An immediate peri-implantitis induction model to study regenerative peri-implantitis treatments.

OBJECTIVES: The aim of this study was to evaluate the validity of the immediate peri-implantitis model to test regenerative therapies in peri-implantitis defects. MATERIAL AND METHODS: In an immediate peri-implantitis model in beagles, the mandibular third premolars were extracted, and dental implants were immediately placed in the distal extraction sockets. Without a healing period, experimental peri-implantitis was induced by ligature placement for 3 months. In the conventional peri-implantitis model, dental implants were placed in the healed mandibular fourth premolar region and were submerged for osseointegration. After 3 months of healing, peri-implantitis induction was performed for another 3 months. After peri-implantitis defects were formed in both models, regenerative therapy was performed in both models. RESULTS: After 3 months in the immediate model and 9 months in the conventional model, similarly shaped horizontal bone defects (wide and craterlike) were observed. However, buccal bone defects were deeply formed in the immediate model compared with the conventional model (6.02 ± 1.20 and 4.34 ± 0.86 mm, respectively; P = 0.009), but the amounts of bone regeneration were not significantly different between the models (P = 0.107). On the lingual side, re-osseointegration was significantly greater in the conventional model than in the immediate model (0.72 ± 0.50 and 1.77 ± 0.87 mm, respectively; P = 0.009), although lingual bone defects were not significantly different between the models (P = 0.248). CONCLUSIONS: Although the immediate peri-implantitis model is challenging for regeneration, it may be able to replace the conventional model to study regenerative peri-implantitis treatment due to its short experimental time and similar defect configuration.

Synthetic peptide-conjugated titanium alloy for enhanced bone formation in vivo.

There are growing demands for bioactive titanium implants that could shorten the healing period, promote faster rehabilitation, and thereby increase the success rate of treating patients with poor bone quality. A synthetic receptor-binding peptide mimicking bone morphogenetic protein-2 (BMP-2) was covalently linked to a titanium alloy with two types of topography--machined (TiMA) and rough (TiGB)--by using a chemical conjugation process. In vivo osseointegration capacity was evaluated chronologically using histomorphometric analysis at 2, 4, and 8 weeks after implantation in the distal femurs of rabbits. In the histologic examinations, peri-implant bone formation was more active around TiGB than TiMA. Compared to the control groups (nonconjugated TiMA and TiGB) at 2, 4, and 8 weeks, the peptide-conjugated groups (TiMA-P and TiGB-P) had more mature new bone, thicker trabeculae, more rapid bone maturation, and higher affinity index (percentage of new bone contact length) in histomorphometric analysis. Particularly, differences in the affinity index between the peptide-conjugated and nonconjugated groups were more pronounced at the early phase of peri-implant healing (2 and 4 weeks). However, at 8 weeks, enhanced bone formation was less prominent according to peptide conjugation, especially in specimens with a rough surface. The titanium alloys in the rabbit femurs led to a significant increase of bone growth when modified with bioactive peptides, especially during the early phase of bone healing. These results confirm that biochemical modifications of titanium surfaces can enhance the rate of bone healing compared with that of untreated titanium surfaces.

Biocompatibility and osteogenic potential of mineral trioxide aggregate mixed with hydrophilic synthetic polymer: An in vitro and in vivo study.

This study aimed to investigate in vitro biologic properties of mineral trioxide aggregate (MTA) mixed with 3% PVA (MTA-3% PVA) and in vivo dental pulp responses to direct capping in comparison with MTA mixed with distilled water (MTA-DW). Cell proliferation and osteogenic differentiation in culture of human dental pulp cells (hDPCs), and pH changes were evaluated. Pulps in 24 mandibular premolars of four 9-month-old beagle dogs were mechanically exposed and direct pulp capping was performed. Histological specimens were scored according to the degree of mineralization. MTA-3% PVA showed similar cell proliferation and similar or superior osteogenic differentiation of hDPCs compared with MTA-DW. All specimens were associated with calcified bridge formation and there were no significant differences in mineralization scores between the groups (p>0.05). The results suggested that MTA-3% PVA exhibited favorable biocompatibility and osteogenic differentiation in vitro compared with MTA-DW. Furthermore, both groups demonstrated similar results when used as pulp-capping agents in vivo.

Effect of grain size of dental zirconia on shear bond strength of composite resin cement.

The effect of grain size of dental zirconia on the shear bond strength of composite resin cement was newly studied. Disc-shaped dental zirconia with small (sample S) and large (sample L) grains were made by sintering of pre-sintered dental zirconia at 1450°C for 0.5 h and 40 h, respectively. After the sintering, the average grain size of sample S was 1.37 ± 0.15 µm, while that of sample L was 3.74 ± 0.50 µm. The sintered discs were successively polished with different grades of diamond and alumina slurries. The interfacial free energies were 63.5 ± 4.2 dyne/cm for sample S and 52.1 ± 5.5 dyne/cm for sample L. Stainless steel cylinders, previously sandblasted with 50 µm alumina powder, were bonded to the zirconia discs using composite resin cement. Next, samples were kept in an oven for 7 d at 36.5°C. The shear bond strength of sample S was 23.0 ± 4.5 MPa while that of sample L was 17.5 ± 4.6 MPa. After the fracture, the areal % values of composite resin cement remaining on the zirconia surfaces were 89.7 ± 5.9% for sample S and 61.6 ± 5.5% for sample L. The results suggest that grain size reduction has a potential to enhance the degree of bonding between a composite resin cement and a dental zirconia due to the increase of interfacial free energy.

Comparison of experimental peri-implantitis models after application of ex vivo BMP2 gene therapy using periodontal ligament stem cells.

Peri-implantitis is an inflammatory disease that results in bone destruction around dental implants. A preclinical study using beagle models is frequently performed prior to clinical application in dentistry. Previously, we proposed an immediate peri-implantitis experimental model with a shorter experimental duration and less expense than the conventional experimental model. However, the differences in the regenerative outcomes between the immediate and conventional models were not fully revealed. In this study, we aimed to compare the regenerative outcomes between both models when ex vivo BMP2 gene therapy using autologous periodontal ligament stem cells (B2/PDLSCs) was applied to peri-implantitis defects. The results showed that the defect depths were significantly different between both models. New bone formation occurred in both models, but there were significant differences between the models. More than 70% of the defects were filled with newly formed bone in the conventional model, whereas 30-40% of the defects were filled in the immediate model. However, after adjustment for the differences in the defect depths between the models, the statistically significant differences in the regenerative outcomes between the models were lost. In conclusion, the inferior regenerative outcome of an immediate peri-implantitis model at B2/PDLSCs transplantation resulted from the defect depths, not the model itself.

Synthesis of a Ca3 SiO5 -Ca2 SiO4 -Ca3 Al2 O6 cement system with rapid setting capacity by spray-pyrolysis coupled with sol-gel method.

A modified mineral-trioxide-aggregate (mMTA) with rapid setting capacity was newly synthesized by spray-pyrolysis following a sol-gel reaction. Its faster setting capacity and initially higher compressive strength compared with Portland cement (PC) were evaluated. The precursor solution of the mMTA was prepared through condensation following hydrolysis among Ca(NO3 )2 ·4H2 O, Si(OC2 H5 )4 , and Al(NO3 )3 ·9H2 O under nitric acid. The mMTA powder was then synthesized by spray-pyrolysis at 1500°C. The particle shape was spherical with an average particle size of 0.8 ± 0.3 µm, while PC particles were irregular and 3.9 ± 3.0 µm in size. The mMTA consisted of mostly Ca3 SiO5 , Ca3 Al2 O6 , and partial Ca2 SiO4 phases, while the PC comprised mainly Ca3 SiO5 , Ca2 SiO4 , and partial Ca3 Al2 O6 phases. The final setting times of mMTA and PC measured under 95% relative humidity were about 11 min and 3 h, respectively. The early stage of setting in mMTA was dominated by the rapid formation of hexagonal-plate-like Ca3 Al2 O6 ·6H2 O crystals, while that in PC was dominated by needle-like calcium-silicate-hydrate gels and columnar-shaped Ca(OH)2 crystals. The late stage of setting in mMTA was dominated by calcium-silicate-hydrate gels and Ca(OH)2 crystals, while that in PC was dominated by Ca3 Al2 O6 ·6H2 O crystals. The compressive strengths of mMTA and PC after 30 min of setting were 4.5 and 0.2 MPa, respectively. The results suggest that mMTA has potential to be used as a filling material for accidental pulp-exposure or pulpal floor perforation cases that require rapid setting capacity and initial good strength. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1440-1451, 2019.

Influence of filler distribution on the color parameters of experimental resin composites.

OBJECTIVES: Simulating the optical properties of natural tooth would be the final goal for esthetic restorative materials. Filler distribution in resin composites determines the scattering in composite materials, which in turn would influence the color parameters such as lightness, chroma and hue. The objective of this study was to determine the influence of filler size and amount on the color parameters of experimental resin composites. METHOD: Color of 11 experimental resin composites with two different sized fillers (LG: 0.77 microm and SG: 0.50 microm) in 10-70 wt% was measured by a spectrophotometer. Color coordinates (CIE L*, a* and b*), chroma and hue angle were determined. Optical constants including scattering coefficient (S), absorption coefficient (K) and light reflectivity (RI) were calculated. To determine the influence of the amount of filler on the optical parameters, Pearson correlations between the amount of filler (%) and color parameters and optical constants were calculated. Correlations between the optical constants (S, K and RI) and color parameters were calculated (p<0.05). RESULTS: S value increased as the amount of filler increased. RI value generally increased as the amount of filler increased for LG filler group, and increased up to 40% filler for SG filler group. CIE L* value increased as the amount of filler increased in both of LG and SG filler groups. CIE L* value was highly correlated with S and RI values for both filler groups (r=0.961-0.974). CONCLUSION: Lightness was highly correlated with the amount of filler, S and RI values (r=0.932-0.974). But the correlation coefficients between the amount of filler and chroma/hue were moderate (r=0.406-0.827); therefore, pigmentation would be tried to simulate the color of resin composites to those of natural tooth. Optical properties of resin composites could be partly simulated to those of teeth by controlling the filler distribution.

Preparation of fluoride-loaded microcapsules for anticariogenic bacterial growth using a coaxial ultrasonic atomizer.

A new method to deliver fluoride using biodegradable poly(lactic-co-glycolic acid) microcapsules to suppress cariogenic bacterial growth during orthodontic treatment was investigated. A coaxial ultrasonic atomizer was used to encapsulate KF solution into microcapsules. The orthodontic adhesive resin disk containing fluoride loaded microcapsules (DFLM) was prepared by LED light curing. The microstructure of microcapsules, successful loading of KF, fracture strength, and shear bonding strength were assessed by FE-SEM, confocal laser scanning microscope, and general purpose testing machine, respectively. Fluoride release from the DFLM in phosphate buffered saline and pH changes were measured after different periods of soaking time. Antibacterial activity of the DFLM was assessed in tryptic soy broth containing mutant streptococci. The starting inoculum and the orthodontic resin disk containing microcapsules not loaded with KF were used as negative and positive controls, respectively. As results, the cumulative amount of KF after 49 days was about 85% of the initial amount of fluoride contained in the microcapsules. The fracture and shear bonding strengths of the orthodontic resin disks with and without the microcapsules were similar to each other. The DFLM showed lower bacterial growth than the control groups, whereas no statistically significant differences were found between the negative and positive controls. It can be concluded that the microcapsules loaded with fluoride prepared by a coaxial ultrasonic atomizer have good potential for application as an antibacterial agent due to their excellent cariogenic antibacterial activity when incorporated into orthodontic adhesive resin. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 31-39, 2018.

Effect of acidic degradation products of poly(lactic-co-glycolic)acid on the apatite-forming ability of poly(lactic-co-glycolic)acid-siloxane nanohybrid material.

The effect of poly(lactic-co-glycolic) acid (PLGA) degradation products on the apatite-forming ability of a PLGA-siloxane nanohybrid material were investigated. Two PLGA copolymer compositions with low and high degradability were used in the experiment. The PLGA-siloxane nanohybrid materials were synthesized by end-capping PLGA with acid end-groups using 3-isocyanatopropyl triethoxysilane following the sol-gel reaction with calcium nitrate tetrahydrate. Two nanohybrid materials that had different degradability were exposed to simulated body fluid (SBF) for 1-28 days at 36.5 degrees C. The low degradable PLGA hybrid showed apatite-forming ability within 3 days of incubation while the high degradable one did not within 28 days testing period. The results were explained in terms of the acidity of the PLGA degradation products, which could directly influence on the apatite dissolution.

Enhanced bone regeneration in beagle dogs with bovine bone mineral coated with a synthetic oligopeptide.

BACKGROUND: Recombinant human bone morphogenic protein-2 stimulates bone augmentation in animal models. The aim of this study was to evaluate the capacity of bovine bone mineral coated with synthetic oligopeptides to enhance guided bone regeneration in the beagle 3-wall defect model and the clinical implications. METHODS: The second and fourth mandibular premolars of four adult beagle dogs were extracted bilaterally, and the extraction sites were allowed to heal for 2 months. An L-shaped defect was prepared at the central part of the extraction site with a round bur on a low-speed motor. Peptide-coated bone mineral was implanted on one side, and uncoated bone mineral was implanted on the other side. The membrane was tucked underneath the mobilized lingual flap. New bone formation at the test and control sites was determined at 4 weeks. RESULTS: No specimen revealed any evidence of infection or foreign body reaction, and all wounds showed a good healing response. Sites augmented with peptide-coated bone mineral and uncoated mineral exhibited excellent maintenance of the ridge contour. There was more new bone at sites with peptide-coated bone mineral than at control sites. The new bone in sites with peptide-coated bone mineral was deposited evenly around the graft material, and bone mineral was integrated fully into the new bone. CONCLUSION: Deproteinized cancellous bovine bone coated with synthetic oligopeptides enhanced new bone formation, and it seemed to be a better material for guided bone regeneration in the beagle L-shaped defect model.

Osteopromotion with synthetic oligopeptide-coated bovine bone mineral in vivo.

BACKGROUND: Recombinant human bone morphogenetic protein (rhBMP)-2 has been shown to stimulate significant regeneration of alveolar bone and cementum in periodontal defects clinically. The aim of this study was to evaluate the osteopromotive effect of oligopeptide domain-coated bovine bone mineral granules in a rabbit calvarial defect model. METHODS: The peptide-coated bovine bone was fabricated by incubating the graft material in a solution of oligopeptide domain. The cell attachment and proliferation were measured in vitro. Peptide-coated (test group) or uncoated (control group) bone minerals were implanted into 10-mm calvarial defects in rabbits, and the animals were sacrificed at 1, 2, or 4 weeks post-surgery. RESULTS: The cells grown with peptide-coated bone showed significantly higher proliferation activity at all times compared to cells grown with peptide-uncoated bone mineral. At 2 weeks post-surgery, the control wounds showed a limited amount of osteoid formation in a centripetal pattern around the grafted bone, but the oligopeptide domain-coated grafted bone had formed new bone around the grafted area. At 4 weeks post-surgery, the control sites showed increased new bone formation, but they still showed a significant difference from the peptide-coated bone-implanted sites. CONCLUSIONS: At 2 and 4 weeks, accelerated new bone formation was observed within the experimental sites compared to control groups. The use of deproteinized bovine bone combined with a synthetic oligopeptide seems to be a more beneficial material for bone regeneration in the early healing period.

The effect of nanofiller on the opacity of experimental composites.

The purpose of this study was to evaluate the effect of the nanofiller in experimental composites on opacity (contrast ratio). Thirteen experimental composites were prepared with three different sizes of fillers: barium glass minifiller (1 microm; 69-76 wt %), silica microfiller (0.04 microm; 0-6 wt %), and silica nanofiller (7 nm; 0-7 wt %). After disk-type specimens were irradiated with a halogen light curing unit at 500 mW/cm(2) for 30 s, the specimens were aged for 6 h at room conditions and were stored in deionized water for 1, 7, 14, 21, 28, 56, and 84 days. The contrast ratios of the specimens were measured as a function of aging period using a spectrophotometer. The distribution morphology of the filler particles in the resin matrix was also examined using energy-filtering transmission electron microscopy. The experimental composites that contained more than 3% nanofiller had significantly lower contrast ratios (p < 0.05). The composites that contained 6 wt % nanofiller had contrast ratios 34-65% lower than the composite that did not contain nanofiller. The values of the contrast ratio from the composites that excluded microfiller were lower than the values from the composites that included microfiller. From the comparison with the 3 different sizes of filler, the contrast ratio of the composite that contained 70 wt % minifiller and 6 wt % microfiller was the highest, the contrast ratio of the composite that contained only 76 wt % minifiller was the median value, and the contrast ratio of the composite that contained 70 wt % minifiller and 6 wt % nanofiller was the lowest. When the microfiller content was decreased from 6 wt % to 0 wt %, the contrast ratio decreased 6-9%. Energy-filtering transmission electron microscopy images indicated that the contrast ratio of experimental composites is related to the distribution morphology of the filler particles in the resin matrix.

Changes in scattering and absorption properties of esthetic filling materials after aging.

OBJECTIVES: Assuming that color changes after aging are related to changes in translucency of materials, the purpose of the present study was to determine the correlation between the changes in color and the changes in scattering and absorption properties after accelerated aging with representative dental esthetic restorative materials: glass ionomer, resin-modified glass ionomer, compomer, and resin composite. METHODS: Color was measured according to the CIELAB color scale in the transmittance and reflectance modes and used to calculate changes in color (deltaE*(ab)), color coordinates (deltaL*, delta a*, and delta b*), translucency parameter (deltaTP), scattering coefficient (deltaS), absorption coefficient (deltaK), and light reflectivity (deltaRI) after accelerated aging. Simple correlations between each pair of the changes in optical values were calculated, and multiple regression analysis was used to determine the parameters influencing the changes in color and color coordinates (p = 0.05). RESULTS: In the resin composite and compomer, deltaS, deltaK, and deltaRI values were approximately zero, whereas deltaS was as high as 8.9 in the glass ionomer. For most comparisons, correlation coefficient (r) was between 0.700 and 0.997. DeltaL* was found to have a major influence on color changes, and deltaS, deltaTP, and deltaRI influenced deltaL*. Therefore, changes in scattering and absorption properties, after aging, were closely correlated with changes in color and color coordinates, especially in glass ionomer-based filling materials.

Comparative in vitro and in vivo studies using a bioactive poly(epsilon-caprolactone)-organosiloxane nanohybrid containing calcium salt.

Comparative in vitro and in vivo studies were conducted using a bioactive poly(epsilon-caprolactone)-organosiloxane nanohybrid containing calcium, which was prepared by sol-gel method. The behavior of human bone marrow stromal cells (hBMSCs) during in vitro osteogenic differentiation were evaluated on poly(epsilon-caprolactone)-organosiloxane nanohybrid and poly(epsilon-caprolactone)-organosiloxane nanohybrid coated with apatite, which mimicked in vivo events. hBMSCs cultured on tissue culture plates (TCPs) were used as a control. For comparative studies, in vivo testing was also conducted using poly(epsilon-caprolactone)-organosiloxane nanohybrid and poly(epsilon-caprolactone)-organosiloxane nanohybrid coated with apatite in the diaphyseal bone defects of rabbit tibiae. Initial attachments and early proliferations of hBMSCs onto poly(epsilon-caprolactone)-organosiloxane with or without the apatite layer were comparable those onto TCPs. However, the late proliferation and the osteogenic differentiation activities on poly(epsilon-caprolactone)-organosiloxane nanohybrid were significantly lower than the hybrid coated with apatite or TCPs. These results were caused by the delayed detachment of hBMSCs induced by the upward growth of spire-shaped apatite granules on the flat apatite layer through mixed nucleation (heterogeneous and homogeneous nucleation) and growth of apatite crystals during cell culture. However, the poly(epsilon-caprolactone)-organosiloxane nanohybrid showed excellent osteoconductivity as same as poly(epsilon-caprolactone)-organosiloxane nanohybrid coated with apatite in vivo even though the cell testing results in vitro were poor. This discrepancy can be explained by the difference in initial degree of supersaturation of apatite in cell culture medium and buffering ability between cell culture medium and body fluid with respect to calcium, which directly affects the nucleation mechanism of apatite crystals and the morphology of grown apatite granules. These findings imply that much attention is required and an optimal method should be used to assess cell responses in vitro. Our results suggest that precoating the apatite layer before in vitro testing is desirable for bioactive materials that release calcium quickly and in large amount because this treatment can more closely mimic in vivo events.

Metameric effect between dental porcelain and porcelain repairing resin composite.

OBJECTIVES: The objectives were to evaluate the metameric color and hue angle (degrees) changes between dental porcelain and porcelain repairing resin composites. METHODS: Color of three shades (A2, A3, A3.5) of one brand of dental porcelain and three original shades (A2, A3, A3.5) and three combinations (A2-A3, A3-3.5, A2-A3.5) of three brands of porcelain repairing resin composites (ABT, FSP, TCR) were measured relative to the three standard illuminants (D65, A and F2). Specimen was 2mm in thickness, and 1mm of each shade was layered to make combined shades. Color differences (DeltaEab*) between each shade of dental porcelain and repairing resin composites relative to the three illuminants were calculated, and the ratios of color difference (modified metamerism index) by the change of illuminant were calculated. The ratios of hue angle changes were also compared. RESULTS: Differences in modified metamerism index and the ratio of hue angle changes were influenced by the porcelain shade, brand of resin composites and shade of resin composites. In all three brands of resin composites, A3.5 shade showed the smallest values in modified metamerism index regardless of the shade of porcelain. The average ratio of hue angle changes between each porcelain shade and all the shades of each resin composites showed similar trend when illuminant was changed from D65 to F2. SIGNIFICANCE: Metameric effect between dental porcelain and repairing resin composites varied depending on the shade of porcelain, brand of resin composite and the illuminant. Therefore, shade matching between porcelain and repairing resin composite should be performed carefully. This study confirmed that shades should be matched under the light corresponding to that of use.

Preparation of a non-woven poly(ε-caprolactone) fabric with partially embedded apatite surface for bone tissue engineering applications by partial surface melting of poly(ε-caprolactone) fibers.

This article describes a novel method for the preparation of a biodegradable non-woven poly(ε-caprolactone) fabric with a partially embedded apatite surface designed for application as a scaffold material for bone tissue engineering. The non-woven poly(ε-caprolactone) fabric was generated by the electro-spinning technique and then apatite was coated in simulated body fluid after coating the PVA solution containing CaCl2 ·2H2 O. The apatite crystals were partially embedded or fully embedded into the thermoplastic poly(ε-caprolactone) fibers by controlling the degree of poly(ε-caprolactone) fiber surface melting in a convection oven. Identical apatite-coated poly(ε-caprolactone) fabric that did not undergo heat-treatment was used as a control. The features of the embedded apatite crystals were evaluated by FE-SEM, AFM, EDS, and XRD. The adhesion strengths of the coated apatite layers and the tensile strengths of the apatite coated fabrics with and without heat-treatment were assessed by the tape-test and a universal testing machine, respectively. The degree of water absorbance was assessed by adding a DMEM droplet onto the fabrics. Moreover, cell penetrability was assessed by seeding preosteoblastic MC3T3-E1 cells onto the fabrics and observing the degrees of cell penetration after 1 and 4 weeks by staining nuclei with DAPI. The non-woven poly(ε-caprolactone) fabric with a partially embedded apatite surface showed good water absorbance, cell penetrability, higher apatite adhesion strength, and higher tensile strength compared with the control fabric. These results show that the non-woven poly(ε-caprolactone) fabric with a partially embedded apatite surface is a potential candidate scaffold for bone tissue engineering due to its strong apatite adhesion strength and excellent cell penetrability. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1973-1983, 2017.

Comparison of mechanical and biological properties of zirconia and titanium alloy orthodontic micro-implants.

OBJECTIVE: The aim of this study was to compare the initial stability as insertion and removal torque and the clinical applicability of novel orthodontic zirconia micro-implants made using a powder injection molding (PIM) technique with those parameters in conventional titanium micro-implants. METHODS: Sixty zirconia and 60 titanium micro-implants of similar design (diameter, 1.6 mm; length, 8.0 mm) were inserted perpendicularly in solid polyurethane foam with varying densities of 20 pounds per cubic foot (pcf), 30 pcf, and 40 pcf. Primary stability was measured as maximum insertion torque (MIT) and maximum removal torque (MRT). To investigate clinical applicability, compressive and tensile forces were recorded at 0.01, 0.02, and 0.03 mm displacement of the implants at angles of 0°, 10°, 20°, 30°, and 40°. The biocompatibility of zirconia micro-implants was assessed via an experimental animal study. RESULTS: There were no statistically significant differences between zirconia micro-implants and titanium alloy implants with regard to MIT, MRT, or the amount of movement in the angulated lateral displacement test. As angulation increased, the mean compressive and tensile forces required to displace both types of micro-implants increased substantially at all distances. The average bone-to-implant contact ratio of prototype zirconia micro-implants was 56.88 ± 6.72%. CONCLUSIONS: Zirconia micro-implants showed initial stability and clinical applicability for diverse orthodontic treatments comparable to that of titanium micro-implants under compressive and tensile forces.

Difference in color and color parameters between dental porcelain and porcelain-repairing resin composite.

The objective of this study was to measure the differences in color and color parameters between dental porcelain and porcelain-repairing resin composites. The colors of three shades (A2, A3, A3.5) of one brand of dental porcelain, three original shades (A2, A3, A3.5), and three combinations (A2/A3, A3/3.5, A2/A3.5) of three brands of porcelain-repairing resin composites (ABT, FSP, TCR) were measured. The specimens were 2 mm thick, and 1 mm of each shade was layered to make combined shades. Differences in color (DeltaE(ab) (*)), lightness (DeltaL*), chroma (DeltaC(ab) (*)), and hue (DeltaH(*)) between porcelain and resin composite were calculated. Color difference was calculated as DeltaE(ab) (*) = (DeltaL*(2) + Deltaa*(2) + Deltab*(2))(1/2), chroma difference was calculated as DeltaC(ab) (*) = (Deltaa*(2) + Deltab*(2))(1/2), and hue difference was calculated as DeltaH(ab) (*) = (DeltaE(ab) (*2) - DeltaL*(2) - DeltaC(ab) (*2))(1/2). The influence of porcelain shade, brand of resin composites, and shade of resin composites were analyzed by three-way analyses of variance, and the differential influence of color parameters on color difference was analyzed with multiple regression analysis (alpha = 0.05). Differences in color and color parameters were influenced by the porcelain shade, brand and shade of resin composites. The DeltaE(ab) (*) value was in the range of 2.2-16.9. The DeltaE(ab) (*) value was correlated with DeltaC(ab) (*) (standardized correlation coefficient, beta = - 0.85), DeltaL* (beta = - 0.52), and DeltaH(ab) (*) (beta = 0.08). Between the same shade designated pairs of porcelain and repairing composite, color difference was perceptible. Therefore, studies to improve the color matching between porcelain and repairing resin are recommended.

Changes in color and translucency of porcelain-repairing resin composites after thermocycling.

The objective of this study was to determine the changes in color and translucency of dental porcelain-repairing resin composites compared to dental porcelain after thermocycling. Color and spectral reflectance of three shades (A2, A3, and A3.5) of one brand of dental porcelain and three basic shades (A2, A3, and A3.5) and three combinations (A2/A3, A3/3.5, and A2/A3.5) of three brands of porcelain-repairing resin composites (ABT, FSP, and TCR) were measured, before and after thermocycling for 3000 cycles, relative to the illuminant D65. The specimen was 2 mm in thickness, and 1 mm of each shade was layered to make combined shades. Changes in color (DeltaE*ab) and translucency parameter (DeltaTP) were calculated. A general linear model by the material (porcelain or resin composite) and shade was used to compare differences (alpha = 0.05). The range of color changes was 0.68-1.67 in porcelain, 0.56-1.30 in ABT, 2.28-3.10 in FSP, and 0.36-1.15 in TCR. The range of DeltaTP was 0.45-0.96 in porcelain, -0.48 to 0.94 in ABT, -1.31 to 0.82 in FSP, and -0.51 to 1.91 in TCR. After thermocycling, changes in color and TP were correlated with the shade of the material, but not with the material. The discrepancy in the changes of color and translucency after thermocycling between porcelain and porcelain-repairing resin composites should be considered when selecting repairing materials.

Color and translucency of A2 shade resin composites after curing, polishing and thermocycling.

This study determined the differences in values and changes of color and translucency of eight brands of A2 shade resin composites after curing, polishing and thermocycling (TC). The color of specimens 10-mm in diameter and 2-mm thick was measured on a reflection spectrophotometer with SCE geometry under D65 illumination over a white and black background. Measurements were obtained before curing, after curing, after polishing and after TC. The color change (deltaE*ab), translucency parameter (TP) and contrast ratio (CR) were then compared. The range of deltaE*ab after curing was 3.8 to 10.2 (average deltaE*ab for the eight composites = 6.4), which was deemed perceptible to the observer. Polishing caused deltaE*ab of 1.9 to 4.5, which was perceptible in five of the eight composites. After 2,000 TC, deltaE*ab was 0.4 to 1.3. TP values tended to increase after curing and decrease after TC (range before curing was 7.1 to 17.2). Changes in TP values after curing were statistically significant in all composites (p<0.05). Changes in CR values were similar to the translucency changes in TP. Though the composite shades were all designated as A2, color coordinates, TP and CR values, changes in color and translucency after curing, polishing and thermocycling varied by brand.