The effect of aging on the accuracy of marginal adaptation and fracture resistance of CAD/CAM PEEK single crown restoration

Aim: In recent years, great advances have been made in the use of CAD/CAM to prepare fixed restorations. The marginal and internal fit of these restorations is a principal determinant for their clinical success. In addition, the nature of the oral environment affects the mechanical properties of these restorations. Therefore, this study aimed to investigate the effect of aging process under conditions that simulate the oral environment on the marginal adaptation, and, fracture resistance of crowns fabricated from polyether ether ketone (PEEK) using CAD/CAM methods. Methods: Twenty identical crown restorations were fabricated by using CAD/CAM methods to mill polyether ether ketone (PEEK) material. These crowns were produced by using a software design of an epoxy resin replica of the prepared maxillary first premolar tooth. All PEEK crowns were cemented and randomly divided into two equal groups (A, B). Each group was divided into subgroups (A1, A2 and B1, B2). Group A1 and A2 were used to measure marginal adaptation and fracture resistance, respectively, before aging, while group (B1 and B2) were measured after aging. The cemented crowns were mounted in resin molds to facilitate the sectioning process. The measurements of the marginal gap were performed after sectioning at four points using a stereomicroscope. The fracture resistance of the crowns was investigated using a universal testing machine. A statistical analysis was performed using the GraphPad Prism® software version and unpaired Student's t-test. Results: The results revealed that aging affected the marginal gap, and the fracture resistance of the PEEK crowns. While aging, negatively affected the conditions under investigation, however the least significant difference of marginal gap was found in the margin region. Conclusions: PEEK-CAD/CAM is considered as a good alternative prosthodontic material for fixed prostheses. The CAD/CAM technique used to make PEEK crown restorations in our study offers the advantages of high marginal accuracy and fracture resistance for long-term performance in the oral environment

Adaptación marginal e interna de cofias fabricadas por métodos convencionales, CAD/CAM de fresado y sinterizado por láser / Marginal and internal adaptation of copings manufactured by conventional methods, CAD/CAM milling and laser sintering

Introducción: la adaptación marginal e interna de nuestras restauraciones fabricadas por fundición sistemas de fresado y sinterización láser es uno de los factores clínicos más importantes para el éxito de las prótesis fijas, previniendo el riesgo de microfiltración y enfermedad periodontal. Objetivo: evaluar la adaptación marginal e interna de cofias metálicas en aleación Cr-Co confeccionadas por técnicas convencionales, CAD/ CAM de fresado y sinterizado por láser. Material y métodos: estudio de tipo experimental, comparativo e in vitro. Se imprimió un modelo maestro en Cr-Co, proveniente del escaneo de un premolar preparado para corona completa, sobre el cual se diseñaron 30 cofias divididas en tres grupos: el primero que corresponde al grupo cofias fundidas fresadas en disco de cera A (A = 10), el segundo grupo cofias fresadas en disco de metal presinterizado B (B = 10) y el tercer grupo cofias impresas por sinterización láser C (C = 10). Se empleó la réplica de silicona, colocando silicona al interior de cada cofia, sobre el modelo maestro, simulando al cemento, mediante una máquina de ensayo universal se realizó una compresión de 50 N. Luego de retirar cada cofia se rellenaron con silicona pesada de adición, obteniendo una réplica de silicona. Se efectuaron dos cortes transversales en sentido vestíbulolingual y mesiodistal. Se observó el espesor de silicona VPS (vinil poliéter silicona) mediante un estereomicroscopio (Nikon SMZ745T), obteniendo valores en micrómetros. Para el análisis estadístico se utilizó el software SPSS 25 con el fin de realizar la prueba de normalidad y ANOVA de dos vías bajo un nivel de confianza del 95%. Resultados: el menor gap lo obtuvo el grupo de fresadas, seguido de las impresas y por último las fundidas por métodos convencionales. ANOVA de dos vías reveló diferencias estadísticamente significativas entre los tres grupos (p < 0.0001). Conclusiones: se encontró que el gap varía con cada método de fabricación, la técnica convencional de fundido mostró un mayor gap, ninguna excediendo el rango clínicamente aceptable (AU)

Introduction: the marginal and internal adaptation of our restorations manufactured by casting, milling systems and laser sintering is one of the most important clinical factors for the success of fixed prostheses, preventing the risk of microleakage and periodontal disease. Objective: evaluate the marginal and internal adaptation of metal copings in Cr-Co alloy made by conventional techniques, CAD/CAM milling and laser sintering. Material and methods: an experimental, comparative and in vitro study, a Cr-Co master model was printed from the scan of a premolar prepared for a full crown. An experimental, comparative and in vitro study, a Cr-Co master model was printed from the scan of a premolar prepared for a full crown, on which 30 caps divided into three groups were designed; the first group corresponds to the cast copings milled on a wax disc A (A = 10), the second group milled copings on a presintered metal disc B (B = 10) and the third group printed by laser sintering copings C (C = 10). The silicone replica was used, placing silicone inside each coping, on the master model, simulating cement, using a universal testing machine, a 50 N compression was performed. After removing each coping, they were filled with heavy addition silicone, obtaining a silicone replica. Two cross-sections were made in the buccolingual and mesiodistal direction., observing the thickness of the VPS (vinyl polyeter silicone) silicone using a stereomicroscope (Nikon SMZ745T), obtaining values in micrometers. For the statistical analysis, the SPSS 25 software was used in order to perform the normality and two-way ANOVA tests under a 95% confidence level. Results: the smallest gap was obtained by the milled group, followed by the printed ones and finally those cast by conventional methods. Two-way ANOVA revealed statistically significant differences between the three groups (p < 0.0001). Conclusions: the gap was found to vary with each fabrication method, the conventional casting technique showed a larger gap, none exceeding the clinically acceptable range (AU)

Reabilitação oral com próteses parciais removíveis após restabelecimento de dimensão vertical de oclusão e tratamento multidisciplinar: relato de caso / Oral rehabilitation with removable partial dentures after restoration of the vertical dimension of occlusion and multidisciplinary treatment: case report

As próteses parciais removíveis (PPRs) são uma alternativa de tratamento viável na prática clínica para reabilitar arcos parcialmente desdentados. Entretanto, o planejamento dessas próteses e preparo bucal prévio são frequentemente negligenciados. O presente artigo tem como objetivo relatar o caso clínico de uma reabilitação oral com PPRs superior e inferior após abordagem multidisciplinar, de modo a enfatizar as fases de um planejamento criterioso e de preparo prévio dos dentes pilares, visando o sucesso e a longevidade da reabilitação. Paciente do sexo masculino de 57 anos de idade compareceu à clínica da Faculdade de Odontologia de Bauru, Universidade de São Paulo, queixando-se da estética de seu sorriso e de algumas ausências dentárias. O indivíduo utilizava uma PPR provisória inferior insatisfatória e apresentava perda de dimensão vertical de oclusão (DVO). Após o exame clínico, radiográfico e estudo do caso em articulador semi-ajustável, realizou-se o planejamento com abordagens restauradoras, endodônticas, periodontais e protéticas. Após tratamento periodontal, foi realizada endodontia dos elementos 12, 15 e 47, confecção de núcleos e coroas nos dentes 12 e 15, restauração a nível gengival para apoio residual no dente 47, restaurações nos dentes 11, 13, 22, 24 e 44 e, por fim, a confecção das PPRs superior e inferior. A abordagem multidisciplinar utilizada neste caso clínico viabilizou o restabelecimento da DVO e possibilitou o sucesso da reabilitação protética(AU)

Removable partial dentures (RPDs) are a viable treatment alternative in clinical practice to rehabilitate partially edentulous arches. However, the planning of these dentures and prior oral preparation are often neglected. This article aims to report the clinical case of an oral rehabilitation with upper and lower RPDs after a multidisciplinary approach, to emphasize the phases of careful planning and prior preparation of the abutment teeth, aiming at the success and longevity of the rehabilitation. A 57-year-old male patient came to the clinic of the Bauru School of Dentistry, University of São Paulo, complaining about the esthetics of his smile and some missing teeth. The subject was using an unsatisfactory lower provisional prosthesis and had a loss of vertical dimension of occlusion (OVD). After the clinical and radiographic examination and the case study in a semi-adjustable articulator, planning was carried out with restorative, endodontic, periodontal and prosthetic approaches. After periodontal treatment, endodontics were performed on elements 12, 15 and 47, creation of cores and crowns on teeth 12 and 15, restoration at the gingival level for residual support on tooth 47, restorations on teeth 11, 13, 22, 24 and 44 and, finally, the making of the upper and lower PPRs. The multidisciplinary approach used in this clinical case enabled the restoration of the OVD and enabled the success of the oral rehabilitation(AU)

Reabilitação estética anterior em abordagem multidisciplinar: relato de caso / Aesthetic rehabilitation in a multidisciplinary approach: case report

A estética tem um papel importante na aceitação e autoestima das pessoas e, em virtude disso, os pacientes buscam cada dia mais ter um sorriso harmonioso. As reabilitações estéticas devem envolver um planejamento completo, atrelando função e estética, avaliando tamanho dos dentes, perfil e alturas gengivais, altura do sorriso e corredor bucal. Por conta disso, a odontologia nos permite uma série de abordagens terapêuticas diferentes que chegam a resultados satisfatórios para o paciente. Sendo assim, o presente trabalho tem como objetivo descrever um relato de caso de uma paciente com queixa estética do seu sorriso devido à diferentes tonalidades, formas e tamanhos dos dentes. Após anamnese, exame clínico e radiográfico, o plano de tratamento proposto foi de harmonizações periodontal com aumento de coroa e enxerto gengival, além de coroas em cerâmicas de dissilicato de lítio. Dentro desse contexto, mostra-se que uma abordagem multidisciplinar para reabilitação estética e funcional do sorriso é fundamental, a qual nos proporciona equilíbrio e naturalidade entre estética branca e vermelha no resultado do tratamento reabilitador(AU)

Aesthetics plays an important role in people's acceptance and self-esteem and, as a result, patients increasingly seek to have a harmonious smile. Aesthetic rehabilitations must involve a complete planning, linking function and aesthetics, evaluating tooth size, gingival profile and heights, smile height and buccal corridor. Because of this, dentistry allows us a series of different therapeutic approaches that reach satisfactory results for the patient. Therefore, the present work aims to describe a case report of a patient with an aesthetic complaint of her smile due to different shades, shapes and sizes of teeth. After anamnesis, clinical and radiographic examination, the proposed treatment plan was periodontal harmonization with crown augmentation and gingival graft, in addition to lithium disilicate ceramic crowns. Within this context, it is shown that a multidisciplinary approach to the aesthetic and functional rehabilitation of the smile is fundamental, which provides us with balance and naturalness between white and red aesthetics in the result of the rehabilitation treatment(AU)

Benefícios do planejamento digital para cirurgias periodontais estéticas: relato de caso / Benefits of digital planning for esthetic periodontal surgeries: case report

Sorriso gengival é comumente conhecido pela exposição excessiva das gengivas ao sorrir, acarretando assim na diminuição das coroas dos elementos. No que tange a etiologia dessa condição, ela se apresenta de maneiras diversas e sua identificação é fundamental para o desenvolvimento de um plano de tratamento eficaz. O planejamento clínico pode ser feito usando uma abordagem dinâmica e digital do sorriso, como softwares, exames de imagem, modelos virtuais 3D e guias cirúrgicos, melhorando a qualidade e precisão do tratamento, oferecendo diversos benefícios aos pacientes. Sendo assim esse estudo teve como objetivo demonstrar a importância dos processos digitais no planejamento e correção do sorriso gengival. Paciente queixou-se da desproporção do sorriso, caracterizado por coroas curtas nas regiões de pré-molares e incisivos ligadamente com a exposição excessiva da gengiva ao sorrir. Após estudos clínicos e de imagem, a etiologia foi diagnosticada como erupção passiva alterada, tipo I (fenótipo espesso). O tratamento de escolha foi o remodelamento gengival associado à osteotomia e osteoplastia obtendo assim uma maior precisão no tratamento, sendo confeccionado um guia cirúrgico duplo. Sendo assim, é possível contemplar que o planejamento digital permite uma maior previsibilidade da execução, compatibilidade em relação a expectativa do paciente e profissional, além da total individualização do caso, tornando os resultados mais favoráveis e exatos e minimizando as chances de iatrogenias(AU)

Gummy smile is commonly known for exposing the gums to the smile, thereby increasing the crowns elevation of the elements. Regarding a condition, it presents itself in different ways and its identification is fundamental for the development of a treatment plan. The clinician can be done using a dynamic and digital approach to image treatment, such as software, imaging exams, various 3D virtual models and elaborate guides, improving the quality and precision of treatment, offering benefits to patients. Therefore, this study aimed to demonstrate the importance of digital processes in planning and correcting the gummy smile. Patient complained of disproportion of the smile, facing the regions of premolar crowns and incisors of the smile, facing the exposure of the gingiva when smiling. After clinical and imaging exams, the diagnostic studies were diagnosed as passive eruption, type I (phenotype and specific). The choice of choice was remodeling associated with surgery treatment and surgery treatment, thus providing a greater precision in the treatment, being a double guide elaborated. Therefore, it is possible that the digital is possible a predictability of execution, compatibility in relation to patient and professional care, in addition to the greater possibility of individualization planning than it allows, making the results more planned as possibilities and exactly the iatrogenic(AU)

Reabilitação estética com facetas e coroas cerâmicas em dissilicato de lítio: relato de caso / Aesthetic rehabilitation with ceramic facets and crowns in lithium disilicate: case report

Introdução: A procura pela estética do sorriso é crescente na Odontologia, pois, muitas vezes um sorriso alinhado e periodonto saudável não são o bastante. A cerâmica odontológica apresenta-se como uma ótima possibilidade restauradora, visto o avanço das técnicas de adesão entre o substrato dentário e as cerâmicas, torna-se mais previsível o resultado com este tipo de reabilitação. Objetivo: O presente artigo tem como objetivo descrever um caso clínico com envolvimento de diversos níveis de desgaste dentário para reabilitação estética com cerâmica de dissilicato de lítio. Relato de caso: Paciente 36 anos, gênero feminino, apresentava insatisfação com seu sorriso devido a forma e a alteração de cor dos seus dentes superiores anteriores e pré-molares. O plano de tratamento consistiu em realizar a troca da coroa metalocerâmica por coroa total cerâmica da unidade 14, coroa total cerâmica nas unidades 11, 21 e 22, facetas cerâmicas nas unidades 15, 13, 12, 23, 24 e 25, osteotomia e gengivoplastia das regiões de 2º prémolar superior esquerdo ao 2º pré-molar superior direito, clareamento dental caseiro da arcada inferior e placa oclusal superior de proteção. O material de escolha para a resolução do caso clínico foi a cerâmica vítrea reforçada à base de dissilicato de lítio, pois, possui um índice de refração de luz semelhante à estrutura dentária, sem interferência significativa da translucidez, além de ser passível de cimentação adesiva por se tratar de uma cerâmica ácido sensível e o tamanho do cristal e a sua disposição favorecem o aumento das propriedades mecânicas da restauração. Conclusão: O plano de tratamento realizado permitiu o restabelecimento da função e estética, com reprodução das características dos dentes naturais e promoção da jovialidade e da harmonia no sorriso(AU)

Introduction:The demand for smile aesthetics is growing in Dentistry, because, often a smile aligned and healthy periodontium are not enough. Dental ceramics, presented as an excellent restorative possibility, since the advancement of adhesion techniques between the dental substrate and the ceramics, becomes more predictable the result with this type of rehabilitation. Objective: This article aims to describe a clinical case involving several levels of dental wear for aesthetic rehabilitation with ceramics. Case Report: A 36-year-old female patient presented dissatisfaction with her smile due to the shape and color alteration of her anterior and premolar upper teeth. The treatment plan consisted of exchanging the metal-ceramic crown for the total ceramic crown of unit 14, total ceramic crown in units 11, 21 and 22, ceramic veneers in units 15, 13, 12, 23, 24 and 25, osteotomy and gingivoplasty of the regions from 2nd left upper premolar to 2nd right upper premolar, home tooth whitening of the lower arch and upper occlusal plate of protection. The material of choice for the resolution of the clinical case was the glass ceramic reinforced on the basis of lithium disilicate because it has a refractive index of light similar to the dental structure, without significant interference of translucency, besides being liable to adhesive cementation because it is a sensitive acid ceramic and the size of the crystal and its disposition favor the increase of the mechanical properties of the restoration. Conclusion: The treatment plan performed allowed the restoration of function and aesthetics, with reproduction of the characteristics of natural teeth and promotion of joviality and harmony in the smile(AU)

Evaluation of the occlusal contact area of molar dental implants comparing two different thicknesses (16 µm and 200 µm) of articulating occlusal papers and forces (200 and 250 N): a pivot in vitro study

Introduction: The goal of this pilot study was to evaluate the differences between checking occlusion on implants crowns using 16 or 200 µm thickness of articulating occlusal paper, and to compare the stained occlusal area between the groups after bite forces of 200 and 250 N. Methods: It was included 10 casts of articulated-type IV gypsum, 10 NiCr crowns, articulating occlusal papers (16 µm and 200 µm thick), and a compression test machine. Compressive forces (200 and 250 N.mm) were applied on models, to check the occlusal contact area of fixed and cemented crowns. The contact areas on the crowns were measured through images obtained by the scanning electron microscope. Statistical tests were performed considering the significant level of 5% (p≤0.05). Results: The stains found using 200 µm of articulating paper were higher than those with 16 µm, independent of the force applied. However, the stains obtained in lower teeth with different strengths (200 and 250N) marked with 16 µm articulating paper were not possible to score. The articulating paper variable had significant statistical results (p=0.002), while the variables force (p=0.443) and articulating paper-force interaction (p=0.607) were not significant. The mean area found in staining using the 200 µm and 16 µm papers was, respectively, 8.3380 mm2 and 3.4759 mm2. Conclusion: It was possible to confirm that 200 µm of articulating occlusal paper showed better and significant results to stain the occlusal area, permitting a more accurate adjustment independent of the force applied.

The infection control of post-and-core crown restoration / 华西口腔医学杂志

Post-and-core crown is one of the most common forms of restoration of tooth after root canal therapy (RCT). Infection control is the core objective of RCT, which is usually well realized by endodontists. However, many prosthodontists often neglect the infection control of the tooth and the maintenance of the curative effect of RCT during the process of post-and-core crown, which may lead to the failure of the final restoration. The concept of integrated crown-root treatment advocated recently requires clinicians to consider the RCT and final restoration as a whole, rather than simply divided into two parts-endodontic treatment and restorative treatment. As the core content of integrated crown-root treatment, infection control should be taken seriously by clinicians and implemented throughout the whole treatment process, especially in the restorative treatment that is easily overlooked after RCT. Therefore, this article describes the infection control of post-and-core crown restoration, classifies the tooth requiring post-and-core crown restoration, and puts forward the measures of infection control before and during post-and-core crown restoration, in order to provide reference and guidance for clinical practice.

Three-dimensional finite element analysis of cement flow in abutment margin-crown platform switching / 北京大学学报(医学版)

OBJECTIVE@#To analyze the cement flow in the abutment margin-crown platform switching structure by using the three-dimensional finite element analysis, in order to prove that whether the abutment margin-crown platform switching structure can reduce the inflow depth of cement in the implantation adhesive retention.@*METHODS@#By using ANSYS 19.0 software, two models were created, including the one with regular margin and crown (Model one, the traditional group), and the other one with abutment margin-crown platform switching structure (Model two, the platform switching group). Both abutments of the two models were wrapped by gingiva, and the depth of the abutment margins was 1.5 mm submucosal. Two-way fluid structure coupling calculations were produced in two models by using ANSYS 19.0 software. In the two models, the same amount of cement were put between the inner side of the crowns and the abutments. The process of cementing the crown to the abutment was simulated when the crown was 0.6 mm above the abutment. The crown was falling at a constant speed in the whole process spending 0.1 s. Then we observed the cement flow outside the crowns at the time of 0.025 s, 0.05 s, 0.075 s, 0.1 s, and measured the depth of cement over the margins at the time of 0.1 s.@*RESULTS@#At the time of 0 s, 0.025 s, 0.05 s, the cements in the two models were all above the abutment margins. At the time of 0.075 s, in Model one, the gingiva was squeezed by the cement and became deformed, and then a gap was formed between the gingiva and the abutment into which the cement started to flow. In Model two, because of the narrow neck of the crown, the cement flowed out from the gingival as it was pressed by the upward counterforce from the gingival and the abutment margin. At the time of 0.1 s, in Model one, the cement continued to flow deep inside with the gravity force and pressure, and the depth of the cement over the margin was 1 mm. In Model two, the cement continued to flow out from the gingival at the time of 0.075 s, and the depth of the cement over the margin was 0 mm.@*CONCLUSION@#When the abutment was wrapped by the gingiva, the inflow depth of cement in the implantation adhesive retention can be reduced in the abutment margin-crown platform switching structure.

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.

Changing scanning angles on improving finish line trueness of the full crown preparation / 中华口腔医学杂志

Objective: To explore the effect of scanning methods on finish line trueness of the full crown preparation. Methods: The standard full crown preparation model of the right maxillary first molars was prepared by using the maxillary standard resin dentition model. The standard preparation was scanned by imetric scanner and data were used as the true value. CEREC Omnicam and 3Shape TRIOS were used to scan the standard preparation. According to the scanning methods, they were divided into parallel scanning group, occlusal wave scanning group and buccolingual wave scanning group. Each group was scanned repeatedly 6 times. The data were imported into Geomagic Studio 2013 software, and the local finish line image data of the mesial, distal, buccal and lingual regions of the full crown preparation were extracted respectively. Three-dimensional deviation analysis was performed with the reference true value, and the root- mean-square error (RMSE) was the evaluation index of scanning trueness. The statistical method was one-way ANOVA. Results: Parallel scanning group: in general, the RMSE value of complete finish lines of scanner B [(35±6) μm] was significantly lower than that of scanner A [(44±7) μm](P<0.05). After scanner A occlusal wave scanning, the RMSE values of the mesial and distal finish lines [(33±5) and (50±12) μm] were significantly lower than those of parallel scanning group (P<0.05). After buccal and lingual wave scanning, the RMSE values of local finish lines in the mesial, distal, buccal and lingual regions [(37±3), (50±6), (28±6) and (29±8) μm] were significantly lower than those in parallel scanning group [(45±9), (63±7), (38±3) and (40±3) μm] (P<0.05). No significant difference was found in the RMSE values of the mesial, distal, buccal and lingual regions of scanner B between parallel scanning group, occlusal wave scanning group and buccolingual scanning group (P>0.05). Conclusions: The scanning trueness of the full crown preparation finish line obtained by the active triangulation scanning equipment can be improved by changing the scanning method to wave scanning.

Fracture strength and failure load of CAD/CAM fabricated endocrowns performed with different designs

Aim: Endocrown restorations are commonly used to rehabilitate endodontically treated posterior teeth and their use is well-founded in these cases. However, to date, there is little scientific evidence of their behavior in anterior teeth. The aim of this in vitro study was to evaluate the compressive strength of upper central incisors teeth, restored with glass-ceramic total crowns by the conventional anatomical core technique, and compare them to teeth restored with endocrowns with and without the presence of ferrule. Methods: Thirty teeth were randomly distributed into three groups: GE2 - endocrown group with 2 mm ferrule, GE0 - endocrown group without a ferrule, and GC - conventional crown with intraradicular post group. Crowns were cemented and teeth submitted to the 45o compression test until the fracture happened. Fractured specimens were analyzed to determine the fracture pattern. Descriptive analysis of the variables was performed and one-way analysis of variance was utilized to analyze the data for significant differences at p < 0.05. Results: The results of the control group (284.5 ± 201.05N) showed the highest fracture resistance value, followed by the 2mm group (274.54 ± 199.43N) and by the 0mm group (263.81 ± 80.05N). There was no statistically significant difference between all the groups (p = 0.964). Conclusions: The absence of a cervical enamel necklace favored a debonding of the pieces and endodontically treated anterior teeth could be restored with endocrown, which could be considered a conservative and viable treatment option

Fit of metal-ceramic crowns: effect of coping fabrication method and veneering ceramic application

Aim: To evaluate the influence of cobalt-chromium (Co-Cr) coping fabrication methods and ceramic application on the marginal and internal fit of metal-ceramic crowns. Methods: Co-Cr copings for metal-ceramic crowns were prepared by lost wax casting or CAD-CAM machining of sintered blocks. The fit was analyzed using the silicone replica technique at four assessment points: marginal gap (MG), axial wall (AW), axio-occlusal (AO) angle, and central occlusal (CO) wall. After the initial analysis, the copings were ceramic-veneered with the layering technique, and the fit was again determined. Data were statistically analyzed by paired and unpaired Student's-t test (α=0.05). Results: Marginal and internal fit before ceramic application according to the coping manufacturing method showed significant differences only at CO (p < 0.001), with milled copings (137.98±16.71 µm) showing higher gap values than cast copings (112.86±8.57 µm). For cast copings, there were significant differences at MG (before 109.13±8.79 µm; after 102.78±7.18 µm) and CO (before 112.86±8.57 µm; after 104.07±10.63 µm) when comparing the fit before and after ceramic firing. For milled copings, there was significant difference only at AO (before 116.39±9.64 µm; after 108.54±9.26 µm). Conclusion: This study demonstrated that the coping fabrication method influenced the internal fit. Ceramic firing maintained or improved the fit of the metal-ceramic crowns. The marginal discrepancy of all restorations, before and after ceramic firing, can be considered clinically acceptable

Comportamento dos tecidos peri-implantares pós- reabilitação unitária em região estética comparando pilares protéticos pré-fabricados versus personalizados / Behavior of peri-implant tissues after unitary rehabilitation in the aesthetic region comparing prefabricated versus customized prosthetic abutments

A estética e estabilidade dos tecidos moles e ósseo ao redor do implante é um componente crítico para o sucesso do implante em longo prazo e pode ser influenciado por fatores como os tipos de conexões protéticas. OBJETIVO: Comparar o comportamento do tecido peri-implantar em reabilitação com coroas implantossuportadas cimentadas na região estética usando um pilar protético pré-fabricado em titânio (GT) e um pilar protético personalizado em zircônia (GZ). METODOLOGIA: Neste estudo longitudinal do tipo ensaio clínico controlado, cego e não randomizado, 30 coroas cimentadas sobre implantes dentários unitários em região estética anterior foram alocados sequencialmente: 15 reabilitados sobre um sistema de implante com pilar protético pré-fabricado em titânio (GT) e 15 sobre um sistema de implantes com pilar protético personalizado em zircônia (GZ). O comportamento do tecido peri-implantar foi avaliado em T0 (início do condicionamento tecidual), T1 (fim do condicionamento tecidual), T2 (7 dias após cimentação final), T3 (6 meses após cimentação final). Índice de Placa Visível (IPV), Índice de Sangramento Gengival (ISG), Sangramento a sondagem (SS), Profundidade de Sondagem (PS), Relação Altura/Largura da papila interdental (AP/LP), Faixa de Mucosa Ceratinizada (MC), Espessura gengival (EG), Fenótipo periodontal (FP), Recessão Gengival (RG), distância radiográfica da crista óssea para o ponto de contato e Pink Esthetic Score (PES) foram avaliados. A análise dos dados foi realizada utilizando os seguintes testes estatísticos: Friedman, Mann-Whitney e Qui- quadrado/Exato de Fisher, com nível de significância de 5%. RESULTADOS: Não houve diferenças estatísticas significativas entre os grupos para nenhum dos parâmetros clínicos periodontais nos tempos avaliados (p>0,05). Entretanto, a análise intragrupo mostrou uma redução estatística no IPV e ISG entre T1 e T2 apenas para o GZ (p<0,05). Houve diminuição significativa entre os tempos T0 e T3 para o parâmetro de EG (1,67 mm - 1,47 mm no GT; 1,70 mm -1,47mm no GZ) e aumento da razão AP/LP (0,56 ­ 0,80 no GT; 0,70-0,83 no GZ) em ambos os grupos (p<;0.001). O PES também aumentou significativamente para ambos os grupos (9 ­ 12 no GT; 7 ­ 12 no GZ) de T0 para T1, mantendo-se elevado nos demais tempos analisados. CONLUSÃO: Os resultados mostraram que os pilares protéticos utilizados não impactaram em diferenças nas variáveis clínicas e estética relacionadas ao comportamento dos tecidos periimplantares ao longo do tempo. Sendo assim, a decisão pela seleção dos componentes para a reabilitação em região estética poderia se basear em aspectos como o custo, fluxo e tempo de trabalho (AU).

The esthetics and stability of the soft tissue and bone around the implant is a critical component to the long-term success of the implant and can be influenced by factors such as the type of prosthetic connections. OBJECTIVE: To compare the behavior of the periimplant tissue of single implant-supported crowns in the anterior aesthetic area using prefabricated titanium prosthetic abutments (GT) and customized zirconia prosthetic abutments (GZ). METHODOLOGY: In this controlled, blinded, non- randomized clinical trial, 30 single cemented crown over anterior implants were sequentially allocated: 15 implants rehabilitated on implant system with a prefabricated titanium prosthetic abutment (GT) and 15 on implant system with customized zirconia prosthetic abutment (GZ). The behavior of the peri- implant tissue was evaluated at T0 (beginning of tissue conditioning), T1 (end of tissue conditioning), T2 (7 days after final cementation), T3 (6 months after final cementation). Visible Plaque Index (VPI), Gingival Bleeding Index (GBI), Bleeding on Probing (BoP), Probing Depth (PD), Interdental Papilla Height/Width Ratio (PH/PW), Keratinized Mucosa Width (KM), Gingival Thickness (PT), Periodontal Phenotype (PF), Gingival Recession (GR), radiographic distance from the bone crest to the contact point and Pink Esthetic Score (PES) were registered. The results were analyzed with the following statistical tests: Friedman, Mann-Whitney and Chi- square/Fisher; Exact test with a significance level of 5%. RESULTS: No statistically significant differences were observed between groups for any of the clinical parameters in any, (p>0.05). However, intragroup analysis showed a statistical reduction in VPI between T1 and T2 only for GZ (p< 0.05). There was a significant decrease between T0 and T3 for GT (1.67 mm - 1.47 mm in GT, and 1.70 mm -1.47 mm in GZ) and increase in the ratio PH/PW (0.56 - 0.80 in GT and 0.70- 0.83 in GZ) in both groups (p<0.0001). PES also increased significantly for both groups (9 ­ 12 in GT and 7 ­ 12 in GZ) from T0 to T1 and remained high in the other periods. CONCLUSION: The results showed that the prosthetic abutments used did not impact differences in clinical and aesthetic variables related to the behavior of peri-implant tissues during the study. Therefore, the decision to select components an aesthetic area should be based on aspects such as cost, workflow and timing (AU).

Técnica endocrown como alternativa restauradora para dentes tratados endodonticamente: relato de caso clínico / Endocrown technique as a restorative alternative for endodontically treated teeth: a case report

Este trabalho teve como objetivo apresentar um relato de caso clínico de uma restauração do tipo coroa endocrown cerâmica em um dente molar tratado endodonticamente. Paciente com 45 anos de idade, sexo feminino, procurou a clínica do Centro Universitário da Serra Gaúcha (FSG) relatando a necessidade de reabilitação protética no primeiro molar inferior do lado esquerdo. Com base no exame radiográfico e exame clínico foi constatado um primeiro molar inferior do lado esquerdo com tratamento endodôntico satisfatório, mas uma extensa destruição coronária. Após a aprovação da paciente e indicações para a utilização da técnica, optou-se pela confecção de uma coroa endocrown em cerâmica reforçada por dissilicato de lítio. Foi realizado o preparo do remanescente dentário, envolvendo a câmara pulpar, com ângulos arredondados e expulsivos e, após a moldagem do mesmo com silicone de adição, utilizando a técnica simultânea e duplo fio. O provisório foi realizado com resina quimicamente ativada na cor 62 e, na sessão seguinte a coroa endocrown foi ajustada e polida. Após receber o protocolo de condicionamento adequado da peça, a mesma foi cimentada com cimento autopolimerizável Multilink N. Pode-se concluir que a alternativa restauradora Endocrown é um tratamento conservador e favorável para dentes com extensa destruição coronária, permitindo adequada estética e função(AU)

This study aimed to present a clinical case report of an endocrown ceramic crown restoration in na endodontically treated molar tooth. A 45-year-old female patient sought the clinic at the Centro Universitário da Serra Gaúcha (FSG), reporting the need for prosthetic rehabilitation on the lower left first molar. Based on the radiographic and clinical examination, the first molar presented satisfactory endodontic treatment, but extensive coronary destruction. After the approval of the patient and indications for the use of the technique, it was decided to make an endocrown with reinforced ceramic by lithium disilicate. The remaining tooth was prepared, involving the pulp chamber, with rounded and expulsive angles and, after the impression with silicone using the simultaneous and double wire technique was taken. The provisional was made with chemically activated resin in color 62 and, in the following session, the endocrown crown was adjusted and polished. After receiving the proper conditioning protocol, it was lutted with Multilink N self-curing cement. It can be concluded that the Endocrown restorative alternative is a conservative and favorable treatment for teeth with extensive coronary destruction, allowing adequate aesthetics and function(AU)

Esthetic evaluation of conventional and socket shield technique immediate implant restoration / 中华口腔医学杂志

Objective: To evaluate the pink and white esthetics of conventional and socket shield technique (SST) immediate implant restoration. Methods: Thirty volunteers were recruited according to preset criteria, and were assigned to 3 groups. Natural teeth group (ten undergraduates or postgraduates from Peking University School and Hospital of Stomatology in January 2020, n=10): all volunteers' maxillary anterior teeth were natural teeth with healthy gingiva, and none of the teeth were restored by crowns or composite. Conventional group and SST group (patients had a maxillary central incisor immediate implant placed in Department of Prosthodontics, Peking University School and Hospital of Stomatology during October 2016 to January 2021, n=10 for each group): the volunteer had an unrestored natural maxillary central incisor, and the contralateral maxillary central incisor was restored by conventional or SST immediate implant placement, temporization and all ceramic final restoration, photos were taken 12 months post-surgery. Three groups of evaluators namely layperson (staff from Second Clinical Division of Peking University School and Hospital of Stomatology and 2 family members, n=10), dental students (class 2015 undergraduates from Peking University School and Hospital of Stomatology, n=10) and prosthodontists (from Department of Prosthodontics, Peking University School and Hospital of Stomatology, n=10) were invited to assess the esthetics using pink esthetic score (PES) and white esthetic score (WES). The results were statistically analyzed. Results: PES and WES of natural teeth group [9(8, 10) and 8(7, 10)] were significantly higher than conventional group [7(6,8) and 7(6,9)] (H=287.08, 132.79,P<0.01) and SST group [7(6, 9) and 8(7, 9)] (H=216.01, 101.21, P<0.01). SST group yielded higher PES than the conventional group (H=-71.06, P<0.01), yet had similar WES (H=-31.57, P>0.05). Dental students had significant lower PES and WES than prosthodontists (H=-120.90, -218.86, P<0.01) and layperson (H=-109.55, 134.97, P<0.01). Prosthodontists and layperson got similar PES (H=-11.36, P>0.05), however yielded different WES (H=-83.89, P<0.01). Conclusions: SST immediate implant placement obtained better pink esthetics than conventional protocol 12-month after implant surgery, profession may have significant impact on evaluators during pink and white esthetic evaluation.

Clinical outcome of single posterior implant-supported monolithic zirconia crowns fabricated using full digital workflow and conventional workflow: a 3-year follow-up / 中华口腔医学杂志

Objective: To compare the clinical performance of posterior single implant-supported monolithic zirconia crowns fabricated by full digital workflow and that of those fabricated by conventional workflow. Methods: This is prospective clinical research. Thirty-five patients who participated in a previous study during August 2017 to October 2018 at Department of Prosthodontics, Peking University School and Hospital of Stomatology were included in this 3-year follow-up study. The 35 patients, 17 females and 18 males, aged (49.0±15.4) years (24-86 years old), was allocated into two groups. In the full digital workflow group, intraoral scanning was taken immediately after implant placement, and a full zirconia implant crown was fabricated using model-free computer aided design/computer aided manufacturing (CAD/CAM) procedure (n=14). In the conventional group, a conventional impression was taken 3 months after implant placement and the stone model was produced. A full zirconia implant crown was fabricated using conventional model-based procedure (n=21). Three years following crown delivery, all the prostheses were evaluated in the aspect of color, surface roughness, contour and marginal integrity using modified US Public Health Service criteria (MUSPHS criteria). The soft and hard tissue around implant was evaluated using modified plaque index, probing depth (PD), number of implants with bleeding on probing, marginal bone loss (MBL). The biological and mechanical complication were also recorded. Statistical analysis was performed using independent samples t test, Mann-Whitney U test and Fisher's exact test. Results: The total survival rate of prosthesis and implant was 100% (35/35). No significant difference in MUSPHS criteria ratings on color, surface roughness, contour and marginal integrity of these crowns were found between the full digital workflow group and the conventional group (P>0.05). Sixteen out of the 35 crowns had a contour score of B due to loss of interproximal contact. Ten out of the 35 crowns had the screw hole sealing resin sinking or falling off, four in the full digital workflow group and six in the conventional group. There was no significant difference in the rate of prostheses mechanical complications between the two groups (P=1.000). For all the implants, there was no significant difference in MBL, PD, the modified plaque index, and number of implants with bleeding on probing between the two groups (U=119.50,133.00,142.50, t=-0.53, P>0.05). Conclusions: The clinical performance of implant-supported posterior single monolithic zirconia crowns fabricated by full digital workflow was stable. There was no significant difference in the clinical performance of the single implant crowns between the full digital workflow group and the conventional group.

Design of non-metallic crown for primary molars and analyzation of stress distribution: a finite element study / 中华口腔医学杂志

Objectives: To study the design of nonmetallic crowns for deciduous molars by means of computer aided design and to analyze the key parameters of the nonmetallic crowns of deciduous molars using finite element method. Methods: The three-dimensional model of a mandibular second primary molar was constructed by using a micro-CT system. The thickness of the crown was limited to 0.5 mm and four different crown shapes (chamfer+anatomic, chamfer+non-anatomic, knife edge+anatomic and knife edge+non-anatomic) were designed. Then, the crown shape was limited as chamfer+non-anatomic and five different thicknesses of the crown (0.50, 0.75, 1.00, 1.25, 1.50 mm) were designed, and three different materials, including polyetherketoneketone (PEKK), polymethylmethacrylate (PMMA) resin and resin-infiltrated ceramic, were applied to make the crown. Stress distribution and fatigue of each component of the model under vertical and oblique loadings were analyzed by using finite element method. Non-axial retention analysis was performed on chamfer+non-anatomic crowns, made of PMMA resin, with thicknesses of 0.50, 0.75, 1.00, 1.25 and 1.50 mm. Results: Among the four crown shape designs, the chamfer+non-anatomic type crown showed the lowest von Mises stress and the highest safety factor. By comparing three different materials, the resin-infiltrated ceramic group showed obvious stress concentration on the buccal edge of the crown and the PEKK group showed stress concentration in the adhesive layer. Results of non-axial retention analysis showed that the torques required by the crowns with five thicknesses at the same rotation angle were as follows: 4 856.1, 4 038.1, 3 497.3, 3 256.3 and 3 074.3 N⋅m, respectively. The comparison of areas of the adhesives fracture among groups were as follows: 0.5 mm group < 0.75 mm group < 1.00 mm group < 1.25 mm group < 1.50 mm group. Conclusions: In the design of nonmetallic crowns for primary molars, the edge of the crown should be designed as chamfer, the shape of the inner crown should be non-anatomical and the minimum preparation amount of the occlusal surface should be 1.00 mm. Among the three materials, PMMA resin, of which elastic modulus is similar to the dentin and the dental adhesive, might be the most suitable material for the crowns of primary molars.

Initial establishment of digital reference standardized crown models of the primary teeth / 北京大学学报(医学版)

OBJECTIVE@#To explore the construction process of the digital reference crown models, and to initially establish the digital reference crown models of the primary teeth to lay the foundation for the establishment of the standardized crown models and the future related applications of computer-aided design/computer-aided manufacture (CAD/CAM) technology to pediatric dentistry.@*METHODS@#This study randomly selected children who were caries free, aged from 4 to 5 years in several kindergartens of Haidian District of Beijing.Plaster dental models were made for the children after taking complete impressions.The digital dental models were reconstructed by using the three-dimensional (3D) dental model scanner.And then, Geomagic Studio, a 3D reverse engineering software, was employed to extract the single dental crown data, the mesiodistal and buccolingual diameters and the height of the crowns were measured.The object was reduced or enlarged by a numerical factor, and then the size of each dental crown was standardized.A total of 3-5 points features on the crown were created, and all the objects were aligned through the functions of feature-based alignment.Finally, through average-based object creation and smoothing, the digital models of reference crowns of the primary teeth were established.@*RESULTS@#A total of 40 plaster dental models from 16 boys and 26 girls were selected out for our further study.The digital dental models were reconstructed, and the mesiodistal and buccolingual diameters and the height of the crowns were measured by using reverse engineering technology.Comparing the results of using mesiodistal diameter, buccolingual diameter and height as the standards, we chose the mesiodistal diameters of crowns to do the standardization, and successfully established the digital reference models of 20 primary teeth crowns with detailed surface characteristics.@*CONCLUSION@#In this study, the digital reference crown models of the primary teeth were established by reverse engineering technology, providing reference value for the standardized crown models and application for clinical practice, scientific research and teaching.Furthermore, this study also contributes to the extensive application of CAD/CAM technology in pediatric dentistry and the development of CAD/CAM dental systems with independent intellectual property rights.

Percepção e conhecimento de odontopediatras sobre o uso de coroas pré-fabricadas de aço e zircônia na reabilitação de dentes decíduos / Perception and knowledge of pediatric dentists about the use of prefabricated steel and zirconia crowns in the rehabilitation of deciduous teeth

Objetivo: O presente trabalho tem como objetivo avaliar o conhecimento dos odontopediatras e suas percepções, conhecendo as dificuldades que estes encontram frente ao desafio da reabilitação de dentes decíduos. Métodos: A pesquisa foi realizada por meio da aplicação de questionários on-line e a análise estatística foi descritiva e comparativa, com tabelas de frequência para as variáveis quantitativas. O teste não paramétrico de Qui-quadrado foi utilizado para estimar a associação entre as diferentes categorias dos dados e em todo o estudo, estipulou-se o nível de significância em 5%. Resultados: Os resultados da pesquisa mostraram que a maioria dos entrevistados conhecem as coroas pré-fabricadas de aço, porém sua aplicação em atendimentos de crianças com extensas destruições coronárias limita-se a 34,1% destes profissionais, sendo que a baixa utilização se deve à dificuldade de aquisição do material e falta de habilidade técnica. Já com relação às coroas pré-fabricadas de zircônia, 82,4% das odontopediatras as conhecem, mas a grande maioria não as utiliza devido à dificuldade de aquisição, falta de habilidade técnica e o seu alto custo. Não foi encontrada associação entre a dificuldade de planejamento dos casos e a consideração estética e o âmbito de trabalho do entrevistado, bem como o fato de conhecer as coroas pré-fabricadas e utilizá-las. Conclusão: Conclui-se que os materiais reabilitadores, como coroas pré-fabricadas de aço e de zircônia, são de certa forma bem conhecidos pelos odontopediatras, mas sua utilização em reabilitação de dentes decíduos ainda é limitada.

Aim: The present study aims to evaluate the knowledge of pediatric dentists and their perceptions, knowing the difficulties they face in the challenge to rehabilitate deciduous teeth. Methods: This study was carried out through the application of online questionnaires. The statistical analysis was descriptive and comparative, with frequency tables for the quantitative variables. The non-parametric chi-square test was used to estimate the association between the different categories of data, and the significance level was set at 5%. Results:The survey results showed that most respondents know about prefabricated steel crowns, but their application in the care of children with extensive coronary destruction is limited to 34.1% of these professionals. The low use is due to the difficulty of acquiring the material and the lack of technical skills. It was found that 82.4% of the pediatric dentists have knowledge about prefabricated zirconia crowns, but the vast majority do not use them due to the difficulty of acquisition, their lack of technical skills, and the product's high cost. No association was found between the difficulty of planning the cases and the esthetic consideration and sphere of work of the interviewee, nor regarding the fact of their having knowledge about the prefabricated crowns and using them. Conclusion: It can therefore be concluded that rehabilitation materials, such as prefabricated steel and zirconia crowns, are well-known by pediatric dentists, but their use in the rehabilitation of deciduous teeth is still limited.