Accuracy of Different Implant Impression Techniques: Evaluation of New Tray Design Concept.

PURPOSE: To evaluate implant impression accuracy with a new tray design concept in comparison to nonsplinted and splinted impression techniques for a 2-implant situation. MATERIALS AND METHODS: A reference bar titanium framework was fabricated to fit on 2 parallel implants. The framework was used to generate a resin master model with 2 implants that fit precisely against the framework. Three impression techniques were evaluated: (1) nonsplinted, (2) splinted, and (3) nonsplinted with modified tray impressions. All the trays were fabricated from light-cured acrylic resin material with openings that corresponded to the implant impression copings. Ten impressions were taken for each technique using poly(vinyl siloxane) impression material. The impressions were poured with type IV dental stone to generate the test casts. A rosette strain gauge was bonded to the middle of the framework. As the framework retaining screws were tightened on each test cast, the developed strains were recorded until the completion of the tightening to 35 Ncm. The generated strains of the rosette strain gauge were used to calculate the maximum principal strain. RESULTS: A statistically significant difference was observed among the different impression techniques. The modified tray design impression technique was associated with the least framework strains, which indicates greater accuracy compared with the other techniques. There was no significant difference between the splinted and the nonsplinted impression techniques. CONCLUSIONS: The new tray design concept appeared to produce more accurate implant impressions than the other techniques. Despite the statistical difference among the impression techniques, the clinical significance of this difference is yet to be determined.

Profilometric changes of peri-implant tissues over 5 years: A randomized controlled trial comparing a one- and two-piece implant system.

OBJECTIVES: To assess the profilometric changes of the buccal soft tissues between baseline and 5 years of loading using a one- and two-piece dental implant system. MATERIALS AND METHODS: Sixty patients randomly received dental implants of either a two-piece type (BRA) or a one-piece type (STM). Casts were obtained at baseline (after crown insertion), at the 1-year and at the 5-year follow-up. Stereolithography files were obtained from the casts for digital superimposition. One implant and the contralateral natural tooth were selected for the analysis. Thirty-three patients (BRA = 16; STM = 17) were included. Measurements included changes for crown height (CH) and estimated soft tissue thickness, as well as the profilometric change at the implant and the tooth site. Nonparametric methods were applied for the statistical analyses and medians and quartiles presented. RESULTS: The BRA group lost -0.39 mm and the STM group lost -0.40 mm of volume between baseline and the 5-year follow-up at the implant site (p > 0.05). The tooth site lost -0.18 mm (BRA) and -0.12 mm (STM) (p > 0.05). Volume differences between implants and teeth amounted to -0.05 mm (baseline to 1 year) and -0.25 mm (baseline to 5 years) for BRA, while for STM, the values were 0.03 mm (baseline to 1 year) and -0.16 mm (baseline to 5 years). The changes for implant CH at 1 and 5 years of follow-up amounted 0.10 and 0.09 mm (BRA) and to 0.03 and 0.22 mm (STM). The changes in tissue thickness at 1 and 5 years in the BRA group amounted to -0.28 and -0.66 mm at 1 mm, -0.21 and -0.46 mm at 3 mm, and -0.32 and -0.45 mm at 5 mm, respectively. The changes in the STM group amounted to -0.15 and -0.54 mm at 1 mm, -0.24 and -0.48 mm at 3 mm, and -0.32 and -0.57 mm at 5 mm, respectively. No significantly different medians were observed. CONCLUSIONS: Minimal profilometric and linear changes occurred at implant sites between baseline and 5 years, between implant and tooth sites and between the two implant systems.

Intraoral scan bodies in implant dentistry: A systematic review.

STATEMENT OF PROBLEM: Intraoral scan body (ISB) design is highly variable and its role in the digital workflow and accuracy of digital scans is not well understood. PURPOSE: The purpose of this systematic review was to determine the relevant reports pertaining to ISBs with regard to design and accuracy and to describe their evolution and role in the digital dentistry workflow. Special attention was placed on their key features in relation to intraoral scanning technology and the digitization process. MATERIALS AND METHODS: A MEDLINE/PubMed search was performed to identify relevant reports pertaining to ISB usage in dentistry. This search included but was not limited to scan body features and design, scan body accuracy, and scan body techniques and the role of ISBs in computer-aided design and computer-aided manufacturing (CAD-CAM) processes. Commercially available scan bodies were examined, and a patient situation was shown highlighting the use of ISBs in the digital workflow. RESULTS: Deficiencies in the reports were found regarding various scan body topics, including ISB features/design, accuracy, and the role of ISBs in CAD-CAM processes. CONCLUSIONS: ISBs are complex implant-positioning-transfer devices that play an essential role in the digital workflow and fabrication of accurately fitting implant-supported restorations. With scanner technology rapidly evolving and becoming more widespread, future studies are needed and should be directed toward all parts of the digital workflow when using ISBs. By understanding the basic components of ISBs and how they relate to digital scanning and CAD-CAM technology, more emphasis may be placed on their importance and usage in the digital workflow to ensure accurate transfer of implant position to the virtual and analog definitive cast. Efforts should be made by clinicians to identify an optimal ISB design in relation to the specific intraoral scanning technology being used.

Three-Dimensional Static Articulation Accuracy of Virtual Models-Part II: Effect of Model Scanner-CAD Systems and Articulation Method.

PURPOSE: Accurate maxillomandibular relationship transfer is important for CAD/CAM prostheses. This study compared the 3D-accuracy of virtual model static articulation in three laboratory scanner-CAD systems (Ceramill Map400 [AG], inEos X5 [SIR], Scanner S600 Arti [ZKN]) using two virtual articulation methods: mounted models (MO), interocclusal record (IR). MATERIALS AND METHODS: The master model simulated a single crown opposing a 3-unit fixed partial denture. Reference values were obtained by measuring interarch and interocclusal reference features with a coordinate measuring machine (CMM). MO group stone casts were articulator-mounted with acrylic resin bite registrations while IR group casts were hand-articulated with poly(vinyl siloxane) bite registrations. Five test model sets were scanned and articulated virtually with each system (6 test groups, 15 data sets). STL files of the virtual models were measured with CMM software. dRR , dRC , and dRL , represented interarch global distortions at right, central, and left sides, respectively, while dRM , dXM , dYM , and dZM represented interocclusal global and linear distortions between preparations. RESULTS: Mean interarch 3D distortion ranged from -348.7 to 192.2 µm for dRR , -86.3 to 44.1 µm for dRC , and -168.1 to 4.4 µm for dRL . Mean interocclusal distortion ranged from -257.2 to -85.2 µm for dRM , -285.7 to 183.9 µm for dXM , -100.5 to 114.8 µm for dYM , and -269.1 to -50.6 µm for dZM . ANOVA showed that articulation method had significant effect on dRR and dXM , while system had a significant effect on dRR , dRC , dRL , dRM , and dZM . There were significant differences between 6 test groups for dRR, dRL dXM , and dZM . dRR and dXM were significantly greater in AG-IR, and this was significantly different from SIR-IR, ZKN-IR, and all MO groups. CONCLUSIONS: Interarch and interocclusal distances increased in MO groups, while they decreased in IR groups. AG-IR had the greatest interarch distortion as well as interocclusal superior-inferior distortion. The other groups performed similarly to each other, and the overall interarch distortion did not exceed 0.7%. In these systems and articulation methods, interocclusal distortions may result in hyper- or infra-occluded prostheses.

Three-Dimensional Static Articulation Accuracy of Virtual Models - Part I: System Trueness and Precision.

PURPOSE: To evaluate the 3D static articulation accuracy of 3 model scanner-CAD systems (Ceramill Map400 [AG], inEos X5 [SIR], Scanner S600 Arti [ZKN]) using a coordinate measuring machine (CMM). Trueness and precision for each system will be reported in Part I. MATERIALS AND METHODS: The master model simulated a single crown opposing a 3-unit fixed dental prosthesis. Five mounted stone cast sets were prepared, and one set was randomly selected. Reference values were obtained by measuring interarch and interocclusal reference features with the CMM. The stone cast set was scanned 5 times consecutively and articulated virtually with each system (3 test groups, n = 5). STL files of the virtual models were measured with CMM software. dRR , dRC , and dRL , represented interarch global distortions at right, central, and left sides, respectively, while dRM , dXM , dYM , and dZM represented interocclusal global and linear distortions between preparations. RESULTS: For trueness values, mean interarch global distortions ranged from 13.1 to 40.3 µm for dRR , -199.0 to -48.1 µm for dRC , and -114.1 to -47.7 µm for dRL . Mean percentage error of interarch distortion did not exceed 0.6%. Mean interocclusal distortions ranged from 16.0 to 117.0 µm for dRM , -33.1 to 101.3 µm for dXM , 32.9 to 49.9 µm for dYM and -32.0 to 133.1 µm for dZM. ANOVA of trueness found statistically significant differences for dRC , dRL , dRM , dXM , and dZM . For precision values, absolute mean difference between the 10 superimposition combinations ranged from 25.3 to 91.0 µm for dRR , 21.5 to 85.5 µm for dRC , 24.8 to 70.0 µm for dRL . Absolute mean difference ranged from 49.9 to 66.1 µm for dRM , 20.7 to 92.1 µm for dXM , 86.8 to 96.0 µm for dYM , and 36.5 to 100.0 µm for dZM . ANOVA of precision of all test groups found statistically significant differences for dRR , dRC , dRL , dXM and dZM , and the SIR group was the least precise. CONCLUSION: The overall interarch global distortion of all three model scanner-CAD systems was low and did not exceed 0.6%. Variations in scanner technology, virtual articulation algorithm, and use of physical articulators contributed to the differences in distortion observed among all three groups.

A Novel Methodology to Validate the Accuracy of Extraoral Dental Scanners and Digital Articulation Systems.

PURPOSE: The aim of the current study is to develop a novel method to investigate the accuracy of 3D scanners and digital articulation systems. MATERIALS AND METHODS: An upper and a lower poured stone model were created by taking impression of fully dentate male (fifty years old) participant. Titanium spheres were added to the models to allow for an easily recognisable geometric shape for measurement after scanning and digital articulation. Measurements were obtained using a Coordinate Measuring Machine to record volumetric error, articulation error and clinical effect error. Three scanners were compared, including the Imetric 3D iScan d104i, Shining 3D AutoScan-DS100 and 3Shape D800, as well as their respective digital articulation software packages. Stoneglass Industries PDC digital articulation system was also applied to the Imetric scans for comparison with the CMM measurements. RESULTS: All the scans displayed low volumetric error (p⟩0.05), indicating that the scanners themselves had a minor contribution to the articulation and clinical effect errors. The PDC digital articulation system was found to deliver the lowest average errors, with good repeatability of results. CONCLUSION: The new measuring technique in the current study was able to assess the scanning and articulation accuracy of the four systems investigated. The PDC digital articulation system using Imetric scans was recommended as it displayed the lowest articulation error and clinical effect error with good repeatability. The low errors from the PDC system may have been due to its use of a 3D axis for alignment rather than the use of a best fit.

Accuracy of Intraoral Scanners: A Systematic Review of Influencing Factors.

Digital impressions by intraoral scanning (IOS) have become an increasingly popular alternative to conventional impressions. This systematic review aimed to evaluate the accuracy of the available IOS systems for dental impression, and identify the influencing factors on accuracy. The literature search was completed to retrieve all the studies that investigated the IOS accuracy when used to scan teeth. A total of 2305 studies were initially obtained. After applying the inclusion criteria, 32 studies were suitable for the analysis. The following systems were included in the review: Cerec Bluecam, Cerec Omnicam, Cadent iTero, Lava C.O.S, Lava True Definition, TRIOS, TRIOS Color, E4D, Planscan, MHT, Carestream 3500 and Zfx IntraScan. In comparison to conventional impressions, the IOS systems can be reliably used for diagnostic purposes and short-span scanning. However, for whole arch scanning, the IOS is susceptible for more deviation. The studies indicated variable outcome of the different IOS systems. While the accuracy of IOS systems appears to be promising and comparable to conventional methods, they are still vulnerable to inaccuracies. For prosthesis fabrication, the IOS accuracy is enhanced by reducing the span of scanning, and ensuring the scanned surfaces exhibit minimal irregularities.

Fracture resistance of zirconia-based all-ceramic crowns after bur adjustment.

Intra-oral grinding is often required to optimize occlusion of all-ceramic restorations. The effect of burs of different grit size on the fracture resistance of veneered zirconia crowns was investigated in this study. Forty-eight standardized zirconia copings were produced. The ceramic veneer was designed with a positive ellipsoidal defect on the palatal aspect of the crowns. To simulate adjustment of dental restorations by burs, this palatal defect was removed by use of three different diamond-coated burs with grit sizes 46, 107, or 151 µm (fine, medium, or coarse, respectively). Each different grit size of bur was used to grind 16 crowns. All crowns were then polished and surface roughness was measured. Half of the specimens underwent thermomechanical aging (10,000 thermocycles between 6.5°C and 60°C) and 1.2 million cycles of chewing simulation (F = 108 N). A linear regression model was computed to test the effect of aging and grinding grit size at a level of significance of α = 0.05. Fracture loads increased with decreasing grit size. Grit size and aging had a significant effect on the fracture resistance of the crowns. Use of fine and coarse burs for intra-oral adjustments resulted in different fracture resistance of veneered zirconia crowns. Coarse burs should be avoided in the final stage of grinding before polishing.

Trueness of four different milling procedures used in dental CAD/CAM systems.

OBJECTIVES: Milling is a crucial step in producing restorations using computer-aided design and computer-aided manufacturing (CAD/CAM) systems. In this study the trueness of currently available milling devices was evaluated. MATERIALS AND METHODS: Thirty clinical cases (ten inlays, ten crowns, ten onlays) were milled from ceramic blocks using four different milling approaches: five axis with IMES CORiTEC 450i, four axis with CEREC MCXL, four axis with CEREC MCXL-EF and five axis with inLab MCX5. The milled restorations were scanned and the occlusal and inner surfaces compared to the originally calculated 3D surface using difference analysis software. The (90-10 %) / 2 percentile of the distances were calculated and analysed using one-way ANOVA with the post hoc Scheffé test (α = 0.05). Chipping of marginal areas were visually examined and analysed using one-way ANOVA with a post hoc Tamhane test (α = 0.05). RESULTS: At inner surfaces, the milling trueness of IMES (33.9 ± 16.3 µm), X5 (32.3 ± 9.7 µm) and MCXL-EF (34.4 ± 7.5 µm) was significantly better (p < 0.001) than that of MCXL (62.1 ± 17.1 µm). At occlusal surfaces, MCXL-EF (25.7 ± 9.3 µm) showed significant higher accuracy (p < 0.001) than MCXL (48.7 ± 23.3 µm) and X5 (40.9 ± 20.4 µm). IMES produced the most chipping (p < 0.001). CONCLUSIONS: Five-axis milling devices yield high trueness. MCXL-EF is competitive and may allow chairside fabrication with good milling results. CLINICAL RELEVANCE: Accurate milling is required for well-fitting restorations and thereby requires fewer manual finishing steps, yields smaller marginal gaps, resistance to secondary caries and longevity of restorations.

In vitro evaluation of marginal discrepancy of monolithic zirconia restorations fabricated with different CAD-CAM systems.

STATEMENT OF PROBLEM: Dental laboratories use different computer-aided design and computer-aided manufacturing (CAD-CAM) systems to fabricate fixed prostheses; however, limited evidence is available concerning which system provides the best marginal discrepancy. PURPOSE: The purpose of this in vitro study was to evaluate the marginal fit of 5 different monolithic zirconia restorations milled with different CAD-CAM systems. MATERIAL AND METHODS: Thirty monolithic zirconia crowns were fabricated on a custom-designed stainless steel die and were divided into 5 groups according to the type of monolithic zirconia crown and the CAD-CAM system used: group TZ, milled with an MCXL milling machine; group CZ, translucent zirconia milled with a motion milling machine; group ZZ, zirconia milled with a dental milling unit; group PZ, translucent zirconia milled with a zirconia milling unit; and group BZ, solid zirconia milled using an S1 VHF milling machine. The marginal fit was measured with a binocular microscope at an original magnification of ×100. The results were tabulated and statistically analyzed with 1-way ANOVA and post hoc surface range test, and pairwise multiple comparisons were made using Bonferroni correction (α=.05). RESULTS: The type of CAD-CAM used affected the marginal fit of the monolithic restoration. The mean (±SD) highest marginal discrepancy was recorded in group TZI at 39.3 ±2.3 µm, while the least mean marginal discrepancy was recorded in group IZ (22.8 ±8.9 µm). The Bonferroni post hoc test showed that group TZI was significantly different from all other groups tested (P<.05). CONCLUSIONS: Within the limitation of this in vitro study, all tested CAD-CAM systems produced monolithic zirconia restorations with clinically acceptable marginal discrepancies; however, the CAD-CAM system with the 5-axis milling unit produced the best marginal fit.

Impression technique for a complete-arch prosthesis with multiple implants using additive manufacturing technologies.

This article describes an impression technique for a complete-arch prosthesis supported by multiple implants where additive manufacturing technologies were used to fabricate a splinting framework and a custom tray. The technique presented uses a shim method to control the homogenous splinting acrylic resin and impression material during the procedure, thereby reducing laboratory and chairside time and the number of impression copings and laboratory analogs needed.

Evaluation of the safety and efficiency of novel metallic implant scaler tips manufactured by the powder injection molding technique.

BACKGROUND: Although many studies have compared the properties of ultrasonic scaling instruments, it remains controversial as to which is most suitable for implant scaling. This study evaluated the safety and efficiency of novel metallic ultrasonic scaler tips made by the powder injection molding (PIM) technique on titanium surfaces. METHODS: Mechanical instrumentation was carried out using four types of metal scaler tips consisting of copper (CU), bronze (BR), 316 L stainless steel (316 L), and conventional stainless steel (SS) tips. The instrumented surface alteration image of samples was viewed with scanning electron microscope (SEM) and surface profile of the each sample was investigated with confocal laser scanning microscopy (CLSM). Arithmetic mean roughness (Ra) and maximum height roughness (Rmax) of titanium samples were measured and dissipated power of the scaler tip was estimated for scaling efficiency. RESULTS: The average Ra values caused by the 316 L and SS tip were about two times higher than those of the CU and BR tips (p < 0.05). The Rmax value showed similar results. The efficiency of the SS tip was about 3 times higher than that of CU tip, the 316 L tip is about 2.7 times higher than that of CU tip, and the BR tip is about 1.2 times higher than that of CU tip. CONCLUSIONS: Novel metallic bronze alloy ultrasonic scaler tip minimally damages titanium surfaces, similar to copper alloy tip. Therefore, this bronze alloy scaler tip may be promising instrument for implant maintenance therapy.

Two-Colored Dental Surveying Tool as an Alternative for Carbon Marker.

Various tools are used with a dental surveyor, including analyzing rods, carbon markers, undercut gauges, and protective sheaths for a specific function. A carbon marker is a parallel-sided carbon rod used to mark the survey line on a cast or a crown on a cast. The carbon marker (with or without protective sheath) cannot differentiate more than one survey line on the cast if needed. The wear of the carbon marker along the parallel walls after repeated use may give an incorrect survey line. We suggest a simple modification in the analyzing rod to prepare a two-colored surveying tool. An analyzing rod is a parallel-sided rod used to analyze the relative parallelism of two or more surfaces of a cast and to mark survey lines on wax patterns. With the modified analyzing rod, the survey lines can be marked with two colors, and the problem of breaking of the carbon marker also can be eliminated.

A Retrospective 2-Year Clinical Study of Immediate Prosthetic Rehabilitation of Edentulous Jaws with Four Implants and Prefabricated Bars.

PURPOSE: The purpose of this retrospective investigation was to evaluate the use of a prefabricated bar system for immediately loaded implants placed and restored according to the All-on-Four concept with up to 24-month follow-up. MATERIALS AND METHODS: A total of 51 patients (31 males and 20 females; mean age 63.4 years) presented with edentulous or partially edentulous jaws with severe atrophy of the posterior regions. All patients were treated with full-arch fixed prostheses (28 maxillary, 34 mandibular) each supported by four implants (two vertical, two distally tilted). The implants were immediately loaded with screw-retained full-arch restorations. Each prosthesis was supported by a prefabricated metal bar combined with high-density acrylic resin. Follow-up visits were scheduled at 6, 12, and 24 months after initial prosthetic loading. Intraoral radiographs were obtained immediately after surgery and at each follow-up visit by using a custom radiograph holder and parallel technique. Marginal bone levels were assessed using digital image analysis. Implant and prosthetic survival and success rates were evaluated. Patient satisfaction was further assessed using a 100-mm visual analog scale (VAS). Data were compared by means of the Mantel-Haenszel test. RESULTS: No drop-outs occurred. The overall implant survival rates were 100% and 98.38% for the vertical and tilted implants respectively. Two of the 62 definitive fixed prostheses were lost during the observation period due to implant failure. Since restoration replacement due to implant failure was not judged a prosthodontic failure according to the survival criteria provided in this study, the overall prosthetic survival rate was 100%. No statistically significant differences in marginal bone levels between vertical and tilted implants were detected at 24-month follow-up evaluation in either jaw. All participants were functionally and esthetically satisfied with their definitive restorations after 2 years functioning, as confirmed by the average VAS scores (masticatory function: 99.7; phonetic function: 99.5, esthetics: 99.2). CONCLUSIONS: The preliminary 24-month results indicate that immediate loading of vertical and tilted implants using the evaluated prefabricated bar system may be a viable solution for edentulous jaw rehabilitation; however, more long-term prospective clinical trials are needed to affirm the effectiveness of this surgical-prosthetic protocol.

Digital approach to a ceramic-pressed-to-metal restoration.

Even though a traditional metal ceramic restoration is still popular, it demands both time and effort. A ceramic-pressed-to-metal restoration (PTM) can be an alternative because this restoration reduces the complicated laboratory procedure and risk of ceramic chipping. However, no method has yet been reported for fabricating a PTM without a stone cast. This article describes an accelerated technique for a PTM with an intraoral scanner and computer-aided design and computer-aided manufacturing technology.

Comparison of marginal and internal fit of 3-unit ceramic fixed dental prostheses made with either a conventional or digital impression.

STATEMENT OF PROBLEM: For 20 years, the intraoral digital impression technique has been applied to the fabrication of computer aided design and computer aided manufacturing (CAD-CAM) fixed dental prostheses (FDPs). Clinical fit is one of the main determinants of the success of an FDP. Studies of the clinical fit of 3-unit ceramic FDPs made by means of a conventional impression versus a digital impression technology are limited. PURPOSE: The purpose of this in vitro study was to evaluate and compare the internal fit and marginal fit of CAD-CAM, 3-unit ceramic FDP frameworks fabricated from an intraoral digital impression and a conventional impression. MATERIAL AND METHODS: A standard model was designed for a prepared maxillary left canine and second premolar and missing first premolar. The model was scanned with an intraoral digital scanner, exporting stereolithography (STL) files as the experimental group (digital group). The model was used to fabricate 10 stone casts that were scanned with an extraoral scanner, exporting STL files to a computer connected to the scanner as the control group (conventional group). The STL files were used to produce zirconia FDP frameworks with CAD-CAM. These frameworks were seated on the standard model and evaluated for marginal and internal fit. Each framework was segmented into 4 sections per abutment teeth, resulting in 8 sections per framework, and was observed using optical microscopy with ×50 magnification. Four measurement points were selected on each section as marginal discrepancy (P1), mid-axial wall (P2), axio-occusal edge (P3), and central-occlusal point (P4). RESULTS: Mean marginal fit values of the digital group (64 ±16 µm) were significantly smaller than those of the conventional group (76 ±18 µm) (P<.05). The mean internal fit values of the digital group (111 ±34 µm) were significantly smaller than those of the conventional group (132 ±44 µm) (P<.05). CONCLUSIONS: CAD-CAM 3-unit zirconia FDP frameworks fabricated from intraoral digital and conventional impressions showed clinically acceptable marginal and internal fit. The marginal and internal fit of frameworks fabricated from the intraoral digital impression system were better than those fabricated from conventional impressions.

Subjective qualitative assessment of the finish line of prosthetic preparations submitted to different finishing instruments.

STATEMENT OF PROBLEM: Different instruments have been developed to improve crown finish lines after conventional preparation with diamond rotary instruments. However, more evidence on the effectiveness of these instruments is required. PURPOSE OF STUDY: The purpose of this in vitro study was to assess the effectiveness of 4 different instruments used for cervical margin finishing in regard to the external line angle (ELA). MATERIAL AND METHODS: Forty-eight freshly extracted third molar teeth with similar dimensions were conventionally prepared for crowns and randomly allocated into 4 groups (n=12) according to the finishing instrument: hand trimmer (HT), tungsten carbide bur (TCB), ultrasonic instrument (UI), and diamond rotary instrument (DRI) mounted in a contra angle handpiece with reduced speed. Photomicrographs from the margin profiles of each tooth were obtained with scanning electron microscopy (×40) before and after finishing procedures. The images were qualitatively analyzed (scores 1-4) by 9 experienced dental professionals. Average results were assessed with the paired t test and repeated measures ANOVA followed by Tukey HSD test (α=.05). RESULTS: HT, TCB, and UI demonstrated no significant differences between unfinished and finished mean ELA scores. DRI was the only group to demonstrate a significantly improved ELA (P<.001). Except for HT in relation to TCB (P=.989), all the other groups demonstrated statistically significant different ELA scores. CONCLUSION: DRI mounted in a contra angle handpiece was the only finishing instrument capable of significantly improving the ELA, while TCB and UI produced nonsignificant improvement, and HT was detrimental to the ELA.

A 2-part facebow for CAD-CAM dentistry.

Converting the patient's clinical information into the virtual world is a prerequisite for the computer-aided design and computer-aided manufacturing (CAD-CAM) of dental restorations. This article describes a modified facebow which facilitates the radiation-free registration of the maxillary teeth to a 3-dimensional face image for transfer to a virtual articulator. This facebow can be easily fabricated with minimal materials and adjusted to fit different patients; its error in tooth registration was demonstrated to be less than 1 mm.

In vitro evaluation of marginal, axial, and occlusal discrepancies in metal ceramic restorations produced with new technologies.

STATEMENT OF PROBLEM: Marginal and axial discrepancies of metal ceramic restorations are key to their long-term success. Little information is available for metal ceramic restorations fabricated with soft metal milling and laser sintering technologies. PURPOSE: The purpose of this in vitro study was to compare the marginal, axial, and occlusal discrepancies in single-unit metal ceramic restorations fabricated with new production techniques with those in a single-unit restoration fabricated using a conventional technique. MATERIAL AND METHODS: After the artificial tooth was prepared, impressions were made, and 40 dies were obtained. Dies were randomly divided into 4 groups (n=10). Cobalt-chromium (Co-Cr) cast (C), hard metal milled (HM), laser sintered (LS), and soft metal milled (SM) copings were fabricated. Marginal, axial, and occlusal discrepancies of these copings were measured using the silicone replica technique before and after the application of veneering ceramic. Data were analyzed with repeated measurements 2-way ANOVAs and Bonferroni post hoc tests (α=.05). RESULTS: Significant differences were found in the increase of marginal discrepancy after the application of veneering ceramic in the LS group (P=.016). However, no significant differences in marginal discrepancy were found whether veneering ceramic was applied to copings before or after in the other groups (P>.05). With regard to marginal and occlusal discrepancies, significant differences were found among the production techniques (P<.001 and P<.05, respectively). No significant differences in axial discrepancies were found among the groups (P>.05). CONCLUSION: This in vitro study showed that metal ceramic restorations produced with HM and newly introduced SM techniques exhibited better marginal adaptations than those produced with the LS or C technique.

Complete-mouth rehabilitation using a 3D printing technique and the CAD/CAM double scanning method: A clinical report.

According to evolving computer-aided design/computer-aided manufacturing (CAD/CAM) technology, ceramic materials such as zirconia can be used to create fixed dental prostheses for partial removable dental prostheses. Since 3D printing technology was introduced a few years ago, dental applications of this technique have gradually increased. This clinical report presents a complete-mouth rehabilitation using 3D printing and the CAD/CAM double-scanning method.