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Biomedical subjects

A Schulman

Publications and source records attributed to A Schulman.

At least 19 recordsLinked to original sources
PubMed2001

Shear bond strength of six restorative materials.

The purpose of this study was to determine and compare the shear bond strength of a conventional glass-ionomer cement, a resin modified glass-ionomer, a composite resin and three compomer restorative materials. Dentin of the occlusal surfaces from sixty extracted human permanent molars were prepared for shear bond strength testing. The specimens were randomly divided into six groups of 10 each. Dentinal surfaces were treated according to the instructions of manufacturers for each material. Each restorative material was placed inside nylon cylinders 2 mm high with an internal diameter of 3 mm, which were placed perpendicular to dentin surfaces. Shear bond strengths were determined using an Universal Testing Machine at crosshead speed of 0.5 mm/min in a compression mode. Conventional glass-ionomer, Ketac-Molar aplicap showed the lowest mean shear bond strength 3.77+/-1.76 (X +/- SD MPa) and the composite resin, Heliomolar showed the highest mean shear bond strength 16.54+/-1.65 while the mean bond strength of Fuji II LC was 9.55+/-1.06. The shear bond strengths of compomer restorative materials were 12.83+/-1.42, 10.64+/-1.42 and 11.19+/-1.19 for Compoglass, Hytac and Dyract respectively. ANOVA revealed statistically significant differences in the mean shear bond strengths of all groups (P<0.001). No statistically significant difference was found between the three compomer materials (P>0.5). Ketac-Molar and composite resin showed statistically significant difference (P<0.0005). The mode of fracture varied between materials. It is concluded that the compomer restorative materials show higher shear bond strength than conventional glass-ionomer and resin modified glass-ionomer, but less than composite resin. The fracture mode is not related to the shear bond strengths values.

Acid Etching, Dental↗
PubMed2000

Tumor development is retarded in mice lacking the gene for urokinase-type plasminogen activator or its inhibitor, plasminogen activator inhibitor-1.

In vivo tumor progression in mice with targeted deficiencies in urokinase-type plasminogen activator (UPA-/-) and its inhibitor, plasminogen activator inhibitor-1 (PAI-1-/-), was studied using a fibrosarcoma tumor model. Murine T241 fibrosarcoma cells were s.c. implanted into three groups of mice with the following genotypes, wild-type (WT), UPA-/-, and PAI-1-/-. A significantly diminished primary tumor growth in UPA-/- and PAI-1-/- mice occurred, relative to WT mice. Tumors in UPA-/- and PAI-1-/- mice displayed lower proliferative and higher apoptotic indices and displayed a different neovascular morphology, as compared with WT mice. These results are consistent with the decreased growth rates of this tumor in these gene-deleted mice. Immunohistochemical analyses of the tumors revealed a decrease in vascularity and vascular endothelial growth factor expression only in tumors in PAI-1-/- mice. Analyses of the relative extents of corneal angiogenesis in these same animals, induced by basic fibroblast growth factor, corroborated the resistance of PAI-1-/- mice to neovascularization. The results obtained suggest that the host fibrinolytic system plays an important role in tumor growth in this model. Alterations in host expression of components of this system may alter tumor growth and dissemination by affecting the balance between tumor cell death and proliferation, as well as extracellular matrix changes needed for invasiveness and angiogenesis.

Animals↗
PubMed2000

Torsional resistance of crowns cemented to composite cores involving three stainless steel endodontic post designs.

STATEMENT OF PROBLEM: There are no studies analyzing the effects of a crown in relationship to torsional resistance for a titanium-reinforced core material supported by a post. PURPOSE: This study investigated the effects of post design on the torsional resistance of a crown supported by a titanium-reinforced composite core material (Ti-Core) and 3 endodontic posts (AccessPost, Flexi-Post, and ParaPost). MATERIAL AND METHOD: Three groups of 10 specimens per group were studied. A total of 30 recently extracted human single-rooted (incisors) teeth with their crowns removed were used. Post holes preparations were created according to manufacturer's instructions. All posts were cemented using Flexi-Flow with titanium cement. Scotchbond Multi-Purpose bonding system was used as the bonding system for all groups. All cores were fabricated with Ti-Core with titanium core material with hard copper bands as the matrix. The Ti-Core core material was allowed to set for 1 hour. Metal crowns were fabricated and cemented with zinc phosphate cement. Specimens were placed in a special jig and a clockwise torsional force was applied. Torsional force was measured on a Lebow 1102-200 torque transducer and recorded on a Hewlett Packard 7015B X-Y recorder in inch x ounce. A 1-way analysis of variance (ANOVA) was used to test for statistical significance (P < .001). RESULTS: The torsional values (inch x ounce) were AccessPost 77.2 +/- 30.3, Flexi-Post 162.2 +/- 51.2, and ParaPost 60.9 +/- 28.4. SNK and Scheffé comparison tests revealed that the Flexi-Post group had significantly greater resistance to torque loading than the AccessPost and ParaPost groups, which were statistically similar to each other. CONCLUSION: Post design has an effect on torsional resistance of a crown supported by titanium-reinforced core build-up and post. The threaded split-shank design of the Flexi-Post dowel offers significantly greater resistance to torsional loading than the passive posts studied.

Analysis of Variance↗
PubMed1999

Calpain inhibitors protect auditory sensory cells from hypoxia and neurotrophin-withdrawal induced apoptosis.

Inhibitors of calpain have been shown to protect nerve growth factor (NGF)-deprived ciliary ganglion neurons and hypoxic cortical neurons. Calpains have been identified in the cochlea and are active during ischemic injury. Since apoptosis can be initiated by loss of neurotrophic support, hypoxia, and ototoxins (e.g., cisplatin, CDDP), the role of calpain inhibitors under these conditions was examined in auditory hair cells and neurons. Dissociated spiral ganglion neuron (SGN) cell cultures and organ of Corti explants from P3 rats were used to test the efficacy of calpain inhibitors as otoprotective molecules. Our results indicate that calpain inhibitor I, calpain inhibitor II, and leupeptin all provided significant protection of SGNs against neurotrophin-withdrawal and hypoxia-induced apoptosis. The increase in neuronal survival ranged from 2.16 to 2.31 times greater than in untreated neurotrophin-withdrawn SGN cell cultures. BOC-Asp(Ome)-Fluoromethyl Ketone (B-D-FMK), a general caspase inhibitor, increased neuronal survival 2.16 times more. Neuronal survival rates were from 1.88 to 2.27 times greater than in untreated, hypoxic neurons and hair cell survival rates were from 1.98 to 2.03 times greater than untreated, hypoxic organ of Corti explants. However, protection of auditory hair cells and neurons from CDDP-induced damage (10 and 6 micrograms/ml, respectively) was limited with any of these calpain inhibitors. Apoptotic pathways initiated by neurotrophin-deprivation and ototoxic stress (e.g., CDDP) have been shown to be different. Our results agree with this finding, with neurotrophin-withdrawal and hypoxia, but not CDDP damage-induced apoptosis being calpain-dependent.

Animals↗
PubMed1999

Children on the move and vaccination coverage in a low-income, urban Latino population.

OBJECTIVES: The purpose of this study was to determine the impact of childhood moves and foreign birth on vaccination coverage among Latino children in New York City. METHODS: Vaccination coverage was assessed in a survey of 314 children younger than 5 years at 2 immunization clinics. RESULTS: Forty-seven percent of the study children had moved abroad. After adjustment for health insurance, regular source of care, and country of birth, child moves had no independent effect on vaccination coverage. Foreign-born children had diphtheria-pertussis-tetanus, oral polio vaccine, and measles-mumps-rubella vaccination coverage rates similar to those of US-born children, but they were underimmunized in regard to Haemophilus influenzae type b and hepatitis B. CONCLUSIONS: Foreign birth, but not childhood moves, is a barrier to vaccinations among low-income, urban Latino children.

Adolescent↗
PubMed1999

Clinical effectiveness of a Class V flowable composite resin system.

This clinical study evaluated a Class V flowable composite resin restoration system and its ability to reduce dentin sensitivity. Twenty-one patients required Class V restorations because of erosion, abrasion, or decay at the cervical area. Each patient exhibited moderate or severe sensitivity and required replacement of tooth structure. The degree of sensitivity was determined by either tactile scraping of the tip of an explorer over the surface of the tooth or by an air blast from a syringe for 5 seconds. A total of 52 restorations were performed. According to phone conversations and questionnaires, 1 patient experienced continued sensitivity on 1 treated tooth for a duration of 1 week, but this sensitivity was gone at 1-month, 3-month, 6-month, and 1-year recalls. None of the other patients exhibited sensitivity at any phone checks or during recall visits.

Composite Resins↗
PubMed1999

Enhanced retention of glass-ionomer sealant by enamel etching: a microleakage and scanning electron microscopic study.

OBJECTIVE: A microleakage study and a scanning electron microscopic investigation were conducted to test whether etching of enamel would improve adhesion of glass-ionomer cement sealants to fissure enamel. METHOD AND MATERIALS: Forty-eight extracted human molars and premolars were divided into 2 equal groups, and their crowns were cleaned with pumice. In group 1 enamel was etched for 45 seconds with 37% phosphoric acid. In group 2, enamel was not etched. Glass-ionomer sealant was applied to all 48 teeth. Twenty teeth from each group were thermocycled in water (120 cycles between 0 degree C and 56 degrees C) and stained with 0.5% methylene blue solution. The remaining 4 teeth from each group served as a control for the scanning electron microscopic evaluation. Twelve teeth from each group were cut into 5 sections, and 12 were cleaved into 3 sections in a buccolingual direction. RESULTS: Statistically significant differences in amounts of microleakage were found between group 1 and group 2. Minimal microleakage was detected in 90% of the etched teeth, whereas extensive microleakage was observed in 85% of nonetched teeth. The scanning electron microscopic evaluation correlated positively with the microleakage observations. The etched teeth revealed a cohesive failure within the sealant material, while the nonetched teeth demonstrated an adhesive failure at the sealant-enamel interface. Observation of the nonthermocycled teeth confirmed those findings. CONCLUSION: Results suggested that etching prior to application enhances the bonding of glass-ionomer sealant to fissure enamel.

Acid Etching, Dental↗
PubMed1998

Clinical evaluation of cell demodulated targeted electronic anesthesia.

Electronic anesthesia is an effective adjunct for the management of dental pain, and has been used in medicine and dentistry for several decades. The purpose of this study was to evaluate the effectiveness of dental electronic anesthesia while preparing teeth for large restorations and full crown coverage. The single-blind study involved the use of two identical units (Cedeta Mk3). One was a fully operational, commercially available unit (active unit), while the other had been modified to prevent current from reaching the electrodes (control unit). Both the non-working control device and the active unit had a normally functioning indicator light that glowed when the unit was turned on. The study participants consisted of 100 patients selected from the roster at New York University College of Dentistry. Subjects were selected if (1) their prescribed treatment plans required large class I, II, III, IV, or V restorations or full coverage crowns, (2) they had previous treatment performed with the use of an injectable local anesthetic, and (3) their medical history showed a lack of medical contraindications. The active unit group had 31 subjects with large restorations required, 5 patients needing inlay/onlay preparations and 14 subjects requiring full coverage. The control unit group had 43 subjects needing large operative restorations, 1 onlay and 6 subjects needing full coverage. Each subject was informed that he/she would be able to eliminate the pain from the dental procedure by maintaining control of the electronic dental anesthesia unit (reaching a therapeutic level). If unmanageable discomfort occurred, intraligamentous local anesthesia would be administered. Two of the 50 subjects who received the control device were able to tolerate the dental procedure, the rest were given the rescue anesthetic upon request. Forty-three of the 50 subjects who received the active unit responded with an excellent or very good evaluation for pain control, with no rescue anesthetic required. Seventy-four dental procedures were performed on the 50 subjects who received the active unit. Forty-five of the subjects in the active unit group said they would prefer to have electronic anesthesia for their next dental treatment, rather than the novocaine they had previously experienced. Forty-eight of the subjects in the control unit group said that they would prefer the traditional novocaine injection for their next dental treatment.

Analgesia, Patient-Controlled↗
PubMed1997

A review of all-ceramic restorations.

To select the most appropriate type of all-ceramic system for clinical use, the clinician must be familiar with the differences between systems. This article discusses five categories of all-ceramic restorative systems relative to their processing techniques, strength and wear characteristics. The authors present and compare results of published in vitro studies and short-term clinical studies.

Compressive Strength↗
PubMed1996

Comparison of fatigue for three prefabricated threaded post systems.

Post designs may have a direct effect on fracture resistance of endodontically treated teeth. This in vitro study compared the resistance of three prefabricated threaded post systems with lateral shearing forces. After endodontics were completed, prefabricated posts were inserted according to the manufacturer's instructions. A silver amalgam core was placed, and extracted human teeth were prepared to a standard size with a 1 mm gingival chamfer finished on sound dentino A cast was fabricated and cemented, and the specimens were thermocycled. The test samples were secured to an Instron testing machine and loaded until failure. Fracture patterns were recorded, fractured surface areas were measured, and compressive stresses were calculated. However, there were no statistically significant differences among threaded posts in each test group.

Cementation↗
PubMed1994

Regional changes in amino acid levels of the neonate rat brain during anoxia and recovery.

The aim of this study was to compare the changes in amino acids (alanine, aspartate, GABA, glutamate, glutamine, glycine, serine taurine) that are produced in different regions of the neonate brain (telencephalon, diencephalon cerebellum, brain stem) following a survivable period of anoxia and after the re-establishment of air respiration. Anoxia provoked different responses in the different regions. The changes during the anoxic period were as follows. In the brain stem there was a decrease in aspartate, in the telencephalon there was a significant increase in GABA and alanine and a decrease in aspartate, in the diencephalon, glutamate and GABA increased, and in the cerebellum, glycine and alanine levels were enhanced. The changes during recovery were even more dissimilar. Here the greatest shifts were seen in the brain stem with increases in glutamine, GABA, aspartate, glycine, serine, alanine, and taurine. In the telemcephalon glutamate fell and alanine increased, in the diencephalon GABA increased, and in the cerebellum, glutamate fell while glycine and alanine increased. In none of the major brain regions did the pattern of changes in neurotransmitters correspond to that seen in anoxic tolerant species.

Amino Acids↗
PubMed1994

A comparison of the apical seals achieved using retrograde amalgam fillings and the Nd:YAG laser.

The purpose of this in vitro study was to compare the apical seals achieved using retrograde amalgam fillings or the Nd:YAG laser. Freshly extracted teeth were randomly separated into groups that would have their apices treated either with a Nd:YAG laser or retrograde amalgam. After instrumentation and obturation, bacterial reservoirs were prepared in the coronal portion of canals. Teeth to receive retrofillings had their apices prepared and amalgams placed. Teeth to be lasered had no apical preparations. Teeth and culture media were then sterilized by irradiation. Streptococcus salivarius was deposited in the opened bacterial reservoirs. At intervals, culture media with an indicator in culture chambers was observed for color change. Specimens that demonstrated color change were cultured for S. salivarius. Under the conditions of this in vitro study, no statistically significant difference was found in bacterial leakage between the laser-treated group and the retrograde amalgam group.

Apicoectomy↗
PubMed1994

[Crisis intervention and requests for organ donation--impossible to reconcile?].

A request for organ donation after a patient's death imposes a strong emotional impact both on the family and on the medical staff. How well the family copes with the loss of a close relative is subject to a variety of factors including the immediate emotional support provided by the staff. On the other hand, a donation request, if made with sensitivity, may in combination with adequate psychological support facilitate the grieving process. Health care professionals need emotional support and training to help them deal with the difficulties of caring for bereaved families, of breaking bad news, and of making organ donation requests.

Crisis Intervention↗