Dimensional change of a calcium aluminate cement for posterior restorations in aqueous and dry media

A randomized controlled evaluation of posterior resin restorations of an altered resin modified glass-ionomer cement with claimed bioactivity

OBJECTIVE

The objective of this randomized controlled prospective clinical trial was to evaluate the short time clinical behaviour of an altered resin modified glass-ionomer cement (RMGIC), which is claimed to possess bioactivity, in posterior restorations and to compare it intraindividually with a nanofilled resin composite.

METHODS

Totally 78 pairs Class II and 4 pairs Class I restorations were placed in 29 female and 38 male participants with a mean age of 58.3 years (range 37-86). Each patient received at random at least one pair of, as similar as possible, Class II or Class I restorations. In the first cavity of each pair, the modified flowable RMGIC (ACTIVA Bioactive; AB) was placed after phosphoric acid etching of the cavity and without adhesive, according to the instructions of the manufacturer. In the other cavity a well established nanofilled resin composite (CeramX; RC) with a single step self-etch adhesive (Xeno Select) was placed. The restorations were evaluated using slightly modified USPHS criteria at baseline, 6 and 12 months. Caries risk and parafunctional habits of the participants were estimated.

RESULTS

158 restorations, 8 Class I and 150 Class II, were evaluated at the one year recalls. At baseline two failed restorations were observed (2AB), at 6 months six failures (5AB, 1RC) and at 12 months another thirteen failed restorations were observed (12AB, 1RC). This resulted in annual failure rates of 24.1% for the AB and 2.5% for RC (p<0.0001). The main reasons for failure for AB were lost restorations (5), postoperative symptoms (4) and secondary caries (3). Do to the unacceptable very high one-year failure frequency, the clinical study was stopped and no further evaluation will be performed.

SIGNIFICANCE

The use of the AB restorative in Class II cavities, applied as instructed by the manufacturer after a short phosphoric acid pretreatment but without adhesive system, resulted in a non-acceptable very high failure frequency after a one year period. Further studies should be conducted using a bonding agent.

Capping a pulpotomy with calcium aluminosilicate cement: comparison to mineral trioxide aggregates

INTRODUCTION

Calcium aluminate cements have shown little affinity for bacterial growth, low toxicity, and immunogenicity when used as a restoration material, but calcium aluminate cements have not been tested in vivo in pulpotomy procedures.

METHODS

To address this question, a calcium aluminosilicate cement (Quick-Set) was tested along with 2 mineral trioxide aggregates, ProRoot MTA and MTA Plus. These cements were used as a capping agent after pulpotomy. Control rats had no pulpotomy, or the pulpotomy was not capped. Proinflammatory cytokines interleukin (IL)-1β and IL-1α were measured, and histology was performed at 30 and 60 days after capping. The nociceptive response was determined by measuring the lengthening of the rat's meal duration.

RESULTS

and

CONCLUSIONS

IL-1β and IL-1α concentrations were reduced in the capped teeth, but no differences were observed among the 3 cements. Dentinal bridging could be detected at both 30 and 60 days with each of the 3 cements, and the pulps were still vital 60 days after capping. Meal duration significantly shortened after placement of the 3 different cements, indicating a nociceptive response, but there were no differences among the materials. Calcium aluminosilicate cement had similar properties to mineral trioxide aggregates and is a viable option for pulpotomy procedures.

Hygroscopic dimensional changes of self-adhering and new resin-matrix composites during water sorption/desorption cycles

OBJECTIVES

To study hygroscopic dimensional changes in new resin-matrix composites during water sorption/desorption cycles.

METHODS

Five materials were examined: a self-adhering flowable composite: Vertise® Flow (VF), a universal composite: GC Kalore (GCK), two micro-fine hybrid composites: GC Gradia Direct Anterior (GDA) and GC Gradia Direct Posterior (GDP), and a posterior restorative composite: Filtek® Silorane (FS). Five disk-shaped specimens of each material were prepared (15 mm diameter × 2 mm thickness) according to ISO 4049. The mean diameter of each specimen was measured by a custom-built laser micrometer (to a resolution of 200 nm) periodically over 150d water immersion and 40d recondition periods at (37 ± 1)°C. Perspex controls were used. Data analysis was performed by repeated measures ANOVA, one-way ANOVA and Tukey's post hoc test (p<0.05).

RESULTS

Differences in hygroscopic expansion were found for all test materials during sorption, ranging from 0.74% (± 0.05) for FS to 4.82% (± 0.13) for VF. The differences were significant for all materials (p<0.001), except between GCK and GDA. The mathematical relationship between diametral expansion and square root of time was non-linear. VF exhibited significant dehydration shrinkage.

SIGNIFICANCE

The silorane composite FS had the lowest hygroscopic expansion. The extent of compensation of polymerization shrinkage by hygroscopic expansion depends on materials, specimen dimensions and time-scale. So the clinical situation must be taken into consideration in the application of these findings.

Selected physicochemical properties of the experimental endodontic sealer

This study explores water sorption, hygroscopic expansion, mechanical strength and ion release from the experimental amorphous calcium phosphate (ACP) composites formulated for application as endodontic sealers. Light-cure (LC) and dual-cure (DC; combined light and chemical cure) resins comprised urethane dimethacrylate (UDMA), 2-hydroxyethyl methacrylate (HEMA), methacryloyloxyethyl phthalate (MEP) and a high molecular mass oligomeric co-monomer, poly(ethyleneglycol)-extended UDMA (PEG-U) (designated UPHM resin). To fabricate composites, a mass fraction of 60% UPHM resin was blended with a mass fraction of 40% as-made (am-) or ground (g-) ACP. Glass-filled composites were used as controls. Both DC and LC ACP UPHM composites exhibited relatively high levels of water sorption accompanied by a significant hygroscopic expansion. The latter may potentially be useful to offset high polymerization stresses that develop in these materials. Ion release profiles of the experimental materials confirmed their potential for regeneration of mineral-deficient tooth structures. Their moderate to low mechanical strength after 3 months of aqueous immersion did not diminish the enthusiasm for the proposed use as endodontic sealers. For that application, DC g-ACP composites appear to be the most adequate, but micro-leakage and quantitative leachability studies are needed to fully establish their suitability.

Mutans streptococci and lactobacilli in plaque on a leucite-reinforced dental ceramic and on a calcium aluminate cement

In this in vivo study, the proportions of mutans streptococci and lactobacilli in plaque were examined (1) on proximal surfaces of bonded, leucite-reinforced ceramic crowns and (2) on class V restorations of calcium aluminate cement (CAC). The examined proportions were intraindividually compared with those of resin composite and enamel. Mutans streptococci and lactobacilli in samples from plaque that was accumulated for 10 days on the following surfaces were determined by cultivation on blood agar plates and species-selective plates: (1) proximal leucite-reinforced ceramic crown, class II composite and enamel (n=11); and (2) class V restoration of CAC and composite, and enamel (n=17). Mutans streptococci and lactobacilli in the samples were distributed in three groups: 0, >0-1, and >1% of total bacteria. The surfaces with detected mutans streptococci were similarly distributed between the materials and enamel. The highest proportion of mutans streptococci and lactobacilli were observed on ceramic followed by composite and enamel. A higher proportion of lactobacilli, but not of mutans streptococci, was detected on enamel compared to CAC and composite. However, no significant differences were found between the surfaces. Conclusively, the materials investigated did not show different relative proportions of mutans streptococci and lactobacilli in plaque, compared to enamel.