RelyX™ Fiber Post FAQs

RelyX Fiber Post is made of glass fibers which are embedded in a cured epoxy-resin matrix containing zirconia filler which aids in the radiopacity of the post. The post contains 60 - 70% (by weight) of glass fibers. The fibers are oriented longitudinally in the post and are dispersed homogeneously within the cross section of the post. The adhesion of the epoxy-resin to the glass fibers is a key point for excellent fatigue properties of the post.

The composition of the RelyX Fiber Post provides an elastic modulus similar to dentin, allowing functional stresses to be dissipated rather than concentrated in the root. Therefore the likelihood or potential for root fractures is reduced. The outer surface of RelyX Fiber Posts has a micropourous surface which aids in good mechanical retention of RelyX Unicem cement which aids in the adhesive strength between the post and the cement.

RelyX Fiber Posts have a tapered shape which is similar to the anatomical form of the root. The posts are parallel walled (cylindrical) at the coronal end and conical at the apical end.

The various long term studies are sometimes hard to compare and show a wide range of results. In some studies metal post failure rates with a high share of root fractures range between 2-8% per year (e.g. Mentink; Torbjorner).

Glass fiber post failure rates were reported to be between 1.6-3.2%, with none or very minor incidents of root fracture among these general failures. (Ferrari).

It is important to know, that the failure modes are very different between metal and fiber posts.

Teeth restored with fiber posts have fewer failures that are non-restorable, while stiff material such as metal posts leads more commonly to non-restorable, catastrophic failures with loss of tooth or deep root fracture (Akkayan; for review article see R.S. Schwartz, J. Endo.; 30 (5) 2004; p. 289).

No. There is no corrosion of the fiber posts. Therefore, there is no risk of an allergic reaction due to metal.

Removal of an endodontic post requires extreme caution whether the post is metal or glass fiber reinforced. Use an x-ray to visualize the drilling depth and position of the post and use an x-ray during the actual post removal procedure.

In most cases a fiber post is far easier to remove than a metal post. Removal of a metal post can be difficult in the following situations:

1. Long post cemented with resin modified glass ionomer or resin cement
2. Severe trauma to tooth an metal post such that top of metal post sheared off

Some fiber post manufacturers offer a special removal kit, which, may not be necessary in the experts' view.

A typical procedure would involve the following steps:

• Drill an orientation hole into the fiber post using a fine ball-shaped diamond drill (e.g. 15,000 rpm).
• Drill into the prepared hole with the RelyX™ Fiber Post drill of the appropriate size for removal of all post and cement residues.
• The post is now removed and the canal is ready for endodontic retreatment. Typically a new post will not be placed immediately after removal of the old post. The placement of a new post will depend on the endodontic retreatment and condition of the root canal.

Metal or zirconia ceramic posts cannot be disintegrated or removed in this way. If the cement does not give way easily, removal of these posts are extremely difficult and lead to additional loss of tooth structure, if not fracture.

The tapered shape is closer to the anatomical form of a root canal. This means the root canal preparation can be done in a conservative way, without excessive removal of root canal dentin. More tooth reduction means increase weakening of the tooth.

ISO standards recommend that the smallest post in a set be yellow and the largest post be blue. Depending on the amount of offerings additional post colors can be added in between yellow and blue.

The Fiber Post sizes/colors are similar, but do not exactly match other post manufacturers.

RelyX Fiber Post does not require pre-treatment when cemented with RelyX Unicem cement. Tests showed that applying a ceramic primer (3M™ ESPE™ RelyX™ Ceramic Primer) or use of bonding agents do not increase the bond strength to the post significantly. The bond strength between RelyX Unicem cement and RelyX Fiber Post is very high, actually much higher than the typical cement-dentin bond strength. Therefore any attempt to increase the bond strength of the cement-post interface should be clinically not relevant.

If RelyX Unicem cement is used in combination with glass or quartz fiber posts other than RelyX Fiber Post follow the pre-treatment recommendation of the manufacturer of the fiber post. If no pre-treatment is described we recommend the use of a silane ceramic primer on the post after cleaning with alcohol solution.

The fiber posts are not coated with any type material.

A radiopacity of 200% Al (aluminum) is the same as saying the radiopacity of the number 3 post is 2. It is as radiopaque as 2 mm of aluminum (Al).

Currently there is no correlation data available.

According to the instructions for use it is recommended to select the post size and the matching drill as indicated by X-rays and according to the diameter of the prepared root canal.

	Millimeters (mm)	Inches (in.)
Fiber Posts Length	20	0.79
Diameter Yellow	1.3	0.051
Diameter Red	1.6	0.063
Diameter Blue	1.9	0.075

They should be exchanged after 10 post placements. Using dull drills will lead to extensive heat generation and unfitting root canals.

The drills have a blade geometry that provides better cutting performance.

These drills fit standard handpieces.

The general rule is that 2/3 of the overall post length (after cutting to length) should be cemented and just 1/3 of the post be incorporated into the core build-up. Four millimetres of guttapercha is the minimum amount that should be left in the apex of the root canal.

Yes. The Universal drill cuts and removes the thermafil material very well. The color coded drills may also be used to remove any remnants of the thermafil material.

The RelyX™ Fiber Post drills are stainless steel. They comply with ISO 71531 1, part 1 4034 for dental instruments.

The universal drill is end cutting. The three color coded drills are side cutting.

The drills do not cut external tooth structure.

Other fiberposts may contain principally the same amount of fibers, even the same type of fibers, yet the overall properties can vary. In fact they vary especially if fatigue is considered. Other fiberposts contain zirconia based quartz fibers or ytterbiumfluorid or other radiopacifiers within the matrix. The refractive indices of the components of RelyX Fiber Posts are very well balanced and the post is still translucent. Other fiberposts use Bis-GMA/UDMA as resin matrix.

Yes, most fiber posts do have a micropourous surface. However, the RelyX Fiber Posts do not require any type of pretreatment (etch, prime, bond) when used with RelyX Unicem cement. Besides the mechanical interlocking of the cement to the post, there is also a chemical bond between Unicem cement and the composite matrix of the posts. Competitive fiber posts require pretreatment of their posts.

Currently there is no table of size conversion comparison between RelyX Fiber Posts and competitive fiber posts. The instructions for use does describe the posts dimensions which a dentist would be able to use and compare to other competitive fiber posts.

A variety of cements (zinc phosphate, glass ionomer, resin modified glass ionomer and resin cements) are used today. Fiber posts require adhesive resin cements. Conventional cements should only be used for metal posts with retentive surfaces, if at all. We recommend RelyX™ Unicem™ cement along with the RelyX™ Unicem™ Aplicap Elongation Tip for direct dispensing of the cement into the root canal.

Many dentists still believe more in mechanical retention which is why active screws and retention grooves on metal posts are offered. There is doubt about the reliability of adhesive bonding to dentin as well as the technique sensitivity due to multi-step cementation procedures. RelyX™ Unicem cement overcomes the objection of technique sensitivity of the multi-step cementation procedures.

The working time of 2:00 to 2:30 minutes after the start of mixing is stated in the instructions for use of RelyX Unicem Aplicap cement. Since the dentist is working inside the root canal it is hard to define distinct intra oral times. However internal in vitro experiments were made which demonstrated that 2:00 minutes appeared to be close to the end of the working time. There were no complaints regarding the working time of the cement during a clinical application test of more than 250 fiber post placements with RelyX Unicem cement and the RelyX Unicem Aplicap Elongation Tip. It is advisable that the dentist works quickly once the cement has been filled into the canal.

In the self-cure mode both Kerr Maxcem™ and Ivoclar Vivadent® Multilink cement has the same 5 minute set time from the start of mix as Unicem cement. The post cementation procedure time with Unicem cement is far easier compared to Maxcem, Multilink and total etch resin cements. RelyX™ Unicem Aplicap Cement with the Elongation tip reduces cement application time into the root canal. Furthermore there is no need to etch, prime or bond when Unicem cement is used.

No. RelyX Unicem cement has such a low expansion that it can be safely used for ceramic restorations and root canal cementations. This was proved by various internal and external studies (e.g. CRA, Oct 2004) and by now more than 4 years of clinical experience.

There is no clear cement shade preference considering the cement is placed inside the root canal. Some dentists like an opaque cement for better identification of tooth cement interface when considering the possibility of a potential post removal in the future.

No. Unicem cement is thixotropic and therefore flows easily with increasing pressure. Therefore the cement easily passes through the elongation tip. In vivo field tests as well as in vitro evaluation with dentists have confirmed the ease of use with the elongation tip without any complaint of difficulty to extrude the cement. Furthermore, lab tests proved that the setting characteristics are not influenced when extruding through the elongation tip instead of the normal nozzle.

The cure time is 40 seconds to ensure enough light reaches deep into the root canal.

There is internal 3M ESPE bond strength data of RelyX™ Unicem cement with other fiber posts. Most metal posts used are serrated, have retention grooves or some other type of shape which aids in mechanical retention. Currently there is no bond strength data on file between RelyX Unicem cement and metal based posts. But other tests about adhesion of RelyX Unicem cement to typical dental metal alloys show good bond strength. (see RelyX Unicem study booklet).

RelyX Fiber Post does not require pre-treatment when cemented with RelyX Unicem cement. Tests showed that applying a ceramic primer (3M™ ESPE™ RelyX™ Ceramic Primer) or use of bonding agents do not increase the bond strength to the post significantly. The bond strength between RelyX Unicem cement and RelyX Fiber Post is very high, actually much higher than the typical cement-dentin bond strength. Therefore any attempt to increase the bond strength of the cement-post interface should be clinically not relevant.

If RelyX Unicem cement is used in combination with glass or quartz fiber posts other than RelyX Fiber Post follow the pre-treatment recommendation of the manufacturer of the fiber post. If no pre-treatment is described we recommend the use of a silane ceramic primer on the post after cleaning with alcohol solution.

All types of core build-up materials may be used with RelyX™ Fiber Post. However, composite core build-up materials are recommended due to its physical properties and esthetics. We recommend any of the Filtek™ composite products along with an Adper™ adhesive product.

RelyX Unicem cement is not yet indicated for core-build up, mainly because it has a viscosity that is not necessarily considered ideal for core-build up. Secondly quantity of cement in an Aplicap capsule would not typically have enough material for a full core-build up.

The micropourous surface contributes to the adherence of the core build-up material onto the post. If a composite core build-up is used, it is advisable to apply adhesive onto the post prior to placement of the composite core build-up. It is necessary to follow the instructions for use of any core build-up material.

Gutta percha is a synthetic version of rubber which is melted and injected to fill the root canal passages. There is no oily residue.

Gutta percha does not contain eugenol.