The bond strength of a highly cross-linked denture tooth to denture base polymers: a comparative study

PURPOSE

This study compared shear bond strength and type of bond failure between a highly cross-linked tooth and different denture base polymers.

MATERIALS AND METHODS

Cross-linked denture teeth were bonded to either a heat-, an auto-, a microwave-polymerized denture base resin or a relatively new injection-molded, microwave-polymerizable polyurethane-based resin. Six experimental groups were established for each of the shear and peel tests. In four of the groups, teeth were used as received and bonded to each of the denture base resins; in the remaining two groups, they were treated with dichloromethane to determine its effect on the bonding with heat or auto-polymerized denture base resins. Bond strength was determined by compressive load applied at 45 degrees on the palatal surface of each tooth until fracture; the type of bond failure was assessed by the peel test.

RESULTS

The results showed that heat-cured PMMA groups failed cohesively and demonstrated significantly higher bond strengths than the other resins used. The application of dichloromethane on the ridge lap areas of teeth resulted in a significant improvement of bond strengths in heat- and auto-cured resins.

CONCLUSION

Within the limitations of this experimental study, the results suggest that type of denture base material and processing methods may have an influence upon the bond strength between interpenetrating polymer network (IPN) denture teeth and base materials. Treatment of denture teeth with dichloromethane could provide substantial improvement in the bond strength of teeth with heat and auto-cured denture base resins; however, this finding should be validated in further investigations on the long-term effect of such treatment on the bond strength.

Composite Piezoelectric Sensors and Actuators

Composite materials have found a number of structural applications, but their use in the electronics industry has been relatively limited. As the function of electroceramic composites are better understood, we can expect this picture to change. In this paper some of the piezoelectric composite sensor and actuator studies carried out in our laboratory during the past decade will be reviewed. The ideas that provide a basic understanding of functional composites have previously been discussed [1]. This paper describes recent advances in the processing and properties of composites possessing 0-3, 1-3, and 2-2 connectivity made of polymers, metals and ferroelectric ceramics. The introduction of open spaces in the previous connectivity patterns allows the development of new designs of several piezoelectric composites with connectivity patterns of 0(0)-3, 1(0)-3, 2(0)-2-2, and 2-0-2. As in most electronic systems that are developed with improved properties a push toward lower cost and smaller sizes of the piezoelectric ceramics, together with improved reliability and performance occurs. The piezocomposites with open spaces in their structures clearly demonstrate the growth of the functional ceramics into the field of the smart ceramics as the materials for the beginning of the next century.

Femoral artery complications associated with the Mynx closure device

BACKGROUND AND PURPOSE

Devices to close a femoral arteriotomy are frequently used after catheterization for interventional radiology and cardiac procedures to decrease the time to hemostasis and ambulation and, potentially, to decrease local complications. The Mynx vascular closure device uses a sealant designed to occlude the access tract, resulting in hemostasis.

MATERIALS AND METHODS

We retrospectively reviewed all cases in which the Mynx device was used and for which follow-up angiography was available. A total of 146 devices were deployed in 135 patients. A follow-up vascular study visualizing the femoral artery was performed in 26 patients (27 studies).

RESULTS

There were 5 (5/27, 18%) cases of intravascular Mynx sealant on follow-up vascular imaging. Three pseudoaneurysms (3/27, 11%) were identified.

CONCLUSIONS

In this small study, intravascular sealant and pseudoaneurysms were found frequently after femoral arterial closure with the Mynx vascular closure device.

The effect of pretreatment with renin-angiotensin-aldosterone system blockers on cardioversion success and acute recurrence of atrial fibrillation

BACKGROUND

Renin-angiotensin-aldosterone system (RAS) may be activated during atrial fibrillation (AF). It is unclear whether RAS inhibition may facilitate cardioversion from AF and may prevent acute recurrence of AF (ARAF). We thus investigated the effect of pretreatment with RAS blockers on cardioversion success and ARAF in patients with AF scheduled for elective cardioversion.

METHODS

This observational study included 356 patients with AF undergoing elective pharmacological or electrical cardioversion. Of these patients, 135 were not included based on exclusion criteria and the remaining 221 patients were divided into RAS group (n = 116, 69 male) or non-RAS group (n = 105, 58 male) based on precardioversion use of any RAS blocker.

RESULTS

Hypertension, coronary heart disease and heart failure were more frequent in the RAS group. Cardioversion from AF was more successful in the RAS group than in the non-RAS group (%92 vs. %82, p = 0.026). The rate of ARAF was lower in RAS group compared with that in non-RAS group (17% vs. 31%, p = 0.026). In multivariate analysis, pretreatment with RAS blockers in addition to shock number and enlarged left atrium, independently predicted ARAF (OR: 0.33, 95% CI: 0.15-0.75, p = 0.008). Independent predictors of cardioversion success were shock number and left atrial dilatation, but not use of RAS blocker.

CONCLUSION

Precardioversion use of RAS blockers may reduce ARAF following successful cardioversion of AF, but did not improve electrical cardioversion.

The role of saliva in dental erosion and a prosthetic approach to treatment: a case report

AIM

The aim of this report is to describe the relationship of some salivary parameters to dental erosion resulting from excessive citric acid consumption and present a description of a prosthetic approach used to restore the damaged dentition of a patient with severe erosion.

BACKGROUND

The high consumption of dietary sources of acids can lead to erosion or the excessive wear of dental hard tissues. Erosion may be modified by salivary parameters such as flow rate, pH, and buffering capacity. Porcelain-fused-to-metal (PFM) restorations and composite resin veneers can be used successfully to restore impaired esthetics and eliminate tooth hypersensitivity in such cases.

RESULTS

A 37-year-old woman with a history of excessive lemon consumption presented with a complaint of tooth hypersensitivity and the poor appearance of her dentition due to erosion. Stimulated and unstimulated salivary samples of the patient were evaluated for flow rate, pH, and buffering capacity before and after treatment. The pre-treatment values were found to be higher than post-treatment values. Stimulated samples showed an increase of salivary flow rate, pH, and buffering capacity. The measured parameters put forth the defensive potential of saliva against the acidic diet, and the salivary flow rate and buffering capacity decreased after reducing acidic consumption. The excessively eroded teeth were restored using PFM restorations whereas the superficially eroded teeth were restored with composite resins.

SUMMARY

The introduction of acidic foods, beverages, or other agents can exceed the natural buffering capacity of saliva. The result is a lowering of the pH of the oral environment which can lead to erosion of enamel and dentin. Loss of tooth structure due to erosion can compromise the esthetics of the dentition and lead to hypersensitivity of the teeth. Teeth damaged by erosion can be successfully restored by composite resin or porcelain restorations and esthetics and function of dentition can be improved.

CLINICAL SIGNIFICANCE

This report is a profound example of how the over consumption of acidic agents affect not only dental tissues but also the chemical balance of the oral environment as well as the oral habitat.

Effects of light curing modes and resin composites on temperature rise under human dentin: an in vitro study

The influence of three curing modes of a high-powered LED curing unit on temperature rise under 2-mm-thick dentin was investigated during the polymerization of resin composite samples of Admira, Filtek P60, Premise, Tetric Flow, Tetric Ceram, and Filtek Z250. Ninety standard specimens were prepared. The bonding agents and resin composites were cured with standard, pulse, or soft-start mode (n=5 for each curing mode). Temperature rise was measured using a type L thermocouple. Data were analyzed by two-way ANOVA and Tukey's test. Soft-start curing led to statistically higher temperature rises compared than the other two modes. The highest temperature rise was observed for Admira and Tetric Flow cured with soft-start mode. The lowest temperature rise was observed for Premise cured with pulse mode. However, temperature rise did not reach the critical value that can cause pulpal damage by virtue of a prominent safety feature of the high-powered LED LCU, which ensures that no excessive heat is produced by all the three curing modes.

The effect of conversion type on P wave dispersion in patients with atrial fibrillation

AIM

The aim of this study was to investigate whether conversion type of atrial fibrillation (AF) to sinus rhythm affects the P wave dispersion (PD) in patients with AF.

METHODS

Based on conversion type, 95 consecutive patients with AF<3 months were divided into 3 groups: spontaneous cardioversion (SC) (N.=33, mean age: 60.6+/-11.6 years), pharmacologic cardioversion (PC) (N.=32, mean age: 59.2+/-9.6 years) and electrical cardioversion (EC) (N.= 30, mean age: 65.3+/-10.6 years). P wave duration (maximum and minimum) were measured in 12-lead ECG, and PD was calculated.

RESULTS

Left atrial diameter and AF duration were significantly higher in EC (43.6+/-4.8 mm and 794.1+/-815.1 h) than SC (38.5+/-3.9 mm and 13.8+/-18.3 h) and PC (40.9+/-4.5 mm and 65.3+/-148.5 h) groups (P<0.01). P maximum was much longer in EC group compared with SC and PC group (121.6+/-9.7, 108.4+/-6.4 and 115.8+/-8.6 ms, P=0.01, respectively). There was a significant difference in PD among SC, PC and EC groups (44.4+/-9.2, 49.5+/-8.7 and 53.5+/-8.8 ms; P=0.005, respectively). PD correlated with AF duration (r=0.36, P=0.03), left atrial diameter (r=0.45, P=0.002) and conversion type (r=0.29, P=0.03). However, there was no significant association between PD and conversion type in multivariate analysis. The prolonged PD resulted from AF duration (P=0.01) and the left atrial size P=0.001).

CONCLUSION

This study suggests that conversion type of AF to sinus rhythm has no effect on P wave duration and independent of AF duration and the left atrial diameter.

Effect of bleaching on color change and refractive index of dental composite resins

This study investigated the effects of three bleaching agents (Whiteness Perfect, Whiteness Super, and Whiteness HP) on the color change and refractive index of three dental composites (Admira, Durafill VS, and Gradia Direct). Twenty disk-shaped specimens (10 x 2 mm) of each composite were prepared and divided into four subgroups (n=5). An unbleached group was used as a control, while the remaining specimens in the three subgroups were bleached with one of the bleaching agents respectively. Color change was assessed according to CIELAB color system and refractive indices were determined by phase modulated spectroscopic ellipsometry. Color differences between bleaching and baseline value (DeltaE) were less than 3.3 for all groups. However, bleaching with Whiteness HP led to noticeable color changes for Admira and Durafill VS. While this agent had no effect on the refractive indices of these composites, the other two agents containing carbamide peroxide increased their refractive indices. Therefore, results suggested that replacement of such composite restorations may be required after bleaching.

Splenic marginal zone lymphoma proposals for a revision of diagnostic, staging and therapeutic criteria

Since the initial description of splenic marginal zone lymphoma (SMZL) in 1992, an increasing number of publications have dealt with multiple aspects of SMZL diagnosis, molecular pathogenesis and treatment. This process has identified multiple inconsistencies in the diagnostic criteria and lack of clear guidelines for the staging and treatment. The authors of this review have held several meetings and exchanged series of cases with the objective of agreeing on the main diagnostic, staging and therapeutic guidelines for patients with this condition. Specific working groups were created for diagnostic criteria, immunophenotype, staging and treatment. As results of this work, guidelines are proposed for diagnosis, differential diagnosis, staging, prognostic factors, treatment and response criteria. The guidelines proposed here are intended to contribute to the standardization of the diagnosis and treatment of these patients, and should facilitate the future development of clinical trials that could define more precisely predictive markers for histological progression or lack of response, and evaluate new drugs or treatments.

The pneumatic compression test and modified pneumatic compression test in the diagnosis of carpal tunnel syndrome

There are no precise criteria for the diagnosis of carpal tunnel syndrome (CTS): the history is useful but the value of the various provocative tests is questionable. The purpose of this study was to examine the diagnostic value of a new provocative test, the 'modified pneumatic compression test' in CTS. The study group consisted of 37 patients with 50 symptomatic CTS hands. A control group of 50 healthy volunteers was recruited. The diagnosis was based on a combination of the history, the clinical findings on examination and electrophysiological criteria. Sensitivity for the pneumatic compression and the modified pneumatic compression tests were 68% and 84%, respectively. Specificities for these tests were 97% and 95%, respectively. The modified pneumatic compression test demonstrated high sensitivity and specificity for CTS. This test facilitated the diagnosis and was easy to use. It may reduce referrals for neurophysiology testing, and so reduce costs.