Optical microscopy evaluation of root canal filling removal by beginner operators in posterior teeth.

This study analyzed the effectiveness of root canal filling removal in lower molars performed by beginner operators using optical microscopy. A total of 55 mandibular first and second molars with mesial roots exhibiting an average curvature of 10-20° were selected based on preoperative radiographs. Instrumentation was done with ProTaper Gold (Dentsply Sirona) up to F2 (25/.08), using 2ml of 2.5% NaOCl irrigation solution after each file. Root canal obturation was performed using gutta-percha points with cold lateral condensation and Sealapex (Kerr Dental). Coronal fillings were made with composite resin and stored in distilled water for two years. Removal of the root canal fillings was performed with AF Retreatment Rotary (AFRR) and AF Blue R3 (AFBR3) (Fanta Dental Materials) under reciprocating motion with 2.5% NaOCl irrigation. Cross-sections of the coronal, middle, and apical thirds were analyzed at 40x magnification using a STEINDORFF POL microscope with a digital camera. Image analysis was conducted using Image J software, version 1.54, to determine the efficiency of root canal filling removal by percentage. Statistical analysis via one-way ANOVA revealed significant differences between distal and mesial roots (P < 0.05). Specifically, for mesial roots, the removal efficiency was 70.65% in the coronal third, 54.66% in the middle third, and 21.32% in the apical third. Significant difficulties were noted due to fractured files, calcifications, and debris accumulation in the isthmuses. The study concluded that the protocol using Fanta files demonstrated significant differences in removal efficiency correlated with root curvature, compounded by the inexperience of beginner operators. The findings highlight the challenges faced by novice practitioners in achieving effective root canal filling removal.

Effect of sublingual fast-dissolving piroxicam premedication on postoperative pain experience in mandibular molars with non-vital pulp: a randomized double-blind controlled trial.

BACKGROUND: The aim of this trial was to evaluate the effect of a preoperative, single dose sublingual fast-dissolving piroxicam (20 mg) compared to placebo on postoperative pain at rest (POP), on biting (POPB) and on percussion (POPer) after single-visit endodontic treatment of asymptomatic mandibular molars with non-vital pulp. METHODS: Seventy patients randomly received either piroxicam or placebo 1 h before treatment (n = 35). Patients recorded their pain (POP and POPB) level 6 h, 12 h, 24 h, 48 h, 72 h and 7 days postoperatively using an 11-point numerical rating scale; POPer was assessed after 7 days. Resuce-analgesic intake (RAI) and flare-up incidence (FUI) were recorded. Data were statistically analyzed. RESULTS: Both groups had similar baseline characteristics (P > 0.05). Piroxicam showed less POP intensity and incidence than placebo at 6, 12 and 24 h, less POPB intensity and incidence at all timepoints, less POPer intensity and incidence and less RAI (p > 0.05), but similar FUI (P > 0.05). A significant rise in pain compared to baseline occurred with placebo from 6 to 72 h for POP and to 7 days with POPB (p > 0.05); such rise was not detected with piroxicam. POPB showed higher pain intensity than POP at all time points (p < 0.05). No swelling or adverse effects occured. CONCLUSIONS: A preoperative single dose of sublingual fast-dissolving piroxicam can be effective in reducing spontaneous pain up to 24 h, stimulated pain up to 7 days, and RAI incidence in asymptomatic mandibular molars with non-vital pulp; it can prevent rise in POP and POPB postoperatively. Stimulated postoperative pain can be more severe and longer lasting than spontaneous pain. TRIAL REGISTRATION: Clinicaltrials.gov ID: NCT03998826 (2019).

Efficacy evaluation of zirconia crown on primary molars with caries defects.

OBJECTIVES: This study aimed to estimate the therapeutic effects of preformed metal crown (PMC) and prefabricated zirconia crowns (ZC) on decayed primary morals in children, as well as to analyze the possible influencing factors. METHODS: A retrospective cohort study was performed on the data of 192 patients (aged 3 to 8) in the Stomatological Department of Shenzhen Children's Hospital from October 2021 to December 2021. The decayed mandibular first molars were selected and restored by vital-pulp therapy followed by PMC and ZC, including 96 cases (96 caries) in the PMC group and 96 cases (96 caries) in the ZC group. Oral clinical examination was performed at 3 months, 1 year, and 2 years after treatment, overwiewing the clinical therapeutic effects and periodontal status of PMC and ZC groups, as well as recording the crown integrity, gingival index (GI), probing bleeding index (BI), plaque index (PLI) and various prosthetic indices. RESULTS: No significance differences existed in the periodontal status of PMC and ZC groups at 3 months, 1 year, and 2 years after treatment (P>0.05). However, the GI, BI, and PLI in the PMC group were higher than those in the ZC group at 3 months, 1 year, and 2 years after treatment, and the difference was dramatically significant (P<0.05). No significances difference existed in various prosthetic indices (P>0.05), as well as in the GI, BI, and PLI, between the two groups (P>0.05). No significant differences existed in various prosthetic indices between genders after PMC restoration (P>0.05). The scores of girls in various prosthetic indices after ZC restoration were higher than those of boys (P<0.05). Pearson correlation analysis indicated an inverse correlation between age in the PMC group and the GI, BI, PLI, and FDI indices (P<0.01), rather than in the ZC group (P>0.05). CONCLUSIONS: PMC and ZC can be applied to restore deciduous molar caries. The periodontal status of deciduous teeth in ZC group was superior to that in the PMC group. The periodontal status of deciduous teeth in PMC group may be stable with increased age.

The effect of calcium hydroxide and double antibiotic paste on radiographic outcomes and periapical MMP-8 levels in regenerative endodontic procedures: a randomized clinical trial.

OBJECTIVE: The primary goal is to evaluate the effects of two different intracanal medicaments, calcium hydroxide [Ca(OH)2] and double antibiotic paste (DAP), on radiographic outcomes during regenerative endodontic procedures (REP) of immature permanent mandibular first molars with symptomatic irreversible pulpitis and symptomatic apical periodontitis (SIP/SAP). Additionally, the secondary goal was to evaluate MMP-8 levels during REP using two different intracanal medicaments. METHODOLOGY: The study included 20 patients with immature mandibular first molars exhibiting SIP/SAP. Participants were randomly assigned into two groups based on the applied intracanal medicament. Ca(OH)2 (n=10) was prepared by mixing it with sterile distilled water, while the same amount of powdered metronidazole and ciprofloxacin were mixed and combined with sterile distilled water for DAP (n=10). MMP-8 in periapical samples were measured at baseline and on the 14th day using immunofluorometric assay. Image-J software with TurboReg plug-in was utilized to determine changes in root length, root width, radiographic root area (RRA) during the 12-month follow-up period. Data were analyzed by SPSS 25.0 (p<.05). RESULTS: Significant increase in MMP-8 on the 14th day compared to baseline in both groups (p<0.001). There was no significant difference between the two groups in terms of the increase in MMP-8 (p>0.05). Root length significantly increased in both groups (p=0.001), with Ca(OH)2 showing a greater increase (p=0.046). Root width and RRA increased similarly in both groups at 12th month. CONCLUSION: Both Ca(OH)2 and DAP applications resulted in a significant increase in periapical MMP-8 levels. Increase in radiographic root width and root area was similar between two groups, but Ca(OH)2 led to a significantly greater increase in root length. Further studies with larger sample sizes are necessary to validate our findings during REP of vital immature permanent mandibular molars. Clinical Trials database: NCT05581706.

Exploring fiberglass post numbers for enhanced fatigue resistance in molars without coronary remnants.

This study aimed to assess the fatigue resistance of molars lacking a coronary remnant, using zero, one, two, or three fiberglass posts. Forty caries/crack-free human molars with coronal portions removed at the pulp chamber floor were randomly allocated into four groups (n=10). Following endodontic treatment, posts (Whitepost DC/DC.E 0.5, 1.0, FGM) were silanized (silane agent, Angelus) and cemented with a resin cement (RelyX U200, 3M ESPE). Resin composite cores (Z350, 3M ESPE) were built, and metal crowns were fabricated and cemented using the same luting system. Samples underwent cyclic fatigue testing at 45°, applying load in the occlusal surface at 10 Hz and 100 N initial load for 10,000 cycles, with 50 N increments every 10,000 cycles until failure. Fatigue failure load and cycles for failure data were recorded and subjected to survival analysis through Kaplan-Meier and Mantel-Cox post hoc tests, and Weibull analysis. Fractography patterns of failed crowns were qualitatively analyzed. The group without posts exhibited the lowest fatigue performance (p < 0.05) for both fatigue failure load and cycles to failure. Superior fatigue performance was observed in the three-post group, followed by groups with one or two posts, corroborated by the Weibull characteristic strength parameter. Weibull moduli were similar among conditions. All specimens exhibited failure involving detachment of the restorative set (posts/core/crown) with a portion of the dental remnant, without tooth fracture. Thus, when restoring mandibular molars without crown remnants, the use of fiberglass posts promotes greater fatigue resistance to oblique loads.

CBCT assessment of mandibular molar furcation following root canal retreatment using engine-driven instruments.

This study employed e-Vol DXS cone beam computed tomography (CBCT) software to assess dentin remnants in the furcation area of mesial canals in mandibular molars during root canal retreatment (RCR). Four groups (Reciproc®, ProTaper Next®, Race Evo®, Protaper Gold®) were subjected to RCR, and CBCT images were captured before (T1) and after (T2) treatment. Measurements of remaining dentin thickness at 1 mm and 3 mm below the furcation were scrutinized. Results revealed no significant differences in mean thicknesses of mesiobuccal (MB) and mesiolingual (ML) canals at 1 mm and 3 mm from the furcation pre-treatment (T1). Post-treatment (T2) showed analogous findings, with no significant differences in mean thicknesses. However, disparities were found between MB and ML canals at both distances, both before and after retreatment. In essence, the evaluated instruments exhibited safety in RCR, implying that they are appropriate for use in critical areas of mandibular molars without inducing excessive wear. This study underscores the reliability of these instruments in navigating danger zones during RCR, and contributes valuable insights for dental practitioners who handle complex root canal scenarios in mandibular molars.

Single-cell RNA-seq analysis of rat molars reveals cell identity and driver genes associated with dental mesenchymal cell differentiation.

BACKGROUND: The molecular mechanisms and signaling pathways involved in tooth morphogenesis have been the research focus in the fields of tooth and bone development. However, the cell population in molars at the late bell stage and the mechanisms of hard tissue formation and mineralization remain limited knowledge. RESULTS: Here, we used the rat mandibular first and second molars as models to perform single-cell RNA sequencing (scRNA-seq) analysis to investigate cell identity and driver genes related to dental mesenchymal cell differentiation during the late bell hard tissue formation stage. We identified seven main cell types and investigated the heterogeneity of mesenchymal cells. Subsequently, we identified novel cell marker genes, including Pclo in dental follicle cells, Wnt10a in pre-odontoblasts, Fst and Igfbp2 in periodontal ligament cells, and validated the expression of Igfbp3 in the apical pulp. The dynamic model revealed three differentiation trajectories within mesenchymal cells, originating from two types of dental follicle cells and apical pulp cells. Apical pulp cell differentiation is associated with the genes Ptn and Satb2, while dental follicle cell differentiation is associated with the genes Tnc, Vim, Slc26a7, and Fgfr1. Cluster-specific regulons were analyzed by pySCENIC. In addition, the odontogenic function of driver gene TNC was verified in the odontoblastic differentiation of human dental pulp stem cells. The expression of osteoclast differentiation factors was found to be increased in macrophages of the mandibular first molar. CONCLUSIONS: Our results revealed the cell heterogeneity of molars in the late bell stage and identified driver genes associated with dental mesenchymal cell differentiation. These findings provide potential targets for diagnosing dental hard tissue diseases and tooth regeneration.

Establishing legal threshold of 18-years based on the assessment of mandibular molars using three different methods - An observational study.

BACKGROUND: The study evaluates the feasibility of employing the radiographic visibility of the root pulp and periodontal ligament in mandibular molars for age estimation, particularly focusing on the 18 years of age threshold. This study additionally investigates the potential of root canal width reduction in mandibular molars, as a reliable method for forensic age estimation in living individuals. MATERIALS AND METHODS: A cross-sectional study was conducted to assess the radiographic visibility of the root pulp (RPV) and the root canal width (RCW) of mandibular first, second, and third molars along with the radiographic visibility of the periodontal ligament (PLV) of mandibular third molars, in a sample of 403 individuals aged 16-25 years (220 males and 183 females). Data regarding age for different stages of RPV and PLV and various types of RCW were recorded and observed for sex-based differences. Results obtained were tabulated and descriptive statistics were applied to summarise the findings. RESULTS: Individuals over 18 years old were classified with higher accuracy using stage 3 of the RPV scoring system in all mandibular molars (first, second, and third) compared to stage 2, which was also effective for the second and third molars. This result held regardless of sex and side examined. Additionally, root canal width (RCW) assessment demonstrated that individuals with RCW types A, B, and C were more likely to be under 18 years old in both sexes. Conversely, individuals with RCW type U on the right side for males and the left side for females exhibited a higher likelihood of being above 18 years old. CONCLUSION: The study suggests that the assessment of mandibular molars could potentially serve as an auxiliary tool in age estimation methods, particularly for approximating individuals around the 18 years of age threshold. Further investigation is warranted to explore the potential application of root canal width measurements in forensic age estimation.

Spatial and angular alterations in the dental arch after premature loss of primary molars: Immediate and 9-month computed tomography evaluation.

BACKGROUND: Contemporary imaging methods and quickly advancing technologies have increased the number of diagnostic tools available in medicine and orthodontics. The current study aimed to determine three-dimensional (3D) space changes that occurred after the extraction of either the maxillary or mandibular primary molars during the mixed dentition period. MATERIALS AND METHODS: The present study was a longitudinal split-mouth study with a study group and a control group. The sample consisted of 20 children aged between 6 and 9 years. Clinical examination, radiological analysis, and 3D digital images of the plaster casts were used sequentially to gather all the data. The dental cast measurements recorded were arch width, arch length, hemi-perimeter, dental space at the extraction site, and angulation of the first permanent molar. The children were recalled for follow-up after 9 months, and all dental cast measurements were repeated using nondestructive 3D computed tomography software. For repeated measurements, the test applied was a paired t-test, and for independent samples, the test was a Student's t-test. RESULTS: A significant decrease in arch width (P = 0.001), arch length (P < 0.001), hemi-perimeter (P < 0.001), D-space (P < 0.001), and E-space (P = 0.001) was observed following extraction. A significant increase in angulation measurements was observed (P = 0.001). CONCLUSION: The study revealed a comparative reduction in mandibular arch width, a reduction in arch length in both the maxilla and the mandible, a reduced hemi-perimeter of dental arches, loss of dental extraction space, and a change in angulation of the erupted first permanent molars following premature loss of the primary molar.

Clinical and histological efficacy of a new implant surface in achieving early and stable osseointegration: An in vivo study.

An advantage of treated implant surfaces is their increased degree of hydrophilicity and wettability compared with untreated, machined, smooth surfaces that are hydrophobic. The present preclinical in vivo study aimed to compare the two implant surface types, namely SLActive (Straumann, Basel, Switzerland) and nanohydroxyapatite (Hiossen, Englewood Cliffs, NJ, USA), in achieving early osseointegration. The authors hypothesised that the nanohydroxyapatite surface is comparable to SLActive for early bone-implant contact. Six male mixed foxhounds underwent mandibular premolar and first molar extraction, and the sockets healed for 42 days. The mandibles were randomised to receive implants with either SLActive (control group) or nanohydroxyapatite surfaces (test group). A total of 36 implants were placed in 6 animals, and they were sacrificed at 2 weeks (2 animals), 4 weeks (2 animals) and 6 weeks (2 animals) after implant surgery. When radiographic analysis was performed, the difference in bone level between the two groups was statistically significant at 4 weeks (P = 0.024) and 6 weeks (P = 0.008), indicating that the crestal bone level was better maintained for the test group versus the control group. The bone-implant contact was also higher for the test group at 2 (P = 0.012) and 4 weeks (P = 0.011), indicating early osseointegration. In conclusion, this study underscored the potential of implants with nanohydroxyapatite surfaces to achieve early osseointegration.

Effects of minimally invasive endodontic access cavity in molar teeth on polymerization, porosity and fracture resistance.

Minimally invasive access cavities have been proposed in the last decade to reduce tooth tissue loss during endodontic treatment and mitigate compromised fracture resistance of endodontically treated teeth. Fracture resistance of molars with different types of access cavity design may be affected by restorative materials and aging. Insufficient literature data exist on the effect of cavity design and type of restorative materials on restorative aspects such as material adaptation or photo-polymerization in restricted access cavities. This study analyses quality of polymerization, material adaptation and fracture resistance of molars with different types of access cavities restored with glass-ionomer, high-viscosity fiber-reinforced bulk-fill and nanofilled resin composite. Plastic molar teeth with truss (TREC) and traditional endodontic access cavity (TEC) were restored with nanofilled composite (Filtek Supreme), glass-ionomer Fuji IX and Filtek or fiber-reinforced everX Posterior and Filtek. Porosity was determined using microcomputer tomography and the degree of conversion of resin-based materals using micro-Raman spectroscopy. Human molars prepared and restored in the same way were used for fracture resistance testing at baseline and after thermocycling. The results demonstrate that high-viscosity fiber-reinforced composite was difficult to adapt in TREC cavity leading to greater porosity than Filtek or Fuji. TREC design did not affect composite polymerization and led to higher fracture resistance of restored molars compared to TEC but also more unrestorable fractures.

Chemo mechanical caries removal CMCR: Efficacy of Carisolv gel in primary molar teeth.

Objectives: To evaluate the efficacy of CariSolv gel with respect to chemo-mechanical caries removal in primary molar teeth. METHODS: The cross-sectional study was conducted at the Department of Paediatric Dentistry, Bakhtawar Amin Dental College and Hospital, Multan, Pakistan, from July to December 2022, and comprised patients of either gender aged 6-12 years having vital, primary molar teeth with clinical and radiographic evidence of carious lesion. Freshly prepared CariSolv gel 0.2 ml to 1.0ml was applied to carious dentine for a minimum of 30 seconds, using chemo-mechanical caries removal hand instruments. The cavity preparation was rinsed and dried. Image caries detector dye was applied by micro brush for 10 seconds. After the cavity preparation was washed and dried, any red-stained dentine indicated residual infected dentine. A maximum of 3 chemo-mechanical caries removal cycles were allowed. Data was analysed using SPSS 26.0. RESULTS: Of the 134 patients, 74(55.2%) were boys and 60(44.8%) were girls. The overall mean age was 8.55±1.58 years. The procedure was successful in 115(85.8%) cases. Age and gender were not significantly associated with the outcome (p>0.05). CONCLUSIONS: Chemo-mechanical caries removal method using CariSolv gel was found to be a viable alternative to traditional drilling techniques for caries removal in primary molar teeth.

Molar enamel-dentine junction shape of Pliobates cataloniae and other Iberian pliopithecoids.

The phylogenetic relationships of the small-bodied catarrhine Pliobates cataloniae (∼11.6 Ma, NE Iberian Peninsula) have been controversial since its original description. However, the recent report of additional dentognathic remains has supported its crouzeliid pliopithecoid status. Based on the available hypodigm, the molar enamel-dentine junction (EDJ) shape of P. cataloniae is compared with that of other pliopithecoids from the same basin as well as both extinct and extant hominoids to further evaluate its pliopithecoid affinities. We also quantitatively compare the EDJ shape among these taxa by means of landmark-based three-dimensional geometric morphometrics using principal component analysis (PCA), canonical variate analysis, and between-group PCA. Permutation tests are performed to test whether Pliobates variation exceeds that of extant hominoid genera. Results indicate that Pliobates is similar in molar EDJ shape to other pliopithecoids, particularly crouzeliids. The variation displayed by Pliobates upper molars is less marked at the EDJ level than at the outer enamel surface, probably owing to differential enamel wear and intraspecific differences in enamel thickness. Multivariate analyses of EDJ shape show that all pliopithecoids (including Pliobates) cluster together in the PCAs, canonical variate analyses, and between-group PCAs and occupy a different portion of the morphospaces from extinct and extant hominoids. Posterior and typicality probabilities strongly support the classification of Pliobates as a pliopithecoid, wheras permutation tests fail to reject the single-genus hypothesis for the P. cataloniae hypodigm. We conclude that P. cataloniae is a crouzeliid pliopithecoid, as recently supported by cladistic analyses of craniodental characters, and that previous cladistic results that supported a stem hominoid status are attributable to postcranial convergences with crown hominoids. Our results further highlight the potential of three-dimensional geometric morphometrics analyses of the EDJ shape for better informing fossil primate alpha-taxonomy by means of quantitatively testing hypotheses about tooth shape variation.

Postoperative pain after total pulpotomy and root canal treatment in mature molars according to the new and traditional classifications of pulpitis: a prospective, randomized controlled trial.

BACKGROUND: The aim of this study was to compare postoperative pain following total pulpotomy (TP) and root canal treatment (RCT) in mature molar teeth with irreversible pulpitis. To compare the traditional pulpitis classification system with the Wolters system in evaluating postoperative pain. METHODS: Eighty mandibular molars with irreversible pulpitis were included and classified according to the Wolters (moderate/severe pulpitis). The teeth were randomly assigned to two groups (RCT or TP). RCT was performed following standardized protocols. TP was performed to the level of the canal orifices, and hemostasis was achieved with 2.5% sodium hypochlorite. A 3 mm layer of MTA was placed as the pulpotomy material. The teeth were restored with glass ionomer cement followed by composite. Pain scores were recorded preoperatively and, at 6, 12, 24, 48, and 72 h and 7 days after the interventions. The data were statistically analyzed using the Mann-Whitney U test, the Friedman test, the Wilcoxon signed-rank test, and the Spearman's correlation test. The significance level was set at 0.05. RESULTS: Sixty-four patients were analyzed at the one-week follow-up and all were diagnosed as irreversible pulpitis according to the AAE; 22 teeth were classified as moderate and 42 teeth were classified as severe pulpitis according to Wolters. There was no significant difference between TP and RCT in pain scores in moderate pulpitis patients (p > 0.05). There was a significant difference between TP and RCT at 24 and 72 h of severe pulpitis; higher pain scores were observed in the RCT (p < 0.05). CONCLUSIONS: In patients with moderate pulpitis, the TP procedure allowed symptom relief more quickly than RCT. In patients with severe pulpitis, TP provided for significantly lower pain scores compared to RCT at both 24 and 72 h. CLINICAL TRIAL REGISTRATION: The study was retrospectively registered with ClinicalTrials.gov (NCT05923619). Date of Registration: 06/16/23.

Wilson curve modification in permanent dentition: a retrospective comparison between clear aligners and continuous archwire treatment.

OBJECTIVES: To evaluate leveling of the Curve of Wilson (COW) by two different treatment appliances (clear aligners [CA] and continuous archwire fixed appliances [FA]) in a permanent dentition sample of patients. MATERIALS AND METHODS: Digital casts of 40 patients (CA group = 20 patients; FA group = 20 patients) were collected. Angular values for COW, right and left vertical height difference of lower first molars, and linear distance between lower teeth and the WALA ridge were analyzed for pre- (T1), posttreatment (T2) and on final virtual (ClinCheck) models (T2-CC) of the CA group. An unpaired t-test was used to evaluate significant intergroup differences (P < .05), while a paired t-test was used for posttreatment CA intragroup comparison. RESULTS: FA group showed better control of second molar crown positions compared to CA group (47-WALA = -0.2 ± 0.1 mm, 37-WALA = -0.6 ± 0.3 mm). No significant difference was detected for linear distance of lower first molars and the WALA ridge or for vertical height difference. CA group showed a greater reduction of distance between lower premolars and the WALA ridge (mean difference: -0.5 mm for both 45-WALA and 35-WALA; mean difference: -0.5 mm for 44-WALA, -0.6 mm for 34-WALA). Predictability for the CA group was high for every measurement (87% Right COW, 89% Left COW, 88% 46 Vertical Diff, 87% 36 Vertical Diff). CONCLUSIONS: Clear aligner and continuous archwire mechanics were effective in leveling COW. FA was more effective in changing crown position of lower second molars with respect to the WALA ridge, while CA provided a greater distance reduction between lower premolars and WALA ridges compared to FA.

Evaluation of maxillary dimensional changes in the mixed dentition: clear aligners vs acrylic expanders.

OBJECTIVES: To compare changes in upper arch dimension and molar inclination between Invisalign First (IF) and removable acrylic expander (RE) treatments during the mixed dentition period. MATERIALS AND METHODS: Seventeen patients meeting inclusion criteria underwent IF treatment and were age matched with a group that received treatment with a removable acrylic expander (RE). Intercanine width (ICW), intermolar width, arch depth, buccolingual inclination of the first molars (MI), surface area (SA) and volume (VAP) of the anterior palate, and expansion were compared before and after treatment. The predictability of expansion was calculated for the IF group. Analysis of variance and Kruskal-Wallis tests were used to assess differences. RESULTS: The ICW increased significantly by 2.14 mm in the IF group and 3.49 mm in the RE group, with no significant intergroup difference. Both groups exhibited significant increases in intermolar width (P < .05), except for intermolar distopalatal width in the IF group (P = .246). Mesiobuccal rotation of the first molar was observed with IF treatment. Although SA and VAP increased in both groups, the changes were not significant for the IF group (P > .05). The RE group exhibited significantly higher increases (P < .05), with an SA increase of 34.32 mm2 and VAP increase of 119.15 mm3. MI changes were in the opposite directions. The prediction accuracy of expansion was 70.28% for canines and 34.12% for first molars. CONCLUSIONS: Both appliances effectively expanded the intercanine region in growing patients. Expansion predictability was lower in first molars than in canines for the IF group. Removable acrylic expanders could be a choice of preference for expansion targeted to the molar region.

Effects of transpalatal arch wire dimension and temporary skeletal anchorage device position on maxillary molar intrusion.

OBJECTIVES: To investigate the effects of transpalatal (TPA) wire dimension and temporary skeletal anchorage device (TSAD) position on maxillary molar intrusion. MATERIALS AND METHODS: The maxillary molar intrusion measurement system included a maxillary acrylic model, TPA, TSADs, and a three-dimensional Force/Moment (F/M) sensor. The intrusion patterns were categorized into six groups: buccal-mesial, buccal-distal, buccal-mesiodistal, palatal-mesial, palatal-distal, and palatal-mesiodistal. TPA wire dimensions were designed to be 0.7 mm, 0.9 mm, and 1.2 mm. The force and moment loads of the maxillary first molar were measured by the F/M sensor. RESULTS: Single buccal or palatal TSADs induced torquing movement, and single mesial or distal TSADs tended to promote tipping movement. Mesiodistal TSADs would have eliminated tipping, but accentuated torquing movement. The TPA significantly reduced the force and moment experienced by the maxillary first molar along three-dimensional axes. The thicker the TPA wire, the smaller the force and moment to which the maxillary first molar was subjected. CONCLUSIONS: Precise placement of TSADs might have a substantial influence on tooth movement and should be determined in accordance with specific clinical requirements. Increasing the TPA wire dimension could diminish the tipping, torquing, and rotation during TSAD-assisted maxillary molar intrusion, but these tendencies could not be completely eliminated.

Inhibition of 12/15-lipoxygenase reduces orthodontically induced root resorption in rats.

OBJECTIVES: To investigate whether the inhibition of 12/15-lipoxygenase (12/15-LOX), one of the core enzymes of the arachidonic acid cascade, suppresses orthodontically induced root resorption (OIRR), and examine the involvement of the hyaline degeneration of periodontal ligament cells and odontoclast differentiation. MATERIALS AND METHODS: The left maxillary first molars of 10-week-old male Wistar rats were moved mesially for 14 days using a closed-coil spring (25 cN) inserted between the first molar and incisor. The rats were intraperitoneally administered with a 12/15-LOX specific inhibitor (ML-351; 0.05 mmol/kg) daily in the experimental group or vehicle (dimethyl sulfoxide) in the control group. Tooth movement was measured using microcomputed tomography on day 14. The appearance of OIRR, hyaline degeneration, osteoclasts, and odontoclasts was evaluated via histological analysis. Immunohistochemical staining for receptor-activated NF-kB ligand (RANKL) and osteoprotegerin was performed. RESULTS: OIRR observed on day 14 in the control group was strongly suppressed by ML-351 treatment. Hyaline degeneration observed on the compression side on day 3 and the appearance of osteoclasts and odontoclasts on days 3 and 14 were significantly suppressed by ML-351. RANKL expression on day 3 was significantly suppressed by ML-351. These key processes in OIRR were substantially suppressed by ML-351 treatment. CONCLUSIONS: Inhibition of 12/15-LOX reduced OIRR by suppressing hyaline degeneration and subsequent odontoclast differentiation.

Fluctuating arch symmetry: a comparison of two methods of assessment - applicability and efficiency.

INTRODUCTION: Symmetry is balance, some correspondence in the size, form, and arrangements of parts on opposite sides of a plane, line, or point. The opposite of this concept is asymmetry, or imbalance. OBJECTIVE: This retrospective study compared two methods for assessing arch symmetry with linear measurements based on triangles, to determine their applicability and efficiency. METHODS: Two groups were enrolled: children (n=20) and adults (n=20), and the arch symmetry was assessed from linear measurements. Method 1: the incisor-canine (INC), canine-molar (CM), and incisor-molar (INM) distances (paired t-test and Pearson correlation). Method 2: a mathematical equation between the cusps measurements of the canines and the distobuccal of the first molars leading to result 1 (t-test for one sample and bootstrapping analysis). Dental casts were digitized and analyzed using a software program. The Bland-Altman test compared the methods (α=0.05). RESULTS: The Bland-Altman test revealed concordance between the methods; however, separately the results were different: In method 1, the mandibular arch did not demonstrate correlation (children, INC r=0.33; CM r=0.45; INM r=0.51; adults, CM r=0.46; INM r=0.35), however, the maxilla revealed a strong correlation in children and a strong/moderate correlation in adults. In method 2, both arches were symmetrical (p>0.05). CONCLUSION: Method 1 may be appropriate during orthodontic treatment, and method 2 may be indicated for final treatment. These methods are useful; however, only method 1 identified the side of asymmetry. The methods can contribute to future studies in syndromic and non-syndromic patients, before and after orthognathic surgeries and orthodontic treatment, comparing results.

Onset and progression of dental erosion in a mouse model.

OBJECTIVE: Purpose of this research was to examine the onset, progression and wear rates of dental erosion in an established mouse model. MATERIAL AND METHODS: Dental erosion in mice was experimentally induced, and the acidic effects of cola drink on their teeth after 2, 4 and 6-weeks were closely analysed by scanning electron microscopy. The tooth height and enamel or dentin loss were established.  Results: The dental erosion on the molars showed clear progression from 2 to 6 weeks. By the 2-week mark, a significant portion of enamel was already eroded, revealing the dentin on the lingual cusps. When adjusted for attritional wear, molars exposed to cola for 2 weeks showed a 35% drop in lingual tooth height compared to controls (533 µm vs. 818 µm). At 4 and 6 weeks, the cola-exposed group continued to display decreased lingual tooth heights by 40% (476 µm vs. 799 µm) and 43% (440 µm vs. 767 µm), respectively. CONCLUSION: This study revealed significant acidic effects of cola drink on mouse molars as early as 2 weeks. These findings highlight the challenge of monitoring dental erosion clinically and underscore the importance of early preventive and intervention measures.