Journal of Dental Rehabilitation and Applied Science
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v.27
no.1
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pp.51-61
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2011
Recently, restoring implants in the esthetically demanding region, zirconia-based materials are widely used due to their superior mechanical properties, accuracies, and esthetics. The purpose of this study was to investigate the load transfer and mechanical stability of zirconia and titanium implant abutments by using the three-dimensional finite element analysis model. The internal conical joint type and external butt joint type implant system was selected as an experimental model. Finite element models of bone/implant/prosthesis complex were constructed. An load of 250N was applied vertically beside 3mm of implant axis. Stress distribution of zirconia and titanium implant abutment is similar. The maximum equivalent stress of titanium implant abutment is lower than zirconia implant abutment about 15%. Howevere considering a high mechanical strength that exceed those of titanium implant abutment, zirconia implant abutment had similar mechanical stability of titanium implant abutment clinically.
Purpose: The purpose of this study was to evaluate the stability of abutment screws used with the zirconia fixture-based implant system and compare them with those used with the existing titanium fixture system via the finite element method. Methods: A single implant-supported restoration was designed for the finite element analysis. A universal analysis program was used to set 8 occlusal points along the direction to the long axis of the implant, and an occlusal load of 700 N was applied. Results: In all models (Zir and Ti-fixture model), the screw threads presented with the highest von Mises stress (VMS) values, whereas the head and end presented with the lowest VMS values. The VMS of the screw used in the zirconia-fixture model was 5.97% lower than that used in the titanium-fixture model (261.258 vs. 276.911 MPa, respectively) despite statistical significance. Furthermore, the zirconia fixture (352.912 MPa) had a higher stress value (8.42%) than the titanium fixture (332.331 MPa). In a completely tightened titanium fixture implant system, the stress was concentrated in the implant-abutment connection interface, the zirconia fixture presented with a stable stress distribution. Conclusion: Although the zirconia fixture demonstrated a high VMS value, owing to the stiffness and elasticity coefficients of the material, the stress generated in the abutment screws was similar in all models. In conclusion, the zirconia fixture-based implant system presented with a more stable stress distribution in the abutment screws than the titanium fixture-based implant system.
The purpose of this study was to observe bone apposition and marginal bone loss and to check the possibility of success on titanium implant, HA coated implant and the implant with natural coral that were place immediately after teeth extraction in dogs. Experimental subjects were divided into 4 groups ; the 1st group is the titanium implant, second the HA coated implant, third the implant with natural coral, and the last the control group that was prepared in the extraction sockets. After 12 weeks, the dogs were sacrificed for visual observation and microscopic examination approaching histologic and histomorphometric analysis. The results were as follows : 1. Neither the infection nor the exposure of implant was found at the sites of all implant. 2. In a histomorphometric analysis, mean percentage of direct bone contact with the titanium implant was 80.7% and the HA coated implant showed 81.5% apposition, but the implant with natural coral showed 64.9% apposition(P<0.05). 3. In a microscopic examination, mature lamellated bone was found around the immediate implants and control group, while unabsorbed natural coral around the immediate implants with natural coral was found. 4. All immediate implant groups showed the loss of marginal bone in order from implant with natural coral, titanium implant, and HA coated implant. 5. Implant with natural coral that was placed by the type I interface of the Barzilay's classification immediately after teeth extraction showed low percentage of direct bone contact area, low success rate and a lot of marginal bone loss. Above results suggested that the immediate implants are osseointegrated successfully, although slightly marginal bone was loss.
The present study was performed to evaluate the effect of citric acid on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface, titanium plasma-sprayed surface, and sand-blasted, large grit, acid etched surface were utilized. Implant surface was rubbed with pH 1 citric acid for $\frac{1}{2}$ min., 1 min., 1 $\frac{1}{2}$ min., 2 min., and 3min, respeaively in the test group and implant surface was not treated in the control group. Then, the specimens were processed for scanning electron microscopic observation. The following results were obtained. 1. Both test and control group showed a few shallow grooves and ridges in pure titanium machined surface implants. There were not significant differences between two groups. 2. In titanium plasma-sprayed surfaces, round or amorphous particles were deposited irregularly. The irregularity of titanium plasma-sprayed surfaces conditioned with pH 1 citric acid was lessened and the cracks were increased relative to the application time of pH 1 citric acid. 3. Sand-blasted, large grit, acid etched surfaces showed the macro/micro double roughness. The application of pH 1 citric acid didn't change the characteristics of the sand-blasted, large grit, acid etched surfaces. In conclusion, the application of pH 1 citric acid to titanium plasma-sprayed surface is improper. And pure titanium machined surface implants and sand-blasted, large grit, acid etched surface implants can he treated with pH 1 citric acid for peri-implantitis treatment if the detoxification of these surfaces could be evaluated.
PURPOSE. The success of an implant-prosthetic rehabilitation is influenced by good implant health and an excellent implant-prosthetic coupling. The stability of implant-prosthetic connection is influenced by the rotational tolerance between anti-rotational features on the implant and those on the prosthetic component. The aim of this study is to investigate the rotational tolerance of a conical connection implant system and its titanium abutment counterpart, in various conditions. MATERIAL AND METHODS. 10 preparable titanium abutments, having zero-degree angulation (MegaGen, Daegu, Korea) with an internal 5-degree conical connection, and 10 implants (MegaGen, Daegu, Korea) were used. Rotational tolerance between the connection of implant and titanium abutments was measured through the use of a tridimensional optics measuring system (Quick Scope QS250Z, Mitutoyo, Kawasaki, Japan) in the as-received condition (Time 0), after securing with a titanium screw tightening at 35 Ncm (Time 1), after tightening 4 times at 35 Ncm (Time 2), after tightening one more time at 45 Ncm (Time 3), and after tightening another 4 times at 45 Ncm (Time 4). RESULTS. The group "Time 0" had the lowest values of rotational freedom (0.22 ± 0.76 degrees), followed by the group Time 1 (0.46 ± 0.83 degrees), the group Time 2 (1.01 ± 0.20 degrees), the group Time 3 (1.30 ± 0.85 degrees), and the group Time 4 (1.49 ± 0.17 degrees). CONCLUSION. The rotational tolerance of a conical connection is low in the "as received" condition but increases with repetitive tightening and with application of a torque greater than 35 Ncm.
Weigl, Paul;Trimpou, Georgia;Grizas, Eleftherios;Hess, Pablo;Nentwig, Georg-Hubertus;Lauer, Hans-Christoph;Lorenz, Jonas
The Journal of Advanced Prosthodontics
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v.11
no.1
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pp.48-54
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2019
PURPOSE. The aim of the present randomized controlled study was to compare prefabricated all-ceramic, anatomically shaped healing abutments followed by all-ceramic abutments and all-ceramic crowns and prefabricated standard-shaped (round-diameter) titanium healing abutments followed by final titanium abutments restored with porcelain-fused-to-metal (PFM) implant crowns in the premolar and molar regions. MATERIALS AND METHODS. Forty-two patients received single implants restored either by all-ceramic restorations (test group, healing abutment, final abutment, and crown all made of zirconia) or conventional titanium-based restorations. Immediately after prosthetic incorporation and after 12 months of loading, implant survival, technical complications, bone loss, sulcus fluid flow rate (SFFR) as well as plaque index (PI) and implant stability (Periotest) were analyzed clinically and radiologically. RESULTS. After 12 months of loading, an implant and prosthetic survival rate of 100% was observed. Minor prosthetic complications such as chipping of ceramic veneering occurred in both groups. No statistical significant differences were observed between both groups with only a minimum of bone loss, SFFR, and PI. CONCLUSION. All-ceramic implant prostheses including a prefabricated anatomically shaped healing abutment achieved comparable results to titanium-based restorations in the posterior region. However, observational results indicate a benefit as shaping the peri-implant soft-tissue with successive provisional devices and subsequent compression of the soft tissue can be avoided.
The surface characteristics of titanium have been shown to have an important role in contact ossseointegration around the implant. Anodizing at high voltage produces microporous structure and increases thickness of surface titanium dioxide layer. The aim of present study was to analyse the response of rat calvarial osteoblast cell to commercially pure titanium and Ti-6A1-4V anodized in 0.06 mol/l ${\beta}$-glycerophosphate and 0.03 mol/l sodium acetate. In this study, rat calvarial osteoblasts were used to assay for cell viability and cell proliferation on the implant surface at 1,2,4,7 days. 1. Surface roughness was 1.256${\mu}m$ at 200V, and 1.745${\mu}m$ at 300V. 2. The thickness of titanium oxide layer was increased 1 ${\mu}m$ with the increase of 50V. 3. The proliferation rate of osteoblastic cells was increased with the increase of the surface roughness and the thickness of titanium oxide layer. 4. There was no difference in cell viability and cell proliferation between commercially pure titanium and Ti-6A1-4V anodized at the same condition. In conclusion, the titanium surface modified by anodizing was biocompatible, produced enhanced osteoblastic response. The reasons of enhanced osteoblast response might be due to reduced metal ion release by thickened and stabilized titanium dioxide layer and microporous rough structures.
Statement of problem. There have been previous studies about instability according to screw material by means of calculating preload in tightening screw or recording of the torque necessary to loosen screw after tightening screw. Purpose. The purpose of this study was to evaluate screw joint stability through the analysis of fitness at the mating thread surfaces between implant and screw after tightening screws made of different materials. Material and methods. In this study, screws were respectively used to secure a cemented abutment to a hexlock implant fixture; teflon coated titanium alloy screw and titanium alloy screw(Steri-Oss), gold-plated gold-palladium alloy screw and titanium alloy screw(Implant Innovation), gold screw and titanium screw(AVANA Dental Implant System). Each abutment screw was secured to the implant with recommended torque value using a digital torque controller. Each screw was again tightened after 10minutes. All samples were cross sectioned with sandpaper and polished. Then samples were evaluated with an scanning electron microscope analysis. Results. In titanium alloy screw, irregular contact and relatively large gap was present at mating thread surface. Also in teflon-coated titanium screw, incomplete seating and only partially contact was present at the mating thread surface. In gold-plated gold-palladium alloy screw, relatively close and tight contact without the presence of large gap was present by existing of gold coating at the mating thread surfaces. In gold alloy screw, relatively small gap between the mating components was seen. Conclusions. This result suggested that gold plated gold-palladium alloy screw and gold alloy screw achieved a greater degree of contact at the mating thread surfaces compared to titanium alloy screw and teflon-coated titanium alloy screw.
Purpose: With the significance of stable adhesion of alveolar bone and peri-implant soft tissue on the surface of titanium for successful dental implantation procedure, the purpose of this study was to apply microgrooves on the titanium surface and investigate their effects on peri-implant cells and tissues. Methods: Three types of commercially pure titanium discs were prepared; machined-surface discs (A), sandblasted, large-grit, acid-etched (SLA)-treated discs (B), SLA and microgroove-formed discs (C). After surface topography of the discs was examined by confocal laser scanning electron microscopy, water contact angle and surface energy were measured. Human gingival fibroblasts (hGFs) and murine osteoblastic cells (MC3T3-E1) were seeded onto the titanium discs for immunofluorescence assay of adhesion proteins. Commercially pure titanium implants with microgrooves on the coronal microthreads design were inserted into the edentulous mandible of beagle dogs. After 2 weeks and 6 weeks of implant insertion, the animal subjects were euthanized to confirm peri-implant tissue healing pattern in histologic specimens. Results: Group C presented the lowest water contact angle ($62.89{\pm}5.66{\theta}$), highest surface energy ($45{\pm}1.2mN/m$), and highest surface roughness ($Ra=22.351{\pm}2.766{\mu}m$). The expression of adhesion molecules of hGFs and MC3T30E1 cells was prominent in group C. Titanium implants with microgrooves on the coronal portion showed firm adhesion to peri-implant soft tissue. Conclusions: Microgrooves on the titanium surface promoted the adhesion of gingival fibroblasts and osteoblastic cells, as well as favorable peri-implant soft tissue sealing.
Journal of Dental Rehabilitation and Applied Science
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v.27
no.2
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pp.185-195
/
2011
In this study, titanium abutments and zirconia abutments were connected to each implant in external type implants. After that they were loaded 10000 times with 20Kg as occlusal force. The surface changes of external hexgon part and platform were observed in FESEM image. Viker's hardness of an implant, a titanium abutment and a zirconia abutment were measured respectively. 1. Viker's hardness of an implants, a titanium abutment and a zirconia abutment was $309.80{\pm}11.78$ HV, $318.40{\pm}11.82$ HV, and $1495.30{\pm}16.21$ HV respectively. There was no statistical significance between an implant and a titanium abutment (P>0.05, Anova). However, there was statistical significance between an implant and a zirconia abutment(P<0.05, Anova). 2. The wear was observed at the joint of implant and abutment in both a titanium abutment group and a zirconia abutment group after loading 10,000 times. The zirconia abutment showed more remarkable wear than the titanium one. In conclusion, the wear of external hexagon and platform was much more notable in a zirconia abutment group than a titanium one. It was suggested that it could result from the difference of surface hardness between titanium and zirconia. The wear of junction between an implant and a zirconia abutment becomes more severe, the connection of an implant and an abutment is much more unfit. This is likely to cause loosening and fracture of the abutment screw. so it is considered that the possibility of implant supra-structure failure can be increased.
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