美白凝胶及酸性饮料对离体牙釉质结构的影响

目的:观察漂白剂对牙齿脱矿的作用.方法:分别用Beyond美白胶贴片、可乐、橙汁在人工唾液中浸泡离体牙,经过即刻,7天,14天后分别用扫描电镜观察分析表面形貌和Ca/P含量变化,显微硬度仪检测釉质改变.结果:处理后3组样品的即刻Ca/P比值和平均显微硬度均降低,且明显小于对照组(P＜0.05);7天后逐渐提高,14天后与对照组差异无统计学意义(P＞0.05).橙汁组的Ca/P比值和平均显微硬度在处理后即刻处理组内对比中略小于漂白和可乐组.结论:漂白剂对人牙釉质有一过性脱矿作用,随着时间推移,釉质可再矿化而修复;漂白剂引起的脱矿与日常饮用的酸性饮料比较属于正常脱矿范围.     

光学相干成像无创检测不同漂白方法对釉质白斑治疗效果的实验研究

目的 探讨采用光学相干成像技术(OCT)检测不同漂白方法对釉质白斑的治疗效果,评价其用于釉质白斑治疗效果监测的可行性。方法 选取因正畸拔除的完整离体前磨牙48颗,在牙冠颊面正中切取4 mm×4 mm×2 mm釉质块。在其表面(除颊侧面外)涂布抗酸指甲油后,置于脱矿溶液中浸泡18 d,建立釉质白斑体外脱矿模型。将样本随机分为4组(n=12),A组为对照组仅脱矿处理;B组为40%过氧化氢漂白处理;C组为Icon渗透树脂处理;D组为40%过氧化氢漂白联合Icon渗透树脂处理。每组随机抽取8个样本,应用OCT扫描釉质块颊侧面,观察各组釉质表层成像变化并测量表层光强改变;将釉质块用环氧树脂包埋固定(仅暴露颊侧面),显微硬度仪测量并记录各组硬度值变化。各组剩余4个样本纵向切开,扫描电镜观察各组样本超微结构变化。结果 OCT显示,各组釉质表层光散射特性均发生改变,可见高亮层形成,但C、D组的高亮层厚度显著低于A、B组(P<0.05)。各组样本显微硬度值分别是(214.99±31.70)、(250.66±33.64)、(312.42±18.01)、(286.53±26.65)kg/mm^...     

ƫ�����������ϼ��������ͼ���������������ȥ�Ժ������ѿ�̶ȵ��о�

目的探讨偏振数码照相结合计算机辅助图像分析法评价邻面去釉后釉质脱矿程度的准确性。方法于2010年3月选取青岛大学医学院附属医院口腔外科门诊因正畸需要拔除的上颌第一前磨牙40颗,沿牙冠颊舌向磨切得到80个标本,随机分为A（空白对照,未进行任何去釉处理）、B（邻面去釉）、C（邻面去釉后使用氟化泡沫）、D（邻面去釉后使用护牙素）4组。体外pH循环60d后,用偏振数码照相结合计算机辅助图像分析法定量测量各组标本邻面去釉及再矿化后的灰度值,以此来评价其釉质脱矿程度。同时用显微硬度仪定量测量各组标本的硬度值作为对照。结果（1）灰度值：A组灰度值最低,B组灰度值最高,C组和D组经过再矿化处理后灰度值较B组降低,差异有统计学意义（P〈0．05）。c组和A、D组之间灰度值差异无统计学意义（P〉0．05）。（2）硬度值：A组硬度值最高,B组硬度值最低,c组和D组经过再矿化处理后硬度值升高,但均较A组低。B组硬度值和其他3组之间比较,差异均有统计学意义（P〈0．05）,而A组与c组、c组与D组之间硬度值比较,差异均无统计学意义（P〉0．05）。结论偏振数码照相结合计算机辅助图像分析法得出的结果与显微硬度仪的定量检测结果相符合,表明了其是一种有效的定量评价釉质脱矿及再矿化效果的方法,值得临床推广。     

多乐氟预防碳酸饮料对乳牙釉质脱矿的体外研究

目的:证实多乐氟能预防碳酸饮料对乳牙牙釉质的脱矿作用。方法:将72个乳牙釉质块随机分成4组,每组18块。人工唾液为对照组(A);可乐碳酸饮料浸泡组(B);多乐氟处理后可乐浸泡组(C);氟化泡沫处理后可乐浸泡组(D)。A组试件不作处理,B组试件浸泡于可乐中30 min,取出后用去离子水冲洗干净放置约4 min,再次浸泡于可乐中30 min,如此循环直至12 h。实验C、D组釉质块分别浸在多乐氟、氟化泡沫涂抹4 min后,后续处理同B组。上述处理后试件分别用扫描电镜、能谱分析仪检测釉质表面的形态变化及Ca²⁺、P³⁺含量( 重量百分比)。结果:对A组相比,可乐浸泡可致乳牙釉质表面脱矿;氟化物处理后可降低釉质表面的脱矿程度,并使晶体颗粒体积变大,其表面Ga²⁺、P³⁺含量的降低程度也低于B组,差异有统计学意义(P<0.05)。结论:多乐氟可抑制乳牙釉质在碳酸饮料中的脱矿,效果较好,并能促进其再矿化。     

次氯酸钠和EDTA预处理对釉质白斑树脂渗透效果影响的实验研究

目的:比较不同预处理剂对釉质白斑表面孔隙暴露率、树脂渗透效果和表面显微硬度的影响。方法:96颗完整离体前磨牙在牙冠颊面正中切取4 mm×4 mm×2 mm釉质块。经体外脱矿3 d建立釉质白斑脱矿模型。将样本随机分为4组(n=24):A组为对照组;B组用5.25%NaClO预处理;C组用17%EDTA预处理;D组用5.25%NaClO+17%EDTA联合处理,所有样本预处理结束后均使用15%盐酸酸蚀处理。每组各8个样本观察计算釉质表面孔隙暴露面积和暴露率;每组另取8个样本经树脂渗透治疗后观察树脂渗透深度和渗透面积百分比;每组剩余8个样本测量树脂渗透前后釉质表面显微硬度值。结果:与A组相比,B、C、D组样本的釉质表面孔隙暴露面积、暴露率、树脂渗透深度、渗透面积百分比和树脂渗透后釉质表面显微硬度均显著提高(P<0.05);经17%EDTA或5.25%NaClO+17%EDTA处理后,C、D组脱矿釉质的显微硬度值明显低于A、B组(P<0.05)。结论:5.25%NaClO和17%EDTA预处理均可显著增加釉质孔隙暴露率,提高树脂渗透深度和表面显微硬度,但17%EDTA预处理会降低脱...     

多乐氟、护牙素及含氟牙膏促进釉质再矿化的体外研究

目的:比较多乐氟、护牙素和含氟牙膏促进脱矿釉质再矿化的效果。方法:将40个牛牙釉质块人工龋试样随机分为4组(n=10),A组(对照组)置于人工唾液中浸泡12 d;B组(多乐氟组)釉质表面涂覆多乐氟涂膜,12 h后去除涂膜,置于人工唾液中浸泡12 d;C组(护牙素组)釉质表面涂覆护牙素1 min后,置于人工唾液中浸泡12 d;D组(含氟牙膏组)分别于每天早、晚将样本浸泡于含氟牙膏浆3 min,其余时间浸泡于人工唾液中,共12 d。脱矿前及处理前后,用硬度计测定各组釉质表面的显微硬度,计算其表面硬度恢复率(SMHR%);SEM观察表面结构。结果:SEM观察发现,B、C、D组再矿化处理前后釉质表面有新形成的羟基磷灰石晶体沉积。A、B、C、D组的SMHR(%)分别为20.43±5.91、60.55±14.05、67.69±11.74、52.82±3.61;除B、C组无统计学差异(P>0.05),其他各组间两两相比均有统计学差异(P<0.05)。结论:含氟材料或亚稳定无定形磷酸钙材料(护牙素)均可显著促进脱矿釉质的再矿化,护牙素的效果最好。     

渗透树脂治疗乳牙釉质早期龋的体外研究

目的：探讨渗透树脂治疗人工脱矿乳牙釉质早期龋对其釉质显微硬度的影响。方法：选取5～7岁儿童因滞留拔除的无龋下颌乳中切牙21颗,制备人工脱矿釉质模型后,随机将其分为空白对照组、脱矿组、渗透树脂治疗组,每组7个样本,采用显微硬度测试仪测量各组牙釉质显微硬度,观察釉质显微硬度的变化。结果：空白对照组、渗透树脂治疗组牙釉质表面显微硬度明显高于脱矿组,差异具有统计学意义（P＜0．01）;渗透树脂治疗组显微硬度低于空白对照组,差异具有统计学意义（P＜0．01）。结论：乳牙釉质脱矿后牙釉质表面显微硬度降低,渗透树脂治疗釉质脱矿可提高牙釉质表面的显微硬度。     

渗透树脂和多乐氟处理脱矿釉质后的抗酸性和再矿化能力比较

目的 通过观察渗透树脂与多乐氟处理脱矿釉质后其牙齿表面显微硬度和粗糙度的变化,对两种材料在釉质抗酸性和再矿化能力方面的性能进行评估。方法 选择正畸拔除的健康前磨牙48颗,建立釉质表面脱矿模型,按照不同材料的处理条件随机分为4组,A（不做任何处理）,B（渗透树脂）,C（多乐氟）;D（渗透树脂+多乐氟）,分别经脱矿液组（1d,3d）和再矿化液组（7d）浸泡处理后,测定牙齿表面的显微硬度和粗糙度。结果 不同材料处理脱矿模型后即刻,B、D组的显微硬度、粗糙度均明显增加（P<0.001）,B、D组之间无统计学差异（P>0.05）;而C组显微硬度、粗糙度均明显减低（P<0.001）。继续脱矿（1d,3d）后,各组的显微硬度均下降,而粗糙度却明显增加;再矿化7d后,A、C组显微硬度和粗糙度均显著增加（P<0.001）,B、D组增加不明显（P>0.05）。结论 渗透树脂具有良好的改善牙齿表面硬度的作用,但在抗酸性和促进牙齿再矿化方面无明显优势。而氟化物则在抗酸性和促进再矿化方面有突出表现。当两者联合应用时,可以起到较好协同作用,明显增强牙齿的硬度、抗酸性和再矿化性能。     

三种天然药物对脱矿牛切牙釉质显微硬度的影响

目的:比较观察天然药物黄芪、板蓝根、隔山消醇提取物溶液对脱矿牛切牙釉质表面显微硬度的影响.方法:将牛切牙在pH =4.0的脱矿溶液中脱矿10d,形成人工釉质龋模型;选取硬度在305 kg/mm2左右的脱矿标本40个,随机分为5组:分别用80 mg/mL黄芪、板蓝根、隔山消醇提取物溶液和20 mg/L NaF溶液(阳性对照)、去离子水(阴性对照),涂擦釉质表面,每天处理4次,每次处理3 min;连续处理15d后,用显微硬度仪测量各标本釉质表面的硬度值,观察再矿化前后显微硬度值的变化.结果:经80 mg/mL黄芪、板蓝根、隔山消醇提取物溶液及20 mg/L NaF溶液处理后的釉质硬度值均较基线值显著增大(P＜0.05),阴性对照组变化不明显(P＞0.05);再矿化处理后各组硬度值由高到低依次为NaF、隔山消、黄芪、板蓝根、去离子水,组间两两相比,除黄芪组与板蓝组间无显著性差异(P＞0.05)外,其余两两之间差异均具有统计学有意义(P＜0.05).结论:80mg/mL的3种天然药物均可明显增强脱矿牛切牙釉质表面的显微硬度,其中以隔山消组的效果最好.     

�ҵ����������������������ѿ����õ�����ʵ���о�

目的探讨体外酪蛋白磷酸肽(CPPs)抑制人牙釉质脱矿的作用。方法选择2006年6—8月在山西医科大学口腔医院因正畸治疗拔除的健康前磨牙30颗,制作30粒圆形平面开窗区釉质块(直径4mm),其余部分由抗酸指甲油涂抹封闭。根据开窗区釉质的显微硬度(HK0.02),将30粒釉质块完全随机分为5组,每组6粒,分别进行5种不同处理(A组:去离子水和去离子水;B组:CPPs和去离子水;C组:去离子水和乳酸;D组:CPPs和乳酸;E组:氟保护剂和乳酸),使用原子吸收光谱分析法检测釉质表面溶出钙量,比较各组溶出钙量的差别。结果A组、B组和E组间钙溶出量差异无统计学意义(P>0.05),C组和D组间钙溶出量差异无统计学意义(P>0.05),但A组、B组和E组均比C组和D组溶出钙量少,差异有统计学意义(P<0.05)。结论CPPs没有直接阻止脱矿的作用,但也不会使釉质表面发生脱矿;氟保护剂形成的漆膜能够有效抵抗酸的腐蚀作用。     

Determining chewing efficiency using a solid test food and considering all phases of mastication

ObjectivesFollowing chewing a solid food, the median particle size, X₅₀, is determined after N chewing cycles, by curve-fitting of the particle size distribution. Reduction of X₅₀ with N is traditionally followed from N ≥ 15–20 cycles when using the artificial test food Optosil^®, because of initially unreliable values of X₅₀. The aims of the study were (i) to enable testing at small N-values by using initial particles of appropriate size, shape and amount, and (ii) to compare measures of chewing ability, i.e. chewing efficiency (N needed to halve the initial particle size, N(1/2-Xo)) and chewing performance (X₅₀ at a particular N-value, X_50,N).Design8 subjects with a natural dentition chewed 4 types of samples of Optosil particles: (1) 8 cubes of 8 mm, border size relative to bin size (traditional test), (2) 9 half-cubes of 9.6 mm, mid-size; similar sample volume, (3) 4 half-cubes of 9.6 mm, and 2 half-cubes of 9.6 mm; reduced particle number and sample volume. All samples were tested with 4 N-values. Curve-fitting with a 2nd order polynomial function yielded log(X₅₀)-log(N) relationships, after which N(1/2-Xo) and X_50,N were obtained.ConclusionsReliable X₅₀-values are obtained for all N-values when using half-cubes with a mid-size relative to bin sizes. By using 2 or 4 half-cubes, determination of N(1/2-Xo) or X_50,N needs less chewing cycles than traditionally. Chewing efficiency is preferable over chewing performance because of a comparison of inter-subject chewing ability at the same stage of food comminution and constant intra-subject and inter-subject ratios between and within samples respectively.     

Simultaneous determination of epinephrine and uric acid at a gold electrode modified by a 2-(2,3-dihydroxy phenyl)-1, 3-dithiane self-assembled monolayer

In the present paper, the use of a gold electrode modified by 2-(2,3-dihydroxy phenyl)-1,3-dithiane self-assembled monolayer (DPDSAM) for the determination of epinephrine (EP) and uric acid (UA) was described. Initially, cyclic voltammetry was used to investigate the redox properties of this modified electrode at various scan rates. The apparent charge transfer rate constant, k_s, and transfer coefficient, α, were calculated. Next, the mediated oxidation of EP at the modified electrode was described. At the optimum pH of 8.0, the oxidation of EP occurs at a potential about 155 mV less positive than that of an unmodified gold electrode. The values of electron transfer coefficients (α = 0.356), catalytic rate constant (k = 1.624 × 10⁴ M⁻¹ s⁻¹) and diffusion coefficient (D = 1.04 × 10⁻⁶ cm² s⁻¹) were calculated for EP, using electrochemical approaches. Based on differential pulse voltammetry, the oxidation of EP exhibited a dynamic range between 0.7 and 500.0 μM and a detection limit (3σ) of 0.51 μM. Furthermore, simultaneous determination of EP and UA at the modified electrode was described. Finally, this method was used for the determination of EP in EP ampoule.     

Network structures of Bis-GMA/TEGDMA resins differ in DC, shrinkage-strain, hardness and optical properties as a function of reducing agent

Objectives

To evaluate the influence of different tertiary amines on degree of conversion (DC), shrinkage-strain, shrinkage-strain rate, Knoop microhardness, and color and transmittance stabilities of experimental resins containing BisGMA/TEGDMA (3:1 wt), 0.25 wt% camphorquinone, 1 wt% amine (DMAEMA, CEMA, DMPT, DEPT or DABE). Different light-curing protocols were also evaluated.

Methods

DC was evaluated with FTIR-ATR and shrinkage-strain with the bonded-disk method. Shrinkage-strain-rate data were obtained from numerical differentiation of shrinkage-strain data with respect to time. Color stability and transmittance were evaluated after different periods of artificial aging, according to ISO 7491:2000. Results were evaluated with ANOVA, Tukey, and Dunnett's T3 tests (α = 0.05).

Results

Studied properties were influenced by amines. DC and shrinkage-strain were maximum at the sequence: CQ < DEPT < DMPT ≤ CEMA ≈ DABE < DMAEMA. Both DC and shrinkage were also influenced by the curing protocol, with positive correlations between DC and shrinkage-strain and DC and shrinkage-strain rate. Materials generally decreased in L* and increased in b*. The strong exception was the resin containing DMAEMA that did not show dark and yellow shifts. Color varied in the sequence: DMAEMA < DEPT < DMPT < CEMA < DABE. Transmittance varied in the sequence: DEPT ≈ DABE < DABE ≈ DMPT ≈ CEMA < DMPT ≈ CEMA ≈ DMAEMA, being more evident at the wavelength of 400 nm. No correlations between DC and optical properties were observed.

Significance

The resin containing DMAEMA showed higher DC, shrinkage-strain, shrinkage-strain rate, and microhardness, in addition to better optical properties.     

Differential interactions of Streptococcus gordonii and Staphylococcus aureus with cultured osteoblasts

The impedance of normal osteoblast function by microorganisms is at least in part responsible for the failure of dental or orthopedic implants. Staphylococcus aureus is a major pathogen of bone, and exhibits high levels of adhesion and invasion of osteoblasts. In this article we show that the commensal oral bacterium Streptococcus gordonii also adheres to and is internalized by osteoblasts. Entry of S. gordonii cells had typical features of phagocytosis, similar to S. aureus, with membrane protrusions characterizing initial uptake, and closure of the osteoblast membrane leading to engulfment. The sensitivities of S. gordonii internalization to inhibitors cytochalasin D, colchicine and monensin indicated uptake through endocytosis, with requirement for actin accumulation. Internalization levels of S. gordonii were enhanced by expression of S. aureus fibronectin‐binding protein A (FnBPA) on the S. gordonii cell surface. Lysosomal‐associated membrane protein‐1 phagosomal membrane marker accumulated with intracellular S. aureus and S. gordonii FnBPA, indicating trafficking of bacteria into the late endosomal/lysosomal compartment. Streptococcus gordonii cells did not survive intracellularly for more than 12 h, unless expressing FnBPA, whereas S. aureus showed extended survival times (>48 h). Both S. aureus and S. gordonii DL‐1 elicited a rapid interleukin‐8 response by osteoblasts, whereas S. gordonii FnBPA was slower. Only S. aureus elicited an interleukin‐6 response. Hence, S. gordonii invades osteoblasts by a mechanism similar to that exhibited by S. aureus, and elicits a proinflammatory response that may promote bone resorption.     

Cytotoxicity of alloying elements and experimental titanium alloys by WST-1 and agar overlay tests

ObjectiveThis study was performed to evaluate the biocompatibility of nine types of pure metals using 36 experimental prosthetic titanium-based alloys containing 5, 10, 15, and 20 wt% of each substituted metal.MethodsThe cell viabilities for pure metals on Ti alloys that contain these elements were compared with that of commercially pure (CP) Ti using the WST-1 test and agar overlay test.ResultsThe ranking of pure metal cytotoxicity from most potent to least potent was: Co > Cu > In > Ag > Cr > Sn > Au > Pd > Pt > CP Ti. The cell viability ratios for pure Co, Cu, In, and Ag were 13.9 ± 4.6%, 21.7 ± 10.4%, 24.1 ± 5.7%, and 24.8 ± 6.0%, respectively, which were significantly lower than that for the control group (p < 0.05). Pure Pd and Pt demonstrated good biocompatibility with cell viabilities of 93.8 ± 9.6% and 97.2 ± 7.1%, respectively. The Ti–5Pd alloy exhibited the highest cell viability (128.4 ± 21.4%), which was greater than that of CP Ti. By alloying pure Co or Cu with Ti, the cell viabilities for the Ti–xCo and Ti–xCu alloys increased significantly up to 10 wt% of the alloying element followed by a gradual decrease with a further increase in the concentration of the alloying element. Based on the agar overlay test, pure Ag, Co, Cr, Cu, and In were ranked as ‘moderately cytotoxic’, whereas all Ti alloys were ranked as ‘noncytotoxic’.SignificanceThe cytotoxicity of pure Ag, Co, Cr, Cu, and In suggests a need for attention in alloy design. The cytotoxicity of alloying elements became more biocompatible when they were alloyed with titanium. However, the cytotoxicity of titanium alloys was observed when the concentration of the alloying element exceeded its respective allowable limit. The results obtained in this study can serve as a guide for the development of new Ti-based alloy systems.     

Occlusal alterations in unilateral coronal craniosynostosis

There are few studies on maxillomandibular skeletal alterations. Twenty-one patients with unilateral coronal craniosynostosis were analysed and compared with controls. Landmarks analysed were: sella-nasion-point A and B angles, point A-nasion-point B angle, interincisal angle, angle of superior incisor axis on the sella-nasion plane, lower incisor to mandibular plane angle, Frankfort mandibular plane angle, zygomatic-frontal suture (Z), point on the most concave part of pyramidal apophysis of the upper maxilla (Mx), antegonial incisure (AG), upper (UMT) and lower (LMT) molar teeth. Differences were significant for class II dentoskeletal occlusion (p < 0.0001), mandibular hyperdivergence (p < 0.0001), lingualization of superior incisor (p < 0.005), deviation of inferior interincisal contralateral line to the synostosis (p < 0.0001) in the plagiocephalic population. Compared with contralateral counterpoints, Z (p < 0.05), Mx (p < 0.005) and UMT (p < 0.0005) on the affected side were closer to the midline; AG (p < 0.0005) and LMT (p < 0.05) were further from it. On the frontal plane, Z, Mx, UMT, LMT and AG on the affected side were higher. Vertical and transversal contraction of the jaw of the synostotic side and laterodeviation of the mandibular interincisal line of the contralateral synostotic were clear. The altered position of the glenoid cavity, anteriorized in unilateral coronal craniosynostosis, could be the cause of mandibular dentoskeletal asymmetry.     

Effects of connective tissue growth factor on human periodontal ligament fibroblasts

ObjectiveThe aim of this study was to evaluate the effects of different concentrations of connective tissue growth factor (CTGF) on human periodontal ligament fibroblasts(HPLFs).DesignHPLFs were cultured and identified. Then, different concentrations of CTGF (1, 5, 10, 50, 100 ng/ml) were added to the HPLF culture. Next, CCK-8 assays, alkaline phosphatase (ALP) assays, hydroxyproline determination, alizarin red staining methods, Transwell chambers and real-time PCR methods were applied to observe the effects of CTGF on the proliferation, ALP activity, synthesis of collagen, formation of mineralized nodules and migration. We also studied expression of ALP, fiber link protein (FN), integrin-binding sialoprotein (IBSP), osteocalcin (OC), and integrin beta 1 (ITGB1) mRNA by HPLFs. Statistical significance was assumed if P < 0.05 or P < 0.01.ResultsThe addition of CTGF (1, 5, 10 ng/ml) remarkably promoted the proliferation and collagen synthesis of HPLFs compared with controls. CTGF (1, 5, 10, 50 ng/ml) improved ALP activity of HPLFs, and at all concentrations, CTGF (1, 5, 10, 50, 100 ng/ml) improved the expression of ALP, FN, IBSP and ITGB1 mRNA. In addition, CTGF (1, 5, 10, 50, 100 ng/ml) promoted the migration of HPLFs, which was dose-dependent, with maximal promotion in the 10 ng/ml group (P < 0.05 or P < 0.01).ConclusionsThus, in a certain range of concentrations, CTGF can promote the biological effects, including proliferation, migration and collagen synthesis of HPLFs, to promote the differentiation of HPLFs in the process of osteogenesis.     

Wear performance of substructure ceramics and veneering porcelains

Aim

The aim of this in vitro study was to compare the two-body wear resistance of substructure zirconia and veneering porcelain versus steatite and human enamel antagonists, respectively.

Materials and methods

Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists (enamel cusps). A pin-on-block design with a vertical load of 50 N for 1.2 × 10⁵ cycles; (f = 1.6 Hz; lateral movement: 1 mm, mouth opening: 2 mm) was used for the wear test. For quantification of the wear resistance, wear tests were performed with standardized steatite spheres. Human enamel was used as a reference. Five zirconia ceramics and four veneering porcelains were investigated. One zirconia ceramic was tested with superficial glaze, which was applied after polishing or sandblasting, respectively. Surface roughness R_a (SP6, Perthen-Feinprüf, G) and wear depth were determined using a 3D-Profilometer (Laserscan 3D, Willytec, G). SEM (Quanta FEG 400, FEI, USA) pictures were used for evaluating wear performance of both, ceramics and antagonists.

Results

No wear was found for zirconia substructures. Veneering porcelain provided wear traces between 186.1 ± 33.2 μm and 232.9 ± 66.9 μm (steatite antagonist) and 90.6 ± 3.5 μm and 123.9 ± 50.7 μm (enamel). Wear of the steatite antagonists varied between 0.812 ± 0.256 mm² and 1.360 ± 0.321 mm² for zirconia and 1.708 ± 0.275 mm² and 2.568 ± 0.827 mm² for porcelain. Enamel generally showed wear, cracks or even fractures at the ridge, regardless whether opposed by zirconia or porcelain/glaze. Enamel was polished, when opposed to zirconia, or plowed, provoked and grinded, when opposed to porcelain/glaze.

Conclusion

The results of the wear test with steatite or enamel antagonists indicated no measurable wear on zirconia surfaces. Porcelain showed higher wear than zirconia, but comparable or lower wear than an enamel reference. Antagonistic wear against zirconia was found to be lower than wear against porcelain.     

Electron transfer kinetics and morphology of cytochrome c at the biomimetic phospholipid layers

Electrochemistry of cytochrome c (cyt c) at biomimetic phospholipid layers was studied in a phosphate buffer solution, which were formed with dilauroyl phosphatidic acid (DLPA, C12:0), dipalmitoyl phosphatidic acid (DPPA, C16:0), distearoyl phosphatidic acid (DSPA, C18:0), and palmitoyl–oleoyl phosphatidic acid (POPA, C16:0–18:1). The lipid-layers formed firstly at the air/water interface were immediately transferred onto the electrode surface using the Langmuir–Blodgett (LB) technique. The electrochemical properties of cyt c at the lipid covered electrodes depended on the orientation, number of layers of phospholipids, tail (or head) group down, and vice versa. Atomic force microscopy (AFM) images of cyt c adsorbed on the POPA monolayer (showing the head group diameter of POPA to be ca. 0.7 nm) formed on highly oriented pyrolytic graphite (HOPG) displayed uniform surface morphology of lipid layer and clumps of aggregated cyt c molecules with a minimum size corresponding to four cyt c molecules. The heterogeneous electron transfer rate constants, k⁰ values, of cyt c were determined to be 1.02 × 10⁻³, 0.98 × 10⁻³, and 0.67 × 10⁻³ cm/s for the lipid monolayer in the tail down orientation (X-type) of POPA, DLPA, and DPPA, and 0.67 × 10⁻³ and 0.50 × 10⁻³ cm/s for the head down orientation (Z-type) of POPA and DLPA monolayers, respectively.     

Prevalence of periodontitis based on retrospective radiographic evaluation at dental hospital in Eastern Province of Saudi Arabia: A retrospective study

ObjectivesThe contemporary information on the prevalence of periodontitis and associated risk factors is deficient in the Kingdom of Saudi Arabia. Our aim was to measure the prevalence of periodontitis and associated risk factors among the Saudi population in the Eastern Province of Saudi Arabia who visited the University Dental Hospital.MethodsIn this retrospective study, the demographic data and medical and dental records of 700 subjects were examined. Bitewing radiographs were analyzed to measure the alveolar bone loss in posterior teeth by measuring the distance between the cementoenamel junction and the crest of the alveolar bone. A chi-square test was performed to compare the severity of periodontitis. A comparison of multivariate mean bone loss was performed using a t-test. Logistic regression analysis was used to evaluate the predictors of periodontitis. A P-value equal to or under 0.05 reflected statistical significance.ResultsAmong 700 cases, the patients’ mean age was 35.6 ± 12.1; 52.6 % were male and 47.4 % were female. Overall periodontitis prevalence was 52.1 %. The distribution of mild, moderate, and severe periodontitis prevalence was 36.1 %, 14.1 %, and 1.8 %, respectively. The severity of periodontitis was statistically similar between males and females (p = 0.148); however, significantly more Saudi than non-Saudi patients had moderate periodontitis. Higher proportions of severe periodontitis were seen in the age group of over 50-years-old (p < 0.001) and in patients with poor oral hygiene (p < 0.001), diabetes mellitus (p < 0.005), and hypertension (p < 0.002). Six total predictors of periodontitis were depicted, i.e., age > 50 years (OR = 3.73), poor OH status (OR = 2.24), BOP (OR = 3.35), presence of plaque (OR = 2.61), diabetes mellitus (OR = 3.19), and hypertension (OR = 3.62).ConclusionThe primary factors associated with the prevalence of periodontitis were age, nationality, diabetes, hypertension, BOP, plaque, and OH status. However, no association was observed between gender or cardiovascular disease and the prevalence of periodontitis in the studied population.