ERA Attachments

The ERA attachment, by Sterngold, is an extracoronal semi-precision attachment intended for combination cases utilizing fixed crown & bridge and a Kennedy Class I or Class II removable cast metal partial. ERA attachments, being resilient attachments, place the occlusal load on both the abutment teeth and the edentulous ridge. They provide vertical resiliency through the use of a nylon male that fits into the metal extracoronal female. The female is a plastic pattern which is waxed into the pattern of the crown or bridge restoration for a single piece casting. The male part is retained directly in processed acrylic or retained inside an ERA® metal jacket that is then processed into the acrylic. The metal jacket is made of stainless steel so that it can be soldered or welded to the cast framework, if desired. Sterngold offers six color coded males for six levels of retention. From lightest to heaviest in retention, they are white, orange, blue, grey, yellow and red.

Two sizes of the ERA attachment are available. Due to its size, we prefer the Micro ERA, as it can be
used in most instances. The Micro ERA attachment is 20% smaller than the ERA-RV, making it the smallest extracoronal resilient attachment in the world (only 2mm tall and 3.4mm wide).

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eraPlease refer below for information regarding the space requirements for both the RV (Reduced Vertical) and Micro sizes. If a metal jacket is to be used for housing the nylon male, please add 0.3mm to the required space. If a patient has a very strong bite, it is recommended that you add 1mm to the height requirement. Take notice that allowance has already been made for the acrylic, which will surround and hold the attachment component. The acrylic thickness occlusal to the male component is 1mm and the acrylic thickness lateral to the male attachment is 1mm on each side.

 

ERA-RV
Minimum Space Required
Height FC Width Prep Depth RC Width
3.5mm 2.8mm Normal Crown 6.3mm

 

Micro ERA
Minimum Space Required
Height FC Width Prep Depth RC Width
3.0mm 2.2mm Normal Crown 5.4mm

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FC Width (Fixed Component of the attachment) = Minimum buccal-lingual space necessary for the female component on the mesial or distal wall of the fixed restoration.

RC Width (Removable Component of the attachment) = Minimum buccal-lingual space required in the removable partial male component.

 

When choosing the ERA attachment, please take into consideration the following information provided by Sterngold, the manufacturer of the ERA attachment.

The following are general guidelines that may be used to help you to decide on which attachment might be best for a particular situation. They are based on 80 years of experience with dental attachments, but the final choice must be based on the particular dentist's philosophy, education, and experience. Based on your answers to the following question you will choose either Non-Resilient Attachments or Resilient Attachments.

  • Bone Support Around the Abutments - If the bone support is good (0-20% bone loss), or if abutments can be made strong by splinting, non-resilient attachments are the connectors of choice. If the bone support is fair (20%-40% bone loss), the choice will most often be resilient attachments. If the bone loss is 40% or greater, more than likely the abutments need to be reduced to the height of the gingival tissue and the roots used to retain an overdenture.
  • The Condition of The Ridge - If the edentulous ridge has little loss of bone, either resilient or non-resilient attachments could be used. But, if the ridge is significantly resorbed, non-resilient attachments would most likely be indicated.
  • Is the opposing arch non-resilient (rigid) or resilient? Two resilient prostheses should generally not oppose each other, as two mobile occlusal planes will impair chewing efficiency.

 

The choice in partial denture attachments is between Non-resilient and Resilient. Non-resilient (rigid)
attachments are highly stable connectors with very slight movement in function. Some may be used for
segmenting fixed partial dentures to simplify future case conversion to a removable restoration. In distal
extension partial denture cases, occlusal forces are directed relatively evenly to both the abutment teeth
and the edentulous ridge. Therefore, rigid attachments are kinder to the edentulous ridge than are resilient
attachments. When abutment teeth are stable, rigid attachments are often the connectors of choice.