Principles of Attachment Selection for Implant Supported Overdentures

If the patient has a small mandible, with limited room for four implants, putting the distal implants as far back as possible distal to the mental nerve can enhance the A-P distance. In addition, the anterior implants should be brought forward as far as possible. These steps will improve the A-P distance to ensure that the basic biomechanical rules of avoiding an excessive cantilever, minimizing lateral forces on the supporting implant, and maximizing compressive forces, are not violated. The maximum cantilever in these cases is generally 8 mm to 12 mm.

If the patient has a square arch, the ­implants will be in a straight line in the ­anterior segment of the mandible. In this situation, any cantilever design must be avoided because the A-P distance will be small or non-existent. We suggest resilient bar assemblies for these patients. The prosthesis should be implant- and tissue-borne so that the buccual shelf and retromolar pad will each receive a share of the occlusal load. To minimize the compressive load on the bar, the denture base can be relieved in the area over the distal ­extensions.

Guidelines for Denture Base Extension

For mainly tissue-supported implant overdentures, the anterior borders of the overdenture should not extend to the end of the sulcus. There should be minimum ­extension in the anterior region but maximum extension in stress bearing areas such as the buccal shelves. The denture base should extend distally onto the retromolar pads and

For tissue-implant-supported overdentures the borders of the overdenture are significantly shorter than in conventional dentures; however, they can’t be eliminated because this type of prosthesis is still partially tissue-supported. For fully implant-supported overdentures flanges can be eliminated because the prosthesis is completely implant-borne.

Hader Bar

In 1973, Helmut Hader, master technician and dental manufacturer, developed a unique attachment system that even today is mainly known in the USA as the Hader bar or the Hader vertical. The Hader bar is a semi-precision bar attachment that provides hinge movement as long as a single Hader bar has been utilized in the attachment assembly ­design. This function of this bar is based on the mechanical snap-retention concept. (Figs. 15A, 15B, on P. 22)

There are three color-coded clips/riders with three retentive strengths. In order, from lightest to strongest, they are white, yellow and red. We strongly recommend using a metal housing with Hader plastic clips/riders. In addition to plastic clips/riders, the adjustable gold alloy clips/riders are an available option. (Figs. 15C, 15D)

Hader Clip Placement

Hader clips can wear out prematurely due to improper bar design and overloading. The denture base should sufficiently contact

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Volume 19.6