الفهرس 
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Abstract
The current study evaluated the effect of different scaling methods on surface roughness, color stability and bacterial accumulation of lithium disilicate ceramic.
Seventy disc shaped IPS e.max Press samples; were constructed using the lost wax technique.
The samples were divided according to the scaling method into three groups:
group I: Control, No scaling (10 samples)
group II: Manual scaling (30 samples)
group III: Ultrasonic scaling (30 samples)
Then the manual and ultrasonic groups were further subdivided according to the material of the scaling instrument into 3 subgroups:
A) Stainless steel
B) Titanium
C) plastic
The disc shaped samples were cemented into preparations on the labial surface bovine teeth using adhesive resin cement and were subjected to different scaling methods using different instruments.
The surface roughness the samples was measured before and after scaling to determine the Δ surface roughness using profilometer and atomic force microscopy.
The color parameters of the samples were measured according to the CIE Lab system before and after scaling to determine the Δ color using spectrophotometer.
The bacterial count was determined using colony counter.
Results of Δ surface roughness:
The plastic instruments (ultrasonic and manual) showed a statistically significant lower mean values of ΔRa than the titanium instruments (ultrasonic and manual) and the ultrasonic stainless steel tip. They showed no statistically significant difference in the mean values of ΔRa than the manual stainless steel curette.
There was no statistically significant difference between mean values of ΔRa of the two scaling methods for each tip material.
Results of color change (ΔE):
The manual titanium curette showed the statistically significant highest mean values of ΔE. It showed a statistically significant higher mean values of ΔE than the plastic curettes (ultrasonic and manual) and the control groups. While it showed no statistically significant difference in the mean values of ΔE than the ultrasonic titanium and the stainless steel curettes (ultrasonic and manual).
There was no statistically significant difference between mean values of ΔE of the two scaling methods for each tip material.
Results of Bacterial accumulation:
The plastic groups showed the least statistically significant mean values of bacterial count which was not statistically significant different from the control group. The stainless steel and titanium groups showed the statistically significant highest mean values of bacterial count.
There was no statistically significant difference between mean values of bacterial count of the two scaling methods for each tip material.
Results of Atomic Force Microscopy:
AFM of litium disilicate discs showed that scaling using titanium instruments either ultrasonic or manual resulted in the most aggressive changes in the surface morphology followed by scaling using the stainless steel instruments both ultrasonic and manual. Plastic instruments; ultrasonic- and hand-driven, showed the least surface morphology alterations.
Within the limitations of this in vitro study, the following conclusions were drawn:
1. The surface roughness of lithium disilicate ceramics is affected by prophylactic periodontal treatment.
2. Ultrasonic and manual scaling methods induced similar effects on the surface roughness, color stability and bacterial accumulation of lithium disilicate ceramics.
3. Plastic instrumentation induced comparatively less surface roughness in lithium disilicate ceramic than titanium and stainless steel.
4. Increased surface roughness after prophylactic periodontal treatment adversely affect the color stability and bacterial accumulation in lithium disilcate ceramic.