Biomedical subjects

Barbara H Miller

Publications and source records attributed to Barbara H Miller.

8 recordsLinked to original sources

PubMed2006

Distance and time effect on shear bond strength of brackets cured with a second-generation light-emitting diode unit.

OBJECTIVE: The aims of this study were to evaluate increasing exposure times and distance between source (light-emitting diode) and adhesive composite on the shear bond strength (SBS) of stainless steel brackets. MATERIALS AND METHODS: Stainless steel maxillary incisor brackets (3M Unitek, Monrovia, Calif) were bonded to the facial surfaces of 120 bovine incisors. The bond of each specimen in eight randomly divided groups was tested to failure using an Instron Universal Testing Machine (Instron Corp, Canton, Mass). The mode of failure was evaluated using the adhesive remnant index (ARI). RESULTS: There were significant SBS differences between exposure times; 5-second exposures were significantly less than at 20-and 40-second exposures; SBS increased in a curvilinear fashion. Significant differences were recorded neither in the frequencies of ARI scores nor the SBS in relation to distance. Significant differences in the frequencies of ARI scores were observed when comparing the 5-second cure time to other time periods, indicating incomplete polymerization in the bracket base. CONCLUSIONS: SBS increased with increasing time periods in a curvilinear fashion, with no difference between the distances evaluated from source to specimen.

Acid Etching, Dental↗

PubMed2006

Orthodontic bonding with varying curing time and light power using an argon laser.

OBJECTIVE: To test the effects of curing time and light intensity on the shear bond strength of adhesive composites for stainless-steel orthodontic brackets. MATERIALS AND METHODS: An argon laser at four different power settings (100, 150, 200, and 250 mW) and four different exposure times (5, 10, 15, and 20 seconds) was used to bond adhesive-precoated (APC) stainless-steel incisor brackets to the facial surfaces of 154 bovine incisors. The shear bond strength of each specimen in 16 randomly divided groups was randomly tested to failure using an Instron universal testing machine. Each mode of failure was described using the adhesive remnant index (ARI). RESULTS: The ARI scoring system showed that the location of bond failure did not differ significantly in relation to exposure time (P = .40). However, the location of bond failure was significantly different in relation to light power (P = .03). CONCLUSIONS: A short exposure time and a low power setting produce shear bond strengths equivalent to those produced by longer exposure times and higher power settings.

Acid Etching, Dental↗

PubMed2004

Mycobacteria inhibit nitric oxide synthase recruitment to phagosomes during macrophage infection.

Inducible nitric oxide synthase (iNOS) is a cytoplasmic protein responsible for the generation of nitric oxide (NO. ) in macrophages. In this work, we hypothesized that the intracellular localization of iNOS is significant for effective delivery of NO. to phagosomes containing ingested microorganisms. Using immunofluorescence microscopy and Western blot analysis, iNOS was shown to localize in the vicinity of phagosomes containing latex beads in stimulated macrophages. iNOS also localized to phagosomes containing Escherichia coli. The colocalization of iNOS with ingested latex beads was an actin-dependent process, since treatment with the actin microfilament disrupter cytochalasin D prevented iNOS recruitment to latex bead phagosomes. In contrast to E. coli and inert particle phagosomes, mycobacterial phagosomes did not colocalize with iNOS. This study demonstrates that (i). iNOS can be recruited to phagosomes; (ii). this recruitment is dependent on a functional actin cytoskeleton; (iii). certain microorganisms have the ability to prevent or reduce colocalization with iNOS; and (iv). spatial exclusion of iNOS may play a role in Mycobacterium tuberculosis pathogenesis.

Actins↗

PubMed2003

Effects of bur abrasive particle size and abutment composition on preparation of ceramic implant abutments.

STATEMENT OF PROBLEM: Amid increasing use of preparable ceramic implant abutments, there is a lack of quantitative data to show which abrasive particle size of diamond bur yields the fastest reduction and provides the smoothest surface. PURPOSE: The research aim was to determine the effects of diamond bur abrasive particle size and abutment material composition on preparation efficiency, prepared surface roughness, and surface deterioration of diamond burs. MATERIAL AND METHODS: Fifteen alumina (Cera Base) and 15 zirconia (ZiReal) implant abutments were each machined using a high-speed hand piece with a diamond bur having 1 of 3 abrasive particle sizes (150, 100, or 30 microm) (n=5). Control abutments (n=5) were analyzed without machining. Abutments were weighed before starting and between machining cycles. Three profilometry measurements (root mean square surface roughness) were made for each abutment. Scanning electron micrographs were made of each bur. Lost abrasive particles were then counted on each micrograph through a randomly placed template. Two-way analysis of variance (alpha=0.05) was used to test for significant effects. RESULTS: Bur abrasive particle size and ceramic type had a significant interactive effect on the amount of material removed (P<.001). Super coarse (150 microm) burs yielded the roughest surfaces for each abutment material (P<.001), and prepared alumina surfaces were rougher than zirconia surfaces (P<.001). Super coarse burs showed the highest proportion of lost particles (P<.001). Abutment composition did not significantly affect bur wear. CONCLUSION: Super coarse burs yielded the most efficient material removal for alumina abutments. All abrasive particle sizes removed a similar amount of material from zirconia abutments. Fine-grained alumina abutments experienced greater material removal and rougher prepared surfaces compared with zirconia abutments. Material was removed by an intergranular fracture mechanism for alumina abutments, in contrast to transgranular fracture for zirconia abutments.

Aluminum Oxide↗

PubMed2003

Effects of high-speed curing devices on shear bond strength and microleakage of orthodontic brackets.

This study evaluated the shear-peel bond strength and mode of bond failure of 3 curing devices (plasma arc light, argon laser, and conventional halogen light) and 2 orthodontic bracket adhesives with different filler contents (Transbond XT and Adhesive Precoated [APC]). Observations of microleakage were also reported. Ninety human adolescent premolars were randomly divided into 6 groups, and standardized brackets were bonded according to the manufacturers' recommendations. The plasma arc light produced significantly (P =.006) higher bond strength than did the halogen light or the argon laser when Transbond was used. When APC was used, the plasma arc light and the halogen light produced similar results, and they both produced significantly (P =.015) higher bond strengths than did the argon laser. Overall, the APC showed substantially less variation in bond strength than did the Transbond. Although all curing methods showed significant microleakage (P <.001), differences among the 3 curing lights occurred only when APC was used. Microscopic evaluations demonstrated that 95% of the specimens failed for adhesion at the bracket or tooth surface; the argon laser produced the highest adhesive remnant index scores. On the basis of bond strength and microleakage results, the plasma arc light was comparable with or superior to the other curing devices, depending on the adhesive used.

Adolescent↗

PubMedDate not supplied

Immediate bonding to bleached enamel.

This research sought to determine the shear bond strength, degree of resin infiltration and failure mode when organic solvent-based adhesives (acetone or ethanol) were used in immediate bonding to enamel bleached with 10% carbamide peroxide or 38% hydrogen peroxide systems. Seventy-two non-carious bovine incisors were randomly assigned to three groups of 24 specimens each-control group (deionized water), 38% hydrogen peroxide bleach group and 10% carbamide peroxide bleach group. Each group was further subdivided into two subgroups of 12 specimens each according to the adhesive system used to bond the resin composite to enamel surfaces. The two adhesive systems used were Single Bond, an ethanol-based adhesive, and One Step, an acetone-based adhesive. The shear bond strengths of 38% hydrogen peroxide and 10% carbamide peroxide were significantly lower compared to the non-bleached controls. Fractography revealed an adhesive failure mode in all specimens. Qualitative comparisons of resin tags present in the bleached and unbleached specimens using scanning electron microscopy (SEM) revealed few, thin and fragmented resin tags when 38% hydrogen peroxide and 10% carbamide peroxide were used.

Acetone↗

PubMedDate not supplied

Evaluation of the ITI Morse taper implant/abutment design with an internal modification.

PURPOSE: The purpose of this study was to compare internal Morse taper connections in 2 separate modes: repeated torque/reverse-torque values and compressive bending at a 30-degree off-axis angle. MATERIALS AND METHODS: Three sample groups (n = 12 in each group)--a solid-screw implant paired with a 5.5-mm solid abutment (SSI), a synOcta implant with a 5.5-mm solid abutment (SOI), and a synOcta implant with a synOcta 5.5-mm solid abutment (SOSA)--were torqued to 35 Ncm, and the reverse torque to remove the abutment was recorded. This was repeated for 3 trials. Additionally, the sample groups were loaded 30 degrees off-axis, and the ultimate compressive values were recorded. RESULTS: There was a significant difference in the initial reverse-torque values. The SOSA setup showed significantly lower torque than the SOI and SSI setups (P < .05). In addition, the compressive bending test showed that the SOSA setup was significantly different (P < .05) from the SSI and SOI setups. Radiographic survey of the test groups following compressive bending revealed no implant fractures, but bending of the implant-abutment complex occurred. DISCUSSION: The alteration within the Morse taper did not reduce the strength of the implant-abutment connection, ie, the reduction in surface area did not significantly reduce the torque properties or tensile properties. The new 2-piece synOcta 5.5-mm solid abutment was shown to have a stronger implant-abutment connection when torqued down a second time. CONCLUSIONS: In this in vitro study, alteration of the Morse taper with an internal octagon indexing did not significantly reduce the strength of the implant connection. Sufficient strength was exhibited, which would indicate this implant-abutment design for anterior as well as posterior edentulous sites.

Analysis of Variance↗

PubMedDate not supplied

Resin bonding to sclerotic, noncarious, cervical lesions.

Noncarious, cervical, wedge-shaped, sclerotic lesions are commonly encountered in clinical practice. In such lesions, dentin has been pathologically altered, often resulting in partial or complete obliteration of the dentinal tubules. These lesions are known to respond to etching and bonding differently from normal dentin, leading to complications during clinical treatment. A search of the literature was performed to obtain background information on the most commonly cited etiologic factors, clinical diagnoses, and morphologic and chemical characterizations along with an extensive review of all potential obstacles to bonding the most recent adhesives to such a dentinal substrate. Recent progress in adaptive strategies to render dentin more receptive to resin bonding is emphasized in this article, and the major drawbacks of these strategies are discussed.

Acid Etching, Dental↗