Tensile Bond Strength of a Highly Cross-Linked Denture Tooth to the Compression-Molded and Injection-Molded Denture Base Polymers

This study compared tensile bond strengths between conventional compression-molded heat (HC)-, auto (AP)-, and microwave-polymerized (MC) poly(methyl methacrylate)-based denture resins and a relatively new injection-molded, microwave-polymerized polyurethane based resin (MI) bonded to a highly cross-linked denture tooth. In the first part of the experiments, denture teeth were used as received. In the second part, they were treated with dichloromethane to see its effect on bonding of conventional denture bases (HCS and APS). Bond strength was tested in tension according to ADA specification No.15. The results showed that the HC group failed cohesively because of higher interface bonding (49.95 MPa) compared with those of the others (AP: 25.41 MPa; MC: 22.06 MPa; MI: 20.02 MPa). The application of dichloromethane improved bond strengths of HCS and APS groups (60.61 and 32.03 MPa, respectively). It was suggested that dichloromethane could be applied on the denture teeth ridge lap area prior to denture base processing to enhance adhesion between the tooth/resin.     

Residual monomer content and its release into water from the denture base nanocomposite using organic montmorillonite as reinforcement

A novel kind of denture base nanocomposite was prepared by polymethyl methyacrylate（PMMA） and cethyltrimethylammonium bromide modified organic montmorillonite （OMMT）. The dispersion of montmorillonite in the polymer matrix was characterized by x-ray diffraction （XRD） and transimission electron microscope （TEM）.The content of residual MMA in nanocomposites and the amount of MMA released to water from nanocomposites were determined by gas chromatography （GC）. The analysis of TEM and XRD showed that exfoliated-intercalated and intercalated nanocomposites were formed when the content of OMMT was 3% and 5% in the PMMA powder respectively. The results of GC showed that the residual MMA increased with the increase of OMMT content in the polymer matrix. After 7 days in water, the amount of MMA released into water from the nanocomposites tended to be stable. The results of one-way ANOVA and t-test showed that OMMT gave a significant increase of residual MMA concentration （p〈0.05） in nanocomposites.     

Color stability of denture shade tabs is affected by exposure to daylight and decontamination protocols

The purpose of this study was to investigate the effect of light exposure and decontamination protocols on the color stability of denture shade guide tabs. Fifty tabs for shades 62, 66, and 69 (Biotone IPN, Dentsply Sirona) were submitted to baseline L*a*b* measurements (EasyShade, Vita), separated into 5 experimental groups (n = 10), and subjected to one of the following conditions: G1–distilled water (DW‐H₂O)–control; G2 ?70% alcohol; G3–sodium hypochlorite 1% (NaClO); G4–no light exposure; G5–natural light exposure for 6 months. The experimental conditions were designed to simulate 6 months of clinical use. After the test period, final color measurements were recorded. The mean tristimulus coordinate difference (ΔL*,Δa*,Δb*) and total color difference values () were analyzed using 2‐way ANOVA and the Tukey test, α = .05. G2 (alcohol) produced less (P < .05) color change in shade 69 than G3 (NaClO). G5 (light exposure) affected the color stability for all shades, producing a statistical difference (P < .05) from G4 (no light exposure). It was concluded that natural light changes the color stability of the shade guides and that decontamination with 70% alcohol had the least impact on the color stability of the shade guide tabs.     

可摘局部义齿设计专家系统的研制及应用

本文讨论了可摘局部义齿设计专家系统的研制及应用．这一系统是计算机强大功能与口腔修复专家的临床经验的有机结合,对于口腔修复的教学与临床都具有一定的实际意义．     

Toughening effect of comonomer on acrylic denture base resin prepared via suspension copolymerization

In this article, three copolymers used as denture base resins were prepared via suspension copolymerization using butyl acrylate (BA), butyl methacrylate (BMA), or methyl acrylate (MA) with methyl methacrylate (MMA), respectively. The homopolymers and copolymers were characterized by ¹³C nuclear magnetic resonance (¹³C NMR). The influence of the three comonomers on the mechanical property was investigated in details and the fracture surfaces of copolymer specimens were examined using scanning electron microscopy (SEM). Meanwhile, the T_g values of three copolymers were examined by differential scanning calorimetry (DSC). The results indicate that, poly(methyl methacrylate) (PMMA) copolymers with BA, BMA, or MA have been successfully prepared via suspension copolymerization. The presence of BA, BMA, or MA could improve the mechanical property especially the impact strength, the toughness of the materials was remarkably improved. The toughening effect of BMA monomer is most significant. When the content of BA is 2 wt %, the flexural strength improves by 51% and the impact strength improves by 81.3%. The T_g values of three copolymers all decrease. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of different denture adhesives on retention of complete dentures: an in vivo study

The increase in prevalence of tooth loss with the effect of population aging produces the growing need for complete dentures. The success and acceptance of complete dentures by the patient depends on sufficient retention and stability. Therefore, denture adhesives are regularly used by denture wearers to improve the function of complete denture. We evaluated the effect of three different denture adhesives (Corega, Protefix, Fittydent) on the retention of maxillary complete denture (MCD) using with digital dynamometer (DD). For this purpose, denture adhesives were applied on MCDs of 30 participants. After chewing procedure, the force was applied at 45° to the palatal surface of denture by DD. Dislodgement force was recorded by means of Newton. There were four measurements on each patient including; group of control: Group C; Group CR: Corega; Group F: Fittydent; Group P: Protefix. The result of the study was statistically evaluated by using analysis of variance (ANOVA) and Tukey HSD test. Statistics of ANOVA showed a significant difference among all the four groups (p = 0.00, <0.05). Tukey HSD test indicated that there was a statistical difference between Group F and the other groups, but there was not a significant difference between the other groups. The highest adhesive strength value was observed in group F, the lowest in group C. Use of denture adhesives improved the retentive strength of complete denture.     

开口式牙齿保护器在麻醉中应用研究

目的寻找一种方法避免牙齿活动或缺失患者在麻醉插管操作过程中的进一步损伤。方法通过将开口式牙齿保护器的上下牙托套在上下牙齿或牙床上,撑开撑开器使病人张口度达到插管的要求。结果 13例门齿活动或缺失的老年患者,使用开口式牙齿保护器喉镜放置时间5-7秒,喉镜置入到会厌或声门暴露平均需要27秒左右,无牙齿或牙龈损伤。未使用保护器喉镜置入时操作有困难,60秒内无法完成插管操作,且2例牙齿脱落,4例喉镜片卡在缺失的牙齿中。结论开口式牙齿保护器的使用大大减少插管操作中喉镜对牙齿和牙龈的损伤,同时增大口腔的张口度,缩短操作的时间,对初学者尤为实用。     

Antimicrobial Activity of Ozone against Pathogenic Oral Microorganisms on Different Denture Base Resins

ABSTRACT

The present study aimed to evaluate the antimicrobial effect of gaseous ozone against specific oral pathogens on denture base resins. 1080 round samples were prepared (10mm-diameter, 2mm-thickness). Candida albicans, Streptococcus mutans, Streptococcus gordonii, and Aggregatibacter actinomycetemcomitans, polyamide-Deflex, heat-cured polymethyl-methacrylate (PMMA)-QC-20, and cold-cured-PMMA-Meliodent. The doses and durations: 25, 50 and 100µg/ml, 5, 10, 20, 30 minutes. For Cell viability (CV) MTT was used. 100µg/ml was most effective dose for C. albicans, S .gordonii, and A. actinomycetemcomitans were in heat-cured-PMMA and polyamide for S.mutans. For polyamide, lowest CV was 43% in S.mutans and A.actinomycetemcomitans. CV of heat-cure and cold-cure PMMA were 31% and 32% in S.gordonii, respectively. CV was similar for all resins and durations in S.mutans and A.actinomycetemcomitans and for polyamide for C.albicans and for heat-cure PMMA for S.gordonii. 30-min ozone application killed 80% of all microorganisms in all resins except for C.albicans in polyamide (65% cell death) and cold-cure PMMA (57% cell death). Optimal dose/duration combination was 100 µg/ml-10 min. Gaseous ozone can be considered as an effective cleansing agent for denture base resins.     

上颌全口义齿组织的力学分析

对上颌全口义齿组织通过有限元模型作了力学分析；展示了其受力时的变形和应力分布情况。为合理地设计与制作义齿提供了一些分析结果和有益的建议。     

An intelligent dental robot

An intelligent dental robot (IDR) is reported for the purpose of artificial denture verification and test. Methods: The IDR is composed of power system, intelligent control and driving system, sensor system and supporting system. Five Maxon motors are adopted to provide the driving force for the IDR. Novel motor linear actuators are developed to mimic the movement of human’s masticatory muscles. Forward and inverse kinematics of the IDR are analyzed. Seven high-precision pressure sensors are utilized to detect the force on individual artificial tooth. Results: Motion and force experiments are conducted on the IDR. The maximum biting force provided by the IDR is 490?N. Hysteresis rate of the biting force loading and unloading is less than 3%. The largest displacement for the mandible movement test is found to be 60, 9 and 22?mm in the vertical, protrusive and lateral directions, respectively. Conclusion: IDR can complete simulated human masticatory movement and provide sufficient biting force. Significance: The IDR provides clinical guidance for the design and performance test of artificial denture.