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PubMed2006

Long-term bond between dual-polymerizing cementing agents and human hard dental tissue.

OBJECTIVES: To examine the long-term adhesion of seven dual-polymerizing cementing agents to human dentin in vitro. METHODS: Two hundred and eighty extracted non-carious human molars were ground flat to expose dentin surfaces. The bond strengths of cementing agents with their respective bonding systems were examined: one compomer cement (PermaCem), five resin cements (RelyX ARC, Panavia F, Variolink II, Nexus 2, Calibra) and one self-adhesive universal resin cement (RelyX Unicem). One subgroup (n=10) was tested after 150 days of storage in water at 37 degrees C (time t(1)), the other subgroup (n=10) was tested after 150 days of storage plus 37,500 thermal cycles (time t(2)). All specimens were stressed in shear at a constant crosshead speed of 0.5mm/min until failure. Statistical analysis was performed by ANOVA, taking effect interactions into account. The Tukey method was used for multiple paired comparisons (alpha=0.05). RESULTS: The three-way ANOVA (cementing agents, polymerization methods, times of measurements) showed Variolink II to have the highest strength at 9.9+/-4.5MPa. Values were slightly higher at t(1) (5.9+/-4.7MPa) than at t(2) (4.9+/-4.2MPa) (p=0.0044). Polymerization with light activation (6.5+/-5.1MPa) yielded higher strengths than polymerization without (4.3+/-3.3MPa) (p<0.0001). Separate two-way ANOVAs for t(1) and t(2) showed that the two main effects (cementing agent, polymerization method) and their interactions differed significantly. SIGNIFICANCE: Cementing agents/adhesive systems and the polymerization method influence the long-term bond to hard dental tissues.

Acid Etching, Dental↗
PubMed2006

A novel comonomer-free light-cured glass-ionomer cement for reduced cytotoxicity and enhanced mechanical strength.

OBJECTIVE: The objective of this study was to develop a novel comonomer-free light-cured glass-ionomer system based on the 4-arm star-shape poly(acrylic acid). The mechanical strengths and in vitro cytotoxicity of the formed system were evaluated and compared with those of several representative commercial glass-ionomer cements. MATERIALS AND METHODS: The 4-arm poly(acrylic acid) was synthesized using ATRP and tethered with glycidyl methacrylate (GM). The GM-tethered polymer was formulated with water, photo-initiators, and Fuji II LC filler. Fuji II, Fuji II LC and Vitremer were used for comparison. Compressive strength (CS) and MTT assay were used as tools to evaluate the mechanical strengths and in vitro cytotoxicity of the cements, respectively. RESULTS: The experimental cement exhibited significantly high compressive, diametral tensile and flexural strengths as compared to commercial glass-ionomer cements, Fuji II, Fuji II LC and Vitremer. The effects of polymer/water (P/W) ratio, GM-grafting ratio, glass powder/polymer liquid (P/L) ratio and aging in water on strengths were significant. Similar to conventional glass-ionomer cement Fuji II, the eluates from the experimental cement showed little in vitro cytotoxicity to Balb/c mouse fibroblast cells, as compared to Fuji II LC and Vitremer that contain HEMA as a comonomer. CONCLUSIONS: It appears that this novel comonomer-free light-cured glass-ionomer cement will be a promising dental restorative because it demonstrated significantly improved mechanical strengths and almost no in vitro cytotoxicity as compared to current commercial light-cured glass-ionomer cements.

Acrylic Resins↗
PubMed2006

In vitro biocompatibility of a novel Fe2O3 based glass ionomer cement.

INTRODUCTION: Since their invention in the late 1960s, glass ionomer cements (GICs) have been used extensively in dentistry but recently they have also been utilised in ear nose and throat (ENT) surgery. Unfortunately, Al3+, a component of conventional ionomer glasses, has been linked to poor bone mineralisation and neurotoxicity. OBJECTIVE: The aim of the research was to modify a commercial ionomer glass composition by substituting Al2O3 with Fe2O3. METHODS: Glasses with the following molar compositions were fabricated: 4.5SiO2*3M2O3*XP2O5*3CaO*2CaF2 (M = Al or Fe, X = 0-1.5). The glasses were characterised using X-ray fluorescence (XRF) and X-ray powder diffraction (XRD). Cements were prepared using a standard ratio of; 1 g of glass powder: 0.2 g of dried polyacrylic acid: 0.3 g of 10% tartaric acid solution. Cement formation was assessed using a Gilmore needle and in vitro biocompatibility was investigated for novel cement formulations. RESULTS: XRF revealed that the Fe2O3-based glasses had Al2O3 contamination from the crucibles and also had undergone substantial F- losses. XRD gave peaks that corresponded to magnetite Fe3O4 (JCPDS # 19-629) in all compositions. Apatite Ca5(PO4)3(OH,F) (JCPDS # 15-876) was identified in P2O5 containing glasses. It was possible to fabricate cements from all of the Fe2O3-based ionomer glasses. Good in vitro biocompatibility was observed for the Fe2O3-based cements. CONCLUSION: Ionomer glasses may be prepared by entirely replacing Al2O3 with Fe2O3. Cement setting times appeared to be related to P2O5 content. Fe2O3-based cements showed good in vitro biocompatibility.

Animals↗
PubMed2006

Ion processes in glass ionomer cements.

Ion processes are involved in many aspects of glass-ionomer cements. The ions released from the glass take part in the formation of the cement matrix. Although this process has been investigated, particularly using model cement systems, no study provides a complete matrix composition. Combining results from different studies enables an approximate composition to be derived. The importance of Phosphorous in controlling ion release from the glass surface has been identified in a number of studies. The release of ions from the set cement into water (and other aqueous liquids) has been much reported, particularly for fluoride. Over most of the release periods studied (i.e. from >7 days up to 3 years), release of F ion is related to t1/2 indicating a diffusion-controlled process. Other ions, except possibly Na+ also show this relationship. The amount of cumulative F release whilst maintaining this relationship indicates that more F than is in the matrix is involved. Ion chromatography would probably elucidate the precise form of the ionic species released. Glass-ionomer cements take up ions from solutions in which they are immersed. The levels are much higher than required to produce as internal/external equilibrium. Studies using dynamic SIMS and XPS give some information on ion location and elemental association. It is suggested that ToF SIMS would elucidate these further. Re-release of uptaken ions can vary considerably for different cements and ion species. Surface disruption of glass ionomers is caused by both F ion and monofluorophosphate ion and occurs much more readily in F containing cements than in F free ones. The mechanism of this process has not been elucidated. Analysis of the ions released from the cement as disruption occurs should provide an indication of the site of attack.

Aluminum Silicates↗
PubMed2005

Mechanical characteristics of the bone-graft-cement interface after impaction allografting.

Impaction allografting is an attractive procedure for the treatment of failed total hip replacements. The graft-cement-host bone interface after impaction allografting has not been characterized, although it is a potential site of subsidence for this type of revision total hip reconstruction. In six human cadaveric femurs, the cancellous bone was removed proximally and local diaphyseal lytic defects were simulated. After the impaction grafting procedure, the specimens were sectioned in 6 mm transverse sections and push-out tests were performed. From the adjacent sections the percentage cement contact of the PMMA cement with the endosteal bone surface was determined. The host bone interface mechanical properties varied significantly along the femur largely due to different interface morphologies. The apparent host bone interface shear strength was highest around the lesser trochanter and lowest around the tip of the stem. A significant positive correlation was found between the percentage cement contact and the apparent host bone interface shear strength (r2 = 0.52). The sections failed in 69% of the cases through a pure host bone interface failure without cement or allograft failure, 19% failed with local cement failure, and 12% with a local allograft failure. The apparent host bone interface strength was on average 89% lower than values reported for primary total hip replacements and were similar to cemented revisions proximally and lower distally. This study showed that cement penetration to the endosteal surface enhanced the host bone-graft interface.

Biomechanical Phenomena↗
PubMed2005

Hydroxyapatite cement in craniofacial reconstruction.

OBJECTIVES: To evaluate the long-term efficacy of hydroxyapatite cement in craniofacial reconstruction, specifically examining the role (if any) of radiation, implant location, and cement type. STUDY DESIGN: A retrospective chart review was conducted of all patients presenting to the senior surgeon (Y.D.) for craniofacial reconstruction from September 1997 to April 2004. METHODS: Data were collected including type of cement used, size of defect, complications, need for removal of cement, reason for defect, and pathologic results of examination of removed cements. RESULTS: One hundred two patients were identified who underwent craniofacial reconstruction with hydroxyapatite cements, 7 of whom required complete implant removal (6 Norian and 1 Mimix), and 4 (2 Norian and 2 Bone source) of whom required partial implant removal for foreign body reaction. Five of the removals were in patients who underwent postoperative radiation. CONCLUSIONS: Hydroxyapatite cements are safe in craniofacial reconstruction. The highest risk of implant infection comes from reconstruction in the area of the frontal sinus, immediately beneath coronal incisions, and in patients who receive postoperative radiation treatment. Based on our results, there does appear to be a statistically significant difference in rates of infection and foreign body reaction between the different types of hydroxyapatite cement. We would not recommend implantation of this material in contact with the frontal sinus. Caution should be exercised when it is placed directly beneath an incision or in patients receiving postoperative radiation, particularly if a boost dose is given.

Bone Cements↗
PubMed1998

In vivo retrospective study of cement thickness under crowns.

PURPOSE: This study evaluated the cement thickness under crowns cemented with zinc phosphate cement that had been in clinical use for at least 10 years. MATERIAL AND METHODS: A total of 97 teeth were extracted because of periodontal disease as part of a new treatment plan. Teeth were sectioned and the cement thickness measured at predetermined points on the occlusal and axial walls with a measuring microscope at x150 magnification. RESULTS: Mean cement thicknesses on buccal and lingual walls were similar (116 microns and 109 microns, respectively), but much smaller than on occlusal walls (310 microns). Cement thicknesses at occlusal locations were significantly thicker in molars than in premolars. Poor correlations existed between cement thicknesses on buccal and lingual walls (0.26) and between these and the occlusal walls (0.35) implying that incomplete seating is strongly related to tilting or oblique seating. CONCLUSION: Under clinical conditions where more inherent difficulties exist, special measures must be taken to alleviate the consequences of cement fluid dynamics.

Analysis of Variance↗
PubMed1999

Retention of provisional crowns fabricated from two materials with the use of four temporary cements.

STATEMENT OF PROBLEM: Practitioners often choose resin materials and temporary cements with little understanding about their effect on provisional crown retention. PURPOSE: This study evaluated the retention of provisional restorations made with 2 materials and cemented with 4 temporary cements. METHODS AND MATERIAL: Recently extracted molars were prepared with a flat occlusal surface, 4-mm axial length and 20-degree angle of convergence. Specimens were distributed into equivalent groups. Provisional crowns were constructed for each preparation with polymethyl methacrylate (Temporary Bridge Resin) or bis-acrylic composite (Protemp Garant) and later cemented with Temp-Bond, Temp-Bond NE, Temrex, and an experimental calcium hydroxide temporary cement. A second group with Temrex was evaluated using half the recommended liquid. A cementing force of 2.5 kg for 5 minutes was used. After initial bench set followed by 24 hours in room temperature water, the crowns were removed with an Instron mechanical testing machine at 0.5 mm/min. A 2-factor ANOVA was used with alpha=.05 (n = 10). Mode of debonding was analyzed with a nonparametric chi-square test of association. RESULTS: Mean dislodgment stresses ranged from 670 to 1072 kPa for polymethyl methacrylate crowns and 554 to 884 kPa for those made of composite. Differences were nearly significant for the type of provisional material (P =.061) and the cross-product interaction (P =.376) was not significant, whereas there were significant differences among the cements (P =.002) and the mode of debonding (P =.0034). CONCLUSIONS: Excluding Temp-Bond to eliminate a cross-product interaction demonstrated that the polymethyl methacrylate crowns were 19.3% more retentive than the composite crowns (P =.015). There was no statistically significant difference among the 4 temporary cements when the manufacturer's mixing instructions were followed (P =.186). However, the thicker consistency Temrex was more retentive than the recommended Temrex mix and Temp-Bond.

Analysis of Variance↗
PubMed1999

The influence of clinically induced variability on the distribution of compressive fracture strengths of a hand-mixed zinc phosphate dental cement.

OBJECTIVES: Conventional approaches to comparing dental cements use standard property tests under manufacturers' specified conditions. Zinc phosphate cements are supplied in powder/liquid form and manipulation frequently involves mixing the components by eye so a range of mixing ratios will inevitably occur in practice. Unfortunately, the physical, chemical, biological and mechanical properties of cements are known to be dependent on the mixing ratio. METHODS: Forty dental nurses prepared a series of three cement samples to a luting consistency they considered acceptable for use in practice. RESULTS: It was found that each dental nurse produced consistent cement mixes, although, the mixing ratios varied from 1.7 to 3.2 g/ml between nurses. The mean compressive strength, standard deviation and associated Weibull Moduli (m) of the cements were determined as a function of this mixing ratio range and showed considerable variation ranging from 33.5 +/- 3.2 MPa (m = 11.0) at 1.7 g/ml to 71.4 +/- 8.4 MPa (m = 8.6) at 2.6 g/ml and 42.5 +/- 10.0 MPa (m = 5.0) at 3.2 g/ml. SIGNIFICANCE: An analytical approach was adopted which facilitated an integrated analysis of the mixing ratio variability with the strength data. It was found for the test group of dental nurses that 25% of cement mixes produced would have achieved strengths below 40 MPa whilst strengths below the standard value were produced in at least 70% of mixes. These results indicate that a simple analysis of the properties of cements manipulated under optimum conditions, provides little information on the material characteristics obtained in practice because of clinically induced variability.

Analysis of Variance↗
PubMed1999

Properties of fluoride-releasing light-activated resin cement.

OBJECTIVES: Fluoroaluminosilicate glass and poly(acrylic acid) in small water phase was incorporated into resin composite cements to reduce or prevent secondary caries around luted restorations. The purpose of this study was to investigate the physical properties and the amounts of fluoride released from four types of visible light-activated resin cements. METHODS: A powder was composed of silanized SiO2 filler and 4.5 wt.% (G-4.5), 9.5 wt.% (G-9.5) or 19.5 wt.% (G-19.5) fluoroaluminosilicate glass and 0.5 wt.% reducing agent. The 45.25 wt.% triethylene glycol dimethacrylate (TEGDMA), 45.25 wt.% 2-hydroxyethyl methacrylate (HEMA), 9 wt.% poly(acrylic acid) solution in water and 0.5 wt.% camphorquinone were contained in a liquid. The powder and liquid were mixed at a 3:1 ratio by weight and the three types of specimen disks were cured using a photo-curing lamp. The TEGDMA-based composite cement was used as control (G-0). The specimens were immersed in water at 37 degrees C for 24 h or 6 months and compressive strength (CS) and diametral tensile strength (DTS) were evaluated for the four experimental materials. Disks prepared from the four resin cements were also immersed in deionized distilled water at 37 degrees C, and the fluoride released was measured over a period of 24 weeks. RESULTS: G-9.5 specimens showed almost the same CS and DTS as G-4.5 and G-0 specimens and significantly higher values for both parameters than G-19.5 specimens after 6 months of water storage. The amount of fluoride released from the three fluoride-containing resin cements continued to increase over the entire experimental period. The fluoride release rates of G-9.5 and G-19.5 resin cements were almost the same and were significantly greater than that of the G-4.5 resin cement. SIGNIFICANCE: G-9.5 containing 9.5 wt.% fluoroaluminosilicate glass may be a clinically useful resin cement due to its favorable physical properties and fluoride release.

Analysis of Variance↗
PubMed2000

Surface roughness, porosity and wettability of gentamicin-loaded bone cements and their antibiotic release.

In this study, the release of gentamicin as a function of time was measured for six different gentamicin-loaded bone cements and related with the surface roughness, porosity and wettability of the cements. Initial release rates varied little between the six bone cements (CMW1, CMW3, CMW Endurance, CMW 2000, Palacos, and Palamed) and ranged from 8.6 to 14.1 microg/cm2/h. The total amounts of gentamicin released after 1 week varied between 4.0 and 5.3% of the total amount of antibiotic incorporated for the CMW cements and was 8.4% for Palacos. Palamed released after 1 week significantly more of the gentamicin incorporated (17.0%). The wettability of all cements was similar (water contact angles between 70 and 80 degrees), but the surface roughness and the porosity of the cements varied markedly. Initial release rates increased with surface roughness, although the correlation coefficient was low (0.64), while total amounts released increased linearly (correlation coefficient 0.97) with the bulk porosity of the cements. Consequently, it can be concluded that the release kinetics of gentamicin from bone cements is controlled by a combination of surface roughness and porosity.

Bone Cements↗
PubMed2001

Development of a new calcium phosphate cement that contains sodium calcium phosphate.

A cement powder consisting of sodium calcium phosphate, Na3Ca6(PO4)5, in addition to tetracalcium phosphate and beta-tricalcium phosphate was prepared by pulverizing blocks of 4 wt% sodium-, 11 wt% carbonate-containing apatite samples that were heated at 1700 degrees C for 5 h. When mixed with 30 wt% malic acid or citric acid at a powder liquid ratio of 3:1, the cement set in 3 or 7 min at room temperature with compressive strength being around 52 or 27 MPa. In HeLa-cell cultures, the cement mixed with malic acid was less cytotoxic than the cement mixed with citric acid, which was far less cytotoxic than a commercial carboxylate cement used as a negative control, suggesting malic acid to be superior to citric acid as a liquid in this regard. Similar findings were also obtained with osteoclasts, of which culture experiments clearly suggested that the number of osteoclasts on the cement mixed with malic acid was significantly greater than that on the cement mixed with citric acid. Since osteoclastic response to substrates could be used as a maker in evaluating their bioresorbability associated with osteoclasts, the above finding may suggest that the cement that is to be mixed with malic acid would be more useful as bone substitutes.

Animals↗
PubMed2001

Influence of mixing techniques on the physical properties of acrylic bone cement.

Palacos R bone cement was prepared using three commercially available mixing techniques, first generation, second generation and third generation, to determine the mechanical properties and porosity contents of the bone cement. The compressive strengths, bending strengths and flexural moduli were expressed as a function of void content. The volume of pores within the cement structure was found to be a contributing factor to the physical properties of acrylic bone cement. The lower the volume of voids in the cement the better the compressive and flexural properties, hence stronger bone cement. It was found that the best results were obtained from cement that had been mixed using the Mitab Optivac or Summit HiVac Syringe systems at a reduced pressure level of between -72 and -86 kPa below atmospheric pressure, resulting in cement of porosity 1.44-3.17%; compressive strength 74-81 MPa; flexural modulus 2.54-2.60 GPa; and flexural strength 65-73 MPa.

Acrylates↗
PubMed2002

Development of calcium phosphate cement using chitosan and citric acid for bone substitute materials.

We developed a calcium phosphate cement that could be molded into any desired shape due to its chewing-gum-like consistency after mixing. The powder component of the cement consists of alpha-tricalcium phosphate and tetracalcium phosphate, which were made by decomposition of hydroxyapatite ceramic blocks. The liquid component consists of citric acid, chitosan and glucose solution. In this study, we used 20% citric acid (group 20) and 45% citric acid (group 45). The mechanical properties and biocompatibility of this new cement were investigated. The setting times of cements were 5.5 min, in group 20 and 6.4 min, in group 45. When incubated in physiological saline, the cements were transformed to hydroxyapatite at 3, and 6 weeks, the compressive strengths were 15.6 and 20.7 MPa, in group 45 and group 20, respectively. The inflammatory response around the cement implanted on the bone and in the subcutaneous tissue in rats was more prominent in group 45 than in group 20 at 1 week after surgery. After 4 weeks, the inflammation disappeared and the cement had bound to bone in both groups. These results indicate that this new calcium phosphate cement is a suitable bone substitute material and that the concentration of citric acid in the liquid component affects its mechanical properties and biocompatibility.

Animals↗
PubMed2002

Transforming growth factor-beta1 incorporation in an alpha-tricalcium phosphate/dicalcium phosphate dihydrate/tetracalcium phosphate monoxide cement: release characteristics and physicochemical properties.

The osteoconductive properties of calcium phosphate cements (CPCs) may be improved by the addition of growth factors, such as recombinant human transforming growth factor-beta1 (rhTGF-beta1). Previously we have shown that rhTGF-beta1 was released from cement enriched with rhTGF-beta1 and subsequently stimulated the differentiation of pre-osteoblastic cells from adult rat long bones. It is unknown whether the addition of rhTGF-beta1 changes the material properties of this alpha-tricalcium-phosphate (alpha-TCP)/tetracalcium-phosphate-monoxide (TeCP)/dicalcium-phosphate-dihydrate (DCPD) cement, and what the characteristics of the release of rhTGF-beta1 from this CPC are. Therefore, in the present study we determined the release of rhTGF-beta1 from cement pellets in vitro. The possible intervening effects of the CPC modification for intermixing rhTGF-beta1 on physicochemical properties were studied by assessing the compressive strength and setting time, as well as crystallinity, calcium to phosphorus ratio, porosity and microscopic structure. Most of the previously incorporated rhTGF-beta1 in the cement pellets was released within the first 48 h. For all concentrations of rhTGF-beta1 intermixed (100 ng-2.5 mg/g CPC), approximately 0.5% of the amount of rhTGF-beta1 incorporated initially was released in the first 2 h, increasing to 1.0% after 48 h. The release of rhTGF-beta1 continued hereafter at a rate of about 0.1% up to 1 week, after which no additional release was found. The initial setting time, nor the final setting time was changed in control cement without rhTGF-beta1 (standard CPC) or in cement modified for rhTGF-beta1 (modified CPC) at 20 degrees C and 37 degrees C. Setting times were more than six times decreased at 37 degrees C compared to 20 degrees C. The compressive strength was initially low for both standard CPC and modified CPC, after which it increased between 24 h and 8 weeks. The compressive strength for the modified CPC was significantly higher compared with standard at 1, 2, and 8 weeks after mixing. X-ray diffraction revealed that both standard and modified CPC changed similarly from the original components into crystalline apatite. The calcium to phosphorus ratio as determined by an electron microprobe did not differ at all time points measured for standard CPC and modified CPC. In both standard CPC and modified CPC the separated particles became connected by crystals, forming a structure in which the particles could hardly be recognised in a densifying matrix with some small pores. The present study shows that the calcium phosphate cement is not severely changed by modification for the addition of rhTGF-beta1. The addition of rhTGF-beta1 in CPC enhances the biologic response as shown in our previous study and did not interfere with the aimed physical and chemical properties as shown in this study. We conclude that the addition of rhTGF-beta1 enlarges the potential of the CPC in bone replacement therapy.

Animals↗
PubMed2003

The relationship between porosity and fatigue characteristics of bone cements.

In this study, the fatigue strengths of acrylic cement prepared by various commercially available reduced pressure mixing systems were compared with the fatigue strength of cement mixed by hand (control) under atmospheric conditions. The following observations were made from this investigation. The mean fatigue strength of reduced pressure mixed acrylic bone cement is double that of cement mixed by hand using an open bowl, 11,354+/-6,441 cycles to failure for reduced pressure mixing in comparison with 5,938+/-3,199 cycles for mixing under atmospheric conditions. However, the variability in mean fatigue strengths of reduced pressure mixed bone cement is greater for some mixing devices. The variation in fatigue strengths for the different mixing techniques is explained by the different porosity distributions. The design of the reduced pressure mixing system and the technique employed during mixing strongly contribute to the porosity distribution within the acrylic bone cement. The level of reduced pressure applied during cement mixing has an effect on the fatigue strength of bone cement, but the mixing mechanism is significantly more influential.

Biocompatible Materials↗
PubMed2003

Compositional changes of a dicalcium phosphate dihydrate cement after implantation in sheep.

A hydraulic calcium phosphate cement having dicalcium phosphate dihydrate (DCPD) as end-product of the setting reaction was implanted in a cylindrical defect in the diaphysis of sheep for up to 6 months. The composition of the cement was investigated as a function of time. After setting, the cement composition consisted essentially of a mixture of DCPD and beta-tricalcium phosphate (beta-TCP). In the first few weeks of implantation, the edges of the cement samples became depleted in DCPD, suggesting a selective dissolution of DCPD, possibly due to low pH conditions. The cement resorption at this stage was high. After 8 weeks, the resorption rate slowed down. Simultaneously, a change of the color and density of the cement center was observed. These changes were due to the conversion of DCPD into a poorly crystalline apatite. Precipitation started after 6-8 weeks and progressed rapidly. At 9 weeks, the colored central zone reached its maximal size. The fraction of beta-TCP in the cement was constant at all time. Therefore, this study demonstrates that the resorption rate of DCPD cement is more pronounced as long as DCPD is not transformed in vivo.

Animals↗
PubMed1997

Comparison of the porosity of hand-mixed and capsulated glass-ionomer luting cements.

The strength of dental glass-ionomer cements will be influenced by defects present within its structure. This study measured the surface area porosity, percentage surface area porosity, and mean surface area of small bubbles (<0.01 mm2) and the surface area porosity, percentage surface area porosity and diameter of large bubbles within 40-microm-thick layers of four cements, using image analysis software. Two hand-mixed cements (Fuji I and KetacCem) and two capsulated cements (Fuji Cap I and KetacCem Maxicap) were viewed under transmitted light at x117.6 magnification. For each selected area (64.75 mm2) of each cement sample, five independent measurements were made of each of these parameters. Analysis of variance (ANOVA) indicated that there were no significant differences between the four cements in the small bubble parameters measured, whilst there were significant differences in the surface area porosity, percentage surface area porosity and diameter of the large bubbles. It was concluded that the hand-mixed cements tested had a greater number of larger diameter bubbles compared with the capsulated cements.

Analysis of Variance↗