Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions

Objectives

The aim of this study is to compare the fit of all-ceramic crowns fabricated from conventional silicone impressions with the fit of all-ceramic crowns fabricated from intraoral digital impressions.

Methods

Twenty patients with 26 posterior teeth with a prosthetic demand were selected for the study. Two crowns (Straumann-Zerion) were made for each preparation. One crown was fabricated from an intraoral digital impression system (IDI group; Cadent-iTero), and the other crown was fabricated from a conventional one-step silicone impression (CI group; Express Penta Putty and Body Light). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation with ultra-flow silicone (Express Ultra Light Body). Each crown was embedded in resin to stabilize the registered interface, cut in 2-mm-thick slices in a buco-lingual orientation. Internal misfit was measured in microns using stereomicroscopy with a magnification of ×40. Measurements were taken at different landmarks: margin, chamfer angle, axial, crest, and occlusal fosse. After checking for normality, data was analyzed using paired Student’s t test (α?=?0.05).

Results

Fit values were significantly affected by the impression technique (p?=?0.000). Mean internal misfit and mean marginal misfit were 111.40 μm (SD?=?54.04)/80.29 μm (SD?=?26.24) for the crowns of the IDI group and 173.00 μm (SD?=?92.65)/133.51 μm (SD?=?48.78) for the CI group.

Conclusion

All-ceramic crowns fabricated from intraoral digital impressions with parallel confocal technology demonstrated a clinically acceptable internal and marginal fit as conventional impression.

Clinical significance

Intraoral digital impressions as initial step to the digital workflow could further improve the marginal adaptation of all ceramic single crowns.

Trial registration

http://www.isrctn.com/ISRCTN16111844

     

Influence of conventional and digital intraoral impressions on the fit of CAD/CAM-fabricated all-ceramic crowns

Objectives

To compare the fit of all-ceramic crowns fabricated from conventional silicone impressions with the fit of all-ceramic crowns fabricated from intraoral digital impressions.

Methods

Thirty patients with 30 posterior teeth with a prosthetic demand were selected. Zirconia-based ceramic crowns were made using an intraoral digital impression system (Ultrafast Optical Sectioning technology) (digital group, D) and 2-step silicone impression technique (conventional group, C).To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation using ultra-flow silicone. Each crown was embedded in resin to stabilize the registered interface. Specimens were sectioned in buccolingual orientation, and internal misfit was measured at different areas using stereomicroscopy (×40).Data was analysed using Student’s t test and Mann-Whitney test (α = 0.05).

Results

No statistically significant differences were found (P > 0.05) between two groups. The mean internal misfit and mean marginal misfit were 170.9 μm (SD = 119.4)/106.6 μm (SD = 69.6) for group D and 185.4 μm (SD = 112.1)/119.9 μm (SD = 59.9) for group C.

Conclusion

Ceramic crowns fabricated using an intraoral scanner are comparable to elastomer conventional impressions in terms of their marginal and internal fits. The mean marginal fit in both groups was within the limits of clinical acceptability.

Clinical significance

Impressions based on Ultrafast Optical Sectioning technology can be used for manufacturing ceramic crowns in a normal workflow, with the same results as silicone conventional impressions.

     

Clinical evaluation of all-ceramic crowns fabricated from intraoral digital impressions based on the principle of active wavefront sampling

Objectives

The aim of the present study was to compare the fit of all-ceramic crowns fabricated from intraoral digital impressions with the fit of all-ceramic crowns fabricated from silicone impressions.

Methods

Twenty patients agreed to take part in the study to receive two Lava™ crowns each for the same preparation. One crown was fabricated from intraoral scans using the Lava™ Chairside Oral Scanner (Lava C.O.S.), and the other crown from a two-step silicone impression. Prior to cementation the fit of both crowns was clinically evaluated by two calibrated and blinded examiners; the marginal fit was also scored from replicas. Data from the replica scores were analysed by Anderson–Darling test, Levene's test and Mann–Whitney test. All tests were performed with α-level of 0.05.

Results

Median marginal gap in the conventional impression group was 71 μm (Q1:45 μm; Q3:98 μm), and in the digital impression group 49 μm (Q1:32 μm; Q3:65 μm). Mann–Whitney test revealed a significant difference between the groups (p < 0.05). No differences were found regarding the occlusion, and there was a trend for better interproximal fit for the digitally fabricated crowns.

Conclusions

1.

Crowns from intraoral scans revealed significantly better marginal fit than crowns from silicone impressions.

2.

Marginal discrepancies in both groups were within the limits of clinical acceptability.

3.

Crowns from intraoral scans tended to show better interproximal contact area quality.

4.

Crowns from both groups performed equally well with regard to occlusion.

     

Accuracy of single crowns fabricated from ultrasound digital impressions

Objective

This in vitro study aimed to evaluate marginal and internal fit of single crowns produced from high-frequency ultrasound based digital impressions of teeth prepared with finish lines covered by porcine gingiva, in comparison with those obtained by optical scanners with uncovered finish lines.

A 3 years retrospective study of survival for zirconia-based single crowns fabricated from intraoral digital impressions

Objective

To evaluate the clinical performance of glass-ceramic/zirconia crowns fabricated using intraoral digital impressions – a retrospective study with a three-year follow-up.

Methods

70 consecutive patients with a total of 86 glass-ceramic/zirconia crowns were treated by a single clinician using standardized clinical and laboratory protocols. A complete digital workflow was adopted for the purpose except for the veneering procedure for the glass-ceramic crowns. Occlusal adjustments were made before the ceramic glazing procedure. Before cementation, all abutments where carefully cleaned with a 70% alcoholic solution and air dried. Cementation was performed using dual-curing, self-adhesive resin cement. Patients were re-examined after 12, 24 and 36 months, to assess crown chipping/fractures.

Results

After the three-year follow-up, none of the zirconia-based restoration was lost (“apparent” survival rate 100%) otherwise, the chipping rate of the veneering material increased from 9.3% after 12 months, to 14% after 24 months to 30.2% after 36 months. As a consequence, the “real” success rate after 3 years was 69.8%.

Conclusions

After 3 years the success rate of zirconia-based crowns was 69.8%, while the incidence of the chipping was 30.2%. Assuming an exponential increase in chipping rate between 12 and 36 months it can be argued that, among others, the fatigue-mechanism could be advocated as the main factor for the failure of glass-ceramic veneered zirconia especially after 24 months.     

Fractographic analyses of all-ceramic crowns: A study of 27 clinically fractured crowns

ObjectivesThe use of all-ceramic restorations has been steadily increasing in the decades since the introduction of high-strength core ceramics as an alternative to metal cores. Even with high-strength ceramic cores, the crowns are susceptible to fractures during clinical function, probably the major concern associated with all-ceramic restorations. The aim of this study was to analyze fracture features of clinically fractured crowns in order to determine crack initiation sites and crack propagation paths.MethodsFractographic methods were used to analyze 27 all-ceramic full coverage crowns with alumina cores and feldspatic veneering ceramic. The fractured crowns were supplied by dentists in private and public practices with information of type of cement and time in function if available.ResultsThe fractured crowns comprised 13 incisors, 3 premolars and 11 molars. The results revealed that all fractures initiated in the cervical margin of the crowns and usually from the approximal area close to the most coronally placed curvature of the margin. There was no statistically significant association between the cement used and time in function.SignificanceFractography of clinically failed all-ceramic crowns can provide information on the fracture modes and design considerations. The findings are in contrast to fracture modes from in vitro tests. The results suggest that more clinically relevant in vitro test methods to study the durability of ceramic crowns should be developed.     

Computer-aided direct all-ceramic crowns: preliminary 1-year results of a prospective clinical study

The objective of this study was to investigate the clinical performance of: (1) adhesively placed Cerec crowns with reduced stump preparations, and (2) Cerec endo crowns. The crowns were examined at baseline using modified USPHS criteria in 20 patients with 10 Cerec crowns with reduced stump preparations and 10 Cerec endo crowns. All crowns had been produced chairside with the Cerec 3 CAD/CAM method using the function mode. The crowns were machined from Vita Mk II feldspathic ceramic blocks, polished manually, and placed with dual-curing composite luting agent using a functional adhesive. After 1 year, a follow-up examination of the crowns was conducted; all 20 Cerec crowns were rated with a clinically acceptable A or B rating. Fractures or loss of retention were not observed. The method of producing and placing all-ceramic crowns with reduced stump preparations and endo crowns chairside in one appointment can be implemented successfully in private practice.     

A clinical study comparing marginal and occlusal accuracy of crowns fabricated from double-arch and complete-arch impressions

BACKGROUND: The double-arch impression technique is widely used in the provision of laboratory fabricated restorations. However, there is little clinical evidence to support or refute its use. The aim of this prospective clinical study was to evaluate the occlusion and marginal fit of posterior full crowns made from double-arch impressions, and to compare these to control crowns fabricated from conventional complete-arch impressions. METHODS: Ten patients requiring single posterior ceramo-metal full crowns had both double-arch and complete-arch impressions taken of the prepared tooth. Two crowns were fabricated for each tooth, using the casts made from both impression methods. Both crowns were tried in and the occlusion and margins evaluated. The results were composed using nonparametric statistical analysis with the probability level for significance at alpha=0.05. RESULTS: The crowns fabricated from the double-arch impression were found to be more accurate in closure to the intercuspal position and had fewer interferences in lateral excursions. There were no significant differences between the two crown groups regarding protrusive interferences and margin quality. CONCLUSIONS: Crowns fabricated from the double-arch impressions were equivalent in marginal accuracy and superior occlusally to crowns fabricated from the complete-arch impressions.     

Six-year clinical performance of all-ceramic crowns with alumina cores

PURPOSE: The aim of the study was to evaluate the clinical performance of Procera Alumina AllCeram crowns (Nobel Biocare). MATERIALS AND METHODS: In 70 patients, 61 anterior and 46 posterior teeth were provided with single crowns and cemented with a glass-ionomer cement. RESULTS: Four patients were lost to follow-up. Six crowns had to be removed, all because of nonreparable fracture. At 6 years, the cumulative survival rate was 94.3% for all crowns, 96.7% for anterior crowns, and 91.3% for posterior crowns (survival = not removed). Most of the defects occurred within the first 1.5 years. CONCLUSION: The findings indicate a good clinical prognosis of both anterior and posterior Procera Alumina crowns.     

Micro-CT evaluation of marginal and internal fit of cemented polymer infiltrated ceramic network material crowns manufactured after conventional and digital impressions

Purpose

Purpose of this study was to evaluate the accuracy of fit of cemented polymer infiltrated ceramic network (PICN) material crowns manufactured after digital and conventional impression techniques using micro computed tomography (CT). Furthermore to determine the cement space volume and porosities in the cement layer.

基于口内数字化印模制作的全瓷单冠的适合性研究

目的 检测基于口内数字化印模制作的全瓷单冠的适合性,为口内数字化印模在牙体缺损中的临床应用提供数据参考。方法 选择右下第一磨牙全冠树脂标准预备模型作为实验对象,实验组采用口内扫描法,对照组使用传统硅橡胶印模翻制石膏模型,再通过口外扫描仪扫描石膏模型,两组分别扫描10次。通过数字切削加工技术制作全瓷冠共20个。利用硅橡胶薄膜法测量内冠的内部适合性和边缘适合性。结果 实验组的全瓷单冠在近中边缘（49.04±19.71）μm、近中轴转角（210.52±55.65）μm、面中点（313.34±83.97）μm的适合性优于对照组[近中边缘（80.08±31.76）μm、近中轴转角（371.14±104.62）μm、面中点（441.60±171.21）μm],差异有统计学意义（P<0.05）,而其余位点实验组[近中轴面中点（126.51±35.29）μm,远中轴转角（281.09±95.22）μm,远中轴面中点（94.65±23.81）μm,远中边缘（80.99±37.85）μm]与对照组[近中轴面中点（114.48±23.23）μm,远中轴转角（379.19±149.39）μm,远中轴面中点（109.06±31.45）μm,远中边缘（81.64±24.57）μm]之间的差异无统计学意义（P>0.05）。结论 采用口内扫描法制作的全瓷单冠其适合性可满足临床要求。     

Customization of milled zirconia copings for all-ceramic crowns: a clinical report

Generically milled zirconia copings for all-ceramic crowns may not provide optimal thickness and form for the coping or the porcelain veneer. This article describes the customization of milled zirconia copings to provide even and controlled porcelain thickness with the aim of decreasing cohesive porcelain fracture and other failures. A full-contour waxing and cut back in conjunction with a dual-scan technique was used to ensure adequate coping thickness, adequate, even porcelain thickness, and butt joints at the porcelain-to-coping junctions.     

Fit of 4-unit FDPs from CoCr and zirconia after conventional and digital impressions

Objectives

To evaluate the marginal and internal fit of CAD/CAM-generated frameworks for 4-unit, fixed dental prostheses (FDPs) from zirconia (Z) and cobalt-chromium alloy (C) made with conventional (CI) and digital impressions (DI).

Materials and methods

A titanium model was digitized with an intraoral scanner (DI, LAVA? C.O.S.; 3M ESPE; Seefeld, Germany; n = 12). Additionally, 12 conventional impressions were taken, and referring plaster casts were digitized by a laboratory-scanner (CI, LAVA? Scan ST; 3M ESPE; n = 12). Frameworks were fabricated (3M ESPE) from cobalt-chromium (DI-C, n = 12; CI-C, n = 12) and zirconia (DI-Z, n = 12; CI-Z, n = 12) from the same datasets. A replica technique was applied to measure the accuracy. The Mann–Whitney U statistical test was applied to detect statistical differences between each material and methodology groups in terms of fit.

Results

Frameworks from DI-C (median 19.07 μm) showed significantly better marginal fit than CI-C (median 64.64 μm, p < 0.001). Frameworks from DI-Z (median 52.50 μm) showed significantly better marginal fit than CI-Z (median 72.94 μm, p = 0.001). Additionally, frameworks from DI-C showed a significantly better marginal fit than DI-Z (p < 0.001).

Conclusions

CI and DI led to a clinically acceptable marginal fit of 4-unit FDPs from cobalt-chromium and zirconia. DI leads to better marginal fit of the cobalt-chromium frameworks; however, no effect on zirconia was found.

Clinical relevance

The results indicate that DI is suitable for fabricating 4-unit, cobalt-chromium and zirconia frameworks with regard to fit requirements.

     

Esthetic outcomes with porcelain-fused-to-ceramic and all-ceramic single-implant crowns: a randomized clinical trial

Objectives: The aim of this randomized‐controlled clinical trial was to compare the objective and subjective esthetic outcomes of two types of screwed‐retained single‐implant crowns. Materials and methods: Participants were randomly assigned to the test (all‐ceramic) and control [porcelain‐fused‐to‐ceramic (PFM)] groups and were seen under investigation at baseline (B), crown insertion (CI), 1‐year follow‐up (1Y), and 2‐year follow‐up (2Y). Objective parameters were assessed by an intra‐oral digital photograph (1 : 1 ratio), a study cast, a standardized radiograph, periodontal/peri‐implant measurements, and questionnaires were obtained for the subjective parameters. In addition, pink esthetic score (PES) and white esthetic score (WES) were calculated for both groups. For the subjective evaluation, a visual analogue scale (VAS) questionnaire was used to assess the level of patient satisfaction regarding the esthetic outcome. Then, nine expert clinicians visually inspected and assessed subjective evaluation at the professional level. Statistical analysis was used to compare between groups and investigational appointments. Results: Twenty patients were included in the study, 10 allocated to the all‐ceramic group and 10 to the PFM group. No statistically significant differences were observed for the objective measurements comparing the test and control groups. Minor chipping of the ceramic veneering material was observed in the two patients of control group. The mean difference for all groups comparing objective parameters revealed an increase of papilla height between time points. A slight recession (0.26 mm) of the peri‐implant mucosal margin at the implant site was observed between 1Y and 2Y. Mean values for PES and WES were 13.9 and 13.1 for the PFM group and for the all‐ceramic group, respectively. These values were not statistically significant. Implant crown volume, outline, translucency, and characterization showed major discrepancies with the contra‐lateral natural teeth. As for subjective parameters, VAS patients' responses regarding their perceptions of the esthetic outcome showed no statistical differences betwen groups and clinicians' accuracy scores were 50% and 47% for PFM and all‐ceramic crowns, respectively. Conclusion: PFM and all‐ceramic single‐implant restorations may be indistinguishable from each other regarding the objective/subjective assessment of esthetic integration. The material chosen for fabricating an implant crown per se does not ensure an optimal esthetic outcome if other esthetic parameters are not present. To cite this article:
Gallucci GO, Grütter L, Nedir R, Bischof M, Belser UC. Esthetic outcomes with porcelain‐fused‐to‐ceramic and all‐ceramic single‐implant crowns: a randomized clinical trial.
Clin. Oral Impl. Res. 22 , 2011; 62–69.
doi: 10.1111/j.1600‐0501.2010.01997.x