www.dta-uk.org
June 2018 | volume 5 | issue 3
articulate the bi-monthly e-newsletter of the dental technologists association
This issue contains 30 minutes of CPD for DTA members
Kestrel Court, Waterwells Drive Waterwells Business Park Gloucester GL2 2AT Telephone: 01452 886366 Email: sueadams@dta-uk.org Web: http://www.dta-uk.org
DTA nominated charity of the year 2018 DTA members have selected Den-Tech as DTA’s nominated charity of the year for 2018. If you’d like to find out more about their work, go to www.den-tech.org
Interesting Aspect of Partial Frameworks Sourced by Tony Griffin By using a dental surveyor, a model can be tilted in different angles to determine the best path of insertion for a removable partial denture (RPD). An undercut can be a useful and desirable feature for engaging the tip of a clasp to provide retention. Undesirable undercuts are those not used for retention whether on soft tissue overlying the alveolar bone or on hard tooth tissue. Standards for Dental Professionals: Aim: ● To consider how partial denture design can assist in retention
CPD Outcome(s): (i) To review the positioning of clasp tips via use of undercut gauges (ii) To be aware of how the choice of material affects the depth of undercut used (iii) To be aware of how one example of a digital design system enables the dental technician to create a partial denture pattern
Development outcome: C
W
hen surveying a model, we tend to look for a path of insertion that reduces the actual amount of undesirable undercut, thus reducing the need to block out too much undercut. e.g. a Kennedy Class I (bilateral free-end saddles) with the 11, 12, 13, 14, and 21, 22, 23, 24 standing. If a model is slightly tilted down in the anterior region by tilting the surveyor table, the undesirable undercut on the distal of the premolars can be reduced and engaged by the hard denture base. This assists in retaining the RPD because the denture fits close to the distal side of the premolars. The desirable undercut is then sought in which to place the flexible tip of the clasp. The amount of undercut engaged by the flexible tip depends on the type of material (gold wire, stainless steel wire, etc.) and its structure (i.e. wrought wire, cast metal or flexible plastic) being used for the clasp. Careful engagement of the retentive arm clasp tip into the correct depth of undercut can only be determined by using undercut gauges on the surveyor at the chosen path of insertion. The standard undercut gauge is a rod of metal similar to a bur shank with a
Fig. 1: Three undercut gauge size ranges
raised area or lip of varying small areas representing the normal three main undercut gauge sizes (as shown in Fig. 1). The normal undercut size ranges are 0.010 inch/0.25 mm, 0.020 inch/0.50 mm or 0.030 inch/0.75 mm. The presenter introduces a selection of clasps e.g. the i-bar and half T, and there is even reference to an extra coronal precision attachment used for retention of a partial denture. In viewing the public domain video: ■ https://www.youtube.com/ watch?v=zbTA_Go5dxo
Dental Technologists Association, Kestrel Court, Waterwells Drive, Waterwells Business Park, Gloucester GL2 2AT. call: 01452 886 366 email: sueadams@dta-uk.org web: www.dta-uk.org