Micro-Tensile Bond Strength Analysis

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Table of Contents

Summary and literature review
Research Hypothesis and Aims
Materials and Methods
Specimen Preparation
References

Summary and literature review

Significant advances in dental technologies provoke researchers and practitioners to speak about no need for removable denture prostheses in the future. However, the clinical evidence shows that there is still a great need for complete dentures made of strong materials. Patients prefer complete dentures either due to financial constriction or due to fears associated with the surgical placement of dental implants. Moreover, principles of placing the removable denture prosthesis are similar to the principles of implant-supported or implant-retained restoration. The research indicates a growing need for such prostheses because of the increased number of the elderly population globally, and the composition of dentures needs to be discussed in detail (4, 10).

In spite of advances in technologies, clinicians still encounter the same complications associated with this type of prosthesis. Patients can still experience teeth fracture, teeth deboned from the denture base, and fracture of the denture base itself. The previous research by Darbar, Huggett, and Harrison showed that 33% of denture repairs were direct results of debonding (1). Moreover, 29% of repairs were discussed as caused by midline fractures, and they were commonly seen in upper complete dentures. The remaining 38% were associated with other types of fractures (1). Goodacre and the group of researchers noted that this complication can also be encountered with complete or partial dentures and implant-retained/supported prostheses (2). Although researchers and clinicians attempt to improve the denture teeth and their chemical composition as well as the physical properties of the bond between denture teeth and the resin base, clinicians still face these challenges.

There have been many denture teeth developed during recent years. These dentures can be divided into four categories: conventional acrylic resin teeth (minimally cross-linked PMMA), highly cross-linked acrylic resin teeth, composite resin teeth (UDMA ), and porcelain teeth (3). Many studies reported the increased wear resistance of highly cross-linked acrylic resin teeth and composite resin teeth while comparing them with conventional acrylic resin teeth (4, 5). When it comes to the bonding of different denture teeth to acrylic resin bases, BlueLine DCL and Phonares II NHC were examined to have the higher μTBS than Portrait IPN to Ivocap Plus acrylic, while BlueLine DCL and Phonares II NHC denture teeth had the higher μTBS to the Luctione 199 acrylic resin (6).

Five types of acrylic resin denture bases are determined. Type 1 is associated with the heat-curing polymer, type 2 with the self-curing polymer, type 3 with thermoplastic materials, type 4 with light-curing materials, and type 5 with materials for microwave polymerization. This classification is according to the EN ISO 20795-1 classification of base polymers in dentistry published in 2008 (9, 10). Focusing on the composition and polymerization temperature, scientists determine IvoBase as a self-curing polymer, while Luctione 199/Success and SR-Ivocap Plus/Ivocap are heat-cured polymers. IvoBase material is known as an MMA/PMMA denture base resin.

IvoBase system is an injection molding system that combines the advantages of heat-curing and self-curing polymers. The IvoBase material is initially polymerized by forming radicals. This process can be based on using heat and can be discussed as heat-curing. Additionally, this process can be formed by a chemical reaction. In this case, the self-curing polymer is produced under the impact of a catalyst. Radicals create many chain molecules, and the process continues until a solid matrix is formed. As a result, the filler particles are enveloped. The IvoBase system can apply for different polymerization programs in order to enhance the composition process. Separate programs are used for Ivobase Hybrid and Ivobase High Impact materials. The programs also differ in the time necessary for polymerization is 35 minutes for Ivobase Hybrid materials, and the time is 50 minutes for Ivobase High Impact materials. As a result, the IvoBase system adds to the Ivocap system of fabricating acrylic materials that were actively used previously.

In previous studies, researchers focused on the bonding of heat-polymerized denture base resins to different denture teeth (6, 7, 8). The study by Lang and researchers compared the bond strength of cold-cured resin and heat-cured resin to denture teeth (9). Another group of researchers led by Palitsch tested the light-cured denture base material bonded to denture teeth (10). In this context, previous studies ignored testing the micro tensile bond strength of different denture teeth to IvoBase polymer and the digital denture base material.

Some studies recommended the use of micro-tensile bond strength (μTBS) to measure the bond strength between the denture teeth and the resin bases (6, 11, 12). Thus, the micro-tensile bond strength test gives the freedom to control the bonded surface area, allowing a researcher to have a standardized distribution of interfacial stresses in each specimen (6, 11). From this point, the focus on measuring the micro-tensile bond strength is important to discuss differences in denture teeth and bases.

Research Hypothesis and Aims

Purpose: To study the micro-tensile bond strength of new denture bases to three commercially available teeth.

Hypothesis 1: No significant difference in μTBS of the different denture teeth related to the various denture base resins can be observed.

Aim 1: The bond strength between each denture tooth and each resin type would be evaluated by thermocycling the specimen; then, the universal testing machine will be used to evaluate the μTBS.

Materials and Methods

15 experimental groups with 3 teeth each are planned to be formed, and 45 molar teeth are needed. The focus is on examining the denture base acrylic/processing technique (Ivobase hybrid, Success-Lucitone 199, Ivobase high impact, and SR-Ivocap-Ivocap Plus) and on a specific type of tooth (BlueLine DCL-PMMA, Portrait IPN-PMMA, Phonares II). It is planned to make particular rectangular bar specimens that are characterized by a 1 mm2 cross-sectional area. The next step is thermocycling. It is expected to conduct 10,000 cycles. The most appropriate temperature is between 5°C and 50°C (6). The proposed dwell time is 15 seconds. Testing of specimens will be conducted with the help of a universal testing machine. The most appropriate crosshead speed to measure the μTBS is 0.5 mm/min. In this case, the focus is on a possible load cell is 1 kN. Two-way ANOVA will be used to analyze and measure the data because there are two main effects: a resin type and a tooth type. It is also possible to measure the resin tooth interaction.

	Ivobase high impact / Ivobase x3	Ivobase hybrid/ivobase X3	digital dentures	Sr-ivocapplus/ivocap
blueline DCL	mean	mean	mean
phonares II	mean	mean	mean

Statistical measures will be checked with the Tukey’s post hoc test or Scheffe’s test (α = 0.05). These tests are necessary to measure the difference in chemical polymerization mechanisms. Thus, Ivobase can heat the polymerized resin, and it can be self-cured at the same time. This characteristic should be compared with Ivocap and its impact on heating polymerized resin.

Specimen Preparation

The first step is to roughen teeth. Colebeck and the group of researchers propose to roughen teeth “on their occlusal surface with a carbide bur (H251.11.060, Brasseler USA, Savannah, GA)” (6). The teeth need to be “embedded in clear auto polymerizing acrylic resin (Ortho Resin; Dentsply International) contained within a 25 mm diameter polypropylene mounting cup (Struers, Ballerup, Denmark)” (6). The second step is to flatten acrylic denture teeth. This procedure is performed at the “exposed bonding surface with 400-, 600-, and 800-grit silicon carbide paper” (6). The necessary condition to perform this procedure in a polishing machine (MetLab Corp., Niagara Falls, NY) is the cool water (6). The next step is to place teeth in ultrasonic units that contain distilled water. The time period for the procedure is 10 minutes. Then, the teeth need to be dried.

It is planned to use traditional denture processing methods. Therefore, the next step is the work with Baseplate wax. The tooth in acrylic resin is placed in a polypropylene cup to contact the compressed wax by its bonding surface. The completed specimens are manufactured and prepared from flaking. The following step is the use of a tinfoil substitute. The temperature for further manufacturing received flasks in tanks is 90°C. The time period is 5 minutes. The next 5 minutes are set after the flask is cleared from the wax. The process of clearing flasks from wax needs much attention and the use of both soapy and water. All the wax can be removed only after examining specimens with the help of a microscope. Tooth surface treatment and a flask injection are going to be done according to manufacturer instructions for each system. Resin sets are specifically improved with the help of diamond blades, and the next stage is numerous thermocyclers. The temperature is between 5°C and 50°C. The time period is 15 seconds.

The following stage is the use of a universal testing machine. It is important to record possible failures regarding specimens. Referring to Colebeck and the group of researchers, it is possible to use the equation for measuring μTBS: R = F/A (6). “R” is used for micro-tensile strength, and “F” is the load when “A” is the interface area (6). When the results are received, it is necessary to use a microscope to check possible failures and their type. The examination of specimens with the help of a microscope is important to select the representative ones.

References

Darbar UR, Huggett R, Harrison A. Denture fracture – a survey. Br Dent J. 1994; 176(9):342-5.

Goodacre CJ, Bernal G, Rungcharassaeng K, Kan JYK. Clinical complications with implants and implant prostheses. J Prosthet Dent. 2003; 90(2):121-32.

Suwannaroop P, Chaijareenont P, Koottathape N, Takahashi H, Arksornnukit M. In vitro wear resistance, hardness and elastic modulus of artificial denture teeth. Dent Mater J. 2011; 30(4):461-8.

Ghazal M, Hedderich J, Kern M. Wear of feldspathic ceramic, nano-filled composite resin and acrylic resin artificial teeth when opposed to different antagonists. Eur J Oral Sci. 2008; 116(6):585-92.

Coffey JP, Goodkind RJ, DeLong R, Douglas WH. In vitro study of the wear characteristics of natural and artificial teeth. J Prosthet Dent. 1985; 54(2):273-80.

Colebeck AC, Monaco EA, Jr., Pusateri CR, Davis EL. Micro tensile bond strength of different acrylic teeth to high-impact denture base resins. J Prosthodont. 2015; 24(1):43-51.

Dalal A, Juszczyk AS, Radford DR, Clark RK. Effect of curing cycle on the tensile strength of the bond between heat-cured denture base acrylic resin and acrylic resin denture teeth. Eur J Prosthodont Restor Dent. 2009; 17(4):146-9.

Morrow RM, Matvias FM, Windeler AS, Fuchs RJ. Bonding of plastic teeth to two heat-curing denture base resins. J Prosthet Dent. 1978; 39(5):565-8.

Lang R, Kolbeck C, Bergmann R, Handel G, Rosentritt M. Bond of acrylic teeth to different denture base resins after various surface-conditioning methods. Clin Oral Investig. 2012; 16(1):319-23.

Palitsch A, Hannig M, Ferger P, Balkenhol M. Bonding of acrylic denture teeth to MMA/PMMA and light-curing denture base materials: the role of conditioning liquids. J Dent. 2012; 40(3):210-21.

Chaves CA, Regis RR, Machado AL, Souza RF. Effect of ridge lap surface treatment and thermocycling on micro tensile bond strength of acrylic teeth to denture base resins. Braz Dent J. 2009; 20(2):127-31.

Saavedra G, Valandro LF, Leite FP, Amaral R, Ozcan M, Bottino MA, et al. Bond strength of acrylic teeth to denture base resin after various surface conditioning methods before and after thermocycling. Int J Prosthodont. 2007; 20(2):199-201.

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