An orthodontic gauge looks like a small object. In the practice, though, it is the instrument that decides exactly where the bracket will be bonded, to a tenth of a millimetre. A badly calibrated gauge, and the whole alignment goes off.
We produced these bracket positioning gauges in injection-moulded PPSU, in four colours, ready for the autoclave.
The need: a precise, readable orthodontic instrument
The orthodontist places the gauge on the tooth, reads the height and positions the bracket. That is all. It takes three things:
- accurate dimensions, because a wrong bonding height repeats across the whole arch;
- readable markings on the part: the slot size (.022) and the 3.5 and 4.0 mm heights;
- a part that survives sterilisation without warping, cycle after cycle.
The real challenge: precision on very small dimensions
On an orthodontic gauge, everything comes down to a few tenths of a millimetre. The measuring heads, notches and positioning holes are tiny, and they are what sets the bonding height. If a dimension drifts, the bracket ends up too high or too low.
That is what took the most care on this project:
- a mould that faithfully reproduces every small feature: notches, holes, shoulders;
- markings a few millimetres high, sharp and readable, moulded in;
- thin sections that fill completely, without distortion;
- a part identical from one shot to the next, across the whole run.
A precision project, where every detail counts.
The part
Each gauge is about 155 mm long, with a measuring head at each end, one per bonding height. Two sizes were developed to suit different brackets.
The markings are moulded into the material. No ink, no label, nothing that wears off in the washer or the autoclave.
Four colours, through and through
Yellow, pink, mauve and green. The colour runs through the whole part and never wears off.
The colour has a clear job: the dentist recognises the right gauge at a glance, without looking for the marking, even with gloves on and a full tray.
PPSU, made for the autoclave
The gauges leave production clean and ready for the practice sterilisation cycle.
The material is PPSU (polyphenylsulfone), the reference plastic for reusable dental instruments:
- it withstands steam sterilisation at 134 °C, the standard dental autoclave cycle;
- it keeps its dimensions and colour over hundreds of cycles, where polypropylene yellows and warps much sooner;
- it can be coloured through, which made the four shades possible.
A reusable orthodontic instrument that swells or warps after a few autoclave cycles no longer measures anything. With PPSU, the gauge stays accurate.
Why injection moulding for orthodontic instruments
Machining or 3D printing a gauge works for a prototype. For a production run, injection moulding changes everything:
- every part is identical to the previous one;
- markings come straight out of the mould, sharp, with no finishing;
- the cost per part drops sharply from a few hundred units;
- changing colour does not require a new mould.
A medical or dental instrument project?
Developing an orthodontic instrument, a dental gauge or another plastic part for the medical sector? Send us your 3D file, or even an existing part: we scan it and make it again.
See also our page on medical injection moulding.
Already have a file? Send it here.