PubMed Health⌕ Search

Biomedical subjects

H Schäffer

Publications and source records attributed to H Schäffer.

At least 19 recordsLinked to original sources
PubMed1991

Determination of the etching surface of metal frameworks in resin-bonded prostheses.

The aim of electrolytic etching of the metal framework of resin bonded retainers is a microretentive surface. The results of metal etching depend on various factors such as metal alloy, casting conditions, etching solution, and constant electrolytical conditions. Precise knowledge of the inner metal surface is necessary for an exact setting of the current density per time unit. The indirect method of copying the contours from tinfoil to graph paper reduced the error rate to a mean value of +/- 2.3 mm2. This practical method of determining the metal surface before etching can be accomplished without complicated equipment.

Acid Etching, Dental↗
PubMed1991

[The Pontic. Preventive consideration of pontic design].

When fixed partial dentures are provided for edentulous areas of the alveolar ridge, the previously impaired masticatory and phonetic functions as well as esthetics are restored immediately; in the long run, the restoration helps to stabilize the occlusion, thus maintaining the integrity of the temporomandibular joints and the neuromuscular system. The reabsorption of connective tissues following the loss of teeth as well as the changes in the dimensions of edentulous areas that occur over time will have to be taken into account in that the basic shape of the tooth or teeth to be replaced needs to be modified. Pontics usually present a larger surface than natural teeth; on this surface, plaque may accumulate. The self-cleaning mechanisms are ineffective on the surfaces facing the adjacent teeth or the tissues of the alveolar ridge. For this reason, the pontics and their flexible or rigid connectors to the abutments must be considered the weakest parts of the restoration. The long-term success of the restoration, once periodontal treatment and optimum prosthodontic care have been provided, depends on whether considerations of periodontal prevention played a role in the design of the restoration and on postinsertion periodontal care.

Adult↗
PubMed1991

Functional preprosthetic orthodontics and prosthetic reconstruction with resin-bonded fixed partial dentures.

When a resin-bonded fixed partial denture is planned in the maxillary anterior region, special attention must be paid to occlusal diagnosis. Specific instrumental diagnosis is necessary to define the functionally important factors: the anterior teeth, the occlusal plane, the temporomandibular joint, and their three-dimensional relation. The optimal treatment in an anterior-guided occlusion is a complete integration of the retainers in the given tooth form without altering the original inclination of the palatal guiding surfaces of the anterior teeth. In many cases, preprosthetic orthodontics is indicated because of functional and esthetic reasons. The objective is to achieve an anterior tooth position that allows the retainers of a resin-bonded fixed partial denture to be incorporated with the designed inclination of the guiding surfaces, using noninvasive preparation techniques. Preprosthetic orthodontic treatment planning, possible problems, and limiting factors as well as the subsequent prosthetic reconstruction have been described in detail. The interdisciplinary treatment has to be planned individually for each patient, depending on the functional diagnosis and the clinical and anatomic situation.

Adult↗
PubMed1991

Complete restoration with resin-bonded porcelain inlays.

The use of porcelain inlays, instead of composite resin, as a restorative material for posterior teeth has greatly improved the standards of esthetic dentistry. The development of compatible materials enables the fabrication of all-ceramic restorations on refractory investment material without expensive technical equipment. Special care in and knowledge of this new technique by the dentist and the technician are necessary to obtain restorations with excellent marginal adaptation and a highly esthetic appearance.

Composite Resins↗
PubMed1990

Evaluation of the electrolytic etching depth of a nickel-chromium base alloy used in resin-bonded cast restorations.

This study examined the relation of the electrolytic etching depth of a nickel-chromium base alloy to the etching time. Cast samples (22 mm long, 4 mm wide, 1.5 mm thick) were etched in the Eltrokor etching unit, using Korolyt A as the etching solution with a constant current density of 400 mA/cm2. On each sample an approximately 3 mm long area was etched for 5, 7, 9, and 11 minutes. Between each etched area, a field of approximately 2 mm long remained unetched. The surface of each sample was scanned with a profilometer. The distance of the compensation plane of the scanned etched profile to the unetched areas was then measured for each etching time. The average etched depth with an etching time of 5 minutes is 30.4 microns (SD 2.39); with a time of 7 minutes the depth is 44 microns (SD 3.49); with a time of 9 minutes the depth is 59.8 microns (SD 4.10); and with an etching time of 11 minutes the depth is 72.9 microns (SD 2.94). Taking the average of all etching depths per etching time, the average loss of substance is 6.409 microns per minute etching time.

Acid Etching, Dental↗
PubMed1990

[The shearing strength with the silicoater procedure of conditioned bonded retaining elements].

The shear-bond strength of 120 sandblasted and silicoated metal elements (Wiron 88, Ni-Cr alloy) bonded with three different composites (ABC-cement, Superbond, Comspan opaque) to the plane of the prepared enamel surface of extracted teeth was measured. The effect of the interval between silicoating and bonding and that of 30 days' water storage was evaluated. The silicoating technique resulted in significantly higher bond strength than pure sandblasting, regardless of the composites used. After a one-day water storage the lowest bond strength was obtained with ABC-Cement and the highest with Superbond and Comspan opaque, independent of the interval between silicoating and bonding. After 30 days water storage elements bonded 30 min or 4 to 5 h after the silicoating procedure showed a loss of bond strength of an average of 25% regardless of the composites used. This decrease could not be measured with silicoated metal elements which were preserved by application of a bonding agent and bonded 24 h later.

Dental Alloys↗
PubMed1990

[The biomechanics of space closure and its dependence on the periodontal attachment].

The biomechanics of space closure in adult patients with loss of periodontal attachment is described. In order to achieve an even force distribution in the periodontium, force was reduced and the moment to force relationship was increased. beta-TMA-T Loops of 0.016 inch x 0.022 inch and 0.017 inch x 0.025 inch cross sections were investigated. With an automatic testing device force and moment values were determined.

Adult↗
PubMed1990

[Clinical results of partial denture anchorage using extracoronal bonded attachments].

16 caries-free partially edentulous patients were treated with 36 extracoronal adhesive attachments to support 4 removable partial dentures in the upper and 14 in the lower jaw. The cast nonprecious metal retainers were electrochemically etched and bonded with Superbond to the prepared abutment teeth. No debonding of the retainer occurred during the incorporation time of maximal 52 and minimal 3 months.

Adhesives↗
PubMed1989

[Long-lasting treatment technic in the periodontally reduced dentition].

A precondition for satisfactory (long-lasting) prosthetic results is a good occlusion. This can sometimes only be achieved with the aid of orthodontics. This article concludes that orthodontics can be carried out in patients with reduced periodontal support provided thorough periodontal treatment is carried out initially and treatment goals and biomechanics are carefully considered.

Adult↗
PubMed1989

Distance alterations of dies in sagittal direction in dependence of the die material.

The distance alterations between the first premolar and second molar in the sagittal direction were measured on complete arch models in two planes. Two dental stones, three resins, and silver-plating were used to make reproductions of a master cast under standardized conditions. Special emphasis was directed to the distinction between the right half of the model with teeth between the dies and the left side edentulous between the dies. The stones Die Keen and Fuji Rock showed the least distortion, identical bilaterally. The epoxy resins Blue Star E and Metapox exhibited a significant distinction between the right and the left sides. In addition to the pronounced distance reduction caused by polymerization shrinkage, a divergence between the dies and the model base on the side with teeth was measured. This phenomenon was also observed with polyurethane Blue Star P resin, but was less substantial. Silver-plating recorded a slightly greater reduction in distance between the dies than Fuji Rock. However, no significant differences were found between both sides.

Calcium Sulfate↗
PubMed1989

[Transverse dimensional stability of whole jaw models of different materials].

Whole jaw models of 6 different materials were examined for their transverse dimensional stability. Under standardized conditions impressions were made of a mandibular phantom with 4 stylized crown stumps using the double mix-spray technique with additively cross-linking silicon. Of these, test models were prepared and measured using the original model as reference. The high-strength dental stones Die Keen and Fuji Rock showed the highest dimensional stability. On account of their shrinkage during polymerization, the epoxy resins Blue Star E and Metapox as well as Blue Star P, a polyurethane, were found to have smaller transverse stump interspaces. Data for electroplated silver models were between those for dental stones and plastic materials.

Calcium Sulfate↗
PubMed1989

[Surface structures and substance loss during the etching of ceramic materials].

The progressive development of all-ceramic systems used in prosthetic dentistry gives material-specific aspects a new significance. It was the purpose of this study to examine the surface morphology of various ceramics (Mirage, Dicor, Optec, Vitadur N, Ceramco II) etched with various solutions (Super-Etch, Stripit, hydrofluoric acid 40%, Dicor retention gel) and etching times (1, 2, 3, and 4 min), using a SEM. With the exception of Dicor, the etched surface of ceramics showed similar structures within each material group, regardless of the etching time and the etching solution used. Dicor showed a different pattern depending on the etching time. An additional measurement of the surface roughness revealed an advisable etching time of 1 min with an average loss of ceramic material of 1.6 microns for those ceramics treated with the etching solutions Super-Etch, Stripit and Dicor retention gel. Hydrofluoric acid 40% caused a significant loss of substance and should not be used. A qualitative evaluation of the surface structure of composite cements (Chameleon, Dicor, Optec and Dual cement) in etched ceramics and in etched enamel showed completely filled microretentions.

Acid Etching, Dental↗
PubMed1989

[Free mucosal grafting--clinical experiences].

Free mucosal grafting is a simple, safe and predictable procedure. It is indicated in the treatment of progressive recessions in patients with reduced attached gingiva, in recurrent traumatic marginal lesions inspite of correct tooth brushing, in refractory dental neck hypersensitivity and for cosmetic reasons in patients with recessions. In these situations advancement grafting is done as a secondary procedure. To prevent the potential occurrence of recessions free mucosal grafting may also be indicated prophylactically before orthodontic or prosthetic management. The management concept in patients with recessions as well as the indications of the procedure, the technique used at our department and aspects of planning surgery are discussed.

Epithelial Attachment↗
PubMed1989

[The use of modern ceramics for inlays and onlays].

If ceramic inlays and onlays are considered in restorative work, some operations which, more than in other areas of dental engineering, decide upon the success or failure should be given special attention. During the preparation of ceramic inlays care should be taken to produce well rounded rather than rectangular edges approximally. In the case of onlays there should ideally be a smooth circular step rounded axially with a sharp-edged near-rectangular interface with the non-ground tooth. Ceramic inlays and onlays are best inserted with the adhesive technique, which provides for an improved strength of the ceramic material, an adequate marginal adaptation and a satisfactory cosmetic appearance. As long-term results are not yet available, the use of ceramic inlays and onlays is still experimental.

Dental Bonding↗
PubMed1989

[Adhesive bonding system Wiron 88--Superbond--enamel, dentin. A study based on scanning electron microscopy and profile scanning].

The components of the bonding system Wiron 88--Superbond enamel, dentin were examined by scanning electron microscopy and profile scanning. Wiron 88 was corroded electrolytically using Korolyt A in the Eltrokor system. At 400 mA/cm2 and an exposure time of 7 minutes an optimal microretentive surface morphology was seen on SEM. Both shorter and longer exposure times did not produce the desired results. Profile scanning of corroded Wiron 88 to determine vertical and horizontal surface changes showed that surface roughness increased as a function of increasing exposure times. On SEM of the Superbond material placed in contact with corroded metal and enamel, retentive structures were found to spread, thus producing a micromechanical bond. Phosphoric acid treatment increased the diameter of the dentin canals so that penetration of Superbond in corroded dentin was better than in non-corroded dentin. These results and several years of clinical experiences in adhesive denture work establish the usefulness of combining electrolytically corroded Wiron 88 and Superbond.

Boron Compounds↗