Rajiv Gandhi University of Health Sciences s35
RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES
BANGALORE, KARNATAKA
ANNEXURE – II
PROFORMA FOR REGISTRATION OF SUBJECT FOR DISSERTATION
1. /NAME OF THE CANDIDATE
AND ADDRESS(in block letters) / DR. MANISH AIRAN
POST GRADUATE STUDENT,
DEPARTMENT OF PROSTHODONTICS,
BAPUJI DENTAL COLLEGE AND HOSPITAL, DAVANGERE - 577004
KARNATAKA.
2. / NAME OF THE INSTITUTION / BAPUJI DENTAL COLLEGE AND HOSPITAL, DAVANGERE - 577004
KARNATAKA.
3. / COURSE OF THE STUDY AND SUBJECT / MASTER OF DENTAL SURGERY IN PROSTHODONTICS (INCLUDING CROWN AND BRIDGE)
4. / DATE OF ADMISSION TO COURSE / 15.05.2012
5. / TITLE OF THE STUDY / “EVALUATION AND COMPARISON OF BOND STRENGTH OF ACRYLIC DENTURE TEETH TO CONVENTIONAL HEAT CURE AND HYPOALLERGENIC DENTURE BASE RESIN” – AN INVITRO STUDY
6.
7. /
BRIEF RESUME OF THE INTENDED WORK:
6.1 Need for the study:Essential requirements for denture base polymers are adequate mechanical properties, sufficient aesthetics, biocompatibility, easy handling of resin and minimal release of residual compounds such as residual monomers.1
Various materials and fabrication techniques have been used to fabricate dentures. The material which has stood the test of time as denture base resin is PMMA. Also, use of acrylic resin teeth for dentures provided the added advantage of chemical bonding to denture base resin. Unfortunately, the number of patients with allergies is increasing and, as a consequence, dentists are confronted with more patients reporting allergic reactions to polymethyl methacrylate denture base materials.2
Apart from patients, compounds of denture base resin prior to polymerization can cause hypersensitization and allergy to the dentists and dental laboratory personnel.1 Therefore, the use of a hypoallergenic denture base material for patients susceptible to allergic reactions and requiring a removable prosthesis is desirable for dental personnel as well.2
Another frequently encountered problem is of recurrent denture fractures, which also remains an unresolved problem causing inconvenience for denture wearers. Among these fractures, a survey report concluded that commonest type of fracture is debonding or fracture of denture teeth in both complete and partial dentures.3
Therefore, to overcome these shortcomings of PMMA denture base resin, a material is required which is hypoallergenic as well as bonds well to denture acrylic teeth. However to overcome former problem modified methacrylate based denture base resins like Sinomer (heat polymerized) are available which exhibits lower residual
monomer content than heat polymerized PMMA material.4 But there are no reports claiming the efficient bonding of such material to acrylic denture teeth.
Hence, the aim of this in vitro study is to evaluate the bond strength of acrylic denture teeth to hypoallergenic denture base resin.
6.2 Review of Literature:
Author conducted a study on allergic sensitization of the skin and oral mucosa to acrylic resin denture materials and concluded that methyl methacrylate liquid monomer is a sensitizer and can cause an allergic contact type of eczematous reaction on the skin and the oral mucosa.5
Authors carried out a survey to determine the prevalence of type of fracture by the distribution of questionnaires to three different laboratories and concluded that 33% of the repairs carried out were due to debonded/detached teeth. 29% were repairs to midline fractures, more commonly in upper complete dentures. The remaining 38% repairs were other types mainly in maxillary removable partial dentures.3
Authors conducted a study to examine the bond strength between two types of denture teeth and three denture base resins and concluded that conventional resin teeth possess higher bond strength than cross-linked denture teeth to denture base resins. The descending order of bond strength, according to denture base resin is: heat-cured denture base resin, microwave-cured denture base resin, and pour-type denture base resin.6
In a study conducted by authors to check mechanical properties, water sorption and release of residual compounds, on Alldent Sinomer® denture base resin. They concluded that all the properties fulfill the requirements of ISO standard.1
Authors conducted a study to compare the amount of residual monomer, quantity of water sorption, and solubility of four denture base materials claimed to be hypoallergenic with those of a PMMA heat polymerizing acrylic resin and concluded that significantly lower residual MMA monomer was shown for Sinomer and Polyan compared to the PMMA control group. The tested denture base materials fulfilled the requirements regarding water sorption (<32 µg/mm3) and solubility (<1.6 µg/mm3).7
In a study by authors to compare flexural strength and flexural modulus, four hypoallergenic denture base resin with a PMMA heat-polymerizing acrylic resin, they concluded that Microbase and Sinomer exhibited significantly lower flexural strength and flexural modulus, respectively, than PMMA.4
6.3 Objectives of the Study:
1. To evaluate the bond strength of acrylic denture teeth to conventional acrylic denture base resin.
2. To evaluate the bond strength of acrylic denture teeth to a hypoallergenic denture base resin.
3. To compare the bond strength of acrylic denture teeth to conventional acrylic denture base resin and hypoallergenic denture base resin.
MATERIALS AND METHOD:
7.1 Source of data
All the materials will be purchased through regular commercial channels and data will be obtained from laboratory based studies.
7.2 Sample size determination
Based on the information available from the previous studies, a sample size was determined using the formula,
Sample size ( n ) = 2×t² ×s²d²
Where, t = theoretical value of ‛t’ distribution with a 95%
Confidence limit
= 2.13
s = maximum variation expected within the group
(from previous studies)
= 0.5 MPa
d = minimum expected difference between two groups
= 0.3 MPa
Level of significance = 5%
Power of the study = 1-β =1-.20=.80=80%
Therefore, n = 2×2.13×2.13×0.5×0.50.3×0.3 = 25.205
Due to unknown observer instrumentation error, the sample size is increased to 30 in each group. Therefore, total number of samples will be 60.
7.3 Materials:
1. Heat cure Trevalon denture base polymer
(Conventional denture base resin)
2. Heat cure Alldent Sinomer® denture base polymer
(Hypoallergenic denture base resin)
3. Acrylic denture teeth
7.4 Method of collection of data:
a) Grouping:
For the purpose of study, total of 60 specimens will be fabricated and will be further sub-divided into two groups as mentioned below:
Groups / Sample / Sample Size
(To evaluate bond Strength )
Group 1
(Control) / Acrylic denture teeth bonded to conventional denture base resin / 30
Group 2 (Experimental) / Acrylic denture teeth bonded to hypoallergenic denture base resin / 30
b) Preparation of molds:
A custom-made mould of brass will be made to make wax cylinders of 6mmX6mm dimensions.
d) Preparation of the specimens:
Teeth selection and modification:
Molars from acrylic teeth mould will be selected and there ridge lap surface will be flattened with an acrylic trimmer and will be polished.
Fabrication of specimens:
For the fabrication of samples to be included in both the groups, cleaned denture teeth surfaces will be attached to wax patterns and will be invested with Type III dental stone into Kavo metal flask and will be dewaxed.
For GROUP 1 (Control) dewaxed Kavo metal flask will be packed with conventional heat cure denture base resin in dough stage. After packing flasks will be kept under 3000 psi pressure in a hydraulic press and then clamped and will be allowed to bench cure for 30 minutes. After bench curing the flask will be placed in the acrylizer for processing for 9 hours at 165ºF. The flask will be allowed to bench cool for 2½ hours before deflasking. Following bench cooling, specimens will be retrieved and will be finished and polished.
For GROUP 2 (Experimental) dewaxed Kavo metal flask will be packed with hypoallergenic denture base resin and will be placed directly into the water at 158ºF-176ºF for 20 minutes and then will be boiled in water at 203ºF for another 20 minutes. The cooling will be done in air. After cooling, specimens will be retrieved and will be finished and polished.
e) METHOD FOR MEASURING BOND STRENGTH:
To measure bond strength, each specimen will be embedded in autopolymerizing resin to transfer it to mounting jig of Universal Testing Machine. After embedding, the specimen will be stored in water at room temperature for 4 weeks before testing.
All specimens will be tested on the same day at room temperature using Universal Testing Machine. The acrylic resin blocks will be held on mounting jig and
force will be applied parallel to the bonding surface at tooth-base interface. Amount of force at fracture will be recorded in Newton (N) and maximum stress will be recorded in MegaPascals(MPa).
f) STATISTICAL ANALYSIS:
The data obtained from the study will be tabulated and subjected to statistical analysis. Unpaired‘t’ test will be used to compare flexural strength between control and experimental groups.
7.5: Does the study require any investigation or interventions briefly to be conducted on patients or other humans or animals? If so, please describe
NOT APPLICABLE
7.6: Has ethical clearance been obtained from your institution in case of 7.5?
NOT APPLICABLE
8. / LIST OF REFERENCES:
1. Lassila LVJ, Vallittu PK. Denture base polymer Alldent Sinomer®: mechanical properties, water sorption and release of residual compounds. J Oral Rehabil 2001;28:607-13.
2. Pfeiffer P, An A, Schmage P. Repair strength of hypoallergenic denture base materials. J Prosthet Dent 2008;100:292-301.
3. Darbar UR, Huggett R, Harrison A. Denture fracture – a survey. Br Dent J 1994;176:342-5.
4. Pfeiffer P, Rolleke C, Sherif L. Flexural strength and moduli of hypoallergenic denture base materials. J Prosthet Dent 2005;93:372-7.
5. Fisher AA. Allergic sensitization of the skin and oral mucosa to acrylic resin denture materials. J Prosthet Dent 1956:593-602.
6. Takahashi Y, Chai J, Takahshi T, Habu T. Bond strength of denture teeth to denture base resins. Int J Prosthodont 2000;13:59-65.
7. Pfeiffer P, Rosenbauer EU. Residual methyl methacrylate monomer, water sorption, and water solubility of hypoallergenic denture base materials. J Prosthet Dent 2004;92:72-8.
8. Thean HPY, Chew CL, Goh KI. Shear bond strength of denture teeth to base: A comparative study. Quintessence Int 1996;27(6):425-8.
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