Horizontal impaction of primary mandibular bilateral central incisors identified in 2-year-8-month-old girl

A girl aged 2 years and 8 months came to our clinic for consultation with regard to unerupted primary mandibular bilateral central incisors. An intraoral examination revealed that the teeth had not emerged into the oral cavity and showed a tooth crown morphology similar to that of the primary mandibular incisors, which appeared in the lingual submucosal area outside of the mandibular dental arch. Periapical radiographs demonstrated that the tooth crowns of both affected teeth were severely displaced to the lingual side. Computed tomography examinations were performed to clarify the three-dimensional positions of the affected teeth and their permanent successors, which revealed that the affected teeth were located in their estimated positions and had a standard root morphology. In addition, the permanent successors, which had not initiated root formation, were located close to the affected teeth. We decided to postpone extraction of the affected teeth and perform periodical examinations until the roots of the permanent successors are sufficiently formed. At the age of 2 years and 10 months, the edge of the tooth crown of the primary mandibular left central incisor was found emerged into the oral cavity. According to her parents, the patient did not complain of the emerging edge and no abnormal conditions were observed around the tooth.     

Comparison of Implant Stability Before Prosthetic Loading of Two Dental Implant Systems

Dental implantology is the state of the art technique to replace missing teeth. Implant stability of implant jeopardizes its longevity and success of treatment. This study evaluates the implant stability of implant before and after 4 months of the implant placement, but before prosthetically loading it. Ten two-stage implants of Life care and Nobel Biocare dental implants were placed in 20 patients. Digital OPG was taken on the day of implant placement. After 4 months, at the time of second stage surgery, the implant stability was evaluated by the Periotest instrument. Four months after the implant placement, Periotest evaluation showed a mean of 1.9, which indicated that implants were well osseointegrated and stable. Even before prosthetically loading the two-stage implant, crestal bone loss of 0.6–0.9 mm occurred around the implant. The smooth polished collar design of the implant may have contributed to crestal bone loss.     

LED固化灯光照强度对光固化复合树脂聚合收缩的影响

目的采用数字图像相关法动态研究LED光固化灯不同光照强度对光固化复合树脂聚合收缩的影响。方法收集12颗大小接近的新鲜离体磨牙,随机分为3组,制备大小为2.0 mm×2.0 mm×2.0mm的邻(?)面洞形,洞面酸蚀冲洗后涂粘接剂光照10 s,充填3M Z350纳米复合树脂,邻面快速制造散斑,LED固化灯垂直(?)面光照40s,3组光照强度分别为300 mW/cm~2、500 mW/cm~2和800 mW/cm~2,数码相机同步实时采集光照过程中试件表面散斑的变化序列图像,用数字图像相关法计算获得各序列图上逐个像素点水平方向(x)和垂直方向(y)位移,统计线性收缩率,描绘各像素点的时域变化曲线,并用SPSS 12.01统计软件包进行方差分析和配对t检验。结果 3种光照强度下树脂x方向线收缩率分别为0.081%～0.486%、0.004%～0.316%和0.063%～0.560%,y方向线收缩率分别为0.088%～0.981%、0.003%～0.77%和0.157%～1.252%,3组之间差异有统计学意义(P<0.05);3组第20 s树脂游离面收缩x方向位移差异无统计学意义,y方向位移差异有统计学意义。结论 LED光固化灯500 mW/cm~2光照时引起的树脂聚合收缩最小。     

复合树脂联合脱敏剂对楔状缺损牙敏感性及修复疗效的影响

目的：评价复合树脂充填楔状缺损时,联合应用脱敏剂对术后敏感和远期临床疗效的影响。方法：将167例542颗因楔状缺损导致牙本质敏感的患者按简单随机化分组方法,分为三组：涂布iBond七代自酸蚀粘接剂后复合树脂充填（A组）、涂布自酸蚀粘接剂可乐丽菲露后复合树脂充填（B组）及涂布舒齿灵脱敏剂后涂布可乐丽粘接剂七代自酸蚀粘接剂后复合树脂充填（C组）,比较术后脱敏疗效,并于充填后6、12及24个月用改良USPHS系统评价其远期临床疗效。结果：楔状缺损修补术后,各组牙牙本质敏感症状均有明显的缓解（尸〈0．05）;无牙本质敏感症状的牙所占比例A、C组显著性高于B组（P〈0．05）;三组在6、12个月时充填体成功率无显著差异,但C组24个月修复体成功率显著性低于A,B组。结论：对因牙本质敏感求治的楔状缺损患者,推荐术前使用脱敏剂或使用含有脱敏成分的粘接剂;使用iBond粘接剂进行复合树脂充填,能显著减少牙敏感症状,并且具有良好的粘接性能。     

Effect of Mica Reinforcement on the Flexural Strength and Microhardness of Polymethyl Methacrylate Denture Resin

Purpose : Conventional denture base polymethyl methacrylate (PMMA) is low in strength, soft, and brittle on impact. Improvements in the mechanical properties of denture base materials have been sought by adding different reinforcing phases to the PMMA matrix. The purpose of this work was to study the effects of mica reinforcement on the mechanical properties, flexural strength, and microhardness of PMMA denture base resin. Materials and Methods : Wet ground muscovite mica and Lucitone 199 original shade denture base resin were used. Two micas were tested: W200 and P66 with average particle sizes (d50) of 131 μm and 30 μm, respectively. The mica was silane treated in a solution of 3‐methacryloxypropyl trimethoxysilane, ethanol, and water, and then dried. The specimens were fabricated using the denture base resin manufacturer's instructions with a powder : liquid ratio of 21 g/10 ml and a mixing time of 30 seconds. Five treatment groups were produced with differing amounts of mica added to the PMMA denture base resin: (A) control group with 0 vol% mica, (B) 10 vol% W200 mica, (C) 20 vol% W200 mica, (D) 10 vol% P66 mica, (E) 20 vol% P66 mica. The mica replaced equal volumes of the PMMA powder component to minimize changes in viscosity. The three‐point bending flexural strength specimens were 70 × 11 × 3 mm³. Seven specimens were prepared for each treatment group. The hardness specimens were prepared from the ends of the three‐point bend specimens after they were broken (N = 7). After deflasking, the specimens were polished with 600 grit silicon carbide paper to achieve smooth surfaces. A standard three‐point bending jig with a span length of 50 mm was attached to an Instron universal testing machine. The specimens were placed on the jig, and loading was carried out using a 1 mm/min crosshead speed until failure. Microhardness was measured using a Clark microhardness tester with a Knoop indenter. The load was set to 200 g and the dwell time to 15 seconds. ANOVA and Tukey tests were used for statistical analyses (Alpha = 0.05). Results : The flexural strength of the control group was between 77% and 94% higher than all the mica‐containing groups (p≤ 0.05). No significant differences were found within the four mica groups. Microhardnesses of the 20% mica groups (both fine and coarse) were 33% and 26% higher than the control (p≤ 0.05). The 10% mica groups had higher hardness than the control group, but the increase was not statistically significant (p > 0.05). Conclusion : Mica additions to denture PMMA reduced flexural strength; however, with the specimens containing highest mica concentrations (20%), microhardness significantly increased.     

Biomechanical and Bone Histomorphological Evaluation of Two Surfaces on Tapered and Cylindrical Root Form Implants: An Experimental Study in Dogs

Purpose: The aim of this study was to evaluate the early bone response of tapered and cylindrical root form implants with two different surface treatments in fresh extraction sockets after 4 and 8 weeks. Materials and Methods: Surface treatments and implant design comprised (n = 9 each): tapered with dual acid‐etched surface; tapered with dual acid‐etched and sandblasted surface (T DAE SB); cylindrical with dual acid‐etched surface (C DAE); and cylindrical with dual acid‐etched and sandblasted surface (C DAE SB). Implants were placed in the distal sockets of mandibular premolars (₂P_2,3P_3,4P₄) of six beagle dogs, remaining in vivo for 4 and 8 weeks. After sacrifice, the implants were subjected to torque to the point of interface fracture and subsequently nondecalcified for histomorphological study. Statistical analysis was performed by a General Linear Model (GLM) analysis of variance model with a significance level of 5%. Results: Torque to interface fracture was significantly greater for the C DAE SB group than for the other groups (p < .001). Histomorphological analysis showed woven bone formation around all implant surfaces at 4 weeks and its replacement by lamellar bone at 8 weeks. Study time (4 or 8 weeks) did not affect torque measures. Conclusions: The double acid‐etched and sandblasted sample surface increased early bone biomechanical fixation of both cylindrical and tapered root form implants. The cylindrical root form implants showed higher torque to interface fracture values when compared with the tapered root form implants. The C DAE SB surface group showed the highest biomechanical fixation values (p < .001).     

Stereoscopic Technique for Conversion of Radiographic Guide into Implant Surgical Guide

Purpose: The aim of this study was to develop and evaluate a new stereoscopic technique for conversion of radiographic guide into surgical guide for dental implant placement. Materials and Methods: Ten partially dentate patients requiring 18 implants for tooth replacement were recruited. Radiographic guides were modified with the addition of index rods for double computed tomography scanning. Implant positions were planned with implant planning software, and the stereoscopic angulations were measured. The radiographic guides were converted into surgical guides using either a generic bench drill (Group A, n = 9) or a milling machine (Group B, n = 9). Stereolithographic surgical guides were also made for three patients (Group S, n = 5). Differences between the planned and actual angulations were tested by pair‐sample t‐test. Difference of mean angle deviation among groups was tested by Brown–Forsythe test. Differences were considered significant if p < .05. Results: Eighteen implant sites were successfully treated with the converted surgical guides. The mean angle deviation of Group A (1.3 ± 0.6°) was significantly greater than Group S (0.4 ± 0.6°), while no differences were found between Group B (0.9 ± 0.3°) and Group S. The linear error was greatest in Group A with 1.5 mm at the head and 1.8 mm at the apex of the implant. Conclusions: The use of this new stereoscopic technique appears to be an acceptable alternative method for converting radiographic guide into surgical guide.     

Enamel gloss changes induced by orthodontic bonding

ABSTRACT

Objective: The purpose of this study was to assess enamel gloss changes induced by orthodontic bracket bonding with a light-cured composite or a light-cured resin-reinforced glass ionomer cement.

Setting: The Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Greece.

Design: Laboratory study.

Methods: A total of twenty extracted upper human first premolars were included in this study and each tooth served as a control for itself. Their buccal surfaces were subjected to 60^o-angle gloss measurement (G%60) with a standardized and secure repeated analysis of the same site. After baseline evaluation, a bracket was bonded on the buccal surface of each tooth. Half of the specimens were bonded with acid-etching and a light-cured composite whereas the other half with a light-cured resin-reinforced glass ionomer cement without prior enamel conditioning. Gloss measurements were repeated after bracket debonding and removal of the composite/glass ionomer cement with an 18-fluted carbide bur. Gloss differences between the two measurement conditions (baseline and post-debonding) were analyzed through linear regression with standard errors derived using the bootstrap method. Level of significance was set at a?<?0.05.

Results: A statistically significant difference was detected between the tested groups for the outcome of interest. Teeth bonded with light-cured composite exhibited larger enamel gloss changes as compared to resin-reinforced glass ionomer cement (β?=?0.74; 95% CIs: 0.10, 1.38; p?=?0.02).

Conclusions: Bracket bonding with two common bonding protocols (acid-etching with a light-cured composite vs. no etching with resin reinforced glass-ionomer cement) and subsequently debonding and adhesive removal with an 18-fluted carbide bur induced enamel gloss changes.     

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目的对比4种充填材料的边缘微渗漏情况,为其临床应用提供合理指导。方法选择2013年1—6月青岛大学医学院附属医院口腔科因牙周病或阻生齿而拔除的健康新鲜后牙60颗,备洞后随机分为6组,每组10颗,分别使用Fihek Z250复合树脂（A1、A2组）、Ketac N100树脂加强型玻璃离子（B1组）、Ketac MolarEasymix型玻璃离子（B2、B3组）、F2000Compomer玻璃离子复合体（B4组）充填窝洞。其中A2组充填后充填体表面涂布AdperSingleBond2粘接剂,B3组充填后充填体表面涂布凡士林,而其他各组充填后表面不做任何处理。经冷热交替实验后,记录各组染料渗入窝洞壁与充填体之间的深度,并进行统计分析。结果A2组微渗漏最小,B2组微渗漏最大,与其他组（A1、B1、B3、B4）相比差异有统计学意义（P〈0．05）;A1、B1、B3、B4组间两两比较差异均无统计学意义（P〉0．05）。结论复合树脂、树脂加强型玻璃离子、玻璃离子复合体的边缘微渗漏均小于传统型玻璃离子;表面涂布隔湿剂后能增强上述材料的边缘封闭性能。     

Mechanical testing of thin-walled zirconia abutments

Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bicomponent aesthetic abutments has been suggested.

Objective:

Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments.

Material and Methods:

Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25º angle inclination (n=10 each group). Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20ºC±5ºC. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p≤0.05. Failed samples were inspected in a polarized-light and then in a scanning electron microscope.

Results:

Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, the dynamic loading mean F^max was 237.4 N and 240.7 N, respectively. No significant differences resulted between the straight and angled bi-component abutments in both static (p=0.253) and dynamic testing (p=0.135). A significant difference in the bending moment required for fracture was detected between the groups (p=0.01). Fractures in the angled group occurred mainly at the point of load application, whereas in the straight abutments, fractures were located coronally and close to the thinly designed areas at the cervical region.

Conclusion:

Angled or straight thin-walled zirconia abutments presented similar F^max under fatigue testing despite the different bending moments required for fracture. The main implication is that although zirconia angled or straight abutments presented similar mechanical behavior, the failure mode tended to be more catastrophic in straight (fracture at the cervical region) compared to angled abutments.