|Year : 2013 | Volume
| Issue : 1 | Page : 11-17
Effect of alcoholic and non-alcoholic beverages on the wear and fracture toughness of teeth and resin composite materials: In vitro study
Fatema Yusuf, A Srirekha, Jayshree Hegde, Rupali Karale, Kusum Bashetty, Savitha Adiga
Department of Conservative Dentistry and Endodontics, The Oxford Dental College and Hospital and Research Centre, Bangalore, Karnataka, India
|Date of Web Publication||29-Apr-2013|
Postgraduate Student, Department of Conservative Dentistry and Endodontics, The Oxford Dental College and Hospital and Research Centre, Bangalore
Source of Support: None, Conflict of Interest: None
Background: Tooth wear is becoming more apparent in the early stages of life. Consumption of alcoholic beverages and non-alcoholic beverages have highest buffering capacity and low pH values show pronounced erosive effect on enamel and degradation rate of composite materials. Hence the purpose of this study is to compare wear and degradation of two resin composite materials and teeth in presence of different alcoholic and non-alcoholic beverages. Materials and Methods: Total 75 specimens comprising of composite blocks (Z350 and P90) and mandibular molars were divided into experimental groups (A, B, and C) ( n = 25). The experimental liquids were water, Sprite® , Coke® , Kingfisher® Beer, and Golconda® Wine ( n = 5). The specimens were weighed using a digital weighing balance. Wear was carried in Wet Abrasive Wear Tester. SEM evaluation was done. Fracture toughness performed with universal testing machine. Results: In Groups A and B significant weight loss in all experimental beverages, maximum in alcoholic beverages ( P < 0.05). SEM showed surface irregularities, filler/matrix interfacial failure, and significant decrease in fracture toughness in Groups A and B. In Group C significant weight loss and decrease in fracture toughness maximum in non-alcoholic beverages ( P < 0.05). SEM showed significant wear and surface irregularities. Conclusions: It was concluded that significant amount of wear of dental composite materials and teeth seen in presence of alcoholic and non-alcoholic beverages. All the experimental groups displayed statistical significant decrease in fracture toughness in presence of all beverages.
Keywords: Alcoholic and non alcoholic beverages, composite resin, composite restorations, degradation, fracture toughness, teeth, wear
|How to cite this article:|
Yusuf F, Srirekha A, Hegde J, Karale R, Bashetty K, Adiga S. Effect of alcoholic and non-alcoholic beverages on the wear and fracture toughness of teeth and resin composite materials: In vitro study. J Res Dent 2013;1:11-7
|How to cite this URL:|
Yusuf F, Srirekha A, Hegde J, Karale R, Bashetty K, Adiga S. Effect of alcoholic and non-alcoholic beverages on the wear and fracture toughness of teeth and resin composite materials: In vitro study. J Res Dent [serial online] 2013 [cited 2019 Aug 21];1:11-7. Available from: http://www.jresdent.org/text.asp?2013/1/1/11/111227
| Introduction|| |
Tooth wear is a common entity with increased incidence in the recent years. Old age, lifestyle trends, urbanization, dietary habits associated with excessive consumption of soft drinks and alcoholic drinks have increased the risks of erosion of tooth and restoration. Soft drinks, fruit juices, sports, and energy drinks are highly acidic. , Unfortunately, these drinks are popular as thirst quenchers amongst the youth of today and the habit is carried over into adulthood leading to a major cause of erosion. Wear of teeth is commonly presented with increased dentinal sensitivity and cervical lesion due to erosion and abrasion. Clinicians understanding on the mechanism of wear on tooth and restorative material are important considering the erosive potential of acidic drinks.
Clinically-worn composite restorations revealed extensively damaged layers on non-stress bearing areas. Accordingly, it was assumed that the oral environment has an appreciable influence on the in vivo degradation of these materials.  Wear of restorations is quantified as vertical loss of substance, is material-specific and most obvious in the occlusal contact point areas.  Damage in dental composites may result in matrix and/or filler deterioration, due to mechanical and/or environmental loads, interfacial debonding, microcracking, and/or filler particle fracture leading to a decrease in mechanical strength.  Hence fracture occurs when the stress concentration inside the material reaches the critical level. It is not known if the alcohol in typical alcoholic beverages has a negative effect on the wear resistance of composite materials.
The hypothesis tested in this study was to evaluate wear, degradation, and fracture toughness of methacrylate-based and silorane-based resin composite materials in alcoholic and non-alcoholic beverages.
| Materials and Methods|| |
The experimental groups were as follows: Group A - Methacrylate-based composite blocks (Filtek Z350 XT; 3M ESPE, St. Paul, MN, USA) (n = 25). Group B - Silorane-based composite blocks (Filtek P90 XT; 3M ESPE) (n = 25). Group C- Intact human permanent mandibular molar teeth (n = 25).
The Groups A and B composite cylindrical blocks were prepared by applying 2-mm increments and were light cured in four overlapping segments using a standardized plastic mould of 8-mm length and 5-mm diameter. The samples were cured as per manufacturer's instructions. Each block was polished using the Super-Snap polishing system according to the manufacturer's instructions (Shofu Inc, Kyoto, Japan). All the samples were stored at 37°C in distilled water for 24 hours. In Group C, intact human mandibular molars were collected and sectioned horizontally at the cement-enamel junction.
Abrasive slurry was prepared using a combination of white rice and whole wheat. The seeds were ground dry in a blender for 30 seconds prior to mixing with the experimental liquids. Seven hundred grams of powdered wheat and rice were mixed in 2 l of experimental liquid and 1 g of sodium azide to inhibit bacterial growth.  The experimental liquids were water (control), Sprite® , Coke® , Kingfisher® Beer, and Golconda® Wine.
Subsequently, Group A, B, and C were further divided into 5 subgroups (abrasive slurry + experimental liquid) (n = 5).
The specimens of Group A, B, and C were weighed before subjecting it to experimental liquids using a digital weighing balance (GE812 Sartorius, Germany) having an accuracy of 0.001 g. The wear was carried out in Wet Abrasive Wear Tester (Flow and Force Engineers, Bangalore) for 2,50,000 revolutions at 100 rpm. The abrasive mixtures were mixed fresh for each specimen wheel and rotated at 1 revolution per second and the slip rate was 15% during the tests.  In between the experimental period the samples were stored temporarily in distilled water to mimic oral environment. After the experiment was completed immediate weight loss was analyzed and the difference in weight was evaluated. Scanning electron microscope (SEM) evaluation was carried out for all the specimens at ×1000 magnification (JEOL JSM-5200 SEM).
Fracture toughness was measured using a universal testing machine (LR 50K; LLOYD Instruments) under a compressive force at a strain rate of 0.5 mm per min and the force needed to fracture each sample was recorded in Newtons.
| Results|| |
The results were subjected to statistical analysis using Analysis of variance (ANOVA) and post hoc Tukey test for pair wise comparison of groups, Student ' t' test (two tailed, dependent) was used to find the significance of study parameters on continuous scale within each group. Statistical significance was set as P ≤ 0.05 and presented as follows:
The results of the present study revealed that in Group A, beer showed significant weight loss followed by Sprite, Coke, and wine [Table 1], [Graph 1[Additional file 1]], [Figure 1]. Fracture toughness results indicate least values with wine followed by Coke and Sprite. Beer showed insignificant decrease in fracture toughness [Table 2], [Graph 2[Additional file 2]].
|Figure 1: Group A shows filler dislodgement and softening of resin matrix in all sample.|
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|Table 1: Comparative evaluation of effect on weight (mg) in experimental groups|
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|Table 2: Comparative evaluation of fracture toughness (N) in different beverages in experimental groups|
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In Group B, beer and wine showed maximum weight loss, followed by Coke and Sprite [Table 1], [Graph 1], [Figure 2]. The fracture toughness results revealed that Coke showed least fracture toughness followed by wine, Sprite, and beer [Table 2], [Graph 2].
|Figure 2: Group B large amount of filler dislodgement and softening of resin matrix have been observed among all samples|
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In Group C, non-alcoholic beverages like Coke and Sprite showed maximum weight loss in comparison to alcoholic beverages [Table 1], [Graph 1], [Figure 3]. Some amount of surface irregularities and pitting were also seen with alcoholic beverages. Sprite and Coke showed strongly significant decrease in fracture toughness in comparison to water [Table 2], [Graph 2].
|Figure 3: Group C, acidic drinks promoted a significant wear in the form of etching like pattern with loss of inter prismatic substances on the dental enamel. Also some amount of surface irregularities and pitting was seen with alcoholic beverages as well|
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| Discussion|| |
Tooth wear is a universal condition with most people affected during their lives. Excessive consumption of soft drinks and alcoholic drinks has increased the risks of erosion of tooth and restoration. The dominance of the market by these drinks in our country in the recent years has resulted in a broad segment of the population consuming these beverages. Consequently the erosive potential of these drinks on teeth and restoration need to be studied.
Despite improvements in composite materials, wear is still a cause of clinical failure, particularly in high stress areas such as molar restorations and for patients with occlusal parafunction. Generalized three body wear occurs from movement of abrasive food slurries during mastication. Three-body wear of composites involves the process of resin matrix loss between filler particles and subsequent dislodgement of the filler.  Filler loading, size, and inter-particle spacing are important in protecting the resin matrix from wear. Filler/matrix cracking caused by water adsorption and hydrolytic degradation of the filler surface is known to increase the wear of composites. 
The present investigation was initiated to evaluate the wear and degradation of methacrylate, silorane-based resin composite materials and teeth in alcoholic and non-alcoholic beverages. Epidemiological studies have shown carbonated and non-carbonated beverages cause erosion. , Hence, non-alcoholic beverages like Sprite and Coke and alcoholic beverages like wine and beer were investigated in this study.
Coarse abrasive slurry was prepared according to the guidelines followed by de Gee et al.  One gram of sodium azide was added in the mixture to inhibit bacterial growth and fermentation. All experimental liquids except wine were allowed to stand in an open container for 48 h in a refrigerator to allow the carbonation to decrease, this was necessary to prevent abrasive slurry from foaming during the wear experiments.
The result of the present study revealed that, in Group A beer showed increased wear and significant weight loss ( P = 0.003) which could be attributed to the ethanol concentration in beer (8% volume) combined with pH levels of 3.9. A likely reason for increased wear caused by ethanol has been postulated by Sarrett.  Following beer, Sprite has contributed to significant amount of weight loss ( P = 0.006) and fracture toughness ( P ≤ 0.001), which might be due to the low pH of 3.2, high sugar content, and titrable acidity. Citric acid is the predominant acid in non-cola drinks; its ability to chelate calcium at higher pH levels makes it especially erosive. Coke and wine also showed significant weight loss ( P = 0.034, P = 0.040) and decreased fracture toughness ( P ≤ 0.001, P = 0.001). Irrespective of high ethanol concentration (9% volume) and pH (3.3), wine showed least significant weight loss as it does not contain phosphoric acid and contains citric acid only in minute quantities. , The degree of erosion for Coke may depend on its pH (2.5) and presence of caffeine. Also the type of acid, total acid level, calcium, phosphate, fluoride concentration, calcium chelating properties of the beverages and salivary flow may be more important factors affecting the overall clinical wear of tooth and restorations.
SEM results in Group A revealed filler/matrix interfacial failure. Also filler dislodgement, softening of resin matrix, increased chipping and wear of the filler was seen [Figure 1].  This could be caused by leaching of the diluents such as triethylene glycol dimethacrylate (TEGDMA).  This is in accordance with the results of previous studies done by Wongkhantee et al., Studies have shown that organic acids were found to induce softening of bisGMA-based polymers.  Aging of composites in water appeared to increase filler particle pull-out on the surface, possibly due to breakdown of the silane bond between the resin and the filler particle. 
In Group B, beer and wine showed maximum weight loss ( P = 0.004) followed by Coke ( P = 0.016). As previously discussed various factors such as pH value, titrability, and other factors may have contributed to this result. Alcoholic and non-alcoholic beverages showed significant decrease in fracture toughness as well.
SEM also revealed large amount of filler dislodgement and softening of resin matrix [Figure 2]. Increased loss of filler may be seen due to the degradation of siloxane and oxirane hybrid monomer system. No studies have been done regarding the wear properties of silorane composites hence future research may provide some insight on the wear patterns observed in silorane composites.
In Group A and B, the decrease in fracture toughness could be a result of degradation of the cross-linked matrix in the dental composite, and hydrolysis of the filler-matrix interfaces eventually leading to a decrease in mechanical properties.  Other theories as to the cause of degradation of dental resin include the formation of microcracks through repeated sorption/desorption cycles, leading to hydrolytic degradation of the polymer. The degradation of polymers may be due to passive hydrolysis or enzymatic reaction, oxidation reactions and potentially transesterification, in water or alcohol.  Lee et al. used micro FTR analysis to provide evidence for degradation attributable to either hydroperoxidation or transesterification of composites in alcohol. 
In Group C, maximum weight loss and least fracture toughness was seen in Coke ( P = 0.003), the reasons for this remain the same as mentioned above. This is closely followed by Sprite (P = 0.009). These variables may have also been influenced by the concentration of different ions such as phosphate, fluoride, and calcium.  In carbonated beverages, the type and the concentration of the acid influences the erosive potential. The acid dissolution constant (pKa) is inversely related to enamel demineralization. Hence, citric acid is more destructive on tooth because of its low pKa value.  The alcoholic beverages also showed significant weight loss with wine (P = 0.229) and beer (P = 0.3). Presently, literature presents data of experiments conducted on tooth surfaces exposed to 75% ethanol concentration have shown indications of wear.  In Group C, although water alone will not have an effect on teeth, the combination of water mixed with abrasive slurry may have caused degradation of the tooth structure affecting its physical properties.
In Group C, SEM photographs showed that non-alcoholic beverages promoted a significant wear and presented an etching pattern with loss of interprismatic substances on the dental enamel as observed in previous studies [Figure 3].  In addition, some amount of surface irregularities and pitting were also seen with alcoholic beverages as well.
The constant exposure of the materials to the beverages during wear testing is not consistent with the intermittent exposure that occurs in vivo and thus is a limitation of the experiment.
Further studies need to be done to provide some insight to clinicians regarding wear and sensitivity in teeth and also the longevity of restorations in oral cavity.
| Conclusions|| |
Metharcylate-based (Group A) and silorane-based (Group B) composite resins displayed significant increase in weight loss and decreased fracture toughness in the presence of alcoholic beverages and non-alcoholic beverages (P < 0.05).
- Teeth (Group C) displayed increased weight loss and decreased fracture toughness in presence of non-alcoholic beverages than alcoholic beverages.
- On inter group comparison silorane-based composite were affected maximum in weight loss and fracture toughness followed by metharcylate-based composites and teeth.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]