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Biomedical subjects

I Naert

Publications and source records attributed to I Naert.

At least 55 records · Page 3Linked to original sources
PubMed1998

The effect of titanium plasma-sprayed implants on trabecular bone healing in the goat.

The bone response to different titanium plasma-sprayed implants was evaluated in a goat model. Therefore, beam-shaped implants were installed into the trabecular femoral condyles of 10 goats. These implants were provided with three different titanium plasma-sprayed coatings (Ti2, Ti3 and Ti4) with a Ra of 16.5, 21.4 and 37.9 microm, respectively. An Al2O3 grit-blasted implant (Ti-un) with a Ra of 4.7 microm was used as control. After an implantation period of 3 months, the implants were evaluated histologically and histomorphometrically. Only one implant (Ti3) was not recovered after the evaluation period. Light microscopy showed a limited amount of bone for the various implants. Most of the implants showed a different degree of fibrous tissue alternating with direct bone contact. Complete fibrous encapsulation of the implants was observed in some of the sections. No signs of delamination of the plasma-sprayed coating was visible. No significant difference in bone contact were measured between the different types of implants (P > 0.05). Histomorphometrical analysis revealed significantly higher bone mass close to the implant (0-500 microm) for the Ti3, Ti4 and Ti-un implants placed in the medial femoral condyle and the Ti4 implants placed in the lateral condyle. At distance (500-1500 microm), no difference in bone mass measurements between the different implants was observed (P > 0.05).

Aluminum Oxide↗
PubMed1998

The influence of bone mechanical properties and implant fixation upon bone loading around oral implants.

Finite element models were created to study the stress and strain distribution around a solitary Brånemark implant. The influence of a number of clinically relevant parameters was examined: bone-implant interface (fixed bond versus frictionless free contact), bone elastic properties, unicortical versus bicortical implant fixation and the presence of a lamina dura. Bone loading patterns in the vicinity of the implant seem to be very sensitive to these parameters. Hence they should be integrated correctly in numerical models of in vivo behaviour of oral implants. This necessitates the creation of patient-dependent finite element models.

Biomechanical Phenomena↗
PubMed1998

A 5-year randomized clinical trial on the influence of splinted and unsplinted oral implants in the mandibular overdenture therapy. Part I: Peri-implant outcome.

Thirty-six completely edentulous patients were enrolled for a 5-year prospective study testing the treatment outcome between splinted and unsplinted implants retaining a mandibular hinging overdenture. The patients were randomized into 3 groups of equal size depending on the attachment system used such as: magnets, ball attachments or bars (reference group). Only 1 implant out of the 72 had failed at the abutment stage. Not a single implant failed during the 5-year loading period. The accumulation of plaque was significantly higher for the Magnet than for the Ball group. Bleeding on probing, as well as marginal bone level, attachment level and Periotest values did not statistically differ among the groups, neither at year 1 nor at year 5. However, the Periotest values were significantly lower at year 5 compared to year 1 for all groups, which indicates a higher rigidity at the bone-implant interface. No correlation was found between bleeding on probing and marginal bone loss. We conclude that the connection state of 2 implants retaining a hinging overdenture did not influence the peri-implant outcome.

Adult↗
PubMed1998

The EsthetiCone abutment: three-year results of a prospective multicenter investigation.

The EsthetiCone abutment, designed for subgingival restorative margins, makes it possible to achieve ideal esthetics, function, and predictability. This study included 200 EsthetiCone abutments placed in 50 partial or complete edentulous patients participating in a multicenter study performed in Europe and the United States. The patients were followed for 3 years and the marginal bone level of the implants was determined from intra-oral radiographs. During the follow-up period, a total of 9 of patients were withdrawn from the study. Based on the remaining patients, a total of 164 EsthetiCone abutments (82%) were evaluated through the 3-year follow-up visit. Only 1 EsthetiCone abutment failed during the study period, resulting in a cumulative success rate of 99.2% in the maxilla and 100% in the mandible after 3 years. No bone loss due to the usage of short abutment collars (1 mm) was seen in this study. The marginal bone resorption during the 3-year period did not exceed 1 mm as a mean neither for the 1 mm nor the higher abutments when analyzed separately. During the follow-up period, few complications were reported and they were all easily rectified without compromising the treatment success. The outcome of this study indicates that safe long-term and esthetically good results can be achieved when the Brånemark implants are loaded with EsthetiCone abutments. The reported need of a 3 mm peri-implant sulcus with an animal model was not confirmed with patients in this study.

Alveolar Bone Loss↗
PubMed1998

Bone healing capacity of titanium plasma-sprayed and hydroxylapatite-coated oral implants.

The influence of surface quality, in particular surface topography and implant material, was evaluated by inserting titanium- and hydroxylapatite plasma-sprayed coated implants into the maxilla of 10 goats. Three types of plasma-spray coatings were applied to tapered, screw shaped implants; titanium plasma-spray coating (TPS), titanium plasma-spray coating with additional acid passivation (TPSA) and a bilayered coating (TPS/HA) consisting of titanium plasma-spray coating (TPS) and a hydroxylapatite part (HA). In addition, as-machined implants (TiM) were used as control. A total of 40 implants were inserted according a balanced split plot design. At the end of a 3-month healing period, it appeared that 5 implants (2 TPS, 1 TPSA, 1 TPS/HA and 1 TiM) were lost. Histological examination revealed a stronger bone response to TPS/HA coated implants. Even the TPS/HA coated implants induced bone formation on the part of the implant inserted into the sinus. No signs of delamination of the TPS coatings were visible. The HA part of the dual coating showed signs of degradation. Histomorphometrical analysis confirmed these findings. A significant difference in bone contact (P < 0.05) was measured between the TPS/HA coated implants and the other types of implants. Linear regression (r = 0.27) showed no correlation between the inscrew values at the base line and the bone contact measurements 3 months after healing. On the basis of these results, we can conclude that the chemical composition of the HA coating has a positive influence on the bone reaction. The influence of roughness is less evident.

Alveolar Process↗
PubMed1997

The effect of Ca-P plasma-sprayed coatings on the initial bone healing of oral implants: an experimental study in the goat.

The response of bone of low density to uncoated, fluorapatite (FA), hydroxyapatite (HA), and hydroxyapatite heat treated (HAHT) plasma-sprayed coated implants was investigated 3 and 6 months after installation. Forty-eight threaded implants of commercially pure titanium were inserted into the maxilla of twelve goats according to a split-plot design. One goat died shortly after installation of the implants, five goats were sacrificed 3 months after installation, and the other six goats 6 months after installation. Histological evaluation revealed no difference in bone reaction between the 3- and 6-month implantation periods. In addition, probably due to the wide inter- and intra-animal variability, no significant difference between the 3- and the 6-month periods could be observed in the histomorphometrical measurements performed. Further, no significant differences were found in bone reaction among the various implant materials. Finally, qualitatively it appeared that all coatings showed reduction in coating thickness and that such reductions were most pronounced for the HA coatings.

Animals↗
PubMed1997

A histological and histomorphometrical evaluation of the application of screw-designed calciumphosphate (Ca-P)-coated implants in the cancellous maxillary bone of the goat.

Various studies already have shown that the occurrence of oral implant failure is higher in the maxilla than in the mandible. To learn whether Ca-P coatings can improve the success rate of oral implants in the maxilla, three different plasma-sprayed, Ca-P-coated, self-tapping Brånemark implants were inserted in the trabecular bone of the maxilla. Before the insertion of the implants, the two first upper premolars of 16 goats were bilaterally extracted. Four months later, each animal received four types of implants: three different Ca-P-coated types and one uncoated. After an endosseous period of 6 months, the implants were provided with permucosal abutments. Four months later the animals were killed. At the end of the experiment, it appeared that 10 of the 16 installed noncoated implants had failed while of the 48 Ca-P-coated implants, only 6 had failed. All successful implants were retrieved and prepared for histomorphometrical evaluation of the bone and gingiva response. The Ca-P-coated implants showed a significantly greater percentage of bone in contact with the implant surface compared with the uncoated implants. The length of the epithelium was not significantly different for the coated compared to the uncoated implants, but the connective tissue was significantly thicker for the noncoated implants than for the Ca-P-coated implants. Also, measurements revealed that all coatings showed reduction in thickness. On the basis of these findings, we concluded that the application of Ca-P coatings (1) improves the bone-implant reaction, although all coatings reduced in thickness, and (2) is of benefit during the healing period in less mineralized trabecular bone.

Animals↗
PubMed1997

The rehabilitation of the severely resorbed maxilla by simultaneous placement of autogenous bone grafts and implants: a 10-year evaluation.

The long-term success of Brånemark implants has been previously reported. The success rate of the same implants, when associated with autologous grafts, seemed much less predictable. In the present study it is demonstrated that when these implants are installed in conjunction with an autologous corticocancellous hip graft, either onlay or inlay, the cumulative success rate remains at 95% for individual implants in non-smokers. The short extracorporal time might be an explanation. On the other hand, the same approach in patients with congenital defects or who underwent radiotherapy is deceptive. The use of hyperbaric oxygen may dramatically improve these results.

Adult↗
PubMed1997

Implant supported overdentures--the Leuven experience.

OBJECTIVES: This report covers a series of three different clinical longitudinal studies on the outcome of overdenture therapy when two (mandible) or four (maxilla) implants retaining a resilient overdenture are used. CONCLUSIONS: The resilient mandibular bar-retained overdenture on two implants is a very reliable treatment. Implant failure is low and the stability of the implants improves over time. Marginal bone remains stable once the first year has passed. The applied overdenture design is simple, versatile and very cost effective. In the maxilla such implants do maintain their marginal bone level if splinted by means of a rigidly cast bar and when applied in a resilient overdenture therapy. Correct laboratory fabrication of the prosthesis is critical to the success of treatment. Clinically, overdenture aftercare is limited to renewal of used attachments. Patient satisfaction remains very positive to this form of treatment.

Adult↗
PubMed1997

An animal study on the bone behaviour of Ca-P-coated implants: influence of implant location.

Four different implant materials were installed into the mandibular corner of goats to investigate the trabecular bone response in a mainly unloaded model. The implants were installed using a standardized technique and were left in situ for 12 weeks. One goat had to be sacrificed after surgery because of a broken rib; the other animals healed uneventfully. After sacrifice of the animals, the bone response to the uncoated and the three different Ca-P implants was evaluated histologically and histomorphometrically. Four sections of each implant were evaluated; two were located in the cortical and two in the trabecular bone. Of the 44 retrieved implants, 20 implants appeared to be installed partially in the mandibular canal, as clearly visible on the X-rays. These implants were not used in the histomorphometrical measurements. Histological evaluation showed that the trabecular and cortical bone reactions were similar; there was no significant difference in the percentage of bone contact nor in the amount of bone in contact with the implants. In conclusion this study showed that the mandibular corner is an unsatisfactory model for the installation of implants because of anatomical restrictions. Also, the experiment remained inconclusive about the influence of loading conditions on bone behaviour. Nevertheless, the histological results confirmed the bioactive properties of Ca-P coatings.

Journal Article↗
PubMed1995

Effect of calcium phosphate (Ca-P) coatings on trabecular bone response: a histological study.

The trabecular bone response to noncoated and fluorapatite (FA), hydroxyapatite (HA), and hydroxyapatite heat-treated (HAHT) plasma-sprayed coated implants was investigated in a goat animal model. Forty-eight cylindrical implants were inserted into the trabecular bone of the lateral and medial femoral condyles of twelve goats according to a split plot design. After an implantation period of twelve weeks, the bone-implant interface was evaluated histologically. Quantitative histomorphometrical measurements demonstrated a significant difference in bone contact between implants inserted in the lateral and medial condyles. In addition, a significant difference in bone apposition was observed between the coated and the uncoated implants. Finally, all Ca-P coatings showed reduction in coating thickness. Measurements revealed that FA and HAHT showed less reduction in coating thickness than HA coating. Despite the coating reduction, the bone remained in close contact with the implant surface.

Analysis of Variance↗
PubMed1995

Masseter muscle fatigue before and after rehabilitation with implant-supported prostheses.

To establish whether different implant-supported prosthetic reconstructions influence jaw muscle resistance to clenching efforts, sustained submaximal (50%) clenching was performed in two groups of patients who were edentulous in one or both jaws. One group consisted of patients who were rehabilitated by means of an overdenture on two to four implants connected by a bar; the other group consisted of patients who were rehabilitated with an implant-supported fixed prosthesis on four to seven implants in either the maxilla or the mandible. Results indicated that after rehabilitation with implant-supported fixed reconstructions, the myoelectric output level increased over time, which was parallel to a higher bite force level. For the other group, such a time-dependent change in electromyographic amplitude did not occur. On the other hand, power spectrum analysis revealed a significant downward shift of the mean power frequency during sustained clenching after rehabilitation with implant-supported overdentures but not with implant-supported fixed prostheses. The absence of a spectral shift in the latter group probably expressed a fear of biting too hard and fracturing the prosthesis.

Adult↗
PubMed1995

Damping characteristics of bone-to-implant interfaces. A clinical study with the Periotest device.

The Periotest device was used to evaluate the damping characteristics of different bone-to-implant interfaces of Brånemark implants. Implant and abutment lengths were found to have a significant influence on Periotest value (PTV). There was no statistical difference between PTVs of implants located in the anterior and posterior areas of the same jaw at abutment connection. No differences were found between PTVs of standard and self-tapping implants. PTVs at abutment connection were highly influenced by the bone quality. The contact with two corticals, one at each extremity of the implant, was of a greater influence in the maxillary than in the mandibular jaw, indicating a firmer anchorage between the bi-cortical implants and the surrounding bone. A progressive decrease of PTVs over time was observed, significant up to 5 years of loading.

Adult↗
PubMed1994

A comparative prospective study of splinted and unsplinted Brånemark implants in mandibular overdenture therapy: a preliminary report.

Thirty-six edentulous patients, each provided with two Bränemark implants in the mandible to anchor an overdenture, were selected for this study and randomly divided into three groups of 12 patients each. In each group a different attachment system was used: (1) magnets, (2) ball attachments, and (3) straight bars with clips (control). The mean loading time was 12.4 months (range 3 to 24 months). This study investigated (1) the clinical behavior of loaded implants by means of overdentures related to their connection system (splinted versus unsplinted) and (2) the clinical performance of prosthetic treatment. Preliminary results indicate no differences; no failures occurred and the level of marginal bone height, as well as the probing attachment level, changed similarly in the three groups. Although splinted bar-retained overdentures scored better objectively, subjective satisfaction ratings did not differ. It was concluded that for the short follow-up period, the state of connection did not influence the clinical success of implants. However, no definite conclusions may be drawn until long-term data become available.

Adult↗
PubMed1993

Maxillary bone resorption in patients with mandibular implant-supported overdentures or fixed prostheses.

For several years, implant-supported overdentures have been used with excellent results in rehabilitation of the edentulous mandible. The effect on the antagonistic jaw bone resorption however, has not yet been evaluated. The aim of this study was to examine on orthopantomograms the anterior and posterior maxillary ridge resorption in three groups of patients with different mandibular prosthetic reconstructions: (1) overdentures supported by two implants, (2) fixed prostheses supported by four to six implants, and (3) complete dentures. The results indicated a more pronounced annual bone resorption in complete denture wearers compared to patients with implant-supported overdentures. A limited but continuing bone resorption was observed for the patients with implant-supported overdentures, and a slightly higher annual bone resorption occurred in the implant-supported fixed prosthesis group.

Adult↗
PubMed1993

An in vivo study of the influence of the surface roughness of implants on the microbiology of supra- and subgingival plaque.

In nine patients with fixed prostheses supported by endosseous titanium implants, 2 titanium abutments (transmucosal part of the implant) were replaced by either an unused standard abutment or a roughened titanium abutment. After 3 months of habitual oral hygiene, plaque samples were taken for differential phase-contrast microscopy, DNA probe analysis, and culturing. Supragingivally, rough abutments harbored significantly fewer coccoid micro-organisms (64 vs. 81%), which is indicative of a more mature plaque. Subgingivally, the observations depended on the sampling procedure. For plaque collected with paper points, only minor qualitative and quantitative differences between both substrata could be registered. However, when the microbiota adhering to the abutment were considered, rough surfaces harbored 25 times more bacteria, with a slightly lower density of coccoid organisms. The presence and density of periodontal pathogens subgingivally were, however, more related to the patient's dental status than to the surface characteristics of the abutments. These results justify the search for optimal surface smoothness for all intra-oral and intra-sulcular hard surfaces for reduction of bacterial colonization and of periodontal pathogens.

Bacterial Adhesion↗
PubMed1992

A study of 589 consecutive implants supporting complete fixed prostheses. Part I: Periodontal aspects.

Ninety-one consecutive edentulous patients who had been treated by means of fixed prostheses (n = 103) supported by Brånemark implants (n = 589) were examined. Eighteen fixtures (3%) failed to integrate. After a mean loading time of 32 (range 6 to 80) and 38 months (range 5 to 83) for fixtures in the maxilla and mandible, respectively, an additional 12 fixtures lost integration. The cumulative failure rate for individual fixtures after 6 years was 8.4% and 5% for maxillae and mandibles, respectively. Only one patient had to revert to complete dentures. For fixtures in the maxillae, the mean marginal bone loss was 0.7, 0.1, and 0.2 mm for each of the first 3 years of loading, respectively; for fixtures in mandibles, the corresponding values were 0.7, 0.2, and 0.1 mm. The loss in marginal bone height was equal in both jaws and was not related to bleeding on probing or to the preoperative resorption anatomy.

Adolescent↗