Objectives:  To consider the efficacy of subantimicrobial dose doxycycline (SDD) as an adjunct to scaling and root planing (SRP) when treating smokers and non-smokers with moderate-severe chronic periodontitis (CP).

Methods:  A double-blind, randomized, placebo-controlled, clinical trial was conducted.  210 patients, aged 30-75 years, with baseline clinical attachment levels (CAL) and probing depths (PD) 5-9mm were enrolled.  At baseline, patients were treated by a standardized episode of SRP, and randomized to receive either adjunctive SDD (20mg doxycycline BID) or placebo for 9 months.  Tooth sites were stratified by baseline PD value:  moderately diseased sites (baseline PD 4-6mm) and severely diseased sites (baseline PD ³7mm). Treatment group comparisons of per-patient mean CAL and PD changes were performed using appropriate analysis of variance models utilizing smoking status as factor.

Results:  Retrospective analysis revealed that 67 subjects (32%) were current smokers.  Mean (SE) CAL gains and PD reductions (adjusted for smoking) after 9 months were as follows:

	CAL gain (mm)		PD reduction (mm)
	Baseline PD 4-6mm	Baseline PD ³7mm	Baseline PD 4-6mm	Baseline PD ³7mm
Non-smokers: SDD (n=66)	1.29 (0.07)	2.12 (0.18)	1.33 (0.07)	2.35 (0.18)
Non-smokers: Placebo (n=76)	1.01 (0.07)	1.55 (0.17)	1.00 (0.07)	1.74 (0.17)
Smokers: SDD (n=41)	1.19 (0.07)	2.02 (0.22)	1.19 (0.08)	2.25 (0.16)
Smokers: Placebo (n=26)	0.85 (0.09)	1.88 (0.29)	0.93 (0.10)	1.89 (0.21)

A hierarchical treatment response was observed such that non-smokers who received SDD tended to demonstrate the best treatment response, and smokers who received placebo demonstrated the worst (p<0.01 in moderate sites).  The treatment response observed with SDD was broadly equivalent whether patients were smokers or not (p>0.05). 

Conclusions:  SDD used adjunctively to SRP provides significant benefit for both smokers and non-smokers with CP compared to SRP alone.

Supported by a grant from CollaGenex Pharmaceuticals, Inc.