LMT • August 2015 • www.LMTmag.com 34 LMT • August 2015 • www.LMTmag.com 35

How to Use Perma-Ret to Improve Denture Retention

T oday’s nano-composite, highly cross-linked and hybrid denture teeth con-tinually pose a retention problem in cases with limited space once the

bondable lingual layer of PMMA has been removed. Implant treatment modalities with their rigid foundation and opposition exacer-bate these compromised bonds.

To solve the problem, technicians often use bonding primers, diatoric retention or slot the lingual but I’ve discovered a better solution: Perma-Ret, a pin retention system from Preat Corp. The kit includes twist drills, a drill and wire holder, collets and 80mm-long threaded silver wire (see Figure 1). Similar to the way metal pins are used to retain porcelain den-ture teeth, the Perma-Ret wire is threaded into a drilled hole in the denture teeth; the wire is small and unobtrusive and provides mechanical retention between the teeth and the acrylic base. The placement technique is easy to master and the kit pays for itself by preventing repairs on warrantied dentures.

Here’s my technique; this is done during setup:

1. Adjust the teeth to fit into the allowable space.

2. Using the twist drill, drill a hole into each tooth at a suitable angle and position as dictated by the remaining acrylic and the hori-zontal space before intrusion or perforation.

When I first started learning to use Perma-Ret, I marked the drill bit with a magic marker to indicate the depth of the hole and continue to use this mark as a reference (see Figure 2). Preat recommends a 3mm depth but I’ve drilled to only 1mm depth without any failure in retention.

Using the mark on the drill bit, mark the coinciding depth on the wire and place it into the wire holder; expose only a short length of wire so you don’t bend it. Thread the wire into the hole in the tooth; you’ll feel a fair amount of resistance while threading and your mark ensures the wire hasn’t “bottomed out” which can damage the tooth or wire (see Figure 3).

3. Snip the wire to 1.5-2mm (the porcelain tooth pin length) and bend it to an angle if needed. Don’t re-bend the wire as this will fatigue and weaken it.

4. If needed in very tight situations, use a rubber wheel to conform the tip of the wire to meet the space requirements (see Figure 4).

5. Continue placing the teeth in the setup (see Figure 5).

Figure 1 The Perma-Ret Kit from Preat Corp. contains three twist drills; a drill and wire hold-er; two collets; and 13 pieces of 80mm-long threaded silver wire, which should be enough to retain at least 100 teeth.

Figure 2 When placing the hole and wire, remember that retention is most effective when they are most perpendicular to the dislodging force which, in most cases, places them parallel to the facial. Position C in the center image would be the best choice as it offers space and is the most perpendicular position-ing which provides undercut. Marking the drill bit and wire with a black marker helps to control depth of placement when you’re learning to use Perma-Ret.

Preventing and Repairing Midline FracturesBefore you put your Perma-Ret Kit away, I’d like to share another application: preventing and repairing midline fractures. When a case comes into my lab for a midline repair, I reline it with heat-cured GC Nature-Cryl® because it’s strong and prevents subsequent fractures. Additionally, for habitually fracturing dentures, I like to eliminate any occlusal wedging that may propagate the fracturing and use Preat’s eFiber reinforcement as well as Perma-Ret in the reline/repair.

When using eFiber, place it as close as pos-sible to the stress/fracturing point which, in the majority of cases, coincides with the bottom of the notch used to relieve the frenum. I place Perma-Ret pins in the anterior teeth (see Figure 6) and use them as posts to support the eFiber across the bottom of the notch. This allows me to ideally position the eFiber and provide stable placement of the teeth during acrylic packing or injecting during relining (see Figures 7 and 8). If I know a patient habitually fractures his denture, I’ll pin and place Perma-Ret and eFiber when I’m processing a new one for him.

Thomas Zaleske explains how to use Preat Corp.’s Perma-Ret to provide mechanical retention between the teeth and the acrylic base and prevent midline fractures.

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Figure 8 Here’s the denture rein-serted into the flask and packed as a routine reline us-ing the flask reline technique. The void is finger packed and trial packed to en-sure secure place-ment. To prevent fractures in a new denture, perform the pin bridging, packing and curing.

Figure 6 When relining a midline fracture, I use the closed flask reline technique using PVS putty that al-lows me to remove the denture from the flask, remove the tissue-bearing areas and address the fractured area.

Figure 7 I “pin bridge” across the midline by placing a strip of eFiber across the bot-tom of the frenum cut out (A) and then wrap e-Fiber around the Perma-Ret pins (B) to form a locked bridge. At this point, I rein-sert the denture into the flask and proceed with the closed flask reline.

Figure 3 To gain control and prevent bending or tweak-ing the Perma-Ret wire out of shape while threading it, expose only a short length of wire from the holder.

Figure 4 Examples of various placements of Perma-Ret to ac-commodate available space (from l. to r.): single pinned, dou-bled pinned, tucked close and rubber wheeled.

Figure 5 Perma-Ret can be used to prevent breakage or for repairs and is an ideal way to re-tain denture teeth once the bondable PMMA has been re-moved from teeth. Wire placement is done at setup so the wire angle can be modified for available space.

THOMAS ZALESKE has been a technician specializing in removable prosthetics for 29 years. He’s worked as an in-house technician, laboratory owner, author, technical colum-nist, product developer, product manager, technical support consultant and lecturer.

For more information about Perma-Ret, contact Preat Corp. at 800-232-7732, 805-202-3070,

info@preat.com or www.preat.com