锶强化生物活性玻璃牙釉质粘合树脂的抗菌性能与机械性能测试

目的通过向正畸牙釉质粘合树脂中添加锶强化生物活性玻璃,并对其抗菌性能及机械性能进行测试,寻求合适的添加比例,为正畸临床应用提供理论依据。方法分别将质量分数为1%、2%、3%、4%、5%的锶强化生物活性玻璃掺入到牙釉质粘合树脂中作为实验组,分别为1、2、3、4及5组,未掺入锶强化生物活性玻璃的牙釉质粘合树脂作为对照组,即0组。采用抑菌环法和贴膜法对以上各组进行抑菌活性测试;应用万能试验机对以上各组的剪切强度进行测试,观察并记录托槽脱落后牙面牙釉质粘合树脂残留指数(adhesive resin residual,ARI)。结果各实验组及对照组均未出现抑菌环,实验组4和5组的抗菌率达到99.9%,具有强抗细菌作用。实验各组的剪切强度与对照组相比,均有显著性差异(P<0.05)。实验各组之间比较,随掺入比例增加,剪切强度呈现降低趋势,但无统计学差异(P>0.05)。实验各组剪切强度均在临床可接受的剪切强度范围内,能够满足正畸临床要求。实验各组及对照组牙面均有牙釉质粘合树脂残留,ARI计分均在2~4分之间,各组间ARI计分比较无统计学差异(P>0.05)。结论掺入4%质量分数的锶强化生物活性玻璃的正畸牙釉质粘合树脂既表现出强抗菌作用,剪切强度又能够达到正畸临床需要,并对釉质表面粘合树脂的残留量无影响。     

生物活性玻璃改性树脂粘接剂对牙本质脱矿及树脂粘接强度的影响

目的 研究生物活性玻璃（BG）改性树脂粘接剂抑制牙本质脱矿及对树脂-牙本质微拉伸粘接强度的影响。方法 将硅烷偶联剂表面处理后的BG与Single Bond 2粘接剂混合制备出30%、40%和50%的BG改性的树脂粘接剂,选择上颌前磨牙40颗,随机分为4组,阴性对照组（不添加BG）、30%BG组、40%BG组、50%BG组,每组10颗。根据分组分别采用相应BG含量的粘接剂制备树脂-牙本质粘接试件。将制备的粘接试件在37 ℃水浴中浸泡24 h后进行微拉伸粘接强度测试。每组选择1个牙片浸泡在pH 4.0的人工唾液中1周,每24 h测试溶液的pH值。结果 阴性对照组、30%BG组、40%BG组、50%BG组的粘接强度分别为（27.76±0.29）、（27.05±0.58）、（26.95±0.69）和（25.12±0.24）MPa。对照组和30%BG组的粘接强度无统计学差异（P=0.06）,和40%BG组、50%BG组有统计学差异（P=0.04,P=0.00）;30%、40%BG组的粘接强度高于50%BG组（P=0.00,P=0.00）。随着BG含量的增加,pH值也逐渐增高。结论 含有BG的树脂粘接剂可以有效抑制牙本质的脱矿,30%BG组对短期的粘接强度无明显影响,50%BG组抑制脱矿能力最强,但是粘接强度较低。     

Inhibition of enamel demineralization by buffering effect of S‐PRG filler‐containing dental sealant

The buffering capacity and inhibitory effects on enamel demineralization of two commercially available dental sealants were evaluated in this study. The effects of filler particles were also examined. Disks of enamel and cured sealant materials of BeautiSealant (silica or S‐PRG filler) or Teethmate F‐1 were incubated in lactic acid solutions (pH 4.0) for 1–6 d. The pH changes and amounts of ions released in the solutions were assessed, and enamel surfaces were observed using a scanning electron microscope. The pH of the solution with BeautiSealant (S‐PRG filler) was neutralized from pH 4.0 to pH 6.1 (after incubation for 1 d) and from pH 4.0 to pH 6.7 (after incubation for 6 d). In addition, no release of calcium ions was detected and the enamel surface was morphologically intact in scanning electron microscopy images. However, the pH of the solution with Teethmate F‐1 remained below pH 4.0 during incubation from days 1 to 6. Calcium release was increased in solutions up to and after 6 d of incubation. Scanning electron microscopy images showed that the structures of hydroxyapatite rods were exposed at the specimen surfaces as a result of demineralization. Ions released from S‐PRG filler‐containing dental sealant rapidly buffered the lactic acid solution and inhibited enamel demineralization.     

Wear characteristics and inhibition of enamel demineralization by resin‐based coating materials

In this study, wear and inhibition of enamel demineralization by resin‐based coating materials were investigated. Seven commercially available coating materials, with and without fillers, were used. A mechanical wear test was performed, and the specimens were then examined with a scanning electron microscope. Hardness and elastic modulus measurements for each material were obtained by nanoindentation testing. Thin layers of each material were applied on human enamel surfaces, which were subjected to alternating immersion in demineralizing and remineralizing solutions. The inhibition ability of enamel demineralization adjacent to the coating was estimated with depth‐dependent mechanical properties using the nanoindentation test. The non‐filled coating material showed significantly lower hardness, lower elastic modulus, and higher weight loss. There were no significant differences in weight loss among the six filled coating materials. After the alternating immersion protocol, the enamel specimens having application of coating materials with ion‐releasing ability were harder than those in the other groups in some locations 1–11 μm from the enamel surface and within 300 μm from the edge of the coating materials. In conclusion, clinical use of the resin‐based coating materials with ion‐releasing ability may prevent demineralization of exposed enamel adjacent to the coating during treatment.     

Effect of implant design and bioactive glass coating on biomechanical properties of fiber‐reinforced composite implants

This study aimed to evaluate the influence of implant design and bioactive glass (BAG) coating on the response of bone to fiber‐reinforced composite (FRC) implants. Three different FRC implant types were manufactured for the study: non‐threaded implants with a BAG coating; threaded implants with a BAG coating; and threaded implants with a grit‐blasted surface. Thirty‐six implants (six implants for each group per time point) were installed in the tibiae of six pigs. After an implantation period of 4 and 12 wk, the implants were retrieved and prepared for micro‐computed tomography (micro‐CT), push‐out testing, and scanning electron microscopy analysis. Micro‐CT demonstrated that the screw‐threads and implant structure remained undamaged during the installation. The threaded FRC/BAG implants had the highest bone volume after 12 wk of implantation. The push‐out strengths of the threaded FRC/BAG implants after 4 and 12 wk (463°N and 676°N, respectively) were significantly higher than those of the threaded FRC implants (416°N and 549°N, respectively) and the nonthreaded FRC/BAG implants (219°N and 430°N, respectively). Statistically significant correlation was found between bone volume and push‐out strength values. This study showed that osseointegrated FRC implants can withstand the static loading up to failure without fracture, and that the addition of BAG significantly improves the push‐out strength of FRC implants.     

Acid neutralizing,mechanical and physical properties of pit and fissure sealants containing melt-derived 45S5 bioactive glass

Objectives

The aim of this study was to examine the effects of 45S5 bioactive glass (BAG) on the acid neutralizing, mechanical and physical properties of pit and fissure sealants.

Methods

45S5BAG (<25 μm) was mixed with the silanized glass (180 ± 30 nm) and added into a resin matrix [Bis-GMA/TEGDMA 50/50 (wt%) containing 1% of DMAEMA/CQ 2:1 (wt%)] with varying filler proportions; 0% 45S5BAG + 50% glass (BAG0); 12.5% 45S5BAG + 37.5% glass (BAG12.5); 25% 45S5BAG + 25% glass (BAG25); 37.5% 45S5BAG + 12.5% glass (BAG37.5); and 50% 45S5BAG + 0% glass (BAG50). To evaluate the acid neutralizing properties, specimens were immersed in lactic acid solution (pH 4.0). Then, the change in pH and the time required to raise the pH from 4.0 to 5.5 were measured. In addition, flexural strength, water sorption and solubility were analyzed.

Results

The acid neutralizing properties of each group exhibited increasing pH values as more 45S5BAG was added, and the time required to raise the pH from 4.0 to 5.5 became shorter as the proportion of 45S5BAG increased (P < 0.05). Additionally, the flexural strength decreased according to the increasing proportions of 45S5BAG added (P < 0.05). Water sorption showed an increasing trend with increasing proportions of 45S5 BAG added (P < 0.05). However, the solubility results were similar among the groups (P > 0.05), except for BAG50.

Significance

The novel pit and fissure sealants neutralized the acid solution (pH 4.0) and exhibited appropriate mechanical and physical properties. Therefore, these compounds are suitable candidates for caries-inhibiting dental materials.     

Influence of application method on surface free‐energy and bond strength of universal adhesive systems to enamel

The aim of the present study was to determine the influence of different adhesive application methods and etching modes on enamel bond effectiveness of universal adhesives using shear bond strength (SBS) testing and surface free‐energy (SFE) measurements. The adhesives Scotchbond Universal, All‐Bond Universal, Adhese Universal, and G‐Premio Bond were used. Prepared bovine enamel specimens were divided into four groups, based on type of adhesive, and subjected to the following surface treatments: (i) total‐etch mode with active application; (ii) total‐etch mode with inactive application; (iii) self‐etch mode with active application; and (iv) self‐etch mode with inactive application. Bonded specimens were subjected to SBS testing. The SFE of the enamel surfaces with adhesive was measured after rinsing with acetone and water. The SBS values in total‐etch mode were significantly higher than those in self‐etch mode. In total‐etch mode, significantly lower SBS values were observed with active application compared with inactive application; in contrast, in self‐etch mode there were no significant differences in SBS between active and inactive applications. A reduction in total SFE was observed for active application compared with inactive application. The interaction between etching mode and application method was statistically significant, and the application method significantly affected enamel bond strength in total‐etch mode.     

Relationship between mechanical properties and bond durability of short fiber‐reinforced resin composite with universal adhesive

The purpose of this study was to determine the relationship between mechanical properties and bond durability of short fiber‐reinforced resin composite with universal adhesive. As controls, micro‐hybrid and nano‐hybrid resin composites were tested. The universal adhesives used were Scotchbond Universal, Adhese Universal, and G‐Premio Bond. The fracture toughness and flexural properties of resin composites, and shear bond strength and shear fatigue strength of universal adhesive with resin composite using both total‐etch and self‐etch modes were determined. In the results, short fiber‐reinforced resin composite showed significantly higher fracture toughness than did micro‐hybrid and nano‐hybrid resin composites. The flexural strength and modulus of short fiber‐reinforced and nano‐hybrid resin composites were significantly lower than were those of micro‐hybrid resin composites. Regardless of etching mode, the shear bond strength of universal adhesives with short fiber‐reinforced resin composite did not show any significant differences from micro‐hybrid and nano‐hybrid resin composites. The shear fatigue strength of universal adhesives with short fiber‐reinforced resin composite and micro‐hybrid resin composites were significantly higher than that of nano‐hybrid resin composites. The results of this study suggest that the mechanical properties of short fiber‐reinforced resin composite improve their bond durability with universal adhesive.     

Degradation properties and ion release characteristics of Resilon® and phosphate glass/polycaprolactone composites

Aims To (i) characterise the degradation pattern and ion release characteristics of bioactive glass/polycaprolactone (PCL) composites; (ii) compare the degradation behaviour of composites containing phosphate glass to that of Resilon^®; and (iii) determine the potential to control the degradation of the composites by modifying the iron content of phosphate glasses. Methodology The degradation behaviour of the phosphate glass/PCL samples (n = 3) and that of Resilon^® were determined in two aqueous solutions (buffered distilled water, Hanks Buffered Saline Solution) over a 7‐day period using weight change measurement, ion chromatography, light microscopy (LM) and scanning electron microscopy (SEM). Results An initial increase in weight of the samples was followed by loss. All phosphate glass/PCL composites released various amounts of iron, sodium, calcium and phosphate ions into solution. The Resilon^® samples released only sodium and calcium ions. The visual methods (LM, SEM) showed distinct precipitate (calcium phosphate) formation on the surface of the phosphate glass/PCL composites but only a faint surface residue on the surface of Resilon^®. Conclusions The degradation pattern of the composites containing phosphate glass was different from that of Resilon^®. The phosphate glass/PCL composites encouraged precipitate formation on the material surface, which may be advantageous in creating a marginal and apical seal.