Bacterial sealing ability of calcium silicate-based sealer for endodontic surgery: an in-vitro study.

BACKGROUND: Apical surgery with standard retrograde maneuvers may be challenging in certain cases. Simplifying apical surgery to reduce operating time and streamline retrograde manipulation is an emerging need in clinical endodontics. AIM OF THE STUDY: The aim of the study was to compare the bacterial sealing ability of a calcium silicate-based sealer with the single cone technique combined with root end resection only, and calcium silicate-based sealer as a retrograde filling versus MTA retrofilling, and to analyze bacterial viability using confocal laser scanning microscope (CLSM). MATERIALS AND METHODS: In this in vitro experimental study, 50 extracted human maxillary incisor teeth were instrumented and randomly divided into five groups: three experimental groups, a positive control group, and a negative control group (n = 10/group). In the experimental groups, the roots were obturated using the single cone technique (SCT) and a calcium silicate-based sealer. In group 1, the roots were resected 3 mm from the apex with no further retrograde preparation or filling. In groups 2 and 3, the roots were resected, retroprepared, and retrofilled with either a calcium silicate-based sealer or MTA, respectively. Group 4 (positive control) was filled with a single gutta-percha cone without any sealer. In group 5 (negative control), the canals were left empty, and the roots were sealed with wax and nail varnish. A bacterial leakage model using Enterococcus faecalis was employed to assess the sealing ability over a 30-day period, checking for turbidity and analyzing colony forming units (CFUs) per milliliter. Five specimens from each group were examined using CLSM for bacterial viability. Data for the bacterial sealing ability were statistically analyzed using chi-squared and Kruskal-Wallis tests. RESULTS: The three experimental groups did not show significant differences in terms of bacterial leakage, or bacterial counts (CFUs) (P > 0.05). However, significant differences were observed when comparing the experimental groups to the positive control group. Notably, the calcium silicate-based sealer, when used as a retrofilling, yielded the best sealing ability. CLSM imaging revealed viable bacterial penetration in all the positive control group specimens while for the experimental groups, dead bacteria was the prominent feature seen. CONCLUSION: Within the limitations of this study, it could be concluded that the bacterial sealing ability of calcium silicate-based sealer with the single cone technique combined with root end resection only and calcium silicate-based sealer as a retrograde filling were comparable with MTA retrofilling during endodontic surgical procedures.

Accuracy of Invisalign® aligners in adult patients: a retrospective study of angular tooth movements.

OBJECTIVE: This retrospective study aimed to assess the predictability of Invisalign® aligners regarding rotational, mesio-distal and buccal-lingual tip movements. METHODS: Two materials were included in the analysis - EX30, used until 2013; and SmartTrack, in current use. The study comprised 56 adult patients treated with Invisalign Comprehensive. Data sample were assessed on three sets of digital models; model 1 - initial, model 2 - predicted, and model 3 - achieved. Sixty reference points were marked in each dental arch, and two reference planes assisted the superimposition. The degree of rotation, mesio-distal and buccal-lingual tip was obtained via trigonometric calculations, through a previously published validated method. The accuracy of outcomes was compared according to the types of tooth movement and teeth groups,and the influence of predetermined variables on movement accuracy was also investigated. RESULTS: Rotation and mesio-distal tip did not present any significant difference when comparing EX30 and SmartTrack groups. Only buccal-lingual tip presented a significant difference, incisor and canine groups treated with EX30 aligners presented an increase in accuracy (p= 0.007 and p = 0.007, respectively). For each additional degree planned for rotation movements, there was an increase of 0.35° in the discrepancy, and an increase of 0.40° and 0.41° for mesio-distal and buccal-lingual tip, respectively. EX30 and SmartTrack discrepancies were compared by multilevel linear regression. CONCLUSION: EX30 aligners reached higher accuracy for buccal-lingual tip in anterior teeth. However, for rotation and mesio-distal tip, SmartTrack and EX30 are similarly accurate. The total amount of planned movement has a significant impact on accuracy rates, with a decrease in accuracy for every additional degree.

Microhardness Measurements on Tooth and Alveolar Bone in Rodent Oral Disease Models.

The mechanical property, microhardness, is evaluated in dental enamel, dentin, and bone in oral disease models, including dental fluorosis and periodontitis. Micro-CT (µCT) provides 3D imaging information (volume and mineral density) and scanning electron microscopy (SEM) produces microstructure images (enamel prism and bone lacuna-canalicular). Complementarily to structural analysis by µCT and SEM, microhardness is one of the informative parameters to evaluate how structural changes alter mechanical properties. Despite being a useful parameter, studies on microhardness of alveolar bone in oral diseases are limited. To date, divergent microhardness measurement methods have been reported. Since microhardness values vary depending on the sample preparation (polishing and flat surface) and indentation sites, diverse protocols can cause discrepancies among studies. Standardization of the microhardness protocol is essential for consistent and accurate evaluation in oral disease models. In the present study, we demonstrate a standardized protocol for microhardness analysis in tooth and alveolar bone. Specimens used are as follows: for the dental fluorosis model, incisors were collected from mice treated with/without fluoride-containing water for 6 weeks; for ligature-induced periodontal bone resorption (L-PBR) model, alveolar bones with periodontal bone resorption were collected from mice ligated on the maxillary 2nd molar. At 2 weeks after the ligation, the maxilla was collected. Vickers hardness was analyzed in these specimens according to the standardized protocol. The protocol provides detailed materials and methods for resin embedding, serial polishing, and indentation sites for incisors and alveolar. To the best of our knowledge, this is the first standardized microhardness protocol to evaluate the mechanical properties of tooth and alveolar bone in rodent oral disease models.

Immediate implant placement in a dialysis patient. A case report.

Implant-supported rehabilitation in high-risk patients poses significant challenges for the dental team. The presence of comorbidities and increased infection risk can, for example, lead to a higher risk of implant loss. For the therapy to be completed with as few complications as possible, special anamnesis, detailed diagnostics, and a risk analysis based on those findings are indispensable. The aim of all considerations is to keep the risk of infection for the patient with a disease history to a minimum and to strive for an appropriate functional and esthetic therapeutic success. Particularly in the esthetic zone, in addition to the general health risks of the surgical procedure, esthetic aspects are increasingly taken into account in planning. The present article describes the implant-prosthetic replacement of a single anterior tooth in a dialysis patient. Several aspects (regular dialysis, missing buccal lamella, high smile line, functional risk) increased the risk of complications in this case.

Advanced digital planning approach using a 3D-printed mock-up. A case report.

OBJECTIVE: A diagnostic mock-up is a key tool that allows a preview of the outcome of an esthetic restoration. With recent developments in CAD/CAM technology, it is important to understand the pros and cons of chairside digital dentistry and the restorative materials used. The aim of the present case report is to describe in detail the use of a 3D-printed mock-up fabricated from a polymer-based material for an esthetic treatment plan within a fully digital workflow. CASE REPORT: A 45-year-old female patient presented at the clinic concerned about her esthetic appearance and the color of her anterior incisors. After a conclusive diagnosis, a restoration was planned using ceramic veneers from maxillary premolar to premolar. For a preview visualization of the outcome, an intraoral scanner was used to obtain 3D images and to allow the design of a digital smile. The template STL file was exported to a 3D printer and a 0.6-mm mock-up in A3-shade 3D resin was produced after 25 min. The mock-up was tested through a try-in and approved by the patient. As a result, the printed mock-up was considered predictable and reliable for the final restoration. CONCLUSIONS: The ease, speed, and reduced costs derived from the digital workflow, in conjunction with the accuracy of the mock-up, made the procedure highly efficient and recommendable.

Comparison of treatment effects between clear aligners and fixed appliances in patients treated with miniscrew-assisted molar distalization.

OBJECTIVES: The biomechanics in achieving molar distalization may differ between fixed appliances and clear aligners in the control of tooth movement. The objective of this study was to compare the treatment effects between clear aligners (CA) and fixed appliances (FA) in patients treated with miniscrew-assisted molar distalization. METHODS: The sample consisted of 46 subjects with mild-to-moderate crowding. A total of 22 patients treated with clear aligners (age, 25.66 ±â€…6.11 years old) and 24 patients treated with fixed appliances (age, 24.04 ±â€…4.95 years old) for miniscrew-assisted molar distalization were included in this study. The dental and skeletal changes were evaluated by the pre- and post-treatment lateral cephalograms. RESULTS: Significant changes were found with the vertical variables SN-OP angle (2.24 ±â€…3.22°, P < .05) and SN-MP angle (0.73 ±â€…1.15°, P < .05) for the FA group when compared with the CA group (SN-OP angle 0.41 ±â€…2.26° and SN-MP angle -0.21 ±â€…1.38°, P > .05). Both treatment groups achieved a 2-3 mm. molar distalization with significant intrusion of the upper molars. The CA group showed significantly less distal tipping of molars (U6^PP angle -2.29 ±â€…3.29° and L6^MP angle -2.92 ±â€…2.49°, P < .05) compared to the FA group (-5.24 ±â€…4.28° and -5.53 ±â€…5.03°, P < .05). In addition, significant retraction and lingual inclination of the upper and lower incisors were found in both groups. LIMITATIONS: The changes of tooth position were evaluated by 2D lateral cephalograms, not 3D measurements. CONCLUSIONS: Compared to fixed appliances, clear aligners seemed to have better control of vertical dimension and distal tipping of molars in patients treated with miniscrew-assisted molar distalization.

Fracture resistance and failure mode of three esthetic CAD-CAM post and core restorations.

BACKGROUND: The rising demand for improved aesthetics has driven the utilization of recently introduced aesthetic materials for creating custom post and core restorations. However, information regarding the fracture resistance of these materials remains unclear, which limits their practical use as custom post and core restorations in clinical applications. AIM OF THE STUDY: This study aimed to evaluate the fracture resistance of three non-metallic esthetic post and core restorations and their modes of failure. MATERIALS AND METHODS: Thirty-nine single-rooted human maxillary central incisors were endodontically treated. A standardized post space preparation of 9mm length was performed to all teeth to receive custom-made post and core restorations. The prepared teeth were randomly allocated to receive a post and core restoration made of one of the following materials (n=13): glass fiber-reinforced composite (FRC), polyetheretherketone (PEEK) and polymer-infiltrated ceramic-network (PICN). An intraoral scanner was used to scan all teeth including the post spaces. Computer-aided design and computer-aided manufacturing (CAD-CAM) was used to fabricate post and core restorations. Post and core restorations were cemented using self-adhesive resin cement. All specimens were subjected to fracture resistance testing using a universal testing machine. Failure mode analysis was assessed using a stereomicroscope and SEM. The data was statistically analyzed using One-Way ANOVA test followed by multiple pairwise comparisons using Bonferroni adjusted significance level. RESULTS: Custom PEEK post and core restorations displayed the least fracture load values at 286.16 ± 67.09 N. In contrast, FRC exhibited the highest average fracture load at 452.60 ± 105.90 N, closely followed by PICN at 426.76 ± 77.99 N. In terms of failure modes, 46.2% of specimens with PICN were deemed non-restorable, while for PEEK and FRC, these percentages were 58.8% and 61.5%, respectively. CONCLUSIONS: Within the limitation of this study, both FRC and PICN demonstrated good performance regarding fracture resistance, surpassing that of PEEK.

Laboratory study of fracture resistance and failure mode of porcelain laminate veneers with different preparation depths in endodontically treated teeth.

PURPOSE: To compare the fracture resistance and failure mode of porcelain laminate veneers with different preparation depths in endodontically treated teeth. METHODS: Root canal treatment was performed for 40 maxillary central incisors, and then the teeth were divided into four groups (n= 10). The preparation depths were as follows: Group A: 0.9 mm, Group B: 0.6 mm, Group C: 0.3 mm, and in all three groups, 2 mm butt joint incisal reductions were performed; Group D was a control group with no preparation. Then 30 lithium disilicate porcelain veneers were milled by CAD- CAM method and cemented. After that, all specimens were subjected to cyclic loading and thermal cycling and finally were tested by a universal testing machine until failure occurred. RESULTS: The mean failure loads (N) after exposure to continuous load were as follows: Group A: 625.70 (401.45-1037.77), Group B: 780.32 (222.93-1391.82), Group C: 748.81 (239.68-1241.87) and Group D (control) : 509.88 (84.42-1025.85) and P= 0.216. Analysis of failure mode in four groups showed that P= 0.469. There was no significant difference between the control and the other groups. In this study, 0.3, 0.6 and 0.9 mm depths of preparation for porcelain laminate veneers for endodontically treated teeth had no significant difference in fracture resistance and failure mode with non-prepared teeth. CLINICAL SIGNIFICANCE: Reasonable consideration might be given to porcelain laminate veneer treatment for teeth that have become discolored and resistant to bleaching (such as instances where discoloration is severe following root canal treatment). This approach is considered to be on the conservative side, and has demonstrated that a labial preparation depth reduction of up to 0.9 mm does not have any impact on the failure mode or fracture resistance of endodontically-treated teeth.

Patient-reported outcomes during accelerating the en-masse retraction of the upper anterior teeth using low-intensity electrical stimulation: a randomized controlled trial.

BACKGROUND: Low-intensity electrical stimulation (LIES) is considered a relatively recent technology that has received little attention in orthodontics as a method of acceleration. This study aimed to evaluate patient-reported outcome measures when LIES is used to accelerate the en-masse retraction of the upper anterior teeth. MATERIALS AND METHODS: The sample consisted of 40 patients (8 males, 32 females; mean age 21.1 ± 2.3 years), with Class II division I malocclusion who required extraction of the first premolars to retract upper anterior teeth. They were randomly assigned to the LIES group (n = 20) and the conventional en-masse retraction group (CER; n = 20). Patient responses regarding pain, discomfort, burning sensation, swelling, chewing difficulty, speech difficulty, and painkillers' consumption were recorded at these nine assessment times: 24 h (T1), 3 days (T2), and 7 days (T3) after force application, then in the second month after 24 h (T4), 3 days (T5), and 7 days (T6) of force re-activation, and finally after 24 h (T7), 3 days (T8), and 7 days (T9) of force re-activation in the third month. RESULTS: The mean values of pain perception were smaller in the LIES group than those in the CER group at all assessment times with no statistically significant differences between the two groups except during the second and third months (T5, T6, T8, and T9; P < 0.005). However, discomfort mean values were greater in the LIES group with significant differences compared to CER group during the first week of the follow-up only (T1, T2, and T3; P < 0.005). Burning sensation levels were very mild in the LIES group, with significant differences between the two groups at T1 and T2 only (P < 0.001). Speech difficulty was significantly greater in the LIES group compared to CER group at all studied times (P < 0.001). High levels of satisfaction and acceptance were reported in both groups, without any significant difference. CONCLUSION: Both the LIES-based acceleration of en-masse retraction of upper anterior teeth and the conventional retraction were accompanied by mild to moderate pain, discomfort, and chewing difficulty on the first day of retraction. These sensations gradually decreased and almost disappeared over a week after force application or re-activation. TRIAL REGISTRATION: ClinicalTrials.gov, ClinicalTrials.gov, NCT05920525. Registered 17 June 2023 - retrospectively registered, http://clinicaltrials.gov/study/NCT05920525?term=NCT05920525&rank=1 .

Alveolar bone retention following treatment of dilacerated labial inversely impacted maxillary central incisors-a retrospective study.

The root of late-dental-age labial inversely impacted maxillary central incisors (LIIMCIs) typically develops to severe dilacerated morphology. Therefore, reliable posttreatment periodontal estimates of orthodontic treatment prognosis would be critical to the treatment value of impacted incisors. This study aims to analyze further changes in dimensions of the alveolar bone following the closed-eruption treatment of late-dental-age dilacerated LIIMCIs. Cone beam computed tomography (CBCT) scanning data of 16 patients with unilateral dilacerated late-dental-age LIIMCIs were collected, including the pretreatment (T1) and at the 2.23 ± 0.78 years follow-up stage (T2) respectively. Patients underwent closed-eruption treatments to bring the impacted incisor into the dental arch. Dolphin imaging software was used to measure alveolar bone height labially, palatally, and proximally to the site at T1 and T2, as well as alveolar bone thicknesses at 0, 2, 4, 6 and 8 mm below the initial measurement plane (IMP). The alveolar bone heights on the impacted and contralateral sides increased from T1 to T2 (p < 0.05). Alveolar bone growth on both sides had no significant difference. In T2, the mean values of labial and distal alveolar heights on the contralateral sides were greater than on the impacted sides (p < 0.05). The mean values of total alveolar bone thicknesses on the impacted sides in T1 were significantly smaller than those on the contralateral sides in IMP-0, 2, 4, 6, 8 (p < 0.05). The total thicknesses on the impacted sides in T2 increased and were significantly greater than on the contralateral sides (p < 0.05), except for the thickness in IMP-0. The closed-eruption treatment of dilacerated late-dental-age LIIMCIs results in no significant changes to alveolar bone height, except on the labial and distal sides, with increased alveolar bone thickness, suggesting that this approach may be viable first choice therapy for non-extraction orthodontic cases.

Deciduous pulp tissue implantation into the root canal of mandibular incisor resulted in pulp revascularization: a case report with a 5-year follow-up.

To explore a new method to implant deciduous tooth pulp into the canal of young permanent teeth with necrotic pulps and apical periodontitis for the regenerative endodontic treatment of tooth no: 41 in a 7-year-old male. Briefly, 1.5% Sodium Hypochlorite (NaOCl) irrigation and calcium hydroxide-iodoform paste were used as root canal disinfectant at the first visit. After 2 weeks, the intracanal medication was removed, and the root canal was slowly rinsed with 17% Ethylene Diamine Tetraacetic Acid (EDTA), followed by flushing with 20 mL saline and then drying with paper points. Tooth no: 72 was extracted, and its pulp was extracted and subsequently implanted into the disinfected root canal along with induced apical bleeding. Calcium hydroxide iodoform paste was gently placed over the bleeding clot, and after forming a mineral trioxide aggregate (MTA) coronal barrier, the accessed cavities were restored using Z350 resin composite. The root developments were evaluated via radiographic imaging at 6 months, 1 year and 5 years after treatment. Imaging and clinical analysis showed closure of the apical foramen, thickening of the root canal wall, and satisfactory root length growth. Autologous transplantation might be useful to regenerate dental pulp in necrotic young permanent teeth.

Analysis of prefabricated myofunctional appliances with different overjet and bumper designs: a three-dimensional finite element analysis.

BACKGROUND: Prefabricated myofunctional appliance can guide tooth eruption, improve dentition alignment, correct myofunctional disorders and harmful oral habits. However, its application to skeletal discrepancy may result in unsatisfactory tooth inclination. This study aimed to construct a novel appliance with overjet design to avoid this side effect and investigated its shape and mechanical changes under occlusion using three-dimensional finite element method. METHODS: We established three samples of prefabricated myofunctional appliances. The first one was edge to edge without overjet, and the outer shield of both jaws were flattened. The second one was 3 mm overjet with stepped the outer shield. The last one was 3 mm overjet, and the outer shield of both jaws were flatted, which meant the front wall of lower jaw was strengthened with bumper, termed as lower bumper. A complete dentition model was applied to the study. 150 N occlusal force was applied to each type of appliance and the deformation displacement and the changes in stress was recorded. RESULTS: The deformation was significant in the incisors regions, especially in the vertical and lateral dimensions. The maximum displacements of 3 mm overjet with step shield group were 7.08 mm (vertical), 3.99 mm (lateral), and 2.90 mm (sagittal), while it decreased to 3.92 mm(vertical), 1.94 mm (lateral), and 1.55 mm (sagittal) in overjet with bumper group. Moreover, the upper molar regions exhibited higher vertical and sagittal displacement in 3 mm overjet with step shield group, which were 3.03 mm (vertical) and 1.99 mm (sagittal), and the bumper design could decrease the maximum displacement to 1.72 mm (vertical) and 0.72 mm (sagittal). In addition, the Von Mises stress of appliances was analyzed, and results indicated that 3 mm overjet with step shield generated higher stress than other groups, with the maximum Von Mises stress was 0.9387 MP, which were 0.5858 and 0.5657 MP in edge to edge group and 3 mm overjet with lower bumper group, respectively. CONCLUSION: The prefabricated myofunctional appliances may cause deformation during occlusion. Compared to step shield group, the application of lower bumper exhibited better resistance to occlusal force.

Influence of maternal cholesterol-enriched diet on chemical composition of teeth enamel in offspring of mice.

OBJECTIVE: Aim: To determine the chemical composition of the tooth enamel of two-day-old mice from hypercholesterolemic mothers by energy dispersive X-ray spectroscopy. PATIENTS AND METHODS: Materials and Methods: Forty mature female mice were randomly assigned (n = 20/group) to either a standard chow vivarium diet (control group) or a cholesterol-enriched chow diet (experimental group). After fertilization, pregnancy and birth, on postnatal day 2, the incisor segments of 6 pups form each group were used for energy dispersive X-ray spectroscopy. RESULTS: Results: Influence of maternal hypercholesterolemic diet on tooth development and mineralization was examined, which revealed changes in enamel chemical composition. First, the results indicate the presence of seven elements (Na, Cl, Ca, P, Mg, S, Fe) in the enamel of both the hypercholesterolemic and normal offspring, but the content of element Ca2+ decreased, the content of elements P5+, Na+, Cl- tended to increase in pups from hypercholesterolemic mice. Second, the initial level of mineralization according to the atomic (%) Ca / P in hypercholesterolemic pups ratio was 1.26, comparing with normal pups where level of mineralization was 1.34. Taking into account that irreversible changes in the structure of the enamel were observed when the Ca / P ratio was below 1.33, we can suggest that the eruption of teeth with an imperfect structure could be because of maternal hypercholesterolemic diet. CONCLUSION: Conclusions: Results of this study suggest that hypercholesterolemic diet during gestation and lactation leads to altered enamel mineralization in mice because of changes in chemical composition and may link to the early childhood caries.

Proliferation-driven mechanical compression induces signalling centre formation during mammalian organ development.

Localized sources of morphogens, called signalling centres, play a fundamental role in coordinating tissue growth and cell fate specification during organogenesis. However, how these signalling centres are established in tissues during embryonic development is still unclear. Here we show that the main signalling centre orchestrating development of rodent incisors, the enamel knot (EK), is specified by a cell proliferation-driven buildup in compressive stresses (mechanical pressure) in the tissue. Direct mechanical measurements indicate that the stresses generated by cell proliferation are resisted by the surrounding tissue, creating a circular pattern of mechanical anisotropy with a region of high compressive stress at its centre that becomes the EK. Pharmacological inhibition of proliferation reduces stresses and suppresses EK formation, and application of external pressure in proliferation-inhibited conditions rescues the formation of the EK. Mechanical information is relayed intracellularly through YAP protein localization, which is cytoplasmic in the region of compressive stress that establishes the EK and nuclear in the stretched anisotropic cells that resist the pressure buildup around the EK. Together, our data identify a new role for proliferation-driven mechanical compression in the specification of a model signalling centre during mammalian organ development.

Volumetric Analysis of Peri-implant Tissue Change Over Time: Validating an Innovative 3D Method.

PURPOSE: To validate an innovative 3D volumetric method of evaluating tissue changes proposed by Lee et al in 2020 by comparing the results of this method-in which the scanned peri-implant surfaces were transformed, visualized, and analyzed as 3D objects-to the results reported by an existing method based on calculation of the mean distance between measured surfaces. The null hypothesis was that there was no statistically significant difference between the two methods. Additionally, the present study evaluated peri-implant tissue changes 5 years after single implant placement in the esthetic zone. MATERIALS AND METHODS: Both methods were applied to 11 oral implant site casts (6 maxillary central incisor sites, 5 maxillary lateral incisor sites) taken from 11 patients at crown placement and at follow-up examinations 5 years later. The methods are based on digital workflows in which the reference and 5-year casts are scanned and the resulting STL files are superimposed and analyzed for three regions of interest (mesial papilla, central area, and distal papilla). The volumetric changes reported by the Lee et al method and the mean distance method were calculated and compared using the Spearman rank correlation coefficient (P < .01) and the Wilcoxon signed-rank test (P < .05). RESULTS: The correlation between the two sets of measurements was very high (Spearman rank correlation coefficient = 0.885). The new volumetric method indicated a mean volume loss of 2.82 mm3 (SD: 5.06), while the method based on the measurement of mean distance showed a mean volume loss of 2.92 mm3 (SD: 4.43; Wilcoxon signed-rank test result: P = .77). No statistically significant difference was found. The two methods gave equivalent results, and the null hypothesis was accepted. CONCLUSIONS: The new volumetric method was validated and can be considered a trustworthy tool.

Radiological, histological and clinical side effects of incisor trimming in rabbits.

INTRODUCTION: Incisor malocclusion in rabbits (Oryctolagus cuniculus) is a common clinical problem seen in general practice. Given that the growth rate is about 2 mm per week, a lack of wear quickly leads to feeding difficulties and soft tissue injuries. Therefore, pathologically elongated incisors must be shortened every three to six weeks. The goal of this study was to assess the potential adverse effects on dental and periodontal tissues associated with the three most commonly used trimming methods: nail cutter, diamond-coated cutting disc and diamond burr. The left mandibular incisor of 28 healthy New Zealand rabbits was subjected to four trimmings with one of the three cutting methods. After the fattening period, the mandibles were collected and both mandibular incisors were investigated on dental radiographs, micro-computed tomography scans and histological sections. Dental and periodontal tissue changes were evaluated. This study allowed a more accurate statement of the potential short-term adverse effects of the three trimming methods. At the clinical level, the nail cutter caused the formation of an irregular occlusal surface with sharp edges. Both engine-drive methods allowed the attainment of a smooth surface but the disc was less accurate. Histological evaluation revealed that the primary modifications, including coronal fractures, periodontal ligament widening and inflammation, reparative osteodentine, paracementosis and biofilm accumulation, were found in the nail cutter group.

INTRODUCTION: La malocclusion des incisives chez le lapin (Oryctolagus cuniculus) est un problème clinique courant en médecine générale. Étant donné que le taux de croissance est d'environ 2 mm par semaine, un manque d'usure entraîne rapidement des difficultés d'alimentation et des lésions des tissus mous. Par conséquent, les incisives pathologiquement trop longues doivent être raccourcies toutes les trois à six semaines. L'objectif de cette étude était d'évaluer les effets négatifs potentiels sur les tissus dentaires et parodontaux associés aux trois méthodes de taille les plus couramment utilisées: le coupeongles, le disque de coupe diamanté et la fraise diamantée. L'incisive mandibulaire gauche de 28 lapins néo-zélandais en bonne santé a été soumise à quatre tailles avec l'une des trois méthodes de coupe. Après la période d'engraissement, les mandibules ont été prélevées et les deux incisives mandibulaires ont été examinées sur des radiographies dentaires, des examens micro-tomodensitométriques et des coupes histologiques. Les modifications des tissus dentaires et parodontaux ont été évaluées. Cette étude a permis de mieux cerner les effets indésirables potentiels à court terme des trois méthodes de coupe. Au niveau clinique, le coupe-ongles a entraîné la formation d'une surface occlusale irrégulière avec des bords tranchants. Les deux autres méthodes de taille permettent d'obtenir une surface lisse, mais le disque est moins précis. L'évaluation histologique a révélé que les modifications primaires, y compris les fractures coronaires, l'élargissement et l'inflammation du ligament parodontal, l'ostéodentine réparatrice, la paracémentose et l'accumulation de biofilm, ont été trouvées dans le groupe coupe-ongles.

Long-term follow-up after the treatment of impacted canines in the maxilla causing severe root resorption of the lateral incisors: two case reports.

BACKGROUND: Root resorption of adjacent teeth due to impacted canines is common, and orthodontic treatment often leads to secondary resorption or even loss of adjacent roots. Clinical reports of long-term stability after treatment are rare. CASE PRESENTATION: This study reports two cases of maxillary impacted canines resulting in severe root resorption of the adjacent lateral incisors. Surgical exposure, orthodontic retraction, and alignment of the impacted canines were successful in both cases, and the resorbed lateral incisors were stable with no significant loosening and normal pulp vitality after treatment and at the 5- and 10-year follow-up appointments. CONCLUSIONS: Light orthodontic force may be used to move adjacent teeth with root resorption due to tooth obstruction. The path and direction in which the teeth are moved must be specifically designed so that the adjacent roots are not resorbed and so long-term stability can be achieved.

Bayesian modeling of spatially differentiated multivariate enamel defects of the children's primary maxillary central incisor teeth.

BACKGROUND: The analysis of dental caries has been a major focus of recent work on modeling dental defect data. While a dental caries focus is of major importance in dental research, the examination of developmental defects which could also contribute at an early stage of dental caries formation, is also of potential interest. This paper proposes a set of methods which address the appearance of different combinations of defects across different tooth regions. In our modeling we assess the linkages between tooth region development and both the type of defect and associations with etiological predictors of the defects which could be influential at different times during the tooth crown development. METHODS: We develop different hierarchical model formulations under the Bayesian paradigm to assess exposures during primary central incisor (PMCI) tooth development and PMCI defects. We evaluate the Bayesian hierarchical models under various simulation scenarios to compare their performance with both simulated dental defect data and real data from a motivating application. RESULTS: The proposed model provides inference on identifying a subset of etiological predictors of an individual defect accounting for the correlation between tooth regions and on identifying a subset of etiological predictors for the joint effect of defects. Furthermore, the model provides inference on the correlation between the regions of the teeth as well as between the joint effect of the developmental enamel defects and dental caries. Simulation results show that the proposed model consistently yields steady inferences in identifying etiological biomarkers associated with the outcome of localized developmental enamel defects and dental caries under varying simulation scenarios as deemed by small mean square error (MSE) when comparing the simulation results to real application results. CONCLUSION: We evaluate the proposed model under varying simulation scenarios to develop a model for multivariate dental defects and dental caries assuming a flexible covariance structure that can handle regional and joint effects. The proposed model shed new light on methods for capturing inclusive predictors in different multivariate joint models under the same covariance structure and provides a natural extension to a nested hierarchical model.