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| 1999(5)134. Clinical and radiographic evaluation of early loaded free-standing dental implants with various coatings in beagle dogs |
Corso M. - Sirota C. - Fiorellini J. - Rasool F. - Szmukler-Moncler S. - Weber H.P.
October 1999 - Journal of Prosthetic Dentistry - Vol. 82 No. 4 pp 428-435 |
History is seen to be repeating itself in respect of early loading of dental implants. Pre-osseointegration in the 1950’s, immediate loading protocols were often used albeit with unpredictable results. Since then a healing period without loading has dominated clinical practice. Recently immediate loading of root form implants in cross-arch situations restored with fixed provisional restorations has demonstrated considerable success. In conjunction with changes to the surface preparation of implants early loading applications are being constantly refined and the clinical situations to which they are applicable are becoming more widely accepted.
Hydroxyapatite (HA) coatings of varying types have generally been shown to promote faster rates of osseointegration, a finding which might be beneficial in the context of a study such as this. However, on the basis of a number of more recently published clinical studies, the long-term integrity of such coatings is in some doubt. What remains largely unreported is the immediate loading of free-standing single implants.
It was therefore the purpose of this study to compare free-standing single implants with different surface finishes placed in the posterior mandible of beagle dogs and brought into masticatory function within two days of their surgical placement.
Materials and Methods : The mandibular first molar and all premolars were extracted from 4 adult beagle dogs three months prior to the study. Solid screw ITI titanium plasma-sprayed (TPS) implants 8mm x 3mm were available in 4 surface configurations. There were 3 types of HA coating; 1. conventional thermoplasma sprayed HA, 64% crystallinity, 50µm thick, this being similar to commercially available implant coatings, 2. atom deposited HA, 35% crystallinity, 1µm thickness, 3. atom deposited HA, 35% crystallinity, 5µm thickness. Untreated TPS implants served as the control group. The four animals then had 10 implants randomly placed at 7mm centres. Each implant was placed into a pre-tapped site and gold Octa abutments were fitted to a torque of 35Ncm. Gold copings were then used to transfer the implant position and a combined jaw registration for the fabrication of gold crowns that were fitted 2 days later. None of the crowns were in direct occlusal contact with the opposing teeth, however masticatory loading was ensured by changing the dogs from a soft to a hard diet. Oral hygiene procedures were performed 3x weekly along with recording of routine clinical parameters including standardized radiographs for marginal bone evaluation and Periotest values at baseline, 1, 3 and 6 month intervals.
Results : Of the 40 implants originally placed, 39 showed no clinically discernible signs of mobility or peri-implant radiolucency. The change in marginal bone levels from baseline to 6 months was clinically significant (P < 0.0001) representing an average of 1.3mm of lost bone. However, this effect was independent of implant surface coating and there was considerable consistency between the four groups.
Discussion and Conclusion : The amount of crestal bone loss around the TPS implants in this canine model was largely comparable to that found in previous animal studies after periods of up to six months and is also similar to that found in human subjects. The trend although not specifically examined in this study, would suggest that one could expect very slightly higher levels of marginal bone loss when subjecting these implants to immediate loading. The study was of too short a duration to determine whether or not the marginal bone loss was ongoing or had stabilized by the end of the 6 month observation period.
The authors suggest that on the basis of these very favorable results, that conceptually, where it is possible to achieve high levels of initial implant stability during surgery, it may also be possible to immediately restore the implant, provided that there is restricted masticatory loading and no direct occlusal contact. Using this protocol the initial stability of the implant should be adequate to allow the normal processes of osseointegration to establish themselves during the early weeks of function. |
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