Three decades on, the mesenchymal stem cells (MSCs) have been intensively researched on the bench top and used clinically. However, ambiguity still exists in regard to their anatomical locations, identities, functions, and extent of their differentiative abilities. One of the major impediments in the quest of the MSC research has been lack of appropriatein vivomarkers. In recent years, this obstacle has been resolved to some degree as PDGFRαemerges as an important mesenchymal stem cell marker. Accumulating lines of evidence are showing that the PDGFRα⁺cells reside in the perivascular locations of many adult interstitium and fulfil the classic concepts of MSCsin vitroandin vivo. PDGFRαhas long been recognised for its roles in the mesoderm formation and connective tissue development during the embryogenesis. Current review describes the lines of evidence regarding the role of PDGFRαin morphogenesis and differentiation and its implications for MSC biology.

Aim: The aim of the study was to evaluate the effect of cooling the soft tissue of injection sites on the pain perceptions of pediatric patients during the administration of local anesthesia for routine dental procedures. Methods and Materials: A total of 160 children aged 5-6 years were included in the present study. On a random basis, the subjects were allocated to the without ice pretreatment (WIP) group (topical anesthesia + counterstimulation + distraction) or the ice pretreatment (IP) group (cooling + topical anesthesia + counterstimulation + distraction). During the administration of an inferior alveolar nerve block, the children's behavior was assessed using the sound, eye, and motor (SEM) scale. The statistical analysis of data was performed based on the analysis of variance (ANOVA). Results: There were no significant differences within the groups between the values of the sound, eye, and motor components for either the WIP or the IP groups (P>0.05). All three components of the SEM in the IP group were consistently lower than the WIP group (P<0.05). Moreover, the SEM value for the WIP group surpassed the IP group (P<0.05). Conclusions: Cooling the site of infiltration block prior to the injection of local anesthesia significantly reduced the pain perceived during injection of local anesthetic agent in pediatric patients. Clinical Significance: Pre-cooling of the soft tissues of an injection site prior to the administration of a local anesthetic can minimize the discomfort and anxiety associated with the injection procedure and facilitates the management of pediatric patients during this phase of a dental procedure. Citation: Aminabadi NA, Farahani RMZ. The Effect of Pre-cooling the Injection Site on Pediatric Pain Perception during the Administration of Local Anesthesia. J Contemp Dent Pract 2009 May; (10)3:043-050.

Early life stress can disrupt development and negatively impact long-term health trajectories. Reconstructing histories of early life exposure to external stressors is hampered by the absence of retrospective time-specific biomarkers. Defects in tooth enamel have been used to reconstruct stress but the methods used are subjective and do not identify the specific biological systems impacted by external stressors. Here we show that external physical and social stressors impart biochemical signatures in primate teeth that can be retrieved to objectively reconstruct the timing of early life developmental disruptions. Using teeth from captive macaques, we uncovered elemental imprints specific to disruptions of skeletal growth, including major disruptions in body weight trajectory and moderate to severe illnesses. Discrete increases in heat shock protein-70 expression in dentine coincided with elemental signatures, confirming that elemental signals were associated with activation of stress-related pathways. To overcome limitations of conventional light-microscopic analysis, we used high resolution Raman microspectral imaging to identify structural and compositional alterations in enamel and dentine that coincided with elemental signatures and with detailed medical and behavioural data. Integrating these objective biochemical markers with temporal mapping of teeth enables the retrospective study of early life developmental disruptions and their ensuing health sequelae.