Two-year Randomized, Controlled Clinical Trial of a Flowable and Conventional Composite in Class I Restorations.

OBJECTIVES: This study evaluated the two-year clinical performance and volumetric wear of a flowable resin composite compared to a conventional highly filled composite resin in Class I restorations. METHODS AND MATERIALS: In this single-center, single-blinded, comparator-controlled clinical study (Institutional Review Board approved), 120 carious teeth distributed in 60 patients were randomly assigned to four calibrated practitioners who placed occlusal restorations (n=60 flowable and n=60 conventional composite). Direct and indirect assessment at baseline, six months, one year, and two years occurred during which the modified Cvar and Ryge criteria were evaluated. Volumetric wear was determined by superimposition of profilometer scans of baseline and two-year casts. RESULTS: At two years, there was no significant difference in anatomic form (p=0.80), color match (p=0.08), marginal adaptation (p=0.89), marginal discoloration (p=0.79), surface integrity (p=0.18), secondary caries (p=0.66), cold sensitivity (p=0.522), occlusal sensitivity (p=0.818), or volumetric wear (p=0.661) between materials. Both materials showed a decrease in all criteria except secondary caries (p=0.95) over time. Two-year mean volumetric wear was 3.16 ± 2.38 mm(3) for the flowable composite and 3.43 ± 2.50 mm(3) for the conventional composite. CONCLUSIONS: The flowable and conventional composites used in this study have similar clinical efficacy after two years of service when placed as Class I occlusal restorations having isthmus widths less than one-half the intercuspal distance.

Influence of Etching Protocol and Silane Treatment with a Universal Adhesive on Lithium Disilicate Bond Strength.

OBJECTIVES: To measure the effects of hydrofluoric acid (HF) etching and silane prior to the application of a universal adhesive on the bond strength between lithium disilicate and a resin. METHODS AND MATERIALS: Sixty blocks of lithium disilicate (e.max CAD, Ivoclar Vivadent) were sectioned into coupons and polished. Specimens were divided into six groups (n=10) based on surface pretreatments, as follows: 1) no treatment (control); 2) 5% HF etch for 20 seconds (5HF); 3) 9.5% HF etch for 60 seconds (9.5HF); 4) silane with no HF (S); 5) 5% HF for 20 seconds + silane (5HFS); and 6) 9.5% HF for 60 seconds + silane (9.5HFS). All etching was followed by rinsing, and all silane was applied in one coat for 20 seconds and then dried. The universal adhesive (Scotchbond Universal, 3M ESPE) was applied onto the pretreated ceramic surface, air thinned, and light cured for 10 seconds. A 1.5-mm-diameter plastic tube filled with Z100 composite (3M ESPE) was applied over the bonded ceramic surface and light cured for 20 seconds on all four sides. The specimens were thermocycled for 10,000 cycles (5°C-50°C/15 s dwell time). Specimens were loaded until failure using a universal testing machine at a crosshead speed of 1 mm/min. The peak failure load was used to calculate the shear bond strength. Scanning electron microscopy images were taken of representative e.max specimens from each group. RESULTS: A two-way analysis of variance (ANOVA) determined that there were significant differences between HF etching, silane treatment, and the interaction between HF and silane treatment (p<0.01). Silane treatment provided higher shear bond strength regardless of the use or concentration of the HF etchant. Individual one-way ANOVA and Tukey post hoc analyses were performed for each silane group. Shear bond strength values for each etch time were significantly different (p<0.01) and could be divided into significantly different groups based on silane treatment: no silane treatment: 0 HF < 5% HF < 9.5% HF; and RelyX silane treatment: 0 HF < 5% HF and 9.5% HF. CONCLUSIONS: Both HF and silane treatment significantly improved the bond strength between resin and lithium disilicate when used with a universal adhesive.

Clinical evaluation of self-etch and total-etch adhesive systems in noncarious cervical lesions: a two-year report.

OBJECTIVE: The purpose of this study was to compare the clinical performance of two self-etch dental adhesives with Single Bond Plus, a traditional one-bottle total-etch dental adhesive, for the restoration of noncarious cervical lesions. MATERIALS AND METHODS: A total of 156 restorations were placed in noncarious cervical lesions with a minimum depth of 1.5 mm. Patients had no chronic periodontal disease and had normal salivary function. Each patient received restorations on three teeth, each bonded with either Adper Single Bond Plus, Adper Easy Bond, or Adper Scotchbond SE dental adhesive. All lesions were restored with Filtek Supreme Plus composite resin. All teeth were isolated with a rubber dam, received a short enamel bevel, and were cleaned with flour of pumice. The adhesives and resin composite were applied following the manufacturers' instructions. Restorations were clinically evaluated at baseline, six months, one year, and two years using modified US Public Health Service criteria. RESULTS: Two-year retention was recorded as 97.3%, 90.5%, and 95.2%, for Single Bond Plus, Scotchbond SE, and Easy Bond, respectively. Statistical analysis did not show a significant difference (p>0.05) in clinical performance between any of the three adhesives after a period of two years.

An analysis of the implant-supported overdenture in the edentulous mandible.

This investigation examined the cumulative survival rate of the implant-supported overdenture using two types of attachments in patients treated at Show Chwan Memorial Hospital Implant Center from 1992 to 2006. Fifty-one patients (30 men and 21 women) were treated with mandibular implant-supported overdentures. Attachment systems used were the Hader bar with bilateral, cast ERA attachments (Group A, 31 patients with 15 men and 16 women, 134 implants) and the Hader bar with bilateral, distal extension cantilevers (Group B, 20 patients with 15 men and 5 women, 85 implants). Two hundred and four implants remained at the end of the follow-up period. Among failed implants, 10 implants were in Group A (failure rate: 10/134 = 7·5%), whereas five implants were in Group B (failure rate: 5/85 = 5·9%). Sixty-six point seven per cent (10/15) of failed implants were placed in the distal anterior mandible, and 33·3% (5/15) were placed in the middle anterior mandible. Survival was also examined with respect to condition of the opposing arch. Patients wearing a maxillary removable partial denture had the highest implant failure rate (5/51 = 9·8%), whereas the failure rate of the maxillary complete denture group was only 5·7%. The most frequent need for maintenance was wear over patrix component of ERA or Hader clip (n = 56). Eight patients experienced connector fracture between ERA and Hader bar, and one experienced distal extension cantilever fracture. The implant-supported overdenture can be an effective and reliable alternative to the conventional complete mandibular denture. Fewer prosthetic complications were seen in overdentures retained with distal extension cantilever attachments.

Evaluation of outgassing, tear strength, and detail reproduction in alginate substitute materials.

OBJECTIVE: To compare three alginate substitute materials to an alginate impression material for cast surface porosity (outgassing), tear strength, and detail reproduction. MATERIALS AND METHODS: Detail reproduction tests were performed following American National Standards Institute/American Dental Association (ANSI/ADA) Specification No. 19. To measure tear strength, 12 samples of each material were made using a split mold, placed in a water bath until testing, and loaded in tension until failure at a rate of 500 mm/min using a universal testing machine. For cast surface porosity testing, five impressions of a Teflon mold with each material were placed in a water bath (37.8°C) for the in-mouth setting time and poured with vacuum-mixed Silky Rock die stone at 5, 10, 30, and 60 minutes from the start of mixing. The gypsum samples were analyzed with a digital microscope for surface porosity indicative of hydrogen gas release by comparing the surface obtained at each interval with four casts representing no, little, some, and significant porosity. Data analysis was performed using parametric and Kruskal-Wallis analysis of variance (ANOVA), Tukey/Kramer post-hoc tests (α=0.05), and individual Mann-Whitney U tests (α=0.0167). RESULTS: All alginate substitute materials passed the detail reproduction test. Tear strength of the alginate substitute materials was significantly better than alginate and formed three statistically different groups: AlgiNot had the lowest tear strength, Algin-X Ultra had the highest tear strength, and Position Penta Quick had intermediate tear strength. Significant variation in outgassing existed between materials and pouring times (p<0.05). All alginate substitute materials exhibited the least outgassing and cast porosity 60 minutes after mixing. CONCLUSIONS: Detail reproduction and tear strength of alginate substitute materials were superior to traditional alginate. The outgassing effect was minimal for most materials tested. Alginate substitute materials are superior replacements for irreversible hydrocolloid.

Effect of light activation on resin-modified glass ionomer shear bond strength.

OBJECTIVE: Recent studies confirmed that resin-modified glass ionomers (RMGIs) set on the basis of two competing mechanisms, an acid-base reaction and a light-activated resin polymerization. This study evaluated the effect of the setting mechanism on bond strength by measuring the shear bond strength of three RMGIs to dentin with and without light activation. METHODS: Sixty human molars were ground to midcoronal dentin and randomly divided into six even groups: 1) Ketac Nano (KN), 2) KN without light cure (woLC), 3) Fuji Filling LC (FF), 4) FF woLC, 5) Fuji II LC (FII), and 6) FII woLC. The dentin surfaces of the specimens were conditioned/primed according to the manufacturers' instructions. A 1.54-mm diameter plastic tube was filled with RMGI material and affixed to the dentin surface. Groups 1, 3, and 5 were light cured for 20 seconds, and groups 2, 4, and 6 were immediately placed in a damp dark box with no light curing at 37°C for 24 hours. Shear bond strength testing was performed in an Instron device at 1 mm/min. Data were analyzed with a one-way analysis of variance (ANOVA) and Tukey/Kramer test (α=0.05). RESULTS: Mean ± standard deviation shear bond strength values (MPa) are: 7.1 ± 4.2 (KN), 11.7 ± 3.9 (FF), 10.2 ± 3.2 (FF woLC), 12.5 ± 5.1 (FII), and 0.3 ± 0.4 (FII woLC). Two KN, all KN woLC, and seven FII woLC specimens debonded before testing. Tukey/Kramer analysis revealed no significant differences in bond strength between the three light-cured RMGIs. KN and FII showed significantly lower bond strength without light cure, but no significant difference was observed between FF and FF woLC. CONCLUSIONS: The results of this study strongly suggest that light activation is necessary to obtain optimal bond strength between RMGI and dentin. FF may contain components that chemically activate resin polymerization. Clinically, KN and FII need to be light cured after placement of these RMGIs.

Retention and leakage of implant-supported restorations luted with provisional cement: a pilot study.

Few data exist regarding cement failure load and marginal leakage of castings cemented to implant-supported abutments subjected to load and thermal cycling, especially with newer cements. This study evaluated the cement failure load and marginal leakage of castings cemented to Steri-Oss abutment/analog assemblies with one of seven luting protocols (n = 5). Protocols consisted of a zinc phosphate control, zinc phosphate with petroleum jelly, TempBond, TempBond NE, ImProv, ImProv with petroleum jelly and Provilink. Cemented castings were subjected to cyclic axial compression of 75 N for 100,000 cycles, 1000 thermal cycles (5-55 degrees C), and immersed 24 h in 0.5% basic fuchsin. The castings were then loaded in tension until cement failure. Cement failure load was analysed using anova and Fischer's PLSD (alpha = 0.05). Marginal leakage on the intaglio of the casting was scored with the unaided eye on a scale of 0-2, and analysed with Duncan's multiple range (alpha = 0.05). Similar groups are noted by superscript. Cement failure load (from lowest to highest): ImProv with petroleum jelly(a), TempBond(a), ImProv(a), Tempbond NE(a), Provilink(a), zinc phosphate with petroleum jelly(b), zinc phosphate(c) (P < 0.0001). Marginal leakage scores (from lowest to highest): ImProv(a), Provilink(a), ImProv with petroleum jelly(a), zinc phosphate(ab), zinc phosphate with petroleum jelly(ab), TempBond(bc), and TempBond NE(c) (P = 0.01). Addition of petroleum jelly to zinc phosphate lowered cement failure load without affecting marginal leakage. ImProv and Provilink demonstrated relatively low cement failure load, as well as lowest marginal leakage.

Dynamic behavior of implants as a measure of osseointegration.

Research into the formation, destruction, and adaptation of bone around implants would benefit from a sensitive, nondestructive, noninvasive, and quantitative technique to assess the bone-implant interface. It is hypothesized that osseointegration can be quantified by sensing the mechanical impedance (or micromobility) of the implant when it is subjected to minute vibratory forces superimposed upon a quasi-static preload. To test this hypothesis, a total of 24 identical threaded, titanium root-form implants (10 x 3.75 mm, Osteo-Implant, New Castle, PA) were placed in the mandibles of 4 Walker hounds and allowed to heal submerged for 3 months. The implants were exposed and characterized for osseointegration using clinical observations, quantitative radiography, and a custom-designed impedance instrument. Subsequently, arbitrarily selected implants were ligated to induce bone loss and examined monthly over a 6-month study period. Following the terminal examination and euthanasia, quantitative histologic measurements were made of bone adjacent to the implant, including estimates of both crestal bone height and the percent bone (bone fraction). Linearized dynamic parameters (effective stiffness and effective damping) correlated well with radiographic and histologic measures of bony support (r2 values ranged from 0.70 to 0.89). Moreover, the presence of nonlinear stiffness was clearly associated with a bimodal "clinical impression" of osseointegration (P < .0003, 1-way analysis of variance). These results confirm that, in this animal model, mechanical impedance can be used as a measure of implant osseointegration.

Assessment of osseointegration by nonlinear dynamic response.

Quantitative assessment of osseointegration remains a goal of researchers and clinicians alike. In this study, an instrument was designed for this purpose and tested in an animal model. Effective mechanical impedance, linearized for quasi-static force, was measured in 22 implants placed in the hind tibiae of 2 large hounds. The results demonstrate that in this animal long-bone model, the effective impedance of titanium root-form implants exhibits a degree of nonlinear behavior correlated with their state of osseointegration. This observation may be the basis for useful clinical instrumentation.

Tensile bond strengths of provisional luting agents used with an implant system.

STATEMENT OF PROBLEM: Retrievability of cemented implant-supported fixed prostheses is desirable. Retentive strengths of new provisional luting agents have not been reported. PURPOSE: This study compared the tensile bond strengths of 6 provisional luting agents when used with cemented superstructures and 1 implant system. MATERIAL AND METHODS: Ten castings were fabricated and randomly paired with abutment specimens. Castings were cemented and the assemblies were stored in distilled water at 37 degrees C for 48 hours. Tensile bond strength necessary to remove each casting was measured with a 500-kg load and a crosshead speed of 0.5 cm/min. Crown/abutment specimens were cleaned after testing, and the testing procedure was repeated for a total of 6 luting agents (n = 10). Data were analyzed with 1-way analysis of variance and Scheffé's analysis (alpha=.05). RESULTS: Tensile bond strengths ranged between 1.29 and 4.08 MPa. The lowest tensile bond strengths were found to be statistically similar between Temp Bond and Provilink luting agents. Neo-Temp luting agent exhibited the highest tensile bond strength (P <.01). CONCLUSIONS: Temp Bond and Provilink luting agents exhibited the lowest mean tensile bond strengths. Neo-Temp luting agent exhibited a tensile bond strength more than 3 times that of Temp Bond luting agent.

Vertical height loss: an investigation of four restorative materials opposing enamel.

PURPOSE: The objective of this in vitro investigation was to compare the vertical wear produced by cone-shaped styli of three ceramic restorative materials and a Type III gold alloy opposing flattened human enamel. Vertical wear was measured as enamel height loss, material stylus height loss, and total vertical height loss (the sum of the enamel height loss and the restorative material height loss). MATERIALS AND METHODS: Ten cone-shaped styli were fabricated from each of four restorative materials, which included two machined ceramics, a pressed ceramic, and a Type III gold alloy. To maintain the standardized shape, styli were not polished or glazed. Specimens were subjected to wear in the presence of water for 100,000 cycles at 1.2 Hz under a load of 75 N using a wear simulation device. Enamel wear was evaluated by profilometry, and stylus wear was evaluated by computer imaging. Vertical wear was reported as enamel height loss, material stylus height loss, and total vertical height loss (the sum of the enamel height loss and material height loss). Data were compared using one-way analysis of variance and Scheffe's analysis (alpha = 0.05). RESULTS: Significant differences existed among materials based on material height loss (p = .0001), enamel height loss (p = .0001), and total vertical height loss (p = .0118). No significant difference among the three ceramics was found in mean total height loss, which ranged from 0.280 to 0.305 mm. However, the Type III gold exhibited less mean total wear (0.231 +/- 0.082) than the pressed and one machineable ceramic. This machined ceramic exhibited the most material height loss (0.249 +/- 0.044 mm). With the other ceramics, mean enamel wear was significantly more (0.211 and 0.216 mm, respectively). CONCLUSIONS: During wear simulation, pressed or machineable ceramics opposing flattened enamel exhibited a similar degree of total vertical height loss. One machined ceramic material wore significantly more than the other materials. The other machineable ceramic and the pressed ceramic wore the opposing enamel significantly more.