Dental Pulp Vascular Response to Early Stages of Caries.

OBJECTIVES: During caries progression, dental pulp is increasingly pathologically affected. Since the accurate assessment of pulp is of vital importance in clinical decision-making, this study aimed to evaluate pulpal condition in the early stages of caries via laser Doppler (LD) flowmetry and histologic analysis and determine their agreement. METHODS: Fourteen patients with severe dental crowding were included. Prior to extractions and orthodontic treatment, dental pulp condition of 52 premolars was evaluated via LD flowmetry. Teeth were assessed for the presence of caries and lesions were graded according to the International Caries Detection and Assessment System (ICDAS). After extractions, teeth were split and histologically stained for endothelial cells with anti-von Willebrand factor and Movat pentachrome for collagen. Volume densities of vessels (Vvasc) and collagen were calculated. RESULTS: There was a significant negative correlation between LD flow and Vvasc of the dental pulp with ICDAS grade. Pulpal LD flow and Vvasc in teeth with the initial lesion were increased, decreasing with progressing stages of caries. A significant positive correlation between the the pulpal LD flow and Vvasc, and a negative correlation of LD flow with collagen fibre density were noted. CONCLUSIONS: Caries affects the physiology of the dental pulp, initially with increasing vascularity, and decreasing vascularity at later stges of caries progression. Collagen contents increase with grades of ICDAS. LD flow shows good agreement with the histologic constitution of the dental pulp. Use of clinical measurements of pulpal LD flow could provide a good noninvasive indication of pulpal vascular state and its health.

Expression of CD31, CD34, and smooth muscle actin (SMA) in endothelial cells of dental pulp vessels.

The dental pulp is a highly vascularized and innervated loose connective tissue surrounded by hard dental tissues - enamel and dentine. With the primary dentin formation and the closure of the root apex, the conditions in the dental pulp change and pulp tissue compliance are reduced. Endothelial cells of pulpal blood vessels are highly differentiated and are capable of adaptation to changes in the environment. We aimed to evaluate the phenotypic plasticity of endothelial cells of pulpal blood vessels in permanent premolars with open (N = 6) or closed root apex (N = 30). The pulp tissue was stained with hematoxylin-eosin (HE) for the histological analysis, and immunohistochemically for a cluster of differentiation 31 (CD31), a cluster of differentiation 34 (CD34), and for smooth muscle actin (SMA) to detect vessels with CD31, CD34, and SMA positive endothelial cells. We used the student's t-test and Pearson correlation test for the statistical analysis. We found a significantly higher percentage of the vessels with CD31 (P = 0.005) and CD34 (P = 0.000) positive endothelial cells in the group of teeth with closed root apex compared to the group with open apex. A significant positive correlation between SMA positive and CD31 positive vessels (P = 0.003) and between CD31 positive and CD34 positive vessels (P = 0.031) was also found. We conclude that the endothelial cells of dental pulp vessels express a small amount of CD31, but have a pronounced expression of SMA and CD34, which indicates their progenitor potential and contractile ability.

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

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.

Effects of low-level light therapy on xerostomia related to hyposalivation: a systematic review and meta-analysis of clinical trials.

Hyposalivation is a condition represented by a reduced salivary flow and may include symptoms such as mouth dryness (xerostomia), loss of taste, pain, dysphagia, and dysphonia, all of which greatly affect an individual's quality of life.The aim of the present study was to systematically review the effects of low-level light therapy irradiation (photobiomodulation) on salivary gland function in patients with hyposalivation.The main question of the systematic review was: "Does low-level light irradiation therapy of the salivary glands affect salivary flow rate or indicators of salivary function (ion and protein concentrations) in patients with xerostomia or hyposalivation?" The question was based on the PICO (participant, intervention, control, outcome) principle and followed the PRISMA guidelines. Databases were explored and papers published between the years 1997 and 2020 were reviewed for the following Mesh-term keywords and their corresponding entry terms in different combinations: "Low-level light therapy," "Xerostomia," "Saliva," "Salivary glands," "Salivation."The initial sample consisted of 220 articles. Of those, 47 articles were used for full-text analysis and 18 were used for a systematic review, 14 were used in meta-analysis. According to their individual quality, most articles were classified as high quality of evidence according to the GRADE score. Meta-analysis of the evidence observed increase of unstimulated salivary flow 0.51 SMD compared to placebo (95% CI: 0.16-0.86), I2 = 50%, p = 0.005.The findings of our review revealed evidence of a beneficial effect of photobiomodulation therapy on salivary gland function. The therapy alleviates xerostomia and hyposalivation. However, these effects are reported short term only and did not induce lasting effects of photobiomodulation therapy on patients' quality of life.

Laser-Doppler microvascular flow of dental pulp in relation to caries progression.

Pulpal blood supply can be measured noninvasively and objectively via laser-Doppler fluxmetry. The aim of the study was to measure and compare pulpal laser-Doppler (LD) flux values for permanent non-carious teeth and carious teeth with different degrees of caries progression. Conventional sensitivity tests were also conducted for a comparative analysis to clarify the difference between tooth sensitivity and vitality. Carious lesions were detected and assessed in 15 adult subjects using the International Caries Detection and Assessment System (ICDAS) criteria. Pulpal sensitivity of selected carious teeth (without previous prosthetic restoration or endodontic treatment) and suitable caries-free teeth were then tested with a cold stimulus and subsequently with a weak electric current, whereas their pulpal LD flux was recorded at a separate visit using individually designed silicone probe holders. The LD flux values for teeth with an ICDAS score 6 were significantly lower compared to the values for teeth with an ICDAS score 1 (p < 0.05). Pulpal LD flux values of teeth with active caries were significantly lower than those of teeth with solely inactive carious lesions (p < 0.05). The degree of agreement between sensitivity and vitality testing was fair within both of the pairs: cold test/LDF (κk = 0.232, p = 0.00) and electric test/LDF (κk = 0.354, p = 0.00). Pulpal LD flux measurement proved to be reliable in the pulp vitality assessment of carious and non-carious teeth and might improve the reliability of clinical decisions when used in addition to standard clinical diagnostic protocols.

T2 Mapping as a Tool for Assessment of Dental Pulp Response to Caries Progression: An in vivo MRI Study.

Among radiological methods, magnetic resonance imaging (MRI) excels in its ability to image soft tissue at great contrast and without the need of harmful radiation. This study tested whether in vivo MRI based on standard MRI sequences run on a standard clinical MRI system can be used to quantify dental pulp response to caries progression using the T2 mapping method. In the study, 74 teeth were scanned on a 3-T MRI system, and caries was assessed according to the International Caries Detection and Assessment System (ICDAS). The T2 maps were processed to obtain T2 profiles along selected root canals (from crown to apex), and the profiles were sorted according to both tooth type (single-rooted vs. molar) and ICDAS score. In all the examined dental pulps, it was found that T2 values decrease with an increase in the ICDAS score. In the coronal part of dental pulps, average T2 values of 166, 153, and 115 ms were found in ICDAS groups 0, 1-3, and 4-6, respectively. In single-rooted teeth, T2 values were found approximately constant as a function of dental pulp depth, while in multi-rooted teeth, they were found increasing in the coronal part and decreasing towards the root apex. The study confirmed that T2 mapping of dental pulp can be used to reliably quantify its response to caries progression and that it has a potential to become a complementary diagnostic tool to standard radiographic methods in the assessment of dental pulp response to caries.

The impact of photobiomodulation of major salivary glands on caries risk.

Dental caries is a complex multifactorial chronic infectious disease guided by several risk or protective factors. Saliva has an important role in caries and the remineralization process. Caries risk assessment is defined as the probability of new caries lesion development or the existing lesion progression in a given time period. Caries diagnostics and risk factor assessment are followed by targeted elimination of risk factors and less conservative but abundant preventive therapeutic measures. The aim of our prospective randomized study was to elucidate on how photobiomodulation of major salivary glands with polychromatic light or LED light affects caries risk factors in high caries-risk patients. Thirty-six patients were assigned to one of the following three experimental groups: the first, irradiated with polarized polychromatic light (40 mW/cm2, wavelengths 480-3400 nm); the second, a continuous LED light (16 mW/cm2, wavelengths 625, 660, 850 nm); the third, same LED light in a pulsed mode. The fourth group was the control, for which a non-therapeutic visible light was used. Light was administered extra-orally bilaterally above the parotid and submandibular glands for 10 min and intra-orally above the sublingual glands for 5 min, 3 times a week, for 4 consecutive weeks. Each patient's caries risk was assessed according to Cariogram before and after therapy. Caries risk factors were determined from samples of saliva before therapy, two weeks after it commenced, at the end of therapy, and four weeks after the end of therapy. At the end of treatment, the following findings were obtained: In the group irradiated with polarized polychromatic light and in the group irradiated with continuous LED light, the Streptococcus mutans and Lactobacillus counts decreased and salivary buffering capacity increased (p < 0.05). In the group irradiated with pulsed LED light, Streptococcus mutans counts decreased and unstimulated salivary flow and salivary buffering capacity increased (p < 0.05). In all three experimental groups, caries risk was lower (p < 0.05). In the placebo control group, there were no statistically significant differences between parameters before and after therapy. We concluded that photobiomodulation of major salivary glands in high caries-risk patients can reduce the cariogenic bacteria in saliva and improve some salivary parameters, thus reducing caries risk.

Discrimination between intact and decayed pulp regions in carious teeth by ADC mapping.

The aim of this study was to evaluate an advanced magnetic resonance imaging (MRI) method, apparent diffusion coefficient (ADC) mapping, in the functional assessment of carious teeth. 38 extracted human teeth with scores of 0, 3 and 6 according to International Caries Detection and Assessment System (ICDAS) criteria were screened and subsequently analyzed by MRI at 2.35 T. Histology sectioning of teeth was used for the gold standard by analyzing two extreme cases (intact and severely decayed). ADC maps of the same teeth were calculated from corresponding diffusion-weighted images and used to obtain ADC distributions along dental pulp as functions of the relative pulp length measured from the occlusal pulp side. The measured distributions were analyzed for the best fit by a four-parameter three-segment linear regression model for ADC distribution along the pulp. MRI results were in good agreement with findings in histological sections of identical teeth. The best fit model parameters, relative decayed region depth, relative transition region width and ADC values of intact and decayed pulp tissue, showed statistically significant differences between the ADC values of intact and decayed pulp tissue (1.0 × 10(-9) m(2)/s vs. 0.74-0.89 × 10(-9) m(2)/s) and the relative decayed region depth progressing with ICDAS score (3 vs. 46% with ICDAS 3 vs. ICDAS 6). The results of this feasibility study confirmed relevance of ADC mapping for the discrimination and localization of intact and decayed regions in dental pulps of carious teeth.

Assessment of the dentin-pulp complex response to caries by ADC mapping.

The prognostic potential of apparent diffusion coefficient (ADC) mapping was studied as complemented by high-resolution 3D T(1)-weighted MRI in the assessment of dentin-pulp complex response to caries. Twenty-six extracted human teeth, with or without caries lesions of different grades in accord with the International Caries Detection and Assessment System (ICDAS), were analyzed by high-resolution MRI at 2.35 T. A signal rise in demineralized hard dental tissues in high-resolution T(1)-weighted MR images enabled assessment of the demineralization depth over the whole range of ICDAS scores. ADC maps of the teeth were calculated from corresponding diffusion-weighted images of four different b values: 0, 132, 317, 635 s/mm(2). These maps enabled reliable differentiation between intact (ADC > 1.0·10(-9) m(2)/s) and affected (ADC < 1.0·10(-9) m(2)/s) regions of dental pulp. Linear regression analyses of demineralization depth in relation to ICDAS score and then also to average ADC of dental pulp showed that a demineralization depth increase of one millimeter corresponds to an ICDAS score increase of 1.2 and an average ADC decrease of 0.07·10(-9) m(2)/s. Results of the study indicate that the average ADC value of dental pulp could be used as a potential marker to assess tissue response to caries comparable to that of ICDAS scoring.

Early odontoblastic layer response to cavity preparation and acid etching in rats.

The aim of this study was to establish the early odontoblastic layer response and quantitatively to estimate the number of odontoblasts after cavity preparation with and without acid etching. Half of 56 cavities prepared on rats' first upper molars were acid etched. Qualitative and morphometric analyses were made on histological and ultrathin sections 5 min, 6 h, 24 h and 72 h post-operatively. Under the etched cavity, a greater disarrangement of odontoblasts was found, modifications in nuclear shape and condensed chromatin 5 min. post-operatively. An additional reduction of odontoblast number was detected and an increase of aspirated cell number 5 min, 6 h and 24 h post-operatively, pronounced hyperaemia 6, 24 and 72 hours post-operatively and increased odontoblast number 72 hours post-operatively, compared to unetched cavities. In conclusion, injury to the odontoblastic layer was greater, but numerical renewal of the odontoblastic layer began earlier in etched cavities compared to unetched cavities.