Q: You’ve been at the bench and working with doctors for about 35 years. How do you make decisions on how to design implant cases?
SA: At Arieno Dental we ask ourselves three important questions. How do we avoid:Bone resorption and tissue recession?Cosmetic failure due to cervical black holes, and shade or profile issues?Perioimplantitis, which could ultimately result in implant failure? The answers to these questions determine if we recommend solid or custom abutments, or screw retained crowns.
Q: What are Arieno Dental’s guidelines for determining if you will use a solid or custom abutment, or screw retained crown?
SA: Although each case is unique, we follow these guidelines:
Key indications that make a tissue-level SOLID IMPLANT ABUTMENT the best choice:
Key indications that make a CUSTOM IMPLANT ABUTMENT the best choice:
Depending on the system, when the implant platform has a tissue depth of 2-6 mm or is placed 3-6mm lingually
When there is a large space to fill proximally
When the implant angulation IS significant
The previous mindset of achieving cost savings for implant cases by using all-inclusive kits with solid abutments or transfer abutment systems may have created more costs on some patients than they saved. The current trend of custom implant design is proving to preserve more tissue and bone structure. In all situations, margin placement is critical to the success of implant cases.
Also, when a custom designed implant is torqued into place, it displaces and deals with all proximal and lingual tissues, not the crown, which makes for a quick crown insert, reducing chair time.
Q: How can we place the margin to minimize bone resorption and tissue loss?
SA: When a crown is cemented with deep implant margins it is difficult or impossible to remove excess cement that is displaced during insertion. It is difficult to see exactly how much cement residue remains even after careful clean up. And cement residue left around the implant and gingival tissue leads to future issues—including bone resorption and possible implant failure.
Some doctors have tricks to get around this problem like placing the crown on a stump shade tab to even the thickness of the cement prior to insertion. This technique does not always solve the problem and sometimes creates a lesser bond, which could result in re-cementing.
To retain tissue and minimize bone resorption, Arieno Dental Lab recommends placing the lingual margin from the center of the proximal, to the center of the proximal, flush with the tissue, and submerging the buccal margin by .7-1.3 mm (dependent on tissue thickness). The only cement cleanup needed is on the buckle surface.
Q: When you are designing a custom abutment case, how do you determine what emergence profile to use…concave, convex, or straight?
SA: Abutment profiles vary from case to case. The current trend, and what I recommend most often, is a fluted, concave emergence profile because it works well in most situations, especially when there’s a lot of space to fill proximally. At times a straight profile may also be indicated. I generally don’t recommend a convex profile because this type of tissue impingement generally results in bone resorption.
I ask myself:
How much space needs to be filled proximally?
How much gingival compression is needed? (Pushing against…bone, tissue, adjacent teeth, implant?)
Is this is single or multi-unit?
What else is going on in the mouth? (Soft bone, gingival recession, etc.)
We are able to achieve whatever design a doctor has in mind. However, these guidelines to profile and margin placement have resulted in long-term success for our doctors and their patients.
Key indications that make a SCREW RETAINED IMPLANT CROWN the best choice:
When there is limited vertical (less than 6mm) from the platform to the opposing dentition; i.e. not enough space to have a cement retained crown on an abutment
When there is an extreme lingually-placed implant with very little tissue depth. (A screw retained crown allows us to bring out the buckle surface to make the proper emergence profile.)
Screw retained abutments are also a current solution for addressing the problem of perioimplantitis. A lot of bone resorption issues in recent years have been created by sub-gingival implant margins. (The custom abutment would also solve many of these issues.)
Advantages to screw retained crowns:
They are easily retrievable, making case management more convenient. New transfer base technology broadens the possibilities of materials for screw retained cases. They could be fabricated metal or ceramic. Regardless of the material, placement of the implant has to be correct (i.e. the cingulum on an anterior).
In the past, costs have been a deterrent to screw retained crowns but there are many cost-effective ways and materials to make them in this day and age. (Some UCLA abutment parts are costly.)