硼酸铝（9Al2O3.2B2O3）晶须的制备和性质

目的：制备硼酸铝晶须及测其物理化学特征。方法：原料在电炉中加热至１１５０℃，４ｈ，获得的晶须采用化学方法确定其组成，物理化学方法检测其表征。结果：获得了晶须的化学组成、Ｘ射线粉末衍射图、ＦＴ－ＩＲ光谱和Ｒａｍａｎ光谱图。结论：制备的晶须为四硼酸十八铝。     

全冠牙预备体表面涂布极固宁TM后对其固位力的影响

目的探讨涂布极固宁TM后对全冠固位力的影响。方法制作面聚合度(TOC)为10°和20°的全冠牙预备体各10个,随机分为实验组和对照组。每组TOC10°和20°的全冠牙预备体各5个。制作铸造全冠20个。实验组涂布极固宁TM后玻璃离子黏固剂黏固全冠,对照组直接玻璃离子黏固剂黏固全冠。材料实验机上测两组全冠拉脱时的最大拉力值。扫描电镜观察表面并能谱仪分析。结果TOC为10°的实验组全冠和对照组全冠拉脱时的最大拉力值分别为(443.59±74.20)N和(509.07±69.05)N,两组间的差异无统计学意义(P=0.056);TOC为20°时实验组和对照组全冠拉脱时最大拉力值分别为(291.57±49.27)N和(390.82±91.44)N,两组间的差异有统计学意义(P=0.009)。结论TOC为10°的牙预备体表面经极固宁TM处理后对玻璃离子黏固剂黏固的全冠的固位力没有影响;而TOC为20°时牙预备体表面经极固宁TM处理后的固位力显著下降。     

Atomic analysis and knoop hardness measurement of the cavity floor prepared by Er,Cr:YSGG laser irradiation in vitro

In the present study, the compositional changes and knoop hardness of the cavity floor prepared by Er,Cr:YSGG laser irradiation was compared with that of the conventional bur cavity. Fifteen laser and 15 bur cavities were cross-sectioned, and subjected to atomic analysis by SEM-EDX and knoop hardness test. Statistical analyses were performed using the Mann-Whitney U-test; a value of P < 0.01 was considered significant. Surface characteristics of the prepared cavities were also investigated by light microscopy and scanning electron microscopy (SEM). The results showed that the quantities of Ca (Ca weight %) and P (P weight %) were increased significantly in the laser cavity floor but no significant differences were found between the Ca/P ratio and knoop hardness number of laser and bur cavities. The SEM observation revealed that the lased cavity surface was irregular and there was also the absence of a smear layer; the orifice of dentinal tubules was exposed. Er,Cr:YSGG laser device is considered as one of the most effective and safe devices for cavity preparation because of its many advantages. This includes easy delivery system, minimal thermal damage to the surrounding tissues, minimal thermal-induced changes of dental hard tissue compositions, and favourable surface characteristic.     

ProTaper手动锉预备弯曲根管的临床评价

目的评价ProTaper手动锉预备弯曲根管的临床疗效。方法将40颗具弯曲根管需行根管治疗的患牙随机分为两组：试验组用ProTaper手动锉及冠根向技术预备根管，对照组用K锉及逐步后退技术预备根管。两组均采用侧向加压充填法充填根管，用X线片评价根管预备的效果。结果ProTaper手动锉组无根管偏移、根尖堵塞、台阶形成、器械折断等并发症发生，能维持根管的弯曲度和走向，根管锥度和流畅度佳；操作时间短，且术后疼痛发生率低。结论ProTaper手动锉预备弯曲根管快速、安全、有效，临床应用价值较高。     

试件形状和光滑度对纵折牙牙本质黏接微拉伸强度的影响

目的评价试件形状和牙本质黏接面磨光对纵折牙牙本质黏接微拉伸强度的影响。方法选择新鲜拔除的人完整磨牙及前磨牙15颗,用慢速切割机先去除牙齿咬合面的釉质,再沿牙齿近远中向或颊舌向纵切牙体至釉牙骨质界下,作为纵折裂缝,随机分为3组。A组折裂面用Super-Bond C&B树脂水门汀黏接后,制成哑铃形试件;B组黏接后,制成棒状试件;C组的折裂面用800目碳化硅耐水砂纸湿磨光1min后,再黏接,制成棒状试件。分别测试三组的微拉伸强度。结果A、B、C 3组的微拉伸强度分别为(7．75±2．67)MPa、(21．19±4．90)MPa、(27．56±7．60)MPa。棒状试件组(B组)的微拉伸强度高于哑铃形试件组(A组)(P=-0．0000);磨光组(C组)的微拉伸强度高于非磨光组(B组)(P=0．0088)。结论试件形状和对牙本质黏接面磨光与否对纵折牙的牙本质黏接微拉伸强度有影响。     

Er、Cr:YSGG激光根管内照射对根管封闭效果的影响

目的:探讨常规根管预备后使用不同能量的Er、Cr:YSGG激光进行根管内照射对根充后根管封闭效果的影响。方法:选择新拔除的单根管牙105颗,分成7组,每组15颗牙。切除牙冠后,常规进行根管预备。第1组不进行任何处理,作为阳性对照组;第2组为1W、有水激光照射;第3组为1W、无水激光照射;第4组为2W、有水激光照射;第5组为2W、无水激光照射;第6组为3W、有水激光照射;第7组为3W、无水激光照射。根充后进行根尖微渗漏检测,评估根管封闭效果。采用单因素方差分析(Anova)进行多组间总体均数比较,q检验进行组间比较。结果:除3W无水组外,其他各激光组与对照组相比,根尖微渗漏深度均有显著性差异(P<0.05);其中1W无水组与对照组相比具有高度显著性差异(P<0.01)。结论:较低能量(除外3W、无水)Er、Cr:YSGG激光进行根管内照射,能够有效提高根管充填后的封闭效果,其中1W、无水激光照射时根管封闭效果最好。     

An in vitro comparison of canal preparation using two automated rotary nickel-titanium instrumentation techniques

AIM: The aim of this study was to compare the efficacy of root canal preparation using two automated rotary nickel-titanium instrumentation techniques with a double flared balanced forces hand preparation technique, using stainless steel files in extracted human teeth. METHODOLOGY: Sixty root canals in extracted human teeth were matched for curvature, length and diameter and divided evenly between three groups (group 1 = double flare using Flexofiles, group 2 = rotary nickel-titanium using McXIM instruments and group 3 = rotary nickel-titanium using Profile .04 Taper Series 29 instruments). The instruments were used according to the manufacturer's instructions in a torque controlled motor and handpiece (groups 2 and 3) and according to a predetermined procedure in group 1. A standardized radiographic technique using mercury as a contrast medium was used to evaluate the canal shape before and after preparation in the plane of maximum curvature. The pre- and postoperative radiographic images were compared against each other and with a predicted 'ideal preparation' calculated from a projection of the final instrument dimensions. The outcome measures were changes in canal dimensions as quantified by measuring the changes in the position of the inner and outer wall at 1 mm intervals. Alteration in canal curvature could be inferred by comparison with the ideal preparation. RESULTS: The degree of canal curvature did not influence the effectiveness of any of the techniques. The results showed no statistically significant differences in the outcome measures between the groups (two-way ANOVA). There were no significant differences in canal wall position changes at any level except the apical three, where significantly less change occurred in all groups (P = 1%). Instruments fractured in three canals, with acute curves in groups 2 and 3. CONCLUSIONS: Canal curvatures were equally and well maintained following preparation in all the groups, as long as the instrument did not fracture.     

Microleakage in conservative cavities varying the preparation method and surface treatment

Objective

To assess microleakage in conservative class V cavities prepared with aluminum-oxide air abrasion or turbine and restored with self-etching or etch-and-rinse adhesive systems.

Material and Methods

Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37% phosphoric acid; groups II/IV -self-priming etchant (Tyrian-SPe). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50% silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey’s test (α=0.05).

Results

Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37% phosphoric acid; groups II/IV -self-priming etchant (Tyrian-SPe). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50% silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey’s test (α=0.05).

Conclusion

Marginal seal of cavities prepared with aluminum-oxide air abrasion was different from that of conventionally prepared cavities, and the etch-and-rinse system promoted higher marginal seal at both enamel and dentin margins.     

氢氧化钙甘油糊剂对根管壁玷污层的溶解作用研究

目的观察氢氧化钙甘油糊剂对根管壁玷污层的溶解作用。方法30颗离体上前牙随机分为3组。常规预备根管后,A组封入氢氧化钙甘油糊剂,B组封入碘仿糊剂,C组封入樟脑酚。7d后清洗根管壁,并在扫描电镜下观察。结果A组根管壁玷污层明显较少,与B组和C组差异有统计学意义(P<0.01);B组与C组玷污层差异无统计学意义(P>0.05)。结论氢氧化钙甘油糊剂对根管壁玷污层有溶解作用。     

In vivo fractures of endodontically treated posterior teeth restored with amalgam

Abstract The cumulative survival rate (retention of both cusps) and the fracture pattern of 1639 endodontically treated posterior teeth were assessed in a retrospective study. All teeth had an MO/DO or an MOD cavity restored with amalgam without cuspal overlays. The 20-year survival rate of teeth with an MO/ DO cavity was markedly higher than that of teeth with an MOD cavity. The lowest survival rate was found for the upper premolars with an MOD cavity: 28% of these teeth fractured within 3 years after endodontic therapy, 57% were lost after 10 years, and 73% after 20 years. Generally, the cusp most prone to fracture was the lingual one, and lingual fractures caused significantly more damage to the periodontal tissues than did facial or total crown fractures. The severity of periodontal damage increased with posterior location of the tooth. By far the most serious failures, irrespective of the cavity type, were found for the upper second molar, as 10 of 29 fractures led to extraction. It is concluded that amalgam, especially in MOD cavities, is an unacceptable material for restoration of endodontically treated posterior teeth if used without cuspal overlays.