Once again, we are quickly going through poor clinical habits that make it difficult to for your lab to deliver a quality product back to you. As a reminder, your relationship with your lab is a partnership. If either party fails to do their part, the result will be an inferior product. We made it through the first five points last week, so if you missed the previous blog, go back and read it first.
- Poor shade selection: As a lab technician and dentist, I made a point of collecting all sorts of shade guides. Anything will work if you can find the correct shade and then transfer that to the lab. Photos help with proportions and translucency, but not so much with actual color. I would always start with having a female assistant do the initial color determination. It’s scientifically proven that females have better color perception than males. So just accept that women are better at it. I would take all of my existing shade guides and grind off all of the collar at the neck of the tooth. Leaving it on will alter your perception and make at least a half a shade error. Be sure to always use the blue card that came in the box that with the shade guide. I know, you threw it away. You need to place it close to your eyes and then look away to see the color of the teeth. It resets your sensitivity to variations in color. Never use supplemental lighting unless it is designed to be “color corrected”. Never paint your operatories with anything but a light blue or the color will affect your ability to make the proper shade selection. Never use anything other than a blue bib, for the same reason. Make sure your overhead lighting is from color corrected bulbs (99% are not, so make this change ASAP). Always take the shade before you begin to minimize desiccation of the tooth with the resulting shade change. Finally, buy a staining oven, ceramic stains, and learn to modify the shade of your final restorations. Hint: If you are still using a Vita Classic shade guide, you need to give me a call.
- Prep too divergent (5%-8%): This is the non-retentive, butcher the tooth so that the pulp will die and the tooth will be sensitive, do it quick and do it poorly prep for beginners and those that don’t care. There are some tricks to remember. I would stay away from tapered diamonds for the most part. I like a KS-1 and KS-2 because they are not tapered and the 1 and 2 denote bur thickness. Utilizing standard size diamonds allow you to use them for depth cuts and measuring prep parameters. The problem with tapered diamonds is that as you move to the distal of first molars and second molars you have to angle the handpiece so that the final prep divergence becomes too tapered.
- Sharp occlussal line angles: Regardless of the type of crown, achieving smooth line angles with no sharp or pointed areas means a more consistent impression and the likelihood of having no problems on the seating of the crown.
- Lack of retentive grooves: Keeping your preps parallel and axial walls at about a 5-8 degree prep will help, but making a small groove on the mesial and distal of single units, and facial and lingual of bridges, insures that these big boys will not come off.
- Not taking the time to create a functional temporary: More seat problems would be avoided if we took the time to make sure that our temporaries were perfect. Solid interproximal contacts to avoid having any drifting of the teeth and the subsequent problems with tight or loose contacts on the seat date. Good functional occlusion, not absence of occlusion. Make sure you have proper marginal length and integrity to avoid leakage and/or soft tissue trauma. Finally, be sure to use chlorohexidine to scrub the tooth to eliminate bacteria, and be sure and use Hema Glu to seal the tubules and improve bonding.
There you have it: Ten ways to improve your crown and bridge. As a bonus I have also created a link to an article called “The 30 Minute Crown Prep”. All of the burs, tricks, and protocols to insure efficient and effective crown and bridge are described.
Michael Abernathy, DDS