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Copyright of Kieferorthopädie: die Zeitschrift für die Praxis is the property of Quintessenz Verlags GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The restoration of severely damaged teeth challenges dental practitioners because defects are often located at the subcrestal level. In these cases, surgical crown lengthening or orthodontic extrusion procedures are deemed necessary to maintain the biologic width and respect a sufficient ferrule design after preparation. Considering the negative effects of invasive surgical therapy-such as the reduction of alveolar bone support of the neighboring teeth-forced extrusion might be a valid therapeutic alternative. This clinical case report illustrates forced orthodontic extrusion with a minimally invasive appliance that is applicable in daily clinical routine. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the overeruption of unopposed molars and the adaptation of alveolar bone height in young and adult rats.Materials and Methods: A total of 56 4-week-old (young) and 26-week-old (adult) male Wistar rats were followed up longitudinally. In each age group (n = 28), 16 rats were included in the experimental subgroup, in which all the maxillary right molars were extracted, and 12 rats were included in the control subgroup. All rats were scanned at regular intervals with in vivo microcomputed tomography for a 12-week period, and the eruption rate of the mandibular first molars and the surrounding bone were measured, with the reference point at the mandibular canal. The molar categories were unopposed right molars and overloaded left molars in the experimental group and control molars in the control group.Results: The young unopposed molars had the highest mean eruption rate (172 ± 67 μm/day). The overeruption was most marked during the first 3 weeks postextraction, thereafter gradually returning to a level comparable to controls (12.9 ± 6.8 μm/day). The overloaded adult molars did not erupt during the experimental period. Alveolar bone height also increased in young unopposed molars, but at a slower pace than overeruption, causing an increase in clinical crown height.Conclusion: Unopposed young molars overerupt at a higher pace than adult molars during the first weeks postextraction. The alveolar bone grows in response to the tooth eruption but to a lesser extent, which leads to a constant increase in clinical crown height at the same rate in young and adult rats. The increase of clinical crown height was 4.5-fold higher in young unopposed molars compared to control molars. [ABSTRACT FROM AUTHOR]

Copyright of Kieferorthopädie: die Zeitschrift für die Praxis is the property of Quintessenz Verlags GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Crown fractures restored by fragment reattachment are liable to re‐fracture, which may cause fragment dislodgement. There is a paucity of literature regarding management of fragment reattachment cases following a further fracture. Hence the aim of the present in‐vitro study was to evaluate and compare the efficacy of three different management protocols for such scenarios. Methodology: Eighty maxillary bovine incisors without structural deformity and with similar dimensions were fractured as per the standard protocol. They were subjected to drying for 24 hours and the fragments were rehydrated by placing them in a humidification chamber for 15 minutes. They were then reattached by using flowable light‐cured composite resin. The teeth (n=20) were fractured again by fixing them in a mechanical frame and using a mallet. They were randomly allocated to three experimental groups. (Group I mechanical abrasion and fragment reattachment, Group II mechanical abrasion, humidification and reattachment, Group III mechanical abrasion and composite restoration, and Group IV positive control with no re‐fracture). The samples were thermocycled and the force required to fracture was tested by using a universal testing machine (Instron‐3360, USA). This was done by applying a tangential load with a speed of 1 mm/min to the teeth with a 500‐kg load cell. Statistical analysis of the results was performed using ANOVA and the independent t‐test. Results: The highest force required to fracture was reported in Group IV (333.26 ± 66.69N) while the lowest was in Group II (254.86 ± 105.23N). The forces in Group I and Group II were 258.36 ± 65.78N and 298.02 ± 97.94N, respectively (p=0.016, F=3.68). The independent t‐test between the groups revealed a significant difference between Group I and Group IV (p= 0.001) and Group II and Group IV (p=0.009). Conclusion: The force required to fracture was significantly lower in the groups involving attachment of the re‐fractured fragments. Among the experimental groups, the group with composite restoration required the highest force to fracture. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to quantify the coronal tooth structure reductions (CTSRs) resulting from a variety of different types of crown preparations performed by undergraduate dental students in a simulation clinic teaching program.Materials and Methods: A total of 76 students each submitted 21 different crown preparations completed on typodont teeth, which were individually weighed and analyzed in relation to whole and sectioned reference teeth to calculate the CTSR resulting from each preparation.Results: The largest CTSR resulted from preparations for porcelain bonded to zirconia crowns (50.6%), followed by those for porcelain bonded to metal (PBM) crowns (44.3%), PBM fixed partial dentures (32.8%), shell crowns (32.5%), and full gold crowns (24.6%).Conclusion: A wide range of CTSRs resulted from the different types of crown preparations investigated in this study. The crown preparations performed by the undergraduate students produced more conservative coronal reductions than comparable crown preparations generated under controlled in vitro conditions. [ABSTRACT FROM AUTHOR]

The aim of the present case series article was to provide a standardized approach for the early restorative phase after a crown-lengthening surgical procedure. Different advantages can be ascribed to this approach: the clinician can prepare a definitive prosthetic finishing line in the supragingival location; the early postsurgical temporization allows the conditioning of soft tissues, especially the interdental papillae, during their maximum growing phase; and the clinician can choose the time for the definitive prosthetic rehabilitation in a patient-specific manner according to the individual potential and duration of the soft tissue rebound. In this study, this standardized approach was applied to the treatment of two esthetic cases requiring crown-lengthening procedures. [ABSTRACT FROM AUTHOR]

Background/Aim: Clinical studies evaluating the splinting time for surgically extruded teeth with crown‐root fractures are lacking. The aim of this study was to compare 2‐week splinting versus functional splinting times after surgical extrusion. Material and methods: Children aged 8‐13 years who presented with crown‐root fractures were included. Surgical extrusion was performed, and teeth were splinted either for 2 weeks or until normal Periotest values were achieved (functional splinting time). The outcome measures were tooth mobility, tooth loss, root resorption, marginal bone resorption and ankylosis. Measurements were taken at baseline, weekly after splint removal, and after 1, 3, 6 and 12 months. Results: Nineteen patients were included in the analysis. Surgically extruded teeth splinted for 2 weeks showed significantly higher mobility directly after splint removal and at 1 month after splinting compared with the functional splinting time group. The mean differences for horizontal Periotest values were 14.96 (95% confidence interval: 8.52, 21.39) and 6.63 (95% confidence interval: 0.25, 13), respectively. The vertical Periotest values were 10.47 (95% confidence interval: 1.95, 18.99) and 4.81 (95% confidence interval: −1.57, 11.18), respectively. At the 3‐, 6‐ and 12‐month follow‐up intervals, there were no statistically significant differences between the groups. One tooth in the 2‐week splinting group was lost. None of the teeth had ankylosis, marginal bone resorption or root resorption. Conclusions: Although both groups showed neither statistical nor clinically significant differences after 12 months, there was a significant difference immediately after splint removal, with greater tooth mobility in the 2‐week splinting group. Thus, a functional splinting time (4‐6 weeks) can be suggested for better healing and optimal stability to allow placement of the final restoration directly after splint removal. [ABSTRACT FROM AUTHOR]

Background: Dental professionals are the primary care providers for traumatic dental injuries (TDI). The dental traumatology literature has a number of studies evaluating the knowledge of dental professionals from different parts of the world but its global status is unknown. Hence, the aim of this systematic review was to assess the global status of knowledge for the prevention and emergency management of TDI in dental professionals and to provide recommendations for future research. Materials and Methods: The protocol was designed as per the PRISMA guidelines and registered in PROSPERO (CRD42020192381). A broad‐based search using text words and MeSH terms was performed in established databases as per a pre‐defined strategy without any distinction of language and year of publication. Studies without details of the questionnaire, knowledge score, validity and reliability were excluded. Data extraction was performed, risk of bias assessment was done using the Joanna Briggs Institute's critical appraisal tool, and a meta‐analysis was performed. Results: Sixteen studies, which had been published between 2008 and 2020, were included for qualitative synthesis. Most of them were cross‐sectional, used convenience sampling and evaluated knowledge for avulsion. Previous dental trauma training was undertaken by <50% of the participants of five studies, <50% knew about the correct approach in management of complicated crown fractures in three studies and ≤60% in four studies knew the critical time for replantation. There was insufficient level of knowledge in >50% of the included studies. High risk of bias was found in three studies. Conclusion: The knowledge level in several areas of the world was unknown. The studies lacked uniformity in methods and well‐designed questionnaires and they revealed insufficient levels of knowledge among dental professionals. [ABSTRACT FROM AUTHOR]

Background/Aim: When patients have saved tooth fragments in case of crown fractures, reattachment is considered as the treatment of choice. With respect to the need to provide clinical outcome data regarding adhesively reattached fragments, the aim of this practice‐based clinical study was to evaluate the survival of reattached fragments after crown fractures in permanent teeth. Materials and Methods: Records from patients treated at Ludwig‐Maximilians‐University between 2004 and 2017 were analyzed to collect clinical and radiographic data regarding the management of fractured teeth that were treated with an adhesive reattachment. The study population consisted of 109 patients comprising 135 reattached fragments divided into uncomplicated (N = 84/135) and complicated (N = 51/135) crown fractures. The Kaplan‐Meier Survival estimator was used to estimate the survival probability of primary reattachments after uncomplicated and complicated crown fractures. Results: Overall, 77.4% (N = 65/84) and 66.6% (N = 34/51) of the primarily applied reattachments in uncomplicated fractured teeth and complicated fractured teeth, respectively, survived over the period of observation. The survival rate for adhesive reattachment in all teeth was 84.4% (N = 114/135) after 608.2 days (±983.1 days). The data further suggest that in the case of a detachment, repeated reattachment might be a valuable restoration strategy. Conclusions: Adhesive reattachment is a good first‐choice treatment option in cases of crown fractures when the fractured fragment has been saved. [ABSTRACT FROM AUTHOR]

Aim: To develop a laboratory‐based tooth model of simulated blood flow in teeth and evaluate it using ultrasound Doppler flowmetry (UDF). Methodology: A laboratory‐based tooth model for UDF was created based on a microfluidic experimental model proposed by Kim & Park (2016 a,b). Twenty‐one maxillary or mandibular anterior human teeth within 1 month of extraction were used. Four holes were made in each tooth to fit 1.6‐mm diameter polytetrafluoroethylene (PTFE) tubes: at the apical foramen, palatal surface in the centre of the crown, palatal surface apical to the cementoenamel junction (CEJ) and the root centre. Fluid mimicking pulsating blood was pumped (pressure range: 0–200 mbar, flow rate range: 0–80 μL min−1) into the apical foramen via the PTFE tubes, which exited the tooth through the palatal surface in the centre of the crown (control group), palatal surface below the CEJ (group 1) and the palatal surface at the mid‐root level (group 2). An UDF transducer of 20 MHz was placed at a 60° angle to the labial surface of tooth and was used to measure the fluid flow velocity (Vs, Vas, Vm, Vam, Vd, Vad and Vakd). The flow velocity of the different groups was compared using the Wilcoxon signed‐rank test, with a 95% confidence level. Results: UDF facilitated the detection of the simulated pulpal blood flow in the control group and group 1, but not in group 2. The mean and standard deviations of Vas, Vam and Vakd were 0.921 ± 0.394, 0.479 ± 0.208 and 0.396 ± 0.220 cm s−1, respectively, in the control group, and 0.865 ± 0.368, 0.424 ± 0.215 and 0.487 ± 0.279 cm s−1, respectively, in group 1. The pulpal blood flow values of the control group and group 1 were not significantly different (p > 0.05). Conclusions: This laboratory study revealed that ultrasound Doppler flowmetry enabled the detection of simulated blood flow below the level of the CEJ but not at the mid‐root level. [ABSTRACT FROM AUTHOR]

Aim: To assess and correlate three distinct states of severely painful endodontically derived inflammation with their depiction on periapical radiographs using periapical index (PAI) scores. Methodology: During a period of 15 months, 368 consecutively enrolled patients with suspected endodontic emergency conditions were examined at the University of Zurich, Center of Dental Medicine. Cases with a severely painful (numeric rating scale, NRS‐11 > 6) endodontically involved tooth and a clear pulpal and apical diagnosis (n = 162) were selected (one tooth per patient). Teeth were divided into three groups according to the clinically diagnosed main location of the inflammatory process: level 1: pulp (positive response to cold test), level 2: periodontium (no response to cold without swelling) and level 3: periapical tissues (no response to cold with swelling). Periapical radiographs were obtained using a digital unit and analysed by two calibrated observers. For level 2, which had the highest PAI variance (n = 76), the PAI scores were further scrutinized regarding their dependence on tooth location and the duration of pain. Data were analysed using chi‐squared and non‐parametric tests, alpha = 0.05. Results: Overall, the PAI scores correlated well with the clinically diagnosed main location of periapical inflammation (Spearman's rho = 0.5131, P < 0.001), with level 1 having the lowest scores by far (P < 0.001) and level 2 having significantly lower scores compared to level 3 (P < 0.05). However, a PAI score of 5 was found in merely 3 teeth within the entire cohort, and 49% of the teeth in the level 2 group had no radiolucency (PAI < 3). Within level 2, the PAI scores were not dependent on tooth location but were substantially (P < 0.001) higher for teeth which had hurt for more than one week, and for root filled teeth. Conclusions: For the analysed, severely painful endodontically involved teeth, the clinically diagnosed main location of inflammation was reflected by the periapical index. PAI scores were not significantly influenced by anatomical noise, yet in some cases under‐estimated the clinical situation. [ABSTRACT FROM AUTHOR]

Aim: This 60‐month prospective study aimed to evaluate tooth survival and healing rates after root canal treatment in patients taking bisphosphonates (BPs). Secondary outcomes were complications and clinical variables observed during and after treatment. Methods: Root canal treatment was performed using manual K‐file canal instrumentation and a carrier‐based filling technique with an epoxy resin‐based sealer. Teeth without adequate root/crown integrity were restored by trained operators at the tissue level (TL group) to prevent occlusal/mechanical stress and to enable periapical lesion healing without the risk of root fracture. Other teeth were restored with normal occlusal contacts (OC group). Healthy patients who had undergone one or more root canal treatments of the same type constituted the control group. The relationships of the following variables to survival and health status were examined (chi‐squared test and multivariate analysis, P = 0.05): age, gender, smoking habit, tooth location, treatment type, BPs treatment, BPs exposure, initial periapical index (PAI) and occlusal restoration. Survival curves were constructed using Kaplan–Meier analysis, with extraction serving as the end‐point. Results: In total, 65 patients with 109 root canal‐treated teeth who were taking BPs were included. At 60 months, data from 57 patients (52F, 5M; median age 65.7 ± 8.6 years) who had undergone 96 root canal treatments were analysed (drop‐out rate = 16.9%). The survival rate was 85%, and the success rate was 76%. The control group consisted of 46 patients (21F, 25M; median age 60.3 ± 7.2 years) who had undergone 102 root canal treatments. The survival rate was 88%, with 12 teeth lost during follow‐up. The success rate was 73%. In the BP group, 55 teeth were restored normally (OC group) and 41 teeth were restored at the tissue level (TL group). No difference in the success or survival rate was observed between the BP and control groups (P > 0.05). Univariate Kaplan–Meier analysis revealed that only tooth type significantly affected survival status in the BP group. The analysis revealed the clinical relevance of smoking, tooth location and initial PAI on patients' health status (P < 0.05). Conclusion: Root canal treatments and post‐endodontic restoration with tissue‐level filling procedures represent a safe approach for severely damaged teeth in patients receiving BPs having comparable results to root filled teeth restored with occlusal contacts and to the control group. [ABSTRACT FROM AUTHOR]

Five multituberculate species have been reported to date from the upper Lower Cretaceous (Aptian–Albian) Shahai and Fuxin formations in Liaoning Province, northeastern China. We herein describe an additional species of eobaatarid multituberculate from the Fuxin Formation, Dolichoprion lii, gen. et sp. nov., with a long (relative to height) crown of the fourth lower premolar, which is unique among eobaatarids. We also describe the upper dentition possibly referable to another eobaatarid genus previously known only from lower jaws, Liaobaatar, based on a newly discovered specimen. The new species is the sixth multituberculate (and the fourth eobaatarid) species described from the Shahai and Fuxin formations. These species suggest that multituberculates, especially eobaatarids, were taxonomically quite diverse in the mammalian fauna of East Asia at that time. [ABSTRACT FROM AUTHOR]

Background/aim: A new bioceramic material iRoot BP Plus has been introduced and reported to have good biocompatibility, sealing ability and antibacterial activity. It has also been reported to be successfully used for procedures such as pulpotomy, pulp floor perforation repair and so on. However, there are only a few reports on the use of iRoot BP Plus in the management of traumatized teeth with an exposed pulp. The aim of this study was to investigate the clinical and radiographic outcomes of partial pulpotomy with iRoot BP Plus in immature permanent teeth with complicated crown fracture or complicated crown-root fracture.Material and Methods: The study was prospectively designed, and 110 immature permanent teeth with complicated crown fracture or complicated crown-root fracture were randomly allocated into two groups (n = 55). All teeth were clinically and radiographically assessed at 1, 3, 6, 12, 18 and 24 months after partial pulpotomy with iRoot BP Plus (experimental group, n = 50) or calcium hydroxide (control group, n = 49) as the pulp capping agent. Eleven cases were lost during follow up, and 99 teeth were finally analysed.Results: There were no intergroup differences in the survival rate, survival time, root length and dentin wall thickness. The calcific bridge was significantly thinner in the iRoot BP Plus group than in the calcium hydroxide group (0.97 ± 0.13 mm vs 1.36 ± 0.12 mm; F = 5.128, P = .029).Conclusions: iRoot BP Plus may be an effective capping material for partial pulpotomy. [ABSTRACT FROM AUTHOR]

The specifics of age-related variation of tooth crown wear in Dryomys nitedula from Ukraine were analysed. Th e study is based on a morphological sample of 101 specimens (studyskins and skulls), which have been amassed in zoological museums of Ukraine since their establishment. Results suggest that patterns of enamel wear are closely related to the specifics of the species' annual cycle, in particular to periods of activity and hibernation. It was revealed that the longest period of the species' activity lasts 5.3 months, and, respectively, the forest dormouse hibernates during not less than 6.5 months. Based on the level of enamel wear, an improved method of age group determination was developed and applied successfully. Six age groups were selected that largely differ by the number of respective specimens with a clearly expressed decrease from the group SAD1 to group SEN. Similarly, there is also a clear decrease in the duration of active phase of annual cycle among subsequent age groups: in groups JUV to AD1, the active period lasts 6 months, while animals of age groups AD2 to SEN are active only for 1 to 4 months. The period of recorded activity decreases with the age determined by the level of tooth crown wear. Morphometric data presented suggest that definitive means of morphometric characters are already formed until the first wintering. The absence of young specimens in the samples and the sharp decrease in the number of adults (age groups AD2 and SEN) are discussed as well. Most of the species' records are from the forest steppe zone of Ukraine and the portion of the forest dormouse in forest steppe communities seems to be extremely low (its catches on trap-lines are rather occasional). [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to detect microcracks and cuspal deflection in tooth crown following the application of temporary filling using microcomputed tomography (micro-CT). Materials and methods: A mesio-occluso-distal cavity preparation was performed, followed by endodontic access cavity preparation and root canal shaping. Cavities were classified into two groups according to the type of temporary filling material used; Coltosol F (Coltene Whaledent) (Group I) and intermediate restorative material (IRM; Dentsply Sirona) (Group II). Micro-CT images before and after temporary filling material placement were obtained and then compared for the presence of microcracks. Microcracks considered in our data analysis were the new ones that were detected after temporary filling material placement. The mean number of new microcracks per tooth recorded for both groups were compared using Mann–Whitney U test. The number of teeth with new microcracks in both groups was compared by chi-square test. Repeated measures t test was conducted to observe the effect of temporary filling on the intercuspal distance (ICD). Also, the mean difference in the ICDs detected after temporary filling placement in both groups were compared by independent t test. The significance level was set at 5%. Results: Eleven microcracks were detected in group I, whereas only three microcracks were observed in group II (p < 0.01). The mean numbers of new microcracks were 0.84 and 0.21 in group I and II, respectively (p < 0.01). There was no significant difference in the ICDs in group I (0.006±0.02 mm) and group II (0.018 ± 0.03 mm) (p > 0.26). Most of the microcracks were found in the dentin structure. The cavity's box area was more affected by new microcracks, compared with the cavity's coronal area. The new microcracks were mainly observed in the mesiodistal direction. No complete fractures were reported in our study. Conclusions: Both temporary fillings induced microcracks; Coltosol F can induce more microcracks than IRM in premolar teeth after 1-week storage. Most of the microcracks were observed in the dentin structure of the cavity's box area running mesiodistally. Clinical relevance: The results indicated that the tested temporary fillings developed microcracks on the tooth crown with slight deflection of the cusps. [ABSTRACT FROM AUTHOR]

Background/Aims: Uncomplicated crown fracture is the most common traumatic dental injury. The International Association of Dental Traumatology has recommended fragment reattachment as the best method for restoring uncomplicated crown fractures of permanent teeth. Dehydration can affect fracture resistance after reattachment. However, a standard protocol for rehydration is still lacking. Hence, the aim of this study was to design a humidification chamber and assess its efficacy for improving the rehydration of tooth fragments and increasing fracture resistance after reattachment. Materials and Methods: Sixty mandibular bovine incisors with similar dimensions and free of any structural deformities were fractured and randomized into five groups: Group I, Control Group (sound teeth); Group II (dehydrated for 24 hours); Group III (rehydrated in distilled water for 15 minutes); Group IV (rehydrated in a humidification chamber for 15 minutes); and Group V (restored with composite). A humidification chamber was designed and used for rehydration for 15 minutes in Group IV. Fragments in Group III were immersed in distilled water for 15 minutes. Reattachment procedures and materials remained the same in all groups. Fracture resistance was tested in a universal testing machine, and statistical analysis was done by Stata‐14. Results: The Control Group with sound teeth (Group I) exhibited a maximum value of 282 ± 10.32 N, while Group II (fragment reattached without rehydration) had the least fracture resistance, 49.75 ± 5.2 N. Rehydration by means of the humidification chamber protocol (Group IV) resulted in significantly higher fracture resistance (150.54 ± 6.49 N) than in Group III (rehydration by means of immersion). Conclusions: Fracture resistance after fragment reattachment was significantly affected by the rehydration of fragments for 15 minutes in the humidification chamber. Fragment reattachment after rehydration showed better fracture resistance than the composite restorations. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to determine whether the tooth crown sexual dimorphism pattern reported in previous small studies can be generalized for a broader range of populations. Literature review: A systematic literature review was performed by two independent examiners. The following databases were searched from October 2015 to July 2016: PubMed, Scopus, Lilacs, ScienceDirect, Medline, and Cochrane Reviews. No language restrictions were applied to the search. Selection criteria: The inclusion criteria comprised original studies investigating mesiodistal permanent teeth that reported the sample population and standard deviation. All right-sided teeth, except the third molars, were measured and separated by sex in the included studies. Thirty-one studies were included in the quantitative data synthesis and metaanalysis. Studies of non-human teeth, skeletal remains, or an overly specific study population were excluded. Main results: Thirty-one trials, involving 6481 participants, provided data for the meta-analysis of teeth. Sexual dimorphism in mesiodistal crowns was found in all teeth across a range of populations, principally in lower canines (5.73%) and maxillary canines (4.72%), followed by the lower second molars (3.54%) and upper second molars(3.20%), and finally in the lower first molars(3.14%) and upper first molars(2.64%). Conclusions: A small degree of sexual dimorphism exists in all human teeth. Second molars and canines show the greatest sexual dimorphism. Additionally, smaller racial differences are present in mesiodistal crowns among groups living in different geographic areas; however, it is not possible to establish a single value applicable for all populations. [ABSTRACT FROM AUTHOR]

Abstract Saltwater crocodiles (Crocodylus porosus) are farmed in Australia primarily for their belly skin. The desirability and ultimately the value of each skin depends on the extent and location of various industry-defined defects. Anecdotal observations suggest that conspecific interactions are the main contributors with the protrusive 4th dentary teeth (i.e. eye teeth) the most likely cause. It is well known that crocodilians undergo continual tooth replacement, yet no study has investigated tooth replacement rates or tooth growth dynamics in juvenile saltwater crocodiles. In this pilot study, we repeatedly measured eye tooth crown height and observed eye tooth replacement in individually-housed juvenile saltwater crocodiles (n = 98) accounting for 290 individual teeth. The majority of teeth were replaced every three to six months (n = 172) but nine teeth were not replaced over the 15-month study period. After a tooth was lost, the need to replace it quickly was evidenced by a faster tooth growth rate in the first three months (11.07 ± 0.17 mm) but subsequently slowed to a model-adjusted asymptote of 14.03 ± 0.27 mm (p <.001). Interestingly, teeth on the left side of the mandible were, on average, 0.43 ± 0.16 mm shorter than those on the right (p <.001) and, although just outside 5% significance, were replaced 1.20 times as often. Together this is suggestive that crocodiles may preference food capture with the left-hand side of their mouth but requires more structured behavioural observations to confirm. Unusually, the eye-teeth of eight crocodiles did not protrude, which is a normal characteristic of crocodiles compared to alligators, but instead were observed to be growing into the interior of the mouth. This study begins to provide some context to tooth biology when preemptive solutions to tooth-induced blemishes are being sought. Highlights • Teeth cause damage to crocodilian belly skins reducing their value • Tooth reduction strategies are being considered to reduce skin defects. • Crocodile tooth replacement frequency is variable within and between individuals. • Once lost, tooth replacement occurs rapidly with asymptotic growth. • Teeth on the left are significantly shorter than those on the right suggesting a side preference for feeding. [ABSTRACT FROM AUTHOR]

Shape characterizers are metrics that quantify aspects of the overall geometry of a three‐dimensional (3D) digital surface. When computed for biological objects, the values of a shape characterizer are largely independent of homology interpretations and often contain a strong ecological and functional signal. Thus, shape characterizers are useful for understanding evolutionary processes. Dirichlet normal energy (DNE) is a widely used shape characterizer in morphological studies.Recent studies found that DNE is sensitive to various procedures for preparing 3D mesh from raw scan data, raising concerns regarding comparability and objectivity when utilizing DNE in morphological research. We provide arobustly implemented algorithm for computing the Dirichlet energy of the normal (ariaDNE) on 3D meshes.We show through simulation that the effects of preparation‐related mesh surface attributes, such as triangle count, mesh representation, noise, smoothing and boundary triangles, are much more limited on ariaDNE than DNE. Furthermore, ariaDNE retains the potential of DNE for biological studies, illustrated by its effectiveness in differentiating species by dietary preferences.Use of ariaDNE can dramatically enhance the assessment of the ecological aspects of morphological variation by its stability under different 3D model acquisition methods and preparation procedure. Towards this goal, we provide scripts for computing ariaDNE and ariaDNE values for specimens used in previously published DNE analyses. [ABSTRACT FROM AUTHOR]

Objectives: This article presents estimates of narrow‐sense heritability and bivariate genetic correlation for 14 tooth crown morphological variants scored on permanent premolars, first molars, and second molars. The objective is to inform data collection and analytical practices in dental biodistance and to provide insights on the development of molar crowns as integrated structures. Materials and Methods: African American dental casts from the Menegaz‐Bock collection were recorded for the Arizona State University Dental Anthropology System. Estimates of narrow‐sense heritability and genetic correlation were generated using SOLAR v.8.1.1, which included assessment of age, sex, and birth year as covariates. Both continuous scale and dichotomized estimates are provided. Results: Heritability estimates were nonsignificant for the majority of variables; however, for variables yielding significant estimates, values were moderate to high in magnitude and comparable to previous studies. Comparing left and right‐side heritability estimates suggests directional asymmetry in the expression of environmental variance, something not seen in anterior tooth traits. Genetic correlations were moderate among antimeres and metameres and low for different traits scored on the same tooth crown. Although several negative correlations were noted, few reached statistical significance. Results affirm some of the current data cleaning and analytical practices in dental biodistance, but others are called into question. These include the pooling of males and females and combining left and right‐side data into a single dataset. Conclusions: In comparison to anterior tooth crown traits, postcanine heritabilities were more often non‐significant; however, those traits with significant heritability also tended to produce higher estimates. Genetic correlations were unremarkable, in part, because they were underpowered. However, M1 results may provide insight into the complex relationship between genes, environment, and development in determining ultimate crown form. [ABSTRACT FROM AUTHOR]

Crown shapes in mammalian teeth vary considerably from species to species, and morphological characters in crown shape have been used to identify species. Cusp pattern is one of the characters in crown shape. In the processes governing the formation of cusp pattern, the Shh pathway has been implicated as an important player. Suppression of Shh signaling activity in vitro in explant assays appears to induce supernumerary cusp formation in wild-type tooth germs. However, the in vivo role of Shh signaling in cusp pattern formation and the molecular mechanisms by which Shh regulates cusp patterning are not clear. Here, through in vivo phenotypic analyses of mice in which Shh activity was suppressed and compared with wild-type mice, we characterized differences in the location, number, incidence, and shape of supernumerary cusps in molars at embryonic day 15.5. We found that the distances between cusps were reduced in molars of Shh activity-suppressed mice in vivo. These findings confirm and extend the previous idea that Shh acts as an inhibitor in the reaction-diffusion model for cusp pattern formation by negatively regulating the intercuspal distance. We uncovered a significant reduction of expression level of Sostdc1, which encodes a secreted modulator of Wnt signaling, after suppression of Shh activity. The supernumerary cusp formation in Sostdc1-/- mice and compound Sostdc1 and Lrp mutant mice indicates a strong association between Wnt and Shh signaling pathways in cusp patterning. In further support of this idea, there is a high degree of similarity in the supernumerary cusp patterns of mice lacking Sostdc1 or Shh at embryonic day 15.5. These results suggest that Shh plays an inhibitory role in cusp pattern formation by modulating Wnt signaling through the positive regulation of Sostdc1. [ABSTRACT FROM AUTHOR]

Although genes on the human X chromosome reportedly influence tooth crown morphology, little is known about X chromosome activation or inactivation systems relevant to morphological variations. We assessed the relationships between tooth crown size and crown morphological traits in females with Turner syndrome, the variants of which include complete absence of one X chromosome, lack of the short arm (Xp), or duplication of the long arms (Xq), and then estimated the functions of Xp and Xq in the process of unilateral X chromosome inactivation during tooth crown development. The mesiodistal and buccolingual diameters in the maxillary first (M1) and second (M2) permanent molars were compared among X chromosome karyotypes by multiple regression analyses, and their relationships with the development of Carabelli’s cusp and the distolingual cusp were analyzed using logistic regression analysis. The crown sizes increased in the order of the 46,X,i(Xq) karyotype, 45,X and 45,X/46,XX karyotypes, and control group. A lower frequency of Carabelli’s cusp and higher frequency of a reduced distolingual cusp in M1 were characteristics of Turner syndrome. The overall M1 and M2 crown sizes differed among the X chromosome karyotypes, whereas a smaller crown size was associated with a reduced distolingual cusp but not with Carabelli’s cusp. Considering the differences in chromosome arrangement among females with Turner syndrome and the process of unilateral X chromosome inactivation, the observed results can be considered in terms of quantity or number of promoters/inhibitors during tooth crown development. The X chromosome karyotypes have a strong influence on the overall crown sizes of the M1 and M2 molars because those karyotypes with variable numbers of active gene regions directly influence tooth germ development in an early stage of human odontogenesis. The later forming cusps, such as the distolingual cusp and Carabelli’s cusp, may be affected by this developmental prerequisite. [ABSTRACT FROM AUTHOR]

Tooth crown tissue proportions and enamel thickness distribution are considered reliable characters for inferring taxonomic identity, phylogenetic relationships, dietary and behavioural adaptations in fossil and extant hominids. While most Pleistocene hominins display variations from thick to hyper-thick enamel, Neanderthals exhibit relatively thinner. However, the chronological and geographical origin for the appearance of this typical Neanderthal condition is still unknown. The European late Early Pleistocene species Homo antecessor (Gran Dolina-TD6 site, Sierra de Atapuerca) represents an opportunity to investigate the appearance of the thin condition in the fossil record. In this study, we aim to test the hypothesis if H. antecessor molars approximates the Neanderthal condition for tissue proportions and enamel thickness. To do so, for the first time we characterised the molar inner structural organization in this Early Pleistocene hominin taxon (n = 17) and compared it to extinct and extant populations of the genus Homo from African, Asian and European origin (n = 355). The comparative sample includes maxillary and mandibular molars belonging to H. erectus, East and North African Homo, European Middle Pleistocene Homo, Neanderthals, and fossil and extant H. sapiens. We used high-resolution images to investigate the endostructural configuration of TD6 molars (tissue proportions, enamel thickness and distribution). TD6 permanent molars tend to exhibit on average thick absolute and relative enamel in 2D and 3D estimates, both in the complete crown and the lateral enamel. This condition is shared with the majority of extinct and extant hominin sample, except for Neanderthals and some isolated specimens. However, while the total crown percentage of dentine in TD6 globally resembles the low modern values, the lateral crown percentage of dentine tends to be much higher, closer to the Neanderthal signal. Similarly, the H. antecessor molar enamel distribution maps reveal a relative distribution pattern that is more similar to the Neanderthal condition (with the thickest enamel more spread at the periphery of the occlusal basin) rather than that of other fossil specimens and modern humans (with thicker cuspal enamel). Future studies on European Middle Pleistocene populations will provide more insights into the evolutionary trajectory of the typical Neanderthal dental structural organization. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: This article presents estimates of narrow‐sense heritability and bivariate genetic correlation for a series of morphological crown variants of the anterior dentition. These results provide insight into the value of dental phenotypes as evolutionary proxies, as well as the development of tooth crowns as integrated or modular structures. Materials and Methods: African American dental casts from the Menegaz‐Bock collection were scored for a standard set of dental morphological variables using the Arizona State Dental Anthropology System. Estimates of narrow‐sense heritability and genetic correlations were generated using SOLAR v. 8.1.1, controlling for the covariates of age, sex, and birth year. Analyses were run using ordinal/continuous scale variables that were then dichotomized at various breakpoints, consistent with standard practices in dental anthropology. Results: Heritability estimates were low to moderate for most traits, and lower in magnitude than those reported for odontometric data from the same study sample. Only winging, canine shoveling, and canine double shoveling returned narrow‐sense heritabilities that did not differ significantly from zero. Genetic correlations were high among antimeres and metameres and low for different traits scored on the same tooth crown. These results affirm standard data cleaning practices in dental biodistance. Double shoveling was atypical in returning strong negative correlations with other traits, shoveling in particular. Conclusions: Additive genetic variation contributes to dental morphological variation, although the estimates are uniformly lower than those observed for odontometrics. Patterns of genetic correlation affirm most standard practices in dental biodistance. Patterns of negative pleiotropy involving lingual and labial crown features suggest a genetic architecture and developmental complex that differentially constrain morphological variation of distinct surfaces of the same tooth crown. These patterns warrant greater consideration and cross‐population validation. [ABSTRACT FROM AUTHOR]

We used a polymicrobial (PM) biofilm model to examine associations of bacterial adhesiveness with surface characteristics of various dental materials. Four types of dental materials (apatite pellet, zirconia, ceramic, and composite resin) with rough and mirror surfaces were used. Surface roughness, surface free energy, zeta potential, and colony-forming units (CFUs) of the biofilm formations were measured. Biofilms were cultured for 24 h under anaerobic conditions, plated onto blood agar medium, and anaerobically cultured for 4 days. After culturing, CFU per mm2 was calculated, and samples were observed under a scanning electron microscope. Means and standard deviations of the experimental data were estimated, and one-way ANOVA and Tukey multiple comparison assays were performed. Pearson correlation coefficients were obtained for the CFU and surface characteristics. Surface roughness and surface free energy appeared to affect generation of PM biofilms on oral materials, and zeta potential was involved in generation of PM biofilms on mirror-ground oral materials. [ABSTRACT FROM AUTHOR]

A novel fast-setting calcium silicate cement with fluoride (CSC) has been developed for potential application in tooth crowns. This study compared the cytotoxicity of CSC compositions and a variety of dental materials. We tested CSC compositions (Protooth), MTA, Biodentine, Ketac Molar, Fuji II LC, Vitrebond, DeTrey Zinc, Dycal, and IRM, DMEM (negative control) and 1% NaOCl (positive control). After setting of cements for 24 h, specimens were immersed in DMEM for 24 h to obtain material elutes. The elutes were serially diluted in serum-free DMEM to obtain three dilutions. L929 mouse fibroblast cells (1 × 104 cells per well) were treated for 24 h with elute dilutions (n = 3). Cytotoxicity was determined using methyl-thiazolyl-tetrazolium assay in triplicate. CSC compositions, MTA, and Biodentine showed no significant reduction in cell viability compared to DMEM. There was no significant difference in cell viability, at any of three dilutions, between CSC compositions and either MTA or Biodentine. Cytotoxicity was significantly lower for CSC compositions than for Vitrebond, DeTrey Zinc, Dycal, IRM, and 1% NaOCl, at all three dilutions, and undiluted Fuji II LC elute. In contrast to resin-modified glass ionomers, zinc phosphate cements, Dycal, and IRM, the CSC compositions showed no cytotoxic potential. [ABSTRACT FROM AUTHOR]

Dentigerous cyst (DC) is a developmental odontogenic cyst that encloses the crown of an unerupted tooth by expansion of its follicle with accumulation of fluid between the reduced enamel epithelium and the tooth crown and is attached to the neck of the tooth. The lining of DCs shows a potential for neoplastic transformation to ameloblastoma, squamous cell carcinoma, and mucoepidermoid carcinoma. Here, we report a rare case of an ameloblastoma arising in the wall of a DC. [ABSTRACT FROM AUTHOR]

This study reports on the simulation of temperature distribution of human tooth under a laser beam based on non-Fourier models. The temperature in the tooth depth that directly results from the conduction heat transfer process is caused by the lengthy thermal relaxation time in the tooth layers. A detailed tooth composed of enamel, dentin, and pulp with unstructured shape, uneven boundaries, and realistic thicknesses was considered. A finite difference scheme was separately adopted to solve time-dependent equations in solid layers and soft tissue of the tooth. In this study, a dual-phase-lag non-Fourier heat conduction model was applied to evaluate temperature distribution induced by laser irradiation. Results show that for the laser-irradiated tooth, the phase lag time of heat flux (τ) greatly affects the temperature of the early stage, whereas the phase lag time of the temperature gradient (τ) significantly influences the temperature of the later stage. Prediction of temperature profile in the tooth based on this investigation is more real using the non-Fourier model (i.e., τ = 16 and τ = 2 millisecond) compared with experimental studies. Meanwhile, the Fourier model (τ = τ) or classical Fourier form (τ = τ = 0) and the thermal wave model (τ = 16 and τ = 0) led to unreal heated point on the enamel. The effects of laser parameters, such as laser exposure time and laser intensity on the pulp, were also investigated. Increasing the laser duration and simulation time after laser irradiation was a logical approach to pulp ablation compared with increasing the laser intensity. [ABSTRACT FROM AUTHOR]

Background: Scientific evidence is insufficient to answer the question of whether premature birth causes altered tooth-crown dimensions. Objective: To evaluate permanent tooth-crown dimensions in prematurely born children and to compare the findings with full-term born controls. Subjects and Methods: Preterm children of 8-10 years of age were selected from the Swedish Medical Birth Register. One group consisted of 36 extremely preterm children (born before the 29th gestational week); the other group included 37 very preterm children (born during gestational weeks 29-32). The preterm children were compared with 41 matched full-term born children. Clinical examination and study casts were performed on all children. Permanent maxillary and mandibular first molars, central incisors, and laterals were measured with a digital sliding caliper on study casts. The tooth-crowns were measured both mesio-distal and bucco-lingual. Results: Both the mesio-distal and bucco-lingual measurements in the maxillary and mandibular first molars had a significantly smaller width in the extremely preterm group compared with the full-term group. The central incisors and lower laterals were significantly smaller mesio-distally in the extremely preterm group compared to the full-term group. A reduction in tooth size of 4-9% was found between the extremely preterm group and the full-term group for both boys and girls. The maxillary first molars and mandibular left first molar were also smaller mesio-distally in the extremely preterm group compared to the very preterm group. The results indicate that the more preterm the birth, the smaller the tooth-crown dimensions. Independent of gestational age girls had generally smaller teeth than boys. Conclusion: Premature birth is associated with reduced tooth-crown dimensions of permanent incisors and first molars. [ABSTRACT FROM AUTHOR]

With the development of 3-dimensional (3D) scanning technologies in dentistry, high accuracy optical scanning data from the crown and cone beam computed tomography data from the root can be acquired easily. In many dental fields, especially in digital orthodontics, it is useful to fuse the data from the crown and the root. However, the manual fusion method is complex and difficult. A novel automatic fusion method for 2-source data from the crown and the root was researched, and its accuracy was evaluated in this study. An occlusal splint with several alumina ceramic spheres was fabricated using heat-curing resin. A multipoint (center of each sphere) alignment method was performed to achieve rapid registration of the crown data from optical scanning and the root data from cone beam computed tomography. The segmentation algorithm based on heuristic search was adopted to perform extraction and segmentation of the crown from whole optical scanning data. The level set algorithm and the marching cubes (MC) algorithm were used to reconstruct digital imaging and communications in medicine data into a 3D model. A novel multisource data fusion algorithm, which is based on iterative Laplacian deformation (ILD), was researched and applied to achieve automatic fusion. Finally, the 3D errors of the method were evaluated. The 3 groups of typical tooth data were automatically fused within 2 seconds. The mean standard deviation was less than 0.02 mm. The novel method can aid the construction of a high-quality 3D model of complete teeth to enable orthodontists to safely, reliably, and visually plan tooth alignment programs. [ABSTRACT FROM AUTHOR]

The Eda pathway ( Eda, Edar, Edaradd) plays an important role in tooth development, determining tooth number, crown shape, and enamel formation. Here we show that the Eda pathway also plays a key role in root development. Edar (the receptor) is expressed in Hertwig's epithelial root sheath (HERS) during root development, with mutant mice showing a high incidence of taurodontism: large pulp chambers lacking or showing delayed bifurcation or trifurcation of the roots. The mouse upper second molars in the Eda pathway mutants show the highest incidence of taurodontism, this enhanced susceptibility being matched in human patients with mutations in EDA-A1. These taurodont teeth form due to defects in the direction of extension of the HERS from the crown, associated with a more extensive area of proliferation of the neighboring root mesenchyme. In those teeth where the angle at which the HERS extends from the crown is very wide and therefore more vertical, the mutant HERSs fail to reach toward the center of the tooth in the normal furcation region, and taurodont teeth are created. The phenotype is variable, however, with milder changes in angle and proliferation leading to normal or delayed furcation. This is the first analysis of the role of Eda in the root, showing a direct role for this pathway during postnatal mouse development, and it suggests that changes in proliferation and angle of HERS may underlie taurodontism in a range of syndromes. [ABSTRACT FROM AUTHOR]

Tooth is made of an enamel-covered crown and a cementum-covered root. Studies on crown dentin formation have been a major focus in tooth development for several decades. Interestingly, the population prevalence for genetic short root anomaly (SRA) with no apparent defects in crown is close to 1.3%. Furthermore, people with SRA itself are predisposed to root resorption during orthodontic treatment. The discovery of the unique role of Nfic (nuclear factor I C; a transcriptional factor) in controlling root but not crown dentin formation points to a new concept: tooth crown and root have different control mechanisms. Further genetic mechanism studies have identified more key molecules (including Osterix, β-catenin, and sonic hedgehog) that play a critical role in root formation. Extensive studies have also revealed the critical role of Hertwig's epithelial root sheath in tooth root formation. In addition, Wnt10a has recently been found to be linked to multirooted tooth furcation formation. These exciting findings not only fill the critical gaps in our understanding about tooth root formation but will aid future research regarding the identifying factors controlling tooth root size and the generation of a whole "bio-tooth" for therapeutic purposes. This review starts with human SRA and mainly focuses on recent progress on the roles of NFIC-dependent and NFIC-independent signaling pathways in tooth root formation. Finally, this review includes a list of the various Cre transgenic mouse lines used to achieve tooth root formation-related gene deletion or overexpression, as well as strengths and limitations of each line. [ABSTRACT FROM AUTHOR]

Introduction The aim of this study was to evaluate the frequencies of nonsurgical retreatment, root-end surgery, extraction, and further restoration of root-filled teeth in Sweden in 2009 during a follow-up period of 5 years and to compare the outcomes in teeth restored with direct or indirect restorations. Methods Data from the Swedish Social Insurance Agency were analyzed, and the frequencies of nonsurgical retreatment, root-end surgery, extractions, and further restoration were calculated for all teeth registered as root filled during 2009. Chi-square tests were applied to detect any significant differences in the frequency of further treatment in teeth registered as restored with either a direct or an indirect restoration within 6 months of root filling. Results Of the 248,299 teeth reported root filled in Sweden in 2009, nonsurgical retreatment was registered in 2.2%, root-end surgery in 1.0%, and extractions in 9.2% during the follow-up period. Of the teeth restored with a direct restoration within 6 months after the root filling, 30.3% were registered as having undergone at least 1 further direct restoration; the corresponding percentage of teeth with indirect restorations was 6.4%. A statistically significant difference in the frequency of nonsurgical retreatment, extraction, and further restoration was found; teeth restored with an indirect restoration within 6 months of root filling had fewer of these treatments than those restored by direct restoration. Conclusions Low frequencies of nonsurgical retreatment and root-end surgery were reported 5 years after root filling, whereas extraction was more common. Fewer additional treatment procedures were registered for teeth with indirect restorations than for those with direct restorations. [ABSTRACT FROM AUTHOR]

Although many options are proposed for the treatment of cracked posterior teeth, most treatment decisions are not evidence based. Thus, considerable individual variation can occur regarding treatment recommendations for the same scenario. To our knowledge, there are no studies in the literature assessing practitioners' attitudes toward the treatment of cracked teeth. This research recorded variations between general practitioners and specialist groups regarding the treatment approaches of cracked teeth. In a cross-sectional structured questionnaire survey, 32 prosthodontists, 34 endodontists, and 29 general practitioners working in public and private dental health services in Kuwait were assessed regarding their treatment approach to 5 different clinical cracked tooth scenarios. Chosen treatment options varied greatly. Within each scenario, there was a wide range in treatment preferences across all groups and within each group, especially with respect to asymptomatic cracked teeth. Overall, treatment approaches did not relate to specialty training. Statistically significant differences were noticed between endodontists and general practitioners, in case of crowning teeth, in scenario 3 ( P = .032), and in extracting teeth for scenario 5 ( P = .048). This study highlights that, despite suggested guidelines, there are large differences in the approach to treatment planning for cracked teeth by practitioners and specialists, both as a whole and within each group. Further multicountry studies involving larger dental populations are needed to determine factors that influence practitioners' treatment choices and/or whether better or more widely accepted guidelines need to be established. More prospective well-controlled clinical case-based research with long-term follow-ups is required. [ABSTRACT FROM AUTHOR]

Third molars are one of the few biological markers available for age estimation in undocumented juveniles close the legal age of majority, assuming an age of 18 years as the most frequent legal demarcation between child and adult status. To obtain more accurate visualization and evaluation of third molar mineralization patterns from computed tomography images, a new software application, DentaVol©, was developed. Third molar mineralization according to qualitative (Demirjian's maturational stage) and quantitative parameters (third molar volume) of dental development was assessed in multi-slice helical computed tomography images of both maxillary arches displayed by DentaVol© from 135 individuals (62 females and 73 males) aged between 14 and 23 years. Intra- and inter-observer agreement values were remarkably high for both evaluation procedures and for all third molars. A linear correlation between third molar mineralization and chronological age was found, with third molar maturity occurring earlier in males than in females. Assessment of dental development with both procedures, by using DentaVol© software, can be considered a good indicator of age of majority (18 years or older) in all third molars. Our results indicated that virtual computed tomography imaging can be considered a valid alternative to orthopantomography for evaluations of third molar mineralization, and therefore a complementary tool for determining the age of majority. [ABSTRACT FROM AUTHOR]

The isolated adult teeth of titanosaurian sauropods from the Upper Cretaceous Bissekty Formation at Dzharakuduk, Uzbekistan, differ little in overall structure but show considerable variation in enamel sculpturing and wear patterns. The crown shape of unworn juvenile teeth ranges from lanceolate to conical. Most specimens have enamel texture resembling crumpled paper or completely smooth enamel. Longitudinal grooves along the mesial and distal edges are present on only a few tooth crowns and might be developed on both the labial and lingual sides. Among 252 worn tooth crowns there are eight variants of wear patterns, all possible combinations of 0–2 apical and 0–2 lateral wear facets. The most common is wear pattern A1L0 (one apical facet, no lateral facets; 62.7%). The next most common variant has two apical and no lateral facets (A2L0, 12.3%). These apical wear facets include the primary wear facets, which are produced by an opposing functional tooth, and secondary wear facets, which are produced by a replacing upper tooth coming into contact with the functional lower tooth at a late wear stage. The relative abundance of tooth crowns with two apical wear facets possibly suggests incipient development of a tooth battery in the Bissekty titanosaur. [ABSTRACT FROM PUBLISHER]

Talon cusp is an accessory cusp-like structure or an extra cusp on an anterior tooth arising as a result of evagination on the surface of the crown before calcification has occurred. The cusp is composed of normal enamel and dentin containing varying extensions of pulp tissue. It is associated with few developmental anomalies such as peg laterals, dens invaginatus, and mesiodens. Mesiodens is a supernumerary tooth located in the premaxillary central incisor region which is supplemental or rudimentary type. Association of mesiodens with talon cusp is a rare occurrence with 25 cases reported. The presence of Talon cusp or a supernumerary tooth - mesiodens - leads to clinical implications such as poor esthetics, crowding, rotations, and also occlusal discrepancies. In this report, we present a case report of an 18-year-old male having a talon cusp on palatally erupted mesiodens. [ABSTRACT FROM AUTHOR]

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Tooth crown morphological features, studied in palaeoanthropology, provide valuable information about human evolution and development of civilization. Tooth crown morphology represents biological and historical data of high taxonomical value as it characterizes genetically conditioned tooth relief features averse to substantial changes under environmental factors during lifetime. Palaeoanthropological studies are still based mainly on descriptive techniques and manual measurements of limited number of morphological parameters. Feature evaluation and measurement result analysis are expert-based. Development of new methods and techniques in 3D imaging creates a background provides for better value of palaeoanthropological data processing, analysis and distribution. The goals of the presented research are to propose new features for automated odontometry and to explore their applicability to paleoanthropological studies. A technique for automated measuring of given morphological tooth parameters needed for anthropological study is developed. It is based on using original photogrammetric system as a teeth 3D models acquisition device and on a set of algorithms for given tooth parameters estimation. [ABSTRACT FROM AUTHOR]

Identifying human remains is a primary task in forensic science. In this study, we propose a possible new technique, handheld X-ray fluorescence (HHXRF), for determining whether a suspected tooth is an authentic human tooth. A total of 444 teeth obtained from 111 human skulls (male=62, female=49) aged between 30-67 years (51.81±8.37 years) were used as subjects. The teeth were scanned by HHXRF to acquire their elemental profile. Differences in elemental composition were analyzed for different tooth positions (numbers 1-32), between crown and root, and between sexes (male and female); also, the proportion of elements in relation to different human ages was examined. Teeth from 20 different animal species, serving as non-human teeth samples, were used to distinguish between human and non-human teeth through a stepwise discriminant analysis. Our results revealed that different tooth positions, different regions (crown and root) of a tooth, and different sexes demonstrated disparities in the proportion of several elements. The accuracy rate of predicting sex based on the elemental profile of human teeth was 65.5%. Likewise, a dissimilar distribution of elements between human and non-human teeth was observed, leading to a high degree of correctness of 83.2% for distinguishing them. In conclusion, elemental analysis by HHXRF could serve as a promising candidate tool for identifying human teeth in forensic science, but is ineffective for sex determination. [ABSTRACT FROM AUTHOR]

Background/aim: Custom-fitted mouthguards are devices used to prevent dental injuries. The aim of this study was to verify the influence of the antagonist contact on the stresses and strains of the anterior teeth, shock absorption and displacement of EVA custom-fitted mouthguards during a horizontal impact.Materials and Methods: Finite element models of human maxillary central incisors with and without a mouthguard for different occlusion conditions (with and without antagonist contact) were created based on tomography. A nonlinear dynamic impact analysis using the single-step Houbolt method was performed in which a rigid object hit the model at 1 m s-1 . Strain and stress were evaluated by means of Von Mises and Critical modified Von Mises criterion and shock absorption during impact were calculated as well as the mouthguard displacement.Results: The model without mouthguard and without antagonist contact showed the highest stress and strain values at the enamel and dentin in the tooth crown on impact compared to the model without mouthguard and with antagonist contact. Mouthguard presence reduced the stress and strain values regardless of the occlusion condition. The mouthguard displacement decreased with the mandibular antagonist contact.Conclusions: Mouthguards are efficient at decreasing the stress and strain values on the tooth in front of an impact reaching more than 90% of shock absorption. A mouthguard with balanced occlusion and maximum number of contacts with mandibular anterior teeth should be considered because it reduces mouthguard displacement. [ABSTRACT FROM AUTHOR]

The aim of this study was to use microchannels drilled by an Er:YAG laser into a human tooth through the enamel into the dentin for direct injection of hydrogen peroxide (HP) to produce a minimally invasive, rapid, tooth bleaching effect. The experiments were conducted in vitro. Five microchannels with a diameter of ~200 μm and a depth of ~2 mm were drilled through the palatal side of a human tooth crown using the microbeam of an Er:YAG-laser with a wavelength of 2.94 μm. After injection of an aqueous solution of 31%-HP through the microchannels, the tooth color was evaluated using a VITA shade guide and International Commission on Illumination L * ab color parameters. A tooth model used for the evaluation of the distribution of HP concentration was created and the amount of HP which can be injected into tooth dentin to bleach it safely was estimated. Injection of 1.5 ± 0.1 mm3 of 31%-HP into the tooth led to noticeable bleaching within 3 h and significant improvement of tooth color within 24 h. [ABSTRACT FROM AUTHOR]

Congenital diseases of tooth roots, in terms of developmental abnormalities of short and thin root phenotypes, can lead to loss of teeth. A more complete understanding of the genetic molecular pathways and biological processes controlling tooth root formation is required. Recent studies have revealed that Osterix (Osx), a key mesenchymal transcriptional factor participating in both the processes of osteogenesis and odontogenesis, plays a vital role underlying the mechanisms of developmental differences between root and crown. During tooth development, Osx expression has been identified from late embryonic to postnatal stages when the tooth root develops, particularly in odontoblasts and cementoblasts to promote their differentiation and mineralization. Furthermore, the site-specific function of Osx in tooth root formation has been confirmed, because odontoblastic Osx-conditional knockout mice demonstrate primarily short and thin root phenotypes with no apparent abnormalities in the crown (Journal of Bone and Mineral Research 30, 2014 and 742, Journal of Dental Research 94, 2015 and 430). These findings suggest that Osx functions to promote odontoblast and cementoblast differentiation and root elongation only in root, but not in crown formation. Mechanistic research shows regulatory networks of Osx expression, which can be controlled through manipulating the epithelial BMP signalling, mesenchymal Runx2 expression and cellular phosphorylation levels, indicating feasible routes of promoting Osx expression postnatally (Journal of Cellular Biochemistry 114, 2013 and 975). In this regard, a promising approach might be available to regenerate the congenitally diseased root and that regenerative therapy would be the best choice for patients with developmental tooth diseases. [ABSTRACT FROM AUTHOR]

Background/aim: Few studies have assessed the incidence and risk factors to crown fractures in preschool children. The aim of this study was to estimate the incidence of crown fracture in the primary dentition over a 1-year follow-up period, identify risk factors, and test the hypothesis that children with previous crown fracture are more prone to experience further cases of crown fracture independently of other risk factors.Materials and Methods: This study was developed in two phases: cross-sectional and prospective longitudinal study. The cross-sectional study was carried out 261 preschool children. The prospective longitudinal study was carried out 194 children allocated to two groups: exposed group (children with prior exposure to crown fracture) and non-exposed group (children without prior exposure). On both occasions, children were examined for the diagnosis of crown fracture and evaluation of lip coverage and overjet. The parents were interviewed with regard to the socioeconomic indicators. New cases of crown fracture were identified based on the comparison of the two examinations. Data analysis involved Pearson's chi-square test, McNemar's test, and Poisson regression with robust variance.Results: Among the 261 children who participated in the cross-sectional study, 194 were re-examined (65 in the exposed group and 129 in the non-exposed group). The overall incidence of crown fracture was 55.7% (n = 108). The difference in percentage of increased risk of crown fracture in exposed and non-exposed groups was 13.4%. A greater incidence of crown fracture was found in the exposed group (64.6%; P < 0,001). The children exposed (RR: 1.30; 95% CI: 1.01-1.67) had a greater risk of developing new cases of crown fracture in comparison with the non-exposed group.Conclusion: The incidence of crown fracture was high and children with previous crown fracture had a greater risk of suffering new cases of crown fracture during the 1-year follow-up period. [ABSTRACT FROM AUTHOR]

Background/aim: While some studies support the notion that the time elapsed from coronal fracture and treatment with Cvek pulpotomy in permanent teeth plays an important role in minimizing the possibility of pain and discomfort, microbial pulp invasion, and ensuring pulp and periodontal healing, others consider that neither time between the accident and treatment nor size of exposure is critical if the inflamed superficial pulp tissue is amputated to the level of a healthy pulp. This study compares published data in an attempt to assess whether the outcome of Cvek pulpotomies is affected by these factors.Results and Conclusions: Evidence in the literature suggests to treat a permanent tooth with a complicated crown fracture as soon as possible to diminish the possibility of pain and prevent necrosis and infection of the pulp. Delay of treatment by 9 days or less may have minimal effect on the outcome of Cvek pulpotomies. While the literature indicates that pulp exposures of 4 mm or less may have a good prognosis after a Cvek pulpotomy, the prognosis in teeth with pulp exposures of more than 4 mm has not yet been clarified. Although the literature is not conclusive regarding a difference in the outcomes of Cvek pulpotomies in teeth with open or closed apices, it appears that teeth with open apices have a better prognosis. The outcome of a Cvek pulpotomy may be compromised by a luxation injury that diminishes the tooth's blood supply and innervation. A good restoration that prevents bacterial penetration into the tooth is essential for the success of a Cvek pulpotomy. [ABSTRACT FROM AUTHOR]

Objectives Australopithecus sediba is characterized further by providing formerly unpublished and refined mesiodistal and buccolingual crown measurements in the MH1 and MH2 specimens. After size correction, these data were compared with those in other fossil and recent samples to facilitate additional insight into diachronic hominin affinities. Materials and Methods Six comparative samples consist of fossil species: A. africanus, A. afarensis, Homo habilis, Paranthropus robustus, P. boisei, and H. erectus. Others comprise H. sapiens and Pan troglodytes. Re-estimates of 'actual' dimensions in damaged A. sediba teeth were effected through repeated measurements by independent observers. X-ray synchrotron microtomography allowed measurement of crowns obscured by matrix and noneruption. Tooth size apportionment analysis, an established technique for intraspecific comparisons, was then applied at this interspecific level to assess phenetic affinities using both within- and among-group data. Results Comparison of these highly heritable dimensions identified a general trend for smaller posterior relative to larger anterior teeth (not including canines), contra Paranthropus, that allies A. sediba with other australopiths and Homo; however, specific reductions and/or shape variation in the species' canines, third premolars, and anterior molars relative to the other teeth mirror the patterning characteristic of Homo. Discusssion Of all samples, including east African australopiths, A. sediba appears most like H. habilis, H. erectus and H. sapiens regarding how crown size is apportioned along the tooth rows. These findings parallel those in prior studies of dental and other skeletal data, including several that suggest A. sediba is a close relative of, if not ancestral to, Homo. [ABSTRACT FROM AUTHOR]

Supernumerary teeth may affect the tooth eruption negatively if they occur on the eruption way, and the treatment choice is usually the extraction to prevent the impaction of adjacent permanent teeth. CBCT enables clear and three dimensional images, and it may be helpful to determine the exact location and to measure the dimensions of the supernumerary tooth to avoid any complication during the extraction process. The aim of the present study was to evaluate the accuracy of CBCT on measuring the tooth length and crown width of impacted supernumerary teeth. Twenty-five impacted supernumerary teeth were evaluated using CBCT, and each sample's tooth length and crown width were measured prior to the extraction. After all the extractions were completed, the actual measurements were performed on the same samples. The differences between CBCT and actual measurements were evaluated statistically. Measurements on CBCT images were significantly larger than the actual measurements on tooth length and crown width. For tooth length and crown width, p value was found as 0.045, and <0.001, respectively. The results of the present study should be considered as important by clinicians during the treatment planning to decrease any complication risk under certain conditions such as being so close to an important anatomical structure or the root of an adjacent tooth. SCANNING 38:579-584, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

African wild dogs (Lycaon pictus) are endangered and their population continues to decline throughout their range. Given their conservation status, more research focused on their population dynamics, population growth and age specific mortality is needed and this requires reliable estimates of age and age of mortality. Various age determination methods from teeth and skull measurements have been applied in numerous studies and it is fundamental to test the validity of these methods and their applicability to different species. In this study we assessed the accuracy of estimating chronological age and age class of African wild dogs, from dental age measured by (i) counting cementum annuli (ii) pulp cavity/tooth width ratio, (iii) tooth wear (measured by tooth crown height) (iv) tooth wear (measured by tooth crown width/crown height ratio) (v) tooth weight and (vi) skull measurements (length, width and height). A sample of 29 African wild dog skulls, from opportunistically located carcasses was analysed. Linear and ordinal regression analysis was done to investigate the performance of each of the six age determination methods in predicting wild dog chronological age and age class. Counting cementum annuli was the most accurate method for estimating chronological age of wild dogs with a 79% predictive capacity, while pulp cavity/tooth width ratio was also a reliable method with a 68% predictive capacity. Counting cementum annuli and pulp cavity/tooth width ratio were again the most accurate methods for separating wild dogs into three age classes (6–24 months; 25–60 months and > 60 months), with a McFadden’s Pseudo-R2 of 0.705 and 0.412 respectively. The use of the cementum annuli method is recommended when estimating age of wild dogs since it is the most reliable method. However, its use is limited as it requires tooth extraction and shipping, is time consuming and expensive, and is not applicable to living individuals. Pulp cavity/tooth width ratio is a moderately reliable method for estimating both chronological age and age class. This method gives a balance between accuracy, cost and practicability, therefore it is recommended when precise age estimations are not paramount. [ABSTRACT FROM AUTHOR]