Abstract
Type 2 Diabetes (T2D) is a chronic metabolic condition characterised by hyperglycaemia. Patient numbers are increasing exponentially and the disease is associated with significant co-morbidities involving multiple bodily sites. Tissue calcification is not uncommon in the pulp space and its presence creates challenges for clinicians increasing the risk of procedural errors when removing residual pulp tissue and this may obstruct access to root canals. Tissue calcification associated with T2D has not yet been fully characterised and a further understanding of their involvement is needed. Most studies investigating T2D and dental pulp mineralisation have used animals models, so there remains a gap in our understanding of the effect hyperglycaemia has on human dental pulp cells (hDPCs). This research examined the histological differences within the dental pulp space of clinically normal and non-carious molar teeth from T2D and non-T2D
patients, and the development of an in vitro T2D cell culture model to study hDPC mineralisation over an extended time period.
In part 1, clinically normal, intact, non-periodontally compromised molars were collected from well-controlled T2D patients (n=5) and non-T2D patients (n=5). The specimens were decalcified, paraffin-embedded and serial sections cut at 4 μm intervals for histological and special staining analysis. Qualitative analysis showed an increase in the presence of diffuse, amorphous, bone-like calcifications in the pulp chambers of T2D samples compared with non-T2D samples. These areas of calcification were commonly found in the peripheral and central pulp with some extending into the coronal third of the root canals. This finding has significant clinical implications for endodontic treatment planning. In part 2, non-T2D hDPC primary cell lines (n=4) obtained using the explant technique were cultured in normoglycaemic (5.5 mM D-glucose), pre-diabetic (12.5 mM D-glucose) and hyperglycaemic (25 mM D-glucose) conditions up to 21 days. In pre-diabetic and hyperglycaemic conditions, the cell viability of hDPCs reduced over time. In cell culture, formation of calcified nodules were observed using alizarin red S staining and these increased over time in higher D-glucose concentrations and with osteogenic supplements. Multiple gene expression analysis revealed the complexity of the pathways of calcification, the high potential of hDPCs to mineralise in a favourable environment and further validated the in vitro T2D model.
Clinical competence entails recognition of the effects of systemic diseases to individualise treatment plans for every patient. This study has enhanced our understanding of the effects of T2D on the dental pulp and the effects of hyperglycaemia on the behaviour of hDPCs.