|
Sign In to gain access to subscriptions and/or personal tools.
|
Effects of Implant Healing Time on Crestal Bone Loss of a Controlled-load Dental Implant
C.C. Ko1,*,
W.H. Douglas1,
R. DeLong1,
M.D. Rohrer2,
J.Q. Swift3,
J.S. Hodges4,
K.-N. An5 and
E.L. Ritman6
1 MDRCBB, Department of Oral Science,
2 Division of Oral Pathology, Department of Oral Science,
3 Maxillofacial Surgery Division, University of Minnesota, and
4 Division of Biostatistics and School of Dentistry, University of Minnesota, Minneapolis 55455;
5 Orthopedics Biomechanics Laboratory, Mayo Clinic, MN 55905; and
6 Department of Physiology & Biophysics, Mayo Medical School, Rochester, MN 55905;
View larger version (23K):
[in this window]
[in a new window]
|
Figure 1. Study design: surgical schedules, healing and loading times of the implants. The experimental group included 12 pigs; for each pig, 1 implant was used as the experimental implant, and the implant in the contralateral side was used as an internal control. The experimental animals were divided into 3 equal subgroups with one-, two-, and four-month implant healing periods. The daily load was applied for 5 mos for all experimental implants. For the internal control on the contralateral side, the implant was allowed to heal for 1, 2, or 4 mos, the same as the experimental implant in the same pig. Since both the internal control and the experimental implants were recovered at the same time, control implants were placed at appropriate times before the animals’ death. Five animals with 2 bilateral implants were used as external controls to provide a baseline of bone loss. These also were divided into 3 groups with the same healing periods as the experimental implants. The external control implants stayed in the jaw for the appropriate healing period plus an additional 5 mos with no loading.
|
|
View larger version (126K):
[in this window]
[in a new window]
|
Figure 2. Bone loss comparisons between and among different healing groups. (A) Diagram for measurements showing mesial-distal cross-section of the implant-bone and hydraulic device. Two crestal bone loss measurements per implant (a and b, in mm) were taken along the implant surface from the subtracted radiographic images. (B) Averaged crestal bone loss for experimental and external control groups. The symbol n represents number of measurements obtained, 2 from each implant. The data (CBL, in mm) were averaged for the 3 healing-time subgroups. The loading effect on crestal bone loss significantly depends on healing time (loading-by-month interaction, p = 0.03), increasing as time proceeds. * indicates a significant difference between the experiment and the control. (C) Representative digitally subtracted images. Representative radiographs from experimental and control implants show distinct crestal bone loss associated with delayed loading (four-month group). The displayed control implant healed for 4 mos. Grey represents non-changed areas. Blue and pink indicate bone loss, and red-yellow-green indicate bone gain. We created the images by subtracting the after-loading image from the before-loading image using the S3D x-ray method (University of Minnesota). The images were aligned by optimization of optical topology of the selected areas of x-ray films. Neither the before nor the after image was distorted to match landmarks. The bone loss observed, in general, agrees with the conventional warping method (not shown here).
|
|
View larger version (95K):
[in this window]
[in a new window]
|
Figure 3. Micro-computed tomography (µCT) images for qualitative assessments of bony architectures. Upper: After healing but before being loaded, the healing bone near the internal control implant grew more dense as the healing time increased. At one-month healing, the detected bony struts were thin. Perhaps there were thicker unmineralized osteoid seams surrounding the struts, as shown in Fig. 4 . Four months’ healing resulted in mature, thicker, trabeculi with less inter-trabecular space; however, trabeculi were randomly aligned without the preferred orientation. Lower: After five months’ loading (experimental implant), however, bone density decreased as the non-loaded healing period increased. The one-month healing bone appeared to deposit much more dense calcified bone in response to loading than the two- and four-month healing bone. The bone struts in the one-month and two-month experimental groups were aligned in the direction at which the load was applied. The trabecular bone in the four-month experimental group, however, displayed a random pattern, unrelated to loading direction. The bar on the right lower corner of each image indicates a scale of 1 mm.
|
|
View larger version (77K):
[in this window]
[in a new window]
|
Figure 4. Histology of implant-bone interface with Stevenel’s Blue and Van Gieson’s picro-fuschin stain. Calcified bone stains a bright red, with variations in intensity depending on the maturity of the bone. Non-calcified bone and osteoid stain bright green; osteoblasts stain blue. The implant (black) is on the right side of the images. The percentage of osteoid seams over the mineralized areas was 17%, 8.4%, and 4% for the one-, two-, and four-month healing tissue, respectively. These data were sampled within 300 µm by 300-µm squares adjacent to the implant surfaces. For the one-month healing tissue, the newly forming bone was in various degrees of maturity, with numerous spindle-shaped osteoblasts with undistinguishable boundaries between cells and denser nuclei. The four-month healing tissue contained new bone with uniform maturity and relatively fewer osteoblasts, being cuboidal. The bar on the right upper corner of each image indicates a scale of 10 µm.
|
|
Journal of Dental Research, Vol. 82, No. 8,
585-591 (2003)
DOI: 10.1177/154405910308200803
 CiteULike  Complore  Connotea  Del.icio.us  Digg  Reddit  Technorati  Twitter What's this?
|
|
