Microleakage around Class V Composite Restorations after Ultrasonic Scaling and Sonic Toothbrushing around their Margin.

OBJECTIVES: To measure microleakage around class V composite restorations after piezoelectric ultrasonic scaling and sonic toothbrushing. METHODS: 3 mm × 2 mm × 1.5 mm boxes were prepared on buccal and lingual surfaces of extracted molars centered on the cementum-enamel junction. Half the preparations were beveled (0.5 mm). Preparations were restored with composite and polished. Restorations on one side of the teeth were either traced with an ultrasonic scaler (60 seconds, n = 16) or brushed in a sonic toothbrushing machine (2 hours, n = 16). After thermocycling (10,000 cycles/5-55°C), specimens were immersed in 5 wt% Fuchsine solution (24 hours). Samples were sectioned and evaluated for percentage of dye penetration. Data were analyzed with an exact Wilcoxon rank-sum test and exact Wilcoxon signed-rank test (alpha = 0.05). RESULTS: Microleakage was observed at the cementum-composite interface but not the enamel-composite interface. There was not a statistically significant effect of the bevel for ultrasonic scaling or for sonic toothbrushing. Data obtained with and without a bevel were combined and a statistically significant difference in microleakage between the treatment and control sides of the tooth were found for ultrasonic scaling (32.5%±44.9%, n = 16; p = 0.016) but not sonic toothbrushing (2.5% ± 41.2%, n = 16; p = 1.0). CONCLUSIONS: Piezoelectric ultrasonic scaling increased microleakage at cementum-composite interface and there was no difference in microleakage with the use of a bevel. CLINICAL SIGNIFICANCE: Piezoelectric sonic scaling around Class V composite restorations with margins in cementum should be avoided. Beveled margins will not reduce the incidence of microleakge resulting from ultrasonic scaling in Class V restorations. Placing the apical margin of the restoration in enamel should be attempted whenever possible to prevent future microleakage. (J Esthet Restor Dent 29:41-48, 2017).

Color and Gloss of Nano-Filled Resin-Modified Glass Ionomers and Resin Composites.

OBJECTIVE: The study aims to compare in vitro stain resistance, color stability, gloss, and gloss retention of a nano-filled resin-modified glass ionomers (RMGIs) to a traditional RMGI and resin-based composites (RBCs). MATERIALS AND METHODS: Specimens (N = 20) were fabricated from a nano-filled RBC (Filtek Supreme Plus, 3M ESPE, St. Paul, MN, USA), a nanohybrid RBC (Clearfil Majesty Esthetic, Kuraray; Tokyo, Japan), a nano-filled RMGI (Ketac Nano, 3M ESPE), and traditional RMGI (Fuji II LC, GC America, Chicago, IL, USA). L*a*b* values were recorded with a spectrophotometer, and gloss was measured with a glossmeter. For each material, 10 specimens were stored in distilled water in darkness for 1 week and 10 specimens were placed in a staining solution for 1 week. After storage, specimens were cleaned and L*a*b* and gloss measurements were remeasured. RESULTS: Data were analyzed by analysis of variance (ANOVA) and Tukey analyses. Regarding color change, materials ranked: Ketac = Fuji > Filtek > Clearfil in water, and Ketac > Fuji > Filtek > Clearfil in staining solution. Prior to storage, the initial gloss of the materials ranked: Filtek ≥ Clearfil ≥ Ketac > Fuji. After storage, the materials ranked: Filtek = Clearfil > Ketac > Fuji in water, and Filtek > Clearfil > Ketac > Fuji in staining solution. Gloss retention was similar for all materials in water and gloss retention ranked: Filtek = Clearfil > Ketac = Fuji in staining solution. CONCLUSIONS: The nano-RMGI showed less stain resistance but higher gloss than the traditional RMGI. Both RMGIs had more color change, less stain resistance, lower gloss and less gloss retention than the RBCs. CLINICAL SIGNIFICANCE: The clinician should be aware that the use of a nano-RMGI may improve the gloss of an RMGI restoration; however, color change will likely occur, particularly if the patient consumes a staining diet.

Influence of particle abrasion or hydrofluoric acid etching on lithium disilicate flexural strength.

STATEMENT OF PROBLEM: Lithium disilicate is a translucent, glass-containing material used for ceramic restorations. Clinicians frequently use alumina abrading or hydrofluoric acid etching to create micromechanical retention in the intaglio surface before bonding a lithium disilicate restoration to the tooth. Few studies have investigated how the etching or abrasion processes affect the flexural strength of lithium disilicate ceramics. PURPOSE: The purpose of this study was to measure and compare the flexural strength of e.max CAD after alumina abrasion at differing pressures and acid etching at differing concentrations and times. MATERIAL AND METHODS: Bars of e.max CAD (9 groups of 10; 22×2.5×2.5 mm) were prepared, polished sequentially with 180, 320, and 600 abrasive paper, and sintered according to the manufacturer's instructions. Four groups were particle abraded (30-µm alumina particles from 10 mm at 55, 100, 200, or 300 kPa for 10 seconds). Four groups were etched with either 5% hydrofluoric acid (20 seconds or 120 seconds) or 9.5% hydrofluoric acid (20 seconds or 120 seconds). The control was polished and fired only (no treatment). Specimens were placed onto an Instron (1 mm/min crosshead speed) and loaded to failure in a 3-point flexural test. One-way ANOVA and the Dunnett t test determined intergroup differences (α=.05). RESULTS: Compared with the control, the 100, 200, and 300 kPa alumina abraded groups produced significantly lower flexural strengths (P<.001); however, the flexural strength of the 55 kPa abraded group was not statistically different from the control (P=.080). The flexural strength of the 5% and the 9.5% hydrofluoric acid-etched groups also were not significantly different from the control (P>.050); however, the 9.5% hydrofluoric acid at 20 seconds group was nearly statistically significant (P=.051). CONCLUSION: Alumina particle abrasion at pressures of 100 kPa and higher significantly reduced flexural strength by creating stress risers in e.max CAD and should not be used. Hydrofluoric acid etching should be used to increase micromechanical retention and clean the intaglio surface of the restoration before bonding.

The wear of polished and glazed zirconia against enamel.

STATEMENT OF PROBLEM: The wear of tooth structure opposing anatomically contoured zirconia crowns requires further investigation. PURPOSE: The purpose of this in vitro study was to measure the roughness and wear of polished, glazed, and polished then reglazed zirconia against human enamel antagonists and compare the measurements to those of veneering porcelain and natural enamel. MATERIAL AND METHODS: Zirconia specimens were divided into polished, glazed, and polished then reglazed groups (n=8). A veneering porcelain (Ceramco3) and enamel were used as controls. The surface roughness of all pretest specimens was measured. Wear testing was performed in the newly designed Alabama wear testing device. The mesiobuccal cusps of extracted molars were standardized and used as antagonists. Three-dimensional (3D) scans of the specimens and antagonists were obtained at baseline and after 200 000 and 400 000 cycles with a profilometer. The baseline scans were superimposed on the posttesting scans to determine volumetric wear. Data were analyzed with a 1-way ANOVA and Tukey Honestly Significant Difference (HSD) post hoc tests (α=.05) RESULTS: Surface roughness ranked in order of least rough to roughest was: polished zirconia, glazed zirconia, polished then reglazed zirconia, veneering porcelain, and enamel. For ceramic, there was no measureable loss on polished zirconia, moderate loss on the surface of enamel, and significant loss on glazed and polished then reglazed zirconia. The highest ceramic wear was exhibited by the veneering ceramic. For enamel antagonists, polished zirconia caused the least wear, and enamel caused moderate wear. Glazed and polished then reglazed zirconia showed significant opposing enamel wear, and veneering porcelain demonstrated the most. CONCLUSIONS: Within the limitations of the study, polished zirconia is wear-friendly to the opposing tooth. Glazed zirconia causes more material and antagonist wear than polished zirconia. The surface roughness of the zirconia aided in predicting the wear of the opposing dentition.

Acid-etch interval and shear bond strength of Er,Cr:YSGG laser-prepared enamel and dentin.

The formation of a superficial layer of tiny flakes has been observed on teeth prepared by Erbium lasers. It has been suggested that removing this layer (mechanically or chemically) may increase the bond strength of the resin composite. The purpose of this study is to evaluate the effect of various etching times on bond strength of resin composite to enamel and dentin prepared by Er,Cr:YSGG laser. Sixty previously flattened human molars were irradiated for 10 s by an Er,Cr:YSGG laser. Enamel (E) specimens were etched with 37% H(3)PO(4) for 20, 40 or 60 s and dentin (D) specimens were etched for 15 or 30 s. All specimens were prepared for a standard shear bond strength (SBS) test (1 mm/min). Data were analyzed [ANOVA, Tukey post-hoc, a < 0.05)] and the failure mode was studied under SEM. Mean SBS+/-sd (MPa) for each group was 16.97 +/- 7.77 (E20s), 21.34 +/- 3.55 (E40s), 14.08 +/- 4.77 (E60s), 13.62 +/- 7.28 (D15s) and 13.15 +/- 6.25 (D30s). SBS for E40s was significantly higher than E60s (p = 0.023). No difference was noted between the dentin groups. SEM evaluation showed predominantly cohesive failure. Within the limits of this study, etching time significantly influenced the SBS of composite resin to laser-prepared enamel. SEM showed subsurface cracks, fissures, and deformities leading to predominantly cohesive failure in both enamel and dentin.

Enhancement of bonding to enamel and dentin prepared by Er,Cr:YSGG laser.

BACKGROUND AND OBJECTIVE: Erbium lasers are potential tools to remove caries and dental hard tissue but bond strengths of composites to those preparations are reported to be lower than conventional methods. The purpose of this study was to evaluate the effect of mechanical excavation and/or chemical alteration on bond strength of composites to laser irradiated enamel and dentin. MATERIALS AND METHODS: Seventy-two premolars were ground to obtain flat enamel (E, n = 36) or dentin (D, n = 36) surfaces in both buccal and lingual cusps, divided into: LaserExcavation (LEx), LaserNo-excavation (LNex), and Bur (B) groups. The laser groups were irradiated for 10 seconds by Er,Cr:YSGG laser [4.5 W, 60% air, 80% water (enamel) 3 W, 60% air, 70% water (dentin)]. Irradiated surfaces in the excavation groups (Ex) were then mechanically smoothed with a dental excavator, prepared surfaces were then etched (37% H(3)PO(4)) for 20 or 40 seconds (enamel) and 15 or 30 seconds (dentin), washed (20 seconds), adhesive was applied(Single Bond Plus), and light cured (20 seconds). A composite cylinder (Filtek Supreme Plus) formed, placed and light cured (40 seconds). The specimens were stored (37 degrees C,48 hours), shear bond tested (1 mm/minute), and statistically analyzed (P < 0.05). RESULTS: Mixed-model ANOVA showed significant differences between enamel (P = 0.0091) and between dentin groups (P = 0.0035). Tukey/Kramer showed mean shear bond strength (SBS+/-SE) of EB40 (27.01+/-2.38 MPa) was significantly higher than ELNoExc20 (14.39+/-2.5 MPa) and ELExc40 (14.90+/-2.28 MPa). Also DB30 (17.57+/- 1.67 MPa) and DLExc30 (18.6+/-1.74 MPa) were significantly higher than DLNoExc15 (9.56+/-1.86 MPa). CONCLUSION: Increasing the etching time up to 40 seconds or excavation of the laser prepared surface (but not the combination) may increase the bond strength to the level of conventional methods in enamel but excavation has a greater influence in dentin. Also the combination of both methods [excavation+longer etching time (30 seconds)] exhibit significantly better results in dentin.Mode of failure study showed mechanical excavation in both enamel and dentin can significantly reduce the cohesive failure in tooth structure.

Characterization of third-body media particles and their effect on in vitro composite wear.

OBJECTIVES: The purpose of this study was to compare four medium particles currently used for in vitro composite wear testing (glass and PMMA beads and millet and poppy seeds). METHODS: Particles were prepared as described in previous wear studies. Hardness of medium particles was measured with a nano-indentor, particle size was measured with a particle size analyzer, and the particle form was determined with light microscopy and image analysis software. Composite wear was measured using each type of medium and water in the Alabama wear testing device. Four dental composites were compared: a hybrid (Z100), flowable microhybrid (Estelite Flow Quick), micromatrix (Esthet-X), and nano-filled (Filtek Supreme Plus). The test ran for 100,000 cycles at 1.2 Hz with 70 N force by a steel antagonist. Volumetric wear was measured by non-contact profilometry. A two-way analysis of variance (ANOVA) and Tukey's test was used to compare both materials and media. RESULTS: Hardness values (GPa) of the particles are (glass, millet, PMMA, and poppy, respectively): 1.310(0.150), 0.279(0.170), 0.279(0.095), and 0.226(0.146). Average particle sizes (µm) are (glass, millet, PMMA, and poppy, respectively): 88.35(8.24), 8.07(4.05), 28.95(8.74), and 14.08(7.20). Glass and PMMA beads were considerably more round than the seeds. During composite wear testing, glass was the only medium that produced more wear than the use of water alone. The rank ordering of the materials varied with each medium, however, the glass and PMMA bead medium allowed better discrimination between materials. SIGNIFICANCE: PMMA beads are a practical and relevant choice for composite wear testing because they demonstrate similar physical properties as seeds but reduce the variability of wear measurements.

Comparison of root canal preparation using reciprocating Safesiders stainless steel and Vortex nickel-titanium instruments.

OBJECTIVE: The aim of the present study was to assess several parameters related to the clinical usage of 2 root canal preparation instruments: Vortex .06 rotary nickel-titanium instruments, and Safesiders reciprocating stainless steel instruments. STUDY DESIGN: Fifty extracted mandibular molars with mesial root canal curvatures between 20° and 50° were divided into 2 groups and embedded in acrylic resin inside a modified Bramante muffle system. All root canals were prepared to ISO size 40 using either Vortex .06 rotary nickel-titanium-instruments in a low-torque motor or Safesiders stainless steel instruments in a proprietary reciprocating handpiece. The following parameters were evaluated: straightening of curved root canals, working safety issues (perforations, instrument breakages, canal blockages, loss of working length), postpreparation root canal cross-section, and working time. RESULTS: The Vortex .06 instruments maintained canal curvatures well, with the mean degree of straightening recorded as 0.72°. Safesiders instruments demonstrated significantly more canal straightening, with the mean degree of straightening recorded as 15.5°. More than 90% of the root canals prepared with the Vortex .06 instruments resulted in a round or oval cross-section, whereas the Safesiders instruments produced round or oval cross-sections 60% of the time. Neither of the 2 instruments could effectively prepare 100% of the root canal circumference. The area of dentin removed and the remaining dentin thicknesses from each region were similar for the 2 groups. Six procedural incidents were recorded for the Vortex .06 group, compared with 19 for the Safesiders group. There were no instrument fractures recorded in either group. Mean working time was significantly shorter for Vortex .06 (279 s) than for Safesiders (324 s). CONCLUSIONS: Vortex .06 maintained the original root canal curvatures well, whereas Safesiders instruments demonstrated significant straightening and irregular preparation shapes when used in sizes larger than ISO 20. Preparation of the complete circumference of the root canal was not possible with either system. Fewer procedural errors occurred with the Vortex instruments.

Different enamel and dentin mineralization observed in VDR deficient mouse model.

UNLABELLED: Vitamin D plays an important role in the bone mineralization process. Enamel and dentin are two mineralized tissues of different origins that combine to form teeth, but the mechanism by which vitamin D regulates these tissues remains unclear. We hypothesized that vitamin D affects enamel and dentin mineralization through different mechanisms. OBJECTIVE: To examine enamel and dentin mineralization in a vitamin D receptor (VDR) deficient mouse model by micro-computerized tomography (micro-CT) and scanning electronic microscopy (SEM). METHODS: VDR wild type mice (VDR+/+) and VDR deficient (VDR-/-) littermates were sacrificed at 70.5 days old, and their mandibles were dissected. Micro-CT was used to compare mineral density (MD) of enamel and dentin of the two groups at different levels along the axis of mandibular incisors. SEM was employed to examine the ultrastructure of incisors at the levels corresponding to the levels used for the micro-CT studies. Furthermore, an accelerated eruption procedure was performed to exclude the effect of delayed eruption on enamel and dentin mineralization. RESULTS: Different distribution patterns of enamel and dentin MD were observed between VDR+/+ and VDR-/- groups. Early enamel maturation, mineralization, and hypomineralization in dentin were observed in the VDR deficient mice. CONCLUSION: Vitamin D may affect the mineralization of dentin systemically, and enamel mineralization may be regulated locally.

Regulation of enamel and dentin mineralization by vitamin D receptor.

BACKGROUND: Vitamin D plays an important role in bone mineralization. Enamel and dentin are two mineralized tissues of different origins that are part of the tooth structure, but the mechanism by which vitamin D regulates the mineralization of these tissues remains unclear. We examined the mineral deposition pattern of enamel and dentin in continuously erupting incisors in a vitamin D receptor (VDR) deficient mouse model to determine the effect of vitamin D receptor pathway on enamel and dentin mineralization. METHODS: VDR wild-type mice (VDR+/+) and VDR-deficient (VDR--/--) littermates were sacrificed at 70.5 days of age, and their mandibles were dissected. Immunostaining of biglycan and decorin was used to evaluate the dentin maturation. Micro-computerized tomography (micro-CT) was used to compare the mineral density (MD) of enamel and dentin of the two groups at different regions along the axis of the mandibular incisors. Scanning electronic microscopy (SEM) was employed to examine the ultrastructure of enamel and dentin at the levels corresponding to those examined in the micro-CT studies. Furthermore, an accelerated eruption procedure was performed to exclude the effect of delayed eruption on enamel and dentin mineralization. RESULTS: Different mineral deposition patterns of enamel and dentin were observed at different levels of the incisors in the VDR+/+ and VDR--/-- groups. Early enamel maturation and mineralization, and dentin hypomineralization were observed in the VDR--/-- group. CONCLUSION: Vitamin D affects enamel and dentin mineralization through different mechanisms. It may affect the mineralization of dentin systemically while enamel mineralization may be regulated locally.

Surface Roughness of CoCr and ZrO(2) Femoral Heads with Metal Transfer: A Retrieval and Wear Simulator Study.

Metal transfer to femoral heads may result from impingement against the metallic acetabular shell following subluxation/dislocation, or when metallic debris enters the articulation zone. Such transfers roughen the head surface, increasing polyethylene wear in total hip replacements. Presently, we examined the surface roughness of retrieved femoral heads with metallic transfer. Profilometry revealed roughness averages in regions of metal transfer averaging 0.380 mum for CoCr and 0.294 mum for ZrO(2) which were one order of magnitude higher than those from non-implanted controls. Scanning electron microscopy (SEM) revealed adherent transfers on these retrievals, with titanium presence confirmed by electron dispersive spectroscopy. Due to the concern for increased wear, metal transfer was induced on non-implanted heads, which were then articulated against flat polyethylene discs in multidirectional sliding wear tests. Increased polyethylene wear was associated with these specimens as compared to unaltered controls. SEM imaging provided visual evidence that the transfers remained adherent following the wear tests. Pre- and post-test roughness averages exceeded 1 mum for both the CoCr and ZrO(2) heads. Overall, these results suggest that metal transfer increases the surface roughness of CoCr and ZrO(2) femoral heads and that the transfers may remain adherent following articulation against polyethylene, leading to increased polyethylene wear.

Normalisation of calcium status reverses the phenotype in dentin, but not in enamel of VDR-deficient mice.

OBJECTIVE: To determine the effects of vitamin D receptor (VDR) deficiency on mouse dentin and enamel mineralisation, and how normalisation of serum calcium level affects dentin and enamel phenotypes in VDR knockout mice. MATERIALS AND METHODS: Groups of VDR wild-type (VDR+/+), VDR deficient (VDR-/-) and VDR-/- rescued mice were sacrificed at 70.5 days of life. The rescued group was established by a high-calcium diet feeding the VDR-/- mice from postnatal 19 days. Micro-CT was used to compare enamel and dentin mineralisation density (MD) at different levels of mandibular incisors among the groups. The scanning electron microscope (SEM) was used to examine the ultrastructure of the enamel and dentin in the corresponding levels and of surface enamel after acidic treatment. RESULTS: Micro-CT showed that in VDR-/- rescued group, dentin phenotype was reversed and dentin MD was reversed to normal; however, enamel mineralisation was not reversible, and remained as hypermineralisation in molar region and apical region of the incisors. SEM also revealed enamel hypermineralisation in the VDR-/- rescued group. This early enamel hypermineralisation was more susceptible to acidic erosion. CONCLUSION: Vitamin D affects dentin mineralisation systemically, and it regulates enamel mineralisation locally.

Biocompatibility testing of simulated total joint arthoplasty articulation debris.

Surface characterization was performed to evaluate the surface condition of an uncoated cobalt alloy disc (control), and discs with medium and thick boron coatings for total joint articulating surfaces. Discs were characterized by scanning electron microscopy before and after dissolution studies. Chemical analyses of elemental transfer to the solution were assessed to evaluate the surface stability of the new coating. An in vivo biocompatibility study for particulates [of boron (B), titanium alloy (Ti), cobalt alloy (Co), and combinations of B + Ti and B + Co] was performed using a rat air pouch model. The inflammatory reactions to particulates were evaluated histologically and histochemically. No physical alteration was seen in the discs after the dissolution studies, and the elemental transfer to the dissolution solution was minimal. The cytokines, tumor necrosis factor (TNFalpha), and histology results from these simulated debris showed similar and moderate level responses magnitudes for the boron and mixtures and the primary alloy particulates. The conclusion from this initial study was that assessments of the coated discs showed physical properties similar to control. Also results from the in vivo studies of simulated wear debris from boron coatings on titanium and cobalt alloys demonstrated biocompatibility profiles that were mild to moderate and similar to prior analyses of wear debris products in synovial pouch models.

Observations of biofilm growth on human dentin and potential destruction after exposure to antibiotics.

OBJECTIVES: This study was performed to observe biofilm formation on dentin and to then observe effects of clinically achievable antimicrobial drug concentrations on these biofilms. STUDY DESIGN: Wild-strain endodontic bacteria were anaerobically cultured from necrotic pulps of extracted human teeth and used to grow biofilms on sterilized dentin slices in an anaerobic chamber for 12 days. Then these biofilms were exposed to ampicillin, doxycycline, clindamycin, azithromycin, or metronidazole. Each day for 8 days, specimens were fixed using 2% glutaraldehyde and examined with a scanning electron microscope (SEM). RESULTS: The SEM images revealed the presence of a mature biofilm after 8 days of growth and that none of the antibiotics tested was effective in eliminating the biofilm even after 8 days of exposure. CONCLUSION: Biofilms are formed in a few days and are resistant to antimicrobial drugs.

Corrosion on spinal implants.

OBJECTIVE: Modular spine implants are used as an aid to obtaining fusion, but fretting and corrosion occur between modular components in a biologic environment. METHODS: Forty-eight spinal implant constructs manufactured by a variety of companies were retrieved from 47 patients and were subjected to surface analysis stereomicroscopy. RESULTS: Stainless-steel implants (n = 23) had either semirigid constructs with mild or no surface alteration (n = 7) or rigid constructs with moderate or severe alteration (n = 16). Surface damage was consistent with previously observed mechanically assisted crevice corrosion phenomena. Titanium alloy implants (n = 25) showed no significant corrosion but had three constructs with fatigue failure of anchoring screws. One cobalt alloy construct showed no evidence of corrosion. CONCLUSIONS: Long-term effects of fretting and corrosion are unclear, and minimization of these phenomena seems justified. Selection of modular components with similar materials and surface finish may help the surgeon minimize localized changes over time. Stainless-steel implants with rigid interconnections and those with different surface finishes between rods and connectors are most susceptible to corrosion.

Polyethylene damage on the nonarticular surface of modular total knee prostheses.

Modular tibial implants submitted for retrieval analysis were examined for evidence of cold flow, wear, or polyethylene failure. All retrieved components showed areas of cold flow and wear. Significant damage, defined as pitting, gouging, or delamination was observed in 77% of the retrieved implants. Cold flow deformation commonly was observed at the junction of the polyethylene and locking mechanisms or junction of the polyethylene and the edge of the tibial tray. Control implants did not show such areas of damage. Clinical factors such as age, activity status, length of implantation, limb alignment before revision, and thickness of the tibial insert did not correlate with backside wear. No association was found between polyethylene thickness, time of implantation, limb or prosthesis alignment, or activity status or weight of the patient.