Effect of Dehiscences to the Bone Response of Implants With an Acid-Etched Surface: An Experimental Study in Miniature Pigs
Spontaneous early exposure of submerged implants during the healing phase as a factor for early crestal bone loss around the implants is still being controversially discussed. The aim of this study was to examine the potential impact of dehiscences on the osseointegration process of acid-etched dental implants with a shortened healing period in the maxilla. Five animals received a total of 15 titanium implants 8 weeks postextraction. Eight of these implants were placed in the maxilla to osseointegrate within a shortened healing period of 3 months, whereas the remaining implants were inserted in the lower jaw and served as controls with a regular healing time. Polyfluorochrome sequential labeling with xylenol orange, calcein green, and alizarin complexone was performed 2, 5, and 8 weeks after implant placement. After 12 weeks of unloaded and submerged healing, the animals were killed and the implants removed en bloc. After the processing of the undecalcified PMMA-embedded samples, thin ground sections (40–60 µm) were made. The histomorphometric determination of the bone-to-implant contact (BIC) was calculated using light microscopy. The peri-implant bone apposition rate and the direction of bone growth were determined with the fluorescence microscope. For statistical evaluation, the Mann-Whitney U test, Wilcoxon signed ranks test, and Friedman test were chosen. During the healing period, nonartificial dehiscences were observed at 9 implants. The average BIC was 54.19% (14.51%–68.97%). There were significantly lower BIC rates detected for the cervical part of the implants compared with the middle part. An influence of dehiscences on the osseointegration could not be proven. There were no significant differences between the BIC values of the upper and lower jaw. During the observation period from the third to the eighth week after implantation, the average new bone formation rate was 2.32 µm/d (1.76–2.82 µm/d). During this period, the amount of new bone growth decreased insignificantly. Based on the sequence of the polyfluorochrome labeling, an implantopetal (53.03%) as well as an implantofugal bone growth (46.97%) have been observed. It could be assumed that the acid-etched implants offered a prerequisite to osseointegrate under a shortened healing period. The observed dehiscences seemed not to have compromised the rate of osseointegration.Abstract
(a) Division of the acid-etched implants for light microscopic analysis in 5 segments. (b) Division of the acid-etched implants for fluorescence microscopic analysis in 9 segments.
Figure 2 . (a) A panoramic view showed an acid-etched implant inserted in the mandible with a bone-to-implant contact (BIC) of 68.97%. Clearly noticeable was the trabecular bone structure, the dark brown newly formed peri-implant bone, as well as resident bone (gray brown; Von Kossa staining, counterstained by Paragon solution, original magnification ×2.5). (b) Higher magnification of the area outlined in (a) showing clearly a BIC without intermediary soft tissue (Von Kossa staining, counterstained by Paragon solution, original magnification ×10). Figure 3. Coronal region of an acid-etched implant inserted in the upper jaw. Remarkable was the existence of soft tissue in the upper section of the implant. Adjacent to the soft tissue, the bone showed Howship's lacunae including osteoclasts. The newly formed bone showed a brownish color and was partially composed of concentric lamellae (Von Kossa staining, counterstained by Paragon solution, original magnification ×10).
Figure 4. Panoramic view of an acid-etched implant inserted in the mandible. Observable were linear, concentric, and irregularly arranged fluorescences at the peri-implant bone. Especially on the right side, a cluster of fluorescence bands was particularly noticeable, indicating that a high degree of new bone formation occurred in this area (original magnification ×2.5). Figure 5. The xylenol orange band showed the largest distance to the implant surface, followed by the green band of calcein green and the red band of alizarin complexone. At this, the mineralization front of the newly formed bone emanated from the host bed and increased toward the implant surface (distance osteogenesis; original magnification ×10; ⬠= xylenol orange, ○ = alizarin complexone, □ = calcein green, I = implant). Figure 6. (a) In the subsequent detail screen, a reversal of the fluorescent bands was obvious. The xylenol orange band was next to the implant surface, followed by the bands of calcein green and alizarin complexone. The implantofugal ossification started directly at the surface of the implant and continued to grow toward the periphery (contact osteogenesis; original magnification ×10; = xylenol orange, ○ = alizarin complexone, □ = calcein green, I = implant). (b) Contact osteogenesis with close accretion of the xylenol orange band to the implant surface (original magnification ×20; = xylenol orange, ○ = alizarin complexone, □ = calcein green, I = implant). Figure 7. In this illustration, the fluorescent bands showed a concentric formation and the ossification emanated from the host bed as well as from the implant surface. That means that distance and contact osteogenesis coexisted at the same time and location (original magnification ×10; = xylenol orange, ○ = alizarin complexone, □ = calcein green, I = implant, B = resident bone).
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