Blends of palm kernel oil, soybean oil and palm stearin as an alternative to milk fat for frozen dessert application.

In this study, the ternary blends of palm kernel oil (PKO), soybean oil (SBO) and two types of palm stearin (PS) (PS33 and PS38) were systematically prepared and evaluated for their application as an alternative to milk fat in frozen dessert. The physicochemical characteristics namely fatty acids constituent, triacylglycerols (TAGs) composition, melting behavior, solid fat content (SFC) and microstructure were studied. All ternary blends of PKO/SBO/PS33 and PKO/SBO/PS38 had comparable microstructure to that of milk fat. However, 80/15/5 (PKO/SBO/PS33) and 80/15/5 to 80/5/15 (PKO/SBO/PS38) mixtures were found to have similar SFC as milk fat at temperature above 20 °C, allowing these ternary blends to be completely melted at body temperature. With this, 80/15/5 (PKO/SBO/PS33) and 80/15/5 to 80/5/15 (PKO/SBO/PS38) mixtures were able to provide similar meltdown and mouth feel as milk fat at room temperature. Nonetheless, fatty acids constituent, TAGs composition and melting behavior of the blends were different from milk fat. This study showed that ternary blends of PKO, SBO and PS at ratios 80/15/5 (PKO/SBO/PS33) and 80/15/5 to 80/5/15 (PKO/SBO/PS38) can be potentially used as a milk fat alternative for frozen dessert application based on its similar microstructure and SFC profile as the milk fat. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05507-z.

Fabrication of a new composite orthodontic archwire and validation by a bridging micromechanics model.

A new technique based on tube shrinkage is proposed for the fabrication of composite archwires. Compared with a traditional pultrusion method, this new technique can avoid any fiber damage during the fabrication and can provide the archwire with a required curvature in its final clinical usage. The present paper focuses on the technique development and mechanical design and validation in terms of constituent materials by using a micromechanics bridging model. Prototype archwire has been fabricated using fiberglass and an epoxy matrix, with a wire diameter of 0.5mm and a 45% fiber volume fraction. Tensile and three-point bending tests have shown that the mechanical performance of the prototype composite archwire is comparable to that of a clinical Ni-Ti archwire. Another purpose of the present paper is to provide an efficient procedure for a critical design of composite archwires. For this to be possible, the ultimate load especially flexural load carrying ability of the composite archwire must be assessed from the knowledge of its constituent properties. However, difficulty exists in doing this, which comes from the fact that the failure of the utmost filament of the composite archwire subjected to initially the maximum bending stress does not imply its ultimate failure. Additional higher loads can still be applied and a progressive failure process is generated. In this paper, the circular archwire was discretized into a number of parallel laminae along its axis direction, and the bridging micromechanics model combined with the classical lamination theory has been applied to understand the progressive failure process with reasonable accuracy. Only the constituent fiber and matrix properties are required for this understanding. Nevertheless, the ultimate bending strength cannot be obtained only based on a stress failure criterion. This is because neither the first-ply nor the last-ply failure corresponds to the ultimate failure. An additional critical deflection (curvature) condition must be employed also. By using both the stress failure and the critical deflection conditions, the predicted load-deflection up to the ultimate failure agrees well with the measured data. Thereafter, different mechanical performances of composite archwires can be tailored before fabrication by choosing suitable constituent materials, their contents, and the archwire diameters. Several design examples have been shown in the paper.

Marginal gap formation of composites in dentine: effect of water storage.

This study investigated the effects of water storage on the marginal adaptation of two composite resins (Spectrum TPH and Ariston AT), two polyacid-modified composite resins (Dyract AP and F2000) and a new PRG composite (Reactmer) to dentine over time. Two cylindrical dentine cavities (1.5 mm diameter and 1.5 mm deep) were prepared on the horizontally sectioned surfaces of freshly extracted teeth. In each tooth, one cavity was restored using composites with their respective bonding system and the other without the bonding system. The sample size for each material with/without bonding system was 6. The composites were placed in one increment, bulk-polymerized, immediately finished/polished with the Sof-lex discs system and fine polished on 30 microm silicon carbide/9 microm aluminium oxide lapping film discs in a microgrinding system. The specimens were then stored in distilled water at 37 degrees C and the maximum marginal gap width between the material and the dentine wall was determined at 24 h, 1 week, 2 weeks, 3 weeks and 4 weeks using a measurescope at x500 magnification. Results were subjected to statistical analysis using monva, anova/Scheffe's post hoc test and independent samples of t-test at significance level 0.05. At all time intervals, no significant difference in marginal gap formation was observed between materials. Where bonding systems were not used, a decrease in gap widths over time was observed with most materials but only Dyract AP exhibited a significant decrease. The latter was observed after 2 weeks storage in water. The use of bonding systems reduced dentine marginal gaps significantly and is therefore mandatory for all composites evaluated. Marginal gaps arising from polymerization contraction of conventional, polyacid-modified and PRG composites cannot be fully compensated by hydroscopic expansion. Clinical relevance Bonding systems are mandatory for all composites when bonding to dentin. In the event of a bond failure at placement, hygroscopic expansion of composites can reduce marginal gaps but not completely.

Environmental damage and occlusal contact area wear of composite restoratives.

The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in-vivo degradation of composite resins. The resin matrix can be softened and fillers constituents can be leached out when composites are exposed to certain chemicals/food-simulating liquids (FSLs). A reciprocal compression sliding wear device was used to study the effects of the chemical environment on occlusal contact area (OCA) wear of four composite restoratives (Silux Plus, Z100, Ariston pHc and Surefil). The effects of FSL on hardness was also investigated and correlated to wear. Thirty-six hardness/wear specimens of each material were made and stored in artificial saliva at 37 degrees C for 24 h. The specimens were then divided into six groups of six specimens and stored in the following FSL for 1 week at 37 degrees C: distilled water (W), 0.02 N citric acid (C), 0.02 N lactic acid (L), heptane (H) and 75-25% ethanol-water solution (E). Conditioning in artificial saliva (S) was used as control. After conditioning, the specimens were wear tested at 20 MPa contact stress against SS304 counter-bodies in the respective FSL/artificial saliva up to 20 000 cycles. Wear depth (lm, n=6) was measured using profilometry. Change in hardness (DeltaKHN, Knoop hardness number) was determined by microhardness testing pre- and post-conditioning. Results of statistical analyses (ANOVA/Scheffe's at significance level 0.05) of wear data were as follows: Silux - S, W > L, H, E and C, L > H; Z100 - S, W > all other mediums and E > H; Ariston - all other mediums > H; Surefil - W, C > S, L, H, E (> indicates significantly more wear). With the exception of Surefil, the greatest wear was observed with conditioning and wear testing in water. This ranged from 93.18 +/- 21.96 lm for Z100 to 31.43 +/- 2.80 lm for Surefil. For all materials, conditioning in heptane resulted in the least wear. This ranged from 8.9 +/- 2.2 microm for Ariston to 16.5 +/- 5.9 lm for Silux. The effects of the different FSL on OCA wear were material dependent. No correlation was observed between DeltaKHN and wear.

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.

Influence of thermal cycling on OCA wear of composite restoratives.

This study investigated the effects of thermal cycling on wear of four commercial composite resins (Silux, Z100, Ariston and Surefil). Specimens of each material were divided into three treatment groups comprising a control and two different thermal cycling regimes. Control specimens were stored in distilled water at 35 degrees C for 178 hours. Thermal cycled specimens were stored in distilled water at 35 degrees C for 173 hours and subjected to five hours (300 cycles) of a thermal cycling regime consisting of the cycle ABAC, where A and B represent the fixed temperatures of 35 degrees C (28 seconds) and 15 degrees C (two seconds) and C, depending on the treatment group, was either 45 degrees C or 60 degrees C (two seconds). All specimens were subsequently subjected to wear testing at 20 MPa contact stress against SS304 counterbodies with distilled water as the lubricant. Wear depth (microm; n=6) was measured using profilometry every 2,000 cycles up to 10,000 cycles. Results were analyzed using ANOVA/Scheffe's test (p<0.05). The effect of thermal cycling on wear was material-dependent. The wear of Silux and Z100 were not significantly affected by thermal cycling. Thermal cycling of Ariston at an upper temperature of 60 degrees C significantly decreased wear resistance. Thermal cycling affected only the early wear resistance of Surefil.

Mechanical properties of an improved visible light-cured resin-modified glass ionomer cement.

This study investigates the mechanical properties (hardness, flexural strength and compressive strength) of a new light-cured resin-modified glass ionomer cement (Fuji II LC Improved). Effects of the increased powder:liquid ratio on mechanical properties and the correlation between different mechanical properties were also studied. Mechanical properties of the cement at manufacturer's recommended powder:liquid ratio (F), 2% (F2) and 4% (F4) increased powder weight were measured after one day, one week and one month storage in distilled water at 37 degrees C. Hardness testing (KHN; n = 5) was done with a digital microhardness tester (load = 500 g, dwell time = 15 seconds). Flexural and compressive strength testing (MPa; n = 5) were conducted based on ISO 4049 and BS6039, respectively. Results were analyzed using ANOVA/Scheffe's test (p < 0.05) and Pearson's correlation (p < 0.01). The maximum mechanical properties of Fuji II LC Improved were achieved at one week. The hardness, flexural and compressive strength at one week was significantly higher than at one day. A decrease in all mechanical properties was observed at one month. Mechanical properties were significantly affected by increased powder:liquid ratio. After one month storage, significance was as follows: Hardness--F, F2 > F4; Flexural strength--F4 > F, F2 and F > F2; Compressive strength--F, F2 > F4 and F2 > F. A significant very strong and negative correlation was observed between flexural and compressive strengths (r = 0.97).

Bond strengths of glass ionomer restoratives to primary vs permanent dentin.

An in vitro experiment was conducted to evaluate the shear bond strength of a conventional GIC (glass ionomer cement) and a RMGIC (resin modified glass ionomer cement) when applied to dentin of primary and permanent teeth. Results show that the bond strength of the RMGIC was more than thrice that of the conventional GIC. Fracture analysis showed that the bond failures were cohesive in the cement.

Clinical evaluation and microstructural analysis of a direct placement gallium restorative alloy.

OBJECTIVES: The objective of this study was to assess the clinical performance of a direct placement gallium alloy sealed with an established dentine adhesive system. In addition, microanalysis of a few gallium restorations that failed in clinical service was performed. Clinical factors such as pulpal sensitivity, fracture of the restoration and of the tooth, marginal deterioration, and tarnish were assessed. METHODS: Sixty-five restorations of Galloy and 62 of Tytin (49 and 51 Class II restorations, respectively) were placed according to a predetermined scheme for randomisation in 37 patients by two operators using rubber dam isolation. For the Galloy restorations, the enamel and dentine were etched, and then sealed with PAAMA 2 dentine adhesive according to the manufacturer's instructions. After carving, PAAMA 2 was applied to the Galloy and light-cured. Cavity preparations for Tytin received no adhesive sealer. All restorations were polished at least 24 h post-operatively. Microstructural analysis of retrieved fragments of failed restorations was conducted using electron probe microanalysis. RESULTS: At 1 year, only one Tytin restoration was found to have failed due to an isthmus fracture. The remaining restorations of Tytin were intact with no reported sensitivity. Of the 65 Galloy restorations placed, 28 had to be removed, including restorations in teeth, which were symptomatic, non-vital and/or fractured, and teeth with fractured restorations. Tarnish was present on many of the Galloy restorations. Retrieved fragments of failed Galloy restorations exhibited a dark surface at the pulpal wall interface and small cracks were observed in that surface. Internal cracks and extensive corrosion was observed using the microprobe. Gallium oxides and chlorides were identified as the predominant corrosion products. CONCLUSIONS: The gallium alloy, Galloy, sealed with PAAMA 2 dentine adhesive system demonstrated a high clinical failure rate.

Investment strength as a function of time and temperature.

OBJECTIVES: The purpose of this investigation was to evaluate and compare the compressive strength characteristics of selected investments and to determine if these change as a function of time and temperature after mixing. METHODS: Two phosphate-bonded investments and one gypsum-bonded investment were selected and 288 cylindrical specimens were fabricated (n = 9). Baseline compressive strength values were determined for each material at room temperature and compressive strength measurements were made for all materials at 700 degrees C, and at 872 degrees C only for phosphate-bonded investments. Each material was tested at 2, 6, 12, and 24 h after mixing. Specimens were heated at 15 degrees C/min and heat soaked for 5 min in a burnout oven at the applicable testing temperature. They were transferred to a preheated chamber on an Instron testing machine and subjected to a compressive load at a crosshead speed of 2 mm/min until failure. The resulting strength data are presented in MN/m2. RESULTS: The gypsum-bonded investment did not exhibit marked differences in strength as a function of either time or temperature. The phosphate-bonded investments, on the other hand, demonstrated considerable changes in compressive strength and differed in compressive strength characteristics at 700 degrees C and 872 degrees C respectively. CONCLUSIONS: At elevated temperatures, all materials approximated peak strength 2 h after initial mixing. At room temperature, the phosphate-bonded investments in this study were not significantly stronger than the gypsum-bonded investment material. However, they exhibited increased compressive strength as a function of time and temperature that was considerably higher than that exhibited by the gypsum-bonded investments.

An evaluation of bond strengths of denture repair resins by a torsional method.

Chemical cure resin materials are generally used in the repair of dentures. Different repair resins used may yield different results. The bond strength of three autopolymerizing resins were evaluated using a torsional test method. The results showed that Palapress and Caulk resins had a higher repair strength than Rapid Repair resin.

Shear bond strength of denture teeth to base: a comparative study.

Fracture and debonding of plastic teeth from the denture base are common clinical problems. In this study, a shear, or peeling, load was applied to the tooth-denture base junction. The bond strength of a high-impact, heat-cured denture base to three commercial brands of denture teeth, Bioform, Dentacryl, and TNR, was assessed. Ninety-three percent of the specimens exhibited cohesive failure within the body of the tooth and not adhesive failure at the tooth-denture base junction. Some of the teeth exhibited brittle fracture while others underwent distortion on loading. Dentacryl displayed the highest cohesive bond strength, followed by Bioform and TNR.

Direct tooth-colored materials for noncarious lesions: a 3-year clinical report.

One hundred fifty-nine noncarious cervical lesions were restored with glass-ionomer cement, resin composite used with a dentinal bonding agent, or the laminate (sandwich) restoration, which combines both these materials. These restorations were evaluated at baseline, 1 year, and 3 years for color match, cavosurface marginal discoloration, anatomic form, marginal adaptation, and retention. There was a general deterioration of the restorations with time. Lesions restored with resin composite and a dentinal bonding agent exhibited the highest percentage of lost restorations.

Clinical evaluation of tooth-colored materials in cervical lesions.

PURPOSE: To determine the 18-month clinical performance of four tooth-colored restoratives in non-carious cervical lesions. MATERIALS AND METHODS: Buccal abrasion lesions in 83 teeth were restored with each of the following materials: Fuji Cap II, Fuji II LC, APH/Universal Bond 3, Lite Fil II A/Imperva Bond. Baseline and an 18-month recall was carried out using the Ryge (USPHS) method for retention, color match, marginal adaptation, cavosurface marginal discoloration, anatomic form and secondary caries. RESULTS: The USPHS results (% alfa) for the four products were, respectively: color match (9%, 48%, 57%, 55%), marginal discoloration (71%, 76%, 52%, 50%), marginal adaptation (24%, 24%, 33%, 15%), anatomic form (67%, 86%, 95%, 45%) and retention (100%, 95%, 100%, 65%). Results indicated that (1) Fuji Cap II exhibited a poor color match at baseline (2) Color matching of Fuji II LC was comparable to the resin composites and (3) seven Lite Fil II/Imperva Bond restorations (35%) were dislodged after 1 1/2 years.

Interocclusal distance in patients with different skeletal patterns.

A pilot study was conducted to measure the interocclusal distance in patients with class I, II and III skeletal patterns. Ten patients were randomly selected for each skeletal pattern group. The measurements of interocclusal distance were obtained from lateral cephalometric radiographs of each patient. The results indicated that there was a significant difference (p < 0.05) between the interocclusal space of skeletal class II and class III patients.

The influence of temperature on the dimensional stability of poly (vinyl siloxane) impression materials.

It may be desirable to extend the working time of poly(vinyl siloxane) impression materials when making a multiple-unit impression. Alteration of the base-catalyst ratio is not possible with automix systems, but chilling the impression material provides an alternative. This study evaluated the dimensional accuracy of chilled impression material and the effect on accuracy of reheating the impression to mouth temperature prior to pouring. Two brands of poly(vinyl siloxane) impression material were evaluated both after refrigeration and at room temperature. Impressions were poured at room temperature and reheated to mouth temperature prior to pouring. Gypsum dies were recovered and measured. Refrigeration had no statistically significant effect on dimensional accuracy. Reheating the impression had no clinically significant effect on accuracy.

Shear bond strength of orthodontic brackets using Panavia: an in-vitro study.

In this study, Panavia (a phosphonated Bis-GMA resin which is known to develop very high bond strengths with resin-bonded bridges) is compared to a conventional no-mix orthodontic Bis-GMA bracket adhesive. Results showed that there was no statistically significant difference in the shear bond strengths between the two resins when used as adhesives for bonding orthodontic brackets. Coupled with the fact that Panavia requires an anaerobic environment for complete polymerization, its routine use as a bracket adhesive in direct bonding of orthodontic brackets is not indicated.

A comparison of shear bond strengths between new and recycled ceramic brackets.

The recycling of 'used' ceramic brackets in the orthodontic surgery has been previously described. The present study investigated the shear bond strength of both recycled and new ceramic brackets. The mean shear bond strengths of the new and recycled ceramic brackets were 259.7 +/- 88.2 N and 187.2 +/- 60.8 N, respectively. Although significantly lower (P less than 0.01), the bond strength of recycled ceramic brackets appeared to be clinically adequate. There appeared to be little difference in the variation in bond strength between the new and recycled ceramic bracket group. Our results showed that the site of bond failure depended on the magnitude of bond strength. Scanning electron micrograph examination of the failure sites showed enamel fracture in one sample where the bond strength was extremely high.

Long-term dissolution of mercury from a non-mercury-releasing amalgam.

The hazards of mercury from dental amalgams have long been recognized. This study examined the mercury release from a "non-mercury-releasing" dental amalgam, Composil, over a 104-week period. Four cylindrical specimens were incubated in 10 ml of purified water at 37 degrees C. The incubate was changed at the end of each 24-hour period and assayed for its mercury content at biweekly intervals. Mercury estimation was carried out using cold-vapor, atomic absorption spectrophotometry over a 104-week period. Results showed that the overall mean release of mercury was 43.5 +/- 3.2 micrograms/cm2/24 hr, and the amount of mercury released remained fairly constant during the duration of the experiment. This study showed that Composil releases mercury in quantities that far exceed those detected in other amalgam systems.

Significance of hydrogen ion concentration on the dissolution of mercury from dental amalgam.

The potential risks of mercury dissolution from dental amalgam have long been recognized. This study examined the effect of hydrogen ion concentration on the release of mercury from two dental amalgams: an admixed high-copper amalgam and a new tin- and copper-free amalgam. Specimens of each type of amalgam were incubated citric acid buffer of pH 2.5 or pH 7.0. Results showed that, for both types of amalgam, specimens incubated at pH 2.5 released statistically significantly greater (P less than .0001) quantities of mercury than did specimens incubated at pH 7.0. Release of mercury from the tin- and copper-free amalgam was also statistically significantly greater (P less than .0001) than that of the higher-copper amalgam at both pH levels.