Relationship between Physiological Resorption of Primary Molars with Its Permanent Successors, Dental Age and Chronological Age.

The aim of the present study was to analyse root resorption of the primary mandibular molars and their relationship with their permanent successors and the age of the patient. METHODS: The sample consisted of 408 digital panoramic radiographs. The mesial and distal crown-to-root ratios (CRR) of #74 and #75 were calculated by dividing the measures of the length of each root by its coronal height. The Demirjian formation stage of the premolar was established, and dental age was determined. A descriptive and statistical analysis was performed using SPSS to determine the correlation between the variables (Pearson's correlation coefficient) and to identify the differences between them (Student's t-test), with a confidence level of 95%. RESULTS: 723 molars were measured, and tables of CRR depending on dental and chronological age were obtained. The CRR decreased with increasing dental and chronological age, but not uniformly. The CRR of #74 and #75 decreased slightly when the successor premolar was in the initial stages of formation. Gender differences were obtained with respect to chronological age, mainly in girls, because the root resorption of #74 was always more advanced, and the formation of the #34 more advanced. CONCLUSIONS: Root resorption of the molar is slight and progressive when the successor premolar begins formation until stage D, and becomes higher starting at stage E. It is possible to determine the state of the child's maturation and the CRR according to dental and chronological age.

Learning of paediatric dentistry with the flipped classroom model.

INTRODUCTION: The flipped classroom (FC) is a pedagogical model that can be very useful in obtaining a dentistry degree. The main objective of this study was to compare learning between student groups introducing FC in the area of paediatric dentistry at the Complutense University of Madrid in 2019. MATERIALS AND METHODS: In this study, 76 students enrolled for the first time in the Pediatric Dentistry programme and completed a questionnaire (pre-Q) regarding specific theoretical knowledge about pulpotomies. Subsequently, they were divided into two groups: group A, which had free access before the class to an explanatory video about the indications and techniques of pulpotomy and group B, which viewed the same video only one time in class. After that, all students completed the same questionnaire (post-Q) again and a survey on the degree of satisfaction about the teaching method. RESULTS: The differences in score between the post-Q and pre-Q in group A had a mean (SD) value of 3.5 (2.4) and in group B, a mean (SD) of 2.5 (2.2), with a p value of .07. In questions 3, 5 and 8, learning was greater in the experimental group (p = .007, p = .02 and p = .001, respectively). For 74.4% of the students in group A, accessing the video previous to the class was a very useful tool. CONCLUSIONS: These results suggest that implementing FC in paediatric dentistry classes help students to acquire more theoretical knowledge, which is necessary before practical teaching.

A cephalometric method to diagnosis the craniovertebral junction abnormalities in osteogenesis imperfecta patients.

Osteogenesis imperfecta (OI) is a hereditary bone fragility disorder that in most patients is caused by mutations affecting collagen type I. Their typical oral and craneofacial characteristics (Dentinogenesis imperfecta type I and class III malocclusion), involve the dentist in the multidisciplinary team that treat these patients. It is usual to perform lateral skull radiographs for the orthodontic diagnosis. In addition, this radiograph is useful to analyse the junctional area between skull base and spine, that could be damaged in OI. Pathology in the craneovertebral junction (CVJ) is a serious complication of OI with a prevalence ranging from rare to 37%. To diagnosis early skull base anomalies in these patients, previously the neurological symptoms have been appear, we make a simple cephalometric analysis of the CVJ. This method has four measurements and one angle. Once we calculate the values of the OI patient, we compare the result with the mean and the standard deviations of an age-appropriate average in healthy controls. If the patient has a result more than 2,5 SDs above the age-appropriate average in healthy controls, we should to refer the patient to his/her pediatrician or neurologist. These doctors have to consider acquiring another diagnostic images to be used to determine cranial base measurements with more reliability. Thereby, dentists who treat these patients, must be aware of the normal radiological anatomy of the cervical spine on the lateral cephalogram. Key words:Osteogenesis imperfecta, craniovertebral junction, cephalometric.

Dental age estimation in Spanish children.

The objective of this study was to apply the method for calculating dental age proposed by Demirjian et al. to a sample of Spanish children, followed by a comparison between their dental and chronological ages. This study also set out to create tables to convert specific dental age using the maturity data from our sample. This study was performed on a sample of 1010 orthopantograms taken of Spanish children (485 boys and 525 girls) aged 2-16. We found that the mean estimated dental age exceeded the mean chronological age in both boys and girls, with the mean difference being 0.87 and 0.55 years respectively. We adapted Demirjian's method to our study sample to obtain specific conversion tables and curves.

Permanent teeth development in a Spanish sample. Application to dental age estimation.

The purpose of this study is to clarify the chronology of different stages of dental development, according to Demirjian, in a sample of Spanish children, which will enable us to build a database that will be used as a reference in regard to the dental development of individuals of our socio-geographic environment. In the same studied sample, a calculation of the dental age according to Demirjian was carried out. This study was conducted in a final sample consisting of 1010 orthopantograms, corresponding to Spanish children (485 boys and 525 girls) ages 2-16. Comparing the age of onset of the different stages among the children, evidence was found that girls had an earlier general development than boys. These differences were only statistically significant in teeth and concrete stages. The canine teeth revealed greater gender dimorphism, with significant differences in all stages compared with the upper canines. The method proposed by Demirjian for dental age calculation resulted in a significant overestimation of dental age in relation to the chronological age in boys (average of 0.87 years) and girls (average of 0.55 years). Data from this study may be used as reference for dental maturity, as well as a standard for estimating age in Spanish children.

Lanczos iterated time-reversal.

A new iterative time-reversal algorithm capable of identifying and focusing on multiple scatterers in a relatively small number of iterations is developed. It is recognized that the traditional iterated time-reversal method is based on utilizing power iterations to determine the dominant eigenpairs of the time-reversal operator. The convergence properties of these iterations are known to be suboptimal. Motivated by this, a new method based on Lanczos iterations is developed. In several illustrative examples it is demonstrated that for the same number of transmitted and received signals, the Lanczos iterations based approach is substantially more accurate.

Reconstruction of periodic structures from optical scattering measurements using adjoint equations.

A new numerical approach to efficiently reconstruct the profile of a grating from measurements of reflection coefficients is demonstrated. The problem is posed in the mathematical framework of an inverse scattering problem and solved using gradient-based algorithms. The gradient is computed efficiently using adjoint equations, which amounts to an extra scattering computation per iteration. For symmetric profiles it is shown that only knowledge of the scattered field is sufficient to compute the gradient. As a result, complex profiles can be reconstructed rapidly, and the method can be potentially used in metrology applications in semiconductors. The technique is demonstrated for the case of TE polarization.

A one-dimensional finite element method for simulation-based medical planning for cardiovascular disease.

We have previously described a new approach to planning treatments for cardiovascular disease, Simulation-Based Medical Planning, whereby a physician utilizes computational tools to construct and evaluate a combined anatomic/physiologic model to predict the outcome of alternative treatment plans for an individual patient. Current systems for Simulation-Based Medical Planning utilize finite element methods to solve the time-dependent, three-dimensional equations governing blood flow and provide detailed data on blood flow distribution, pressure gradients and locations of flow recirculation, low wall shear stress and high particle residence. However, these methods are computationally expensive and often require hours of time on parallel computers. This level of computation is necessary for obtaining detailed information about blood flow, but likely is unnecessary for obtaining information about mean flow rates and pressure losses. We describe, herein, a space-time finite element method for solving the one-dimensional equations of blood flow. This method is applied to compute flow rate and pressure in a single segment model, a bifurcation, an idealized model of the abdominal aorta, in three alternate treatment plans for a case of aorto-iliac occlusive disease and in a vascular bypass graft. All of these solutions were obtained in less than 5 min of computation time on a personal computer.