Long-term survival of monolithic tooth-supported lithium disilicate crowns fabricated using a chairside approach: 15-year results.

OBJECTIVES: To investigate the clinical performance of chairside fabricated tooth-supported posterior single crowns from lithium disilicate ceramic. MATERIALS AND METHODS: Thirty-four crowns (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein) were inserted between 2006 and 2007 and again evaluated after 15 years. Survival and success rates were calculated according to Kaplan-Meier, and the quality of the crowns was evaluated by using modified United States Public Health (USPHS) criteria. RESULTS: Twenty-two crowns were available for recall; six patients were defined as dropouts. The mean observation period was 15.2 years (± 0.2). Six failures occurred (1 technical/5 biological) resulting in a survival rate of 80.1%. The success rate was 64.2%. The roughness of the crowns increased (p = 0.021) and the majority of adhesive gaps were discolored (p = 0.001) in comparison to baseline. The color, tooth, and crown integrity remained stable over the follow-up period (p ≥ 0.317). CONCLUSION: The fabrication of tooth-supported lithium disilicate crowns using a chairside approach yielded acceptable long-term survival and success rates. Due to discoloration, the long-term use of dual-cure self-adhesive resin cements might result in unpleasing esthetic results. CLINICAL RELEVANCE: The performance of posterior lithium disilicate single crowns revealed excellent to good clinical quality and an acceptable number of events after 15 years of clinical service.

Verification of a digital approach for three-dimensional evaluation of marginal and internal fit.

STATEMENT OF PROBLEM: Internal fit is an important aspect of indirect restorations, but methods for the 3-dimensional (3D) measurement of absolute marginal and intaglio fit are sparse. PURPOSE: The purpose of this in vitro study was to evaluate an innovative 3D measurement method (AIXFit) based on intraoral scanning data for analyzing the fit of dental restorations. MATERIAL AND METHODS: For the evaluation of AIXFit, 12 monolithic zirconia crowns were fabricated on typodont preparations. The fit was measured digitally with the AIXFit system and compared with the results obtained from an established 2-dimensional (2D) sectional procedure. To compare the values of both methods at identical locations, a common reference system was developed, with each die fixed in a gypsum stand with reference points. Using an intraoral scanner (True Definition), each die with its reference points and the intaglio surface of the finished crown were digitalized as standard tessellation language files. The AIXFit software program, with a specially developed best-fit algorithm, was used to match the intaglio surface of the crown with the surface of the preparation. The virtual cement gap was calculated over the entire surface and returned values for x≥0 µm. A 2D comparison method involved adhesively fixing the crown to the die and sectioning it into 4 parts with a diamond band saw. The thickness of the cement gap was determined under a light microscope at ×100 magnification at 5 defined measuring points per quarter, so that a total of 240 measurements were available for comparison. A software program (Blender Foundation) was used to superimpose the data from the AIXFit system with the data from the 2D method and to compare the cement gaps at the same locations. The agreement between these methods was verified using paired t tests and determine correlation coefficients (α=.05). RESULTS: The mean ±standard deviation difference between the AIXFit and 2D methods was 6.7 ±29 µm). Two 1-sided tests showed statistical equivalence between the methods of measurement when considering an interval between -20 and +20 µm. The correlation coefficients showed a positive association for both methods (r=.931). CONCLUSIONS: The AIXFit software program appeared to be accurate for the digital measurement of internal fit when using the True Definition scanner. It enabled a cast-free workflow and allowed the analysis of the entire intaglio surface.

Ten-year clinical performance of zirconia posterior fixed partial dentures.

BACKGROUND: With the constantly increasing demand for metal-free solutions in dental therapy, numerous ceramic restorations have found their way into everyday clinical practice, but long-term clinical data are limited. OBJECTIVE: The aim of this prospective clinical study was to evaluate three- and four-unit fixed partial dentures in the posterior region made of zirconium dioxide frameworks veneered with feldspathic porcelain after 10 years in clinical use. METHODS: Based on the two studies published in 2009 and 2012, in which the all-ceramic FDPs were evaluated after 3 and 5 years of function, a clinical evaluation of a total of 17 restorations after 10 years with regard to their condition and long-term stability was carried out in the course of this study. The restorations were fabricated using feldspathic ceramic-veneered, yttria-stabilised, tetragonal zirconium dioxide as the framework material. The data collection was based on modified CDA criteria and included, for example, the shape, shade, surface condition and the success and survival rates of the restorations. RESULTS: The all-ceramic prostheses embodied excellent biocompatibility and colour reproduction. As a result of an increased incidence of chipping fractures, the success rate was 60%. The survival rate, however, was 88.2%, as 2 of the 17 restorations were lost. CONCLUSION: All-ceramic concepts for FDP constructions in the posterior region achieved satisfactory results in terms of durability after 10 years. The main problem was chipping, as has been generally recognised. Nevertheless, the materials were characterised by excellent aesthetics and biocompatibility, which ultimately makes them a good alternative to conventional restorative options. TRIAL REGISTRATION: This study is registered in DRKS-German Clinical Trials Register with the register number DRKS00021743.

Accuracy of guided implant surgery obtained using 3D-printed surgical guides - An in vitro comparison of four evaluation methods.

AIM: To test four different measurement methods to evaluate deviations between planned and actual implant positions within a digital workflow applying 3D-printed surgical guides. MATERIALS AND METHODS: A fully digital workflow was applied to simulate the single implant insertion to replace a maxillary missing central incisor and first molar in 10 gypsum casts (n = 10). Surgical guides (n = 10 per site) were printed by digital light processing for implant bed preparation and implant insertion. Four methods were used to analyze 3D deviations between the planned (target) and achieved implant positions: Methods 1 and 2 used an automated computer program (ACP) to assess deviations between the initial planning file and a file that represented the actual implant position either by the implant bed [ACP_BED] or by the inserted implant [ACP_IMP]. For Method 3, a standard tessellation language dataset representing the actual implant position was used and equipped with reference planes. This dataset was registered with the target planning, allowing manual measurements [MAN_MEAS]. Method 4 used a reverse engineering approach based on 3D high-resolution scans [REVERSE]. RESULTS: Mean 3D deviations, including for anterior and posterior implant sites, ranged between 0.26 ± 0.11 mm [REVERSE] and 0.40 ± 0.09 mm [ACP_BED] at the implant shoulder, between 0.52 ± 0.24 mm [REVERSE] and 0.91 ± 0.24 mm [ACP_BED] at the implant apex, and between 1.68 and 2.35 degrees in angular deviation. Implant sites did not differ significantly, while some of the evaluation methods differed for shoulder and apex. CONCLUSION: [REVERSE] revealed the smallest deviations between planned and actual implant position. 3D implant deviations were comparable with findings in the literature or even lower.

Cemented versus screw-retained posterior implant-supported single crowns: A 24-month randomized controlled clinical trial.

OBJECTIVES: To compare the incidence of biological and technical complications of cemented and screw-retained monolithic lithium-disilicate implant-supported posterior single crowns. MATERIAL AND METHODS: Forty-one subjects with a total of 56 implants received randomly allocated 28 cemented and 28 screw-retained crowns. In the screw-retained group, monolithic lithium-disilicate restorations were luted to titanium bases extraorally. In the cemented group, monolithic lithium-disilicate crowns were cemented on individualized titanium abutments intraorally. All restorations were examined according to modified FDI criteria within 2 weeks of inserting the crowns (baseline) and after 12 (n = 46) and 24 (n = 43) months. Bone loss was evaluated by standardized radiographs at baseline and 12 months. RESULTS: After 12 months, the incidence of mucositis (positive bleeding on probing) was 14.2% (screw-retained) and 17.9% (cement-retained). The gingival and plaque index and a mean marginal bone loss between 0.03-0.15 mm showed no significant difference between the groups. In the cemented group, cement residues were detected at baseline at two restorations (6.9%) by radiographic examination. A complete digital workflow was realized in most cases (85.7%). At 24 months, no restoration had failed, and no chipping of the ceramic had occurred. In the screw-retained group, screw loosening occurred in one implant. In both groups, there was obvious deterioration in the quality of 32% of the occlusal and of 18% of the proximal contact points. CONCLUSIONS: The type of retention mode of monolithic implant-retained lithium-disilicate posterior crowns had no influence on the biological and technical complication rate.

Do "cut out-rescan" procedures have an impact on the accuracy of intraoral digital scans?

STATEMENT OF PROBLEM: The software programs of digital intraoral scanners typically offers the option to cut out areas from 3D casts, to do rescans, and to merge them with the initial scan. However, evidence of whether this procedure has an impact on the accuracy of the scan is lacking. PURPOSE: The purpose of this study was to determine whether "cut out-rescan" procedures change the accuracy of a 3D cast. MATERIAL AND METHODS: A maxillary master cast was digitized with an industrial structured light scanner to obtain a digital reference cast. This master cast was repeatedly scanned by 3 intraoral scanners: TRIOS 3 [TR], Cerec Primescan [PR], and Cerec Omnicam [OM]. The scan data were duplicated, and the posterior area from the right lateral incisor was cut out and rescanned to obtain complete-arch casts containing the rescanned data [TR_rs], [PR_rs], and [OM_rs]. The trueness and precision of the scans were evaluated by superimposing procedures of the relevant data sets. To evaluate statistical differences, either the Mann-Whitney U test or the t test was used (α=.05). RESULTS: The median precision values of the complete-arch scan data was 19 µm for [OM] and [TR], whereas the median for [PR] was 14 µm. In the "cut out-rescanned" data group, the values were 25 µm for [OM_rs], 16 µm for [TR_rs], and 14 µm for [PR_rs]. Statistically significant differences were found among the scanners [OM]/[PR], [OM_rs]/[TR_rs], and [TR_rs]/[PR_rs]. The mean ± standard deviation values of trueness for the complete-arch scan data were 54 ±4 µm for [OM], 42 ±5 µm for [TR], and 30 ±2 µm for [PR]. In the group of the "cut out-rescanned" data, the mean trueness results were 55 ± 6 µm for [OM_rs], 38 ±5 µm for [TR_rs], and 31 ±5 µm for [PR_rs]. Significant differences were found among the complete-arch scan data and the "cut out-rescanned" data of the different scanners, but not between the complete-arch scan data and the "cut out-rescanned" data within one scanning system. CONCLUSIONS: Significant differences were found among the scanners, but "cut out-rescan" procedures did not affect the accuracy within each scanning system.

Accuracy, trueness, and precision - a guideline for the evaluation of these basic values in digital dentistry.

An increasing number of accuracy studies on 3D digitizing systems, especially intraoral scanning devices, are being published in scientific and educational journals. The methods, measurement values, and statistical parameters of these studies vary. Certain inconsistencies exist, which lead to difficulty in terms of interpretation and sometimes even questionable conclusions being drawn. These issues make it almost impossible to compare the results of such studies. One aspect inherent in this is the mutable use of basic terms describing the quality of measurement outcomes. A clear definition of such terms and clear instructions as to their respective calculation processes is essential for communication among scientists as well as for reporting measurement results to the dental community. Therefore, the aim of the present guideline is to provide a clear definition of the accuracy, trueness, and precision as the basic terms in the context of digital dentistry. The survey for this guideline included the application of ISO Norms and their expansion to special aspects concerning 3D data acquisition and, in particular, surface meshes. Additionally, the literature was screened to collect approaches, which can be seen as useful for dealing with these terms when performing different kinds of studies.

A chairside concept for increasing the vertical dimension of occlusion in the maxilla and mandible.

An entirely digital concept has previously been proposed for the reconstruction of the occlusal plane in the case of wear-induced loss of the vertical dimension of occlusion (VDO). The concept, however, calls for a face scan. Since this technology is less frequently available than a facebow, the concept discussed in this article proposes a combination of analog and digital techniques. It takes into account the problem of redefining the occlusal plane in the case of occlusal alteration, and tries to avoid a situation where the chairside digital design of the occlusal surfaces is performed without any anatomical references. Such a situation poses a significant risk if the treatment indication for bite elevation exists in both the maxilla and the mandible.

Monolithic restorations on customized titanium abutments - a cast-free approach without the necessity of gingiva management for impression taking.

The present application report describes a cast-free and chairside workflow that enables the manufacturing of monolithic restorations on custom-made abutments without damaging the periimplant soft tissue for impression taking. An easily achievable checklist for the individualization of standard abutments is presented so that the shape of the abutment is compatible with especially developed software after optical impressions. The principle of the method contains an extraoral impression of the finish line of the abutment and an intraoral impression that indicates the abutment position in relation to the adjacent teeth. The software needed for the semi-automated registration of the intra- and extraoral impression operates with .stl data and can be provided by the corresponding author on request.

Clinical survival of chair-side generated monolithic lithium disilicate crowns:10-year results.

OBJECTIVES: Nowadays, all-ceramic materials are routinely used within the treatment of patients in dentistry. The objective of this prospective clinical trial was the evaluation of chair-side generated monolithic lithium disilicate crowns after 10 years. MATERIALS AND METHODS: Forty-one posterior full contour crowns made of lithium disilicate ceramics were inserted with a self-adhesive resin cement in 34 patients (20 university/14 private practice) using a chair-side CAD/CAM technique. One crown per patient was randomly selected for evaluation according to the modified US Public Health Service criteria. RESULTS: After a mean examination time of 10.1 years, 26 crowns were available for re-examination. Within the observation period, five failures occurred due to one crown fracture after 2.9 years, an abutment fracture after 6.0 years, one severe endodontic problem after 6.1 years, a root fracture after 7.0 years, and a replacement of one crown caused by a carious lesion after 10 years. Complications occurred as retention loss of one crown, two carious lesions, and a change in sensibility perception of two abutment teeth. All events were associated with molars. The Kaplan-Meier analysis revealed a survival rate of 83.5% and a complication-free rate of 71.0% after 10 years. CONCLUSION: Due to the small amount of technical complications and failures, the clinical performance of monolithic lithium disilicate crowns was completely satisfying. CLINICAL RELEVANCE: The insertion of chair-side fabricated monolithic lithium disilicate crowns can be recommended for long-term use in the posterior region.

Antagonist wear of monolithic zirconia crowns after 2 years.

OBJECTIVES: The aim of this study was to evaluate the amount of wear on the antagonist occlusal surfaces of clinically placed monolithic zirconia premolar and molar crowns (LAVA Plus, 3M ESPE). MATERIALS AND METHODS: Fourteen in situ monolithic zirconia crowns and their opposing antagonists (n = 26) are the subject of an ongoing clinical trial and have been clinically examined at baseline and after 24 months. Silicone impressions were taken and epoxy replicas produced for qualitative SEM analysis and quantitative analysis using optical profilometry. Based on the baseline replicas, the follow-up situation has been scanned and digitally matched with the initial topography in order to calculate the mean volume loss (in mm3) as well as the mean maximum vertical loss (in mm) after 2 years in service. RESULTS: The mean volume loss for enamel antagonist contacts (n = 7) was measured to 0.361 mm3 and the mean of the maximum vertical loss to 0.204 mm. The mean volume loss for pure ceramic contacts (n = 10) was measured to 0.333 mm3 and the mean of the maximum vertical loss to 0.145 mm. The wear rates on enamel contacts were not significantly different from those measured on ceramic antagonists. CONCLUSIONS: Based on the limitations of this study, it can be concluded for the monolithic zirconia material LAVA Plus that the measured wear rates are in consensus with other in vivo studies on ceramic restorations. Further, that no significant difference was found between natural enamel antagonists and ceramic restorations as antagonists. The monolithic zirconia restorations do not seem to be affected by wear within the first 2 years. CLINICAL RELEVANCE: The monolithic zirconia crowns (LAVA Plus) show acceptable antagonist wear rates after 2 years in situ, regardless of natural enamel or ceramics as antagonist materials.

Chair-side generated posterior monolithic lithium disilicate crowns: clinical survival after 6 years.

OBJECTIVES: The objective of this prospective clinical study was to evaluate the clinical performance of chair-side generated monolithic lithium disilicate crowns after 72 months. MATERIALS AND METHODS: Forty-one posterior full contour crowns made of lithium disilicate ceramic were inserted in 34 patients with a chair-side CAD/CAM technique. One crown per patient was randomly selected for evaluation at baseline, 6, 12, 24, 36, 48, 60 and 72 months according to the modified US Public Health Service criteria. RESULTS: After a mean examination time of 73.2 months (SD ± 1.7 months), 25 crowns were available for re-examination. Within the observation period, three failures occurred due to one crown fracture after 2.9 years, an abutment fracture after 6.0 years, and one severe endodontic problem after 6.1 years. One lithium disilicate crown showed a loss of retention after 2 years but could be reinserted. There were two events of caries below the crown margin, one after 24 and another one after 48 months. Both teeth received cervical adhesive composite fillings. Two abutment teeth changed their sensibility perception from positive to negative within the first 13 months. The failure-free rate was 87.6%, and the complication-free rate was 70.1% after 6 years according to the Kaplan-Meier analysis. CONCLUSIONS: Due to the fact that there was only one severe technical complication and the severe biological complications were in a normal range, the clinical performance of monolithic lithium disilicate crowns in the posterior region was completely satisfying. CLINICAL RELEVANCE: The chair-side application of monolithic lithium disilicate crowns can be recommended.

Antagonist wear by polished zirconia crowns.

AIM: The aim of this in vivo study was to measure antagonist wear caused by polished monolithic posterior zirconia crowns over a 24-month period using the intraoral digital impression (IDI) technique. MATERIALS AND METHODS: Thirteen zirconia crowns were placed in nine patients. The crowns and adjacent teeth were captured using an intraoral scanner (Lava C.O.S.). The corresponding antagonist teeth and the respective neighboring teeth were also scanned. Scanning was performed immediately after the restoration (baseline) as well as 12 and 24 months after crown placement. Geomagic Qualify software was used to superimpose the follow-up data sets onto the corresponding baseline data set, identify wear sites, and measure maximum vertical height loss in each individual wear site. Overall antagonist wear was then determined as the mean of wear rates measured in all of the individual antagonist units. In addition, wear rates in enamel and ceramic antagonists were analyzed as part of the scope of this study. RESULTS: The maximum mean wear with standard deviation (SD) in the overall sample with a total of nine patients, 13 antagonist units, and 98 evaluable wear sites was 86 ± 23 µm at 12 months, and 103 ± 39 µm at 24 months. The maximum mean wear in the enamel antagonist subgroup was 87 ± 41 µm at 12 months, and 115 ± 71 µm at 24 months; and in the ceramic antagonist subgroup 107 ± 22 µm at 12 months, and 120 ± 27 µm at 24 months. CONCLUSIONS: The wear rates determined in this study are comparable to those of existing studies. The IDI technique of wear analysis can be carried out in a practical manner and produces useful results.

Optical profilometry versus intraoral (handheld) scanning.

AIM: The aim of this study was to evaluate the difference in maximum height loss values obtained from datasets based on optical profilometry and intraoral scanning. Additionally, two analysis applications were tested with respect to their correspondence. MATERIALS AND METHODS: To obtain baseline data, the occlusal surface of a metal phantom tooth was scanned by optical profilometry [WLP] and an intraoral scanner [IOS]. Then, wear was simulated at two locations of the tooth, three times each ([wear1], [wear2], and [wear3]), and the surface was captured after each status of wear, applying [WLP] and [IOS]. The maximum vertical height loss was evaluated by comparing the 3D datasets of [WLP] and [IOS] at [wear1], [wear2], and [wear3] with the baseline data of [WLP] and [IOS], respectively. For this purpose, two commercially available applications, Geomagic Qualify and Oracheck, were used. RESULTS: Apart from one outlier of 16% difference between the data obtained from [WLP] and [IOS], the maximum difference was 12.6%, which was equal to a metrical value of 15 µm. For the corresponding values, which were calculated with Geomagic Qualify and Oracheck at identical wear facets, maximum differences between +7% and -6.7% were obtained. CONCLUSIONS: According to this in vitro study, the wear measurement on the basis of [IOS] seems to be a cost-effective, quick, and easily applicable tool for clinical screening purposes, with an acceptable reliability. With respect to the minor variations between each other, the Geomagic Qualify and Oracheck measurement applications are equivalent.

The face scan as a means for the visualization of complex prosthetic reconstructions.

The face scan can serve as a means for the visualization of planes relevant for extensive prosthetic reconstructions. The key prerequisite is the availability of data in stl format for further processing in different software programs. The method is described in this article by a patient case.

Three-unit CAD/CAM-generated lithium disilicate FDPs after a mean observation time of 46 months.

OBJECTIVES: Lithium disilicate can easily be machined by CAM techniques in its metasilicate status. Due to slightly inferior material properties, the material is not yet recommended for three-unit fixed dental prosthesis (FDP) as it is the case for the press material up to the second bicuspid. Therefore, the aim of this clinical study was to evaluate the performance of CAD/CAM-fabricated lithium disilicate FDPs. MATERIALS AND METHODS: A total of 32 anterior and posterior FDPs were provided for 32 patients. Twelve FDPs were fabricated chair-side. The first recall took place 6 months after insertion and then annually. The FDPs were rated according to biological and technical complications. As failure, those events were defined, which led to the removal of a FDP. The failure-free (survival) rate and the complication-free rate were calculated according to Kaplan-Meier. RESULTS: After a mean observation time of 46 months (SD ± 8.4 months), three endodontic complications in two FDPs, two minor chippings, and one catastrophic fracture occurred. One FDP had to be removed due to persisting undefined complaints. Thus, the failure-free rate and the complication-free rate were revealed as 93 and 83 %, respectively. CONCLUSIONS: Despite the limited observation period, the results are promising, especially due to the fact that the fractured FDP did not fulfill the recommended connector dimensions. CLINICAL RELEVANCE: Inserted as a full-contour three-unit FDP within its indications, the CAD/CAM lithium disilicate ceramic offers an appropriate alternative to layered restorations.

Options in virtual 3D, optical-impression-based planning of dental implants.

If a 3D radiograph, which in today's dentistry often consists of a CBCT dataset, is available for computerized implant planning, the 3D planning should also consider functional prosthetic aspects. In a conventional workflow, the CBCT is done with a specially produced radiopaque prosthetic setup that makes the desired prosthetic situation visible during virtual implant planning. If an exclusively digital workflow is chosen, intraoral digital impressions are taken. On these digital models, the desired prosthetic suprastructures are designed. The entire datasets are virtually superimposed by a "registration" process on the corresponding structures (teeth) in the CBCTs. Thus, both the osseous and prosthetic structures are visible in one single 3D application and make it possible to consider surgical and prosthetic aspects. After having determined the implant positions on the computer screen, a drilling template is designed digitally. According to this design (CAD), a template is printed or milled in CAM process. This template is the first physically extant product in the entire workflow. The article discusses the options and limitations of this workflow.

Soft tissue-preserving computer-aided impression: a novel concept using ultrasonic 3D-scanning.

Subgingival preparations are often affected by blood and saliva during impression taking, regardless of whether one is using compound impression techniques or intraoral digital scanning methods. The latter are currently based on optical principles and therefore also need clean and dry surfaces. In contrast, ultrasonic waves are able to non-invasively penetrate gingiva, saliva, and blood, leading to decisive advantages, as cleaning and drying of the oral cavity becomes unnecessary. In addition, the application of ultrasound may facilitate the detection of subgingival structures without invasive manipulation, thereby reducing the risk of secondary infection and treatment time, and increasing patient comfort. Ultrasound devices commonly available for medical application and for the testing of materials are only suitable to a limited extent, as their resolution, precision, and design do not fulfill the requirements for intraoral scanning. The aim of this article is to describe the development of a novel ultrasound technology that enables soft tissue-preserving digital impressions of preparations for the CAD/CAM-based production of dental prostheses. The concept and development of the high-resolution ultrasound technique and the corresponding intraoral scanning system, as well as the integration into the CAD/CAM process chain, is presented.

Chair-side generated posterior lithium disilicate crowns after 4 years.

OBJECTIVES: The objective of this prospective clinical study was to evaluate the performance of chair-side generated crowns after 48 months. MATERIALS AND METHODS: Forty-one posterior full contour crowns made of a machinable lithium disilicate ceramic (e.max CAD LT) were inserted in 34 patients applying a chair-side CAD/CAM technique. One crown per patient was randomly selected for evaluation at baseline, after 6, 12, 24, 36, and 48 months according to modified US Public Health Service criteria. RESULTS: After a mean observation time of 51 months (min, 48 months; max, 56 months; SD ± 2.3 months), 29 crowns were available for re-examination. Within the observation period, one failure occurred due to a crown fracture after 2.8 years. Four abutment teeth revealed signs of biological complications: Two abutment changed sensibility perception from positive to negative within the first 13 month. Two abutment teeth showed secondary caries below the crown margin, one after the 24, and another after the 48 month recall. Both abutments received cervical adhesive composite fillings. The failure-free rate was 96.3 % after 4 years according to Kaplan-Meier (CI: upper bound, 4.4 years; lower bound, 4.7 years). CONCLUSIONS: Due to the fact that the secondary caries was not caused as a result of an inaccuracy of the crown margins and the endodontic complications were in a normal range, the clinical performance of the crowns was completely satisfying. CLINICAL RELEVANCE: The chair-side application of lithium disilicate crowns can be recommended.