One-Piece Zirconia Oral Implants for Single Tooth Replacement: Five-Year Results from a Prospective Cohort Study.

The intention of this 5-year prospective cohort investigation was to clinically and radiographically investigate the outcomes of a one-piece zirconia implant system for single tooth replacement. Sixty-five patients received a total of 66 single-tooth implants. All implants immediately received temporary restorations and were finally restored with all-ceramic crowns. Follow-ups were performed at the prosthetic delivery, after 1, 3, and 5 years. Peri-implant and dental soft-tissue parameters were evaluated and patient-reported outcomes recorded. To monitor peri-implant bone remodelling, standardised radiographs were taken at the implant insertion and at the 1-, 3-, and 5-year follow-ups. In the course of 5 years, 14 implants were lost, resulting in a cumulative implant survival rate of 78.2%. The mean marginal bone loss from the implant insertion to the 5-year follow-up amounted to 1.12 mm. Probing depth, clinical attachment level, bleeding, and plaque index increased over time. In 91.5% of the implants, the papilla index showed levels of 1 or 2, respectively. At the end of the study, the patient satisfaction was higher compared to the pre-treatment measurements. Due to the low survival rate after five years and the noticeably high frequency of advanced bone loss observed in this study, the implant has not met the launch criteria, as it would have not been recommended for routine clinical use.

One-Piece Zirconia Oral Implants for the Support of Three-Unit Fixed Dental Prostheses: Three-Year Results from a Prospective Case Series.

The objective was to investigate the clinical and radiological outcome of one-piece zirconia oral implants to support three-unit fixed dental prostheses (FDP) after three years in function. Twenty-seven patients were treated with a total of 54 implants in a one-stage surgery and immediate provisionalization. Standardized radiographs were taken at implant placement, after one year and after three years, to evaluate peri-implant bone loss. Soft-tissue parameters were also assessed. Linear mixed regression models as well as Wilcoxon Signed Rank tests were used for analyzing differences between groups and time points (p < 0.05). At the three-year evaluation, one implant was lost, resulting in a cumulative survival rate of 98.1%. The mean marginal bone loss amounted to 2.16 mm. An implant success grade I of 52% (bone loss of ≤2 mm) and success grade II of 61% (bone loss of ≤3 mm) were achieved. None of the evaluated baseline parameters affected bone loss. The survival rate of the zirconia implants was comparable to market-available titanium implants. However, an increased marginal bone loss was observed with a high peri-implantitis incidence and a resulting low implant success rate.

One-piece zirconia oral implants for single-tooth replacement: Three-year results from a long-term prospective cohort study.

AIM: This 3-year report of a prospective long-term cohort investigation aimed to evaluate the clinical and radiographic outcomes of a one-piece zirconia oral implant for single-tooth replacement. MATERIALS AND METHODS: Sixty-five patients received a 1-stage implant surgery with immediate temporization. Standardized radiographs were taken at implant insertion, after 1 year, and after 3 years to monitor peri-implant bone levels. A univariate analysis of the association of different baseline parameters on marginal bone loss from implant insertion to 36 months was performed. Soft-tissue parameters were evaluated at prosthesis insertion, after 6 months, after 1 year, and at the 3-year follow-up. RESULTS: After 3 years, six posterior site implants were lost, giving a cumulative survival rate of 90.8%. The mean marginal bone loss was 1.45 mm; 35% of the implants lost at least 2 mm bone, and 22% more than 3 mm. The univariate analysis did not identify any parameter associated with marginal bone loss. Probing depth, clinical attachment level, and bleeding index increased over 3 years, and plaque index decreased. CONCLUSIONS: The low survival rate of the presented ceramic implant and especially the high frequency of advanced bone loss are noticeable but remain unexplained.

Bi-layered zirconia/fluor-apatite bridges supported by ceramic dental implants: a prospective case series after thirty months of observation.

OBJECTIVE: The aim of this study was to determine the success and survival rate of all-ceramic bi-layered implant-supported three-unit fixed dental prostheses (IS-FDPs) 3 years after implant placement. MATERIAL AND METHODS: Thirteen patients (seven males, six females; age: 41-78 years) received two one-piece ceramic implants (alumina-toughened zirconia) each in the region of the premolars or the first molar and were finally restored with adhesively cemented bi-layered zirconia-based IS-FDPs (3 in the maxilla, 10 in the mandible) composed of CAD/CAM-fabricated zirconia frameworks pressed-over with fluor-apatite glass-ceramic ingots. At prosthetic delivery and the follow-ups after 1, 2 and 3 years, the restorations were evaluated using modified United States Public Health Service (USPHS) criteria. Restorations with minor veneer chippings, a small-area occlusal roughness, slightly soundable restoration margins, minimal contour deficiencies and tolerable color deviations were regarded as success. In case of more distinct defects that could, however, be repaired to a clinically acceptable level, IS-FDPs were regarded as surviving. Kaplan-Meier plots were used for the success/survival analyses. To verify an impact on subjective patients' perceptions, satisfaction was evaluated by visual analog scales (VAS). RESULTS: All patients were seen 3 years after implant installation. No IS-FDP had to be replaced, resulting in 100% survival after a mean observation period of 29.5 months (median: 30.7). At the 3-year follow-up, 7/13 IS-FDPs showed a veneer chipping, 13/13 an occlusal roughness and 12/13 minimal deficiencies of contour/color. Since six restorations showed a major chipping and/or a major occlusal roughness, the Kaplan-Meier success rate was 53.8%. However, patients' significantly improved perceptions of function, esthetics, sense, and speech at prosthetic delivery remained stable over time. CONCLUSION: Bi-layered zirconia/fluor-apatite IS-FDPs entirely survived the observation period but showed a high frequency of technical complications. Nevertheless, the treatment highly satisfied patients' expectations.

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.

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.

One-piece zirconia oral implants: one-year results from a prospective case series. 2. Three-unit fixed dental prosthesis (FDP) reconstruction.

AIM: To evaluate the clinical and radiological outcome of one-piece zirconia oral implants for three-unit fixed dental prosthesis (FDP) replacement after 1 year. MATERIALS: Twenty eight patients were recruited for the investigation and signed an informed consent. All patients were treated with a one-stage implant surgery and a three-unit immediate temporary restoration on two one-piece zirconia implants. The implants were fabricated of yttria-stabilized tetragonal zirconia (y-TZP). The endosseous part of the implants was tapered with a porous surface. A total of 56 implants were inserted in the 28 patients. A total of 12 implants were placed in the upper jaws (six in the anterior area and six in the posterior area) and 44 in mandibles (all in the posterior area). At implant insertion and after 1 year, standardized radiographs were taken to evaluate the peri-implant bone loss. To evaluate any influences from different baseline parameters on the marginal bone loss a univariate analysis was performed. Clinical soft tissue parameters probing depth (PD), clinical attachment level (CAL), modified bleeding index (mBI) and modified plaque index (mPI) were recorded. Implant cumulative survival rates were calculated using actuarial life table analysis. Changes in the clinical variables were assessed using the Wilcoxon Signed Ranks test (PD, CAL) and the Sign test (mBl, mPl). All significance tests were conducted at a 5% level of significance. RESULTS: After 1 year, one implant was lost resulting in a survival rate of 98.2%. The patient was excluded from further analysis. The marginal bone loss after 1 year amounted to 1.95 mm. In 40% of the patients a bone loss of at least 2 mm and in 28% of the patients a loss of more than 3 mm were observed. The PD decreased for implant and tooth sites over time, the values being significantly higher for implants than for teeth. Over 1 year, the CAL increased slightly around the implants and decreased around the teeth. At the 1-year follow-up, the CAL at the implant sites was statistically significantly higher than at the reference teeth. The mBI was significantly lower at implants than at teeth. The same result was found for the plaque index. CONCLUSIONS: A high frequency of increased radiographic bone loss (>2 mm) after 1 year around the presented one-piece zirconia implant system was found. The bone loss seems to be higher compared to the very limited availability of zirconia implant data. Therefore, within the limits of the present investigation, it may be concluded that the presented zirconia implant system possibly performs inferior to conventional titanium implants and to other zirconia implants regarding peri-implant bone loss.

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.

Sinus augmentation with bovine hydroxyapatite/synthetic peptide in a sodium hyaluronate carrier (PepGen P-15 Putty): a clinical investigation of different healing times.

PURPOSE: Augmentation of the sinus floor with autogenous bone often requires an extra donor site, which is associated with a risk of morbidity, and current grafting protocols involve healing times of up to 9 months. In this prospective in vivo study, the time-dependent efficacy of PepGen P-15 Putty, a combination of bovine hydroxyapatite and synthetic peptide in a sodium hyaluronate carrier, was evaluated in sinus grafting. MATERIALS AND METHODS: Twenty-four edentulous patients received bilateral sinus augmentations with PepGen P-15 Putty, which mimics the cell-binding domain of type I collagen responsible for cell migration, differentiation, and proliferation. The patients were randomly divided into four groups of six patients each, corresponding to 2, 4, 6, and 9 months of healing postaugmentation. After these time intervals, bone biopsy specimens were retrieved through the alveolar bone crest into the augmented sinus, and subsequently oral implants were placed. The specimens were immersed in buffered formalin, scanned with a desktop microcomputed tomography machine, and processed for histologic and histomorphometric evaluation. A mixed model was used for statistical analysis. RESULTS: Three-dimensional microcomputed tomography depicted the distinct structure of trabecular bone encompassing remnants of PepGen, and histologic evaluation revealed osteoblasts and osteoid with osteocytes in the vicinity of the PepGen particles at all healing stages. Histomorphometric results indicated an increase in the newly formed bone fraction in the specimens as follows: 21.3% (± 2.33) at 2 months, 21.9% (± 8.9) at 4 months, 28.5% (± 6.9) at 6 months, and 29.8% (± 11.8) at 9 months. The differences were statistically insignificant. All implants placed in the augmented sites integrated and were restored prosthetically. CONCLUSIONS: PepGen can be used successfully for maxillary sinus augmentation. These data provide evidence that implant placement, even after only 2 months of healing, may be possible.

Interfacial shear strength of endosseous implants.

PURPOSE: Surface roughness is known to affect the load-bearing strength of implants. However, the underlying mechanisms are not completely understood. This study sought to investigate the potential effects of bone-to-implant contact (BIC) and mechanical interlocking on the stability of titanium implants using a newly established assessment system that combines nondestructive microcomputed tomography (ΜCT) and the biomechanical push-in test. MATERIALS AND METHODS: Cylindric implants with a machined or a dual acid-etched (DAE) surface were placed into the distal femurs of Sprague-Dawley rats. At weeks 2 and 4, the femur-implant specimens were harvested and scanned in a desktop ΜCT device, and the BIC was calculated. The implants were then loaded axially using a universal mechanical testing machine and the breakage force was recorded as a push-in value. Machined and DAE implants were also embedded in histology-quality resin to serve as a nonbiologic reference. Two-way analysis of variance and the Mann-Whitney U test were used for statistical analysis. RESULTS: BIC showed no surface- or time-dependent differences. The mean push-in value of DAE implants was four times greater at week 2 and three times greater at week 4 than that of machined implants. The shear strength at the interface (push-in value/BIC) was greater for DAE surfaces than for machined surfaces in a proportionate manner. When the implants were embedded in the resin with virtually 100% implant-resin contact, DAE implants showed 30% greater push-in values and shear strength than machined implants (P < .05). CONCLUSIONS: These findings suggest that the percentage of BIC and mechanical interlocking cannot fully explain the surface roughness-related increase in osseointegration, as opposed to the common understanding of osseointegration. Further studies must include more details to discover the precise understanding of the physiology of osseointegration and the potential biologic mechanisms involved.

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.

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.

The biologic stability of alumina-zirconia implant abutments after 1 year of clinical service: a digital subtraction radiographic evaluation.

The purpose of the present clinical study was to evaluate the biologic stability of alumina-zirconia implant abutments by histologic and radiographic examination. Nineteen partially edentulous patients were treated with 37 external-hexagon implants. After a healing period of 3 to 6 months, alumina-zirconia abutments were connected and restored with cemented single crowns or short-span fixed partial dentures. Periapical radiographs were taken at the time of prosthesis delivery and after 3, 6, and 12 months of follow-up. Crestal alveolar bone level changes were assessed by digital subtraction of consecutive images, and 1-way analysis of variance was used for statistical analysis. No implant, abutment, or restoration failed during the observation period. Bone level changes were statistically insignificant and histologic examination revealed no signs of inflammation. Stable and healthy soft and hard tissue conditions may be expected around alumina-zirconia abutments after 1 year of clinical service. However, long-term data are needed to confirm the present results.

Behavior of CAL72 osteoblast-like cells cultured on zirconia ceramics with different surface topographies.

OBJECTIVES: Because of its inherent strength, biocompatibility, and tooth-like color, zirconia ceramics have the potential to become an alternative to titanium as dental implant material. This study aimed at investigating the osteoblastic response to yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) with different surface topographies. METHODS: CAL72 osteoblast-like cells were cultured on machined (TZP-m), airborne particle abraded (TZP-s), and airborne particle abraded and acid-etched Y-TZP (TZP-sa) surfaces. Polystyrene and airborne particle abraded with large grit and acid-etched (SLA) titanium served as a reference control. The surface topography was examined by scanning electron microscopy (SEM) and profilometry. At culture days 3, 6, and 12, cell proliferation, at day 12 cell morphology, and cell-covered surface area were determined. RESULTS: The surface roughness of Y-TZP was increased by airborne particle abrasion and additionally by acid etching. No statistically significant differences were found between average roughness (R(a)) and maximum peak-to-valley height (R(p-v)) values of airborne particle abraded and acid-etched Y-TZP and SLA titanium. Whereas the cell proliferation assay revealed statistically significant greater values at day 3 for surface-treated Y-TZP and polystyrene cultures as compared with machined Y-TZP, no differences between the Y-TZP groups, SLA titanium, and polystyrene were observed at culture days 6 and 12. CONCLUSIONS: Cell morphology and cell-covered surface area were not affected by the type of substrate. The results suggest that roughened Y-TZP is an appropriate substrate for the proliferation and spreading of osteoblastic cells.

Three-dimensional bone-implant integration profiling using micro-computed tomography.

PURPOSE: The capability of micro-computed tomography (microCT) for quantitative analysis of peri-implant bone has not been previously addressed. This study aimed to establish and validate a method to use this technique for 3-dimensional bone-implant integration profiling. MATERIALS AND METHODS: Unthreaded cylindric implants with a dual acid-etched surface were placed into the right femurs of 7 Sprague-Dawley rats. Two weeks postimplantation, the femurs were harvested and measured with a desktop micro-tomographic scanner with an isotropic resolution of 8 microm. To validate the microCT outcome, ground histologic sections and corresponding CT slices were compared with respect to bone morphometry. RESULTS: Bone-implant integration profiles assessed by microCT revealed that the percentage of cancellous bone gradually increased with proximity to the implant surface, while the percentage of cortical bone was not affected by proximity to the implant. Using the optimized segmentation threshold, the bone configuration in the microCT images corresponded to that observed in the histologic sections. The correlation between microCT and histology was significant for cortical (r = 0.65; P < .05) and cancellous bone (r = 0.92; P < .05) at distances of 24 to 240 microm from the implant surface, but no significant correlation was found for the area from 0 to 24 microm from the surface. DISCUSSION AND CONCLUSION: The results support the usefulness of microCT assessment as a rapid, nondestructive method for 3-dimensional bone ratio measurements around implants, which may provide new perspectives for osseointegration research. Further study is necessary, however, to address the inherent metallic halation artifact, which potentially confounds peri-implant bone assessment.

Glycosaminoglycan degradation reduces mineralized tissue-titanium interfacial strength.

Although the localization of the proteoglycan/glycosaminoglycan (GAG) complex at the bone-titanium implant interface has been implied, the role of proteoglycans on the establishment of bone-titanium integration is unknown. The hypothesis to be tested was that proteoglycans play an important role in establishing bone-titanium interfacial adhesion. The objective of this study is to investigate the effect of proteoglycan knockdown by GAG enzymatic degradation on the interfacial strength between mineralized tissue and titanium having different surface topographies. Rat bone marrow-derived osteoblastic cells were cultured on either a machined titanium disk or an acid-etched titanium disk. At day 21 of culture, one of the three following GAG degradation enzymes was added into the culture; chondroitinase AC, chondroitinase B, or keratanase. After 3 days of incubation (at day 24 of culture), the laser spallation technique was applied to the samples in order to assess the tissue-titanium interfacial strength. In this technique, a laser-generated stress wave is used to separate the tissue-titanium interface, and the interfacial strength is determined interferometrically by recording the transient free surface velocity of the tissue. Mineralized tissue cultured on the acid-etched titanium showed 20-30% higher tissue interfacial strength than that cultured on the machined titanium (p < 0.0001). For both the machined and acid-etched surface cultures, administration of the enzyme reduced the interfacial strength by 25-30% compared with the untreated control cultures (p < 0.0001). There were no differences in the effect among the three different enzymes tested. A nanoindentation study revealed that the enzyme treatment did not affect the elastic modulus of the mineralized tissue. Scanning electron microscopic and energy dispersive spectroscopic analyses revealed less post-spallation tissue remnant on the titanium substrates when treated with the enzymes. The tissue remnant was greater in amount on the acid-etched surface than on the machined surface. The results suggest that there exists not only mechanical interlocking but also biological interfacial adhesion between the mineralized tissue and titanium, in which the proteoglycan/GAG complex is involved.

Osteoblasts generate harder, stiffer, and more delamination-resistant mineralized tissue on titanium than on polystyrene, associated with distinct tissue micro- and ultrastructure.

UNLABELLED: This study revealed that osteoblasts generate harder, stiffer, and more delamination-resistant mineralized tissue on titanium than on the tissue culture polystyrene, associated with modulated gene expression, uniform mineralization, well-crystallized interfacial calcium-phosphate layer, and intensive collagen deposition. Knowledge of this titanium-induced alteration of osteogenic potential leading to enhanced intrinsic biomechanical properties of mineralized tissue provides novel opportunities and implications for understanding and improving bone-titanium integration and engineering physiomechanically tolerant bone. INTRODUCTION: Bone-titanium integration is a biological phenomenon characterized by continuous generation and preservation of peri-implant bone and serves as endosseous anchors against endogenous and exogenous loading, of which mechanisms are poorly understood. This study determines the intrinsic biomechanical properties and interfacial strength of cultured mineralized tissue on titanium and characterizes the tissue structure as possible contributing factors in biomechanical modulation. MATERIALS AND METHODS: Rat bone marrow-derived osteoblastic cells were cultured either on a tissue culture-grade polystyrene dish or titanium-coated polystyrene dish having comparable surface topography. Nano-indentation and nano-scratch tests were undertaken on mineralized tissues cultured for 28 days to evaluate its hardness, elastic modulus, and critical load (force required to delaminate tissue). Gene expression was analyzed using RT-PCR. The tissue structural properties were examined by scanning electron microscopy (SEM), collagen colorimetry and localization with Sirius red stain, mineral quantification, and localization with von Kossa stain and transmission electron microscopy (TEM). RESULTS: Hardness and elastic modulus of mineralized tissue on titanium were three and two times greater, respectively, than those on the polystyrene. Three times greater force was required to delaminate the tissue on titanium than that on the polystyrene. SEM of the polystyrene culture displayed a porous structure consisting of fibrous and globular components, whereas the titanium tissue culture appeared to be uniformly solid. Cell proliferation was remarkably reduced on titanium. Microscopic observations revealed that the mineralized tissue on titanium was composed of uniform collagen-supported mineralization from the titanium interface to the outer surface, with intensive collagen deposition at tissue-titanium interface. In contrast, tissue on the polystyrene was characterized by collagen-deficient mineralization at the polystyrene interface and calcium-free collagenous matrix formation in the outer tissue area. Such characteristic microstructure of titanium-associated tissue was corresponded with upregulated gene expression of collagen I and III, osteopontin, and osteocalcin mRNA. Cross-sectional TEM revealed the apposition of a high-contrast and well-crystallized calcium phosphate layer at the titanium interface but not at the polystyrene interface. CONCLUSIONS: Culturing osteoblasts on titanium, compared with polystyrene, enhances the hardness, elastic modulus, and interfacial strength of mineralized tissue to a higher degree. Titanium per se possesses an ability to alter cellular phenotypes and tissue micro- and ultrastructure that result in enhanced intrinsic biomechanical properties of mineralized tissue.

Enhanced mineralized tissue adhesion to titanium over polystyrene assessed by the nano-scratch test.

The critical load determined by the scratch test is regarded to be a representative measure of coating adhesion in the field of engineering. This study aimed to evaluate the method for its usefulness for assessing the mineralized tissue-titanium interface strength. Osteoblastic cells derived from rat bone marrow were cultured on polystyrene, titanium-coated polystyrene, and titanium disks with either a machined or dual-acid etched surface. Nano-scratch testing was performed on mineralized tissue specimens at culture day 28. The scratch path was monitored by light microscopy until complete delamination of mineralized tissue from the substrate occurred, and the required force was recorded as the critical load. Energy-dispersive spectroscopic analysis was used to verify the delamination. The mean critical load values (+/- standard deviations) were as follows: polystyrene 31 mN (+/-1), titanium-coated polystyrene 67 mN (+/-4), machined titanium 76 mN (+/-4), DAE titanium 107 mN (+/-3), with statistical differences (P < 0.05; ANOVA). No elemental calcium and phosphorous were observed in the delaminated areas. The nano-scratch test applied to cultured mineralized tissue differentiated the critical load from various culture conditions: polystyrene vs. titanium; titanium with different surface topographies. Culturing mineralized tissue on titanium, especially on roughened surfaces, increased the tissue critical load. The nano-scratch test may be useful to evaluate mineralized tissue adhesion properties in titanium cultures.

Fracture strength after dynamic loading of endodontically treated teeth restored with different post-and-core systems.

STATEMENT OF PROBLEM: Prefabricated metal and ceramic posts can be used with direct or indirect cores as an alternative to the conventional cast post and core. It is unclear how the fracture strength of zirconia posts with composite or ceramic cores and titanium posts with composite cores compares to the fracture strength of gold posts and cores after dynamic loading. PURPOSE: This study compared the fracture strength of endodontically treated, crowned maxillary incisors with limited ferrule length and different post-and-core systems after fatigue loading. MATERIAL AND METHODS: Sixty-four caries-free, human maxillary central incisors were divided into 4 groups. After root canal treatment, Group 1 was restored with titanium posts and composite cores, Group 2 with zirconia posts and composite cores, and Group 3 with zirconia posts and heat-pressed ceramic cores. Teeth restored with cast-on gold posts and cores served as the controls (Group 4). Teeth were prepared with a circumferential shoulder including a 1 to 2 mm ferrule; all posts were cemented with an adhesive resin cement, restored with complete-coverage crowns, and exposed to 1.2 million load cycles (30 N) in a computer-controlled chewing simulator. Simultaneous thermocycling between 5 degrees C and 55 degrees C was applied for 60 seconds with an intermediate pause of 12 seconds. All specimens that did not fracture during dynamic loading were loaded until fracture in a universal testing machine at a crosshead speed of 1.5 mm/min; loads were applied at an angle of 130 degrees at the incisal edge. Fracture loads (N) and modes (repairable or catastrophic) were recorded. The Kruskal-Wallis test was used to compare fracture loads among the 4 test groups. Analyses were conducted both with and without the specimens that failed during the chewing simulation. A Fisher exact test was performed to detect group differences in fracture modes. A significance level of P<.05 was used for all comparisons. RESULTS: The following survival rates were recorded after the chewing simulation: 93.8% (Group 1), 93.8% (Group 2), 100% (Group 3), and 87.5% (Group 4). The median fracture strengths for Groups 1 to 4 were 450 N, 503 N, 521 N, and 408 N, respectively. No significant differences were detected among the groups. The use of zirconia posts resulted in a nonsignificant lower number of catastrophic root fractures. CONCLUSION: Within the limitations of this study, the results suggest that zirconia posts with ceramic cores can be recommended as an alternative to cast posts and cores. If a chairside procedure is preferred, zirconia or titanium posts with composite cores can be used. Clinical trials are required to verify these in vitro results.