Effect of staining beverages on color and translucency of CAD/CAM composites.

This study investigated the color (ΔE) and translucency changes (ΔTP) of CAD/CAM composites after exposure to staining solutions using both spectrophotometer and shade-matching device. Direct (Filtek Z350XT [ZT]), indirect (Shofu Ceramage [CE]) and CAD/CAM (Shofu HC Block [HC], Lava Ultimate [LU], Vita Enamic [EN]) composite specimens measuring 12 × 14 × 1.5 mm were fabricated, divided into five groups (n = 8), and immersed in cola, tea, coffee, red wine, distilled water (control) at 37°C for 7 days. Color parameters were determined with both spectrophotometer and shade-taking device at baseline and 1 week. Delta E (ΔE) with white and black backgrounds, and Delta TP (ΔTP) were computed. Statistical testing was performed with ANOVA and Tukey post hoc test (P < .05). Mean ΔE (white) values ranged from 0.20 ± 0.06 to 12.26 ± 1.95 while mean ΔE (black) varied from 0.22 ± 0.11 to 14.21 ± 2.37. Mean ΔTP values ranged from 0.13 ± 0.17 to -3.87 ± 2.16. CAD/CAM composites fared better in red wine than direct and indirect materials. Clinically perceptible color changes (ΔE > 3.3) were observed for almost all materials when exposed to wine, coffee and tea. Direct, indirect, and CAD/CAM composites are all susceptible to various degrees of discoloration and translucency changes after exposure to staining beverages. Red wine caused the most discoloration and translucency changes. Limitations of these materials must be considered when placing an aesthetic restoration. CLINICAL SIGNIFICANCE: Direct, indirect, and CAD/CAM composites are all susceptible to various degrees of discoloration and translucency changes after exposure to staining beverages. Red wine generally caused the most discoloration and translucency changes. Although CAD/CAM composites were more color stable than direct and indirect materials when exposed to red wine, color changes were still clinically perceptible.

Physiological effects of anterior repositioning splint on temporomandibular joint disc displacement: a quantitative analysis.

Anterior repositioning splints (ARS) are used primarily for the management of temporomandibular joint (TMJ) anterior disc displacement with reduction (ADDwR). However, the exact physiological effects of ARS are still unclear. This study investigated the short and long-term effects of ARS on disc and condyle angles/positions by metric analysis. Twenty-two subjects diagnosed with ADDwR were recruited. Maxillary full-coverage ARS were fabricated, and MRI of TMJs was obtained before splint treatment, immediate post-insertion and 6 months after splint treatment. Disc-condyle relationship was determined by disc-condyle angle measurement. Disc and condyle positions were described as X-Y coordinates with the summit of glenoid fossa as the origin of the coordinates. Thirty-two TMJs were classified as ADDwR and 12 were normal. Upon ARS insertion, all TMJs with ADDwR got normal disc-condyle relationships. The condyles moved significantly forward and downward, while the discs moved significantly backward and upward. MRI at 6 months after treatment (without ARS insertion) indicated that only 40·6% (13/32) of the joints were maintained in the normal disc-condyle relationship. The majority of condyles returned to their pre-treatment positions, while the discs generally moved anteriorly again. The use of ARS resulted in forward and downward condyle movement, and a concurrent backward movement of the disc resulting in ideal spatial disc-condyle relationship. The stability of this relationship, however, could not be maintained in the majority of TMJs upon ARS removal. Findings explain the good short-term clinical outcomes with ARS and their relatively lower efficacy in the long term.

Clinical protocol for managing acute disc displacement without reduction: a magnetic resonance imaging evaluation.

This study investigated the efficacy of a sequential combination of arthrocentesis, mandibular manipulation, and anterior repositioning splint (ARS) in the management of acute temporomandibular joint (TMJ) disc displacement without reduction (DDwoR). Twenty-one consecutive patients diagnosed with acute DDwoR by Diagnostic Criteria for Temporomandibular Disorders and magnetic resonance imaging (MRI) were recruited and managed with this method. Clinical and MRI data were obtained before and at 1 week after treatment. The disc-condyle relationship was determined by disc-condyle angle measurement. Condyle/disc positions were described as x-y coordinates with the summit of the articular fossa as the coordinate origin. Statistical analyses including independent/paired samples t-tests were conducted; significance was set at P<0.05. Clinical success was observed in 95.2% of patients (20/21) with 22 joints affected by acute DDwoR. After combined treatment and ARS insertion, TMJs with DDwoR showed (a) normal disc-condyle relationships with substantial forward and downward condyle movement and significant disc reduction in closed position, and (b) discs with an intermediate zone located between the condylar head and articular eminence in open position. The combined approach was highly effective in 'unlocking' acute TMJ DDwoR and achieving spatial full disc reduction and a normal disc-condyle relationship. The duration of acute DDwoR appears to be critical for success.

Association between hypoplastic condyles and temporomandibular joint disc displacements: a cone beam computed tomography and magnetic resonance imaging metrical analysis.

This study investigated the association between hypoplastic condyles and disc displacements without reduction (DDw/oR). Consecutive patients with non-syndromic unilateral condylar hypoplasia were recruited and clinical, cone beam computed tomography (CBCT) and magnetic resonance imaging (MRI) data were acquired. Linear measurements including condylar head width, depth, height and condyle length were determined with CBCT while MRI was used to assess disc position, morphology and displacement. A total of 43 patients were enrolled of which 93.02% had a history of temporomandibular disorders (TMDs) and 83.72% presented with TMD signs and symptoms. Depth and height of the condylar head along with condyle length of hypoplastic joints (6.68±1.67mm, 4.97±1.25mm and 14.49±3.02mm, respectively) were significantly lesser than normal joints (7.77±1.26mm, 6.35±1.45mm and 18.20±3.18mm) (P<0.001). The prevalence of DDw/oR was significantly higher in hypoplastic joints (79.07% versus 13.95%) (P<0.001). Joints with hypoplastic condyles had shorter disc lengths (6.99 ± 2.16 mm vs, 8.45 ± 2.26 mm) (P=0.007). Furthermore, disc displacements were significantly more advanced (8.52 ± 2.84 mm) and severe (76.74% with severe translations) when compared to the contralateral side (4.77 ± 2.97 mm and 32.56%) (P<0.05). A significant association was observed between condylar hypoplasia and temporomandibular joint DDw/oR with hypoplastic joints exhibiting more severely displaced and deformed discs. DDw/oR coupled with repaired degenerative joint disease may mimic condylar hypoplasia radiographically.

Effects of incorporation of HA/ZrO(2) into glass ionomer cement (GIC).

Glass ionomer cements (GICs) are a class of bioactive cements that bond directly to bone. In this paper, a new bioactive hydroxyapatite (HA)/zirconia (ZrO(2))-filled GIC composite was developed to improve the biocompatibility and bioactivity of the GICs with the surrounding bone and connective tissues. Nano-sized HA/30 wt% ZrO(2) powders were heat treated at 700 degrees Celsius and 800 degrees Celsius for 3 h to elucidate the influence of the crystallinity of composite powders on the performance of HA/ZrO(2)-GICs. The effects of different volume percentages of HA/ZrO(2) powders (4, 12, 28 and 40 vol%) substituted within GICs were investigated based on their microhardness, compressive strength and diametral tensile strength. The HA/ZrO(2)-GICs composite was soaked in distilled water for 1 day and 1 week before subjecting the samples to mechanical testing. Results showed that the glass and HA/ZrO(2) particles were distributed uniformly in the GIC matrix. The substitution of highly crystalline HA/ZrO(2) improved the mechanical properties of the HA/ZrO(2)-GICs due to the slow resorption rate for highly crystalline powders in distilled water. The mechanical properties of HA/ZrO(2)-GICs increased with increasing soak time due to the continuous formation of aluminium salt bridges, which improved the final strength of the cements. The compositions 4 and 12 vol% HA/ZrO(2)-GICs exhibited superior mechanical properties than the original GICs. The mechanical properties of HA/ZrO(2)-GICs were found to be much better than those of HA-GICs because ZrO(2) has the attributes of high strength, high modulus, and is significantly harder than glass and HA particles. Furthermore, ZrO(2) does not dissolve with increasing soaking time.

Nanoindentation study of human premolars subjected to bleaching agent.

Bleaching of teeth is gaining popularity due to cosmetic reasons. However, the effect it has on teeth is still largely unknown. This paper seeks to evaluate the effect of a bleaching agent, 30% hydrogen peroxide, on the nanomechanical properties of dentin and enamel using the nanoindentation technique. The Young's modulus and hardness obtained from nanoindentation before and after bleaching were compared. Five newly extracted human premolars were used. Nanoindentation was first done on the sliced enamel and dentin regions to determine their mechanical properties. One batch of samples was kept in Hank's balanced salt solution as control while the other was bleached in 30% hydrogen peroxide for 24h. The same number of nanoindentations was then done near the previously indented regions for both the control and bleached samples and the results compared. Using paired sample t-tests with alpha=0.05, it was found that there were no significant differences in both the Young's modulus and hardness of dentin and enamel kept in control. However, the mechanical properties of the bleached dentin were significantly decreased. For intertubular dentin, the mean hardness decreased by 29-55% and the mean Young's modulus decreased by 19-43%. For enamel, the mean hardness decreased by 13-32% while the mean Young's modulus decreased by 18-32%. The exact mechanism by which hydrogen peroxide affects the dentin and enamel has yet to be fully elucidated. However, it is observed to have an undermining effect on the nanomechanical properties of teeth.

Elastic modulus of resin-based dental restorative materials: a microindentation approach.

This research aimed to determine the elastic modulus of resin-based dental composite restoratives using the microindentation test method. Results were then compared with those obtained with the ISO three-point bending test method. Five materials from the same manufacturer (3M ESPE) were selected for the study. They included microfill (A110), minifill (Z100 and Filtek Z250), poly-acid modified (F2000), and flowable (Filtek Flowable [FF]) composites. The indentation moduli of the composites were determined using a custom-designed microindentation test set up after conditioning in water at 37 degrees C for 1 week and 1 month. The indentation test was carried out at peak load of 10 N and Oliver & Pharr's method was used to determine the maximum projected contact area. Data was analyzed using ANOVA/post-hoc Scheffe's test at significance level 0.05 and Pearson's correlation at significance level 0.01. The mean indentation modulus ranged from 5.80 to 15.64 GPa and 5.71 to 15.35 GPa at 1 week and 1 month, respectively. At both time periods, the indentation modulus of Z100 was significantly higher than all other materials. F2000 was significantly higher than Z250, which was significantly stiffer than A110 and FF. The rankings were in good agreement with the ISO flexural test. A significant, positive, and strong correlation (r = 0.93 and 0.94 at 1 week and 1 month, respectively) in modulus between ISO three-point bending and microindentation test methods was observed. In view of the small specimen size and good reproducibility, the microindentation reflects a potential test method for determining the elastic properties of dental composite restoratives.

Effects of surface finish on indentation modulus and hardness of dental composite restoratives.

OBJECTIVES: The depth-sensing micro-indentation testing was recently introduced for the characterization of dental composites. One of the critical issues raised was the possible influence of surface finish on material properties. The aim of this study was to investigate the effects of surface finish on the indentation modulus and micro-hardness of resin-based dental composite materials. METHODS: The materials used included minifill (Z100, 3M ESPE), microfill (A110, 3M ESPE) and poly-acid modified (F2000, 3M ESPE) composites. The specimens were polished successively using SiC grinding papers of different grit size and diamond suspensions to achieve varying surface roughness. The arithmetic mean of the roughness (R(a)) was measured using profilometry. In the depth-sensing micro-indentation test, specimens (n=7) were indented to 10N with Vickers indenter and the load-displacement (P-h) data was obtained using a universal testing system. The indentation modulus (E(in)) and hardness (H) were then computed using the developed analytical solutions. Data was analyzed using ANOVA/post-hoc Scheffe's test at significance level 0.05. RESULTS: The polished specimens had surface roughness ranging from 0.02 to 0.81 microm. The roughness of F2000 was significantly higher than A110 and Z100. The E(in) and H for Z100 ranged from 14.02 to 14.83GPa and 1.18 to 1.27 GPa, respectively. E(in) for F2000 and A110 ranged from 12.25 to 13.82 GPa and 5.26 to 5.52 GPa and hardness ranged from 0.89 to 0.98 GPa and 0.52 to 0.55 GPa, respectively. SIGNIFICANCE: The indentation modulus and hardness of dental composite restoratives were independent of the surface finish provided indenter penetration is sufficiently deep (h(max)/R(a)>30).

Effect of hydrogen peroxide on intertubular dentine.

OBJECTIVES: To evaluate the effect of 30% hydrogen peroxide on the surface changes and nanomechanical properties of intertubular dentine. METHODS: Five freshly extracted human premolars were sectioned and two specimens were obtained from each tooth. Atomic force microscopy (AFM) images of dentine were taken. Baseline hardness and Young's modulus of intertubular dentine were determined using nanoindentation testing and recorded. The specimens were then treated with either 0.5 ml of Hank's balanced salt solution (control group) or 30% hydrogen peroxide at 24 degrees C for 24 h. AFM imaging and determination of hardness and Young's modulus of intertubular dentine were then repeated. The images were compared and statistical analyses of hardness and Young's modulus were carried out using paired sample t-tests. RESULTS: The AFM images showed recession of the intertubular dentine surface post-bleaching. For the control group, there was no significant change in hardness (p=0.124) and Young's modulus (p=0.438) of intertubular dentine. However, a significant decrease in hardness (p=0.002) and Young's modulus (p=0.001) of intertubular dentine was observed for the experimental group. CONCLUSIONS: Exposure to 30% hydrogen peroxide for 24 h caused surface changes to intertubular dentine and significantly decreased the hardness and Young's modulus of intertubular dentine.

In Vitro Biocompatibility of Contemporary Bulk-fill Composites.

This study evaluated the biocompatibility of contemporary bulk-fill resin-based composites (RBCs) including PRG (pre-reacted glass ionomer) materials based on the International Organization for Standardization 10993. In addition, the effect of composite thickness on cytotoxicity was also assessed. Two standard composites, two bulk-fill PRG RBCs, and three bulk-fill non-PRG RBCs were investigated. Block-shaped specimens of 2-mm and 4-mm thickness were cured with an irradiance of 700 mW/cm(2) for 20 seconds with a light-emitting diode curing light and eluted with culture medium at 37°C for 24 hours. L929 mouse fibroblasts were exposed to extracts at varying dilutions (1:1, 1:2, and 1:10) for 24 hours. Analyses were performed to assess cytotoxicity, phase contrast microscopy, and quantitative cell viability. Among the bulk-fill RBCs, extracts of PRG materials resulted in the lowest cell viability. At 4-mm thickness, undiluted extracts of bulk-fill non-PRG RBCs had significantly higher cell viability than the standard composites. Chemical composition, specimen thickness, and testing concentrations of extracts had significant effects on cell viability and morphology. Cytotoxic effects of composites on cell viability were parallel with cell morphologic changes. Not all bulk-fill RBCs demonstrated high cell viability (>70%) at 4-mm thickness despite manufacturers' recommendations of bulk placement and curing.

Effect of beverages on color and translucency of new tooth-colored restoratives.

This investigation examined the susceptibility to staining and translucency changes of some new tooth-colored restorative materials after immersion in different beverages. The materials studied were 3M Filtek Z350XT (ZT), 3M Filtek 350XT Flowable Restorative (ZF), Shofu Beautifil Flow Plus (BF), Shofu Beautifil II (B2), 3M Ketac Nano (N100), and 3M Photac Fil (PF). Following the manufacturers' instructions, 42 samples were made from each material and placed in an incubator at 100% humidity and 37°Celsius for 24 hours. Baseline L*, a*, b* readings were taken against white and black backgrounds using a photospectrometer. The samples were then randomly assigned to be immersed in seven beverages, namely cola drink, orange juice, red wine, vodka, black coffee, green tea, and distilled water for a period of seven days. Color readings were taken again by recording the L*, a*, b* values. Data was analyzed using t-tests, one-way analysis of variance with Tukey post hoc and Pearson's correlation (p<0.05). BF generally performed as well as the conventional composite resin materials (ZT and ZF) but N100 and B2 did not. PF had the largest staining and translucency changes. Coffee, red wine, and tea resulted in the most staining and negative translucency changes. An inverse correlation between ΔE and ΔTP was observed for all materials and beverages with the exception of orange juice.

Spheroidization of glass powders for glass ionomer cements.

Commercial angular glass powders were spheroidized using both the flame spraying and inductively coupled radio frequency plasma spraying techniques. Spherical powders with different particle size distributions were obtained after spheroidization. The effects of spherical glass powders on the mechanical properties of glass ionomer cements (GICs) were investigated. Results showed that the particle size distribution of the glass powders had a significant influence on the mechanical properties of GICs. Powders with a bimodal particle size distribution ensured a high packing density of glass ionomer cements, giving relatively high mechanical properties of GICs. GICs prepared by flame-spheroidized powders showed low strength values due to the loss of fine particles during flame spraying, leading to a low packing density and few metal ions reacting with polyacrylic acid to form cross-linking. GICs prepared by the nano-sized powders showed low strength because of the low bulk density of the nano-sized powders and hence low powder/liquid ratio of GICs.

Experimental studies on a new bioactive material: HAIonomer cements.

The lack of exotherm during setting, absence of monomer and improved release of incorporated therapeutic agents has resulted in the development of glass ionomer cements (GICs) for biomedical applications. In order to improve biocompatibility and biomechanically match GICs to bone, hydroxyapatite-ionomer (HAIonomer) hybrid cements were developed. Ultra-fine hydroxyapatite (HA) powders were produced using a new induction spraying technique that utilizes a radio-frequency source to spheriodize an atomized suspension containing HA crystallites. The spheriodized particulates were then held at 800 degrees C for 4 h in a carbolite furnace using a heating and cooling rate of 25 degrees C/min to obtain almost fully crystalline HA powders. The heat-treated particles were characterized and introduced into a commercial glass ionomer cement. 4 (H4), 12 (H12) and 28 (H28) vol% of fluoroalumino silicate were substituted by crystalline HA particles that were dispersed using a high-speed dispersion technique. The HAIonomer cements were subjected to hardness, compressive and diametral tensile strength testing based upon BS6039:1981. The storage time were extended to one week to investigate the effects of cement maturation on mechanical properties. Commercially available capsulated GIC (GC) and GIC at maximum powder:liquid ratio (GM) served as comparisons. Results were analyzed using factorial ANOVA/Scheffe's post-hoc tests and independent samples t-test at significance level 0.05. The effect of time on hardness was material dependent. With the exception of H12, a significant increase in hardness was observed for all materials at one week. A significant increase in compressive strength was, however, observed for H12 over time. At 1 day and 1 week, the hardness of H28 was significantly lower than for GM, H4, and H12. No significant difference in compression and diametral tensile strengths were observed between materials at both time intervals. Results show that HAIonomers is a promising material, which possess good mechanical properties. Potential uses of this new material include bone cements and performed implants for hard tissue replacement in the field of otological, oral-maxillofacial and orthopedic surgery.

Flexural strength of dental composite restoratives: comparison of biaxial and three-point bending test.

This study compared two test methods used to evaluate the flexural strength of resin-based dental composites. The two test methods evaluated were the three-point bending test4 and the biaxial flexural test. Materials used in this investigation were from the same manufacturer (3M ESPE) and included microfill (A110), minifill (Z100 and Filtek Z250), polyacid modified (F2000), and flowable [Filtek Flowable (FF)] composites. Flexural strength was determined with the use of both test methods after 1 week of conditioning in water at 37 degrees C. Data were analyzed with the use of an ANOVA/Scheffe test and an independent-samples t test at significance level 0.05. Mean flexural strength (n = 7) ranged from 66.61 to 147.21 and 67.27 to 182.81 MPa for three-point bending and ball-on-three-ball biaxial test methods, respectively. In both test methods, Z100 was significantly stronger than all other composites evaluated. In the three-point bending test, flexural strength of Z250 was significantly higher than A110, F2000 and FF, and FF was significantly stronger than A110 and F2000. The biaxial test method arrived at the same conclusions except that there was no significant difference between Z250 and FF. Pearson's correlation revealed a significantly (p < 0.01) positive and good correlation (R2 = 0.72) in flexural strength between the two test methods. Although the biaxial test has the advantage of utilizing small specimens, the low reproducibility of this test method does not support the proposition that it is a more reliable test method when compared to the ISO three-point bending test.

Effects of cyclic loading on occlusal contact area wear of composite restoratives.

OBJECTIVES: To investigate the effects of cyclic loading on occlusal contact area (OCA) wear and the possible presence of fatigue wear mechanisms in four composite resins (Silux, Z100, Ariston and Surefil) using a reciprocal compression-sliding test apparatus. METHODS: Six specimens were made for each composite material and the amalgam alloy (Dispersalloy) control. The wear specimens were subjected to wear testing at 20 MPa with artificial saliva as lubricant. Wear depth (microm) was measured using profilometry every 20,000 cycles up to 120,000 cycles. The worn specimens were subjected to SEM to determine the presence of fatigue wear mechanisms. Results were analyzed using ANOVA/Scheffe's test (P<0.05) and Pearson's Correlation (P<0.01). RESULTS: Dispersalloy had the lowest wear at all cyclic intervals. For all materials, OCA wear increased with increased number of cycles. Although Dispersalloy, Ariston and Surefil experienced no significant increase in wear between each 20,000 cycles increment, a significant increase was observed with Silux. For Z100, a significant difference was observed only from 40,000 cycles onwards. Both Z100 and Dispersalloy exhibited fatigue wear after wear testing for 120,000 cycles. Cyclic loading resulted in deep and wide microcracks in Silux. Fatigue wear was not observed with Silux, Ariston and Surefil. SIGNIFICANCE: The effects of cyclic loading on wear is material dependent. While some restorative materials exhibit fatigue wear, others exhibit deep microcrack formation with extended cyclic loading. The latter may precipitate catastrophic failure despite the low wear observed. Care should, therefore, be exercised when selecting materials for posterior stress-bearing areas.

Effects of in-office tooth whiteners on hardness of tooth-colored restoratives.

This study investigated the effects of in-office tooth whiteners on the hardness of hybrid (Spectrum TPH), polyacid-modified (Dyract AP), PRG (Reactmer) composites and a resin-modified glass ionomer cement (Fuji II LC). Twenty-seven specimens of each material were fabricated, randomly divided into three groups of nine and treated as follows--Group 1: stored in distilled water at 37 degrees C for three weeks (control); Group 2: treated with carbamide peroxide (Opalescence Quick) for 30 minutes/week for three weeks; Group 3: treated with 35% hydrogen peroxide power bleach (Opalescence Xtra) for 30 minutes/week for three weeks. For Groups 2 and 3, specimens were stored in distilled water at 37 degrees C during the hiatus periods. The treated specimens were subsequently subjected to microhardness testing (load = 500gf; dwell time = 15 seconds). Results were analyzed using ANOVA/Scheffe's test (p<0.05). For all treatment groups, Spectrum was significantly harder than the other materials and Reactmer was significantly harder than Dyract and Fuji II LC. The effects of in-office tooth whiteners on microhardness were material-dependent. No significant difference in hardness was observed between treatment groups for Dyract and Reactmer. For Spectrum and Fuji II LC, specimens treated with Opalescence Quick were significantly harder than those treated with Opalescence Xtra. No significant difference in hardness was observed between the control and bleached groups for all materials. The hardness of resin-modified glass-ionomer cements, hybrid, polyacid-modified and PRG composites is therefore not significantly affected by the use of 35% carbamide peroxide and 35% hydrogen peroxide in-office tooth whiteners.

Effects of cyclic temperature changes on water sorption and solubility of composite restoratives.

This study investigated the effects of cyclic temperature changes on the water sorption and solubility of four commercial composite resins (Silux Plus, Z100, Ariston pHc and Surefil). The methodology was based upon ISO 4049 procedures with modifications for specimen dimension and thermal-cycling. Eighteen disc specimens (10 +/- 1 mm diameter and 1 +/- 0.1 mm thick) were made for each composite and randomly divided into three groups. The specimens were stored in a desiccator maintained at 35 +/- 1 degrees C until a constant mass was achieved and treated as follows: Group 1--stored in distilled water at 356 degrees C for 178 hrs; Group 2--stored in distilled water at 35 degrees C for 173 hours and subjected to five hours of thermal-cycling with an upper temperature of 45 degrees C; and Group 3--stored in distilled water at 35 degrees C for 173 hours and subjected to five hours of thermal-cycling with an upper temperature of 60 degrees C. Mass after treatment was measured and specimens were re-conditioned to constant mass. The volume of the specimens was obtained and water sorption/solubility calculated. Data was analyzed using factorial ANOVA/Scheffe's post-hoc test at significance level 0.05. The effects of thermal-cycling on water sorption was material dependent. Thermal-cycling at an upper temperature of 60 degrees C significantly increased water sorption of Silux Plus. A significant increase in water sorption was also observed when Z100 was thermal-cycled at an upper temperature of 45 degrees C. The water sorption of Ariston pHc and Surefil was not affected by thermal-cycling. Thermal-cycling did not affect the solubility of all composites. For all treatment groups, Surefil had significantly lower water sorption than the other composites evaluated. The water sorption of Z100 and Surefil was significantly lower than Silux Plus and Ariston pHc.

Surface finish of a new hybrid aesthetic restorative material.

This study compared the surface finish of a new hybrid aesthetic restorative material (Reactmer) over time to four different types of existing materials. The latter included a composite (Spectrum TPH), a compomer (Dyract AP) and conventional (Fuji II) and resin-modified glass ionomer cements (Fuji II LC). Six specimens of each material were fabricated and stored in distilled water at 37 degrees C for one week. The materials were subsequently finished with a series of Sof-Lex contouring and polishing disks. The average surface roughness (Ra, microm) of each specimen was measured at three days and three months by a surface profilometer. Storage medium was distilled water at 37 degrees C during the hiatus periods. Data was analyzed by ANOVA/Scheffe's and independent samples t-tests at significance level 0.05. At both time periods, Fuji II and Fuji II LC were significantly rougher than Spectrum, Dyract and Reactmer. For all materials, surface roughness at three days was not significantly different from that at three months. The surface finish of the giomer (Reactmer) was significantly better than conventional/resin-modified glass ionomer cements and comparable to the composite and compomer evaluated. The quality of surface finish for all materials was not significantly affected by long-term storage in water.

Effects of pH on the surface texture of glass ionomer based/containing restorative materials.

This study determined the effect of pH on the surface texture of commonly used posterior glass-ionomer based/containing restorative materials. The materials evaluated included a compomer (Dyract AP), a giomer (Beautifil) and two highly viscous glass ionomer cements (Fuji IX and Ketac Molar). A resin composite (Esthet-X) was used for comparison. Forty-two specimens (3-mm wide x 3-mm long x 2-mm deep) were made for each material. The specimens were divided into six groups and conditioned in the following solutions at 37 degrees C for one week: Citric acid (pH 2, 3, 4, 5 and 6) and distilled water (pH 7). After conditioning, the surface roughness (Ra, microm) of each specimen was measured using a surface profilometer (Surftest, Mitutoyo Corp, Tokyo, Japan). Data was analyzed using one-way ANOVA and Scheffe's test at a significance level of 0.05. The effects of pH on the surface texture of glass-ionomer based/containing restoratives were material dependent. Ra values ranged from 0.02 microm to 0.15 microm and 0.03 microm to 4.40 microm for pH 7 and 2, respectively. With the exception of the composite, the surface roughness of all materials evaluated was significantly affected by acids of low pH. The surface texture of highly viscous glass ionomer cements deteriorated significantly when conditioned in solutions of low pH, which makes them more susceptible to clinical failure.

Post-gel polymerization contraction of "low shrinkage" composite restoratives.

This study compared the post-gel contraction of two "low-shrinkage" composites (InTen-S [IS], Ivoclar-Vivadent; Aelite LS [AL], BISCO Inc) and an ormocer (Admira [AM], Voco) to two conventional mini-filled composites (Renew [RN], BISCO; Z100 [ZO], 3M ESPE). A strain-monitoring device and test configuration were used to measure the linear polymerization shrinkage associated with the various composites (A2 shade) during and up to 60 minutes post light polymerization. Each specimen was irradiated for 40 seconds using a halogen curing light (Max, Dentsply-Caulk) with an intensity of 401 mW/cm2. Five specimens were made for each composite. Data was analyzed using one-way ANOVA/Scheffe's post-hoc test at significance level 0.05. The linear percentage shrinkage immediately after light polymerization and at 60 minutes post light polymerization ranged from 0.10 +/- 0.02 to 0.40 +/- 0.02% and 0.22 +/- 0.02 to 0.60 +/- 0.05%, respectively. Post-gel shrinkage ranking of the materials was as follows: immediately after light polymerization - IS < AL < AM < ZO < RN and at 60 minutes post light polymerization - IS < AL = AM < ZO < RN. The shrinkage associated with IS, AL and AM was significantly lower than for ZO and RN immediately after light polymerization and at 1, 10, 30 and 60 minutes post light polymerization. The post-gel polymerization shrinkage of IS, AL and AM was significantly lower than conventional mini-filled composites.