Bond strength of luting cements to core foundation materials.

PURPOSE: The purpose was to compare the shear bond strength of luting cements to foundation materials and to determine the effect of storage in lactate buffer solution. MATERIALS AND METHODS: Disks that were 8 mm in diameter and 2-mm thick were fabricated from foundation substrates: amalgam, composite resin, resin-modified glass ionomer, and glass ionomer (n = 20). Cylinders that were 2 mm in diameter and 4 mm in length of resin luting cement, resin-modified glass ionomer luting cement, and a glass ionomer luting cement were bonded to the foundation substrate materials. Shear bond strength of each foundation substrate material/cement pair was determined with a universal testing machine after 24 hours. A second set of specimens was tested after storage in a 0.01M lactate buffer solution for 24 hours. A three-way analysis of variance followed by pair-wise comparisons was performed to compare bond strengths (P < .05). RESULTS: The resin cement provided the highest (P < .05) bond strengths to amalgam, composite resin, and resin-modified glass ionomer foundation materials while the glass ionomer cement showed the lowest bond strength (P < .05) to composite resin and glass ionomer foundation restoration materials. After immersion in a 0.01M lactate buffer solution, the shear bond strength of all the material combinations was significantly lower (P < .05) than nonimmersed specimens, except the bonds between composite resin foundation and resin luting cement, which significantly increased (P < .05) in strength. CONCLUSION: The resin cement had the highest bond strength to most foundation substrates investigated. The highest bond was observed between the composite resin foundation and resin cement. This bond was also the most durable on immersion in lactic acid.

Hurler syndrome: a case report of a 5-year follow-up of dental findings after bone marrow transplantation.

Hurler syndrome is a rare autosomal recessive disorder of mucopolysaccharide metabolism. It results from a deficiency in lysosomal enzymes responsible for the breakdown of glycosaminoglycans. Affected individuals may show progressive physical and mental deterioration as glycosaminoglycans are deposited in the organs of the body. Bone marrow transplantation (BMT) is effective in improving some of the clinical manifestations of Hurler syndrome. Death is caused by cardiorespiratory failure and usually occurs before the second decade of life. In this case report, the course of dental development was followed over 5 years, from the primary dentition into the permanent dentition, of a child who was successfully treated with a bone marrow transplant in infancy. The timing of bone marrow therapy has significant and variable effect on the stages of tooth development with implications for the long-term maintenance of the dentition.

Access impediments to health care and social services between Anglophone and Francophone African immigrants living in Philadelphia with respect to HIV/AIDS.

OBJECTIVES: To describe the social and cultural differences between Anglophone and Francophone African immigrants which define the impediments that Francophone African immigrants face trying to access health and human services in Philadelphia, Pennsylvania. METHODS: Surveys and personal interviews were administered to participants in social events, community meetings, and health centers. A Chi-squared analysis was used to contrast the communities. RESULTS: Francophone Africans demonstrated less acculturation, education, English fluency, and more legal documentation problems, and thus face greater challenges accessing health care. Anglophone Africans had a higher level of acculturation, fewer language problems, and perceived fewer barriers in accessing health care than Francophone Africans. CONCLUSIONS: Educating new immigrants, through a more culturally sensitive infectious disease treatment and prevention program, is integral to achieving a higher access and utilization rates of available services; especially in recent Francophone immigrants. A larger study is needed to extend the findings to other cities where immigrants with similar backgrounds or acculturation issues reside.

Effect of liquid rubber additions on physical properties of Bis-GMA based dental resins.

OBJECTIVE: The aim of this investigation was to determine the effect of an experimental liquid rubber (LR) toughening agent on fracture toughness, crosslink density and Barcol hardness of polymerized mixtures of 50/50 wt% Bis-GMA and TEGDMA. METHODS: An experimental LR, was added to a solution of Bis-GMA and TEGDMA containing 1wt% dimethylamino ethyl methacrylate and 0.5 wt% camphoroquinone at concentrations 0-10%. The composites were polymerized by exposure to a visible light curing unit for 60s. Fracture toughness was determined according to ASTM. 399. Crosslink density was evaluated using a swell test in ethanol. RESULTS: Mean fracture toughness values ranged from 0.39 MPa m(1/2) for samples containing 6% to 1.24 MPa m(1/2) for samples containing 8% LR. Fracture toughness of samples containing 2%, 4%, and 8% LR were significantly higher than controls. The highest degree of cross-linkage was obtained in controls and lowest for samples containing 2% LR. Barcol Hardness values ranged from 36.7 for the control and 4% LR composition to 31.2 for samples containing 10% LR. SIGNIFICANCE: Addition of 2, 4 and 8% LR increases the fracture toughness of Bis-GMA/TEGDMA composites. Addition of LR shows promise as a method of improving the fracture toughness of Bis-GMA based dental composites.

Bond strength and microleakage of a new self-etch sealant.

OBJECTIVE: To evaluate and compare shear bond strength and marginal leakage of a new self-etch sealant to enamel of human permanent teeth versus those of a conventional sealant. METHOD AND MATERIALS: Forty-four premolar crowns were mounted to expose flat lingual surfaces and randomly assigned to 1 of 2 test groups: conventional sealant (group 1, control) and self-etch sealant (group 2). Sealants were expressed into hollow plastic cylinders placed on the mounted teeth and polymerized according to manufacturers' instructions. Shear bond strength was measured at a crosshead speed of 0.5 mm/min. Another 44 premolars were randomly assigned to either group 1 or group 2 for microleakage testing. Sealants were applied to the occlusal groove as per manufacturers' instructions, and specimens were thermocycled, stained, sectioned, and examined for marginal leakage. RESULTS: The bond strength of conventional sealant to enamel was significantly (P < .05) higher than that of self-etch sealant. The conventional sealant showed significantly (P < .05) lower microleakage than the self-etch sealant. CONCLUSIONS: Pending clinical validation, the new self-etch sealant under investigation provides lower bond strength and greater marginal leakage than the control (sealant application following standard acid etching).

Enamel bond strength of self-etch sealant with and without prior acid etching.

Our study was undertaken to evaluate the bond strength (BS) of a self-etch sealant to enamel and to determine the effect of prior enamel conditioning with phosphoric acid. Lingual surfaces of permanent human molars were mounted in copper rings and assigned to five groups: Group 1, Clinpro (control); Group 2, Enamel Loc; Groups 3, 4, 5, Enamel Loc with prior phosphoric acid etching of enamel for 5, 10, 15 seconds, respectively. Sealants were applied and BS measured. Clinpro showed significantly higher BS than Enamel Loc. Prior enamel etching for 10 and 15 seconds improved BS of Enamel Loc.

Parental involvement in recruitment of underrepresented minority students.

Recruitment of underrepresented minority (URM) students to dental schools has had limited success, so dental schools need to reach out to high school students with programs to extend the pipeline. The Short Term Enrichment Program (STEP) of the University of Pennsylvania School of Dental Medicine adds a new dimension to these efforts by involving parents, who directly or indirectly impact their children's career decisions. The program consists of an introductory two-day course that includes presentations of the dental profession, laboratory, and virtual classrooms. Biannual follow-up workshops are conducted for both children and parents. Outcomes are measured through pre- and post-program surveys, focus groups, and interviews. STEP attendance has increased over five years, with a total of 163 students participating and 56 percent of their parents attending the program. Eighty participants have graduated from high school, twenty-three of whom are enrolled in a predental program or dental school; twelve are in other prehealth programs. Students in predental programs or dental school have the highest percentage of parents who participated in STEP (96 percent) and engaged them in discussions over career goals (100 percent).

Strategies for recruitment and retention of underrepresented minority students at the University of Pennsylvania School of Dental Medicine.

In 1989, the University of Pennsylvania School of Dental Medicine (UPSDM) found there was an urgent need for new programs that would be effective in recruiting highly qualified and talented underrepresented minority students and ensuring their retention. Major efforts focused on leadership, financial support, institutional commitment, and the creation of an inclusive environment. UPSDM also offers an accelerated program leading to combined bachelor's and dental degrees and has agreements with several undergraduate institutions, including Xavier University in Louisiana and Hampton University, to enroll students in this program. UPSDM encourages minority retention through a Peer Mentorship Program, a Minority Mentorship Program, and course offerings that focus on diversity. Over the past thirteen years, these efforts have successfully garnered a fivefold increase in the number of underrepresented minority students at UPSDM.