Measured diagram
How does a composite filling bond to the edge of the tooth?
A close-up of the filling's cheek-side edge, from the same measured molar as the step-by-step figure, with a 1 mm scale. Acid goes on only where the wall is enamel, the adhesive then covers enamel and dentine alike, and the composite goes in in small layers that copy the tooth: opaque where the dentine was, translucent where the enamel was.
What the drawing is measured from
- Acid on the enamel only, before a universal adhesive: in a randomised trial of 295 back-tooth fillings in 70 patients, fillings bonded this way showed significantly fewer defects at their edges after 24 months than those bonded with the adhesive alone. Barceleiro et al. 2023, Journal of Applied Oral Science. DOI
- In fillings at the necks of teeth, a meta-analysis of 10 randomised trials found less staining and fewer adaptation defects at the edges when the enamel was etched selectively before a self-etch adhesive, and fewer fillings lost at three years. Szesz et al. 2016, Journal of Dentistry, systematic review and meta-analysis. DOI
- Drawn as Dr. Khalid bonds: acid on the enamel only, then the adhesive over enamel and dentine, and the composite in small layers. Where the cavity wall meets the junction of enamel and dentine, the etched band stops and the opaque layers begin. The etched band and the adhesive are drawn wider than life so they can be seen; their widths are not measurements.
- The enamel follows one measured dataset for this tooth, from cone-beam CT of 45 lower first molars: 1.58 mm at the front cheek-side cusp tip and 0.98 mm at the central fossa, its thinnest point. Zhang et al. 2026, BMC Oral Health. DOI
Use this diagram
Free to use, including commercially, with credit.
This diagram is published under CC BY 4.0. You may reproduce it in articles, teaching material, presentations and patient information, print or online, without asking. The one condition is that you credit Dr. Khalid Aletaibi and link back to this page.
It is published this way on purpose. The measurement in this drawing is not something the people selling the treatment tend to publish, so it is more useful spread than kept.
Credit line
The bonded edge. Dr. Khalid Aletaibi, CC BY 4.0. https://khalidaletaibi.com/en/diagrams/composite-filling-bonded-edge
HTML embed
<figure>
<img src="https://khalidaletaibi.com/figures/composite-filling-bonded-edge-en.svg" alt="The bonded edge" width="100%">
<figcaption>
The bonded edge. <a href="https://khalidaletaibi.com/en/diagrams/composite-filling-bonded-edge">Dr. Khalid Aletaibi</a>,
<a href="https://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>
</figcaption>
</figure>