. Specifically, ULD and LD CBCT protocols may be adopted as routine practice for diagnosis and treatment planning.

Prevalence of pre-eruptive intracoronal radiolucencies in Thai children and adolescents: A retrospective study.

AIM: The aim of the present study was to determine the prevalence, location, size, and tooth type of pre-eruptive intracoronal radiolucencies (PEIR) from panoramic radiographs in Thai patients. METHODS: A retrospective study of PEIR was conducted on 1599 panoramic radiographs of 629 Thai males and 970 Thai females with an age range of 4-20 years (average age: 14.0 ± 4.0 years). Each radiograph was reviewed by two calibrated examiners. The age and sex of the patients, location, size, and tooth type of the lesions were recorded. The SPSS program was used for statistical analysis. RESULTS: The PEIR were found in 0.32% of tooth samples (29/9060) and 1.63% of patients (26/1599). There was no statistical difference in the presence of PEIR between both sexes. The mandibular second molars were the most affected teeth. The lesions were mostly located at the central part of the crown. The lesion sizes were mostly limited to less than one-third of dentinal thickness. CONCLUSIONS: The present study showed that the prevalence of PEIR in Thai samples is 1.63%. This could raise dentists' awareness in reviewing unerupted teeth in panoramic radiographs. Early detection of the lesions should aid in proper treatment planning of affected teeth to prevent complications from carious invasion after tooth eruption.

Preeruptive Intracoronal Radiolucencies: Detection and Nine Years Monitoring with a Series of Dental Radiographs.

Preeruptive intracoronal radiolucencies (PEIRs) are mostly incidentally found by routine radiographic examination of unerupted teeth. PEIRs are classified into two types according to the nature of the lesion: progressive and nonprogressive. A case report of a 17-year-old boy with a nonprogressive PEIR on the permanent mandibular left second molar is presented. The lesion was initially detected on an unerupted tooth at age eight years, eight months. It was clinically and radiographically assessed yearly. Cone beam computed tomography (CBCT) was used to evaluate the lesion's size and location when the patient was 11 and 14 years old. The assessments confirmed that the lesion was nonprogressive and had no connection to the pulp or oral cavity. Due to the static nature of the detected PEIR during the nine-year follow-up period, the patient's low caries-risk status, and high patient and parental cooperation in periodic dental care, it was decided to place resin sealant on the affected tooth and monitor the lesion without any operative treatment.

Infection control and patient discomfort with an alternative plastic barrier in intraoral digital radiography.

OBJECTIVES: (1) To compare the efficacy of a commercially available hygienic sheath and an alternative plastic bag in preventing contamination of the imaging plate during intraoral radiography and (2) to compare patient discomfort when using the hygienic sheath and the plastic bag. METHODS: 60 sterilized Size 2 imaging plates covered with either the hygienic sheath (n = 30) or the plastic bag (n = 30) were used to simulate digital periapical radiographic examination in 30 volunteer patients. After disinfection, each plate was swabbed. The swabbed medium was then plated on trypticase soy agar and incubated. Bacterial colonies were counted. Patient discomfort was assessed using a visual analogue scale (VAS) score. The comparison of the number of bacterial colonies and VAS scores between the two groups was tested by paired t-test at p < 0.05. RESULTS: There was no significant difference in the number of bacterial colonies between the two groups (p = 0.745). Of all the plates, 10% plates yielded bacterial colonies. The mean count of bacterial colonies for both groups was 10-20 CFU ml-1. However, there was a significant difference between VAS scores for the two systems (p = 0.000). The mean VAS scores (range 0-10) for patient discomfort for the hygienic sheath group and the plastic bag group were 3.03 and 5.33, respectively. CONCLUSIONS: Based on the design of this study, the alternative barrier provided similar results to those commercially available. Regarding the type of barrier envelope, the hygienic sheath induced less discomfort than the plastic bag.

Accuracy of an equation for estimating age from mandibular third molar development in a Thai population.

PURPOSE: This study assessed the accuracy of age estimates produced by a regression equation derived from lower third molar development in a Thai population. MATERIALS AND METHODS: The first part of this study relied on measurements taken from panoramic radiographs of 614 Thai patients aged from 9 to 20. The stage of lower left and right third molar development was observed in each radiograph and a modified Gat score was assigned. Linear regression on this data produced the following equation: Y=9.309+1.673 mG+0.303S (Y=age; mG=modified Gat score; S=sex). In the second part of this study, the predictive accuracy of this equation was evaluated using data from a second set of panoramic radiographs (539 Thai subjects, 9 to 24 years old). Each subject's age was estimated using the above equation and compared against age calculated from a provided date of birth. Estimated and known age data were analyzed using the Pearson correlation coefficient and descriptive statistics. RESULTS: Ages estimated from lower left and lower right third molar development stage were significantly correlated with the known ages (r=0.818, 0.808, respectively, P≤0.01). 50% of age estimates in the second part of the study fell within a range of error of ±1 year, while 75% fell within a range of error of ±2 years. The study found that the equation tends to estimate age accurately when individuals are 9 to 20 years of age. CONCLUSION: The equation can be used for age estimation for Thai populations when the individuals are 9 to 20 years of age.

Image analysis of the eruptive positions of third molars and adjacent second molars as indicators of age evaluation in Thai patients.

PURPOSE: This study was performed to determine the relationship between the stage of tooth eruption (both vertical and mesio-angular) and chronological age. MATERIALS AND METHODS: Indirect digital panoramic radiographs were used to measure the distances from the dentinoenamel junction (DEJ) of the second molars to the occlusal plane of the second molar teeth and of the adjacent third molars in 264 Thai males and 437 Thai females using ImageJ software. The ratio of those distances was calculated by patient age, and the correlation coefficient of the ratio of the third molar length to the second molar length was calculated. RESULTS: The correlation between the height of the vertically erupted upper third molar teeth and age was at the intermediate level. The age range of ≥15 to <16 years was noted to be the range in which the correlation between the chronological age determined from the eruptional height and actual chronological age was statistically significant. The mean age of the female subjects, in which the position of the right upper third molar teeth was at or above the DEJ of the adjacent second molar but below one half of its coronal height was 19.9±2.6 years. That for the left side was 20.2±2.7 years. The mean ages of the male subjects were 20.1±3.3 years and 19.8±2.7 years for the right and left sides, respectively. CONCLUSION: It might be possible to predict chronological age from the eruption height of the wisdom teeth.

Diagnostic performance of cone-beam computed tomography on detection of mechanically-created artificial secondary caries.

PURPOSE: The aim of this study was to compare the diagnostic accuracy of cone-beam computed tomography (CBCT) images and bitewing images in detection of secondary caries. MATERIALS AND METHODS: One hundred and twenty proximal slots of Class II cavities were randomly prepared on human premolar and molar teeth, and restored with amalgam (n=60) and composite resin (n=60). Then, artificial secondary caries lesions were randomly created using round steel No. 4 bur. The teeth were radiographed with a conventional bitewing technique and two CBCT systems; Pax-500ECT and Promax 3D. All images were evaluated by five observers. The area under the receiver operating characteristic (ROC) curve (A(z)) was used to evaluate the diagnostic accuracy. Significant difference was tested using the Friedman test (p value<0.05). RESULTS: The mean A(z) values for bitewing, Pax-500ECT, and Promax 3D imaging systems were 0.882, 0.995, and 0.978, respectively. Significant differences were found between the two CBCT systems and film (p=0.007). For CBCT systems, the axial plane showed the greatest A(z) value. CONCLUSION: Based on the design of this study, CBCT images were better than bitewing radiographs in detection of secondary caries.