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2006| July-September | Volume 9 | Issue 3
August 6, 2008
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Evaluation of two post and core systems using fracture strength test and finite element analysis
Panna Narang, BV Sreenivasa Murthy, Sylvia Mathew
July-September 2006, 9(3):99-103
To compare the failure load and failure modes of these two post and core systems using Fracture Strength Test and to use Finite Element Models for the comparison of pattern of stress distribution between the two post and core systems.
In FST, 22 maxillary central incisors were selected and RCT was performed. Post spaces were prepared and specimens were divided into 2 groups: - custom cast post and light transmitting post. Posts were then cemented using GIC for custom cast and Panavia F21 for light transmitting posts followed by composite core build up. All the specimens were then mounted on acrylic resin blocks and loaded under UTM until failure. In FEM, CT scan models were used to generate 3D and 2D models of maxillary central incisor with post core assembly and supporting structures. The material properties were assigned and boundary conditions were applied and a force of 100N was applied at 45° on the palatal surface. Analysis was run and stress distribution pattern was studied.
FST indicated a statistically significant difference in the 2 post core systems with light transmitting post failing at a higher load than custom cast post. Also the mode of failure was classified as being favorable for light transmitting post. FEN results indicated less stress distribution on tooth and with in post core system for light transmitting post compared to custom cast post.
The area of maximum stress level for post core systems and level of fracture both coincided in our study. Light transmitting post had a higher failure load and also provides a fail safe mode of failure and thus resulting in less damage to tooth.
Direct composite veneering technique producing a smile design with a customised matrix
Suhas Mohan Lal, S Jagadish
July-September 2006, 9(3):87-92
A recent trend in dentistry has been to conservatively and esthetically restore anterior teeth. This is evident by the growing use of composite resins and other tooth colored restorative systems. Today with trend towards minimum intervention in dentistry, composite veneers have become an answer to discolored anterior teeth. Direct placement of composite veneers has greater control, require a conservative removal of tooth structure and can be easily repaired and modified at any stage. However chair side direct placement of composite veneers is time consuming procedure and is technique sensitive. A new technique for placement of composite in single visit using the modified customized matrix has been proposed. This paper illustrates two case reports of direct composite veneering using a new modified customized matrix technique for treatment of discolored teeth after bleaching.
Evaluation of bacterial contamination of dental unit water Lines and the efficacy of a commercially available disinfectant
Vijay K Venkatesh, Nandini V Vidyashree, Velmurugan , A Parameswaran, D Kandaswamy
July-September 2006, 9(3):93-98
Evaluation of Bacterial Contamination of Dental Unit Water Lines and the Efficacy of a Commercially Available Disinfectant (Sterilex Ultra
dental unit waterlines, disinfection. biofilm, hypochlorite. Microbial colonies that adhere to solid surfaces wherever there is sufficient moisture are referred to as the biofilm. The microbes acquire a slimy covering called glycocalyx, which protects them, in a moist environment. Biofilms formed in dental unit water lines can act as a source of cross infection.
A study was undertaken to evaluate the bacterial contamination of dental unit water lines and to evaluate the efficacy of a commercial disinfectant (Sterilex Ultra
) in eliminating biofilms from dental unit water lines.
Materials and Methods:
To begin with, random water samples were collected from water booster, air-turbine, air water syringe of three dental units and were subjected to bacteriological analysis. A commercially available disinfectant. Sterilex Ultra
, was used to treat the dental unit water lines. Water samples from different parts of dental unit water lines were collected on the third, fifth and seventh day following treatment with the reagent and the samples were sent for bacteriological examination. One inch tubing from the outlet of the booster, air turbine and air/water syringe was also sectioned and processed for bacteriological examination.
Bacterial isolates were observed before treatment with Sterilex Ultra
and but there were no bacterial isolates after treatment with the reagent for a period of six days.
Usage of disinfectant was found to be very effective for a period of six days. For maintenance of sterility of dental unit water lines it is essential to have a good source of water. an
effective disinfectant and the use of an anti-retraction valve.
Prosthodontic considerations of endodontically managed teeth
S Lakshmi, V Gopi Krishna, Sivagami
July-September 2006, 9(3):104-109
A dynamic methodology for measuring fluoride release from restorative materials
Hemamalathi , Suma Ballal, D Kandaswamy, Tina Gupta
July-September 2006, 9(3):113-116
The conventional methodology employed for measuring fluoride release from restorative materials is done by suspending a sample in a static media and measuring the fluoride release at designated time intervals. The main drawback of this methodology is that it does not make allowance for the dynamic system that exists in the oral cavity. Therefore a newer methodology which mimics the oral cavity by employing a continuous flow system to measure fluoride release was compared with that of the existing methodology.
Twenty disc specimens were prepared using conventional glass ionomer cement (Fuji Il, GC Co., Tokyo. Japan) and divided into two groups of ten each. In the first group fluoride release was measured using standard methodology and in the second group fluoride release was measured using a continuous flow system. In the continuous flow system. deionised water is allowed to flow through an intravenous infusion apparatus at a constant rate of 30ml/ hr stimulating the salivary flow rate. A constant volume of medium (2ml) is maintained in the drip chamber where specimen is suspended for fluoride release representing maximum volume of' saliva before swallowing.
: Fluoride ion concentration from the standard and new methodology was compared using student's independent t-test.
Significantly low amounts of fluoride was released from the specimens measured using the new methodology at all time intervals.
Effect of pulpal temperature changes on finishing and polishing of composites- An in-vitro study
Jaya P Daniel, Vasundhara Shivanna
July-September 2006, 9(3):110-112
The aim of the study was to find the pulpal temperature changes during finishing of composite restorative material. 180 teeth were taken and divided into 3 groups with 60 teeth in each group. The 3 groups were again divided into six sub groups with ten teeth in each group. Class v cavities were made in all the teeth and a base of glass ionomer cement was given, and it was then restored with z250 composite. Apical 5 mm of all the teeth were cut and a thermocouple probe was then inserted into the canal till it reached the roof of the pulp chamber. Apical orifice was closed with silicone impression material. The teeth were immersed in a water bath to maintain a steady temperature of 36
C. Finishing was done in all the 3 groups with coarse, medium and fine grit discs respectively with Shofu super snap. In 6 subgroups, 4 were finished with continuous pressure and no water coolant at 4000 rpm, 6000 rpm, 8000 rpm and 10000 rpm. The other two subgroups were finished with intermittent pressure and no water coolant at 10,000 rpm while the other was finished with 10000 rpm in continuous pressure and water coolant. Results showed a lesser rise in temperature with the use of lower speeds, water coolant and intermittent pressure. Coarse discs produced more temperature rise when compared to medium and fine grit discs. The study concluded that finishing should he in lower speeds, with intermittent pressure and with the use of water coolants to reduce the rise in intra pulpal temperature.
Legends- Dr. Clifford M Sturdevant
Gurmeet Singh Sachdeva, Parvinder Singh Baweja
July-September 2006, 9(3):117-118
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