Chamfer

Purpose: Previous studies have reported on the difficulties inherent in preparing the labial aspect of teeth for metal ceramic crowns with consistency and also the implications for the definitive restoration of underprepared and overangled finish lines. In this study, a bur designed to prepare a 1.2-mm deep chamfer was tested and compared with two other bur kits. Materials and Methods: Seventy-two teeth were prepared to receive metal ceramic crowns in vitro by students using one of the two bur kits or the new bur. Using a coordinate measuring machine (CMM), replicas of the prepared teeth were scanned in the mid-labial plane, and shoulder width and cavosurface angles were measured. Results: The new bur produced preparations with a mean shoulder width and cavosurface angle of 1.146 ± 0.241 mm and 108 ± 11 • , respectively, compared with 0.626 ± 0.234 mm and 128 ± 14 • produced by a commercially available standardized crown cutting bur system and 0.626 ± 0.218 mm and 124 ± 15 • produced by the bur kit in use at our center at the time of the study. These differences were statistically significant at the 5% level, using Tukey's comparison of means. Conclusions: Teeth prepared by the new bur had wider shoulders and lower cavosurface angles than teeth prepared either with a standardized crown cutting system or locally selected bur kit. The quality of labial preparations produced by the new bur in terms of closeness to the postulated "ideal" width and angulation warrants further investigation.

En los años 60, en Barcelona confluyeron múltiples circunstancias que permitieron
la aparición de una arquitectura disímil respecto a los bloques de vivienda tradicional
desarrollados en el barrio de la Esquerra de L’eixample. Este estudio pretende
hacer un análisis de los elementos que hicieron posible la construcción del Edificio
Mediterráneo de Antonio Bonet y Puig Torné (1960-1966), evaluando los motivos
e influencias que dieron lugar a este ejemplo de reinterpretación y crítica del Plan
Cerdá, para así generar una arquitectura moderna y diferente a la desarrollada
hasta ese momento en la mayoría del Ensanche. Esta innovación se evidencia en la
propuesta de cambiar la manera de hacer fachada y chaflán, rompiendo el esquema
continuo y homogéneo que se venía desarrollando desde 1860. Las limitaciones
establecidas en la normativa, la promoción del proyecto, las circunstancias económicas
del país y el desarrollo del barrio de la Esquerra, posibilitaron proyectar y
construir este caso de estudio, en búsqueda de revalorizar el sector. Asimismo se
pretende generar una reflexión de por qué no se siguieron desarrollando proyectos
de este tipo en el barrio, teniendo en cuenta el favorable impacto mediático que
tuvo en su momento como elemento de propaganda-manifiesto y promoción del
proyecto para incentivar un cambio en el resto de arquitectos de la ciudad.



In the 60s in Barcelona, the union of multiple circumstances appeared that allowed
the creation of a dissimilar architecture with respect to the traditional housing
blocks developed in the Esquerra of L’eixample district. This study intends to make
an analysis of the elements that made possible the construction of the Antonio
Bonet’s and Puig Torne’s “Edificio Mediterraneo” (1960-1966). For this reason it is
intended to show the reasons and influences that allowed the construction of this
example of reinterpretation and criticism of the Cerdá Plan, in order to generate a
modern and different architecture to that one developed in the most of the widening.
This innovation is evidenced in the proposal to change the way of making facade
and corner-chamfer, breaking the continuous scheme that had been developing
since 1860. The conditions of regulation, promotion of the project, economic
circumstances and the development of the Esquerra neighborhood, put in evidence
the possibility of projecting and constructing this case study in search of revaluing
the sector. It is also intended to question why they didn´t continue developing
projects of this type in the neighborhood, also taking into account the mediatic
impact that had at the time as an element of propaganda-manifesto and promotion
of the project to encourage a change in the rest of architects of the city.

Purpose: The purpose of this study was to evaluate the influence of shoulder and chamfer margin design on stress distribution
pattern in different all ceramic restorations.
Materials and methodology: Six three-dimensional finite element models representing mandibular second premolar tooth
were constructed, using a Finite Element Analysis Software (ANSYS version 14; ANSYS Inc., Canonsburg, PA, USA). Three models
each with shoulder and chamfer finish line were created after tooth preparation by reverse engineering, using Pro E software. Each
model with shoulder finish line margin had Bruxzir (Glidewell labs), Lava (3M ESPEE) and IPS e.max Press (Ivoclar Vivadent) all
ceramic restorations fabricated over them. Same was done with the models having chamfer finish margin. A distributed load of 600
N was applied on the restorations to analyze the stress distribution pattern in different all ceramic restorations having different
marginal geometry. The stress distribution in different groups was compared using one-way ANOVA and Tukey’s honest significance
test.
Results: Von Mises stresses in the margin region were seen to be lowest in Lava (3M ESPEE) all ceramic restoration with
shoulder finish margin when subjected to masticatory bite force. The areas of maximum stress concentration were found in the
cervical portion of the all ceramic restorations when subjected to loading forces.
Conclusion: The type of material used, and the type of margin configuration affects the stress distribution pattern within
posterior all ceramic restorations.

Purpose: Previous studies have reported on the difficulties inherent in preparing the labial aspect of teeth for metal ceramic crowns with consistency and also the implications for the definitive restoration of underprepared and overangled finish lines. In this study, a bur designed to prepare a 1.2-mm deep chamfer was tested and compared with two other bur kits. Materials and Methods: Seventy-two teeth were prepared to receive metal ceramic crowns in vitro by students using one of the two bur kits or the new bur. Using a coordinate measuring machine (CMM), replicas of the prepared teeth were scanned in the mid-labial plane, and shoulder width and cavosurface angles were measured. Results: The new bur produced preparations with a mean shoulder width and cavosurface angle of 1.146 ± 0.241 mm and 108 ± 11 • , respectively, compared with 0.626 ± 0.234 mm and 128 ± 14 • produced by a commercially available standardized crown cutting bur system and 0.626 ± 0.218 mm and 124 ± 15 • produced by the bur kit in use at our center at the time of the study. These differences were statistically significant at the 5% level, using Tukey's comparison of means. Conclusions: Teeth prepared by the new bur had wider shoulders and lower cavosurface angles than teeth prepared either with a standardized crown cutting system or locally selected bur kit. The quality of labial preparations produced by the new bur in terms of closeness to the postulated "ideal" width and angulation warrants further investigation.

Ecologists often rely on unique natural markings to identify individual free-ranging animals without disturbing them. We developed a computer-aided photo-identification system for identifying polar bears (Ursus maritimus) based on whisker spot pattern recognition. We automated our system so that the selection of 3 reference points on the input image is the only manual step required during image preprocessing. Our patternmatching algorithm is unique in that the variability within spot patterns is considered fully rather than representing them as points and applying a point-pattern matching algorithm. We also measured the reliability of our method as probabilities of true positives and false positives using photographs of various qualities taken at different angles. When we excluded photographs of poor quality and angle the probability of true positives was .80% at a false positive probability of 10%. A new photograph could be preprocessed in ,1 min and tested against a reference library of 100 individuals in ,10 min. Our computer-aided identification system could be extended for use in other species with variable spot patterns, which could be useful in efforts to estimate various population dynamics parameters essential for the study and conservation of wildlife, particularly threatened and endangered species.

The purpose of this study was to compare marginal discrepancies of Cerec 3 CAD/CAM composite crowns, fabricated on human prepared teeth with two different finish line designs, chamfer and shoulder. Materials and Methods: Sixteen human molar teeth were used to prepare full crowns. Eight teeth were prepared with a 1-mm-wide chamfer finish line and the other eight with a 1.2-to 1.5-mm circumferential shoulder. Cerec 3 crowns were fabricated from optical impressions using Paradigm MZ100 composite polymer. Marginal adaptation was evaluated in two ways: (1) using modified United States Public Health Service (USPHS) criteria to evaluate eight preselected sites on each crown margin, and (2) using scanning electron microscopy (SEM) to measure marginal gaps on all four axial walls with 15 measurements on each wall (60 measurements per crown). An evaluation of the number of acceptable crowns, determined by having all measured sites per tooth with margin gap size less than 100 μm, as a function of finish line design was also conducted. Results: In both chamfer and shoulder groups, there were only two crowns (out of eight) with clinically acceptable ratings for all eight measurement sites according to USPHS criteria. Fisher's chisquare analysis showed that there was no statistically significant difference in marginal adaptability as a function of finish line design (p > 0.05). With SEM imaging, overall mean marginal gaps for the chamfer group were 65.9 ± 38.7 μm (range 35.0 to 130.0 μm), and for the shoulder group were 46.0 ± 9.2 μm (range 26.3 to 55.6 μm); this difference was not found to be statistically significant (p > 0.05). While crown assessment based on mean marginal discrepancy measurements indicated that both the chamfer and shoulder groups were considered clinically acceptable (<100 μm); crown acceptability based on all measurement sites being less than 100 μm indicated that in the chamfer and shoulder groups there were four and three acceptable crowns out of eight, respectively. The Fisher's chi-square test indicated no statistically significant difference between the groups (p > 0.05). An agreement rate of 81.2% was calculated between the two evaluation methods, modified USPHS criteria and SEM measurements. Conclusions: Based on mean marginal discrepancy measurements, the typical marginal assessment technique, Cerec 3 Paradigm MZ100 crown restorations appear to have acceptable marginal adaptability (mean discrepancies <100 μm). Thus, the evidence from this investigation would suggest that the finish line preparation design had no effect on marginal adaptation for Cerec 3 composite crowns.