Application Note | Medical Device Inspection
Dental Implant Screw Dimensional and Surface Roughness Analysis
Thread Radius, Height, Angle, and Surface Roughness of a Dental Screw in a Single Non-Contact Scan
Research & Experimental Testing
Duanjie Li, Jonathan Thomas & Pierre Leroux
Visual Design & Editorial
Andrew Shore
Introduction
Having precise dimensions and optimal surface roughness are vital to the functionality of dental screws. Many dental screw dimensions require high precision such as radii, angles, distances, and step heights. Understanding local surface roughness is also highly important for any medical tool or part being inserted inside the human body to minimize sliding friction.
Non-Contact Profilometry for Dimensional Study
NANOVEA 3D Non-Contact Profilers use a chromatic light-based technology to measure any material surface: transparent, opaque, specular, diffusive, polished or rough. Unlike a touch probe technique, the non-contact technique can measure inside tight areas and will not add any intrinsic errors due to deformation caused by the tip pressing on a softer plastic material. Chromatic light-based technology also offers superior lateral and height accuracies compared to focus variation technology. NANOVEA Profilers can scan large surfaces directly without stitching and profile the length of a part in a few seconds. Nano through macro range surface features and high surface angles can be measured due to the profiler’s ability to measure surfaces without any complex algorithms manipulating the results.
ℹ️ Learn more about non-contact profilometry lab services for medical devices.
Measurement Objective
In this application, the NANOVEA ST400 Optical Profiler was used to measure a dental screw along flat and thread features in a single measurement. The surface roughness was calculated from the flat area, and various dimensions of the threaded features were determined.
NANOVEA ST400 Standard
Optical 3D Profilometer
Sample
Results: 3D Surface
The 3D View and False Color View of the dental screw shows a flat area with threading starting on either side. It provides users a straightforward tool to directly observe the morphology of the screw from different angles. The flat area was extracted from the full scan to measure its surface roughness.
Fig. 1: 3D view and false color view of the dental screw.
| ISO 25178 height parameter | Value (µm; Ssk and Sku unitless) |
|---|---|
| Sa | 0.9637 |
| Sq | 1.220 |
| Sp | 5.644 |
| Sv | 6.051 |
| Sz | 11.70 |
| Ssk | 0.2352 |
| Sku | 3.218 |
Table 1: Surface roughness of the dental screw flat area.
Results: 2D Surface Analysis
Line profiles can also be extracted from the surface to show a cross-sectional view of the screw. The Contour Analysis and step height studies were used to measure precise dimensions at a certain location on the screw.
| Dimension | Value |
|---|---|
| Radius between threads | 1.729 mm |
| Step height (maximum / mean) | 0.5724 mm / 0.5611 mm |
| Thread heights | 0.4072, 0.4165 and 0.4141 mm (average 0.413 mm) |
| Angles between threads | 61.89° and 60.67° (average 61.3°) |
Table 2: Dimensions of the dental screw threads.
Conclusion
In this application, we have showcased the NANOVEA 3D Non-Contact Profiler’s ability to precisely calculate local surface roughness and measure large dimensional features in a single scan.
The data shows a local surface roughness of 0.9637 µm. The radius of the screw between threads was found to be 1.729 mm, and the threads had an average height of 0.413 mm. The average angle between the threads was determined to be 61.3°.
The data shown here represents only a portion of the calculations available in the analysis software.
Frequently Asked Questions About Dental Screw Inspection
Why measure the dimensions and roughness of dental screws?
Precise dimensions and optimal surface roughness are vital to dental screw function. Many dimensions, such as radii, angles, distances and step heights, require high precision, and local roughness matters for any part inserted into the human body to minimize sliding friction.
Why use non-contact profilometry on dental screws?
Unlike a touch probe, the non-contact technique can measure inside tight areas and adds no intrinsic error from a tip deforming a softer material. Chromatic light technology also offers superior lateral and height accuracy compared with focus variation.
Can roughness and thread dimensions be measured in one scan?
Yes. The NANOVEA ST400 scanned a dental screw along its flat and threaded features in a single measurement: roughness was calculated from the flat area and the thread dimensions from extracted profiles.
What surface roughness did the dental screw show?
The flat area had a local surface roughness Sa of 0.9637 µm, with Sq 1.220 µm and Sz 11.70 µm.
What thread dimensions were measured?
The radius between threads was 1.729 mm, the threads had an average height of 0.413 mm, and the average angle between threads was 61.3°, measured with contour analysis and step height studies.
Which NANOVEA instrument was used for dental screw inspection?
The NANOVEA ST400 optical profiler, which can scan large surfaces without stitching and profile the length of a part in a few seconds.
