Control radiográfico de trasplante dentario: reporte de caso / Radiographic control of dental transplantation: a case report

El trasplante dentario es una opción terapéutica para reemplazar un órgano dental perdido, causado por un proceso carioso extenso, agenesia, trauma-tismos o iatrogenias. Este procedimiento quirúrgico traslada un órgano dental íntegro desde un alveolo donante hacia su lecho receptor; para lo cual debe poseer ciertas características que permitan tener un pronóstico favorable a largo plazo. El presente estudio describe la evolución de un trasplante dental autólogo realizado hace 14 años a una paciente que acudió a la consulta para valoración del órgano den-tal 4.7, el que presentó un pronóstico desfavorable, por lo cual se realizó exodoncia y trasplante inme-diato del diente vital 4.8 al alveolo del órgano dental 4.7. Tras la planificación quirúrgica se procedió con la intervención conservando la vitalidad pulpar del diente a ser trasplantado, se realizó control clínico y radiográfico a los 15 días, 30 días, 6 meses, 1 año, 5 años y 14 años, en el que se observó conservación del paquete vasculonervioso y ligamento periodontal del órgano dental; a su vez se pudo evidenciar rizo-génesis en el diente trasplantado y un aumento de la altura del proceso alveolar, mediante mediciones realizadas en Auto CAD 2023 (AU)

Tooth transplantation is a therapeutic option to re-place a lost dental organ, caused by an extensive carious process, agenesis, trauma or iatrogenesis. This surgical procedure transfers a complete den-tal organ from a donor alveolus to its recipient bed; for which it must have certain characteristics that allow it to have a favorable long-term prognosis. The present study describes the evolution of an autolo-gous dental transplant carried out 14 years ago to a female patient who attended the consultation for evaluation of the dental organ 4.7, the same one that presented an unfavorable prognosis, for which an extraction and immediate transplantation of the 4.8 vital tooth was performed to the alveolus of the den-tal organ 4.7. After surgical planning, the intervention was carried out preserving the pulpal vitality of the tooth to be transplanted; clinical and radiographic control was performed at 15 days, 30 days, 6 months, 1 year, 5 years and 14 years, in which preservation of the vascular-nervous bundle and periodontal liga-ment of the dental organ was observed; in turn, rhizo-genesis in the transplanted tooth and an increase in the height of the alveolar process could be evidenced, through measurements made in Auto CAD 2023 (AU)

Envejecimiento dental prematuro en deportistas / Premature dental aging in athletes

El desgaste natural de los dientes ocurre dependiendo de factores como: calidad de la estructura dental, calidad de la saliva, biotipo facial que determina la fuerza de mordida; de acuerdo a estos factores locales bucales se va envejeciendo la dentadura. Pero los deportistas presentan un patrón de desgaste mayor y continuo debido al tipo de deporte que practican, las horas de entrenamiento, el consumo de bebidas con pH ácido, el cepillado dental vigoroso; todos estos factores pueden conducirlos a que desarrollen lesiones no cariosas (AU)

The natural wear of the teeth occurs depending on factors such as: quality of the dental structure, quality of the saliva, facial biotype that determines the bite force, according to these local oral factors, the teeth age. But in athletes they present a pattern of greater and continuous wear due to the type of sport they practice, the hours of training, the consumption of drinks with an acidic pH, vigorous tooth brushing; all these factors can lead them to develop non-carious lesions (AU)

Comportamiento Mecánico de un Premolar Humano Sano Sometido a Fuerzas Funcionales y Disfuncionales en un MEF / Mechanical Behavior of a Healthy Human Premolar Subjected to Functional and Dysfunctional Forces in a FEM

El propósito de este estudio fue analizar el comportamiento mecánico de la estructura dental sana de un primer premolar inferior humano sometido a fuerzas funcionales y disfuncionales en diferentes direcciones. Se buscó comprender, bajo las variables contempladas, las zonas de concentración de esfuerzos que conllevan al daño estructural de sus constituyentes y tejidos adyacentes. Se realizó el modelo 3D de la reconstrucción de un archivo TAC de un primer premolar inferior, que incluyó esmalte, dentina, ligamento periodontal y hueso alveolar considerando tres variables: dirección, magnitud y área de la fuerza aplicada. La dirección fue dirigida en tres vectores (vertical, tangencial y horizontal) bajo cuatro magnitudes, una funcional de 35 N y tres disfuncionales de 170, 310 y 445 N, aplicadas sobre un área de la cara oclusal y/o vestibular del premolar que involucró tres contactos estabilizadores (A, B y C) y dos paradores de cierre. Los resultados obtenidos explican el fenómeno de combinar tres vectores, cuatro magnitudes y un área de aplicación de la fuerza, donde los valores de esfuerzo efectivo equivalente Von Mises muestran valores máximos a partir de los 60 MPa. Los valores de tensión máximos se localizan, bajo la carga horizontal a 170 N y en el proceso masticatorio en la zona cervical, cuando la fuerza pasa del 60 %. Sobre la base de los hallazgos de este estudio, se puede concluir que la reacción de los tejidos a fuerzas funcionales y disfuncionales varía de acuerdo con la magnitud, dirección y área de aplicación de la fuerza. Los valores de tensión resultan ser más altos bajo la aplicación de fuerzas disfuncionales tanto en magnitud como en dirección, produciendo esfuerzos tensiles significativos para la estructura dental y periodontal cervical, mientras que, bajo las cargas funcionales aplicadas en cualquier dirección, no se generan esfuerzos lesivos. Esto supone el reconocimiento del poder de detrimento estructural del diente y periodonto frente al bruxismo céntrico y excéntrico.

SUMMARY: The purpose of this study was to analyze the mechanical behavior of the healthy dental structure of a human mandibular first premolar subjected to functional and dysfunctional forces in different directions. It was sought to understand, under the contemplated variables, the areas of stress concentration that lead to structural damage of its constituents and adjacent tissues. The 3D model of the reconstruction of a CT file of a lower first premolar was made, which included enamel, dentin, periodontal ligament and alveolar bone considering three variables: direction, magnitude and area of the applied force. The direction was directed in three vectors (vertical, tangential and horizontal) under four magnitudes, one functional of 35 N and three dysfunctional of 170, 310 and 445 N, applied to an area of the occlusal and/or buccal face of the premolar that involved three stabilizing contacts (A, B and C) and two closing stops. The results obtained explain the phenomenon of combining three vectors, four magnitudes and an area of force application, where the values of effective equivalent Von Mises stress show maximum values from 60 MPa. The maximum tension values are located under the horizontal load at 170 N and in the masticatory process in the cervical area, when the force exceeds 60%. Based on the findings of this study, it can be concluded that the reaction of tissues to functional and dysfunctional forces varies according to the magnitude, direction, and area of application of the force. The stress values turn out to be higher under the application of dysfunctional forces both in magnitude and in direction, producing significant tensile stresses for the dental and cervical periodontal structure, while under functional loads applied in any direction, no damaging stresses are generated. This supposes the recognition of the power of structural detriment of the tooth and periodontium against centric and eccentric bruxism.

Autotransplante dentário: da previsibilidade à técnica cirúrgica e resultados do tratamento / Dental Autotransplantation: from predictability to surgical technique and treatment results

Objetivo: apresentar o relato de duas pacientes com agenesias dentárias em que cinco dentes autotransplantados foram utilizados como modalidade de tratamento. Além disso, objetiva-se mostrar questões sobre a técnica cirúrgica, suas indicações e previsibilidade. Relato de caso: Neste estudo, foram relatados 5 casos de autotransplante dentário em duas pacientes jovens, em que a equipe realizou os procedimentos e o acompanhamento clínico e radiográfico por 5 e 7 anos. Devido à alta sensibilidade da técnica, foram seguidos princípios previamente estabelecidos na literatura envolvendo o autotransplante dentário. Durante o período de acompanhamento, os dentes se mantiveram em posição e em função e as pacientes não apresentavam queixas associadas. Considerações finais: a técnica do autotransplante dentário, quando bem indicada e executada, é capaz de promover resultados bastante satisfatórios, sendo uma ótima alternativa reabilitadora, com taxas de sucesso elevadas e custos reduzidos. No entanto, critérios em relação aos sítios doadores e receptores e a habilidade do cirurgião devem ser levados em conta para o sucesso do técnica.

Objective: presenting the report of two patients with tooth agenesis in which five autotransplanted teeth were used as a treatment modality. Furthermore, the aim is to show questions about the surgical technique and its indications and predictability. Case report: In this study, 5 cases of dental autotransplantation were reported in two young patients, in which the team performed procedures and had clinical and radiographic follow-up for 5 and 7 years. Due to the high sensitivity of the technique, principles previously established in the literature involving dental autotransplantation were followed. During the follow-up period, the teeth remained in position and function and the patients had no associated complaints. Final considerations: the dental autotransplantation technique, when well indicated and executed, is capable of achieving very satisfactory results, being a great rehabilitative alternative, with high success rates and reduced costs. However, criteria regarding donor and receptor sites and the surgeon's skill must be taken into account for the success of the technique.

Histological Techniques for the Study of the Dentogingival Junction: A Scoping Review Using the Anatomical Quality Assurance Checklist (AQUA) / Técnicas Histológicas para el Estudio de la Unión Dentogingival: Una Revisión de Alcance Utilizando el Anatomical Quality Assurance Checklist (AQUA)

SUMMARY: The dentogingival junction (DGJ) is an adaptation of the oral mucosa composed of epithelial and connective tissues intimately related with the mineralised tissues of the tooth. The histological evidence available is mainly based on studies in animals, separate evaluations of hard and soft tissues, and studies using conventional histological techniques that eliminate the enamel from preparations. The aim of this study was to carry out a review of the existing evidence on histological techniques available for study of the tooth and periodontium in conjunction in humans. A scoping review was carried out of the available literature referring to study of the tooth and the periodontium in conjunction in humans, in the Web of Science (WoS), EMBASE, Scopus and SciELO databases, using the terms "Histological Techniques"[Mesh]) and "Epithelial Attachment"[Mesh]. One hundred and fifty-nine articles were found, of which 54 were selected for full- text reading. Ten were finally included in the qualitative synthesis, and we applied the Anatomical Quality Assurance (AQUA) checklist for analysis the methodological quality of the selected articles. The results showed that the only articles with a low risk of bias in all five domains according to the AQUA criteria corresponded to Silva et al. (2011) and Agustín-Panadero et al. (2020). Finally, we conclude that the quality of the histological sections to observe tissues that simultaneously contain the tooth and the periodontium, is conditioned by the selected technique and by the care required in certain specific tasks during the histological processing of the samples.

La unión dentogingival (DGJ) es una adaptación de la mucosa oral compuesta por tejidos epitelial y conectivo íntimamente relacionados con los tejidos mineralizados del diente. La evidencia histológica disponible se basa principalmente en estudios en animales, evaluaciones separadas de tejidos duros y blandos y estudios utilizando técnicas histológicas convencionales que eliminan el esmalte de las preparaciones. El objetivo de este estudio fue realizar una revisión de la evidencia existente sobre las técnicas histológicas disponibles para el estudio del diente y el periodonto en conjunto en humanos. Se realizó un scoping review de la literatura disponible referente al estudio del diente y el periodonto en conjunto en humanos, en las bases de datos Web of Science (WoS), EMBASE, Scopus y SciELO, utilizando los términos "Histological Techniques"[Mesh]) y "Epithelial Attachment"[Mesh]. Se encontraron 159 artículos, de los cuales 54 fueron seleccionados para lectura de texto completo. Diez fueron finalmente incluidos en la síntesis cualitativa, y se aplicó la lista de verificación Anatómica Quality Assurance (AQUA) para el análisis de la calidad metodológica de los artículos seleccionados. Los resultados mostraron que los únicos artículos con bajo riesgo de sesgo en los cinco dominios según los criterios AQUA correspondían a Silva et al. (2011) y Agustín-Panadero et al. (2020). Finalmente, concluimos que la calidad de los cortes histológicos para observar los tejidos que contienen simultáneamente el diente y el periodonto, está condicionada por la técnica seleccionada y por el cuidado requerido en ciertas tareas específicas durante el procesamiento histológico de las muestras.

Uso de Hidróxido de Sodio como Alternativa en Técnica de Diafanización de Diente / Use of Sodium Hydroxide as an Alternative in Tooth Clearing Technique

Con el objetivo de conservar material cadavérico, se han creado diferentes técnicas y/o soluciones donde una técnica es la diafanización dental para estudiar la morfología interna del diente. Esta técnica consta en trasparentar el tejido calcificado del diente haciendo visible los conductos radiculares al inyectar una mezcla colorante en ellos. Se han descrito diferentes variantes de la técnica de diafanización como la técnica de Okumura y la técnica de Robertson, pero ambas técnicas utilizan reactivos tóxicos o de difícil acceso, por lo que se ha realizado una búsqueda de reactivos de bajo costo y fácil acceso para realizar la técnica de diafanización, reportándose que la técnica de diafanización por maceración con KOH es válida para diafanizar dientes. El objetivo del presente estudio fue utilizar NaOH en la técnica de diafanización dental por maceración, como una variante de KOH al ser una base de similar característica que el KOH. Se utilizaron 13 dientes (siete tercer molares, cinco premolares y un canino) para realizar tres variantes de la técnica de diafanización: técnica de Robertson, por maceración con KOH y por maceración con NaOH utilizando barra agitadora y agitador magnético en los dientes. Con la técnica de Robertson se obtuvo un diente completamente transparentado, mientras que los dientes diafanizados por maceración, tanto con KOH y NaOH, se transparentaron menos, aunque se hicieron visibles los conductos radiculares, por lo que el uso de NaOH en la técnica de diafanización por maceración es válida, aunque requiere más tiempo que la maceración por KOH.

SUMMARY: To preserve cadaveric material, different techniques, and solutions have been created where one technique is dental diaphanization to study the internal morphology of the tooth. This technique consists of making the calcified tooth tissue transparent and making the root canals visible by injecting a dye mixture into them. Different variants of the diaphanization technique have been described, such as the Okumura and the Robertson techniques. However, both techniques use toxic or difficult-to-access reagents, so a search has been made for low- cost and easily accessible reagents to perform the diaphanization technique, reporting that the diaphanization technique by maceration with KOH is valid for the diaphanization of teeth. This study aimed to use NaOH in the dental clearing technique by maceration as a variant of KOH since it is a base with similar characteristics to KOH. Thirteen teeth (seven third molars, five premolars, and one canine) were used to perform three variants of the diaphanization technique: Robertson technique, KOH maceration, and NaOH maceration using a stirring bar and magnetic stirrer on the teeth. With the Robertson technique, a completely transparent tooth was obtained, while the teeth cleared by maceration, with both KOH and NaOH, were less transparent, although the root canals became visible. Therefore, using NaOH in the diaphanization technique by maceration is valid, although it requires more time than KOH maceration.

Tiempo empleado para estimar edad dental en niños peruanos comparando el método de Demirjian y el cuadro integral del enfoque de Demirjian: un estudio piloto / Time spent to estimate dental age in peruvian children comparing the demirjian method and the comprehensive chart based on demirjian method: a pilot study

El objetivo de este estudio fue comparar el tiempo empleado al estimar la edad dental (ED) entre el método propuesto por Demirjian et al. y el cuadro integral del enfoque de Demirjian (DAEcc) utilizando radiografías panorámicas digitales de individuos peruanos de 5 a 13 años residentes en Lima. Se realizó un estudio no experimental, comparativo, transversal y retrospectivo. Se utilizaron 100 radiografías panorámicas digitales que presentaban siete dientes permanentes mandibulares izquierdos. Una odontóloga forense capacitada y calibrada determinó el tiempo utilizado en evaluar la maduración dental y la estimación de ED con dos métodos (Demirjian y DAEcc). La unidad de medida utilizada fue los minutos (min.). No hubo diferencias en el tiempo de evaluación del estadio de maduración dental entre ambos métodos (p<0,05). El tiempo para estimar ED fue estadísticamente inferior con DAEcc (2,09 min) que con Demirjian (4,19 min). La diferencia del tiempo total de evaluación resultó estadísticamente significativa entre ambos métodos (Δ2,1 min.; 2,05-2,11; p=0,000). La aplicación del DAEcc redujo en 50 % el tiempo empleado en estimar ED en comparación con los cuadros propuestos por Demirjian. Aunque la odontología forense se centra en el estudio de la eficacia de estimación de la edad, es necesario abordar también su uso práctico.

SUMMARY: The objective of this study was to compare the time used to estimate dental age (DA) between the method proposed by Demirjian et al., and the comprehensive chart for dental age estimation (DAEcc) using digital panoramic radiographs of Peruvian individuals aged 5 to 13 years residing in Lima. A non- experimental, comparative, cross-sectional and retrospective study was carried out. 100 digital panoramic radiographs showing seven mandibular left permanent teeth were used. A trained and calibrated forensic odontologist determined the time used to assess tooth maturation and DA estimation with two methods (Demirjian and DAEcc). The unit of measurement used was minutes (min.). There were no differences in the evaluation time of the dental maturation stage between both methods (p<0.05). The time spent to estimate DA was statistically less with DAEcc (2.09 min) than with Demirjian (4.19 min). The difference in total evaluation time was statistically significant between both methods (Δ2.1 min; 2.05-2.11; p=0.000).The application of DAEcc reduced by 50 % the time spent estimating DA compared to the method proposed by Demirjian. Although forensic odontology focuses on the study of the effectiveness of age estimation, its practical use needs to be addressed as well.

Rehabilitación del sector anterior con disilicato de litio. Relato de un caso / Rehabilitation of the previous sector with lithium disilicate. Case report

Mediante este caso se describen los criterios de selección del color en restauraciones indirectas con disilicato de litio en el sector anterior. Mujer de 34 años, atendida en la Facultad de Odontología de la Universidad Nacional de Concepción (FOUNC), Paraguay, por una preocupación estética del sector anterior, en especial la diferencia de color de las piezas dentarias. La rehabilitación consistió en la confección de coronas de disilicato de litio de las piezas 11, 12, 13, 14, 21, 22, 24, 25 y laminado para carillas de la pieza 23. Fueron aplicadas técnicas de selección de color individualizadas, pruebas de color y cementación antes del cementado final para obtener resultados altamente estéticos. Gracias a los resultados fue posible observar la conjunción de factores como la correcta selección del color del sustrato dentario, el cemento resinoso, el material de restauración y la comunicación eficiente con el laboratorio, fundamental para el éxito del tratamiento.

This case describes the color selection criteria for indirect lithium disilicate restorations in the anterior sector. A 34-year-old woman treated at the Faculty of Dentistry of the National University of Concepción (FOUNC), Paraguay, due to an aesthetic concern in the anterior sector, especially the difference in color of the teeth. The rehabilitation consisted of making lithium disilicate crowns for teeth 11, 12, 13, 14, 21, 22, 24, 25 and laminate for veneers for tooth 23. Individualized color selection techniques, color and cementation prior to final cementation for highly esthetic results. Thanks to the results, it was possible to observe the conjunction of factors such as the correct selection of the color of the dental substrate, the resinous cement, the restorative material, and efficient communication with the laboratory, essential for the success of the treatment.

Process of Forensic Medicine in DNA Identification of Aged Human Remains / 法医学杂志

Skeleton and teeth are important biological samples. Due to their special structure and strong ability to resist degradation, they are ideal biological materials to retain DNA under natural condition. In many cases, such as historical figure identification, aged skeleton and teeth are usually the only biological samples. However, their DNA is in a state of trace, damage and degradation to different degrees, which requires special experimental treatment to achieve identification. This paper reviews the sample selection, DNA extraction, DNA enrichment and analysis approaches based on relevant research reports in recent years, aiming to promote the further development and improvement of the aged skeleton and teeth identification system.

Study on quantitative analysis of bracket-induced nonlinear response of labio-cheek soft tissue during the orthodontic process / 生物医学工程学杂志

In the orthodontics process, intervention and sliding of an orthodontic bracket during the orthodontic process can arise large response of the labio-cheek soft tissue. Soft tissue damage and ulcers frequently happen at the early stage of orthodontic treatment. In the field of orthodontic medicine, qualitative analysis is always carried out through statistics of clinical cases, while quantitative explanation of bio-mechanical mechanism is lacking. For this purpose, finite element analysis of a three-dimensional labio-cheek-bracket-tooth model is conducted to quantify the bracket-induced mechanical response of the labio-cheek soft tissue, which involves complex coupling of contact nonlinearity, material nonlinearity and geometric nonlinearity. Firstly, based on the biological composition characteristics of labio-cheek, a second-order Ogden model is optimally selected to describe the adipose-like material of the labio-cheek soft tissue. Secondly, according to the characteristics of oral activity, a two-stage simulation model of bracket intervention and orthogonal sliding is established, and the key contact parameters are optimally set. Finally, the two-level analysis method of overall model and submodel is used to achieve efficient solution of high-precision strains in submodels based on the displacement boundary obtained from the overall model calculation. Calculation results with four typical tooth morphologies during orthodontic treatment show that: ① the maximum strain of soft tissue is distributed along the sharp edges of the bracket, consistent with the clinically observed profile of soft tissue deformation; ② the maximum strain of soft tissue is reduced as the teeth align, consistent with the clinical manifestation of common damage and ulcers at the beginning of orthodontic treatment and reduced patient discomfort at the end of treatment. The method in this paper can provide reference for relevant quantitative analysis studies in the field of orthodontic medical treatment at home and abroad, and further benefit to the product development analysis of new orthodontic devices.

One-year clinical observation of the effect of internal bleaching on pulpless discolored teeth / 华西口腔医学杂志

OBJECTIVES@#This study aimed to observe the color rebound and rebound rates of non-pulp discolored teeth within 1 year after routine internal bleaching to guide clinical practice and prompt prognosis.@*METHODS@#In this work, the efficacy of bleaching was observed in 20 patients. The color of discolored teeth was measured by using a computerized colorimeter before bleaching; immediately after bleaching; and at the 1st, 3rd, 6th, 9th, and 12th months after bleaching. The L*, a*, and b* values of the color of cervical, mesial, and incisal parts of the teeth were obtained, and the color change amounts ΔE*, ΔL*, Δa*, and Δb* were calculated. The overall rebound rate (P*) and the color rebound velocity (V*) were also analyzed over time.@*RESULTS@#In 20 patients following treatment, the average ΔE* of tooth color change was 14.99. After bleaching, the neck and middle of the teeth ΔE* and ΔL* decreased in the 1st, 3rd, 6th, 9th, and 12th months, and the differences were statistically significant. Meanwhile, from the 9th month after bleaching, the rebound speed was lower than that in the 1st month, and the difference was statistically significant. The incisal end of the tooth ΔE* and ΔL* decreased in the 6th, 9th, and 12th months after bleaching, and the differences were statistically significant. No significant difference was found in the rebound speed between time points. However, this rate settled after the 9th month, with an average color rebound rate of 30.11% in 20 patients.@*CONCLUSIONS@#The results indicated that internal bleaching could cause a noticeable color change on pulpless teeth. The color rebound after bleaching was mainly caused by lightness (L*), which gradually decreased with time, and it was slightly related to a* and b*. The color of the teeth after internal bleaching rebounded to a certain extent with time, but the color rebound speed became stable from the 9th month. Clinically, secondary internal bleaching can be considered at this time according to whether the colors of the affected tooth and the adjacent tooth are coordinated and depending on the patient's needs.

Study on mandibular movement trajectory and virtual occlusal pre-adjustment under light and heavy bite force / 中华口腔医学杂志

Objective: To investigate the influence of light and heavy bite force on the mandibular movement trajectories, and the influence of bite force on virtual occlusal pre-adjustment of digital full crown. Methods: From October 2021 to March 2022, 10 postgraduate volunteers (3 males and 7 females, aged 22-26 years) were recruited from Peking University School and Hospital of Stomatology. Maxillary and mandibular digital models of the participants were obtained by intraoral scanning. Jaw relations were digitally transferred under heavy bite force and mandibular movement trajectories under light and heavy bite force were recorded by jaw motion analyser. Three mandibular markers were chosen, namely the mesial proximal contact point of the central incisor (incisal point) and the mesial buccal cusp tips of the bilateral first molars. The three-dimensional displacements of the markers under two kinds of bite force in the intercuspal position (ICP), the sagittal projection of the three-dimensional displacements in the protrusive edge-to-edge position, and the coronal projection of the three-dimensional displacements in the lateral edge-to-edge position of upper and lower posterior teeth were measured. Single-sample t-test was used to compare the three-dimensional displacements and the corresponding sagittal projection and coronal projection with 0, respectively. The left maxillary central incisor and left mandibular first molar were virtually prepared by the reverse engineering software. Then dental design software was used to design digital full crown using the copy method. The mandibular movement trajectories under light and heavy bite force were separately used to guide virtual occlusal pre-adjustment. The three-dimensional deviations (mean deviations and root mean square) between the lingual surface of the left maxillary central incisor or the occlusal surface of the left mandibular first molar and that of the natural tooth before preparation were calculated (light bite force group and heavy bite force group), and the differences between the two groups were compared by the paired t-test. Results: Under the two kinds of bite force, the three-dimensional displacements of the markers in the ICP were (0.217±0.135), (0.210±0.133) and (0.237±0.101) mm, respectively; the sagittal projection of the three-dimensional displacements of the markers in the protrusive edge-to-edge position were (0.204±0.133), (0.288±0.148) and (0.292±0.136) mm, respectively; the coronal projection of the three-dimensional displacements of the mesial buccal cusp tips of the bilateral first molars in the lateral edge-to-edge position were (0.254±0.140) and (0.295±0.190) mm, respectively. The differences between the above displacements and 0 were statistically significant (P<0.05). The results of occlusal pre-adjustment showed that the mean deviations of the lingual surface of the left maxillary central incisor in the light and heavy bite force groups were (0.215±0.036) and (0.195±0.041) mm (t=3.95, P=0.004), respectively. The mean deviations of the occlusal surface of the left mandibular first molar were (0.144±0.084) and (0.100±0.096) mm (t=0.84, P=0.036), respectively. Conclusions: Both the light and heavy bite force have an influence on the mandibular movement trajectories. Virtual occlusal pre-adjustment of prostheses with mandibular movement trajectories under heavy bite force can obtain morphology of lingual or occlusal surfaces closer to the natural teeth before preparation.

Applications of digital medical techniques for dental dysplasia / 中华口腔医学杂志

Dental dysplasia are abnormalities in teeth structure, morphology, number and eruption caused by genetic and environmental factors during dental development. Digital medical techniques, as the current hot spot of medical research, bring great challenges and opportunities to modern stomatology. The applications of digital techniques, such as digital diagnosis method, digital virtual simulated design, three-dimensional printing, static and dynamic guidance and artificial intelligence, can provide a more accurate, efficient, automatic and intelligent modern concepts and patterns for epidemiology, diagnosis, multidisciplinary treatment and outcome assessment of dental developmental anomalies.

mTORC1 signaling pathway regulates tooth repair / 国际口腔科学杂志·英文版

Tooth germ injury can lead to abnormal tooth development and even tooth loss, affecting various aspects of the stomatognathic system including form, function, and appearance. However, the research about tooth germ injury model on cellular and molecule mechanism of tooth germ repair is still very limited. Therefore, it is of great importance for the prevention and treatment of tooth germ injury to study the important mechanism of tooth germ repair by a tooth germ injury model. Here, we constructed a Tg(dlx2b:Dendra2-NTR) transgenic line that labeled tooth germ specifically. Taking advantage of the NTR/Mtz system, the dlx2b+ tooth germ cells were depleted by Mtz effectively. The process of tooth germ repair was evaluated by antibody staining, in situ hybridization, EdU staining and alizarin red staining. The severely injured tooth germ was repaired in several days after Mtz treatment was stopped. In the early stage of tooth germ repair, the expression of phosphorylated 4E-BP1 was increased, indicating that mTORC1 is activated. Inhibition of mTORC1 signaling in vitro or knockdown of mTORC1 signaling in vivo could inhibit the repair of injured tooth germ. Normally, mouse incisors were repaired after damage, but inhibition/promotion of mTORC1 signaling inhibited/promoted this repair progress. Overall, we are the first to construct a stable and repeatable repair model of severe tooth germ injury, and our results reveal that mTORC1 signaling plays a crucial role during tooth germ repair, providing a potential target for clinical treatment of tooth germ injury.

Tooth number abnormality: from bench to bedside / 国际口腔科学杂志·英文版

Tooth number abnormality is one of the most common dental developmental diseases, which includes both tooth agenesis and supernumerary teeth. Tooth development is regulated by numerous developmental signals, such as the well-known Wnt, BMP, FGF, Shh and Eda pathways, which mediate the ongoing complex interactions between epithelium and mesenchyme. Abnormal expression of these crutial signalling during this process may eventually lead to the development of anomalies in tooth number; however, the underlying mechanisms remain elusive. In this review, we summarized the major process of tooth development, the latest progress of mechanism studies and newly reported clinical investigations of tooth number abnormality. In addition, potential treatment approaches for tooth number abnormality based on developmental biology are also discussed. This review not only provides a reference for the diagnosis and treatment of tooth number abnormality in clinical practice but also facilitates the translation of basic research to the clinical application.

A prevalence survey of cone-beam computed tomography use among endodontic practitioners / 北京大学学报(医学版)

OBJECTIVE@#To investigate the clinical application of cone-beam computed tomography (CBCT) among endodontic practitioners, and to analyze the indications and reasonability of CBCT in the diagnosis and treatment of pulpal and periapical diseases.@*METHODS@#The clinical data were collected from patients who visited the Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology and underwent CBCT examination from January to December, 2021. The data with their complete clinical information (including clinical records, radiology request forms/reports, two-dimensional and three-dimensional imaging data) were included. Those who underwent CBCT examination for orthodontic or prosthodontics were excluded. The experience and training background of the endodontic specialists, the number of patients treated in the whole year, the objective and region of interest (ROI) of CBCT examination, technical parameters, such as machine type, field of view (FoV) and radiographic reports were collected and analyzed to evaluate the impact on diagnosis. Wilcoxon and Mann-Whitney tests were used to compare the distribution of CBCT ROI. Chi-squared test and pairwise comparison were used to compare the application of CBCT by endodontic specialists with different clinical experience (senior, middle and junior).@*RESULTS@#In 2021, a total of 3 308 CBCT scans were prescribed by 61 endodontic specialists who treated 34 952 patients throughout the year. 3 218 patients (male ∶female about 1 ∶2) amounting for 10% of the patients treated in the whole year who received CBCT scans with an median age of 35 years (28, 49). Around 98% CBCT examinations were performed after clinical examination and two-dimensional periapical radiographs were taken. The FoV of CBCT scanning less than 10 cm×10 cm accounted for 96% of the total number of the images. Among the 3 308 CBCT scans, 83% of the ROI were in posterior teeth, with a higher number of anterior teeth (Z=-2.278, P < 0.05). Maxillary and mandibular first molars accounted for 35% of the examined teeth. The objectives of CBCT scanning included three aspects: clarifying clinical diagnosis, guiding surgical and non-surgical endodontic treatment (including management of endodontic complications), and outcome assessment, accounting for 1 111 (34%), 1 745 (54%), 311 (10%), respectively. and the others 2%. In the diagnosis process, CBCT was mainly used for the diagnosis of chronic periapical periodontitis, root fracture, root resorption and dental trauma. In the study, 353 CBCT were used in the diagnosis of root fracture, with a positive diagnosis rate of 35% (125/353). 846 CBCT used to reveal the anatomy of the root canal system, of which 297 cases were used to find missed/extra canals after treatment failure, and 58% (171/297) were used to confirm the missed/extra canals. In the management of complications or errors, CBCT was mainly used to assist the diagnosis of perforation and to locate the separated instruments. In the study, 311 CBCT scans were used for outcome assessment, including 240 cases related to non-surgical treatment and 71 cases related to surgical endodontic treatment for follow-up or presence of clinical symptoms, and persistent lesions on 2D films. Among the 61 endodontic specialists who used CBCT, 23 (45%) were with senior experience, 15 (30%) with middle experience, and 23 (25%) with junior experience. The proportion of senior or junior experience prescribing CBCT examination was 10%, higher than that of middle experience (8%, χ12=39.4, χ22=29.1, P < 0.001). The application rate of chief endodontists was 18%, which was higher than that of associate chief endodontists (9%, χ12=139.4, P < 0.001). 31% (1 109/3 308) cases of diagnosis or treatment plans were changed after CBCT was taken.@*CONCLUSION@#Use of CBCT in endodontic practice could provide more clinical information, which is helpful for diagnosis, accurate treatment and prognosis evaluation.

Multivariable analysis of tooth loss in subjects with severe periodontitis over 4-year natural progression / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the characteristics of severe periodontitis with various number of tooth loss during 4-year natural progression, and to analyze the factors related to higher rate of tooth loss.@*METHODS@#A total of 217 patients aged 15 to 44 years with severe periodontitis were included, who participated in a 4-year natural progression research. Data obtained from questionnaire survey, clinical examination and radiographic measurement. Tooth loss during 4-year natural progression was evaluated. The baseline periodontal disease related and caries related factors were calculated, including number of teeth with bone loss > 50%, number of missing molars, number of teeth with widened periodontal ligament space (WPDL), number of teeth with periapical lesions and etc. Characteristics of populations with various number of tooth loss and the related factors that affected higher rate of tooth loss were analyzed.@*RESULTS@#In 4 years of natural progression, 103 teeth were lost, and annual tooth loss per person was 0.12±0.38. Nine patients lost 3 or more teeth. Thirty-four patients lost 1 or 2 teeth, and 174 patients were absent of tooth loss. Molars were mostly frequent to lose, and canines presented a minimum loss. The number of teeth with WPDL, with periapical lesions, with intrabony defects, with probing depth (PD)≥7 mm, with PD≥5 mm, with clinical attachment loss≥5 mm, with bone loss > 50% and with bone loss > 65% were positively correlated to number of tooth loss. Results from orderly multivariate Logistic regression showd that the number of teeth with bone loss > 50% OR=1.550), baseline number of molars lost (OR=1.774), number of teeth with WPDL (1 to 2: OR=1.415; ≥3: OR=13.105), number of teeth with periapical lesions (1 to 2: OR=4.393; ≥3: OR=9.526) and number of teeth with caries/residual roots (OR=3.028) were significant risk factors related to higher likelihood of tooth loss and multiple tooth loss.@*CONCLUSION@#In 4 years of natural progression, the number of teeth with bone loss > 50%, baseline number of missing molars, number of teeth with WPDL, baseline number of teeth with periapical lesions and number of teeth with caries/residual roots were significantly related to higher risk of tooth loss and multiple tooth loss among Chinese young and middle-aged patients with severe periodontitis in rural areas.

Expert consensus on digital guided therapy for endodontic diseases / 国际口腔科学杂志·英文版

Digital guided therapy (DGT) has been advocated as a contemporary computer-aided technique for treating endodontic diseases in recent decades. The concept of DGT for endodontic diseases is categorized into static guided endodontics (SGE), necessitating a meticulously designed template, and dynamic guided endodontics (DGE), which utilizes an optical triangulation tracking system. Based on cone-beam computed tomography (CBCT) images superimposed with or without oral scan (OS) data, a virtual template is crafted through software and subsequently translated into a 3-dimensional (3D) printing for SGE, while the system guides the drilling path with a real-time navigation in DGE. DGT was reported to resolve a series of challenging endodontic cases, including teeth with pulp obliteration, teeth with anatomical abnormalities, teeth requiring retreatment, posterior teeth needing endodontic microsurgery, and tooth autotransplantation. Case reports and basic researches all demonstrate that DGT stand as a precise, time-saving, and minimally invasive approach in contrast to conventional freehand method. This expert consensus mainly introduces the case selection, general workflow, evaluation, and impact factor of DGT, which could provide an alternative working strategy in endodontic treatment.

Sclerostin antibody improves alveolar bone quality in the Hyp mouse model of X-linked hypophosphatemia (XLH) / 国际口腔科学杂志·英文版

X-linked hypophosphatemia (XLH) is a rare disease of elevated fibroblast growth factor 23 (FGF23) production that leads to hypophosphatemia and impaired mineralization of bone and teeth. The clinical manifestations of XLH include a high prevalence of dental abscesses and periodontal disease, likely driven by poorly formed structures of the dentoalveolar complex, including the alveolar bone, cementum, dentin, and periodontal ligament. Our previous studies have demonstrated that sclerostin antibody (Scl-Ab) treatment improves phosphate homeostasis, and increases long bone mass, strength, and mineralization in the Hyp mouse model of XLH. In the current study, we investigated whether Scl-Ab impacts the dentoalveolar structures of Hyp mice. Male and female wild-type and Hyp littermates were injected with 25 mg·kg-1 of vehicle or Scl-Ab twice weekly beginning at 12 weeks of age and euthanized at 20 weeks of age. Scl-Ab increased alveolar bone mass in both male and female mice and alveolar tissue mineral density in the male mice. The positive effects of Scl-Ab were consistent with an increase in the fraction of active (nonphosphorylated) β-catenin, dentin matrix protein 1 (DMP1) and osteopontin stained alveolar osteocytes. Scl-Ab had no effect on the mass and mineralization of dentin, enamel, acellular or cellular cementum. There was a nonsignificant trend toward increased periodontal ligament (PDL) attachment fraction within the Hyp mice. Additional PDL fiber structural parameters were not affected by Scl-Ab. The current study demonstrates that Scl-Ab can improve alveolar bone in adult Hyp mice.

Feasibility analysis of digital method for measuring supracrestal tissue height crest around implant / 华西口腔医学杂志

OBJECTIVES@#This study aimed to investigate the feasibility of measuring the soft tissue height of bone cristae around implant by digital method.@*METHODS@#A total of 36 patients with dental implants were selected from the Dental Medicine Center of the First Affiliated Hospital of University of Science and Technology of China (Anhui Provincial Hospital) from August 2022 to December 2022. A total of 43 dental implants were enrolled. All postoperative cone beam CT (CBCT) imaging data and intraoral digital impressions obtained before surgery were immediately obtained by the patients on the day of completion of oral implant surgery and they were imported into oral implant surgery planning software for image fitting. Then, virtual implants of the same specification were placed in the planting area, and the implant position was adjusted to overlap with the implant shadow in the CBCT image. Supracrestal tissue height (STH) was measured at the implant view interface (digital group). During the operation, implant holes were prepared step by step in accordance with the standard preparation method, and implants were implanted. The upper edge of the implant was flushed with the crest of the alveolar ridge. STH was measured by perio-dontal probing (periodontal probe group). Paired t-test was used to compare the STH differences between the digital and periodontal probe groups. Bland-Altman test was used to analyze the consistency of the two methods. Intra-group correlation coefficient (ICC) was used to verify the reliability of the results measured by different surveyors using di-gital methods.@*RESULTS@#No statistical significance was observed in the STH difference between the two methods (P>0.05). Bland-Altman test showed good consistency between the two methods, but the measurement of mandibular posterior teeth showed that the results of periodontal probe were greater than those of digital method. The ICC and 95%CI of the STH results measured digitally by different surveyors are 0.992 (0.986-0.996).@*CONCLUSIONS@#The digital me-thod is in good agreement with the periodontal probe method in measuring the soft tissue height of the bone cristae around the implant.