Table 3.

The outcomes and the outcome measures used in the trial.

Outcome	Outcome measure	Description
Plaque	Orthodontic Modification of Plaque Index (OMPI) (Williams et al., 1991) or Plaque Index (PI) (Silness and Loe, 1964)	Adaptation of the PI (Silness and Loe, 1964) for patients wearing fixed appliances. All teeth from first molar to first molar in both arches were painted with disclosing solution (TePe PlaqSearch™ Advanced Disclosing Solution; TePe Munhygienprodukter AB, Malmö, Sweden) the and patient rinsed with water. Clinical photographs were taken for assessment of intra-rater reliability. Four sites on each tooth (mesial, distal, gingival and incisal to the bracket) were scored 0–3. Scoring criteria are the taken from the PI and shown in Supplement 1. Mean score for mouth was calculated. At T0, PI (Silness and Loe, 1964) was used to measure the plaque coverage on six index teeth, one in each sextant of the mouth. The index teeth are the UR6, UR2, UL4, LL6, LL2 and LR4. This was used instead of OMPI because OMPI requires brackets to be in situ. If a UL4 or LR4 had been extracted, UL5 or LR5 was used instead. Mean score for mouth was calculated.
Gingival health	Gingival index (GI) (Loe and Silness, 1963)	All upper and lower permanent teeth from first molar to first molar. Periodontal probe gently inserted into the gingival crevice of four sites on each tooth (mesial, distal, buccal and lingual), and a score of 0–3 allocated to each surface. The scoring criterion are shown in Supplement 2. Mean score for mouth was calculated.
	Interdental Bleeding Index (IBI) (Caton and Polson, 1985)	Wooden interdental stick was used to depress each of the interdental papillae from first molar to first molar. The interdental stick was inserted buccally and the papillae depressed 1–2 mm four times. The presence, or lack, of bleeding within 15 Seconds was recorded and a percentage bleeding score calculated. Where a tooth was missing, or significantly displaced so much that an obvious papilla was not present (such as in the case of a palatally ectopic canine), the sites mesial and distal to the tooth were not recorded.
Trauma	Soft-tissue examination	Soft-tissue examination was performed at each appointment to assess for soft-tissue trauma secondary to oral hygiene regime.
Adherence to oral hygiene regime	Frequency of oral hygiene practices	Participants were given oral hygiene diaries to take home and complete for the duration of the trial. They were asked to complete the diary every time they cleaned their teeth, estimating in minutes for how long their teeth were cleaned, and state whether the WaterPik® was used. These data were to be used to assess frequency of toothbrushing, time spent toothbrushing and frequency of WaterPik® use.
Satisfaction with oral hygiene regime	Participant satisfaction measured with questionnaire	Participants were asked to complete a satisfaction questionnaire following their appointment at 8 weeks and 56 weeks. Two separate questionnaires were completed to avoid the control group being asked questions about using the WaterPik®. The intervention group answered all the questions on the control questionnaire, with additional questions regarding the WaterPik®. The questionnaires were adapted from those used a similar trial (Saini, 2016).