Clinical Oral Implants Research

Aim: To analyse possible effects of titanium surface topography on bone integration.

Materials and methods: Our analyses were centred on a PubMed search that identified 1184 publications of assumed relevance; of those, 1064 had to be disregarded because they did not accurately present in vivo data on bone response to surface topography. The remaining 120 papers were read and analysed, after removal of an additional 20 papers that mainly dealt with CaP‐coated and Zr implants; 100 papers remained and formed the basis for this paper. The bone response to differently configurated surfaces was mainly evaluated by histomorphometry (bone‐to‐implant contact), removal torque and pushout/pullout tests.

Results and discussion: A huge number of the experimental investigations have demonstrated that the bone response was influenced by the implant surface topography; smooth (S_a<0.5 μm) and minimally rough (S_a 0.5–1 μm) surfaces showed less strong bone responses than rougher surfaces. Moderately rough (S_a>1–2 μm) surfaces showed stronger bone responses than rough (S_a>2 μm) in some studies. One limitation was that it was difficult to compare many studies because of the varying quality of surface evaluations; a surface termed ‘rough’ in one study was not uncommonly referred to as ‘smooth’ in another; many investigators falsely assumed that surface preparation per se identified the roughness of the implant; and many other studies used only qualitative techniques such as SEM. Furthermore, filtering techniques differed or only height parameters (S_a, R_a) were reported.

Conclusions: • Surface topography influences bone response at the micrometre level.

• Some indications exist that surface topography influences bone response at the nanometre level.

• The majority of published papers present an inadequate surface characterization.

• Measurement and evaluation techniques need to be standardized.

• Not only height descriptive parameters but also spatial and hybrid ones should be used.

In the present multi‐center study. non‐submerged ITI implants were prospectively followed to evaluate their long‐term prognosis in fully and partially edentulous patients. In a total of 1003 patients, 2359 implants were consecutively inserted. Following a healing period of 3–6 months, the successfully integrated implants were restored with 393 removable and 758 fixed restorations. Subsequently, all consecutive implants were documented annually up to 8 years. At each examination, the clinical status of all implants was evaluated according to predefined criteria of success. Therefore, the data base allowed the evaluation of 8‐year cumulative survival and success rates for 2359 implants. In addition, cumulative success rates were calculated for implant subgroups divided per implant type, implant length. and implant location. Furthermore, the actual 5‐year survival and success rates could be determined for 488 implants. During the healing period, 13 implants did not successfully integrate, whereas 2346 implants fulfilled the predefined criteria of success. This corresponds with an early failure rate of 0.55%. During follow‐up, 19 implants were classified as failures due to several reasons. In addition, 17 implants (= 0.8%) demonstrated at the last annual examination a suppurative periimplant infection. Including 127 drop out implants (= 5.4% drop out rate) into the calculation, the 8‐year cumulative survival and success rates resulted in 96.7% and 93.3%, respectively. The analysis of implant subgroups showed slightly more favorable cumulative success rates for screw type implants (> 95%) compared to hollow‐cylinder implants (91.3%). and clearly better success rates for mandibular implants (= 95%) when compared to maxillary implants (= 87%). The actual 5‐year survival and success rates of 488 implants with 98.2% and 97.3%. respectively, were slightly better than the estimated 5‐year cumulative survival and success rates of 2359 implants indicating that the applied life table analysis is a reliable statistical method to evaluate the long‐term prognosis of dental implants. It can be concluded that non‐submerged ITI implants maintain success rates well above 90% in different clinical centers for observation periods up to 8 years.

Background: From an ecological viewpoint, the oral cavity, in fact the oro‐pharynx, is an ‘open growth system’. It undergoes an uninterrupted introduction and removal of both microorganisms and nutrients. In order to survive within the oro‐pharyngeal area, bacteria need to adhere either to the soft or hard tissues in order to resist shear forces. The fast turn‐over of the oral lining epithelia (shedding 3 ×/day) is an efficient defence mechanism as it prevents the accumulation of large masses of microorganisms. Teeth, dentures, or endosseous implants, however, providing non‐shedding surfaces, allow the formation of thick biofilms. In general, the established biofilm maintains an equilibrium with the host. An uncontrolled accumulation and/or metabolism of bacteria on the hard surfaces forms, however, the primary cause of dental caries, gingivitis, periodontitis, peri‐implantitis, and stomatitis.

Objectives: This systematic review aimed to evaluate critically the impact of surface characteristics (free energy, roughness, chemistry) on the de novo biofilm formation, especially in the supragingival and to a lesser extent in the subgingival areas.

Methods: An electronic Medline search (from 1966 until July 2005) was conducted applying the following search items: ‘biofilm formation and dental/oral implants/surface characteristics’, ‘surface characteristics and implants’, ‘biofilm formation and oral’, ‘plaque/biofilm and roughness’, ‘plaque/biofilm and surface free energy’, and ‘plaque formation and implants’. Only clinical studies within the oro‐pharyngeal area were included.

Results: From a series of split‐mouth studies, it could be concluded that both an increase in surface roughness above the R_a threshold of 0.2 μm and/or of the surface‐free energy facilitates biofilm formation on restorative materials. When both surface characteristics interact with each other, surface roughness was found to be predominant. The biofilm formation is also influenced by the type (chemical composition) of biomaterial or the type of coating. Direct comparisons in biofilm formation on different transmucosal implant surfaces are scars.

Conclusions: Extrapolation of data from studies on different restorative materials seems to indicate that transmucosal implant surfaces with a higher surface roughness/surface free energy facilitate biofilm formation.

It has been postulated that the wound healing in a closed submerged location is one of the prerequisites for osseointegration of dental implants. The purpose of the present study was to evaluate the tissue integration of intentionally non‐submerged titanium implants inserted by a one‐stage surgical procedure. 100 ITI implants were consecutively placed in 70 partially edentulous patients. After a healing period free of masticatory loading for at least 3 months, the implants were examined. The clinical status showed for all implants neither detectable mobility nor signs of a peri‐implant infection. Therefore, prosthetic abutments were inserted, and the patients were restored with fixed partial dentures. All patients were regularly recalled at 3‐month intervals, and no patient dropped out of the study. Thus, all 100 implants were re‐evaluated 12 months following implantation. Plaque‐ and sulcus bleeding indices, probing depth, clinical attachment level, width of keratinized mucosa, and periotest scores were assessed. In addition, standardized radiographs were analyzed for the presence of peri‐implant radiolucencies and for the location of alveolar bone levels around the implants. Based on predefined criteria, the implants were classified as successful or failing. 98 implants were considered successful, and 1 implant failing. The remaining implant exhibited a peri‐implant infection requiring local and systemic antimicrobial treatment. The results of this short‐term study indicate that intentionally non‐submerged ITI implants yield a high predictability for successful tissue integration.

Abstract: Occlusal forces affect an oral implant and the surrounding bone. According to bone physiology theories, bones carrying mechanical loads adapt their strength to the load applied on it by bone modeling/remodeling. This also applies to bone surrounding an oral implant. The response to an increased mechanical stress below a certain threshold will be a strengthening of the bone by increasing the bone density or apposition of bone. On the other hand, fatigue micro‐damage resulting in bone resorption may be the result of mechanical stress beyond this threshold. In the present paper literature dealing with the relationship between forces on oral implants and the surrounding bone is reviewed. Randomized controlled as well as prospective cohorts studies were not found. Although the results are conflicting, animal experimental studies have shown that occlusal load might result in marginal bone loss around oral implants or complete loss of osseointegration. In clinical studies an association between the loading conditions and marginal bone loss around oral implants or complete loss of osseointegration has been stated, but a causative relationship has not been shown.

Bacterial adhesion to intra‐oral, hard surfaces is firmly influenced by the surface roughness of these structures. Previous studies showed a remarkable higher subgingival bacterial load on rough surfaces when compared to smooth sites. More recently, the additional effect of a further smoothening of intra‐oral hard surfaces on clinical and microbiological parameters was examined in a short‐term experiment. The results indicated that a reduction in surface roughness below R_a=0.2 μm, the so‐called “threshold R_a”, had no further effect on the quantitative/qualitative microbiological adhesion or colonisation, neither supra‐ nor subgingivally. This study aims to examine the long‐term effects of smoothening immoral hard transgingival surfaces. In 6 patients expecting an overdenture in the lower jaw, supported by endosseus titanium implants, 2 different abutments (transmucosal part of the implant): a standard machined titanium (R_a=0.2 μm) and one highly polished and made of a ceramic material (R_a=0.06 μm) were randomly installed. After 3 months of intra‐oral exposure, supra‐ and subgingival plaque samples from both abutments were compared with each other by means of differential phase‐contrast microscopy (DPCM). Clinical periodontal parameters (probing depth, gingival recession, bleeding upon probing and Periotest‐value) were recorded around each abutment. After 12 months. the supra‐ and subgingival samples were additionally cultured in aerobic, CO,‐enriched and anaerobic conditions. The same clinical parameters as at the 3‐month interval were recorded after 12 months. At 3 months, spirochetes and motile organisms were only detected subgingivally around the titanium abutments. After 12 months, however, both abutment‐types harboured equal proportions of spirochetes and motile organisms, both supra‐ and sub‐gingivally. The microbial culturing (month 12) failed to detect large interabutment differences. The differences in number of colony forming units (aerobic and anaerobic) were within one division of a logarithmic scale. The aerobic culture data showed a higher proportion of Gram‐negative organisms in the subgingival flora of the rougher abutments. From the group of potentially “pathogenic” bacteria, only Prevotellu inter‐media and Fusobacterium nucleatum were detected after anaerobic culturing and again the inter‐abutment differences were negligible. Clinically, the smoothest abutment showed a slightly higher increase in probing depth between months 3 and 12, and more bleeding on probing. The present results confirm the findings of our previous short‐term study, indicating that a further reduction of the surface roughness, below a certain “threshold R_a”(0.2 μm), has no major impact on the supra‐ and subgingival microbial composition.

Abstract: Gingival esthetics around natural teeth is based upon a constant vertical dimension of healthy periodontal soft tissues, the Biologic Width. When placing endosseous implants, however, several factors influence periimplant soft and crestal hard tissue reactions, which are not well understood as of today. Therefore, the purpose of this study was to histometrically examine periimplant soft tissue dimensions dependent on varying locations of a rough/smooth implant border in one‐piece implants or a microgap (interface) in two‐piece implants in relation to the crest of the bone, with two‐piece implants being placed according to either a submerged or a nonsubmerged technique. Thus, 59 implants were placed in edentulous mandibular areas of five foxhounds in a side‐by‐side comparison. At the time of sacrifice, six months after implant placement, the Biologic Width dimension for one‐piece implants, with the rough/smooth border located at the bone crest level, was significantly smaller (P<0.05) compared to two‐piece implants with a microgap (interface) located at or below the crest of the bone. In addition, for one‐piece implants, the tip of the gingival margin (GM) was located significantly more coronally (P<0.005) compared to two‐piece implants. These findings, as evaluated by nondecalcified histology under unloaded conditions in the canine mandible, suggest that the gingival margin (GM) is located more coronally and Biologic Width (BW) dimensions are more similar to natural teeth around one‐piece nonsubmerged implants compared to either two‐piece nonsubmerged or two‐piece submerged implants.

Abstract Objectives: The aim of this study was to assess the biological rationale for the use of platelet‐rich plasma (PRP) by evaluating the effect of different concentrations of PRP on osteoblasts (OB) and fibroblasts (FB) function in vitro.

Material and methods: PRP was obtained from volunteer donors using standard protocols. Primary human cultures of oral FBs and OBs were exposed to both activated and non‐activated plasma as well as various concentrations of PRP (2.5 ×, 3.5 × and max (4.2–5.5 ×)). Cell proliferation was evaluated after 24 and 72 h using an MTT proliferation assay. Production of osteocalcin (OCN), osteoprotegerin (OPG) and transforming growth factor β1 (TGF‐β1) was evaluated in OB after 24 and 72 h. Statistical analysis was performed using one‐way ANOVA.

Results: PRP‐stimulated cell proliferation in both OBs and FBs. The effect of different PRP concentrations on cell proliferation was most notable at 72 h. The maximum effect was achieved with a concentration of 2.5 ×, with higher concentrations resulting in a reduction of cell proliferation. Upregulation of OCN levels and downregulation of OPG levels were noted with increasing PRP concentrations at both 24 and 72 h. TGF‐β1 levels were stimulated by increasing concentrations of PRP, with the increased levels being maintained at 72 h.

Conclusions: PRP preparations exert a dose‐specific effect on oral FBs and OBs. Optimal results were observed at a platelet concentration of 2.5 ×, which was approximately half of the maximal concentrate that could be obtained. Increased concentrations resulted in a reduction in proliferation and a suboptimal effect on OB function. Hence, different PRP concentrations may have an impact on the results that can be obtained in vivo.

Abstract: Although it is generally accepted that adverse forces can impair osseointegration, the mechanism of this complication is unknown. In this study, static and dynamic loads were applied on 10 mm long implants (Brånemark System^®, Nobel Biocare, Sweden) installed bicortically in rabbit tibiae to investigate the bone response. Each of 10 adult New Zealand black rabbits had one statically loaded implant (with a transverse force of 29.4 N applied on a distance of 1.5 mm from the top of the implant, resulting in a bending moment of 4.4 Ncm), one dynamically loaded implant (with a transverse force of 14.7 N applied on a distance of 50 mm from the top of the implant, resulting in a bending moment of 73.5 Ncm, 2.520 cycles in total, applied with a frequency of 1 Hz), and one unloaded control implant. The loading was performed during 14 days. A numerical model was used as a guideline for the applied dynamic load. Histomorphometrical quantifications of the bone to metal contact area and bone density lateral to the implant were performed on undecalcified and toluidine blue stained sections. The histological picture was similar for statically loaded and control implants. Dense cortical lamellar bone was present around the marginal and apical part of the latter implants with no signs of bone loss. Crater‐shaped bone defects and Howship’s lacunae were explicit signs of bone resorption in the marginal bone area around the dynamically loaded implants. Despite those bone defects, bone islands were present in contact with the implant surface in this marginal area. This resulted in no significantly lower bone‐to‐implant contact around the dynamically loaded implants in comparison with the statically loaded and the control implants. However, when comparing the amount of bone in the immediate surroundings of the marginal part of the implants, significantly (P<0.007) less bone volume (density) was present around the dynamically loaded in comparison with the statically loaded and the control implants. This study shows that excessive dynamic loads cause crater‐like bone defects lateral to osseointegrated implants.

Roughened implant surfaces are thought to enhance osseointegration. Torque removal forces have been used as a biomechanical measure of anchorage or osseointegration in which the greater forces required to remove implants may be interpreted as an increase in the strength of osseointegration. The purpose of this study was to compare the torque resistance to removal of screw shaped titanium implants having an acid etched (HCl/H₂SO₄) surface (Osseotite®) with implants having a machined surface. Two custom screw shaped implants, 1 acid etched and the other machined, were placed into the distal femurs of 10 adult New Zealand White rabbits. These implants were 3.25 mm in diameter x 4.00 mm in length without holes, grooves or slots to resist rotation. Following a 2 month healing period, the implants were removed under reverse torque rotation with a digital torque measuring device. Two implants with the machined surface preparation failed to achieve osseointegration. All other implants were found to be anchored to bone. Resistance to torque removal was found to be 4 x greater for the implants with the acid etched surface as compared to the implants with the machined surface. The mean torque values were 20.50 ± 6.59 N cm and 4.95 ± 1.61 N cm for the acid etched and machined surfaces respectively. The results of this study suggest that chemical etching of the titanium implant surface significantly increases the strength of osseointegration as determined by resistance to reverse torque rotation.