Human Teeth Research Articles

Knowledge, attitudes and practices related to tooth morphology among dental students and dental technician students

Objectives: Students are introduced to the morphological features of primary and permanent human dentition in a dental anatomy course, which is a part of the basic core sciences program in the Department of Dentistry and Dental Prosthesis Technology. The purpose of this study was to compare dental students' (DSs’) and dental technician students' (DTSs’) knowledge, attitudes, and practices related to dental morphology. Materials and Methods: Using a 26-item self-administered questionnaire, the DSs and DTSs participated in a descriptive cross-sectional study. Three components made up the questionnaire: four items for demographic profile, ten items for dental morphology knowledge level, seven items for attitude toward tooth morphology, and five items for practice in tooth morphology. There were 274 student answers in all. The data were analyzed using an independent t test and one-way ANOVA. A p value of less than 0.05 was considered to indicate statistical significance for each test. Results: Between DSs and DTSs, there was a statistically significant difference in their knowledge and practices of tooth morphology (p< .001). However, DTSs knowledge of dental morphology was significantly greater, and DSs practice scores were significantly greater. There was no significant difference in the attitude of tooth morphology between the two groups (p=0.379). Both groups had low levels of dental morphology knowledge, with an average of 3.86 correct answers for DTSs and an average of 3.16 correct answers for DSs. In the DSs group, first-year students had a greater knowledge level (4.22±1.63 correct answers) than did the other students. Conclusions: Knowing the variations in dental morphology knowledge, attitudes, and practices between a dentist and dental technician may help us take preventative measures. While preclinical dentistry students and dental technician students had different levels of expertise, both groups were less knowledgeable about tooth morphology. Both groups had similarly high attitudes toward tooth morphology.

Recycling of human teeth for piezoelectric energy harvesting

In the human body, non-centrosymmetric biological structures exhibit piezoelectric effect across from microscopic biomolecular building blocks to macroscopic tissues and organs. However, the fabrication of piezoelectric devices from discarded natural tissues and organs has rarely been exploited for energy harvesting applications. Herein, the extracted human teeth were recycled as an active layer in a piezoelectric nanogenerator for power generation. Due to the piezoelectric effect of enamel and dentin, a human teeth-based sandwiched piezoelectric nanogenerator was fabricated, producing high and stable power outputs with an open-circuit voltage of approximately 0.9 V under an external force at 60 N. Furthermore, the high mechanical durability of the piezoelectric nanogenerator was also verified after 1600 pressing-and-releasing cycles without noticeable output degradation. Notably, for the first time, a light-emitting diode (LED) was illuminated by the human teeth-based piezoelectric device. This work exemplifies a sustainable strategy to recycle the extracted human teeth by fabricating a piezoelectric nanogenerator for energy harvesting, providing inspiration for converting waste into wealth toward green energy in bionanotechnology.

Dental anomalies in congenital error of immunity

Developmental disorders of the teeth and maxillofacial region are part of a symptoms complex that often occur with inborn errors of the immune system. The purpose of the study is to identify the frequency of various dentofacial anomalies occurrence in patients with diagnosed immunodeficiencies. The study involved 64 patients of the Sverdlovsk Regional Clinical Hospital No. 1 and the Regional Children’s Clinical Hospital (Ekaterinburg) with various diagnoses: combined immunodeficiencies, antibody defects, autoinflammatory disorders, defects in the number and functions of phagocytes, defects in immune dysregulation, complement defects, and unverified diagnosis with signs of immunodeficiency. All patients underwent examination of the oral cavity, hard dental tissues, periodontal tissue and jaw bone tissue. It was found that an anomaly in jaw size is characteristic of all studied patient groups, except for the group with complement defects. Along with this, such pathology as quantitative and qualitative changes in teeth was identified in four classification groups: “combined immunodeficiencies” (25% of cases from the subgroup), “antibody defects” (31% of cases from the subgroup), “phagocyte defects” (10 % of cases from the subgroup), and “immune dysregulation defects” (50% of cases from the subgroup). The same frequency of occurrence of tissue repair defects: in “combined immunodeficiencies” (16.6% of cases from the subgroup), “autoinflammatory disorders” (26.7% of cases from the subgroup), “phagocyte defects” (10% of cases from the subgroup), in “unverified diagnoses” (20% of cases from the subgroup). The highest percentage of quantitative manifestations of such anomalies as jaw size (26% of cases from the entire study group) and facial dysmorphism (27% of cases from the entire study group). In patients with “combined immunodeficiencies”, all the dental anomalies described in the work were identified. However, the highest percentage of people in this group had delayed teething (33.3%) and facial dysmorphism (33%). The only patient diagnosed with “complement defects” had no dental anomalies. The minimum number of manifestations of the studied anomalies was observed in groups with “antibody defects” and “immune dysregulation defects”. The accumulated experience in describing various dental diagnoses will contribute to the creation of dental criteria for the diagnosis of primary immunodeficiencies.

The effect of laser therapy for the treatment of dentin hypersensitivity on surface roughness and bacterial adhesion

The aim of the study was to measure the degree of dentine surface roughness caused by five distinct lasers used to treat dentine hypersensitivity, as well as to evaluate the subsequent bacterial colonization on these irradiated surfaces. Sixty human maxillary premolar teeth without caries or restoration which were extracted for periodontal reasons were used in this study. Five different types of lasers were applied to the root dentin surface. Tested samples were divided into six groups of 10 samples each; control, diode (810 nm), diode (980 nm), Nd: YAG, Er: YAG, and Er, Cr: YSGG laser groups. The arithmetic mean of the surface roughness values (Ra) and the average roughness over a measurement area (Sa) were measured pre- and post-application using any of the laser types. Swab samples were then collected from the dentin surface. Following a 24-hour incubation period at 37 °C, the colony forming units were counted using a stereoscope. The results demonstrated a statistically significant difference in the surface roughness values pre- and post-application (Ra and Sa, respectively) in the Er, Cr: YSGG laser group (p = 0.037,p = 0.007). No significant difference was observed in the other groups (p > 0.05). There was no statistically significant difference in the number of bacterial colonies observed between the test and control groups. Diode and Nd: YAG lasers showed either a decrease or no change in surface roughness; however, the hard tissue lasers (Er: YAG, Er, Cr: YSGG) showed an increase. The Er: YAG and Nd: YAG laser groups exhibited decreased bacterial adhesion compared to the other groups.

Validation of clinically related aging models based on enamel wear.

Physiological and erosive wear reported in clinical studies were reviewed, and in vitro aging models were developed to simulate and compare the effect of aging on human teeth with the review data obtained from clinical studies. A review of clinical studies and randomized clinical trials that quantify enamel wear was performed in the PubMed database. The first in vitro analysis evaluated the effect of mechanical chewing simulation only. Enamel specimens were aged in the chewing simulator (up to 1.2 million cycles) with two occlusal loads (30 and 50 N). In the second in vitro analysis, specimens were aged in two aging models. The first model (MT) simulated mechanical and thermal oral challenges: MT1- 240,000 chewing and 10,000 thermal cycles, MT2- 480,000 chewing and 20,000 thermal cycles, MT3- 1.2 million chewing and 50,000 thermal cycles. The second model (MTA) simulated mechanical, thermal, and acidic oral challenges as follows: MTA1- 240,000 chewing, 10,000 thermal and 3-h acidic cycles; MTA2: 480,000 chewing, 20,000 thermal and 6-h acidic cycles, MTA3- 1.2 million chewing, 50,000 thermal and 15-h acidic cycles. The review included 13 clinical studies evaluating tooth wear (eight physiological and five erosive). The results estimated the annual average physiological wear as 38.4µm (9.37-51). In comparison, the MT1 showed wear of 60 (24) µm. Also, the average annual erosive wear in the literature was 179.5µm (70-265) compared to MTA1-induced wear of 209 (14) µm. There was wide variation in tooth wear reported in clinical studies, suggesting a critical need for more accurate studies, possibly based on scanning technologies. Despite this, the data reported using the novel aging models are within a range to be considered consistent with and to simulate tooth wear measured in vivo.

Bond strength and surface roughness assessment of novel antimicrobial polymeric coated dental cement

Resin cement integrated with zein-incorporated magnesium oxide nanoparticles has previously been found to inhibit oral microbes and decrease bacterial biofilm. However, the bond strength and surface features of this biomaterial have yet to be investigated. The objective of this study was to evaluate the shear bond strength, mode of fracture, and surface roughness of resin cement modified with zein-incorporated magnesium oxide nanoparticles. Characterization of the cement was performed by X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. 126 human teeth were divided into 3 groups and cemented to lithium disilicate ceramic using resin cement with zein-incorporated magnesium oxide nanoparticles at concentrations of 0%, 1%, and 2% (n = 42). 21 samples of each group were subjected to the shear bond strength test, while the other 21 underwent thermocycling for 10,000 cycles before the test, after which all samples were evaluated for the mode of fracture. To assess surface roughness, resin cement disks were analyzed by a profilometer before and after undergoing thermocycling for 10,000 cycles. The shear bond strength of the cement with 1% and 2% nanoparticles was significantly higher than the control before thermocycling. The mode of fracture was found to be mainly adhesive with all groups, with the unmodified cement presenting the highest cohesive failure. There was no significant difference in surface roughness between the groups before or after thermocycling. The addition of zein-incorporated magnesium oxide nanoparticles to resin cement improved or maintained the shear bond strength and surface roughness of the resin cement.Graphical abstract

Surface porosity of enamel white spot lesions and penetration of fluorapatite nanocrystals into their subsurface: proof-of-concept study

ObjectivesIn this study, we used atomic force microscopy (AFM) to quantify the size of surface pore apertures of enamel white spot lesions and then demonstrated the penetration of fluorapatite nanocrystals (nFA) into the subsurface of these lesions. MethodsFor the porosity study, enamel lesions were created on three sound human teeth using a demineralizing gel for 8 days. The interface between sound enamel and the artificial lesion was analyzed by AFM. To visualize the penetration of nFA tagged with a calcium-binding fluorophore (Fluo-4) into the subsurface of white spot lesions, we used two-photon microscopy. Sixteen extracted human teeth with either active, natural, or in vitro-created carious lesions in enamel were randomly divided into three groups. The teeth were treated for 2 min with either a suspension of tagged nFA crystals, Fluo-4 alone, or deionized water, and left for 30 min before being washed with distilled water and examined microscopically. ResultsA greater concentration of surface pores with larger areas was observed on the in vitro demineralized enamel (29 % of pores greater than 1.0 µm2) when compared with the adjacent sound enamel (8 % of pores greater than 1.0 µm2) (p=0.012, Fisher exact test). In vitro and natural lesions treated with tagged nFA showed fluorescence at depths ranging from 50 to 170 µm, demonstrating penetration of the nFA into the lesion subsurface. The lesions treated with Fluo-4 alone with no crystals showed mostly surface fluorescence (restricted to the outer 25 µm), while those treated with deionized water showed minimal (restricted to the outer 20 µm) to no fluorescence. ConclusionWe have demonstrated the use of AFM to quantify the surface pore apertures and two-photon microscopy to visualize nFA crystals in the subsurface of non-cavitated enamel lesions. Clinical SignificanceThe restoration of the subsurface of non-cavitated caries lesions is a clinical challenge. This study demonstrated that a 2 min application of nFA could penetrate through the surface apertures of non-cavitated enamel lesions into their subsurface.

Assessment of the Effectiveness of Desensitizing Dentifrices on Management of Dental Hypersensitivity: An In Vitro Study.

The current study aimed to assess the efficiency of two desensitizing dentifrices on the management of dental hypersensitivity. For the purpose of this investigation, 60 extracted human sound premolar teeth that were removed for orthodontic purposes were collected. On the buccal cervical areas, an inverted-cone bur was used to create cavities that were 2 mm deep and 3 mm wide. The blocks were submerged in 17% ethylenediaminetetraacetic acid (EDTA) for 40 minutes in order to ensure the complete dentin tubule opening. Following preparation, all samples were split into three groups, each containing 20 samples, Group A: Control, Group B: Dentifrice containing calcium sodium phosphosilicate, Group C: Dentifrice containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). Scanning electron microscopy (SEM) was used to assess the occlusion of dentinal tubules. One-way analysis of variance (ANOVA) was used to assess the desensitization efficacy of dentifrices. At a p-value less than 0.05, statistical significance was determined. Before application of different dentifrices, the maximum dentinal tubules opened in dentifrice containing CPP-ACP group (4.24 ± 0.10) followed by control group (4.18 ± 0.01) and dentifrice containing calcium sodium phosphosilicate (4.12 ± 0.06). And there was no significant difference between the different dentifrice groups (p > 0.001). After application of different dentifrices, the highest occlusion of dentinal tubules found in dentifrice containing CPP-ACP group (2.50 ± 0.05) followed by dentifrice containing calcium sodium phosphosilicate (2.84 ± 0.10) and control group (4.02 ± 0.07) and there was a highly significant difference between the different dentifrice groups (p < 0.001). On conclusion, dentifrice containing CPP-ACP exhibited the highest level of dentinal tubule occlusion in comparison to the control group and dentifrice containing calcium sodium phosphosilicate. Dentinal hypersensitivity (DH) is a condition that is frequently experienced. With variable outcomes, a number of products are utilized in the management of DH. Need is felt in dentistry for a material that chemically reacts, physically occludes and adheres intimately to dentinal tubules to reduce the possibility of its recurrence. How to cite this article: Pulipaka S, Ramanna PK, Samson A, et al. Assessment of the Effectiveness of Desensitizing Dentifrices on Management of Dental Hypersensitivity: An In Vitro Study. J Contemp Dent Pract 2024;25(5):494-497.

Microleakage Assessment of Single Cone Gutta Percha Obturation Technique Using Different Types of Sealers

This study was carried out to compare the coronal and apical seal of canals obturated with single cone technique using different types of epoxy resin root canal sealers. A total of sixty extracted human upper molars with fully formed and sound palatal roots were used in this study. The crown of each tooth was decoronated at cement-enamel junction and the palatal root canal was prepared using ProTaper gold rotary instruments. Sixty specimens were used and divided into 3 equal groups(n=20) for single cone obturation using two different types of epoxy resin sealers AH26 and vioseal sealers respectively and one control group without sealer. All the specimens were exposed varnish application followed by dye penetration test using 2% methylene blue dye then root sectioning. Samples were evaluated under a stereomicroscope to detect the linear measurement of the dye penetration from the apical constriction. The image transferred to a computer equipped with the image analysis software program where the dye penetration along the filling dentine interface was evaluated. The collected data was statistically analysis by using Graph Pad Instat software for windows. One-way ANOVA was done for compared results followed by Tukey’s pair-wise. The results showed that, the difference in dye penetration microleakage means between groups was statistically significant as revealed by one-way ANOVA test (p &lt; 0.05). Pair-wise Tukey’s post-hoc test showed non-significant (p&gt;0.05) difference between (AH26 and Vioseal sealers) groups. None of the tested root canal sealers could eliminate the dye infiltration or microleakage formation. Single cone gutta-percha combined with AH26 sealer exhibited less microleakage than vioseal sealer although there were no statically significant differences between them.

Novel co-initiators of polymerization: Cytotoxicity profile and modulation of inflammatory mediators in human dental pulp stem cells

ObjectivesThe aim of this study was to assess the cytotoxicity of novel polymerization co-initiators and their effect on cytokine release from human dental pulp stem cells (hDPSCs), comparing them with commonly used co-initiators. MethodsCells were isolated from the dental pulp of healthy human third molars. The new co-initiators, namely HDa1, HD4, HD1, and MHPTm, were evaluated and compared with the compounds dimethylaminoethyl amine benzoate (EDAB) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). These compounds were diluted in dimethylsulfoxide (DMSO) at concentrations ranging from 1 to 8 mM. hDPSCs were seeded onto 96-well plates and incubated for 48 h. Subsequently, the cells were exposed to different concentrations of the co-initiators mentioned for 24 h. After this period, the culture medium was removed, and mitochondrial metabolism was evaluated using the MTT assay, while cytokine release (IL-1β, IL-6, IL-8, IL-10, TNF-α) was analyzed by the MAGPIX assay. Cells without exposure to the tested compounds served as controls. The data were analyzed using one-way ANOVA and Tukey’s test. ResultsThe compounds showed low toxicity, with 8 mM concentration causing the most significant reduction in mitochondrial metabolism. MHPTm was the most toxic co-initiator tested (compound bearing an amine functionality). All compounds up-regulated TNF-α, IL-10, IL-6, and IL-8, with HD4 exhibiting the most pronounced increase in IL-6 and IL-8. SignificanceThe newly proposed co-initiators demonstrated reduced impact on mitochondrial metabolism, comparable to some traditional co-initiators. Despite their lower toxicity, HD4 increased IL-6 and IL-8 release, suggesting its potential involvement in triggering an inflammatory reaction, particularly in the short term.

Developing an optimised method for accurate wear testing of dental materials using the ‘Rub&Roll’ device

Dental materials are challenged by wear processes in the oral environment and should be evaluated in laboratory tests prior to clinical use. Many laboratory wear-testing devices are high-cost investments and not available for cross-centre comparisons. The ‘Rub&Roll’ wear machine enables controlled application of force, chemical and mechanical loading, but the initial design was not able to test against rigid antagonist materials. The current study aimed to probe the sensitivity of a new ‘Rub&Roll’ set-up by evaluating the effect of force and test solution parameters (deionized water; water + abrasive medium; acid + abrasive medium) on the wear behaviour of direct and indirect dental resin-based composites (RBCs) compared with human molars against 3D-printed rod antagonists. Molars exhibited greater height loss than RBCs in all test groups, with the largest differences recorded with acidic solutions. Direct RBCs showed significantly greater wear than indirect RBCs in the groups containing abrasive media. The acidic + abrasive medium did not result in increased wear of RBC materials. The developed method using the ‘Rub&Roll’ wear machine in the current investigation has provided a sensitive wear test method to allow initial screening of resin-based composite materials compared with extracted human molars under the influence of different mechanical and erosive challenges.

Influence of viscosity and fiber reinforcement of resin composite on fracture strength and failure mode of restored molars.

To evaluate the fracture behavior of human molars with extensive MOD restorations using short-fiber-reinforced resin composite of varying viscosities. Human molars were randomly divided into seven groups (n = 12): intact teeth (control); restoration using conventional high-viscosity resin composite without (Filtek Z350XT, 3M) or with fibers (everX Posterior, GC); conventional low-viscosity resin composite without (Filtek Supreme Flowable, 3M) or with fibers (everX Flow Dentin Shade, GC); bulk-fill low-viscosity resin composite (Filtek Bulk Fill Flow, 3M) or with fibers (everX Flow Bulk Shade, GC). Restorations were performed on extensive MOD preparations, following the manufacturers' recommendations for each material. Specimens underwent fracture strength testing (N) and fracture pattern (%) categorized as repairable, possibly repairable, or non-repairable. Results were analyzed using a generalized linear model (N) and Fisher's exact test (%), with α = 0.05. Restorations performed with high-viscosity materials showed fracture strength values similar to the control and higher than those of restorations using low-viscosity resin composites (p < 0.0001), except for the bulk-fill low-viscosity resin composite with fibers (p > 0.05). Teeth restored using low-viscosity resin composite with fibers showed a higher % of repairable and possibly repairable fractures than the control (p = 0.0091). The viscosity of materials mediated the fracture strength, with restorations using high-viscosity resin composites promoting values similar to the intact tooth; however, the presence of fibers influenced the fracture pattern. Teeth with MOD cavities restored with high-viscosity resin composites showed similar fracture strength to intact teeth. Fiber-reinforced low-viscosity resin composite for the base of restoration resulted in a more repairable/possibly repairable fracture pattern.

Non-surgical endodontic treatment of a type III dens invaginatus with large perirradicular radiolucency using bioceramic materials: Case report

Dens invaginatus (DI), also known as dens in dente, is an uncommon dental anomaly in humans, characterized by irregular morphological development during odontogenesis, which can manifest in various coronal and radicular anatomies. Endodontic treatment of teeth with this variation demands anatomical knowledge, detailed planning, and the use of specialized techniques and materials. The objective of this research is to detail, through a case report, the non-surgical endodontic treatment of type III dens invaginatus in the upper lateral incisor with extensive periapical lesion, using bioceramic materials. An 18-year-old female patient was referred to the referral center by an orthodontist after radiographic examination revealed an extensive periapical lesion on tooth 12. Consequently, cone beam computed tomography was requested to assess the lesion and internal/external anatomy. The endodontic treatment was performed entirely under operative microscopy, utilizing mechanized instrumentation and thermoplasticized obturation. Disinfection was enhanced through activated irrigation technique and intracanal placement of bioceramic medication, with periapical repair achieved using bioceramic sealer cement. Long-term follow-up demonstrated that conservative endodontic treatment, employing modern techniques alongside bioceramic materials, proved effective in resolving complex cases.

Comparing the efficacy of adrenaline, clonidine, and dexmedetomidine in enhancing local anesthesia for impacted third molar extraction: a randomized controlled trial.

In human dentition, the most commonly impacted teeth are the mandibular third molars (M3M). The removal or extraction of these teeth often causes anxiety in patients due to the perceived pain involved in the process. Therefore, pain must be effectively managed using anesthesia. The use of newer local anesthetic drugs can help minimize side effects and drug interactions. Traditionally, adrenaline is used as a vasoconstrictor along with lignocaine. When combined with lignocaine, the alpha agonists dexmedetomidine and clonidine can extend the duration of anesthesia, thereby reducing the need for additional pain-relieving medications. This study used a randomized, triple-blind, parallel-arm design. Sixty patients were screened, and 45 systemically healthy patients requiring unilateral surgical removal of impacted mandibular third molars with similar difficulty (moderate-to-difficult according to the Modified Pederson's Index) were included in the study. Patients were allocated into three groups as follows: Group A: 2% Lignocaine Hydrochloride with 1:100,000 Adrenaline, Group C: 2% Lignocaine Hydrochloride with 15 µg/mL Clonidine, and Group D: 2% Lignocaine Hydrochloride with 1 µg/mL Dexmedetomidine. The evaluated parameters were the time of onset of anesthesia, depth of anesthesia, hemodynamic parameters, and duration of postoperative analgesia. Group D had a faster onset of action and prolonged duration of postoperative analgesia compared with Groups A and C. No statistically significant differences were observed between the three groups in terms of the depth of anesthesia and hemodynamic parameters. Group D exhibited a significantly more rapid onset of anesthesia than Groups A and C, and the postoperative analgesic effect in Group D was significantly prolonged (7.22 hours) compared with that in Groups A (4.54 hours) and C (2.1 hours). Patients receiving the Group D solution experienced an extended period of comfort without the need for analgesics for up to 7.22 hours post-procedure.

Mahidol Study 2: Treatment Outcomes and Prognostic Factors of Regenerative Endodontic Procedures in Immature Permanent Teeth

IntroductionStudies on the clinical outcomes and prognostic factors of regenerative endodontic procedures (REPs) in a large population and long-term recall period have been limited. Therefore, the aims of this study were to evaluate treatment outcomes and prognostic factors of REPs. MethodsImmature permanent teeth treated with REPs with a minimum one-year follow-up period were included. Treatment outcomes (functional retention, healed rate, root development, and sensibility test response) and any prognostic factors were analyzed with multivariable Cox regression, linear regression, and modified Poisson regression. ResultsOne-hundred-twenty REPs teeth with a mean 41.7-month recall period were included with a functional retention rate of 97.5%. The healed, healing, and diseased rates of REPs were 80%, 9.2%, and 10.8%, respectively. Significant prognostic factors for healed were age (<12 years old) and root development stage (stages 4 and 5). Changes in the apical diameter, root length, root width, and radiographic root area after REPs were 56.8%, 8.3%, 23.2%, and 21.7%, respectively. Significant prognostic factors for continued root development were age and etiology of pulpal disease (from caries or dental anomalies). The sensibility test response rate was 41.7% with significant positive factors of ethylenediaminetetraacetic acid irrigation and capping material level above the cemento-enamel junction. ConclusionREPs demonstrated high functional retention and healed rates. Patients <12 years old presented a higher healed rate and continued root development (excluding root length). Dental caries or anomalies had higher continued root development compared with dental trauma. The sensibility test response was related to ethylenediaminetetraacetic acid irrigation and level capping material.

Evaluation of effect of various drinks on tooth surface morphology under scanning electron microscope.

The study aimed to evaluate and compare the effect of various beverages carbonated drinks, i.e., thumps up, fresh fruit juice (apple and pomegranate) and packaged fruit juice (apple and pomegranate) on tooth surface morphology under scanning electron microscope. Thirty recently extracted intact caries-free human permanent teeth were disinfected with 5.25% of sodium hypochlorite solution and autoclaved at 240°F, 20 psi pressure for 40 min. Each tooth was sectioned into 4 enamel sections yielding 120 sections which were embedded in resin using a prefabricated mold. Prepared samples were immersed as Group I - thumps up, Group II - fresh apple juice, Group III - packaged apple juice, Group IV - fresh pomegranate juice, Group V - packaged pomegranate juice, and Group VI - normal saline. Each immersion was done daily for 30 min over 14 days after which samples were scanned under scanning electron microscope (SEM). The data obtained were subjected to statistical analysis using Statistical Package for the Social Sciences (SPSS Version 23; Chicago Inc., IL, USA). The highest surface roughness was noted in the fresh pomegranate and packaged pomegranate groups with a mean of 2.9000 ± 0.30779 followed by thumbs up group. The greatest mean of cracks was noted in thumbs up group with a mean of 2.500 ± 0.51299 which was significant at P = 0.000. The greatest mean of score was noted in thumbs up group with a mean of 2.3000 ± 0.65695 which was significant at P = 0.000. The present study demonstrated that all drinks were erosive in nature with thumps and pomegranate juice showing significantly higher erosiveness than apple juice (P < 0.01).

Expression patterns of interleukin-6 and microRNA-146A during orthodontic relapse in a rat model.

In this study, we established an experimental rat model to simulate orthodontic tooth movement relapse and a human periodontal ligament stem cell (PDLScs) model. Our aim was to explore the relationship between microRNA-146a (miR-146a) expression in periodontal tissue, the inflammatory factor interleukin-6 (IL-6), and orthodontic relapse subsequent to mechanical intervention. In the animal experiment, a total of 30 healthy male Wistar rats were randomly allocated to either the control group (n=6) or the model group (n=24). In the model group, the orthodontic appliance was removed 14 days after force application. Gingival crevicular fluid (GcF) and periodontal tissue samples were collected at intervals of days 0, 7, 14, and 21 following removal of the orthodontic appliance to assess alterations in miR-146a and IL-6 expressions. In the in vitro cell culture study, human premolar tooth tissue was isolated 24 hours following the addition of the transfection reagent to harvest PDLScs. Reverse transcription quantitative polymerase chain reaction was employed to evaluate the expression levels of the miRNA-146a gene, while Western blot analysis was utilized to assess the production of the IL-6 protein. As a result in comparison to the control group, the protein expression of IL-6 notably escalated to its peak value in the model-day 7 group (p<0.05). Subsequently, although experiencing a slight decline, the IL-6 expression in the model-day 14 group remained significantly elevated compared to control group (p<0.05). In the model-day 21 group, the protein expression of IL-6 approached that of the control group, with no significant difference observed (p>0.05). conversely, in relation to the control group, the gene expression of miR-146a drastically decreased to its lowest point in the model-day 7 group (p<0.05). While exhibiting a slight increase, the miR-146a expression in the model-day 14 group remained significantly diminished compared to control group (p<0.05). Following the identification of human periodontal ligament cells (hPDLcs) through immunofluorescence in the in vitro study, a subsequent experiment was conducted to specifically inhibit miR-146a expression. In comparison to the control group, the protein expression of IL-6 demonstrated a significant increase in the anti-miRNA oligodeoxyribonucleotide (AMO) group, where miR-146a expression was effectively suppressed (p<0.05). Throughout the process of orthodontic tooth movement relapse in rats, there was a notable reduction in the gene expression of miR-146a, accompanied by a significant increase in the expression of IL-6.

Influence of diode laser irradiation on microtensile bond strength of etch-and-rinse adhesive to dentin using two different etchants: An in vitro study

Aim: The aim of this study was to evaluate the influence of 970 nm diode laser (DL) irradiation on the microtensile bond strength (µTBS) of etch-and-rinse adhesive (ERA) to dentin using phosphoric acid (PA) or alpha-hydroxy glycolic acid (GA) as etchants. Materials and Methods: A total of 32 human third molars were selected and assigned randomly among two different groups and four subgroups based on etching protocols and DL irradiation: PA, PA-DL, GA, and GA-DL. After tooth preparation and subsequent incremental composite build-up, the samples were stored in distilled water for 24 h at 37°C. µTBS values were obtained using the universal testing machine. The failure modes observed in dentin were categorized as adhesive, cohesive within dentin/resin, or mixed. Statistical Analysis: The data were analyzed using one-way analysis of variance, followed by Tukey’s post hoc test (P ≤ 0.001). Results: GA showed better or similar bond strength values to PA. Furthermore, irradiation of DL increased the µTBS to dentin when both PA or GA are used as etchants. Conclusion: GA can be used as an alternative etchant to PA. DL irradiation stands as a promising approach for elevating the performance of ERA adhesive systems to dentin.

Microhardness and characterization of human dental tissue after application of enzymatic chemical agents: In vitro study.

The use of enzymatic chemical agents are papain-based materials used in the selective removal of decayed dentin tissue, assisting in conservative techniques and reducing the chances of accidental pulp exposure. A research protocol was subjected to and approved by an Ethics Committee. Using a reporting guide for laboratory studies (CRIS). Healthy human teeth comprised the produced dentin discs subjected to polishing and washing in an ultrasonic bath. Next, the discs received material application according to the experimental groups: water-soluble gel for two minutes, 37% phosphoric acid for 15 seconds in dentin and 30 seconds in enamel, Papacárie Duo (PD) for 30 seconds and two minutes, and Brix 3000 (BX) for two minutes and 30 seconds. The measurement of material pH used solutions at concentrations of 0.1 ml and 2.7 ml prepared for each enzymatic agent. Then, a bench pH meter (n=10) and pH indicator strips determined pH values. The discs underwent the Knoop hardness test (n=10). The sample calculation was performed using the GPower software with α = 0.05, effect 0.63 and power of 95%. Descriptive statistical analysis was carried out for pH, one way ANOVA supplemented by Tukey for knoop hardness and Spearman correlation for pH measurement techniques. The enamel hardness findings indicated that, after material application, ECAs do not statistically differ from water-soluble gel (p<0.05). The dentinal hardness analysis presented a statistical difference in phosphoric acid from the other groups (p<0.05). In the pH test, BX values were lower (4.37 ± 0.01) than PD (4.85 ± 0.06). The groups statistically differed (p<0.05). ECAs for removing decayed dentin tissue did not significantly alter the hardness of enamel and dentin, removal of the smear layer is time-dependent and presents acidity. Key words:Dental caries, Hardness, Dental materials, Papain.

An SEM study on the effect of 9.3-µm CO2 laser on dentinal tubules for hypersensitivity treatment.

In-vitro studies were performed on dentin of extracted human molars to investigate the effectiveness of 9.3μm CO2 laser irradiation to occlude dentinal tubules. The observed occlusion of dentinal tubules with the irradiation was compared with application of three reagents: 2% Sodium Fluoride gel, an aqueous solution of hydroxyapatite nanoparticles and an equal mix of the two. We show that 9.3μm CO2 laser irradiation occludes dentinal tubules, and the use of laser irradiation produces better occlusion of the opened tubules compared to the use of topical reagents. Nine extracted and cleaned human molars were cut to obtain dentin disks of thickness of 3-5mm. Each disc was divided into four quarters, and each quarter served as two samples corresponding to irradiated and non-irradiated group counterparts. Five disks were used to study the effect of various laser irradiation energies on the dentinal tubules to find a good pulse fluence for occlusion of the dentinal tubules, and four disks were used for studying the effects of reagents and irradiation at the pulse fluences found in the first part of the study. The samples were irradiated with a beam diameter of 1mm (1/e2) at 15Hz pulse repetition rate, scanned automatically using a set of scanning mirrors. Samples were imaged using Scanning Electron Microscope (SEM) which were processed to determine tubule diameter. Safety of the irradiation treatment was investigated on 6 samples by measuring pulpal temperature rise. The effect of three topical reagents corresponding to 2% Sodium Fluoride gel (F), Hydroxyapatite nanoparticles (HA) and an equal mix of F and HA (HAF) on dentinal tubule occlusion was evaluated and compared with the laser irradiation. In all examined cases, laser irradiation at a fluence of 0.81J/cm2 resulted in a temperature increase less than 3°C which is safe, and no surface cracking was observed. There is a threshold pulse fluence of 0.27J/cm2 above which, laser produced surface melting. At a pulse fluence of 0.81J/cm2 a layer of recast of melted dentin was formed. Under this layer, peritubular dentin melting and occluding of the dentinal tubules was observed. Application of either F or HA or HAF did not produce visible occlusion effect on open tubules after washing and microbrushing with excess distilled water. 9.3μm CO2 laser irradiation on extracted human molar dentin at pulse fluence of 0.81J./cm2 resulted in tubule area reduction by 97% without rising pulpal temperatures to unsafe levels.