Backscatter from therapeutic doses of ionizing irradiation does not impair cell migration on titanium implants in vitro.

OBJECTIVE: The influence of radiation backscatter from titanium on DNA damage and migration capacity of human osteoblasts (OBs) and mesenchymal stem cells (MSCs) may be critical for the osseointegration of dental implants placed prior to radiotherapy. In order to evaluate effects of radiation backscatter, the immediate DNA damage and migration capacity of OBs and MSCs cultured on titanium or plastic were compared after exposure to ionizing irradiation. MATERIALS AND METHODS: Human OBs and MSCs were seeded on machined titanium, moderately rough fluoride-modified titanium, or tissue culture polystyrene, and irradiated with nominal doses of 2, 6, 10, or 14 Gy. Comet assay was performed immediately after irradiation, while a scratch wound healing assay was initiated 24 h post-irradiation. Fluorescent live cell imaging documented the migration. RESULTS: DNA damage increased with higher dose and with backscatter from titanium, and MSCs were significantly more affected than OBs. All doses of radiation accelerated the cell migration on plastic, while only the highest dose of 10 Gy inhibited the migration of both cell types on titanium. CONCLUSIONS: High doses (10 Gy) of radiation inhibited the migration capacity of both cell types on titanium, whereas lower doses (2 and 6 Gy) did not affect the migration of either OBs or MSCs. CLINICAL RELEVANCE: Fractionated doses of 2 Gy/day, as distributed in conventional radiotherapy, appear not to cause severe DNA damage or disturb the migration of OBs or MSCs during osseointegration of dental implants.

Comparison of postoperative intraoral scan versus cone beam computerised tomography to measure accuracy of guided implant placement-A prospective clinical study.

OBJECTIVE: To evaluate the accuracy of implant placement with a digitally planned guided implant procedure. Two methods for identifying the actual postoperative positioning of the implants were compared: CBCT and IO scanning. MATERIAL AND METHODS: Twenty-eight implants with a sandblasted and acid-etched surface were placed in thirteen patients using tooth-supported surgical guides following a digital planning procedure. The implants were submerged for 12-15 weeks. New CBCT images were taken for identification of the implant position. After second stage surgery, scan bodies were mounted on the implants and scanned with an IO digital scanner. The recordings from the CBCT images and the IO scans were compared with respect to the identified positions of the implants. RESULTS: The study did not resolve any significant differences of the identified positioning of the implants as measured by CBCT or IO, except for the apical deviations at the coronal and apical points. The angular difference between CBCT and IO scanning at the coronal point was -0.011 (±0.6) degrees, whereas the 3D deviation was 0.03(±0.17) mm. The distal deviation between CBCT and IO scanning was 0.01(± 0.16) mm, and the vestibular deviation 0.033(± 0.16) mm and the apical deviation difference was 0.09(± 0.16) mm. The 3D deviation at the apical point was 0.04(± 0.22) mm. The distal deviation between CBCT and IO scanning was 0.06(± 0.19) mm, and the vestibular deviation 0.032(± 0.23) mm and the apical deviation difference was 0.09(± 0. 16) mm. CONCLUSION: The study demonstrated that accuracy measurements using IO scanning yields comparable results to those obtained by CBCT.

TiO2 scaffolds in peri-implant dehiscence defects: an experimental pilot study.

OBJECTIVES: The primary objective was to assess osseointegration of implants with dehiscence defects grafted with a TiO2 scaffold. The secondary objective was to assess the performance of the scaffold in terms of mechanical stability and bone fill. MATERIAL AND METHODS: Five minipigs had the mandibular premolars extracted. After healing, two dental implants (SLActive® , Institut Straumann AG, Basel, Switzerland) with associated semi-cylindrical dehiscence defects (Ø = 6 mm, height = 10 mm) were installed in each quadrant. The defects were grafted with test scaffolds (n = 10) or control autologous bone blocks (n = 10). After 3 months submerged healing, the pigs were euthanized and the sites analysed by microcomputed tomography and histology. RESULTS: Four minipigs were available for second stage surgery; (n = 9) experimental and (n = 7) control sites. The mean bone-to-implant contact on the defect side was 82% (±10%) and 79% (±11%) in the test and control groups respectively. The mean level of first bone-to-implant contact was more coronal on the defect side in the test group 3.2 mm (±0.4 mm) than in the control group 3.6 mm (±1.1 mm). The defect area occupied by bone within the extent of the scaffold varied, but averaged 37% (±14.6%) whereas the material itself occupied 7.4% (±3.5%). CONCLUSIONS: Within the limitations of the study, the results suggest that the novel synthetic scaffold material perform similar to the autologous bone block control with respect to implant osseointegration. The mechanical properties of the scaffold appeared sufficient to withstand clinical load in the present experimental model.

The influence of surface nanoroughness, texture and chemistry of TiZr implant abutment on oral biofilm accumulation.

OBJECTIVES: The aim of the study was to examine surface nanoroughness, texture and chemistry of dental implant abutment and to investigate how these parameters influence oral biofilm formation in healthy subjects. MATERIALS AND METHODS: Eight different nanorough TiZr surfaces were produced by polishing, machining, cathodic polarization and acid etching. Surface topography was examined using field emission scanning electron microscope and a blue light laser profilometer. Surface chemistry was analyzed by secondary ion mass spectrometry and X-ray photoelectron spectroscopy. Surface hydrophilicity was tested by measuring contact angle on the surfaces. A human in vivo study using a splint model was employed to evaluate oral biofilm accumulation on these surfaces. RESULTS: Different surface textures (flat, grooved and irregular) were created with nanoroughness from 29 to 214 nm. Some test surfaces were incorporated with hydrogen by cathodic polarization and/or acid etching with HCl/H(2)SO(4). Nanoroughness (S(a)) positively correlated with microbial adhesion. Biofilm accumulation was less pronounced on flat and grooved than on irregular surfaces. No significant association between hydrogen content or hydrophilicity of the surface and biofilm accumulation was observed. CONCLUSIONS: Nanoroughness (< 214 nm) and surface texture influence oral biofilm accumulation independent of surface chemistry and hydrophilicity. Surface hydrogen, which has previously been shown to promote fibroblast growth, does not affect biofilm formation.

The effect of hydrofluoric acid treatment of titanium and titanium dioxide surface on primary human osteoblasts.

OBJECTIVE: The aim of the study was to investigate solely the effect of fluoride on the surface chemistry of polycrystalline ceramic titanium dioxide (TiO2 ) and metallic titanium (Ti) and its effect on proliferation and differentiation of primary human osteoblasts (NHO). MATERIALS AND METHODS: The NHO cells were exposed to fluoride-modified and unmodified samples for 1, 3, 7, 14 and 21 days. The fluoride effect on the mRNA expression was quantified and measured. The secretion of cytokines and interleukins in the cell culture medium was measured by Luminex, gene expression by RT-PCR, and compared with untreated controls. The effect on cell growth after 1 and 3 days in culture was measured using [(3) H]-thymidine incorporation. Fluoride release was measured using an ion-selective electrode. The surfaces were examined by X-ray photoelectron spectroscopy and profilometry. RESULTS: The fluoride release study detected that fluoride content easily washed off in TiO2 coins when compared with Ti coins. No increase in cell proliferation was found among fluoride-modified TiO2 surfaces compared with controls, except for washed Ti coins with fluoride modification. The cell differentiation with regard to gene expression showed no significant differences in both fluoride-modified and unmodified samples and less effect on protein release for all groups. CONCLUSIONS: The fluoride from hydrofluoric acid treatment on Ti and TiO2 surfaces gave no specific effect on primary human osteoblast cells. The study indicates that the released fluoride is not the unique factor for the bioactivity of Ti and TiO2 surfaces.

The dose-dependent impact of γ-radiation reinforced with backscatter from titanium on primary human osteoblasts.

In head and neck cancer patients receiving dental implants prior to radiotherapy, backscatter from titanium increases the radiation dose close to the surface, and may affect the osseointegration. The dose-dependent effects of ionizing radiation on human osteoblasts (hOBs) were investigated. The hOBs were seeded on machined titanium, moderately rough fluoride-modified titanium, and tissue culture polystyrene, and cultured in growth- or osteoblastic differentiation medium (DM). The hOBs were exposed to ionizing γ-irradiation in single doses of 2, 6 or 10 Gy. Twenty-one days post-irradiation, cell nuclei and collagen production were quantified. Cytotoxicity and indicators of differentiation were measured and compared to unirradiated controls. Radiation with backscatter from titanium significantly reduced the number of hOBs but increased the alkaline phosphatase activity in both types of medium when adjusted to the relative cell number on day 21. Irradiated hOBs on the TiF-surface produced similar amounts of collagen as unirradiated controls when cultured in DM. The majority of osteogenic biomarkers significantly increased on day 21 when the hOBs had been exposed to 10 Gy, while the opposite or no effect was observed after lower doses. High doses reinforced with backscatter from titanium resulted in smaller but seemingly more differentiated subpopulations of osteoblasts.

A Comparative Investigation of Chemical Decontamination Methods for In-Situ Cleaning of Dental Implant Surfaces.

Surface chemistry evaluation is crucial in assessing the efficacy of chemical decontamination products for titanium implants. This study aimed to investigate the effectiveness of chemical decontamination solutions in cleaning a contaminated dental implant surface and to evaluate the potential of combining Pluronic gel with hydrogen peroxide (NuBone®Clean) by evaluating pellicle disruption and re-formation on implant surfaces. In addition, ensuring safety with in vitro and human testing protocols. X-ray Photoelectron Spectroscopy (XPS) was utilised for surface analysis. All the tested gels had some effect on the surface cleanness except for PrefGel®. Among the tested chemical decontamination candidates, NuBone®Clean demonstrated effectiveness in providing a cleaner titanium surface. Furthermore, none of the tested chemical agents exhibited cytotoxic effects, and the safety assessment showed no adverse events. The results of this study highlight the significance of conducting comprehensive evaluations, encompassing safety and efficacy, before introducing new chemical agents for dental treatments. The findings suggest that NuBone®Clean shows potential as a chemical decontamination solution for implant surfaces. However, further investigation through randomised clinical trials is necessary. By adhering to rigorous testing protocols, the development of safe and efficient chemical decontamination strategies can be advanced, benefiting patients and promoting progress in implant dentistry.

Immunohistochemical comparison of lateral bone augmentation using a synthetic TiO2 block or a xenogeneic graft in chronic alveolar defects.

OBJECTIVES: To evaluate osteogenic markers and alveolar ridge profile changes in guided bone regeneration (GBR) of chronic noncontained bone defects using a nonresorbable TiO2 block. MATERIALS AND METHODS: Three buccal bone defects were created in each hemimandible of eight beagle dogs and allowed to heal for 8 weeks before GBR. Treatment was assigned by block randomization: TiO2 block: TiO2 -scaffold and a collagen membrane, DBBM particulates: Deproteinized bovine bone mineral (DBBM) and a collagen membrane, Empty control: Only collagen membrane. Bone regeneration was assessed on two different healing timepoints: early (4 weeks) and late healing (12 weeks) using several immunohistochemistry markers including alpha-smooth muscle actin (α-SMA), osteopontin, osteocalcin, tartrate-resistant acid phosphatase, and collagen type I. Histomorphometry was performed on Movat Pentachrome-stained and Von Kossa/Van Gieson-stained sections. Stereolithographic (STL) models were used to compare alveolar profile changes. RESULTS: The percentage of α-SMA and osteopontin increased in TiO2 group after 12 weeks of healing at the bone-scaffold interface, while collagen type I increased in the empty control group. In the defect area, α-SMA decreased in the empty control group, while collagen type I increased in the DBBM group. All groups maintained alveolar profile from 4 to 12 weeks, but TiO2 group demonstrated the widest soft tissue contour profile. CONCLUSIONS: The present findings suggested contact osteogenesis when GBR is performed with a TiO2 block or DBBM particulates. The increase in osteopontin indicated a potential for bone formation beyond 12 weeks. The alveolar profile data indicated a sustained lateral increase in lateral bone augmentation using a TiO2 block and a collagen membrane, as compared with DBBM and a collagen membrane or a collagen membrane alone.

Identification of early response genes to roughness and fluoride modification of titanium implants in human osteoblasts.

PURPOSE: Tissue response after implantation determines the success of the healing process. This response is not only dependent on the chemical properties of the implant surface but also by the surface topography or its roughness. Although in vitro and in vivo studies show improved results with rough- and fluoride-modified implants, the mechanisms behind these findings are still unknown. METHODS AND MATERIALS: Here, we have used a two-step procedure to identify novel genes related to the early response of primary human osteoblasts to roughness and fluoride-modified titanium implants. RESULTS: Two hundred seventeen genes responding to roughness were identified by microarray analysis and 198 genes responding to fluoride, 33 genes were common. Those identified genes related to bone and mineralization were further investigated by real-time reverse-transcriptase polymerase chain reaction. After 1 day of culture, toll-like receptor 3, ankylosis-progressive homolog, decorin, osteocalcin, and runt-related transcription factor-2 were classified as responsive genes to roughness; Distal-less homeobox-2 and Tuftelin-1 as responsive genes to fluoride treatment. Responsive genes to both treatments were collagen type I, parathyroid hormone-like hormone, hairy and enhancer of split-1, follistatin, ectonucleotide pyrophosphatase/phosphodiesterase-1, and thyroid hormone receptor-alpha. CONCLUSION: Our strategy was useful for identifying novel genes that might be involved in the early response of osteoblasts to rough and fluoride-modified titanium implants.

Impact of simultaneous placement of implant and block bone graft substitute: an in vivo peri-implant defect model.

BACKGROUND: Insufficient bone volume around an implant is a common obstacle when dental implant treatment is considered. Limited vertical or horizontal bone dimensions may lead to exposed implant threads following placement or a gap between the bone and implant. This is often addressed by bone augmentation procedures prior to or at the time of implant placement. This study evaluated bone healing when a synthetic TiO2 block scaffold was placed in circumferential peri-implant defects with buccal fenestrations. METHODS: The mandibular premolars were extracted and the alveolar bone left to heal for 4 weeks prior to implant placement in six minipigs. Two cylindrical defects were created in each hemi-mandible and were subsequent to implant placement allocated to treatment with either TiO2 scaffold or sham in a split mouth design. After 12 weeks of healing time, the samples were harvested. Microcomputed tomography (MicroCT) was used to investigate defect fill and integrity of the block scaffold. Distances from implant to bone in vertical and horizontal directions, percentage of bone to implant contact and defect fill were analysed by histology. RESULTS: MicroCT analysis demonstrated no differences between the groups for defect fill. Three of twelve scaffolds were partly fractured. At the buccal sites, histomorphometric analysis demonstrated higher bone fraction, higher percentage bone to implant contact and shorter distance from implant top to bone 0.5 mm lateral to implant surface in sham group as compared to the TiO2 group. CONCLUSIONS: This study demonstrated less bone formation with the use of TiO2 scaffold block in combination with implant placement in cylindrical defects with buccal bone fenestrations, as compared to sham sites.

Rosuvastatin promotes osteoblast differentiation and regulates SLCO1A1 transporter gene expression in MC3T3-E1 cells.

Rosuvastatin (RSV) is a synthetic statin with favourable pharmacologic properties including minimal metabolism, hepatic selectivity and enhanced inhibition of HMG-CoA reductase. An induction of osteoblast differentiation has been reported in vitro with lipophilic statins but not with RSV, which, like pravastatin, is relatively hydrophilic compared with other statins. To mediate its action, an active transport mechanism via solute carrier (SLC) transporters from the SLC16, SLC21/SLCO and SLC22 gene family - specifically Slc16a1, Slco1a1, Slco2b1 and Slc22a8 - may be present to allow effective entry in osteoblastic cells. In this study, we demonstrate that RSV induced osteoblast differentiation, as measured by increased BMP-2 gene expression and secretion, and ALP activity in MC3T3-E1 osteoblast cells, without significantly affecting cell proliferation within the concentration range of 0.001-10 µM. Low concentrations of RSV (0.001-0.01 µM) were protective against cell death whereas higher concentrations (10-100 µM) showed cytotoxicity. Moreover, MC3T3-E1 osteoblasts expressed high levels of Slco1a1 and Slc16a1 mRNA and low levels of Slco2b1 and Slc22a8 mRNA, when compared with kidney and liver tissues from mice. Slco1a1 gene expression increased 12-fold during osteoblast differentiation and was further regulated after RSV treatment. In conclusion, as for other statins, RSV promotes osteoblast differentiation, and also, demonstrated for the first time, regulates the expression of Slco1a1, which may constitute the transport system for RSV across the cell membrane in mature osteoblasts.

Porous titanium granules promote bone healing and growth in rabbit tibia peri-implant osseous defects.

OBJECTIVES: The aim of this study was to investigate the osteoconductive properties and biological performance of porous titanium granules used in osseous defects adjacent to titanium implants. MATERIAL AND METHODS: In this animal experimental study, calibrated defects were prepared in the tibias of 24 New Zealand rabbits. The defects were randomized into two tests and one control group. The test defects were grafted with either metallic or oxidized porous titanium granules (PTG or WPTG, respectively), whereas control defects were left empty (sham). The defects were closed with a submerged coin shaped titanium implant. Defects were left for healing for 4 weeks. After healing, the implants were removed and the new bone tissue formed onto the implant surface was analyzed for run x 2, osteocalcin, collagen-I, tartrate-resistant acid phosphatase, H(+)-ATPase, tumor necrosis factor-alpha, interleukin (IL)-6 and IL-10 gene expression using reverse transcriptase polymerase chain reaction. Wound fluid from the healed defects was analyzed for lactate dehydrogenase and alkaline phosphatase activity. Finally osteoconductivity was analyzed by micro-computed tomography and histology. RESULTS: Significantly more new bone formed in PTG and WPTG grafted defects compared with sham. The new bone grew both through the porosities of the granules and onto the implant surfaces. The WPTG group showed significantly less expression of key inflammation markers, but with no significant difference in a marker for necrosis. The WPTG also showed a significant increase in collagen-I mRNA expression compared with PTG. CONCLUSION: The results suggest that PTG and WPTG are both osteoconductive materials that can be used to promote bone formation in osseous defects adjacent to titanium implants without hampering implant osseointegration.

Ultra-porous titanium oxide scaffold with high compressive strength.

Highly porous and well interconnected titanium dioxide (TiO(2)) scaffolds with compressive strength above 2.5 MPa were fabricated without compromising the desired pore architectural characteristics, such as high porosity, appropriate pore size, surface-to-volume ratio, and interconnectivity. Processing parameters and pore architectural characteristics were investigated in order to identify the key processing steps and morphological properties that contributed to the enhanced strength of the scaffolds. Cleaning of the TiO(2) raw powder removed phosphates but introduced sodium into the powder, which was suggested to decrease the slurry stability. Strong correlation was found between compressive strength and both replication times and solid content in the ceramic slurry. Increase in the solid content resulted in more favourable sponge loading, which was achieved due to the more suitable rheological properties of the ceramic slurry. Repeated replication process induced only negligible changes in the pore architectural parameters indicating a reduced flaw size in the scaffold struts. The fabricated TiO(2) scaffolds show great promise as load-bearing bone scaffolds for applications where moderate mechanical support is required.

Hydrofluoric acid treatment of titanium surfaces enhances the proliferation of human gingival fibroblasts.

The attachment of implants relies on bone and soft tissue biocompatibility. The aim of this article is to investigate the effect of fluoride-modified metallic titanium (Ti) surfaces (Ti-F) on proliferation and differentiation of human gingival fibroblasts. Human gingival fibroblast cells were exposed to hydrofluoric acid-modified Ti coins (Ti-F) for 1, 3, 7, 14 and 21 days, and untreated coins were used as controls. A five- to six-fold increase in the proliferation of human gingival fibroblasts on Ti-F compared to Ti surfaces was observed. Enhanced gene expression of interleukin-6 and osteoprotegerin was found at 7 days. Increased levels of sclerostin, interleukin-6 and osteoprotegerin in the media from human gingival fibroblasts cultured on Ti-F coins were found compared to controls. Our results confirm that hydrofluoric acid-modified surface may indirectly enhance the firm attachment of implant surface to junction epithelium, soft tissue epithelium, which would give protection for underlying osseous structures making osseointegration of the dental implant possible.

In Vivo Accuracy of Implant Placement Using a Full Digital Planning Modality and Stereolithographic Guides.

PURPOSE: The aim of this study was to investigate a guided implant surgery procedure performed without any manual processes, by assessing the in vivo results following a digital planning and placement of dental implants using surgical templates. MATERIALS AND METHODS: Eligible patients were screened and enrolled in this prospective clinical study. A cone beam computed tomography (CBCT) scan was acquired, and the remaining dentition and soft tissues were recorded by an intraoral scanner after enrollment. The CBCT data and intraoral scan were fused in the planning software. The prosthetic reconstructions were digitally designed by a prosthodontist, and the ideal position of the dental implants was determined. The surgical template was digitally designed based on this plan, and a guide design was exported and manufactured in a stereolithographic process. The entire surgical procedure was performed with the aid of the template. An intraoral scan was performed 10 days after stage-two surgery using scan bodies placed on the implants. Digital preoperative and postoperative models were compared, and the metric difference between the planned and achieved implant positions was calculated. RESULTS: Twenty-seven implants were placed in 20 patients using tooth-supported surgical templates after a digital planning procedure. No implants were lost during the study period. The mean lateral deviation measured at the coronal point was 1.05 mm (SD: 0.59; range: 2.74 to 0.36). The mean lateral deviation measured at the apical point was 1.63 mm (SD: 1.05; range: 5.16 to 0.56). The mean depth displacement was + 0.48 mm (SD: 0.50; range: 1.33 to -0.52). The mean angle deviation was 3.85 degrees (SD: 1.83; range: 8.6 to 1.25). CONCLUSION: A simplified full digital planning procedure yields results comparable to conventional guided implant surgery. The main deviation between the planned and achieved implant positions in this prospective clinical study was angular. More clinical studies are needed to verify the procedure further.

In vivo expression of osteogenic markers and bone mineral density at the surface of fluoride-modified titanium implants.

The aim of the present study was to investigate the biological mechanisms of the functional attachment of fluoride-modified titanium implants to cortical bone by studying the association of the pull-out test results with gene expression of osteoblast (runx2, osteocalcin, collagen-I and IGF-I), osteoclast (TRAP, H(+)-ATPase and calcitonin receptor) and inflammation (TNF-alpha, IL-6 and IL-10) markers from peri-implant bone tissue using real-time RT-PCR, following a 4- and 8-week healing period. After implant detachment, wound fluid from the implant site was collected for LDH and ALP activity analysis. A new method to study volumetric bone mineral density (vBMD) of sub-implant cortical bone was developed using micro-computed tomography. Our results show lower LDH activity and TRAP mRNA levels in fluoride implants after 4 weeks of healing, yet no differences were found either on the pull-out force or expression of bone formation marker genes. After 8 weeks of healing, both pull-out, vBMD and osteocalcin, runx2 and collage type I gene expression were higher in fluoride implants. In conclusion, fluoride-modified implants seem to modulate both inflammation and bone resorption/formation events at the bone-implant interface, suggesting that these biological effects are an intrinsic part of the clinical performance of this surface.

THEMATIC ABSTRACT REVIEW: Implantoplasty: A Valuable Method for the Management of Peri-implantitis?

No abstract available.