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Background To evaluate disturbances in primary tooth eruption and their management with nonpharmacological remedies. Methods In this nonrandomized clinical trial, 270 children aged between 8 and 36 months were selected and divided into 5 groups with 54 children initially enrolled in each group. The children were seen during an 8-day period during tooth eruption. At each appointment data were recorded from oral examination, tympanic temperature measurement and a questionnaire. The five methods used as remedies to reduce teething symptoms were: 1) cuddle therapy, 2) ice, 3) rubbing the gums, 4) teething rings and 5) food for chewing. Teething symptoms, the type of erupted tooth, symptoms of recovery and the mother’s satisfaction with treatment were evaluated. Results Two hundred and fifty four children (mean age 16 ± 7.2 months) completed the study. The most frequent teething symptoms were drooling (92 %), sleep disturbances (82.3 %) and irritability (75.6 %). These symptoms were more pronounced in low birth weight children ( p  > 0.05). Canine eruption led to more loss of appetite than incisor ( p  = 0.033) or molars eruption ( p  = 0.014). Low grade increases in body temperature were observed only on the day of eruption (36.70 ± 0.39 °C), when body temperature was significantly different compared to the day before and the day after eruption (both p  < 0.001). There was no significant correlation between fever as reported by mothers and temperature readings obtained by the investigators. The most favorable results for time to recovery and the mother’s satisfaction were seen when teething rings were used, followed by cuddle therapy and rubbing the gums. Conclusions There was no association between teething and symptoms such as fever or diarrhea. Low birth weight children may have more teething symptoms. Teething rings, cuddle therapy and rubbing the gums were the most effective methods to reduce symptoms. Trial registration Iranian Registry of Clinical Trials: code IRCT201211127402N3

Early modern humans (EMH) are often touted as behaviorally advanced to Neandertals, with more sophisticated technologies, expanded resource exploitation, and more complex clothing production. However, recent analyses have indicated that Neandertals were more nuanced in their behavioral adaptations, with the production of the Châtelperronian technocomplex, the processing and cooking of plant foods, and differences in behavioral adaptations according to habitat. This study adds to this debate by addressing the behavioral strategies of EMH (n = 30) within the context of non-dietary anterior tooth-use behaviors to glean possible differences between them and their Neandertal (n = 45) counterparts. High-resolution casts of permanent anterior teeth were used to collect microwear textures of fossil and comparative bioarchaeological samples using a Sensofar white-light confocal profiler with a 100x objective lens. Labial surfaces were scanned, totaling a work envelope of 204 x 276 μm for each individual. The microwear textures were examined for post-mortem damage and uploaded to SSFA software packages for surface characterization. Statistical analyses were performed to examine differences in central tendencies and distributions of anisotropy and textural fill volume variables among the EMH sample itself by habitat, location, and time interval, and between the EMH and Neandertal samples by habitat and location. Descriptive statistics for the EMH sample were compared to seven bioarchaeological samples (n = 156) that utilized different tooth-use behaviors to better elucidate specific activities that may have been performed by EMH. Results show no significant differences between the means within the EMH sample by habitat, location, or time interval. Furthermore, there are no significant differences found here between EMH and Neandertals. Comparisons to the bioarchaeological samples suggest both fossil groups participated in clamping and grasping activities. These results indicate that EMH and Neandertals were similar in their non-dietary anterior tooth-use behaviors and provide additional evidence for overlapping behavioral strategies employed by these two hominins.

Interaction between adult stem cells and their progeny is critical for tissue homeostasis and regeneration. In multiple organs, mesenchymal stem cells (MSCs) give rise to transit amplifying cells (TACs), which then differentiate into different cell types. However, whether and how MSCs interact with TACs remains unknown. Using the adult mouse incisor as a model, we present in vivo evidence that TACs and MSCs have distinct genetic programs and engage in reciprocal signaling cross talk to maintain tissue homeostasis. Specifically, an IGF-WNT signaling cascade is involved in the feedforward from MSCs to TACs. TACs are regulated by tissue-autonomous canonical WNT signaling and can feedback to MSCs and regulate MSC maintenance via Wnt5a/Ror2-mediated non-canonical WNT signaling. Collectively, these findings highlight the importance of coordinated bidirectional signaling interaction between MSCs and TACs in instructing mesenchymal tissue homeostasis, and the mechanisms identified here have important implications for MSC–TAC interaction in other organs.

Objective This study employed finite element analysis to evaluate the biomechanical effects of different aligner trimline designs (scalloped vs. high trimline) and intrusion methods (sequential vs. simultaneous) during mandibular anterior teeth intrusion. Methods A finite element analysis model was developed to evaluate stress distribution and displacement patterns. Two trimline designs (scalloped and high trimline) and two intrusion protocols (sequential and simultaneous) were compared. Parameters measured included initial tooth displacement, root stress, periodontal ligament (PDL) stress, and stress concentration patterns. Results Finite element analysis demonstrated that sequential intrusion with scalloped trimline aligners produced greater initial displacement (0.062–0.108 mm in central incisors) and a more favorable stress distribution compared to simultaneous intrusion. The scalloped design showed superior performance by generating 13–40% lower root stress (0.053–0.060 MPa) compared to high trimline aligners. Stress concentration patterns differed notably between intrusion methods. Sequential intrusion localized stress at the lingual cervical third of the central incisors, whereas simultaneous intrusion shifted peak stress to the canines and increased PDL stress three-fold (0.005–0.006 MPa). Posterior anchorage control was also better preserved with sequential intrusion protocols. Conclusion This study confirms that sequential intrusion using scalloped trimline aligners is biomechanically optimal for mandibular anterior intrusion. This method provides greater displacement efficiency and reduced stress on dental structures. The findings offer clinically relevant evidence supporting the preference for scalloped trimline designs over high trimlines. Moreover, sequential protocols are recommended over simultaneous intrusion in managing deep overbites with clear aligners. These results enable clinicians to make informed decisions regarding intrusion mechanics, potentially enhancing treatment outcomes and minimizing adverse effects.

Optical diagnostic techniques represent an attractive complement to conventional pulp vitality tests, as they can provide direct information about the vascular status of the pulp. However, the complex, multi-layered structure of a tooth significantly influences the detected signal and, ultimately, the diagnostic decision. Despite this, the impact of the various dental components on light propagation within the tooth, particularly in the context of diagnostic applications, remains insufficiently studied. To help bridge this gap and potentially enhance diagnostic accuracy, this study employs digital optical twins based on the Monte Carlo method. Using incisor and molar models as examples, the influence of tooth and pulp geometry, blood concentration, and pulp composition, such as the possible presence of pus, on spectrally resolved transmission signals is demonstrated. Furthermore, it is shown that gingival blood absorption can significantly overlay the pulpal measurement signal, posing a substantial risk of misdiagnosis. Strategies such as shifting the illumination and detection axes, as well as time-gated detection, are explored as potential approaches to suppress interfering signals, particularly those originating from the gingiva.

Background In clear aligner therapy, tooth movement can be designed individually by computer software. However, the deformation of the aligner created by the virtual movement of one tooth may affect the actual movement of other teeth. This study aimed to evaluate the impact of the amount of canine movement on the responses of incisors and posterior teeth during maxillary anterior en-masse retraction with clear aligner. Methods A three-dimensional finite element model of maxillary dentition was constructed for first premolar extraction. The incisors were retracted by 0.15 mm with an intrusion of 0.10 mm. The canine was bodily retracted in six groups with different amount of 0 mm, 0.10 mm, 0.15 mm, 0.20 mm, 0.25 mm, and 0.30 mm. The groups were named after the amount of canine movement. Separate canine retraction of 0.25 mm was set in an additional group. ANSYS® software was used to calculate the initial displacements and forces on the dentition in each group. Results In incisor retraction with no canine movement (group 0), the incisors underwent uncontrolled lingual tipping and the canine exhibited mesial tipping. As the amount of canine movement increased, the lingual retraction force and clockwise moment on the incisors gradually weakened. The incisors exhibited less lingual inclination with more extrusion, while the canine displayed more distal inclination and less extrusion. The central and lateral incisors showed controlled lingual tipping and lingual root movement respectively in group 0.25, and both the incisors inclined labially in group 0.30. During separate canine retraction, the canine experienced distal tipping and the incisors showed labial tipping. Posterior teeth exhibited mesial tipping in all groups, the amount of which was in positive correlation with the amount of canine movement. Conclusion During en-masse retraction with clear aligner, the uncontrolled lingual tipping of incisors can be eliminated by increasing the amount of canine retraction. Practitioners need to pay attention to the reciprocal effects of the designed tooth movements during clear aligner therapy.

The present study reports an in vivo, novel methodology for the dynamic measurement of the bite force generated by individual tooth using a Fiber Bragg Grating Bite Force Recorder (FBGBFR). Bite force is considered as one of the major indicators of the functional state of the masticatory system, which is dependent on the craniomandibular structure comprising functional components such as muscles of mastication, joints and teeth. The proposed FBGBFR is an intra-oral device, developed for the transduction of the bite force exerted at the occlusal surface, into strain variations on a base plate, which in turn is sensed by the FBG sensor bonded over it. The FBGBFR is calibrated against a Micro Universal Testing Machine (UTM) for 0–900N range and the resolution of the developed FBGBFR is found to be 0.54N. 36 volunteers (20 males and 16 females) performed the bite force measurement test at molar, premolar and incisor tooth on either side of the dental arch and the obtained results show clinically relevant bite forces varying from 176N to 635N. The bite forces obtained from the current study for a substantial sample size, show that the bite forces increases along the dental arch from the incisors towards the molars and are found to be higher in male than in female. The FBG sensor element utilized in FBGBFR is electrically passive, which makes it a safe in vivo intra-oral device. Hence the FBGBFR is viable to be employed in clinical studies on biomechanics of oral function.

Objectives To evaluate the biomechanical effects on mandibular anterior teeth during second molar protraction using different movement patterns following unilateral mandibular first molar loss. Materials and methods A 3D finite element model was developed to simulate unilateral mandibular first molar absence. Three protraction movement patterns were studied: (A) traction hook, (B) anchorage screw, and (C) anchorage screw with extended arm. A 2 N traction force was applied with an archwire-bracket friction coefficient of 0.2. Tooth displacement and movement direction were analyzed. Results All three movement patterns affected mandibular anterior teeth differently. The traction hook method showed minimal influence on both anterior teeth and molar displacement. The anchorage screw method demonstrated improved protraction but caused significant displacement of anterior teeth away from the edentulous site and pronounced labial inclination. Adding an extended arm reduced labial inclination and enhanced intrusion of anterior teeth while increasing molar displacement, however, anterior dental movement away from the edentulous site is notably increased. Conclusions Adverse effects on anterior teeth are inevitable during mandibular second molar protraction, regardless of the space closure technique employed. The traction hook produced minimal displacement overall. The anchorage screw with extended arm effectively reduced anterior teeth labial inclination while enhancing molar protraction, though careful attention to midline control is necessary.

Introduction Obesity is a major health threat of modern civilization with substantially increased prevalence which affects children’s health, growth, and development. Also, tooth eruption is certainly linked to the somatic development of the person. Aim This study aimed to assess the association between the eruption of permanent teeth and obesity among a sample of primary school children from Tanta City. Methods A case-control study was carried out on 2520 healthy students aged 6–12 years selected from 10 primary schools in Tanta City (equally included from public and private schools). The selected students were divided into equal sub-groups according to age, gender, and obesity status using a stratified random sampling technique. Obesity was assessed using BMI method while tooth eruption was recorded when any part of the crown was visible through the oral mucosa for twenty-eight permanent teeth. Statistical analysis was done for the collected data. Results All permanent teeth in the maxillary and mandibular arches erupted earlier in private school children, except for the lower right second molar showed earlier eruption in public school children with no significant difference. The mean eruption age of all permanent teeth differed significantly between public and private institutions except for upper and lower right and left second molars, lower right first premolar, and lower right and left central incisors. Conclusion This population-specific research revealed a highly significant positive association between the total number of permanent teeth erupted and BMI among school children aged 6–12 years from Tanta City.

Dental enamel is a structure that is formed as a result of the regular functioning of ameloblasts. The knowledge of the patterns of enamel secretion allows an analysis of their disruptions manifested in pronounced additional accentuated lines. These lines represent a physiological response to stress experienced during enamel development. The aim of this study was to assess the occurrence of accentuated lines in the tooth enamel of autistic boys. The width of the neonatal line and the periodicity of the striae of Retzius were also assessed. The study material consisted of longitudinal ground sections of 56 primary teeth (incisors and molars): 22 teeth from autistic children and 34 teeth from the control group. The Mann–Whitney U test indicates that the accentuated lines were found significantly more often in autistic children (Z = 3.03; p = 0.002). No differentiation in the rate of enamel formation and in the rate of regaining homeostasis after childbirth were found. The obtained results may indicate a higher sensitivity of autistic children to stress factors, manifested in more frequent disturbances in the functioning of ameloblasts or may be a reflection of differences in the occurrence of stress factors in the first years of life in both analyzed groups.