Bonding polycarbonate brackets to ceramic: effects of substrate treatment on bond strength.

This study evaluated the effects of 5 different surface conditioning methods on the bond strength of polycarbonate brackets bonded to ceramic surfaces with resin based cement. Six disc-shaped ceramic specimens (feldspathic porcelain) with glazed surfaces were used for each group. The specimens were randomly assigned to 1 of the following treatment conditions of the ceramic surface: (1) orthophosphoric acid + primer + bonding agent, (2) hydrofluoric acid gel + primer + bonding agent, (3) tribochemical silica coating (silicon dioxide, 30microm) + silane, (4) airborne particle abrasion (aluminum trioxide, 30microm) + silane, and (5) airborne particle abrasion (aluminum trioxide, 30microm) + silane + bonding agent. Brackets were bonded to the conditioned ceramic specimens with a light-polymerized resin composite. All specimens were stored in water for 1 week at 37 degrees C and then thermocycled (1000 cycles, 5 degrees C to 55 degrees C, 30 seconds). The shear bond strength values were measured on a universal testing machine at a crosshead speed of 1 mm/min. Brackets treated with silica coating with silanization had significantly greater bond strength values (13.6 MPa, P =.01) than brackets treated with orthophosphoric acid (8.5 MPa). There was no significant difference (P =.97) between the bond strengths obtained after airborne abrasion with aluminium trioxide particles followed by silanization (12 MPa) and hydrofluoric acid application (11.2 MPa) (ANOVA and Tukey test). Although brackets conditioned with orthophosphoric acid exhibited only adhesive failures of the luting cement from the ceramic surface, other conditioning methods showed mixed types of failures. Airborne particle abrasion with aluminium trioxide or silica coating followed by silanization gave the most favorable bond strengths. The types of failures observed after debonding indicated that the critical parameter was the strength of the adhesive joint of the luting cement to both the bracket and the ceramic.     

Macrocytosis as a Consequence of Alcohol Abuse among Patients in General Practice

Macrocytosis, a common finding in patients without anemia or other hematologic abnormalities, is often ignored. The purpose of this prospective study was to investigate 300 consecutive, adult health-center patients with a mean cell volume (MCV) value greater than or equal to 100 fl. The incidence of macrocytosis was 2.4%. Of the 177 male and 123 female patients, only 14 (4.7%) were anemic; 80.2% of the men (89.3% of those under 60 years) and 34.1% of the women were alcohol abusers, representing the largest diagnostic group. The highest MCV value found in alcoholics without folate or vitamin B12 deficiency was 120 fl. The most useful laboratory test for identifying alcohol abuse among macrocytic patients was the measurement of serum gamma-glutamyltransferase. Of the several morphologic abnormalities in the marrow the only specific finding were vacuoles in the granulocyte or erythrocyte precursors. No underlying cause was found for macrocytosis in 6.8% of the men and 35.8% of the women. Even when it is not associated with anemia, macrocytosis should not be ignored. It may be the only indicator of a disease which often, particularly in young and middle-aged men, is alcohol abuse.     

Effects of Volatile Anesthetics on Atrial and AV Nodal Electrophysiological Properties in Guinea Pig Isolated Perfused Heart

Background: Knowledge of the anesthetic effects on atrial and atrioventricular (AV) nodal electrophysiologic properties is fundamental to understand the modulatory role of anesthetics on the pathogenesis of supraventricular tachycardias, and to individualize the perioperative management of patients with supraventricular tachycardias or AV nodal conduction disturbances. Therefore the authors studied the effects of three commonly used volatile anesthetics on the electrophysiologic properties of the atrium and AV node.

Methods: The concentration-dependent electrophysiologic effects of halothane, isoflurane, and desflurane (0 - 2 minimum alveolar concentration [MAC]) were studied in guinea pig Langendorff-perfused hearts fit with instruments to simultaneously measure atrial and AV nodal conduction times and atrial monophasic action potential duration. Atrial and AV nodal effective refractory periods were measured simultaneously using a computer-assisted premature stimulation protocol. The concentrations of anesthetics in the gas phase were monitor by an infrared gas analyzer.

Results: Volatile anesthetics caused markedly different concentration-dependent effects on atrial conduction, repolarization, and refractoriness, and on AV nodal function. At equianesthetic concentrations, halothane depressed atrial conduction the most, whereas desflurane caused the greatest shortening of atrial monophasic action potential duration. Halothane had no significant effect on atrial refractoriness, whereas at 2 MAC desflurane significantly shortened and isoflurane significantly prolonged atrial effective refractory periods by 18.1 +/- 13.5% and 13.2 +/- 14.7%, respectively. On an equi-MAC basis, the rank order of potency for the anesthetics to prolong AV nodal conduction time and AV nodal ERP was halothane > desflurane > isoflurane.     

Incidence and Prognosis of Ischemic Heart Disease with Respect to Geographical Area

ABSTRACT. Ischemic heart disease is more common in East Finland than in West Finland, but systematic comparison and follow-up of incidence figures have not been possible. In 1972 the personal identification number became included in the hospital discharge records, which made it possible to link death certificate data with hospital records from the whole country. The results of this study suggest that high mortality from IHD in some regions is more closely associated with high incidence than a high fatality rate. The proportion of deaths outside hospitals showed large variation by province but this had rather little effect on the total one-year survival rates.     

The effect of a 3-methacryloxypropyltrimethoxysilane and vinyltriisopropoxysilane blend and tris(3-trimethoxysilylpropyl)isocyanurate on the shear bond strength of composite resin to titanium metal.

OBJECTIVES: The aim of this study was to evaluate the reactions of silanes prior to attaching the composite to titanium and evaluate these silanes as coupling agents. Veneered titanium may be used as a prosthetic material. METHODS: Two silane solutions, a mixture of both gamma-methacryloxypropyltrimethoxysilane and vinyltriisopropoxysilane, and tris(3-trimethoxysilylpropyl)isocyanurate were prepared as 2 wt% in two different (95% 2-propanol and 90% acetone) solutions. A control, 2 wt% gamma-methacryloxypropyltrimethoxysilane was prepared in both solutions. These six silane solutions were applied onto flat titanium surfaces. The samples (N = 250) were divided into two main groups: air-dried (room temperature) and heat cured for 1 h at 110 degrees C. Sinfony veneering composite was applied and light-cured on the titanium. The control group was non-silanized. The specimens were assigned to two subgroups: not thermocycled, and thermocycled (5000 cycles, 5-55 degrees C). Shear bond strength of the composite was tested at a crosshead speed of 1.0 mm min(-1). Fresh silane solution hydrolysis, and condensation reaction on titanium surface were monitored by FTIR spectrometry. RESULTS: Dry samples could be successfully tested, while thermocycling after 3700 cycles had gradually de-bonded the composite from the silanized titanium substrate. For dry samples, statistical analysis (ANOVA) showed that solvent and silane significantly affected the shear bond strength. The silane mixture in 2-propanol reacted at room temperature yielded 11.3 MPa (Standard deviation, SD, 3.6 MPa) and on the other hand, tris(3-trimethoxysilylpropyl)isocyanurate in 2-propanol yielded 10.7 MPa (SD 8.0 MPa) and gamma-methacryloxypropyltrimethoxysilane 20.4 MPa (SD 12.2 MPa). Non-silanized samples yielded 4.8 MPa (SD 2.1 MPa). SIGNIFICANCE: In all solvents used, silanes reacted chemically with the titanium surface and covalent Si-O-Ti- and -Si-O-Si- bonds were evident.     

Acoustic emission analysis of fiber-reinforced composite in flexural testing.

OBJECTIVES: The aim of this study was to examine the emission of acoustic signals from six commercially available fiber-reinforced composites (FRC) used in the frameworks of fixed partial dentures in material bending. METHODS: FRC test specimens were made of six commercially available fiber products of polyethylene or glass and five light-curing resins. FRC test specimens were polymerized with a hand light-curing unit or with a light-curing oven. The flexural test for determination of ultimate flexural strength of test specimens (n = 6) was based on the ISO 10477 standard after the specimens were stored in air or in water for two weeks. The acoustic emission (AE) signals were monitored during three-point loading test of the test specimens using a test with increasing loading levels until the specimens fractured. RESULTS: Generally, stress level required for the AE activity initiation ranged from 107 MPa (Ribbond) to 579 MPa (everStick). The ultimate flexural strength of FRC specimens were higher, ranging from 132 to 764 MPa, being highest with everStick and Vectris FRC, and lowest with Ribbond FRC. ANOVA showed a statistically significant difference between the initiation of AE activity and the ultimate flexural strength according to the brand (p < 0.001) storing conditions (p < 0.001) and polymerization procedure (p < 0.001). AE activity and ultimate flexural strength correlated significantly (p < 0.010, r = 0.887). SIGNIFICANCE: The result of this study suggested that AE activity in FRC specimens started at a 19-32% lower stress level than occurred at final fracture.     

Assessment of material- and technique-related complications following sagittal split osteotomies stabilized by biodegradable polylactide screws

OBJECTIVE: The aim of this retrospective clinical study was to determine whether there are any material-related problems and increased occurrence of postoperative mandibular nerve and temporomandibular joint dysfunctions in connection with the use of biodegradable self-reinforced poly-L-lactide (SR-PLLA) screws for bone fixation after bilateral sagittal split osteotomies (BSSO). STUDY DESIGN: Forty consecutive patients who underwent BSSO and mandibular advancement that included fragment fixation using SR-PLLA screws were monitored for an average of 2.2 years postoperatively. RESULTS: The osteotomy sites healed uneventfully with no adverse reactions. The incidence of postoperative sensory disturbances of the inferior alveolar nerve was 27%. Symptoms of temporomandibular joint disorders (TMJD) observed preoperatively in 73% of patients were reduced to 48% after surgery. CONCLUSION: The occurrence of postoperative sensory disturbances and TMJD symptoms in this study did not deviate strikingly from that of other studies using conventional osteosynthesis. No specific complications related to the screw material were observed.