Figure 1. High-frequency acceleration (HFA) stimulates alveolar bone formation in the extraction socket and surrounding alveolar bone.
(A) Schematic of area/volume used for micro–computed tomography quantitative analysis, with dashed lines marking the borders in 3 planes of space.
(B) Three-dimensional micro–computed tomography reconstructions show a higher level of bone formation and faster filling of alveolar socket in the area of the upper right third molar in the HFA samples in comparison with the static group at all time points after extraction. Occlusal view (furcation level), sagittal view (midsagittal section of alveolar ridge), and coronal view (distal root of right maxillary third molar) of the right hemimaxillae in both static and HFA groups after 0, 14, 28, and 56 d.
Figure 2. High-frequency acceleration (HFA) preserves alveolar bone height and increases bone volume in the extraction area. (A) Schematic of the midsagittal section of the alveolar ridge (between buccal and palatal cortical plate). This section was used for the measurement of bone height in the thinnest part of alveolar bone in the area of the distal root socket after extraction of upper right maxillary third molar. Each number represents the mean ± SEM collected from 5 animals. *Significantly different from baseline (day 0, shown in the middle). #Significantly different from static group at same time point. (B) Schematic of the area of analysis with zones identified in the micro–computed tomography section of the distal root of right maxillary third molar. Average bone volume fraction (bone volume/total volume [BV/TV]) was calculated for the apical (zone 1), middle (zone 2), and cervical thirds (zone 3) in both static and HFA groups after 56 d. Each value represents the mean ± SEM of 5 animals. *Significantly different from static group. #Significantly different from zone 1 for the same group. (C) Three-dimensional micro–computed tomography reconstructions of alveolar socket in area of distal root of upper right third molar at 0, 14, 28, and 6 d. Buccal and palatal cortical plate height was measured in 3 sections of alveolar ridge in the area of extraction (mesial, middle, and distal). Each number represents the mean ± SEM of measurements from 5 animals. *Significantly different from baseline (day 0, shown in the middle). #Significantly different from static group at same time point.
Figure 3. High-frequency acceleration (HFA) stimulates intramembranous bone formation. RNA was collected from baseline (day 0) and static and HFA groups at days 7 and 14 after extraction of upper right maxillary third molar, and the expression of different transcription factors (A) and osteogenic and chondrogenic factors (B) were evaluated by reverse transcription polymerase chain reaction. Data shown as fold change in comparison to day 0. Except for Sox9 expression, all data presented are significantly different from day 0. *Significantly different from static group
at same time point. (C) Cell extract was also collected from different samples for analysis of alkaline phosphatase (ALP) activity at days 0, 3, 7, 14, and 28. *Significantly different from day 0. #Significantly different from static group at same time point. (D) Histologic staining for cartilage at day 14 for both static and HFA groups (toluidine blue staining) demonstrate absence of cartilage during socket healing in both groups. (E) Fluorescence microscopy of sagittal sections at days
28 and 56 shows increased intensity of the labels in extraction area of HFA samples indicative of extensive bone formation.
Figure 4. High-frequency acceleration (HFA) inhibits bone resorption after tooth extraction. RNA was collected from the right hemimaxillae of baseline (day 0) and static and HFA animals
at days 7 and 14, and the expression of different regulators of osteoclastogenesis genes (A) and inflammatory genes (day 7; B) was evaluated by reverse transcription polymerase chain reaction. Data shown as fold change in comparison to day 0. HFA reduces the expression of genes that participate in osteoclastogenesis and inflammation. (C) TRAP (tartarate-resistant acid phosphatase) staining of right hemimaxillae after 28 and 56 d. Sagittal sections of right maxilla were produced through the roots of second molar in static and HFA samples. TRAP staining sections shown with magnified detail of marked square area. At 28 d, sections demonstrate higher number of osteoclasts (arrowheads) in the static group than in the HFA group. At 56 d, lamellar bone gradually replaces the woven bone, while the static group still demonstrates higher number of osteoclasts. (D) Mean numbers of osteoclasts at 28 and 56 d in extraction area. Each value represents the mean ± SEM of 5 animals. *Significantly different from static group at similar time points.
