Cleaning Teeth Reduces the Inflammatory Response of Macrophages to Acid Dentine Lysate

Acid Dentin Lysate Modulates Macrophage Polarization and Osteoclastogenesis In Vitro

Dentin prepared from extracted teeth is used as autograft for alveolar bone augmentation. Graft consolidation involves the acid lysis of dentin thereby generating a characteristic paracrine environment. Acid lysate of dentin is mimicking this environment. Acid dentin lysate (ADL) potentially targets hematopoietic cells thereby affecting their differentiation towards macrophages and osteoclasts; however, the question remains if ADL controls macrophage polarization and osteoclastogenesis. Here, we show that ADL reduced lipopolysaccharide (LPS)-induced macrophage polarization of the pro-inflammatory (M1) phenotype, indicated by attenuated Interleukin 1 (IL1), Interleukine 6 (IL6)and cyclooxygenase 2 (COX2) expression. This decrease in M1 macrophages was confirmed by the reduced phosphorylation and nuclear translocation of p65 in the LPS-exposed RAW 264.7 macrophages. Similarly, when RAW 264.7 macrophages were incubated with other agonists of Toll-like receptor (TLR) signaling e.g., FSL1, Polyinosinic-polycytidylic acid High Molecular Weight (Poly (1:C) HMW), Pam3CSK4, and imiquimod, ADL reduced the IL6 expression. We further show herein that ADL decreased osteoclastogenesis indicated by the reduced formation of multinucleated cell expressing cathepsin K and tartrate-resistant acid phosphatase in murine bone marrow cultures. Overall, our results suggest that acid dentin lysate can affect the differentiation of hematopoietic cells to M1 macrophage polarization and a decrease in osteoclastogenesis in bone marrow cultures.

Proteomic and genomic analysis of acid dentin lysate with focus on TGF-β signaling

Particulate autologous tooth roots are increasingly used for alveolar bone augmentation; however, the proteomic profile of acid dentin lysate and the respective cellular response have not been investigated. Here we show that TGF-β1 is among the 226 proteins of acid dentin lysate (ADL) prepared from porcine teeth. RNA sequencing identified 231 strongly regulated genes when gingival fibroblasts were exposed to ADL. Out of these genes, about one third required activation of the TGF-β receptor type I kinase including interleukin 11 (IL11) and NADPH oxidase 4 (NOX4). Reverse transcription-quantitative polymerase chain reaction and immunoassay confirmed the TGF-β-dependent expression of IL11 and NOX4. The activation of canonical TGF-β signaling by ADL was further confirmed by the phosphorylation of Smad3 and translocation of Smad2/3, using Western blot and immunofluorescence staining, respectively. Finally, we showed that TGF-β activity released from dentin by acid lysis adsorbs to titanium and collagen membranes. These findings suggest that dentin particles are a rich source of TGF-β causing a major response of gingival fibroblasts.

Acid Dentin Lysate Failed to Modulate Bone Formation in Rat Calvaria Defects

Autogenous tooth roots are increasingly applied as a grafting material in alveolar bone augmentation. Since tooth roots undergo creeping substitution similar to bone grafts, it can be hypothesized that osteoclasts release the growth factors stored in the dentin thereby influencing bone formation. To test this hypothesis, collagen membranes were either soaked in acid dentin lysates (ADL) from extracted porcine teeth or serum-free medium followed by lyophilization. Thereafter, these membranes covered standardized 5-mm-diameter critical-size defects in calvarial bone on rats. After four weeks of healing, micro-computed tomography and histological analyses using undecalcified thin ground sections were performed. Micro-computed tomography of the inner 4.5 mm calvaria defects revealed a median bone defect coverage of 91% (CI: 87-95) in the ADL group and 94% (CI: 65-100) in the control group, without significant differences between the groups (intergroup p > 0.05). Furthermore, bone volume (BV) was similar between ADL group (5.7 mm³, CI: 3.4-7.1) and control group (5.7 mm³, CI: 2.9-9.7). Histomorphometry of the defect area confirmed these findings with bone area values amounting to 2.1 mm² (CI: 1.2-2.6) in the ADL group and 2.0 mm² (CI: 1.1-3.0) in the control group. Together, these data suggest that acid dentin lysate lyophilized onto collagen membranes failed to modulate the robust bone formation when placed onto calvarial defects.

Tooth shell technique: A proof of concept with the use of autogenous dentin block grafts

BACKGROUND

Autogenous bone block graft is considered the gold standard for lateral bony defects. Dentin has been identified to be a suitable autogenous bone graft material due to its structural and chemical similarities to the alveolar bone.

METHODS

This proof of concept study describes the clinical application of the tooth shell technique in 24 sites with 27 implants of 22 patients. A tooth shell was fixed laterally to the defect with microscrews. Distance between the shell and the residual bone was filled with particulate remnants of the tooth root. Implant was inserted simultaneously. Cone beam computed tomography was done after implant insertion (T1) and 3 months later at time of implant exposure (T2). Target parameters were biological complications and the resorption of hard tissue graft.

RESULTS

Even though a graft exposure occurred in one case (4.5% on patient-level), all implants showed enough implant stability and were able to be loaded. At T2, the evaluation of the X-rays showed no case with hard tissue loss at the mesial or distal implant shoulder. All implants were completely osseointegrated.

CONCLUSIONS

The tooth shell technique showed promising results for the reconstruction of lateral alveolar crest defects. It may be considered to serve as an alternative material to avoid bone harvesting procedures.