ABSTRACT
@#The problems caused by proximal contact loss (PCL) of dental implants have been a mainstream research topic in recent years, and scholars are unanimously committed to analyzing their causes and related factors, aiming to identify solutions to the problems related to PCL. The effects of the anterior component of force (ACF), the lifelong remolding of the adult craniofacial jaw and alveolar socket, and the osseointegration characteristics of dental implants are the main causes of PCL. On the one hand, the closing movement of the mandible causes the ACF of the tooth to move through the posterior molar cusp. Moreover, drifting between the upper and lower posterior teeth and mandibular anterior teeth can cause the anterior teeth of the upper and lower jaws to be displaced labially. On the other hand, reconstruction of the jaw, alveolar socket and tooth root, the forward horizontal force of the masticatory muscles, the dynamic component of the jaw and the forward force generated by the oblique plane of the tooth cusp can cause the natural tooth to experience near-middle drift. Additionally, natural teeth can shift horizontally and vertically and rotate to accommodate remodeling of the stomatognathic system and maintain oral function. Nevertheless, the lack of a natural periodontal membrane during implant osseointegration, the lack of a physiological basis for near-medium drift, the small average degree of vertical motion and the integrated silence of dental implants without the overall drift characteristics of natural teeth increases the probability of PCL. The high incidence of PCL is clearly associated with the duration of prosthesis delivery and the mesial position; but it is also affected by the magnitude of the bite force, occlusion, the adjacent teeth, restoration design, implant location, jaw, and patient age and sex. PCL has shown a significant correlation with food impaction, but not a one-to-one correspondence, and did not meet the necessary and sufficient conditions. PCL is also associated with peri-implant lesions as well as dental caries. PCL prevention included informed consent, regular examinations, selection of retention options, point of contact enhancement, occlusal splints, and the application of multipurpose digital crowns. Management of the PCL includes adjacent contact point additions, orthodontic traction, and occlusal adjustment. Existing methods can solve the problem of food impaction in the short term with comprehensive intervention to seek stable, long-term effects. Symmetric and balanced considerations will expand the treatment of issues caused by PCL.
ABSTRACT
Objective@#COVID-19 epidemic can be associated with a variety of anxious responses and safety behaviors. The present research explored the psychological implications associated with COVID-19 during the outbreak in 2020 to date. Pakistani media has given particular attention to this outbreak in the region. @*Methods@#Three hundred and forty-seven undergraduate university students from Pakistan completed a battery of questionnaires focusing fear of COVID-19, associated safety behaviors, factual knowledge of COVID-19, and other psychological pointers hypothesized to be as predictors of anxious responses to COVID-19 threat and associated safety behaviors. @*Results@#The sample appeared to be fearful of COVID-19 and this fear was related to disgust sensitivity, anxiety sensitivity-related physical concerns, body vigilance, contamination cognitions, and general distress. Results suggested that the tendency of overestimating the severity of contamination and anxiety sensitivity towards physical concerns are significant predictors of COVID-19 related fear and consequent safety behaviors. @*Conclusion@#It is suggested that people with a greater concern of contamination are likely to respond fearfully to COVID-19 and that people with higher fear of COVID-19 are likely to feel contamination concerns.
ABSTRACT
The objective of this study was to construct three-dimensional (3D) images of premolars to measure the length, surface area and volume of crown and root and to analyze the mathematical relation among crown-to-root ratios in terms of length, surface area and volume. Twenty-five premolars were scanned using micro-computed tomography (micro CT) in vitro to build 3D models. The long axis and enamelo-cemental junction of each tooth were determined with the help of Geomagic Studio software, and the length, surface and volume of crown and root were measured. The crown-to-root ratios in terms of length, surface and volume were calculated and the relationship among length, surface area and volume of crown and root as well their ratios were analyzed using SPSS software. The interrelationship among crown length (x), surface area (y) and volume (z) could be expressed as z= -808.2 0+ 124.80x +3.35y -5.59x2-0.14xy+3.47y 2*10-4 (R2 = 0.99) and that of root length (x1), surface area (y1) and volume (z1), as z1= -207.50 +13.87x1+1.75y1 + 5.03x12*10-2-8.05x 1y1 *10-2+ 2.58*10-3y12 (R2 = 0.93) . The correlation among crown-to-root ratio in length(x2), crown-to-root ratio in surface area (y2) and crown-to-root ratio in volume (z2) could be expressed in z2= -4.48*10-2 -1.25x2*10-2+1.20y2 + 3.29x22-5.05x2y2 + 2.00y22 (R2 = 0.96). The length, surface area and volume of crown and root of premolars share a close relationship, while, a definite mathematical relation could be observed amongst their ratios. Crown to root ratio in terms of length, surface and volume, may provide a novel multi-criterion method for evaluating tooth function.
El objetivo de este estudio fue construir imágenes tridimensionales (3D) de los dientes premolares para medir la longitud, superficie y volumen de la corona y raíz, junto con analizar la relación matemática entre las proporciones de la corona a la raíz en términos de longitud, superficie y volumen. Veinticinco premolares fueron escaneados mediante microtomografía computadorizada (microTC) in vitro para construir modelos en 3D. Con el software Geomagic se determinaron el eje y la unión amelo-cementaria de cada diente, y se midieron la longitud, superficie y volumen de la corona y la raíz de los dientes premolares. Con el programa SPSS se calcularon y analizaron las proporciones de la corona a la raíz en términos de longitud, superficie y volumen y la relación entre la longitud, superficie y volumen de la corona y de la raíz. La interrelación entre la longitud de la corona (x), superficie (y) y el volumen (z) puede ser expresado como z= -808,2 0+ 124,80x + 3,35y -5,59x2-0,14xy + 3.47y2*10-4 (R2= 0,99) y la de longitud de la raíz (x1), área de superficie (y1) y el volumen (z1), como z1= -207,50 + 13.87x1 + 1.75y1 + 5.03x12 * 10-2-8.05x1y1 * 10-2 + 2,58 * 10-3y12 (R2= 0,93). La correlación entre la relación de corona a raíz en longitud (x2), la relación corona a raíz en superficie (y2) y la relación corona a raíz en volumen (Z2) podría expresarse en z2 = -4,48 * 10-2 * 10-2 -1.25x2 + 1.20y2 3.29x22-5.05x2y2 + 2.00y22 (R2= 0,96). La longitud, superficie y volumen de la corona y la raíz de los dientes premolares comparten una estrecha relación, mientras que, una relación matemática definida se pudo observar entre sus proporciones. La relación entre la corona y raíz en términos de longitud, superficie y volumen, puede proporcionar un nuevo método multi-criterio para evaluar la función de los dientes.