The more we learn about adhesive dentistry, the more critical it has become to have control over the placement of phosphoric acid etchant. I utilize a variety of techniques clinically for creating a strong durable bond. When I have chosen to use a total etch approach to a restoration, then it is critical that I control the timing of the etching process. If the phosphoric acid gel is in contact with the enamel less than twenty-five seconds, I will have inadequately prepared the tooth surface. More than fifteen seconds on dentin, and now I have over-etched and run the risk of decreased bond strengths and post operative sensitivity.
A recurring joke in our office is about the blue spots we all see after using a light-curing unit. Some of the time we remember to utilize the orange shield and protect our eyes, others we place the tip of the light curing unit and look away. Today I found out how poor an idea this last one is.There is still a lot we don’t know about light curing efficiency and efficacy, but one thing is for sure. Inadequate curing contributes to premature failure of the restoration. How we hold the tip of the light-curing unit against the tooth is a critical factor we need to understand.
I have heard it estimated that in the next five years 31% of all dental impressions will be captured digitally. So why are so many dentists making the investment? I have had the opportunity to take digital impressions with the Cerec System by Sirona for the last few years. Both as a practitioner and as an educator I love the technology and I have experienced many advantages. The foundation of the advantages is that you get to see your own preparations and the final impression and model in real-time while the patient is still present. One of the most frustrating things in private practice is getting a call from the lab that an impression I took has flaws. Often there is no question, and we will have to call the patient and have them come back in, get them numb, take off the provisional and take a new impression. This is an in inconvenience for the patient, diminishes the productivity of the procedure and can potentially impact how the patient feels about our office. Other times the lab is calling so that
I learned a very interesting statistic today: 68% of the time when a dentist switches laboratories it is because of inconsistent clinical results from their current lab. When I heard this, I wasn’t surprised as consistent, accurate clinical results are a must. We all need to know when we sit down to seat a restoration that the process will be predictable and the finished product excellent. A single forty-minute episode of adjusting in the occlusion on a crown ruins not just that day, but also the whole week. What I wondered about was the process that led to the dentist switching labs. Working with a new lab can be nerve-racking. It takes time to build confidence and get comfortable with the systems around simply sending work in and getting it back.
It can be an incredibly frustrating clinical situation, when you have been meticulous about preparing a posterior tooth, (most commonly a molar) for a crown. Using your burs you created depth cuts to ensure adequate occlusal clearance. After the impression you leave your assistant to fabricate the temporary only to have them come get you. Why? Because the temp is thin or perforated on the occlusal. When you go back to check, and have the patient bite, sure enough the opposing tooth is touching your prep.
Accurate impressions are a critical ingredient in our ability to deliver quality restorations to our patients. They are also the one thing that laboratory technicians agree dentists need to do better. An accurate well taken impression has many qualities, but a key ingredient is obtaining adequate margin flash. Flash is the amount of the impression material that captures the tooth beyond the preparation margin. This “extra” material that has gone past the margin is vital to the technician as they fabricate the final restoration. The first question is how much flash do we need to deem an impression accurate.
Last week at the ADA Annual Session I taught a hands on workshop about posterior tooth preparation. Both in the morning and afternoon sessions I was asked the age-old question, how do you decide when to save a cusp or cover it? The answer is ambiguous, much like how we decide as practitioners when to fill a carious lesion we see on a radiographic versus watch it. When we evaluate radiographic caries there are many lesions that all of us would agree need to be filled. Preparing posterior teeth is much like this, there are many clinical situations where full coverage is the correct choice without question. In this day of being conservative and saving tooth structure, it is the restorations that fall between a direct composite and a crown that cause us the most question.
So the trend in my life for the past week or so has been circling around inferior alveolar nerve blocks, both managing when I miss and answering questions for other dentists about this technique. Periodically over my twenty plus years in practice I hit a spell where I miss this block more often than usual. I have learned over the years that when this happens going back to basics, and reviewing the technique and the current thoughts always helps get me back on track, so that’s what I did this week.
What were you taught in school; six degrees, seven or eight? I hear a variety of numbers as I travel around the country and ask dentists what they were taught as the proper taper for a crown or onlay preparation. So when we are preparing teeth for indirect restorations what is the purpose of the taper? The opposing walls of the prep are what creates retention form.
The last few weeks I have been working on putting together a composite bur block for Brasseler. They were surprised by two of the burs that I requested on the block, a friction grip brownie point and a friction grip white stone. There are several burs on my block that I could see myself switching out based on recommendations from another clinician, but not my brownie and white stone. I can’t imagine doing composite restorations without them.