Dental Orthodontic Spring Mechanical Testing Procedures

1. Testing principle

The dental orthodontic spring tensile test mainly applies axial tensile force to the spring sample through a universal material testing machine to measure its mechanical response at different elongation rates.The test focuses on the following key performance indicators:

Maximum elongation (Emax): The maximum elongation that the spring can withstand during the stretching process as a percentage of the original length

Permanent deformation point: elongation when 1% permanent deformation occurs

Grading force value: corresponding spring force value when reaching 80%, 60%, 40% and 20% maximum elongation (L80%max, L60%max, L40%max, L20%max)

These parameters reflect the elastic performance, force stability and durability of orthodontic springs and are an important basis for evaluating their clinical applicability.

2. Implementation standards

This test strictly follows the YY/T 1703-2020/ISO 17254:2016 standard, which is equivalent to the international standard ISO 17254:2016 and is suitable for the mechanical property testing of dental orthodontic springs.The standard stipulates the environmental conditions, sample preparation requirements, measurement methods and result judgment criteria for testing to ensure the reliability and comparability of test results.

3. Test instruments and equipment

Ensure there is no unbalanced load in axial stretching

Anti-slip design on the clamping end to prevent samples from slipping

3. Measuring instruments

Caliper or micrometer with an accuracy of 0.005mm

Optical measuring instrument (optional)

4. Testing process

Step 1. Sampling and preparation

Randomly select 6 samples from the same batch of products

Check that the sample surface is free of visible defects and damage

Clean the sample surface to remove oil and impurities

Step 2. Size measurement
Use measuring instruments with an accuracy of 0.005mm to measure the following parameters:

Inner diameter(d)

Outer diameter(do)

full length(lo)

Unloaded spring length (l or le)

Measure each dimension three times, take the average, and record to the nearest 0.01mm.

Step 3. Mechanical property testing

1. Environment settings

Conventional spring: (23±2)℃

Temperature sensitive spring: (36±1)℃

Relative humidity is controlled at 50±10%

2. Device settings

Set the crosshead speed to 0.5-10.0mm/min (selected according to spring characteristics)

Calibrating force sensors and displacement sensors

Install custom fixtures

3. Sample installation

The length of the sample is (20±0.2) mm. If the length is less than 20mm, the length of the unloaded spring is taken.

Make sure the spring axis is consistent with the stretching direction

Preload 0.1N initial force to eliminate installation gap

4. Test execution

Stretch the spring uniformly at a set speed

Record force-displacement curve

The following parameters were determined:

a) Maximum elongation (Emax)

b) Spring force values at 80%, 60%, 40% and 20% maximum elongation

c) Elongation when 1% permanent deformation occurs

Step 5. Result processing and analysis

Calculate the average and standard deviation of various parameters for 6 samples

Check that all results are within the range specified by the manufacturer

Evaluate force consistency, elastic properties and permanent deformation characteristics of springs

Issue test reports, including:

a. Test conditions

b. Original data

c. Calculation results

d. Compliance determination

5. Things to note

Vibration and impact interference should be avoided during testing

Temperature-sensitive springs need to be stable in a constant temperature environment for at least 30 minutes

The permanent deformation test needs to be unloaded and left to stand for 10 minutes before measuring.

Regularly calibrate test equipment to ensure measurement accuracy

Operators need to undergo professional training and be familiar with standard requirements