仿真牙结合离体牙对口腔医学生综合素质提高的效果评价

目的:评价用仿真牙结合离体牙进行试验教学的效果。方法:对河北联合大学2008级(为对照组)实验教学中单纯采用石膏牙模型;2009级(实验组)实验教学中加入离体牙和仿真牙。在学期结束后进行综合素质考试成绩对比,并且进行学生满意度评价。结果:实验组理论、实验操作成绩各项目及总成绩均高于对照组(P<0.05);自我评价中除团队合作无明显差异以外,其余各项目实验组均高于对照组(P<0.05)。结论:在口腔实验教学中加入仿真牙和离体牙,可提高学生临床综合素质。     

改良的离体牙桩冠实验模型的制作

口腔修复学 (Prosthodontics)主要是研究口腔颌面缺损、牙体牙列缺损和缺失修复治疗的一门学科 ,同时也是一门实践性很强的修复学科 ,而实验室是口腔修复学基本技能实习训练三基 (基础理论、基本知识、基本技能 )的重要基地 ,实验室也是学生牢固掌握理论知识和操作技术的重要环节。通过实验 ,使学生掌握修复学各类器械的使用和材料、生物力学、美学及治疗的基本操作方法。1　材料与方法1 .1　标本来源及处理　离体牙来自各医院口腔门诊病人拔除的患病牙 ,用 1 0 %的福尔马林浸泡 ,煮沸半小时 ,用自来水冲洗 ,刮除肉芽组织及牙垢 ,用 3%过氧…     

笑气吸入镇静在牙体预备中的应用研究

目的:探讨笑气吸入镇静技术在口腔固定修复患者牙体预备中的应用研究.方法:选择需进行口腔固定修复治疗的患者80例,随机分为两组,每组40例.干预组在笑气吸入镇静下进行牙体预备,对照组进行常规牙体预备,观测术中患者血压,心率等临床指标,术前术后的牙科焦虑评分变化,以及术后填写患者Frankl 治疗依从性量表和Houpt行为量表.结果:两组患者在整个牙体预备治疗过程中,牙科焦虑评分比较、Frankl 治疗依从性评分值和Houpt行为评分值差异均有统计学意义(P＜0.05).结论:笑气吸入镇静应用于口腔固定修复中的牙体预备治疗,减轻口腔治疗患者的焦虑和恐惧,具有良好的止痛镇静作用.     

基牙牙体预备的科学观念

口腔修复医生在进行牙体预备 (ａｂｕｔｍｏｎｔｐｒｅｐａｒａｔｉｏｎ)时 ,除必须严格掌握牙体预备的一般原则和要求外 ,还必须树立科学的临床修复治疗观念 ,以防因不合理的牙体预备而导致一系列医源性的牙体、牙髓、牙周组织病变的发生。1　基牙牙体预备的基本要求牙体预备是口腔修复临床中 ,为了使修复达到良好的效果 ,按照设计方案要求对患牙 (或健康基牙 )作必要的预备 ,磨除一定的牙体组织。牙体预备应符合生物学和机械力学的原则 ,因此必须达到和满足下列目的和要求 :①去除病变组织 ,防止病变发展 ;②消除轴壁倒凹 ,获得良好的就位…     

厦门市370名老年人缺牙和牙体磨损情况调查

目的:探讨厦门地区部分老年人牙磨损的特点及相关因素。方法:调查厦门地区370名离退休老干部缺牙和磨损的情况,并进行比较分析。结果:老年人牙体磨损率70.2%,Ⅱ°磨损率占52.6%;Ⅲ°占25.3%;磨损牙位分布,前牙磨损率为45.4%。结论:牙体磨损亦是损害老年口腔健康的常见病,临床医生应重视查找和消除牙磨损的潜在因素,并采取积极广泛的牙体修复治疗和提高对老年人口腔保健的宣传。     

复合树脂嵌体经离体光照固化后修复牙体严重缺损的临床研究

目的：探讨一种适宜的修复牙体严重缺损的方法。方法:复合树脂嵌体经离体光固化后再黏结修复，并与其它传统修复方法比较。结果：1－1．5年临床效果显示：离体光照优于在体光照、银汞合金充填或离子充填。结论：光固化复合树脂嵌体离体固化黏结修复牙体严重缺损是一种值得临床推广的好方法。     

活髓牙与去髓牙的牙体脆性比较研究

150颗离体牙中,正常活伪髓牙50颗。离体干燥牙50颗,去髓牙50颗。将其制成含牙釉质和牙本质的牙体硬组织标本,置于电子万能试验机下测定抗压强度和抗剪切强度。结果表明,三组标本之间,平均抗压强度和抗剪切强度差别无显著性。     

牙体修复失败原因探讨

目的 通过对256颗牙体修复失败原因分析，探讨提高牙体修复质量的各种相关因素。方法 收集因牙体修复失败需重新治疗235位患者的256颗牙齿，其中银汞修复146颗牙;高分子材料修复110颗牙。分别对其修复失败原因和修复体在口腔中存在时间长短，进行总结分析。结果 无论用银汞合金，还是高分子材料修复，失败比例最高为继发龋，分别占28．76％和23．64％；其次，银汞合金为牙折、洞型设计不良、根尖炎、He创伤、修复体脱落、修复体折断、牙髓炎、食物嵌塞和悬突。高分子材料为色素沉积、He创伤、修复体折断、修复体脱落、牙髓炎、修复体磨损、根尖炎、悬突和食物嵌塞。分析修复体存在口腔中存留的时间发现，银汞合金和高分子材料修复中，1～3年组失败最高，分别占44．52％和32．73％。结论 在牙体修复中，预防继发龋的发生，调整咬合关系，对延长修复体的使用寿命是至关重要的。     

牙体牙周软硬组织形态及其相关性研究进展

口腔修复是牙体缺损、牙列缺损和牙列缺失的主要治疗方法,除了要恢复牙体外形和功能以外,还需维持牙周长期健康稳定。因此,在口腔修复过程中应注意协调牙体牙周软硬组织形态。文章就牙体外形突度、牙龈生物型及其覆盖的牙槽骨厚度的相关研究进展做一综述,为临床口腔修复方案的制定提供参考,为技师制作修复体提供指导。     

活髓牙与去髓牙的牙体脆性比较研究

１５０颗离体牙中，正常活髓牙５０颗。离体干燥牙５０颗，去髓牙５０颗，将其制成含牙釉质和牙本质的牙体硬组织标本，轩于电子万能试验机下测定抗压强度和抗剪切强度。结果表明，三组标本之间，平均抗压强度和抗剪切强度差别无显著性。     

Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth

STATEMENT OF PROBLEM: A restored endodontically treated tooth is less likely to fracture when there is axial tooth structure between the core base and preparation finish line. However, an accurate prognosis requires knowing whether fracture resistance depends on a complete circumferential distribution of tooth structure or tooth structure in a specific location related to the applied force. PURPOSE: This in vitro study investigated the fracture resistance of restored endodontically treated teeth when residual axial tooth structure was limited to one half the circumference of the crown preparation. MATERIAL AND METHODS: Fifty extracted maxillary anterior teeth were sectioned 18 mm from their apices, endodontically treated, and divided into 5 groups of 10 teeth each. Four groups were prepared with full shoulder crown preparations having axial wall heights of 2 mm around the preparation circumferences. In 3 of the groups with axial tooth structure, one half of the axial tooth structure was removed, palatally, labially, or proximally, and groups were identified according to the site of retained coronal tooth structure. For the fifth group, all axial tooth structure was removed to the level of the preparation shoulder. Thus, in 1 group the axial walls were circumferential, 360 degrees around the preparations (Complete group), in 3 groups the axial walls were continuous for 180 degrees (Palatal, Labial, and Proximal groups), and the last group had no retained coronal tooth structure incisal to the finish line (Level group). All 50 prepared teeth were then restored with quartz fiber posts (Bisco), composite resin (Bisco) cores, and metal crowns. A universal testing machine compressively loaded the tooth specimens from the palatal at a crosshead speed of 0.5 cm/min at an angle of 135 degrees to the long axis of teeth until failure occurred. A survival analysis was conducted using a log-rank test followed by Holm-Sidak pairwise tests (alpha=.05) to detect significant differences in median failure load between groups. The mode of failure was determined by visual inspection of all specimens. RESULTS: The median failure load (P<.001) was 607 N, 782 N, 358 N, 375 N, and 172 N for the Complete, Palatal, Labial, Proximal, and Level groups, respectively. The predominant mode of failure was an oblique palatal to facial root fracture for the groups with remaining coronal tooth structure. In the Level group, post debonding was the predominant mode of failure. CONCLUSION: For restored endodontically treated teeth that do not have complete circumferential tooth structure between the core and preparation finish line, the location of the remaining coronal tooth structure may affect their fracture resistance.     

Use of natural teeth in an interim partial denture

A clinical case is presented in which the patient's natural teeth were used in an interim partial denture. The patient accepted this treatment despite his reluctance to have the periodontally hopeless anterior teeth extracted. This technique may be used when the patient is emotionally unprepared for tooth loss, when the teeth to be replaced are highly characterized, or when no suitable denture tooth is available.     

Influence of prefabricated post material on restored teeth: fracture strength and stress distribution

AIMS: This work studied how prefabricated intraradicular post material affects the mechanical performance of restored teeth. The effect of using two different materials (glass fiber and stainless steel) with significantly different elastic moduli was studied. METHODS: A combined theoretical and experimental method was used: first, an experimental fracture strength test was performed on 60 extracted human maxillary central incisors. The teeth were decoronated, treated endodontically and restored, 30 with glass fiber posts and 30 with stainless steel posts. The data were recorded and the results compared using an ANOVA test. Then, the finite element technique was used to develop a model of the restored tooth. For both post systems, the model allowed for the study of stress distribution patterns on the restored tooth under external loads. RESULTS: For teeth restored with stainless steel posts, a significantly lower failure load was found, as compared with those teeth restored with glass fiber posts (520 N versus 803 N). The estimated distributions confirmed a worse mechanical performance on teeth restored using stainless steel posts, with a high stress concentration due to the significant difference between the elastic moduli of the steel and the surrounding materials. CONCLUSION: Within the limitations of this study, post systems, where the elastic modulus of the post is similar to that of dentin and core, have a better biomechanical performance.     

Electric current induced in teeth by electromagnetic fields from electric toothbrushes and curing lights

PurposeThe purpose of this study was to examine the electric current induced in teeth and tooth-bonded brackets by electromagnetic fields from electric toothbrushes and the curing lights used for photo-activating light-cured resins.Materials and methodsCuring lights-generated low-frequency magnetic fields (1–2000 Hz) were measured with a spectrum analyzer. Temperature changes induced in the enamel and pulpal dentin surface of extracted upper premolar teeth (with or without a stainless steel or zirconia bracket) by electric toothbrushes and curing lights were estimated using an infrared thermometer. Electric current induced in these extracted teeth by electric appliances was estimated using a digital multimeter.ResultsCuring lights generated low-frequency magnetic fields. Irradiation of the tooth surface by curing lights elevated the temperature of the enamel and pulpal dentin surfaces, but there were no differences between curing lights. About electric current induced in extracted teeth (with or without a bracket) by electric toothbrushes and curing lights, the highest current was induced in teeth to which a zirconia bracket was bonded, whereas the lowest current was in unmodified teeth. Intermediate currents were generated in teeth bonded to stainless steel brackets.ConclusionThe low-frequency magnetic fields induced by electric toothbrushes and light curing units induce electric current in tooth tissue, irrespective of whether these teeth are bonded to stainless steel or zirconia brackets.     

Tooth structure removal associated with various preparation designs for anterior teeth

STATEMENT OF PROBLEM: The conservation of sound tooth structure helps preserve tooth vitality and reduce postoperative sensitivity. Innovative preparation designs, like those for porcelain laminate veneers, are much less invasive than conventional complete-coverage crown preparations. However, no study has quantified the amount of tooth structure removed during these preparations. PURPOSE: The purpose of this study was to quantify and compare the amount of tooth structure removed when various innovative and conventional tooth preparation designs were completed on different teeth. MATERIAL AND METHOD:. A new comprehensive tooth preparation design classification system was introduced. Typodont resin teeth representing the maxillary left central incisor, maxillary left canine, and mandibular left central incisor were prepared with the following designs: partial (V1), traditional (V2), extended (V3), and complete (V4) porcelain laminate veneer preparations; resin-bonded retainer preparation with grooves (A1) and with wing/grooves (A2); all-ceramic crown preparation with 0.8 mm axial reduction and tapering chamfer finish line (F1), all-ceramic crown preparation with 1.0 mm axial reduction and rounded shoulder finish line (F2), and metal-ceramic crown with 1.4 mm axial reduction and facial shoulder finish line (F3). After tooth preparations (10 per group), the crown was separated from the root at the CEJ. The removed coronal tooth structure was measured with gravimetric analysis. Means and standard deviations for tooth structure removal with different preparation designs were calculated and analyzed with analysis of variance at a significance level of P<.05. RESULTS: Significant differences in the amount of tooth structure removal were noted between preparation designs. Ceramic veneers and resin-bonded prosthesis retainers were the least invasive preparation designs, removing approximately 3% to 30% of the coronal tooth structure by weight. Approximately 63% to 72% of the coronal tooth structure was removed when teeth were prepared for all-ceramic and metal-ceramic crowns. For a single crown restoration, the tooth structure removal required for an F3 preparation (metal-ceramic crown) was 4.3 times greater than for a V2 preparation (porcelain laminate veneer, facial surface only) and 2.4 times greater than for a V4 preparation (more extensive porcelain laminate veneer). CONCLUSION: Within the limitations of this study, tooth preparations for porcelain laminate veneers and resin-bonded prostheses required approximately one-quarter to one-half the amount of tooth reduction of conventional complete-coverage crowns.     

A study into the variations in the labial reduction of teeth prepared to receive porcelain veneers--a comparison of three clinical techniques

OBJECTIVES: Various techniques have been suggested to enable the operator to produce an even reduction of 0.5 mm of labial tooth enamel during preparation for a porcelain veneer. For example, in addition to the traditional free hand method, longitudinal or horizontal depth orientation grooves and the use of small round burs to produce dimples as depth guides have been suggested. However, there is no published data that compares how effective these techniques are at producing the 'ideal' veneer preparation. In this study three techniques were compared using the technique of co-ordinate metrology. METHOD: A single operator using the above three techniques prepared 84 extracted teeth. Impressions of the prepared and unprepared teeth were scanned using a co-ordinate measuring machine (CMM). Measurements of maximum labial reduction along the mid-labial plane were taken and analysed. RESULTS: The study showed that among the three techniques studied the use of small round burs (D001-012), when used side on at an angle of 45 degrees to the tooth surface to produce dimples as depth guides, resulted in the greatest frequency of tooth reductions closer to the 'ideal' depth chosen for this study, ie within the 0.4 mm-0.6 mm range. CONCLUSION: The study concluded that even after using techniques designed to produce consistent preparations, a single operator still produced preparations with considerable variation from the ideal. The study showed that among the three techniques compared the use of small round burs, when used side on at an angle of 45 degrees to the tooth surface to produce dimples as depth guides, resulted in the greatest frequency of tooth reduction closer to the 'ideal' depth chosen for this study only, ie within the 0.4 mm-0.6 mm range. It is stressed that this range may not be the ideal in all clinical situations.     

Comparative bond strengths of plastic teeth to microwave-curing, heat-curing and 4-META containing denture base resins

Bond strength of hardened plastic teeth or acrylic resin teeth to microwave-curing, conventional heat-curing and 4-META-containing denture base resins were comparatively investigated in this study. Effects of grinding and monomer coating of the tooth ridge lap were also studied. Bond strength of plastic denture teeth to microwave-curing denture base resin was slightly higher than the other two resins. With all denture base resins used, an increased bond strength was obtained with hardened plastic teeth by treatment of tooth ridge lap but not with acrylic resin teeth. However, scattering of the bond strength was reduced by treatment of tooth ridge lap in acrylic resin teeth specimens. With hardened plastic teeth specimens, fracture in the base resin was increased by monomer coating. With acrylic resin teeth specimens, no specific fracture patterns were demonstrated by treatment of tooth ridge lap. Fracture occurred mostly in the acrylic resin teeth. These results suggest that bond strength of both denture teeth to microwave-curing or 4-META-containing denture base resin was increased or solidified by grinding or monomer coating of tooth ridge lap.     

Stiffness of endodontically-treated teeth related to restoration technique

Endodontically-treated posterior teeth are susceptible to fracture; consequently, full-occlusal-coverage restorations are recommended. We designed this study to examine the potential for alternative restorative techniques for pulpless teeth, using strain gauges mounted on extracted maxillary second premolars to measure strains generated by nondestructive occlusal loading. Cuspal stiffness was evaluated on the following sequentially performed procedures: unaltered tooth, completion of all endodontic procedures, appropriate restorative preparation, and restoration. The restorative procedures evaluated were: (1) amalgam, (2) cast gold onlay, (3) composite restoration with enamel etch, and (4) composite restoration with enamel and dentin etch. Finally, all teeth were loaded to fracture. Cast gold was the strongest restorative material tested (2.11 relative stiffness, compared with that of the unaltered tooth at 1.00), and amalgam was the weakest (0.35 relative stiffness). Composite restoration and enamel plus dentin etch were almost as strong as the unaltered tooth (0.87 relative stiffness), while enamel-etch-only yielded lower stiffness (0.51).     

A cognitive systematic approach to analyzing preparation design for a difficult space management case

There are at least two different techniques for preparing teeth prior to bonded porcelain restorations. The first involves using depth cutters guided by the existing tooth structure. A more recently developed approach integrates an additive wax-up that represents the final volume of the teeth, with indices used to guide the preparation design. This article illustrates in detail a clinical case that was prepared by combining the earlier simplified depth cutter approach with recontouring and preparation design principles determined clinically by the dentist. The same case was prepared in the laboratory on plastic models, using labial and incisal reduction preparation guides fabricated from a diagnostic wax-up. This combination of techniques will simplify preparation design for difficult space management cases and facilitate predictable and repeatable results that meet current esthetic standards while staying conservative and preserving tooth structure.     

Effects of Er:YAG laser irradiation on human extracted teeth

The ablation effects of the Erbium:YAG laser (wave length: 2.94 microns) on the human extracted teeth were examined histopathologically. The enamel surface of the human extracted tooth was irradiated by the laser at 500 mJ, 1 pps or 3 pps: 3, 15, 30, 50 and 100 shots. After observation under a dissecting microscope, the teeth were placed in a demineralizing solution of 0.1 M lactate buffer with 6% hydroxyethyl cellulose (pH 4.5) in order to evaluate the acid resistance of the enamel adjacent to the ablated area. After 4 days, the degree of demineralization of the surrounding enamel was assessed by contact microradiography. The result showed that every irradiated tooth had a clear-cut defect, and almost all the teeth had acquired acid resistance at the enamel surrounding the ablated portion. The other experiment was carried out to estimate the effects of the Er:YAG laser through a contact probe. The enamel, dentin and cementum of the extracted teeth were irradiated at 39 mJ or 74 mJ, 10 pps; 10 shots. The teeth were observed under a dissecting microscope. The result clearly indicated that the Er:YAG laser guided by the contact probe could also produce a defect in the dental hard tissue. The above-mentioned findings suggested that the Er:YAG laser could pave the way for the cavity preparation with acid-resistant cavity margin.