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Background: This study aims to propose the combinations of image processing and machine learning model to segment the maturity development of the mandibular premolars using a Keras-based deep learning convolutional neural networks (DCNN) model., Methods: A dataset consisting of 240 images (20 images per stage per sex) of retrospect digital dental panoramic imaging of patients between 5 and 14 years of age was retrieved. In image preprocessing, abounding box with a dimension of 250 × 250 pixels was assigned to the left mandibular first (P1) and second (P2) permanent premolars. The implementation of dynamic programming of active contour (DP-AC) and convolutions neural network on images that require the procedure of image filtration using Python TensorFlow and Keras libraries were performed in image segmentation and classification, respectively., Results: Image segmentation using the DP-AC algorithm enhanced the visibility of the image features in the region of interest while suppressing the image's background noise. The proposed model has an accuracy of 97.74%, 96.63% and 78.13% on the training, validation, and testing set, respectively. In addition, moderate agreement (Kappa value = 0.58) between human observer and computer were identified. Nonetheless, a robust DCNN model was achieved as there is no sign of the model's over-or under-fitting upon the learning process., Conclusions: The application of digital imaging and deep learning techniques used by the DP-AC and convolutions neural network algorithms to segment and identify premolars provides promising results for semi-automated forensic dental staging in the future., (© 2022. The Author(s).)

Introduction: The determination of skeletal maturity stages is very important in orthodontic treatment planning, especially skeletal discrepancies in growing individuals. A hand-wrist radiograph is considered the most accurate approach for skeletal maturity detection. Dental calcification stages have been suggested as an alternative diagnostic method to decrease radiation exposure. The recent study is aimed at detecting the efficacy of dental calcification stages in assessing skeletal maturity during the prepubertal and pubertal growth periods., Methods: Patients' records were collected from the Aleppo Orthodontic Center. Dental maturity stages were assessed from a panoramic radiograph using the Demirjian method, while skeletal maturity stages were determined using the Björk method. Four permanent left mandibular teeth were included (canine, 1st premolar, 2nd premolar, and 2nd molar) for the study., Results: From 517 records, 295 records (145 males and 150 females) were included. The Spearman rank-order correlation coefficients between skeletal maturation and dental maturation were strong and statistically significant (ranging from 0.789 to 0.835). The highest correlation was between skeletal stages and the second molar ( r = 0.829 and 0.88 in males and females, respectively). Receiver operating characteristic (ROC ) curve suggested a high validity of the sum of dental stages for the four teeth in identifying MP3= stage (sensitivity was 70%, specificity was 92.77%, and ROC area was 0.81) but not for MP3cap (sensitivity was 50.85%, specificity was 81.36%, and ROC area was 0.66)., Conclusions: The correlation between the skeletal maturity stages and the dental calcification stages was high. The orthodontist can use the dental stages as a definite diagnostic tool for prepubertal growth period., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2021 Ayah Jourieh et al.)

Unlike bones, teeth are remarkably resilient and can withstand severe trauma, making age assessment based on the dentition essential for forensic analysis. Modern techniques for age estimation focus on pulp-chamber volume measurements using radiographs and computerized tomography (CT); however, these are applicable only for complete teeth (i.e., with intact crown and root). In the current study, we developed a new approach using high-resolution micro-computerized tomography (μCT) to visualize the secondary dentin (SD), an inner layer surrounding the pulp which accumulates with age, thus facilitating age estimation of fragmented and broken teeth.The growth pattern of the SD with age was analyzed for 77 lower premolars from two anthropological collections. A comparison of SD virtual segmentation and histological measurement was highly correlative (ICC = 0.95). SD was measured per volume (mm 3 ) of a 1 mm thick slice directly below the cemento-enamel junction. Regression analysis using SD measurements increased the success rates of age estimation (82%) compared with the "gold-standard" pulp/dentin method (54%) in the range of ± 10 years. The accuracy of age estimation based on SD analysis was improved to a range of 7-8 years.The SD method thus allows age estimation with greater prediction rates and better accuracy based on only a small fragment of a tooth in a non-invasive manner. This novel methodology is easy to use, accessible, and bears implications in various fields such as forensic sciences and anthropological research.

Background: The timing of eruption of permanent teeth can be a precious help to the pediatric practitioner in identifying an appropriate treatment plan. Usually, it presents a more precise sign of an early or late growth of the child., Aims: It is to determine whether the timing of the permanent teeth eruption in Lebanese pediatric population can be considered as standard Lebanese values, since no other study was previously performed., Materials and Methods: A cross-sectional study is conducted, and the clinical emergence data are collected for a sample of 2317 Lebanese children aged between 5.5 years and 13 years (1129 girls and 1188 boys) from different socioeconomic groups in rural and urban communities spread over different regions in Lebanon. The study investigates dental emergence patterns., Results: Statistical analysis is performed with the SPSS Software. A confidence interval of 95% and significance level of 5% are adopted. The trend is for males to begin their permanent teeth eruption later than girls. Emergence of all permanent mandibular teeth is earlier than maxillary ones. Symmetry is found between the right and left teeth in the maxilla, as well as in the mandibula., Conclusion: In this study, the results indicate that premolars and second permanent molars erupt earlier in the Lebanese children compared to children of other countries reflected in several studies., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2020 Nahla Nassif and Elia Sfeir.)

Background: The innate immune activation which promotes inflammation responses in the dental pulp tissue leads to the progression of dentin caries. Accordingly, toll-like receptors (TLRs) are key molecules of the innate immune system that identify pathogen-associated molecular patterns (PAMPs) on microorganisms and may have a critical role in a dental injury. Therefore, this study aimed to investigate the expression of TLR2, TLR3, and TLR4 in the human dental pulp of opened and closed apex teeth., Methods: Human dental pulps were derived from the healthy opened and closed apex premolar, in which extraction was indicated for orthodontic reasons. The extraction of RNA was performed and the gene expression determined by real-time polymerase chain reaction (RT-PCR). The result from real-time PCR was confirmed using western blot analysis., Results: Real-time PCR data analysis showed that the expression TLR2 and TLR4 were significantly increased in closed apex premolar teeth compared to open apex teeth, whereas TLR3 expression was not significantly different in these two groups (p < .05)., Conclusion: The results of the present study suggested increased expression of TLR2 and TLR4 by the maturation of the apex, which may be due to the presence of microorganisms in the normal or destructed dental pulp tissue. Thus, identifying the expression of TLRs molecules in dental pulp tissue helps to develop a deeper knowledge of the immune responses in the oral cavity., (© 2020 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals LLC.)

The mandibular third premolar (P 3 ) exhibits substantial differences in size and shape among hominoid taxa, and displays a number of discrete traits that have proven to be useful in studies of hominin taxonomy and phylogeny. Discrete traits at the enamel-dentine junction (EDJ) can be accurately assessed on moderately worn specimens, and often appear sharper than at the outer-enamel surface (OES). Here we use microtomography to image the P 3 EDJ of a broad sample of extant apes, extinct hominins and modern humans (n = 100). We present typologies for three important premolar discrete traits at the EDJ (transverse crest, marginal ridge and buccal grooves), and score trait frequencies within our sample. We find that the transverse crest is variable in extant apes, while the majority of hominins display a transverse crest which runs directly between the two major premolar cusps. Some Neanderthals display a unique form in which the transverse crest fails to reach the protoconid. We find that mesial marginal ridge discontinuity is common in Australopithecus anamensis and Australopithecus afarensis while continuous marginal ridges largely characterize Australopithecus africanus and Paranthropus. Interrupted mesial and distal marginal ridges are again seen in Homo sapiens and Neanderthals. Premolar buccal grooves, previously identified at the OES as important for hominin systematics, are again found to show a number of taxon-specific patterns at the EDJ, including a clear difference between Australopithecus and Paranthropus specimens. However, their appearance may be dependent on the morphology of other parts of the crown such as the protoconid crest, and the presence of accessory dentine horns. Finally, we discuss rare variations in the form of dentine horns that underlie premolar cusps, and their potential homology to similar morphologies in other tooth positions., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The goal of this project is to validate the Cameriere's method applied to the upper and lower second premolars in a Portuguese population, regarding the forensic estimate of age. The applied sample consisted in 100 panoramic radiographs, of 60 males and 40 females, patients of the Faculty of Dental Medicine of the University of Lisbon, whose ages vary between 15 and 35 years old. Thus, a total of 400 teeth were investigated (200 upper second premolars and 200 lower second premolars). Each radiograph was analysed using draw and measurement tools featured in Adobe Photoshop, applying the Cameriere's method, and then the pulp/tooth ratio was computed for the 15, 25, 35 and 45 teeth. All data were statistically analysed with the SPSS program, using a significant level of 5%. It was not observed any kind of relation, linear or not linear, between age and the pulp/tooth ratio. Linear regressions with considerably low values for the coefficient of determination were achieved, which indicates a low reliability for these models. Accordingly, we conclude that the knowledge of the pulp/tooth ratio does not allow the identification of an individual based on the Cameriere's method, in the scope of a forensic age estimate applied to panoramic radiograph. Further investigations with larger samples and broader age groups are required in order to provide suitable evidence to the legal and social aspects of age estimate in Forensic Dentistry., (Copyright © 2018 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.)

Objectives: To compare the alveolar bone dimensions in patients with lower second premolar (P2) agenesis prior to and after primary molar loss on CT scans, and assess the possibility for straightforward implant placement., Methods: Alveolar bone dimensions were evaluated on 150 mandibular CT scans in three groups: (i) agenesis of P2, with the primary tooth in situ, and regularly erupted first premolar (P1) and molar (M1) (AW); (ii) agenesis of P2, without the primary tooth in situ for ≥3 m, but regularly erupted P1 and M1 (AWO); and (iii) P1, P2, and M1 regularly erupted (CTR). The possibility of straightforward placement of an implant 3.5 or 4.3 mm in Ø × 10 mm long was digitally simulated and compared to the actually performed treatment., Results: Buccolingual width (7.3 ± 2.0 mm) at the coronal aspect of the ridge in the AWO group was statistically significantly smaller comparing with both the AW (9.2 ± 1.4 mm) and the CTR (9.5 ± 1.1 mm) group; width reduction appeared to be mainly due to "collapse" of the buccal aspect of the ridge. Simulated straightforward placement of implants with a diameter of 3.5 or 4.3 mm was possible in 62% and 56% of the cases in the AWO vs. 86% and 84% in the AW group (p = .006 and .002, respectively). Straightforward implant placement was actually possible in all patients (22) in the AW group, while 28% (11 of 39) of the patients in the AWO group needed additional hard tissue augmentation., Conclusions: Significant dimensional differences exist in the alveolar ridge, especially in the coronal part, at lower P2 agenesis sites missing the primary tooth for ≥3 m, when compared to P2 agenesis sites with the primary tooth in situ. It seems thus reasonable to advise that the primary second molar should be kept as long as possible, in order to facilitate straightforward implant installation and reduce the probability of additional bone augmentation procedures., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Objectives: This study aimed to examine the applicability of the pulp/tooth area ratio in the lower premolar teeth using panoramic radiography in age estimation of Korean adults., Methods: 402 digital panoramic images of Korean adults between 20 and 78 years were analyzed. Following Cameriere et al.'s method, two observers measured the pulp and tooth areas of the lower second premolar on digital panoramic images, and the ratio of pulp to tooth area in the whole tooth (PTR) was calculated. In addition, the whole tooth was divided into coronal and root parts at the cementoenamel junction, and the ratios in the coronal part (PcCR) and root part (PrRR) were also calculated separately. Independent t-test, Analysis of covariance, linear regression, and the standard error of the estimate (SEE) were computed using statistical software. To justify the use of linear regression models for purposes of prediction, diagnostic tests of principal assumptions were also performed., Results: Independent t-test revealed significant differences in genders. PrRR produced the best age correlation (male, SEE=10.8; female, SEE=9.8; total, SEE=10.4 years), followed closely by PTR (male, SEE=11.1; female, SEE=10.3; total, SEE=10.7 years) and a relatively lower accuracy for PcCR (male, SEE=14.7; female, SEE=14.4; total, SEE=14.6 years). Model assumptions and accuracy for purposes of prediction in PTR and PrRR were satisfied., Conclusions: The pulp/tooth area ratio using panoramic radiography has the potential as an effective tool for age estimation in the Korean adult population, and the pulp/tooth area ratio in the root part is more accurate than that of the whole tooth. Notably, female has shown higher accuracy compare to male subject., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: To evaluate and compare the eruption rates of lower second premolars (LPm2) at different developmental stages using cone-beam computed tomography (CBCT)., Materials and Methods: Retrospectively, 31 individuals (9.77 ± 1.25 years) had their LPm2 scored according to the Demirjian method, and afterwards they were split into three groups according to developmental stage, as follows: D = complete-formed crowns; E = root length less than crown height; and F = root length greater than or equal to crown height. Linear distances from the LPm2 crown tip to the anatomical reference line (ARL) and to the occlusal plane line (OPL) were measured in paired CBCT scans (T1, T2), taken with an average interval of 8.6 months between them. Eruption rates (mm/y) were calculated and then compared between groups., Results: Eruption rates were greater for LPm2 at stage F than at stages D or E (P < .01) regardless of whether they were measured from the ARL (D = 2.84 mm/y; E = 2.55 mm/y; F = 5.38 mm/y) or from the OPL (D = 1.82 mm/y; E = 2.02 mm/y; F = 5.26 mm/y). Eruption rates evaluated from the ARL and the OPL had no statistically significant differences (P = .052), and a positive correlation (r = .79, P < .001) between them was observed., Conclusions: LPm2 at Demirjian stage F showed greater eruption rates than at stages D or E, regardless of whether rates were measured from the ARL or the OPL. Faster eruption is expected for LPm2 at stage F. Evaluation of the LPm2's developmental stage using CBCT can aid in clinical decision making regarding the correct timing for intervention.

Dental maturity is associated with skeletal maturity, which is advanced in girls with central precocious puberty (CPP). We investigated the performance of dental maturity as a screening method for CPP using mandibular second premolar and molar calcification stages, assessed the associated anthropometric and laboratory factors, and evaluated pubertal response predictors using the gonadotropin-releasing hormone stimulation test (GnRHST) in prepubertal and pubertal girls. A prospective case-control study was conducted in girls, aged 7.0-8.9 years, classified into pubertal (peak luteinizing hormone [LH] after GnRHST ≥ 5 IU/L), prepubertal (peak LH < 5 IU/L), and control groups. Auxological and biochemical tests, panoramic radiographs, and GnRHSTs in participants with breast development were conducted. Dental maturity was assessed using the Demirjian index (DI). We included 103 girls (pubertal, 40; prepubertal, 19; control, 44). Chronological age (CA) was not significantly different between groups. Bone age (BA) and BA advancement was higher in the pubertal and prepubertal groups. Increased DI values at the mandibular second premolar and molar were significantly associated with CA, BA, BA advancement, height standard deviation score (SDS), peak LH after GnRHST, and insulin-like growth factor-I (IGF-I) (all P < 0.05). Moreover, odds ratio (OR) of the mandibular second premolar and molar (a DI value of ≥ E) for predicting a positive response to GnRHST was 8.7 (95% confidence intervals [CI], 2.9-26.1) and 5.2 (95% CI, 2.2-12.7), respectively. Dental maturity was a strong predictor for diagnosing CPP. Determining dental maturity in girls with suspected precocious puberty might help determine the performance of GnRHSTs., Competing Interests: The authors have no potential conflicts of interest to disclose.

Purpose: The purpose of this study was to retrospectively evaluate the Latham-type appliance's effect on the development and eruption of posterior teeth during the mixed dentition stage before palatal expansion and secondary alveolar bone graft(s)., Methods: The charts of complete cleft lip and palate (CLP) patients treated with and without the Latham-type appliance were screened using the following inclusion criteria: nonsyndromic; CLP; and available panoramic radiographs and clinical photographs in the mixed dentition prior to palatal expansion and secondary alveolar bone grafts. Surgical repair for Latham-type appliance patients followed the Latham-Millard protocol. The differences in outcomes were analyzed using Fisher's exact tests., Results: The sample consisted of 65 patients treated with the appliance (Latham group) and 36 subjects who were not (non-Latham group). Similar incidences were found between the non-Latham group and the Latham group for maxillary second premolar agenesis (11 percent versus 10 percent) and enamel defects in the maxillary arch (17 percent versus 14 percent). The incidence of ectopic permanent maxillary first molars was higher in the Latham group than in the non-Latham group (28 percent versus one percent, P=0.01)., Conclusions: A higher incidence of ectopic permanent maxillary first molars was found in patients treated with the Latham-type appliance.

Hypodontia, or tooth agenesis, is the most prevalent craniofacial malformation in humans. It may occur as part of a recognised genetic syndrome or as a nonsyndromic isolated trait. Excluding third molars, the reported prevalence of hypodontia ranges from 1.6 to 6.9%, depending on the population studied. Most affected individuals lack only one or two teeth, with permanent second premolars and upper lateral incisors the most likely to be missing. Both environmental and genetic factors are involved in the aetiology of hypodontia, with the latter playing a more significant role. Hypodontia individuals often present a significant clinical challenge for orthodontists because, in a number of cases, the treatment time is prolonged and the treatment outcome may be compromised. Hence, the identification of genetic and environmental factors may be particularly useful in the early prediction of this condition and the development of prevention strategies and novel treatments in the future.

Introduction: Our aim in this study was to investigate the association between dental mineralization stages and the periods of the pubertal growth spurt (PGS)., Methods: The sample included panoramic and hand-wrist radiographs from 491 subjects (222 boys, 269 girls) aged 7 to 17 years. Dental development was rated, and skeletal maturation was evaluated. The relevant associations were investigated by analysis of ordinal multinomial logistic regression., Results: The second molar (odds ratio [OR] = 4.34) and the first premolar (OR = 2.45) were the best growth predictors for girls. For boys, the second molar (OR = 6.80), second premolar (OR = 2.41), and canine (OR = 3.21) proved to be the best predictors. Stages D and E of the second molar for girls, and stages E and F for boys, corresponded to the onset of the accelerated growth spurt. Stage F of the second molar for girls and stage G for boys corresponded to the peak of the PGS. At the end of the PGS, most teeth had already attained apical closure. In girls, however, most second molars were found at stage G., Conclusions: An association exists between the dental mineralization stages and the periods of the PGS, especially for second molars. Panoramic radiographs can be used as the first diagnostic tool to estimate the pubertal growth period., (Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

There is increasing interest in diseases of infundibula of equine maxillary cheek teeth. Imperfect infundibular cementogenesis has been recognized as an aetiopathological factor for the onset of infundibular necrosis. In this article, infundibular development was examined with particular attention to infundibular blood vessels and cementogenesis. Forty-one deciduous maxillary premolars prior to eruption were investigated using routine histological and immunohistological methods to visualize blood vessels and the enamel organ. Selected specimens were scanned by micro-computed tomography to analyze the three-dimensional configuration of the developing infundibulum. Before eruption, the infundibula are supplied by a central infundibular artery entering the infundibulum from an occlusal direction and by arteries entering the mesial infundibulum from the mesial aspect, and the distal infundibulum from the distal aspect. The central infundibular artery is destroyed shortly after tooth eruption but the lateral arteries remain vital for a time after eruption. As the arteries of the distal infundibulum are located in a more apical position, blood is received for a longer period compared with the mesial infundibulum. Cementogenesis starts first at distinct enamel in-foldings in the occlusal part of the infundibula, advancing in an apical direction. The results suggest a distinct asymmetry between the infundibula with the mesial infundibulum prone to incomplete cementogenesis due to early blood supply cessation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Introduction: The aims of the study were; to evaluate the applicability of the Moyers and Tanaka-Johnston Methods to individuals with a Spanish ancestry, to propose new regression equations using the lower four permanent incisors as predictors for the sum of the widths of the lower permanent canine and premolars, and to compare the new data to those from other populations., Methods: A total of 359 Spanish ancestry adolescents were selected. Their dental casts were measured using a 2D computerized system. Real teeth measurements were compared with those predicted using Moyers probability tables and Tanaka and Johnston equations, and standard regression equations were then developed., Results: Results showed that Upper and Lower Canine and Premolar (UCPM, LCPM) predictions are quite different depending on the used method. Moyers tables can only be validly applied to a 75% percentile for the mandible in both, males and females, 85% in males and 90-92% in females., Conclusions: Moyers predictions tend to underestimate UCPM and LCPM whereas Tanaka-Johnston predictions tend to overestimate them. Equations for estimating the combined width of the unerupted canine and premolars were; Male: UCPM = 12.68 + 0.42 LI and LCPM = 11.71 + 0.44 LI. Female: UCPM = 12.06 + 0.43LI and LCPM = 10.71 + 0.46 LI.

The main objective of treatment of an undeveloped tooth (immature) is to provide vital pulp therapy to allow continued development of root dentin. A case report is presented that demonstrates the use of calcium hydroxide (CaOH₂) as an indirect pulp-copping material for the purpose of continued maturogenesis of an early-erupted permanent tooth with severe mobility and almost-begun root formation. Seven-year radiographic and clinical follow-up demonstrated a vital pulp and physiologic root development without any endodontic failure clinically or radiographicaly.

Introduction: Autogenous transplantation of a natural tooth to another site has significant advantages over dental implants, particularly in cases of agenesis, accidental tooth loss, or poor prognosis for the maintenance of tooth function., Methods: This report describes a case of autogenous premolar transplantation into an artificial socket in the site of a missing maxillary lateral incisor in a 13-year-old girl. Clinical examination and radiography revealed tooth agenesis (#4, #10, #13, and #20) and microdontia (#7). The occlusion and skeletal maxillomandibular relations were normal., Results: Tooth #29 was chosen for transplantation into the site of tooth #10 because of its size, stage of root formation, and possible closure of the spaces created by agenesis., Conclusions: Autogenous transplantation is a feasible alternative to dental implants in cases of tooth agenesis or tooth loss because of trauma. Autotransplantation was indicated in this case because it ensures the natural (facial) growth of the alveolar process and preserves the function of periodontal tissues. A multidisciplinary approach (ie, combining techniques from different dental specialties) was important for treatment success. Clinical and radiographic follow-up confirmed that the transplanted premolar was esthetically comparable with the lateral incisor and that root development and pulp canal obliteration were complete., (Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The objective of this study was to determine whether dental calcification can be used as a first-level diagnostic tool for assessment of skeletal maturity., Methods: A total of 150 healthy subjects (79 boys, 71 girls; mean age, 12.19 ± 2.03 years; range, 8-16 years) were enrolled in the study. Dental maturity was assessed through the calcification stages from panoramic radiographs of the mandibular canine, the first and second premolars, and the second molar. Determination of skeletal maturity was according to the modified middle phalanx of third finger (MP3) stages method on digital radiographs., Results: Diagnostic ability was evaluated according to the dental maturation stages for each tooth for identification of the MP3 stages and the growth phases (prepubertal, pubertal, postpubertal) using positive likelihood ratios. Dental maturation stage E of the first premolars and the combination of canine stage F, first premolar stage E, second premolar stage E, and second molar stage D (FEED) gave the highest values for identification of the prepubertal growth phase, and stage H of the second molar had the highest value for identification of the postpubertal growth phase., Conclusions: Dental maturation assessment is only useful for diagnosis of the prepubertal and postpubertal growth phases., (Copyright © 2014 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Purpose: The purpose of this study was to investigate root resorption patterns of primary mandibular molars and to describe the premolar successors' location throughout the resorption., Methods: A total of 271 radiographs of primary mandibular molars (56 first molars and 171 second molars) of 187 5- to 12-year-old patients were reviewed, and the patterns of root resorption and the premolars' location were evaluated., Results: In the primary first molar, approximately 55 percent of the root resorption occurred in the distal root, and 41 percent of the root resorption was symmetrical. In the primary second molar, approximately 56 percent of the root resorption was symmetrical, and 36 percent was in the distal root. More mesial root resorption (~71 percent) occurred when the second premolar was mesial., Conclusions: Primary mandibular first molars begin to resorb at seven years old. The premolars' location between the primary roots is associated with root resorption. Distal root resorption should be expected when caries is present in the distal aspect of a primary second molar.

Introduction: The aim of this prospective clinical trial was to examine the predictability of the protocol for premolar transplantation when applied by an inexperienced surgeon. Additional objectives were to examine the hard and soft tissues and to compare the findings with control premolars and also to record the patients' opinions of the treatment provided., Methods: The sample comprised 23 consecutively transplanted developing premolars in 19 patients. Their mean age at surgery was 12 years 8 months (range, 9 years 10 months-17 years). The mean observation time was 35 months (range, 6-78 months). Plaque accumulation, pocket depth, gingival recession, mobility, and pulp sensitivity were recorded for the transplanted and the control teeth. Standardized radiographs were used to examine hard tissues and crown-to-root ratios. Questionnaires were used to register each patient's opinion about the treatment and its outcome., Results: The survival rate was 100%, and the success rate was 91.3%. No significant differences were recorded between transplanted and control teeth. The patients' perceptions of the surgical management and the treatment outcome were favorable., Conclusions: The protocol for autotransplantation of developing premolars in growing patients was successfully adopted, regardless of lack of previous experience with this type of treatment., (Copyright © 2013 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

The present meta-analysis initially evaluates the reliability of dental maturation in the identification of the circumpubertal growth phases, essentially for determining treatment timing in orthodontics. A literature survey was performed using the Medline, LILACS and SciELO databases, and the Cochrane Library (2000 to 2011). Studies of the correlation between dental and cervical vertebral maturation methods were considered. The mandibular canine, the first and second premolars, and the second molar were investigated. After the selection, six articles qualified for the final analysis. The overall correlation coefficients were all significant, ranging from 0.57 to 0.73. Five of these studies suggested the use of dental maturation as an indicator of the growth phase. However, the diagnostic performance analysis uncovered limited reliability only for the identification of the pre-pubertal growth phase. The determination of dental maturity for the assessment of treatment timing in orthodontics is not recommended.

Clinically the condition Molar Incisor Hypomineralization (MIH),varies considerably between individuals, where any number of molars, from one to all four permanent first molars, may be affected with different degrees of hypomineralized enamel within the same dentition. An explanation to these variations could be that the start of the enamel mineralization differs between homologues teeth. The aim of this study was to compare the dental development between homologues teeth in digital panoramic radiographs (PRs),from children aged 7 to 11 years, using the Gleiser & Hunt method on second and third molars and to calculate the crown/root ratio for the mandibular premolars.77 PRs, from individuals between 7.3 and 11.0 years of age, were studied. Differences in developmental stages between homologues teeth (second and third molars) were studied. In 72 of these PRs, the crown/root ratio of mandibular premolars was also compared. In 31 of the PRs, a difference in development was found between the right and left maxillary second molar. In 22 PRs, a difference in development between the right and left mandibular second molar was found. In 17 of the PRs, a difference in development was found between the right and left maxillary third molars. In 26 PRs,a difference in-between the right and left mandibular third molar was found. In 72 PRs, the crown/root ratio of mandibular premolars was measured and differences were found. All these differences were significant. A possible explanation to the variations in expressivity of MIH may be a result of differences in the start of mineralization between homologues teeth. Timing of mineralization of homologues permanent teeth--An evaluation of the dental maturation in panoramic radiographs.

The aim of this study was to examine the accuracy of regression equation for prediction of the mesiodistal diameter (MDD) of the crowns of canines and premolars (C, P1, P2), and to determine whether an incisal indexs can serve as a reliable predictor. MDD and vestibulooral diameter (VOD) of the crowns of central and lateral incisors (I1, I2), C, both P1, and P2, and first permanent molars (M1) in both jaws were measured on the plaster casts of 150 subjects (75 boys and 75 girls). The obtained measurements were compared and correlated with predicted values (by linear regression equation derived previously), with respect to gender, jaw side and value of the interincisal index. The correlation coefficients between measurements and predicted MDD of the C, P1, and P2 were calculated with respect to gender and jaw. The values varied from 0.62 to 0.81. It could be concluded that normal values of the interincisal index of the I1 and I2 are highly associated with measured and predicted MDD of the C, P1, and P2 crowns. Correlation coefficients ranged from 0.84 to 0.99.

Objective: To evaluate the relationship between the stages of dental formation and the timing of eruption of mandibular second premolars., Materials and Methods: The sample comprised panoramic radiographs of 25 children, 7 to 12 years old, observed by space supervision during development of dentition. The initial radiograph (T1) was taken in the mixed dentition period and the progress radiograph (T2) close to the eruption of mandibular second premolars. The stages of dental formation were determined by the proportion between crown length and total length (CL/TL) as well by the Simpson and Kunos index. Average values between right and left sides (35, 45) were correlated to the time elapsed until dental eruption (T2-T1). Statistical analysis was performed by Pearson correlation analysis., Results: The proportion CL/TL presented higher correlation index with time to eruption than the Simpson and Kunos index. The linear regression equation for prediction of timing of eruption showed high coefficient of determination, low deviation, and good accuracy. According to survival analysis, mean deviation at 95% confidence level was between 3.6 and 6.4 months. There was no difference in contralateral measurements, with high intraclass correlation coefficient for both CL/TL proportion and Simpson and Kunos index., Conclusions: More advanced stages of dental formation indicate less time until dental eruption. The strong correlation with crown length/total length proportion (CL/TL) provides a linear regression equation for prediction of the timing of eruption of mandibular second premolars.

Introduction: This report describes the clinical management of a case in which a maxillary central incisor was lost after a traumatic injury., Methods: A mandibular premolar with incomplete root development was transplanted into the alveolar socket of the lost central incisor., Results: The case evolved favorably for 12 years, remaining vital to pulp sensitivity tests and developing a favorable crown-root ratio even after it was orthodontically moved., Conclusions: Premolar autotransplantation should be considered an important and valid biological alternative in cases of premature tooth loss both in young patients and adults in order to avoid or delay implant placement or other type of restoration., (Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

The main criteria used in dental age estimation in living young individuals are mineralisation and eruption of the third molars. In order to further diversify the spectrum of characteristics after completion of third molar development, tests were undertaken to determine whether the characteristics studied by Gustafson can be ascertained with the required forensic certainty with the aid of the orthopantomogram and whether the evaluation of these could render forensic odontological age diagnoses possible beyond the 18th year of life. For this purpose, 1,299 conventionally produced orthopantomograms of 650 female and 649 male Germans aged from 15 to 40 years were studied. The characteristics of secondary dentin formation, cementum apposition, periodontal recession and attrition were evaluated in all the mandibular premolars. The correlation of the individual characteristics with chronological age was studied with the aid of a multiple regression analysis in which chronological age formed the dependent variable. Depending on the tooth studied, the R values amounted to 0.65 to 0.73; the standard error of estimate was 5.3 to 5.7 years. Basically, the regression equations calculated can be recommended for age estimation in living individuals, although it should be borne in mind that the applicability of the new method presented is limited by the quality of the X-ray images.

Teeth development is widely used for age estimation in forensic science. The aims of this study were as follows: first, to establish Indian data on canine and first premolar development for age estimation and second, to investigate population differences in teeth development. Orthopantomograms of 340 Indian children aged between 5 and 14 years were analyzed. Demirjian's stages were recorded for the developmental evaluation of canine and first premolar and for further descriptive statistical analysis. A two-way ANOVA was performed to test the significance of difference in teeth development by sex and stage. A one-way ANOVA was performed to investigate population differences in teeth development. Results showed statistically significant differences in teeth development by sex and stage. Accordingly, teeth development was earlier in girls. No statistically significant differences were observed in timings of Demirjian's stages among different populations. In conclusion, the findings of this study could be used for age estimation of Indian children., (© 2012 American Academy of Forensic Sciences.)

The shape and size of tooth roots are genetically and phylogenetically predetermined. Clinical defects in root formation can manifest in the form of shortened roots caused by either root agenesis or root resorption. We report on a patient who came at age 7 years for space management. In the 2-year period after the initial visit, maxillary arch expansion was performed, followed by serial extractions of all 4 first premolars. A radiograph taken about 18 months after the serial extraction showed that although the crowns of all 4 second premolars had erupted fully into the arch, the roots were only about half of their normal length. With a family history of 1 sibling with a missing second premolar and the symmetrical distribution and pattern of the teeth in the 4 dental quadrants, we speculated that the arrested root development was due most likely to a genetic predisposition. Arrested root development is difficult to predict, but a potential warning sign is a family history of malformed or missing teeth. Proper, adequate, and accurate records continue to remain critical for both medical and legal purposes in the treatment of patients with potential problems in root agenesis., (Copyright © 2012 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Introduction: Our objective was to compare vertical alveolar growth in areas adjacent to infraoccluded deciduous molars with growth in areas of deciduous molars and normal occlusion for a period of at least 1 year by using digital subtraction radiography., Methods: This case-control study included 40 pairs of panoramic radiographs of growing patients with infraoccluded deciduous molars and 40 pairs of radiographs of patients without infraoccluded deciduous molars. One radiograph at baseline was obtained at diagnosis, and the other at least 1 year later. The subjects and the controls were matched according to chronologic age and time interval between the 2 radiographs. The 2 groups were compared with regard to vertical alveolar growth and vertical tooth movement. Measurements were assessed by using nonparametric tests (Mann-Whitney and Friedman) and a multiple comparison test. Significance was set at 5%., Results: A statistically significant difference was observed between the groups with regard to vertical alveolar growth measured on the bone crest between the first permanent molars and second premolars., Conclusions: Vertical alveolar growth between the first permanent molar and the second premolar adjacent to the infraoccluded teeth was smaller than in areas adjacent to teeth with normal occlusion., (Copyright © 2012 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

The molecular and developmental factors that regulate tooth morphogenesis in nonmammalian species, such as snakes and lizards, have received relatively little attention compared to mammals. Here we describe the development of unicuspid and bicuspid teeth in squamate species. The simple, cone-shaped tooth crown of the bearded dragon and ball python is established at cap stage and fixed in shape by the differentiation of cells and the secretion of dental matrices. Enamel production, as demonstrated by amelogenin expression, occurs relatively earlier in squamate teeth than in mouse molars. We suggest that the early differentiation in squamate unicuspid teeth at cap stage correlates with a more rudimentary tooth crown shape. The leopard gecko can form a bicuspid tooth crown despite the early onset of differentiation. Cusp formation in the gecko does not occur by the folding of the inner enamel epithelium, as in the mouse molar, but by the differential secretion of enamel. Ameloblasts forming the enamel epithelial bulge, a central swelling of cells in the inner enamel epithelium, secrete amelogenin at cap stage, but cease to do so by bell stage. Meanwhile, other ameloblasts in the inner enamel epithelium continue to secrete enamel, forming cusp tips on either side of the bulge. Bulge cells specifically express the gene Bmp2, which we suggest serves as a pro-differentiation signal for cells of the gecko enamel organ. In this regard, the enamel epithelial bulge of the gecko may be more functionally analogous to the secondary enamel knot of mammals than the primary enamel knot., (Copyright © 2011 Wiley Periodicals, Inc., A Wiley Company.)

Determination of the skeletal maturation is extremely important in clinical orthodontics. Cervical vertebral maturation is an effective diagnostic tool for determining the adolescent growth spurt. The aim of this study was to investigate the correlation between the stages of calcification of teeth and the cervical vertebral maturity stages.

The purpose of the study was to investigate the relationship between Demirjian's method and the improved cervical vertebrae maturation (CVM) method. The material consisted of the clinical files and panoramic and lateral cephalometric radiographs of 718 children (431 girls and 287 boys) aged from 6 to 17 years, inhabitants of the Mazovia region (Central Poland). Dental age according to Demirjian was estimated using panoramic radiographs and the cervical stages (CS) of the CVM were evaluated on cephalometric radiographs. Descriptive statistics of the chronological and dental ages of the patients for a particular CS of skeletal maturity was calculated for girls and boys separately. Linear regression analysis and correlation (Pearson's r coefficient), as well as the Spearman rank correlation coefficient (R) were applied to measure the association between CS and dental calcification stages of all analysed teeth. A consistently earlier occurrence (by about 6 months) for each CS was observed in females. A moderate, but statistically significant, correlation between Demirjian's dental developmental stages and CS was determined. The level of the correlation was different for individual teeth: the teeth showing the highest relationship with CVM were the second premolars and canines (in female and male subjects, respectively). The central incisor demonstrated the poorest correlation in both genders. The findings confirmed that both dental and skeletal maturity should be assessed if the maturity stage of a growing child is to be relevant to clinical practice. The results indicate the usefulness of dental calcification stages as a simple first-level diagnostic test to determine the skeletal maturity status of a subject.

Purpose: The purpose of this study was to evaluate the efficacy of Mineral trioxide aggregate (MTA) clinically and radiographically as material used to induce root end closure in nonvital permanent teeth with immature apices (apexification) in children., Methods: The study included 30 non vital young permanent, single rooted teeth of 22 children between 8 and 13 years of age. Treatment followed a standard non-surgical root canal treatment protocol and the root canal was filled with a apical plug of 4-5 mm of MTA (white MTA--Angelus, Brazil), followed by gutta-percha obturation. The children were reviewed for 1 year at 3 month interval and the teeth were assessed clinically and radiographically., Results: MTA showed success rate of 100% both clinically and radiographically at the 12th months follow up and root end closure was seen in 86.6% of cases and root growth in 30% of cases., Conclusions: MTA showed clinical and radiographic success as an apexification material by inducing root end closure and root growth in non-vital young permanent teeth.

Objective: The aim of this study was to investigate the association between dental and skeletal maturity., Study Design: Digital panoramic radiographs and lateral skull cephalograms of 302 patients (134 boys and 168 girls, ranging from 8 to 16 years of age) were examined. Dental maturity was assessed by calcification stages of the mandibular canines, first and second premolars, and second molars, whereas skeletal maturity was estimated by the cervical vertebral maturation (CVM) stages. The Spearman rank-order correlation coefficient was used to measure the association between CVM stage and dental calcification stage of individual teeth., Results: The mean chronologic age of girls was significantly lower than that of boys in each CVM stage. The Spearman rank-order correlation coefficients between dental maturity and cervical vertebral maturity ranged from 0.391 to 0.582 for girls and from 0.464 to 0.496 for boys (P < 0.05). In girls, the mandibular second molar had the highest and the canine the lowest correlation. In boys, the canine had the highest and the first premolar the lowest correlation., Conclusions: Tooth calcification stage was significantly correlated with cervical vertebral maturation stage. The development of the mandibular second molar in females and that of the mandibular canine in males had the strongest correlations with cervical vertebral maturity. Therefore, it is practical to consider the relationship between dental and skeletal maturity when planning orthodontic treatment., (Copyright © 2010 Mosby, Inc. All rights reserved.)

Aim: To determine the correlation among chronologic age, skeletal maturity, and dental age in reference to both sexes., Methods: In 380 subjects (147 males and 233 females) between 7 and 17 years of age, skeletal maturity was assessed using the cervical vertebral maturation stages described by Baccetti et al. Dental age was determined using the Demirjian method. The correlation between skeletal maturity and chronologic age on one side and between skeletal maturity and dental age on the other was assessed with Spearman rank correlation coefficients. Pearson correlation coefficients were used to assess the correlation between chronologic and dental age., Results: For both sexes, significant correlations among chronologic age, skeletal maturity, and dental age were found. The mandibular first premolar had the highest correlation with skeletal maturation in both sexes., Conclusion: As skeletal maturity and dental age are significantly correlated, tooth development may be used to assess a patient's skeletal maturity at an early age., (© 2011 BY QUINTESSENCE PUBLISHING CO, INC.)

Objectives: To evaluate dental maturity in the mandibular canine/premolar and molar innervation fields in children with agenesis of the 2nd mandibular premolar and to associate these findings with normal control material., Setting and Sample Population: Department of Orthodontics, Institute of Odontology, University of Copenhagen. Eighty-three panoramic radiographs (27 girls and 31 boys with agenesis of one mandibular 2nd premolar and 17 girls and eight boys with agenesis of both mandibular 2nd premolars) represented all mandibular second premolar agenesis cases from a material of 2847 radiographs., Material and Methods: On each radiograph, dental maturity of all available mandibular premolars, canines and 2nd molars was evaluated and categorized in maturity stages according to Haavikko whose material served as control material. Descriptive statistics given by sample mean, standard deviation and range for each tooth stratified by gender and agenesis. Ninety-five percentage confidence limits and T-statistics were used. p-values <5% were considered significant., Results: In unilateral agenesis, the canines are specifically delayed in both girls and boys, with a larger delay in girls (p=0.009). The second molar is not delayed in boys (p=0.98) but is in girls (p=0.04). The differences in delay for the canine compared to the second molar are significant for both girls and boys. The results show a considerable delay in tooth maturation within the canine/premolar innervation field predominantly in girls. The 2nd molar is delayed in girls but not in boys., (© 2010 John Wiley & Sons A/S.)

The objectives of this study were to determine the effects of dentition on feed-oriented behavior and feed consumption before weaning at 28 d, and whether premolar eruption or occlusion at the time of weaning influenced postweaning growth or behavior. Over 3 trials, 24 litters of Yorkshire piglets (n = 233) were provided with creep feed marked with 1% chromic oxide on d 5. Dental exams were performed on d 2, 6, 9, 13, 16, 20, 23, and 27. Fecal samples were visually assessed for feed consumption (via fecal color) on the same day as dental exams, beginning on d 6. The duration of time spent at, and frequency of visits to, the creep feeder were determined from continuous video recordings on d 7, 10, 14, 17, 21, and 24 for 6 h/d (0700 to 1000 h, 1300 to 1600 h). After weaning, behavior was recorded every 5 min for three 2-h time periods (0600 to 0800 h, 1100 to 1300 h, and 1600 to 1800 h) on d 2, 4, 6, 8, 10, and 12. Piglets younger than 17 d with their premolars erupted and occluded spent less time at the creep feeder and visited it less often than piglets without their premolars erupted and occluded [duration: p(3) (premolar position 3 on maxilla), d 7 (P = 0.005); p(4) (premolar position 4 on mandible), d 7 (P < 0.0001), d 10 (P = 0.003); p(4 )(premolar position 4 on maxilla), d 17 (P = 0.012); occlusion, d 7 (P < 0.0001), d 10 (P = 0.0004); visits: p(3), d 7 (P < 0.0001); p(4), d 7 (P < 0.0001), d 10 (P = 0.001); p(3 )(premolar position 3 on mandible), d 14 (P = 0.037); p(4), d 17 (P = 0.024); occlusion, d 7 (P < 0.0001), d 10 (P = 0.003)]. By d 21 of age, this trend reversed such that piglets with premolars erupted and occluded spent more time at the feeder and visited it more frequently [duration: p(3), d 24 (P = 0.025); p(4), d 24 (P = 0.0005); occlusion, d 21 (P = 0.001), d 24 (P = 0.0001); visits: p(3), d 21 (P = 0.0002), d 24 (P < 0.0001); p(4), d 24 (P = 0.0002); occlusion, d 21 (P < 0.0001), d 24 (P < 0.0001)]. The percentages of piglets with positive fecal scores were 0, 1.4, 4.6, 8.0, 29.0, 44.9, and 60.6% on d 7, 10, 14, 17, 21, 24, and 27, respectively (P < 0.0001 between each day). No associations were found between the eruption or occlusion of premolars and feed consumption before weaning (P > 0.05), and no dental measures influenced growth rates (P > 0.10) or behavior (P > 0.10) after weaning. A more precise method may be necessary for detecting associations between dental eruption and feed consumption. However, the behavioral results indicate that, before weaning at 28 d, younger piglets are inhibited from feeding when their premolars first erupt, whereas older piglets with a more advanced dentition are more attracted to feed.

Unlabelled: Autotransplantation of immature teeth has good survival rates, and has benefits over ossointegrated implants in the growing child, but is very technique sensitive. Spiral CT imaging has been previously used in adult patients to enable computer-aided prototyping to produce a surgical template of the donor tooth, further increasing success rates., Case Report: The case presented describes management of a 9-year-old girl with the combination of hypodontia affecting the upper lateral incisors as well as a severely ectopic maxillary canine. Cone beam CT was used in combination with computer-aided prototyping to produce a surgical template of an immature mandibular second premolar. The surgical template was used to prepare the transplant site before the donor tooth was extracted, greatly reducing the time from extraction to implantation. By 6 months posttransplant the tooth was clinically sound, and continued root development and laying down of dentine was visible radiographically., Discussion: This paper demonstrates the use of a novel technique to aid the surgical procedure of autotransplantation of immature premolar teeth. The use of autotransplantation in this case allowed the difficult situation of two missing units in the upper left quadrant to be reduced to one unit, while retaining symmetry in the upper arch. Compared to previous studies, the use of cone beam CT to create a 3D prototype reduced radiation dose compared to spiral CT and drastically reduced the extra-oral time of the donor tooth from extraction to transplantation.

The standard age estimation methods of Moorrees, Fanning & Hunt (1963) and that of Demirjian, Goldstein & Tanner (1973) have been shown by several authors to be inaccurate when applied to their juvenile population. This was similarly found to be true in South African children. Pantomographic radiographs of samples of South African children of White, Coloured, Indian and Black origin were used to develop dental age related tables for these ethnic groups. These dental age estimation tables were tested and are presented.

Numerous studies of dental development focusing on eruption (clinical emergence) exist in the literature, but fewer studies examine dental development as a process extending across years or decades, and root development is commonly assessed using fractional root lengths. Here, we examine the growth of mandibular canine and premolar roots in a mixed-longitudinal sample of orthodontic patients (77 females and 74 males) from north central Texas. Multilevel models are generated for root lengths as a percentage of total tooth lengths (within films) as well as for absolute root lengths (across films). As a percentage of tooth length, roots grow with decreasing velocity through time between 7 and 14 years of age. More complex patterns appear for absolute growth in root length, with girls showing an earlier maximum growth rate for the canine than for the premolars. Substitution of dental age for chronological age reduces between-subject variation (assessed at age 11), especially for boys. A better understanding of dental maturation, including root length growth, should allow improved prediction models.

The aim of this study was to determine if Häävikko's maturation standards are applicable to Italian children. The sample included 500 healthy Caucasian children 3.9-15.4 years of age: 267 girls [mean age 9.6 years, standard deviation (SD) 2.1] and 233 boys (mean age 9.9 years, SD 2.1), living in Italy. All dental ages were assessed from panoramic films by one examiner using Häävikko's method. A second examiner independently scored 48 panoramic films to evaluate the reproducibility of the dental age measurements. A good correlation (0.95) was found, as shown by Cohen's kappa. To evaluate the relationship between dental age estimated by Häävikko's standards and the chronological age of the Italian sample, Bland and Altman's graphical method was employed. Moreover, centiles of dental age were constructed both for girls and boys using the LMS (L=skewness, M=median, S=coefficient of variation) method of Cole and Green. It was found that Häävikko's standards tended to underestimate chronological age in this Italian sample. Dental maturation standards as described by Häävikko do not appear suitable for Italian children; instead, centile curves constructed for girls and boys using the LMS method could be used for the estimation of dental age in the Italian population.

Reasons for Performing Study: There are few published data to support the ages of emergence of permanent dentition widely reported in horses., Objectives: To clarify the chronology and sequence of permanent premolar (PM) tooth emergence in Thoroughbred racehorses., Methods: A prospective study was undertaken in which records were kept of deciduous PM 'cap' extractions performed during routine dental examinations in Thoroughbred racehorses. Mixed effects multiple regression analysis was used to relate the observed ages, measured in days, for PM 'cap' extractions simultaneously with different predictive variables. Care was taken to account for clustering of multiple observed outcomes within individual horses., Results: A total of 508 deciduous premolar 'caps' were removed from 207 horses, mean ages at removal from PM2, PM3 and PM4 were 35.1, 37.7 and 45.1 months, respectively. Age at which deciduous 'cap' removal occurred was associated significantly with tooth row, upper or lower jaw and gender of the horse concerned. There was a significant trend for later 'cap' extraction age with more caudal teeth, teeth in the upper jaw and female gender., Conclusions: Age at removal of deciduous premolar 'caps' in this population differed considerably from the ages of emergence of permanent dentition reported widely in equine publications. The results provide the first evidence of sexual dimorphism in the eruption of the permanent premolar dentition in horses. These findings strongly support a model of cheek tooth eruption in the horse in which chronology and sequence of emergence are more complex than previously thought, but which is consistent with understanding of tooth eruption in species that have been studied in greater detail., Potential Relevance: Abnormalities of cheek tooth eruption are thought to be a factor in the pathogenesis of a variety of dental conditions, and a thorough understanding of the process of eruption is fundamental to the development of rational strategies for prevention and treatment.

The purpose of this study was to investigate the use of cheek tooth occlusal surface morphology as an indicator of age in the horse using a blinded cross-sectional design. Twenty horses of varying age, breed and sex were used. Horses of known age (foaling date) were euthanized for reasons other than dental disease. Following disarticulation of the head and sectioning of the mandibles, cheek teeth were cleaned using running water and photographs were taken of each arcade. Using a computer-based program, the total surface area of each premolar and molar, the outer enamel ridge perimeter distance, infundibular surface areas and perimeter distances were measured. Further anatomical data were calculated from these measurements and a statistical analysis of the relationship between horse age and cheek tooth occlusal morphology was performed. Results indicated that multiple anatomical regions within the occlusal surface of the equine cheek tooth can be used as an indicator of age. There are important differences between mandibular and maxillary teeth as well as between teeth in the same dental arcade. Horse size is also of significance. The mesial infundibular surface area as a percentage of the total surface area of tooth 111, and the mesiodistal length of 1/2/3/4 09 teeth, most closely approximates age within our mathematical model. Cheek tooth morphological data can be used to predict age in horses that possess all their permanent dentition. In cases in which the age of horses cannot be accurately determined from incisor examination, cheek teeth may be used.

A characteristic feature of mammalian dentition is the evolutionary reduction of tooth number and replacement. Because mice do not replace teeth, here we used Sorex araneus, the common shrew, as a model to investigate the loss of tooth replacement. Historically, shrews have been reported to initiate the development of several, milk or deciduous teeth but these soon become rudimentary and only the replacement teeth erupt. Shrews thus offer a living example of a derived mammalian pattern where the deciduous tooth development is being suppressed. Based on histological and gene expression analyses of serial sections, we suggest that S. araneus has discernible tooth replacement only in the premolar 4 (P4) position. Both generations of teeth express Shh in the enamel knot and in the inner enamel epithelium. Nevertheless, the deciduous P4 (dP4) is reduced in size during embryogenesis and is eventually lost without becoming functional. Analysis of growth shows that P4 replaces the dP4 in a "double-wedge" pattern indicative of competitive replacement where the suppression of the deciduous tooth coincides with the initiation of its replacement. Because activator-inhibitor mechanisms have been implicated in adjacent mouse molars and in transgenic mice with continuous tooth budding, we suggest that evolutionary suppression of deciduous teeth may involve early activation of replacement teeth, which in turn begin to suppress their deciduous predecessors.

A recent study demonstrated that variation in enamel cap crown formation in the anterior teeth is greater than that in the molars from two geographically distinct populations: native indigenous southern Africans and northern Europeans. Eighty southern African and 69 northern European premolars (P3 and P4) were analyzed in the present study. Cuspal, lateral, and total enamel formation times were assessed. Although cuspal enamel formation times were not consistently different between the two populations, both lateral and total enamel formation times generally were. Bonferroni-corrected t-tests showed that southern Africans had significantly shorter lateral enamel formation time for five of the six cusps, as well as significantly shorter total enamel formation time for these same cusps. An analysis of covariance performed on the lingual cusps of the upper third and fourth premolars showed that differences in enamel formation times between these populations remained when crown height was statistically controlled. A further goal of this study was to ascertain, based on perikymata counts, what Neandertal periodicities would have to be in order for their teeth to have lateral enamel formation times equivalent to either southern Africans or northern Europeans. To this end, perikymata were counted on 32 Neandertal premolars, and the counts were inserted into regression formulae relating perikymata counts to periodicity for each population and each tooth type. Neandertal enamel formation times could be equivalent to those of southern Africans or northern Europeans only if their hypothetical periodicities fall within the range of periodicities for African apes and modern humans (i.e., 6-12 days). The analysis revealed that both populations could encompass Neandertal timings, with hypothetical periodicities based on the southern African population necessitating a lower range of periodicity (6-8 days) than those based on the northern European population (8-11 days).

Objective: The purpose of this study was to establish reference values for maturity of permanent canines, premolars, and permanent 2nd molars in Danish children, and to focus on differences between the right and left sides, males and females, and the maxilla and mandible., Material and Methods: Panoramic radiographs from 106 males (8-14 years) and 137 females (7 years 2 months to 13 years 8 months) were analyzed, along with the maturity of the canines, premolars, and 2nd molars in each radiograph. Each tooth was categorized according to Haavikko's crown and root morphology. Inter-observer reliability was performed. For statistical analysis, Bowker's test was used for symmetry evaluation and comparison of maturity in the maxilla and mandible. The association between stage and age was presented by cumulative distributions. The Wilcoxon rank sum test was used for evaluating differences between genders., Results: Differences in maturity between the left and right sides were non-significant. A significant difference in dental maturity was observed between males and females, except for the maxillary 2nd premolar. Females matured earlier than males. The mandibular canines matured significantly earlier than the maxillary canines in females. No significant differences between the jaws were observed in the maturation of the premolars and 2nd molars., Conclusion: These reference values for dental maturity can be useful in orthodontic treatment planning and as a reference for odontological forensic age determination.

Introduction: The purpose of this study was to determine whether there were differences in bond strength between mature and newly erupted teeth when using both conventional and self-etching primer techniques for bonding orthodontic appliances. The nature of adhesive bond failure among the groups was also compared by using the adhesive remnant index (ARI)., Methods: Premolars were collected, randomly divided, and bonded with either the conventional or the self-etching technique. Brackets were debonded on a testing machine with a shear-testing device. Bond strengths were compared with ANOVA and the Weibull analysis., Results: There were no statistically significant differences in bond strength values between the conventional etching and the self-etching primer groups or between newly erupted and mature teeth. ARI scores differed between mature and newly erupted teeth. Newly erupted teeth had more adhesive failures, and mature teeth had more cohesive bond failures at the enamel-composite resin interface., Conclusions: Based on these results, bond strength does not appear to be affected by the posteruptive enamel maturation process.

Normal and abnormal jaw growth and tooth eruption are topics of great importance for several dental and medical disciplines. Thus far, clinical studies on these topics have used two-dimensional (2D) radiographic techniques. The purpose of the present study was to analyse normal mandibular growth and tooth eruption in three dimensions based on computer tomography (CT) scans, extending the principles of mandibular growth analysis proposed by Björk in 1969 from two to three dimensions. As longitudinal CT data from normal children are not available (for ethical reasons), CT data from children with Apert syndrome were employed, because it has been shown that the mandible in Apert syndrome is unaffected by the malformation, and these children often have several craniofacial CT scans performed during childhood for planning of cranial and midface surgery and for follow-up after surgery. A total of 49 datasets from ten children with Apert syndrome were available for study. The number of datasets from each individual ranged from three to seven. The first CT scan in each of the ten series was carried out before 1 year of age, and the ages for the 49 scans ranged from 1 week to 14.5 years. The mandible and the teeth were segmented and iso-surfaces generated. Landmarks were placed on the surface of the mandible, along the mandibular canals, the inner contour of the cortical plate at the lower border of the symphysis menti, and on the teeth. Superimposition of the mandibles in the longitudinal series was performed using the symphysis menti and the mandibular canals as suggested by Björk. The study supported the findings of stability of the symphysis menti and the mandibular canals as seen in profile view previously reported by Björk & Skieller in 1983. However, the mandibular canals were, actually, relocated laterally during growth. Furthermore, the position of tooth buds remained relatively stable inside the jaw until root formation started. Eruption paths of canines and premolars were vertical, whereas molars erupted in a lingual direction. The 3D method would seem to offer new insight into jaw growth and tooth eruption, but further studies are needed.