Posterior Composites Research Articles

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.

Composites for use in posterior teeth: composition and conversion.

The purpose of this investigation was to determine the composition, as well as the conversion after polymerization, of some dental composite materials. Eight posterior composites and two anterior composites were investigated. The weight and volume fractions of inorganic fillers were determined by combustion and pycnometric analyses. The monomers were analyzed qualitatively and quantitatively by high performance liquid chromatography, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Infrared multiple internal reflection spectroscopy was applied for determination of conversion of the methacrylate groups. The conversion in light activated materials was examined at shallow depths, that is, the level of optimal conversion. This investigation demonstrated that the conversion can be correlated with the composition of monomers and oligomers used in the materials.

Surface characteristics of posterior composites after polishing and toothbrushing.

The surface characteristics of eight posterior and two anterior composite resins were studied by SEM and profilometric tracings. The materials included both chemically cured and light-cured resin systems. Two posterior materials were microfilled composites; the others were conventional or hybrid types. The anterior composites were of conventional and hybrid types. At various steps in the procedures the following polishing/brushing treatments were evaluated: 1) dry polishing with Sof-lex discs followed by brushing with toothpaste; and 2) wet polishing with diamond pastes of increasing fineness, followed by brushing with toothpaste. The base line before the polishing/brushing procedures was obtained by wet polishing on silicon-carbide paper (4000 grit). All materials could be polished to a comparable smoothness by the Sof-lex discs, but this polishing procedure was associated with the development of an amorphous surface layer. Polishing with diamond pastes gave various results, with a 20-fold difference in surface roughness values from the smoothest to the roughest material. Toothbrushing after polishing with the Sof-lex system increased the surface roughness for all materials, but to various degrees. The two microfilled and four of the conventional posterior composites showed comparable surface roughness values, whereas two remaining posterior and the two anterior materials showed two to three times higher surface roughness values after toothbrushing.

Influence of the patient and type of articulation on the loss of substance from possterior composites: preliminary results

This short communication reports the preliminary findings of a study of the influence of the patient and type of articulation on the loss of substance from posterior composites. The results obtained are consistent with the view that loss of substance from posterior composites may be relatively small if restorations of these materials are free of contact areas with opposing teeth. Loss of substance from posterior composites may initially be greater in patients with group articulation rather than cuspid guidance.

The wear of a posterior composite in an artificial mouth: a clinical correlation

Abstract The wear of a posterior composite against a maxillary palatal cusp was studied in an artificial mouth. The coefficient of wear for the composite was 2.58×10 −5 . A retrospective clinical correlation with composite wear in the artificial mouth showed a correlation coefficient of 0.84 at 1 year of wear. The artificial mouth studies support a parabolic relationship between depth of composite wear and time. The ratio of 6 months depth of wear compared to 3 years was found to be 41% which supports the Leinfelder finding (5) of 49%. However, the correlation with the linear studies of Braem (2,3) was good as far as the mean depth of wear at 1 year was concerned. The disagreement between the linear and parabolic studies is small during the early wear process, but becomes serious during a longer term. It is important for future clinical wear studies to resolve the question of the nature of the wear rate curve in posterior composites, if accurate prediction of long term performance is to be achieved.

Water sorption and filler characteristics of composites for use in posterior teeth.

The purpose of this investigation was to determine the water sorption and solubility, as well as the filler composition and extent of chemical degradation in water, of eight different posterior composites. With one exception, the materials with the largest quantity of fillers had the least water sorption and solubility after three months in water at 37 degrees C. The emission spectroscopy results showed that silicon was the major element in all the fillers except one, which had both silicon and strontium as major elements. Other components registered in quantities of 5-10 wt-% were barium, aluminum, zinc, and zirconium. The leaching of inorganic ions into water from the fillers varied depending on filler composition and filler treatment.

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.

Radiopacity of posterior composites

The radiopacity of 21 posterior composites was determined with reference to an aluminium step wedge and an equivalent thickness of enamel and dentine. Thirteen composites exhibited a radiopacity equal to, or greater than, that of the enamel. Five materials were less radiopaque than the dentine examined.

In vivo evaluation of four posterior composites: quantitative wear measurements and clinical behavior.

In vivo evaluation of four posterior composites: quantitative wear measurements and clinical behavior.

Composites for use in posterior teeth: mechanical properties tested under dry and wet conditions.

The purpose of this investigation was to determine some mechanical properties of eight different posterior composites, and how they are affected by water sorption. Creep characteristics in compression were expressed as compliance/log time functions. Stress-strain relationship at a constant loading rate was determined both in compression and flexure, and presented as elastic modulus, ultimate strength, and ultimate strain. Water sorption increased creep values for all materials. Generally, the materials with the highest water sorption had the highest increase in creep. Water sorption decreased the elastic modulus and ultimate strength values. The creep values decreased and the elastic modulus increased with increasing quantity of inorganic fillers.

Loss of substance of dental composite restorations.

Abstract A method for the direct in vivo measuring of loss of substance of Class I and II restorations was tested. On models of the teeth involved, silver caps were made. The occlusal surface was relieved by a piece of tinfoil. With the silver cap, silicone impressions were made for baseline registration and also at 3 recall periods, 6, 12 and 18 months after baseline registration respectively. The average thickness of the loss of substance was computed by the weight, the density and the thickness of both the enclosed impression material and the piece of tinfoil. The results show the in vivo repeatability of the test method to be in good agreement with data obtained in a previous in vitro study. The error of the test method accounts only for a relatively small part of the total experimental variance (7, 9 and 12%). The wear values show that the method registers, with adequate accuracy, wear rates of approximately 20 μm/year. Because of its simplicity, inexpensiveness and accuracy, the method is highly productive and suitable for clinical screening tests of the wear behaviour of restorations, especially for the registration of losses of substance of posterior composites.

P-10--its potential as a posterior composite.

P-10, a hybrid composite resin marketed as a genuine resin-based amalgam substitute, has been evaluated for its effectiveness in stress-bearing posterior restorations. Radiopacity and marginal adaptation were assessed in vitro in MOD-restorations; wear data were derived from 8 MOD's after 2.5 years in vivo . The insufficient radiopacity, the poor marginal adaptation and the high wear rate preclude P-10 as an amalgam substitute.

In vivo wear of posterior composites and its counterplan before or after insertion

In vivo wear of posterior composites and its counterplan before or after insertion

Color and optical properties of posterior composites under accelerated aging.

Color and optical properties of posterior composites under accelerated aging.

A method to determine the loss of substance of dental restorations.

A method is described for quantitative in vivo wear measurements on Class I and II composite restorations. Class I gold inlays were made in an acrylic premolar and molar. Over the occlusal parts of the teeth cast silver caps were made after releasing the surface of the inlay with tinfoil. Wear on the restorations was simulated by grinding away some gold from the inlay. Silicon impressions of the teeth were made with the caps both before and after this simulation. The volume and the average thickness of the removed gold was measured from the weight of the enclosed impression material in the cap before and after the wear simulations, the density of the tinfoil and the impression material as well as thickness and the weight of the tinfoil-release. Values expected for the volume and the average thickness of the removed gold were calculated from the weight of the restored acrylic teeth before and after the wear simulation, the weight, the density and the thickness of the tinfoil and the density of the gold used for the inlays. Measured and expected values are linearly correlated (r = 0.97). An average wear thickness of the occlusal surface of a particular tooth of at least 30 micron can be detected. Because of its simplicity, inexpensiveness and accuracy the wear measurement method is highly productive and suitable for large scale and long-term clinical research on the wear behaviour of posterior composites.

In vivo evaluation of occlusal wear of two experimental composites versus amalgam

Two experimental inhomogeneous microfilled composites with spherical prepolymerized particles and an interpenetrating network (IPN), which provides a stable bond between prepolymerized spheres and the matrix (B-21 and B-51), and amalgam were used for Class II MOD fillings in mandibular molars. After 3 and 6 months of clinical use, wear of the material was measured with a replica technique and a modified surface roughness test. The failure mode was analysed with SEM photographs also using a replica technique. After 6 months the wear of the composites in the occlusal contact area was more than twice as high as the substance loss of amalgam. It was concluded that the composites were not suitable for fillings bearing occlusal load. However, the failure mode seen in the SEM for B-21 indicated that the IPM leads to a stable incorporation of the spherical prepolymerized particles into the matrix. Due to its good surface characteristics B-21 should be further investigated for its use as an anterior composite. B-51 was especially designed as a posterior composite. Beside the construction elements of B-21 it contained also barium glass spheres to obtain radiopacity. This hybrid construction failed due its wear mode.