Surface deterioration of dental materials after simulated toothbrushing in relation to brushing time and load

Abstract

Objectives

(1) To evaluate the changes in surface roughness and gloss after simulated toothbrushing of 9 composite materials and 2 ceramic materials in relation to brushing time and load in vitro; (2) to assess the relationship between surface gloss and surface roughness.

Methods

Eight flat specimens of composite materials (microfilled: Adoro, Filtek Supreme, Heliomolar; microhybrid: Four Seasons, Tetric EvoCeram; hybrid: Compoglass F, Targis, Tetric Ceram; macrohybrid: Grandio), two ceramic materials (IPS d.SIGN and IPS Empress polished) were fabricated according to the manufacturer’s instructions and optimally polished with up to 4000 grit SiC. The specimens were subjected to a toothbrushing (TB) simulation device (Willytec) with rotating movements, toothpaste slurry and at three different loads (100 g/250 g/350 g). At hourly intervals from 1 h to 10 h TB, mean surface roughness Ra was measured with an optical sensor and the surface gloss (Gl) with a glossmeter. Statistical analysis was performed for log-transformed Ra data applying two-way ANOVA to evaluate the interaction between load and material and load and brushing time.

Results

There was a significant interaction between material and load as well as between load and brushing time ( p < 0.0001). The microhybrid and hybrid materials demonstrated more surface deterioration with higher loads, whereas with the microfilled resins Heliomolar and Adoro it was vice versa. For ceramic materials, no or little deterioration was observed over time and independent of the load. The ceramic materials and 3 of the composite materials (roughness) showed no further deterioration after 5 h of toothbrushing. Mean surface gloss was the parameter which discriminated best between the materials, followed by mean surface roughness Ra. There was a strong correlation between surface gloss and surface roughness for all the materials except the ceramics. The evaluation of the deterioration curves of individual specimens revealed a more or less synchronous course suspecting hinting specific external conditions and not showing the true variability in relation to the tested material.

Significance

The surface roughness and gloss of dental materials changes with brushing time and load and thus results in different material rankings. Apart from Grandio, the hybrid composite resins were more prone to surface changes than microfilled composites. The deterioration potential of a composite material can be quickly assessed by measuring surface gloss. For this purpose, a brushing time of 10 h (=72,000 strokes) is needed. In further comparative studies, specimens of different materials should be tested in one series to estimate the true variability.

Introduction

The surface texture of dental materials has an influence on the accumulation of plaque, which may lead to gingival and periodontal inflammation as well as the discoloration of restorations and thus impair their esthetical appearance. Furthermore, a smooth surface adds to the patient’s comfort as already differences in surface roughness of 0.3 μm can be detected by the tip of the patient’s tongue . Increasing surface roughness is correlated with increased deposition of plaque and roughness is a determining factor for staining . In vivo studies on the threshold surface roughness for bacterial plaque retention showed that a mean roughness of above 0.2 μm was related to a substantial increase in bacterial retention .

While ceramic materials are considered to be rather inert, i.e. they do not change very much during their service life in the oral cavity, composite materials suffer degradation due to mechanical and/or chemical interaction with the oral environment. In addition to intrinsic roughness, brushing with a toothbrush and abrasive toothpaste plays an important role in the changes of surface roughness observed with restorative materials. In particular, full-coverage composite crowns and bridges have been shown to demonstrate loss of lustre, increasing roughness and staining in various clinical studies conducted with different materials .

Studies that evaluated the effect of toothbrushing on the deterioration of composite resin materials for direct and indirect use showed a rapid increase in surface roughness and found differences between the materials . As different parameters (number of strokes, load, toothpaste) were used in the studies, the results can hardly be compared. The evaluation of the deterioration capacity by simulated toothbrushing in vitro might be a surrogate parameter to assess the ability of a material to maintain its gloss and smoothness and prevent staining of the material. Systematic studies with regard to in vitro / in vivo comparisons are missing.

Little information is available about the influence of the toothbrush and toothpaste on the surface texture of current dental materials including ceramics as a function of brushing time and pressure load.

The objective of the present study was to measure the surface roughness and gloss of current dental materials (composite, ceramic) before and after brushing with toothpaste slurry in a device for simulated toothbrushing as a function of brushing time and load.

The following hypotheses were formulated:

  • 1.

    The surface roughness and surface gloss of composite materials will increase with increasing brushing time and load while that of ceramic will remain unchanged. There are, however, material-dependent differences.

  • 2.

    It is possible to establish a brushing time which is considerably shorter than 10 h after which no major changes of the surface roughness and surface gloss will occur.

  • 3.

    There is a close correlation between surface roughness and surface gloss.

Materials and methods

Eleven materials were selected, i.e. 9 composite resins for direct and indirect use and 2 ceramic materials ( Table 1 ).

Table 1
List of the products used in the present study, abbreviation, batch number and material group code. Data on filler particles and matrix derive from instructions of use or technical data sheets.
Composite materials Abbreviation Batch number Material group code Mean particle size (μm) Particle type Matrix type
Adoro ADO F33584 Microfilled 0.4 SiO 2
Copolymer
DMA
UDMA
Four Seasons FOS F45485 Microhybrid 0.6 YbF 3
Ba–Al-fluorsilicate
SiO 2 mixed oxide
Bis-GMA
UDMA
TEGDMA
Compoglass F COG E40043 Hybrid 1.0 YbF 3
Ba–Al-fluorsilicate mixed oxide
UDMA
TEGDMA
Dicarboxylic acid DMA
Filtek Supreme SUP 3910 Microfilled 0.4 Zirconia/silica clusters Bis-GMA
UDMA
TEGDMA
Bis-EMA
Grandio GRA 431787 Macrohybrid 2.0 SiO 2 Bis-GMA
TEGDMA
Heliomolar HEL F63962 Microfilled 0.1 YbF 3
SiO 2
Copolymer
Bis-GMA
UDMA
Decandio-DMA
Targis TAR F44880 Hybrid 1.0 Ba–Al-fluorsilicate
SiO 2 mixed oxide
Bis-GMA
UDMA
TEGDMA
Decandio-DMA
Tetric Ceram TC E70886 Hybrid 0.7 YbF 3
Ba–Al-fluorsilicate
SiO 2 mixed oxide
Bis-GMA
UDMA
TEGDMA
Decandio-DMA
Tetric EvoCeram TEC G24606 Microhybrid 0.6 YbF 3
Ba–Al-fluorsilicate
SiO 2
Copolymer
Bis-GMA
UDMA
Decandio-DMA
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Nov 30, 2017 | Posted by in Dental Materials | Comments Off on Surface deterioration of dental materials after simulated toothbrushing in relation to brushing time and load
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