Biomedical subjects

N H J Creugers

Publications and source records attributed to N H J Creugers.

11 recordsLinked to original sources

PubMed2006

Implant surface roughness and bone healing: a systematic review.

A systematic review was performed on studies investigating the effects of implant surface roughness on bone response and implant fixation. We searched the literature using MEDLINE from 1953 to 2003. Inclusion criteria were: (1) abstracts of animal studies investigating implant surface roughness and bone healing; (2) observations of three-month bone healing, surface topography measurements, and biomechanical tests; (3) provision of data on surface roughness, bone-to-implant contact, and biomechanical test values. The literature search revealed 5966 abstracts. There were 470, 23, and 14 articles included in the first, second, and third selection steps, respectively. Almost all papers showed an enhanced bone-to-implant contact with increasing surface roughness. Six comparisons were significantly positive for the relationship of bone-to-implant contact and surface roughness. Also, a significant relation was found between push-out strength and surface roughness. Unfortunately, the eventually selected studies were too heterogeneous for inference of data. Nevertheless, the statistical analysis on the available data provided supportive evidence for a positive relationship between bone-to-implant contact and surface roughness.

Animals↗

PubMed2006

[In vitro fracture behaviour of composite crowns with and without posts].

The failure load and failure mode of severely damaged endodontically treated maxillary premolars were examined within a laboratory study. The premolars were divided into 4 groups. The first of which was restored with prefab metal posts, the second with prefab fibre posts and the third with custom-made fibre posts; all 3 receiving direct resin crowns. In a 4th (control) group no post-space preparation was performed and no posts were placed; a direct resin composite complete crown was made. After thermocycling, all specimens were statically loaded in a universal test machine until failure, under an angle of 30 degrees. There was no significant difference between the mean failure loads. Failure was merely due to unfavourable, non-repairable fractures (ending below the simulation of bone level). This study suggests that posts are not necessarily required to increase the failure load of direct resin composite crowns, however, clinical studies are necessary to confirm these findings.

Bicuspid↗

PubMed2005

A comparison of fatigue resistance of three materials for cusp-replacing adhesive restorations.

OBJECTIVES: To investigate the fatigue resistance and failure behaviour of cusp-replacing restorations in premolars using different types of adhesive restorative materials. METHODS: A class 2 cavity was prepared and the buccal cusp was removed in an extracted sound human upper premolar. By using a copy-milling machine this preparation was copied to 60 human upper premolars. In groups of 20 premolars each, direct resin composite restorations, indirect resin composite restorations and ceramic restorations were made. All restorations were cusp replacements made in standardized shape and with adhesive techniques. Cyclic load (5 Hz) was applied starting with a load of 200 N (10,000 cycles) followed by stages of 400, 600, 800 and 1000 N at a maximum of 50,000 cycles each. Samples were loaded until fracture or to 2,10,000 cycles maximum. In case of fracture, the failure mode was recorded. RESULTS: No differences were seen in fracture strength between the three groups (Wilcoxon P = 0.16). No differences were observed with regard to failure mode above or below the cemento enamel junctions (chi2 P = 0.63). The indirect resin composite and ceramic restorations showed significantly more combined cohesive and adhesive fractures than the direct resin composite restorations, which showed more adhesive fractures (chi2 P = 0.03 and 0.002). CONCLUSIONS: The results of this study suggest that ceramic, indirect resin composite and direct resin composite restorations provide comparable fatigue resistance and exhibit comparable failure modes in case of fracture, although the indirect restorations tend to fracture more cohesively than the direct restorations.

Acrylic Resins↗

PubMed2005

Ex vivo fracture resistance of direct resin composite complete crowns with and without posts on maxillary premolars.

AIM: To investigate ex vivo the fracture resistance and failure mode of direct resin composite complete crowns with and without various root canal posts made on maxillary premolars. METHODOLOGY: The clinical crowns of 40 human extracted single-rooted maxillary premolars were sectioned at the cemento-enamel junction. The canals were prepared with Gates Glidden drills up to size 4. Thirty samples were provided with standardized post spaces in the palatal canal and all roots were embedded in acrylic. Minimal standardized preparations in the canal entrances were made. Groups of 10 samples were treated with (i) prefabricated metal posts, (ii) prefabricated glass fibre posts, (iii) custom-made glass fibre posts, and (iv) no posts (control). Posts were cemented with resin cement and resin composite complete crowns were made. All specimens were thermocycled (6000x, 5-55 degrees C). Static load until fracture was applied using a universal loading device (crosshead speed 5 mm min(-1)) at a loading angle of 30 degrees . Failure modes were categorized as favourable and unfavourable failures. RESULTS: No significant difference was observed between the mean failure loads (group 1: 1386 N, group 2: 1276 N, group 3: 1281 N, and group 4: 1717 N, P > 0.05), nor between frequencies of failure modes (P > 0.05). All failures were fractures of the resin composite crown in combination with tooth material (cohesive failures). CONCLUSIONS: Within the limits of this laboratory investigation it is concluded that severely damaged and root filled maxillary premolars, restored with direct resin composite complete crowns without posts have similar fracture resistances and failure modes compared to those with various posts, which suggest that posts are not necessarily required.

Bicuspid↗

PubMed2005

Can internal stresses explain the fracture resistance of cusp-replacing composite restorations?

The aim of this study was to explore and compare the results of occlusal load application to cusp-replacing composite restorations, studied by means of finite element (FE) analysis and in vitro load tests. A three-dimensional (3D) FE model was created with a set up similar to an in vitro load test that assessed the fatigue resistance of upper premolars with buccal cusp-replacing resin composite restorations. Occlusal load was applied to two geometries (with and without palatal cuspal coverage), and the tooth-restoration interface and composite material stresses were calculated. Subsequently, safety factors were calculated by dividing the material strength values by the obtained stresses. The highest safety factors were observed for the restorations with cuspal coverage. This was consistent with the load test, in which cuspal coverage led to higher fracture resistance. Furthermore, the FE analysis predicted that failure of the tooth-restoration interface is more likely than failure of the composite material. Correspondingly, the load test showed predominantly adhesive failures of the restorations. Although the described test methods did not lead to a complete understanding of the failure mechanism, it can be concluded that the FE analysis provides additional information with regard to the differences in fracture behaviour of these types of restorations.

Adhesiveness↗

PubMed2004

[Cast partial restorations: outdated!].

The decision to apply a certain therapy is the outcome of a process in which the advantages and disadvantages of this therapy are weighed and compared to alternative therapies. Key words in this process are effectiveness and efficiency. Comparison of inlays and onlays with direct resin composite restorations in terms of effectiveness and efficiency suggests that inlays and onlays are more effective (more durable) than direct resin composite restorations. In contrast, resin composite restorations require fewer resources and thus may be more efficient. However the value of a therapy is not only determined by quantitative measures. It is suggested that appropriateness and adequacy of a therapy should be considered as well. If restorative treatment using cast partial restorations is compared with a treatment using direct resin composite restorations, the latter is considered more appropriate because of its conservative approach. Both types of restorations are considered adequate in terms of protecting the tooth and restoring its function.

Biocompatible Materials↗

PubMed2004

[Research methods in dentistry 5. The finite element method].

The finite element method is a commonly applied experimental research technique. The method comprises computer simulation of constructions under load and of internal mechanical processes, which enables the study of effects of geometrical and material variations. The analysis shows internal stresses and, consequently, predictions can be made of possible failure. In dentistry, the method is applied in disciplines, such as orthodontics, oral and maxillofacial surgery, implantology en restorative dentistry.

Computer Simulation↗

PubMed2003

[A finite element model of a cusp-replacing adhesive restoration].

This article describes the development of a three-dimensional finite element model of a premolar, based on a micro-scale computed tomographic data-acquisition technique. Using the model shrinkage stresses were analysed during and after the polymerisation process of resin composite. The stress patterns generated were three-dimensional. The results of this study indicate that failure of the interface is more probable than failure of the composite material. The described procedure is a relatively easy method to produce a highly detailed 3-D finite element model of a premolar with an adhesive cups-replacing restoration.

Bicuspid↗

PubMed2003

[Minimal invasive dentistry. A revolutionary concept?].

This article describes the mutual relations between three important dental concepts. 'Minimal invasive dentistry', 'adhesive dentistry' and the 'dynamic treatment concept' are concepts which have changed restorative dentistry substantially during the last decade. The ultimate goal of restorative dental care, which is the maintenance of a healthy and functional dentition for life, is unchanged and as applicable as ever. To achieve maximal results from applying minimal invasive dentistry, a clear understanding of adhesive dentistry as well as the implications and goals of the dynamic treatment concept is needed. Dentists must realize that as invasiveness of interventions is decreasing, the need for monitoring and aftercare of restorative work is increasing. It is important to involve the patient in this process by providing sufficient information and achieving informed consent.

Dental Care↗

PubMed2002

Five years of aftercare of implant-retained mandibular overdentures and conventional dentures.

The purpose of this multicentre randomized clinical trial was to analyse surgical and prosthetic aftercare and clinical implant performance of edentulous patients with implant-retained mandibular overdentures and of patients with conventional dentures, either or not after pre-prosthetic vestibuloplasty and deepening of the floor of the mouth. The evaluation period was 5 years. The implant systems evaluated were the IMZ implant system, the Brånemark implant system and the Transmandibular Implant system. The centre in Groningen had five groups (n=149) and the centre in Nijmegen had three groups (n=86). The evaluation comprised of surgical and prosthetic aftercare, together with clinical implant performance (CIP). The highest implant loss (29%) is found in the Transmandibular Implant group. All groups had prosthetic revisions and complications according to the CIP-scale. The majority of the patients in the endosseous implant groups were subject to minor complications. The CIP-score of the Transmandibular Implant group is significantly higher than the scores of the other groups, because of the high number of lost posts. In 26;1% of the patients in this group score 4 is given, which means failure of the implant system. From this study it can be concluded that the endosseous implant systems used in this study have less surgical aftercare and a better clinical implant performance than the Transmandibular Implant system and are therefore the systems of choice for the edentulous mandible.

Aftercare↗

PubMed2002

[The shortened dental arch concept: a treatment strategy for the mutilated dentition].

The minimum number of teeth needed to satisfy functional demands has been subject of several studies. However, since functional demands can vary from individual to individual, this number cannot be defined exactly. It has been demonstrated that shortened dental arches comprising the front teeth and the premolars, can meet the requirements of a functional dentition. The shortened dental arch concept may be considered a strategy to reduce the need for complex restorative treatment in the posterior regions of the mouth. It implies that the prompt replacement of absent molars by a removable partial denture leads to overtreatment and discomfort. The shortened dental arch concept is based on circumstantial evidence, and not contradict current theories of occlusion and fits well in a problem-solving approach.

Adult↗