It has been well established that the origin of gingivitis and periodontal diseases occurs by the colonization, accumulation and subsequent maturation of bacterial plaque, (Loe et al 1965, Socransky 1970), and mediated by the host immunological response (Lewis et al, 2004). Since, oral bacteria in plaque biofilms are an essential component in the dental diseases processes, most of current preventive oral health care focuses on thorough plaque removal so as to prevent, reduce or even reverse the disease condition. (Suomi 1971, Schmid et al 1976). In such endeavors of thorough plaque removal and especially prevention of its further accumulation, dental surgeons and hygienists have commonly recommended daily mechanical plaque removal, specifically tooth-brushing. Use of toothbrush to mechanically remove plaque is extremely effective, but yet is not able to remove it thoroughly from interdental areas when used alone (Hansen \& Gjermo 1971) Routine use of dental floss in conjunction with tooth-brushing has been shown to reduce the onset and severity of gingivitis (Bergenholtz \& Britton 1980, Carter-Hanson et al 1996) Patients' reluctance and inability to perform flossing on a regular basis has been mentioned (Kresh 1976). In addition, to plaque control, patients also utilize flossing to clear the interdental areas wherein food impaction has occurred (Gjermo \& Flotra 1970). Schmid (1984) has classified interdental embrasures, depending upon the filling of the gingival embrasure by the interdental papilla. Hence in Type I, floss is used, and in Type II and III the incrementally wider proxabrush and unitufted brush are used respectively. Gomes et al have presented a modification in the use of knotted floss in wider embrasure areas. (Gomes et al 2016). The modification in the dental floss had been done so as to increase the effective width of the floss. This enables it to be used in embrasures wider than that recommended for conventional floss. In this modification, a knot is tied in the floss at any distance in the middle third of the floss length. The floss is inserted past the interdental contact point by the conventional finger flossing technique in the non-knotted area and then during the 'to and fro movement' on the tooth surface cervical to contact point, the knotted area is engaged through the embrasure (Gomes et al 2016) The purpose of this study is to compare the reduction of the clinical signs of plaque accumulation, gingival inflammation and gingival trauma in the area the knotted floss technique has been utilized versus the area where conventional flossing has been utilized in Type I gingival embrasures. Patients' acceptability of the knotted flossing technique will also be evaluated. This study is part of a larger study protocol involving different sample groups comparing the knotted floss technique with conventional dental flossing, use of inter-dental brushes and unitufted brushes in type II and type III embrasures as well.

Study Design:

A sample size of thirty subjects will be selected based on the model used by Carter-Hanson et al 1996. Prior to commencement of the actual study, each volunteer will receive written and verbal instructions on the two techniques. The principal and third investigator will demonstrate to the volunteers both techniques on models, for half hour counseling session, for three consecutive days. Each counseling session will not have more than 10 participants. On the third day the volunteer's proficiency on models in both techniques will be confirmed by both demonstrators separately, informed consent will be taken and the volunteer will be enrolled as subject into the fourteen week, 2-phase crossover, single (examiner) blind study protocol with washout in-between phases. Failure by the volunteer to perform the techniques as instructed will result in another counseling session of half hour or he/she will not be included in the study protocol.

In the first phase, 50% of the subjects will be randomly assigned to use either conventional flossing technique, while the other 50% will be assigned to use the knotted floss technique. Only the first author know about which subject will be assigned to which technique. The treatment phase will consist of 6 weeks of daily use of the assigned technique followed by a 'washout period' of 14 days, following which will start the second treatment phase wherein the subject will use the other flossing technique. i.e those using the conventional flossing technique will now use the knotted flossing technique and vice versa. At the baseline appointment for each phase, every subject will be given their assigned floss products. Subjects that will be assigned to conventional flossing will receive ninety pieces of waxed floss, fifteen centimeters in length each piece, (Reach¬® by Johnson \& Johnson Inc.) equally divided in three ziplock® bags. Subjects that will be assigned to knotted flossing technique will receive the same except that every floss thread will have a simple knot at around the middle. Each subject also will receive a sample of Colgate® Soft Toothbrush and Dentifrice (Colgate® Inc). The registered subjects will be instructed to brush their teeth twice a day in their customary manner using the above toothbrush and dentifrice provided and cautioned not to use any other oral hygiene aid except for the assigned floss twice a day. They will be instructed to wrap the floss around their middle or index finger and gently slide the floss between the teeth and move it along the gum margin, curved into "c" shape. After this, they will have to move the floss up and down several times between each tooth without using excessive pressure, finally allowing it out through embrasure. The subjects will have to return to the third author any unused floss products at the end of the phase. During the 'washout period' the subjects will be instructed to perform normal oral hygiene practices of tooth-brushing with dentifrice and refrain from using any floss or any additional plaque control aids. The "washout" period is designed so as to give subjects time to return to their original oral status and establish parity in baseline clinical measurements prior to starting the second treatment phase. Such a 'washout' in study design allowed use of 50% lesser subjects.

Clinical evaluations:

Clinical evaluations of all subjects will be done at 2-weekly intervals, namely baseline, 2 weeks, 4 weeks and 6 weeks of each treatment phase. Both adjacent teeth and gingiva at test sites will be scored for the Rustogi Modification of Navy Plaque Index, the Modified Gingival Index (Lobene 1986) and the Modified Papillary Bleeding Index (Barnett 1980). A plaque disclosing agent will be used to identify the location and amount of plaque. Additionally, gingival trauma will be assessed as presence or absence of signs of trauma in the marginal and papillary gingiva of adjacent teeth. The facial and lingual surfaces will be examined visually for gingival lacerations. Presence of laceration, floss cut, or demarcation line/indentation at the site will be scored as one, while a score of zero (0) will be recorded in the absence of any signs of trauma. The score per subject will be obtained by totaling all scores and dividing by number of sites examined (Carter-Hanson 1996).

The indices will be recorded by second and fourth investigator. Intra- and inter-examiner reliability will be established prior to commencement of the study and at two weekly intervals. The study schedule will be so distributed such that not more than six subjects report for examination on any given day of the week. The two examiners will have no knowledge as to which technique the subject is using and the amount of unused floss if any at end of phase.

Subject compliance A compliance diary will also be given to each subject at the baseline appointment of each treatment phase and will be collected at the end of each phase by third investigator. The subjects will be instructed to record each flossing experience in this diary and any other event he/she felt significant. Compliance will further be established by dispensing a specific amount (90 pieces) of assigned floss product per treatment phase. At the conclusion of each treatment phase, the subjects will return to principal or third investigator, any unused portion of floss product and thus non-compliance will be estimated. Additionally, the patient satisfaction questionnaire will substantiate subject compliance. This questionnaire will be answered by every subject at the end of the second and final phase.