Biomedical subjects
Publications and source records attributed to R Hickel.
1310 three-unit resin-bonded bridges were examined for their failure rates. After five years 86% (+/- 4%) were still in situ. 64% (+/- 5%) didn't need rebonding. Significant prognostic factors were: preparation of abutments, surface treatment (net retention, silicoating), type of luting agent (Bis GMA) and mobility of the abutments.
Midazolam might be an alternative to general anesthesia for noncooperative children. 40 children were treated during 94 midazolam sedations to evaluate the potential dental therapy. An average of 2 fillings and 1 endodontic treatment was possible per sedation. The initial Midazolam dosage was 0.6 mg/kg. Every 15 min another 0.3 mg Midazolam/kg were administered to maintain the treatability of the children. 30 min after the initial Midazolam dosage dental treatment could be started. The average duration of a sedation was 76 min. Our results suggest that sedations complement under dental treatment general anesthesia.
In an interdisciplinary study starting 2.5 years ago patients with various symptoms, which they associate with amalgam fillings, were examined. According to the first results of this study with 50 patients, the Hg-concentration in urine does correlate with the amount of amalgam fillings before and after taking DMPS (2,3-Dimercapto-1-propane-sulfonic-acid), but with a maximum of 66.4 micrograms Hg (24 h urine) the amounts of mobilization measured were significantly below toxicologically critical limits. Only in 3 patients did the individual immunological values (CD4/8 ratio, antinuclear antibodies) by far exceed standard values. In one case an allergy to amalgam is suspected. 40% of the patients showed a pathological psychiatric status (neurosis, depression, etc.). Another quarter had psychological problems like alcoholism or drug abuse. There is no reason at the moment to reject amalgam as filling material either because of the measured Hg-concentrations or because of any immunological or allergological findings.
Individual controlled sedation using Midazolam proves to be a valuable addition to the range of therapeutic options for non-cooperative children. In a clinical study the oral and rectal routes of administration were compared with each other. Rectal application allowed considerably better dose adjustment. While the quality of sedation and the therapeutic range were equal with both routes, rectal application had the advantage that treatment can be commenced sooner. The sedation was of shorter duration and left the patient with less unpleasant memories. Rectal application was easier and required a smaller amount of Midazolam than oral administration.
This study demonstrated that both congenital cardiovascular defects and the cytogenetic form of trisomy 21 have considerable effects on the chronology of the first dentition. The delay in the eruption of the deciduous teeth was even greater in children with congenital heart defects than in those with free trisomy 21. So-called mosaic-types of Down's syndrome, on the other hand, were associated with almost regular times of eruption.
Supply of extensively destroyed primary molars with preformed stainless steel crowns has been a method approved for decades and can be carried out in practice without taking a lot of time and financial costs. Maintenance and reconstruction of primary anterior teeth by ready made or individually manufactured crowns is necessary also for phonetic reasons. Depending on the grade of destruction of the clinical crown different possibilities for restoration are available: that is for the group of preformed types pedoformstripcrowns, polycarbonate crowns and stainless steel crowns with a composite facing, and for the group of individual manufactured crowns as resin crowns and short-pin crowns.
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.
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.
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.
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.
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.
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.
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.
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The frequency and aetiology of missing front teeth was ascertained in 1118 patients aged between ten and 20 years. Nearly every tenth patient had one ore more missing front teeth. Congenitally absent teeth accounted for 59.4% of the total.
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.
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.
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.