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.     

Neuro-ophthalmological manifestations of systemic lupus erythematosus in Asian patients

Purpose : To report eight patients with diagnosed systemic lupus erythematosus (SLE) who presented with a variety of neuro‐ophthalmological complications and outcomes. Methods : A review of the follow up, subsequent management and outcomes of the neuro‐ophthalmological complications of eight patients with SLE. Results : The patients presented with a myriad of symptoms of varying severities. The most common manifestations were that of optic neuropathy and eye movement abnormalities. The outcome was variable ranging from complete recovery to optic atrophy with navigational visual acuity. Treatment was often empirical, although early treatment with corticosteroids has been tried with varying success. Conclusions : The pathophysiology in the neuro‐ ophthalmological manifestations of SLE is thought be due to vaso‐occlusive disease of the small vessels of the nerve and brain, secondary to an autoimmune process. Ophthalmologists may need to consider the diagnosis of SLE in young women who present with a recent onset of neuro‐ophthalmological symptoms and signs.     

In vivo retrospective study of cement thickness under crowns

Purpose. This study evaluated the cement thickness under crowns cemented with zinc phosphate cement that had been in clinical use for at least 10 years.Material and methods. A total of 97 teeth were extracted because of periodontal disease as part of a new treatment plan. Teeth were sectioned and the cement thickness measured at predetermined points on the occlusal and axial walls with a measuring microscope at ×150 magnification.Results. Mean cement thicknesses on buccal and lingual walls were similar (116 μm and 109 μm, respectively), but much smaller than on occlusal walls (310 μm). Cement thicknesses at occlusal locations were significantly thicker in molars than in premolars. Poor correlations existed between cement thicknesses on buccal and lingual walls (0.26) and between these and the occlusal walls (0.35) implying that incomplete seating is strongly related to tilting or oblique seating.Conclusion. Under clinical conditions where more inherent difficulties exist, special measures must be taken to alleviate the consequences of cement fluid dynamics. (J Prosthet Dent 1998;79:621-5.)     

Knowledge and practice of behavioral management principles among dentists treating adults with learning disabilities

This study investigated U.K. dentists’ knowledge and practice of behavioral management principles (BMPs) as applied to adults with learning disabilities (AWLD). A postal questionnaire enquired into the dentists’ experience in managing AWLD, utilization of behavioral management techniques, and knowledge of BMPs. The response rate was 41% (N = 53). Two groups were investigated: specialists (dentists registered on the Special Care Dentistry specialists’ list, n = 37) and nonspecialists (dentists not on the list, n = 16). Although specialists treated more AWLD than nonspecialists, both groups of dentists reported they felt highly confident in managing AWLD. However, all dentists’ knowledge of the principles of nonpharmacological BMPs was low. Specialists had a tendency to use a greater range of nonpharmacological behavioral management techniques compared to non‐specialists. These results suggest that dental team members need more training in the theory and practice of BMPs, which might lead to less reliance on costly pharmacological interventions and a clinical experience that is more respectful of the dignity and independence of AWLD.     

Effect of Distance on the Power Density from Two Light Guides

Purpose: This study determined the effect of distance on the power density from standard and Turbo light guides (Demetron/Kerr, Danbury, Connecticut). Materials and Methods: Power density was measured from 0 to 10 mm away from the tip of standard 8‐mm curved light guides and 13/8‐mm Turbo curved light guides. To determine the effect of distance on power density, a polynomial regression line was fitted. The Kolmogorov‐Smirnov (K‐S) statistic and the Wilcoxon rank sum (WR) tests were used to determine if there was a difference in the rate at which the power density decreased for the standard and Turbo light guides as the distance from the tip increased. Photographs of the light dispersion from each tip were also taken. Results: At 0 mm, the mean (± SD) power density from the two standard light guides was 743 ± 6.1 mW/cm² and from the four Turbo light guides was 1128 ± 22.1 mW/cm². As the distance from the tip of the light‐guide tip increased, the power density decreased, but the rate of decrease was greater from the Turbo light guides than from the standard light guides. At 6 mm the power density from the standard light guides fell to 372 mW/cm² (50% of the original value) and the power density from the Turbo light guides fell to 263 mW/cm² (23% of the original value). Both the K‐S statistic and the WR sum test indicated that the distribution of light intensities was significantly different from the two light guides (WR p‐value = .0246, K‐S p‐value < .0001). The two estimated polynomials intersected at 3.66 mm, and the 95% prediction intervals intersected at about 2.8 and 4.8 mm. Therefore, beyond 5 mm away from the tip of the light guide, the standard light guides gave higher power density readings than the Turbo light guides. Photographs showed that the light dispersed at a wider angle from the Turbo light guides than from the standard light guide. CLINICAL SIGNIFICANCE The design of the light guide of a light curing unit affects light dispersion, power density, and ultimately the dentist's ability to properly cure composite. For these reasons, manufacturers should report the power density at the tip of the light guide and 6 mm from the tip of the light guide, since significant differences exist between light guide designs.     

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.     

Implications of Recent Dental Health Services Research on the Future of Operative Dentistry

Recent dental health services research has shown that restorations often last only a few years and has suggested that the compromising nature of some basic operative skills is at least partly responsible. Further, gross inconsistencies of diagnosis and treatment planning exist among dentists, leading to a considerable lack of agreement about when restorative treatment is necessary. In the interests of high-quality dental care, some of the long-standing dogma concerning restorative dental services and attitudes toward them should be questioned. At the public health level, the dental profession should strive to find ways of achieving satisfaction with less emphasis upon restoring and re-restoring teeth so that dentistry will attract the public and remain fully relevant to their needs.     

Predoctoral Implant Dentistry Programs in US Dental Schools

Surveys of US dental schools over the last 20 years have reported a continual increase in the number and types of predoctoral and postdoctoral implant dentistry programs being taught. The purpose of the following article is to report on the results of a survey intended to update the status of predoctoral programs with respect to their curricular placement, departmental jurisdictions, and course contents. In June 1993, 54 US dental schools received the implant dentistry curriculum survey, and 50 of the schools (93%) returned responses. Results indicate that the trend toward implementation of more predoctoral implant dentistry programs has been sustained, with 86% of schools reporting the existence of implant curricula. This compares with 33% and 73% of US schools having such programs in 1974 and 1989, respectively. The major reasons that schools gave for not having implant dentistry courses for predoctoral students are a lack of curriculum time and scarce financial resources. The dental disciplines most frequently guiding such programs are oral surgery and periodontics. Schools offer varying degrees of lectures, laboratories, and clinical experiences in predoctoral implant dentistry, with the number of curriculum hours peaking in years three and four. General curricular topics most commonly include a historical overview of implant dentistry, diagnosis and treatment planning, classifications and types of dental implants, and surgical and prosthodontic procedures. Seventeen percent of schools require some form of undergraduate clinical implant dentistry exposure for all of their students.