Jai Young Koak

Effect of bone quality and implant surgical technique on implant stability quotient (ISQ) value

PURPOSE This study investigated the influence of bone quality and surgical technique on the implant stability quotient (ISQ) value. In addition, the influence of interfacial bone quality, directly surrounding the implant fixture, on the resonance frequency of the structure was also evaluated by the finite element analysis. MATERIALS AND METHODS Two different types of bone (type 1 and type 2) were extracted and trimmed from pig rib bone. In each type of bone, the same implants were installed in three different ways: (1) Compaction, (2) Self-tapping, and (3) Tapping. The ISQ value was measured and analyzed to evaluate the influence of bone quality and surgical technique on the implant primary stability. For finite element analysis, a three dimensional implant fixture-bone structure was designed and the fundamental resonance frequency of the structure was measured with three different density of interfacial bone surrounding the implant fixture. RESULTS In each group, the ISQ values were higher in type 1 bone than those in type 2 bone. Among three different insertion methods, the Tapping group showed the lowest ISQ value in both type 1 and type 2 bones. In both bone types, the Compaction groups showed slightly higher mean ISQ values than the Self-tapping groups, but the differences were not statistically significant. Increased interfacial bone density raised the resonance frequency value in the finite element analysis. CONCLUSION Both bone quality and surgical technique have influence on the implant primary stability, and resonance frequency has a positive relation with the density of implant fixture-surrounding bone.

Fracture Strength Study of Internally Connected Zirconia Abutments Reinforced with Titanium Inserts

PURPOSEnThe implant-abutment connection area is known to be the weakest part of an internal-connection zirconia abutment and therefore the most likely to fracture. The aim of this study was to evaluate the complementary effect of a titanium insert on the fracture strength of a zirconia abutment.nnnMATERIALS AND METHODSnThree types of abutments with internal connection structures were selected and assembled: titanium abutment-titanium abutment screw (Ti-Ti), zirconia abutment-titanium abutment screw (Zr-Ti), and zirconia abutment-titanium insert-titanium abutment screw (Zr+Ti-Ti). Fifteen abutments and 15 implants were used and divided into three groups of five specimens each. Compressive loading was applied to the specimens at 30 degrees off-axis with dislocation speed of 1 mm/min and was increased until deformation occurred.nnnRESULTSnThe Ti-Ti specimens showed the highest maximum fracture load, followed by the Zr+Ti-Ti specimens; the Zr-Ti assemblies were the weakest. Significant differences in fracture strength were found between the groups. All of the investigated Zr abutments fractured. However, in the Zr+Ti-Ti specimens, 60% of the Ti abutment screws fractured and 40% bent, whereas all of the abutment screws in the Zr-Ti group were only bent.nnnCONCLUSIONnThe Ti insert, as a substitute for the weakest part of a Zr abutment in an implant with an internal friction connection, can reinforce the fracture strength of a Zr abutment.

Biochemical Responses of Anodized Titanium Implants with a Poly(lactide-co-glycolide)/Bone Morphogenetic Protein-2 Submicron Particle Coating. Part 2: An In Vivo Study

PURPOSEnA biochemical approach to implant surfaces can improve bone growth, resulting in desirable bone-implant interfaces. This study was conducted to identify the effect on osseointegration of direct coating of titanium (Ti) implants with poly(D,L-lactide-co-glycolide)(PLGA)/recombinant human bone morphogenetic 2 (rhBMP-2) submicron particles by electrospray.nnnMATERIALS AND METHODSnAnodized Ti implants were used as a control group, and implants coated with 80 μL of PLGA/rhBMP-2 (50 μg/mL rhBMP-2 per implant) submicron particles by electrospray were used as the experimental group in an in vivo rabbit tibia model. After 3 or 7 weeks of healing, specimens were obtained and prepared for histologic and histomorphometric analyses.nnnRESULTSnThe implant surface coated with submicron PLGA/rhBMP-2 showed new bone growth in the apical direction earlier than control implants. In the experimental group at 3 weeks, the bone-to-implant contact ratio and bone area of the three best consecutive threads were significantly higher than those in the control group. However, there was no significant difference between groups at 7 weeks.nnnCONCLUSIONnWithin the limitations of this study, the PLGA/rhBMP-2-coated implants facilitated osseointegration between bone and the Ti surface during the early healing phase.

Effects of fluoride-modified titanium surfaces with the similar roughness on RUNX2 gene expression of osteoblast-like MG63 cells

Chemical modification of titanium surfaces by hydrofluoric acid (HF) is an effective method to improve bone responses on titanium implant surfaces. In this study, titanium disks were sandblasted with titanium oxide grits and modified with 0.2% and 0.4% of diluted HF under different exposure times of 40 and 60 s. Surface characteristics, such as surface chemical composition, surface topography, and surface wettability, were investigated. To examine MG63 osteoblast-like cell responses to fluoride-modified titanium surfaces with roughness similar to that of nonmodified surfaces, a cell proliferation assay was performed and gene expression levels of Runx2 were evaluated using real-time PCR. Fluoride-modified titanium surfaces revealed no significant roughness difference but with hydrophilic properties than control group SB. Moreover, the relative atomic concentration percentages of fluoride were 0.7, 1.5, and 2.8. As fluoride concentrations increased, surface wettability increased and cell proliferation began earlier. However, the gene expression levels of Runx2 increased earlier on surfaces with 1.5% fluoride, with significantly high surface skewness. There seems to be an optimal fluoride concentration percentage when gene expression levels of Runx2 were taken into consideration. In addition, surface parameters, such as surface wettability and surface skewness, seem to be important factors in the enhancement of osteoblast differentiation by HF.

A Histomophometric Analysis of Bone Healing around Zirconia Implant

Zirconia was introduced into the dentistry as a metal-replacement material because of its outstanding mechanical properties like high flexural strength and fracture toughness. The purpose of this study was to evaluate bone response and examine the surface characteristics of zirconiabased implant. Screw shaped c.p. titanium implants(group 1), HA-based composite implants(group 2), HA/FA coated ZrO2 implants(group 3) and FA coated ZrO2 implants(group 4) were installed in rabbit tibias. After 4 and 12 weeks of healing period, the histomorphometric analysis was performed with an Olympus BX microscope connected to a computer. The percentage of bone-to-implant contact in the 3 best consecutive threads and the percentage of bone inside the same threads were calculated. the present study demonstrated the excellent bone response of ZrO2-based implants fabricated by various methods to combine the advantages of ZrO2, HA, and FA.

A Three-Dimensional Finite Element Analysis with Various Implant Designs

Various studies recommend that threaded type implants should be used to maximize initial contact, improve initial stability, enlarge implant surface area, and favor dissipation of interfacial stress. The objective of this study was to compare four types of screw implants placed in posterior region of mandible model and evaluate the influences of implant shape, configuration, length, diameter and abutment connection method on stress distribution using a three-dimensional finite analysis. Four types of two-length implant models — 8.5 and 13 mm — were selected and the wide diameter was also used. Four groups were classified by implant outline and connection manner A load of 100 N was applied vertically on the center of the implant. Oblique and horizontal loads were taken as equal to that of the vertical load. The TMJ area in mandibular model was constrained in all directions. Results show that the stress of two-length implants was similar in all groups and the internal connection implant with appropriate thickness of inner part of the implant had better stress distribution.

Bone Response to Cyclic Loading with Anodized Implants

The purpose of this study was to evaluate the bone interface response to different surface using bone remodeling rate (BRR) under cyclic loading. The tibiae of 10 New Zealand white rabbits were used. Each tibia of rabbits received 2 implants, one with anodic oxidation surface and the other with machined surface. Dynamic loading, a cyclic load of 100 N with 100 cycles was applied for 2 weeks. All implants were divided into 4 groups according to surface treatment and loading; (1) machined surface, unloaded, (2) anodic oxidation surface, unloaded, (3) machined surface, loaded, and (4) anodic oxidation surface, loaded. To determine the rate of bone formation, a series of fluorochrome bone labeling materials (tetracycline, alizarin red, and calcein green) were administrated intramuscularly at 10, 11, 12 weeks. To study the formation time of new bone, ground sections were examined under confocal laser scanning microscopy. Resonance frequency analysis (RFA) values were measured at the time of first surgery, second surgery and sacrifice. From this study, it was concluded that implants with anodic oxidation surface had higher value than machined surface on RFA measurement and anodic oxidation surface has more resistance to loading than machined surface.