Understanding your borders
Just because you took the time to do border moulding doesn’t mean that you actually capture the borders correctly. And that is perhaps the reason why many despise the border moulding steps or they believe it is not necessary.
Border moulding with compound sticks is an art, much like the art of making hard candies…where you have to cook the sugar to a certain level and then cooling it enough so it is mouldable. Similarly, you have to heat up the compound stick to a consistency that is mouldable, but before it starts cooling off completely to become hard again, it needs to be tempered and moulded in a way to capture the soft tissue extension. This requires many things to be done in a short time. This includes the accurate placement of the softened compound on the custom tray, the proper manipulation of the border moulding material, the timely placement of a well extended custom tray, as well the manipulation of the vestibular tissue. It really becomes an art on how to accomplish all these steps in less than a 15 seconds period, segment by segment, if you are using compound sticks.
Even if you go through the motions of the above, you may not have done it correctly and the resulting border may be inadequate, underextended or overextended.
The picture is an impression taken for a cast RPD. This impression captures all the necessary information for a tooth-borne cast RPD. However, I want to use this as a learning case to show you how to read the borders properly.
Let’s first look at the right and left buccal flange area. Notice two things here:
- The asymmetry of the right and left side
- The show through of a bit of the compound sticks on the left side of the tray
As I analyze these two areas, I am not confident that I have captured the left buccal flange area correctly. I suspect this area is overextended from the overextended tray with the compound sticks as well as not manipulating the left buccal flange tissue adequately while the impression material is setting.
Now look at the lingual flange and the frenum area. Notice how both sides look more symmetrical and more physiologically formed from the muscle attachment demonstrating the mild s shape of the typical retromylohyoid fossa.
In the end, for such a case where the support comes primarily from teeth, the soft tissue extension is not as critical. But I want to highlight these areas so next time you can evaluate your own borders and learn how to improve your techniques better.
I have found that many students can learn border moulding with compound sticks very quickly once I show them how to do it once. Next time if you would like to learn about this art, do not hesitate to reach out to me so I can pass on my secrets to you! For those of you who have learned from me on border moulding, please leave me a comment on your experience!
Thank you for reading!