Comparison of the vitality tests used in the dental clinical practice and histological analysis of the dental pulp

Abstract

In dentistry, indirect diagnostic methods such as electrical sensibility testing and pulse oximetry are used to assess the status of the pulp. Our study aimed to determine the correlation between hemoglobin oxygen saturation and vascular volume density (Vvasc). We also wanted to examine an electrical sensibility test and the volume density of myelinated nerve fibers (Vnerv). Twenty-six intact permanent premolars were included in the study. For histological analysis, the pulp tissue was stained with hematoxylin-eosin and immunohistochemically for von Willebrand factor and S100 to detect blood vessels and myelinated nerve fibers, respectively. The stereological analysis was used to determine the Vvasc and Vnerv. Statistical analysis was done using the Pearson correlation test and Welch's ANOVA test. Histological analysis showed that the pulp tissue was strongly vascularized and innervated. A significant positive correlation was found between Vvasc and hemoglobin oxygen saturation levels (p=0.030). A significant negative correlation was found between Vnerv and the lowest electrical voltage that patient felt (p=0.033). According to the maturity of the dental apex, teeth were divided into a group with open (N=6, OA group) and closed apex (N=20, CA group). We found that pulps in the CA group had higher Vnerv than the OA group (p=0.037). In contrast, there were no significant differences in Vvasc of the pulp tissue (p=0.059), oxygen saturation (p=0.907), or electrical voltage (p=0.113) between both groups. We can conclude that the measurement of pulse oximetry and electrical sensibility test reflect the morphology of healthy pulp tissue independently of the maturity of the dental apex.

FIGURE 1

“Y” sensor on each branch of dental forceps placed on the dental crown.

FIGURE 2

The preparation process of the extracted teeth.

FIGURE 3

Crown part of dental pulp with closed (CA group) and open apex (OA group) stained with HE (objective magnification ×4, bar=300μm), anti-vWf (objective magnification ×4, bar=300μm), and anti-S100 (sub-odontoblast zone, objective magnification ×20, bar=150μm). Note that the pulp tissue is insignificantly more vascularized (HE, vWf) and significantly more innervated (S100) in the CA group than in the OA group. ↑: Vessels with the thin wall; ▲: Branching of the vessels in the right angels.

FIGURE 4

(A) Linear correlation between the vascular volume density of the pulp tissue (Vvasc) and levels of hemoglobin oxygen saturation (SpO₂) (R=0.426, p=0.030, Pearson correlation); (B) linear correlation between the volume density of nerve fibers (Vnerv) and the lowest electrical voltage (EV) felt by the patient (R=−0.420, p=0.033, Pearson correlation).

FIGURE 5

The differences between the CA and OA groups in (A) vascular (Vvasc) and nerve fibers (Vnerv) volume density of the pulp tissue; (B) oxygen saturation (SpO₂) and (C) the lowest electrical voltage (EV) felt by the patient. (*Significantly different; ANOVA, Welch test [p<0.05]).