The transmembrane Semaphorin Sema I is required in Drosophila for embryonic motor and CNS axon guidance.

The semaphorins comprise a large family of conserved glycoproteins, several members of which have been shown to function in repulsive neuronal growth cone guidance. We show here that Drosophila Semaphorin I (Sema I), a transmembrane semaphorin expressed on embryonic motor and CNS axons, is required for correct guidance of motor axons and for the formation of CNS pathways. In mutant embryos lacking Sema I, motor axons stall and fail to defasciculate at specific choice points where normally they would project to their muscle targets. In addition, a specific CNS fascicle fails to form correctly in these embryos. Rescue and ectopic expression experiments show that Sema I is required in neurons to mediate axon guidance decisions. These studies further suggest that like secreted semaphorins, transmembrane semaphorins can function as repulsive guidance cues for specific axon guidance events during neurodevelopment.

Problems in identifying "bursts" of periodontal attachment loss.

A theory of periodontal attachment loss which postulates discrete bursts of activity has recently been proposed. This paper identifies several problems in the interpretation of the experimental data that have been used to support the burst model. Major obstacles to valid inferences are associated with the following: substantial measurement error, insufficient evidence supporting a dichotomy of disease state and the use of diagnostic decision criteria with undesirable properties. The nature of these problems is discussed from the framework of receiver operating characteristic (ROC) analysis. "Bursts" of attachment loss can be explained, in whole or in part, by these factors in the absence of real change. Types of research evidence that would offer more compelling support for the burst model are identified. The questionable validity of evidence supporting the burst model may impact on both the direction of future research efforts and clinical applications.

Distributions of periodontal attachment levels. Mathematical models and implications.

Distributions of periodontal attachment levels at probing sites within patients have traditionally been used in clinical diagnosis and treatment planning. Progression from mild to moderate to severe disease is generally associated with increasing magnitudes of attachment loss at greater percentages of sites. Recent analyses of distributions of periodontal attachment levels have suggested three general patterns of loss defined by: (1) loss at less than about one third of all sites, (2) more widespread disease with multiple peaks and (3) normally distributed loss with virtually all sites being affected. In attempting to stimulate these three patterns using a model based on the burst theory of periodontal attachment loss, divergent assumptions about burst magnitude, frequency, and possible local immunity were required. These findings were used to support the hypothesis that distinctly different disease processes are associated with the different patterns of attachment level. In the present investigation an alternative model was developed which was theoretically consistent with the view that the three patterns reflect arbitrary stages in a continuous disease "aging" process. Simple assumptions concerning attachment loss probabilities and rates enabled the generation of attachment level distributions that matched all three patterns previously attributed to separate disease processes, depending only upon the duration of the process.

Dental management of a patient with glycogen storage disease type I.

Patients with glycogen storage disease type I (GSD I) have varied medical problems, including a bleeding diathesis characterized by a prolonged bleeding time. A case of a patient with GSD I having a history of medical problems, some of which were related to oral and dental bleeding, was presented. The patient was cariesfree and had generalized moderate to severe periodontal breakdown. A treatment regimen in a hospital setting, using cryoprecipitate and aminocaproic acid, permitted dental care and control of oral bleeding and associated complications.

Computer-assisted dental diagnosis.

Computer-assisted dental diagnosis has been discussed from the perspective of applications, decision-making processes, and a specific example of a diagnostic system. Rapid technologic advancement and anticipated developments in the field of artificial intelligence will undoubtedly change both our expectations of future evolutions and our capacity to transform these expectations into reality. The ability of computers to enhance the diagnostic capabilities of practitioners will make automation integral to future dental practice.

A computerized dental examination record system.

A computerized record system has been developed which is capable of capturing, storing, and displaying, in a standard clinical format, the information generated during comprehensive general dental examinations. This system has been tested during examination of 200 patients.

Evaluation using sequential trials methods.

Dental school faculty members, as well as many practitioners, are interested in evaluating products and procedures used in clinical practice. Research design and statistical analysis, however, can pose problems to some, while others would like to avoid detailed consideration of protocol until after a preliminary investigation. Sequential trials methods provide an analytical structure that is both easy to use and statistically valid.

Stomatitis areata migrans affecting the gingiva.

A 62-year-old male patient with a varied medical history and oral lesions consistent with stomatitis areata migrans is discussed. The stomatitis areata migrans affected essentially all oral soft tissues, including rarely involved gingival tissues. Clinical and histologic documentation of the gingival involvement is presented.

Periodontopathic micro-organisms in the rice rat (Oryzomys palustris).

The rice rat spontaneously develops periodontal disease, and this process can be accelerated if the animal is placed on a high sucrose diet. As the aetiological agent(s) is unknown, this study was undertaken to determine the micro-organisms associated with bone loss. Animals at weaning were placed on either a high sucrose diet or on regular rat chow and were sampled periodically for a variety of micro-organisms. Bacteroides spp., spirochetes, and Actinobacillus actinomycetemcomitans were not isolated from any animals, but fusiform-like organisms and Capnocytophaga spp. were isolated occasionally. An unidentified organism which had characteristics of both A. actinomycetemcomitans and Haemophilus aphrophilus was isolated from all animals at every sampling. Whether this organism is the primary aetiological agent of periodontal disease in the rice rat remains to be determined. Over the 12 week experimental period the animals on the high sucrose diet had significantly more exposed root surface than animals on regular rat chow.

Effects of fixed-appliance orthodontic treatment on DMF indices.

An investigation was conducted to clarify the relationship between orthodontic treatment and caries incidence. DMF indices from 308 orthodontically treated and 305 untreated naval recruits were compared. Contrary to expectations, there was no evidence that orthodontic treatment increases caries experience. Orthodontically treated subjects had significantly fewer diseased surfaces--a difference averaging one less diseased surface per patient. Treatment status did not generally affect the number of filled surfaces. Treated subjects had more missing teeth if first premolars were considered, but untreated subjects had more missing teeth if first premolars were not considered. No significant correlation was found between caries incidence and duration of orthodontic treatment. The epidemiologic basis and significance of these findings are discussed.