Posterior Composite Materials Research Articles

Clinical Performance of Direct Posterior Composite Restorations in Patients with Amelogenesis Imperfecta.

The objective of this study was to analyze and assess the clinical performance of direct composite restorations using a nanohybrid and a nanofill composite material for posterior teeth in patients with amelogenesis imperfecta (AI). This study involved 15 patients between the ages of 14 and 30 years suffering from amelogenesis imperfecta (AI). During the study, the patients received direct composite restorations using either the Clearfil Majesty ES-2 (Kuraray Medical Inc, Tokyo, Japan) and Clearfil Universal Bond (Kuraray) or Filtek Ultimate Universal Restorative (3M ESPE, St Paul, MN, USA) and Single Bond Universal Adhesive (3M ESPE). The evaluations of the restorations were conducted per the modified USPHS criteria at the time of baseline as well as during the first-, second-, third-, and fourth-year follow-up sessions. After four years, it was observed that the cumulative success rate of direct posterior restorations was 98.1% for Clearfil Majesty ES-2 and 92.2% for Filtek Ultimate. During the study one Clearfil Majesty ES-2 restoration and four Filtek Ultimate restorations failed. There was a significant difference between Clearfil Majesty ES-2 and Filtek Ultimate in the color match in posterior restorations after three and four years. The causes of failure included marginal discoloration and caries, as well as fracture of the restoration. Hence, it can be stated that the use of nanohybrid or nanofill composites in posterior direct restorations in patients with AI looks promising. The failure rate of Clearfil Majesty ES-2 was found to be lower than that of Filtek Ultimate restorations. Clinically, the rate of optimum restorations conducted for partial discoloration, marginal adaptation, color match, and surface texture were observed to be higher when Clearfil Majesty ES-2 was used. However, additional studies are needed to assess the clinical performance of direct posterior composite materials in patients with AI.

Clinical Performance of Direct Posterior Composite Restorations in Patients with Amelogenesis Imperfecta.

The objective of this study was to analyze and assess the clinical performance of direct composite restorations using a nanohybrid and a nanofill composite material for posterior teeth in patients with amelogenesis imperfecta (AI). This study involved 15 patients between the ages of 14 and 30 years suffering from amelogenesis imperfecta (AI). During the study, the patients received direct composite restorations using either the Clearfil Majesty ES-2 (Kuraray Medical Inc, Tokyo, Japan) and Clearfil Universal Bond (Kuraray) or Filtek Ultimate Universal Restorative (3M ESPE, St Paul, MN, USA) and Single Bond Universal Adhesive (3M ESPE). The evaluations of the restorations were conducted per the modified USPHS criteria at the time of baseline as well as during the first-, second-, third-, and fourth-year follow-up sessions. After four years, it was observed that the cumulative success rate of direct posterior restorations was 98.1% for Clearfil Majesty ES-2 and 92.2% for Filtek Ultimate. During the study one Clearfil Majesty ES-2 restoration and four Filtek Ultimate restorations failed. There was a significant difference between Clearfil Majesty ES-2 and Filtek Ultimate in the color match in posterior restorations after three and four years. The causes of failure included marginal discoloration and caries, as well as fracture of the restoration. Hence, it can be stated that the use of nanohybrid or nanofill composites in posterior direct restorations in patients with AI looks promising. The failure rate of Clearfil Majesty ES-2 was found to be lower than that of Filtek Ultimate restorations. Clinically, the rate of optimum restorations conducted for partial discoloration, marginal adaptation, color match, and surface texture were observed to be higher when Clearfil Majesty ES-2 was used. However, additional studies are needed to assess the clinical performance of direct posterior composite materials in patients with AI.

Do the monomers release from the composite resins after artificial aging?

The aim of this study is to measure the effect of thermal cycling on the amount of monomer released from three different composite materials by HPLC analysis method. Three different composite materials, inlay composite, posterior composite and micro-hybrid composite were used. Sixty cylinder specimens each with a dimension of approximately 1 cm width and 3 mm depth, were prepared before experiments were carried out. Inlay composite material was polymerized according to manufacturers' instructions. Thermal cycling device was used to simulate thermal differences which occur in the mouth media. Monomers were analyzed using HPLC technic after thermal cycling process. The amount of ethoxylated Bis-GMA and urethane dimethacrylate (UDMA) in inlay composite material, the amount of ethoxylated Bis-GMA in posterior composite material, the amount of ethoxylated Bis-GMA and triethyleneglycol dimethacrylate (TEGDMA) in micro-hybrid composite material were investigated. Monomer release of thermal cycles levels showed a linear increase in UDMA and TEGDMA (P < 0.05). In terms of thermal cycles levels, Bis-EMA released from posterior composite showed a cubic change (P < 0.001). It was observed that use of additional polymerization processes might have positive effect on the decrease of residual monomer. In the light of the results, we suggest that indirect composite resins have more outstanding features than direct composite resins in terms of biocompatibility.

In vitro measurement of cuspal strain and displacement in composite restored teeth

Objectives: This study was carried out to measure changes in cuspal strain and displacement occurring during placement and polymerization of bonded composite restorations in extracted human teeth in vitro. Methods: Strains were measured using electrical resistance strain gauges bonded to the buccal and lingual cusps of each specimen and cuspal displacement was recorded with a linear variable differential transformer. Mesio-occluso-distal cavities of two types were prepared in lower molar teeth. Following enamel acid etching and application of a dentine adhesion promoter, specimens were restored incrementally with a light curing posterior composite material. Results: It was shown that the shrinkage of a composite material during polymerization generated stresses which resulted in tensile strains on the tooth surface. Strains of up to 882 μm/m were recorded and a maximum cusp displacement of 14 μm was also measured. These strains were reduced but not eliminated by preparation and restoration a mesio-distal slot running the full length and depth of the restoration. Statistical analysis revealed significantly higher strains and displacement produced on the buccal cusps of teeth that had a reduced cusp width ( P < 0.001). Conclusions: The in vitro restoration of posterior teeth with a bonded composite material generates polymerization stresses which can be recorded as tensile strains and displacements on the tooth surface. Strains measured during composite placement were greater when the remaining cusp width was less. A stress relief procedure resulted in a decrease in cuspal strain and displacement of approximately 30–40%.

Meta-analysis on long-term clinical performance of posterior composite restorations

Meta-analysis is a formalized method of combining results of different studies to provide conclusions about the effectiveness of a treatment modality. The aims of this study were to use meta-analysis to determine the clinical performance of posterior composite restorations using the assessment criteria of the USPHS guidelines by combining data from selected multiple studies and to estimate the overall survival rates of posterior composite restorations over time. A computer-aided search of the literature revealed 97 publications on clinical trials of posterior composites in the last 10 years. Following specific selection criteria, which included the year and language of publication, duration of study, class of cavities restored and type of resin composite material used and clinical characteristics assessed; 16 studies were found to be suitable for, and included in a meta-analysis. These involved eight different resin composite materials. Assessment criteria data were extracted from each selected study and tabulated on the basis of years of follow-up and materials. The criteria were coded as binary variables. Homogeneity amongst studies was assessed using Woolf's statistic prior to combining the data. Weighted average proportions and standard errors were determined for each of the assessment criteria. Using Kaplan-Meier estimates, survival analyses of individual assessment criteria (outcomes) for two posterior composite materials were conducted and the resultant survival curves for these outcomes for the two materials are presented. Considering the limited number of studies of variable length available for meta-analysis, the results indicate generally high clinical performance of the various posterior composites for the number of outcomes analysed.

An unusual hypoplastic premolar: a case report

This case report describes an unusual hypoplastic maxillary first premolar tooth that was diagnosed radiographically in a 10-year-old boy. The maxillary primary first molar had been extracted. When the tooth erupted the hypoplasia was seen to be confined to the mesial aspect of the tooth. The cause of this unusual distribution was considered to be either infection associated with the mesiobuccal root of the primary first molar or trauma during extraction of the primary tooth. The tooth was restored using dentine adhesive and posterior composite material.

Three-year follow-up of five posterior composites: SEM study of differential wear

Assessing the wear of both enamel and composite at a shared occlusal contact area offers the opportunity to determine the differential wear between enamel and composite on the same tooth. Differential wear measurements were carried out on five posterior composite materials with an accurate 3D-measuring technique. The distinct wear step between enamel and composite was visualized by means of scanning electron photomicrographs. Both investigated ultrafine midway-filled and fine compact-filled composites (Willems et al., 1992a) have a considerably higher differential wear value and are, therefore, less suitable for rehabilitation of posterior teeth than are the ultrafine compact-filled composites, which have, in this study, a very satisfactory differential wear rate and appear to be highly wear resistant materials suitable for use in stress-bearing areas.

Cure profiles of visible-light-cured class II composite restorations in vivo and in vitro

The degrees of conversion of posterior composite material in Class II restorations performed in vivo and in vitro were studied by means of the Raman spectroscopy method. Class II restorations in 13 contralateral pairs of premolars were analyzed. The average difference of the ratio I 1610 cm −1/I 1640 cm −1 between the in vivo- and in vitro-performed restorations was 0.42. This indicates a higher grade of conversion in the in vivo situation.

Radiopacity of restorations and detection of secondary caries

The aim of this study was to compare the accuracy of radiographic diagnosis of secondary carious lesions adjacent to filling materials with different radiopacities. Class II preparations were made in extracted teeth. One group of teeth (n = 49) had caries in the gingival wall, simulating secondary caries. The control teeth (n = 29) had no caries. Three posterior composite materials (P-30™ and two experimental composites) with different radiopacities and amalgam were successively inserted into each cavity. After being radiographed, the “restorations” were removed and a new material inserted. The radiographs were interpreted by 11 dentists, and secondary caries was diagnosed according to a five-point confidence rating. The results obtained with the receiver operating characteristics (ROC) method showed that a semi-radiopaque restoration seemed favorable and that the best radiopacity slightly exceeded that of enamel.

The polymerization contraction of visible-light activated composite resins

The polymerization contraction of a number of commercially available composite resin restorative materials has been determined using a minimal load transducer to monitor dimensional change. The putative posterior composite materials underwent least contraction during setting, and there was moderate correlation between polymerization contraction and both the exotherm on polymerization and the filler loading (for non-microfine materials). Polymerization contraction was influenced by the shade of the material under test and the duration of the exposure to the activating light source.

In vitro temperature rises during visible-light curing of a lining material and a posterior composite.

The aim of this study was to measure the rise in temperature during: (i) a single cycle of a curing light unit, (ii) the polymerization of a layer of light-cured lining material, and (iii) the polymerization of a light-cured posterior composite material, and also during combinations of these individual procedures. Experimental work was undertaken in vitro and measurements were made using a thermocouple placed centrally in an insulated PTFE well. Large temperature rises occurred with the use of the curing light alone. The lining material itself did not contribute significantly to the rise in temperature during curing, nor did it provide thermal insulation from the output temperature emitted by the light guide. The presence of a layer of posterior composite reduced the temperature transmitted from the light but the residual temperature rise transmitted was still of such a magnitude as to cause concern regarding possible thermal injury to the pulp.

Microleakage of dentine-bonded posterior composite restorations

This in vitro investigation assesses the marginal leakage of extensive class II preparations that had been restored with light-cured posterior composite materials using dentine-bonding agents or glass-ionomer cement linings. The restored teeth were immersed in a marker dye solution while being subjected to thermal cycling treatment and, after sectioning the restorations, dye penetration at the restoration/tooth interface was assessed and quantified using digital imaging microscopy. Microleakage was observed at the cervical wall of all the restorations and was more extensive when the cervical cavity margin was located below the cemento-enamel junction. The use of a glass-ionomer cement lining significantly reduced the extent of cervical marginal leakage in this situation. Continued development of dentine-bonding agents and/or composite resin restoratives is required before a satisfactory marginal seal can be guaranteed when using these materials in the restoration of extensive cavities in posterior teeth.

Wear of posterior composite resins.

In vitro wear of sixteen posterior composite resins was determined by the glass beads abrasion test. The wear was remarkably greater with the thick slurry than with the thin slurry. Microfilled posterior composites were higher wear-resistant than highly loaded and blended posterior composites. There is little difference in wear between submicrofilled resins and microfilled resins with the thick slurry. This suggests that the filler particle size is relatively important to wear resistance of the posterior composite material. There was a close parallel between the results of the glass beads abrasion test and clinical observations. There is no consistency among the wear measurements in the toothbrushing abrasion test.

The development of surface hardness in visible light-cured posterior composites

The surface microhardness of four visible light-cured posterior composite materials was measured at a series of time intervals up to 1 month, commencing from the end of the light irradation period. The microhardness steadily increased with time and tended towards a maximum, usually reached after 1 week. In all cases the rate of increase was substantial over the first hour and was greater for samples stored at 37°C as compared with 20°C. These results reflect the progressive cross-linking reaction in the resin phase of the materials which continues after photoactivation. The surfaces of samples stored in water were softened compared to dry samples. Differences between materials may be attributed to compositional differences and extent of cure.