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Table of Contents   
ORIGINAL RESEARCH  
Year : 2013  |  Volume : 24  |  Issue : 3  |  Page : 321-325
Evaluation of shear bond strength of three different types of artificial teeth to heat cure denture base resin: An in vitro study


1 Department of Prosthodontics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, Nalgonda (Dt), Andhra Pradesh, India
2 Private Practice, H.No: 4, OM Nilaya, Rampure Bank Colony, Bidar, India

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Date of Submission06-Sep-2012
Date of Decision21-Sep-2012
Date of Acceptance04-Nov-2012
Date of Web Publication12-Sep-2013
 

   Abstract 

Context: Bonding of artificial teeth and denture base material remained a significant problem for successful prosthetic treatment.
Aim: The purpose of this in vitro study was to evaluate shear bond strength of three different artificial teeth with heat cure denture base material after various surface conditioning methods and thermocycling.
Materials and Methods: Ninety mandibular first molar denture teeth were selected. They were divided into three groups, Group I: Nanocomposite resin (Veracia), Group II: Composite teeth (Endura), and Group III: Cross-linked acrylic denture teeth (Acry rock). All groups were further subdivided into subgroups based on surface conditioning methods. Subgroup A: No surface conditioning (control group), Subgroup B: Surface conditioning with methyl methacrylate-based bonding agent (Vitacoll), and Subgroup C: Air abrasion with 50 μm aluminum oxide powder particles plus silane-coupling agent (Monobond-S) and Vitacoll bonding agent. Evaluation of shear bond strength of all the specimens was done using universal testing machine.
Results: Mean shear bond strength of Group I, Subgroup B (6.87 ± 0.934) showed higher value when compared with Group II, Subgroup B (6.76 ± 1.84) and Group III, Subgroup B (5.66 ± 2.18). The control group (untreated surface) of all three types of artificial teeth used in this study showed significantly lower shear bond strength values than experimental groups (surface conditioning methods; P < 0.05).
Conclusion: The results of this study suggest that there were significant differences in shear bond strength among control group and surface treatment groups of denture teeth bonded to heat cure denture base resin.

Keywords: Composite teeth, heat cure denture base resin, nanocomposite teeth, shear bond strength, surface conditioning

How to cite this article:
Chittaranjan B, Taruna M, Sudheer N, Patil NS. Evaluation of shear bond strength of three different types of artificial teeth to heat cure denture base resin: An in vitro study. Indian J Dent Res 2013;24:321-5

How to cite this URL:
Chittaranjan B, Taruna M, Sudheer N, Patil NS. Evaluation of shear bond strength of three different types of artificial teeth to heat cure denture base resin: An in vitro study. Indian J Dent Res [serial online] 2013 [cited 2019 Dec 13];24:321-5. Available from: http://www.ijdr.in/text.asp?2013/24/3/321/117994
Modern technology has offered considerable advances in the materials used to make artificial teeth and improved techniques for affixing them to the denture base resin. Acrylic teeth have long been used in the fabrication of complete dentures. Newer materials like composite denture teeth are used in prosthodontic practice. In implant dentistry, these teeth could be used in either implant-supported or implant tissue-supported dentures. The acrylic teeth have a linear polymer chain structure, whereas all modified resin teeth have cross-linked structure. Besides adding cross-linking agents to methyl methacrylate monomer, acrylic resin can be improved by interpenetrating polymer network, which sinters the cross-linking agent into acrylic polymer chain. [1]

Composite resin artificial teeth are considered to be advantageous when used as the super structure for implants because of their greater shock absorbing capacity. [2],[3] These multilayered structures provide improved esthetic appearance. Adequate bonding of denture teeth to denture base resin is necessary because it increases stiffness and strength since teeth become an integral part of prosthesis. [4] Pre-fabricated acrylic resin teeth for dentures were introduced in 1940. Since then, this material has become the most popular artificial material for denture teeth. Apart from economical advantage, it also bonds chemically to the denture base. [5] However, the fracture and debonding of acrylic teeth from acrylic resin denture base are common clinical problems. Cunningham et al. [6] in a review of bond strength of denture teeth to acrylic resin also noted that as many as one-third of denture repairs are mainly due to debonding of teeth from denture base.

The purpose of this in vitro study was to evaluate the shear bond strength of three commercial brands of denture teeth of varied composition: Cross-linked acrylic resin (Acry rock), composite teeth (Endura), and nanocomposite teeth (Veracia) to the heat cure denture base resin after various surface conditioning methods and thermocycling.


   Materials and Methods Top


Materials and preparation of the specimens: A total of 90 mandibular first molar artificial denture teeth were selected. All the samples were divided into three groups depending upon the composition of the teeth and each group further divided into subgroups depending on surface conditioning methods [Table 1].
Table 1: Distribution of samples

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Initially, the base surfaces of all acrylic teeth were planned. A hollow aluminum block of 25 × 15 mm was filled with modeling wax. A total of 90 wax blocks with aluminum shield were prepared. Teeth representing each of the three groups were manually positioned and fused with wax onto each of the fabricated wax blocks [Figure 1] and [Figure 2]. Wax block patterns were invested in the flask and dewaxing was done. Base and counter of the flask were then separated and the residual wax was removed by flushing boiling water into the mold.
Figure 1: Nanocomposite teeth (Veracia) positioned in aluminum wax blocks

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Figure 2: Composite teeth (Endura) positioned in aluminum wax blocks

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Surface conditioning methods

Thirty teeth from each of different compositions, used in this study, were further subdivided into three subgroups of 10 each, which were subjected to different surface conditioning methods.

Subgroup A: No surface conditioning (control group).

Subgroup B: Methyl methacrylate-based bonding agent (Vitacoll) was applied on the prepared ridge lap area of tooth surface following the manufacturer's instructions and allowed to evaporate [Figure 3].
Figure 3: Surface conditioning with methyl methacrylate bonding agent (Vitacoll)

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Subgroup C: Air abrasion with 50-μm aluminum oxide particles modified with silicon oxide (blasting protocol pressure, 2.8 bar; distance, 10 mm; perpendicular to ridge surface; time, 20 s) was applied to the prepared ridge lap area of tooth surface. Thereafter, a silane-coupling agent (Monobond-S) was applied and the teeth were allowed to dry for 5 min and then Vitacoll bonding agent was applied [Figure 4].
Figure 4: Surface conditioning with silane‑coupling agent (Monobond‑S)

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Packing and curing

Heat cure denture base resin (Dental Products of India™) was used in this study as denture base material. Polymerized blocks were removed from plaster mold and cleaned.

Thermocycling

All specimens were stored in distilled water for 7 days at 37°C and 100% humidity and then they were thermocycled 1000 times from 5°C to 55°C with a dwell time of 1 min at each temperature.

Shear bond strength testing and measurements

Autograph 50 KN Universal testing machine was used in this study to evaluate the shear bond strength. The data were analyzed using relevant statistical analysis ANOVA, Tukey multiple post-hoc test in consultation with statistician.


   Results Top


In Group I, the mean shear bond strength in Subgroup A was 3.87 ± 0.89, whereas in Subgroup B and Subgroup C, it was 6.87 ± 0.934 and 6.88 ± 1.41, respectively, and the difference was found to be statistically significant.

In Group II, the mean shear bond strength in Subgroup A was 4.61 ± 0.88, whereas in Subgroup B and Subgroup C, it was 6.76 ± 1.84 and 5.95 ± 1.86, respectively, and the difference was found to be statistically significant.

In Group III, the mean shear bond strength in Subgroup A was 3.62 ± 1.04, whereas in Subgroup B and Subgroup C, it was 5.66 ± 2.18 and 5.34 ± 2.25, respectively, and the difference was found to be statistically significant [Table 2], [Figure 5].
Table 2: Mean, standard deviation, and coefficient of variation according to main and subgroups

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Figure 5: Mean and standard deviation of bond strength according to main and subgroups

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   Discussion Top


The success of complete denture over a period of prolonged function depends not only on the expertise of operator but also on nature and properties of dental materials involved in denture fabrication. Three important criteria required for the structure and function of durable denture teeth are as follows:

  • Hardness/wear resistance,
  • bond strength to the denture base resin, and
  • esthetics.
The wear resistance of artificial teeth is very important for the life of removable prosthesis especially in edentulous patients. [7],[8] Several studies indicated that micro-filled composite teeth possess superior wear resistance compared to conventional acrylic resin teeth. [9],[10] Cross-linked acrylic resin artificial teeth have been reported to demonstrate lower bond strength to denture base resin when compared to conventional acrylic resin teeth. Some clinical problems with these teeth are poor bonding to denture bases, [11] brittle properties, and superficial staining. [12]

A remarkable difference in filler morphology existed between two different denture teeth taken up in this study, nanocomposite teeth (Veracia) and composite teeth (Endura) which had similar filler contents but showed greater difference in hardness. The composite teeth are heterogeneously micro-filled with splintered pre-polymerized silica particles, whereas nanocomposite teeth had spherical pre-polymerized silica nanofillers with urethane as intrahomogenous polymer matrix. [13]

Debonding of denture teeth increases the appointment frequency and laboratory costs. Failure of bond between the denture tooth and denture base resin may be caused by excessive stress failure or by fatigue. [14] Studies conducted by Cunningham and Benington [6] and Thean [5] affirmed that the bond failure between denture base material and resin teeth remained a significant problem for treatment success and that wax or sodium alginate contaminated surfaces produced highly significant weaker bonds. According to Kawara et al., [4] failures probably caused by gap and crack propagation in areas of load concentration. Buyukyilmaz and Ruyte [15] also found that bond characteristics changed from adhesive failure to cohesive failure due to increasing temperature, especially for over 50°C.

Mosharraf and Mechanic [16] compared four pre-bonding preparation methods on the ridge lap surface of one multilithic denture tooth by determining its bond strength to denture base resin. The results showed that creating retention hole in the ridge lap surface of the multilithic tooth can increase its bond strength with denture base resin to the denture teeth. Takahashi et al. [17] described that the application of dichloromethane to ridge lap area of denture teeth resulted in a significant increase in bond strength values compared to the application of diatoric. Vergani et al. [18] recommended different kinds of tooth surface treatment before bonding teeth to denture bases.

In this study, results showed that in Subgroup A (control group), Group II: Composite denture teeth showed highest mean shear bond strength value of 4.6046 Mpa followed by Group I: Nanocomposite denture teeth showed the mean shear bond strength value of 3.8696 Mpa and Group III: Cross-linked acrylic denture teeth showed the least mean shear bond strength value of 3.6199 Mpa. This suggests that greater bond strength of the composite teeth (Endura) with the denture base than that seen with either nanocomposite (Veracia) or cross-linked acrylic teeth (Acry rock).

In Subgroup B (surface conditioning with methyl methacrylate-based bonding agent: Vitacoll), Group I: Nanocomposite denture teeth showed highest mean shear bond strength value of 6.8690 Mpa, Group II: Composite denture teeth showed mean shear bond strength value of 6.7589 Mpa, and Group III: Acrylic denture teeth showed the least bond strength of 5.6571 Mpa. The results showed that there was no significant difference between the nanocomposite and composite denture teeth in their bond strengths when treated with Vitacoll, but these two groups showed significantly higher bond strengths when compared to Acrlic denture teeth.

In Subgroup C (surface conditioning with air abrasion plus silane-coupling agent [Monobond-S] and Vitacoll bonding agent), Group I: Nanocomposite denture teeth showed highest mean shear bond strength value of 6.8786 Mpa, Group II: Composite denture teeth showed mean shear bond strength value of 5.9495 Mpa, and Group III: Acrylic denture teeth showed the least bond strength value of 5.3449 Mpa. These results indicated that although there was no significant difference in the bond strength of nanocomposite teeth between Subgroups B and C (6.8690 and 6.8786 Mpa, respectively), significant differences were seen in composite teeth between Subgroups B and C (6.7589 and 5.9495 Mpa, respectively). However, all subgroups showed relatively greater bond strengths when the surfaces were treated with Vitacoll (Subgroup B) as against a combination of air abrasion plus Monobond-S and Vitacoll (Subgroup C).

The results of this study are in agreement with other in vitro studies [19],[20] in which the shear bond strength of denture teeth was evaluated after subjecting them to different surface treatments and surface-treated specimens showed higher shear bond strength. Analysis of the fractured specimens revealed that more number of adhesive failures occurred in the control group as compared to experimental group subjected to surface conditioning with methyl methacrylate bonding agent (Vitacoll). The adhesive failure demonstrated in the control group showed weaker shear bond strengths as compared to more cohesive and mixed fractures in surface conditioning with Vitacoll bonding agent group showing higher shear bond strengths.


   Conclusion Top


From this study, it is concluded that there are significant differences in shear bond strength among the surface treatment groups of artificial teeth bonded to heat cure denture base resin. The bond strength improved with surface conditioning methods over the control group. Composite denture teeth (Endura) showed greater bond strength to denture base resin in the control group over nanocomposite teeth (Veracia) and cross-linked denture teeth (Acry rock). Vitacoll (methyl methacrylate-based bonding agent) application provided greater bond strength in all the three groups. Nano composite denture teeth (Veracia), after application of Vitacoll bonding agent, showed highest shear bond strength to denture base resin among all the groups.


   Acknowledgment Top


The authors thank staff and college authorities of CIPET engineering college, Hyderabad, for their kind support and technical help.

 
   References Top

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3.Kawano F, Ohguri T, Ichikawa T, Mizuno I, Hasegawa A. Shock absorbability and hardness of commercially available denture teeth. Int J Prosthodont 2002;15:243-7.  Back to cited text no. 3
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4.Kawara M, Carter JM, Ogle RE, Johnson RR. Bonding of plastic teeth to denture base resins. J Prosthet Dent 1991;66:566-71.  Back to cited text no. 4
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5.Thean HP, Chew CL, Goh KI. Shear bond strength of denture teeth to base: A comparative study. Quintessence Int 1996;27:425-8.  Back to cited text no. 5
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6.Cunningham JL, Benington IC. Bond strength variation of synthetic resin teeth in dentures. Int J Prosthodont 1995;8:69-72.  Back to cited text no. 6
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7.Ghazal M, Yang B, Ludwig K, Kern M. Two-body wear of resin and ceramic denture teeth in comparison to human enamel. Dent Mater 2008;24:502-7.  Back to cited text no. 7
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10.Reis KR, Bonfante G, Pegoraro LF, Conti PC, Oliveira PC, Kaizer OB. In vitro wear resistance of three types of polymethyl methacrylate denture teeth. J Appl Oral Sci 2008;16:176-80.  Back to cited text no. 10
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11.Suzuki S, Sakoh M, Shiba A. Adhesive bonding of denture base resins to plastic denture teeth. J Biomed Mater Res 1990;24:1091-103.  Back to cited text no. 11
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12.Suzuki S, Sakoh M, Shiba A. Impact resistance of highly crosslinked plastic denture teeth. J Biomed Mater Res 1990;24:1661-71.  Back to cited text no. 12
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14.Meng GK, Chung KH, Fletcher-Stark ML, Zhang H. Effect of surface treatments and cyclic loading on the bond strength of acrylic resin denture teeth with autopolymerized repair acrylic resin. J Prosthet Dent 2010;103:245-52.  Back to cited text no. 14
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15.Büyükyilmaz S, Ruyter IE. The effects of polymerization temperature on the acrylic resin denture base-tooth bond. Int J Prosthodont 1997;10:49-54.  Back to cited text no. 15
    
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Correspondence Address:
B Chittaranjan
Department of Prosthodontics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, Nalgonda (Dt), Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.117994

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