Premolars Research Articles

The chromatograph evaluation of white spot lesion treated with magnesium gel and diode laser: an in vitro study

Objective. White spot lesions are one of the most common concerns of orthodontic therapy. The present study was accomplished to evaluate the ability of Magnesium gel at different concentration and diode laser in combination compared with commercially available 1.23% APF in color restoring of WSL on permanent teeth. Methods. 42 extracted sound upper premolar teeth were recruited for this study. WSL was artificially induced, until it appears in wet and dry condition on buccal surface of each tooth. Different approaches have been utilized for treatment WSL. 6 experimental groups were involved: Group A: Control, Group B: 0.5%MgCl2 gel, Group C: 1%MgCl2 gel, Group D: 0.5%MgCl2 gel and Diode laser, Group E: 1%MgCl2 gel and Diode laser and Group F: 1.23%APF. The difference between the displayed color and the original color standard (ΔE) was assessed by colorimeter. The surface topography of teeth samples from each tested group was examined by a SEM. Collected data were investigated using one-way ANOVA followed by Duncan post hoc test at p ≤0.05. Result. A significant difference in (ΔE) was noticed among groups (p = 0.006). Group (B) showed the lowest ΔE value (9.4 ± 1.6), followed by group (D) (10.2 ± 1.1), group (F) (10.4±2.6), group (A) (11.6 ± 1.3), group (C) (12.9 ± 2.3) and group (E) (13.2 ± 1.3). Conclusion. In present study, topical application of 0.5% MgCl2 gel ensure color reinstating compared to other groups.

Evaluation of the Remineralization Potential of an Herbal Non-fluoridated Dentifrice on Carious Lesions: An In Vitro Study

Background: This in vitro study compared the remineralization potential of Dabur red (DR), a non-fluoridated herbal toothpaste, with Colgate Strong Teeth (CST), a fluoride-based toothpaste, on permanent teeth with artificially created white spot lesions. Vickers microhardness (VMH), quantitative light-induced fluorescence system (QLF), and scanning electron microscopy (SEM) were used for data analysis. Methods: Enamel samples were prepared from the buccal surface of forty-five extracted maxillary premolars and subjected to demineralization to achieve adequate fluorescence loss (ΔF). The samples were divided into DR, CST, and control groups (n=15) and underwent 21 days of pH cycling. VMH was measured at baseline and after 21 days. QLF imaging was performed on days 7, 14, and 21. One randomly selected sample from each group underwent SEM examination to compare morphological variations. The statistical analysis was conducted using SPSS 22.0. Intra-group comparisons were made with repeated measures of analysis of variance (ANOVA), and one-way ANOVA with Tukey’s post-hoc test was utilized for inter-group comparisons (P<0.05). Results: Mean VHN increased significantly in all three groups from baseline (DR=40.47, CST=41.91, control=36.42) to the 21st day (DR=119.47, CST=120.36, control=74.36) (P=0.00). Significant differences were found between the control and test groups, but not between DR and CST. No statistically significant difference was observed in ΔF at baseline and 7 days, but there were significant differences among the groups at 14 and 21 days. SEM images revealed dense mineralization for both DR and CST. Conclusion: After 21 days of in vitro remineralization, both DR and Colgate toothpaste demonstrated similar remineralizing potential as evaluated by surface MH and QLF.

Evaluation of Etching Time Effect on Shear Bond Strength of Orthodontic Brackets Bonded with Self-Adhesive Composite: An in-Vitro Study

Introduction: Precise acid etching of the tooth surface is a significant factor in the strength of the bracket bond. The current study aimed to determine the effect of different application times of acid etching on the shear bond strength of metallic orthodontic brackets under controlled laboratory conditions. Methods: Sixty intact premolar teeth were selected for this in-vitro study. The samples were divided into four groups based on the different acid etching times: 20, 25, 30, and 35 seconds. The teeth surfaces were etched with 37% phosphoric acid according to the specified times, and brackets were bonded to the enamel surface using GC Ortho connect composite. Shear bond strength values of the brackets was measured using a Universal Testing Machine. The amount of Adhesive Remnant Index was also observed using a stereomicroscope. Additionally, the surface roughness of the tooth enamel after bracket bonding was examined using SEM. The results related to shear bond strength were analyzed with one-way ANOVA statistical test and using SPSS version 16 software. The non-parametric Kruskal Wallis (Wallis-Kruskal) test was also used to check the frequency of ARI index. Results: The highest shear bond strength was observed at 25 seconds, and the lowest at 30 seconds. However, there was no significant difference in the shear bond strength of brackets was observed among the four groups (p=0.186). The highest ARI score was observed at 35 seconds, and the lowest at 20 seconds. No statistically significant difference was observed in the ARI scores in different groups. SEM images revealed that the enamel surface porosity was highest at 20 seconds. Conclusion: The results indicate that the shear bond strength and ARI at different acid etching times do not significantly differ. Therefore, orthodontic bracket bonding can be performed with less acid etching time.

Tooth Eruption Disorders: Literature Review and Clinical Case Reports

Introduction and purpose: Tooth eruption disorders are complex issues that can affect both primary and permanent teeth. The process of tooth eruption is a natural stage of development, but it can sometimes be disrupted. Common eruption disorders include delayed eruption, tooth impaction, premature eruption, and abnormalities in the location and direction of eruption. In each case, consultation with a specialist is required, along with early diagnosis and subsequent planning of appropriate treatment. State of knowledge: Impacted teeth are a common occurrence in dentistry and they occur in 0.8–3.6% of the general population The most frequently impacted teeth, in decreasing order of prevalence, are third molars, maxillary canines, mandibular premolars, and maxillary central incisors. Factors contributing to tooth impaction can be general, local, or genetic. Impacted teeth and difficulties with eruption may be associated with complications such as follicular cysts and a variant of these cysts known as eruption cysts. Summary: Tooth eruption disorders require an individualized diagnostic and therapeutic approach. Depending on the issue, treatment may involve observation, orthodontic interventions, and in some cases, surgical procedures. Early diagnosis and appropriate treatment are crucial to prevent complications such as malocclusion, damage to adjacent teeth, or unsatisfactory aesthetics. Radiographs can help confirm the presence of impacted teeth or in some cases, CBCT may be used for more detailed imaging.

Fractal Dimension and Lacunarity Analysis in the Dentulous and Edentulous Mandibular Posterior Region Using Cone-beam Computed Tomography: A Cross-sectional Retrospective Study.

This cross-sectional retrospective study was conducted to assess the differences in the microarchitecture of the trabecular bone of the posterior mandibular region at dentulous and edentulous sites with the help of fractal dimension (FD) and lacunarity using cone-beam computed tomography (CBCT). Ninety CBCT scans were analyzed for the purpose of the present study. Inclusion criteria included subjects with unilaterally missing mandibular molars or premolars and an with intact contralateral opposing tooth. The coronal view of the dentulous and edentulous sites was used, and the region of interest (ROI) was selected 2.6 mm below the apex of the tooth present. These images were then transferred to ImageJ Software, and fractal analysis was done using the box-counting method of the FracLac plug-in. A paired samples t-test was performed to compare the means of FD and lacunarity, and a Kendall correlation was performed to check correlations. A p-value less than 0.05 was considered to indicate statistical significance. Statistical analysis revealed that the mean FD of the edentulous side was significantly greater than that of the dentulous side (p-value = 0.011). Additionally, the mean lacunarity of the edentulous side was marginally significantly greater than that of the dentulous side (p-value = 0.089). A significant negative correlation was detected between the FD and lacunarity of the edentulous region (p-value = 0.017), and a marginally significant negative correlation was detected between edentulous lacunarity and dentulous lacunarity (p-value = 0.081). The differences in occlusal forces exerted in dentulous and edentulous regions can lead to a change in the trabecular pattern of the bone in these regions. This change in the microarchitecture of bones can be detected by FD and lacunarity, which can further help us assess changes pre- and post-implant. The advanced technology, the assessment of microarchitecture of the bone has been made easy, using FD and lacunarity, as done in the present study. This analysis can further aid us in both pre- and post-implant analysis to prevent failure of the implant. How to cite this article: Bhoraskar M, Denny C, Srikant N, et al. Fractal Dimension and Lacunarity Analysis in the Dentulous and Edentulous Mandibular Posterior Region Using Cone-beam Computed Tomography: A Cross-sectional Retrospective Study. J Contemp Dent Pract 2024;25(6):581-587.

Comparative Evaluation of Micro-tensile Bond Strength in Non-carious Lesions After Different Pre-surface Treatments.

Non-carious cervical lesions (NCCLs) present themselves as smooth saucer lesions with variable height and depth. Treatment of choice for these lesions should be aimed at conservative management by restoring the teeth. The present study aims to evaluate the micro-tensile bond strength in NCCLsafter various surface pre-treatments. Sixty-six human permanent maxillary first premolars were subjected to artificial wedge-shaped lesions on the buccal aspect of the cervical regions of all the teeth. Samples were divided into two groups (n = 33 per group). Group 1 received a 37% orthophosphoric acid treatment for 30 seconds and a 17% ethylene diamine tetraacetic acid (EDTA) application for 10 seconds. Group 2 received a 10% citric acid treatment for 30 seconds, followed by a 17% EDTA application for 10 seconds. These groups were further subdivided according to the bonding agent applied as subgroup A: 3M™ Single Bond™; Subgroup B:Prime & Bond Universal group; and Subgroup C:Tetric N-Bond Universal. Samples were subjected to incremental restoration and then segmented to fit into Geraldelli jig with cyanoacrylate adhesive. A universal testing machine was used to assess the micro-tensile bond strength and the data obtained were subjected to statistical analysis. In this study, statistically significant differences in micro-tensile strength were observed between the pre-treatment groups and the effect of the bonding agent. Consequently, the null hypothesis was rejected, and the research hypothesis was accepted. The micro-tensile strength for both groups was compared with various pre-conditioning methods. It was noted that the micro-tensile strength was maximum when Tetric N Bond was used along with 37% orthophosphoric acid followed by Prime Bond with highly statistically significant values (p = 0.000). Contrary to this, in the 10% citric acid group, the micro-tensile strength was equally comparable in the 3M ESPE and Tetric N bond groups compared to the Prime Bond group, with highly statistically significant differences (p = 0.000). Surface pre-treatment in NCCLs improves the bonding strength of the restoration used. Analysis using scanning electron microscopy and long-term assessment of the failure of restoration should be carried out in future studies.

Metal artifact reduction tool and mA levels impact on the diagnosis of fracture extension in endodontically treated teeth using cone-beam CT.

To evaluate the influence of different levels of metal artifact reduction (MAR) tool and milliamperage (mA) on the diagnosis of fracture extension in endodontically treated teeth using cone beam CT (CBCT). Ten maxillary premolars were endodontically treated and positioned in the empty sockets of a human maxilla covered with wax. CBCT acquisitions were performed using the Eagle Edge device (Dabi Atlante, Brazil) adjusted to 120 kVp, FOV of 4 × 6cm, exposure time of 24s and voxel size of 0.2mm in 8 different conditions with different MAR (1, 2 and 3) and mA (3.2 and 6.3) levels. Crown-root fractures were simulated in the universal testing machine, and CBCT images were acquired again. Five radiologists evaluated the presence and extension of fractures with a 5-point scale. Statistical analysis was performed by analysis of variance, Tukey and Kappa test (α = 0.05). Although different mA levels did not significantly (p > 0.05) affect the diagnosis values for fracture presence and extension, when evaluated the different levels of MAR, AUC and sensitivity showed significantly higher values (p < 0.05) for MAR 0 using 6.3mA and kappa agreement showed significantly higher values (p < 0.05) for MAR 0 and 2 using 6.3mA. Although mA levels do not have a diagnostic effect when isolating the MAR level; in 6.3mA, MAR 0 and 2 can positively influence the diagnosis of fracture extension in endodontically treated teeth using CBCT. The isolate evaluation of dental fracture presence can overlook diagnostics error of its extension.

Effectiveness of supplementary antimicrobial procedures in disinfecting lateral canals as evaluated by a novel ex vivo analytical approach

This ex vivo study devised an analytical ex vivo method for infection/disinfection of simulated lateral canals located in the middle and apical segments of the root. The antibacterial effects of supplementary approaches were tested in this model. Extracted mandibular premolars had their main root canals enlarged and then two lateral canals (100 μm in diameter) were created in the root, one in the apical and the other in the middle portion. Micro-computed tomography was used for specimen selection and to confirm the quality of the simulated ramifications. The specimens were contaminated with a mixed bacterial culture from subgingival bacterial biofilm added to pure Enterococcus faecalis strain ATCC 29212 grown overnight, using special strategies to facilitate culture medium penetration within the lateral canals. The following procedures were tested for disinfection: NaOCl/passive ultrasonic irrigation (PUI), NaOCl/XP-endo Finisher, ozonated water/continuous ultrasonic irrigation (CUI), and NaOCl/conventional irrigation with 30-G needles (control). Bacteriological samples were taken from the main canal before (S1) and after (S2) each supplementary protocol, and also from each lateral canal after treatment (S3). DNA extracted from the samples was subjected to quantitative real-time polymerase chain reaction. All S1 main canal samples were positive for bacterial presence. Bacterial counts in the main root canal substantially decreased by 99.2% after PUI, 99.1% after ozone/CUI, 99% after XP-endo Finisher, and 96% in the control group (P < 0.01 for all groups). There were no significant differences between groups (P > 0.05). The same was observed when comparing the effects of the supplementary approaches in the apical and middle lateral canals (P > 0.05). Only a few lateral canals showed no detectable bacteria. The method proposed here proved effective for ex vivo infection/disinfection studies. All supplementary approaches induced a substantial bacterial reduction in the main canal, with no significant differences between them. However, in terms of lateral canal disinfection, none of the tested approaches showed significant effects when compared to the control group.

Assessment of the onset of analgesia and length of analgesia following the use of PBM with different wavelengths: a clinical study

This clinical study assessed photobiomodulation (PBM) induced analgesic effects of diode lasers and an LED light source on the dental pulp. Baseline responses to electric pulp testing (EPT) were recorded in 93 healthy unrestored premolar teeth in 26 adults (age range 22–63 years) attending a private dental practice. The teeth were irradiated on buccal and lingual aspects of the crown, by placing the tips on the middle third of the crown of the teeth, on separate days for each of 4 different light sources (660, 808, or 904 nm diode lasers, or a novel multi-wavelength LED light source (700–1100 nm)) using comparable parameters (100 mW, 30 s, 6 J). EPT scores were measured after a further 1-, 2-, 5- and 20-min. Discomfort caused by PBM therapy was recorded using the Wong-Baker scale. EPT changes were tracked over time using repeated measures analysis of variance. Baseline EPT scores were very consistent between different days (linear regression r2 0.9422–0.9648). All PBM devices caused a significant elevation in EPT at 5 min, with an earlier onset at 2 mins for 904 nm and LED. The LED was the only light source that elevated scores at 20 min. Across 2–20 min, when ranked by effectiveness, the greatest EPT elevations were seen for LED, followed by 904 nm, then 660 nm and finally 808 nm. Discomfort during PBM was most common with 904 nm, followed by 808 nm. No discomfort occurred from the LED. Among the light sources utilized, the LED multi-wavelength system demonstrated the largest increase in EPT readings, suggesting its potential as a non-pharmacological alternative for achieving dental analgesia compared to diode lasers.

Computed tomographic findings of nasal and paranasal disease in domestic rabbits highlight maxillary sinusitis and close association with dental disease: 100 studies (2004-2024).

To describe CT findings and epidemiologic features of nasal and paranasal disease of rabbits (Oryctolagus cuniculus). An electronic search was performed for rabbits that underwent skull CT from 2004 to 2024 and had findings consistent with nasal/paranasal or maxillary dental disease. History, signalment, and physical examination findings were recorded and reevaluated retrospectively for evidence of changes to the nasal passages, paranasal sinuses, and nearby associated anatomy. Data were analyzed with descriptive statistics, ordinal mixed logistic regression, and correlation analysis. 100 studies from 69 rabbits were reviewed. Lop-eared rabbits represented 30 of 69 cases. Upper respiratory signs (48 of 69 [69.6%]) and dental-related disorders (21 of 69 [31.9%]) were primary complaints. Rhinitis (49 of 69 [71.0%]), sinusitis (50 of 69 [72.5%]), and both (40 of 69 [60.0%]) were most diagnosed, with turbinate destruction (48 of 69 [69.6%]) and alveolar bone loss of adjacent teeth (51 of 69 [73.9%]) being common findings. Sinusitis was most common in the ventral (48 of 50 [96.0%]) and dorsal (33 of 50 [66.0%]) recesses of the maxillary sinus. Multiple CT variables were significantly correlated (P < .05); of those, maxillary alveolar bone loss of the incisor teeth and the second premolar tooth were, respectively, correlated with rhinitis grade and with sinusitis and sinusitis grade within the ventral recess of the maxillary sinus (P < .001). Computed tomographic evaluation allowed characterization of nasal and paranasal disease in rabbits and the association of rhinitis, sinusitis, and dental disease. The correlation between the maxillary dentition, rhinitis, and sinusitis highlights the need for thorough evaluation in CT of the teeth in rabbits with upper respiratory signs.

Shear Bond Strength of Orthodontic Brackets to Resin-Infiltrated Enamel

Abstract Objectives This study aims to evaluate shear bond strength (SBS) of orthodontic brackets to enamel after resin infiltration pretreatment using different adhesive systems. Materials and Methods Sixty extracted maxillary first premolars were divided into five groups (n = 12). Group I: sound enamel + Transbond XT; group II: resin-infiltrated enamel (ICON) + Transbond XT; group III: ICON + Scotchbond Universal Plus; group IV: ICON + Assure PLUS; group V: ICON + Transbond Plus Self Etching. The SBS was measured using universal testing machine and analyzed using analysis of variance (ANOVA). The adhesive remnant index (ARI) score after debonding was determined under stereomicroscope with a 10× magnification. Statistical Analysis A one-way ANOVA and post hoc Tukey's test were used to compare the data. Further, the ARI scores were evaluated using a chi-squared test. The level of significance was set at p = 0.05. Results SBS of group I, II, III, IV, and V were 11.70 ± 3.17, 11.23 ± 3.06, 9.52 ± 1.73, 8.97 ± 1.12, and 9.14 ± 0.70 MPa, respectively. SBS of group IV and V was significantly lower than group I and II (p &lt; 0.05). There was no significant difference in the ARI scores among the five groups (p &gt; 0.05). Conclusion The SBS of enamel resin infiltration pretreatment depends on the adhesive system. The SBS of all groups was within adequate SBS range in clinical use. The most common ARI score was 2, which indicated lower risk of enamel fractures when debonding.

Impact of different activation procedures on sodium hypochlorite penetration into dentinal tubules after endodontic retreatment via confocal laser scanning microscopy

BackgroundInfected dentinal tubules are a possible source of bacteria that are responsible for the failure of root canal treatment. Therefore, disinfection of dentinal tubules by increasing the penetration of the irrigation solution is important for success in retreatment cases. This study utilized confocal laser scanning microscopy (CLSM) to assess and compare the impact of XPR, ultrasonic irrigation (UI) and sonic activation (SA) on NaOCl penetration into dentinal tubules following endodontic retreatment.MethodsA total of forty mandibular premolars were enrolled in this investigation. Following root canal preparation up to ProTaper X3 file (30/0.07), root canals were obturated with gutta-percha and bioceramic root canal sealer with single cone technique. The root canal filling materials were removed using ProTaper nickel-titanium rotary retreatment files until the working length was reached. The retreatment procedure was finalized using the ProTaper Next X4 (40/0.06). The teeth were divided into four groups based on the irrigation activation technique: control (conventional needle irrigation), SA, UI and XPR. During the final irrigation procedure, Rhodamine B dye was introduced to 5% NaOCl for visualization via CLSM. Subsequent to image acquisition, the maximum penetration, penetration percentage, and penetration area were calculated. Data were statistically analyzed using the Kruskal-Wallis, Friedman, and Bonferroni Dunn multiple comparison tests through R software (p < 0.05).ResultsIn the middle third, UI yielded a significantly higher penetration percentage than the control group (p < 0.05). The UI and XPR groups showed increased penetration percentages in the coronal and middle thirds compared with the apical third (P < 0.05). Maximum penetration was notably reduced in the apical third than in comparison with the coronal and middle thirds in all groups (p < 0.05). In the control, SA and XP groups, the penetration area was ranked in descending order as coronal, middle and apical (p < 0.05). Conversely, in the ultrasonic group, the penetration area was significantly lower in the apical third than in the middle and coronal thirds (p < 0.05).ConclusionsUI enhanced the penetration percentage in the middle third of the root compared with that in the control group. XPR and SA showed no significant effect on NaOCl penetration following retreatment.

The influence of different radiotherapy doses on the mechanical properties and microstructure of the enamel and dentin of human premolar teeth.

Radiation therapy is applied in the treatment of head and neck cancer patients. However, oral-health-related side effects like hyposalivation and ahigher prevalence of caries have been shown. This study aims to assess the influence of different radiotherapy doses on the mechanical properties, roughness, superficial microstructure, and crystallinity of the enamel and dentin of human premolar teeth. Specimens (n = 25) were categorized into five groups based on the radiation dose received (0, 10, 30, 50, and 70 Gy). The enamel and dentin of these specimens were subjected to amicrohardness tester, profilometer, atomic force microscopy (AFM), scanning electron microscopy (SEM), and X‑ray diffraction (XRD) before and after different irradiation doses and compared to hydroxylapatite in each group. The data were analyzed using repeated-measures analysis of variance (ANOVA). Therapeutic radiation doses of 30, 50, and 70 Gy led to adecrease in the microhardness and an increase in the average roughness of the enamel, and rougher surfaces were observed in the mixed three-dimensional images. Moreover, in the dentin, asimilar outcome could be observed for more than 10 Gy. The main crystalline phase structure remained hydroxylapatite, but the crystallinity decreased and the crystalline size increased above 10 Gy. The superficial micromorphology revealed granulation, fissures, and cracks in adose-dependent manner. Radiation below 70 Gy had little effect on the hydroxylapatite concentration during the whole experiment. Above aradiation dose of 30 Gy, the micromorphology of the tooth enamel changed. This occurred for dentin above 10 Gy, which indicates that dentin is more sensitive to radiotherapy than enamel. The radiation dose had an effect on the micromorphology of the hard tissues of the teeth. These results illustrate the possible mechanism of radiation-related caries and have guiding significance for clinical radiotherapy.

Effect of Newer Intraorifice Barriers on the Fracture Resistance of Endodontically Treated Teeth: An In Vitro Study.

This study aimed to assess and compare the fracture resistance of endodontically treated teeth using three new intraorifice barrier materials. A total of 60 extracted human mandibular premolars having single roots were decoronated to 14 mm length, prepared up to rotary F3 ProTaper Gold files, and sealed with gutta-percha and AH Plus sealer. Specimens were divided into one control and three experimental groups (n = 15): Group 1, control; Group 2, Biodentine (Septodont, Saint Maur des Fosses, France); Group 3, resin-modified glass ionomer cement (RMGIC, GC Gold Label 2 LC, GC Corporation, Tokyo, Japan); and Group 4, flowable nanohybrid composite (G-aenial Universal Flo, GC Corporation, Tokyo, Japan). A 3 mm coronal gutta-percha was replaced with respective intraorifice barrier materials in the experimental groups, and the fracture resistance of all the groups was tested using the universal testing machine. One-way analysis of variance andTukey's post-hoc test were conducted. The experimental groups showed higher mean load values than the control group. The flowable composite showed the highest mean loads followed by Biodentine and RMGIC. The mean fracture resistance of flowable nanohybrid composite and Biodentine was significantly higher than that of the control. No statistically significant differencewas observed among the other groups. The flowable nanohybrid composite and Biodentine significantly improved resistance to fracture of endodontically treated teeth when compared to the control.

Assessment of surface microhardness of enamel surface treated with Nano- HAP serum before and after bleaching

Background: Although bleaching is typically considered a safe procedure, various investigations have found minor negative effects and changes in mineral composition. The aim was to Evaluate and compare the efficacy of using Nanohydroxyapatite serum on surface microhardness of enamel surface before and after bleaching with chemically cured Boost bleaching. Material and methods: ten sound human permanent upper and lower premolar teeth were used and their roots were removed 2 mm apically to the cementoenamel junction, the crowns were sectioned mesiodistally into two halves buccal and lingual/palatal, the buccal surface was further subdivided into two halves. The samples were embeded in an acrylic resin, resulting in 30 specimens divided into 3 groups: Control group: using Boost bleaching and stored in artificial saliva for 14 days, prevention group: nanohydroxyaptite (n-HAP) serum applied 2-3 min once daily for 10 days followed by bleaching then stored for 14 days in artificial saliva and treatment group: in which bleaching used before nanohydroxyapatite serum and stored in artificial saliva for 14 days. The samples were subjected to a Vickers microhardness test measured at 4 times: base line, after nanohydroxyapatitem, after one day of bleaching and after storage in artificial saliva for 14 days in all groups. The data were analyzed statistically using repeated analysis of variance (ANOVA) test followed by Tukey's test. Results: there was a significant increase in microhardness in the prevention group (p&lt;0.05) while there was no significant difference in microhardness readings in control and treatment groups (p&gt; 0.05). Conclusion: n-HAP may enhance the microhardness of a bleached enamel surface when used as a preventive &amp; treatment measure. Suggested that a higher increase in enamel microhardness occurs when n-HAP is used for 2-3 min once daily for 10 days before bleaching and maintaining this increase even after storage for 14 days in artificial saliva.

Fracture resistance and fractographic analysis of pressable glass-ceramics with different partial coverage designs for maxillary premolars

BackgroundPartial coverage concepts have met the main goal of conservative dentistry. Vonlays, which combine features of veneers and onlays, are a recent alternative to full coverage designs and overlay partial coverage restorations. This in vitro study was conducted to compare the fracture resistance of the newly introduced pressable zirconia-reinforced lithium silicate with pressable lithium disilicate ceramic and to determine the optimal preparation design for partial coverage on upper premolars.MethodsFifty-two duplicated epoxy resin dies were prepared following vonlay and overlay preparation guidelines. For each preparation (n = 26), the specimens were divided into two subgroups to be restored with lithium disilicate (IPS e.max Press) or zirconia-reinforced lithium silicate (Vita Ambria) (n = 13 each). Ceramic vonlays and overlays were bonded using dual cure resin cement, subjected to thermomechanical fatigue, and the load to fracture was tested by using a universal testing machine. The specimens were fractographically analyzed via scanning electron microscopy (SEM). The normality of the fracture resistance data was checked using the Shapiro‒Wilk test and Q‒Q plots, and two-way ANOVA was used to assess the effect of the type of preparation and ceramic material on the fracture resistance.ResultsThe group of overlays restored with zirconia-reinforced lithium silicate showed the highest mean fracture load (1218.69 N), while the group of vonlays restored with lithium disilicate had the lowest mean fracture resistance (967.15 N). The effect of preparation design and material type on fracture resistance was significant for both factors, p = 0.003 and p < 0.0001, respectively. Different features of the fracture surfaces, such as arrest lines, hackles, and directions of crack propagation, were observed.ConclusionsZirconia-reinforced lithium silicate exhibited greater resistance to fracture compared to lithium disilicate, making it a potential substitute for partial coverage restorations. Additionally, the overlay showed superior fracture resistance when compared to the vonlay preparation design.

Cone-Beam Computed Tomography Study of Root and Canal Morphology of Mandibular First and Second Premolars in Nepalese Population

Cone-Beam Computed Tomography Study of Root and Canal Morphology of Mandibular First and Second Premolars in Nepalese Population

The effect of two preparation designs on the fracture resistance and marginal adaptation of two types of ceramic crowns using CAD/CAM technology (In vitro study)

BackgroundRecently, prosthodontic approaches involve more conservative procedures that include less invasive finish line preparations that use less ceramic thickness.Aim of the studyThis in vitro study aimed to evaluate the effect of vertical preparation and modified vertical preparation designs on the marginal adaptation and fracture resistance of two types of ceramic crowns using CAD/CAM technology.Materials and methodsTwo typodont maxillary first premolars were embedded in acrylic resin. Forty positive replicas of epoxy resin dies were used that were divided into two groups depending on the preparation design (n = 20); Group V (Vertical): dies with feather edge finish line and Group MV (Modified vertical): dies with feather edge finish line, where a reverse shoulder of 1 mm depth was placed on the buccal surface 1.5 mm from the occlusal surface. Each group was further subdivided into two subgroups according to the type of ceramic material (n = 10): Subgroup Va and subgroup MVa for lithium disilicate (e.max CAD) and subgroup Vb and subgroup MVb for zirconia (zolid ht+). Crown restorations were made with CAD-CAM technology. The marginal adaptation was assessed using a stereomicroscope both prior to cementation and after cementation and aging. Fracture resistance was tested with a universal testing machine, and the data were statistically analyzed.ResultsMarginal adaptation showed no significant differences between subgroups before or after cementation and aging. Three-way ANOVA indicated that preparation design (p = 0.516) and material (p = 0.269) had no significant effect, but cementation had a significant effect (p < 0.0001) on the marginal adaptation. According to two-way ANOVA test, Subgroup (MVb) showed the highest result followed by subgroup (Vb) and subgroub (MVa) and the least was subgroub (Va). Fracture modes showed no significant differences among the subgroups (p = 0.982).ConclusionsMarginal adaptation of lithium disilicate and zirconia crowns remained clinically acceptable regardless of preparation design. While the modified vertical preparation with a reverse shoulder notably enhanced the fracture resistance of both materials, with zirconia demonstrating superior fracture resistance compared to lithium disilicate with average values exceeding premolar biting force.

Impact of LASER activated irrigation on the retrievability of Guttaflow bioseal (in-vitro study)

BackgroundThis study aimed to evaluate the efficiency of diode LASER activated irrigation in the removal of GuttaFlow Bioseal root canal filling material during retreatment.Materials and subjectsRoot canals of forty-five single-rooted human mandibular premolar teeth were prepared with ProTaper Universal rotary system and obturated with lateral condensation obturation technique using Gutta Percha and Roeko GuttaFlow Bioseal root canal sealer. All specimens were retreated with ProTaper Universal Retreatment System files then divided to three different groups according to the technique of activation of irrigation. Samples were sectioned, and the residual filling remnants were captured using digital camera attached to microscope. Data was collected by three different interpreters, to eliminate the subjectivity of the process, using the ImageJ Software. The mean value of the data was obtained and evaluated statistically. The significance level was set at P ≤ 0.05.ResultsThe remaining filling materials in the canals irrigated with ultrasonic activation (6.17 ± 1.42 at coronal level, 10.93 ± 1.91at middle level, and 14.58 ± 2.23 at apical level) were less than these irrigated with LASER activation (15.87 ± 3.78 at coronal level, 21.28 ± 4.44 at middle level, and 27.06 ± 2.68 at apical level). Maximum amount of remaining filling materials was present in the canals irrigated with passive side-vented syringe (23.07 ± 3.22 at coronal level, 38.09 ± 7.27 at middle level, and 34.24 ± 9.77 at apical level).ConclusionThe activation of irrigation techniques used were incapable of complete removal of filling material at root canal walls.

A Comparative Ex Vivo Study on Apex Locator Precision in Mature Teeth and Immature Teeth With Divergent Canals.

This study investigates the accuracy of an apex locator in mature andimmature teeth with divergent root canals ex vivo. Fifty extracted premolar teeth were utilized for the study, with 25 mature teeth (Nolla stage 9 or 10) and 25 immature teeth (Nolla stages ≤ 8). The discrepancies between the actual length (AL) and the electronic length (EL), measured using a Bingo 1020 apex locator, were compared and analyzed. Statistical analysis included Pearson's correlation analysis, a T-test for independent samples, and multiple linear regression. Statistical significance was set at p < 0.05. The difference between AL and EL in immature teeth was significantly higher than in mature premolar teeth. Nonetheless, patient gender or jaw type (upper/lower) did not affect the accuracy of electronic apex locator (EAL) measurements. EAL readings are less accurate in immature teeth than in mature teeth. Supplementary measures, such as radiographic length determination and wet-dry paper point tests, are required to confirm theworking length for improved treatment outcomes and patient compliance.