Search PubMed⌕ Search

Biomedical subjects

R Hickel

Publications and source records attributed to R Hickel.

At least 91 records · Page 5Linked to original sources
PubMed1990

[The influence of cavity preparation on the width of marginal gaps in Cerec inlays].

In a study of the influence of the proximal box shape on the marginal fit of Cerec inlays, MOD cavities were prepared in 10 extracted teeth. One box was prepared with sharp edges as recommended by Mörmann (1989), the other was conventionally U-shaped. The width of the marginal gap was measured with a microscope at five different points. The results showed with high significance that the marginal gap of the U-shaped box preparation is smaller. It is recommended to use conventional U-shaped proximal box preparations for Cerec-inlays, too.

Dental Cavity Preparation↗
PubMed1990

[Fine polishing of Cerec inlays using diamond polishing systems].

The surface roughness of Cerec-inlays after polishing with diamond polishing pastes or Diafinish-disks was compared to polishing with aluminium oxide disks (AOD). SEM evaluation of the occlusal surface of extracted teeth revealed that diamond polishing pastes or Diafinish-disks produced smoother surfaces than AOD. The pastes, however, damaged the bonding resin. It is recommended to use AOD and diamond polishing systems for the approximal surfaces of the inlays extraorally. Intraorally AOD or Diafinish-disks are recommended.

Dental Polishing↗
PubMed1990

[Stress profile during curing contraction of composite resin adhesives].

The wall-to-wall curing contraction of thin composite resin layers was recorded with a tensometer. The composite resin was applied to cylindrically shaped ceramic sample holders with diameters of 3 mm, 4 mm and 8 mm. The distances of the sample holders was set at 50 microns, 100 microns, 150 microns, 200 microns and 300 microns. The shrinkage stress recordings clearly show that the shrinkage forces are governed by the distance of the sample holders and not by the volume or the configuration factor of the composite resin layers.

Adhesives↗
PubMed1990

[Middle course between group and individual preventive programs].

A pilot study was initiated to prove the effectivity of a prophylaxis programme for small groups of preschool children. A total number of 190 children was examined twice a year at the Dental School of Erlangen. The dental examination included df-s index and plaque index according to Quigley-Hein. Tooth cleaning was performed in small groups under professional supervision. Professional plaque removal and local fluoridation concluded each session. Twice a year the parents were offered oral hygiene instructions and informed about the relationship between sugar and caries. After two years the dfs-values were significantly lower in the test group than in the control group. Mean dfs scores ranged from 1.9 for the experimental to 3.8 for the control group. These comparatively low recordings--as against other investigations--may be due to the relatively high social standing of the children.

Child↗
PubMed1990

[Chances for the intraoral use of screen films?].

The development of film/screen combinations has reached a point where they can be used intraorally for many indications. Compared with the fastest non-screen films the dose can be reduced by the factor 8, at the moment. For a wide-spread clinical usage, however, practicable application techniques still have to be developed for the intraoral film/screen combination.

Humans↗
PubMed1990

[The problem of tooth hypersensitivity following the placement of acid-etch retained inlays].

Placement of 225 resin or ceramic inlays using the acid etch technique resulted in post-operative pain of the tooth in 16.1% of the cases. The hypersensitivity decreased in most cases within 4 to 8 weeks, 8 inlays had to be removed. Teeth with bases of phosphate cement showed similar results as those with glass ionomer cement. Possible reasons for post-operative hypersensitivity include etching the base, polymerization shrinkage and marginal gaps and, first of all, etching the dentin.

Acid Etching, Dental↗
PubMed1990

[Precision of the Cerec-System: the milling unit].

The Cerec-System is a computer-assisted method for fabrication of customized ceramic inlays. Until now there are no data available to judge the precision of this system, which is a function of several variables. This study investigated the tolerance of the milling unit by using computer-constructed data sets for test purposes. REM pictures show how the diamond bur is affected by several milling cycles. Overall precision along the x- or z-axis is largely independent of the inherent properties of the milling instrument used, such as wear. Precision along the y-coordinate, however, is dependent on the number of milling cycles and the feed along the horizontal axis. Best results can be obtained by using a new bur and slow feed.

Dental Polishing↗
PubMed1989

[Care of anterior diastemata in patients with lip-jaw-palate clefts].

Missing or peg-shaped upper lateral incisors in cleft patients require different treatment. The Maryland bridge, recontouring the tooth with composite or reconstruction of the alveolar bone with subsequent prosthetic treatment influences the result of orthodontic treatment in a positive procedures way: the procedures help to shorten the retention period and to improve the aesthetic result.

Adolescent↗
PubMed1989

[Sequelae of unsecured elastic bands (the status after 7 years)].

The use of elastic bands without an adequate appliance mechanism to close a diastema represents a professional error on behalf of the dentist. Two case reports are presented showing both the consequences of such malpractice and the successful periodontal and orthodontic treatment over a period of seven years. The reasons for this successful treatment are discussed as well as points of special interest.

Child↗
PubMed1989

Lactate influx and efflux in the 'Streptococcus mutants group' and Streptococcus sanguis.

Lactate influx was measured in Streptococcus sanguis and in several strains of Streptococcus mutans by comparing the intra- and extracellular distribution of (14C)-lactate. Lactate efflux was followed enzymatically against rising external lactate concentration. The glucose concentration was monitored in the same way. With S. sanguis OMZ 9, lactate was transported into the cells when a high external lactate concentration and a pH gradient were established. The transport rate was approximately 1,000 nmol lactate per minute and milligram protein. No lactate influx could be measured with four strains of the 'S. mutans group' (OMZ 51, 634, T3/13 and NCTC 10449). Metabolizing cells of S. mutans NCTC 10449 were able to transport lactate even against an external lactate concentration of 92 mmol/l at pH = 7. The transport rates ranged from 1,200 to 750 nmol lactate/min mg protein decreasing with increasing external lactate concentration. While an external pH = 9 had little influence on transport, transport rates decreased to 440 nmol/min mg protein at pH = 5.

Biological Transport↗
PubMed1989

[Cermet cements for milk tooth fillings. Preliminary results].

106 Ketac-Silver fillings in deciduous molars were reevaluated after 1 to 3.3 years, i.e. 25 month on the average. About 90% of 50 occlusal fillings and about 84% of 56 multisurface restorations were unchanged. Without claiming statistical evidence for their conclusiveness, we consider these results as an indication that cermet cements are a useful alternative to amalgam fillings in deciduous teeth, particularly since the life of these fillings is limited to the time until the milk tooth is physiologically lost.

Cermet Cements↗
PubMed1989

[Comparative studies on fissure sealing: composite versus Cermet cement].

Fifty two molars sealed with either composite or Cermet cement were compared. The composite sealant was applied after enamel etching using a rubber dam. Before sealing with Cermet cement the enamel was only cleaned with pumice powder and sodium hypochlorie and the material was applied without enamel etching. After an average follow-up of 1.6 years composite sealants proved to be significantly more reliable. Cermet cement sealings showed defects more frequently.

Cermet Cements↗
PubMed1989

[In vitro studies on the quality of proximal margins of Cermet fillings in posterior teeth].

Since Cerment-cement has been recommended also for Black's Class II cavities in posterior teeth, it was the goal of this study to compare its marginal adaptation with that of amalgam after alternating thermal loads. Black's Class II cavities were prepared in extracted premolar teeth and filled with amalgam or Cermet. Three different application techniques were used for the Cermet fillings: 1. syringe only, 2. syringe and amalgam plugger, 3. individual occlusal plugger. Before and after alternating thermal loads the proximal margins were studied by SEM using replicas. The poorest results were found in the Cermet fillings applied with the syringe only. In the other three groups the results were comparable. These findings suggest that cermet cement should not be applied with exclusive use of the syringe, but should always be additionally adapted with a plugger.

Bicuspid↗
PubMed1989

[Do root canal filling materials enter dentin tubules?].

After removal of the smear layer all root filling materials tested were able to infiltrate dentin tubules. With the cement types studied, filled dentin tubules were found even at a distance of 100 microns from the root canal. The infiltration of the dentin tubules now explains the outstanding results of pigment penetration tests. The question, if the smear layer is to be removed or not, can now be answered "yes".

Dentin↗
PubMed1989

[Improved measuring instruments for endodontic radiography].

Fine steel instruments used for the radiographic length measurement of root canals are not always imaged clearly enough on the x-ray film, due to lacking absorption of radiation. Although silver points have a higher radiopacity, they lend themselves less to practical use, since they are too soft, tend to bend easily and fail to convey any sense of touch. Improved measuring instruments made from a hard gold alloy combine the elastic properties of steel and the radiopacity of silver and can be recommended for routine application in length measurement radiographs.

Radiography, Dental↗