Investigação ex vivo do diâmetro anatômico do canal mesiopalatino de primeiros molares superiores humanos / Ex vivo investigation of the anatomical diameter of the mesiopalatal canal of human maxillary first molars

Objetivou-se investigar ex vivo o diâmetro anatômico e conicidade do canal mesiopalatino de primeiros molares superiores. Para tanto, trinta e três primeiros molares superiores humanos foram acessados, explorados para confirmação da existência do canal mesiopalatino, identificados, suas raízes mesiovestibulares seccionadas transversalmente em três níveis e, então, os fragmentos foram fotografados com microscópio digital, que permitiu a realização das determinações dos diâmetros anatômicos deste canal em cada amostra. Os resultados foram calculados em função dos valores médios e de desvio padrão dos diâmetros em cada nível, obtendo-se respectivamente 0,20 mm e ±0,09 mm (nível cervical), 0,20 mm e ±0,08 mm (nível médio) e 0,17 mm e ±0,06 mm (nível apical). Nas condições deste estudo, de acordo com caráter atrésico e baixa conicidade do conduto mesiopalatino, sugere-se a necessidade de uso de instrumentos de diâmetro de ponta mínimo de 0,25 mm e conicidade 0,03 para o seu preparo.

The aim was to investigate ex vivo the anatomical diameter and taper of the mesiopalatine canal of maxillary first molars. To this end, thirty-three human maxillary first molars were accessed, explored to confirm the existence of the mesiopalatine canal, identified, their mesiobuccal roots transversely sectioned at three levels and then the fragments were photographed using a digital microscope, which allowed the anatomical diameters of this canal to be determined in each sample. The results were calculated according to the mean and standard deviation values of the diameters at each level, obtaining 0.20 mm and ±0.09 mm (cervical level), 0.20 mm and ±0.08 mm (middle level) and 0.17 mm and ±0.06 mm (apical level) respectively. Under the conditions of this study, given the atresic nature and low taper of the mesiopalatine canal, it is suggested that instruments with a minimum tip diameter of 0.25 mm and a taper of 0.03 should be used for its preparation.

"Evaluation of Silver Diamine Fluoride Modified Atraumatic Restorative Treatment (SMART) on hypomineralized first permanent molar"- a randomized controlled clinical study.

BACKGROUND: Restoring first permanent molars affected with molar incisor hypomineralization (MIH) is challenging. Focusing on improving the quality of life for children affected by MIH, at least until the complete eruption of first permanent molars to receive full coverage, to decrease the hypersensitivity and to be able to perform proper oral hygiene measures, the purpose of this study was to compare silver modified atraumatic restorative technique (SMART) versus the conventional restoration and fluoride varnish application on moderate to severe hypomineralized molars. The comparison considered the restoration survival, hypersensitivity, and digital surface area changes after one year follow up. METHODS: Twenty-eight children were selected (20 girls and 8 boys) with at least 2 MIH molars with the same defect severity. The study comprised 2 groups; MOD group (moderate hypomineralized molar severity) and SEV group (Severe hypomineralized molar severity) (n = 28 tooth). Each group was further subdivided into 2 subgroups according to the technique of restoration: SMART subgroup and CONV subgroup (high viscosity glass ionomer restoration and fluoride varnish application) (each = 14 tooth). Evaluation was done in terms of the restoration survival (6 months and 12 months), hypersensitivity at 1 weak, 6 months and 12 months and occlusal surface area changes at 12 months). Professional Fluoride varnish application and home prophylaxis using MI paste were the protocol for each child patient. RESULTS: There was no significant difference between the 4 subgroups, regarding tooth restoration integrity at 6-months vs. 12-months. However, a statistically significant difference in tooth restoration integrity between the 4 subgroups at 12-months (P = .049). Also, the hypersensitivity score, there was a statistically significant difference between the 4-time intervals (P < .001) and a statistically significant difference in surface area changes between the 4 subgroups. CONCLUSIONS: Selective removal of carious tissue and SMART restoration, combined with dental home and professional preventive measures every 3 months maintained the integrity of restorations in severely and moderately affected permanent molars up to 1 year. TRIAL REGISTRATION: The study protocol was retrospectively registered on Clinical Trials (NCT05931822-05/ 07/2023).

Impact of refrigeration of different Resin composite restorative materials on the marginal adaptation in class II restorations.

BACKGROUND: The pre-polymerization temperature of resin composite restorative materials could influence their adaptation to cavity details. As a current debate is existing about the refrigeration of resin composite restorative materials, this study was designed to assess the effect of refrigeration of 3 types of resin composite restorative materials with different matrix systems on their marginal adaptation in Class II restorations. METHODS: Forty-two sound maxillary molars, each with two separated Class II cavities, were used in this study. The teeth were assigned into 3 main groups (n = 14) according to the restorative /adhesive system used; an Ormocer-based composite (Admira Fusion/Futurabond M+, Voco GmbH, Cuxhaven, Germany), a methacrylate modified Ormocer-based (Ceram.X SphereTEC One/Prime&Bond Universal, Dentsply Sirona GmbH Konstanz, Germany), and a methacrylate-based (Tetric N-Ceram/Tetric N-Bond Universal, Ivoclar Vivadent AG, Schaan, Liechtenstein). Each group was then divided into 2 subgroups (n = 14) according to the gingival margin location; 1 mm above and 1 mm below the cemento-enamel junction (C.E.J). Each subgroup was further divided into 2 categories (n = 7) according to the storage temperature; stored at room temperature or stored in refrigerator at 4°- 5° C. Epoxy resin replicas were observed under scanning electron microscope (SEM) to examine the marginal gaps. A gab scoring system was used to assess the marginal adaptation of each restoration by giving scores on the basis of measurements of the maximum marginal gaps. The data obtained were statistically analyzed using the Chi-square test at a significance level of p < 0.05. RESULTS: None of the tested groups exhibited 100% gap-free margins irrespective of margin location or storage temperature. For both storage temperatures, no statistically significant difference was observed among all tested groups either with margins located above or below C.E.J (p > 0.05). As well, there was no statistically significant difference when comparing both marginal locations for each material (p > 0.05). Regarding the effect of storage temperature, statistically significant difference was only observed between the room-temperature stored groups with margins located above C.E.J and their corresponding groups stored in refrigerator (p < 0.05). CONCLUSION: The refrigeration of resin composite restorative materials prior to the restorative procedures revealed a deleterious effect on marginal adaptation of the restorations with margins located in enamel regardless the type of material used.

Influence of curing mode and aging on the bonding performance of universal adhesives in coronal and root dentin.

BACKGROUND: This study aims to evaluate the microtensile bond strength (µTBS) of different resin composite restorations bonded to mid-coronal dentin and proximal root dentin using light-cured, chemical-cured, and dual-cured adhesives immediately and after aging. Nanoleakage and degree of cure were also assessed. METHODS: Eighty-four molars were divided into mid-coronal dentin and proximal root dentin. Each group was further subdivided into three subgroups based on the restorative systems used, which involved the utilization of light-cured, chemical-cured, and dual-cured adhesives. Half of the specimens underwent µTBS testing after 24 h, while the other half after aging. Representative specimens were analyzed for nanoleakage. The degree of cure of the tested adhesive systems was also assessed. RESULTS: Aging showed a significant negative effect on µTBS results and led to increased nanoleakage (p < 0.001). Furthermore, in all subgroups, the µTBS values of proximal root dentin were lower compared to mid-coronal dentin, except in the aged subgroup for the system utilizing the dual-cured adhesive. The restorative systems with chemical and dual-cured adhesives demonstrated comparable bonding properties. However, the system with the light-cured adhesive exhibited the worst bonding properties after aging when bonded to proximal root dentin and cured at a large distance (p < 0.05). CONCLUSIONS: All tested restorative systems were negatively affected by aging, and the regional dentin had variable effects on the bonding properties. Clinicians should exercise caution when using the tested light-cured adhesive in areas where the curing distance exceeds 3 mm.

In-vitro comparison of fracture resistance of CAD/CAM porcelain restorations for endodontically treated molars.

BACKGROUND: This study evaluates the fracture strength and patterns of feldspathic porcelain restorations made using CAD/CAM technology for lower first molars with extensive crown destruction. The restorations include post-core and full-contour crown, composite resin core and full-contour crown, and endocrown. This research provides insights into effective restorative options to address tooth fracture risk, supporting minimally invasive procedures and CAD/CAM integration in dental practices. METHODS: This study utilized 80 permanent mandibular first molars, which were divided into four groups: Group I (Post-Core-Full-contour crown), Group II (Core- Full-contour crown), Group III (Endocrown), and Group IV (Control). Root canal treatment was performed on all samples except for the control group. Following access cavity preparation, restorations for each tooth were fabricated using the CAD/CAM system and cemented with resin cement. The specimens were embedded in acrylic blocks. After undergoing thermomechanical aging, the samples were subjected to fracture resistance testing using a universal testing machine, which applied force until fracture occurred. The fracture patterns were subsequently analyzed, and the data were statistically evaluated using the Kruskal-Wallis and Chi-Square tests (p < 0.05). RESULTS: A significant difference in fracture values under axial forces was observed (p < 0.05). The control group had the highest fracture strength (1830 ± 277 N), while the Core- full-contour crown group showed the lowest (1532 ± 371 N). Failure types varied significantly among the groups (χ2 = 26.886, df = 9, p = 0.001). The most common failure type was Type-2 (33.75%), characterized by restorable fractures, while Type-3 fractures, unrestorable, were the least common (12.5%). CONCLUSIONS: The findings underscore the significance of technological advancements in CAD/CAM for effectively restoring endodontically treated teeth with extensive crown damage. This study contributes valuable insights, emphasizing the clinical relevance of selecting appropriate restorative options to mitigate the risk of tooth fracture associated with coronal restoration failures.

Effect of preparation design on fracture resistance of molars restored with occlusal veneers of different CAD-CAM materials: an in vitro study.

BACKGROUND: Occlusal veneer had been evaluated for mechanical properties using lithium disillicate. However, studies evaluating the mechanical properties of occlusal veneer with different preparation designs and ceramic materials are lacking. So, this in vitro study aimed to evaluate the fracture resistance of occlusal veneers with two designs fabricated from two different ceramic materials. MATERIAL AND METHODS: Fourty mandibular third molars were distributed to 2 groups (n = 20) according to preparation design: group (O) anatomical occlusal reduction and group (OA) anatomical occlusal and 1 mm axial reduction. Each group was additionally subdivided into two subgroups (n = 10) according to ceramic materials; in subgroup X, lithium disilicate (e.max CAD, Ivoclar AG, Schaan, Liechtenstein) was used, and in subgroup S, zirconia-reinforced lithium silicate (ZLS) (Vita Suprinity, VitaZahnfabrik, Bad Säckingen, Germany) was used. All specimens were cemented with a light-cure resin cement (Choice 2, Bisco, Schaumburg, USA). 5000 thermocycles were applied to all specimens with both temperatures of 5 °C and 55 °C in two water baths; the dwell time was 30s at each bath, and the transfer time was 10s. Then all specimens were subjected to a fatigue simulation under dynamic loading of 200 N for 250,000 cycles. A universal testing machine (5500R/1123, Instron, Norwood, USA) was used to evaluate the fracture strength with a crosshead speed of 1 mm/min. All data were analyzed statistically by using a two-way ANOVA, and for some violations of assumptions, these results were compared with those obtained by the nonparametric test (Scheirer Ray Hare) (α = 0.05). RESULTS: A statistically significantly higher fracture resistance in the 'OA' (3389 N) compared to the 'O' (2787 N) group regardless of the ceramic material (P < .001) and a statistically significantly higher fracture resistance in the 'X' (3295 N) compared to the 'S' (2881 N) regardless of the preparation design (P = .015). CONCLUSIONS: For occlusal veneers, all preparation designs and materials (such as Vita Suprinity and e.max CAD) had clinically acceptable fracture resistance values that were greater than the maximal biting forces. On the other hand, the e.max CAD with occlusal veneer, including axial reduction design, demonstrated the maximum fracture resistance value. Finally, no relationship between fracture strength and mode of failure was found.

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).

Skeletal effects of posterior crossbite treatment with either quad helix or rapid maxillary expansion: a randomized controlled trial with 1-year follow-up.

OBJECTIVES: To assess skeletal and dental effects and evaluate possible side effects of maxillary expansion with two different appliances, directly after expansion and 1 year postexpansion. MATERIALS AND METHODS: Forty-two patients with unilateral posterior crossbite (mean 9.5 ± 0.9 years) were randomized to either rapid maxillary expansion (RME) banded on the deciduous second molars and bonded to the primary canines or slow expansion with quad helix (QH) on the permanent first molars. Cone-beam computed tomography records were taken at baseline, directly after correction of the posterior crossbite and at follow-up 1 year after expansion. RESULTS: All patients were analyzed. RME opened the midpalatal suture more anteriorly and inferiorly (mean 4.1 mm) and less posteriorly and superiorly (mean 1.0 mm). No effect on midpalatal suture could be shown in the QH group after expansion, P < .001. Buccal bone width had significantly decreased (P < .001) in the QH group compared with the RME group. Buccal fenestrations and root resorption on the left first molar had a higher prevalence directly after expansion finished in the QH group (P = .0086, P = .013) but were not significant at 1-year follow-up (P = .11, P = .22). CONCLUSIONS: Opening of the suture with RME was more anterior and inferior, and the QH did not open the midpalatal suture at all. More buccal bone loss and fenestrations were seen on the permanent first molar in patients treated with conventional QH than RME anchored to deciduous teeth.

Evaluation of anchorage loss after en masse retraction in orthodontic patients with maxillary protrusion using friction vs frictionless mechanics: randomized clinical trial.

OBJECTIVES: To evaluate anchorage loss after en masse retraction in bimaxillary dentoalveolar protrusion patients using friction vs frictionless mechanics. MATERIALS AND METHODS: Thirty patients with bimaxillary dentoalveolar protrusion needing extraction of upper first premolars and en masse retraction with maximum anchorage were included in this two-arm, parallel, single-center, single-blinded randomized clinical trial with a 1:1 allocation ratio using fully sealed opaque envelopes. Friction group retraction utilized elastomeric power chain between miniscrews and hooks crimped mesial to upper canines on 17 × 25 stainless steel archwire. Frictionless group used customized T-loop springs loading upper first molars indirectly anchored to miniscrews. Activation was every 4 weeks until full retraction. The primary outcome assessed was anchorage loss evaluated at cusp tip and root apex of the first molar. First molar rotation, incisor tip and torque, and root resorption of anterior teeth were evaluated on digital models and cone beam computed tomography taken before and after space closure. RESULTS: Anchorage loss at crown of first molar was significantly more in frictionless group by 2.1 mm (95% CI = -0.4 to 3.5), (P = .014), while there was no significant difference in anchorage loss at root apex between groups. Significant mesial in molar rotation of 6.672° (95% CI = 12.2-21.2), (P = 0.02) was greater in the frictionless group. Both groups showed comparable tip, torque, and root resorption values. No severe harms were reported. There was mild gingival overgrowth and inflammation in the frictionless group due to T-loop irritation. CONCLUSIONS: Extra anchorage considerations are needed during en masse retraction when frictionless mechanics is implemented as higher anchorage loss and molar rotation were detected. No difference in tip, torque, and root resorption was observed.

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.

The effects of fulvic acids and low-level laser therapy on orthodontic retention in rats.

BACKGROUND: Shortening retention time and minimizing relapse rates are ongoing challenges in orthodontics. This study investigated the effects of natural fulvic acids (FAs) and low-level laser therapy (LLLT) on orthodontic retention in rats. METHODS: Seventy-two male Sprague-Dawley rats underwent mesial movement of the left maxillary first molar using a 50 g force via a nickel-titanium tension spring. After three weeks of movement, the rats entered the retention phase with retainer wires and were divided into four groups: Control (no intervention), FAs (80 mg/kg orally daily), LLLT (808 nm laser twice weekly), and FAs + LLLT (both treatments). Retainers were removed on days 7, 14, and 21 for a 3-day relapse assessment. Maxillary impressions were analyzed for relapse rates using 3Shape software, alongside histological and immunohistochemical evaluations of bone morphogenetic protein-2 (BMP-2) expression in periodontal tissues, with differences among groups analyzed using an ordinary two-way analysis of variance (ANOVA). RESULTS: The relapse rate decreased over time, particularly at 10, 17, and 24 days (p < 0.001). The FAs group did not significantly affect relapse rates compared to the control group (p = 0.084). In contrast, both the LLLT and FAs + LLLT groups significantly reduced relapse rate (p < 0.001), with no significant difference between these groups (p = 0.555). Histological examination revealed active osteoclasts on day 10, decreasing by days 17 and 24. The LLLT and FAs + LLLT groups showed less local cementum resorption and better periodontal fiber arrangement. All treatment groups significantly increased BMP-2 expression (P < 0.05) compared to controls. with LLLT and FAs + LLLT differing significantly from FAs (P < 0.001), though no difference was observed between LLLT and FAs + LLLT (P = 0.578). CONCLUSIONS: FAs did not significantly reduce relapse rate with retainers, while LLLT effectively reduced relapse rates, showing no additional benefit from combining FAs with LLLT. Both FAs and LLLT increased BMP-2 expression in PDL fibroblasts but with no synergistic effect.

Evaluation of Stresses Generated with Two Different Self-Ligating Orthodontic Bracket Systems - A Finite Element Analysis.

AIM: To determine stresses generated in the posterior teeth region by two different self-ligating systems, 3M Unitek SmartClip and Damon Q Self-ligating brackets, using the finite element method (FEM). METHODOLOGY: Computed tomography (CT) scan of maxilla was taken using Mimics software, and the Dicom data were imported into Hypermesh 13.0 software to convert it into a geometric model and then into FEM. Physical models of both the brackets were constructed and positioned on the teeth. Post archwire modeling, contact is defined between the bracket slot and 0.014" NiTi arch wire. The final assembled model was exported to ANSYS 12.1 for analysis, and 60 grams of load was applied at the ends of the arch wire. RESULTS: On using 0.014" CuNiTi in both the bracket systems, stresses generated on the root surface were found to be maximum on the first molar region, followed by the first premolar, second molar, canine, and second premolar regions. Comparison between the two bracket systems showed differences in the stresses generated, where higher stresses were generated at all regions in the Damon Q bracket system, except the inter-second premolar region. CONCLUSION: Maximum stresses were observed with the 3M Unitek SmartClip bracket system at the second premolar cervical region when compared to the Damon Q system. In both the cortical bone and cancellous bone, maximum stresses were observed at the second premolar cervical in the Damon Q bracket system region.

Microleakage of Class II Posterior Composite Restorations with and Without use of Liners - A Comparative Study.

AIM: This study aims to compare the effect of liner on microleakage in Class II restorations at the occlusal and gingival levels when restored with a nanocomposite. METHODOLOGY: A total of 60 mandibular molars were selected and divided into three groups. Cavities in Group A were restored with posterior nanocomposite without liner, samples of Group B were restored with posterior nanocomposite with flowable composite liner and in Group C samples were restored with posterior nanocomposite with resin-modified glass ionomer cement (RMGIC) liner. Samples were stored at 37°C in 100% humidity for 14 days. Samples were subsequently immersed in 0.5% methylene blue dye and then placed under water for 15 mins. Teeth were sectioned mesiodistally with a diamond disc and examined under a stereomicroscope. RESULTS: All the cavities exhibited dye penetration along the occlusal and gingival margins of the restored cavities. Group A showed maximum leakage compared to Groups B and C, which was statistically significant ( P = 0.001 and P < 0.0001). No significant difference in microleakage was observed between Groups B and C. Microleakage was more in gingival margins as compared to occlusal margins in all the groups. CONCLUSION: Based on the results of the present study, it may be concluded that the placement of liner beneath nanocomposite restoration results in a significant reduction in microleakage.

Cone beam computed tomography analysis of the root and canal morphology of the maxillary second molars in a Syrian subpopulation.

AIM: To investigate the root number and morphology of the maxillary second molars in the Syrian population besides bilateral symmetry, and the effect of gender. METHODS: 250 Cone Beam Computed Tomography (CBCT) images (140 females, 110 males) were examined by two endodontists. The detailed analysis included the number of roots, the number of canals and their configurations, bilateral symmetry, and relation to gender. The evaluation was made according to Vertucci classification by analyzing the CBCT images at all levels (Axial, Coronal, Sagittal, Oblique, and 3D). The Chi-square statistical analysis was performed to compare the canals' morphologies and bilateral symmetry in both genders via SPSS. RESULT: The most common shape of the upper second molars is three roots (90.4%). There were significant differences between males and females regarding the symmetry of the number of roots (P < 0.05). The root canal configuration was mainly Vertucci type I classification in the Distobuccally (93.4%) and palatal root (99.6%). The most common type in the mesial root was type I (29.5%), showing all varieties of Vertucci classifications (except VII, and VIII) percentage of MB2 of 70.5%. The ratio of symmetry was (59.6%) with no significant statistical difference between the genders (P = 0.708). CONCLUSION: Most maxillary second molars in the examined Syrian population were types (II) (associated with MB2 cases with three roots and four canals). In terms of symmetry, the number of roots surpassed the canal configuration. Males had a greater symmetrical tendency in the number of roots than females.

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.

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.