Surface treatment of indirect resin composite surfaces before cementation

Statement of problem. Controversy surrounds the use of hydrofluoric acid to prepare precementation surfaces of indirect composites.Purpose. This study was conducted to compare effects of combining hydrofluoric or orthophosphoric acid with microetching as precementation treatments.Material and methods. Nine specimens of three composite materials were prepared to simulate heat-cured indirect restorations. The specimen surfaces were prepared with one of three treatments. Adhesive Bond II and Twinlook cements were used to bond a phosphoric acid-etched disk of P50 to the treated surface. Analysis of variance and Scheffé tests were used to assess the bond strength data. Scanning electron microscopy and microscopic analysis of the fractured and treated surfaces were also performed.Results. Bond strengths for all surface treatments did not significantly differ. Hybrids had a higher bond strength with etching than microfills, and mechanical roughening produced the greatest bond strengths with microfills. Microetching with orthophosphoric acid produced higher bond strengths than microetching with hydrofluoric acid on hybrids.Conclusions. Acid etching alone is not sufficient to produce effective bond strengths, and hydrofluoric acid treatments are detrimental to the resin composite. (J Prosthet Dent 1997;77:568-72.)     

A comparison between LCM virus-specific secondary cytotoxic T lymphocytes generated by Con A and by the homologous antigen.

An investigation was made of the properties of cytotoxic T cells induced by Con A and exposure to LCM virus-infected cells. As a basis for such studies, the optimal conditions for in vitro Con A stimulation of in vivo LCM virus-primed C3H mouse splenocytes were determined. The most potent cytotoxicity was obtained when responder cells were cultured in the presence of Con A in a concentration of 2 micrograms/ml for 3 days, but strong cytotoxicity was also measured on days 2 and 4. When stimulation was performed by the homologous antigen maximal response was seen on day 4 although marked cytotoxicity was also noted on day 3. Effector cells produced by the two different procedures showed equally high degrees of cytotoxicity against LCM virus-infected target cells, whereas they did not appear cytotoxic against non-infected targets. If LCM virus-immune mice were treated intravenously with 280 micrograms of Con A per animal, moderate cytotoxicity was demonstrable in splenocytes from these mice 1, 2 and 3 days after treatment. The in vitro generation of secondary cytotoxicity by Con A as well as by the homologous antigen was found to be totally dependent on DNA synthesis. The reactivated cells were investigated for in vivo anti-viral effect by measuring their ability to protect intracerebrally LCM virus-infected mice from a fatal outcome of this infection. LCM virus-primed splenocytes stimulated by the homologous antigen caused complete protection, while Con A-reactivated cells did not protect at all. Secondary cytotoxic cells stimulated by Con A and by LCM virus showed fairly similar in vitro characteristics, but fundamentally different in vivo qualities.     

CCR2+ and CCR5+ CD8+ T cells increase during viral infection and migrate to sites of infection

Chemokines and their receptors play a critical role in the selective recruitment of various leukocyte subsets. In this study, we correlated the expression of multiple chemokine and CC chemokine receptor (CCR) genes during the course of intracerebral (i.c.) infection with lymphocytic choriomeningitis virus (LCMV) and vesicular stomatitis virus (VSV), which are prototypic of a noncytopathic and a cytopathic virus, respectively. Infection of mice with either virus resulted in rapid activation and overlapping cerebral expression of a number of chemokine genes. Infection with VSV i.c. causes a rapidly lethal, T cell-independent encephalitis, and infection resulted in a dramatic early up-regulation of chemokine gene expression. Similar marked up-regulation of chemokine expression was not seen until late after LCMV infection and required the presence of activated T cells. Cerebral CCR gene expression was dominated by CCR1, CCR2 and CCR5. However, despite a stronger initial chemokine signal in VSV-infected mice, only LCMV-induced T cell-dependent inflammation was found to be associated with substantially increased expression of CCR genes. Virus-activated CD8+ T cells were found to express CCR2 and CCR5, whereas activated monocytes/macrophages expressed CCR1 in addition to CCR2 and CCR5. Together, these CCR profiles readily account for the CCR profile prominent during CD8+-dependent CNS inflammation.     

Immediate Obturation of the Surgical Defect after Partial Maxillectomy in the Endentulous Patient

Closure of the surgical defect immediately after partial maxillectomy is the treatment of choice. The advantages are: maintaining facial contour, rapid re-establishment of speech, swallowing and mastication. A number of methods for the fixation of the immediate obturator in patients without teeth have been described. A new technique is reported where a transnasal wire holds the existing denture in position after partial maxillectomy. The method has been carried out on 7 patients with sino-nasal cancer during the period 1978-1994. The advantages of the technique are that the wire acts as an axis of rotation which together with the sponge in the cavity provide good stability of the denture. There is minimal preoperative laboratory work and simplification in replacing the surgical dressing.     

Modulation of intracortical inhibition in response to acute psychosocial stress is impaired among individuals with chronic neck pain

Objective

Psychosocial stress has been associated with a variety of chronic pain disorders although the mechanisms responsible for this relationship are unknown. The purpose of this study was to compare the excitability of intracortical and corticospinal pathways to the trapezius muscle in individuals with and without chronic neck pain during exposure to low and high levels of psychosocial stress.

Methods

Single and paired-pulse transcranial magnetic stimulation was used to assess motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) during mental math performed in the presence and absence of social evaluative threat.

Results

All participants demonstrated higher amplitude MEPs in the high stress compared to the low stress condition (p < 0.01). Participants with chronic neck pain had significantly greater SICI than healthy participants in the low stress condition (p = 0.03). During exposure to the stressor, healthy participants showed an increase in SICI, whereas participants with neck pain showed no change (group difference for change in SICI, p < 0.01).

Conclusions

These findings suggest that individuals with chronic neck pain inhibit motor output to the trapezius in the presence of minor stressors, and are unable to compensate for additional stress-evoked increases in corticospinal excitability through further modulation of SICI. This observation has potential implications for the management of patients who have difficulty relaxing painful muscles during times of stress.     

Gram stains have limited application in the diagnosis of infected total knee arthroplasty

Background

The diagnosis of periprosthetic knee infections can present a challenge to surgeons, especially in the case of chronic presentation. Gram stains are regularly performed as part of the microbiological evaluation of suspected infected total knee arthroplasties. Recently, the utility of this test in diagnosing infections has been questioned. The purpose of this study was to assess the effectiveness of Gram stains performed from surgical site samples by comparing their results to the final diagnosis of infection.

Methods

The results of 347 Gram stains performed at a single center at the time of revision total knee arthroplasty for both septic and aseptic reasons were compared to the final diagnosis based on intra-operative findings and histological evaluation.

Results

Gram staining demonstrated a low sensitivity of 7% (95% confidence interval 4–12%), a specificity of 99% (95% confidence interval 97–100%), and positive and negative predictive values of 92% and 57%, respectively.

Conclusions

This study confirmed previous findings of the poor utility of this test for the diagnosis of periprosthetic knee infections. The authors recommend that Gram staining no longer be performed at the time of suspected periprosthetic knee arthroplasty infection.     

Strength properties of soldered joints for a gold-palladium alloy and a palladium alloy

Strength of a soldered palladium alloy, PGC (Engelhard Corp.), and a soldered medium gold alloy, PGX (Engelhard Corp.), was examined. The results obtained were as follows: Highest strength was observed with postsoldered specimens of PGC alloy. Microstructural examination of postsoldered specimens revealed nearly pore-free solder joints with PGC and PGX alloys, and fracture appeared at the solder-alloy interface with PGC and PGX alloys. Microstructural examination of presoldered and presoldered/thermocycled specimens revealed that presoldered specimens of PGC and PGX alloys exhibited intrasolder fracture; PGX solder joints had considerably less porosity, which may explain the equivalent bond strengths of all the soldered specimens and the yield point of the controls; PGC solder joints exhibited large quantities of pores, which may explain the lower strength; pores observed in PGC alloy may be the result of the high fusing temperature of the solder; and these results indicate a need to develop a new presolder for PGC. The best result was obtained with postsoldered specimens of the PGC alloy. However, for PGX alloy, either postsolder or presolder techniques can be used.