Biomolecules and material-tissue interactions in regenerative dentistry

Periodontal disease is a prevalent condition affecting a substantial proportion of the global population. It has a significant impact on the quality of life and its incidence is projected to increase as the population ages. This habilitation work focuses on various aspects of periodontal regeneration, personalized periodontics, and the influence of materials and interventions on periodontal and peri-implant health. The first part of the research explores the role of biomolecules in periodontal regeneration and repair. While common periodontal treatments result in tissue repair, the ultimate objective is achieving complete regeneration. Regenerative procedures that aim to restore lost or injured tissues in periodontal disease are being extensively studied. Two specific biomolecules, amelogenin (component of EMD) and hyaluronic acid (HA), were examined for promoting the regeneration of periodontal tissues. The studies evaluated the effects of these biomolecules on cell proliferation, migration, and differentiation, highlighting their potential in improving periodontal tissue regeneration. One study specifically focused on a recombinant version of the main protein found in EMD, amelogenin, investigating the effects of the full-length protein on periodontal wound healing and its interaction with oral keratinocytes. The results show that amelogenin inhibits the motility and proliferation of keratinocytes, suggesting its potential in preventing the occupation of periodontal ligament space by these cells. Another study explored the influence of different molecular weights of hyaluronic acid on periodontal ligament cells. Hyaluronic acid fragments induce osteogenic differentiation in these cells, with medium molecular weight hyaluronic acid showing the most significant effects. The study highlights the importance of considering the molecular weight of hyaluronic acid in its clinical application for periodontal therapy. The second part of the research focuses on the use of biomolecules in the diagnosis, monitoring, and treatment of periodontal conditions. It discusses the potential of cytokines, such as interleukin-8 (IL-8), as diagnostic markers for periodontitis. The study showed a strong correlation between IL-8 levels in gingival crevicular fluid and the clinical severity of periodontitis. The research also investigated the correlation between IL-8 levels and smoking habits, revealing that for this group IL-8 cannot serve as a biomarker of periodontitis. Additionally, the research explored the effects of prostaglandins E2 (PGE2) and D2 (PGD2) on cell proliferation and osteogenic capacity of human mesenchymal stem cells. It demonstrated that both PGE2 and PGD2 negatively affect osteogenic differentiation and metabolism, suggesting their involvement in periodontitis-induced tissue damage. The third part of the research examines the influence of materials and iatrogenic interventions on periodontal and peri-implant health. One study investigated the ultrastructural changes of titanium implant surfaces caused by metal and plastic periodontal probes. Although slight changes in surface roughness were observed, they did not reach statistical significance. Further studies need to investigate how routine probing might affect the reattachment of osteoblasts after peri-implant defect treatment. Two other studies focused on the cytotoxicity of 3D printed resin materials used for temporary dental restorations. The research evaluated the effects of these materials on human periodontal ligament cells and gingival keratinocytes. The results indicate a higher cytotoxicity of 3D printed resin materials compared to conventional and subtractive manufacturing materials. Overall, this research provides valuable insights into the biological principles of regenerative materials, the potential of biomolecules in periodontal therapy, the use of molecules as diagnostic markers, and the influence of materials and interventions on periodontal and peri-implant health. The findings contribute to the advancement of periodontal treatment and personalized dentistry, aiming to improve patient care and outcomes in the field of periodontology

Full-length amelogenin influences the differentiation of human dental pulp stem cells

Background: Amelogenin is an extracellular matrix protein well known for its role in the organization and mineralization of enamel. Clinically, it is used for periodontal regeneration and, due to its finding also in predentin and intercellular spaces of dental pulp cells, it has recently been suggested for pulp capping procedures. The aim of this study was to analyse in vitro the effect of the recombinant human full-length amelogenin on the growth and differentiation of human dental pulp stem cells (hDPSCs). Methods: Human DPSCs were treated with a supplement of amelogenin at a concentration of 10 ng/ml, 100 ng/ml and 1000 ng/ml. The groups were compared to the unstimulated control in terms of cell morphology and proliferation, mineralization and gene expression for ALP (alkaline phosphatase), DMP1 (dentin matrix protein-1) and DSPP (dentin sialophosphoprotein). Results: Amelogenin affects hDPSCs differently than PDL (periodontal ligament) cells and other cell lines. The proliferation rate at two weeks is significantly reduced in presence of the highest concentration of amelogenin as compared to the unstimulated control. hDPSCs treated with low concentrations present a downregulation of DMP1 and DSPP, which is significant for DSPP (p = 0.011), but not for DMP1 (p = 0.395). Conclusions: These finding suggest that the role of full-length amelogenin is not restricted to participation in tooth structure. It influences the differentiation of hDPSC according to various concentrations and this might impair the clinical results of pulp capping

Ultrastructural changes of smooth and rough titanium implant surfaces induced by metal and plastic periodontal probes.

OBJECTIVES To determine the ultrastructural changes of titanium surfaces of dental implants induced by the tip of periodontal probes. MATERIALS AND METHODS A total of 40 samples of smooth and rough surfaces of titanium implants were randomly assigned for the treatment with metal or plastic periodontal probes under application angles of 20° and 60°. Titanium surfaces have been evaluated with CLSM prior and following to experimental probing determining various standardized 2D and 3D roughness parameters. RESULTS The average profile and surface roughness (Ra and Sa) showed no significant difference between treated and untreated samples on smooth and rough surface areas irrespective of the probe material. On smooth surfaces several amplitude roughness parameters were increased with metal probes but reached significance only for Rp (p = 0.007). Rough surface parts showed a slight but not significant reduction of roughness following to the contact with metal probes. The surface roughness remained almost unchanged on smooth and rough implant surfaces using plastic probes. The surface roughness on implant surfaces was not dependent on the application angle irrespective of the probe material. CONCLUSION Probing of titanium implants with metal probes and even less with plastic probes causes only minor changes of the surface roughness. The clinical significance of these changes remains to be elucidated. CLINICAL RELEVANCE Using plastic probes for the clinical evaluation of the peri-implant sulcus might avoid ultrastructural changes to titanium implant surfaces

Effects of resin materials dedicated for additive manufacturing of temporary dental restorations on human gingival keratinocytes

Objective This study investigated the effect of eluates of conventional and 3D-printed resin materials for manufacturing temporary dental restorations on gingival keratinocytes. Methods Three-dimensional (3D)-printed resin materials: 3Delta temp (Deltamed), NextDent MFH (Nextdent), Freeprint temp (Detax), GC temp (GC), were compared to Grandio disc (Voco) and Luxatemp (DMG). Human gingival keratinocytes (IHGKs) were exposed to eluates of the materials and XTT assays were performed at 24 h, 48 h, 72 h, or 144 h. For quantification of the proinflammatory response, the protein amount of IL-6 and 8 was determined in the supernatants using ELISA. One-way ANOVA with post hoc analysis was used to compare differences in cell viability and IL-6 and IL-8 levels between groups. Results At 24 h, and more remarkably at 48 h, a significant decrease in cell viability occurred for the 3D-printed materials compared to the untreated IHGKs, but also compared to Grandio disc and Luxatemp. Except for the expression of IL-8 in presence of the eluate of Grandio disc at 24 and 48 h, all tested materials caused attenuation of IL-6 and 8 from IHGKs for any observation period. Conclusions The materials for additive manufacturing affect cell proliferation differently than the subtractive manufactured material Grandio disc and the conventional material Luxatemp. Clinical Significance In comparison to conventional and subtractive manufactured restorations, 3D printed temporary restorations might induce more negative effects on the gingival and probably also on pulpal health since viability and the proinflammatory response of oral keratinocytes are more intensively affected by these materials