Abstract
Objectives
To investigate the effects of a silica-based whitening toothpaste containing blue covarine on the colour of restorations in extracted human teeth.
Methods
Human extracted teeth were mounted in acrylic resin. A cavity was cut into the enamel surface and the specimen restored with either glass ionomer or composite dental materials. Following 4 weeks storage in water, specimens were treated with either water, red wine or a toothpaste containing blue covarine (n = 10) for 24 h followed by brushing with a silica-based toothpaste. Specimens were imaged with a digital imaging system at baseline, after 24 h treatment and after brushing with a silica-based toothpaste. CIELAB colour parameters were determined for the restoration and the whole specimen and overall mean colour changes calculated (ΔE). Baseline and post-brushing images were compared subjectively for overall stain and staining around the restoration margin.
Results
Red wine produced the largest ΔE values for whole specimens and for all restoration materials and the largest subjective stain scores for whole specimens and restoration margins. The red wine stain was not completely removed by brushing with a silica-based toothpaste. Comparisons of the red wine group with either the blue covarine toothpaste group or the water group were of statistical significance for all parameters (ANOVA, Tukey-Kramer, p<0.05). Following brushing with the silica-based toothpaste, specimens from the blue covarine toothpaste group were not significantly different (p>0.05) to the water group, for all restoration material types.
Conclusions
Exaggerated treatment with a blue covarine containing toothpaste does not significantly affect the colour of the restoration or the restoration margin of the dental materials tested versus a water alone treatment.
Clinical significance
The silica-based blue covarine containing toothpaste does not permanently stain the restorative materials tested or their margins.
1
Introduction
Tooth whitening and aesthetics are areas of interest for patients and consumers. Typically, tooth whitening approaches are based either on tooth bleaching using peroxide containing products or whitening toothpastes containing enhanced abrasive and cleaning technologies. An alternative approach to tooth whitening is via an optical principle. This is achieved through, for example, the deposition of a blue pigment onto the tooth surface that counteracts the natural yellowness of teeth and thus gives an overall measureable improvement in tooth whiteness. These toothpastes are designed for regular use, producing an instant tooth whitening effect every time they are used. In addition, they also contain a silica abrasive system which can remove and control extrinsic stains without an increase in abrasion towards enamel and dentine versus a non-whitening silica control toothpaste. Thus, the user of these silica based toothpastes containing blue covarine will obtain both immediate and progressive tooth whitening benefits.
With the presence of restorations in many patients and consumers, a number of studies have investigated the colour stability of various restorations when exposed to chromogenic food and drink substances such as coffee and red wine. The interface between a dental restoration and the tooth structure is an important factor for its longevity in the mouth 11 and the aesthetic appearance of a restoration may deteriorate over time particularly by staining of the restoration margin. It is also important to ensure that any new oral care product will not have any adverse effects on dental materials including their potential impact on the dental materials aesthetic qualities such as colour and subsequent surface staining. For example, a study using dental materials fabricated into discs were subjected to an exaggerated 96 hour exposure to either water, a silica whitening toothpaste containing blue covarine or red wine. The study showed that the change in colour of the discs treated with the silica whitening toothpaste containing blue covarine was not significantly different from the water treated discs and in contrast to those discs treated with red wine.
The objective of the current study is to investigate the effects of a silica-based whitening toothpaste containing blue covarine on extracted human teeth restored with a range of typical dental materials. The change in colour was assessed objectively using digital imaging measurements and subjectively by a trained colour assessment panel, including the restoration margins. The null hypothesis to be tested is that the silica-based whitening toothpaste containing blue covarine will have no significant impact on the tested restoration and restoration margin colour versus water and red wine treatment controls.
2
Materials and methods
Human extracted incisors and premolars, obtained with informed consent and handled according to the UK Human Tissue Act, were mounted in acrylic resin blocks by embedding the roots into cold-cure acrylic resin (Simplex Rapid, Kemdent, Wiltshire, UK). They were then subjected to a restoration regime whereby an area of the buccal and labial aspect of the tooth was removed with a diamond bur and the tooth was restored using a selection of anterior restorative materials as described in Table 1 . There was no colour matching of the tooth to the restoration shade used in the experiment. All restoration materials used were shade A2.
| Material | Manufacturer | Description |
|---|---|---|
| Fuji II LC | GC, Belgium | Glass Ionomer |
| Ketac Fil | 3 M ESPE, USA | Glass Ionomer |
| Filtek Supreme | 3 M ESPE, USA | Composite |
| Spectrum | Dentsply, UK | Composite |
1.1 Preparation of tooth specimens restored with Fuji II LC
A cavity of approximately 3 mm wide by 1 mm deep was cut into the buccal and labial aspect of each tooth using a Hi-Di diamond bur, number 544 M. The cavity margins were treated with GC dentin conditioner for 10 seconds, washed, dried, and filled with Fuji II glass ionomer. The restoration material was cured with UV light for 20 seconds. These restorations were trimmed and polished using the ‘Enhance’ finishing system, after which, the finished items were glazed with GC Fuji II LC liquid and cured for 10 seconds.
1.2 Preparation of tooth specimens restored with Ketac Fil
A cavity of approximately 3 mm wide by 1 mm deep was cut into the buccal and labial aspect of each tooth using a Hi-Di diamond bur, number 544 M. The cavity margins were treated with Ketac conditioner for 10 seconds, washed, dried and filled with Ketac Fil glass ionomer. The restoration material was allowed to set for 7 minutes. These restorations were trimmed and polished using the ‘Enhance’ finishing system, after which, the finished items were glazed with Ketac glaze and cured for 10 seconds.
1.3 Preparation of tooth specimens restored with Filtek Supreme
A cavity of approximately 3 mm wide by 1 mm deep was cut into the buccal and labial aspect of each tooth using a Hi-Di diamond bur, number 544 M. The cavity margins were treated with Scotchbond acid etchant for 15 seconds, washed, dried and filled with Filtek Supreme composite resin. The restoration material was cured with UV light for 20 seconds. These restorations were trimmed and polished using the ‘Enhance’ finishing system.
1.4 Preparation of tooth specimens restored with Spectrum
A cavity of approximately 3 mm wide by 1 mm deep was cut into the buccal and labial aspect of each tooth using a Hi-Di diamond bur, number 544 M. The cavity margins were treated with Scotchbond acid etchant for 15 seconds, washed, dried, and filled with Spectrum composite resin. The restoration material was cured with UV light for 20 seconds. These restorations were trimmed and polished using the ‘Enhance’ finishing system.
2.1
Experimental Protocol
Specimens were stored in demineralised water after completion of the restoration procedure. Testing was performed on specimens after storage for approximately 4 weeks. Specimens were uniquely labelled and placed in sterile (gamma irradiated) pooled whole human saliva overnight to allow a salivary pellicle to form. Images at baseline were taken of each tooth using a non-contact digital camera imaging system (DIS) previously validated for measuring tooth colour. Each set of tooth restoration materials (n = 30) was subdivided into 3 treatment groups (n = 10 for each treatment regime). Group 1 was a control group and each specimen was treated with Milli Q water (Millipore, USA). Group 2 was the test group and each specimen was treated with the silica-based toothpaste containing blue covarine (1: 2 toothpaste: water). Group 3 was a positive control group and each specimen was treated with red wine (Cabernet Sauvignon, Wolff Blass, containing 13.5% alcohol by content). Specimens were submerged in the respective treatments and left for a contact time of 24 hours at room temperature. The teeth were rinsed in water and imaged with the DIS. Specimens were then brushed for 1 minute with a slurry of a silica-based toothpaste (1:2 toothpaste: water) and a flat trim toothbrush, rinsed with water and re-imaged with the DIS.
The digital images of the teeth at baseline, after 24hr treatment and after brushing with the silica-based toothpaste were analysed in Adobe Photoshop CS2 version 9 (Adobe System Inc., Seattle, WA, USA). The whole tooth plus restoration or the restoration alone was highlighted using the magnetic lasso tool to obtain values for red, green and blue (RGB) from within the highlighted region ( Fig. 1 ). The RGB values were then converted into CIELAB values using a modified version of the method described by Guan et al. The colour differences (ΔE) between baseline and post-treatment for the whole tooth specimen and restoration only were calculated using the equation below:
Δ E = ( Δ L * 2 + Δ a * 2 + Δ b * 2 )
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