Biomedical subjects

H J Meijer

Publications and source records attributed to H J Meijer.

35 records · Page 2Linked to original sources

PubMed1998

[Templates as an aid in implantology].

The number, position and angulation of implants are of major importance in loading of implants and surrounding bone and in esthetics. Especially in single tooth and partially edentulous cases correct positioning of implants takes a great deal of care. A template is a device that helps to achieve the proper amount of bone and the correct position and angulation of implants. The design and fabrication of radiographic templates, diagnostic templates and surgical templates are described, both in general and specifically for overdentures and non-removable implant-supported restorations.

Dental Casting Technique↗

PubMed1998

Overdentures stabilised by two IMZ implants in the lower jaw--a 5-8 year retrospective study.

Clinical and radiographical parameters were assessed in forty patients with overdentures stabilised by two IMZ implants connected by a bar in the lower jaw in a 5-8 years retrospective study. Results indicated that most patients had healthy peri-implant tissues, the mean pocket probing depth was 3.1 mm and the median periotest value was -4. Three implants were removed after the healing period and replaced by three new implants. One implant was lost after six years. One implant was mobile on palpation. None of the patients showed objective signs of dysaesthesia in the lower lip or chin. The peri-implant bone level of most implants had remained stable after one year of service. The overall success rate was 94% (Albrektsson et al.) and it is therefore concluded that two IMZ implants, connected with a bar in the lower jaw, provide a stable base for long-term support of a mandibular overdenture.

Adult↗

PubMed1997

Radiographic evaluation of mandibular augmentation with prefabricated hydroxylapatite/fibrin glue implants.

PURPOSE: This study radiographically evaluated the stability of mandibular height during a 2-year follow-up after augmentation with prefabricated hydroxylapatite/fibrin glue (HA/FG) implants. PATIENTS AND METHODS: Standardized, lateral oblique cephalometric radiographs were made of 22 patients 6, 12, and 24 months postoperatively and analyzed with a newly developed, computerized image analysis technique. RESULTS: The average height of the HA/FG implants after augmentation was 9.45 mm. Average loss of total height of the augmented mandibles was 2.31 mm after 6 months, 2.90 mm after 12 months, and 3.93 mm after 24 months. Reduction of HA/FG implant height alone was 0.62 mm after 6 months, 1.24 mm after 12 months, and 2.03 mm after 24 months. Reduction occurred mainly during the first 6-month evaluation period and was probably primarily caused by adaptation of the implant to the surface of the mandible. An inferior compression of the implant or resorption of the alveolar crest and underlying basilar bone are possible reasons for loss of total mandibular height. CONCLUSION: The results indicate that prefabricated HA/FG implants used for augmentation of edentulous mandibles show little reduction in height, but are not completely stable during a 2-year evaluation period.

Adult↗

PubMed1996

Loading conditions of endosseous implants in an edentulous human mandible: a three-dimensional, finite-element study.

The design of dental superstructures influences the loading on dental implants and the deformation of the anterior interforaminal bone in an edentulous mandible. This deformation causes stress in the bone around the implants and may lead to bone resorption and loss of the implant. The stress distribution around dental implants in an edentulous mandible was calculated by means of a three-dimensional, finite-element model of the anterior part of the jaw. This model was built from data obtained from slices of a single human mandible and was provided with four endosseous implants in the interforaminal region. The implants were either connected with a bar or remained solitary. The solitary implants or the bars were loaded either uniformly or non-uniformly. In case of a non-uniform distribution, either the central bar or the central implants were loaded or the lateral bars or the lateral implants were loaded. The most extreme stresses in the bone were always located around the neck of the implant. In the case of the uniform distribution of the loading there were more or less equal extreme principal stresses around the central and lateral implants. If the load was not uniformly distributed on the superstructure then the implant that was nearest to the place of loading showed the highest stress concentration; with connected implants there was a reduction in the magnitude of the extreme principal stresses compared to solitary implants.

Bite Force↗

PubMed1995

[Intraoral radiographs of dental implants in the edentulous mandible].

Radiographs of dental implants in the edentulous mandible, which are suitable for evaluation studies, are difficult to obtain. This article describes the development of an aiming device for intraoral radiography of the crestal bone around the neck of dental implants. Error analysis of serial radiographs indicated only small deviations in reproducibility. Subsequently three methods of measurements of marginal bone level around the neck of dental implants are described, measurements with: 1. a computerized image analysis system, 2. a magnifying glass, and 3. a digital sliding gauge. The intra- and interobserver error analysis showed that determining the precise bone height on the image is responsible for a large standard deviation for each method. Measurements with a digital sliding gauge are preferable, since this method is easy to put into practice, whereas the accuracy matches the accuracy of the two other methods.

Dental Implants↗

PubMed1995

The incomprehensible success of the implant stabilised overdenture in the edentulous mandible: a literature review on transfer of chewing forces to bone surrounding implants.

The approach of implant stabilised overdentures has become one of the routine treatment modalities for compromised edentulous ridges. The purpose of this literature review is to analyze survival rates of loaded implants, occlusal forces and stress distributions of implant stabilised overdentures in edentulous mandibles and of fixed loaded implants at least over a medium-term period. which is comparable with fixed prostheses. Patients with implant stabilised overdentures and with fixed bridges on implants generate similar occlusal forces. The number of implants under a prosthetic construction seems to have less influence on stress distribution than design of the superstructure and related direction of forces.

Alveolar Process↗

PubMed1994

Location of implants in the interforaminal region of the mandible and the consequences for the design of the superstructure.

The location and the number of implants to support an overdenture is of major importance for the superstructure design. Sometimes, jaw bone anatomy or posteriorly placed implants enforce the use of an angular bar to achieve a position above the alveolar ridge. Loads on such a bar may introduce a moment on the implants which can result in high bone stresses and eventually the loss of the implants. This study on stress distribution in the bone around the implants in an edentulous mandible was performed using a three-dimensional finite element model. One model with two implants placed just anteriorly of the mental foramen and connected with an anteriorly placed bar, following the curvature of the alveolar ridge, was compared with two other designs. First with a similar model but now without a bar and secondly with a model with four implants connected with straight bars. It is concluded that loading a bar, which is placed anteriorly of the interconnecting line between two implants, causes extremely large compressive and tensile stress concentrations in the bone around the implants. Therefore, in those cases, it is advised not to connect the implants or, in case a bar-clip attachment is preferred, to place additional implants in the frontal region.

Bite Force↗

PubMed1993

A three-dimensional, finite-element analysis of bone around dental implants in an edentulous human mandible.

The design of dental superstructures influences the loading on dental implants and the deformation of the anterior interforaminal bone in an edentulous mandible. This deformation causes stress in the bone around the implants and may lead to bone resorption and loss of the implant. The stress distribution around dental implants in an edentulous mandible was calculated by means of a three-dimensional, finite-element model of an entire lower jaw. This model was built from data obtained from slices of a single human mandible and was provided with two endosseous implants in the interforaminal region. The implants were either connected with a bar or remained solitary, and were loaded with a horizontal bite force of 10 N, a vertical bite force of 35 N, or an oblique bite force of 70 N. The most extreme principal stresses in the bone were always located around the neck of the implant. Stress around the implant was, therefore, not only caused by the local deformation of the bone due to movement of the implant and interface relative to the surrounding bone but also by the bending of the mandible. The most extreme principal stress was found with oblique bite forces. The highest maximum and lowest minimum principal stresses were 7.4 and -16.2 MPa in the model without the bar and 6.5 and -16.5 MPa in the model with the bar. When differences in the amount of bite force were eliminated, the vertical bite force resulted in the lowest stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Bite Force↗

PubMed1993

A comparison of three finite element models of an edentulous mandible provided with implants.

The stress distribution in an edentulous mandible provided with two implants in the interforaminal region was calculated by means of three different finite element models. The implants were connected with a bar or remained solitary. The first model was a three-dimensional representation of the entire mandible, the second model of the interforaminal region of this same mandible, whilst the third model was a two-dimensional representation of the interforaminal region. The differences in stress distribution around the connected implants and the solitary implants between these three models were analysed. It can be concluded that for a parameter study the stress distribution around the dental implants following from a three-dimensional finite element model of only the interforaminal region of an edentulous mandible can be used. For such studies therefore, benefit can be gained from the advantages of reduced modelling and calculation time.

Bite Force↗

PubMed1993

A comparison of methods to assess marginal bone height around endosseous implants.

3 methods of measurements of marginal bone level on intra-oral radiographs of endosseous implants are described: measurements with a computerized image analysis system, with a magnifying-glass and with a digital sliding gauge. The accuracy of each of these methods was investigated and compared. The intra- and inter-observer error analysis showed that determining the precise bone height on the image is responsible for a large standard deviation for each method. It is concluded that measurements with a digital sliding gauge are preferable because it is easy to put into practice, and in addition, accuracy matches the accuracy of the other methods.

Alveolar Bone Loss↗

PubMed1992

Stress distribution around dental implants: influence of superstructure, length of implants, and height of mandible.

The stress distribution around dental implants was investigated by use of a two-dimensional model of the mandible with two implants. A vertical load of 100 N was imposed on abutments or the bar connection. The stress was calculated for a number of superstructures under different loading conditions with the help of the finite element method. The length of the implants and the height of the mandible were also varied. A model with solitary abutments showed a more uniform distribution of the stress when compared with a model with connected abutments. The largest compressive stress was also less in the model without the bar. Using shorter implants did not have a large influence on the stress around the implants. When the height of the mandible was reduced, a substantially larger stress was found in the bone around the implants because of a larger overall deformation of the lower jaw.

Bite Force↗

PubMed1992

Standardized radiographs of the alveolar crest around implants in the mandible.

The techniques currently used for standardized longitudinal radiographic evaluation of the supporting bone around dental implants are not suitable for general application. An aiming device is described for intraoral radiography used to evaluate the crestal bone height around dental implants used as retention for overdentures. This aiming device has been tested on four different implant systems by four dentists. Error analysis of serial radiographs indicates small deviations in reproducibility. It is concluded that this method is suitable for routine evaluation of dental implants.

Alveolar Process↗

PubMed1991

Suddenly symptomatic brain tumors at altitude.

High-altitude cerebral edema can present with a wide variety of neurologic manifestations; these symptoms resolve with descent. The persistence of neurologic symptoms after descent suggests an intracranial lesion. Brain tumors suddenly becoming symptomatic at altitude have not been reported previously. We report three cases of previously unsuspected brain tumors that suddenly became symptomatic at high altitudes.

Adolescent↗

PubMed1990

A new porous polyetherurethane wound covering.

A polyetherurethane (PEU) wound covering with non-interconnected micropores up to approximately 5 microns has been prepared by means of a phase inversion process. This highly elastic, very thin (15-20 microns), pliable wound covering showed good, immediate adherence to wet wound surfaces and high water vapor permeability, but was impermeable to bacteria. In guinea pigs epidermal wound healing of partial-thickness wounds under PEU wound coverings was accelerated compared with uncovered controls and an occlusive wound covering, OpSite. Water in liquid form or wound exudate could not leak through the PEU covering, but its high water vapor permeability induced concentration of the wound exudate into a jellylike clot layer, which apparently accelerated reepithelialization. The main conclusion from a clinical study on 20 donor sites was that the use of the PEU covering reduced pain, besides prevention of fluid retention. No differences in epithelialization were seen in comparison to tulle gras-treated wounds.

Adult↗

PubMedDate not supplied

Influence of patient age on the success rate of dental implants supporting an overdenture in an edentulous mandible: a 3-year prospective study.

The aim of this study was to determine the influence of age on peri-implant tissues in patients treated with implant-supported overdentures in the mandible. A prospective study was carried out with 2 groups of healthy edentulous patients. The mean age of the younger group (n = 32) was 46 years (range 35 to 50 years); the mean age of the older group (n = 26) was 68 years (range 60 to 80 years). Two dental implants were placed in the interforaminal region of the mandible, and after a 3-month healing period, overdentures were fabricated. Clinical and radiographic parameters were evaluated immediately after completion of the prosthetic treatment, after 1 year, and after 3 years. The evaluated clinical parameters were implant loss, Plaque Index, Gingival Index, Bleeding Index, and probing depth. Radiographic evaluation was performed using a standardized long-cone technique with a direction device. Statistical analysis was carried out with SPSS software. One implant in the older group was lost during the healing period. After 3 years, the mean scores for Plaque Index, Gingival Index, and Bleeding Index were between 0 and 1 for both groups (out of possible scores of 0 to 3), and the mean probing depth was 3 mm in both groups. The mean bone loss after 3 years was 1.2 mm in the younger group and 0.8 mm in the older group, but this difference was not significant. It was concluded from this study population that the clinical performance of implant-supported overdentures in the mandible is equally successful in younger and older patients.

Adult↗

PubMedDate not supplied

A three-dimensional finite element study on two versus four implants in an edentulous mandible.

The difference in stress distribution in the bone around dental implants was determined under conditions where either two or four implants were placed in the interforaminal region of the mandible. The purpose was also to determine the influence of the height of the mandible on the stress distribution. The stress distribution around the implants was investigated using three-dimensional finite element models of the interforaminal region of two mandibles with two different stages of resorption. It was concluded that there is no reduction of the extreme principal stresses when the load is distributed over an increasing number of implants. There is a tendency for a gradual stress increase as mandibular height decreases.

Alveolar Bone Loss↗

PubMedDate not supplied

Treatment concept for mandibular overdentures supported by endosseous implants: a literature review.

Edentulous patients with a severely resorbed mandible often experience problems with their dentures. Treatment concepts involving two to four implants for the support of an overdenture have been proposed. The aim of this study was to develop a treatment concept for mandibular overdentures supported by endosseous implants based on a review of the literature. It is proposed that two implants supporting a mandibular overdenture (bar construction) are sufficient for most applications. Four implants were indicated in situations involving a dentulous maxilla, a narrow mandibular arch, extreme resorption of the mandible (bone height greater than 12 mm), and mandibular soreness and pain.

Bone Resorption↗