Research progress on the application of Er: YAG laser removing all-ceramic restorations / 口腔疾病防治

@#All-ceramic restorations are widely used in oral restoration because of their beauty and high strength. Glass ceramics and zirconia all-ceramic materials are the two most widely used all-ceramic materials in the clinic. However, when all-ceramic restorations need to be removed due to marginal microleakage and secondary caries, its high strength and high bonding strength greatly increase the difficulty of removal. In recent years, clinicians have tried to use Er: YAG lasers to remove all-ceramic restorations. The Er: YAG laser can be safely and efficiently applied to the removal of glass restorations, and it can also play a role in thinner zirconia restorations. Various factors, such as the material and thickness of the all-ceramic restoration, the type of cement, and the laser power, can affect the speed of removal of the Er: YAG laser. However, the current research is limited to case reports and in vitro studies, lacking systematic clinical research. The specific mechanism of Er: YAG laser removal of all-ceramic restorations and the influence of laser frequency, adhesive type, and abutment on the removal speed need to be further demonstrated by follow-up research.

Root canal treatment of maxillary second molar with three mesial buccal root canals: a case report and literature review / 口腔疾病防治

Objective@#To explore the key points of clinical diagnosis and treatment of three mesiobuccal root canals.@*Methods@# In the procedure of endodontic therapy for the upper left second molar with pulpitis, through root canal exploration under a dental microscope and cone beam CT (CBCT)-assisted imaging examination, it was confirmed that the left upper second molar contained 3 roots and 5 root canals, among which the third root canal existed in the mesiobuccal root. Combined with perfect root canal preparation, cleaning, disinfection, filling and minimally invasive inlay repair, the clinical symptoms were eliminated. The patients were followed up and the related literatures were reviewed. @* Results @# One- and two-year follow-ups showed that the tooth had no discomfort and could be used normally. X-ray revealed that the filling was complete, and the periapical tissue was normal. The results of the literature review showed that the incidence of three mesiobuccal root canals in maxillary second molars was 0.11%-4.2%. It is difficult to find additional root canals only by X-ray imaging. Dentists should further determine the number and anatomical shape of root canals by CBCT and operating microscopy. When there are three mesiobuccal root canals in maxillary molars, dentists should avoid overpreparation. Healthy tooth tissue is the key to good prognosis. @* Conclusion@#During root canal therapy, clinicians should consider the anatomical variation of the root canal, should always be alert to the existence of an extra root canal, and should use CBCT, operating microscopy, ultrasound and various auxiliary instruments to locate and treat the variant root canal.

The effect of different surface treatments on color and translucency of bilayered translucent nano-crystalline zirconia before and after accelerated aging / O efeito de diferentes tratamentos de superfície na cor e translucidez da zircônia de dupla camada nano-cristalina translúcida antes e depois do envelhecimento

Objective: Despite the higher translucency of nanocrystalline Y-TZP than the conventional Y-TZP, it couldn't be used in the anterior region of the mouth in its fully anatomical form without veneering for better esthetics. This study evaluated the color change (ΔE) and translucency parameter (TP) of the bilayered nano-crystalline zirconia restorations after different treatments of the zirconia surface before and after accelerated aging. Material and Methods: Forty samples of inCoris TZI were cut in the form of discs 15 mm (diameter) and 1mm (thickness) so that after sintering each disc dimensions' would be 12 mm (diameter) and 0.8 mm (thickness). All discs were colored by dipping in aqueous zirconia coloring solution of shade A2, then divided into four groups according to the type of surface treatment received before sintering; being tribochemical silica coating, zirconia powder deposition, glass grading, and a control untreated group. After sintering, all discs were veneered with a layer of porcelain 0.7 mm (thickness) and 12 mm (diameter). (ΔE) and TP were measured using VITA Easyshade Compact spectrophotometer before and after accelerated autoclave aging. Results: Different surface treatments applied had significant effect (P<0.05) over ΔE and TP. Glass graded group showed the highest ΔE value and the least TP value among both un-aged and aged sub-groups. Conclusion: Different surface treatments applied affected the color and translucency negatively where the control untreated group showed the highest TP and the least color deviation from the A2 color parameters. On the other hand, accelerated autoclave aging had no effect over translucency or color. (AU)

Objetivo: Apesar da maior translucidez da Y-TZP nanocristalina em relação à Y-TZP convencional, ela não pode ser usada na região anterior da boca em sua forma totalmente anatômica, sem o recobrimento cerâmico para uma melhor estética. Este estudo avaliou a mudança de cor (ΔE)eoparâmetrodetranslucidez(PT)das restauraçõesde zircônia nano-cristalina em duas camadas após diferentes tratamentos de superfície, antes e após o envelhecimento. Material e Métodos: Quarenta amostras de inCoris TZI foram cortadas na forma de discos de 15 mm (diâmetro) e 1 mm (espessura) para que, após sinterização, cada diâmetro dos discos fosse de 12 mm (diâmetro) e 0,8 mm (espessura). Todos os discos foram corados por imersão em solução aquosa de zircônia corante da sombra A2, divididos em quatro grupos de acordo com o tipo de tratamento de superfície recebido antes da sinterização; sendo revestimento de sílica químico-química, deposição de pó de zircônia, jateamento de vidro e um grupo de controle sem tratamento. Após a sinterização, todos os discos foram revestidos com uma camada de porcelana de 0,7 mm (espessura) e 12 mm (diâmetro). ΔE e TP foram medidos usando o espectrofotômetro VITA Easyshade Compact antes e depois do envelhecimento em autoclave. Resultados: Diferentes tratamentos de superfície aplicados tiveram efeito significativo (P <0,05) sobre ΔE o e maior TP. valor O grupo com de ∆E e o menor jateamento de vidro valor de TP apresentou entre os subgrupos não envelhecidos e envelhecidos. Conclusão: Diferentes tratamentos de superfície aplicados afetaram negativamente a cor e a translucidez, onde o grupo controle sem tratamento apresentou o maior TP e o menor desvio de cor dos parâmetros de coloração A2. Por outro lado, o envelhecimento acelerado da autoclave não teve efeito sobre a translucidez ou a cor. (AU)

Numerical Study on Effects of Different Adhesive Materials for Ceramic Restoration on Stress Distributions / 医用生物力学

Objective To investigate the effect of different adhesive materials on all-ceramic restoration. Methods The all-ceramic restoration system model of mandibular first molar was established by spiral computed tomography (CT) scanning and computer-aided design (CAD) modeling. Four types of resin adhesive materials (Duo Cement,Lute-It,Rely-X ARC,Variolink II) used in clinics were selected, and the stress distribution was calculated using the ABAQUS software. Results The stress at the bonding interface was the highest when low filler adhesive Lute-It was used. Based on the viscoelasticity analysis, resin adhesives with a larger storage modulus and loss modulus could yield lower stress extremes. Conclusions The study suggests that high-filler type resin adhesives with a large energy storage modulus and loss modulus should be used clinically.

Analysis of reasons for failure of chair-side CAD/CAM ceramic restorations / 口腔疾病防治

Objective@#To investigate the failure reasons of all-ceramic restorations fabricated with chair-side CAD-CAM technology (CEREC®) and to improve the clinical survival of all-ceramic restorations. @*Methods @#All-ceramic single-tooth restorations of CEREC® in stomatology hospital of Jiangsu province between 2013 and 2016 were summarized. By clinical examination and CEREC Biogeneric surveying, the failure reasons and related restoration types were evaluated. These results were analyzed with Chi-square test and Spearman correlation analysis. @*Results@#A total of 61 cases with restoration types of 11 inlays, 38 onlays, 2 endocrowns, and 11 all-crowns, resulted in a failure rate of 5.4% in all-ceramic single-tooth restorations in 1-4 years follow-up. The reasons for failure included ceramic fracture (n=33), debonding (n=13), tooth fracture (n=15), which attributed to thin ceramic thickness (n=27), acute line angle (n=6), insufficient enamel bulk (n=3), insufficient retention type (n=10), insufficient resistance type (n=15).@*Conclusion @# The most common reason for failure in CEREC® restorations was insufficient preparation space in occlusal surface.

Esthetic rehabilitation with minimally invasive feldspathic ceramic veneers: 30 months of clinical follow-up / Reabilitação estética com facetas em cerâmicas feldspáticas minimamente invasivas: 30 meses de acompanhamento clínico

Diastemas among maxillary incisors and gingival contour disharmony are common findings among patients in dental practice. Ceramic veneers are indicated for esthetic rehabilitation of anterior diastemas due their predictable results, optical characteristics, fracture resistance and tooth structure conservation. However, because it is a friable material and have a brittle behavior, fractures occurrences are related to trauma, oclusal overload, parafunctional habits and material fatigue. This article describes 30 months follow-up of an esthetic and functional rehabilitation diastemas closure using feldspathic veneers associated with periodontal surgery and a ceramic repair with composite resin. Gingivectomy and frenectomy needs were found and the surgical procedures performed guided by new anatomic aspects of the crowns. Mock-up was performed after waxing and reverse planning. All anterior teeth underwent minimally invasive preparation. Feldspathic ceramic veneers were made, tried using try in paste and luted with light-cure resin cement. After 24 months, a fracture occurred on the right maxillary canine veneer. The ceramic restoration repair was performed with nano-hybrid composite resin, after the conditioning with 5% hydrofluoric acid, 37% phosphoric acid and silane couple agent. The combination between ceramic veneers and gingivectomy enables to obtain conservative treatments and esthetic success. After six months of the repair, resulting 30 months of follow-up, the anterior restorations were aesthetically and functionally satisfactory.

Presença de diastemas entre os incisivos superiores e desarmonia do contorno gengival são achados comuns entre os pacientes atendidos na rotina clínica. Facetas cerâmicas são indicadas para reabilitação estética de diastemas anteriores devido a previsibilidade de resultados, características óticas, resistências à fratura e conservação de estrutura dentária. Entretanto, por este ser um material frágil e apresentar comportamento friável, fraturas podem estar relacionadas a episódios de trauma, sobrecarga oclusal, hábitos parafuncionais e fadiga do material. Este artigo descreve um acompanhamento clínico de 30 meses de reabilitação estética e funcional de fechamento de diastema utilizando facetas minimamente invasivas confeccionadas com cerâmicas feldspáticas associadas à cirurgia periodontal e necessidade de reparo da cerâmica com resina composta. A indicação de plastia gengival e frenectomia foram constatadas e o procedimento cirúrgico guiado pelo planejamento da nova anatomia das coroas dentárias. Todos os dentes anteriores superiores foram minimamente preparados. O mock-up foi realizado depois do enceramento e do planejamento reverso. Facetas em cerâmicas feldspáticas foram confeccionadas, a cor do cimento resinoso selecionada com pastas testes e a cimentação concluída com cimento de polimerização exclusiva física. Depois de 24 meses de acompanhamento, ocorreu fratura da faceta do canino superior direito. O reparo da restauração cerâmica foi realizado com resina nanohibrida, depois da cerâmica condicionada com ácido fluorídrico 5%, ácido fosfórico 37% e aplicação de agente de união silano. A combinação entre facetas cerâmicas e cirurgia de plastia gengival permite alcançar tratamento conservador e sucesso estético. Posteriormente seis meses do reparo, resultando em 30 meses de acompanhamento clínico, as restaurações anteriores permaneciam estética e funcionalmente satisfatórias.

The effect of IDS (immediate dentin sealing) on dentin bond strength under various thermocycling periods

PURPOSE: The purpose of this study was to find out the effect of immediate dentin sealing (IDS) on bond strength of ceramic restoration under various thermocycling periods with DBA (dentin bonding agent system). MATERIALS AND METHODS: Fifty freshly extracted human mandibular third molars were divided into 5 groups (1 control and 4 experimental groups) of 10 teeth. We removed enamel layer of sound teeth and embedded them which will proceed to be IDS, using All Bond II. A thermocycling was applied to experimental groups for 1, 2, 7, 14 days respectively and was not applied to control group. IPS Empress II for ceramic was acid-etched with ceramic etchant (9.5% HF) and silane was applied. Each ceramic disc was bonded to specimens with Duo-link, dual curable resin cement by means of light curing for 100 seconds. After the cementation procedures, shear bond strength measurement and SEM analysis of the fractured surface were done. The data were analyzed with a one-way ANOVA and Tukey multiple comparison test (alpha=.05). RESULTS: There were no statistically significant differences between 4 experimental groups and control group, however the mean value started to decrease in group 7d, and group 14d showed the lowest mean bond strength in all groups. Also, group 7d and 14d showed distinct exposed dentin and collapsed hybrid layer was observed in SEM analysis. CONCLUSION: In the present study, it can be concluded that ceramic restorations like a laminate veneer restoration should be bonded using resin cement within one week after IDS procedure.

Clinical Study of Chair-side Immediate Ceramic Restoration Technique for Large-defected Teeth / 中国医科大学学报

Objective To explore the clinical application of digital chair?side immediate all?ceramic restoration system,design and fabricate inlays and onlays to restore the large?defected molars,and to analyze and evaluate the efficacy of this clinical restoration. Methods Totally 84 inlays and 65 onlays were fabricated with IPS e.max CAD series ceramic blocks by using Cerec AC system to conduct immediate all?ceramic restorations of 149 teeth for 108 patients. The inlays and onlays were applied and cemented to the prepared teeth with dual?cured resin luting agent. The restored molars were re?examined by two dentists after six months. The analysis standard was based on the United States Public Health Service(USPHS criteria) and the results were statistically analyzed(α=0.05). Results There was no statistically significant difference in the case numbers of grade A and grade B for each index comparing the immediate condition to the condition after 6 months. Over 90 percent of ceramic inlays and onlays were quali?fied to be grade A. The restorations were well in the aspects of anatomic morphology,marginal integrity,color match,marginal discoloration,reten?tion,gingival health and secondary caries. Conclusion Computer aided design/computer aided manufacture(CAD/CAM)system combined with machinable glass ceramics can achieve a favorable result in restoration of large?defected teeth. Digital chair?side immediate all?ceramic restoration technique is an ideal solution for large?defected tooth restoration.

Evaluation of the color reproducibility of all-ceramic restorations fabricated by the digital veneering method

PURPOSE: The objective of this study was to evaluate the clinical acceptability of all-ceramic crowns fabricated by the digital veneering method vis-a-vis the traditional method. MATERIALS AND METHODS: Zirconia specimens manufactures by two different manufacturing method, conventional vs digital veneering, with three different thickness (0.3 mm, 0.5 mm, 0.7 mm) were prepared for analysis. Color measurement was performed using a spectrophotometer for the prepared specimens. The differences in shade in relation to the build-up method were calculated by quantifying DeltaE* (mean color difference), with the use of color difference equations representing the distance from the measured values L*, a*, and b*, to the three-dimensional space of two colors. Two-way analysis of variance (ANOVA) combined with a Tukey multiple-range test was used to analyze the data (alpha=0.05). RESULTS: In comparing means and standard deviations of L*, a*, and b* color values there was no significant difference by the manufacturing method and zirconia core thickness according to a two-way ANOVA. The color differences between two manufacturing methods were in a clinically acceptable range less than or equal to 3.7 in all the specimens. CONCLUSION: Based on the results of this study, a carefully consideration is necessary while selecting upper porcelain materials, even if it is performed on a small scale. However, because the color reproducibility of the digital veneering system was within the clinically acceptable range when comparing with conventional layering system, it was possible to estimate the possibility of successful aesthetic prostheses in the latest technology.

Bond and fracture strength of metal-ceramic restorations formed by selective laser sintering

PURPOSE: The purpose of this study was to compare the fracture strength of the metal and the bond strength in metal-ceramic restorations produced by selective laser sintering (SLS) and by conventional casting (CAST). MATERIALS AND METHODS: Non-precious alloy (StarLoy C, DeguDent, Hanau, Germany) was used in CAST group and metal powder (SP2, EOS GmbH, Munich, Germany) in SLS group. Metal specimens in the form of sheets (25.0 x 3.0 x 0.5 mm) were produced in accordance with ISO 9693:1999 standards (n=30). To measure the bond strength, ceramic was fired on a metal specimen and then three-point bending test was performed. In addition, the metal fracture strength was measured by continuing the application of the load. The values were statistically analyzed by performing independent t-tests (alpha=0.05). RESULTS: The mean bond strength of the SLS group (50.60 MPa) was higher than that of the CAST group (46.29 MPa), but there was no statistically significant difference. The metal fracture strength of the SLS group (1087.2 MPa) was lower than that of the CAST group (2399.1 MPa), and this difference was statistically significant. CONCLUSION: In conclusion the balling phenomenon and the gap formation of the SLS process may increase the metal-ceramic bond strength.

The influence of cervical collar height on the compressive strength of CAD/CAM zirconia-ceramic restora-tion / 实用口腔医学杂志

Objective:To evaluate the influence of cervical collar height on the compressive strength of CAD/CAMzirconia-ceramic restoration.Methods:Zirconia cores were manufactured and divided into 5 groups (n =1 0)based on the cervical collar height(mm):0.0(A),1 .0(B),1 .5(C),2.0(D)and 2.5(E).After veneered with porcelain,all the samples were cemented on the metal tooth analog and then mounted in an universal test machine.The force was applied at a crosshead speed of 1 mm/min until catastrophic fail-ure occurred.Fracture loads and failure modes were recorded.Results:Mean of the fracture strength values(kN)in group A,B,C, D and E were 0.95 ±0.39,1 .29 ±0.50,1 .54 ±0.28,2.04 ±0.1 9 and 2.27 ±0.53 respectively(among groups,P <0.05).Two types of fracture modes were observed:chipping of the veneering porcelain and fracture of the veneering porcelain together with the framework.Conclusion:Zirconia coping design with 1 .5 mm cervical collar height may increase the compressive strength of CAD/CAMzirconia-ceramic restoration.

Impact of rehabilitation with metal-ceramic restorations on oral health-related quality of life

Dental ceramics present excellent ability to reproduce the natural teeth regarding esthetic and biomechanics. Recently, due to the advancement of ceramic technology, metal-free restorations were developed. However, the traditional metal-ceramic restorations still present the requirements of high strength, long survival in the oral environment and favorable aesthetics. In this context, it is essential to know the specificity of each ceramic system available in order to apply it properly to various clinical situations. This report describes an integrated rehabilitation using metal-ceramic restorations of a patient at 50 years of age, who presented edentulous spaces, and previous unsatisfactory composite and amalgam restorations, and indirect metallic restorations, leading to compromised quality of life in both functional and psychosocial aspects. The impact on quality of life was measured using a generic instrument, OHIP-14, validated for the World Health Organization, which covers both the biological and the psychosocial dimensions. This instrument was applied to the patient before and after treatment. The patient had an overall OHIP-14 score of 28 before the treatment and after treatment the score decreased to 0, showing that dental and oral health conditions are factors that do impact on the quality of life. Rehabilitation has provided functional and aesthetic restorations, harmony of the stomatognathic system and improvement of life quality.

As cerâmicas dentais são conhecidas pela excelência em reproduzir artificialmente dentes naturais. Recentemente, devido ao aprimoramento da tecnologia cerâmica, surgiram as restaurações livres de metal. Entretanto, as tradicionais metalocerâmicas ainda preenchem adequadamente os requisitos de alta resistência, longa sobrevida em meio bucal e estética favorável. Neste contexto, é fundamental conhecer a especificidade de cada sistema cerâmico a fim de indicá-lo adequadamente às diversas situações clínicas. Este artigo relata um caso de reabilitação integral e integrada de paciente de 50 anos de idade, portador de espaços edêntulos, restaurações protéticas posteriores e restaurações diretas anteriores insatisfatórias, resultando em comprometimento da qualidade de vida nos âmbitos funcional e psicossocial, utilizando coroas metalocerâmicas. O impacto na qualidade de vida foi mensurado utilizando um instrumento genérico, OHIP-14, validado pela Organização Mundial de Saúde, que abrange tanto a dimensão biológica, como a dimensão psicossocial. Este instrumento foi aplicado à paciente antes e após o tratamento, obtendo pontuação total de 28 e 0 respectivamente, o que mostra que a condição de saúde oral representa fator de grande impacto sobre a qualidade de vida. A reabilitação oral proporcionou restabelecimento funcional e estético, harmonia do sistema estomatognático e melhoria da qualidade de vida da paciente.

Alternate metal framework designs for the metal ceramic prosthesis to enhance the esthetics

PURPOSE: The objective of the present study was to evaluate the effect of five different metal framework designs on the fracture resistance of the metal-ceramic restorations. MATERIALS AND METHODS: For the purpose of this study, the central incisor tooth was prepared, and the metal analogue of it and a master die were fabricated. The counter die with the 0.5 mm clearance was used for fabricating the wax patterns for the metal copings. The metal copings with five different metal framework designs were designed from Group 1 to 5. Group 1 with the metal collar, Group 2, 3, 4 and 5 with 0 mm, 0.5 mm, 1 mm and 1.5 mm cervical metal reduction respectively were fabricated. Total of fifty metal ceramic crown samples were fabricated. The fracture resistance was evaluated with the Universal Testing Machine (Instron model No 1011, UK). The basic data was subjected to statistical analysis by ANOVA and Student's t-test. RESULTS: Results revealed that the fracture resistance ranged from 651.2 to 993.6 N/m2. Group 1 showed the maximum and Group 5 showed the least value. CONCLUSION: The maximum load required to fracture the test specimens even in the groups without the metal collar was found to be exceeding the occlusal forces. Therefore, the metal frameworks with 0.5 mm and 1 mm short of the finish line are recommended for anterior metal ceramic restoration having adequate fracture resistance.

Relationship between alexithymia and patients' satisfaction in anterior esthetic restorations / 中华行为医学与脑科学杂志

Objective To analyze the relationship between alexithymia and patients' satisfaction under the condition of good quality in the esthetic characters. Methods 211 patients requiring single anterior tooth restoration were treated with all ceramic crowns which were assessed by the good and moderate degrees. Patients received 20-item Toronto Alexithymia Scale (TAS-20) and a visual analogue scale assessing patients' satisfaction (VAS). Chi-squared analysis, correlation analysis and the general linear modeling procedure were calculated for TAS total and factors scores according to age, gender and dichotomized satisfaction. Results 85. 3% patients belonged to the high satisfaction group(VAS scores 80 or higher) and 7.1% reported alexithymia ( total score 61 or higher). No difference across gender was observed in the prevalence of alexithymia and satisfaction. Age was correlated with the TAS scores ( r=0.629) and satisfaction scores ( r= -0.429). According to dichotomized satisfaction,TAS total and factor 1&2 scores were significantly different. When adjusting for the effect of age,the association was existed between TAS scores and san'sfaction( r= -0.68). Conclusion Alexithymia has effect on dental satisfaction.

Collarless metal ceramic restorations to obscure the umbrella effect.

Esthetics with porcelain fused to metal restoration in the anterior region can be adversely affected due to the inadequate teeth preparations and design of the prosthesis. We presented here a case report where esthetics was compromised due to darkening of the interdental papilla and marginal gingival and overcontoured restorations in relation to porcelain fused to metal restorations. Good esthetic results were obtained by using basic principles of tooth preparation and using collarless metal ceramic restorations.

An effect of immediate dentin sealing on the shear bond strength of resin cement to porcelain restoration

PURPOSE: The aim of this study was to determine differences in shear bond strength to human dentin using immediate dentin sealing (IDS) technique compared to delayed dentin sealing (DDS). MATERIAL AND METHODS: Forty extracted human molars were divided into 4 groups with 10 teeth each. The control group was light-cured after application of dentin bonding agent (Excite(R) DSC) and cemented with Variolink(R) II resin cement. IDS/SE (immediate dentin sealing, Clearfil(TM) SE Bond) and IDS/SB (immediate dentin sealing, Adapter(TM) Single Bond 2) were light-cured after application of dentin bonding agent (Clearfil(TM) SE Bond and Adapter(TM) Sing Bond 2, respectively), whereas DDS specimens were not treated with any dentin bonding agent. Specimens were cemented with Variolink(R) II resin cement. Dentin bonding agent (Excite(R) DSC) was left unpolymerized until the application of porcelain restoration. Shear strength was measured using a universal testing machine at a speed of 5 mm/min and evaluated of fracture using an optical microscope. RESULTS: The mean shear bond strengths of control group and IDS/SE group were not statistically different from another at 14.86 and 11.18 MPa. Bond strength of IDS/SE group had a significantly higher mean than DDS group (3.14 MPa) (P < .05). There were no significance in the mean shear bond strength between IDS/SB (4.11 MPa) and DDS group. Evaluation of failure patterns indicates that most failures in the control group and IDS/SE groups were mixed, whereas failures in the DDS were interfacial. CONCLUSION: When preparing teeth for indirect ceramic restoration, IDS with Clearfil(TM) SE Bond results in improved shear bond strength compared with DDS.

An in-vitro wear study of human enamel opposing heat-pressed ceramics / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare the wear characteristics of human enamel opposing 2 heat-pressed ceramics (e.max Press and Empress Esthetic), conventional feldspathic porcelain (Ceramco 3) and type III gold alloy. MATERIAL AND METHODS: Intact cusps of extracted premolars were used for enamel specimens. Five disk samples were made for each of two heat-pressed ceramics groups, conventional feldspathic porcelain group and type III gold alloy group. Wear tests were conducted in distilled water using a pin-on-disk tribometer. The amount of enamel wear was determined by weighing the enamel specimens before and after wear tests, and the weight was converted to volumes by average density. The wear tracks were analyzed by scanning electron microscopy and surface profilometer to elucidate the wear characteristics. RESULTS: 1. Ceramco 3 led to the greatest amount of enamel wear followed by Empress Esthetic, e.max Press and type III gold alloy. However, there was no significant difference between Ceramco 3 and Empress Esthetic (P > .05), and there were also no significant differences among Empress Esthetic, e.max Press and type III gold alloy (P > .05). 2. The average surface roughness of e.max Press after wear test was smallest followed by Empress Esthetic and Ceramco 3, but there was no significant difference between Empress Esthetic and Ceramco 3 (P > .05). 3. There were no significant differences among the depth of wear tracks of all the groups (P > .05). The group that showed the largest width of wear track was Ceramco 3 followed by Empress Esthetic, e.max Press and type III gold alloy. However, there was no significant difference between e.max Press and Empress Esthetic (P > .05), and there was also no significant difference between Empress Esthetic and Ceramco 3 (P > .05). CONCLUSION: Within the limits of this study, heat-pressed ceramics were not more abrasive than conventional feldspathic porcelain.

Comparison of marginal fit before and after porcelain build-up of two kinds of CAD/CAM zirconia all-ceramic restorations / 대한치과보철학회지

PURPOSE: Marginal fit is one of the important components for the successful prosthodontic restoration. Poor fitting margin of the restoration causes hypersensitivity, secondary caries, and plaque accumulation, which later result in prosthodontic failure. CAD/CAM zirconia all-ceramic restorations, such as LAVA(R) (3M ESPE, St.Paul, MN) and EVEREST(R) (KaVo Dental GmbH, Biberach, Germany) systems were recently introduced in Korea. It is clinically meaningful to evaluate the changes of the marginal fit of the CAD/CAM zirconia systems before and after build-up. The purposes of this study are to compare the marginal fit of the two CAD/CAM all-ceramic systems with that of the ceramometal restoration, before and after porcelain build-up. MATERIAL AND METHODS: A maxillary first premolar dentiform tooth was prepared with 2.0 mm occlusal reduction, 1.0 mm axial reduction, chamfer margin, and 6 degree taperness in the axial wall. The prepared dentiform die was duplicated into the metal abutment die. The metal die was placed in the dental study model, and the full arch impressions of the model were made. Twenty four copings of 3 groups which were LAVA(R), EVEREST(R), and ceramometal restorations were fabricated. Each coping was cemented on the metal die with color-mixed Fit-checker II(R) (GC Cor., Tokyo, Japan). The marginal opening of each coping was measured with Microhiscope(R) system (HIROX KH-1000 ING-Plus, Seoul, Korea. *300 magnification). After porcelain build-up, the marginal openings of LAVA(R), EVEREST(R),and ceramometal restorations were also evaluated in the same method. Statistical analysis was done with paired t-test and one-way ANOVA test. RESULTS: In coping states, the mean marginal opening for EVEREST(R) restorations was 52.00 +/- 11.94 micrometer, for LAVA(R) restorations 56.97 +/- 10.00 micrometer, and for ceramometal restorations 97.38 +/- 18.54 micrometer. After porcelain build-up, the mean marginal opening for EVEREST(R) restorations was 61.69 +/- 19.33 micrometer, for LAVA(R) restorations 70.81 +/- 12.99 micrometer, and for ceramometal restorations 115.25 +/- 23.86 micrometer. CONCLUSION: 1. LAVA(R) and EVEREST(R) restorations in comparison with ceramometal restorations showed better marginal fit, which had significant differences (P .05). 3. EVEREST(R), LAVA(R) and ceramometal restorations showed a little increased marginal opening after porcelain build-up, but did not show any statistical significance (P > .05).

The influence of porcelain layer thickness and color on the final shade of ceramic restorations / 대한치과보철학회지

STATEMENT OF PROBLEM: Ceramic restorations should be made of porcelain layers of different opacity, shade, and thickness in order to provide a natural appearance. Lithium disilicate glassceramic system has superior color reproducibility, because it uses the ceramic ingot which is similar to teeth shade and uses the staining technique and layering technique. However, staining technique has a fault of discoloration. Also, porcelain is divided core and dentin layer, it is not enough to study about the influence of porcelain layer thickness and shade on the shade of ceramic restorations. PURPOSE: The purpose of this study was to evaluate the influence of porcelain layer thickness and color on the final shade of ceramic restorations. MATERIALS AND METHOD: The CIE L*a*b*(CIELAB) values of 72 assembled specimens, each consisting of 3 discs (enamel porcelain 0.2 mm/dentin porcelain - 1.2, 0.9, 0.7, 0.5 or 0.3 mm/ceramic core - 0.3, 0.5, 0.7, 0.9 or 1.2 mm, diameter is 1.0 mm) were evaluated with a spectrophotometer (Model Chromaview 300, Spectron Tech Co, Korea) for the shade A1, A2, A3 and A4. Distilled water (refractive index: 1.7) was used to attain optical contact between the layers. White, white gray, and white brown backgrounds were used to assess the influence of the background on the final shade. And the mean color difference value(delta E) was calculated. RESULTS AND CONCLUSION: The results obtained from this study were as follows. 1. There was a significant correlation between the thickness ratio of the ceramic core/dentin porcelain system and L*, a* and b* values when the total thickness of specimen combination was smaller than 1.4 mm( p<0.05). 2. The specimen which the ceramic core thickness was more than 0.7 mm had the best masking effect against background colors. 3. The mean color difference value(delta E) is smaller than 2 (delta E<2) when the ceramic core thickness was larger than 0.7 mm and the total thickness of specimen was more than 1.4 mm.

Effect of water content on the flexural strength during refiring in dental porcelain / 대한치과보철학회지

STATEMENT OF PROBLEM: Long-term exposure of dental porcelain to saliva during temporary cementation of a porcelain-fused to metal (PFM) restoration could affect mechanical strength of dental porcelain if the restoration is refired. PURPOSE: This work was performed to verify the effect of water on the mechanical strength in aged dental porcelain. MATERIAL AND METHOD: 63 specimens(Vintage Metalbond opaque and opal powder) were distributed to three experimental groups; non-water immersed control, immersed and pedried, and immersed and non-predired groups. The changes in flexural strength and fracture toughness after specimen refiring related to Fourier Transform Infrared (FT-IR) spectroscopy. RESULTS: 1. The FT-IR reflectances assigned to molecular bonds of H2O were noted as significantly different between the first-fired group and three refired groups and between two water-immersed groups and control group after refiring( p<0.05). They were also significantly different between predried group and non-predried group after refiring( p<0.05). 2. For opal specimens, FT-IR absorbances for hydrogen bond of H2O and silanols were significantly higher in non-predried group than in predreid group( p<0.05). 3. Predried opal group showed the highest mean flexural strength( p<0.05). Non-predried group indicated higher mean flexural strength than control group( p<0.05). 4. The mean fracture toughness for predired group was higher than non-predried group( p<0.05). 5. The difference of leucite crystal size is noted between control group and water-immersed, predried group in scanning electron microscopic study(x10000).