Improve On-Time Delivery with Root Cause Analysis

Dentists generally don’t want to change labs. Dentists and their staff get into a routine, set objectives and have a baseline for expectations from their labs. This includes a consistent product, on-time delivery, predictable results and quality technical information as needed. That said, likely the two primary reasons dentists change labs is due to late case delivery and inconsistent product. Late delivery can happen once, but more than this in a short period of time is unacceptable. Keep in mind that a dentist’s operating cost is $500+ per hour. A production hour lost due to a case not being delivered as planned, likely cost much more than the lab fee for the crown. Not good.

Looking closer at the late delivery issue as a cost to both the dentist and lost business for the lab one can quickly see the importance of on-time every time. The obvious question, how does a lab fix or improve on-time delivery? First, all staff must be onboard. Production objectives must be met on a daily basis. Staff should not leave at the end of the day unless all the scheduled work is complete. The putting off till tomorrow what can be done today attitude must be removed from the lab. Once all are onboard, the second most common reason for late cases is likely due to inhouse remakes. Unfortunately, there are many reasons for inhouse remakes and most labs have them. If you have none, your work may lack consistency, another reason dentists leave labs. That said, in-house remakes is part of the business and requires a unique workflow if these cases are to be delivered on time.

Let’s dig into in-house remakes. Do you ever notice that many units are not just remade once but twice or even three times? These cases likely result in a delayed delivery and a disappointed patient and customer.  I would suggest multiple remakes of the same unit to be a chronic problem, managed incorrectly. For example, if you mill zirconia, have you ever had the same unit chip multiple times? If so, it’s time to think about problems in a different light. A most successful approach is to determine why the crown chipped before a second time. This leads you to perform a root cause analysis (RCA).  This can result in a process that eliminates the second or repeated same mill chip from happening again. In addition, depending on the specifics of any single problem a RCA can potentially eliminate the problem altogether or at least minimize the frequency of occurrence.

Looking at just one chipped unit from a batch of units in a mill job, you need to do more than try to mill it again. Here is what I would suggest for a mill chip under these circumstances:

  1. Check STL file for extra margin thickness
  2. Crown design around the margin
  3. Overextensions in margin marking can cause mill chips
  4. Check tools for wear or deformation
  5. Check mill strategy & CAM file

If the batch has several units chipped, we would go through the following RCA:

  1. Check tools
  2. Tighten chuck and then be sure to have the mill measure of the calibration tool (for Roland)
  3. Calibrate mill
  4. Do a CAM file simulation
  5. Check tool path

By going through a logical RCA we will at least have a chance to determine the reason for the mill chip and thus have a greater chance of success when remilling the defective unit(s). This will hopefully enable us to deliver on-time in spite of the problem during the first mill attempt. In reality, we only lost 15-20 minutes of mill time and getting the case back on schedule should not be a problem. The best way to get through an RCA and get staff on board, ask “WHY”. Asking why the error or problem has occurred is the start to getting staff to work through a RCA.

By doing this with nearly every internal technical and business problem, you will become more efficient, reduce costs, improve consistency and profitability. It will also help you and your customers thrive.

Thanks for reading,

Bob Cohen, CDT

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