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.

     

口内数字化印模扫描重复性的研究

目的：通过研究口内数字化扫描仪多次扫描的重复性来评价其扫描精度。方法：根据原始研究模型上牙备后基牙的分布不同分为5小组（1.右侧上颌中切牙为牙备后形态,余牙完整;2.右侧上颌第一磨牙为牙备后形态,余牙完整;3.右侧上颌中切牙和尖牙为牙备后形态,上颌侧切牙缺失,余牙完整;4.右侧上颌7颗牙齿为牙备后形态,左半侧完整;5.上颌全部牙齿为牙备后形态）。实验组中,每一小组的研究模型均用TRIOS口内扫描仪10次;对照组中,每一小组的研究模型先分别翻制10副石膏模型,再用3Shape口外扫描仪扫描。实验组和对照组分别得到扫描生成的50个STL三维图像文件,将总共100个STL文件通过Geomagic Studio 12软件进行处理和分析来评价两组扫描的重复性和精度。结果：实验组（口内组）3D标准偏差分别是第1小组：13.33μm,第2小组：7.0μm,第3小组：16.33μm,第4小组：41.56μm,第5小组：88.44μm。对照组的3D标准偏差分别是第1小组：14.89μm,第2小组：8.67μm,第3小组：24.33μm,第4小组：14.22μm,第5小组：12.67μm。实验组和对照组的3D标准偏差在第2,3,4,5小组中有统计学差异（P〈0.05）。结论：口内数字化印模扫描精度随着牙弓扫描范围增大而降低,其在扫描范围小于半个牙弓时表现出的精度符合临床要求;而口外台式扫描仪在扫描任意范围牙弓时均表现出较好的精度。     

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.

带金属托槽牙列的口内扫描数字模型的精度研究

目的 研究带金属托槽牙列的口内扫描数字模型的精度,为临床及科研工作提供精确的研究模型.方法 选择北京大学口腔医院正畸科门诊患者15例,分别在金属托槽粘接前后使用口内扫描仪(Trios,3Shape,丹麦)获取上颌数字模型.对第一磨牙近中颊尖顶点到同侧中切牙近中切角顶点距离(L1_6;R1_6);第一磨牙间宽度(6_6);尖牙间宽度(3_3);中切牙切缘中点到唇侧龈缘最高点距离(h11;h21)进行测量.重复测量两次并计算组内相关系数(ICC)进行一致性检验.应用配对t检验分析各测量项目在两组模型间的差异.结果 两组模型的所有重复测量ICC＞0.90,测量方法可信.第一磨牙近中颊尖顶点到同侧中切牙近中切角顶点距离(L1_6;R1_6)、第一磨牙间宽度(6_6)、尖牙间宽度(3_3)以及右侧中切牙切缘中点到唇侧龈缘最高点距离(h11)无统计学差异(P＞0.05);在左侧中切牙切缘中点到唇侧龈缘最高点距离(h21)之间差异有统计学意义(P＜0.05),治疗前为(9.51±0.62)mm,粘接托槽后为(9.65±0.68)mm.结论 TRIOS口内扫描仪扫描得到的正畸治疗中带有金属托槽的牙体硬组织的口内数字模型具备较高的扫描精度,基本可以用于治疗过程中模型分析.     

Patient satisfaction and quality of single-tooth restorations

Abstract: This retrospective study focuses on patient opinion and professionally assessed quality of single‐tooth restorations of Brånemark fixtures. Patients were treated by periodontists for fixture installation and/or abutment connection and by referring general practitioners for prosthetic rehabilitation. Seventy‐eight consecutively treated patients were sent a questionnaire regarding aesthetics, phonetics and overall satisfaction. Forty‐eight patients (52 fixtures) returned the questionnaire. Forty were able to attend a clinical examination by an independent examiner. The quality of 43 single implant crowns was evaluated according to the modified guidelines for assessment of quality and professional performance used for evaluation of design, fit, occlusion/articulation and aesthetics. Bone to implant level was assessed radiographically. Patients were very positive about aesthetics, phonetics, eating comfort and overall satisfaction. Nevertheless, 6/40 patients would not undergo the same treatment again, yet all of them would recommend it to others. The professionally rated quality of the crowns was perfect in 17 and acceptable in 25 cases. One crown needed modification to prevent future complications. Two crowns had already been replaced as a result of porcelain fracture; one restoration showed abrasion and one was damaged. With a mean loading time of 33 months (range: 3–89 months), none of the patients returning the questionnaire had encountered fixture loss. All except five fixtures showed bone remodelling at or above the first implant thread. It is concluded that single Brånemark fixtures installed by periodontists and restored by general practitioners are of an acceptable clinical quality to satisfy the patient.     

Accuracy of intraoral data acquisition in comparison to the conventional impression

The achievable accuracy is a decisive parameter for the comparison of direct intraoral digitization with the conventional impression. The objective of the study was therefore to compare the accuracy of the reproduction of a model situation by intraoral digitization vs. the conventional procedure consisting of impression taking, model production, and extraoral digitization. Proceeding from a die model with a prepared tooth 16, the reference data set of the teeth 15, 16 and 17 was produced with an established procedure by means ofextraoral digitization. For the simulated intraoral data acquisition of the master model (Cerec 3D camera, Sirona, Bensheim), the camera was fastened on a stand for the measurement and the teeth digitized seven times each in defined views (occlusal, and in each case inclined by 20 degrees, from the mesio-proximal, disto-proximal, vestibular and oral aspect). Matching was automated (comparative data sets B1-B5). A clinically perfect one-step putty-and-wash impression was taken from the starting model. The model produced under defined conditions was digitized extraorally five times (digi-SCAN, comparative data sets C1-C5). The data sets B1-B5 and C1-C5 were assigned to the reference data set by means of best-fit matching and the root of the mean quadratic deviation (RMS; root mean square) calculated. The deviations were visualized, and mean positive, negative and absolute deviations calculated. The mean RMS was 27.9 microm (B1-B5) or 18.8 microm (C1-C5). The mean deviations for the prepared tooth were 18 microm/-17 microm (B1-B5) and 9 microm /-9 microm (C1-C5). For tooth 15, the mean deviations were 22 microm/-19 microm (B1-B5) and 15 microm/-16 microm (C1-C5). The intraoral method showed good results with deviations from the CAD starting model of approx. 17 microm, related to the prepared tooth 16. On the whole, in this in-vitro study, extraoral digitization with impression taking and model production showed higher accuracy than intraoral digitization. Since the inaccuracies in the conventional impression under real clinical conditions may be higher than the values determined above, a comparison under clinical conditions should be performed subsequently.     

Marginal adaptation of zirconia complete-coverage fixed dental restorations made from digital scans or conventional impressions: A systematic review and meta-analysis

Statement of problemIntraoral scanners have been increasingly used in recent years. However, the accuracy of digital scans as it affects marginal adaptation is unclear.PurposeThe purpose of this systematic review and meta-analysis was to compare the marginal adaptation of single-unit zirconia crowns fabricated with digital scans or with conventional impressions.Material and methodsThe electronic databases PubMed (MEDLINE), Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science (ISI), Scopus, and EMBASE were searched and complemented by a manual search. Risks of bias were assessed by using a modified methodological index for nonrandomized studies (MINORS). Mean ±standard deviation (SD) values of marginal accuracy of studies were extracted for both methods. Mean marginal difference and 95% confidence interval (CI) were calculated to evaluate the marginal accuracy of each method. Pooled data were statistically analyzed by using a random-effect model.ResultsSeventeen studies were used to perform the meta-analysis. Subgroup analysis was performed based on intraoral scanners. Standardized mean marginal difference and 95% CI of each subgroup were as follows: Lava: -0.85 μm (95% CI: -1.67, -0.03) (P=.043); CEREC: -1.32 μm (95% CI: -2.06, -0.59) (P<.001); iTero: -0.44 μm (95% CI: -1.35, 0.47) (P=.338); TRIOS: -1.26 μm (95% CI: -2.02, -0.51) (P=.001); unknown scanner: -0.21 μm (95% CI: -1.14, 0.72); all studies: -0.89 μm (95% CI: -1.24, -0.54) (P<.001).ConclusionsDigital scanning of prepared teeth for single-unit zirconia restorations resulted in better marginal accuracy than conventional techniques using elastomeric impression materials.     

Digital versus conventional impressions for full-coverage restorations: A systematic review and meta-analysis

Background

The primary objective of this systematic review was to investigate the survival of full-coverage restorations fabricated by using digital impressions (DIs) versus that of those fabricated by using conventional impressions. The authors also compared secondary outcomes of marginal and internal fit and occlusal and interproximal contacts.

Current practice in conventional and digital intraoral radiography: problems and solutions

In summary, it can be said for digital radiography that digital exposures can be taken just as well as dental film exposures. The problems found when using holders for the paralleling technique are similar in conventional and digital radiography. Good intraoral x-ray images can be produced as a rule with practice, good will and a skilful hand. The bisected angle technique should no longer be used, as this no longer corresponds to the state of the art and of dental medicine. It is therefore important that all intraoral dental exposures are taken with corresponding holders and the paralleling technique. Thus, the bite wing and measuring exposures are no longer taken with the finger or other aids, but suitable holders are used. However, being able to place the film, the storage phosphor or the sensor in the oral cavity correctly is just as important as the choice of exposure technique. Theoretical knowledge and practical skill are therefore closely related.     

Accuracy of single-abutment digital cast obtained using intraoral and cast scanners

Statement of problem

Scanners are frequently used in the fabrication of dental prostheses. However, the accuracy of these scanners is variable, and little information is available.

Accuracy of full-arch digital impressions: an in vitro and in vivo comparison

Clinical Oral Investigations - Comparison of full-arch digital impressions to conventional impressions in vitro and in vivo. A straight metal bar was fixed between the second upper molars as a...     

In vitro accuracy of digital and conventional impressions in the partially edentulous maxilla

Clinical Oral Investigations - This in vitro study compared the dimensional accuracy of conventional impressions (CI) with that of digital impressions (DI) in a partially edentulous maxilla. DIs...     

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