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Simple Summary: Tooth roots are increasingly applied for bone reconstruction before implant placement. Growth factors stored in the dentin are assumed to enhance bone regeneration, however, the evidence is low. To this aim, collagen membranes were coated with dentin lysates obtained from extracted porcine teeth or remain untreated. The collagen membranes were tested for their capacity to stimulate bone formation in rat calvarial bone defects. After four weeks of healing, micro-computed tomography and histological analyses revealed that dentin lysates coating had no significant impact on the rather strong bone regeneration reaching a nearly complete defect closure even in untreated defects. It can thus be concluded that dentin lysates do not hinder bone regeneration. Conclusions concerning a possible stimulation of bone regeneration by dentin lysates should not be drawn.
Abstract: 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.
Particulate autogenous tooth roots are used for alveolar bone augmentation surgery; however, dental plaque may provoke an inflammatory response that may counteract the desired graft consolidation process. Traditional mechanical cleaning of extracted teeth may be of support to lower a possible inflammatory response of the autograft. To test this assumption, extracted porcine teeth were left either uncleaned or underwent mechanical cleaning with a toothbrush and toothpaste before being fragmented and subjected to acid lysis, termed as unclean acid dentine lysate (ucADL) and clean acid dentine lysate (cADL), respectively. The inflammatory responses of murine macrophage RAW 264.7 cells being exposed to the respective acid dentine lysates were evaluated at the level of inflammatory gene expression and IL6 immunoassays. We report here that acid lysates obtained from uncleaned teeth provoked a robust increase in IL1β, IL6, and COX2 in RAW 264.7 cells. The mechanical removal of dental plaque significantly reduced the inflammatory response. Consistently, Limulus tests revealed that tooth cleaning lowers the presence of endotoxins in dentine lysates. To further prove the involvement of endotoxins, a toll-like receptor 4 (TLR4) inhibitor TAK242 was introduced. TAK242 abolished the inflammatory response provoked by acid lysates obtained from uncleaned teeth in RAW 264.7 cells. Moreover, nuclear translocation and phosphorylation of the TLR4 downstream NFκB-p65 were attenuated at the presence of cleaned versus uncleaned dentine lysates. Taken together, our data support the importance of dental plaque removal of teeth being extracted for alveolar bone augmentation surgery.
