A meta-analysis of gum health studies: 3-month versus 6-month results

Objectives: The objective was to assess whether the results obtained in gum health studies after three months would give rise to the same conclusions that have been made after six months.

Methods: MEDLINE was used to identify relevant published studies; sixty-six studies passed a screening process for inclusion. The main criteria were: data available for (approximately) 3 and 6-months;  the study tested efficacy of toothpaste or mouthwash; publication date between 1977 and 2007 . The following oral health measures were analysed:  plaque - Modified Quigley Hein Index (MQHI), Plaque Index (PI); gingivitis - Gingival Index (GI), Modified Gingival Index (MGI) and Bleeding Index (BI). Standard techniques used in meta-analyses, correlation and regression analyses were applied to all data and to sub-sets defined by product type (toothpaste or mouthwash; non-active controls (NAC) or test/positive controls (TPC)).

Results: Overall, the mean (sd) 3-month and 6-month changes in index values from baseline (for n cases) were:

	MQHI (n=125)	PI (n=40)	GI (n=104)	MGI (n=37)	BI (n=66)
3-month	0.47 (0.37)	0.22 (0.24)	0.22 (0.22)	0.27 (0.27)	8.7 (10.7)
6-month	0.50 (0.46)	0.22 (0.24)	0.28 (0.27)	0.41 (0.36)	9.9 (13.4)

The changes from baseline for NAC were less than those for TPC, ranging from 40% less for PI to 74% less for BI. The differences between the 3-month and 6-month index values were similar for toothpastes and mouthwashes.

The conclusions regarding differences in product efficacy based on 3- and 6-month data were compared. The proportion of agreement (i.e. where 3- and 6-month data led to the same conclusion) was calculated for each index studied; these proportions ranged from 79% (for BI) to 97% (for PI). No publication bias was indicated in the analysed studies.

Conclusion: This meta-analysis suggests that studies could be designed to run for three months only, giving ethical gain, efficiency gain and lower costs.