Prediction, analysis and application of learning curve of tooth preparation for all ceramic crowns of maxillary central incisors / 北京大学学报(医学版)

OBJECTIVE@#To predict the learning curve of tooth preparation for all ceramic crowns of maxillary central incisors on phantom head simulators for graduate students participating in standardized dental resident training based on the modified Wright learning curve model, then to analyze and applicate the learning curve.@*METHODS@#Twelve graduate students participating in standardized dental resident training were selected to prepare the resin maxillary central incisors on phantom head simulators for all ceramic crowns 4 times. The results of preparation were evaluated by 3 prosthetic experts with at least 10 years' experience focusing on the reduction, contour, taper, shoulder, finish line, margin placement, adjacent tooth injury, and preparation time for tooth preparation. The learning rate of tooth preparation was calculated by scores of tooth preparation of 4 times. The learning curve of tooth preparation was predicted based on the modified Wright learning curve model. According to the criteria of standardized training skill examinations for dental residents in Beijing, 80 was taken as the qualified standard score. The minimum training times for tooth preparation to satisfy the qualified standard score (80) was calculated, to analyze the characteristics of learning curve and evaluate the effectiveness of tooth preparation.@*RESULTS@#The scores of 4 tooth preparation were 64.03±7.80, 71.40±6.13, 74.33±5.96, and 75.98±4.52, respectively. The learning rate was (106±4)%, which showed the learning curve an upward trend. There were no significant differences between the qualified standard score and the predicted scores of tooth preparation from the 5th preparation to the 13th preparation (P > 0.05). The predicted score of the 14th preparation was higher than the qualified standard score (P < 0.05).@*CONCLUSION@#The trend of the learning curve of tooth preparation for all ceramic crowns of maxillary central incisors on phantom head simulators for graduate students participating in standardized dental resident training is upward, which predicts the minimum training times higher than the qualified standard score is 14 times.

Tratamiento ortopédico funcional y mecánico para la corrección de la clase II esqueletal / Functional and mechanical orthopedic treatment for the correction of skeletal class II

Objetivo: Analizar las distintas alternativas de tratamiento basadas en Ortopedia Funcional y Mecánica, su efecto a nivel esqueletal, sus beneficios. Método: Revisión bibliográfica. Resultados: Se seleccionaron 15 artículos de un universo de 45, por cuanto eran los que tenían relación directa con el tema de investigación. Conclusión: Se ha logrado identificar las distintas alternativas de tratamiento con ortopedia funcional o mecánica que se pueden utilizar para el tratamiento de la Clase II esqueletal, corroboradas con resultados que evidencian Su efectividad tanto en los cambios craneofaciales, de tejidos blandos y dentales obtenidos al final de la terapéutica, los autores recomiendan la correcta evaluación de los pacientes, antes de determinar la aparatología a utilizar así cómo aprovechar los estadios tempranos de maduración y crecimiento para que los cambios en el patrón esqueletal sean más representativos, efectivos y alcancen el objetivo de mejorar la relación maxilo-mandibular.

Objective: To analyze the different treatment alternatives based on Functional and Mechanical Orthopedics, their effect at skeletal level, their benefits. Method: Bibliographic review. Results: 15 articles were selected from a universe of 45, as they were those directly related to the research topic. Conclusions: We have been able to identify the different treatment alternatives with functional or mechanical orthopedics that can be used for the treatment of skeletal Class II, corroborated with results that show their effectiveness in craniofacial, soft tissue and dental changes obtained at the end of the therapy, the authors recommend the correct evaluation of the patients before determining the appliances to be used, as well as taking advantage of the early stages of maturation and growth so that the changes in the skeletal pattern are more representative, effective and achieve the objective of improving the maxillomandibular relationship.

Marginal adaptation and mechanical strength of endocrowns with different materials and tooth prepration design: a review / 口腔疾病防治

@#The endocrown, a modified overlay or crown, is considered to have the advantages of adhesive retention and mechanical retention. Marginal adaptation and mechanical strength are common criteria for evaluating endocrowns. This review studied these aspects of endocrowns to guide further clinical application. Results from previous academic studies indicate that endocrowns made of different materials, such as glass-based ceramics, zirconia-based ceramics and resin-based ceramics, exhibit clinically acceptable marginal adaptation. Zirconia is a common dental material, but when used in endocrowns, it tends to present a risk of irreparable tooth root fractures. Compared with products manufactured with zirconia, endocrowns manufactured with resin-based ceramics and glass-based ceramics, such as lithium disilicate ceramics, do not tend to cause irreparable results, such as tooth root fracture, but their mechanical strengths are not as good as those of zirconia. At the same time, the tooth prepration design such as the types of endocrowns, the pulp chamber extension depth and angles, the endocrown thickness can influence the mechanical strength of endocrowns as well. Compared with traditional zirconia, self-glazed zirconia, a new type of material used to restore defective teeth, has the similar elasticity modulus（210 GPa）and better aesthetic advantages, and is suitable for short crown patients with insufficient occlusal space. Further study is warranted to improve the performance of endocrowns made from ceramic materials to prevent root fracture.

Survival of Hybrid Laminate Veneers using two different tooth preparation techniques: Randomized Clinical Trial

Abstract The aim of this study was to evaluate the survival of laminate veneers constructed using a recent polymer-infiltrated ceramic network material following the aesthetic pre-evaluative temporary (APT) technique of tooth preparation in comparison to traditional technique. Six patients received 54 laminate veneers. They were divided into two equal groups (n=27) according to the technique of tooth preparation: group T: traditional technique and group A: aesthetic pre-evaluative temporary technique. VITA ENAMIC material was used for CAD/CAM construction of laminate veneers. Cementation was performed using a light cured resin cement. The laminate veneers were evaluated at baseline, after 3, 6 and 12 months according to the modified United States Public Health Service (USPHS) criteriea. The data was collected, tabulated and statistically analyzed. Secondary caries, endodontic complications, cracks and loss of retention were not noted in any laminate veneer. Extensive fractures were not detected in both study groups through the study period. There was a statistically significant decrease of color match criteria between the two groups at the 6 and 12 months recalls. Based on this study, both preparation techniques resulted in successful clinical performance. After 12 months, all the veneers in both groups showed no post-operative sensitivity and all patients were highly satisfied regarding their veneers. However, there was a deterioration in color match criteria through the study period in both study groups.

Resumo O objetivo deste estudo foi avaliar a sobrevivência de facetas laminadas construídas utilizando um material recente de rede de cerâmica impregnada de polímero, seguindo a técnica estética pré-avaliadora temporária (APT) de preparação de dentes em comparação com a técnica tradicional. Seis pacientes receberam 54 facetas de laminados. Foram divididos em dois grupos iguais (n=27) de acordo com a técnica de preparação do dente: grupo T: técnica tradicional e grupo A: técnica temporária pré-avaliativa estética. O material VITA ENAMIC foi utilizado para a construção de facetas de CAD/CAM de laminados. A cimentação foi realizada utilizando um cimento de resina fotopolimerizável. Os laminados foram avaliados na linha de base, após 3, 6 e 12 meses de acordo com os critérios modificados do Serviço de Saúde Pública dos Estados Unidos (USPHS). Os dados foram recolhidos, tabulados e analisados estatisticamente. Cáries secundárias, complicações endodônticas, fissuras e perda de retenção não foram observadas em nenhuma faceta laminada. Não foram detectadas fraturas extensas em ambos os grupos de estudo durante o período do estudo. Verificou-se uma diminuição estatisticamente significativa dos critérios de correspondência de cor entre os dois grupos nos 6 e 12 meses. Com base neste estudo, ambas as técnicas de preparação resultaram num desempenho clínico bem sucedido. Após 12 meses, todos os laminados de ambos os grupos não mostraram qualquer sensibilidade pós-operatória e todos os pacientes ficaram altamente satisfeitos com os seus laminados. No entanto, houve uma deterioração dos critérios de correspondência de cor durante o período de estudo em ambos os grupos de estudo.

Resistencia a la fractura de coronas dentales fabricadas análogamente vs tecnología cad-cam. Estudio In vitro / Fracture resistance of analogally made dental crowns vs cad-cam technology. In vitro study

Resumen Antecedentes. La resistencia a la fractura de las coronas puede tener influencia en su ocurrencia, de acuerdo con el método de fabricación usado, ya sea análogamente o por medio de tecnología Cad-Cam. Objetivo. Comparar la resistencia a la fractura de las coronas individuales realizadas por dos métodos de fabricación, bajo diseño asistido por ordenador y fabricación computarizada (CAD-CAM) e inyectadas. Método. Estudio in vitro. Tamaño de la muestra 20 coronas en dos grupos: 10 coronas bajo tecnología CAD-CAM y 10 coronas inyectadas. Fueron sometidas a cargas compresivas en una máquina de ensayos universal, con una velocidad de 1mm/min y una carga de celda de 5kN hasta obtener la fractura máxima de estas. Los datos se analizaron estadísticamente utilizando las pruebas Shapiro Wilk, Mann Whitney p=0,05. Resultados. Las coronas fabricadas por Cad-Cam obtuvieron un mínimo de 602,5 Newton y un máximo de 1093 Newton, mientras que las coronas fabricadas análogamente obtuvieron un mínimo de 525,2 Newton y un máximo de 1773 Newton en el experimento con la máquina de ensayo universal para lograr su fractura. Se obtuvo una diferencia significativa en la prueba de resistencia a la factura entre ambos métodos de fabricación (p <0,001). Conclusión. Las coronas de Disilicato de litio Prensadas obtuvieron una mayor resistencia a la fractura que las coronas fabricadas via CAD-CAM.

Abstract Background. The fracture resistance of the crowns may have an influence on their appearance, according to the method of making them, either analogously or by means of Cad-Cam technology. Objective. To compare the resistance to the fracture of the individual crowns made by two manufacturing methods, under computer-aided design and computerized manufacturing (CAD-CAM) and injected. Methods. In vitro study. Sample size 20 crowns in two groups: 10 crowns using CAD-CAM technology and 10 crowns injected. Crowns were subjected to compressive loads in a universal testing machine, with a speed of 1mm / min and a cell load of 5kN until obtaining the maximum bill for these. Data were statistically analyzed using the Shapiro Wilk tests, Mann Whitney p = 0.05. Results. Crowns manufactured by Cad-Cam obtained a minimum of 602.5 Newton and a maximum of 1093 Newton, while the crowns manufactured analogously obtained a minimum of 525.2 Newton and a maximum of 1773 Newton in the experiment with the machine Universal test to achieve their fracture. A significant difference was obtained in the invoice resistance test between both manufacturing methods (p <0.001). Conclusion. Pressed Lithium Disilicate crowns obtained higher fracture resistance than crowns under design and manufacturing by computer (CAD-CAM).

Fracture resistance and strain analysis of zirconia copings with vertical knife edge and three horizontal finish line designs; chamfer, deep chamfer and shoulder with two cementation techniques / Resistência à fratura e análise de deformação de copings de zircônia com término cervical em lâmina de faca e três términos horizontais; chanfro, chanfro largo e ombro com duas técnicas de cimentação

Objective: The purpose of this in vitro study is to evaluate the effect of four finish line configurations and two cement types on the fracture resistance of zirconia copings. Material and Methods: Forty yttrium tetragonal zirconia polycrystals copings were manufactured on epoxy resin dies with four preparation designs: knife edge, chamfer, deep chamfer 0.5, 1 mm and shoulder 1 mm. The copings were cemented with two cement types (glass ionomer and resin cement); (n = 5). Two strain gauges were attached on each coping before they were vertically loaded till fracture with a universal testing machine. Data were analyzed by 2-way analysis of variance ANOVA (p < .05). Fractured specimens were examined for mode of failure with digital microscope. Results: Knife edge showed the highest mean fracture resistance (987.04 ± 94.18) followed by Chamfer (883.28 ± 205.42) followed by Shoulder (828.64 ± 227.79) and finally Deep chamfer finish line (767.66 ± 207.09) with no statistically significant difference. Resin cemented copings had higher mean Fracture resistance (911.76 ± 167.95) than glass ionomer cemented copings (821.55 ± 224.24) with no statistically significant difference. Knife edge had the highest strain mean values on the buccal (374.04 ± 195.43) and lingual (235.80 ± 103.46) surface. Shoulder finish line showed the lowest mean strain values on the buccal (127.47 ± 40.32) and lingual (68.35 ± 80.68) with no statistically significant difference. Resin cemented copings had higher buccal (295.05 ± 167.92) and lingual (197.38 ± 99.85) mean strain values than glass ionomer copings (149.14 ± 60.94) and (90.27 ± 55.62) with no statistically significant difference. Conclusion: Vertical knife edge finish line is a promising alternative and either adhesive or conventional cementation can be used with zirconia copings (AU)

Objetivo: O objetivo deste estudo in vitro é avaliar o efeito de quatro configurações de términos cervicais e dois tipos de cimentos na resistência à fratura de copings de zircônia. Material e Métodos: Quarenta copings de zircônia tetragonal policristalina estabilizada por ítrio foram confeccionados em matrizes de resina epóxi com quatro tipos de términos cervicais: lâmina de faca, chanfro, chanfro largo 0,5, 1 mm e ombro 1 mm. Os copings foram cimentados com dois tipos de cimento (ionômero de vidro e cimento resinoso); (n = 5). Dois extensômetros foram fixados em cada coping antes de serem carregados verticalmente até a fratura com uma máquina de teste universal. Os dados foram analisados por análise de variância ANOVA 2 fatores (p < 0,05). Os espécimes fraturados foram examinados quanto ao modo de falha com microscópio digital. Resultados: A Lâmina de faca apresentou a maior média de resistência à fratura (987,04 ± 94,18) seguida pelo Chanfro (883,28 ± 205,42), pelo Ombro (828,64 ± 227,79) e finalmente o Chanfro largo (767,66 ± 207,09), sem diferença estatisticamente significativa. Os copings cimentados com cimento resinoso apresentaram maior média de resistência à fratura (911,76 ± 167,95) em relação aos copings cimentados com ionômero de vidro (821,55 ± 224,24), sem diferença estatisticamente significativa. A lâmina de faca apresentou os maiores valores médios de deformação na superfície vestibular (374,04 ± 195,43) e lingual (235,80 ± 103,46). O término em ombro apresentou os menores valores médios de deformação na superfície vestibular (127,47 ± 40,32) e lingual (68,35 ± 80,68), sem diferença estatisticamente significativa. Os copings cimentados com resina apresentaram maiores valores médios de deformação na superfície vestibular (295,05 ± 167,92) e lingual (197,38 ± 99,85) do que os copings cimentados com ionômero de vidro (149,14 ± 60,94) e (90,27 ± 55,62), sem diferença estatisticamente significativa. Conclusão: O término cervical em lâmina de faca é uma alternativa promissora e a cimentação adesiva ou convencional pode ser usada na cimentação de copings de zircônia. (AU)

Questions about the numerical value and quantitative data transfer of tooth preparation-from experience guidance to digital guidance / 华西口腔医学杂志

Tooth preparation is a common operation in dental clinical practice. This procedure is irreversible and invasive from the point of view of tooth preservation. Conditions of the abutment tooth, treatment methods, and restoration materials for target restoration affect tooth preparation. To achieve the goals of tooth tissue preservation, dental pulp protection, and periodontal health, dentistry professionals agreed on the importance of minimizing the amount of tooth reduction. The foundations for realizing this consensus are as follows. First, the available restoration materials with improved comprehensive performance need less target restoration space. Next, teeth can be prepared under a digital guide, and the real-time measurement of restoration space can be verified due to the invention of digital technologies for the analysis of the quantity and shape of the prepared tooth and tooth measurement. Moreover, guiding methods for preparation have been developed from freehand operation under the naked eye based on accumulated personal experience to digital-guidance jointing microscope. These innovations indicate the creation of a prototype of guided prosthodontics that is precise and applies real-time measurement throughout the process of tooth preparation. From the perspective of the evolution of digital, guided, and micro prosthodontics, this article raised seven questions about the numerical value and quantitative data transfer of tooth preparation and evaluated the authenticity of existing numerical requirements from the perspective of the four elements of measurement. Identifying unified measuring methods and developing measuring tools with a precision of hundred or ten microns will be the key to solving the problem about the authenticity of numerical measurement. Furthermore, this paper summarizes the methods of how to control tooth reduction and explains in depth why the currently dominant tooth preparation technology, which is based on empiricism, cannot effectively achieve the goals in digital prosthodontics. Therefore, we strongly call for rebuilding the digital foundation of prosthodontic treatment immediately.

Ángulos de convergencia en preparaciones dentarias realizadas en tipodontos por estudiantes de Odontología, Unach / Convergence angles in dental preparations performed on typodont by students of dentistry, UNACH

El objetivo de esta investigación fue analizar los ángulos de convergencia en preparaciones dentarias para coronas realizadas en tipodontos, por estudiantes de décimo semestre de Odontología Unach. Las preparaciones dentales para coronas poseen características de retención y resistencia, principios fundamentales que ofrecen éxito y longevidad de la corona definitiva. Varios investigadores a nivel mundial han desarrollado diversos métodos para evaluar los ángulos de convergencia de las preparaciones extracoronarias; sin embargo, en nuestro medio, no existen estudios acerca de la medición de estos ángulos. Esta investigación fue de carácter experimental, transversal y observacional, se obtuvieron 32 preparaciones dentarias para coronas de recubrimiento completo, cada estudiante tuvo 60 minutos para tallar dos preparaciones dentarias en simuladores clínicos. Los tipodontos fueron escaneados y digitalizados mediante el escáner CAD-CAM Ceramill Database versión 1.0 año 2010 del Laboratorio "BrothersDent" para producir imágenes tridimensionales. El software iTero midió los ángulos vestíbulo-lingual (VL) y mesio-distal (MD) de cada preparación. Los ángulos más pequeño y más grande observados fueron 3.1° y 102.5° para molares mandibulares. El promedio del ángulo VL para dientes anteriores fue 40,38 ±4,38° en varones y 36,97 ±3,95° en mujeres y el promedio del ángulo MD fue 44,68 ±5,51° en varones y 40,08 ±3,99° en mujeres. Para dientes posteriores el promedio VL fue 27,46 ±7,82° en varones y 40,98 ±4,63° en mujeres; y el promedio del ángulo MD fue 40,73 ±5,95° en varones y 50,62 ±7,00° en mujeres. En conclusión, los ángulos de convergencia logrados por estudiantes fueron mayores que los ideales recomendados según Shillingburg.

This research aimed to analyze the angles of convergence in dental preparations for crowns performed on typodont, by 10th semester students of school of dentistry, UNACH. Dental preparations for crowns have retention and resistance characteristics, fundamental principles that offer success and longevity of the final crown. Various researchers worldwide have developed various methods to evaluate the convergence angles of extra coronary preparations; however, in our context, there are no studies on the measurement of these angles. This research was experimental, cross-sectional and observational, 32 dental preparations were obtained for fully covered crowns, each student had 60 minutes to carve two dental preparations in clinical simulators. The typodonts were scanned and digitized using the scanner CAD-CAM Ceramill Database version 1.0 - 2010 of "BrothersDent" Laboratory in order to produce three-dimensional images. The iTero software measured the vestibule-lingual (VL) and mesio-distal (MD) angles of each preparation. The smallest and largest angles observed were 3.1 ° and 102.5 ° for mandibular molars. The mean VL angle for anterior teeth was 40.38 ± 4.38 ° in males and 36.97 ± 3.95 ° in females, and the mean MD angle was 44.68 ± 5.51 ° in males and 40, 08 ± 3.99 ° in women. For posterior teeth the average VL was 27.46 ± 7.82 ° in men and 40.98 ± 4.63 ° in women; and the mean MD angle was 40.73 ± 5.95 ° in men and 50.62 ± 7.00 ° in women. In conclusion, the convergence angles achieved by students were greater than the recommended ideals according to Shillingburg.

Precise tooth preparation technique guided by 3D printing guide plate with quantitative hole / 华西口腔医学杂志

The minimum amount of tooth preparation that can be fully controlled is crucial in achieving long-term, stable, and effective aesthetic restoration, which is also a major difficulty in aesthetic restoration. The tooth preparation can be imple-mented efficiently and accurately through digital technology based on the fixed-deep hole guiding technology. Prior the actual tooth preparation, the technology first designs the virtual contour, layering, and virtual occlusion of the prosthesis on the computer. Then, virtual tooth preparation is carried out by cutting back according to the virtual prosthesis. Next, the virtual drilling operation plan is designed according to the shape of the virtual tooth preparation and the contour of the abutment tooth. Finally, the tooth preparation guide plate is designed and printed in 3D. It realizes the whole process of quantitative and precise guidance of dental preparation, visualizes the restoration space, reduces the clinical operation time, and guarantees the quality of dental preparation. It also promotes the improvement of the teaching quality of digital practical exercises.

Clinical pathway and preparation method of high-precision tooth shoulder platform / 华西口腔医学杂志

A clear shoulder platform that can be easily identified by doctors and technicians or machines (mouth scan and warehouse scan) is important to obtaining a good long-term and stable fixed prosthesis treatment effect. At present, the pre-paration of the shoulder platform is usually based on free hands, and the practical operation is mainly guided by experience. Moreover, no comprehensive and objective preoperative design, intraoperative verification, and final test are available. Thus, the accuracy of shoulder platform preparation needs to be improved. In this study, the clinical pathway of "three determination, three selection, and three steps" with high accuracy of preparation and the precise shoulder preparation method of "bur-tip guidance" are proposed in detail.

Adaptación de cofias metálicas de Co-Cr realizadas sobre dos líneas de terminación y fabricadas con dos técnicas / Adaptation of Co-Cr metal copings made on two termination lines and manufactured with two techniques

Las nuevas tecnologías digitalizadas han permitido migrar de la técnica de cera perdida colada por centrifugación (CPC) a la fabricación sustractiva por CAD/CAM como la técnica de fresado de bloque blando (SMB). Objetivo: El propósito de este estudio fue comparar las adaptaciones marginales e internas en cofias metálicas de Co-Cr sobre dos líneas de terminación: chamfer y bisel confeccionadas mediante dos técnicas: CPC y SMB. Material y Métodos: Se confeccionaron dos modelos maestros de Co-Cr con terminación chamfer y bisel, se formaron 4 grupos de estudio y se fabricaron 13 cofias por grupo. Para la evaluación de las adaptaciones marginal e interna se usó el método de la réplica en silicona, luego con un estéreo microscopio se evaluó las discrepancias marginales e internas. Resultados: Para la discrepancia marginal entre las dos técnicas, para la terminación bisel sólo se observó diferencias estadísticamente significativas (p<0,05) en los puntos A1 y A2 y en la terminación chamfer se observó diferencias estadísticamente significativas (p<0,05) en los puntos A1 y F1. En la adaptación interna comparando ambas técnicas en la terminación bisel se obtuvo diferencias estadísticamente significativas (p<0,05) en los puntos E1, E2, D1, C2 y D2. En la terminación chamfer los resultados mostraron diferencias estadísticamente significativas (p<0,05) en todos los puntos. Conclusiones: Las cofias que presentaron mejor adaptación marginal fueron las confeccionadas por SMB con la línea de terminación chamfer, en la línea de terminación bisel no se pudo concluir cuál de las dos técnicas es mejor en adaptación marginal. Las que presentaron mejor adaptación interna en ambas líneas de terminación, en la zona axial fueron las cofias realizadas mediante la técnica CPC y en la zona oclusal presentaron mejor adaptación interna el SMB.

The new digitized technologies have allowed to migrate from the technique of lost cast wax by centrifugation (CPC) to the subtractive manufacturing by CAD / CAM as the technique of soft-block milling (SMB). Objective: The purpose of this study was to compare the marginal and internal adaptations in metal Co-Cr copes on two termination lines: chamfer and bevel made by two techniques: CPC and SMB. Material and Methods: Two Co-Cr master models with chamfer and bevel termination were made, 4 study groups were formed and 13 copings were made per group. For the evaluation of the marginal and internal adaptations the replication method was used in silicone, then with a stereomicroscope the marginal and internal discrepancies were evaluated. Results: For the marginal discrepancy between the two techniques, only statistically significant differences were observed for the bevel termination (p <0.05) in points A1 and A2 and in the chamfer termination statistically significant differences were observed (p <0.05) in points A1 and F1. In the internal adaptation comparing both techniques in the bevel termination, statistically significant differences were obtained (p <0.05) in points E1, E2, D1, C2 y D2. And in the chamfer termination, the results showed statistically significant differences (p <0.05) in all the points. Conclusions: The copes that presented better marginal adaptation were those made by SMB with the chamfer termination line, in the bevel termination line it was not possible to conclude which of the two techniques is better in marginal adaptation. The ones that presented better internal adaptation in both lines of termination, in the axial zone were the copings made using the CPC technique and in the occlusal area the SMB had better internal adaptation.

To Estimate and Compare the Incidence of Dentin Hypersensitivity Among Men and Women Before and After Tooth Preparation

Dentin hypersensitivity following tooth preparation is a frequently encountered oral health problem. The present study was conducted to estimate and compare the incidence of dentin hypersensitivity among men and women in an adult population sample who required replacement of missing tooth/teeth with a fixed partial prosthesis. Methods: The present study was conducted among 32 participants in which 16 were male and 16 were females who want replacement of missing tooth/teeth with a fixed partial prosthesis. The informed consent of all the participants who participated in this study was obtained. Detailed clinical and radiographic investigations were performed on all participants to exclude conditions of teeth, which might have caused pain similar to dentin hypersensitivity. There was at least one vital abutment tooth in each FPD. Each abutment tooth received two stimuli: tactile stimulus and thermal stimulus. Sensitive teeth were identified with an explorer passed cervically over the abutment tooth. Immediately following stimulation, the participants were asked to grade their overall sensitivity using a 10 cm Visual Analogue Scale (VAS). After the VAS was recorded before tooth preparation, the subjects underwent tooth preparation of the abutment teeth for the fixed partial denture. The VAS was recorded immediately after tooth preparation. The data was compiled and subjected to statistical analysis. Statistical analysis was done by using SPSS, version 22 (SPSS, Inc., Chicago, IL) and p<0.05 was considered statistically significant. Results: In the present study; total participants were 32, out of which 16 were male and 16 were females. The comparison of dentin hypersensitivity between men and women in which women reported more dentin hypersensitivity than men, although results were statistically non-significant. Conclusion: It was concluded that women reported more dentin hypersensitivity than men before and after tooth preparation

The contribution of ceramic thickness and adhesive type on the de-bonding strength of dental ceramic veneers using Er, Cr: YSGG laser / La contribución del espesor de la cerámica y el tipo de adhesivo a la resistencia de desunión de las carillas dentales de cerámica con láser Er, Cr: YSGG

Purpose: De-bonding strength of ceramic veneers by laser use needs to be evaluated in detail. The aim of this study, is to determine the contribution of ceramic thickness and cementing agents to the de-bonding strength of ceramic veneers using Er,Cr:YSGG laser. Methods: A total of 120 maxillary central incisors specimens were randomly divided into twelve groups on the basis of disc thickness, cementing agent, and Er,Cr:YSGG laser use. Under laboratory conditions, 120 IPS Empress II system discs 0.5mm, 1mm, and 2mm in thickness were applied to the tooth surfaces, for laser use. An Er,Cr:YSGG laser system was applied to the central surface of the IPS Empress II discs on specimens in all laser groups (Groups 1,3,5,7,9,11). Then the shear bond strength (SBS) for all specimens were tested with a testing machine at a speed of 0.5mm/min. The SBS values were considered as the de-bonding strength. Results: The mean de-bonding strength values for Groups 9 and 11 (0,5 mm disc thickness + laser application) have the lowest median load (0.000 N), while Group 4 (2mm disc thickness + no laser) has the highest median load (573.885 N). The de-bonding strengths of all the groups without laser application were higher than those of all groups with laser use. When laser is applied, the mean de-bonding strength decreases with decreasing disc thickness, and it reaches zero at 0.5mm thickness of discs cemented by self- or total-etch adhesives. Conclusions: The de-bonding strength decreases with laser use, and decreasing disc thickness. In the absence of laser, the mean de-bonding values of discs cemented by a total etch adhesive system are always higher than those of discs cemented with a self-etch adhesive system. Without any extra load, all 0.5mm thick discs were dislodged from teeth while applying or testing the laser.

Propósito: La resistencia de desunión de las carillas de cerámica mediante el uso del láser debe evaluarse en detalle. El objetivo de este estudio es determinar la contribución del espesor de la cerámica y los agentes de cementación a la resistencia de desunión de las carillas de cerámica utilizando el láser Er, Cr: YSGG. Métodos: Un total de 120 incisivos centrales maxilares se dividieron al azar en doce grupos según el grosor del disco, el agente de cementación y el uso del láser Er, Cr: YSGG. En condiciones de laboratorio, se aplicaron en las superficies de los dientes 120 discos del sistema IPS Empress II de 0,5mm, 1mm y 2mm de grosor, para uso con láser. Se aplicó un sistema láser Er, Cr: YSGG a la superficie central de los discos IPS Empress II en muestras de todos los grupos de láser (Grupos 1,3,5,7,9,11). Luego, la resistencia de la unión al cizallamiento (SBS) para todas las muestras se probó con una máquina de prueba a una velocidad de 0.5mm/min. Los valores de SBS se consideraron como la fuerza de desunión. Resultados: Los valores medios de resistencia de desunión para los Grupos 9 y 11 (espesor de disco de 0,5mm + aplicación de láser) demostró la carga media más baja (0,000 N), mientras que el Grupo 4 (espesor de disco de 2 mm + sin láser) tuvo la carga media más alta (573.885 N). Las fuerzas de desunión de todos los grupos sin aplicación de láser fueron superiores a las de todos los grupos con uso de láser. Cuando se aplica el láser, la fuerza media de desunión disminuye al disminuir el grosor del disco, y llega a cero con el grosor de 0,5mm de los discos cementados, para ambos adhesivos de grabado. Conclusiones: la fuerza de desunión disminuye con el uso del láser y disminuye con el grosor del disco. En ausencia de láser, los valores medios de desunión de los discos cementados con un sistema de adhesivo de grabado total son siempre más altos que los de los discos cementados con un sistema de adhesivo de autograbado. Sin ninguna carga adicional, todos los discos de 0,5mm de grosor se desprendieron de los dientes al aplicar el láser.

Irrigación del conducto radicular y tratamiento de superficie de pernos de fibra, previo a la cementación: revisión de tema / Root canal irrigation and fiber post treatments, before cementation: subject review

Introducción: el tratamiento endodóntico es muy solicitado para preservar las piezas dentales, así como la utilización de pernos de fibra cuando el remanente coronario no es el adecuado para recibir una prótesis coronaria, permitiendo de esta manera reconstruir el muñón dental para la posterior colocación de la restauración definitiva. Objetivo: identificar tanto el tratamiento de superficie de pernos de fibra como el irrigante radicular idóneos para conseguir una cementación adecuada; así como conocer cuál es el tratamiento de superficie que produce menos desintegración de las fibras del perno de fibra. Materiales y métodos: se incluyeron 47 artículos publicados en inglés, durante los últimos 20 años, teniendo en cuenta que los mismos se obtuvieron hasta octubre del 2018. Conclusiones: previa la cementación de pernos sean estos de fibra o de cuarzo es indispensable realizar tratamiento de superficie para así mejorar la adhesión, estos pueden ser químicos o físicos, los que ofrecen mejor resultado sin alterar de manera significativa la estructura del mismo es el enarenado con partículas de diamante sintéticas de 1-3 µm seguido de silanización y dentro de los químicos H2O2 al 10% por 1 min seguido de silano. Para obtener mejores resultados se debe accionar el silano a una temperatura de 80°C. En cuanto a protocolos de irrigación depende del sistema de cementación que se vaya a emplear EDTA 18% + Hipoclorito de sodio al 5,25% o EDTA 18% + clorhexidina al 2% cuando se va emplear un cemento autoadhesivo y NaOCl al 11% cuando se utilice el acondicionamiento ácido de lavado y secado.

Introduction: nowadays the aim is to keep the dental organ in function as long as possible, in many cases the endodontic treatment is used to preserve the dental pieces; and the use of fiber post when the coronary remnant is not adequate to receive a crown prosthesis, allowing us in these cases rebuilt the thoot for the subsequent placement of the final restoration. Objective: to identify wich is the better surface treatment of fiber post and the root irrigator for adequate cementation; as well as know, which is the surface treatment that produces less fibers' disintegration of the fiber post. Materials and methods: it were included 47 articles published in English, during the last 20 years, considering that they were obtained until October 2018. Conclusions: Before posts cementation are these fiber or quartz it is indispensable to carry out the surface pretreatment to increase adhesion, the same ones that can be chemical or physical within these that offer the best result it is the sanded with particles of diamond synthetic of 1-3 µm followed by silanization and with 10% H2O2 for 1min followed by silane. For better results silane must be dryed at a temperature of 80 °C. And for irrigation protocols depends of the cementing system to be used EDTA 18% + sodium hypochlorite 5.25% or EDTA 18% + 2% chlorhexidine when a self-adhesive cement is to be used and 11% NaOCl when washing and drying acid conditioning is used.

Influence of angulation and height of tooth preparation on the distribution of tensions in prosthetic crowns for upper central incisor: in silico analysis

Aim: it was to use tridimensional finite element analysis (FEA) to analyze the effect of height and angulation of prosthetic preparations on the distribution of stresses for lithium disilicate prosthetic crowns, the underlying resin cement, and the prosthetic preparation of a superior central incisor. Methods: a CAD modeling software, SolidWorks 2013, was used to generate three-dimensional virtual models comprising the dimensions of the preparation parameters. Three angles (6, 12 and 16 degrees) were simulated on the prepared walls and two wall heights were utilized (4 and 5 mm), for a total of six model groups according to the height and angulation of the walls. A vertical line in the Y-axis was used as a reference for determining the degrees of convergence (inclination of the preparations). The chamfer finish and preparation width were standardized for all groups. Results: the 4 mm preparations behaved more appropriately when the axial wall convergence was approximately 6 degrees. The 5 mm preparations required 12 degrees of angulation. In relation to resin cement, there was better stress distribution when the angle of incisal convergence was between 6 and 12 degrees. An increase to 16 degrees led to a considerable increase in peak stress at the preparation margin. Conclusion: it was concluded that the convergence of the axial walls of coronal preparations with 4 and 5 mm heights should be 6 and 12 degrees, respectively, to avoid high tension spikes in the underlying resin cement

Application value of non-flapping technique in immediate implant prosthesis in aesthetic area of anterior teeth / 中国基层医药

Objective@#To explore the application value of non-flapping technique in immediate implant prosthesis in aesthetic area of anterior teeth.@*Methods@#From March 2016 to September 2017, 104 patients who received immediate implant restoration of anterior teeth in the First Hospital of Jiaxing were divided into observation group (53 cases) and control group (51 cases) according to random number table method.The control group was treated with conventional flap immediate implantation, while the observation group was treated with non-flap immediate implantation.The red aesthetic index (EPS), alveolar bone resorption and patients' satisfaction were compared between the two groups.@*Results@#The PES scores of the observation group were (6.17±1.21)points, (5.94±1.03)points and (5.12±0.85)points, respectively after repair 3 months, 6 months and 12 months, which were significantly higher than those of the control group [(5.38±0.96)points, (4.79±0.76)points, (4.05±0.70)points] (t=3.679, 6.459, 6.993, all P<0.05). At 3 months, 6 months and 12 months after restoration, the alveolar bone resorption in the observation group was(0.29±0.04)mm, (0.63±0.12)mm, (1.07±0.17)mm, respectively, which was significantly lower than that in the control group [(0.36±0.07)mm, (0.95±0.24)mm, (1.28±0.26)mm] (t=6.291, 8.649, 4.893, all P<0.05). At 12 months after repair, the satisfaction rate of patients in the observation group was 98.11% (52/53), which was significantly higher than 84.31% (43/51) in the control group (χ2=4.637, P<0.05).@*Conclusion@#The application of non-flapping technique in immediate implant prostheses in aesthetic area of anterior teeth has good effect, which can obtain better aesthetic effect, reduce alveolar bone absorption and improve patients'satisfaction with prostheses.However, in clinical work, it is necessary to strengthen preoperative examination and measurement of patients, accurately grasp the direction of implants and avoid the occurrence of bone wall perforation during operation.

Minimal invasive microscopic tooth preparation based on endodontic, periodontal and functional health / 华西口腔医学杂志

Tooth preparation is the primary and core operation technique for dental esthetic restoration treatment, due to its effect of providing restoration space, bonding interfaces and marginal lines for dental rehabilitation after tooth tissue reduction. The concept of microscopic minimal invasive dentistry put forward the issue of conducting high-quality tooth preparation, conserve tooth-structure, protect vital pulp and periodontal tissue simultaneously. This study reviewed the concepts, physiology background, design and minimal invasive microscopic tooth preparation, and in the meantime, individualized strategies and the two core elements of tooth preparation (quantity and shape) are listed.

Influence of fracture resistance of prosthesis with different thickness of ferrule restored with fiber post and resin core and crown / 中华口腔医学杂志

Objective@#To evaluate the influence of fracture resistance of endodontically treated teeth with different thickness of ferrule by mechanical fatigue test and static loading test, and so as to provide a reference for the clinical treatment planning.@*Methods@#Fifty bovine incisors were divided into 5 groups by random number table method (n=10). Group A was the control group in which the incisors were prepared without a ferrule design (0 mm). The other four groups (B, C, D, E) were experimental groups, and the thickness of the dentin ferrule prepared for specimens in each group was 0.5, 1.0, 1.5, and 2.0 mm. The height of ferrules in all the specimens was 2 mm. Cyclic fatigue loading (2.33 Hz, 50 N) was applied on each specimen until either the specimen was dislodged/fractured or the 300 000 cycles were finished. After fatigue loading, the mode of failure was observed. Those intact specimen after fatigue loading were tested under a gradually increasing force using a universal testing machine (0.05 mm/min) until fracture occurred. The forces required to fracture and failure model was recorded.@*Results@#The results of cyclic loading tests showed that: all specimens survived the 300 000 cycles of intermittent loading. The results of static loading tests showed that: the fracture force of A, B, C, D and E groups respectively were (226.4±67.7), (369.7±34.5), (400.7±48.2), (528.1±56.3), and (555.4±98.5) N (F=15.227, P=0.000). There was a significant difference in fracture resistance between group A and the other four groups, and between group B, C and group D, E (P<0.05). No statistical difference were found in fracture resistance among the other groups (P>0.05). There was strong correlation between the thickness of ferrule and the fracture force by Pearson correlation analysis (r=0.973, P=0.002).@*Conclusions@#Within the limitations of this study, the following conclusions can be drawn: The different thickness of ferrule can influence the fracture resistance of the teeth, and when the height of the ferrule is 2.0 mm, the fracture force increased significantly with an increasing ferrule thickness.

Research status of tooth preparation quantitative guide technique / 中华口腔医学杂志

Tooth preparation is a basic operation in prosthodontics treatment and the quality of preparation influences the effect of treatment directly. How to achieve a precise and quantitative tooth preparation is always one of the main aims of dental prosthodontics. The known types of tooth preparation guide technique can be divided into visual guidance, passive constraint guidance and active constraint guidance (automated tooth preparation), respectively represented by silicon rubber index, tooth preparation guide plate and computerized numerical control cutting system (CNC cutting system). Studies in advanced manufacturing technologies such as robot systems and numerical control ultra-short pulse laser (USPL) have also been reported recently. This review comprehensively introduced tooth preparation quantitative guide techniques and partially summarized the application effects and limitations to provide reference for relative researches and clinical application.

Research progress in pulpless posterior tooth restored with ceramic onlay / 华西口腔医学杂志

Minimal invasive restoration is a common technique in the restoration of pulpless posterior teeth. The development of bonding techniques and ceramic materials in recent years has increased the use of high-strength ceramic onlay in the restoration of endodontically treated posterior teeth because of its minimal invasiveness, improved aesthetics, and low requirement of mechanical retention. This study conducts a retrospective analysis on the material, tooth preparation, bonding, and clinical considerations of ceramic onlay in endodontically treated posterior tooth.