Determining the effectiveness of various gingival retraction techniques included cord,paste,laser on the periodontal indicators ,after impression in fixed prosthesis:a randomized clinical trial study

Determining the effectiveness of various gingival retraction techniques included cord,paste,laser on the rate of bleeding,inflammation and gingival resorption and periodontal plaque,after impression in fixed prosthesis

In this Randomized Triple blinded Clinical trial study, 60 patients with maxillary and mandibular first molar in need of crown reconstruction that have inclusion criteria and visit the prosthodontist's clinic in Kermanshah are randomly assigned to intervention groups.

Teeth in need of crown reconstruction are randomly divided into3 intervention groups.clinical treatment is done by a prosthodontist with 10 years of work experience in a dental clinic.one of gingival retraction techniques used for each group of patients. Patients were followed after 7 and14 days by another prosthodontists and student. In this triple blinded study, only the prosthodontist who insert the restorations knows about the groups and participants, outcome evaluators and result analyst were blinded.

Inclusion criteria: Patients who need their maxillary or mandibular first molar to be restored; have the opposite teeth in functional occlusion and at least one proximal contact with the adjacent teeth; have clinical sulcus depth between 2-3 mm and thick gingiva biotype; no smoking; acceptable oral hygiene and periodontally healthy (plaque index and bleeding on probing had to be below 20% previously to the prosthodontic treatment);.ready to take part in the study and sign the testimonial. Exclusion criteria: have previous periodontal surgery; have mobility in tooth; use drugs having effect on periodontium; patients have systemic disease.

1.gingival retraction with cord 2.gingival retraction with paste 3.gingival retraction with laser

Recession; plaque index; gingival index; bleeding index

Based on the random allocation law, after determining 60 maxillary and mandibularfirst molars based on statistical calculations, 20 cards for the cord group and 20 cards for paste group and 20 cards for laser group will be placed in a draw glass, then the cards will be dropped out randomly and without replacement and the resulting sequence will be recorded.Then,60 envelopes are prepared and each random sequence created is recorded on a card and the cards are inserted into the envelope respectively. In order to maintain a random sequence, the envelopes are numbered to the same. In the end, the door covers are enclosed in boxes and placed in a box respectively. At the time of the start of the registration of the participants, according to the order of entry of qualified participants to study, one of the envelopes are opened in sequence and the participant's assigned group is revealed

in this clinical trial study, only the prosthodontist who do gingival retraction techniques knows about the groups and the outcome evaluators(other prosthodontist and the calibrated examiner) are blind to the assignment of each participant in each of the study groups. Participants in the study are blind toward their own group when they are aware of the similar costs and benefits of clinical treatments based on studies. Also the result analyst, have no information about the data of each group.It should be mentioned as the retraction have no differences in appearance after do ,double blinding is available.