Dental Pulp Is a Complex Adaptive System

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Department of Pediatric Dentistry, Selcuk University, Faculty of Dentistry, Konya, Turkey
 
Abstract
The damaged or lost structure of teeth caused by caries or trauma can be treated clinically by replacement with an artificial material (fillings) and the outcome is usually satisfactory. Yet, tooth loss is the most common organ failure. The complex biological structure of the tooth organ including the enamel, dentin, cementum, and pulp create obstacles for any ambitious dream of the substitution of artificial material with a bio-tooth. Although the focus of the most regenerative studies is toward achieving a means to repeat evolutionary signals secondarily and initiate development secondarily, lack of understanding of the nature and interactions of tooth creating cells blocks this goal. Efforts to discover possible lineage-specific propensities within one group of cells are progressing more favourably. Although stem cells have been taken out of the body and manipulated ex vivo, there are many steps for successful cell-based therapies due to committed cells being unable to orchestrate the regeneration of complex tooth structures (Yildirim et al. 2011a).

The damaged or lost structure of teeth caused by caries or trauma can be treated clinically by replacement with an artificial material (fillings) and the outcome is usually satisfactory. Yet, tooth loss is the most common organ failure. The complex biological structure of the tooth organ including the enamel, dentin, cementum, and pulp create obstacles for any ambitious dream of the substitution of artificial material with a bio-tooth. Although the focus of the most regenerative studies is toward achieving a means to repeat evolutionary signals secondarily and initiate development secondarily, lack of understanding of the nature and interactions of tooth creating cells blocks this goal. Efforts to discover possible lineage-specific propensities within one group of cells are progressing more favourably. Although stem cells have been taken out of the body and manipulated ex vivo, there are many steps for successful cell-based therapies due to committed cells being unable to orchestrate the regeneration of complex tooth structures (Yildirim et al. 2011a).
Regeneration of dental pulp, dentin, periodontium including cementum, periodontal ligament, and alveolar bone, and regeneration or synthesis of enamel-like structures have been reported (Zeichner-David 2006; Foster et al. 2007; Huang et al. 2008a, b; Huang 2009; Kim et al. 2010a). Moreover, regeneration or de novo formation of an entire, anatomically correct tooth has been shown (Ikeda et al. 2009; Kim et al. 2010a, b). However, there is no clinical outcome yet, since the difficulties in obtaining proper cells (embryonic tooth bud cells, allogenic human cells, xenogenic embryonic tooth bud cells), and cell delivery approaches (scaffolds), cause the signaling molecules to encounter several translational barriers. In summary, albeit considerable progression for teeth regeneration with both cell transplantation and cell homing approaches has been achieved, we still need more tangible methods and approaches toward clinical translation (Yildirim et al. 2011a).

9.1 Changing Concepts in Cell Biology

The central dogma of molecular biology states that the molecular basis of genetic inheritance is established by a linear relationship between genetic information encoded in DNA and translated protein (DNA  →  mRNA  →  protein) (Li and Xie 2011; Huang 2012). However, with the aid of advanced single-cell fluorescence microscopy, transcriptomes and proteomes have been quantified with single-molecule sensitivity showing that the mRNA copy number does not correlate with the protein copy number for the same gene in an E. coli cell (Yu et al. 2006a, b; Taniguchi et al. 2010). There is accumulating evidence showing that genotype might not be translated in an obvious manner into a corresponding phenotype and genes are not even the sole basis of inheritance. In conclusion, “the complexity in the relationship between genotype and phenotype has emerged with inescapable clarity” (Huang 2012).

9.2 The Tooth as a Complex Adaptive System

Since many phenomena in life are neither linear nor able to be reduced to their simplistic units (or both), the inability of linear analysis to explain nonlinear systems has been accepted at the beginning of 1900s. A nonlinear system is more than the sum of its parts and small inputs can have large system effects (or vice versa) and there is sensitivity to initial conditions, which makes prediction almost impossible (Waldrop 1992).
Aydinoglu stated that:

The problem in working with non-linear systems was beyond human computational ability. When non-linear relations are realized, the related data was not preserved and/or the non-linear relations cannot be measured/calculated due to their complexity. This happens because “modeling the nonlinear outcomes of many interacting components has been so difficult that both social and natural scientists have tended to select more analytically tractable problems” (Anderson 1999), which produces deficient and incomplete reflections of reality. Thus, scholars end up having a discipline that is not connected to life and it does not help us to control or predict phenomenon as a result of its dependency on linear modeling.
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Nov 16, 2015 | Posted by in General Dentistry | Comments Off on Dental Pulp Is a Complex Adaptive System
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