Wednesday 8 February 2012

Crestal vs. Basal implants



Crestal vs. Basal implants

  

Criteria
Crestal (Axial / Screw)Implants
Basal Implants
Shape and structure
Root form - designed to imitate roots of a tooth

The implants look like an inverted T


Endosseous section
Screw shaped with machined / sandblasted / HA coated surfaces.
Flat / blade like surfaces with spaces permitting bone in growth.
Technique
Insertion thro’ crestal bone and communication with oral cavity much more than basal implants
Insertion thro’ lateral aspect of basal bone. Load bearing area of implant has no communication with the oral cavity.
Bone requirement
Vertical bone – both crestal and rarely a small portion of basal bone.
Basal bone is what is needed. Horizontal aspects of the bone are fully utilized along with the inner and outer cortices.
Armamentarium
A large set of instruments are necessary for procedures
Instrumentation relatively a lot simpler
Bone grafting procedures
Essential in cases of deficiency in bone height. Grafting procedures give unpredictable results
Not essential.
Bone displacement
Considerable bone substance displacement / loss occurs and varies with size and length of implant. Crestal bone is more susceptible to resorption
Displace upto 60% less bone substance. Bone integrity and perfusion are barely impaired. Basal bone - highly resistant to resorption
Mucosal penetration diameter
Larger. Chances of peri implantitis, vertical bone loss, crater like bone loss and infections are relatively high
Smaller (1.9 – 2.3mm. only). The whole vertical implant part is polished – hence,  chances  of problems seen as in the case of crestal implants relatively very low.
Anatomy – proximity to Maxillary Sinus & Inf.Alveolar Nerve
Very important consideration and technique is to be modified accordingly. Bone augmentation essential in most cases.
Overcoming unfavorably placed MS and IAN is possible
Abutment angulations
Two piece implants have to have pre-angulated abutments. KOS single piece implants provide angulated as well as bendable abutment provisions.
All BOI implants have bendable abutments.
Loading
Two piece implants often require delayed loading & two surgical phases at times
Immediate loading
Healing
Prolonged healing time – clinically significant
Bone healing time not clinically significant

Masticatory forces
Act in the vertical direction along the sides of the screw structure
Transferred to the basal plate deep into the cortical bone areas which are able to accept large loads and have great capacity for regeneration.
Resterilization of implant including abutments
 Impossible
Possible after pre-cleaning
Applications in destructive periodontitis & after multiple extractions of teeth
Placement nearly impossible and success is unpredictable.
Placement of implants very much possible and results are excellent.
Smoking patients
Failure rate is nearly 100%
Best option for smoking patients
Controlled diabetic patients
Crestal implants always run a risk of failure in cases where there are blood sugar variations
Blood sugar variations may not affect the survival of the implant at all.

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