Subgingival plaque control by a simplified oral hygiene regime plus local chlorhexidine or metronidazole

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Abstract
This study determined the effects of a simplified oral hygiene regime plus local applications of metronidazole or chlorhexidine on the subgingival microflora. Twenty‐one patients, with periodontal pockets 4 mm or deeper, underwent one session of scaling, root planing, and oral hygiene instruction (Bass method but without emphasis on interdental cleaning). Eight patients performed once daily subgingival irrigation with 0.2% chlorhexidine gluconate solution for 28 days. Thirteen patients had either 0.5% metronidazole in dialysis tubings or 40% metronidazole in acrylic resin strips inserted subgingivally once weekly, also for four weeks.For each subject, subgingival plaque was obtained from two chemically treated (test) and one non‐chemically treated (control) pockets at days 0 (prior to scaling and root planing), 7, 14, 21, 28, 56, and 84. The subgingival microflora was assessed using darkfield microscopy. Bacteria were characterized as cocci, motile organisms, spirochaetes, and others (straight and curved rods, filaments and fusiforms).Both chlorhexidine and metronidazole groups showed beneficial change still apparent at the end of the study (3 months). Great increases in proportions of cocci and reductions in spirochaetes and all other forms of bacteria were observed. Metronidazole reduced spirochaetes more but, unlike chlorhexidine, had a variable effect on motiles. Root planing alone had less effect. Generally, metronidazole and chlorhexidine appeared equally beneficial. It was concluded that in spirochaete‐dominated plaque, metronidazole may be preferred agent. Where motiles predominate, chlorhexidine may be the topical agent of choice.