Haibin Xia

The effect of platform switching on stress in peri-implant bone in a condition of marginal bone resorption: a three-dimensional finite element analysis.

PURPOSE The aim of the present study was to investigate the stress distribution in the bone around a platform-switched implant with marginal bone loss. MATERIALS AND METHODS Finite element models of an implant-supported crown on a mandibular first molar were constructed and included an osseointegrated implant, a metal crown, and cancellous and cortical bone. Two kinds of abutments, conventional and platform-switched, were imported into the model. A variety of different levels of conical marginal bone resorption, from 0 to 2.0 mm in height and width, was created around the implant neck. The stresses generated in the peri-implant bone tissue were analyzed under 200 N of vertical or oblique loading. RESULTS The location of stress concentration extended from the implant neck toward the apex in association with increases in bone resorption depth. In the bone-resorbed models, the platform-switched implant showed lower maximum equivalent stresses in the peri-implant bone than the conventional abutment. The difference between the two implant models decreased as bone resorption increased. CONCLUSION Within the limitations of this study, the results suggest a biomechanical advantage for platform switching in a condition of marginal bone resorption, but this advantage may be weakened when bone resorption is dramatic. Additional animal or clinical studies are necessary to better clarify the effects of peri-implant bone defects on the biomechanical features of a platform-switched configuration.

Effect of Nd:YAG laser-nitriding-treated titanium nitride surface over Ti6Al4V substrate on the activity of MC3T3-E1 cells.

Ti6Al4V discs with a thickness of 2.5 mm and dimensions of 15 × 15 mm2 were fabricated. The titanium nitride (TiN) surface was formed via Nd:YAG laser-nitriding. A sandblast acid-etched (SA) surface was used as a control. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and surface roughness tests were conducted to study the surface and cross-section morphologies as well as the properties of TiN and SA surfaces. MC3T3-E1 osteoblast-like cells were cultured on the TiN and SA surfaces to evaluate the effect of TiN surface on cellular behaviors, including attachment, proliferation and differentiation. Morphological testing results revealed that the cross-section of TiN exhibited dendritic crystallization without cracking. The proliferation and differentiation of MC3T3-E1 cells on the laser-nitriding TiN surface were significantly increased compared to those cultured on SA surface. These findings suggested that the TiN surface generated from Nd:YAG laser-nitriding were favorable for the proliferation and differentiation of MC3T3-E1 cells, which is significant for implant surface modification.

Three-Dimensional Culture of Human Periodontal Ligament Cells on Highly Porous Polyglycolic Acid Scaffolds in vitro

Periodontal tissue engineering represents a possible approach to regenerate the human periodontal ligament (PDL) around dental implants. The aim of this study was to observe the morphological and biological property of the human periodontal ligament cells that were three-dimensional (3D) cultured onto PGA scaffolds in vitro. The human periodontal ligament cells were seeded and cultured onto PGA 3D scaffolds, and then the cellular morphology and structure, adhesion and biocompatibility with scaffolds were evaluated by light microscope and scanning electronic microscope, and the cellular type I collagen synthesis was observed by method of immunohistochemical staining with anti-type I collagen antibody. The results indicated that the human periodontal ligament cells adhere to scaffolds well and exhibit the excellent matrix secretion ability under light microscope and scanning electronic microscope, type I collagen was expressed positively in cell-scaffolds complex by immunohistochemical staining. These results suggested that delivery of PDL cells via non-woven PGA mesh may serve as a viable approach for promoting periodontal tissue regeneration and provides a possibility of PDL regeneration on dental implants

Confocal laser scanning microscope evaluation of early bacterial colonization on zirconium oxide and titanium surfaces: An in vivo study

To investigate the bacterial colonization on zirconium oxide and titanium surfaces in vivo quantitatively using a confocal laser scanning microscope (CLSM). Ten samples of zirconium oxide ceramic and commercially pure titanium were fabricated and polished using silicon carbide abrasive paper. One sample from each group was evaluated topographic pattern under a scanning electron microscope. One sample from each group was to evaluate roughness using a profilometer. Eight volunteers were selected. The samples were cemented at the buccal surfaces of upper first molars. All samples were removed after 48 hours, immersed in SYTO-9 and propidium iodide fluorescent to stain for adherent bacteria and observed with CLSM. Fewer bacteria were observed in zirconia group than titanium group. However, there was no statistical difference between two groups. The experimental results demonstrate that zirconium oxide may be considered as a promising material for dental implant abutments.

Assessment of polyglycolic acid scaffolds for periodontal ligament regeneration

ABSTRACT Periodontal tissue engineering is a possible strategy for regeneration of human periodontal ligaments (PDLs) around dental implants. The aim of this study was to investigate the feasibility of three-dimensional polyglycolic acid (PGA) fibre mesh as a scaffold for human PDL cells in periodontal tissue engineering with a nude mouse model. Human PDL cells at a density of 2 × 107/mL were seeded onto porous PGA scaffolds. After seven days of incubation in vitro, the PGA–cell constructs and cell-free scaffolds were subcutaneously implanted on the back of BALB/c-nu mice bilaterally. The mice were sacrificed in batches at 2, 4, 6 and 8 weeks after implantation, and the harvests were examined histologically. In our study, PGA scaffolds promoted mRNA expression of collagen type I, collagen type III and fibronectin in PDL cells. Massons trichrome staining showed that after two weeks, the implants were well vascularised in vivo. Fluorescence microscopy indicated that the newly formed tissues were derived from the GFP-labelled human PDL cells. Our study suggested that the delivery of PDL cells via a non-woven PGA mesh might serve as a viable approach to promote periodontal tissue regeneration.