Ramón J Baez

Effect of acid etching on the flexural strength of a feldspathic porcelain and a castable glass ceramic

This project studied the effect of altering surface topography by chemical etching on the strength of a feldspathic porcelain and castable glass ceramic. Fifty specimens of each ceramic material were subjected to five different etch times (in groups of 10). A silane coupling agent and composite resin cement were applied. Specimens were then subjected to a three-point flexural strength test. Representative specimens were examined under scanning electron microscope to elucidate more information on the effect and the depth of etch. There was no significant difference in the mean flexural strengths between the etched and nonetched groups and no significant difference between the different etching times for either material. Photomicrographs revealed dissimilar etch depths and selective dissolution of the phases. It appears that chemical etching can improve the retention of ceramic laminate veneers without significant loss of strength.

Marginal accuracy and geometry of cast titanium copings

The biocompatibility of titanium with human tissue is well established; its potential as an alternate metal for crown restorations has yet to be fully investigated. This study measured the geometry and accuracy of coping margins cast in Ti, 99.5% chemically pure. Twenty castings with 45-degree facial and 90-degree palatal margins were made by indirect technique with a commercial system using recommended procedures. They were then cemented with ZnPO4 cement. The coping and die assemblies were embedded in resin, sectioned longitudinally, and measured with a microscope at x50 power. Casting shrinkage was characteristic, particularly along the horizontal axis in the plane of the shoulder. Although horizontal linear shrinkage of 45-degree margins was greater than that for the 90-degree form, the surface of marginal discrepancy was greatest with the 90-degree configuration.

Oral health care systems in developing and developed countries

Health care systems are essential for promoting, improving and maintaining health of the population. Through an efficient health service, patients can be advised of disease that may be present and so facilitate treatment; risks factors whose modification could reduce the incidence of disease and illness in the future can be identified, and further, how controlling such factors can contribute to maintain a good quality of life. In developed countries, clinics or hospitals may be supported by health professionals from various specialties that allow their cooperation to benefit the patient; these institutions or clinics may be equipped with the latest technical facilities. In developing countries, health services are mostly directed to provide emergency care only or interventions towards certain age group population. The most common diseases are dental caries and periodontal disease and frequently intervention procedures aim, at treating existing problems and restore teeth and related structure to normal function. It is unfortunate that the low priority given to oral health hinders acquisition of data and establishment of effective periodontal care programmes in developing countries but also in some developed countries where the periodontal profile is also less than satisfactory. Despite the fact that in several developed countries there are advanced programmes oriented to periodontal disease treatments, the concern is related to the lack of preventive oriented treatments. According to data available on periodontal status of populations from developed countries, despite the number of dentists and trained specialists, dental health professionals do not presently meet adequately the need for prevention, focusing mainly on curative care. The need for strengthening disease prevention and health promotion programmes in order to improve oral health conditions and particularly periodontal status in the majority of countries around the world is evident. Unfortunately, in many countries, the human, financial and material resources are still insufficient to meet the need for oral health care services and to provide universal access, especially in disadvantaged communities, in both developing and developed countries. Moreover, even though the most widespread illnesses are avoidable, not all population groups are well informed about or able to take advantage of the proper measures for oral health promotion. In addition, in many countries, oral health care needs to be fully integrated into national or community health programmes. Improving oral health is a very challenging objective in developing countries, but also in developed countries, especially with the accelerated aging of the population now underway and intensifying over the coming years.

A method for determining adequate resistance form of complete cast crown preparations

A diagram with various degrees of occlusal convergence, which takes into consideration the length and diameter of complete crown preparations, was designed as a guide to assist the dentist to obtain adequate resistance form. To test the validity of the diagram, five groups of complete cast crown stainless steel dies were prepared (3.5 mm long, occlusal convergence 10, 13, 16, 19, and 22 degrees). Gold copings were cast for each of the 50 preparations. Displacement force was applied to the casting perpendicularly to a simulated 30-degree cuspal incline until the casting was displaced. Castings were deformed at margins except for the 22-degree group. Castings from this group were displaced without deformation, and it was concluded that there was a lack of adequate resistance form as predicted by the diagram. The hypothesis that the diagram could be used to predict adequate or inadequate resistance form was confirmed by this study.

Community-oriented Administration of Fluoride for the Prevention of Dental Caries A Summary of the Current Situation in Asia

Dental caries is the most prevalent chronic disease affecting human populations around the world. It is recognized that fluoride plays a significant role in dental caries reduction. Meanwhile, several low- and middle-income countries of Asia have not yet implemented systematic fluoride programs; contributing factors relate to misconceptions about the mechanisms of fluoride, low priority given to oral health in national health policy and strategic plans, and lack of interest among public health administrators. A workshop on the effective use of fluoride in Asia took place in Phang-Nga, Thailand, in 2011. A series of country presentations addressed some of the topics mentioned above; in addition, speakers from countries of the region provided examples of successful fluoride interventions and discussed program limitations, barriers encountered, and solutions, as well as possibilities for expanding coverage. Participants acknowledged that automatic fluoridation through water, salt, and milk is the most effective and equitable strategy for the prevention of dental caries. Concerns were expressed that government-subsidized community fluoride prevention programs may face privatization. In addition, the use of affordable fluoride-containing toothpastes should be encouraged. The workshop identified: strengths and weaknesses of ongoing community-based fluoride programs, as well as the interest of countries in a particular method; the requirement for World Health Organization (WHO) technical assistance on various aspects, including fluoridation process, feasibility studies, and implementation of effective epidemiological surveillance of the program; exchange of information; and the need for inter-country collaboration. It was acknowledged that program process and evaluation at the local and country levels need further dissemination. The meeting was co-sponsored by the World Health Organization, the International Association for Dental Research, and the World Dental Federation.