الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 124 |  |  |
| | | from | 124 | | |
Abstract
Summary
First permanent molars are the most caries-susceptible teeth during their first three years of eruption. Enamel has not fully matured and coalesced during this time, moreover, maintaining good oral hygiene of the erupting teeth might be challenging due to the lack of awareness of the newly emerged teeth.2 Pit and fissure sealants have proved to be an effective method in reducing the rate of occlusal caries on posterior teeth by creating a protective barrier between the tooth surface and the oral environment.
The mechanical movements and temperature fluctuations within the oral cavity can adversely impact the physical structure of those sealants and the success of applied treatments. Thus, the study’s aim is to assess microleakage and penetration depth of two different fissure-sealant materials as well as compare their wear resistance.
A total of twenty-eight sound human permanent molars were collected. The teeth were thoroughly debrided and cleaned using an ultrasonic scaler and a non-fluoridated pumice with a prophy cup mounted on a low-speed contra-angle handpiece. The teeth were then stored in distilled water, to prevent their dehydration, at room temperature. The distilled water was changed on weekly basis until experiment time.
Teeth specimens were serially numbered and then randomly distributed into two major groups of teeth (14 specimens each) according to type of sealant they received. The specimens that received the Beautisealant fissure sealant were pretreated with a self-etching primer, while the specimens that received the ClinproTM fissure sealant were pretreated with a 34% phosphoric acid etch.
Depth of penetration and microleakage testing:
Specimens were subjected to thermocycling at 500 cycles between temperature of 5℃ and 55℃ in controlled water bath with a dwell time of 30 seconds in each water bath and transfer time of 15 seconds. A double layer of nail varnish was then applied, leaving a 1 mm window between the varnish and the sealant material.
Following that, teeth specimens were embedded in chemical cured acrylic resin and immersed in 2% methylene blue at room temperature for 24 hours.160 Afterwards, the teeth were washed under running water to remove the excess dye. Specimens were then buccolingually sectioned through the sealant using an Isomet 4000 precision saw, Buehler, Germany and examined under stereomicroscope and photographs were taken using Microscope professional HD Camera (Mechanic, DX-230 ).160 Sealant microleakage and penetration depth were evaluated for all specimens using stereomicroscope.
Mann- Whitney U test was used to analyse data and Depth of penetration results showed that ClinproTM had higher scores than Beautisealant, yet the difference was not statistically significant (p=0.717), while the microleakage results showed a statistically significant difference where Beautisealant had higher scores than ClinproTM (p<0.001).
Wear resistance testing
Sixteen Disk specimens (eight of each sealant) were prepared by injecting the material into a costume made split Teflon mold with an internal diameter of 8 mm and internal height of 3 mm.120 Following this, a Mylar strip was placed on top of the mold, followed by a glass plate. Gentle pressure was placed on the glass plate to remove any extruded excess. Each specimen was cured, using the MiniLED curing light (Acteon, France).
Specimens were scanned using the 3-Dimensional scanner Sirona ineos X5 and an STL file was produced for each specimen as a reference for the surface before the aging process. Afterwards, the specimens were subjected to thermocycling in the thermocycling apparatus at 500 cycles between temperature of 5℃ and 55℃ in controlled water bath with a dwell time of 30 seconds in each water bath and transfer time of 15 seconds.
After thermocycling, the specimens were mounted in the chewing simulator CS-4 (Willytec/SD Mechatronik GmbH, Feldkirchen- Westerham, Germany) and was set to 75,000 cycles to be equivalent to 6 months chewing conditions under the load of 49N.120 The specimens were then scanned again to obtain the STL file post aging. Wear was accounted for by quantitative changes in volume and changes in height by utilizing the Geomagic software to superimpose the STL files post-aging process with the STL files that were taken pre-aging process. 130
Independent t-test was used to analyse data and results showed that ClinproTM had a significantly higher wear value than Beautisealant (p<0.001).
Using Spearman’s rank-order correlation coefficient a statistically significant, inversely proportional correlation was found to exist between microleakage and wear, while (rs=-0.782, p<0.001), while other correlations were not statistically significant (p>0.05)