Dental materials: 1979 literature review Part II

This paper, which is presented in two parts, reviews the work on dental materials published in 1979. Included in Part II are sections on impression materials, model, die and investment materials, waxes, acrylic resins, denture base polymers, soft lining materials and tissue conditioners, cast and wrought dental alloys, ceramics, implants and, finally, corrosion. Part I included sections on dental biomechanics, fissure sealants, cements, amalgam, composite filling materials, endodontic materials and microleakage.     

Ethnic variations in sagittal condylar guidance angles

Observations of a Chinese population seem to indicate that certain ethnic differences exist which may invalidate the use of dental articulators constructed as the result of measurements made on a Caucasian population. A group of Caucasian students had been examined for a previous study. Upper and lower study models of the jaws of a group of Singaporean Chinese students were articulated in the tooth position on a Dentatus ARL articulator. Measurements were made of the angle between the occlusal plane and the Frankfort plane, the S. C. G. As and the Balkwill angle.

The results indicate that considerable anatomical differences do exist between these two distinctive ethnic groups. These findings have important implications for all restorative and prosthetic dentistry which requires the use of a dental articulator.     

An unanticipated copy number variant of chromosome 15 disrupting SMAD3 reveals a three‐generation family at serious risk for aortic dissection

Several genes involved in the familial appearance of thoracic aortic aneurysms and dissections (FTAAD) have been characterized recently, one of which is SMAD3. Mutations of SMAD3 cause a new syndromic form of aortic aneurysms and dissections associated with skeletal abnormalities. We discovered a small interstitial deletion of chromosome 15, leading to disruption of SMAD3, in a boy with mild mental retardation, behavioral problems and revealed features of the aneurysms‐osteoarthritis syndrome (AOS). Several family members carried the same deletion and showed features including aortic aneurysms and a dissection. This finding demonstrates that haploinsufficiency of SMAD3 leads to development of both thoracic aortic aneurysms and dissections, and the skeletal abnormalities that form part of the aneurysms‐osteoarthritis syndrome. Interestingly, the identification of this familial deletion is an example of an unanticipated result of a genomic microarray and led to the discovery of important but unrelated serious aortic disease in the proband and family members.     

The nature of the interface between polymethyl methacrylate denture base materials and soft lining materials

Four of the commonly used resilient denture lining materials were investigated. They were of different chemical composition, physical forms and processing cycles. Scanning electron microscope examinations of the interface between the liners and the regular acrylic resin base material were carried out in an attempt to assess the bonding of these materials to the denture base, and to evaluate the reliability of their use. The physical and mechanical bonding properties of the resilient lining materials to acrylics were studied, which included tensile, shear, peel and compression tests to measure the efficacy of the joint between the acrylic and the lining materials and its resistance to various external damaging loads. The effect of water on the liner/denture base interface and on the liner's bonding properties to acrylics was also investigated, and the validity of roughening the tissue surface of the denture base prior to processing the liner was assessed.

The findings point to the advisability of using the acrylic type of soft liners whenever resilient liners are indicated. Roughening the fitting surface of the denture base to which the resilient lining materials are to be applied has a weakening effect on the bond between the lining and the denture base. Long-term exposure of the liners to water has a destructive effect. The infusion of the water into the material leads to swelling and stresses build up at the denture base interface and these tend to promote distortion and reduction in bonding.     

The bond strengths of various adhesives used for Maryland Bridges

The tensile bond strengths of three groups of adhesives to two electrolytically etched alloys were studied. It was found that the bis-GMA composite resins gave statistically similar bond strengths. The newer Japanese acrylics tested gave statistically higher results than the bis-GMA resins. The clinical significance of these results is discussed.     

The Prevalence and Perceived Health Consequences of Hunger in Emergency Department Patient Populations

Objectives: Hunger is associated with chronic poor health and may force patients to make choices that acutely impact their health. This study was conducted to determine the prevalence of hunger, some of the choices it forces, and its perceived health effects among emergency department (ED) patients. Methods: A validated survey about hunger, choosing between food and medicine, and perceived adverse health outcomes was administered in English, Spanish, and Somali to non-critically ill ED patients or their parents. Demographics, rates of hunger, numbers of yearly ED visits, and decisions between buying commodities or medications were assessed. Relationships between variables were summarized with odds ratios (ORs), 95% confidence intervals, and logistic regression. Results: Of 930 respondents, 23.7% screened positive for hunger and 17.6% bought food instead of medications. Among the hunger-positive respondents, 44% believed this choice caused illness, and of these, 69% sought ED assessment and 35% believed they were hospitalized because of this choice. Predictors of hunger were low income (OR = 3.3), illicit drug use (OR = 5.5), chronic illness (OR = 2.1), Hispanic ethnicity (OR = 1.9), and lack of insurance (OR = 1.8). Buying food instead of medicine was predicted by low income (OR = 2.5), chronic illness (OR = 2.4), and lack of insurance (OR = 3.4). Predictors of illness were chronic illness (OR = 1.8), lack of insurance (OR = 2.8), African American race (OR = 2.0), and "poor" health (OR = 1.9). Conclusions: These ED patients have high rates of hunger and often choose to buy food instead of medications. Many believe that this choice results in ED visits and hospitalizations. Socioeconomic factors may predict hunger and subsequent ill health.