Assessment of the fit of zirconia-based prostheses fabricated with two different scan methods / 대한치과보철학회지

PURPOSE: This research was conducted to compare the marginal and internal fit of zirconia prostheses fabricated with the model scan method and the intraoral scan method. MATERIALS AND METHODS: In this study, 20 extracted human mandibular first molar was used in the preparation of abutment tooth for the fabrication of zirconia prostheses. In the first group, the model scan method was applied on 10 prepared teeth. In the other group, the intraoral scan method was used on other 10 prepared teeth. Datum of both groups were transmitted to the software system. Afterwards, 20 zirconia prostheses were fabricated using the Ceramill system. Weight technique was used to evaluate the internal gap of the zirconia prostheses. In the Replica technique, marginal gap of the zirconia prostheses were analyzed by optical microscopy. Statistical analysis was based on one-way ANOVA. RESULTS: Model scan group showed lower average weight than intraoral scan group when weight technique was applied, which has significance (P < .05). Also, model scan group showed significantly lower figures in all 5 measurements of replica technique than intraoral scan group (P < .05). CONCLUSION: Zirconia prostheses of both groups demonstrated clinically acceptable margin and internal fit. However, model scanned zirconia prostheses showed higher marginal and internal fit than intraoral scanned crowns.

Marginal and internal fit of all ceramic crown using the replica technique and the triple-scan protocol / 대한치과보철학회지

PURPOSE: This study was conducted to compare the marginal and internal fit of all ceramic crown using the replica technique and the triple-scan protocol. MATERIALS AND METHODS: Twenty zirconia ceramic crowns were fabricated using titanium abutment model. All crowns were divided into two groups of 10 each, depending on the replica technique and the triple-scan protocol. The internal and marginal fit of 10 zirconia ceramic crowns were measured at 17 points for each specimen using the replica technique. The other 10 ceramic crowns were measured using the triple-scan protocol. Statistical analysis was performed by t-test (α= .05). RESULTS: The mean and standard deviation of marginal and internal fit were significantly different between the replica technique (49.86 ± 29.69 µm) and triple-scan protocol (75.35 ± 64.73 µm, P.343). CONCLUSION: There was a statistically significant difference in the marginal fit measured by the two methods. However, there was no statistically significant difference in the internal fit between the two methods.

Verification of a computer-aided replica technique for evaluating prosthesis adaptation using statistical agreement analysis

PURPOSE: The purpose of this study was to evaluate the reliability of computer-aided replica technique (CART) by calculating its agreement with the replica technique (RT), using statistical agreement analysis. MATERIALS AND METHODS: A prepared metal die and a metal crown were fabricated. The gap between the restoration and abutment was replicated using silicone indicator paste (n = 25). Gap measurements differed in the control (RT) and experimental (CART) groups. In the RT group, the silicone replica was manually sectioned, and the marginal and occlusal gaps were measured using a microscope. In the CART group, the gap was digitized using optical scanning and image superimposition, and the gaps were measured using a software program. The agreement between the measurement techniques was evaluated by using the 95% Bland-Altman limits of agreement and concordance correlation coefficients (CCC). The least acceptable CCC was 0.90. RESULTS: The RT and CART groups showed linear association, with a strong positive correlation in gap measurements, but without significant differences. The 95% limits of agreement between the paired gap measurements were 3.84% and 7.08% of the mean. The lower 95% confidence limits of CCC were 0.9676 and 0.9188 for the marginal and occlusal gap measurements, respectively, and the values were greater than the allowed limit. CONCLUSION: The CART is a reliable digital approach for evaluating the fit accuracy of fixed dental prostheses.

Evaluation of the marginal and internal gaps of three different dental prostheses: comparison of the silicone replica technique and three-dimensional superimposition analysis

PURPOSE: The purposes of this study were to evaluate the marginal and internal gaps, and the potential clinical applications of three different methods of dental prostheses fabrication, and to compare the prostheses prepared using the silicone replica technique (SRT) and those prepared using the three-dimensional superimposition analysis (3DSA). MATERIALS AND METHODS: Five Pekkton, lithium disilicate, and zirconia crowns were each manufactured and tested using both the SRT and the two-dimensional section of the 3DSA. The data were analyzed with the nonparametric version of a two-way analysis of variance using rank-transformed values and the Tukey's post-hoc test (α = .05). RESULTS: Significant differences were observed between the fabrication methods in the marginal gap (P .350), deep chamfer (P > .719), and axial wall (P > .150). As the 3DSA method is three-dimensional, it allows for the measurement of arbitrary points. CONCLUSION: All of the three fabrication methods are valid for measuring clinical objectives because they produced prostheses within the clinically acceptable range. Furthermore, a three-dimensional superimposition analysis verification method such as the silicone replica technique is also applicable in clinical settings.

Comparison of the fit accuracy of zirconia-based prostheses generated by two CAD/CAM systems

PURPOSE: The purposes of this study are to evaluate the internal and marginal adaptation of two widely used CAD/CAM systems and to study the effect of porcelain press veneering process on the prosthesis adaptation. MATERIALS AND METHODS: Molar of a lower jaw typodont resin model was prepared by adjusting a 1.0 mm circumferential chamfer, an occlusal reduction of 2.0 mm, and a 5° convergence angle and was duplicated as an abrasion-resistant master die. The monolithic crowns and copings were fabricated with two different CAD/CAM system-Ceramil and Zirkonzahn systems. Two kinds of non-destructive analysis methods are used in this study. First, weight technique was used to determine the overall fitting accuracy. And, to evaluate internal and marginal fit of specific part, replica technique procedures were performed. RESULTS: The silicone weight for the cement space of monolithic crowns and copings manufactured with Ceramil system was significantly higher than that from Zirkonzahn system. This gap might cause the differences in the silicone weight because the prostheses were manufactured according to the recommendation of each system. Marginal discrepancies of copings made with Ceramil system were between 106 and 117 µm and those from Zirkonzahn system were between 111 and 115 µm. Marginal discrepancies of copings made with Ceramil system were between 101 and 131 µm and those from Zirkonzahn system were between 116 and 131 µm. CONCLUSION: Marginal discrepancy was relatively lower in Ceramil system and internal gap was smaller in Zirkonzahn system. There were significant differences in the internal gap of monolithic crown and coping among the 2 CAD/CAM systems. Marginal discrepancy produced from the 2 CAD/CAM systems were within a reported clinically acceptable range of marginal discrepancy.

Evaluation of marginal and internal gap under model-free monolithic zirconia restoration fabricated by digital intraoral scanner / 대한치과보철학회지

PURPOSE: The aim of this study was to evaluate the marginal and internal adaptation of monolithic zirconia restoration made without physical model by digital intraoral scanner. MATERIALS AND METHODS: A prospective clinical trial was performed on 11 restorations as a pilot study. The monolithic zirconia restorations were fabricated after digital intraoral impression taking by intraoral scanner (TRIOS, 3shape, Copenhagen, Denmark), computer-aided designing, and milling manufacturing process. Completed zirconia crowns were tried in the patients' mouth and a replica technique was used to acquire the crown-abutment replica. The absolute marginal discrepancy, marginal gap, and internal gap of axial, line angle, and occlusal part were measured after sectioning the replica in the mesiodistal and buccolingual direction. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U test (α=.05). RESULTS: From the adaptation analysis by replica, the statistically significant difference was not found between mesiodistal and buccolingual sections (P>.05), but there was significant difference among the measurement location (P<.01). The amount of absolute marginal discrepancy was larger than those of marginal gap and internal gap (P<.01). CONCLUSION: Within the limitations of this study, the adaptation accuracy of model-free monolithic zirconia restoration fabricated by intraoral scanner exhibited clinically acceptable result. However, the margin of zirconia crown showed tendency of overcontour and cautious clinical application and follow up is necessary.

Marginal and internal discrepancies of zirconia copings: Effects of milling system and finish line design.

Context: Discrepancies at the abutment/crown interface can affect the longevity of zirconia restorations. Aim: The aim was to evaluate the marginal and internal discrepancies (MD and ID) of zirconia copings manufactured by two milling systems with different finish lines. Materials and Methods: Three aluminum‑master‑dies (h = 5.5 mm; Ø =7.5 mm; 6°), with different finish lines (large chamfer [LC]; tilted chamfer [TC]; rounded shoulder [RS]) were fabricated. Twenty impressions were made from each master die and poured. Sixty zirconia copings were manufactured and divided according to the factors “finish line” and “milling system” (n = 10): CADLC = Computer‑aided design/computer‑aided manufacturing (CAD/ CAM) + LC; CADTC = CAD/CAM + TC; CADRS = CAD/CAM + RS; MADLC = manually aided design/manually aided manufacturing (MAD/MAM) + LC; MADTC = MAD/MAM + TC; and MADRS = MAD/MAM + RS. For MD analysis, each coping was fixed, and the distance between the external edges of the coping and the edge of the cervical preparation was measured (50 points). Using the same copings, the ID of each coping was evaluated, by the replica technique, at 12 points equally distributed among the regions (n = 10): Ray (R), axial (A), and occlusal (Occl). The measurements were performed by optical microscopy (×250). The data (μm) were subjected to parametric and non‑parametric statistical analyses. Results: For the MAD/MAM system, the “finish line” (P = 0.0001) affected significantly the MD median values (μm): LC = 251.80a, RS = 68.40a and TC = 8.10b (Dunn’s test). For the CAD/CAM system, the median MD values (μm) were not affected by the factor “finish line” (P = 0.4037): LC = 0.82a, RS = 0.52a, and TC = 0.89a. For the ID, it was observed interaction between the finish line types and the region (P = 0.0001) and between region and milling system (P = 0.0031) (RM‑ANOVA). Conclusions: The CAD/CAM system presented lower MD values, regardless the finish line. However, the MAD/MAM system showed ID values smaller than those of CAD/CAM.

Avaliação do assentamento de coroas totais à base de dissilicato de lítio produzidas por três diferentes fluxos de trabalho: convencional, digital ou parcialmente digital / Fit of lithium dissilicate crowns made by three workflows: conventional, partially digital and totally digital

Este estudo avaliou os assentamentos marginal e interno em 4 áreas predeterminadas de coroas totais à base de dissilicato de lítio produzidas por 3 fluxos de trabalho distintos. Um modelo-mestre de titânio com um preparo para coroa total em um molar foi confeccionado. Foram produzidas 36 coroas totais à base de dissilicato de lítio. As coroas foram divididas em 3 grupos, de acordo com o fluxo de trabalho: Totalmente Convencional (TC): moldagem do modelo-mestre com polieter, vazagem com gesso tipo IV e confecção de 12 coroas (IPS e.max PRESS) no laboratório de prótese; Totalmente Digital (TD): escaneamento do modelo-mestre com a Bluecam™ e usinagem de 12 coroas totais (IPS e.max CAD™) no CEREC 3™; e Parcialmente Digital (PD): moldagem do modelo-mestre com polieter, vazagem com gesso tipo IV, escaneamento do modelo de gesso com a Bluecam™ e usinagem de 12 coroas totais (IPS e.max CAD™) no CEREC 3™. Para a avaliação do assentamento foi utilizada a técnica da réplica, onde a base leve do silicone de adição simulou um cimento. Duas réplicas por coroa total foram confeccionadas, gerando imagens de interfaces vestíbulo-palatal e mesio-distal sob magnificação de 50x. Quatro áreas foram definidas para a avaliação: Abertura Marginal (AM); Chanfro (CH); Parede Axial (PA); e Parede Oclusal (PO). Um software realizou a medição dos valores em toda a área demarcada, gerando aproximadamente 6.000 pontos de avaliação por interface. Os resultados foram estatisticamente analisados por meio dos testes One-Way-Anova e Scheafer's Post-Hoc, com grau de significância estabelecido em 5%. Todas os grupos testados no estudo apresentaram médias de valores clinicamente aceitáveis para os assentamentos marginal e interno. Não houve diferença significativa em AM, CH e PO entre os três grupos testados. Em PA, o grupo TC apresentou valores significativamente maiores do que PD e TD (p = 0,001). Os diferentes fluxos de trabalho, convencional ou digitais, aplicados neste estudo, foram capazes de prover adequados assentamentos marginal e interno, dentro dos valores clínicos estabelecidos para coroas totais à base de porcelana.

The aim of this study was to evaluate the marginal and internal fit of porcelain indirect restorations produced by three distinct workflows in four pre-determined interface areas. A titanium master model - simulating a full crown molar preparation - was built to this study. 36 lithium dissilicate full crowns coverage were produced. The restorations were divided in 3 groups, according to the workflow: Totally Conventional (TC), where a polieter impression of the master model was poured with type IV gypsum, and 12 full crown coverages (IPS e.max PRESS™) were produced in the dental technician; Totally Digital (TD), where the master model was scanned with the Bluecam™ and 12 full crown coverages (IPS e.max CAD™) were milled in the CEREC 3™; Partially Digital (PD), where a polieter impression of the master model was poured with type IV gypsum, with the Bluecam™ scanning the working model and the 12 full crown coverages (IPS e.max CAD™) being milled by the CEREC 3™. The replica technique, where the light body silicone simulate the cement, was used to evaluate the fit of the crowns. Two cross sectioned replicas per crown were obtained, generating images of the bucco-palatal and mesio-distal interfaces under 50x magnification. Four interface areas were choosen to the evaluation: Marginal Opening (AM); Chamfer (CH), Axial Wall (PA); and Occlusal Wall (PO). The hole interface area of each image was evaluated, generating approximately 6.000 points to be rated per interface. Results were statistical analyzed with one-way-Anova and Scheafer's post hoc with a 5% level of significance. All the 3 tested groups showed clinically acceptable mean values for marginal and internal fit. For the areas AM, CH and PO, similar results were found between the 3 groups. For the PA area, TC group showed significantely higher values than PD and TD groups (p = 0,001). The different workflows, conventional or digitals, used in this study were proven capable to present elegible marginal and internal fit, based on the accepted current values for porcelain full coverage crowns.