In a prior post I discussed my rationale for immediate loading. It offers the restorative dentist an opportunity to create better soft tissue contours, patients are more comfortable, other provisionals are subject to higher fracture rates, and no need for stage II surgery.
But there are three qualifications for immediate loading that absolutely, positively must be met before considering using this technique. Failure to meet all of these criteria is a recipe for disaster.
(1) Adequate bone and soft tissue
If there is insufficient bone and soft tissue, the implant probably shouldn’t even be placed, let alone load it immediately!
The height, width, contour and quality of bone are assessed pre-operatively by exam and/or 3-D scanning. The height, thickness, contour and quality of the gingiva area are assessed pre-operatively by exam. Numerous surgical and non-surgical techniques are available to augment insufficient dimensions of both.
One of the more common mistakes in implant surgery is when a dentist places an implant (immediately loaded or not) into a fresh socket that has adequate soft tissue but inadequate buccal bone. Elian, et al described this as a Class 2 extraction socket.
Here’s an example of how deceptive a Class 2 socket can appear. A patient with poor hygiene, generalized mild-moderate periodontal disease, and multiple carious lesions requires extraction of tooth #12:
Soft tissue height and contour appear relatively normal
Radiograph shows interproximal bone levels are acceptable, despite mild periodontal bone loss
Okay, pretty straight forward. However the pre-operative CT scan was quite revealing:
Note the perforation of the buccal plate
This socket should be cleaned out and grated with delayed placement of the implant.
For more information on extraction socket classification, check out a webinar I did with Dr. Scott Froum.
(2) Protective occlusion
Another factor to assess pre-operatively is the occlusal scheme. Protrusive, working and non-working lateral movements should all be evaluated. If it looks like I will not be able to design an immediately-loaded provisional that is entirely out of occlusion, then this technique cannot be used.
Deep overbites, tight envelopes of function, and parafunctional habits are among the conditions that will make me think twice about an immediate load.
(3) High initial stability
So you have plenty of bone and soft tissue and the occlusion will permit the provisional to be protected. Both of these factors can be assessed pre-operatively. But the last qualification can only be truly known intra-operatively: initial stability of the implant in the osteotomy site.
Even though the provisional tooth won’t be in occlusion, it will still be subject to various forces during osseointegration. Muscles such as the tongue, lip and cheek will inadvertently brush by. Food being chewed elsewhere in the mouth will come into contact. Unless there is sufficient initial stability of the implant, failure is almost certain.
So how much initial stability is enough and how do you measure?
Many implant surgeons will use the reverse-torque test. After the implant is placed, if a torque wrench is unable to back out the implant at 20 Ncm, then sufficient initial stability has been met.
A more accurate method to determine stability is the Osstell ISQ. Resonance frequency analysis is a fast and harmless way to measure mechanical stability.
It totally looks like an iPOD
The folks at Osstell are hesitant to give an absolute number for immediate loading and I don’t blame them. But I’ve found support for values above 65 ISQ in the literature.