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Biomedical subjects

H Spiekermann

Publications and source records attributed to H Spiekermann.

50 records · Page 3Linked to original sources
PubMed1975

[Follow-up studies on model cast prostheses after 4 years wear].

Over a period of 4-1/2 years, patients having model cast dentures that had been inserted in the dental office were checked and submitted to follow-ups. It became evident that the socalled pre-prosthetical measures had been performed in a non-satisfying manner. In 69% of the patients, teeth had been extracted directly before inserting the model cast denture. As a result thereof, a majority of the dentures was sagging after a relatively short time and 70% of the dentures revealed non-occlusion in the final follow-up. 47% of the dentures had to be modified because of necessary tooth extractions, thereby reducing the original number of abutment teeth by 19%. About a third of the inserted model cast dentures showed gross deficiences, the percentage of socalled "collar" constructions was relatively high.

Dental Casting Technique↗
PubMedDate not supplied

Maxillary sinus augmentation prior to placement of endosseous implants: A histomorphometric analysis.

The aim of this prospective study was to histomorphometrically evaluate at various time intervals the mineralization stage and process of an allogeneic-xenogeneic bone graft used in sinus augmentation procedures. One biopsy was taken from 20 patients at either 6, 8, 10, or 12 months after sinus augmentation. Immediately following the biopsy, an endosseous implant was placed into the biopsy site. This protocol provided 4 groups of 5 patients each, based on healing time following sinus augmentation. Using backscattered electron image analysis, the specimens were histomorphometrically analyzed to determine the volume fractions of residual cancellous bone, newly formed bone, soft tissue, bovine hydroxyapatite, and "remineralized" freeze-dried demineralized bone allograft (rDFDBA). "Remineralization" of DFDBA particles was observed in a few areas in all specimens. Polarized light microscopy showed that only the 12-month biopsies had a predominance of lamellar bone formation. The area within the biopsies that represented the residual alveolar ridge consisted of 32.6% +/- 8.6% (mean +/- SD) of bone. In the grafted area of the biopsies the volume fraction of newly formed bone at 12 months (20.7% +/- 8.3%) was significantly higher (P < .05, analysis of variance) than at 6 months (8.1% +/- 3.0%). There was no statistically significant difference between newly formed bone in the inferior, central, and superior grafted areas in all 4 time intervals. This prospective study indicates that the mineralization process of an allogeneic-xenogeneic sinus graft is incomplete 6 months after the sinus augmentation procedure. New bone formation increased up to 12 months postaugmentation; however, it remained lower than the volume of residual bone.

Analysis of Variance↗
PubMedDate not supplied

Maxillary sinus augmentation with the xenograft Bio-Oss and autogenous intraoral bone for qualitative improvement of the implant site: a histologic and histomorphometric clinical study in humans.

The aim of the present clinical study was to determine, through histologic and histomorphometric investigations of human bone specimens, whether the addition of autogenous bone to the bone substitute material Bio-Oss can produce a high-quality implant site. To improve vertical bone height, 13 sinus floor elevations were carried out in a total of 12 patients. Augmentation of the maxillary sinus floor was completed using a mixture of Bio-Oss and bone harvested intraorally from the mandibular symphysis, the retromolar space, or the tuberosity region. Following an average of 7.1 months of healing, 36 Brånemark System implants were placed. During this surgical intervention, 23 cylinder-shaped bone biopsies were taken from the augmented maxillary region using trephine burs. Histologic analysis of the bone biopsies revealed that the Bio-Oss granulate was well-integrated into the newly formed bone; 33.1% (+/- 12.4%) of the substitute material surface was in direct contact with bone. Histomorphometric analysis of the samples revealed an average percentage proportion of bone of 18.9% (+/- 6.4%). The bovine substitute material and soft tissue occupied, respectively, 29.6% (+/- 8.9%) and 51.5% (+/- 9.4%) of the measured surface. When the implants were uncovered after an average healing phase of 6 months, all 36 implants had become osseointegrated. The combination of osteoconductive Bio-Oss and osteoinductive autogenous bone thus proved to be a material suitable for application in sinus floor augmentation.

Adult↗
PubMedDate not supplied

Fracture resistance of lithium disilicate-, alumina-, and zirconia-based three-unit fixed partial dentures: a laboratory study.

PURPOSE: The purpose of this study was to determine the fracture resistance of three-unit fixed partial dentures (FPD) made of new core ceramics. MATERIALS AND METHODS: A base metal three-unit master FPD model with a maxillary premolar and molar abutment was made. Tooth preparation showed 0.8-mm circumferential and 1.5-mm occlusal reduction and a chamfer margin design. FPDs were constructed with a uniform 0.8-mm-thick core ceramic and a porcelain veneer layer. In-Ceram Alumina, In-Ceram Zirconia, and DC-Zirkon core ceramics were machined by a computer-aided design/manufacturing system, whereas IPS Empress 2 core ceramic was indirectly built up using the fabrication technology of waxing and heat pressing. FPDs of IPS Empress were heat pressed as complete restorations without core material. To ensure standardized dimensions, the FPDs were controlled at different points. All FPDs were cemented with ZnPO4 on the master model and loaded on a universal testing machine until failure. The failure load and mode of failure were recorded. RESULTS: The highest failure loads, exceeding 2,000 N, were associated with FPDs of DC-Zirkon. FPDs of IPS Empress and In-Ceram Alumina showed the lowest failure loads, below 1,000 N, whereas intermediate values were observed for FPDs of IPS Empress 2 and In-Ceram Zirconia. Differences in mean values were statistically significant. CONCLUSION: The high fracture resistance evaluated for FPDs made of DC-Zirkon underscores the remarkable mechanical properties of high-performance ceramic, which could be useful for highly loaded all-ceramic restorations, especially in the molar region.

Aluminum Oxide↗
PubMedDate not supplied

Marginal fit of alumina-and zirconia-based fixed partial dentures produced by a CAD/CAM system.

Clinical long-term success of all-ceramic dental restorations can be significantly influenced by marginal discrepancies. As a result, this in vitro study evaluated the marginal fit of alumina- and zirconia-based fixed partial dentures (FPDs) machined by the Precident DCS system. Different master steel models of three-, four- and five-unit posterior FPDs with an 0.8 mm chamfer preparation were produced. FPDs made of DC-Zirkon and In-Ceram Zirconia core ceramics were machined by the Precident DCS system. The marginal fit of the milled frameworks placed on the master steel models was determined by a replica technique using a light-body silicone to fill the discrepancies between crown and tooth and a heavy-body material to stabilize the light-body impression material. The impressions were poured into an epoxy resin material and each model was cross-sectioned with a low speed diamond saw to better visualize marginal discrepancies. The marginal fit of the FPDs was evaluated by scanning electron microscopy. The measurements of the marginal fit exhibited mean marginal discrepancies in a range between 60.5 and 74.0 microm, mean marginal gaps in a range from 42.9 to 46.3 microm, mean vertical discrepancies in a range from 20.9 to 48.0 microm and mean horizontal discrepancies in the range of 42.0 to 58.8 microm. Statistical data analysis was performed using the non-parametric test of Kruskal-Wallis and Mann-Whitney. The analysis revealed no significant differences (p>0.05) between the mean marginal gaps and vertical and horizontal discrepancies. However, for some FPDs the mean values of the marginal discrepancies were significantly different (p < or =0.05). The wide range of the measured values may be attributed to the complex geometrical design of long span FPDs and difficulties regarding the milling process of brittle ceramic materials. Based on the selection of 100 microm as the limit of clinical acceptability, the results of this study can conclude that the level of marginal fit for alumina- and zirconia-based FPDs achieved with the Precident DCS system meet the clinical requirements.

Aluminum Oxide↗
PubMedDate not supplied

Healing of bone defects in combination with immediate implants using the membrane technique.

Twenty Brånemark implants were placed with membranes (Gore-Tex Augmentation Material) as immediate or delayed implants in the extraction sockets of 15 patients. Membrane perforations through the mucous membrane occurred in 10 patients after 6 to 24 weeks and once after 2 weeks. Histologic examination of 15 tissue samples taken when the membrane was removed showed genuine bone regeneration in three patients, connective tissue regeneration with intermittent bone regeneration in eight patients, purely fibrous healing in two patients, and inflammatory granulation tissue in two patients. The high proportion of membrane perforations with immediate implants should be taken into account in the assessment and clinical application of this therapy principle.

Alveolar Process↗
PubMedDate not supplied

A 10-year follow-up study of IMZ and TPS implants in the edentulous mandible using bar-retained overdentures.

This study presents data related to 136 patients who were treated with 300 implants in the edentulous mandible anterior to the mental foramina. Two implant systems were used: the titanium plasma-sprayed screw implant (TPS) and the intramobile cylinder implant (IMZ) in three different modifications. The longest observation time was 11 years, with a mean of 5.7 years. Patients were recalled for regular clinical examinations once every 6 months. After prosthesis placement, only a few implant losses were recorded, although critical states could be found according to periodontal standards. This led to the definition of success criteria according to clinically tolerable bone loss or pocket-probing depths. The 5-year survival rate considering the implant loss was greater than 90% for all implant systems and was lowest for the new type IMZ 3.3. Selecting a vertical bone loss of 4 mm or more as failure criterion reduced the survival rates, which then ranged from 83% to 97% (according to the implant system) for the 5-year interval. The mean annual bone-level change was identified individually for each implant using a linear-regression model.

Adult↗
PubMedDate not supplied

The influence of spruing technique on the development of tension in a cast partial denture framework.

Distortions of cast removable partial denture frameworks result more from the method of sprue connection than from other variables in the investment and mold preparation. A standard test pattern and optical measuring equipment were used to evaluate residual casting stresses. Based on the data obtained from the initial study, modified removable partial framework patterns were made and cast under varying conditions. The use of a dorsal spruing technique and a box-type casting flask resulted in less distortion than use of the conventional vertical sprue attachment and investing in a ring flask. Dorsal spruing and use of a box-type casting flask reduced the deformation of a cast partial denture framework in the area of the palatal bar and retentive elements up to 0.3 mm. Such a tension-free casting method means a better fit of the partial framework on the master cast and intraorally.

Dental Casting Investment↗
PubMedDate not supplied

Simultaneous hard and soft tissue augmentation for implant-supported single-tooth restorations.

The replication of nature in the rehabilitation of a single missing anterior tooth is primarily a surgical challenge, as hard and soft tissue deficiencies compromise the achievement of functional and aesthetic implant-supported restorations. Bone defects can be treated using guided bone regeneration (GBR), with or without bone graft materials. The successful application of the GBR technique has been documented in several experimental and clinical studies; the primary challenge associated with single tooth replacement is the creation of an adequate soft tissue recipient site. However, the increased morbidity and prolonged healing period involved in performing hard and soft tissue grafting procedures in two consecutive appointments do not achieve patient expectations. The learning objective of this article is to master a single-tooth replacement technique that allows surgical treatment of bony and soft tissue deficiencies in a single procedure, during either an immediate or delayed implant placement.

Adult↗