The aim of the clinical study is evaluation of the effect of the machined (smooth) cervical collar on marginal bone level. Authors placed 69 modified fixtures Impladent. These implants differed from the standard fixtures by their geometry, surface, and type of cervical collar. Marginal bone level was measured both after the healing period and after one year of functional loading of implants. The marginal bone lost was always more accentuated in the implants with elongated smooth cervical collar. Other parameters (geometry and surface of the fixture) did not have any effect on the bone level. Authors concluded that implants with elongated smooth cervical collar are, from the viewpoint of the marginal bone level, unconvenient.

        Key words: dental implant – osseointegration – hydroxyapatite – coated implant