Biomedical subjects

I Naert

Publications and source records attributed to I Naert.

At least 37 records · Page 2Linked to original sources

PubMed2001

The influence of plaque and/or excessive loading on marginal soft and hard tissue reactions around Brånemark implants: a review of literature and experience.

High implant survival rates are published with more than 15 years of observation time. Failures over time are often caused by ongoing marginal bone loss. Therefore, the need for reliable monitoring of the stability of periimplant attachment and/or bone level is extremely important. Marginal bone loss around osseointegrated implants has often been associated with periimplantitis, but clinical observations cannot prove this relationship. Otherwise, the impact of excessive loading on periimplant bone has been shown in animal studies and has been positively related to implant failure in terms of implant mobility and marginal bone loss. Some clinical observations support this hypothesis.

Alveolar Bone Loss↗

PubMed2000

Time dependent failure rate and marginal bone loss of implant supported prostheses: a 15-year follow-up study.

This study deals with 4971 implants (Brånemark system) installed in 1315 patients, either fully or partially edentulous, and followed from implant installation up to the last control. A predominance of female patients (61%) and a nearly equal number of upper and lower jaws characterised the study group. Patients were scheduled each 6-12 months for recall. The observation time varied from 0.5 to 15 years (mean 5.1). The whole cohort was split up into compromised (n = 59) and non-compromised (n = 1256) patients. The former are defined as grafted (autologous bone) and patients irradiated in the head and neck area. In the compromised patients 24 out of 59 patients (40.6%) showed failures, in whom 59 out of 310 (19%) implants failed. In the non-compromised patients, implant failures were observed in 11.6% of the patients, which corresponds to 5.9% of the installed implants, excluding iatrogenic failures. Failures were further divided chronologically into early (up to 1 year after abutment connection) and late failures. There were early implant failures in 12.5% of the compromised patients and in 3.4% of the others. Late implant failures occurred in 7.4 and 2% of the two patients groups, respectively. While gender did not affect the failure rate, implant lengths, corresponding to the available bone height did, since a 21.5% failure rate for the 7-mm implants contrasts with 4.1 and 3.8% for 13- and 15-mm implants, respectively. Early as well as annual late failures are more frequently found in the maxilla. Implant fractures only occurred in the fixed (both partial and full) prosthesis group but never surpassed the 0.2% annual level. Marginal bone loss, exceeding the third screw thread occurred in 1.8% of the implants at the last control. It appears that this type of implant configuration offers a high long-term predictability. Failures occur before, at or during the first year after abutment connection and in very short implants. Marginal bone as a whole is very stable over the years.

Adolescent↗

PubMed2000

A prospective split-mouth comparative study of two screw-shaped self-tapping pure titanium implant systems.

Clinical data indicate different medium and long-term outcomes of endosseous implants for different implant configurations and in particular implant surfaces. The present study compares 2 very similar implant systems but with different surface characteristics in a split-mouth-randomized design. The Astra-Tech (A) system (Astra-Tech AB, Mölndal, Sweden) consisted of selftapping TiO2-blasted screw-shaped implants made of commercially pure titanium, and the Brånemark (B) System (Nobel Biocare, Gothenburg, Sweden) comprised selftapping Mark II implants with machined surface irregularities. Throughout the 2-years' observation period, no significant differences could be found concerning probing depths, presence of plaque or change in marginal bone level. A statistically significant difference in location of the marginal bone level in relation to the shoulder of the implant was found in favor of the A system both at baseline and after 2 years. Cumulative success rates of 100% (A) and 97.7% (B) were not statistically different. From a prosthetic point of view, more soldering points were needed for A compared to B to reach clinical acceptable fit. More years of observation are needed to compare the fate of the soft and hard tissues surrounding two different implant surfaces.

Adult↗

PubMed2000

A mechanical evaluation of TiO2-gritblasted and Ca-P magnetron sputter coated implants placed into the trabecular bone of the goat: Part 1.

The influence of Ca-P magnetron sputter coated implants on the mechanical anchorage was evaluated in a goat model. Therefore, uncoated and coated screw designed commercially pure titanium TiO2-blasted implants were inserted into the trabecular bone of the femoral condyles of 12 goats. The thicknesses of the coatings were 0.1 micron (CaP-0.1), 1.0 micron (CaP-1) and 4.0 microns (CaP-4). In addition, uncoated TiO2-blasted implants (Ti) were used as control. Evaluation of the interface strength and appearance, using torque test and scanning electron microscopy, was done at implantation periods of 6 and 12 weeks. Although, especially at 6 weeks of implantation, the Ca-P coated implants showed higher failure torque values than the TiO2 blasted implants, the observed differences for type of implant and evaluation period were not significant (P > 0.1). SEM evaluation showed that all implants with failure values of more than 100 N conducted bone growth into their screw threads. In addition, we observed that the fracture plane for the CaP-4 implants was situated at the coating-implant interface or inside the coating. For the CaP-1 and CaP-0.1 the fracture line could not be determined definitely. For the Ti implants, the fracture torque testing resulted in failure at the bone-implant interface. Therefore, we conclude that all implants resulted in a good bonding strength with the surrounding bone. The sputtered Ca-P coatings seemed to improve the initial fixation of the TiO2 blasted implants.

Animals↗

PubMed2000

A histological evaluation of TiO2-gritblasted and Ca-P magnetron sputter coated implants placed into the trabecular bone of the goat: Part 2.

The aim of this study was to investigate the synergetic influence of surface topography and chemical composition of oral implant materials on bone response. For the experiment screw designed implants were used. The implants were grit-blasted with TiO2 particles. The implants were left uncoated (Ti) or provided with three different amorphous/crystalline Ca-P magnetron sputter coatings, resp. 0.1 micron (CaP-0.1), 1 micron (CaP-1) and 4 microns (CaP-4), in thickness. The implants were inserted in the medial femoral condyles of 12 goats. Each femur received 2 implants. After implantation periods of 6 and 12 weeks the implants were retrieved and prepared for histological and histomorphometrical evaluation (bone contact and bone mass). The light microscopy revealed that bone response to CaP-4 and CaP-1 implants was similar. For example, after 12 weeks, screw threads were almost completely covered with bone. In contrast to CaP-0.1 and Ti implants, where bone apposition was less pronounced. Histomorphometry demonstrated that the bone-to-implant contact for the CaP-1 and CaP-4 implants was significantly higher (P < 0.05) than for the CaP-0.1 and Ti implants. This difference existed already after 6 weeks and was even enhanced after 12 weeks. The bone mass measurements revealed that only at 12 weeks CaP-4 implants had significantly more bone contact inside the screw threads than non-coated Ti-implants (P < 0.05). Supported by our findings, we conclude that the additional application of a 1-4 microns thick Ca-P magnetron sputter coating can further improve the healing response to surface roughened oral implants placed into trabecular bone.

Analysis of Variance↗

PubMed2000

Magnitude and distribution of occlusal forces on oral implants supporting fixed prostheses: an in vivo study.

Since loading is increasingly believed to be a determining factor in the treatment outcome with oral implants, there is a need to expand the knowledge related to the biomechanics of oral implants. The aim of this study is to gain insight in the distribution and magnitude of occlusal forces on oral implants carrying fixed prostheses. This is done by in vivo quantification and qualification of these forces, which implies that not only the magnitude of the load but also its type (axial force or bending moment) will be registered. A total of 13 patients with an implant supported fixed full prosthesis were selected. Occlusal forces on the supporting implants were quantified and qualified during controlled load application of 50 N on several positions along the occlusal surface of the prostheses and during maximal biting in maximal occlusion by use of strain gauged abutments. The test was conducted when the prostheses were supported by all (5 or 6) implants and was repeated when the prostheses were supported by 4 and by 3 implants only. Despite considerable inter-individual variation, clear differences in implant loading between these test conditions were seen. Loading of the extension parts of the prostheses caused a hinging effect which induced considerable compressive forces on the implants closest to the place of load application and lower compressive or tensile forces on other implants. On average, higher forces were observed with a decreasing number of supporting implants. Bending moments were highest when 3 implants only were used.

Adult↗

PubMed2000

Three-dimensional force measurements on oral implants: a methodological study.

This paper describes a methodology that allows in vitro and in vivo quantification and qualification of forces on oral implants. Strain gauges are adapted to the outer surface of 5.5 and 7 mm standard abutments (Brånemark System, Nobel Biocare, Sweden). The readings of the strain gauges are transformed into a numerical representation of the normal force and the bending moment around the X- and Y-axis. The hardware and the software of the 3D measuring device based on the strain gauge technology is explained and its accuracy and reliability tested. The accuracy level for axial forces and bending moments is 9.72 N and 2.5 N x cm, respectively, based on the current techniques for strain gauged abutments. As an example, an in vivo force analysis was performed in a patient with a full fixed prosthesis in the mandible. Since axial loads of 450 N and bending moments of 70 N x cm were recorded, it was concluded that the accuracy of the device falls well within the scope of our needs. Nevertheless, more in vivo research is needed before well defined conclusions can be drawn and strategies developed to improve the biomechanics of oral implants.

Aged↗

PubMed2000

Influence of prosthesis material on the loading of implants that support a fixed partial prosthesis: in vivo study.

BACKGROUND: Since loading is increasingly believed to be a determining factor in the treatment outcome with oral implants, there is a need to expand the knowledge related to the biomechanics of oral implants and its influencing factors. PURPOSE: The aim of this study was to investigate the influence of prosthesis material on the distribution and magnitude of load on oral implants carrying a fixed partial prosthesis by in vivo quantification and qualification of this load. METHODS: Eight patients with in total nine three-unit fixed partial prostheses on three implants and three patients with in total four two-unit fixed partial prostheses on two implants were selected. Both metal and acrylic resin prostheses were made. Strain gauged abutments were used to measure the load on the supporting implants during controlled load application of 50 N on several positions along the occlusal surface of the prostheses and during maximal biting in maximal occlusion. Additional tests were conducted when the three-unit prostheses were supported only by two implants, thereby creating an extension pontic. RESULTS: A significantly better distribution of bending moments with the metal prostheses in comparison to the acrylic resin prostheses was observed in the case of the three-unit prostheses on two implants. No other difference in load or load distribution with the different prosthesis materials was noted. CONCLUSION: The clinical significance of the study reveals an increased risk for bending overload of the implants that are closest to the point of load application only in the case of acrylic resin long span prostheses or acrylic resin prostheses with extensions.

Acrylic Resins↗

PubMed2000

Biologic outcome of single-implant restorations as tooth replacements: a long-term follow-up study.

BACKGROUND: The replacement of a single tooth or several teeth by means of single-implant restorations is an increasingly used method that needs long-term validation. PURPOSE: The goal of this study was to evaluate the outcome of single-implant restorations by means of fixed restorations and to define the prognosis through marginal bone level estimations. MATERIALS AND METHODS: From November 1986 to June 1998, 270 Brånemark implants (215 in the upper jaw) were installed in 219 patients (106 males). Both anterior and posterior sites were involved. Of the 263 single restorations, 28 were placed in private dental offices. The patients were followed until June 1999. RESULTS: Twelve implants failed before or at abutment connection or within 6 months afterward. Only four implants failed later. The cumulative success rates were 93% for the implants and 96.5% for the restorations over a period of 11 years. The marginal bone loss during the first 6 months after abutment connection reached 0.71 mm and then dropped to 0.036 mm annually over a period of 10 years. CONCLUSIONS: Single-implant restorations (Brånemark System) are a reliable treatment with a good long-term prognosis. Failures were concentrated during the healing period and early loading phase.

Adolescent↗

PubMed2000

Use of microfocus computerized tomography as a new technique for characterizing bone tissue around oral implants.

Qualitative and quantitative analysis of peri-implant tissues around retrieved oral implants is typically done by means of light microscopy on thin histological sections containing the metal surface and the undecalcified bone. It remains, however, a labor-intensive and thus time-consuming job. Moreover, it is a destructive technique that allows tissue quantification in only a limited number of two-dimensional sections. As an alternative, we evaluated the bone structure around screw-shaped titanium implants by means of microfocus computerized tomography (micro-CT) because it presents a number of advantages compared to conventional sectioning techniques: micro-CT is nondestructive, fast, and allows a fully three-dimensional characterization of the bone structure around the implant. Images can be reconstructed in an arbitrary plane, and three-dimensional reconstructions are also possible. Because of its high resolution, individual trabeculae can be visualized. The accuracy of micro-CT was qualitatively evaluated by comparing histological sections with the corresponding CT slices for the same specimen. The overall trabecular structure is very similar according to both techniques. Even very close to the interface, the titanium implant does not seem to produce significant artifacts. Furthermore, because the complete digital data on the trabecular bone structure around the implant is available, it is possible to create finite-element models of the bone-implant system that model the trabeculae in detail so that mechanical stress transfer at the interface can be studied at the level of individual trabeculae. Therefore, micro-CT seems to be very promising for the in vitro assessment of the three-dimensional bone structure around oral implants. Further research will be needed to evaluate its accuracy in a more quantitative way.

Animals↗

PubMed1999

In vivo forces on oral implants supporting a mandibular overdenture: the influence of attachment system.

This study was designed to gain insight into the influence of the attachment system on the loading conditions of oral implants supporting a mandibular overdenture on two implants. Five patients were selected and were provided with two implants in the canine area of the mandible (Brånemark System). All patients received a new mandibular overdenture that could be mounted on an ovoid-shaped bar (Dolder, C&M): (a) with and (b) without bilateral extensions and (c) on ball-attachments (Nobel Biocare). Using three strain gauges attached to the outer surface of the 5.5-mm standard abutments, the axial forces and bending moments on both supporting implants could be quantified. Load registrations were made during application of 50 N on seven predetermined positions along the occlusal surface of the prosthesis and during maximal biting in maximal occlusion (clenching). The results revealed no differences in induced axial force for the various anchorage devices, unlike the differences in bending moment. Although there is a tendency for better axial load sharing with bars and better sharing of bending moments with ball attachments, these differences were not significant.

Dental Implantation, Endosseous↗

PubMed1999

Bone behavior around sleeping and non-sleeping implants retaining a mandibular hinging overdenture.

Since 1984 2 implants in the symphyseal area have been used in our center to retain a hinging overdenture. Because this technique was unknown at that time 1 extra implant was installed in between the 2 others and was left submerged (sleeping). The extra implant served as a rescue implant in case 1 of the 2 others would fail. It was the aim of the present report to compare the marginal bone behavior around those sleeping and non-sleeping implants. Between 1984 and 1987 20 completely edentulous patients were provided with 3 implants (Brånemark system), where from 2 were used to retain a hinging overdenture. Ten years later half of the patients could still be traced. Retroalveolar radiographs were made at the abutment installation and after 10 years. None of the non-sleeping or sleeping implants lost, at an individual basis, more than 1.6 and 0.7 mm of marginal bone respectively. On average, non-sleeping implants lost at the right- and left-hand side of the mandible 0.33 and 0.57 mm of bone respectively. However, sleeping implants lost on average 0.16 mm only. Thus non-sleeping implants lose on average more bone when compared to sleeping implants. Surgical trauma at the abutment connection is believed to be the most plausible cause of marginal bone loss around non-sleeping implants.

Aged↗

PubMed1999

Predictability of reformatted computed tomography for pre-operative planning of endosseous implants.

OBJECTIVES: To determine the reliability of reformatted 2D-CT for pre-operative planning of implant placement. METHODS: One hundred consecutive partially or fully edentate patients underwent 2-D reformatted CT pre-operative planning and subsequent implant placement. The number, site and size of the implants, the available bone height and anatomical complications were recorded. The pre-operative planning and the outcome at surgery were compared statistically using a percentage agreement and Kendall's correlation coefficient. RESULTS: Agreement between the pre- and intra-operative data was good for the number of implants (60%) and the selected sites (70%). From a total of 416 implants planned, 21 implants could not be placed because of intra-operative findings. Agreement was relatively poor for implant size (44%) and anatomical complications (46%). Kendall's correlation coefficient was highest for the number of implants (0.80) and implant sites (0.81). It was much lower for implant sizes (0.51) and did not reach significance for anatomical complications (0.09). CONCLUSIONS: Reformatted 2D-CT is reliable for the pre-operative assessment of the number and sites of implants in the jaws. It is less predictable for the implant size needed and poor for anatomical complications.

Adolescent↗

PubMed1999

A 5-year prospective randomized clinical trial on the influence of splinted and unsplinted oral implants retaining a mandibular overdenture: prosthetic aspects and patient satisfaction.

Prosthetic outcome and patient satisfaction were evaluated in order to investigate whether there is a need or advantage to splint two implants in the mandible retaining a hinging overdenture. This study included 36 fully edentulous patients randomly divided into three groups according to the attachment system they received: magnets, ball attachments or straight bars (reference group). None of the implants failed during the whole observation period in any of the groups. After 5 years of observation, the Bar group presented the highest retention capacity and the least prosthetic complications but revealed more mucositis and gingival hyperplasia. Patient satisfaction rated similar for all groups although the Magnet group showed lower retention forces. All patients would repeat the same treatment even though the majority of the Magnet group would prefer a more retentive solution because of limited denture stability.

Adult↗

PubMed1999

Influence of inflammatory reactions vs. occlusal loading on peri-implant marginal bone level.

Plaque accumulation on abutments or implant surfaces induces an inflammatory reaction in the gingiva/alveolar mucosa just as around teeth. The longevity of oral implants can be jeopardized by either peri-implantitis and/or an occlusal overload. In the partially edentulous patient in whom pockets around teeth act as a reservoir for the colonization of the pockets around implants, the risk for inflammatory reactions of the peri-implant soft tissues seems especially more plausible than in the fully edentulous patient. This is especially true for implants with a very rough surface (e.g., plasma-sprayed), because of the positive relationship between surface roughness and supra- as well as subgingival plaque formation. Several medium-term (from 5 to 10 years) clinical studies support this hypothesis, through the observation of ongoing bone loss and subsequent decreasing success/survival percentages. Occlusal overload increases the risk for microfractures at the implant-bone interface in two-stage implants, which can result in significant marginal bone loss and even failure. There is ample evidence that occlusal factors are related to marginal angular defects around two-stage implants.

Alveolar Bone Loss↗

PubMed1998

Histomorphometrical and mechanical evaluation of titanium plasma-spray-coated implants placed in the cortical bone of goats.

The aim of this study was to investigate the biological and mechanical response of bone to titanium plasma-sprayed implants of different roughnesses. Three types of titanium plasma-spray coating were applied to beam-shaped implants: 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 a control. In total, 72 implants were inserted in the tibial cortical bone of nine adult female goats. These implants were evaluated histologically and mechanically 3 months after implantation. At the end of the experiment, of the 72 inserted implants, two implants (one Ti2 and one Ti4) were lost. Histological evaluation of the other retrieved implants revealed a uniform bone reaction for all implants. The unloaded plasma-spray coatings showed no signs of delamination at the implant-coating interface. Occasionally, particles of the Ti4 coating broke free and were found near the implant. Histomorphometry revealed no difference in bone contact for the different implants (P > 0.05). Furthermore, the push-out test showed no significant difference (P > 0.05). Linear regression showed no interaction between the push-out values and the roughness values (r = 0.5). On the basis of these results, it may be concluded that the used surface roughnesses did not lead to differences in bone response or mechanical attachment strength in goat cortical bone.

Animals↗

PubMed1998

Failure of oral implants: aetiology, symptoms and influencing factors.

The use of oral implants opened a wide range of prosthetic treatment possibilities in edentulous patients. Although the reported success rates of oral implants are high, failures do occur. This paper reviews the current knowledge about the aetiology, the signs and symptoms and the possible influencing factors of implant failure. Possible causes of implant failure are thought to be infection of the periimplant tissues, occlusal overload, or a combination of both. Nevertheless, pinpointing one of these as the aetiological factor in a particular case is difficult and should be handled reluctantly. Although the cause might seem obvious, influencing factors could play a role as well. Gaining insight into these processes might stimulate the adoption of preventive action and therefore increase the predictability of the treatment outcome with oral implants.

Dental Implants↗

PubMed1998

Rigidly splinted implants in the resorbed maxilla to retain a hinging overdenture: a series of clinical reports for up to 4 years.

STATEMENT OF PROBLEM: The results of the implant overdenture treatment in the maxilla remains inferior to those in the mandible. Different reasons have been alluded to, such as bone quality and quantity, number of implants, as well as the prosthesis design. PURPOSE: To investigate the latter, a new design for the rehabilitation of the resorbed maxillae was set up. MATERIAL AND METHODS: Thirteen patients were selected and provided with four endosseous maxillary implants, splinted with a rigid-cast bar. RESULTS: After a mean loading time of 3 years, six implants were lost; three at abutment and another three shortly after abutment connection, resulting in a cumulative success rate of 88.6% at year 4. A mean marginal bone loss of 0.3 mm was observed within the first year. After the first year, the marginal bone level, the attachment level, and the Periotest scores hardly changed. The main prosthetic complication was the frequent need to renew or to activate the attachments. A strong improvement in patient satisfaction was observed when compared with the old conventional denture. CONCLUSIONS: Within the limits of this study, the outcome confirmed that, on a medium-term base, implant-retained hinging overdentures on four implants were promising.

Adult↗