Finite element analysis of stress distribution in intact and porcelain veneer restored teeth.

UNLABELLED: The aim of this study was to investigate the stress distribution generated in a veneer restoration of an upper central incisor compared to intact teeth using the finite element analysis after applying a lingual buccal loading at the incisal edge. METHODS: Two models were developed: one model contained enamel, dentine, cementum, periodontal ligament, cortical and trabecullar bones, and the other model was a veneer restoration; both models were developed using MSC/Nastran software (MacNeal-Schwendler Corporation, Los Angeles, CA, USA) as the pre- and post-processor. A 10-N load was applied at the incisal edge from the lingual to the buccal side to simulate oral conditions in this area (protrusion). RESULTS: Von Mises stresses were then analysed for three different regions: A-B (enamel elements under the veneer or second enamel layer), A'-B' (buccal enamel and/or veneer element layer) and C-D (lingual enamel elements layer). A higher stress mode was observed for both models at the lingual cervical region. CONCLUSIONS: The presence of a veneer restoration on the incisors is a good alternative to mimic the behaviour of enamel under protrusion loading conditions. The use of veneers to replace enamel during rehabilitations is recommended.

Microleakage in primary teeth restored by conventional or bonded amalgam technique.

The aim of this in vitro study was to evaluate marginal leakage in class V restorations in primary teeth restored with amalgam, using three different techniques. Thirty maxillary anterior primary teeth, clinically sound and naturally exfoliated, were used. In group 1 (n = 10), two thin layers of a copal varnish (Cavitine) were applied. In group 2 (n = 10), Scotchbond Multi-Purpose Plus, a dual adhesive system, was used according to manufacturer instructions. In group 3 (n = 10), One-Step adhesive system in combination with a low-viscosity resin (Resinomer) were used according to manufacturer instructions. All samples were restored with a high-copper dental amalgam alloy (GS 80, SDI). After restoration, the samples were stored in normal saline at 37 degrees C for 72 h. The specimens were polished, thermocycled (500 cycles, 5 degrees and 55 degrees C, 30-s dwell time) and impermeabilized with fingernail polish to within 1.0 mm of the restoration margins. The teeth were then placed in 0.5% methylene blue for 4 h. Finally, the samples were sectioned and evaluated for marginal leakage. The Kruskal-Wallis test showed that the filled adhesive resin (group 3) had the least microleakage. There was no significant difference between groups 1 and 2.

Iontophoresis: an alternative in the treatment of dental caries?

This study deals with some aspects of caries decay etiology and treatment using iontophoresis, when there is no cavity, and discusses remineralization of decayed teeth.

Midtrimester amniocentesis. Subjective maternal responses.

Studies, through questionnaire and interview, of couples who elect or decline midtrimester amniocentesis demonstrate that both groups cope well with new decisions surrounding this procedure. The pregnancy monitored by genetic amniocentesis does not appear to receive special status as viewed by the parents, nor is the developing fetus placed in a special category during the pregnancy.

Diagnosis of a triploid fetus at genetic amniocentesis.

Nearly 20% of spontaneously aborted fetuses with chromosomal errors have been shown to have a triploid karyotype. Such a fetus is rarely encountered during the course of an amniocentesis at midtrimester. Because amniotic fluid cell polyploidy is an occasional finding among normal fetuses at midtrimester, the following report illustrates the importance of gathering corroborative evidence of an affected fetus before arriving at a prenatal diagnosis.

Genetic amniocentesis in multiple pregnancy.

Eleven cases of twin pregnancy presenting for genetic diagnosis in the second trimester are reported. In all 11 cases, a correct chromosomal diagnosis was made on each of the twins. The technique used required only ultrasound and Evan's blue dye for direction of the amniocentesis. Amniography was not performed. The technique used is described in detail, and its advantages over more standard techniques are described.

Fetal exsanguination and other vascular injuries from midtrimester genetic amniocentesis.

A case of fetal exsanguination after midtrimester genetic amniocentesis is reported. Examination of the ration of fetal-to-meternal red cells in the amniotic fluid obtained by amniocentesis for genetic study from 242 consecutive patients, including the reported case, suggests that fetal hemorrhage is relatively common and difficult to avoid during this procedure. It also appears that hemorrhage occurs significantly more oftern when the placenta is located anteriorly. Reasons as to why the accident is rarely fatal are considered, and some recommendations for patient counselling and management are discussed.

Amniocentesis for antenatal diagnosis. Review of problems and outcomes in a large series.

The results of amniocentesis for diagnostic genetic studies on 242 patients are presented in detail. These suggest that obtaining fluid free from contaminating red blood cells is important to successful cell culture. The data also suggest that it is technically more difficult to obtain such fluid tham might be expected, despite the use of ultrasonic localization and experienced operators. Nevertheless, 97 per cent of patients who elect to complete antenatal diagnosis will ultimately obtain the information sought, in time to intervene medically if desired. Moreover, the act of obtaining this information is shown to be without significant risk to the ultimate outcome of pregnancy.