Restorative dentistry
Fig 5
Fixed/movable bridge on model. Note the movable component
Fig 6
Fixed/movable fitted. Note adjustment to movable component
Fig 7
Movable component incorporated in wax-up
Continued »
• Prepare both major retainer and minor retainers. Prepara- tions should be down the long axes of teeth giving consid- eration to retention, resistance, margins, occlusal reduction and functional cusp bevel. • Prepare a box in the distal surface of the minor retainer. Typically, this is 2mm in depth going towards the centre of the tooth, 2mm in buccolingual width and should end just above the marginal finishing line on the minor retainer. The box should be located in the mid-distal area of the minor retainer, directly opposite the mesial surface of the major retainer (Fig 8).
Try-in, adjustment and cementation Smithı0 describes one of the main advantages of fixed/ movable bridgework as being ease of cementation. The appli- ance is supplied in two parts, which are tried in the mouth for marginal fit. Once verified, and prior to cementation, the clinician must make an adjust-
ment to the male portion of the movable component. It should be realised that
during occlusal loading, the fixed/movable bridge functions initially as a fixed cantilever, until the base of the male contacts the base of the female, when the bridge acts as a fixed/ fixed appliance. The clinician must decide how much of the movement should be taken up by cantilever forces and how much should be taken up by fixed/fixed forces, in other words, how much material should be removed from the base of the male. An arbitrary amount of
0.5mm has been suggested, but the decision should be based on the condition of the abutment teeth9. A common clinical example is that the major retainer is a robust molar and the minor is a root-filled premolar. In this situation, it is prudent to allow the appliance to function more as a cantilever, implying that a greater adjust- ment will be required from the base of the male.
Continued » RAISING STANDARDS
The BARD was set up in 2009 and aims to improve the quality of restorative dentistry by promoting educational opportunities. BARD is the only organi- sation of its kind to offer a complete training pathway from membership through Certification, Diploma and on to Fellowship.
All dental professionals can join the academy and members benefit from annual scientific meetings and local study clubs, both offering an opportu- nity to learn from national experts and to
network and socialise with other restorative dental professionals.
® For more information on the BARD and how to join the academy, please visit
www.bard.org.uk Paul Tipton will be lecturing at the first BARD Edinburgh Study Club on 28 May. Places will be limited. To register your interest in this event and to find out more about the BARD Edinburgh Study Club, please contact Stuart Campbell on
campbell986@btinternet.com
Scottish Dental magazine 59
TABLE 2
Acceptable Major Retainer Full coverage crown 3/4 crown Maryland wing
Unacceptable major retainer Post crown MOD inlay
TABLE 3
Acceptable minor retainer Full coverage crown 7/8 Crown 3/4 Crown MOD Onlay Maryland Wing
Unacceptable minor retainer Post crown MOD gold inlay
Silver dies are the ideal for making bridge retainers on, here shown with extra retention in the form of an interproximal groove
Lab work
by A-Plus Dental Lab, Dundee
Fig 8
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