Cone-beam Computed Tomography Analysis of the Root Canal Morphology of Mandibular Incisors Using Two Classification Systems in a Spanish Subpopulation: A Cross-Sectional Study.

OBJECTIVE: This study evaluated the root and canal morphology in permanent mandibular incisors teeth using cone-beam computer tomography imaging in a Spanish subpopulation, and compared these findings with ipsilateral (similarity) and contralateral (symmetry) incisors. In addition, the position of canal splitting was measured. METHODS: A total of 229 datasets comprising four mandibular teeth each (n=916 incisors) were analysed using Vertucci and Ahmed et al. classifications, and, the similarity and symmetry were calculated. The distance from the cemento-enamel junction (CEJ), and the most coronal canal divergence was measured (if present). The role of sex was also assessed. The Cochran Q Test, LOGIS PROC in SUDAAN, Chi-square, and Kappa were used for the different comparisons. A p-value of less than 0.05 was considered significant. RESULTS: All incisors were single-rooted and no significant differences regarding root canal morphology were found according to the sex of the subjects included in the database. The most common morphology was Vertucci type I/Ahmed et al. 1MI1(65.3% for central and 66.8% for lateral incisors respectively), followed by type III/1MI1-2-1 (31% for central and 30.6% for lateral incisors). 1.8% of the samples were considered as non-classifiable with Vertucci but were classified with codes using the Ahmed et al. system. Similarity values were 74.7% for the left side, and 74.2% for the right side, whereas symmetry values were 90% for central and 84.3% for lateral incisors. In the presence of divergences, the main (SD) distances from the CEJ were for type II/1MI1-2-1 3.8+-0.8 (centrals) 4.0+-0.7 mm (laterals); for type V/1MI1-2 this value ranged between 6.0+-1.8 and 5.5+-1.5 mm, whereas values for 1MI1-2-3-2-1 were 1.8 and 2.1 mm. No significant differences were found when the position of the most coronal divergence was compared between lateral and central incisors for the different morphologies. CONCLUSION: A high prevalence of Vertucci I/Ahmed et al. 1MI1 configuration was present in mandibular incisors from Spanish individuals. Similarity and symmetry were common, particularly for central incisors. The position of the coronal splitting of the canals varied according to the root canal morphology.

Alveolar bone morphology in patients with palatally-displaced maxillary lateral incisors before and after orthodontic treatment: A cone-beam computed tomography study.

INTRODUCTION: Palatal displacement of maxillary anterior teeth is common in clinical practice. Previous studies have reported that the labial bone around palatally-displaced incisors is thinner than that around normally-placed teeth. Therefore, it is necessary to elucidate alveolar bone changes after alignment to guide orthodontic treatment. In this study, we investigated the alveolar bone changes around palatally-displaced maxillary lateral incisors before and after treatment, and the effects of extraction and age using cone-beam computed tomography. METHODS: In this retrospective study, 55 patients with unilateral palatally-displaced maxillary lateral incisors were included. Three-dimensional alveolar bone changes were measured at three levels (25%, 50% and 75% of the root length) using cone-beam computed tomography. Group comparisons were made between displaced and control teeth, extraction and non-extraction groups, and adult and minor groups. RESULTS: After orthodontic treatment, labiopalatal and palatal alveolar bone widths decreased at all measured levels. Labial alveolar bone width increased significantly at P25, but decreased at P75. Concavity decreased, while tooth-axis angle, tooth length, B-CEJ and P-CEJ increased. Changes in LB and LP at P75, B-CEJ and P-CEJ were statistically significant. After treatment, the tooth-axis angle on the PD side increased by 9.46°. The change in tooth-axis angle on the PD side was significantly smaller, and LB and LP decreased more at P75, in the extraction group. CONCLUSIONS: Compared to the control teeth, alveolar bone thickness and height for the displaced teeth decreased more significantly after treatment. Tooth extraction and age also influenced alveolar bone changes.

Three-dimensional analysis of the alveolar ridge profiles of maxillary central incisors in children for autotransplantation.

BACKGROUND: Sufficient alveolar housing is fundamental to ensure the favorable prognosis of autotransplanted teeth. However, little is known about the alveolar ridge profiles of the anterior maxilla in children. Therefore, this study aimed to investigate the alveolar ridge profiles of the anterior maxilla in growing children. METHODS: A total of 169 Korean children aged 10-13 years old were included in this retrospective study. Demographic data and cone-beam computed tomography scans of 244 maxillary central incisors were collected. For each tooth, the alveolar ridge thickness was determined at 1-, 3-, and 5-mm levels below the cemento-enamel junction. The alveolar process height and labial concavity were also evaluated. Statistical analyses were performed to evaluate differences according to age and sex. RESULTS: The alveolar ridge thickness did not differ according to age. The alveolar ridge thickness in males was significantly greater than that in females among those aged 10 and 11 years. The average alveolar process height was 17.43 ± 2.22 mm. The alveolar process height hardly changed with age from 10-13 years, whereas the alveolar process height of males was significantly greater compared with that of females among those aged 10 years. The labial concavity was approximately 150˚, with no significant differences between age and sex. CONCLUSIONS: Within the limits of this study, the anatomy of the alveolar ridge in the maxillary central incisors showed sufficient capacity as a recipient site for autotransplantation using mandibular premolars, especially in males. These findings serve as a valuable resource for facilitating autotransplantation in children.

Statistical shape analysis of maxillary palatal morphology in patients with palatally displaced canines.

OBJECTIVE: Maxillary morphology has long been a subject of interest due to its possible impact on palatally and labially displaced canines. This study aims to conduct a comparison of the palate morphology between individuals with palatal and labially displaced canines and control subjects using statistical shape analysis on a coronal cross-sectional of CBCT images. MATERIALS AND METHODS: Patients aged between 12 and 43 years with palatally or labially displaced canines referred to Hamadan School of Dentistry between 2014 and 2019 were recruited for this retrospective study. The sample included 29 palatally displaced canines (PDC), 20 labially displaced canines (LDC), and 20 control groups (CG). Initially, the maxillary palate coronal section was acquired and landmarked in the region between the right and the left first molar. Procrustes and principal component analyses were used to identify the primary patterns of palatal shape variation. Statistical tests were then performed to examine both shape and size differences. RESULTS: According to the results of Hotelling's T2 test, there is a significant difference between the mean shape of palate in PDC and CG (P = 0.009), while the difference between the PDC-LDC and LDC-CG groups is not significant. The longest full Procrustes distance was observed between PDC and CG (distance = 0.043), and the shortest full Procrustes distance was observed between LDC and CG (distance = 0.029). The first two principal components accounted for 84.47% of the total variance. The predictive accuracy of the discriminant analysis model showed that 72.46% of cases were correctly classified into the three study groups. CONCLUSIONS: In terms of centroid size, there was no significant difference in the sectional area between the three groups, but the difference between the mean shape of palate in the PDC and CG groups was significant. The PDC group showed more prominent mid-palatal area in the molar region.

Thermographic examination of gingival phenotypes: correlation between morphological and thermal parameters.

OBJECTIVES: To evaluate the clinical and thermographic aspects of the gingival phenotype (GP) in healthy subjects. MATERIALS AND METHODS: The study sample examined 264 teeth, upper and lower incisors, comprising 132 central incisors (CI) and 132 lateral incisors (LI), in 33 healthy volunteers. Four periodontal parameters were recorded systematically: ratio of width to length of the dental crown (CW/CL), height of the gingival attachment (KGW), probing depth (PD), and gingival transparency (GT). The temperatures of the attached gingiva (KGW temp) and the free gingival margin (FGM Temp) were also recorded by way of infrared thermography (IRT). RESULTS: The average age of the sample was 30.70 ± 7.65 years. Of the 264 teeth evaluated, 76.1% had a thin GP. There was a significant association between CW/CL (p < 0.001), KGW (p < 0.001), PD (p < 0.007), and FGM Temp (p < 0.006) with the tooth groups. The results show a significant and inversely proportional correlation between clinical parameters and gingival temperature (p < 0.05). A significant association was found between CW/CL (p < 0.026); KGW (p < 0.001); and GP. CONCLUSION: CW/CL, KGW, PD, and FGM Temp vary according to tooth group. The majority of the sample presented with the thin GP, which was more prevalent in the lower LIs and CIs. No significant association could be observed between thermographic parameters and GP. CLINICAL RELEVANCE: Knowledge of the temperature of the gingival tissues can be useful in helping to diagnose and plan periodontal treatments. Moreover, our findings will help future studies evaluate the use of IR as an auxiliary diagnostic method in dentistry, eliminating GP as a confounding factor, since it does not seem to influence the temperature of the gingival tissues.

Chewing, dentition and tooth wear in Hippopotamidae (Hippopotamus amphibius and Choeropsis liberiensis).

Among mammals, hippopotamids ('hippos') have been described as the species with the lowest chewing efficacy despite elaborate enamel folds on the occlusal surface or their cheek teeth, which was hypothesized to result from the lack of a grinding chewing motion. We investigated the chewing and dentition of the two extant hippo species, the common hippo (Hippopotamus amphibius) and the pygmy hippo (Choeropsis liberiensis), making (video) observations of live animals and gathering data on museum specimens (n = 86 H. amphibius and 26 C. liberiensis skulls). Hippos have a low degree of anisodonty (differences in width between maxillary and mandibular cheek teeth) and anisognathy (difference in width between the upper and the lower jaw), corresponding to a mainly orthal (up-and-down) chewing motion. The two hippo species differ slightly, but distinctively, in their anterior dental morphology and chewing mode. In both species, the canines do not completely prevent a lateral jaw movement but would, in theory, permit this movement until the mandibular canines get into contact with the maxillary protruding snout. This movement is only realized, to a small extent, in pygmy hippos, leaving distinct wear traces on their incisors and creating relatively wider wear facets on the maxillary canines. In common hippos, the interlocking upper and lower incisors prevent lateral jaw movement. Corresponding contact wear facets are evident on the medial aspect of the upper, and on the lateral aspect of the lower incisors-unless museal reconstructions mispositioned these teeth. If these facets are interpreted as an indication for a relic of a lateral jaw movement that was probably more prominent in hippo ancestors, i.e. if we assume that hippos evolved orthal chewing secondarily, several other characteristics of hippos can be explained, such as a low degree of hypsodonty (in the absence of distinct attrition due to a grinding chewing movement), a secondary loss of complexity in their enamel schmelzmuster, a secondary evolution of a wide mouth gape, a reduction in anisodonty compared to their ancestors, and the evolution of a bilaterally symmetrical ('trifoliate') enamel folding pattern on the molar occlusal surface from an ancestral bunoselenodont condition. As an underlying driving force, selection for intraspecific combat with canines and incisors, necessitating a wide gape and a rigid jaw, has been suggested.

Characteristics of mandibular anterior alveolar bone in patients with different degrees of periodontitis: a retrospective study based on CBCT.

OBJECTIVES: To investigate the alveolar bone characteristics of mandibular anterior teeth in patients with periodontitis. MATERIALS AND METHODS: 100 patients with periodontitis were selected and grouped according to the degrees of alveolar bone resorption, age, gender, and tooth type. The labial thickness of the alveolar bone, the degree of alveolar bone resorption, angulation between the long axis of teeth and alveolar process, alveolar bone height and density of the mandibular anterior teeth were measured. RESULTS: There were significant differences in alveolar bone morphology between these three groups. Compared with the mild and moderate groups, the severe group showed that the alveolar bone in the half of the root crown was thickened, the alveolar bone height was decreased, the cancellous alveolar bone density was increased, and the cortical alveolar bone density was decreased. The resorption of alveolar bone was characterized by greater resorption of proximal bone than that of labial bone with increased bone loss. There were also differences in alveolar bone characteristics among patients of different ages, genders, and tooth types. CONCLUSIONS: The morphology of the mandibular anterior alveolar bone changed accordingly with the degree of periodontitis. Labial alveolar bone thickness and cortical alveolar bone density were negatively correlated with the degree of periodontitis, while alveolar bone height and cancellous alveolar bone density were positively correlated with the degree of periodontitis. CLINICAL RELEVANCE: These results allow clinicians to better understand the alveolar bone morphology of the mandibular anterior teeth in patients with periodontitis, facilitating better treatment design and avoiding complications.

Effect of craniofacial morphology on gingival parameters of mandibular incisors.

OBJECTIVES: To investigate the association between the width of keratinized gingiva (WKG), gingival phenotype (GP), and gingival thickness (GT) with craniofacial morphology in sagittal and vertical dimensions. MATERIALS AND METHODS: WKG, GP, and GT of mandibular anterior teeth in 177 preorthodontic patients (mean age 18.38 ± 5.16 years) were assessed clinically using a periodontal probe, a Colorvue Biotype Probe, and ultrasound by a single examiner. Patients were grouped into skeletal Class I, II, and III and hyperdivergent, normodivergent, and hypodivergent based on ANB and SN-MP angles. Mandibular incisor inclination (L1-NB) was also measured. Clinical and cephalometric measurements were repeated to assess inter- and intraexaminer reproducibility. RESULTS: A significant association was found between thin GP and skeletal Classes I and III for the left mandibular central incisor (MCI; P = .0183). In skeletal Class III patients, L1-NB angle demonstrated a decreasing trend as phenotype thickness decreased. A significant association was found between thin phenotype and normodivergent and hypodivergent groups for MCIs (left: P = .0009, right: P = .00253). No significant association between WKG or GT and craniofacial morphology was found. CONCLUSIONS: Thin GP is associated with skeletal Class I and III for the left MCI. Thin GP is associated with hypodivergent and normodivergent skeletal patterns for the MCIs. There was no association between WKG and GT and craniofacial morphology in both skeletal and vertical dimensions. Dental compensations that exist due to different craniofacial morphology may influence the GP.

Treatment change comparisons between skeletal Class I and II white adolescents with 3 different vertical divergencies-part 1: Frankfort-Mandibular Incisor Angle (FMIA) and soft-tissue profile.

INTRODUCTION: This study investigated the interrelationship between FMIA and soft-tissue profile changes in skeletal Class I and II white adolescents with 3 different vertical skeletal patterns. METHODS: Two hundred seventy cephalometric images were constructed from pretreatment and posttreatment cone-beam computed tomography images of 135 white adolescents (69 females and 66 males with a mean age of 12.8 ± 1.4 years pretreatment and 15.0 ± 1.4 years posttreatment). SNA, SNB, ANB, Frankfort Mandibular Angle [FMA], Incisor Mandibular Plane Angle [IMPA], Frankfort-Mandibular Incisor Angle [FMIA], and Z angle were measured. A mixed-model analysis of variance was performed for patients with an increased posttreatment Z angle to evaluate within-subject and between-subject effects of variables in relation to horizontal and vertical skeletal patterns. Post-hoc tests were conducted to identify statistical significance among the 3 different divergent subgroups. RESULTS: Patients with a skeletal Class I relationship had straighter facial profiles and a larger FMIA than patients with a skeletal Class II relationship before and after treatment. FMA, FMIA, IMPA, and Z angle treatment changes were similar between the skeletal Class I and II groups. The final FMIA means of the 3 divergent subgroups converged at 65° in the skeletal Class I group and 60° in the skeletal Class II group. The mandibular incisors were uprighted during treatment in the hyperdivergent patients whose Z angle values increased after treatment. CONCLUSION: Horizontal skeletal relationships seem more suitable for determining the desired FMIA in Tweed's total space analysis than vertical skeletal divergencies.

Effect of the ethnic, profession, gender, and social background on the perception of upper dental midline deviations in smile esthetics by Chinese and Black raters.

BACKGROUND: The purpose of this study was to compare the perception of upper dental midline deviation on the attractiveness of a smile among raters from different ethnicities, professions, genders, and ages and measure to what extent the presence or absence of the associated smiling structures influence the raters' evaluations. METHODS: A male subject (26 years of age) with adequate smile characteristics was selected by 3 experienced orthodontists, and 561 raters from 2 different ethnic groups (281 Chinese raters and 280 Black raters) rated the subject's smile after the subject's upper dental midline was digitally altered from 0 to 5 mm using a 5-point Likert scale on 12 smile photographs divided into two groups: group 1, in the presence of smile related structures, two-thirds of the nose, lips, and chin (NLC), and group 2, in the absence of smile related structures, the lips only (L). RESULTS: There were statistically significant differences (p < 0.05) between the two ethnicities, in 2 mm and 4 mm in-group NLC and 5 mm in-group L, as well as the raters' profession to each midline shift of both groups (NLC) and (L) for both ethnicities except for 0 mm. Regarding the role of associated smile structures, the smile photos were observed in the presence of smile-associated structures, and in its absence (NLC × L), statistically significant differences (p < 0.05) were found when the deviation was 5 mm among the Chinese raters; in 1 mm, and 4 mm among the Black raters. Among different genders, statistical differences were only reported (p < 0.05) for Chinese raters for 5 mm in NLC, while statistical differences were observed for 2 mm and 3 mm in NLC for Black raters. For age categories, differences were observed (p < 0.05) for 4 mm, 5 mm in NLC and 4 mm, and 5 mm in L for Chinese raters, while 5 mm in NLC and 1 mm in L for Black raters. CONCLUSION: Perception of the upper dental midline deviations was influenced by the factors of ethnicity, profession, presence or absence of smile-associated structures, as well as the gender and age of the raters.

Oclusión basada en evidencia: rompiendo paradigmas / Occlusion based on evidence: breaking paradigms

La odontología basada en evidencias es una metodología que busca que las decisiones clínicas diarias que toman los profesionales en estomatología se encuentren fundamentadas en la evidencia científica, en ella se integran las experiencias clínicas, las necesidades, las preferencias del paciente y la evidencia clínicamente relevante más actual analizada por pares. Estos pilares son parte del proceso en la toma de decisiones para la atención al paciente. La odontología basada en evidencias surge de las exitosas experiencias obtenidas con el desarrollo e implementación de la medicina fundamentada en pruebas, al aplicar el método científico en la evaluación, planificación y toma de decisiones de las prestaciones sanitarias, sobre todo a través de los estudios controlados. En general, toda la práctica odontológica ha tenido grandes avances basados en evidencias, con hechos verídicos comprobados, pero los conceptos fundamentales de oclusión no han tenido una mejora cimentada en el conocimiento científico, prueba de ello es que se siguen ocupando teorías y conceptos de las filosofías de oclusión en la rehabilitación de muchos pacientes, seguimos creyendo en mitos y sofismas que no han podido ser demostrados. En esta revisión, demostramos los grandes avances en los conceptos de oclusión e invitamos a todos los odontólogos a romper los paradigmas de la oclusión antigua sin evidencias científicas y a utilizar las herramientas del método científico en la práctica clínica odontológica (AU)

Evidence-based dentistry is a strategy that seeks to ensure that the daily clinical decisions made by the dental professional are based on scientific evidence. It integrates the clinical experience of the dentist, the needs and preferences of the patient, and the most current relevant clinical evidence. All three are part of the decision-making process for patient care. Evidence-based dentistry arises from the successful experiences obtained with the development and implementation of evidence-based medicine, applying the scientific method in the evaluation, planning and decision-making of health benefits, especially through controlled studies. In general, all dental practice has had great advances based on evidence, with proven true facts, but the fundamental concepts of occlusion have not had an improvement based on scientific knowledge, proof of this is that theories and concepts continue to be used. of the philosophies of occlusion in patient rehabilitation, we follow myths and sophisms that have not been demonstrated, in this review, we demonstrate the great advances in the concepts of occlusion and we know all dentists to break the paradigms of the old occlusion without scientific evidence (AU)

Evaluation of Alveolar Bone Dimensions and Root Positioning of Anterior Teeth in the Maxilla.

Buccal bone walls present significant resorption after tooth extraction, possibly related to the smaller bone thickness, length, and the sagittal position of the root, as well as the bone morphology. The goal of the present study was to measure the thickness of the cortical bone of the vestibular and palatal walls in the anterior maxilla by means of CBCT images. Measurements were taken from CBCT scans of 300 maxillary anterior teeth from 50 patients (25 women, 25 men) aged 18 to 30 years. The parameters evaluated included the thickness of the buccal and palatal cortical bone in the cervical, apical, and middle thirds of the root, as well as six specific angular measurements from each tooth. The lateral incisors showed a significant difference in thickness between each of the buccal and palatal thirds, and measurements were also significantly smaller than the central and canine incisors. Bone anatomy is tooth-and location-specific, and thus the sagittal root position within the alveolus influences the regional bone morphology and may explain the gingival zenith position in the anterior maxilla. These specific buccal and palatal anatomic parameters should be carefully taken into consideration for surgical planning and intervention in the esthetic area.

Avoiding the lockdown: Morphological facilitation of transversal chewing movements in mammals.

The evolution of mammals is characterized, amongst other developments, by an increasing relevance of effective food processing in form of an increasingly durable dentition, complex occlusal surfaces, and transverse chewing movements. Some factors have received increasing attention for the facilitation of the latter, such as the configuration of the jaw joint, the chewing muscle arrangement and lever arms, or the reduction of interlocking cusps on the cheek teeth occlusal surface. By contrast, the constraining effect of the anterior dentition (incisors and canines) on transverse chewing motions, though known, has received less comprehensive attention. Here, we give examples of this constraint in extant mammals and outline a variety of morphological solutions to this constraint, including a reduction of the anterior dentition, special arrangements of canines and incisors, the nesting of the mandibular cheek teeth within the maxillary ones, and the use of different jaw positions for different dental functions (cropping vs. grinding). We suggest that hypselodont anterior canines or incisors in some taxa might represent a compensatory mechanism for self-induced wear during a grinding chewing motion. We propose that the diversity in anterior dentition among mammalian herbivores, and the evolutionary trend towards a reduction of the anterior dentition in many taxa, indicates that the constraining effect of the anterior dentition, which is rigidly linked to the cheek teeth by the osseous jaws, represents a relevant selective pressure in mammalian evolution.

Maxillary lateral incisor agenesis is associated with maxillary form: a geometric morphometric analysis.

BACKGROUND AND OBJECTIVE: Agenesis of the maxillary lateral incisor occurs in up to 4% of all individuals and requires multidisciplinary treatment. Its developmental origins, however, are not fully understood. Earlier studies documented genetic factors contributing to agenesis but also an association with craniofacial morphology. In this study, we assessed the association between maxillary morphology and lateral incisor agenesis by a geometric morphometric approach to disentangle the roles of developmental plasticity and genetic factors. MATERIALS AND METHODS: We quantified the maxillary alveolar ridge by 19 two-dimensional landmarks on cross-sectional images of 101 computed tomography scans. We compared the shape and size of the alveolar ridge across patients with unilateral or bilateral agenesis of maxillary lateral incisors and patients with extracted or in situ incisors. RESULTS: The maxillary alveolar ridge was clearly narrower in patients with agenesis or an extracted incisor compared to the control group, whereas the contralateral side of the unilateral agenesis had an intermediate width. Despite massive individual variation, the ventral curvature of the alveolar ridge was, on average, more pronounced in the bilateral agenesis group compared to unilateral agenesis and tooth extraction. CONCLUSIONS: This suggests that pleiotropic genetic and epigenetic factors influence both tooth development and cranial growth, but an inappropriately sized or shaped alveolar process may also inhibit normal formation or development of the tooth bud, thus leading to dental agenesis. CLINICAL RELEVANCE: Our results indicate that bilateral agenesis of the lateral incisor tends to be associated with a higher need of bone augmentation prior to implant placement than unilateral agenesis.

Effect of smile esthetics on the quality of life in a Han Chinese population.

OBJECTIVE: This study aimed to explore the influence of smile esthetics on the quality of life in a Han Chinese population. METHODS: A total of 110 Han Chinese volunteers (52 males and 58 females, mean age 26.7 years) were recruited, and frontal images of their smiles were collected. A photoediting program was used to evaluate the following components of smile esthetics: the buccal corridor ratios, the angle between the interpupillary and commissural lines, the number of visible teeth, and width-to-length ratios of the maxillary central incisors. Oral health-related quality of life (OHRQoL) in these volunteers was evaluated using the Psychosocial Impact of Dental Aesthetics Questionnaire (PIDAQ) and Oral Health Impact Profile-14 (OHIP-14). Statistical analyses were performed by using Pearson's correlations and multiple linear regression (α = 0.05). RESULTS: Compared to males, females scored higher on psychological impact (p = 0.017). Moreover, the number of visible teeth had a significant effect on social impact, psychological impact and esthetic concern (all p < 0.05). However, the buccal corridor ratios, the angle between the interpupillary and commissural lines, and the width-to-length ratios of the maxillary central incisor did not correlate with the OHRQoL (all p > 0.05). CONCLUSIONS: The number of visible teeth significantly influenced the quality of life in a Han Chinese population. Smile esthetics had a significantly greater psychological impact on females than males. CLINICAL SIGNIFICANCE: This study highlights the effects of smile esthetics on the quality of life in a Han Chinese population. Female patients may raise more esthetic concerns in clinical practice.

Influence of mandibular incisor agenesis and growth pattern on symphysis characteristics: A retrospective cephalometric study.

OBJECTIVE: This study was performed to investigate the effects of mandibular incisor (MnI) agenesis and divergent malocclusion type on mandibular symphysis inclination and morphology. METHODS: A total of 162 selected patients were divided into two groups: one group consisted of patients with one or two congenitally missing MnIs, and another group comprised patients without tooth agenesis. Patients in each group were categorized into three divergent malocclusion groups (hypodivergent, normodivergent and hyperdivergent) according to the Frankfort mandibular plane angle, with 27 patients per group. Lateral cephalograms were used to evaluate mandibular symphysis inclination and morphology. Two-way analysis of variance, simple main effect analysis and Tukey's test were used for statistical comparisons. RESULTS: The agenesis group demonstrated a significantly greater retroclination of the mandibular symphysis than the non-agenesis group in the normodivergent group. In the hypodivergent and normodivergent groups, the agenesis group showed a significantly smaller area of the alveolar bone with thinner width and shorter height than the non-agenesis group. CONCLUSION: For the Japanese orthodontic patients, MnI agenesis caused a significantly great retroclination of the mandibular symphysis in patients with normodivergent malocclusion and significantly small area of the alveolar bone with thin width and short height in patients with hypo- and normodivergent malocclusions.

Genetic, Epigenetic and Environmental Factors Influence the Phenotype of Tooth Number, Size and Shape: Anterior Maxillary Supernumeraries and the Morphology of Mandibular Incisors.

The aim of this study is to investigate whether the genetic, epigenetic and environmental factors that give rise to supernumeraries in the maxillary incisor region and larger dimensions of the adjacent maxillary incisors are also associated with variations in the morphology of the mandibular incisors. If so, this would contribute to understanding the distribution and interactions of factors during dental development and how these can be modelled. The sample consisted of 34 patients with supernumerary teeth in the maxillary anterior region, matched for gender, age and White Caucasian ethnicity with 34 control subjects. The average ages of the supernumerary and control groups were 12.8 and 12.2 years, respectively. Study models of all subjects were constructed and imaged using a previously validated system. Using custom software, each of the mandibular incisor teeth were measured to obtain 17 parameters from the labial view and 17 from the occlusal view. Principal component analysis (PCA) was used to summarize the measurements into a smaller set representing distinct features of the clinical crowns, followed by a comparison between the supernumerary and control groups using 2-way ANOVA. Seven factors of tooth size of the mandibular central incisors and six factors of the mandibular lateral incisors were identified as major features of the clinical crowns. All parameters of both mandibular incisors were greater in the supernumerary group than in the control, with three of these, located in the incisal and cervical regions of the mandibular lateral incisors, being statistically significantly larger. The findings of this study indicate that the aetiological factors associated with supernumerary teeth in the maxillary anterior region also affect tooth crown dimensions of mandibular incisors. This new evidence enhances several models of the interactions of genetic, epigenetic and environmental components of dental development and supports a multi-model approach to increase understanding of this process and its variations.

El canal incisivo: ¿maxilar o mandibular? Revisión narrativa / The incisive canal: a maxillary or mandibular structure? Narrative review

El canal incisivo es una estructura anatómica ósea que, según la terminología anatómica actual, se encuentra ubicada exclusivamente en la premaxila. Sin embargo, a continuación de los canales mandibulares, se desprenden hacia lateral los canales mentonianos (que contiene el paquete vasculonervioso del mismo nombre) y hacia anterior continua un paquete vasculonervioso, también denominado incisivo que inerva e irriga a dichos dientes mandibulares. Con el fin de aclarar lo previamente mencionado y distinguir ambas estructuras incisivas, se pretende agregar un sufijo (maxilar o mandibular) rectificando los nombres de dichos canales. Para lo anterior, se realizó una revisión de la bibliografía disponible en PubMed y Google Académico, con las palabras clave "CANAL INCISIVO" e "INCISIVE CANAL", utilizando como operador booleano la palabra OR. Los criterios de inclusión de los estudios fueron: 1) que se refieran a algún canal incisivo (ya sea maxilar o mandibular) 2) que estén disponibles para ser leídos a texto completo y 3) que su idioma sea inglés o español. De la totalidad de los artículos analizados, un 52 % hablaba exclusivamente del canal incisivo maxilar, un 43 % solo del canal incisivo mandibular y un 5 % sobre ambos. Concluyendo, podemos colegir que es de suma importancia que se regularice la nomenclatura de dichas estructuras anatómicas, debido a que, el hecho de reconocerla como tal permite garantizar su estudio y aporte desde toda la comunidad científica, sin importar la procedencia ni el idioma. Además, el canal incisivo mandibular está bien documentado, por lo que, al no ser reconocido en la terminología anatómica, se pierde la principal misión de la asociación internacional de asociaciones de anatomía (IFAA), la cual es unificar y organizar los nombres de las estructuras anatómicas existentes.

SUMMARY: The incisive canal is an anatomical bone structure that, according to current anatomical terminology, is located exclusively in the premaxilla. However, following the mandibular canals, the mental canals (containing the neurovascular bundle of the same name) branch off laterally and a neurovascular bundle continues anteriorly, also called the incisor, which innervates and irrigates said mandibular teeth. In order to clarify what was previously mentioned and to distinguish both incisive structures, it is intended to add a suffix (maxillary or mandibular) correcting the names of said canals. For the above, a review of the literature available in PubMed and Google Scholar was carried out, with the keywords "INCISIVE CANAL" and "INCISIVE CANAL", using the word OR as a boolean operator. The inclusion criteria of the studies were: 1) that they refer to an incisive canal (whether maxillary or mandibular) 2) that they be available to be read in full text and 3) that their language be English or Spanish. Of all the articles analyzed, 52% spoke exclusively about the maxillary incisive canal, 43% only about the mandibular incisive canal, and 5% about both. In conclusion, we can infer that it is of the utmost importance that the nomenclature of these anatomical structures be regularized, because the fact of recognizing it as such allows guaranteeing its study and contribution from the entire scientific community, regardless of origin or language. In addition, the mandibular incisive canal is well documented, therefore, by not being recognized in anatomical terminology, the main mission of the international association of anatomy associations (IFAA) is lost, which is to unify and organize the names of the anatomy. existing anatomical structures.

A simple method for quick evaluation of the anterior tooth ratio: an observational study.

BACKGROUND: An ideal relationship of anterior teeth is closely related to postoperative function, stability, and aesthetics. Therefore, it is necessary to estimate the proportion of anterior teeth when communicating with patients about possible treatment plans and outcomes. This study aimed to establish a simple method for assessing the proportion of anterior teeth and to identify the standard ratio value to provide references for clinical work. METHODS: Five hundred fourteen patients were divided into derivation, standard, and validation datasets. We first deduced our novel simplified anterior tooth ratio (SATR) by finding the key teeth with the derivation datasets, then established standard values by measuring the standard models, and finally validated the diagnostic performance of SATR. Independent sample t-test was used to select key teeth. Pearson's correlation analysis and linear regression analysis was used to test and verify the correlation between SATR and the anterior Bolton ratio. Chi-square test and diagnostic test were used to verify the diagnostic results using SATR. P values of < 0.05 were considered statistically significant. RESULTS: Patients with an abnormal anterior Bolton ratio were more likely to have variations in the maxillary and mandibular lateral incisors. Therefore, the ratio of maxillary and mandibular lateral incisors was chosen as a simple way to assess the anterior tooth ratio and was defined as SATR (simplified anterior tooth ratio). A positive correlation was observed between SATR and anterior Bolton ratio (r = 0.702, p < 0.001), with the linear regression equation as follows: y = 0.503 + 0.328x, x = SATR, y = anterior Bolton ratio. The standard value of SATR was established (85.69% ± 3.57%) and proven reliable in clinical practice. CONCLUSIONS: The ratio of maxillary and mandibular lateral incisors can be used to estimate the anterior tooth ratio, which showed high reliability and efficiency.

Radiographic assessment of root canal morphology of mandibular central incisors using new classification system: A cross-sectional study.

Lack of basic knowledge about the external and internal anatomies of the root canal system and common variations in teeth may lead to various procedural errors or treatment failure. In this study, the root canal configurations of mandibular incisors and the symmetry of the contralateral incisors of Saudi Arabian subpopulations were analyzed and determined using cone beam computed tomography (CBCT). A retrospective evaluation of 700 patients was conducted, and 1260 fully developed permanent mandibular central incisors were assessed. The number of root canals was determined, and the internal root canal anatomies were categorized based on Ahmed et al.'s criteria. The CBCT images were independently evaluated by 2 trained dentists and an endodontist. The data were assessed using the chi-square and one-way analysis of variance tests. All the mandibular central incisors included in the study were single-rooted. According to Ahmed et al's classification system, the most common classification (82.6%) was 1ManA1 (Vertucci type I), followed by 1ManA1-2-1 (Vertucci type III; 13%). Second canals were more frequently recorded in the male participants than in the female participants. The root canal configuration between contralateral incisors was largely symmetrical. Most of the mandibular incisors in the examined Saudi Arabian population had a single canal. Nevertheless, a substantial number of patients had a complex root morphology. Hence, CBCT can be utilized as a potential supplementary tool during root canal treatment.