Search

Understanding how epigenetic factors impact dental phenotypes can help refine the use of teeth for elucidating biological relationships among human populations. We explored relationships among crown size, principal cusp spacing, and accessory cusp expression in maxillary dental casts of nutritionally supplemented (n = 34) and non-supplemented (n = 39) individuals from Tezonteopan, Mexico. We hypothesized that the non-supplemented group would exhibit smaller molar crowns and reduced intercusp spacing. Since intercusp spacing is thought to be more sensitive to epigenetic influences than crown size, we predicted that the supplemented and non-supplemented groups would differ more in the former than the latter. Previous work suggests that molar accessory cusp expression may be elevated under conditions of stress. We therefore expected evidence of greater Carabelli and Cusp 5 trait expression in the non-supplemented group. We further hypothesized that anterior teeth would be affected by nutritional stress during development, with the non-supplemented group having smaller anterior tooth crowns and therefore limited space to form the tuberculum dentale. Finally, we tested whether the presence of molar accessory traits followed predictions of the Patterning Cascade Model of tooth morphogenesis in the entire sample. Our results supported the expectation that cusp spacing would differ more than molar crown size between the two groups. Carabelli trait showed little evidence of frequency differences between groups, but some evidence of greater trait scores in the non-supplemented group. The non-supplemented group also showed evidence of greater Cusp 5 frequency and expression. In the central incisors and canines, there was strong evidence for smaller crown sizes and reduced tuberculum dentale frequency in the non-supplemented group. With both groups pooled together, there was strong evidence of closer mesiodistal distances among principal cusps in molars with accessory cusps, a finding that is consistent with the PCM. Overall, our findings suggest that nutritional stress may affect accessory cusp expression. [ABSTRACT FROM AUTHOR]

Objective: The Health Action Process Approach (HAPA) describes social cognitive constructs related to behaviour change. A validated questionnaire is needed to measure these constructs in paediatric dentistry. The aim of this study was to improve an existing HAPA-based questionnaire for parents regarding brushing their children's teeth and to assess its validity and reliability in a population of parents of high caries risk children. Methods: Parents of high caries risk children of 3–10 years filled out the adjusted HAPA-based questionnaire. Mokken scale analysis, graded response model analyses, factor analyses and reliability analyses were performed according to the protocol of Dima. Discriminant validity was assessed by comparing the mean scores of the HAPA constructs between two groups of participants, based on different levels of caries experience, brushing frequency and education level of the mother. Results: The Mokken scale analysis and factor analyses indicated a multidimensional eight factor scale. The graded response model did not fit our data. The subscale action control could be identified as a two-factor subscale. Reliability indices from the Dima protocol varied, for instance Cronbach alpha ranged from 0.73 to 0.96. The constructs coping self-efficacy, action planning and action control discriminated between brushing frequencies. Conclusions: The adjusted HAPA-based questionnaire is an improved, valid and reliable instrument that could be used to evaluate HAPA-based interventions to improve children's oral health. [ABSTRACT FROM AUTHOR]

Objectives: To compare immediate implant placement (IIP) with early implant placement (EIP) for single tooth replacement in the aesthetic area in terms of aesthetic, clinical, and patient‐reported outcomes. Materials and Methods: Two independent reviewers conducted an electronic literature search in PubMed, Web of Science, Embase, and Cochrane databases as well as a manual search to identify eligible clinical studies up to February 2023. Randomized Controlled Trials (RCTs) comparing IIP with EIP were included for a qualitative and quantitative analysis. The primary outcome was vertical midfacial soft tissue change. Secondary outcomes were horizontal midfacial soft tissue change, vertical papillary change, pink esthetic score (PES), implant survival, buccal bone thickness, marginal bone level change, patient discomfort, chair time, and patient satisfaction. Results: Out of 1185 records, 6 RCTs were selected, reporting on 222 patients who received 222 single implants (IIP: 112 implants in 112 patients; EIP: 110 implants in 110 patients) in the anterior maxilla or mandible. Patients had a mean age ranging from 35.6 to 52.6 years and were followed between 8 and 24 months. Two RCTs showed some concerns, and four showed a high risk of bias. Four studies could be included in a meta‐analysis on the primary outcome and three only considered cases with an intact buccal bone wall. Meta‐analysis failed to demonstrate a significant difference in terms of vertical midfacial soft tissue change between IIP and EIP (mean difference: 0.31 mm, 95% CI [−0.23; 0.86], p =.260; I2 = 83%, p <.001). No significant differences were found for PES (standardized mean difference: 0.92, 95% CI [−0.23; 2.07], p =.120; I2 = 89%, p <.001), implant survival (RR: 0.98, 95% CI [0.93, 1.03], p =.480; I2 = 0%, p =.980), and marginal bone level change (mean difference: 0.03 mm, 95% CI [−0.12, 0.17], p =.700; I2 = 0%, p =.470). Insufficient data were available for meta‐analyses of other secondary outcomes. Conclusion: In low‐risk patients with an intact buccal bone wall, there seems to be no difference between IIP and EIP in terms of aesthetic and clinical outcomes. The strength of this conclusion is rated as low since studies showed an unclear or high risk of bias. In addition, state‐of‐the‐art therapy was only delivered in a minority of studies. Future RCTs should also provide data on patient‐reported outcomes since these have been underreported. [ABSTRACT FROM AUTHOR]

Objectives: This RCT aimed to compare zirconia and titanium dental implants in the maxillary premolar region. The comparison was based on marginal bone level (MBL) changes, clinical parameters, aesthetic outcomes, and patient related outcome measures (PROMs) 1 year after prosthetic loading. Materials and Methods: Fifty patients were randomly assigned to receive either a zirconia (ZrO2, n = 25) implant or a titanium (Ti, n = 25) bone‐level implant. Implants were provided with a lithium disilicate crown 3 months after placement. Follow‐up was at 1 month and after 1 year. The primary outcome pertained to changes in MBL. Reported secondary outcomes consisted of implant survival, peri‐implant tissue health, aesthetics, and PROMs. Results: Mean MBL change after 1 year was 0.01 mm (SD = 0.45; min = 0.72, max = 0.86) for ZrO2 and −0.09 mm (SD = 0.34; min = 0.53, max = −1.06) for Ti (p =.439). Scores for the other clinical outcome parameters and PROMs were generally favorable, with no significant differences. However, significant differences were found for the aesthetic outcomes regarding two criteria: (a) level of facial mucosa (p =.022), in favor of Ti, and (b) root convexity/soft tissue color and texture (p =.005) in favor of ZrO2. Conclusion and clinical implications: The ZrO2 and Ti implant types used in this study, replacing a single missing maxillary premolar, show a comparable outcome in terms of MBL change after 1 year. Clinical and aesthetic parameters, as well as PROMs, are favorable and similar between both implant types after 1 year of prosthetic loading. These short‐term study results suggest that both are suitable for clinical use. [ABSTRACT FROM AUTHOR]

Objectives: To systematically analyze the accuracy of robotic surgery for dental implant placement. Materials and Methods: PubMed, Embase, and Cochrane CENTRAL were searched on October 25, 2023. Model studies or clinical studies reporting the accuracy of robotic surgery for dental implant placement among patients with missing or hopeless teeth were included. Risks of bias in clinical studies were assessed. Meta‐analyses were undertaken. Results: Data from 8 clinical studies reporting on 109 patients and 242 implants and 13 preclinical studies were included. Positional accuracy was measured by comparing the implant plan in presurgery CBCT and the actual implant position in postsurgery CBCT. For clinical studies, the pooled (95% confidence interval) platform deviation, apex deviation, and angular deviation were 0.68 (0.57, 0.79) mm, 0.67 (0.58, 0.75) mm, and 1.69 (1.25, 2.12)°, respectively. There was no statistically significant difference between the accuracy of implants placed in partially or fully edentulous patients. For model studies, the pooled platform deviation, apex deviation, and angular deviation were 0.72 (0.58, 0.86) mm, 0.90 (0.74, 1.06) mm, and 1.46 (1.22, 1.70)°, respectively. No adverse event was reported. Conclusion: Within the limitation of the present systematic review, robotic surgery for dental implant placement showed suitable implant positional accuracy and had no reported obvious harm. Both robotic systems and clinical studies on robotic surgery for dental implant placement should be further developed. [ABSTRACT FROM AUTHOR]

Working-class health cultures before the National Health Service have long been of scholarly interest but those related to oral health are chronically underexamined. This article examines one important aspect of this history—tooth pulling—in early twentieth-century Lancashire. By highlighting the dynamics of market supply and demand, it demonstrates how and why the tooth pulling services of non-orthodox practitioners called dental mechanics remained popular despite the increasing monopolization of oral health by dentists. Dentists characterized mechanics as quacks, but working-class Lancastrians sought out these mechanics because they formed a trusted part of their communities. This demonstration of a population's preference for unorthodox over orthodox practitioners provides a much-needed counter-narrative to professionalization in oral health and highlights the significance of geographically specific traditions over the values of medicine and science. [ABSTRACT FROM AUTHOR]

Simultaneous avulsion of four or more teeth is a rare event. This case report examines the dental care given to an adult who, during a bicycle accident, experienced the avulsion of a mandibular incisor as well as all of his maxillary incisors. In the immediate aftermath of the accident, four out of the five incisors were located, promptly collected, and stored in a tooth rescue box, all within a 20‐min window. Replantation and splinting were performed on the day of the accident. Endodontic treatment involved sequential intracanal dressing with an antibiotic–corticosteroid paste followed by calcium hydroxide prior to root canal obturation. 3 months post‐accident, signs of external replacement resorption (ERR) began to appear in all the replanted teeth. The gap created by the missing maxillary central incisor was managed with a three‐unit fixed dental prosthesis, despite the onset of ERR in the incisors used as abutment teeth. Regular follow‐ups showed a relatively slow ERR progression rate over a span of nearly 6 years. The patient expressed satisfaction with both the esthetic and functional outcomes. This case, marked by multiple avulsions, underscores the importance of immediate and appropriate intervention alongside the imperative for carefully considered long‐term management strategies. Given the decelerated bone remodeling rate in adults, ERR generally progresses at a slower pace than in children. Accordingly, this case demonstrates the viability of retaining replanted teeth over the long term, even when these teeth have been subjected to nonphysiological storage for extended durations, a factor known to impede periodontal healing. [ABSTRACT FROM AUTHOR]

Background/Aim: Anterior teeth are prone to traumatic dental injuries (TDIs). Although a number of techniques ranging from original tooth fragment reattachment (TFR) to direct composite restoration (DCR) can be used to restore uncomplicated crown fractures, there is no consensus on which method is best. The purpose of this study was to investigate the fracture resistance of bovine incisors restored by two different techniques (TFR and DCR) in three different fracture models. Materials and Methods: Sixty extracted bovine lower incisors were randomly divided into three groups (n = 20). Angle, oblique, or transverse sections of all the teeth in a group were prepared by using a disk. The cut surfaces were scanned, and the cross‐sectional areas (CSA) of the enamel and dentin were measured. Half the teeth in each group were restored by DCR (n = 10) and the other half by TFR (n = 10). The forces required to fracture the restored teeth were then measured using a Universal testing machine, and the fracture modes were analyzed (cohesive, adhesive, or mixed). Results: No statistically significant differences between the TFR and DCR restorations were detected for total and enamel CSAs in any of the restoration shapes (p >.067). The fracture forces required to break DCR angle and transverse restorations were significantly greater than for the corresponding shapes restored with TFR (p <.033). However, the difference in the forces needed to fracture oblique section restorations by DCR or TFR was not statistically significant (p =.239), despite a similar trend (143.4 ± 51 N and 120.9 ± 25 N, respectively). Conclusion: This study revealed that a greater force is required to fracture teeth restored by the DCR than by the TFR technique, especially for a transverse section. This demonstrates that restoring a fractured tooth provides a superior outcome compared to reattaching the fractured fragment. [ABSTRACT FROM AUTHOR]

Background: Crown fracture is the most common injury in permanent teeth. This study aimed to evaluate the treatment outcomes of permanent teeth with uncomplicated and complicated crown fractures and to investigate potential factors. Materials and Methods: This retrospective study included patients who experienced crown fractures in permanent teeth from 2018 to 2021 with at least 12 months of follow‐up. All complicated crown fractured teeth were treated with pulpotomy, while for teeth with uncomplicated crown fractures, three treatments (restoration, indirect pulp capping, or pulpotomy) were employed. The chi‐square test was used to compare the prognosis of teeth with uncomplicated and complicated crown fractures. Potential factors associated with pulp survival including gender, interval, root development, enamel infraction, mobility, concomitant luxation injury, treatment, and coronal restoration were identified via Cox regression analysis. Results: A total of 307 teeth from 220 children (average age = 9.3 ± 1.4 years; age range, 6–14 years) with a median follow‐up of 23 months were included, and 82.1% of all teeth had immature roots. Complicated crown fractured teeth (93.6%, 102/109) had a significantly higher success rate compared with uncomplicated crown fractured teeth (85.4%, 169/198) (p <.05). Pulpotomy (96.9%) had the highest success rate of all treatments for uncomplicated crown fractures, followed by only restoration (85.0%) and indirect pulp capping (76.9%). The success rate of teeth that received pulpotomy was significantly higher than those treated by indirect pulp capping (p <.05). In uncomplicated crown fractures, teeth with Class II mobility were more vulnerable to failure than teeth without abnormal mobility (HR = 34.83; 95% CI, 9.59–126.56; p <.05); teeth that received pulpotomy were less prone to failure than teeth that received indirect pulp capping (HR = 13.53; 95% CI, 1.58–115.72; p <.05). Conclusion: Crown fractures treated with conservative pulp treatments had a relatively highly favorable prognosis. The prognosis of uncomplicated crown fractured teeth was impacted by the severity of periodontal injury and treatment strategies. Accurate diagnosis and identification of micro‐exposures are important. Dentists should take multiple risk factors into account and select optimal treatment strategies. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the indication of the endodontic treatment for vital intact teeth with the root apex involved in large radicular cystic lesions of endodontic origin. Methodology: This prospective cohort study enrolled healthy participants with radicular cysts of endodontic origin and with the root apex of vital intact teeth involved in the bone defect, as determined by cone beam computed tomography (CBCT). Thirty‐two sound vital teeth were analysed by thermal (TPT) and electric pulp tests (EPT) before surgery (T0) and 1 week (T1), 2 weeks (T2), 3 months (T3) and 6 months (T4) post‐surgery. Student's t‐test (p <.05) was used to compare the EPT values at baseline and T4. anova (p <.05) was used to analyse the EPT variations for all maxillary and mandibular teeth. McNemar test (p <.05) was used to compare the results according to variation in EPT values gathering by variation, no variation and no response. Results: At T1, 75 and 65.7% of teeth responded positively whilst 25 and 34.3% did not respond to EPT and TPT, respectively. The variation of the EPT values between T0 and T1 was observed for 50.0% of teeth, whilst no variation was noticed in 25.0% of teeth. At T4, 90.6 and 87.5% of teeth responded positively whilst 9.4 and 12.5% did not respond to EPT and TPT, respectively. At T4, variation of the EPT values between T0 and T4 was observed for 28.1%, whilst no variation was noticed in 62.5% of teeth. There were no statistical differences in EPT results between T0 and T4 (p >.05), but significant differences were observed for EPT values between T1 and T4 (p <.05), and between mandibular and maxillary teeth. The pulp sensibility of maxillary teeth worsened after surgery, before reverting progressively to T0 values, whilst no statistically significant differences were observed for mandibular teeth at the different time points. Conclusions: These data support the inconsistence of the prophylactic endodontic treatment in healthy vital teeth with apex involvement in large cystic lesions of endodontic origin. Post‐surgery follow‐up with TPT and EPT is recommended to assess pulp status. [ABSTRACT FROM AUTHOR]

This study proposes the slope of the engine speed trend line (SlopeESTL) as a new misfire detection index for a four-cylinder engine, not limited to four-cylinder engines. SlopeESTL is defined as angular acceleration between the first and the last teeth of each cylinder in the cycle. SlopeESTL is flat and near 0 when the cylinder is normally combusted. A misfire leads to an abrupt decrease under the threshold. While it is affected by post oscillation just after misfires, there is enough margin between SlopeESTL of the misfired cylinder and post-oscillated SlopeESTL. The mean misfire detection and detection fault rates of the SlopeESTL were over 97% and under 1% in this study, making it a good misfire detection index. However, most of the first misfired cylinder on dual cylinder misfire can seldom be detected as a misfire at the high engine speed over 5000 rpm in the single cylinder misfire pattern. This is caused by the inertia force of the crankshaft system and is a demerit for the misfire detection index. It is one of the two RPM slopes used to calculate the Gap and ΔGap slopes proposed by the author. SlopeESTL can be used with Gap and ΔGap slopes, because they have their specific characteristics as misfire detection indices and their combination logic should be studied more. Furthermore, SlopeESTL can be affected by the machining tolerance of the teeth in the sensor wheel, torsional vibration, and non-uniformity in the stroke operation of the piston. However, it uses the tooth time measured using the existing crankshaft position sensor; an additional sensor is not required, which makes it economical. [ABSTRACT FROM AUTHOR]

Objectives: Prevention complements the curative management of oral diseases. Effective preventive interventions involve the adoption of oral health promoting behaviours. Little is known about the awareness of oral disease and its prevention among Singaporean adults as well as their prevailing oral health attitudes and behaviours. The aim of the study was to describe the oral health knowledge, attitudes and behaviours of adults in Singapore. Methods: A random sample of adults (≥21 years old) in Singapore was selected to complete an interviewer‐administered questionnaire. The questionnaire gathered information about their knowledge of the aetiology, signs and symptoms as well as prevention of dental caries and periodontal disease; attitudes about the value of teeth, locus of control in maintaining oral health and oral health behaviours including toothbrushing, flossing and dental attendance. Results: A total of 1196 adults of weighted mean age 48 years old with almost equal proportions of males and females responded to the questionnaire. Participants were more unaware about the causes of periodontal disease (25.7%) than dental caries (4%). While more than 90% of participants felt that healthy teeth were important and could affect their overall health, many (67.0%) felt it was natural to lose their teeth with old age. Among the participants, 83.5% brushed their teeth twice a day; 41.9% flossed their teeth and 53.9% visited the dentist at least once a year. Conclusions: The study findings showed good knowledge around dental caries but some gaps around periodontal disease. It also found that participants perceived having limited control over preventing tooth loss. Irregular dental attendance and poor denture wearing habits were also noted. The findings shed light on key areas to focus on through oral health promotion to improve overall oral health. [ABSTRACT FROM AUTHOR]

Currently, ceramic dentures are mainly obtained by using computer-assisted cutting block of material to obtain the shape as the removing a model of patient's mouth. Followed by immersion coloring, porcelain stacking, and sintering to obtain dentures similar to a patients' tooth, this is a large-loss and complex process. In this study, 16 standard tooth samples were successfully reduced by adding Fe 2 O 3 , Pr 6 O 10 , Er 2 O 3 , and MnO 2. After the colorful ceramic powder and photosensitive resin were configured into a slurry, a close to the sample tooth dentures was successfully prepared using digital light processing (DLP). The flexural strength and compressive strength of the ceramic specimens prepared by this method reached 821.01 ± 51.72 MPa and 2.67 GPa ± 0.22 MPa. To verify the biosafety of the prepared ceramics, we performed an in vitro biological evaluation of rat fibroblasts (L929). The resulting showed that the extracts of the prepared ceramic teeth had good biosafety, and the cells could also attach to the surface of the prepared ceramics. Hemolysis experiments confirmed good blood compatibility. Thus, our results show that DLP-printed standard tooth-colored ceramic dentures have good mechanical properties and biocompatibility, and can provide a solution to patients seeking quick access to aesthetic dentures. We present a strategy for the development of standard tooth-colored, high-precision, high-mechanical-property and highly biocompatible ceramic dentures based on DLP light-curing printing technology. Through a large number of experiments to find the law of color adjustment, and achieved the reduction of 16 kinds of tooth color. Adjusting the printing parameters, high precision printing was realized. The samples are structurally stable after sintering and have excellent mechanical properties. Through CCK-8, hemolysis rate, live/dead cell staining, cell adhesion and cytoskeletal staining tests, the prepared denture showed excellent biocompatibility. [Display omitted] [ABSTRACT FROM AUTHOR]

The aim was to evaluate the effect of probiotics‐containing beverages on dental caries development by a systematic review and meta‐analysis (PROSPERO CRD42021258010). PubMed, Embase, and Web of Science databases were assessed (up to October 2023) for randomized placebo‐controlled trials that evaluated the consumption of probiotics‐containing beverages having dental caries as endpoint. Risk of bias assessment (Cochrane Handbook) was performed for all studies. Risk ratio (RR), standardized mean difference (SMD) and 95% confidence interval (CI), were calculated for caries prevalence and caries increment, respectively. Meta‐analysis was performed. Qualitative analysis of more than 2000 individuals aged from 1 to 84 years (9 studies) showed inconsistent effects of these probiotics‐containing beverages. Synthesis of more than 1000 children and adolescents did not demonstrate a statistically significant difference in the proportion of individuals with cavitated lesions (RR 0.60 [95 % CI 0.34 to 1.08]; n = 2), but a significantly smaller increment of both cavitated and non‐cavitated carious lesions (SMD −0.23 [95 % CI −0.39 to −0.08]; n = 4) was related to the consumption of probiotics‐containing beverages. Certainty of evidence for caries prevalence and caries increment were moderate and low, respectively. Current evidence is not substantial to strengthen the impact of these beverages on caries development. [ABSTRACT FROM AUTHOR]

For many years, space human factors research has focused on the impact of microgravity on human physiology and the health risks astronauts face during space flights of various durations. Our review paper reveals that microgravity leads to both reversible and non-reversible effects on astronauts' oral health. In addition to oral health concerns, astronauts often experience muscle degeneration during space missions, which is closely tied to bone loss. Despite our knowledge of high bone resorption and rapid mineral and calcium loss in microgravity, the exact underlying mechanisms remain unclear. However, to fully understand these processes and develop effective strategies to counteract the consequences of microgravity, more research is needed. This includes a deeper exploration of how these molecules and other biomarkers work, identification of early mechanotransduction sensors, and a comprehensive understanding of the physiological effects of weightlessness. Current solutions primarily involve administering antioxidants, regular exercise, and appropriate nutrition. Additionally, innovative approaches such as experimental drug therapies using anti -myostatin antibodies and r-irisin have gained attention. Further large-scale, long-term studies are required to understand the effects of microgravity on the oral cavity and prevent its adverse consequences. • Impact of Microgravity on Dental Health: Discuss the physiological changes experienced by astronauts in microgravity environments, including fluid redistribution, decreased mechanical loading, and altered bone metabolism, and their implications for oral health. • Weight-Bearing vs. Non-Weight-Bearing Bones: Examines the relationship between microgravity and bone loss, with a focus on distinguishing its effects on weight-bearing and non-weight-bearing bones. • Comprehensive Impact Assessment: Calls for comprehensive research on how microgravity affects various bones in both animals and humans, including analyses of bone structure, density, and strength. • Bone Loss and Tooth Mobility: Examine how microgravity-induced bone loss affects the integrity of the jawbone, leading to increased tooth mobility and potential dental complications such as loosened crowns, dental implants, or even tooth loss. • Differential Recovery: Investigates how weight-bearing and non-weight-bearing bones recover following bone loss in microgravity conditions and the underlying mechanisms at play. • Addressing Inconsistencies: Highlights the need to resolve inconsistencies in existing literature regarding the influence of microgravity on osteogenic proliferation and differentiation. • Osteocytes and Osteoclasts in Microgravity: Emphasises the importance of understanding the roles of osteocytes and osteoclasts in microgravity-induced bone loss to identify potential therapeutic targets. [ABSTRACT FROM AUTHOR]

Most tooth‐bearing non‐mammalian vertebrates have the capacity to replace their teeth throughout life. This capacity was lost in mammals, which replace their teeth only once at most. Not surprisingly, continuous tooth replacement has attracted much attention. Classical morphological studies (e.g. to analyse patterns of replacement) are now being complemented by molecular studies that investigate the expression of genes involved in tooth formation. This review focuses on ray‐finned fish (actinopterygians), which have teeth often distributed throughout the mouth and pharynx, and more specifically on teleost fish, the largest group of extant vertebrates. First we highlight the diversity in tooth distribution and in tooth replacement patterns. Replacement tooth formation can start from a distinct (usually discontinuous and transient) dental lamina, but also in the absence of a successional lamina, e.g. from the surface epithelium of the oropharynx or from the outer dental epithelium of a predecessor tooth. The relationship of a replacement tooth to its predecessor is closely related to whether replacement is the result of a prepattern or occurs on demand. As replacement teeth do not necessarily have the same molecular signature as first‐generation teeth, the question of the actual trigger for tooth replacement is discussed. Much emphasis has been laid in the past on the potential role of epithelial stem cells in initiating tooth replacement. The outcome of such studies has been equivocal, possibly related to the taxa investigated, and the permanent or transient nature of the dental lamina. Alternatively, replacement may result from local proliferation of undifferentiated progenitors, stimulated by hitherto unknown, perhaps mesenchymal, factors. So far, the role of the neurovascular link in continuous tooth replacement has been poorly investigated, despite the presence of a rich vascularisation surrounding actinopterygian (as well as chondrichthyan) teeth and despite a complete arrest of tooth replacement after nerve resection. Lastly, tooth replacement is possibly co‐opted as a process to expand the number of teeth in a dentition ontogenetically whilst conserving features of the primary dentition. That neither a dental lamina, nor stem cells appear to be required for tooth replacement places teleosts in an advantageous position as models for tooth regeneration in humans, where the dental lamina regresses and epithelial stem cells are considered lost. [ABSTRACT FROM AUTHOR]

Removal of ewes from a flock before the end of their productive life, sometimes described as ewe wastage, can potentially lead to reduced flock productivity. While the main reasons for culling ewes are largely known, their relative importance to New Zealand farmers and farmers' rational behind their culling decisions are not. Therefore, this study involved semi-structured interviews with 38 sheep farmers from throughout New Zealand to explore their ewe culling decisions. Farmers consistently culled mixed-age and two-tooth ewes who failed to become pregnant or who had a vaginal prolapse. For other culling reasons, farmers' use of them and their rationale for doing so was diverse and varied between farmers based on ewe age-group, severity, season, perceived economic consequences and farmers' personal preference. This diversity indicates that there is scope for some farmers to carefully evaluate some of their culling decisions. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the effect of cumulative doses of radiation on the pushout bond strength (BS) of a universal resin cement used in the self‐etch (SE) and self‐adhesive (SA) modes to the intraradicular dentin. Materials and Methods: Forty‐eight human teeth were distributed into three groups (n = 16) according to the radiation therapy dose (RT): NoRT (no‐radiotherapy), 70RT (70 Gy), and 70 + 70RT (70 Gy + 70 Gy). The teeth were redistributed into two subgroups (n = 8), according to the adhesive mode: SE (NoRT‐SE, 70RT‐SE, and 70 + 70RT‐SE) and SA (NoRT‐SA, 70RT‐SA, and 70 + 70RT‐SA). Data were statistically compared after BS test (ANOVA, Tukey's post hoc test, and Fisher's exact test). Results: In the SA mode, BS was significantly higher in nonirradiated teeth compared with 70RT and 70 + 70RT (p < 0.0001). There were no significant differences between SE and SA modes in nonirradiated teeth (p = 0.14). In the 70RT group, SE mode increased BS compared with SA mode (p < 0.0001). Most specimens had adhesive and mixed failures in SA and SE modes, respectively. Conclusions: The universal resin cement in the SE mode had greater BS to the irradiated dentin. When teeth were re‐irradiated, the universal resin cement had similar performance in terms of BS, regardless of the adhesive approach. Clinical Significance: There is no research establishing a correlation between radiotherapy and its impact on the BS of a universal resin cement used in SE and SA modes to intraradicular dentin. [ABSTRACT FROM AUTHOR]

Objective: The aim of this review was to compare various types of restorations used in children and young adults affected with amelogenesis imperfecta (AI) to determine the most effective restorative treatment. Methods: This systematic review included randomized controlled trials, retrospective and prospective cohorts conducted on children and young adults diagnosed with amelogenesis imperfecta and written in French or English. A systematic search was conducted using four databases, namely Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE via PubMed, Science Direct and Scopus, using a selection of MeSH terms: "Amelogenesis Imperfecta," "Therapeutics," "Treatment Outcome," "Adult, young," "Child," "Dental Restoration, Permanent," "Dental Restoration, Temporary," and "Esthetics, Dental." Results: Out of 138 articles identified in the initial search, four articles met all the inclusion criteria. The results showed that ceramic restorations had better quality scores and longevity compared to other restorations. Conclusion: Ceramic restorations could be considered the restorative treatment modality of choice for AI‐affected children and young adults. However, more high‐quality clinical trials involving young patients affected with AI are required to evaluate and compare the outcomes of different restorative approaches. Clinical Significance: Young patients affected with amelogenesis imperfecta usually suffer from low self‐esteem, psychological problems and social avoidance, caused by the alteration of teeth such as discoloration, sensitivity, fractures and reduced size. For the dentist, selecting the appropriate restorative treatment for AI in young patients could be a veritable challenge. Therefore, it is important to have an evidence‐based modality. For this reason, in this review, the different restorative approaches used in AI‐affected young patients were compared to recommend the most effective treatment. [ABSTRACT FROM AUTHOR]

Background: Biomedtrix BFX® cementless total hip replacement (THR) requires the use of femoral broaches to prepare a press-fit envelope within the femur for subsequent stem insertion. Current broaches contain teeth that crush and remove cancellous bone; however, they are not particularly well-suited for broaching sclerotic (corticalized) cancellous bone. In this study, three tooth designs [Control, TG1 (additional V-grooves), TG2 (diamond tooth pattern)] were evaluated with a quasi-static testing protocol and polyurethane test blocks simulating normal and sclerotic bone. To mimic clinical broaching, a series of five sequential broach insertions were used to determine cumulative broaching energy (J) and peak loads during broach insertion. To determine the effect of broach tooth design on THR stem insertion, a BFX® stem was inserted into prepared test blocks and insertion and subsidence energy and peak loads were determined. Results: Broach tooth design led to significant differences in broaching energy and peak broaching loads in test blocks of both densities. In low density test blocks, TG1 required the lowest cumulative broaching energy (10.76 ±0.29 J), followed by Control (12.18 ±1.20 J) and TG2 (16.66 ±0.78 J) broaches. In high density test blocks, TG1 required the lowest cumulative broaching energy (32.60 ±2.54 J) as compared to Control (33.25 ±2.16 J) and TG2 (59.97 ±3.07 J). During stem insertion and subsidence testing, stem insertion energy for high density test blocks prepared with Control broaches was 14.53 ± 0.81 J, which was significantly lower than blocks prepared with TG1 (22.53 ± 1.04 J) or TG2 (19.38 ± 3.00 J) broaches. For stem subsidence testing in high density blocks, TG1 prepared blocks required the highest amount of energy to undergo subsidence (14.49 ± 0.49 J), which was significantly greater than test blocks prepared with Control (11.09 ±0.09 J) or TG2 (12.57 ± 0.81 J) broaches. Conclusions: The additional V-grooves in TG1 broaches demonstrated improved broaching performance while also generating press-fit envelopes that were more resistant to stem insertion and subsidence. TG1 broaches may prove useful in the clinical setting; however additional studies that more closely simulate clinical broach impaction are necessary prior to making widespread changes to THR broaches. [ABSTRACT FROM AUTHOR]

Although tool use may enhance resource utilization, its fitness benefits are difficult to measure. By examining longitudinal data from 196 radio-tagged southern sea otters (Enhydra lutris nereis), we found that tool-using individuals, particularly females, gained access to larger and/or harder-shelled prey. These mechanical advantages translated to reduced tooth damage during food processing. We also found that tool use diminishes trade-offs between access to different prey, tooth condition, and energy intake, all of which are dependent on the relative prey availability in the environment. Tool use allowed individuals to maintain energetic requirements through the processing of alternative prey that are typically inaccessible with biting alone, suggesting that this behavior is a necessity for the survival of some otters in environments where preferred prey are depleted. [ABSTRACT FROM AUTHOR]

Background: This study aimed to investigate the relationship between the Curve of Spee (COS) depth and malocclusion characteristics in a population from Sibiu County, Romania. The research sought to understand how the COS's anatomical dimensions correlate with different classes of malocclusion and the position of the frontal teeth. Methods: A total of 265 participants from the Dentistry Ambulatory of the Military Hospital of Sibiu were included in this study. It employed digital intraoral scanning technology to measure the COS, overjet, and overbite, with malocclusion classification. Statistical analyses, including correlation and regression, were conducted to examine the relationships between COS depth, frontal teeth position, and malocclusion characteristics. Results: The average COS depth measured was 1.0564 mm, presenting variability when compared to existing literature. Most of the study participants had Class I malocclusion. A significant positive correlation between COS depth and overjet was identified, with no notable gender-based differences in these occlusal parameters. Conclusions: The findings affirm the integral role of COS in occlusal dynamics and malocclusion diagnosis. The COS measurement of a mean of 1.0564 mm, when compared to other results emphasizes the differences in occlusal curvature among various populations. The results contribute to a refined understanding of occlusal relationships, supporting the need for personalized orthodontic and prosthetic treatments based on precise anatomical measurements. [ABSTRACT FROM AUTHOR]

The objectives of this study were to evaluate the tooth movement tendency during space closure in maxillary anterior teeth by various combinations of retraction force and intrusive force in a double-archwire lingual orthodontic system. Mini-implant-double slot lingual orthodontics system models of the bilateral maxillary first premolar extraction cases were constructed. Three-dimensional finite element models of the maxilla were constructed with definite position mini-implants (8 mm) and power arms (6 mm). Different retraction forces(50gf、100gf、150gf)were applied with the help of a nickel-titanium closed coil spring on the plate side. Intrusive forces(0gf、50gf、100gf)were applied with the help of the mini-implant between the two central incisors, and the initial displacements of the maxillary anterior teeth were analyzed. Variable amounts of displacements like controlled tipping, uncontrolled tipping, lingual crown tipping, labial root tipping, extrusion and distal crown tipping were observed in all the models, and these tendencies increased as the magnitude of retraction force increased, and these tendencies decreased as the magnitude of intrusive force increased. When the intrusive force was greater than or equal to the retraction force, the maxillary central incisors showed the trend of lingual crown tipping and labial root tipping, resulting in uncontrolled tipping movement. In terms of horizontal changes, the increasing width of bilateral anterior teeth was observed, with canines showing the least increasing trend. Various combinations of retraction force and intrusive force in a double-archwire lingual orthodontic system provide a new choice for torque control of the anterior teeth. Although anterior mini-implants and elastics can achieve incisor intrusion and lingual root torque, they cannot achieve the expected torque without additional torque control methods. [ABSTRACT FROM AUTHOR]

DNA analysis plays a crucial role in forensic investigations, helping in criminal cases, missing persons inquiries, and archaeological research. This study focuses on the DNA concentration in different skeletal elements to improve human identification efforts. Ten cases of unidentified skeletal remains brought to the Institute of Forensic Medicine in Timisoara, Romania, underwent DNA analysis between 2019 and 2023. The results showed that teeth are the best source for DNA extraction as they contain the highest concentration of genetic material, at 3.68 ng/µL, compared to the petrous temporal bone (0.936 ng/µL) and femur bone (0.633 ng/µL). These findings highlight the significance of teeth in forensic contexts due to their abundant genetic material. Combining anthropological examination with DNA analysis enhances the understanding and precision of identifying human skeletal remains, thus advancing forensic science. Selecting specific skeletal elements, such as the cochlea or teeth, emerges as crucial for reliable genetic analyses, emphasizing the importance of careful consideration in forensic identification procedures. Our study concludes that automated DNA extraction protocols without liquid nitrogen represent a significant advancement in DNA extraction technology, providing a faster, more efficient, and less labor-intensive method for extracting high-quality DNA from damaged bone and tooth samples. [ABSTRACT FROM AUTHOR]

The taphonomy and diagenesis of bone and teeth recovered from any environments provide crucial information for forensic sciences and investigations. This leads to the estimation of the postmortem interval (PMI) and the postmortem submersion interval (PMSI) of the organism/s. Aquatic taxa can induce macroscopic and microscopic alterations in biomineralized tissues (e.g., grooves) or can colonize them by attachment (e.g., Bryozoa). Bryozoa are tiny invertebrates that form colonies in freshwater and saltwater. They can survive for years as suspension feeders in all climates. Most marine Bryozoa species have a biomineralized exoskeleton that can be preserved after their death. This research analyzes eight fragments of archeological elephant ivory with a known PMSI of 314 years, which were inhabited by three distinct bryozoan colonies. The variations in the preservation of the bryozoan exoskeletons and the overgrowth of different marine taxa reveal that one colony (lichenoporid cyclostomatid) was alive at the time of the ivory collection from the submerged archeological site while the two other colonies (cheilostomatid) had previously died at different times. The primary objective of this observation is to contribute to the understanding of the taphonomy of terrestrial mammalian biomineralized tissues recovered in marine environments. Additionally, the study discusses the potential forensic implications of this association, such as the evidence of marine submersion and the PMSI. A secondary objective is to present the Bryozoa colonies within a distinctive depositional context, considering that many bryozoan species of the Western Australian coast remain undescribed. The complexity of the Bryozoa ecobiology is also highlighted, with the need of further research (e.g., minimum time for colonization). Finally, this study highlights the urgency of multidisciplinary collaboration to advance aquatic forensic capabilities. [ABSTRACT FROM AUTHOR]

Background: Secondary healthcare data use has been increasing in the dental research field. The validity of the number of remaining teeth assessed from Japanese dental claims data has been reported in several studies, but has not been tested in the general population in Japan. Objectives: To evaluate the validity of the number of remaining teeth assessed from Japanese dental claims data and assess its predictability against subsequent health deterioration. Methods: We used the claims data of residents of a municipality that implemented oral health screening programs. Using the number of teeth in the screening records as the reference standard, we assessed the validity of the claims-based number of teeth by calculating the mean differences. In addition, we assessed the association between the claims-based number of teeth and pneumococcal disease (PD) or Alzheimer's disease (AD) in adults aged ≥65 years using Cox proportional hazards analyses. Results: Of the 10,154 participants, the mean number of teeth assessed from the claims data was 20.9, that in the screening records was 20.5, and their mean difference was 0.5. During the 3-year follow-up, PD or AD onset was observed in 10.4% (3,212/30,838) and 5.3% (1,589/30,207) of participants, respectively. Compared with participants with ≥20 teeth, those with 1–9 teeth had a 1.29 (95% confidence interval [CI]: 1.17–1.43) or 1.19 (95% CI: 1.04–1.36) times higher risk of developing PD or AD, respectively. Conclusion: High validity of the claims-based number of teeth was observed. In addition, the claims-based number of teeth was associated with the risk of PD and AD. [ABSTRACT FROM AUTHOR]

An efficient treatment plan using a temporary anchorage device should be built following the principle of reducing the number of tads to obtain a multiple biomechanical advantage. The following case report concerns the Biga system, a strategy that supports orthodontists during class II corrections and vertical control through treatment. A 12-year-old girl with a high angle of skeletal class II was selected. A novel biomechanical strategy was effectively applied using two tads on the upper arch to obtain sequential distalization of the upper teeth and to correct the lower arch spee curve using third-class elastics. Eventually, on the same tads, a double cantilever was applied to control the overbite and intrusion during incisors' retraction. The Biga system is an easy biomechanical strategy that ensures the three-dimensional control of treatment mechanics in class II patients. [ABSTRACT FROM AUTHOR]

Anterior teeth restoration represents a challenge for dentists, who often rely on the dental technician's wax-up. The proposed Stratified Stamp Technique (SST) allows for clinically reproducing the wax-up in a quick and easy way. A patient with fractures and discoloration on the upper central incisors was treated with resin-based composite direct restorations. Using SST, a 1 mm thick thermoformed polyethylene-terephthalate-glycol (PETG) template, based on the technician's wax-up, was produced. Enamel Selective Area Reduction (SAR) was performed to guarantee adequate space for the restorations, and the fracture margins were rounded and finished. Traditional layering procedures according to the five color dimensions of teeth were performed, except for the final labial layer, which was realized with warm composite loaded inside the template and polymerized through it, in order to ensure accurate tooth morphology reproduction. SST offers a reliable method for transferring technician's wax-up morphology to direct composite restorations in anterior teeth. Compared with other methods, SST allows for better isolation with a rubber dam and permits traditional layering with multiple composite shades, thus leading to satisfactory esthetic outcomes. [ABSTRACT FROM AUTHOR]

Key Clinical Message: This clinical case report focuses on a case of surgery performed on a patient with the aim of cutting the dental apices in the patient's upper jaw. Mineral trioxide aggregate (MTA) was used as a filling material, and monitoring the condition showed that the operation was successful. [ABSTRACT FROM AUTHOR]

Background: There is an increased tendency towards adopting minimally invasive interventions in dentistry, supported by advancement in materials and techniques. However, the decision‐making process in choosing conservative or invasive treatments is influenced by several factors, particularly in permanent teeth with irreversible pulpitis. Objectives: The objective of the study was to systematically review the literature regarding factors that influence decision‐making for vital pulp therapy (VPT) as definitive treatment option in permanent mature teeth diagnosed with irreversible pulpitis. Methods: Two independent reviewers searched five electronic databases (PubMed, Embase, Web of Science, Scopus and Cochrane Library). Grey literature was searched through Google Scholar and contact with experts. Defined search keys were applied, and all peer‐reviewed literature published with no language nor publication date limits were included. The All studies investigating the factors influencing treatment decision‐making in mature permanent teeth with irreversible pulpitis were included. The quality of included studies was assessed by two independent reviewers using the Joanna Briggs Institute quality assessment tool. Results: Six articles were included in the review. All included studies used questionnaires to characterize clinician preferences and attitudes in choosing treatment options for mature permanent teeth with irreversible pulpitis. The available evidence suggests that dentist‐related factors have a significant influence on the chosen treatment in teeth with irreversible pulpitis, with speciality training and years of experience influencing the choice of VPT over other treatment options. COVID‐19 reportedly swayed the dentists' decision to favour VPT. Only one article studied the influence of patient‐related factors, such as age and presence of spontaneous pain on decision‐making. Of note, a history of cardiovascular disease moved dentists towards prescribing VPT. Discussion: Collectively, the included studies demonstrated an overriding influence of dentist‐related factors on choosing among treatment options for painful teeth diagnosed with irreversible pulpitis. Patient‐related factors were acknowledged but there are also potential factors such as socio‐economic constraints that were not included in the component studies. Conclusion: In teeth with irreversible pulpitis clinicians educational background influence the decision towards a specific treatment option. Further data, preferably derived from clinical records, is necessary in future investigations to explore the effect of other important factors related to both dentists and patients. Registration: PROSPERO database (CRD42022339653). [ABSTRACT FROM AUTHOR]

Double-flank measurement is the most commonly used method for full inspection of mass-produced gears and has high measurement efficiency, but it cannot obtain the analytical parameters and is not helpful enough to evaluate the NVH performance of the gears. Based on the double-flank rolling tester with a new principle, a simulation method for double-flank measurement and a solving method for analytical parameters are proposed. Using the simulation method, the double-flank measurements without random error can be obtained through the collision detection algorithm. The solving method uses the iteration to obtain the minimum rolling length of each position of the tooth surface, then obtains the analytical parameters of the gear. In the experiments, the difference between the profile deviations obtained by the solving method and superimposed in the simulation method is less than 0.03 μm. The experiment results have verified the correctness of the simulation method and the solving method. These methods can greatly improve the value of double-flank measurement. [ABSTRACT FROM AUTHOR]

Accurately and fast calculation of single tooth load contact state of a gear pair is the basis for accurate calculation of multi-tooth load contact analysis. Therefore, this study proposed a semi-analytical quick single tooth load tooth contact analysis (Q-SLTCA) method. First, the ease-off tooth contact analysis (ease-off TCA) method was established, and a numerically stable initial contact stress distribution and contact ellipse analytical model was derived. Then, considering the influence of edge contact, the real-time division method of gear tooth slice was derived. Based on this, the equivalent principle of contact elliptical node and the load correction strategy were innovatively proposed. Then, the calculation method of the meshing characteristics of the tooth slice was established by coupling the boundary element method (BEM) with the equivalent cylindrical Hertz contact theory. The bending deformation, tooth root stress distribution, contact stress, contact deformation and meshing stiffness of the tooth slice were analyzed and calculated, and the instantaneous meshing stiffness of the single tooth was determined by combining the parallel method of the gear tooth stiffness. Finally, a single-tooth finite element method (FEM) meshing model was created for comparison with the method in this study, which verified the calculation accuracy and efficiency of the proposed method. This method can be easily developed into a quick multi-tooth load contact analysis algorithm, which can provide a new method for gear tooth crack and failure analysis. • Propose a real-time division method of tooth slice combined with ease-off TCA. • Propose an elliptical node equivalent principle and load correction strategy considering edge contact. • Derive the BEM equation for calculating the mechanical properties of the tooth slice. • Use BEM and Hertz theory to conduct load tooth surface contact analysis. [ABSTRACT FROM AUTHOR]

Summary: Background: Equine odontoclastic tooth resorption and hypercementosis (EOTRH) is being increasingly recognised as a painful and debilitating condition in some affected horses, that can produce pain on prehension or result in infected, fractured and loose incisors. The only known way to completely alleviate the pain and secondary infection associated in many horses affected with EOTRH is by extraction of the diseased incisors. Currently, few large‐scale clinical outcome studies have been performed. Objectives: The purpose of this study was to determine if horses that are diagnosed with clinical EOTRH experience a statistically significant improvement in the quality of their lives after surgical extraction of all incisors and to determine if owners were satisfied with the results of the surgery. Study design: A retrospective web‐based survey was sent out to owners of horses diagnosed with EOTRH who had undergone extraction of all incisors in the previous 3 years. Methods: Forty‐eight surveys were completed, and the answers examined for statistical significance. Results: Statistically significant differences were found in the horses' body condition, dropping of hay, speed of eating, general behaviour, resistance to bridling and headshaking. In addition, owners reported that horses were 'happier' after surgery and that total extraction improved quality and extended the life of their horse. Over 90% of owners would also elect to have the procedure performed on another horse in the future. Main limitations: Retrospective surveys are prone to selection, recall and misclassification bias. Conclusions: Owners were highly satisfied with the total extraction of all incisors as a treatment for horses affected by EOTRH. Survey results showed that post‐extraction horses had improved body condition and exhibited better bridling and eating behaviours which are consistent with a decrease in dental pain. Owners felt that their horse was happier and that the surgery had improved the horse's quality of life. [ABSTRACT FROM AUTHOR]

Purpose: We aimed to establish a model combining MRI volume measurements from the 1st, 2nd and 3rd molars for age prediction in sub-adults and compare the age prediction performance of different combinations of all three molars, internally in the study cohort. Material and method: We examined 99 volunteers using a 1.5 T MR scanner with a customized high-resolution single T2 sequence. Segmentation was performed using SliceOmatic (Tomovision©). Age prediction was based on the tooth tissue ratio (high signal soft tissue + low signal soft tissue)/total. The model included three correlation parameters to account for statistical dependence between the molars. Age prediction performance of different combinations of teeth for the three molars was assessed using interquartile range (IQR). Results: We included data from the 1st molars from 87 participants (F/M 59/28), 2nd molars from 93 (F/M 60/33) and 3rd molars from 67 (F/M 45/22). The age range was 14–24 years with a median age of 18 years. The model with the best age prediction performance (smallest IQR) was 46–47-18 (lower right 1st and 2nd and upper right 3rd molar) in males. The estimated correlation between the different molars was 0.620 (46 vs. 47), 0.430 (46 vs. 18), and 0.598 (47 vs. 18). IQR was the smallest in tooth combinations including a 3rd molar. Conclusion: We have established a model for combining tissue volume measurements from the 1st, 2nd and 3rd molars for age prediction in sub-adults. The prediction performance was mostly driven by the 3rd molars. All combinations involving the 3rd molar performed well. [ABSTRACT FROM AUTHOR]

Aim: This study aims to assess the general health status and factors affecting the general health status in the 0–14 age group in Turkey. Methods: This cross‐sectional study was conducted using the Turkish Statistical Institute Turkey Health Survey 2022 micro data set. Results: This study included 7019 participants. Household heads described the general health status of 91.3% of children and the dental and gum status of 82.4% of children as very good or good, and 9.2% of children had any chronic disease. Although the median breastfeeding duration was 15 months, there is statistical significant association between sex and general health status (p = 0.014) and sex and duration of breastfeeding (p = 0.006). A statistical difference was found between duration of breastfeeding and general health status (p = 0.009) and dental and gum status (p = 0.001). Conclusion: In 2022, the majority of children in Turkey had very good or good general health and dental and gum status. More than a third of children were breastfed for less than 12 months. Considering the possibility of neglecting oral and dental health problems, it is recommended to prioritize oral and dental health literacy trainings and to continue breastfeeding promotion programmes. [ABSTRACT FROM AUTHOR]

Bonebeds occurring in exposures of the Burlington and Keokuk Limestones (Mississippian/Osagean) along the Iowa and Illinois border (USA) contain an abundant and diverse collection of chondrichthyan remains that includes teeth, spines, denticles, and coprolites. These remains represent cochliodont, hybodont, petalodont, ctenacanthid, symmoriid, and acanthodian (stem chondrichthyan) taxa. The thickest of these beds, herein referred to as the Burlington–Keokuk bonebed, occurs at the top of the Burlington Limestone and presents a remarkable opportunity to study the assemblage of mid-continent, Middle Mississippian chondrichthyans. Bulk matrix samples of this bonebed were collected from two quarries (Biggsville Quarry, Biggsville, IL, USA, and Nelson Quarry, Mediapolis, IA, USA) and disaggregated. Among the multitude of previously known taxa, several teeth represented a new genus and species of hybodont shark. Herein, we describe these teeth as Columnaodus witzkei (gen. et sp. nov.), a hybodontiform with dental features comparable to unnamed specimens reported from elsewhere. [ABSTRACT FROM AUTHOR]

Introduction: The COVID‐19 pandemic brought major disruptions to dental teaching and has impacted the delivery of tooth morphology courses where students are introduced to the three‐dimensional features of the dentition. The aim of this study was to assess the implementation of newly developed online teaching modalities for tooth morphology, evaluate their usefulness and identify elements that are beneficial for learners. Materials and Methods: Following the delivery of an online course that included online 3D models, 2D cue cards, live discussion sessions and Socrative™ quizzes, the participants were asked to rate the usability and usefulness of each tool. The participants' knowledge of tooth morphology was assessed through an online examination using 3D‐digitised tooth models. Results: The participants identified lecture handouts and online 3D models as their preferred learning tools, while lecture video recordings and 2D cue cards were viewed as less useful. Data analysis from Socrative™ quizzes demonstrated improvement in tooth identification skills throughout the course delivery. Finally, results from the final assessment are in line with previous in‐person deliveries of this course. Conclusions: The study provides valuable information on the usefulness of teaching modalities that were implemented in response to the COVID‐19 pandemic and their merit to be retained in future deliveries of the course. The 3D models have been identified as particularly useful in this context, but the participants still value the opportunity to learn with extracted teeth. Furthermore, it remains to be confirmed whether tooth identification skills acquired using 3D models can be transferred to the clinical setting. [ABSTRACT FROM AUTHOR]

Introduction: Cavity preparation and direct and indirect pulp capping are difficult processes to learn in dentistry. Although plastic teeth are used in universities in Turkey, the standard model does not teach students how to distinguish between dental hard tissues from caries and how this relates to the pulp. The aim of this study was to investigate the differences in learning when a three‐dimensional (3D)‐printed tooth was employed in comparison with the standard model and extracted teeth. The differences are evaluated in the design, feasibility, and contribution of the 3D‐printed dental tooth in pre‐clinical education. Materials and Methods: The multi‐layer 3D‐printed tooth's authentic design and replication of the dental hard tissues and carious lesions are explored with 55 students for pre‐clinical education, which includes caries excavation and direct and indirect pulp capping. The students completed questionnaires evaluating the 3D‐printed teeth through comparison with the plastic and extracted teeth, rated with scores from 1 to 11 (1: poorest conformity; 11: excellent conformity). Results: The questionnaire results indicated that students approved the printed tooth model for the practice of theoretical knowledge and the model received ratings between good and excellent. The results were statistically analysed using the Wilcoxon signed‐rank test, and the printed teeth had the highest approval from the students (p <.001). Conclusion: The results of this study demonstrated that the use of the designed 3D‐printed tooth is preferred by the students based on their perception of learning cavity preparation and pulp capping in a pre‐clinical environment. Workflow and production were cost‐effective with the use of 3D printing technology. The printed tooth allowed students to gain realistic experience before treating patients. [ABSTRACT FROM AUTHOR]

Introduction: Accurate inlay preparation is extremely important in pre‐clinical training. However, there is a lack of tools to guide students to efficiently practise inlay preparation. Therefore, a 3D‐printed coloured tooth model for inlay preparation was designed to guide beginners to practise inlay preparation by themselves according to different colour prompts. This study aimed to evaluate the benefits of using a 3D‐printed coloured tooth model in the pre‐clinical training on inlay preparation. Materials and Methods: Twenty‐eight students in their fourth‐year undergraduate dental program participated in this study. The participants were randomly assigned to two groups for the inlay preparation. Group 1 prepared a plain tooth model for the first and fourth attempts and a 3D‐printed coloured tooth model for the second and third attempts (n = 14). Group 2 prepared four plain tooth models (n = 14). The first and fourth tooth models prepared by both groups were scored using an evaluation system (Fair Grade 2000, NISSIN). Next, questionnaires answered by students were used to evaluate the benefits of using a 3D‐printed coloured tooth model and self‐evaluate hands‐on ability using a grading system (1 = strongly agree, 2 = agree, 3 = neutral, 4 = disagree, and 5 = strongly disagree). The scores were evaluated statistically using the Mann–Whitney U test, and the given grades are displayed as percentages and mean values. Results: There was an overall increase in the clinical confidence of all students after repeated attempts to prepare an inlay; however, students from group 1, who had used the 3D‐printed coloured tooth model, had more positive experiences and comments. The 3D‐printed coloured tooth model for inlay preparation has been widely praised by participants. Comparing the average score of the first and fourth preparations, the average score of group 1 increased by 12% (Ø 54.46 ± 8.33, Ø 61.11 ± 7.13, p =.090), while that of group 2 increased by 0.72% (Ø 56.39 ± 9.59, Ø 56.80 ± 8.46, p =.925). Conclusion: Students favoured the use of the 3D‐printed coloured tooth model, and this improved the average score for inlay preparation. The 3D‐printed coloured tooth model for inlay preparation is expected to play an important role in dental education in the future. [ABSTRACT FROM AUTHOR]

In this paper, the cycloidal pin wheel drive mechanism of the secondary drive component of the rotary vector (RV) reducer is studied. Under the condition of grease lubrication, considering tooth profile modifications and machining errors, we established a three-dimensional load-bearing contact analysis model of a cycloid pinwheel transmission mechanism. We studied the time-varying contact characteristics of the gear teeth and dynamic joint surfaces of the inner and outer races of a crankshaft bearing. Considering the thermal effects, we proposed an analysis model of the lubrication characteristics of cycloid pinwheel transmission mechanisms. We also studied the thermal lubrication properties, such as load de-formation, lubrication film thickness, contact pressure and temperature increase at the lubrication contact area. The accuracy of the model was verified by temperature experiments on the inner raceway of an RV reducer bearing and the evolution law of the dynamic thermal lubrication characteristics of the inner and outer races of the crankshaft bearing, the meshing gear tooth pair and the whole process of single pin tooth meshing were revealed. This study provides an effective method for analyzing the temperature increases of the key joints of RV reducers. [ABSTRACT FROM AUTHOR]

Objectives: This retrospective study aimed to investigate the differences in tooth loss rate between fixed implant‐supported prostheses (FISPs) and removable partial dentures (RPDs) in cases of unilateral free‐end missing teeth. Materials and Methods: The data of 324 patients who underwent treatment with FISPs or RPDs for unilateral free‐end missing teeth and satisfied the applicable criteria, were evaluated (47 in the FISPs group and 277 in the RPDs group). After propensity score (PS) matching, which was used to extract patients with similar background factors related to prosthetic selection at baseline, survival time analyses were performed with tooth loss as the endpoint. The adjusted variables were age, sex, number of restored teeth, periodontal status, and the practicing dentist's experience in years. The remaining teeth were classified into subcategories in relation to the missing molars. Results: Overall, 58 patients (29 in each group) selected by PS matching were evaluated in the final analysis. The total number of lost teeth was 35 (FISPs group: n = 10; RPDs group: n = 25). The mean (±SD) period to tooth loss and the 10‐year survival rates in the FISPs and RPDs groups were 51.6 (±30.1) months and 42.3 (±29.7) months, 70.5% and 16.4%, respectively. The log‐rank test showed that significantly longer survival time in FISPs compared with RPDs. Conclusions: After adjustments for confounding factors using PS matching, replacing unilateral free‐end missing teeth with FISPs may exhibit a lower tooth loss rate in adjacent and contralateral teeth compared to replacing with RPDs. [ABSTRACT FROM AUTHOR]

Introduction: Human teeth serve many crucial functions, and aesthetics is one of these. Aesthetics and beauty are often correlated with the Golden Divine Ratio (GDR), a unique proportion hypothesised to exist in individuals or things with a harmonious appearance. Aim: To estimate the crown length, root length, and GDR in extracted human permanent maxillary and mandibular Central Incisors (CI) in the population of Tamil ethnicity from South India. Materials and Methods: This in-vitro cross-sectional study was conducted in the Department of Oral Pathology and Microbiology at Saveetha Dental College and Hospitals, Chennai, Tamil Nadu, India, from January 2023 to October 2023. The study included a total of 90 extracted human teeth from the Institutional tooth repository, out of which 27 were upper permanent CIs and the remaining 63 were mandibular CIs. Crown length and root length were measured using digital vernier calipers, and golden ratios were derived. Statistical Package for Social Sciences (SPSS) software version 26.0. was used for descriptive analysis and deriving means and standard deviation. Results: The average crown length, root length, and total length of upper CIs were 8.06±0.09 mm, 13.01±1.47 mm, and 21.06±2.36 mm, respectively. For the remaining 63 extracted permanent mandibular CIs, the mean crown length, root length, and total length were 7.85±0.66 mm, 12.6±0.97 mm, and 20.45±1.49 mm, respectively. The Root-to-Crown (R/C) ratio and Total Length to Root Length (T/R) ratio approximated 1.618 for both sets of teeth. Conclusion: The crown length of maxillary and mandibular CIs from the Tamil population followed the golden ratio in the present study. [ABSTRACT FROM AUTHOR]

This study aimed to describe a support material removal protocol (SMRP) from inside the root canals of three-dimensional printed teeth (3DPT) obtained by the microcomputed tomography (microCT) of a natural tooth (NT), evaluate its effectiveness by comparing the 3DPT to NT in terms of internal anatomy and behaviour toward endodontic preparation, and evaluate if 3DPT are adequate to assess the differences between two preparation systems. After the SMRP, twenty 3DPT printed by PolyJet™ were microCT scanned before preparation and thereafter randomly assigned into two groups (n = 10). One group and NT were prepared using ProTaper Gold® (PTG), and the other group with Endogal® (ENDG). MicroCT scans were carried out after preparation, and the volume increase, volume of dentin removed, centroids, transportation, and unprepared areas were compared. For the parameters evaluated, no significant differences were found between the 3DPT and NT before and after preparation (p > 0.05), and no significant differences were found between the 3DPT PTG group and the 3DPT ENDG group (p > 0.05). It can be concluded that the SMRP described is effective in removing the support material SUP706B™. PolyJet™ is adequate for printing 3DPT. Furthermore, 3DPT printed with high-temperature RGD525™ have similar behaviour during endodontic preparation with PTG as the NT, and 3DPT can be used to compare two preparation systems. [ABSTRACT FROM AUTHOR]

Background: The impaction of the maxillary canine is a common occurrence, and orthodontists must be prepared to manage it. The purpose of this article is to present a study of the efficacy of a double-wire orthodontic appliance compared to a control group in the alignment of impacted maxillary canines in the dental arch. Methods: To diagnose an impacted maxillary canine, a panoramic radiograph was taken and a detailed analysis was performed by the same orthodontist. This article presents the results of 28 impacted maxillary canines with inclusion criteria of A2 (tooth angulation to the midline 16°–45°), V1 (vertical height of the tooth crown above the cementoenamel junction but less than half the length of the root of the maxillary lateral incisor), and O3 (medial position of the canine crown of more than half but less than the entire root width of the lateral incisor) positions in 21 patients (7 males and 14 females) with a mean age of 14.02 years (SD = 1.61) who were treated by the same orthodontist for impacted maxillary canines using a fixed double-wire orthodontic appliance. The analyzed data were compared with the control group (treated with a fixed orthodontic appliance and active ligature), which was matched for pretreatment age and the A2, V1, and O3 positions of the impacted maxillary canine. Results: With both methods, the impacted maxillary canines were aligned and guided into a correct position in the dental arch, but the mean active orthodontic traction of 31 ± 4.2 weeks in the SG was statistically significantly shorter (p < 0.05) in comparison to 37 ± 6.3 weeks in the CG, and the number of visits was statistically significantly (p < 0.05) fewer in the SG (5 ± 2) than in the CG (11 ± 5). Conclusions: The findings of this study are important to the field of orthodontics and show that the alignment of impacted maxillary canines with A2, V1, and O3 positions can be achieved with both methods, but with the double-wire appliance, the treatment time was shorter and the number of visits was statistically significantly fewer. The results of this study suggest that this approach may be more efficient and cost-effective compared to conventional methods. [ABSTRACT FROM AUTHOR]

Background: The attainment of precise posterior occlusion alignment necessitates a deeper understanding of the clinical efficacy of aligner therapy. This study aims to determine whether the treatment goals defined in the virtual planning of aligner therapy are effectively implemented in clinical practice, with a particular focus on the influence of distalization distances on potential vertical side effects. Methods: In this retrospective, non-interventional investigation, a cohort of 20 individuals undergoing Invisalign® treatment was examined. Pre- and post-treatment maxillary clinical and ClinCheck® casts were superimposed utilizing a surface–surface matching algorithm on palatal folds, median palatine raphe, and unmoved teeth as the stable references. The effectivity of planned versus clinical movements was evaluated. Groupings were based on distalization distances, planned vertical movements, and Class II elastic prescription. Statistics were performed with a two-sample t-test and p-value < 0.05. Results: Clinically achieved distalization was significantly lower than virtually planned distalization, regardless of additional vertical movements, where a lack of implementation was contingent upon the extent of distalization, with no mitigating effects observed with the application of Class II elastics. Intriguingly, no adverse vertical side effects were noted; however, the intended intrusions or extrusions, as per the therapeutic plans, remained unattainable regardless of the magnitude of distalization. Conclusions: These findings underscore the imperative for future investigations to delve deeper into the intricacies surrounding translational mesio-distal and vertical movements, thereby enhancing predictability within orthodontic practice. To facilitate successful clinical implementation of vertical and translational movements via aligners, the incorporation of sliders emerges as a promising strategy for bolstering anchorage reinforcement. [ABSTRACT FROM AUTHOR]

Barbaracurus hofereki sp. n. from Djibouti is described and compared with other species of the genus. B. hofereki sp. n. is the only species of the genus with pedipalp movable finger with 8 rows of granules and pectinal tooth count 27-28 in female. Also, its pedipalp chela with very narrow manus (chela length/width ratio 6.07 in female), narrower than in all other African species of the genus. A map of the distribution of the genus in the Horn of Africa and the Arabian Peninsula is provided. [ABSTRACT FROM AUTHOR]

Aiming at the problems of high vibration and high noise in gear transmission systems, a model of gear with staggered tooth phase structure(GSTPS) for reducing vibration is proposed. Without changing the overall structure of the gear transmission system, the purpose of reducing mesh stiffness fluctuations is achieved by staggering adjacent gears at a certain angle along the axis, thereby the vibration of the gear transmission system could be reduced. The characterization method of time-varying mesh stiffness of the GSTPS is studied. Then, the impact of different staggered tooth phases(STP) on reducing vibration of the transmission system are researched, and the basis for selecting the optimal STP are obtained. The experimental platform for reducing vibration with STP is established. And some experimental studies were conducted to validate the theoretical model. [ABSTRACT FROM AUTHOR]

Teeth from the late Mississippian Bangor Limestone, Monteagle Limestone, and Pride Mountain Formation (early to middle Chesterian = late Viséan–early Serpukhovian) of northern Alabama, USA, are designated as Cavusodus whitei, gen. et sp. nov. The species is similar to Cypripediodens cristatus Duffin and Ward, known only from the Eyam Limestone Formation (Mississippian, late Viséan) of Derbyshire, England. Cypripediodens cristatus, the only species of the genus, is distinguished by teeth having an elongate crown, an apical cusp having a nearly circular cross-section, a secondary cusp on the lingual face, and several cristae on the lingual heel. Cavusodus whitei teeth resemble those of Cypripediodens cristatus but differ in lacking the secondary cusp, in having a more labiolingually compressed apical cusp, in possessing more robust lingual cristae, and in possessing a longitudinal groove on the labial face. The genera comprising the Janassidae are reconsidered. It is proposed that only Janassa, Cholodus, and Cypripediodens be retained, in addition to the new genus. [ABSTRACT FROM AUTHOR]