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Mechanical Tests

BTLock S.r.l. requested to the Department of Chemistry, Materials and Chemical Engineering of the Politecnico di Milano (University of Milan - Italy) the mechanical evalutation of its titanium dental implants.

Mechanical testingsand analyses were performed as follows:Static testing were performed according to practice Standards ISO 14801:2003 “Dentistry – Fatigue test for endosseusdental implants”.

 

Materials used:

System T
Fixture 375115 BTICV1 (diameter 3.75mm ; length 11.5mm; titanium grade 4)
Abutment 375 BTIPML (diameter 3.75mm; length 11mm; titanium alloy grade 5)
Connection screw BTIVPC (thread diameter 1.8mm; titanium alloy grade 5).

System S
Fixture 375115 BTIVSM (diameter 3.75mm; length 11.5mm; titanium grade 4)
Abutment 375 BTIPML (diameter 3.75mm; length 11mm; titanium alloy grade 5)
Connection screw BTIVPC (thread diameter 1.8mm; titanium alloy grade 5).

System A
Fixture 375115 BTICV1 (diameter 3.75mm ; length 11.5mm; titanium grade 4)
Abutment 375C BTIPMLI (diameter 3.75mm; length 11mm; titanium alloy grade 5; inclination 25°)
Connection screw BTIVPC (thread diameter 1.8mm; titanium alloy grade 5)

 

 

 

Before static and fatigue testings, each fixture was connected to the abutmentusing its connection screw, applying a torque of 30 N x cm, as prescribed by theproducer, through a specific dynamometric wrench.Test Methods:

Mechanical tests were performed using two Instron machines: an electromechanicalfor static tests and a servo hydraulic for dynamic fatigue tests.

 

Static Test Results
Fatigue tests results (System T)
Torque tests results (System T)
Compression Tests results (System T)
Measurement of the gap between fixture and abutment (System T)
Roughness measurement

 

 

Static Test Results

Static tests were performed applying a ramp at the constant rate of 0.03mm/s and measuring the resistand load.
Tests were performed on 5 specimen. During the test the load level was acquired every 1 second. The tests was concluded when failure or plastic bending deformation higher than 5mm occurred (4mm for System A).

Load vs. position curves for dental
“System T”
Load vs. position curves for dental
“System S”
Load vs. position curves for dental
“System A”

Maximum bending moment was calculated as:

M=0.5 x F x L

Where L is the distance of the clamping plane to the loading center. Considering that the hemisphere has a radius of 5mm and that it is positioned protruding from the abutment of 2.8mm, the loading centre is located 2.2mm below the measure length L.

Results are as follows:

System T:
Calculated maximum average load was 591 ± 52 N
Average maximum bending was 220 ± 11 (N x cm)

System S:
Calculated maximum average load was 774 ± 67 N
Average maximum bending was 337 ± 20 (N x cm)

System A:
Calculated maximum average load was 393 ± 47 N
Average maximum bending was 213 ± 28 (N x cm)

Please note: All specimens (System T) showed a great plastic deformation. Only one was fractured at considered maximum level of strain.

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Fatigue tests results (System T)

A cyclic sinusoidal unidirectional load was applied. The minimum load of the sinusoidal cycle was selected as 10% of the maximum nominal load. The loading frequency was 10 Hz.
The 80% of the average maximum load calculated with the static tests described above, was used as starting load for fatigue tests. All tests were performed in air at 22 ± 3 °C.

Fatigue test results

Sample
Ltot (mm)
Cycle
Max Load (N)
Max bending
moment
(Ncm)
Failure
1
8.6
428,000
472
203
Yes
2
8.7
358,000
472
205
Yes
3
8.7
173,000
413
180
Yes
4
8.5
5.62E+06
413
176
No
5
8.9
570,000
413
184
Yes
6
9.0
5.14E+06
384
173
No
7
8.5
4.20E+06
384
163
Yes
8
8.8
5.92E+06
354
156
No
9
8.7
7.48E+06
354
154
No
10
8.6
5.01E+06
354
152
No

The fatigue limit at 5 million cycles was identified at 354 N, corresponding to a maximum bending moment of 154 N
x cm.

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Torque tests results (System T)

Mechanical tests were performed on System T in order to evaluate the torque resistance of the connection between fixture and abutment

   

Four specimens were acquired and recorded as the following diagram:

The maximum average torque was 366.5 ± 32 (N x cm).

Please note: Failure of all four tested implant took place inside the hollow abutment and the connection between the fixture and the abutment did not fail at all.

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Compression Tests results (System T)

Mechanical compression tests were performed on System T in order to evaluate the compression resistance of the system.

The maximum compression average load was 6625 ± 377 N.

Please note: Specimens’ position change during compression tests was related to the gradual falling of the fixture in the connection jig and it is not connected with the mechanical performance of the connection.

   

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Measurement of the gap between fixture and abutment (System T)

The gap between fixture and abutment was measured on system T, both on not tested specimens and on specimens that survived the fatigue test (5 million cycle at 354 N).

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Roughness measurement

Roughness was measured on the implant surface using a 3D laser profilometer.
Three different surfaces were analysed:

  • BT-Tite (sandblasted and acid-etched)
  • Acid-Etched
  • HA Coated (Hydroxyapatite coated)

Rmax provided the following results:

  • BT-Tite:
    Ra = 2.13 ±0.31
    Rmax = 16.9 ±1.6

  • Acid-Etched:
    Ra = 1.77 ±0.16
    Rmax = 15.18 ±0.66

  • HACoated:
    Ra = 0.58 ±0.13
    Rmax = 4.68 ±2.21

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