The bonding area of intra- and extra-coronal tooth preparations

PURPOSE: To assess the accuracy of preparation surface area measurements (mm2) using the Cerec digital mouth camera in vitro and to analyze a collection of 514 Cerec camera in vivo optical impressions of preparations from 274 patients according to the size of preparation/bonding area (mm2) METHODS: The surface area (mm2) of model preparations with known dimensions namely of one occlusal (1) and one mesio-occluso-distal (2) cavity as well as of one central incisor (3) and one molar (4) crown preparation was calculated from linear (a) design dimensions, (b) slide-gauge and (c) coordinate-measuring-machine data as benchmark measurements and from repeated (n=10) (d) laser-scan (control), (e) Cerec-camera mounted on a support, (f) handheld Cerec-camera measurements. Data of (d), (e) and (f) was statistically analyzed. From a collection of data sets clinically recorded with the Cerec camera, the surface areas of 514 preparations from 274 patients were analyzed according to the type of tooth and type of preparation. RESULTS: Occlusal cavity mm2 data 1(d) 48 +/- 0.4, 1(e) 48 +/- 0.2, 1(f) 48 +/- 0.6 and mod cavity mm2 data 2(d) 137 +/- 2, 2(e) 138 +/- 1, 2(f) 138 +/- 4 did not differ between (d), (e) and (f) (P> 0.05) confirming the hypothesis for inlay cavities. Incisor crown preparation mm2 data 3(d) 82+0.4 differed (P< 0.001) from 3(e) 85 +/- 0.2 and 3(f) 85 +/- 0.6 as well as molar crown preparation mm2 data 4(d) 133 +/- 0.6 differed by 3.5% (P< 0.001) from 4(e) 137 +/- 0.4 and 4f) 138 +/- 1. Clinical cavity and crown preparation area data obtained from in vivo Cerec camera recordings differentiated between type of tooth and type of cavity. 2D data of "classic", "reduced" and "endo" type crown preparations did not differentiate clearly.     

树脂水门汀与氧化锆陶瓷剪切粘接强度的研究

目的评估不同实验条件下树脂水门汀与氧化锆瓷之间的剪切粘接强度（SBS）。 方法使用计算机辅助设计与制作（CAD/CAM）设备切割并烧结制作6个边长为2 cm的正方体氧化锆试件。按不同实验条件将8种双固化树脂水门汀分为13组（n = 20）：（1）Monobond N + Multilink N（MMN组）;（2）Ivoclean + Monobond N + Multilink N（IMM组）;（3）Ivoclean + Monobond N + Multilink N[无喷砂,IMM（ns）组];（4）Tetric N-Bond Universal + Multilink Speed（TUM组）;（5）Multilink Speed（MLS组）;（6）Z-Prime Plus + TheraCem（ZPT组）;（7）Z-Prime Plus + Duo-Link（ZPD组）;（8）Single Bond Universal + RelyX U200（SRU组）;（9）RelyX U200（RXU组）;（10）Single Bond Universal + RelyX Ultimate Clicker（SRU组）;（11）OptiBond Versa + Kerr NX3（OVK组）;（12）Clearfil Universal Bond + Clearfil SAC（CUS组）;（13）Clearfil SAC（SAC组）。将每组树脂水门汀自混合注入透明模具并将其无压力置于氧化锆面后进行光照固化。所有试件在37 ℃水中存储24 h后进行SBS测试。采用SPSS 19.0软件One-Way ANOVA（P<0.05）对SBS进行统计学分析。利用电子体视显微镜观察氧化锆端断裂界面。 结果本实验中13组树脂水门汀的SBS（单位：MPa）降序排列依次为：OVK（27.51 ± 3.65）>IMM（27.28 ± 3.79）>SRC（26.77 ± 3.62）>CUS（25.36 ± 3.10）>TUM（25.22 ± 4.88）>ZPD（23.96 ± 6.25）>MLS（23.13 ± 2.74）>MMN（23.07 ± 3.71）>SAC（22.20 ± 3.59）>IMM（ns）（21.99 ± 3.50）>SRU（19.19 ± 2.27）>ZPT（18.62 ± 2.08）>RXU（15.04 ± 4.02）。 结论（1）不同树脂水门汀的SBS具有材料依赖性;（2）在氧化锆表面进行喷砂处理、使用专用清洗剂或将通用型粘接剂作为底漆使用有利于提高树脂水门汀的SBS。     

Strength and fracture pattern of monolithic CAD/CAM-generated posterior crowns.

OBJECTIVES: This study evaluated the strength and fracture pattern of monolithic posterior CAD/CAM crowns hypothesizing that zinc-phosphate cemented lithium disilicate crowns might show the same fracture strength as adhesively cemented crowns. METHODS: Two sets of monolithic posterior crowns each with uniform occlusal and lateral wall thickness of 1.5mm were fabricated from three types of block ceramic (1) lithium disilicate glass, (2) leucite glass and (3) feldspathic ceramic using CEREC 3 CAD/CAM. Crowns (n = 15) of ceramics (1), (2) and (3) each were (A) zinc-phosphate cemented, (B) adhesively cemented on resin-based composite dies and loaded until fracture. Load data was analyzed using ANOVA and Scheffé tests. Crack pattern was evaluated on an additional three sample cross-sections for each group at start of fracture. RESULTS: Radial cracks originated early at the cementation interfaces and cone cracks were observed finally at the loading sites. Mean load values (SD) of A-crowns at fracture start/end (1) 807 (91) N/2082 (192) N; (2) 915 (193) N/1130 (166) N; (3) 985 (199) N/1270 (301) N were all significantly (P < 0.001) lower when compared to their B-crown analogs (1) 1456 (205) N/2389 (84) N; (2) 1684 (395) N/2469 (171) N; (3) 1548 (304) N/2392 (75) N, rejecting the authors hypothesis. A-1 crowns had significantly (P < 0.001) higher fracture load than A-2 and A-3 crowns. The A-1 crown fracture load data, even if significantly (P < 0.001) lower, came close to the B-1 values. SIGNIFICANCE: Adhesive cementation balanced the strength of weak ceramics with that of strong ceramic and recommended itself for leucite glass ceramic and feldspathic ceramic crowns. Zinc-phosphate cementation appeared feasible for lithium disilicate crowns.     

安氏Ⅱ类错(骀)合并下颌后缩青少年吞咽运动研究

目的 通过对安氏Ⅱ类下颌后缩青少年吞咽时肌肉肌电图和下颌运动描记图进行研究,探索下颌后缩对患者吞咽功能的影响.方法 对29名安氏Ⅱ类下颌后缩青少年(安氏Ⅱ类组)与28名安氏Ⅰ类青少年(对照组)进行吞咽时颞肌前束、咬肌、颏肌肌电幅值及下颌运动范围进行测量,对比两组差异.结果 研究所得的计量数据以(中位数M上(Q25),下(Q75)四分位数)表示.1.安氏Ⅱ类组右侧颞肌前束肌电幅值(3.2(1.7,4.4) μV)小于对照组(5.0(2.7,12.9)μV),双侧咬肌肌电幅值(右3.2(2.2,5.7) μV/左3.1(1.9,4.8)μV)小于对照组(右5.6(3.1,9.7)μV/左4.7(2.6,9.8)μV),双侧颏肌肌电幅值(右22.1(15.2,40.1)μV/左21.9(13.1,36.9) μV)大于对照组(右13.7(7.3,20.7)μV/左10.8(7.0,22.8) μV).2.安氏Ⅱ类组吞咽颌位垂直向偏离(1.2(0.3,2.0)mm)大于对照组(0.5(0.2,1.0) mm)、冠状向偏离(0.4(0.2,0.7)mm)大于对照组(0.2(0.1,0.3)mm),矢状向偏离(-0.4(-1.1,0.3)mm)比对照组(0.1(-0.1,0.4)mm)更为偏前.吞咽过程中下颌垂直向位移(1.6(1.1,3.0) mm)大于对照组(1.0(0.5,1.6) mm),冠状向位移(0.3(0.1,0.8) mm)大于对照组(0.1(0.0,0.2) mm),矢状向位移(-0.4(-1.8,0.5)mm)比对照组(0.0(-0.3,0.4)mm)向前更多.结论 相比于安氏Ⅰ类患者,安氏Ⅱ类下颌后缩青少年中异常吞咽及唇功能不全比例更高.     

Effect of relining, water storage and cyclic loading on the flexural strength of a denture base acrylic resin

OBJECTIVES: This study investigated the effect of relining, water storage and cyclic loading on the ultimate flexural strength (FS(U)) and on the flexural strength at the proportional limit (FS(Pl)) of a denture base acrylic resin (Lucitone 550-L). METHODS: Rectangular bars of L were made (64 mm x 10 mm x 2 mm) and relined (1.3mm) with four relining resins (Kooliner-K, Ufi Gel Hard-UGH, Tokuso Rebase Fast-TR and New Truliner-NT). In addition, specimens relined with L and intact L specimens were made (64 mm x 10 mm x 3.3 mm). A three-point flexural test was applied on the specimens (n=10) after (1) polymerization; (2) water storage (30 days); (3) cyclic loading (10,000 cycles at 5 Hz) and (4) water storage (30 days)+cyclic loading. Data (MPa) were analyzed with three-way ANOVA and Tukey's HSD tests (alpha=0.05). To test for a possible correlation between FS(U) and FS(Pl), a linear regression coefficient "r" was calculated. RESULTS: After water storage, L-UGH and L-TR demonstrated an increased FS(U) (41.49-50.64 MPa and 49.95-57.36 MPa, respectively) (P<0.05). Only L-TR demonstrated an increased FS(Pl) (20.58-24.21 MPa) after water storage (P<0.05). L-L had the highest FS(U) (between 78.57 and 85.09 MPa) and FS(Pl) (between 31.30 and 34.17 MPa) (P<0.05). The cyclic loading decreased the FS(U) and FS(Pl) of all materials (P<0.05). Regression analysis showed a strong linear correlation between the two variables (r=0.941). CONCLUSIONS: Water storage improved the FS(U) of L-UGH and L-TR and the FS(Pl) of L-TR. L-L produced the highest FS(U) and FS(Pl). The FS(U) and FS(Pl) of all materials were detrimentally influenced by cyclic loading.     

Preparation and properties of nano-sized calcium fluoride for dental applications.

OBJECTIVES: The aim of the present study was to prepare nano-sized calcium fluoride (CaF(2)) that could be used as a labile F reservoir for more effective F regimens and as an agent for use in the reduction of dentin permeability. METHODS: Nano-sized CaF(2) powders were prepared using a spray-drying system with a two-liquid nozzle. The properties of the nano-CaF(2) were studied and the effectiveness of a fluoride (F) rinse with nano-CaF(2) as the F source was evaluated. The thermodynamic solubility product of the nano-CaF(2) solution was determined by equilibrating the nanosample in solutions presaturated with respect to macro-CaF(2). Reactivity of the nano-CaF(2) was assessed by its reaction with dicalcium phosphate dehydrate (DCPD). F deposition by 13.2 mmol/L F rinse with the nano-CaF(2) as the F source was determined using a previously published in vitro model. RESULTS: X-ray diffraction (XRD) analysis showed pattern of low crystalline CaF(2). BET measurements showed that the nano-CaF(2) had a surface area of 46.3m(2)/g, corresponding to a particle size of 41nm. Transmission electron microscopy (TEM) examinations indicated that the nano-CaF(2) contained clusters comprising particles of (10-15) nm in size. The nano-CaF(2) displayed much higher solubility and reactivity than its macro-counterpart. The CaF(2) ion activity product (IAP) of the solution in equilibrium with the nano-CaF(2) was (1.52+/-0.05)x10(-10), which was nearly four times greater than the K(sp) (3.9 x 10(-11)) for CaF(2). The reaction of DCPD with nano-CaF(2) resulted in more F-containing apatitic materials compared to the reaction with macro-CaF(2). The F deposition by the nano-CaF(2) rinse was (2.2+/-0.3)mug/cm(2) (n=5), which was significantly (p<0.001) greater than that ((0.31+/-0.06)mug/cm(2)) produced by the NaF solution. SIGNIFICANCE: The nano-CaF(2) can be used as an effective anticaries agent in increasing the labile F concentration in oral fluid and thus enhance the tooth remineralization. It can also be very useful in the treatment for the reduction of dentin permeability.     

氧化锆增韧纳米复合陶瓷粉体粒度与基体强度的关系

目的　探讨氧化锆 (ZrO2 )粉体微观粒度、级配与材料增韧补强效果之间的关系。方法以采用包裹共沉淀法与湿法球磨方法合成的Al2 O3 nZrO2 纳米复合陶瓷粉体为研究对象 ,改变所添加ZrO2 粉体的粒度 ,对粉体形貌进行扫描电镜观察与粉体粒径的测定分析 ;以注浆法将粉体制成样本生坯 ,经 1 4 50℃烧结后 ,测定样本的抗弯强度与断裂韧性。结果　①添加等量、不同粒度ZrO2 的Al2 O3 nZrO2 纳米复合渗透陶瓷材料 ,其基体抗弯强度与断裂韧性差异有显著性 (P <0 0 5) ;②添加粒度分布范围在 0 0 2～ 3 5μm ,包含粒径小于 0 5μm超细颗粒的ZrO2 组 ,增韧增强效果最显著 ,抗弯强度与断裂韧性分别达 (1 1 5 434± 5 31 9)MPa和 (2 0 4± 0 1 0 )MPam1 /2 。结论　添加ZrO2 的粉体粒度与级配是影响Al2 O3 nZrO2 纳米复合渗透陶瓷材料基体强度的重要因素     

Protein free diet feeding: effects on sympathetic activity and salivary evoked secretion in the submandibular gland of the rat

Protein restriction impairs the salivary flow rate and composition in human and rats. The aim of the present work was to establish the effect of low protein (casein 5%) and protein free (casein 0%) isocaloric diets on sympathetic activity and salivary evoked secretion in the submandibular gland (SMG) of the rat. After 21 days, rats fed casein 0% presented: (a) a significant shift to the left of the dose-response curves (DRC) to the autonomic agonists-norepinephrine (NE), methoxamine, isoproterenol (ISO) and methacholine; (b) increased food consumption (p<0.001); (c) decreased body (p<0.001) and SMG (p<0.001) weights maintaining SMG/body (w/w) relation; (d) enhanced submandibular alpha1-adrenoceptor number without changes in the apparent dissociation constant (Kd); (e) increased submandibular NE content (p<0.05) and phosphoinositoside hydrolysis (p<0.001); (f) decreased submandibular tyrosine hydroxylase activity (TH) (p<0.01). Casein 5% feeding increased food consumption (p<0.01) and reduced body weight (p<0.05). This protein restriction increased metacholine-evoked salivation, but it altered neither submandibular sympathetic activity nor sympathetic-induced salivary secretion as compared to the Control group (C) fed a similar diet containing 25.5% protein. Present results suggest that in the adult rat, a protein free diet during 21 days lowers SMG sympathetic and cholinergic activity leading to supersensitivity as revealed by up-regulation of alpha1-adrenergic receptor number and increased autonomic-evoked salivation.     

腮腺肿瘤208例临床发病部位分析

作者总结了208例腮腺肿瘤临床部位分布情况。分析了良性肿瘤(B)、恶性肿瘤(M)的好发部位。指出,B:M约为2:1。耳前、耳垂、下颌角、颧弓及颌后凹五区之比为1:3.76:0.20,0.09:0.76;B为1 :5.83:0.11:0:0.44;M为1:1.43:0.31:0.19:1.12。各区B:M分别是1.12:1;4.56:1,0.40:1;0:3;0.44;1。本文为腮腺肿瘤的临床诊断提供一定的参考价值。     

Parotid secretory protein binds phosphatidylinositol (3,4) bisphosphate

Molecular interactions that direct trafficking of secreted proteins are not well-described in salivary glands. Here, we report that the soluble cargo protein Parotid Secretory Protein (PSP) is bound to the membranes of secretory granules isolated from rat parotids. This is apparently due to specific interaction with phosphatidylinositol phosphates (PtdInsP). PSP binds PtdIns(3,4)P(2), 10-fold greater than PtdIns(3,5)P(2) or PtdIns(4)P, and does not bind PtdIns(3)P or PtdIns(5)P. Human PSP synthesized in vitro also binds PtdIns(3,4)P(2). Bacterially expressed rat PSP binds PtdIns(3,4)P(2) with a K(d) of 2.4 x 10(-11) M. Other major secretory proteins (amylase, proline-rich protein) are not bound to isolated granule membranes and do not bind phosphatidylinositol phosphates. Immunofluorescence shows PtdIns(3,4)P(2) at the secretory granules, and fluorescent PtdIns(3,4)P(2) can flip from the outer leaflet to the inner leaflet of the membrane. Binding of PSP to PtdInsPs may contribute to sorting during the formation of the secretory granules, or sorting by retention during maturation of the granules.     

Effect of titrated mandibular advancement and jaw opening on the upper airway in nonapneic men: a magnetic resonance imaging and cephalometric study.

The aim of this study was to examine adaptive changes in the cross-sectional area of the upper airway during mandibular advancement and jaw opening and to explore whether these changes are directly related to morphologic features of the mandible. Fourteen nonapneic men participated in this study. A custom-made oral device was used to keep the mandible at 0% (F(0)V(0)), 50% (F(50)V(0)), 75% (F(75)V(0)), or 100% (F(100)V(0)) of maximum advancement, and at 50% (F(75)V(50)), 75% (F(75)V(75)), or 100% (F(75)V(100)) of maximum gape at F(75)V(0). Magnetic resonance imaging was used to investigate differences in the upper-airway cross-sectional area in these 7 positions. To eliminate excessive individual variation, changes in the mean (mean%) and minimum (min%) cross-sectional area of the upper airway were calculated as percentages of those at F(0)V(0). Cephalograms were taken to analyze morphologic features of the mandible. A dose-dependent change was seen when the mandible was advanced. The min% in F(100)V(0) was significantly greater than those in F(50)V(0) and F(75)V(0). The change in the upper airway size varied between subjects during jaw opening. At F(75)V(0), the min% of the whole upper airway was significantly associated with morphologic features of the mandible, such as the mandibular plane angle and lengths of the mandibular body and ramus.     

变形链球菌I型Mutans表面蛋白P1的粘附作用

In this study,the surface protein P(1) of Streptococcus mutans MT(6)R(Serotype C) was extracted from the culture supernants,purified by PAGE,identified by the standard antisera and labelled by with (131)I.The adherence of (131)I protein P(1)((131)I-P(1)) to the saliva-coated hydroxyaptite (S-HA) of the CF (caries-free,22,DFS=0) were studied.The adhesion of (131)I-P(1) to the S-HA promoted a greater extent than that to the HA treated with buffer and bovine serum albumin(P<0.01).This result suggested that protein P(1) may be one of the important adhesins of S.mutans.     

Silensor阻鼾器治疗前后阻塞性睡眠呼吸暂停综合征患者上气道结构改变的分析

目的 探讨Silensor阻鼾器治疗前后阻塞性睡眠呼吸暂停综合征(OSAS)患者上气道结构的改变。方法 采用X线头影测量法对42例OSAS患者Silensor阻鼾器治疗前后的上气道及其周围结构的形态进行测量,并对测量的42项结果进行配对t检验。结果 经阻鼾器治疗后,OSAS患者的软腭后气道增大最显著,软腭后-软腭后咽壁距由（9.10±2.25） mm 增加到（12.24±2.61） mm,舌根后气道间隙由（8.99±3.20） mm增至（11.24±3.79） mm,软腭与舌体接触长度由（26.26±6.04） mm 减小至（14.37±8.14） mm,舌骨-下颌平面距由（21.27±6.12） mm减小为（12.14±5.89） mm,会厌谷与颏后点间的距离由（55.15±5.61） mm减小为（51.63±5.87） mm。口咽气道面积和喉咽气道面积分别由（7.01±1.54） mm2和（3.02±0.89） mm2增大为（7.85±1.61） mm2和（3.61±1.61） mm2。结论 Silensor阻鼾器治疗后OSAS患者的上气道间隙明显增大。     

上颌牙弓形态的主要要素分析

目的:寻找一种快速评价牙弓形态的客观标准。方法:从396副(年龄:18～26岁;男性257副,女性139副)牙模型中选出62副(男性36副,女性26副)具有正常牙列及牙合的模型,设定以下参考点:切嵴的中点,尖牙的牙尖顶,前磨牙的颊尖,第一和第二磨牙的近中颊尖,以及I1R-I1L连线的中点(A)。从A作一个垂直线与M2R-M2L连线相交,形成参考点(B)。A-B连线与CR-CL连线相交,形成参考点(E)。进行以下分析:(1)评价尖牙的突度,指标为①:角I2R-CR-P1R(∠R)+角I2L-CL-P1L(∠L);(2)评价前牙的曲度,指标为②:(A-B)/(CR-CL),③:180°-∠(CR-A-CL)和④:(A-E)/(CR-CL);(3)评价牙弓长度与宽度比,指标为⑤:(A-B)/(M2R-M2L);(4)评价牙弓的圆润程度,指标为⑥:(rθ5-rθ4)R+(rθ5-rθ4)L;(5)通过双侧后牙参考点连线⑦:P1-P2-M1-M2(线i)、P1-M2(线ii)的形态和位置评价Ⅰ型和Ⅱ型方圆形牙弓的特征。其中指标①、②、③、④、⑤和⑥的数据经过分析归纳为3个主要要素:①前牙的弯曲度,②牙弓的突度,和③牙弓的长-宽比。结果:(1)60%的上颌牙列为方圆形牙弓,没有明显显示出主要要素的形态特征;(2)正方形上颌牙弓的参数①∠R+∠L明显较小;(3)圆形牙弓的特征是参数⑥(rθ5-rθ4)R+(rθ5-rθ4)L值偏小;(4)尖圆形牙弓的参数②,③和④值较大。结论:上述评价参数可以归类为3种主要要素(第1要素、第2要素、第3要素),通过分析这些要素,可以有效地评价上颌牙弓的形态,并得出了3类牙弓的各自形态特征。     

Protection of short-time enamel erosion by different tetrafluoride compounds

OBJECTIVE: This in vitro study aimed to analyse the protective effect of differently concentrated titanium (TiF(4)), zirconium (ZrF(4)) and hafnium (HfF(4)) tetrafluoride on enamel erosion. METHODS: Polished enamel surfaces of 36 bovine crowns were covered with tape leaving 4 enamel windows each 3mm in diameter exposed. The crowns were randomly assigned to six groups (each n=6) and pretreated with 4% TiF(4), 10% TiF(4), 4% ZrF(4), 10% ZrF(4), 4% HfF(4) or 10% HfF(4) for 4 min (first window), 10 min (second window) or 15 min (third window). The fourth window of each crown was not pretreated and served as control. Erosion was performed stepwise with 1% HCl (pH 2) in five consecutive intervals of each 15 s (total 75 s). Enamel dissolution was quantified by colorimetric determination of phosphate release into the acid. For each tooth, cumulative phosphate loss of enamel pretreated with one of the tetrafluoride compounds was calculated as percentage of the respective control and statistically analysed using two-way ANOVA. RESULTS: Enamel erosion was significantly reduced by TiF(4), ZrF(4) and HfF(4) application. Cumulative phosphate loss (mean % of control, 75s erosion) after 4-15 min application was significantly lower for 4% ZrF(4) (7-11%), 10% ZrF(4) (2-6%), 4% HfF(4) (11-9%) and 10% HfF(4) (12-16%) compared to 4% TiF(4) (42-27%) and 10% TiF(4) (54-33%). Only for 4% and 10% TiF(4), phosphate loss decreased with increasing duration of application, but also increased with increasing acid intervals. CONCLUSION: TiF(4), ZrF(4) and HfF(4) might protect enamel against short-time erosion, but protection was more enhanced by ZrF(4) and HfF(4) compared to TiF(4) application overtime.     

Laboratory-made space maintainers: a 7-year retrospective study from private pediatric dental practice

PURPOSE: The purpose of this study was to report survival times and problems encountered with laboratory made space maintainers placed over 7 years by one pediatric dentist. METHODS: Charts were reviewed for 235 patients with fixed space maintainers placed between January 1, 1997, and December 31, 2003, and followed to December 31, 2005. Problems encountered and appliance lifetimes were recorded and assessed. Failures were recorded as: (1) cement loss; (2) solder breakage; (3) split bands; (4) eruption interference; (5) bent wire; (6) complete loss; or (7) not specified. Appliance outcomes, transferred patients, and those lost to follow-up were recorded. RESULTS: A total of 323 appliances were followed, with: (a) 93 (29%) successes; (b) 110 (34%) still in service; and (c) 104 (32%) known failures. Of the latter, most (62%) were from cement loss (60%) and 13 (12%) were totally lost. No statistically significant differences were noted between types of appliances, gender, and types of failure, except for the fact that bands and loops exhibited more cement loss (P=.045). Mean pooled survival times were between 26 and 27 months.. Of the 104 failures: (a) 34 (33%) were no longer needed (being considered clinically successful); (b) 57 (55%) were recemented; and (c) 13 (12%) were remade. Sixteen appliances were lost to follow-up or transferred. CONCLUSION: A total of 63% of all space maintainers lasted their anticipated lifetimes or were still in use.     

Influence of additives on the properties of Bis-GMA/Bis-GMA analog comonomers and corresponding copolymers.

OBJECTIVES: The purpose of this study was to evaluate the effect of two additives: propionaldehyde (aldehyde) and 2,3-butanedione (diketone) on the properties of Bis-GMA diluted with TEGDMA and the synthesized Bis-GMA analogs, propoxylated Bis-GMA (CH(3)Bis-GMA) and propoxylated fluorinated Bis-GMA (CF(3)Bis-GMA). METHODS: Nine experimental comonomers were prepared combining Bis-GMA and TEGDMA, CH(3)Bis-GMA, CF(3)Bis-GMA, with aldehyde (32mol%) and diketone (32mol%). Photopolymerization was effected by using Camphorquinone (0.2wt%) and N,N-dimethyl-p-toluidine (0.2wt%). Experimental comonomer viscosity (Brookfield viscometer), polymerization shrinkage (gravimetrically), degree of conversion (FT-IR) and contact angles (contact angle goniometer) were determined. Comonomer and copolymer T(g)s (DSC and Fox equation) were also evaluated. Data were analyzed by one-way ANOVA and Tukey test (alpha=0.05). RESULTS: Bis-GMA/CH(3)Bis-GMA and Bis-GMA/CF(3)Bis-GMA with additives exhibited lower viscosities (p<0.01). Inclusion of additives into the comonomer systems did not produce significant increase in polymerization shrinkage (p>0.05). A significant increase in degree of conversion was shown for Bis-GMA/TEGDMA and Bis-GMA/CH(3)Bis-GMA with additives (p<0.01). Additives reduced contact angle and comonomer T(g) values, whereas the corresponding copolymers with additives showed an increase in T(g). SIGNIFICANCE: Use of novel comonomer systems with the addition of aldehyde and diketone functional groups would improve dental resin composite properties.     

The physical and cytological properties of white MTA mixed with Na2HPO4 as an accelerant

The purpose of the present study was to evaluate the physicochemical and cytologic properties of mineral trioxide aggregate (MTA) mixed with distilled water and Na(2)HPO(4) buffer solution. The MTA setting time and pH value were evaluated. An MTA micrograph on scanning electron microscopy (SEM) was observed. Mouse fibroblasts (an L929 cell line) were used to test the toxicity of MTA after the first and seventh day of treatment by mitochondrial colorimetric assay. The results show the Na(2)HPO(4) buffer group reduced the MTA setting time, and the pH value as in the distilled water group is similar with the Na(2)HPO(4) buffer group. The mixed MTA's XRD produced similar peaks of the distilled water and Na(2)HPO(4) buffer solution groups. The L929 cell survival rate of distilled water and H(2)PO(4) buffer solution groups did not exhibit any significant difference (p < 0.05). There are differences in SEM observations both of the MTA surface and of the cells in culture on the surface of the MTA with Na(2)HPO(4) versus distilled water. The results suggest that 15% Na(2)HPO(4) buffer can be successfully used as an accelerator of MTA.     

Adhesive bonding to dentin with iron (II) perchlorate primers and a tri-n-butylborane-initiated luting agent.

OBJECTIVES: This study was conducted to measure the tensile bond strength of a resin to dentin when the dentin was primed with iron (II) perchlorate modified aqueous 2-hydroxyethyl methacrylate (HEMA) or an iron (II) perchlorate modified commercial self-etching primer (ED primer, Kuraray Co.). METHODS: Bovine dentin surfaces were ground flat and each specimen underwent one of the following two treatments: (1) priming with 2.0 x 10(-6) to 5.0 x 10(-4) mol/g iron (II) perchlorate in aqueous HEMA solutions after etching with 10 wt% phosphoric acid; (2) priming with self-etching primers containing 4.0 x 10(-7) to 2.0 x 10(-4) mol/g iron (II) perchlorate. Each specimen was then bonded to a stainless-steel rod with a luting agent (MMA-TBB resin) consisting of methyl methacrylate (MMA), poly(methyl methacrylate) (PMMA), and tri-n-butylborane (TBB) initiator. Tensile strengths of the bonded tooth specimens were then determined after 1 day immersion in water. Results were analyzed using ANOVA and Duncan's new multiple range test (p < 0.05). RESULTS: Tensile testing revealed the maximum mean bond strengths (22.5 MPa) when the dentin was primed with 2.0 x 10(-4) mol/g iron (II) perchlorate after etching with 10 wt% phosphoric acid aqueous solution. The highest level of bond strength with self-etching primer (19.6 MPa) was achieved using 1.0 x 10(-4) mol/g iron (II) perchlorate. SIGNIFICANCE: These bonding techniques, combining the use of iron (II) perchlorate modified HEMA primers with MMA-TBB resin, are potentially applicable for seating resin-bonded restorations.     

Marginal and internal fit of all-ceramic CAD/CAM crown-copings on chamfer preparations

Evaluation of the marginal and internal fit of all-ceramic molar crown-copings hypothesizing that Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) fabrication shows the same accuracy of fit as conventional techniques. A set of six individual crown preparations was duplicated 12 times yielding 72 plaster dies. Slip-cast (In-Ceram Zirconia), heat-pressing (Empress II) and CAD/CAM crown-copings (Cerec inLab, DCS, Decim and Procera) were seated on 12 dies each. Marginal and internal gap width was measured in the SEM at 120x magnification. Marginal gap of slip-cast (25 +/- 18 microm) was significantly (P < 0.05) smaller than that of Empress II (44 +/- 23 microm) copings. Procera (17 +/- 16 microm) and Decim (23 +/- 17 microm) did not differ (P > 0.05) from slip-cast (25 +/- 18 microm) but were smaller (P < 0.001/P < 0.01) than Empress II (44 +/- 23 microm) and Cerec inLab (43 +/- 23 microm) (P < 0.001/P < 0.05). DCS (33 +/- 20 microm) did not differ (P > 0.05) from any of the others. The internal mid-orobuccal gap width of Procera (136 +/- 68 microm) was larger (P < 0.001) than that of Decim (81 +/- 30 microm) and slip-cast (94 +/- 84 microm) (P < 0.05) while Empress II (105 +/- 53 microm), DCS (110 +/- 79 microm) and Cerec inLab (114 +/- 58 microm) did not differ significantly (P > 0.05) from Decim, Procera and slip-cast. Internal mesiodistal gap width was similar. The fit of conventional and CAD/CAM all-ceramic molar crown-copings covered the same range of gap width confirming the assumed hypothesis.