Study Design
The study protocol received the approval of the Ethics Committee of Human Research of the University of Granada (Ref. 1138/CEIH/2020). An observational prospective one cohort study pre‑post test was performed, involving undergraduate dental students from the School of Dentistry of the University of Granada (Spain), in the first semester of academic year 2019‑2020. All patients were referred to the Periodontology service of the School of Dentistry and underwent nonsurgical periodontal treatment.
Inclusion criteria were age >18 years with diagnosis of periodontitis according to the following criteria: presence of at least 2 sites with pocket probing depth (PPD) ≥ 4 mm at 2 different teeth, clinical attachment loss (CAL) ≥ 3 mm, with bleeding on probing (BOP) and bone loss ≥ 2 mm confirmed by orthopantomography.(7) Exclusion criteria were antibiotic and/or anti-inflammatory therapy 3 months before the study, previous history of periodontal therapy in the last year, ischemic cardiopathy, anticoagulated patients, hepatitis or HIV-positive patients, or diagnosis of any psychological disorder that could interfere in the comprehension of the questionnaire. The number of present teeth was not considered as an exclusion criterion. Informed consent was obtained from all participants. This manuscript was prepared according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.(8)
Sample size
This pilot study was designed to study the association between scaling and root planing (# of treated teeth) and OIDP after treatment. We decided to have at least 25 patients to detect a large effect size (r=0.5, i.e., the association is measured by correlation) according to Cohen,(9) with alpha=0.05 and power=0.8. Finally, 34 patients were enrolled in the study.
Periodontal examination and treatment
All diagnostic exams and treatments were performed by undergraduate students. A complete periodontal examination was performed on each patient, gathering the following periodontal variables in a periodontal chart: PPD, CAL, BOP,(10) Plaque Index,(11) gingival recession and number of periodontal teeth. The exam was performed with PCP‑UNC 15 (Hu‑Friedy, Chicago, IL, USA) manual periodontal probe.
All patients received non-surgical periodontal treatment, which consisted of oral hygiene instructions, supragingival plaque control and subgingival scaling and root planning (SRP). In the first appointment, clinical examination and supragingival calculus elimination by ultrasonic device were performed (Woodpecker G1 tips, mod. HW‑3H, Guilin, China). The second appointment was programmed in the following week, and dental students performed SRP per quadrant, under local anesthesia, with Manual periodontal Gracey curettes 5/6, 7/8, 11/12, 13/14 (Hu-Friedy, Chicago, IL, USA) to eliminate calculus and subgingival biofilm. Maintenance appointments were programmed 4‑6 weeks after treatment, with a periodontal examination and reassessment of initial periodontal parameters, performed by the same student.
OIDP Questionnaire
The OIDP questionnaire, validated for adults in Spain by Montero et al in 2008,(6) was administered to each patient before treatment and at the 4-6 weeks appointment. All students received previous training in OHRQoL and specific characteristics, usage and interpretation of the OIDP survey, as well as the procedure to perform the interview and administer the survey, regarding data gathering and bias prevention. This training was done through a specific seminar by one of the researchers participating in the study, with previous experience in the topic, and the supervision of a professor was provided while collecting first survey data. The survey was interview‑administered by each student to its corresponding patient.
The questionnaire consisted of 8 structured aspects asked to the patient, regarding 8 dimensions or activities in daily life (eating, speaking, cleaning teeth, working, social relation, sleeping/relaxing, smiling and emotional status). First, the patient answered on a dichotomous format (yes/no) if each dimension has been affected in a previously-established period of time (6 months for the baseline evaluation and 1 month -i.e. for the post-treatment evaluation). If any answer was “yes”, the frequency was assessed by the following score: 1 (less than 1 time/month), 2 (1‑2 times/month), 3 (1‑2 times/week), 4 (3‑4 times/week) and 5 (almost every day). If the frequency affected a certain period of time, a different scoring was applied: 1 (< 5 days), 2 (> 5 days), 3 (> 1 month), 4 (> 3 months) and 5 (the whole period). Likert scale was then applied to assess “severity” from 0 (null effect) to 5 (very severe effect).(6) The rating scale on each dimension was between 0 (zero) and 25. The total score of the patient, was obtained by multiplying frequency by severity on each dimension, and adding up the individual values of all dimensions. Maximum score of the questionnaire was 200. Impact index was obtained by the formula (total score x 200)/100. Individual rating was therefore expressed as a percentage of impact. The higher the percentage of impact, the lower the OHRQoL they had and vice versa.
All data regarding the survey, were collected hand written by the students, and then converted to excel sheets that calculated the total score of each patient and individual OIDP impact index on OHRQoL.
Statistical analysis
Statistical analysis was performed using SPSS 20 (IBM Corp., Armonk, NY, USA). Statistical tests used are described in table footnotes. To assess the effect of periodontal treatment, the pre-post OIDP comparison was not considered to be the most adequate approach, due to the absence of control group and also to the fact that the questionnaire was administered by dental students that are being supervised, and that a bond student-patient is formed that may alter (improve) the answers while administering the post-treatment OIDP questionnaire. Therefore, we analyzed the possible association between the extension of periodontal treatment (measured as number of treated periodontal teeth) and final OIDP score, adjusted for age, sex, and baseline OIDP score, by multiple linear regression. If the periodontal treatment is the cause of the improvement in OHRQoL, a dose-response relationship would be expected (between number of treated teeth and final OIDP score).