Chang Mo Jeong

Effects of anodized titanium with Arg-Gly-Asp (RGD) peptide immobilized via chemical grafting or physical adsorption on bone cell adhesion and differentiation

PURPOSE This study examined the effects of the immobilization of Arg-Gly-Asp (RGD) peptide (CAAALLLKERGDSK) on anodized titanium (Ti) via chemical grafting or physical adsorption methods on cell adhesion and osteoblast differentiation. MATERIALS AND METHODS The RGD peptide was immobilized on the anodized Ti surface by means of physical adsorption or chemical grafting. The chemical composition of each RGD-immobilized Ti substrate was examined by x-ray photoelectron spectroscopy. The level of cell proliferation was investigated via tetrazolium (XTT) assay. Alkaline phosphatase activity and calcium deposition were evaluated by alizarin red S staining, and mRNA expression of the differentiated osteoblast marker genes was analyzed by reverse-transcriptase polymerase chain reaction. RESULTS Cell adhesion was enhanced on the RGD-immobilized Ti substrates compared to the anodized Ti surfaces. In addition, significantly increased cell spreading and proliferation were observed with the cells grown on the RGD-immobilized Ti (P < .05). Furthermore, the osteoblasts on the RGD-immobilized Ti showed significant increases in the integrin ?1 and type I collagen levels and small increases in osteonectin and osteocalcin levels (P < .05). Interestingly, the chemical grafting method resulted in significantly greater effects on adhesion and differentiation than the physical adsorption method (P < .05). CONCLUSION RGD-immobilized Ti substrates might be effective in improving the osseointegration of dental implants. In particular, the chemical grafting method of RGD immobilization is more favorable and is expected to provide positive outcomes with future animal and clinical studies.

The effects of Mg‐ion implantation and sandblasting on Porphyromonas gingivalis attachment

OBJECTIVES The purpose of this study was to evaluate the effect of titanium surface treatment on Porphyromonas gingivalis bacterial attachment. MATERIALS AND METHODS Titanium disks of 15 mm in diameter and 1 mm in thickness (n=40) were subjected to mechanical grinding, or sandblasting. Magnesium (Mg) ions were implanted onto the titanium surface using a plasma source ion implantation method. The structure, chemistry, and surface morphologies of the titanium surfaces were analyzed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and Auger electron spectroscopy. Surface roughness was measured using a laser profilometer. Half of the titanium disks in each group were dipped in saliva for 24 h. All of the titanium specimens were rinsed with distilled water. A P. gingivalis strain was cultured in anaerobic conditions at 37°C for 72 h, and all titanium specimens were dipped in the bacterial suspension at 37°C for 24 h. Specimens were examined at × 3000 magnification using a SEM. The number of bacteria in each of 10 separate fields was determined by directly counting the number of bacterial colonies that adhered to each specimen. The mean values were calculated afterward. The resulting data were analyzed to assess the significance of observed differences based on the method of the surface treatment, ion implantation, and saliva dipping. RESULTS The amount of P. gingivalis attached to the sandblasted specimens was greater than that on the ground specimens (P<0.001). Moreover, surfaces with Mg-ion implantation had more attachments than nonimplanted surfaces (P<0.001). Saliva dipping acted synergistically with surface roughness and chemical composition of the specimens. CONCLUSIONS Chemically modified surface increase the attachment of a major periodontopathic bacterium, P. gingivalis.

Influence of Implant transmucosal design on early peri‐implant tissue responses in beagle dogs

OBJECTIVES This study was undertaken to evaluate the influences of concave, machined and concave-roughened profiles of transmucosal implant designs on early peri-implant tissue responses. MATERIALS AND METHODS Implants were used and classified by transmucosal profile and surface type as straight-machined implants (SM), concave-machined implants (CM), or concave-roughened implants (CR). A total of 30 implants (10 per each type) with matching transmucosal profiles were placed directly on alveolar crests in randomized order in the edentulous mandibular ridges of three beagle dogs. Healing abutments were connected 4 weeks after implant placement, and prostheses were connected 8 weeks after implant placement and functionally loaded. All animals were sacrificed at 16 weeks. Peri-apical radiographs were obtained and measured to evaluate peri-implant marginal bone levels. Histological specimens were prepared to measure bone resorption, connective tissue contact, epithelial tissue height, biological width, and length of implant-abutment junction to the apical portion of junctional epithelium. RESULTS Radiographic and histometric analysis showed that least bone resorption occurred around CM implants and greatest bone resorption around SM implants (P < 0.05). Histometric analysis showed that highest connective tissue attachment and shortest biological width had formed around CM implants. CONCLUSION Concave-machined profiled implants with a transmucosal design may induce less bone resorption and better connective tissue attachment around implants than the straight-machined profiled implants during the early healing phase.

Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems

PURPOSE This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukeys HSD post-hoc test was performed. RESULTS Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.

Effects of Mg-ion and Ca-ion implantations on P. gingivalis and F. nucleatum adhesion

The purpose of this study was to evaluate the effects of ion implantation on Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum) bacterial adhesion. Titanium (Ti) discs of 15 mm diameter and 1 mm in thickness (n = 42, 7 per group) were fabricated. Magnesium (Mg) and calcium (Ca) ions were implanted into the Ti surfaces using a plasma-source ion-implantation method. The roughness, chemistry, morphology, and contact angle of the titanium surfaces were analyzed using scanning electron microscopy, Rutherford back-scattering spectroscopy, Auger electron spectroscopy, and contact angle meter. P. gingivalis and F. nucleatum strains were cultured in anaerobic conditions at 37°C for 72 hours, and all titanium specimens were dipped in the bacterial suspension at 37°C for 24 hours. Specimens were examined at 1,000× magnification using a fluorescence microscope. The number and total area of bacteria in each of 10 separate fields were determined by computer imaging analysis method. The resulting data was analyzed to assess the significance of observed differences based on the method of the surface treatment, ion implantation. The number of P. gingivalis and F. nucleatum attached to the Mg-(927 and 227, respectively) and Caionimplanted (1325 and 231, respectively) surfaces were greater than those attached to the non-implanted surfaces (306 and 98, p <.001). Total area occupied by P. gingivalis adhesion was greater than those of F. nucleatum in the Mgand Caion-implanted surfaces (p <.001). The types of ion and bacteria did not affect the amount of bacterial adhesion. Ion implantation enhanced the adhesions of P. gingivalis and F. nucleatum. Non-specific bonding derived from the electrostatic force affected by positively charged ions might be the predominant factor in bacterial adhesion. The possibility of specific bonding could not be ruled out in the Ca-ion- implanted surface.

Comparison of changes in retentive force of three stud attachments for implant overdentures.

PURPOSE The aim of this study was to compare the changes in retentive force of stud attachments for implant overdentures by in vitro 2-year-wear simulation. MATERIALS AND METHODS Three commercially available attachment systems were investigated: Kerator blue, O-ring red, and EZ lock. Two implant fixtures were embedded in parallel in each custom base mounting. Five pairs of each attachment system were tested. A universal testing machine was used to measure the retentive force during 2500 insertion and removal cycles. Surface changes on the components were evaluated by scanning electron microscopy (SEM). A Kruskal-Wallis test, followed by Pairwise comparison, was used to compare the retentive force between the groups, and to determine groups that were significantly different (α<.05). RESULTS A comparison of the initial retentive force revealed the highest value for Kerator, followed by the O-ring and EZ lock attachments. However, no significant difference was detected between Kerator and O-ring (P>.05). After 2500 insertion and removal cycles, the highest retention loss was recorded for O-ring, and no significant difference between Kerator and EZ lock (P>.05). Also, Kerator showed the highest retentive force, followed by EZ lock and O-ring, after 2500 cycles (P<.05). Based on SEM analysis, the polymeric components in O-ring and Kerator were observed to exhibit surface wear and deformation. CONCLUSION After 2500 insertion and removal cycles, all attachments exhibited significant loss in retention. Mechanism of retention loss can only be partially explained by surface changes.

Influence of Transmucosal Designs of Dental Implant on Tissue Regeneration in Beagle Dogs

This study was conducted to evaluate the influence of concave machined and concave microgrooved profiles of the transmucosal portion of implants on early peri-implant tissue regeneration. We assessed implants with 3 different transmucosal profiles: the bevel group that had only a bevel in the transmucosal part, bioseal group and bioseal/groove group that had a micro-groove in the S-shaped portion of the implant. A total of 36 implants (12 of each type) were placed in the edentulous mandibular ridges of 6 beagle dogs. We used radiographs to investigate the mesio-distal change of the marginal bone. Bucco-lingual bone resorption and soft tissue reactions were evaluated histologically. Radiographic and histological analysis did not show any difference in mesio-distal or bucco-lingual marginal bone resorption among any of the 3 groups (p > 0.05). The bioseal and bioseal/groove groups had more rigid connective tissue attachment than that in the bevel group. However, the bevel group had significantly long junctional epithelium attachment and the bioseal and bioseal/groove groups had long connective tissue attachment (p < 0.05). Implants with S-shaped concavity of the transmucosal portion resulted in a firmer connective tissue barrier, and thus, a better soft tissue regeneration, than implants with straight bevel.