PubMed Health⌕ Search

Biomedical subjects

Ignace Naert

Publications and source records attributed to Ignace Naert.

At least 19 recordsLinked to original sources
PubMed2006

Dynamics of initial subgingival colonization of 'pristine' peri-implant pockets.

BACKGROUND: Periodontitis and peri-implantitis are linked to the presence of several key pathogens. The treatment of these infectious processes therefore involves the reduction/eradication of bacteria associated with periodontitis. METHODS: This prospective, split-mouth, single-blind study followed the colonization of 'pristine' sulci created in 42 partially edentulous patients during implant surgery (e.g. abutment connection). The hypothesis was that the composition of the maturing subgingival plaque in these 'fresh' peri-implant pockets would soon (within 2 weeks) be comparable to the subgingival microbiota of teeth with similar clinical parameters (reference sites), including the presence of bacteria associated with periodontitis. Per patient, four subgingival plaque samples were taken from shallow and medium pockets around implants (test sites), and teeth within the same quadrant (undisturbed microbiota as control sites), 1, 2, 4, 13, 26 and 78 weeks after abutment connection, respectively. The samples were analysed by either checkerboard DNA-DNA hybridization, or cultural techniques, or real-time polymerase chain reaction (PCR) for intra-subject comparisons (teeth vs. implant, for comparable probing depths). RESULTS: Checkerboard DNA-DNA hybridization and real-time PCR revealed a complex microbiota (including several pathogenic species) in the peri-implant pockets within 2 weeks after abutment connection. After 7 days, the detection frequency for most species (including the bacteria associated with periodontitis) was already nearly identical in samples from the fresh peri-implant pockets (5% and 20% of the microbiota belonging to red and orange complex, respectively) when compared with samples from the reference teeth. Afterwards (e.g. between weeks 2 and 13), the number of bacteria in peri-implant pockets only slightly increased (+/-0.1 log value), with minor changes in the relative proportions of bacteria associated with periodontitis (8% and 33% of the microbiota belonging to red and orange complex, respectively). Although small differences were seen between teeth and implants at week 2 with cultural techniques, a striking similarity in subgingival microbiota was found with this technique from month 3 on, with nearly identical detection frequencies for bacteria associated with periodontitis for both abutment types. CONCLUSIONS: This study indicates that the initial colonization of peri-implant pockets with bacteria associated with periodontitis occurs within 2 weeks.

Bacteria↗
PubMed2006

Early cellular responses in cortical bone healing around unloaded titanium implants: an animal study.

BACKGROUND: A clear understanding of the early cellular events leading to osseointegration of implants is currently lacking. To gain better insight, titanium implants were inserted in a rabbit model and histologic and histomorphometric analyses were performed at early time points after insertion. METHODS: Thirty-six cylindrical implants were inserted in the tibial diaphysis of six rabbits and left to heal for 1 to 42 days. Samples were processed into paraffin or methylmethacrylate sections, on which the surface of new bone, region of altered nuclear morphology, relative surface of basic multicellular units (BMUs) and blood vessels, and bone-to-implant contact were measured. RESULTS: After coagulum formation, osteoclasts and osteoblasts were observed at the bone surface 1 week after healing. In the preexisting bone, osteocytic lacunae appeared to be devoid of cells. This region of altered nuclear morphology continued to extend for 28 days (P <0.05) after implant insertion. This expansion was accompanied by an invasion of the damaged bone by BMUs that initiated intensive bone remodeling, which reached its maximum after 4 weeks (P <0.05) but was ongoing after 6 weeks of implant insertion. CONCLUSIONS: This study evaluated the early cellular events in cortical bone surrounding titanium implants. The insertion of an implant into bone initiates a series of biologic processes, including the formation of a hematoma, altered nuclear morphology of the osteocytes surrounding the implantation site, intensive bone remodeling, and the formation of new bone, eventually leading to the osseointegration of the implant.

Animals↗
PubMed2006

Specialisation and specialist education in prosthetic dentistry in Europe.

This presentation reports on the results of a meeting of prosthodontists from selected European countries. The aim of the meeting was to analyse and promote specialisation and specialist education in Prosthetic Dentistry in Europe. Representatives for Europe were selected from the European Prosthodontic Association (EPA) board, the Education and Research Committee of International College of Prosthodontists (ICP), countries with a legally recognised speciality, countries without a recognised speciality but organised training programmes and countries with neither of these situations. Data about specialisation and specialist training in Prosthodontics in Europe was scrutinised and discussed. The programmes for countries with specialist training had relatively similar content, mostly of three years duration. There was strong agreement that a recognised speciality raises the level of care within the discipline for both specialists and non-specialists. In several of the countries where a speciality had been introduced it had been initiated by pressure from public health planning authorities. The conclusions are that from a professional viewpoint an advancement of the speciality over Europe would develop the discipline, improve oral health planning and quality of patient care. A working group for harmonisation was recommended.

Education, Dental, Graduate↗
PubMed2005

Microbiological and clinical outcomes and patient satisfaction for two treatment options in the edentulous lower jaw after 10 years of function.

BACKGROUND: Long-term data on microbiological and clinical outcome as well as on patient satisfaction after implant therapy in the edentulous mandible are limited. Especially comparisons between fixed full prostheses (FFPs) and overdentures (ODs), or between anchoring systems for the latter are scarce. AIM: This study aimed to evaluate both of these parameters at the 10-year follow-up in a group of fully edentulous patients rehabilitated via an OD or a FFP (the latter to allow inter-group comparison). MATERIAL AND METHODS: A total of 37 fully edentulous patients (25 ODs, 12 FFPs, age at implant installation ranged from 36 to 85 years) participated in this study. All subjects received their implants (Branemark System, Nobel Biocare AB, Gothenburg, Sweden) 10 years previously. For the ODs different attachment systems (bar, magnets, ball) had been applied that allowed a further intra-group comparison. At the follow-up visit, 10 years after the abutment insertion, a series of periodontal parameters were recorded, long-cone radiographs were taken and subgingival plaque samples were collected for analysis using checkerboard DNA-DNA hybridization. The clinical and radiographic data were recorded at abutment connection and after 1 and 10 years. RESULTS: After 10 years of loading, mean plaque and bleeding indices and changes in attachment or marginal bone level were not significantly different, neither between the OD and FFP group, nor within the OD group. The marginal bone loss between abutment connection and year 10 was 0.86 and 0.73 mm for OD and FFP groups, respectively. The subgingival microbiota at implant sites from all (sub)-groups was comparable, with low numbers of DNA counts (+/-10 x 10(5)) but high detection frequencies of Actinobacillus actinomycetemcomitans (>90%), Porphyromonas gingivalis (>85%) and Tannerella forsythensis (30%). The composition of the subgingival microbiota was influenced by probing depth and bleeding tendency. Patient satisfaction was very high for both types of prosthetic rehabilitation. The FFP group scored only slightly better for chewing comfort and general satisfaction. CONCLUSION: These data indicate that from the clinical and microbiological standpoint, as well as patient satisfaction, both an OD and a FFP offer a favourable long-term outcome.

Adult↗
PubMed2005

Predisposing conditions for retrograde peri-implantitis, and treatment suggestions.

BACKGROUND: Recent case reports introduced the term retrograde peri-implantitis as a lesion (radiolucency) around the most apical part of an osseointegrated implant. It develops within the first months after insertion. This retrospective study aimed to find predisposing conditions for such peri-apical lesions and to evaluate treatment strategies. METHODS: All single implants (426 in the upper, 113 in the lower jaw, all Brånemark system type) placed at the department of Periodontology of the University Hospital (Catholic University Leuven) were included in this retrospective evaluation to check the incidence of retrograde peri-implantitis. Eventual predisposing factors such as patient characteristics (age, medical history), recipient site (local bone quality and quantity, cause of tooth loss), periodontal and endodontic conditions of neighboring teeth, implant characteristics (length, surface characteristics), and surgical aspects (guided bone regeneration, osseous fenestration, or dehiscency) were considered. Moreover, implants with retrograde peri-implantitis were followed longitudinally to verify their treatment outcome by means of different parameters (Periotest values (PTV), marginal bone level, radiological size of peri-apical defect). RESULTS: Seven implants in the upper (1.6%) and 3 in the lower jaw (2.7%) showed retrograde peri-implantitis, before or at abutment connection. In comparison with successful implants, such peri-apical lesions occurred preferably at sites with a history of an obvious endodontic pathology of the extracted tooth to be replaced. The incidence of retrograde peri-implantitis was significantly higher (P<0.0001) for TiUnite implants when compared with the machined implants (8/80 vs. 2/459). The machined implant surface, however, showed a higher failure rate (6.8%) than the TiUnite implants (2.5%). Failures with machined surfaces preferably occurred at extraction sites of teeth with a history of endodontic pathology or sites adjacent to teeth with an obvious endodontic pathology. No other predisposing factors could be identified. A curettage of the peri-apical lesions and the use of a bone substitute material prevented further progression of such lesions in the upper jaw (implants maintained their marginal bone and low PTV scores). A treatment in the lower jaw was less successful. CONCLUSIONS: Within the limitations of a retrospective study, these results seem to indicate that retrograde peri-implantitis is provoked by remaining scar or granulomatous tissue at the recipient site: endodontic pathology of extracted tooth (scar tissue-impacted tooth) or possible endodontic pathology from a neighboring tooth.

Causality↗
PubMed2005

Positive effect of early loading on implant stability in the bi-cortical guinea-pig model.

Loading, early after implant placement, has gained rapid interest in dentistry. Primary implant stability, as e.g. defined by resonance frequency instrumentation, has been isolated as a predicator when immediate and early implant loading is applied. The aim of this study was to investigate the effect of early (after 7 days) mechanical loading on the establishment of osseointegration by means of resonance frequency analysis (RFA). Percutaneous titanium implants were installed in both tibiae of 10 guinea-pigs. One week after implant installation, one implant (test) was loaded daily for 6 weeks, while the contra-lateral served as the unloaded one (control). A sinusoidally varying bending moment was applied at a frequency of 3 Hz and a force amplitude of 5 N, for 1800 cycli. Resonance frequency was measured at implant installation and from then on weekly using the RFA-device (Osstell). Contrary to control implants, that showed a decrease in stability 1 week after installation, reaching a minimum at 3 weeks (-200 Hz), test implants showed a progressive increase in stability over time. After 6 weeks, the mean resonance frequency of test and control implants reached the same values. As confirmed by recent literature, early loading does not have to endanger the establishment of osseointegration of titanium implants. On the contrary, controlled loading is beneficial to maintain the implant stability during the early critical healing period as determined by RFA-measurements.

Animals↗
PubMed2005

Biologic response of immediately versus delayed loaded implants supporting ill-fitting prostheses: an animal study.

BACKGROUND: Computer-assisted preoperative implant planning and transfer toward the patient allow the production of a prosthesis prior to surgery. This implies that the prosthesis can be installed immediately following implant insertion. An inherent disadvantage of this is a cumulated error, which can lead to prosthesis misfit owing to topographic deviations of the planned versus the installed implants. PURPOSE: The aim of this study was to determine whether prosthesis misfit is compromising the osseointegration of immediately versus delayed loaded implants and whether freshly installed implants adapt to the prosthesis. MATERIALS AND METHODS: In each of five New Zealand White rabbits, two experimental conditions were compared. One tibia harbored the so-called test implant, which originally showed a vertical misfit of about 500 microm with the prosthesis to which it was tightened immediately after implant installation. The control implant was installed in the other tibia and was allowed to heal during 9 weeks before the prosthesis with the vertical misfit of about 500 microm was connected to it. The prostheses were left in place for 12 weeks, after which the animals were sacrificed. RESULTS: All implants healed uneventfully. There were no statistically significant differences between the biologic responses of test and control implants. With a three-dimensional laser scanner, significantly more displacement of the test implants toward the prostheses was observed compared with the control implants. This led to a significant decrease in prosthesis misfit for the test implants compared with the control implants. CONCLUSIONS: This study indicates that prosthesis misfit does not per se lead to biologic failure of immediately loaded or of already osseointegrated implants. In addition, immediately loaded implants seem to topographically adapt to the prosthesis, thereby minimizing the existing misfit.

Alveolar Bone Loss↗
PubMed2004

A repeated sampling bone chamber methodology for the evaluation of tissue differentiation and bone adaptation around titanium implants under controlled mechanical conditions.

A repeated sampling bone chamber methodology was developed for the study of the influence of the mechanical environment on skeletal tissue differentiation and bone adaptation around titanium implants. Via perforations, bone grows into the implanted outer bone chamber, containing an inner bone chamber with a central test implant. An actuator--easily mounted on the outer bone chamber--allows a controlled mechanical stimulation of the test implant. After each experiment, the inner bone chamber--with its content--can be harvested and analysed. A new inner bone chamber with a central implant can be inserted consecutively in the outer bone chamber and a new experiment can start. Pilot studies led to a reliable surgical protocol and showed the applicability of the methodology, offering the possibility to study skeletal tissue differentiation and adaptation around implants under well-controlled mechanical conditions, and this protected from external loading. Repeated sampling of the bone chamber allows conducting several experiments within the same animal at the same site, thereby excluding subject- and site-dependent variability and reducing the amount of experimental animals.

Adaptation, Physiological↗
PubMed2004

Implant design and interface force transfer. A photoelastic and strain-gauge analysis.

OBJECTIVES: To compare stress and strain magnitudes of butt-joint and internal-cone oral implants in a bone simulant. MATERIAL AND METHODS: Photoelastic and strain-gauged models of solitary Brånemark, ITI and Astra Tech implants were obtained. Vertical and 20 degrees oblique forces of 100 and 150 N were applied on the abutments in separate load cases. Isochromatic fringe patterns around implants were observed and photographed in the field of a polariscope. Strain-gauge measurements were performed and principal strains induced around implants were calculated. RESULTS: Isochromatic fringe orders of all designs were similar under both loading conditions (P>0.05). Strains around Brånemark implants were lower than around Astra Tech and ITI implants, particularly under vertical loads. The latter implants had similar strain magnitudes (P>0.05), although strains around the conical Astra Tech implant were lower under vertical load. CONCLUSIONS: Butt-joint and internal-cone oral implants have similar force distribution characteristics. The implant-abutment mating design is not a decisive factor affecting stress and strain magnitudes in a bone simulant.

Biomechanical Phenomena↗
PubMed2003

Bone augmentation by means of a stiff occlusive titanium barrier.

It has already been shown that occlusive titanium barriers have osteoconductive properties. These barriers, however, cover only a limited surface area and have only been used in animal experiments. The aim of this study was to evaluate bone neogenesis under a pre-shaped titanium barrier placed over the top of the rabbit skull and the top of highly resorbed edentulous upper-jaw bone in patients. Computed tomography (CT) scans made it possible to pre-shape the titanium barrier according to individual bone shape in human experiments. On the rabbit skull, tissue augmentation of up to 6 mm 1 year after barrier placement was observed, while the original thickness of skull bone was on average between 1.5 and 2.5 mm. The bone, which remained histologically immature for 1 year, grew systematically along the titanium surface, illustrating its osteoconductivity. Even after removal of the barrier, on average, 75.3 and 59.4% of the newly created tissue volume was maintained after 3 and 9 months, respectively. Clinical observations on 10 consecutive patients showed that, in those (5/10) in which the barrier remained unexposed for several months, an increase of the jawbone height and width of up to 16 mm could be observed when the barrier was removed after 12-18 months. As in the rabbits at barrier removal, the bone demonstrated a limited degree of mineralization as ascertained from biopsies. This newly formed osteoid tissue allowed the insertion of 33 screw-shaped titanium implants which in most cases (30/33) successfully osseointegrated to support a fixed prosthesis. The surrounding marginal bone level remained stable even up to 5 years after implant placement. Both animal and clinical data demonstrate that guided bone neogenesis under a subperiosteally placed titanium barrier can reach large volumes.

Adult↗
PubMed2003

Quality of dental implants.

BACKGROUND: Clinicians need quality research data to decide which dental implant should be selected for patient treatment. AIM(S)/OBJECTIVE(S): To present the scientific evidence for claims of relationship between characteristics of dental implants and clinical performance. STUDY DESIGN: Systematic search of promotional material and Internet sites to find claims of implant superiority related to specific characteristics of the implant, and of the dental research literature to find scientific support for the claims. MAIN OUTCOME MEASURES: Critical appraisal of the research documentation to establish the scientific external and internal validity as a basis for the likelihood of reported treatment outcomes as a function of implant characteristics. RESULTS: More than 220 implant brands have been identified, produced by about 80 manufacturers. The implants are made from different materials, undergo different surface treatments and come in different shapes, lengths, widths and forms. The dentist can in theory choose among more than 2,000 implants in a given patient treatment situation. Implants made from titanium and titanium alloys appear to perform well clinically in properly surgically prepared bone, regardless of small variations of shapes and forms. Various surface treatments are currently being developed to improve the capacity of a more rapid anchorage of the implant into bone. A substantial number of claims made by different manufacturers on alleged superiority due to design characteristics are not based on sound and long-term clinical scientific research. Implants are, in some parts of the world, manufactured and sold with no demonstration of adherence to any international standards. CONCLUSIONS: The scientific literature does not provide any clear directives to claims of alleged benefits of specific morphological characteristics of dental implants.

Clinical Trials as Topic↗
PubMed2002

Peri-implant bone tissue strains in cases of dehiscence: a finite element study.

When patients with a narrow alveolar bone ridge are treated with oral implants, a dehiscence can occur. The lack of bony support at the buccal or lingual side of the implant may present an unfavourable situation from a biomechanical point of view. The hypothesis as to whether the presence of dehiscence leads to an increased risk of marginal bone overload was tested by means of the finite element method. Three different situations for a cylindrical oral implant, which was placed in a mandible, were modelled: i) no dehiscence, ii) a dehiscence at the buccal side and iii) dehiscences at the buccal and lingual sides. It was found that the presence of buccal and/or lingual dehiscences led to a marked increase in marginal bone strains at the mesial and distal sides of the implant, thus increasing the risk of bone tissue overload at these locations. Marginal bone strains at the buccal and/or lingual sides, however, did not increase.

Alveolar Process↗
PubMed2002

Biologic outcome of implant-supported restorations in the treatment of partial edentulism. part I: a longitudinal clinical evaluation.

The purpose of this study was to predict the outcome of implant restorations in the treatment of partial edentulism, taking into account implant interdependency and the effect of several confounding variables. Between December 1982 and June 1998, 1956 Brånemark system implants (1212 and 744 in the maxilla and mandible, respectively, 846 distal to first premolars) were installed in 660 patients (248 males) at the Department of Periodontology of the University Hospitals of the Catholic University of Leuven. Of the 810 restorations installed at the Department of Prosthetic Dentistry of the same hospital, 235 were single crowns, 166 were supported by implants and teeth and 409 were free-standing fixed partial prostheses. An additional 87 restorations was placed in private dental offices and were not included. The patients were followed from implant installation until June 1999. The estimated cumulative survival rates were 91.4% for all implants and 95.8% for all restorations over a period of 16 years. Estimated cumulative survival rates from loading for implant-tooth connected and free-standing implants were, respectively, 93.6% and 97.2%. Neither jaw site nor implant position (anterior-posterior) had any significant effect on the outcome. Short implant length, high number of implants per patient, low number of implants per prosthesis, implants loaded by acrylic-veneered restorations and implants combined with bone grafting present a higher risk hazard for implant failure. The idea of not splinting the implants in a fixed partial prosthesis is promising but needs replication before accepting it.

Acrylic Resins↗
PubMed2002

Biologic outcome of implant-supported restorations in the treatment of partial edentulism. Part 2: a longitudinal radiographic study.

The purpose of this study was to evaluate over time the marginal bone level changes around implants installed to treat partial edentulism and to investigate the possible effect of several confounding variables. Consecutive intraoral radiographs taken with the paralleling technique were used. In all, 660 partially edentulous patients ever treated in the departments (248 males; 15-83 years of age) with 1655 implants, which were successfully integrated at abutment connection, were loaded by means of fixed partial prostheses. The observation period starting at abutment connection reached 16 years (mean 5.1). Implants were divided into three groups: 235 implants supported single-tooth crowns, 398 supported implant-tooth connected and 1022 free-standing fixed partial prostheses. Implants were placed in maxilla and mandible, both anteriorly and posteriorly. No significant difference in bone level evolution was predicted between the three groups of implants, either for posterior or for anterior sites. The estimated marginal bone loss for the first 6 months is 0.31 mm/year and after that 0.015 mm/year higher in the maxilla than in the mandible. More bone loss was predicted for the first 6 months when dehiscences existed, when a membrane or a bone graft were used, or when metal/ceramic prosthesis material was applied. Age and gender did not affect the change in bone level. The use of subsequently situated single-implant crowns to restore an edentulous space did not lead to more marginal bone loss than around splinted implants. Based on marginal bone height maintenance, the excellent prognosis of the presently used implants to support restorations in the treatment of partial edentulism was confirmed.

Adolescent↗
PubMed2002

Rating of statements in an internal course evaluation: comparison between different groups of assessors.

The increased concern for accountability and quality improvement is inducing universities throughout Europe to evaluate and control performance. The establishment of criteria for educational quality, a requirement for a successful evaluation, was studied as part of an evaluation of the dental education programme at the Catholic University of Leuven. Criteria suggested by different groups (members of the internal evaluation commission including graduate and postgraduate students; members of the academic staff of the School of Dentistry, Oral Pathology and Maxillo-facial Surgery, and other members of the academic staff, not directly belonging to the school), were analysed by means of ANOVA with Scheffé posthoc tests to identify intergroup differences. It was hypothesized that a closer connection to the dental curriculum or a higher responsibility in the evaluation process would result in stricter criteria. For 108 different questions (in the form of statements with a six point Likert-type scale), members of the three groups had to indicate the score below which the quality would be considered suboptimal. Except for one question, no significant differences were found between ratings given by the members of the internal evaluation commission and other members of the School. Significant differences were found between non-school members and school- and/or commission-members. This study indicates that agreement on educational quality may be presupposed within an academic faculty and between members of the internal evaluation commission. However, the study also indicated that some caution should be exercised when 'external' teachers are included in the evaluation process.

Analysis of Variance↗
PubMedDate not supplied

Influence of prosthesis fit and the effect of a luting system on the prosthetic connection preload: an in vitro study.

PURPOSE: It was the aim of this study to evaluate the efficiency of a luting technique that is said to compensate for misfits of implant-supported prostheses by means of a combined screw retained-luted fixation of the prostheses to the supporting abutments. MATERIALS AND METHODS: One three-unit prosthesis was made on cylindric abutments, and one was made on conical abutments. Two more prostheses were made, one on the cylindric and one on the conical abutments, with the luting system. The preload was measured in different fit and misfit situations, with and without the use of the luting system. The preload is a combination of internal preload (positive axial forces), which is a clamping load that keeps the implant-prosthesis components together, and external preload (axial forces and bending moments), which is the result of a deformation of the implant-prosthesis complex during fixation caused by prosthesis misfit. The external preload on the supporting abutments after screw tightening the prostheses was used as an indicator for the quality of fit of the prostheses. RESULTS: The axial forces were lower and the bending moments were higher in cases of misfit in comparison with the optimal fit situation. The luting system generally did not decrease the registered external preload. Except for one test condition, even higher bending moments were registered on the supporting abutments when the luting system was used. CONCLUSION: For the prostheses evaluated in this study, the luting system was not effective in reducing the external preload on the supporting implants caused by prosthesis misfit. Although the luting system could compensate for visual misfit, it failed to really improve the load conditions of the supporting implants.

Cementation↗
PubMedDate not supplied

A custom template and definitive prosthesis allowing immediate implant loading in the maxilla: a clinical report.

PURPOSE: The purpose of the present investigation was to examine to what extent precision data from 3-dimensional planning software for oral implants can be transferred to the operative field by means of a drilling template, containing high-precision drilling sleeves, fitted on the jawbone. It was investigated whether this procedure would allow advance preparation of a fixed definitive prosthesis that could be placed at the completion of surgery. MATERIALS AND METHODS: This procedure was experimentally carried out in 2 cadavers and later in 8 consecutive human patients. RESULTS: The results indicated a nearly perfect match between the positions and axes of the placed implants and those planned. DISCUSSION: This procedure permitted the placement of a definitive fixed prosthesis with limited freedom of space between the abutments and the metallic cylinders incorporated into the prosthesis. CONCLUSION: These encouraging results of the Leuven information technology-based oral rehabilitation by means of implants (LITORIM) are presently being further investigated at the clinical level.

Cadaver↗