Marina Marechal

An in vivo Study of the Influence of the Surface Roughness of Implants on the Microbiology of Supra- and Subgingival Plaque

In nine patients with fixed prostheses supported by endosseous titanium implants, 2 titanium abutments (trans-mucosal part of the implant) were replaced by either an unused standard abutment or a roughened titanium abutment. After 3 months of habitual oral hygiene, plaque samples were taken for differential phase-contrast microscopy, DNA probe analysis, and culturing. Supragingivally, rough abutments harbored significantly fewer coccoid micro-organisms (64 us. 81%), which is indicative of a more mature plaque. Subgingivally, the observations depended on the sampling procedure. For plaque collected with paper points, only minor qualitative and quantitative differences between both substrata could be registered. However, when the microbiota adhering to the abutment were considered, rough surfaces harbored 25 times more bacteria, with a slightly lower density of coccoid organisms. The presence and density of periodontal pathogens subgingivally were, however, more related to the patients dental status than to the surface characteristics of the abutments. These results justify the search for optimal surface smoothness for all intra-oral and intra-sulcular hard surfaces for reduction of bacterial colonization and of periodontal pathogens.

The Influence of Surface Free-energy on Planimetric Plaque Growth in Man

The purpose of this study was to examine the change in plaque area over nine days in vivo on four materials with different surface free-energies (s.f.e.). Twelve healthy dental students participated in a crossover, split-mouth, double-blind study. Supragingival plaque formation was recorded over a nine-day period, on four different materials: fluorethylenepropylene (Teflon) (FEP), parafilm (PAR), cellulose acetate (CA), and enamel (E) with s.fe. of 20, 26, 57, and 88 erg/cm2, respectively. Strips made from the first three materials were stuck to the buccal surface of an upper incisor. The remaining incisor was carefully polished and served as an enamel surface. The increase in plaque was evaluated after three, six, and nine days. A planimetrical analysis was used so that the plaque area could be expressed as a percentage of the total buccal tooth surface. This procedure was repeated on each subject, so that at the end, each pair of central or lateral incisors received the four tested materials. The results indicated that the adherence of micro-organisms on pellicle-coated substrata was influenced by the materials s.f.e.; there was an association between the s.f.e. of the substrata and the supragingival plaque extension in vivo. High surface free-energy substrata in the oral cavity attracted more micro-organisms than did low energetic materials. Additionally, the bacterial adhesion seemed very weak on surfaces with a low s.f.e.

The bacterial colonization of intra‐oral hard surfaces in vivo: Influence of surface free energy and surface roughness

The recolonization rate of a tooth surface after perfect cleaning follows an exponential curve with a very slow growth rate during the first 24 h. After 4 days of undisturbed plaque formation, more than 30% of the tooth surface will be covered by plaque. During the night, plaque growth rate is up to 50% less than during the day. Plaque growth pattern was found to correlate closely with irregularities in the tooth surface. A positive correlation exists between the recolonization rate and the substratum surface free energy (sfe). On surfaces with a low sfe the rate of bacterial recolonization is slower and the strength of adhesion on these surfaces is weaker. Moreover, the composition of the plaque depends on the substratum sfe. Low sfe bacteria adhere preferentially to low sfe surfaces (Teflon), and high sfe bacteria prefer high sfe substrata (enamel). The rate of bacterial colonization of intra‐oral hard surfaces is positively correlated with surface roughness (sr), as is the speed of plaque maturation. C...

Deciphering the combined effect of bone morphogenetic protein 6 and calcium phosphate on bone formation capacity of periosteum derived cell-based tissue engineering constructs

Cell based combination products with growth factors on optimal carriers represent a promising tissue engineering strategy to treat large bone defects. In this concept, bone morphogenetic protein (BMP) and calcium phosphate (CaP)-based scaffolds can act as potent components of the constructs to steer stem cell specification, differentiation and initiate subsequent in vivo bone formation. However, limited insight into BMP dosage and the cross-talk between BMP and CaP materials, hampers the optimization of in vivo bone formation and subsequent clinical translation. Herein, we combined human periosteum derived progenitor cells with different doses of BMP6 and with three types of clinical grade CaP-scaffolds (ChronOs®, ReproBone™, & CopiOs®). Comprehensive cellular and molecular analysis was performed based on in vitro cell metabolic activity and signaling pathway activation, as well as in vivo ectopic bone forming capacity after 2 weeks and 5 weeks in nude mice. Our data showed that cells seeded on CaP scaffolds with an intermediate Ca2+ release rate combined with low or medium dosage of BMP6 demonstrated a robust new bone formation after 5 weeks, which was contributed by both donor and host cells. This phenomenon might be due to the delicate balance between Ca2+ and BMP pathways, allowing an appropriate activation of the canonical BMP signaling pathway that is required for in vivo bone formation. For high BMP6 dosage, we found that the BMP6 dosage overrides the effect of the Ca2+ release rate and this appeared to be a dominant factor for ectopic bone formation. Taken together, this study illustrates the importance of matching BMP dosage and CaP properties to allow an appropriate activation of canonical BMP signaling that is crucial for in vivo bone formation. It also provides insightful knowledge with regard to clinical translation of cell-based constructs for bone regeneration. STATEMENT OF SIGNIFICANCE: The combination of bone morphogenetic proteins (BMP) and calcium phosphate (CaP)-based biomaterials with mesenchymal stromal cells represents a promising therapeutic strategy to treat large bone defects, an unmet medical need. However, there is limited insight into the optimization of these combination products, which hampers subsequent successful clinical translation. Our data reveal a delicate balance between Ca2+ and BMP pathways, allowing an appropriate activation of canonical BMP signaling required for in vivo bone formation. Our findings illustrate the importance of matching BMP dosage and CaP properties in the development of cell-based constructs for bone regeneration.

36 Parodontale regeneratieve chirurgie

De succesvolle behandeling van furcatieletsels blijft een moeilijk probleem De introductie van de regeneratieve technieken deed hoopvolle verwachtingen ontstaan, die niet helemaal werden ingelost. Het gebrek aan reproduceerbaarheid van de gebruikte methoden blijft een obstakel dat een veralgemeende toepassing in de weg staat.