PubMed · 15440673
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H JOLY. 1950-07-08. [Nylon sutures].. https://pubmed.ncbi.nlm.nih.gov/15440673/
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Aesthetic requirement in dentistry is getting more and more important every day. One of its basic principles is the correct selection of colour for the restorations. Colour is a quality which is modulated by a series of factors, environmental and individual, that the clinic must know. Colour measurement by the human eye can induce to an appreciation mistake if it doesn't follow a correct protocol of light conditions and observation technique, checked by the authors, simplifying it with a practical focusing. Colour measurement instruments have appeared recently, trying to correct the problems of conventional technique.
OBJECTIVES: The aim of this paper was to investigate the influence of lesion shape and depth as well as the direction of occlusal loading on the mechanical response of cervical GIC restorations. METHODS: A finite element model of a lower first premolar was created. Both wedged and rounded lesions were then modelled with incremental depth after which the tooth was loaded at different angles. First principal stress (tension) was employed as an indicator of material failure, by contrasting our calculated stresses with the ultimate tensile strength of the GIC and known values of bond strength between material and tooth substrate. RESULTS: Obliquely loaded teeth exhibited significantly higher tensile stress in the cervical region of the restoration. For forces inclined at angles of 30 degrees and higher to the vertical tooth axis, the tensile stresses in the cervical margin of the restoration exceeded the ultimate material and bond strength. In contrast, lesion shape and depth have only a minor influence on tensile stress development. CONCLUSIONS: Lesion depth and shape are not of primary concern from a mechanical perspective for a restorative treatment decision. By contrast, occlusal diagnosis and subsequent re-adjustments of tooth contacts do form a critical part of the treatment of non-carious cervical lesions (NCCLs).
OBJECTIVES: The aim of the overview is to critically analyse the contributing factors to the biological wear process and to screen the wear simulators in dentistry for their capacity to mimic the wear conditions. An overview of the types of wear, grouped as biotribocorrosion, combined with a description of the different wear simulating devices will allow us to better understand the multifactorial nature of wear. METHODS: A search on keywords highlights the most common in-vitro wear simulators and their use in the laboratories for various simulation applications. RESULTS: Wear is a complex process that can hardly be simulated while controlling all variables. Especially the extrapolation of the in-vitro wear results to the in-vivo situation is difficult because there is a lot of interplay with biological factors that are difficult to mimic. SIGNIFICANCE: It is not the degree of sophistication, but the right mix of controllable variables that will make a wear simulator predictive.