Correlation Between Quality Evaluation Metrics and Teeth Detection Results in Panoramic X-Rays Using Deep Learning.

Panoramic images are one of the most requested exams by dentists for allowing the visualization of the entire mouth. Interpreting X-ray images is a time-consuming task in which misdiagnoses can occur due to the inexperience or fatigue of professionals. In this work, we applied different image enhancement techniques as a pre-processing step to determine which image features correlate with improvements in teeth detection in panoramic images using deep learning architectures. We contrasted the performance of five object-detection architectures using 300 panoramic images of a public dataset. We evaluated the enhancement in the pre-processing step and the detection performance. Quality and detection metrics were considered, and the cross-correlation between them was computed for every object-detection method contemplated. We observe the dependence of the detection performance with some image enhancement techniques, especially those that introduce less noise and preserve the global contrast of the image.

Sustracción Radiográfica Digital de la Estructura Dentaria Removida Durante el Acceso Endodóntico En Incisivos Mandibulares

RESUMEN: El objetivo de este estudio fue comparar la estructura dentaria removida utilizando dos técnicas de acceso endodóntico diferentes en incisivos mandibulares. Treinta y cinco incisivos mandibulares extraídos fueron pesados individualmente con una balanza de precisión. Después de las radiografías iniciales tomadas por vestibular y proximal, los dientes fueron codificados y asignados aleatoriamente a dos grupos: acceso convencional (n = 17) o acceso incisal (n = 18). Luego se volvieron a pesar los dientes y se repitieron las radiografías. Las radiografías digitales se cargaron a un editor de imágenes (Adobe Photoshop) para la sustracción digital de las imágenes por las incidencias VP y MD. Dos observadores independientes y calibrados realizaron las mediciones de las áreas sustraídas. La concordancia inter-observador fue casi perfecta; coeficiente de correlación intraclase igual a 0,94 y 0,98 para las incidencias MD y VP, respectivamente. La prueba de Mann-Whitney encontró diferencias estadísticamente significativas entre los tipos de acc esos en cuanto a la diferencia mediana de los pesos (p = 0,0073) y el área VL (p = 0.0023). También encontró una diferencia estadísticamente significativa entre los tipos de acceso en cuanto al área MD (Prueba t de Welch, p < 0,001). La diferencia de peso fue menor para el acceso incisal que para el acceso convencional. El acceso incisal removió menos tejido dentario que el acceso convencional.

ABSTRACT: The aim of this study was to compare the area of tooth structure removed during two different endodontic access techniques in lower incisors. Thirty-two extracted lower incisors were weighed individually on a precision scale. After initial digital radiographs were taken from buccal and proximal, the teeth were coded and randomly assigned to two different groups: conventional access and incisal access. Once this stage was completed, each tooth was weighed again and 2 postoperative radiographs was taken again, buccal and proximal. Using an image processing software and digital subtraction technique, 2 independent and calibrated evaluators measured difference in tooth structure after access procedures. Interobserver agreement was almost perfect: intraclass correlation coefficient equal to 0,94 and 0,98 for proximal and buccal incidences, respectively. The Mann-Whitney test found statistically significant differences between the types of accesses in terms of weight difference (p = 0.0073) and area VL (p = 0.0023). Additionally, a statistically significant difference between the types of access in the MD area (Welch's t test, p <0.005) was observed. The difference in weight was less for incisal access than for conventional access with a statistically significant difference, in terms of MD and VL area, incisal access and areas of smaller size than conventional access.

Panoramic Dental Radiography Image Enhancement Using Multiscale Mathematical Morphology.

Panoramic dental radiography is one of the most used images of the different dental specialties. This radiography provides information about the anatomical structures of the teeth. The correct evaluation of these radiographs is associated with a good quality of the image obtained. In this study, 598 patients were consecutively selected to undergo dental panoramic radiography at the Department of Radiology of the Faculty of Dentistry, Universidad Nacional de Asunción. Contrast enhancement techniques are used to enhance the visual quality of panoramic dental radiographs. Specifically, this article presents a new algorithm for contrast, detail and edge enhancement of panoramic dental radiographs. The proposed algorithm is called Multi-Scale Top-Hat transform powered by Geodesic Reconstruction for panoramic dental radiography enhancement (MSTHGR). This algorithm is based on multi-scale mathematical morphology techniques. The proposal extracts multiple features of brightness and darkness, through the reconstruction of the marker (obtained by the Top-Hat transformation by reconstruction) starting from the mask (obtained by the classic Top-Hat transformation). The maximum characteristics of brightness and darkness are added to the dental panoramic radiography. In this way, the contrast, details and edges of the panoramic radiographs of teeth are improved. For the tests, MSTHGR was compared with the following algorithms: Geodesic Reconstruction Multiscale Morphology Contrast Enhancement (GRMMCE), Histogram Equalization (HE), Brightness Preserving Bi-Histogram Equalization (BBHE), Dual Sub-Image Histogram Equalization (DSIHE), Minimum Mean Brightness Error Bi-Histogram Equalization (MMBEBHE), Quadri-Histogram Equalization with Limited Contrast (QHELC), Contrast-Limited Adaptive Histogram Equalization (CLAHE) and Gamma Correction (GC). Experimentally, the numerical results show that the MSTHGR obtained the best results with respect to the Contrast Improvement Ratio (CIR), Entropy (E) and Spatial Frequency (SF) metrics. This indicates that the algorithm performs better local enhancements on panoramic radiographs, improving their details and edges.

The influence of periapical lesions on the repeatability of two electronic apex locators in vivo.

OBJECTIVES: To determine the influence of periapical lesions on the repeatability of two electronic apex locators (EALs), Root ZX II, and RomiApex A-15, in maxillary anterior teeth, in vivo. MATERIALS AND METHODS: After approval by the local ethics committee, 43 maxillary anterior teeth scheduled for root canal therapy were assigned to two groups. The periapical lesion (PAL) group included 21 teeth with necrotic pulps and radiographically visible periapical lesion, and the normal periapex (NPA) group consisted of 22 teeth with vital pulps and no periapical lesion. In each canal, Root ZX II and RomiApex A-15 were used to determine working length defined as the "zero" reading on the display. Two consecutive measurements were performed with each EAL on each tooth and a second operator measured the endodontic file with a digital caliper without knowledge of the EAL being used or the tooth diagnosis. The absolute value of the difference between the first and second measurement (measurement pairs) was calculated. Repeatability was evaluated by the Bland-Altman method, and an aligned ranks transformation ANOVA was conducted to compare the EALs. RESULTS: The median absolute difference between measurement pairs was significantly lower (p < 0.001) and the limits of agreement were narrower in the NPA group. Among the EALs, median absolute differences were significantly smaller for Root ZX (p < 0.001). CONCLUSIONS: Measurements were more repeatable when no periapical lesion was present. Root ZX showed better repeatability than RomiApex. CLINICAL RELEVANCE: Periapical lesions seem to influence successive in vivo measurements with EALs.