An In Vitro Investigation of a Comparison of Bond Strengths of Composite to Etched and Air-Abraded Human Enamel Surfaces

PURPOSE: The purposes of the study were to measure the tensile bond strength of composite resin to human enamel specimens that had been either etched or air-abraded, and to compare the quality of the marginal seal, through the assessment of microleakage, of composite resin to human enamel specimens that had been either etched or air-abraded. MATERIALS AND METHODS: Thirty mandibular molar teeth were decoronated and sectioned mesio-distally to produce six groups, each containing ten specimens that were embedded in acrylic resin using a jig. In each of the four treatment groups, the specimen surfaces were treated by either abrasion with 27 or 50 microm alumina at 4 mm or 20 mm distance, and a composite resin was bonded to the treated surfaces in a standardized manner. In the two control groups the specimens were treated with 15 seconds exposure to 36% phosphoric acid gel and then similarly treated before being stored in sterile water for 1 week. All specimens were then subjected to tensile bond strength testing at either 1 or 5 mm/min crosshead speed. For the microleakage study, the degree of dye penetration was measured 32 times for each treatment group, using a neutral methylene blue dye at the interface between composite and either 27 or 50 microm air-abraded tooth structure or etched enamel surfaces. RESULTS: The mean bond strength values recorded for Group 1 (phosphoric acid etch, 5 mm/min crosshead speed) was 25.4 MPa; Group 2 (phosphoric acid etch, 1 mm/min), 22.2 MPa; Group 3 (27 microm alumina at 4 mm distance), 16.8 MPa; Group 4 (50 microm alumina at 4 mm distance), 16.9 MPa; Group 5 (27 microm alumina at 20 mm distance), 4.2 MPa; and for Group 6 (50 microm alumina at 20 mm distance) 3.4 MPa. An analysis of variance (ANOVA) demonstrated significant differences among the groups, and a multiple comparison test (Tukey) demonstrated that conventionally etched specimens had a greater bond strength than air-abraded specimen groups. No significant difference in dye penetration could be demonstrated among the groups (p= 0.58). CONCLUSIONS: Composite resin applied to enamel surfaces prepared using an acid etch procedure exhibited higher bond strengths than those prepared with air abrasion technology. The abrasion particle size did not affect the bond strength produced, but the latter was adversely affected by the distance of the air abrasion nozzle from the enamel surface. The crosshead speed of the bond testing apparatus had no effect on the bond strengths recorded. The marginal seal of composite to prepared enamel was unaffected by the method of enamel preparation.     

Antibiotic prophylaxis for dentoalveolar surgery: is it indicated?

Usually dentists in Australia give patients oral antibiotics after dentoalveolar surgery as a prophylaxis against wound infection. When this practice is compared to the principle of antibiotic prophylaxis in major surgery it is found to be at variance in a number of ways. In major surgery, the risk of infection should be high, and the consequences of infection severe or catastrophic, before antibiotic prophylaxis is ordered. If it is provided then a high dose of an appropriate spectrum antibiotic must be present in the blood prior to the first incision. Other factors which need to be considered are the degree of tissue trauma, the extent of host compromise, other medical comorbidities and length of hospitalization. Standardized protocols of administration have been determined and evaluated for most major surgical procedures. Dentoalveolar surgery is undoubtedly a skilled and technically challenging procedure. However, in contrast to major surgical procedures, it has a less than five per cent infection rate and rarely has severe adverse consequences. Dentoalveolar surgery should be of short duration with minimal tissue damage and performed in the dental chair under local anaesthesia. Controlled studies for both mandibular third molar surgery and placement of dental implants show little or no evidence of benefit from antibiotic prophylaxis and there is an adverse risk from the antibiotic. This review concludes that there is no case for antibiotic prophylaxis for most dentoalveolar surgery in fit patients. In the few cases where it can be considered, a single high pre-operative dose should be given.     

Localization of Lower Right Molars in a Panoramic Radiograph, Lateral Cephalogram and Dental CT

In this investigation, the radiological status of angular measurements in the wisdom tooth area was examined. The angles of the tooth center lines of the second and third lower molars (48,47) to the occlusal plane and to one another in 25 orthodontically untreated patients (average age: 16.3 years) were measured and compared with angular values of the patients concerned measured in a dental CT. The assessment of these 3 radiological documents in an absolute comparison revealed closely corresponding angular values. However, the dental CT provided a considerably more accurate and, in addition, a three-dimensional topographical localization of lower wisdom teeth. Zusammenfassung: In der vorliegenden Untersuchung wurde der radiologische Stellenwert von Winkelmessungen im Weisheitszahnbereich überprüft. Im Fernröntgenseitenbild und Orthopantomogramm wurden die zur Okklusionsebene und zueinander gemessenen Zahnachsenwinkel des dritten und zweiten unteren Molaren (48, 47) von 25 kieferorthopädisch unbehandelten Patienten (Durchschnittsalter: 16,3 Jahre) vermessen und mit im Dental-CT gemessenen Winkelwerten des jeweiligen Patienten verglichen. Die Beurteilung dieser drei radiologischen Unterlagen ergab im absoluten Vergleich annährend sich entsprechende Winkelwerte. Das Dental-CT gestattete jedoch eine wesentlich genauere und zudem dreidimensionale topographische Lagebestimmung unterer Weisheitszähne.     

Implant-Supported Rehabilitation of the Severely Atrophic Maxilla: A Clinical Report

Implant-supported rehabilitation in the posterior maxillary region presents a series of challenges because of the possibility of increased pneumatization of the maxillary sinus after dental loss. In cases where significant maxillary bone resorption has occurred, efforts center on maximizing the use of the remaining bone to afford primary stability to the implants. This clinical report describes a patient with extreme maxillary atrophy for whom fixed rehabilitation supported on 8 implants was accomplished. A zygomatic implant, a pterygomaxillary implant, and 2 implants mesial and distal to both canine eminences were placed. This rehabilitation was accomplished with a less invasive technique and in a much shorter time period compared to a sinus lift procedure. One year after prosthetic loading, the clinical and radiological results remain satisfactory.     

Impact testing of a polysulphone denture base polymer

A bstract — The impact resistance of a polysulphone denture base polymer has been determined, and for comparison the impact resistance was also determined of a linear poly(methyl methacrylate) and four rubber-modified methacrylate denture base polymers. When tested under mouth conditions the polysulphone had an impact resistance more than four times as high as the poly(methyl methacrylate) and about twice as high as the most impact resistant rubber-modified methacrylate. Unlike some of the other materials tested, the polysulphone did not suffer a reduction in impact resistance on extended ageing under mouth conditions.     

微型种植钉的长度直径对生物力学的影响

目的对比评价临床常用的3种类型(不同长度、直径)微型种植钉的生物力学特点。方法应用种植钉48枚,新西兰大白兔8只。采用拉出试验,扭转强度试验,在即刻与愈合4周后进行生物力学测量。结果长度为6mm,直径为1.9mm的种植钉相对于同等长度,直径为1.5mm的种植钉在“种植后即刻”与“愈合4周”时,最大剪切力均表现出显著性优势。愈合4周后,直径为1.9mm的种植体在最大扭转强度上表现出显著性的优势。结论在骨质量较差的部位选择较大直径的种植体有利于种植体的稳定。     

44例老年患者慢性根尖周炎伴皮瘘牙的治疗

自1992年以来,共诊治慢性根尖周炎致颌面部皮瘘的老年患者59例,其中15例因病源牙无保留价值,采取拔牙法而治愈皮瘘.其余44例的病源牙进行了保存治疗,经临床观察,疗效满意,报道如下. 临床资料:44例,男性27例,女性17例;年龄60～76岁,平均65.2岁.病程最短3个月,最长3年;本组病例颌骨均未发现伴有慢性骨髓炎.皮瘘发生的部位与牙位见附表.     

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目的探讨螺旋CT三维重建技术在埋伏尖牙正畸牵引中的应用价值。方法2006年3月至2007年12月,南京大学医学院附属口腔医院正畸科对12例颌骨内尖牙埋伏阻生患者进行螺旋CT检查、颌面骨三维重建,并与曲面断层X线片进行对比观察。结果CT三维重建能对颌骨内埋伏阻生尖牙准确定位,与颌骨内的实际情况所见完全一致,极大的提高了埋伏尖牙正畸牵引的成功率,有效地缩短了患者的治疗时间,减少了患者的痛苦。结论螺旋CT三维重建影像可以直观地显示埋伏阻生尖牙在颌骨内的生长情况,对上颌骨埋伏阻生尖牙的定位、治疗方案的制定具有重要指导作用。