Immediate and delayed loading of fixed dental prostheses supported by single or two splinted implants: A histomorphometric study in dogs

Abstract

To evaluate presumptive differences in osseointegration at implants supporting crowns that are physiologically loaded either immediately or 3 months after installation. All premolars and first molars were extracted bilaterally in six dogs. After 3 months of healing, three implants were installed on the premolar region and two in the molar region in one side of the mandible. Likewise, after another 3 months, five implants were installed in the contralateral side, and impressions were taken bilaterally. Within 48 hours, two single crowns were screwed bilaterally onto two implants in the premolar region, and two splinted crowns reproducing the shape of the first molar were screwed bilaterally onto the implants in the molar region. The mesial implants were used as no-loaded controls. Sacrifices were performed after 3 months, and histological analyses were performed. At the premolar sites, mineralised bone-to-implant contact (MBIC%) was 78.0 ± 4.0% and 70.9 ± 7.9% at the delayed and immediately loaded sites, respectively. This difference was statistically significant. At the control implants, MBIC% was 61.4 ± 14.7% and 63.1 ± 13.1% at the delayed and the immediately loaded sites, respectively. At the molar sites, MBIC% was 79.2 ± 10.9% and 61.1 ± 10.3% at the delayed and immediately loaded sites, respectively. Applying a delayed loading to fixed dental prostheses supported by single or two splinted implants yielded higher proportions of bone-to-implant contact (osseointegration) compared to immediately loaded implants. Moreover, both types of loading protocols yielded a higher rate of osseointegration compared to unloaded implant sites after 3 months following implant installation.

Immediate loading at single crowns and 2‐unit bridges supported by implants installed in a healed alveolar bony ridge or immediately after tooth extraction. An experimental study in dogs

“…Osseointegration and bone density were found to a higher degree at the immediately loaded compared to the unloaded sites. In the light of the results reported in other studies, the masticatory function may have favoured the chewing at the loaded implants maybe due to premature contacts at these sites.…”

“…The physiologic chewing in the dogs includes two movements, a vertical and a lateral, instead of the four movements performed by humans . It seems unlikely to reproduce correctly in dogs a load applied to the chewing elements in humans.…”

“…In these unloaded sites of the mandible, the occlusal surfaces of the prosthesis were reduced to eliminate any possible contacts with the opposing jaw. However, the reproduction of chewing with flat surfaces does not correspond to the physiologic function in the dog and may affect the chewing efficacy. In the unloaded sites, no adjustments were made to the teeth of the maxilla.…”

“…Occlusion and masticatory function were frequently discussed in recent years . It was shown that the dogs bite, pull, grab and tear food using the anterior teeth in a centric occlusion, while they triturate and chew the food in the molar region, using both centric and lateral occlusion.…”

“…In a recently published paper, immediate and delayed load was studied in dogs . Two crowns supported by single implants in the premolar region, and a crown supported by two implants in the molar region were incorporated in both sides of the mandible within 48 hours, allowing immediate loading in one side of the mandible, and a delayed load in the opposite side.…”