Biomedical subjects

Mark A Latta

Publications and source records attributed to Mark A Latta.

10 recordsLinked to original sources

PubMed2006

Effect of polymerization mode of adhesive and cement on shear bond strength to dentin.

PURPOSE: To investigate the shear bond strength to dentin when two resin adhesive systems in light-cure, dual-cure, and auto-cure modes were used with three resin cements. This was done to determine the degree of compatibility that exists when resin products with different polymerization mechanisms are used together. METHODS: Three hundred non-carious human molars were divided into 30 test groups in which Prime & Bond NT and ScotchBond Multi-Purpose were used as adhesives with Calibra, Nexxus and Variolink cements to attach Rexillium III posts to flattened dentin surfaces. Debonding was achieved with an Instron testing machine and mean shear bond strengths were determined for each test group. The data were subjected to three-way ANOVA and post-hoc LSD testing to determine whether significant differences existed between the test groups. RESULTS: Bond strengths achieved were affected by the adhesive, the cement, and the cement curing mode. In general, the auto-cure application of the three cements demonstrated reduced shear bond strengths, both with respect to the different adhesives and their curing modes as well as compared to the dual-cure technique of the same cement. Additionally, Prime & Bond NT demonstrated considerably more variability than ScotchBond Multi-Purpose when used with both dual-cure and auto-cure varieties of the three cements. The bond strengths of resin cements depend on the curing mode of the cement and the adhesive. Unlike with direct light-cured resin composites, combining adhesive systems and dual-cured resin cements from different manufacturers may be contraindicated.

Adhesives↗

PubMed2005

Physical properties of four acrylic denture base resins.

Resistance to impact fracture and high flexural strength are desirable properties of denture base acrylics. The purpose of this laboratory study was to determine the Izod impact strength, the flexural strength, the flexural modulus, and the yield distance for four premium denture resins. Bar specimens 86 x 11 x 3 mm of Lucitone 199, Fricke Hi-I, ProBase Hot, and Sledgehammer Maxipack were fabricated following the manufacturer's instructions for heat processing. The bars were surface finished using silicon carbide paper to 600 grit. Ten specimens from three lots of each material were made (n=30). Flexural strength, flexural modulus, and yield distance were determined by testing the specimens to failure using a three-point test fixture. Izod impact strength was determined using an Izod tester on un-notched specimens generated from the flexural test (n=60). Analysis of variance (ANOVA) and post-hoc Tukey's test were used for statistical comparison of each property. There were significant differences in the physical properties among the denture acrylics tested. Lucitone 199 demonstrated the highest impact strength, flexural strength, and yield distance (p<0.05). Lucitone 199 with an Izod impact strength of 5.5+/-1.2 N'm, a flexural strength of 99.5+/-4.5 MPa, and yield distance of 9.9+/-0.76 mm exhibited statistically greater results than Fricki Hi-I, ProBase Hot, and Sledgehammer Maxipack. Fricki Hi-I with a yield distance of 7.3+/-1.1 mm was statically greater than ProBase Hot and Sledgehammer Maxipack. Fricki Hi-I, ProBase Hot, and Sledgehammer Maxipack were statistically similar for the Izod impact strength and flexural strength tests performed. ProBase Hot and Sledgehammer Maxipack yielded statistically similar results for all tests performed. Flexural modulus had an inverse relationship to the impact strength, flexural strength, and yield distance.

Acrylic Resins↗

PubMed2005

Bonding and curing considerations for incipient and hidden caries.

Contemporary adhesive systems and restorative composite materials can successfully seal and restore teeth and can facilitate the use of a minimally invasive cavity preparation technique. These systems give the operator the potential to reinforce damaged teeth and preserve healthy tooth structure. The adhesion principles rely on strict adherence to excellence in clinical technique. Differences in clinical results may depend may more on the operator's adherence to good clinical technique than the specific material selected.

Dental Bonding↗

PubMed2005

Microtensile bond strength of total-etch and self-etch adhesives to the enamel walls of Class V cavities.

PURPOSE: To determine the difference in microtensile bond strengths (MTBS) of resin-based composite bonded to the enamel of cavity preparations using a conventional or a self-etching adhesive. METHODS: Buccal and lingual Class V cavities were prepared in each of 12 caries-free human molars. Six teeth were randomly selected to be restored with Spectrum TPH resin-based composite and Prime & Bond NT adhesive. The remaining six teeth were restored with the same composite and Prompt L-Pop self-etching adhesive. Enamel/composite sticks were cut from each specimen and subjected to microtensile bond testing. Each debonded specimen was evaluated by SEM to determine the mode of failure. RESULTS: The mean MTBS for Prime & Bond NT specimens was 15.2+/-13.1 MPa. The mean MTBS for Prompt L-Pop self-etching adhesive samples was 18.2+/-14.3 MPa. ANOVA demonstrated no statistically significant difference between the mean MTBS associated with the two adhesives (P> 0.05). The results of SEM analysis revealed that the bonding failures occurred primarily at the interface between the adhesive and the enamel, suggesting a primarily adhesive failure.

Acid Etching, Dental↗

PubMed2005

Bond strength of composite to dentin using self-etching adhesive systems.

PURPOSE: To determine the shear bond strength to dentin of five newer-generation self-etching adhesive systems. METHOD AND MATERIALS: Flat bonding sites were prepared on 100 extracted human molar teeth with 600-grit silicon carbide paper, which exposed the dentin. The systems tested were: Clearfil SE Bond; Optibond Solo Plus Self-Etch; Xeno CF III; Tyrian SPE; and Adper Prompt L-Pop. Following application of each adhesive system, bonded assemblies of Z-100 were prepared using a gelatin capsule matrix (n = 20). Ten specimens in each group were debonded after water storage for 24 hours at 37 degrees C, and 10 were stored for at least 30 days, followed by thermocycling for 850 cycles between water baths at 5 degrees C and 55 degrees C, with a dwell time of 1 minute in each bath. Specimens were loaded to failure in an Instron Model 1123 testing machine with a crosshead speed of 5 mm/min. Statistical analysis included a two-way analysis of variance (adhesive and time) and Tukey's post hoc test. RESULTS: Mean shear bond strengths (MPa) at 24 hours were: Clearfil, 26.4+/-4.2; Optibond, 23.5+/-4.4; Xeno, 19.5+/-4.2; Tyrian, 16.5+/-3.7; and Adper, 15.3+/-3.3. Mean shear bond strengths (MPa) after storage and thermocycling were: Optibond, 27.5+/-5.7; Clearfil, 25.5+/-4.9; Adper, 21.5+/-3.3; Xeno, 20.4+/-2.2; and Tyrian, 19.2+/-6.4. Both adhesive system and storage time were significant factors affecting shear bond strength (P < .05). CONCLUSION: There are significant differences in the in vitro dentin shear bond strength among the self-etching adhesive materials tested. Water storage and thermocycling did not significantly degrade the shear bond strength of the materials in this study.

Acrylic Resins↗

PubMed2004

Comparison of laboratory and clinical wear rates of resin composites.

OBJECTIVE: The purpose of this study was to use wear simulation to develop wear rates for two modern composite systems and then compare these rates with clinical studies on the same materials. METHOD AND MATERIALS: A spring-loaded piston wear simulator was used to generate localized wear rates for P50 and Z100 at 100,000, 200,000, 300,000, and 400,000 cycles. Clinical studies on P50 and Z100 conducted at Creighton University and the Catholic University of Leuven were used for comparison of clinical wear to the laboratory values. Regression analysis was employed to define the wear rates. RESULTS: The laboratory wear rates determined with simulation for P50 and Z100 were similar. Clinical occlusal contact area (OCA) wear for P50 and Z100 had small differences and were pooled to provide comparison with laboratory data. Wear rates determined from linear regression analysis provided equivalency factors between laboratory localized wear and clinical OCA wear that could be used for future studies. Further regression analysis comparing OCA and generalized clinical wear allowed a conversion factor of 4.5 to be determined. CONCLUSION: Localized wear from laboratory simulation may be a useful predictor of localized clinical wear and also clinical generalized wear using a conversion factor.

Analysis of Variance↗

PubMed2004

An accelerated in vitro model for adhesive testing.

PURPOSE: To develop a pilot in vitro accelerated laboratory testing protocol for assessing marginal sealing capability of dental adhesives. METHODS: Occlusal cavities were prepared in 20 human molar teeth and restored with Spectrum TPH resin composite. Prime & Bond NT and Prompt L-Pop served as the adhesive for eight teeth each. An experimental self-etching adhesive system was used on the remaining four teeth. Each specimen was subjected in sequential fashion to the following challenges: 400,000 wear cycles in a Leinfelder simulator; 5000 thermocycles between water baths maintained at 5 degrees C and 55 degrees C with a dwell time of 40 seconds in each; and a repetition of the 400,000 wear cycles. Polyvinyl siloxane impressions were made at baseline and after each challenge. Microleakage was assessed following silver nitrate staining and marginal degradation was evaluated using light microscopy and the stone casts made from the impressions taken during the project. RESULTS: Microleakage analysis yielded the following median leakage values: Prime & Bond NT - 0; Prompt L-Pop - 1; and experimental self-etching adhesive - 3. The Wilcoxon sign rank test demonstrated significant differences between all three adhesives (P < or = 0.05). Evaluation of the stone casts demonstrated that marginal gaps were more prevalent after the second wear challenge.

Acid Etching, Dental↗

PubMed2003

Use of yellow plastic food wrap to retard composite resin polymerization.

BACKGROUND: Dental chair lights can rapidly polymerize light-reactive composites beyond the point of workability, preventing adequate time for the shaping and sculpting of large direct composite restorations. PURPOSE: The purpose of this study was to determine whether yellow plastic food wrap placed over a dental chair light would perceptibly retard the polymerization rate of a light-cured composite (Esthet-X, shade A1, Dentsply/Caulk, Milford, DE, USA). MATERIALS AND METHODS: Zero, one, and two thicknesses of yellow plastic food wrap (Reynolds Metals Company, Richmond, VA, USA) were, in turn, used in the following scenarios: (1) placed in a spectrophotometer and compared for percentage transmission of 470 nm light; (2) placed over a curing unit light wand and compared for milliwatts of output on a radiometer; (3) placed over a dental chair light positioned 64 cm from 0.22 mm thick composite specimens, with Fourier Transform Infrared Spectrometry readings made every 40 seconds to measure degree of composite polymerization; (4) placed over a dental chair light positioned 64 cm from a direct veneer preparation (clinical simulation), which was then restored by four experienced clinicians who reported working times. RESULTS: Results for the scenarios were as follows: (1) zero sheets 100%, one sheet 34%, two sheets 6%; (2) zero sheets 580 mW, one sheet 190 mW, two sheets 20 mW; (3) percent conversion at 80 seconds--zero sheets 8%, one sheet 0.65%, two sheets 0.76%; percent conversion at 120 seconds--zero sheets 19.11%, one sheet 12.22%, two sheets 0.42%; (4) mean working times--zero sheets 34 seconds, one sheet 72 seconds, two sheets 155 seconds. CONCLUSIONS: Yellow plastic food wrap placed over a dental chair light markedly extended the working time of a light-cured composite in each of four assessments performed. Two sheets of plastic wrap were more than twice as effective as one sheet. CLINICAL SIGNIFICANCE: The suggested filtering technique with yellow plastic wrap placed over a dental chair light is a highly effective, expedient, and inexpensive method for increasing the working time of light-cured composites.

Color↗

PubMedDate not supplied

An in vitro study of enamel surface microhardness following argon laser irradiation and acidulated phosphate fluoride treatment.

PURPOSE: The purpose of this in vitro study was to evaluate the effect of low-fluence argon laser (AL) irradiation and acidulated phosphate fluoride (APF) gel treatment on enamel microhardness. METHODS: Twelve mandibular permanent molars were selected for this study. The teeth were sectioned generating 4 flat enamel surfaces per tooth. The flattened enamel tooth surfaces were randomly assigned to 1 of 4 treatment groups: (1) no treatment (control); (2) the enamel surface was exposed to a 4-minute, 1.23% APF gel treatment; (3) the enamel surface was exposed to AL irradiation of 11.5 J/cm2 (0.23 1-W, 5-mm beam size, 10 seconds); and (4) the enamel surface was exposed to the same AL irradiation followed by an APF gel treatment. Using a Buehler Micromet II Digital Microhardness Tester, Knoop hardness was determined using a 1,000-gram load and a dwell time of 12 seconds. Five hardness values were recorded for each enamel surface. Data were analyzed using ANOVA and Fisher's least significant difference post-hoc test. RESULTS: Mean surface hardness values (+/-SD) were 298+/-37 Knoop hardness (HK) for the no treatment (control), 270+/-70 HK for the APF-only group, 316+/-5 HK for the AL-only group, and 317+/-25 HK for the AL-before-APF group. The AL-only and AL-before-APF groups had significantly higher (P<.05) surface hardness values vs the APF-only group. CONCLUSIONS: Enamel surface microhardness is higher when exposed to low AL irradiation only or AL before APF vs a no treatment (control) enamel surface.

Acidulated Phosphate Fluoride↗

PubMedDate not supplied

Effects of adhesive liner and provisional cement on the bond strength of nickel/chrome/beryllium alloy cemented to dentin.

OBJECTIVE: Treating teeth with adhesive agents before placing a provisional restoration can prevent tooth sensitivity. This study evaluated the bond strength of resin cements to dentin treated with 2 adhesive agents and 2 provisional cements. METHODS AND MATERIALS: Extracted human molars were prepared by exposing dentin and were treated with either Prime & Bond NT or Clearfil SE Bond. After a simulated impression technique, the teeth were provisionalized with either a eugenol or noneugenol temporary cement. Teeth were cleaned for bonding by either mechanical removal of the cement or use of an acid conditioner. Panavia F and Calibra resin cements were used to cement nickel/chrome/beryllium alloy to the tooth surfaces, and the specimens were debonded. Mean shear bond strengths for each group were calculated. RESULTS: Mean shear bond strengths ranged from 26.6 +/- 5.8 MPa for Calibra bonded to dentin treated with Prime & Bond NT, a noneugenol cement, and mechanically cleaned, to 10.6 +/- 4.4 MPa for Panavia F bonded to unlined (no adhesive) dentin treated with a eugenol cement and mechanically cleaned. Of the 14 groups tested, significant differences were observed related to the adhesives and resin cements. Both temporary cements reduced the bond to dentin not treated with a resin adhesive. Use of an acid conditioner for cleaning the temporary cement also reduced bond strengths in all groups. CONCLUSIONS: Placement of a dentin adhesive before provisionalization may prevent the temporary cement from affecting the bond of the final resin cement to the tooth. For the products used in this study, use of phosphoric acid to clean the tooth surface is not recommended.

Cementation↗