Intraoral scanning systems - a current overview.

There is no doubt today about the possibilities and potential of digital impression-taking with the aid of intraoral optical impression systems, and the past few years have seen a considerable increase in the range of optical intraoral scanners available on the market. On the strength of numerous innovations and a wider range of indications in orthodontics and implantology, intraoral scanning systems appear to be a highly promising development for the future. Digital impression-taking with intraoral scanners has already shown itself in some respects to be clearly superior to conventional impression- taking. Particularly worthy of mention is the versatile integration of digital impressions into diagnostic and treatment concepts to provide a customizable healthcare solution for the patient. It remains exciting to look forward to future developments that will allow us to observe digital impression-taking--as with other digital applications already established in everyday life--becoming firmly established in the routine of dentistry and dental technology. This article presents an overview of the benefits and limitations of digital impression-taking using intraoral scanning systems, and includes a summary of all the relevant intraoral scanners available on the market at present.

Clinical performance of chairside CAD/CAM feldspathic ceramic posterior shoulder crowns and endocrowns up to 12 years.

In 55 patients, 25 endocrowns (test) and 40 shoulder crowns (control) were produced chairside in a private practice using the Cerec 3 (CAD/CAM) method and Vita Mark II feldspathic ceramic. The crowns were examined at baseline and after up to 12 years using modified USPHS criteria. The survival estimate was assessed by Kaplan-Meier analysis. The 12 years survival estimate of the shoulder crowns was 95% on molars and 94.7% on premolars. Endocrowns showed 90.5% survival on molars and 75% on premolars. Statistically, the differences between the survival estimates were not significant (P > 0.05). The longevity of Vita Mark II Cerec 3 shoulder crowns on molars and premolars, as well as of endocrowns on molars, proved to be--for private practice--a very acceptable result, while the premolar endocrowns tended to show a higher risk for failure.

Thin-wall ceramic CAD/CAM crown copings: strength and fracture pattern.

The strength and fracture pattern of posterior CAD/CAM-generated crown copings with 0.4 mm wall thickness were evaluated in vitro hypothesizing that fracture resistance of YTZP-zirconia copings might be independent of mode of cementation whether resin-bonded or cemented because of the high strength of YTZP-zirconia. Two sets of copings (n = 15) each were fabricated using CEREC inLab CAD/CAM from (i) lithiumdisilicate glass-ceramic, (ii) infiltration ceramic as controls and (iii) YTZP-zirconia. Copings (n = 15) of ceramics (i), (ii) and (iii) each were (a) zinc-phosphate cemented, (b) adhesively seated on resin-based composite dies and loaded until fracture. Load (N) data was analysed using anova and Scheffé tests. Crack pattern was evaluated on additional three sample cross-sections for each group at fracture-start. Radial cracks originated early at the cementation interfaces and cone cracks were observed finally at the loading sites. Mean load (N) values (+/-s.d.) of A-copings at fracture-start/-end (i) 804 +/- 195/862 +/- 162, (ii) 923 +/- 180/975 +/- 147, (iii) 697 +/- 110/1607 +/- 145, were all significantly (P < 0.01) lower when compared with their B-crown coping analogs (i) 1183 +/- 318/1919 +/- 326, (ii) 1621 +/- 165/1820 +/- 211, (iii) 731 +/- 115/1973 +/- 287 except for A3 and B3 at fracture-start. This confirmed our hypothesis at fracture-start (P > 0.05) but rejected it at fracture-end (P < 0.01). The A3 fracture-end data, even if significantly (P < 0.01) lower, came close to the B3 values by 18%. A3 was significantly (P < 0.001) stronger by 86/74% than A1/A2 at fracture-end. The data indicates that YTZP-zirconia copings have the potential to provide support for all-ceramic core crowns, which may be adequate for non-adhesive cementation.

Marginal and internal fit of all-ceramic CAD/CAM crown-copings on chamfer preparations.

Evaluation of the marginal and internal fit of all-ceramic molar crown-copings hypothesizing that Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) fabrication shows the same accuracy of fit as conventional techniques. A set of six individual crown preparations was duplicated 12 times yielding 72 plaster dies. Slip-cast (In-Ceram Zirconia), heat-pressing (Empress II) and CAD/CAM crown-copings (Cerec inLab, DCS, Decim and Procera) were seated on 12 dies each. Marginal and internal gap width was measured in the SEM at 120x magnification. Marginal gap of slip-cast (25 +/- 18 microm) was significantly (P < 0.05) smaller than that of Empress II (44 +/- 23 microm) copings. Procera (17 +/- 16 microm) and Decim (23 +/- 17 microm) did not differ (P > 0.05) from slip-cast (25 +/- 18 microm) but were smaller (P < 0.001/P < 0.01) than Empress II (44 +/- 23 microm) and Cerec inLab (43 +/- 23 microm) (P < 0.001/P < 0.05). DCS (33 +/- 20 microm) did not differ (P > 0.05) from any of the others. The internal mid-orobuccal gap width of Procera (136 +/- 68 microm) was larger (P < 0.001) than that of Decim (81 +/- 30 microm) and slip-cast (94 +/- 84 microm) (P < 0.05) while Empress II (105 +/- 53 microm), DCS (110 +/- 79 microm) and Cerec inLab (114 +/- 58 microm) did not differ significantly (P > 0.05) from Decim, Procera and slip-cast. Internal mesiodistal gap width was similar. The fit of conventional and CAD/CAM all-ceramic molar crown-copings covered the same range of gap width confirming the assumed hypothesis.

Chairside multi-unit restoration of a quadrant using the new Cerec 3D software.

The new Cerec 3D design software for inlays and partial and full crowns simplifies work when producing several restorations in one session. Quite significant progress has been achieved, in that the entire row of teeth of a quadrant can be acquired completely and displayed by successively overlapping optical impressions. The digital working model of a quadrant in which all preparations are acquired is the result. The restorations can be designed individually and inserted virtually. Thanks to virtual insertion, the proximal contacts to neighboring restorations can be designed perfectly and all restorations finally designed, milled, and inserted in one sitting. This method provides a significant rationalization effect.

Flexural strength of Cerec 2 machined and jointed InCeram-Alumina and InCeram-Zirconia bars.

OBJECTIVE: The flexural strength of Cerec 2 InCeram-Alumina and InCeram-Zirconia bars is evaluated. The focus of the in vitro study is to identify a jointing procedure for InCeram which may be used for producing full-ceramic fixed-partial-denture frameworks. METHODS: Six groups (n=15) of machined and jointed InCeram-Alumina (T1-T5) and InCeram-Zirconia (T6) bars (3x4x13mm(3)), respectively, were examined using a 3-point-bending test. InCeram-Alumina joint-free controls were: machined (C1), slip cast (C2, C3) and cut from the block (C4) bars. Machined joint-free InCeram-Zirconia bars were used as controls (C5). InCeram-Alumina slip was used for jointing T1-T5 and InCeram-Zirconia slip for bars T6. Bars were jointed in groups T1 and T2 using butt joint (S1), in T3 and T4 oblique (S2, S3) and in T5 and T6 rounded (S4) joint shapes. RESULTS: Two-way analysis of variance showed significant differences between materials (p<0.001) and jointing shapes (p<0.001). The rounded (S4) shape showed the highest flexural strength of 434 (65) MPa of InCeram-Alumina (T5) and 475 (54) MPa of InCeram-Zirconia (T6) bars, respectively but machined/joint-free InCeram-Alumina (511 (59) MPa, C1) and machined/joint-free InCeram-Zirconia (624 (58) MPa, C5) were significantly (p<0.01/p<0.001) stronger. No significant differences (p>0.05) were found between machined/jointed InCeram-Zirconia (475 (54) MPa, T6), joint-free InCeram-Alumina slip cast (498 (125) MPa, C2) and joint-free InCeram-Alumina machined bars (511 (59) MPa, C1). SIGNIFICANCE: Compared to conventional slip cast InCeram-Alumina the flexural strength of machined/jointed InCeram-Zirconia appears to be adequate for fixed-partial-denture frameworks.

The Cerec 3--a quantum leap for computer-aided restorations: initial clinical results.

The Cerec 3 system simplifies and accelerates the fabrication of ceramic inlays, onlays, veneers, and quarter, half, and complete crowns for anterior and posterior teeth. Cerec 3 software simplifies occlusal and functional registration. Proper occlusion is established accurately and quickly; manual adjustment is reduced to a minimum. The separate grinding device, working true to morphologic detail and with fine surface quality, is connected to the optical unit by radio control. Equipped with a laser scanner, it can also be used for indirect application through a standard personal computer. The Cerec 3 system is network and multimedia ready and, in combination with an intraoral color videocamera or a digital radiography unit, can be used for patient education and for user training. The Cerec 3 system thus is a diagnostic, restorative, training, and documentation center for the dental practice.

Clinical and scanning electron microscopic evaluation of fiber-reinforced inlay fixed partial dentures: preliminary results after one year.

STATEMENT OF PROBLEM: Restorative dentistry searches for nonmetal reinforcement of esthetic fixed partial dentures (FPDs). PURPOSE: This clinical study evaluated conservative fiber-reinforced composite FPDs bonded to inlay abutments. MATERIAL AND METHODS: Twenty fiber-reinforced composite inlay FPDs were made for 15 patients. Restorations were manufactured with the Targis Vectris glass-fiber-reinforced composite system and a simplified laboratory technique. The 20 bonded inlay FPDs were examined clinically and by SEM after 1 year. RESULTS: All 20 FPDs were intact at the 1-year examination. There were no signs of fracture, surface defects, or excessive wear with SEM. SEM marginal analysis exhibited 91.6% +/- 5% excellent margins at the tooth-luting composite interface and 86. 1% +/- 8% excellent margins at luting composite/restoration interface. CONCLUSION: On the basis of the results of this descriptive study, bonded glass-fiber-reinforced composite inlay FPDs were considered clinically successful at the 1-year examination.

Clinical evaluation of adhesively placed Cerec endo-crowns after 2 years--preliminary results.

PURPOSE: Non-vital endodontically treated posterior teeth with complete loss of coronal hard tissues were prepared with a circular equigingival butt margin and central retention cavity of the entire pulp chamber ("endo-preparation"). Computer-generated ceramic corono-radicular restorations (Cerec endo-crowns) were bonded to these preparations. The purpose of this study was to evaluate the survival rate and the clinical quality of CAD/CIM endo-crowns after 2 years. MATERIALS AND METHODS: 19 Cerec endo-crowns (4 premolars and 15 molars) in 13 patients were examined using modified USPHS criteria at baseline and after an average time of 26 months. The ratings of the two examinations were compared. RESULTS: The service time of the 19 endo-crowns was 14 to 35.5 (mean +/- SD: 26 +/- 6) months. One molar endo-crown failed after 28 months because of recurrent caries. CONCLUSION: The overall clinical quality of the Cerec endo-crowns was very good, and so far, the clinical concept appears feasible.

Full-ceramic CAD/CIM anterior crowns and copings.

The purpose of the investigation was to examine the marginal and internal fit of Cerec anterior crowns and crown copings. The marginal and internal fit of Cerec anterior crowns (n = 18) and copings was examined on each of six anterior model tooth preparations, with different types of butt-margin crown preparation design on different teeth: 1.) straight flat (tooth 22), 2.) following the CEJ with mid-approximally steep curvature angles of 90 degrees mesial and 40 degrees distal (tooth 21) and 3.) same as 2, but with obtuse angles of 130 degrees and 150 degrees (tooth 41). The anterior crowns were machined on Cerec 2 units using Mark II ceramic (Vita), and the Cerec copings using In-Ceram Spinell (Vita). Laboratory slip-cast In-Ceram spinell anterior crown copings served as controls (n = 18). All reconstructions were seated (with adhesive) on the preparations, and the width of the marginal interface was measured circumferentially using SEM at 150x magnification. After cross-sectioning all samples in the bucco-oral direction, the internal fit was measured using this same technique. The marginal width of computer machined Cerec CAD/CIM anterior crowns (59.9 +/- 5.6 microns) was significantly (p < 0.01) lower than that of machined (73.4 +/- 12 microns) and slip-cast In-Ceram spinell copings (75.5 +/- 17 microns). The internal fit values of the slip-cast copings (94.1 +/- 20 microns) were significantly (p < 0.001) lower than those of the Cerec Mark II anterior crowns (141.3 +/- 21 microns) and copings (146.8 +/- 17 microns). Cerec CAD/CIM machined anterior full-ceramic crowns and copings showed excellent fit in comparison with slip-cast In-Ceram spinell copings. In terms of the marginal and internal fit, there were no significant differences (p > 0.05) between the different butt-margin preparation designs. Selected clinical cases demonstrate the high esthetics of anterior Cerec crowns.

Effects of preparation and luting system on all-ceramic computer-generated crowns.

PURPOSE: Computer-aided design/computer-integrated machining (CAD/CIM) allows defect-oriented custom-shaping of the inside surfaces of all-ceramic crowns. The purpose of this study was to examine the effect of inside crown form on fracture strength of cemented and bonded crowns. MATERIALS AND METHODS: Four preparation types were used: (1) "classic" with a butt shoulder of 1.2 mm, abutment height of 4 mm, and 6-degree convergence, (2) like type 1 with mesio-occlusodistal cavity, (3) like type 1 with height reduced by 50%, and (4) like type 1 with abutment reduced by 100% plus a pulp chamber cavity. Crowns were CAD designed on preparations 1 to 4 using identical outside morphology. Machined crowns were placed on abutments (a) without any media as controls (n = 15), (b) cemented (n = 15), and (c) bonded (n = 15), and were loaded until fracture. RESULTS: Zinc phosphate-cemented crowns (1b, 2b, 3b, and 4b) showed significant (P < 0.001) increase of fracture load values compared to uncemented control crowns (1a, 2a, 3a, 4a). Fracture load values of bonded crowns (1c, 2c, 3c) were significantly (P < 0.001) higher than those for cemented crowns. Bonded crowns with thick occlusal dimensions (3c and 4c) showed the highest fracture load values. CONCLUSION: Bonded all-ceramic CAD/CIM crowns with defect-oriented inside morphology and increased occlusal dimensions showed high fracture load values.

Grinding precision and accuracy of fit of CEREC 2 CAD-CIM inlays.

The authors conducted research to determine the grinding precision and accuracy of fit of ceramic inlays generated with the completely redesigned CEREC 2 computer-assisted design/computer-integrated manufacturing, or CAD-CIM, unit. They found that the grinding precision of the CEREC 2 unit was 2.4 times greater than that of CEREC 1. With CEREC 2, the mean (+/-standard deviation) luting interfaces were 56 +/- 27 micrometers, which is a 30 percent improvement in the accuracy of fit compared with that of CEREC 1.

The new creativity in ceramic restorations: dental CAD-CIM.

The efficiency of the Cerec 2 system, introduced in September 1994, is briefly presented. The system provides improved accuracy of fit, an automatically generated occlusion, free (unrestricted) cavity design, unlimited anatomic veneer preparation with incisal edge coverage, and automated and simplified operation.

[The computer-generated occlusion of Cerec-2 inlays and onlays]. / Computergenerierte Okklusion von Cerec-2 Inlays und Overlays.

The Cerec-2 unit offers three different options to generate the occlusion: anatomically extrapolated ("Extrapolation"), correlated to a wax-up or functionally generated path ("Correlation") and bucco-orally flat ("Linear") as known from Cerec-1. These three computer-generated occlusions were evaluated by measuring the vertical discrepancy and the specific time needed for manufacturing (design, machining, contouring and adjusting the occlusal relation) of inlays and overlays. The occlusion of inlays generated with "Extrapolation" (0.42 +/- 0.16 mm) and "Correlation" (0.80 +/- 0.17 mm) showed significantly (p < 0.001) less vertical discrepancy than "Linear" (2.46 +/- 0.50 mm). The specific production time of inlays differed significantly (p < 0.001) between "Extrapolation" (16.05 +/- 0.80 min), "Linear" (19.25 +/- 1.14 min) and "Correlation" (27.33 +/- 0.75 min). The vertical discrepancies of overlays generated with "Correlation" (1.26 +/- 0.43 mm) were significantly (p < 0.001) lower than with "Extrapolation" (2.46 +/- 0.50 mm) and "Linear" (2.75 +/- 0.57). The specific overlay production time was significantly (p < 0.001) longer with "Correlation" (39.44 +/- 1.36) than with "Linear" (23.9 +/- 1.26 min) and "Extrapolation" (23.71 +/- 1.01 min). Related to the technical status of 10/1994 and as a result of the present evaluation, "Extrapolation" was chosen to be the most practical of the computer-generated occlusions evaluated in the present study.

[The curing of composites under Cerec inlays]. / Die Aushärtung von Komposit unter Cerec-Inlays.

96 Cerec CAD/CIM inlays (Vita Cerec Mk II, shades A2C and B3C) were seated into one reusable mod-cavity in a human molar. Light- (Brilliant Lux Incisal, Coltène) and dual- (Vita Duo Cement) curing composite resin respectively were used and the proximal areas were irradiated using a curing light (Coltolux II) with 4 different procedures: A) 210 s; B) 120 s (including 30 s Luciwedge, LW); C) 120 s (no LW) and D) 60 s. Vickers hardness (VHN) of the cured resin was measured at the pulpo-axial walls of the removed inlays. Polymerization-% of the resin was calculated relative to VHN of control samples, whose polymerization was scored as 100%. Two way Anova and Scheffé test were used for statistical comparison of the data. The results for the light-/dual-curing groups for shade A2C were: A) 97/89%, B) 89/90%, C) 91/88% D) 79/69%. Results for shade B3C were: A) 97/87%, B) 86/87%, C) 89/88% and D) 71/69%. No significant differences (p > 0.05) were found between light- and dual-curing. With procedures A, B and C light- and dual-curing resulted in adequate polymerization rates (PR > 85%) whereas D (PR < 80%) was significantly (p < 0.001) lower than A, B and C. Dual-curing resin had no advantages vs. light-curing with respect to polymerization rate when seating Cerec CAD/CIM inlays. The overall handling of the light-curing composite resin was judged to be easier than that of the dual cure material.

[Grinding precision and accuracy of the fit of Cerec-2 CAD/CIM inlays]. / Schleifpräzision und Passgenauigkeit von Cerec-2-CAD/CIM-Inlays.

The grinding precision of one Cerec-1 (C1) and one Cerec-2 (C2) CAD/CIM unit each was evaluated using standardized inlay-like (mod) samples (n = 40) of Vita Cerec Mk II porcelain and Dicor MGC glass ceramic. Typical dimensions (B, E, F, H) of the sampleS were measured and the standard deviations (SD) analysed statistically using the F-test. SD of C2-machined sample dimensions were significantly lower using both Vita, B: p < 0.05; E: p < 0.001; F: p < 0.001; H: p < 0.001, and Dicor MGC, B: p < 0.05; E: p < 0.001; F: p < 0.001; H: p < 0.01, than those machined with C1, indicating a strong improvement of grinding precision of C2 compared to C1. Accuracy of fit to human molar cavities of mod inlays machined with C1 (n = 6) and C2 (n = 6) was evaluated using a scanning electron microscope with 100x magnification. The width of the interfacial luting gap was generally lower in C2 inlays (56 +/- 27 microns) than with C1 (84 +/- 38 microns). Significant differences (t-test) were seen in margin sections "cervical line angles above CEJ" (C1 = 124 +/- 44/C2 = 59 +/- 30 microns, p < 0.05), "cervical line angles at CEJ" (C1 = 109 +/- 55/C2 = 67 +/- 27 microns, p < 0.05) and "gingival margin above CEJ" (C1 = 81 +/- 32 microns/C2 = 31 +/- 18 microns, p < 0.05).

[The preparation of ceramic restorations with superfine diamond instruments]. / Die Ausarbeitung von Keramikrestaurationen mit superfeinen Diamantinstrumenten.

Four groups of computer machined (Cerec 64 microns) Vita Mk II porcelain samples with six blocks (12 x 7 x 1.5 mm) each were finished, using super-fine diamond burs (15, 8, 4 microns) and Proxoshape files (15, 8, 4 microns) and additionally polished with standard round and experimental angular cut discs. Surface roughness was measured after each treatment. For control, porcelain surfaces were high-gloss polished with a laboratory polishing machine (LPM). The roughness values R15/8/4 achieved with 15/8/4 microns diamond burs, were significantly different between the diamond grain sizes used: R15 = 1.49 +/- 0.44 > R8 = 0.86 +/- 0.25 (p < 0.05); R8 = 0.86 +/- 0.25 > R4 = 0.56 +/- 0.10 (p < or = 0.055); R4 = 0.56 +/- 0.10 > RLPM = 0.05 +/- 0.01 (p < 0.001). The diamond coated Proxoshape files caused the following roughness values RP15 = 0.53 U +/- 0.17 > RP8 = 0.24 +/- 0.06 (p < 0.01) and the Proxoshape file with 4 microns diamond coating did not achieve lower roughness values. The 8 microns diamond coating of burs and Proxoshape files caused a very fine "pre-polish" surface quality on porcelain. Angular discs had the same polishing ability as standard round discs but were more effectively used in fissures.