Biomedical subjects
Publications and source records attributed to R Jacobi.
Devices used to increase retention of restorations to severely damaged posterior teeth are described, with an emphasis on pins and dowels. Advantages and disadvantages of different techniques and measures to help prevent and correct problems are presented.
A type III gold alloy and six different ceramic surfaces were secured in an abrasion machine opposing extracted teeth to determine their relative abrasiveness and resistance to wear. The rankings of restorative materials from least abrasive to most abrasive were: gold alloy, polished; cast ceramic, polished; porcelain, polished; cast ceramic, polished and shaded; porcelain, polished and glazed; cast ceramic, cerammed skin shaded; and cast ceramic, cerammed skin unshaded. The ranking of materials from most wear-resistant to least wear-resistant was: gold alloy, cast ceramic cerammed, cast ceramic cerammed and shaded, porcelain polished, porcelain glazed, cast ceramic polished and shaded, and cast ceramic polished.
The laboratory procedures for making a Hi-ceram porcelain anterior reserve three-quarter crown are described. A core of high-fusing aluminum oxide is used as a coping on which tooth contours are restored with a compatible porcelain. Standard dental laboratory equipment is used and the technique can be quickly learned by any experienced ceramics technician.
A new preparation design of the ceramic reverse three-quarter crown for anterior teeth offers a way to improve the appearance of anterior teeth with slight to moderate structural damage. Advantages and indications of the new design are discussed.
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A method has been described by which a paste of shoulder porcelain and light-curing resin is used to correct deficient porcelain margins. The resin-bonded porcelain is fired in an oven for final hardening.
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Fixed partial dentures cemented to dies of adjustable mobility were subjected to repeated impacts at three different sites. Immobile abutments retained their prostheses longer than mobile abutments. Impacts that fell between the centers of rotation of the abutments were withstood longer than impacts that fell nearer the ends of the prostheses. This study failed to show a significant difference between the effect of impacts perpendicular to the occlusal plane and impacts angled 45 degrees toward the lingual plane. The results of this study suggest that (1) crowns that anchor rigid prostheses to mobile teeth require greater retentive ability than crowns on relatively immobile abutments and (2) occlusal impacts are best withstood when they fall on the areas of the fixed partial denture over and between the centers of rotation of the abutment teeth. If a fixed partial denture must withstand loading outside these areas, as is the case with cantilevered pontics and some tilted abutments, the retainer furthermost from the anticipated eccentric load must have exceptionally good retention.
The preservation of a severely damaged tooth with a cast restoration requires that the preparation be modified to make use of remaining tooth structure. Preexisting preparation features, such as boxes and isthmuses, and new ones, such as boxes, grooves, and pin holes, are employed to provide adequate retention and resistance. When destruction of coronal tooth structure exceeds one-half of the clinical crown, a pin-retained amalgam or composite resin core should be used to build up the tooth to receive a cast restoration.
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A prospective double-blind clinical trial was carried out to determine whether ambroxol (bromhexine metabolite VIII) treatment (1000 mg/day for a period of 5 days) reduces the risk of hyaline membrane disease (HMD) in potentially premature infants. Amniocentesis was performed before the first and 24 h after the last application of ambroxol or placebo to assess the development of the total phospholipid phosphorus content, the L/S ratio, the P/S ratio, and the properties of the surface tension of the amniotic fluid after ambroxol or placebo. There were 246 infants born to 224 mothers. Of the 116 infants with less than or equal to 36 completed weeks' gestation, 56 were in the ambroxol and 60 in the placebo group. No differences between groups occurred in risk factors for HMD (diabetes, asphyxia, male sex, cesarean section). Statistically significant differences in favor of the infants in the ambroxol group were found in the HMD incidence: 23.2% in the ambroxol group compared with 41.7% in the placebo group (p less than 0.05). There was no reduction of the HMD incidence in the less than or equal to 32-week gestational age category in the ambroxol group compared with the placebo group inspite of the fact that all the examined parameters for determining lung maturity reflected a stimulatory effect of ambroxol compared with the results of the placebo group, particularly before the 33rd week of gestation. Prolonged rupture of the membranes played no protective role against HMD.
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