PubMed Health⌕ Search

Biomedical subjects

M A van Waas

Publications and source records attributed to M A van Waas.

At least 19 recordsLinked to original sources
PubMed2001

Transforming growth factor-beta1 incorporated in calcium phosphate cement stimulates osteotransductivity in rat calvarial bone defects.

Bone regeneration of the alveolar crest around dental implants is an important factor in the success of implant use. Calcium phosphate cement can be used as a bone substitute and applied clinically as a paste to fill micro- and macroscopic bone defects. We have shown earlier that the intermixing of the recombinant human transforming growth factor-beta1 (rhTGF-beta1) in hardening calcium phosphate cement stimulated osteoblastic differentiation of rat primary bone cells in vitro. The aim of the present study was to examine whether the similar enrichment with rhTGF-beta1 affects the replacement of calcium phosphate cement by bone (osteotransduction) in calvarial critical size defects (csd) of adult rats. Two bone defects of 5 mm diameter were created bilaterally in each skull of 10 adult male rats. Both defects were filled with 53 mg of calcium phosphate cement without rhTGF-beta1 (control) at one side, and with 10 or 20 ng rhTGF-beta1 at the other side. After 8 weeks, defects with surrounding skull were analysed histologically and histomorphometrically. The addition of rhTGF-beta1 in the cement increased the amount of bone in rat skull defects. This finding coincidences with our in vitro observations, that intermixing of rhTGF-beta1 in calcium phosphate cement stimulates bone cell differentiation. Addition of rhTGF-beta1 stimulated bone formation as indicated by an increased bone volume of 50% and an increased bone/cement contact of 65%, in comparison to control defects with cement without rhTGF-beta1. In addition, rhTGF-beta1 reduced the remaining volume of cement, by 11% at 10 ng rhTGF-beta1, and by 20% at 20 ng rhTGF-beta1 in the cement. Defect closure was not affected. We conclude that the intermixing of rhTGF-beta1 in a fast-setting calcium phosphate cement stimulates bone growth and the osteotransduction of the cement. For bone regeneration procedures around endosseous implants, calcium phosphate cement with rhTGF-beta1 might be an appropriate combination for early osseointegration and implant use.

Animals↗
PubMed2001

[Three treatment modalities for mandibular overdentures on implants. Clinical and radiological aspects].

The results are presented of 3 treatment modalities for overdentures on implants in the mandible: 2 implants with ball attachment, 2 implants interconnected with a bar and 4 implants interconnected with bars. The patients, in total 110, were at random treated and evaluated 3, 9 and 19 months after insertion of the implants. Six implants were lost out of 283 implants during the osseointegration period. There were hardly any differences found between the groups with respect to the clinical and radiologic parameters. De first group showed less bleeding around the implants after 19 months then the other groups. Around the medial implants there was significantly more bone resorption then around the distal implants and the implants in the other groups. No conclusions can be drawn with respect to the best treatment modality since the period of evaluation is too short and the other parameters like patients' experiences are not included.

Alveolar Bone Loss↗
PubMed2001

[Dental--mental].

Explore the source record for details and available documents.

Dental Anxiety↗
PubMed2000

Transforming growth factor-beta1 incorporated during setting in calcium phosphate cement stimulates bone cell differentiation in vitro.

Growth stimulation of periimplant tissues by growth factors like transforming growth factor-beta1 (TGF-beta1) may increase the indication for and success of implant use. Calcium phosphate as a material for implants or for coating of implants is known for its good biologic interaction with bone. Therefore, calcium phosphate implants combined with TGF-beta1 might improve osseointegration. In this study we hypothesise that the addition of recombinant human TGF-beta1 (rhTGF-beta1) to calcium phosphate cement (CPC) affects the differentiation of bone cells growing on the cement layer. rhTGF-beta1 incorporated during setting in a CPC layer at 20 ng rhTGF-beta1/60 mg cement was found to be gradually released into tissue culturing medium leading to a 20% release after 24 h. Two cell populations were obtained from collagenase-treated fragments of adult rat long bones: preosteoblastic cells, which were released by the collagenase treatment, and osteoblastic cells, which grew from the collagenase-stripped bone fragments. Both cell populations were tested for their osteoblastic characteristic phenotype by measuring their alkaline phosphatase (ALP) activity after vitamin D treatment and cyclic AMP after parathyroid hormone stimulation. After preculture the cells were plated on a layer of CPC containing 0 (control), 10, or 20 ng rhTGF-beta1/60 mg CPC. Bone cell differentiation was analyzed after 10 days by measuring the ALP activity, as well as the protein content of the cell layer. Incorporation of rhTGF-beta1 in the CPC did not change the ALP activity in osteoblastic cells, but a significant (analyzed by multivariate analysis of variance) increase was observed in preosteoblastic cells. Incorporation of 10 ng of rhTGF-beta1 in 60 mg of CPC increased the ALP activity in preosteoblastic cells by threefold and 20 ng rhTGF-beta1/60 mg CPC increased it by fivefold. The total protein content was not affected by rhTGF-beta1 in either of the cell populations. We conclude that rhTGF-beta1 incorporated during setting in CPC stimulates the differentiation of preosteoblastic cells in vitro. These results provide a basis for further studies on the use of this combination as an implant material in vivo.

1-Methyl-3-isobutylxanthine↗
PubMed2000

[Needs for implant therapy in cancer patients; a retrospective study].

After cancer treatment in the head and neck area, mastication and speech are often affected. Some of the problems encountered can be solved by adequate dental rehabilitation. However, dental rehabilitation is often compromised, for various reasons. The change in anatomy due to surgery often results in lack of denture bearing mucosa. The effects of radiotherapy of the salivary glands and the mucosa result in dry oral tissues and diminished retention of removable dentures. Osseointegrated implants can help to solve these problems. Implant treatment has, so far, not been widely used in cancer patients. An analysis was made of 95 consecutive patients with a tumor in the head and neck area. The indication for treatment with osseointegrated implants was reviewed and the need for implants as experienced bij patients was evaluated. Results show that 45% did not need specific prosthetic rehabilitation, and approximately 25% of the patients could benefit from osseointegrated implants. Due to general and local contra-indications and patients' refusal, only 3% actually have been treated. For complete oral rehabilitation of this group of patients the use of osseointegrated implants should be considered at an early stage, before the initial tumor treatment.

Adult↗
PubMed2000

[Combined periodontal treatment with dental implants].

Implant treatment of partial edentulous periodontal compromised patients have led to a change in indication and therapy. After an adequate periodontal treatment for most of the patients there are no obstructions for implant treatment. However untreated periodontal disease and refractory periodontitis patients are at risk for complications. The diagnosis, treatment planning, treatment and maintenance of periodontal compromised patients need a multidisciplinary approach. A regular and tight maintenance program is essential to keep the periodontal and peri-implant tissues in a good condition.

Adult↗
PubMed1999

Clinical and radiological results of patients treated with three treatment modalities for overdentures on implants of the ITI Dental Implant System. A randomized controlled clinical trial.

In a randomized controlled clinical trial carried out at the Ignatius teaching hospital in Breda, The Netherlands, 110 edentulous patients with severe mandibular bone loss were treated with implants of the ITI Dental Implant System using 3 different treatment strategies: a mandibular overdenture supported by either 2 implants with ball attachments, 2 implants with an interconnecting bar, or by 4 interconnected implants. In this study, results of clinical and radiographic parameters were evaluated and compared over a period of 19 months after implant placement. A total of 283 ITI Dental Implants were placed. Six implants (2%) were lost during the osseointegration period. No further implant losses occurred after that. At the 19 month evaluation mean values and standard deviations for bleeding index were 0.51 +/- 0.5 (bleeding incidence = 70%) and for plaque index they were 0.46 +/- 0.5 (plaque incidence = 45%). The mean values and standard deviations for probing depth and loss of attachment were 2.7 +/- 1.1 mm and 0.26 +/- 0.6 mm respectively. The radiographic evaluation showed a mean bone loss of 1.5 mm +/- 0.26 after 19 months for all the implants. In cases with 4 interconnected implants there was significantly more bone loss around the central 2 implants (2.1 +/- 0.31 mm) in comparison with the lateral 2 (1.4 +/- 0.25 mm). No significant correlations were found between plaque and bleeding indices and bone loss.

Alveolar Bone Loss↗
PubMed1999

Masticatory performance and chewing experience with implant-retained mandibular overdentures.

The relationship between masticatory performance and chewing experience has not yet been explored for patients with implant-retained overdentures. Although many relationships have been found between parameters of objective and subjective oral function, the structure of these relationships remain unclear. Therefore, we studied in a randomized clinical trial the relationship between the comminution of an artificial test food, i.e. masticatory performance, and the subjective chewing experience. The trial involved a comparison between two groups receiving implant treatment and one group receiving conventional complete dentures (CD). The implant treatment involved either a mainly implant-supported mandibular overdenture on a transmandibular implant (TMI) or an implant-tissue-supported mandibular overdenture on two IMZ implants (IMZ). Masticatory performance as well as chewing experience were substantially better for the implant-retained overdentures compared with the complete denture group. No significant differences emerged between the TMI and the IMZ group. A multiple regression analysis did not provide any comprehensibility in the relationship between masticatory performance and the variables of chewing experience. In the linear structural relation analysis (LISREL) no direct relationship was found between masticatory performance and functional complaints mandibular denture. The results show that an improvement in masticatory performance does not imply the same improvement in chewing experience and vice versa.

Adult↗
PubMed1999

[CAD/CAM-copings for partial coverage].

Aim of the study was to evaluate the Computer Integrated Ceramic Reconstruction (CICERO)-system and the Ceramic Reconstruction (CEREC)-system for the production of all ceramic copings for partial coverage. Posterior teeth were prepared and the stone dies were made. Accuracy analyses were performed on ceramic restorations made by means of the CICERO and by means of the CEREC technique. The marginal gaps were compared to that of a control cast metal restoration. The results demonstrate that the marginal gaps of the CICERO and CEREC copings varied respectively for the premolar 58-80 microns (mean 69 microns) and 71-91 microns (mean 81 microns). For the upper molar 63-92 microns (mean 78 microns) and 68-110 microns (mean 89 microns) and for the lower molar 54-98 microns (mean 76 microns) and 73-99 microns (mean 86 microns). Control cast metal partial coverage restorations showed marginal gaps of 33, 49 and 41 microns. It is concluded that computers can produce copings for partial coverage preparations on stone dies with a mean marginal gap for CICERO copings of 74 microns and for CEREC copings of 85 microns. These values were obtained before optimizing the marginal fit by means of porcelain veneering.

Ceramics↗
PubMed1999

[Considerations of single tooth replacement. The choice between different treatment options].

When a single tooth is lost both functional and aesthetic aspects have to be restored. A fixed prosthodontic restoration such as a conventional bridge, a resin-bonded bridge or a solitary implant is the treatment of choice. The final choice between these three treatment modalities strongly depends upon specific characteristics in the patients' dentition and his preferences. There is a vast amount of clinical experience with the conventional fixed bridge and it is available in every dental office. Without a doubt the resin-bonded bridge is the cheapest option. However, the patient does run the risk of loosening of the bridge, usually at an inconvenient moment. It then has to be recemented or replaced. The solitary implant has several advantages over the fixed and resin-bonded bridge. For optimal results, it does require a physician with a vast experience in the field of oral implantology. For young individuals closure of the diastema by means of orthodontics is also possible. A partial denture is only an option as a temporary provision or when more teeth were lost or are bound to be lost.

Dental Implants, Single-Tooth↗
PubMed1999

[Reproducible marginal gap measurements of partial ceramic crowns].

Aim of this research was to test the hypothesis that marginal gap measurements by a digital microscopic image processing computer are reproducible. Light microscopic images of the margins of Artglass partial crowns on stone dies were obtained with a 3CCD color video camera, digitized and processed. Ten measuring points were painted on a 0.5 mm section of the finish line of the preparation. The opposite corresponding measuring points on the margin of the partial crown were painted as well. The distance (marginal gap) between two corresponding points was painted and calculated by the computer. Reproducibility (precision) is reflected in the ability to reproduce the same measurement results in repeated measurements (n = 5). The reproducibility error was expressed as the coefficient of variation (CV) in percent (%). The localization of the corresponding measurement points and the calculation of the marginal gap were performed without errors. For a marginal gap between 15-50 microns the average measurement error was 3% or 0.45-1.5 microns. It was concluded that the measurement of the gap between two points by the digital image processing computer was reproducible. The measurement error was neglectable given that a clinically acceptable marginal gap is 100 microns.

Ceramics↗