الفهرس 
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Abstract
The aim of this study was to evaluate the effect of diode laser in activating the irrigation protocol of Sodium hypochlorite and EDTA 17%. The comparison was done with ultrasonic activation in terms of root canal decontamination, smear layer removal and the effect on subsequent sealer properties. The effect on sealer was evaluated through two aspects namely sealer bond strength and sealer adaptation of two sealers; EndoSequence Bioceramic sealer and AH Plus.
Disinfection power was assessed using count of colony forming units under stereomicroscope, sealer bond strength was measured using push-out bond strength test, while both smear layer and sealer adaptation were assessed via scanning electron microscope.
A total of one hundred and thirty human permanent mandibular premolars were used in this study. Decoronation was done and mechanical preparation followed.
The study was then divided into two phases, the first phase examined canal cleanliness and the second examined subsequent sealer properties after obturation using lateral condensation technique.
First Phase
Disinfection evaluation using CFU:
Samples were infused by E. Faecalis, incubated, and then disinfected using the two protocols in comparison: NaOCl plus EDTA 17% with ultrasonic activation and NaOCl plus EDTA 17% with Diode laser activation. Dentin samples were then collected via round bur at low speed from three levels of the root canal and CFU test was performed. Data were collected then statistical analysis was performed.
Smear layer removal assessment:
Longitudinal sections of samples were examined using the scanning electron microscope then images were observed and scores were recorded according to the scoring system by Gutmann et al. Data were collected and statistically analyzed.
Second Phase
Samples were divided into two groups, one for every activation protocol, then the two groups were further divided into two subgroups, one obturated using AH Plus sealer and the other by EndoSequence Bioceramic sealer.
Evaluating the bond strength of both sealers:
Push out test was done on transverse sections of the samples to record the dislodgement forces, then using an equation the bond strength was calculated. Data were collected and statistically analyzed.
Evaluating sealer’s adaptation:
Longitudinal sections were scanned using SEM and maximum gap width as well as maximum gap surface area were measured as a function of sealer adaptation at two levels of the root canal. Data were collected and statistically analyzed.
Results:
Concerning the antibacterial effect, both methods of activation managed to achieve huge reduction of bacterial load yet neither achieved total sterilization and the difference between both methods was insignificant.
Concerning the smear layer removal capacity, both protocols managed to efficiently remove smear layer with no significant difference between them.
Concerning bond strength of sealers, Bioceramic sealers showed higher bond strength than AH Plus and there was no significant difference between ultrasonic and laser activation.
Concerning sealer adaptation, AH Plus showed better adaptation and once more the activation method made no impact.
Conclusion:
Under the conditions of the study the following was concluded:
1. Regarding canal cleanliness, diode laser activation of canal irrigation did not show any advantage or added benefit over activation using ultrasonic.
2. The efficiency of Diode laser in activating NaOCl and EDTA is comparable to ultrasonic activation producing comparable disinfection and smear layer removal.
3. Neither ultrasonic activation nor diode laser activation achieved total sterilization of the root canal.
4. Neither ultrasonic activation nor diode laser activation had a direct effect on sealer bond strength or adaptation.
5. Regarding bond strength and adaptability, EndoSequence Bioceramic sealer showed higher bond strength while AH Plus resin sealer showed better adaptation.
Recommendations:
1. Ultrasonic irrigation activation is still the technique to be recommended in clinical use.
2. Future researches involving laser activation shall better try other types of lasers that have water as their chromophore.