Frank Butz

Ceramic abutments and ceramic oral implants. An update

Dental implants are considered an essential treatment modality. Published data have demonstrated high success rates for implants placed in partially edentulous arches for the replacement of both single teeth (42, 66, 88) and multiple teeth (87, 117, 121, 163, 200). However, the use of implants to replace missing teeth in the aesthetic zone is challenging (64, 127, 211). The restorations are subjected, especially in patients with a gummy smile or a high lip line, to direct visual comparison with the adjacent natural teeth (81, 118). Perfect three-dimensional implant positioning and well-designed superstructures are therefore essential to mimic the appearance of a natural tooth and to achieve an optimal aesthetic outcome (118, 197, 209). Dental implants and abutments are usually fabricated out of commercially pure titanium, primarily because of its well-documented biocompatibility and mechanical properties (2). However, despite numerous modifications to the fabrication and design of metal abutments, there is still the disadvantage of metallic components showing through when such abutments are used (81, 83, 85, 126). The resultant dull grayish background may give the soft tissue an unnatural bluish appearance (64, 118, 209). The presence of a gray gingival discoloration may be attributed to a thin gingival biotype that is incapable of blocking reflective light from the metallic abutment surface (64, 209). Gingival biotype switching has been suggested when using a metal abutment to increase the thickness of the gingiva; this thicker gingiva will block the reflective light from the abutment s surface from showing through and thus improve the aesthetic outcome (91, 104, 105, 192). Biotype switching, however, requires an additional surgical procedure, which is unpleasant for most patients (105). Recent years have shown a consistent trend toward aesthetic improvements in implant restorative materials and in treatment outcome. To achieve optimal mucogingival aesthetics, ceramic abutments were developed (Figs 1 and 2).

Biomechanical and histological behavior of zirconia implants: an experiment in the rat

OBJECTIVE This study aimed at evaluating the integration of zirconia implants in a rat femur model. MATERIAL AND METHODS Zirconia implants with two distinct surface topographies were compared with titanium implants with similar topographies. Titanium and zirconia implants were placed into the femurs of 42 male Sprague-Dawley rats. Four groups of implants were utilized: machined zirconia implants, zirconia implants with a rough surface, machined titanium implants, and titanium implants with an electrochemically roughened surface. After a healing period of 28 days, the load-bearing capacity between the bone and the implant surface was evaluated by a push-in test. Additionally, after a healing period of 14 and 28 days, respectively, bone tissue specimens containing the implants were processed and histologically analyzed. RESULTS The mean mineralized bone-to-implant contact showed the highest values after 14 and 28 days for the rough surfaces (titanium: 36%/45%; zirconia: 45%/59%). Also, the push-in test showed higher values for the textured implant surfaces, with no statistical significance between titanium (34 N) and zirconia (45.8 N). CONCLUSIONS Within the limits of the animal investigation presented, it was concluded that all tested zirconia and titanium implant surfaces were biocompatible and osseoconductive. The presented surface modification of zirconia implants showed no difference regarding the histological and biomechanical results compared with an established electrochemically modified titanium implant surface.

One‐piece zirconia oral implants: one‐year results from a prospective cohort study. 1. Single tooth replacement

AIM To investigate the clinical and radiographic outcome of a one-piece zirconia oral implant for single tooth replacement after 1 year. MATERIALS AND METHODS A total of 65 patients received a one-stage implant surgery with immediate temporization. Standardized radiographs were taken at implant insertion and after 1 year to monitor peri-implant bone loss. A univariate analysis of the influence of different baseline parameters on marginal bone loss from implant insertion to 12 months was performed. Soft tissue parameters were evaluated at prosthesis insertion and at the 1-year follow-up. RESULTS After 1 year, three implants were lost, giving a cumulative survival rate of 95.4%. The marginal bone loss after 1 year was 1.31 mm. Thirty-four per cent of the implants lost at least 2 mm bone, and 14% more than 3 mm. The univariate analysis could not depict any parameter influencing marginal bone loss. Probing depth, Clinical Attachment Level, Bleeding and Plaque Index decreased over 1 year. CONCLUSIONS The cumulative survival rate of the presented ceramic implant was comparable to the reported survival rate of titanium implants when immediately restored. However, the frequency of increased radiographic bone loss (>2 mm) after 1 year was considerably higher as compared to conventional two-piece titanium implants. The presented zirconia implant can therefore not be recommended for clinical usage.

Osteoblast and bone tissue response to surface modified zirconia and titanium implant materials

OBJECTIVE This study examined the in vitro and in vivo response of osteoblasts to a novel, acid-etched and sandblasted zirconia surface. METHODS Osteoblastic hFOB 1.19 cells were cultured either on electrochemically anodized titanium (TiUnite(®)), machined titanium (Ti-m), sandblasted and acid-etched zirconia (TZP-proc), and machined zirconia (TZP-A-m). The surface topography of the various substrates was analyzed by 3D laserscan measurements and scanning electron microscopy. At culture days 1, 3, 7, 14, 21, and 28, cell proliferation was determined. Gene expression was analyzed using RT-PCR. Histologic analysis and biomechanical testing was performed on miniature implants placed in the rat femur. RESULTS During the first 7 days, a retarded cell proliferation was observed on the TiUnite(®) surface. After 28 days of cultivation, cell proliferation reached similar levels on all surfaces. An up-regulation of bone and extracellular matrix specific genes could be seen for TZP-proc at day 21. The mean bone-implant contact rate after a healing period of 14 and 28 days, respectively, was higher for TiUnite(®) than for TZP-proc. At 28 day, the biomechanical test showed significantly higher values for TiUnite(®) than for all other surfaces. SIGNIFICANCE The novel, rough zirconia surface was accepted by hFOB 1.19 cells and integrates into rat bone tissue. However, osseointegration seemed to proceed more slowly and to a lesser extent compared to a moderately roughened titanium surface.

In vitro reaction of human osteoblasts on alumina-toughened zirconia.

OBJECTIVES Alumina toughening enhances the mechanical properties of zirconia ceramics but the biocompatibility of this material has rarely been addressed. In this study, we examined the osteoblast response to alumina-toughened zirconia (ATZ) with different surface topographies. MATERIAL AND METHODS Human osteoblasts isolated from maxillary biopsies of four patients were cultured and seeded onto disks of the following substrates: ATZ with a machined surface, airborne-particle abraded ATZ, airborne-particle abraded and acid etched ATZ. Airborne-particle abraded and acid etched titanium (SLA) and polystyrene disks served as a reference control. The surface topography of the various substrates was characterized by profilometry (R(a), R(p-v)) and scanning electron microscopy (SEM). Cell proliferation, cell-covered surface area, alkaline phophatase (ALP) and osteocalcin production were determined. The cell morphology was analyzed on SEM images. RESULTS The surface roughness of ATZ was increased by airborne-particle abrasion, but with the R(a) and R(p-v) values showing significantly lower values compared with SLA titanium (Mann-Whitney U-test P<0.05). The proliferation assay revealed no statistically significant differences between the ATZ substrates, SLA titanium and polystyrene (Kruskal-Wallis test, P>0.05). All substrates were densely covered by osteoblasts. ALP and osteocalcin production was similar on the examined surfaces. Cell morphology analysis revealed flat-spread osteoblasts with cellular extensions on all substrates. CONCLUSIONS These results indicate that ATZ may be a viable substrate for the growth and differentiation of human osteoblasts. Surface modification of ATZ by airborne-particle abrasion alone or in combination with acid etching seems not to interfere with the growth and differentiation of the osteoblasts.

Evaluation of alumina toughened zirconia implants with a sintered, moderately rough surface: An experiment in the rat

OBJECTIVE Alumina toughened zirconia (ATZ) is more fracture resistant than unmodified zirconia and has been shown to be a viable substrate for the growth of osteoblasts. In this study, we examined the histological and biomechanical behavior of moderately roughened ATZ implants in rat femoral bone. METHODS Miniature implants made of ATZ with pore-building polymers sintered onto the surface and electrochemically anodized titanium (TiUnite®) were placed into the femurs of Sprague-Dawley rats. Implant surface topography was analyzed by 3D laserscan measurements and scanning electron microscopy (SEM). After a healing period of 14 and 28 days, respectively, histologic and biomechanical testing was performed. RESULTS Under the SEM, the TiUnite® surface could be clearly distinguished from the ATZ surface, but 3D laserscan measurements indicated a moderately rough surface topography for both, TiUnite® (Sa=1.31μm) and ATZ (Sa=1.51μm). The mean mineralized bone-to-implant contact showed the highest values after 14 and 28 days for TiUnite® (58%/75%) as compared to ATZ (24%/41%). The push-in values after a healing period of 14 and 28 days, respectively, increased from 20N to 39N for TiUnite® and from 10N to 25N for ATZ. SIGNIFICANCE Our findings suggest that the moderately roughened ATZ implant surface is well accepted by rat bone tissue. However, compared to titanium, the osseointegration-process of ATZ seems to proceed more slowly in that early phase of implant integration.