TO EVALUATE THE COMPRESSIVE RESISTANCE AND DIMENSIONAL STABILITY OF THREE COMMERCIALLY AVAILABLE BITE REGISTRATION MATERIAL DISINFECTED BY THREE DISINFECTANTS AT DIFFERENT TIME INTERVALS.

Dr.Sidhartha S.P Behera,Dr.Girish Galagali and Dr.Prakash Nidawani. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 04 July 2019 Final Accepted: 06 August 2019 Published: September 2019 Copy Right, IJAR, 2019,. All rights reserved.

1. To compare and evaluate the compressive resistance of three different brands of bite registration materials of 2mm,5mm,10mm,20mm thickness and 10 mm in diameter when 25 N of constant force was applied to the test samples at 12 hrs,24 hrs intervals. 2. To compare and evaluate the dimensional stability of three different brands of bite registration materials when immersed in three different disinfectant solutions for 2 min, 5 min, and 60 min time intervals.
Bite registrations consist of a dimensionally stable material which is capable of recording the desired anatomic area. The impression then displays the anatomy of the impressed area. During this procedure, the material has contact with saliva and blood, which are sources of contamination, and carries a great number of microorganisms of the oral flora upon removal from the mouth. Some of the several types of impression materials currently employed in dentistry have a great potential to retain microorganisms on their surfaces. Poulos and Antonoff stated that the polyvinyl siloxane is the most resistant to the retention of microorganisms, followed by the polysulphide. Besides, the number of microorganisms in these materials is quickly reduced through disinfection procedures. Reversible and irreversible hydrocolloids, both hydrophilic, are the materials that retain more bacteria after impression. 4 Occupational safety and health association (OSHA) guidelines requires dentists, dental laboratory employers, and other employers in health care fields to provide protection for their employees against the possibility of infection transmission by implementation of conscientious and consistent barrier controls. These universal precautions however, do not address specific issues that involve the decontamination of particular devices that contact a patient's oral cavity or body fluids. The OSHA subsection that relates to dentistry does not state how a particular dental Metal cylinders (stainless steel) of 2 mm, 5 mm, 10mm and 20 mm length and 10mm diameter were used to prepare the samples to study the compressive resistance.
Three addition silicone materials that are supplied in the form of cartridges were mixed by using mixing tips and dispensing gun.Each mixed material was injected into 10mm diameter stainless steel cylinders of height 2 mm, 5 mm, 10 mm and 20 mm, and allowed to set. Five specimens were fabricated for each recording material of four different lengths,for a total number of 60 specimens .Each specimen was subjected to a constant compressive force of 25N for 60 seconds by means of Universal Testing Machine (UTM).
Specimens were tested for 12 hours, 24 hours interval, readings were recorded. The amount of compression of each specimen after 25N loading are recorded and compared by means of statistical analysis. Results were evaluated using appropriate statistical analysis.
To analyse the dimensional stability, ADA Specification No.19 for Elastomeric Dental Impression materials was used to make the specimens. This apparatus consisted of a detail reproduction test block -part A, a ring mold -part B (this simulated a tray orcontainer for the impression material), and a riserpart C, the riser is 29.97 mm in diameter and 3 mm in height where as the ring is 30 mm in diameter and 6 mm in height. This would allow the riser to fit inside the ring. The bite registration materials would occupy the difference in height between the riser and the ring mold. The riser places pressure on the impression materials and the excess impression material would flow outward around the riser. There are five lines on the top surface of the testing block. Lines X, Y, Z, and cross lines CD and C'D'. All lines are at 90 degree angle with the top surface of testing block.
The width of lines X, Y, Z 58, 24, 83 µm and for CD and C'D' were 70 and 40 µm respectively these were measured and provided by the manufacturer of the apparatus and guaranteed to be within +/-0.008μm. The reproducibility of these lines is used to test the ability of the impression material to reproduce fine detail. The die has a highly polished surface, which eliminated the need for a separator and minimized cleaning operations, which could damage the ruled surface of the die. In this study, line Z was selected for measurements from where it crosses line CD (to be called point A) to where it crosses line C'D'(to be called poin The distance from point A to point B (25 mm) was selected in this study using the inside edge of lines as references for measurements. Top surface of the test block. The distance between points A and B was selected for all measurements in this study. The manufacturer provided all line widths. Lines X=58, Y=24, and Z=83 µm Cross lines CD=70, and C'D'=40 µm. All lines include 90 degree angle.

Measured distance for AB (mm) -Actual distance for AB (mm) divided by Actual distance for AB (mm) multiplied by 100 = Percent Dimensional Changes (%)
The bite registration material were prepared according to manufacturer's instructions.36 specimens were made from the three different bite registration material using the ADA specification no 19 die ,all the 108 specimens were then immersed in a controlled water bath at 37 degree Celsius . 6 specimens from each material were immersed in each of the three different type of disinfectant for three different intervals of time, so 54 specimens were disinfected and 54 specimens served as a control group. Linear dimensions were measured for the control group and for the disinfected group using a profile projector.

Statistical Analysis:-
Data was expressed in terms of mean and SD. Comparison of compressive resistance between three commercially available addition silicone bite registration materials was done by ANOVA test followed by post hoc Tukey's multiple comparison tests. Comparison the dimensional stability of three commercially available addition silicone bite registration materials when immersed in three different disinfectant solutions was done by ANOVA test 227 followed by post hoc Dunett's t test. A p-value less than 0.05 were considered as significant. Data analysis was done using software Minitab v.14.0.     Graph No: 2 Graph 1:-Shows comparison of compression resistance between different bite registration materials of 2mm thickness specimens for 12 hrs. Graph 2:-Shows comparison of compression resistance between different bite registration materials of 5mm thickness specimens for 12 hrs.

Graph No: 3
Graph No: 4 Graph 3:-Shows comparison of compression resistance between different bite registration materials of 10mm thickness specimens for 12 hrs. Graph 4:-Shows comparison of compression resistance between different bite registration materials of 20mm thickness specimens for 12 hrs.

Discussion:-
According to Millstein and Hsu, "The interocclusal record should be an accurate and dimensionally stable representation of an interocclusal space that is subsequently transferred to an articulator. 7 Recording maxillomandibular relationships is an important step in oral rehabilitation. This relationship is transferred to the articulator, so that the laboratory procedures done on the casts will correspond with the patient's mouth. There are various methods of recording maxillomandibular relationships namely, graphic, functional, cephalometric and direct interocclusal. 8 Direct interocclusal records are most commonly used to record maxillomandibular relationships because of their simplicity.The first interocclusal registration was made in 1756 by Philip Pfaff.Plaster, wax, modelling compound, zinc oxide -eugenol paste, autopolymerizing acrylic resin, condensation type silicones, polyether and polyvinylsiloxane are the commonly used materials for recording maxillomandibular relationship. 9 TomislavIvanis, Jansenka. Concluded that elastomers that underwent 24 hour immersion showed linear dimensional change within clinically acceptable range, they found that the obtained dimensional changes depended on the impression material, the medium and time of exposure. All the differences in dimensional changes were statistically significant. 10 The thickness of the interocclusal recording materials was selected to simulate clinical situations. A limited thickness of recording material is usually indicated between prepared teeth on one arch opposing an unprepared dental arch compared with a thickness of material between two opposing edentulous arches. The specimens were stored at room temperature for 12 hours and 24 hours to simulate the time between clinical and laboratory phases (registration and mounting).Among the 2mm thickness specimens at 12 hr interval, CAD bite registration material showed the least compression distance value of 1.44 than Jet bite of 1.67, O bite of 1.89. (Table: 10)