Substantial evidence exists that show that effective plaque control leads to reduction in prevalence and severity of gingival inflammation [1-6]. Use of toothbrush with dentifrice is a common mean for removing plaque on many tooth surfaces [7,8], research has shown that it cannot completely clean the interdental surfaces when used without other interproximal aids [9,10]. Dental flossing is useful in cleaning interproximal surfaces of teeth from the contact point to the sulcus [5,10-14] especially in Type I interdental embrasures[13]. Interdental brushes are used by patients with sufficient space between their teeth or the Type II interdental embrasures [13,15]. To make the dental floss effective in wide embrasure areas Gomes et al, have recently presented a modification in the technique of flossing and called it the ‘Knotted Floss Technique’ [16]. Unpublished data by the same authors in a crossover study shows that knotted floss technique is equally safe and effective method for reducing plaque, inflammation and bleeding when compared to conventional finger flossing in Type I gingival embrasures [17].

The purpose of this study is to compare the reduction of the clinical signs of plaque accumulation, gingival inflammation and gingival trauma in type II gingival embrasures that the knotted floss technique has been used with similar embrasures that a conventional flossing technique has been used, as well as with identical type embrasures wherein an inter-dental brush has been utilized. Patients’ acceptability of the knotted flossing technique will also be evaluated.

Materials and Methods:

Criteria for Sample Selection: For this triple phase, examiner blind, crossover clinical trial, a sample size of thirty individuals who were eighteen years and above will be randomly selected from the outpatients of the Department of Periodontology and Oral Implantology at the college hospital. The inclusion and exclusion criteria will be as described later. The trial will be conducted as per the guidelines in the WHO-Handbook for Good Clinical Practice [20] and the research protocol is approved by the Institutional Ethics Committee of the college.

Design of Study: A sample size of thirty subjects will be selected based on the criteria above. Prior to commencement of the actual study, each volunteer will receive written and verbal instructions on the two techniques. Investigator 1 & 3 will demonstrate to the volunteers all 3-techniques on models, for ½hour counseling session, for 3 consecutive days. Each counseling session will have not more than 10 participants. The techniques demonstrated on models will be conventional finger flossing, knotted floss technique and cleaning of interdental area with interdental brush. The conventional finger flossing technique will be demonstrated to the volunteers as follows: 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. For the knotted floss technique, the volunteers will perform the same way as the conventional finger flossing technique, except that the insertion of floss will have to be in the non-knotted area and during the to and fro movements the knotted area of the floss will have to be engaged in the interdental area. When using the interdental brush, the volunteers will be demonstrated to gently insert the brush into the interdental area with an inclination akin to the angle of the interdental gums (gingiva), and perform to and fro buccal to lingual movements and a little apico-coronal movement such that the gingiva is not impinged, and finally removing the brush out buccally. On the 4th day, after both investigators will be separately satisfied with the volunteer’s proficiency on models, with respect to each of the three techniques demonstrated, an informed consent will be taken and the volunteer will be enrolled as a subject into the 16-week, 3-phase crossover, single (examiner) blind study protocol with washout phases of 2-weeks each in-between the intervention phases. Failure by the volunteer to perform the techniques as instructed will mean another counseling session of 1-hour, followed by another check of proficiency by volunteer on models by the above investigators on subsequent day. If the investigators are not satisfied with the ability of the volunteer to perform any one of the 3 demonstrated techniques of interdental cleansing even after an extra counselling session, then the volunteer will not be recruited into the study protocol.

Investigator#1 will be randomly placed into three groups (Group A, Group B, Group C) by the draw of lots. Each group will participate in three treatment phases of 4-weeks each with a 2-week washout phase in between the 3-treatment phases. Group A will perform conventional finger flossing in 1st phase, followed by knotted floss technique and interdental brushing in the 2nd and 3rd treatment phase respectively. Group B will perform knotted floss technique, interdental brushing and conventional finger flossing in the 1st, 2nd and 3rd treatment phase respectively; while Group C will perform interdental brushing, conventional finger flossing and knotted floss technique in their 1st, 2nd, 3rd treatment phases respectively. Only the 1st investigator will be responsible for this allocation and coding of subjects to respective treatment groups and the other investigators will be blind as to which technique the subject will be assigned to. Each treatment phase will consist of 4-weeks of daily use of the assigned interdental cleansing technique. At the baseline appointment for each treatment phase, every subject will be given their assigned interdental cleansing products by the 1st investigator (only). Subjects assigned to conventional flossing will receive 60-pieces of waxed floss [Reach­®-Johnson & Johnson Consumer Inc.], 15-centimeters in length each piece, equally divided in 3-bags [Ziplock®-S.C. Johnson & Son, Inc.]. Subjects assigned to knotted flossing aid will receive the same except that every floss thread will have a simple knot at around the middle. Subjects assigned to the interdental brush cleansing regimen will receive 60-pieces of interdental brushes [Thermoseal® Proxa ns interdental brushes-ICPA Health Products Ltd] equally divided in 3-bags, instead of the pieces of floss. Each subject will also receive a sample of toothbrush [Oral-B® Allrounder Soft Toothbrush-Procter & Gamble India Ltd.]  and dentifrice [Colgate® Strong Teeth Dentifrice-Colgate-Palmolive Company Ltd.]. The subjects will be instructed to brush their teeth twice a day in their customary manner using the above toothbrush and dentifrice and will be cautioned not to use any other oral hygiene aid except for the assigned interdental cleansing device twice a day. The subjects will have to return to the 1st author any unused interdental cleansing product(s) at the end of the treatment phase. The 1st and 2nd treatment phase will be followed by a ‘washout period’. 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, interdental brush 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 next treatment phase. Such a ‘washout’ in crossover-study design will allowed use of 50% lesser subjects [17].

Clinical evaluations: Clinical evaluations of all subjects will be done at 2-weekly intervals, namely baseline, 2-weeks and 4-weeks of each treatment phase. Both adjacent teeth and gingiva at test sites will be scored for the Rustogi Modification of Navy Plaque Index [21], Lobene’s Modified Gingival Index [22], and Barnett’s Modified Papillary Bleeding Index [23]. The sequencing of examination is specifically chosen as plaque index, gingival index and bleeding index, so as to avoid the possibility that the plaque will be removed during the recording of the other two indices [7,24]. A plaque disclosing agent will be used to identify the location and amount of plaque. Additionally, gingival trauma will also be assessed as presence or absence of signs of trauma in the marginal and papillary gingiva of adjacent teeth as per the methodology proposed by Carter-Hanson et al [7]. 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 when there is absence of any signs of trauma. The score per subject will be obtained by totaling all scores and dividing by number of sites examined [7].

The indices will be recorded by investigators #2 & 4. Intra- and inter-examiner reliability will be recorded prior to commencement of the study and at 2-weekly intervals throughout the study. A rate of concordance will also be established. The study schedule will so be distributed, such that not more than six subjects reported for examination on any given day of the week. These two investigators will be blinded as to which technique the subject is using and the amount of unused floss if any at end of respective treatment 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 the investigator #1. The subjects will be instructed to record each interdental cleansing experience in this diary and any other event he/she will feel is significant. A patient satisfaction questionnaire will be answered by every subject at the end of the third and final treatment phase. Compliance or non-compliance by the subject will thus tried to be established by calculating the amount of any unused portion of interdental cleansing product and by the entries in the diary. Investigator #3 will contact the subjects after completion of the study to verify any unusual entries in the compliance diary or to ascertain the reasons of excess unused floss returned to the department if any.

Analysis of Data: Data will be recorded by investigator #2 &4 into coded case sheets per subject. This data after decoding by investigator #1 will be tabulated wherein the scores at respective time periods of conventional flossing technique from all three treatment groups, will be tabulated together and similarly those of knotted floss technique and interdental brushing. The scores for plaque, gingival inflammation, gingival bleeding and gingival trauma will be tabulated separately. The mean differences and standard deviations will be calculated. The mean differences of scores at respective time intervals of each of the index scored will be compared between the three interdental cleansing techniques by using the analysis of variance (ANOVA) and the paired sample test. This will determine the statistical difference between scores of the three different techniques whilst calculating a specific index at respective time interval. Also, a statistical analysis by paired t-test will be done of difference of scores recorded between 2-weeks and baseline, 4-weeks and baseline, 4-weeks and 2-weeks of that specific index within the same treatment technique. This will determine the improvement/worsening/no effect of respective scores of plaque, gingival inflammation, gingival bleeding and gingival trauma over a 4 week period while using the same interdental cleansing technique. The responses given by the patient to the end-study questionnaire will be aggregated and analyzed on a percentage scale to compare preference between each technique.

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