ORIGINAL ARTICLE |
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Department of Prosthodontics, M R Ambedkar Dental College, Bangalore, India
Corresponding Author: Dr. Vinaya Kundapur, Reader, Department Of Prosthodontics, M R Ambedkar Dental College, Bangalore, India 560005. Tel: +91 8904073488; E-mail: drvinni@gmail.com.
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ABSTRACT |
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INTRODUCTION |
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REVIEW OF LITERATURE |
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MATERIALS AND METHODS |
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RESULTS |
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CONCLUSION |
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REFERENCES |
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ABSTRACT
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Background: Denture teeth made of acrylic resin are preferred because they chemically bond to denture base material but the problem of debonding is also common with the use of acrylic teeth. Many attempts have been done to improve bond strength of acrylic teeth which involves mechanical and chemical means. With the use of recently introduced thermoplastic denture base materials, the problem of tooth debonding has been increased due to the mechanical nature of the bond between these materials and the acrylic teeth. There is limited literature on bond strength of acrylic teeth and flexible denture materials and the methods to enhance it. The present study evaluates and compares the bond strength between acrylic teeth and heat cure resins and thermoplastic resins after different known denture tooth surface treatment methods, including use of methyl methacrylate; sandblasting and prefabricated vertical groove.
Method: A total of 180 maxillary right central incisors were selected and divided into six groups of 30 samples each, according to the surface treatments and denture base material (heat cure or thermoplastic resins) used for processing. The bond strength of all specimens were tested in Universal Testing Machine. The obtained data were subjected to statistical analysis.
Result: Results showed that there was statistical significant difference in mean bond strength after various surface treatments and processing of acrylic teeth with either heat cure or flexible denture material.
Interpretation & Conclusion: The present findings suggest that vertical groove in the ridge lap area has highest bond strength amongst the groups processed with flexible denture material, and treatment of specimens with methyl methacrylate monomer for 5 sec has highest bond strength amongst all groups.
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INTRODUCTION![]() |
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Failure of prosthesis is a problem which is frequently encountered by prosthodontists, which require repair of dentures. A survey was carried out to determine the prevalence of types of failure of prosthesis by the distribution of questionnaire to three different laboratories. Results obtained showed that 33% of the repairs carried out were due to debonded teeth (1). Determination of the bond strength of denture teeth inserted into resin bases is an issue of crucial importance as most of the detachment phenomenon of artificial teeth from their resin bases under functional loads occur because stresses at tooth-base interface exceed bond strength (2). With the use of recently introduced thermoplastic denture base materials, problem of tooth debonding has increased due to mechanical nature of the bond between these materials and acrylic teeth (3). There is much discussion in dental literature regarding the effects of surface treatment on bond strength of acrylic teeth to heat cure acrylic resins. However, there is little literature available on the comparison of effects of surface treatments on bond strength of acrylic teeth to heat cure acrylic resin and to thermoplastic denture base material.
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REVIEW OF LITERATURE![]() |
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Failure of prosthesis is a problem which is frequently encountered by prosthodontists, which require repair of dentures. A survey was carried out to determine the prevalence of type of fracture by the distribution of questionnaires to three different laboratories. Results obtained showed that 33% of the repairs carried out were due to debonded/detached teeth. Twenty-nine per cent were repairs to midline fractures, more commonly seen in upper complete dentures. The remaining 38% were other types of fracture, the majority of which constituted repairs to upper partial dentures (1). A study was done to compare the bond strengths of denture teeth to autopolymerized repair acrylic resin after various surface treatments, before and after cyclic loading. Mandibular lateral incisor denture teeth were selected and ground on the ridge-lap portion using a standardized jig. Specimens with a ground surface were used as controls. The experimental groups included: ground plus airborne-particle abraded, ground plus diatoric recess, and ground plus an experimental bonding agent. The specimens were then examined using 10 × magnifications, and fractures were categorized as adhesive, cohesive, or mixed. It was found on microscopic examination that the bonding agent group obtained the highest percentage of mixed-type fracture (4). A study was done to assess the bond of the acrylic teeth to conventional heat cure acrylic resin and to thermoplastic resin denture base material and methods to enhance it. Acrylic resin teeth were bonded to heat cure acrylic resin with and without wetting the ridge laps of the teeth with monomer and acrylic teeth with prefabricated retentive holes, unmodified and modified, in their ridge laps were processed with Valplast thermoplastic resin denture base material. It was found that the chemical bond strength of acrylic teeth and heat cure acrylic resin was greater than the mechanical bond strength of the teeth with the Valplast thermoplastic denture base material (3). A study was done which presented a case report of a dissatisfied patient treated with a conventional removable partial denture, which was replaced by a modified metal framework without metal clasps in combination with flexible resin, and a literature review about this material focusing on the dental practitioner. The study also reported how these polymers can be used, their indications, and their clinical and laboratory considerations (5). A study was done to determine if retention grooves (horizontal and vertical) of various shapes would improve the tooth-denture base bonding. The study was conducted on 180 acrylic resin teeth (Maxillary Central incisors, Lateral incisors, Canines) and heat cure denture base acrylic resin. The teeth were mechanically prepared and divided into groups, according to the types of grooves. In the control group, no grooves were prepared. Specimens were tested in Universal Testing Machine by applying force at 130° to the long axis of each tooth. The data obtained was statistically analyzed by ANOVA. It was found: Shear compressive bond strength of specimens with vertical retention grooves (inverted cone) was greater than vertical grooves (straight fissure), horizontal grooves (inverted cone), horizontal grooves (straight fissure) and the control group (6).
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MATERIALS AND METHODS![]() |
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In this study, one hundred and twenty maxillary right central incisor acrylic teeth will be used.
According to different treatments, specimens will be divided into 3 groups with 40 samples in each group. These groups will be divided into subgroups of 20 each.
Group 1 will be prepared as follows: Surface treatment of ridge lap area of acrylic teeth with monomer (methylmethacrylate) for 180 seconds
Subgroup a: Teeth processed with heat cure acrylic resin after surface treatment.
Subgroup b: Teeth processed with thermoplastic denture base material after surface treatment.
Group 2 will be prepared as follows:
Sandblasting with alumina- This group will be treated with airborne particle abrasion after grinding the ridge lap area. The ground ridge lap surface will be abraded with 50-µm aluminium oxide particles with a circling motion at a distance of 5mm for 5 sec. After treatment the teeth will be placed in ultrasonic cleaner with distilled water for 10 minutes to remove any residual aluminium oxide particles.
Subgroup a: teeth processed with heat cure acrylic resin after sandblasting with alumina.
Subgroup b: teeth processed with thermoplastic denture base material after sandblasting with alumina
Group 3 will be prepared as follows:
Mechanical surface treatment by preparing a vertical groove of 2mm width and 2mm depth with straight fissure bur on the ridge lap portion of teeth.
Subgroup a: teeth processed with heat cure acrylic resin after preparation of groove.
Subgroup b: teeth processed with thermoplastic denture base material after preparation of groove.
Universal testing (5mm/min) will be used at 135-degree angle to determine the force at which the tooth gets debonded. After compression testing the debonded surfaces will be examined with an optical microscope at 10x magnification. The failure mode will be classified as cohesive failure (within the tooth or acrylic resin), adhesive failure (between the tooth and acrylic resin), or mixed failure (with both adhesive and cohesive failure).
An in vitro study in which the specimens obtained from the above procedure will form the source of data. Universal testing machine will be used to perform compression test to determine bond strength between tooth and denture base material of the above mentioned three different groups. Data collected will be analyzed statistically with Analysis of Variance (ANOVA) using software.
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RESULTS![]() |
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The results of this in-vitro study conducted at M.R. Ambedkar Dental College and Hospital, and IISC, Bangalore, India are as follows:
The present study evaluated several known denture tooth surface treatment methods, and processing these denture teeth with either heat cure or thermoplastic denture base material.
The bond strength between the denture teeth and denture base material was tested using universal testing machine. The bond strength values were evaluated for each group (Table 1-Table 6). The mean bond strength and standard deviation for each group was calculated (Table 7). This in vitro study rejected the null hypothesis as there was a significant difference between the bond strength among all the groups.
ANOVA test was done to compare the mean bond strength among different groups (Table 7). Highest mean bond strength was recorded in group 3a, followed by group 1a, 2a, 1b, 3b and 2b. Difference in mean bond strength among the groups was found to be statistically significant.
ANOVA test was done again to compare the mean bond strength within groups processed with heat cure denture base material (Table 8).
ANOVA test was done to compare the mean bond strength within groups processed with flexible denture base material (Table 8, Table 9 & Table 10).
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CONCLUSION![]() |
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Within the limitations of this study, the following conclusions were drawn:
1. There were significant differences in mean bond strength amongst six groups of acrylic resin denture teeth bonded to heat cure acrylic resin or flexible denture material, with highest bond strength in the group treated with methyl methacrylate.
2. The group of specimens with vertical groove has highest bond strength amongst the groups processed with flexible denture material because of mechanical bond between acrylic teeth and flexible denture material.
3. There was no statistical significant difference in mean bond strengths amongst groups processed with heat cure acrylic resins.
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REFERENCES![]() |
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