Tooth Position Determination by Automatic Cutting and Marking of Dental Panoramic X-ray Film in Medical Image Processing

This paper presents a novel method for automatic segmentation of dental X-ray images into single tooth sections and for placing every segmented tooth onto a precise corresponding position table. Moreover, the proposed method automatically determines the tooth’s position in a panoramic X-ray film. The image-processing step incorporates a variety of image-enhancement techniques, including sharpening, histogram equalization, and flat-field correction. Moreover, image processing was implemented iteratively to achieve higher pixel value contrast between the teeth and cavity. The next image-enhancement step is aimed at detecting the teeth cavity and involves determining the segment and points separating the upper and lower jaw, using the difference in pixel values to cut the image into several equal sections and then connecting each cavity feature point to extend a curve that completes the description of the separated jaw. The curve is shifted up and down to look for the gap between the teeth, to identify and address missing teeth and overlapping. Under FDI World Dental Federation notation, the left and right sides receive eight-code sequences to mark each tooth, which provides improved convenience in clinical use. According to the literature, X-ray film cannot be marked correctly when a tooth is missing. This paper utilizes artificial center positioning and sets the teeth gap feature points to have the same count. Then, the gap feature points are connected as a curve with the curve of the jaw to illustrate the dental segmentation. In addition, we incorporate different image-processing methods to sequentially strengthen the X-ray film. The proposed procedure had an 89.95% accuracy rate for tooth positioning. As for the tooth cutting, where the edge of the cutting box is used to determine the position of each tooth number, the accuracy of the tooth positioning method in this proposed study is 92.78%.

Growth rate as a modulator of tooth patterning during adaptive radiations

The discovery of mechanistic rules that underlie phenotypic variation has been a longstanding goal of evolutionary biology. Developmental processes offer a potential source for such rules because they translate genomic variation into the population-scale phenotypic variation. However, our understanding of developmental rules is based on a handful of well-established model species which hindered identifying rules and investigating their evolution. Recent methodological advances, such as µCT scanning on soft tissues, two-photon imaging and modelling have facilitated the study of how developmental processes shape phenotypic variation in diverse, non-traditional model species. Here, we use the outstanding dental diversity of bats to investigate how the interplay between developmental processes can explain the morphological diversity in teeth. We find that the inhibitory cascade model, which has been used to predict the proportions of teeth and other serial organs, poorly predicts the variation in tooth number and size in bats. Instead, by tinkering with reaction/diffusion processes, we identify jaw growth as a key driver of the phenotypic evolution of tooth number and size critical to the different diets. By studying developmental processes in the context of adaptive evolution, we are able to discover a new developmental rule that explain and predict interspecific variation in serial organ number and proportion.

Gas1 Regulates Patterning of the Murine and Human Dentitions through Sonic Hedgehog

The mammalian dentition is a serially homogeneous structure that exhibits wide numerical and morphological variation among multiple different species. Patterning of the dentition is achieved through complex reiterative molecular signaling interactions that occur throughout the process of odontogenesis. The secreted signaling molecule Sonic hedgehog (Shh) plays a key role in this process, and the Shh coreceptor growth arrest-specific 1 (Gas1) is expressed in odontogenic mesenchyme and epithelium during multiple stages of tooth development. We show that mice engineered with Gas1 loss-of-function mutation have variation in number, morphology, and size of teeth within their molar dentition. Specifically, supernumerary teeth with variable morphology are present mesial to the first molar with high penetrance, while molar teeth are characterized by the presence of both additional and absent cusps, combined with reduced dimensions and exacerbated by the presence of a supernumerary tooth. We demonstrate that the supernumerary tooth in Gas1 mutant mice arises through proliferation and survival of vestigial tooth germs and that Gas1 function in cranial neural crest cells is essential for the regulation of tooth number, acting to restrict Wnt and downstream FGF signaling in odontogenic epithelium through facilitation of Shh signal transduction. Moreover, regulation of tooth number is independent of the additional Hedgehog coreceptors Cdon and Boc, which are also expressed in multiple regions of the developing tooth germ. Interestingly, further reduction of Hedgehog pathway activity in Shhtm6Amc hypomorphic mice leads to fusion of the molar field and reduced prevalence of supernumerary teeth in a Gas1 mutant background. Finally, we demonstrate defective coronal morphology and reduced coronal dimensions in the molar dentition of human subjects identified with pathogenic mutations in GAS1 and SHH/GAS1, suggesting that regulation of Hedgehog signaling through GAS1 is also essential for normal patterning of the human dentition.

Incidence And Risk Factor Analysis For Swelling After Apical Microsurgery

The aim of this prospective observational cohort study is to evaluate developing periapical swelling after apical microsurgery and determine potential risk factors. Ninety-eight apical microsurgery patients were selected for this study. Before surgery, bone shadow volume and density of pathological tissue were measured by CBCT. The other variables (age, gender, operative teeth number, fistula, preoperative swelling, drug use and pre-surgery root canal treatments) were assessed during examination. Swelling degree was confirmed by questionnaires for patients on the 1st, 7th, 14th, and 21st days respectively after surgery. Statistical analyses were performed to identify predictors for swelling. Majority of patients reported moderate (45.9%) or severe (34.7%) swelling on day 1, and moderate (44.9%) or mild (45.9%) on day 7. 99% patients had no or mild swelling on day 14. The average swelling level peaked on day 1 postoperatively and gradually decreased. Of statistical significance, age, bone shadow volume and density of pathological tissue acted as predictors of swelling(P<0.05). However, there was no significant difference in gender, tooth number, fistula, preoperative swelling, drug use, or pre-surgery root canal treatments (P > 0.05). We conclude that younger patients with larger shadow volume and density were significantly more likely to develop swelling after apical microsurgery.

Deep learning for automated detection and numbering of permanent teeth on panoramic images

Objective: This study aimed to evaluate an automated detection system to detect and classify permanent teeth on orthopantomogram (OPG) images using convolutional neural networks (CNNs). Methods: In total, 591 digital OPGs were collected from patients older than 18 years. Three qualified dentists performed individual teeth labelling on images to generate the ground truth annotations. A three-step procedure, relying upon CNNs, was proposed for automated detection and classification of teeth. Firstly, U-Net, a type of CNN, performed preliminary segmentation of tooth regions or detecting regions of interest (ROIs) on panoramic images. Secondly, the Faster R-CNN, an advanced object detection architecture, identified each tooth within the ROI determined by the U-Net. Thirdly, VGG-16 architecture classified each tooth into 32 categories, and a tooth number was assigned. A total of 17,135 teeth cropped from 591 radiographs were used to train and validate the tooth detection and tooth numbering modules. 90% of OPG images were used for training, and the remaining 10% were used for validation. 10-folds cross-validation was performed for measuring the performance. The intersection over union (IoU), F1 score, precision, and recall (i.e. sensitivity) were used as metrics to evaluate the performance of resultant CNNs. Results: The ROI detection module had an IoU of 0.70. The tooth detection module achieved a recall of 0.99 and a precision of 0.99. The tooth numbering module had a recall, precision and F1 score of 0.98. Conclusion: The resultant automated method achieved high performance for automated tooth detection and numbering from OPG images. Deep learning can be helpful in the automatic filing of dental charts in general dentistry and forensic medicine.

Numerical abnormalities of permanent dentition - a case report

Tooth number abnormalities may occur under the influence of genetic or environmental factors which intervene in the tooth formation stages (induction and proliferation), most commonly the permanent dentition being affected. The result is the appearance of dental anomalies with numerical deficiency (hypodontia, anodontia), or with dental excess (hyperodontia, over-teeth). In this paper we report a case of a 15-year-old boy with associated abnormalities of permanent dentition: mesiodens and palatal impacted cuspid at the maxillary dental arch and incisor anodontia at the mandibular dental arch. Orthodontic treatment aimed at resolving maxillary dental crowding, obtaining dental alignment, a stable and functional occlusal relationship and a satisfactory smile for the patient.

Failure of Tooth Development: Prevalence, Genetic Causes and Clinical Features

In dental practice may be encountered a wide variability in the clinical dental phenotype of tooth number. Failure of tooth development at the bud stage causes tooth agenesis and reduction in tooth number in the dental arch which involves various complications. Tooth agenesis is one of the most common developmental anomalies of human permanent dentition and tends to run in families, may aggregate within families, suggesting a genetic cause. Tooth agenesis can occur in association with a variety of craniofacial syndromes, but it is also found as an isolated trait (familial or sporadic). Other tooth anomalies, such as tooth shape and size, delayed eruption of teeth, malposition, short roots or taurodontism, have been noted in association with non-syndromic tooth agenesis as well. Both the deciduous and permanent dentitions may be affected by missing teeth. Variations in the number of missing teeth can be determined by a mutation in one gene, by mutations in multiple genes, induced by local or systemically acting environmental factor, caused by a combination of gene mutations and environmental factors acting together, or by damage to chromosomes. As the number of missing teeth increases, so does the severity of clinical consequences and the impact on oral health–related quality of life.

Evaluation of smile esthetics in adults with different overjets

Our aim was to quantitatively assess the relationship of smile esthetics variables with various types of anterior overjet (OJ) malocclusion, and identify the cephalometric factors affecting smile measurements in different types of anterior overjet malocclusion. 90 patients undergoing orthodontic treatment in the Department of Orthodontics were selected for this retrospective study based upon the inclusion criteria. The patients were divided into the following groups according to their OJ: Group 1 (0-4mm), Group 2 (&#62;4mm), Group 3 (&#60;0mm).The upper lip height, and inter-labial gap differed significantly among the groups, whereas arc ratio, tooth number, upper midline, buccal corridor, smile index, arch form index and lower tooth exposure did not significantly among the groups. Some smile variables (upper lip height, inter-labial gap) differed significantly among different types of anterior overjet malocclusion. This study confirmed that the smile pattern varies between different types of malocclusion.

Management of a Complex Dentoalveolar Traumatic Injury with Multiple Avulsions

Background. Dentoalveolar trauma is a major cause of tooth loss in children. Avulsion, luxation, crown, and root fracture are the injuries to primary and permanent dentition. The incidence of trauma for maxillary anterior teeth ranges for 4%-91%. Many case reports have been published regarding the treatment of trauma to anterior teeth; however, case reports comprising multiple avulsions including canines and premolars are rare in literature. Method. After mouth rinsing was done with 2% betadine solution, the luxated teeth numbers 31 and 42 were repositioned into the tooth socket and were secured with the composite resin-wire splint. Tooth number 32 was extracted because it was disarticulated from the socket, and the socket was disrupted because of the alveolar fracture. The maxillary avulsed teeth could not be reimplanted because of the alveolar socket damage which was due to the alveolar bone fracture. Results. The patient was reevaluated for the removable prosthesis in recall visits; the patient was well adapted to the appliance with no complaints regarding mastication and speech. The patient was advised to report periodically for further adjustments in the prosthesis and for radiographic evaluation. Conclusions. This case report includes proper history taking, diagnosis, and treatment of a complex dentoalveolar trauma along with short-term prosthetic rehabilitation for improvement of aesthetics, phonetics, and mastication of growing child.