PROTOCOL FOR POST STRENGTH TESTS

 

June 07, 2004

 

I. Test Questions

 

Part A. Post & Core Buildup Testing

How do different non-metal esthetic posts compare in strength to each other and to carbon fiber, stainless steel, and titanium posts? 

 

Part B. Post Strength Test and Fatigue Cycling

Does fatigue cycling decrease the strength of different non-metal esthetic posts?

 

II. Test Products

 

 

1. Post Type                                                           Brand (Size)                         Manufacturer

Light Cure Core Paste / no post (Control)............Core Paste ......................... DenMat

Carbon fiber post................................................ GF (x)................................. J.Morita

Stainless steel....................................................... Parapost XP ..................... Whaledent

Titanium (99% pure)............................................ Parapost XP ...................... Whaeldent

Glass Fiber Post.................................................. C-1 White Post................... Parkell

Glass Fiber Post.................................................. D.T. Lightpost..................... Bisco

Glass Fiber Post.................................................. FiberKor Post .................... Pentron

Glass Fiber Post.................................................. FRC Postec ....................... Ivoclar

Glass Fiber Post.................................................. GF ..................................... J. Morita

Glass Fiber Post.................................................. Glass Fibre Post.................. Ellman

Glass Fiber Post.................................................. Luscent Anchors ................ Dentatus

Glass Fiber Post.................................................. Mirafit White....................... Hagar

Glass Fiber Post.................................................. Parapost Fiber White.......... Whaledent

Glass Fiber Post.................................................. Snowpost .......................... Danville

Glass Fiber Post.................................................. Twin Luscent Anchors ....... Dentatus

Glass Fiber Post.................................................. Snowlight........................... Danville

Zircon-dioxide ceramic........................................ Cosmopost.........................Ivoclar

Zircon-dioxide ceramic........................................ Cerapost ............................Brassler

 

 

2. Teeth

90 extracted human maxillary cuspids.

3. Equipment & Materials needed

5 mm circular molds

Air / water syringe

Bowls

Calipers

Centrix syringes

Core Paste kit

Diamond rotary instruments #1116.8c (mfr)

Drills associated w/ each post systems

Explorers (several of misc. sizes)

High speed drill (1)

Kimwipes

Panavia F 2.0 kits (2)

Paper points (various sizes)

Sandblaster

Slow speed drills

Slow speed saw

Snap resin

Syringe gun

Thermocycler

Timers (3)

Waterbath 37°C

 

 

 

III. Test Method

 

Part A. Post & Core Buildup Testing

 

1.      Select 90 extracted human maxillary cuspids based on dimensional requirements (Root length measured from facial CEJ= 15-25 mm / facial CEJ diameter = 6.0 - 7.5 mm) and lack of decay, fractures, large cracks, abrasions and/or restorations. During all steps teeth must remain wet in tap water.

 

2.      Prepare Teeth.

 

a.       Cut off the tooth crown at the facial surface CEJ using a diamond saw creating a flat surface perpendicular to the tooth root. This results in a root length of approximately 15-25 mm and a cut CEJ surface diameter that is apx 6.0-7.5 mm.

b.      Prepare a consistent size root canal using conventional step back method. Remove the least amount of dentin as possible.

c.       Fill root canal completely with gutta percha.

d.      Store prepared samples in refrigerated tap water for testing.

 

3.      Embed prepared teeth to a level 2 mm below the facial CEJ in resin (Snap-Parkell).

 

4.      Construct 5 samples for each post material type.

 

a.       Cut posts to 13 mm in length.

b.      Prepare posts as instructed by manufacturer (see appendix).

c.       Drill post hole using appropriate drills to receive a post approximately 1.25-1.35 mm diameter (depending on the post) that are to be placed 9 mm deep into the root.

d.      No pins or potholes will be placed.

e.       Thoroughly rinse the post hole with water and dry with paper points.

f.        Set the post with Panavia F 2.0 as directed by instructions (see appendix) to a depth of 9 mm leaving 4 mm of the post extended above the CEJ.

g.       Place mold over tooth and center over post. Syringe Core Paste into mold and pack. Fill mold to the top.

h.   Light cure Core Paste for 40 seconds and then remove mold from the Core Paste.

 

 

 

 

 

 

 

 

 

 

 


Figure 1. Cross section view of constructed sample.

 

 

5.      Stress Samples.

 

a.       Store samples in 37 °C waterbath for 30 to 60 minutes.

b.      Transfer samples to thermocycler.

c.       Thermocycle samples 2000 cycles between 5°C and 55°C distilled water (dwell time = 15 sec, transfer time = 10 sec, total apx. time = 35 hours).

 

6.      Break Samples.

 

a.       Remove samples from thermocycler after thermocycling and store in room temperature tap water until tested. Break all samples as described below in the same order as they were built.

b.      Using a slow speed diamond saw, carefully remove Core Paste until the coronal aspect of the post is visible.

c.       Using a rotary diamond in a handpiece, carefully remove core buildup material at a 45° angle to the lingual/occlusal aspect so the breaking probe can be placed directly on the edge of the post and there is a flat surface to apply the breaking force. (See Figure 2.)

 

 

 

 

 

 

 

 

 

 

 

 

 


Figure 2. View of final ground sample

 

 

d.      Place sample in test jig and align sample so the post is centered under the ball probe so the ball probe can apply pressure as close to the end of the post as possible.

e.       Apply a load on the lingual side of the sample centered on the 45° angled surface using a crosshead speed of 1.00 mm/min until sample reaches ultimate failure. (See Figure 3.)

f.        Record any intermediary breaks that may occur during ramping.

g.       Record modes of failure and maximum load that was applied at that failure.

h.       Record maximum load exerted on sample.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Figure 3. MTS setup for Compression Test of Post Reinforced Tooth

 

 

Part B. Strength Tests and Fatigue Cycling

 

1.      Construct 10 samples for each post material type.

 

a.       Prepare posts as instructed by manufacturer.

b.      Set the post with Snap resin to the full length of the post leaving at least 3 mm of the post extended above the methacrylate surface.

c.       Using a slow speed saw, cut the post so 3 mm extends from the surface of the methacrylate. Verify and record final length of the extend post. (See Figure 4.)

 

 

 

 

 

 

 

 

 


Figure 4. View of sample for fatigue test

 

2.      Break 5 baseline control samples for each brand of post.

 

a.       Test 5 posts of each brand, which will act as baseline controls, by applying a load on the end of the post at a 45° angle to the long axis using a crosshead speed of 1.00 mm/min, until the sample reaches ultimate failure. (See Figure 5.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Figure 5. MTS setup for Fatigue Cycling and Strength Testing of Post

 

 

b.      Record any intermediary breaks that may occur during ramping.

c.       Record the modes of failure and the maximum load that was applied at that failure.

d.      Record the yield force that results from each sample.

 

3.      Fatigue and break 5 samples for each brand of post.

 

a.       Fatigue 5 samples for each material type 15,000 cycles using an alternating load of 5-50 N at 1.4 Hz.

b.      Break samples as described in Part B.2. above for all fatigued samples.

 

4.      Compare the mean baseline strength value to its mean fatigued strength value for each post brand.

Appendix:  Panavia F 2.0 Instructions

 

1.      Rinse and clean canal using air/water spray.

2.      Dry canal with paperpoint.

3.      Dispense 1 drop each of ED Primer A and B, mix 3-5 seconds, and place on any coronal dentin and into canal.

4.      After 30 seconds, evaporate volatiles using an airwater syringe and remove excess with paperpoint.

5.      Mix Panavia F 2.0 paste for 20-30 seconds. (Leave spread thin until ready to use.)

6.      Load mixed paste into Centrix syringe.

7.      Inject Panavia F 2.0 into canal.

8.      Set the post and apply pressure for 20 sec.

9.      Lightly air thin Panavia over whole dentin bonding surface.

10.  Light Cure Panavia F 2.0 for 20 seconds using Optilux 500 halogen curing light (11 mm tip, 725 mW/cm2).