Dentists' Perception and Clinical Use of Preformed Metal Crowns to Restore Primary Molar Defects in Chengdu City, China: A Cross-Sectional Study.

BACKGROUND: Preformed metal crowns (PMCs), as an effective technique recommended for the enduring restoration of primary molar defects, have not been widely implemented in China as well as that in Western countries. This study is aimed at assessing the knowledge on the clinical use of the PMC technique and its effective factors among dentists in Chengdu, China. Thus, the present study is aimed at providing the best available evidence on clinical decision-making to manage dental caries in children and the overall benefits. METHODS: The self-designed questionnaire in this study consisted of two main sections, including the sociodemographic characteristics of the respondents and their perception and use of PMCs. The anonymous questionnaire was distributed among 1000 dentists practicing in Chengdu via SO JUMP. RESULTS: The response rate was 45%. Most respondents (69.6%) did not use PMCs. Academic qualification, working specialty, and professional experience were associated with dentists' use of PMCs. The lack of knowledge about the PMC technique was the main obstacle to the dental practitioners' use of PMCs (41.7%). The lack of understanding of the rationale behind PMCs was the main reason for parents' acceptance of PMC restorations (43.6%). Attending continuing education programs was the main approach to learning the PMC restorative technique (59.1%). CONCLUSIONS: The clinical use of PMCs was not very popular in Chengdu city. To promote this restorative technique, knowledge and practical training should be incorporated into routine courses of undergraduate dental education.

Effect of elasticity on stress distribution in CAD/CAM dental crowns: Glass ceramic vs. polymer-matrix composite.

OBJECTIVES: Further investigations are required to evaluate the mechanical behaviour of newly developed polymer-matrix composite (PMC) blocks for computer-aided design/computer-aided manufacturing (CAD/CAM) applications. The purpose of this study was to investigate the effect of elasticity on the stress distribution in dental crowns made of glass-ceramic and PMC materials using finite element (FE) analysis. METHODS: Elastic constants of two materials were determined by ultrasonic pulse velocity using an acoustic thickness gauge. Three-dimensional solid models of a full-coverage dental crown on a first mandibular molar were generated based on X-ray micro-CT scanning images. A variety of load case-material property combinations were simulated and conducted using FE analysis. The first principal stress distribution in the crown and luting agent was plotted and analyzed. RESULTS: The glass-ceramic crown had stress concentrations on the occlusal surface surrounding the area of loading and the cemented surface underneath the area of loading, while the PMC crown had only stress concentration on the occlusal surface. The PMC crown had lower maximum stress than the glass-ceramic crown in all load cases, but this difference was not substantial when the loading had a lateral component. Eccentric loading did not substantially increase the maximum stress in the prosthesis. CONCLUSIONS: Both materials are resistant to fracture with physiological occlusal load. The PMC crown had lower maximum stress than the glass-ceramic crown, but the effect of a lateral loading component was more pronounced for a PMC crown than for a glass-ceramic crown. CLINICAL SIGNIFICANCE: Knowledge of the stress distribution in dental crowns with low modulus of elasticity will aid clinicians in planning treatments that include such restorations.

Influence of preparation design on fit and ceramic thickness of CEREC 3 partial ceramic crowns after cementation.

OBJECTIVE: This study investigated the influence of preparation design on the marginal and internal gap and ceramic thickness of partial ceramic crowns (PCCs) fabricated with the CEREC 3 system. MATERIALS AND METHODS: Sixteen extracted human mandibular molars were prepared according to two different preparation designs (n = 8): a retentive preparation design with traditional cusp capping (Group I) and a non-retentive preparation design with horizontal reduction of cusps (Group II). PCCs were fabricated from IPS Empress CAD with the CEREC 3 system. The parameters for luting space and minimum occlusal ceramic thickness were set to 30 µm and 1.5 mm, respectively. The fabricated PCCs were cemented to their corresponding teeth with self-adhesive resin cement and were then scanned by micro-computed tomography. The marginal and internal gaps were measured at pre-determined measuring points in five bucco-lingual and three mesio-distal cross-sectional images. The ceramic thicknesses of the PCCs were measured at the measuring points for cusp capping areas. RESULTS: Group II (167.4 ± 76.4 µm) had a smaller overall mean gap, which included the marginal and internal gap measurements, than that of Group I (184.8 ± 89.0 µm). The internal gaps were larger than the marginal gaps, regardless of preparation design. Group I presented a thinner ceramic thickness in the cusp capping areas than the minimum occlusal ceramic thickness parameter of 1.5 mm. CONCLUSION. Preparation design had an influence on fit, particularly the internal gap of the PCCs. Ceramic thickness could be thinner than the minimum ceramic thickness parameter.

Using dental students' preclinical performance as an indicator of clinical success.

The purpose of this study was to evaluate part of one dental school's predoctoral curriculum by investigating correlations between students' final grades in two preclinical courses and their performance in the related clinical courses. The sample consisted of 301 students at Tufts University School of Dental Medicine who graduated in 2010 and 2011. All final grades used as data were obtained from the Registrar's Office and evaluated anonymously. The average preclinical final grades differed significantly for students in the 2010 (M=84.92, SD=3.35) and 2011 (M=79.67, SD=4.67) classes, as did their average clinical final grades (2010: M=88.38, SD=2.13; 2011: M=87.45, SD=2.06). The data for each class were therefore examined separately. Results showed that the correlation between students' preclinical grades and clinical grades in operative dentistry and fixed prosthodontics was statistically significant (2010: r(2)=0.144, p<0.001; 2011: r(2)=0.261, p<0.001). This finding suggests there may be a positive relationship between preclinical and clinical performance of these students; however, the discrete factors contributing to that relationship were not investigated in this study and require further research.

Effect of the crown, post, and remaining coronal dentin on the biomechanical behavior of endodontically treated maxillary central incisors.

STATEMENT OF PROBLEM: It is unclear how the amount of remaining coronal dentin and the type of post and core rehabilitation affect the strain, stress distribution, and fracture resistance of endodontically treated teeth. PURPOSE: The purpose of this study was to evaluate the effects of the type of post, type of crown, and the amount of remaining coronal dentin on the biomechanical behavior of endodontically treated teeth. MATERIAL AND METHODS: The investigation was conducted by using 3-dimensional finite element analysis and laboratory tests. Three-dimensional models of a maxillary central incisor were generated: without remaining coronal dentin, with 1.0 mm of remaining coronal dentin, with 2.0 mm of remaining coronal dentin, and restored with a glass-fiber post or a cast post and core in combination with a metal crown or an alumina-reinforced ceramic crown. The results were evaluated by using the von Mises criterion and Maximum Principal Stress. One hundred twenty bovine incisors were selected and divided into 12 treatment groups (n=10). Specimens were loaded at a 135-degree angle to perform strain measurements and were then loaded until fracture. The strain and fracture resistance results were analyzed with 3-way analysis of variance and the Tukey honestly significant difference test (α=.05). RESULTS: The alumina-reinforced ceramic crowns and metal crowns associated with a glass-fiber post showed a homogeneous stress distribution within the root. The cast post and core concentrated higher stresses at the post-dentin interface. Significant differences were found among the mean fracture resistance values for all groups (P<.05). The presence of 2.0 mm of coronal remnants resulted in lower strains and higher fracture resistance for both the metal and ceramic crowns. Roots restored with glass-fiber posts exhibited more favorable fractures. CONCLUSIONS: The presence of 2 mm of remaining coronal dentin improved the mechanical behavior of the endodontically treated maxillary incisors. Teeth restored with glass-fiber posts and composite resin cores showed a homogeneous stress distribution within the root dentin.

Influence of coronal restorations on the fracture resistance of root canal-treated premolar and molar teeth: a retrospective study.

To evaluate the influence of coronal restorations on the fracture resistance of endodontically treated teeth, 676 root canal-filled and restored posterior teeth were evaluated after a mean period of 9.7 (± 2.8; minimum: 5) years. A total of 86.2% of the endodontically treated and restored teeth survived the mean observation period of 9.7 years without fracture. The overall survival period was 13.6 (± 0.2) years. All teeth with gold partial crowns survived without fractures (n = 24). Teeth with crowns and adhesively sealed access cavities showed a mean survival period of 15.3 (± 0.4) years, with crown and bridge restorations 14.0 (± 0.3), with individual metal posts 13.9 (± 0.2), with composite fillings 13.4 (± 0.5), with prefabricated metal posts 12.7 (± 0.6), with amalgam fillings 11.8 (± 0.6) and with glass ionomer cements (GIC) 6.6 (± 0.5) years. Teeth with one or two surfaces restored by amalgam, composite or GIC showed a significantly lower fracture rate than teeth with three and more restored surfaces (P < 0.05). The mean fracture rate of teeth restored with GIC was significantly higher when compared with all other groups (P < 0.001). In general, endodontically treated teeth restored with prosthetic restorations demonstrated a significantly lower mean fracture rate than teeth restored with fillings. Cavities with up to three surfaces may well be successfully restored adhesively with composite filling material.

Rasgos morfológicos y métricos dentales coronales de premolares superiores e inferiores en escolares de tres instituciones educativas de Cali, Colombia / Morphologics and metric dental crown traits of upper and lower premolars in scholars of Cali, Colombia

El objetivo de este trabajo fue determinar la frecuencia y variabilidad de doce rasgos morfológicos dentales coronales y de dos rasgos métricos dentales coronales en los primeros y segundos premolares superiores (UP1/UP2) e inferiores (LP1/LP2) de 112 modelos de yeso obtenidos de una muestra de jóvenes escolares del municipio de Santiago de Cali. Se trata de un estudio descriptivo transversal cuantitativo que evaluó doce rasgos morfológicos dentales coronales mediante los sistemas ASUDAS (Arizona State University Dental Anthropology System): cresta accesoria mesial, cresta accesoria distal y premolar tricúspide; Higa et al.: tubérculos intersticiales mesial y distal; van Reenen et al.: hipostilo, surco vestibular, cresta central, surco meso-lingual y surco disto-lingual; Hillson: número de cúspides linguales y patrón cuspideo. Y dos rasgos métricos dentales coronales, los dißmetros mesio-distal mediante el método de Moorrees et al. y vestíbulo-palatino (lingual) mediante el de Kieser et al. La frecuencia de los rasgos morfológicos y las dimensiones dentales evidencia que los primeros premolares cuentan con una morfología mucho mas simplificada y dimensiones menores (caninización; mientras que los segundos son mucho mas caracterizados y de mayor tamaño (molarización). La frecuencia de los rasgos morfológicos es ambigua, no presentan dimorfismo sexual y cuentan con bilateralidad en su expresión, a excepción del surco meso-lingual. La correspondencia entre los primeros y segundos premolares superiores e inferiores varía en cada rasgo. Las dimensiones dentales presentan bilateralidad y dimorfismo sexual a excepción de los segundos premolares inferiores. El dendograma obtenido sugiere que la muestra consiste en mestizos con características caucasoides, de fuerte influencia negroide y conservación mongoloide.

The objective is determining the frequency and variability, sexual dimorph, bilateral asymmetry and correspondence between twelve non-metric dental traits and two metric dental traits on the first and second upper and lower premolars in dental casts from 110 subjects from a Colombian racially mixed population. In this descriptive and quantitative study, frequency and variability of twelve non-metric dental crown traits were observed, through the ASUDAS (mesial and distal accessory crest and tricuspid premolar), Higa et al. (mesial and distal interstitial tubercle), van Reenen et al. (hypostile, bucal furrow, transverse ridge, meso-lingual furrow and disto-lingual furrow; and Hillson (lingual cusp number and groove pattern). The frequency of the metric and non-metric dental traits demonstrates that the first premolars present a minor dimensions and simplified morphology (caninization); whereas the second premolars ones are many characterized and of major size (molarization). The frequency of the non-metric dental traits is ambiguous; they do not present sexual dimorphism and present bilateral symmetry, with the exception of the meso-lingual furrow. The correspondence between the first and second upper and lower premolars changes in every trait. The dental dimensions present bilateral symmetry and sexual dimorphism with the exception of the second lower premolars. The dendogram suggests that the sample consists in mixed population with Caucasoid characteristics, negroid influence and mongoloid conservation.

Classification system for conventional crown and fixed partial denture failures.

The dental literature is replete with reports on the many aspects of failure encountered with traditional fixed prosthodontic treatment, including longitudinal survival studies of crowns and fixed partial dentures and reasons for failures. However, criteria for grading or classifying the type and severity of these failures are inadequate. A classification system for conventional fixed prosthodontic failures based on severity is presented.

Crowns and other extra-coronal restorations: preparations for full veneer crowns.

Preparations for full veneer crowns is the eighth in the series on crowns and other extra-coronal restorations. Whilst handpiece skills are important, many other factors combine to ensure provision of a satisfactory full veneer crown (also termed 'full coverage crown'). Our aim in writing this article is to consider the principles which influence crown preparation, seasoned with clinical advice our undergraduate and postgraduate students have found useful.

Crowns and other extra-coronal restorations: aesthetic control.

A pleasing dental appearance is the subjective appreciation of the shade, shape and arrangement of the teeth and their relationship to the gingiva, lips and facial features. Achieving such a pleasing appearance in our patients is not always easy but is critical, not least because our work is effectively on display and this has implications for patients' perceptions of our practice. To be successful, thorough assessment, careful planning and precise clinical execution is required. Every bit as important though, is good communication, both with the dental laboratory and particularly with the patient. In few areas of dentistry can effective communication be as critical as it is here.

Coronas de ceramica pura o vitroceramicas / Crowns of dental ceramics pure or glassceramic

Cuando el odontologo realiza una restauracion, cualquiera sea su tipo, siempre se persigue el mismo fin: que esta sea resistente, duradera, funcional y estetica. Cuando se trata de elementos anteriores, la estetica adquiere un plano preponderante, pues sera seguramente la primera inquietud o exigencia que nos expresara el paciente. Frecuentemente, los profesionales nos familiarizamos con un determinado sistema para la confeccion de nuestras restauraciones coronarias, pero este no siempre es el indicado o el adecuado para determinadas situaciones clinicas. Es por ello que el profesional debe conocer y aplicar las diferentes alternativas de tratamiento para adecuarlas e implementarlas en las distintas exigencias clinicas. Este articulo es una recopilacion y descripcion de los sistemas para la confeccion de restauraciones coronarias totalmente ceramicas.

Coronas, sus eventuales falencias y soluciones a las mismas (Parte I) / Crowns, its eventual defects and its solution. (Part I)

Es muy común tener que reemplazar coronas defectuosas, y para este propósito se describen las tecnicas más adecuadas y el instrumental más utilizado. Asimismo, se detallan los pasos a seguir para recuperar coronas cuyos pilares presentaban falencias que pueden ser corregidas