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Strain-guided mineralization in the bone – PDL – cementum complex of a rat periodontium

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ABSTRACT

Objective: The objective of this study was to investigate the effect of mechanical strain by mapping physicochemical properties at periodontal ligament (PDL)–bone and PDL–cementum attachment sites and within the tissues per se.

Design: Accentuated mechanical strain was induced by applying a unidirectional force of 0.06 N for 14 days on molars in a rat model. The associated changes in functional space between the tooth and bone, mineral forming and resorbing events at the PDL–bone and PDL–cementum attachment sites were identified by using micro-X-ray computed tomography (micro-XCT), atomic force microscopy (AFM), dynamic histomorphometry, Raman microspectroscopy, and AFM-based nanoindentation technique. Results from these analytical techniques were correlated with histochemical strains specific to low and high molecular weight GAGs, including biglycan, and osteoclast distribution through tartrate resistant acid phosphatase (TRAP) staining.

Results: Unique chemical and mechanical qualities including heterogeneous bony fingers with hygroscopic Sharpey's fibers contributing to a higher organic (amide III — 1240 cm− 1) to inorganic (phosphate — 960 cm− 1) ratio, with lower average elastic modulus of 8 GPa versus 12 GPa in unadapted regions were identified. Furthermore, an increased presence of elemental Zn in cement lines and mineralizing fronts of PDL–bone was observed. Adapted regions containing bony fingers exhibited woven bone-like architecture and these regions rich in biglycan (BGN) and bone sialoprotein (BSP) also contained high-molecular weight polysaccharides predominantly at the site of polarized bone growth.

Conclusions: From a fundamental science perspective the shift in local properties due to strain amplification at the soft–hard tissue attachment sites is governed by semiautonomous cellular events at the PDL–bone and PDL–cementum sites. Over time, these strain-mediated events can alter the physicochemical properties of tissues per se, and consequently the overall biomechanics of the bone–PDL–tooth complex. From a clinical perspective, the shifts in magnitude and duration of forces on the periodontal ligament can prompt a shift in physiologic mineral apposition in cementum and alveolar bone albeit of an adapted quality owing to the rapid mechanical translation of the tooth.

No MeSH data available.


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Transverse micro-XCT images of control (a) and experimental (b) specimens indicated the gross general movement of teeth in the mesial direction after applied force, accompanied by an increased distal PDL-space, and decreased mesial PDL-space. With higher resolution, (c) and (d) new bone formation in the form of bone-like fingers is noted extending into the PDL-space. TRAP staining for osteoclastic activity demonstrated a shift in resorption from predominantly mesial sites in (e) control specimens to distal sites in (f) the experimental group, contributing to the overall movement of teeth in the mesial direction. (g) The average bone volume fraction (BV/TV) and canal volume fraction (Ca.V/TV) were calculated from subvolumes with an average total volume (TV) of 0.11 mm3. BV: alveolar bone volume; Ca.V: canal volume (blood vessels, endosteal spaces); TV: total volume, TV = BV + Ca.V. AB: alveolar bone, NB: new bone, T: tooth, C: cementum, PDL: periodontal ligament.
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f0005: Transverse micro-XCT images of control (a) and experimental (b) specimens indicated the gross general movement of teeth in the mesial direction after applied force, accompanied by an increased distal PDL-space, and decreased mesial PDL-space. With higher resolution, (c) and (d) new bone formation in the form of bone-like fingers is noted extending into the PDL-space. TRAP staining for osteoclastic activity demonstrated a shift in resorption from predominantly mesial sites in (e) control specimens to distal sites in (f) the experimental group, contributing to the overall movement of teeth in the mesial direction. (g) The average bone volume fraction (BV/TV) and canal volume fraction (Ca.V/TV) were calculated from subvolumes with an average total volume (TV) of 0.11 mm3. BV: alveolar bone volume; Ca.V: canal volume (blood vessels, endosteal spaces); TV: total volume, TV = BV + Ca.V. AB: alveolar bone, NB: new bone, T: tooth, C: cementum, PDL: periodontal ligament.

Mentions: Transverse micro-XCT images (Fig. 1) were used to determine the gross macroscale movements of the teeth relative to the bone after force application. The virtual sections demonstrated movement of the teeth in mesial direction, accompanied by an enlarged PDL-space on the distal side of roots (Fig. 1c), and decreased PDL-space on the mesial side. Resorption pits were observed in cementum opposite to bony finger extensions (Fig. 1d) (Fig. S1, Movie S1a, Movie S1b, Movie S1c).


Strain-guided mineralization in the bone – PDL – cementum complex of a rat periodontium
Transverse micro-XCT images of control (a) and experimental (b) specimens indicated the gross general movement of teeth in the mesial direction after applied force, accompanied by an increased distal PDL-space, and decreased mesial PDL-space. With higher resolution, (c) and (d) new bone formation in the form of bone-like fingers is noted extending into the PDL-space. TRAP staining for osteoclastic activity demonstrated a shift in resorption from predominantly mesial sites in (e) control specimens to distal sites in (f) the experimental group, contributing to the overall movement of teeth in the mesial direction. (g) The average bone volume fraction (BV/TV) and canal volume fraction (Ca.V/TV) were calculated from subvolumes with an average total volume (TV) of 0.11 mm3. BV: alveolar bone volume; Ca.V: canal volume (blood vessels, endosteal spaces); TV: total volume, TV = BV + Ca.V. AB: alveolar bone, NB: new bone, T: tooth, C: cementum, PDL: periodontal ligament.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663464&req=5

f0005: Transverse micro-XCT images of control (a) and experimental (b) specimens indicated the gross general movement of teeth in the mesial direction after applied force, accompanied by an increased distal PDL-space, and decreased mesial PDL-space. With higher resolution, (c) and (d) new bone formation in the form of bone-like fingers is noted extending into the PDL-space. TRAP staining for osteoclastic activity demonstrated a shift in resorption from predominantly mesial sites in (e) control specimens to distal sites in (f) the experimental group, contributing to the overall movement of teeth in the mesial direction. (g) The average bone volume fraction (BV/TV) and canal volume fraction (Ca.V/TV) were calculated from subvolumes with an average total volume (TV) of 0.11 mm3. BV: alveolar bone volume; Ca.V: canal volume (blood vessels, endosteal spaces); TV: total volume, TV = BV + Ca.V. AB: alveolar bone, NB: new bone, T: tooth, C: cementum, PDL: periodontal ligament.
Mentions: Transverse micro-XCT images (Fig. 1) were used to determine the gross macroscale movements of the teeth relative to the bone after force application. The virtual sections demonstrated movement of the teeth in mesial direction, accompanied by an enlarged PDL-space on the distal side of roots (Fig. 1c), and decreased PDL-space on the mesial side. Resorption pits were observed in cementum opposite to bony finger extensions (Fig. 1d) (Fig. S1, Movie S1a, Movie S1b, Movie S1c).

View Article: PubMed Central - PubMed

ABSTRACT

Objective: The objective of this study was to investigate the effect of mechanical strain by mapping physicochemical properties at periodontal ligament (PDL)–bone and PDL–cementum attachment sites and within the tissues per se.

Design: Accentuated mechanical strain was induced by applying a unidirectional force of 0.06 N for 14 days on molars in a rat model. The associated changes in functional space between the tooth and bone, mineral forming and resorbing events at the PDL–bone and PDL–cementum attachment sites were identified by using micro-X-ray computed tomography (micro-XCT), atomic force microscopy (AFM), dynamic histomorphometry, Raman microspectroscopy, and AFM-based nanoindentation technique. Results from these analytical techniques were correlated with histochemical strains specific to low and high molecular weight GAGs, including biglycan, and osteoclast distribution through tartrate resistant acid phosphatase (TRAP) staining.

Results: Unique chemical and mechanical qualities including heterogeneous bony fingers with hygroscopic Sharpey's fibers contributing to a higher organic (amide III — 1240 cm− 1) to inorganic (phosphate — 960 cm− 1) ratio, with lower average elastic modulus of 8 GPa versus 12 GPa in unadapted regions were identified. Furthermore, an increased presence of elemental Zn in cement lines and mineralizing fronts of PDL–bone was observed. Adapted regions containing bony fingers exhibited woven bone-like architecture and these regions rich in biglycan (BGN) and bone sialoprotein (BSP) also contained high-molecular weight polysaccharides predominantly at the site of polarized bone growth.

Conclusions: From a fundamental science perspective the shift in local properties due to strain amplification at the soft–hard tissue attachment sites is governed by semiautonomous cellular events at the PDL–bone and PDL–cementum sites. Over time, these strain-mediated events can alter the physicochemical properties of tissues per se, and consequently the overall biomechanics of the bone–PDL–tooth complex. From a clinical perspective, the shifts in magnitude and duration of forces on the periodontal ligament can prompt a shift in physiologic mineral apposition in cementum and alveolar bone albeit of an adapted quality owing to the rapid mechanical translation of the tooth.

No MeSH data available.


Related in: MedlinePlus