THE NEW MARGINAL PLAQUE INDEX MAY ALLOW A MORE VALID ASSESSMENT OF GINGIVAL PLAQUE LEVEL THAN THE TURESKY MODIFICATION OF THE QUIGLEY AND HEIN INDEX

Abstract

Subjects Study 1 was conducted from May 2013 to November 2013 on 64 participants (32 men and 32 women, age: 18-66 years; mean +/- standard deviation age: 34.49 +/- 11.91 years). Study 2 was conducted from November 2009 to September 2010 on 67 participants (15 men and 52 women, age: 20-29 years; mean age: 23.3 years). The participants of study 2 were students who had not majored in dental medicine or medicine. Key Exposure/Study Factor No oral hygiene instructions were provided to the subjects of study 1. The proximal sites of 2 opposite quadrants of the dentition were cleaned with dental floss and/or interproximal brushes by a dental hygienist, whereas the other 2 were left untreated. A blinded examiner assessed the areas using the Turesky Modification of the Quigley and Hein Index (TQHI) and Marginal Plaque Index (MPI). The subjects of study 2 were randomly assigned either to a control group that received training on the basics of toothbrushing only or to 1 of the 2 intervention groups that were provided with additional training using a modified Bass or Fones technique, respectively. Data were assessed 2 weeks before the intervention and 6, 12, and 28 weeks later by 4 trained and calibrated examiners. Main Outcome Measure Gingivitis was assessed using a modified papillary bleeding index (PBI) with World Health Organization (WHO) probe. The bleeding responses were rated as follows: (1) 0 = no bleeding; (2) 1 = single bleeding point; (3) 2 = bleeding from a narrow area; (4) 3 = interdental triangle filled with blood; and (5) 4 = profuse bleeding. Dental plaque deposits revealed by a disclosing solution were assessed by the TQHI and MPI. In study 1, all stained plaque was assessed after proximal surfaces of the teeth were cleaned. In study 2, old plaques having blue coloration stained with Mira-2-Ton solution were assessed before toothbrushing as an indicator of habitual oral hygiene. The subjects were instructed to completely remove plaque using a toothbrush and dental floss. All residual plaques staining pink and blue were assessed immediately. TQHI assesses plaque in 6 grades (at oral and vestibular surfaces) according to the distribution of the plaque. The MPI assesses the presence (score 1) or absence (score 0) of plaque within 8 equal sections of a tooth (4 at the oral and 4 at the vestibular gingival margin, respectively) (Figure 1). To prove whether the new MPI is a promising tool for evaluating proximal and cervical plaque, convergent validity of MPI with TQHI and criterion validity (ie, concurrent and predictive validity) with PBI was assessed. The convergent validity of MPI was assessed with TQHI in study 1 for quadrants without dental flossing and in study 2 for baseline measures. To assess the concurrent validity, the correlations of the plaque and bleeding measures were computed for quadrants without dental floss in study 1 and for baseline hygiene values in study 2. The predictive validity was assessed in the control group of study 2 by evaluating the correlation of hygiene measures (12 weeks after the treatment) and papillary bleeding (28 weeks after the treatment). Moreover, the treatment sensitivity of MPI to TQHI was analyzed by a treatment with proximal hygiene (study 1) or toothbrushing (study 2). Main Results First, convergent validity was analyzed to determine the accuracy of the new MPI in assessing plaque extension as compared to the TxQHI, an international standard. The results showed that there were moderate to excellent correlations (correlation coefficient [Pearson r or Spearman rho] = 0.5-0.9, P <.05) between MPI and TQHI, indicating a high convergent validity of MPI. Second, concurrent validity was analyzed to determine the degree of similarity between the new MPI and PBI while assessing plaque accumulation. The results showed that in study 1, MPI was not correlated with PBI at the proximal site (r or rho = 0.080-0.275, P >.05), and there was only a fair correlation at the cervical site (r = 0.251; rho = 0.398, P <.05). Third, predictive validity was analyzed to determine the predictability of the new MPI for gingivitis. There were moderate correlations (r or rho = 0.549-0.742) between MPI at week 12 and PBI at week 28 after oral hygiene instruction (P <.05), suggesting that MPI can be used to assess gingivitis. Finally, the treatment sensitivity of MPI significantly exceeded that of TQHI. In study 1, the largest treatment sensitivity was observed for proximal MPI measures, whereas study 2 showed the largest effects for cervical measures. This resulted in a reduction of more than 70% of the sample size required to determine significant treatment effects. Conclusions The MPI allows a valid assessment of plaque at the gingival margin. It shows good convergence with TQHI and has similar concurrent and predictive validity for PBI. For oral hygiene interventions, the treatment sensitivity of MPI significantly exceeds that of TQHI.