Incorporating a facial scanner into the digital workflow: A dental technique.

The transfer of extraoral and intraoral clinical information into the virtual environment is necessary to optimize prosthetic treatment planning. The purpose of this article was to describe a digital workflow designed to superimpose the different 3D files obtained with an intraoral scanner, a cone bean computed tomography (CBCT) device, and a facial scanner and their clinical application with the Digital bite device.

Influence of ceramic firing on marginal gap accuracy and metal-ceramic bond strength of 3D-printed Co-Cr frameworks.

STATEMENT OF PROBLEM: The marginal gap and ceramic bond strength of metal-ceramic restorations are important for success. However, studies evaluating the marginal gap and ceramic bond strength of fixed partial dentures (FPDs) produced with 3D printing technologies such as selective laser melting (SLM) are scarce. PURPOSE: The purpose of this in vitro study was to investigate the marginal gap of cobalt-chromium (Co-Cr) alloy frameworks produced by SLM technology before and after ceramic firing. Additionally, the metal-ceramic bond strength was evaluated with the Schwickerath crack-initiation test according to the International Standards Organization (ISO) 9693-1:2012. MATERIAL AND METHODS: Conventional impressions were made, and the definitive cast of a patient requiring a 4-unit FPD was scanned. After designing the FPD, the files were sent to a service center for the fabrication of a metal master model, 80 Co-Cr frameworks, and 80 flat specimens (25×3×0.5 mm) with SLM technology. The marginal gap between frameworks and the abutment tooth of the metal master model was nondestructively measured by using an optical coordinate-measuring machine. A total of 80 sets, consisting of 1 framework and 1 flat specimen, were sent to 80 dental laboratory technicians for ceramic firing. Detailed instructions for correct manipulation of the framework and flat specimen were provided. The marginal gap was remeasured, and the 3-point bend test was used to evaluate metal-ceramic bond strength. RESULTS: Only 28 of the 80 dental technicians returned the specimens within a prespecified time and/or in adequate condition. The mean ±standard deviation marginal gap of the framework before ceramic firing was 25 ±9 µm and 34 ±12 µm after firing. The difference was statistically significant (P=.001). The mean ±standard deviation 3-point bend strength was 33 ±9 MPa. CONCLUSIONS: Ceramic firing affected the marginal gap; however, all Co-Cr frameworks had a marginal gap lower than 120 µm, which is reported to be a clinically acceptable limit. Most of the specimens (80%) had a metal-ceramic bond strength value higher than the 25-MPa ISO 9693 requirement. Five of 28 dental laboratory technicians were not able to comply with ceramic firing instructions.

An In Vitro Evaluation of Alumina, Zirconia, and Lithium Disilicate Surface Roughness Caused by Two Scaling Instruments.

PURPOSE: Plaque control is crucial for the prevention of inflammatory periodontal disease. Hand scaling instruments have been shown to be efficient for the removal of plaque; however, routine periodontal prophylactic procedures may modify the surface profile of restorative materials. The purpose of this study was to assess in vitro the changes in roughness of alumina, zirconia, and lithium disilicate surfaces treated by two hand scaling instruments. MATERIALS AND METHODS: Forty-eight alumina specimens, 48 zirconia specimens, and 48 lithium disilicate specimens, were selected. All specimens were divided into three groups of 16 each; one group for each material was considered the control group and no scaling procedures were performed; the second group of each material was exposed to scaling with steel curettes simulating standard clinical conditions; the third group of each material was exposed to scaling with titanium curettes. After scaling, the surface roughness of the specimens was evaluated with a profilometer. First, a statistical test was carried out to evaluate the difference in surface roughness before the scaling procedure of the three materials was effected (Kruskal-Wallis test). Subsequently, the effect of curette material (steel and titanium) on roughness difference and roughness ratio was analyzed throughout the entire sample and within each material group, and a nonparametric test for dependent values was conducted (Wilcoxon signed-rank test). Finally, the roughness ratios of the three material groups were compared by means of a Kruskal-Wallis test and a Wilcoxon signed-rank test. Upon completion of profilometric evaluation, representative specimens from each group were prepared for SEM evaluation to evaluate the effects of the two scaling systems on the different surfaces qualitatively. RESULTS: After scaling procedure, the roughness profile value increased in all disks. Classifying the full sample according to curette used, the roughness of the disks treated with a steel curette reached a higher median value than that of the titanium group. Zirconia demonstrated the least significant increase in surface roughness. The result was 3.9 times of the initial value as compared to 4.3 times for alumina and 4.6 times for lithium disilicate. CONCLUSIONS: Comparison of profilometer readings before and after instrumentation, carried out with different hand scaling instruments, highlighted both a statistically and clinically relevant increase in material roughness.

An In Vivo Evaluation of the Fit of Zirconium-Oxide Based, Ceramic Single Crowns with Vertical and Horizontal Finish Line Preparations.

PURPOSE: Different types of tooth preparations influence the marginal precision of zirconium-oxide based ceramic single crowns. In this in vivo study, the marginal fits of zirconium-oxide based ceramic single crowns with vertical and horizontal finish lines were compared. MATERIALS AND METHODS: Forty-six teeth were chosen in eight patients indicated for extraction for implant placement. CAD/CAM technology was used for the production of 46 zirconium-oxide-based ceramic single crowns: 23 teeth were prepared with vertical finishing lines, 23 with horizontal finishing lines. One operator accomplished all clinical procedures. The zirconia crowns were cemented with glass ionomer cement. The teeth were extracted 1 month later. Marginal gaps along vertical planes were measured for each crown, using a total of four landmarks for each tooth by means of a microscope at 50× magnification. On conclusion of microscopic assessment, ESEM evaluation was completed on all specimens. The comparison of the gap between the two types of preparation was performed with a nonparametric test (two-sample Wilcoxon rank-sum test) with a level of significance fixed at p < 0.05. All data were analyzed with STATA12. RESULTS: In the group with horizontal finish line preparations, the median value of the gap was 35.45 µm (Iqr, 0.33); for the vertical finish line group, the median value of the gap was 35.44 µm (Iqr, 0.40). The difference between the two groups was not statistically significant (two-sample Wilcoxon rank-sum test, p = 0.0872). CONCLUSIONS: Within the limitations of this study, the gaps of the zirconium-oxide-based ceramic CAD/CAM crowns with vertical and horizontal finish line preparations were not different.

Prosthetic procedure for simultaneous immediate loading of opposing edentulous arches.

For patients with complete edentulism, a significant problem is the transfer of diagnostic data to the definitive casts when an immediate loading technique is used. This article presents a prosthetic procedure to allow simultaneous treatment of opposing edentulous arches with immediate implant loading. This technique uses 2 occlusal acrylic resin devices to transfer the diagnostic cast information to the definitive casts. Esthetic and functional fixed dental prostheses are fabricated from diagnostic information acquired in the presurgical phase without any impression or recording of the maxillomandibular relationship during or after surgery. This methodology is applicable when the simultaneous immediate loading of implants in 2 edentulous arches is indicated.

An in vivo evaluation of fit of zirconium-oxide based ceramic single crowns, generated with two CAD/CAM systems, in comparison to metal ceramic single crowns.

PURPOSE: The purpose of this study was to assess in vivo the marginal fit of single crowns produced using two CAD/CAM all-ceramic systems, in comparison to more traditional metal ceramic crowns. MATERIALS AND METHODS: Thirty vital, caries-free, and previously untreated teeth were chosen in five patients who needed extraction for implant placement and therefore were included in this study. In the control group (C), 10 regular metal ceramic crowns with porcelain occlusal surfaces were fabricated. In the other two groups (Z and E), CAD/CAM technology was used for the fabrication of 20 zirconium-oxide-based ceramic single crowns with two systems. All zirconia crowns were cemented with glass-ionomer cement, always following the manufacturer's instructions. The same dentist carried out all clinical phases. The teeth were extracted 1 month later. Marginal gaps along vertical planes were measured for each crown, using a total of four landmarks for each tooth by means of a microscope at a magnification of 50×. On completion of microscopic evaluation, representative specimens from each group were prepared for ESEM evaluation. Mean and standard deviations of the four landmarks (mesial, distal, buccal, palatal) at each single crown were calculated for each group. Multivariate analysis of variance (MANOVA) was performed to determine whether the four landmarks, taken into consideration together, differed between groups. Two-way ANOVA was performed to study in detail, for each landmark, how the three systems used to produce the FPDs affected the gap measurements. Differences were considered to be significant at p < 0.05. RESULTS: MANOVA revealed no quantitative differences of the four landmarks, when taken into consideration together, between the three groups (p < 0.0001). Two-way ANOVA, performed at each landmark, revealed no quantitative differences between the three groups (p < 0.0001 for each landmark). CONCLUSIONS: Within the limitations of this study, it was concluded that the two zirconium-oxide-based ceramic CAD/CAM systems demonstrated a similar and acceptable marginal fit when compared to more traditional metal ceramic crowns.

Influence of Platform-Switched Restoration on Bone Resorption in Patients Treated with Wide-Diameter, External-Hex-Connection Dental Implants: A 10-Year Follow-up Study.

Purpose: To investigate and assess the differences in crestal bone loss (CBL) between wide-diameter, external-hexagon-connection implants restored with platform-switching (PS) and platform-matching (PM) restorations with a follow-up of 10 years. Materials and Methods: This study retrospectively analyzed the updated and enlarged dataset of a 5-year prospective clinical study at 10-year follow-up. The data concerns 182 healthy adult subjects treated in a private dental practice who received a single wide-diameter implant with an external hexagon connection in the molar area, restored with either a PS restoration (test) or PM restoration (control). The amount of CBL was radiographically measured at each annual follow-up, as well as after 5 and 10 years of implant loading. In evaluating the association between the two types of abutments and bone loss (including change over time), a linear mixed effects model was run for longitudinal data. Results: Implants connected with PS restorations exhibited significantly lower reduction (0.25 mm) in CBL than those joined to PM restorations (P < .001; 95% CI from 0.22 to 0.29). However, both groups presented a higher increase in bone loss during the first year (0.58 mm in PS and 0.83 mm in PM) and a linear increment thereafter until the 10-year follow-up (0.046 mm/year; P < .001; 95% CI from .042 to .049). Conclusion: Notwithstanding the limitations of this study, it can be concluded that after 10 years of follow-up, the implant with a wide diameter and external-hexagon connection restored with a PS abutment seems to be more effective in reducing bone loss compared with the PM abutment.

Internal vs. external connections for abutments/reconstructions: a systematic review.

OBJECTIVES: The objectives of the review were (1) to evaluate the accuracy of implant-level impressions in cases with internal and external connection abutments/reconstructions, and (2) to evaluate the incidence of technical complications of internal and external connection metal- or zirconia-based abutments and single-implant reconstructions. MATERIALS AND METHODS: A MEDLINE electronic search was conducted to identify English language publications in dental journals related to each of the two topics by inserting the appropriate keywords. These electronic searches were complemented by a hand search of the January 2009 to January 2012 issues of the following journals: Clinical Oral Implants Research, The Journal of Prosthetic Dentistry, The International Journal of Prosthodontics, The International Journal of Periodontics and Restorative Dentistry, The International Journal of Oral Maxillofacial Implants, Clinical Implant Dentistry and Related Research. RESULTS: Seven in vitro studies were included in the review to evaluate the accuracy of implant-level accuracy. No clinical study was found. There was no study that directly compared the influence of internal and external implant connections for abutments/reconstructions on the accuracy of implant-level impressions. All in vitro studies reported separately on the two connection designs and they did not use same protocol and, therefore, the data could not be compared. Fourteen clinical studies on metal-based abutments/reconstructions and five clinical studies on zirconia-based abutments/reconstructions satisfied the inclusion criteria and, therefore, were included in the review to evaluate the incidence of technical complications. The most frequent mechanical complication found in both implant connection design when employing metal abutments/reconstructions was screw loosening. CONCLUSIONS: Implant-level impression accuracy may be influenced by a number of variables (implant connection type, connection design, disparallelism between multiple implants, impression material and technique employed). Implant divergence appears to affect negatively impression accuracy when using internal connection implants. Based on the sparse literature evaluating the incidence of technical complications of metal or zirconia abutments/reconstructions, it was concluded that: The incidence of fracture of metal-based and zirconia-based abutments and that of abutment screws does not seem to be influenced by the type of connection. Loosening of abutment screws was the most frequently occurring technical complication. The type of connection seems to have an influence on the incidence of the screw loosening: more loose screws were reported for externally connected implant systems for both types of materials. However, proper preload may decrease the incidence of such a complication.

Evaluation of zirconium-oxide-based ceramic single-unit posterior fixed dental prostheses (FDPs) generated with two CAD/CAM systems compared to porcelain-fused-to-metal single-unit posterior FDPs: a 5-year clinical prospective study.

PURPOSE: The purpose of this prospective clinical study was to determine the success rate of single-unit posterior fixed dental prostheses (FDPs) with zirconia copings generated with two CAD/CAM systems, compared to porcelain-fused-to-metal (PFM) single-unit posterior FDPs after 5 years of function. MATERIALS AND METHODS: From 2005 to 2006, 60 patients who needed a single-unit FDP on a first molar in the mandibular jaw (left or right) in a private office setting were included in this study. The 60 first mandibular molars were randomly divided into three groups (n = 20): in the control group (group C), 20 PFM FDPs were included. In the other two groups CAD/CAM technology was used for the fabrication of the zirconium-oxide copings: 20 single-unit posterior FDPs with zirconia copings were generated with the Procera system (group P, Nobel Biocare); 20 single-unit posterior FDPs with zirconia copings were generated with the Lava system (group L, 3M ESPE). For the ANOVA follow-up data, the clinical life table method was applied. The statistical analysis was performed using two nonparametric tests, the log-rank test for k-groups and the Fisher exact test. RESULTS: No statistically significant difference in the clinical outcome of zirconia-ceramic FDPs of both groups (P and L) evaluated together and metal-ceramic posterior single FDPs was found at 5 years of function; however, clinical data showed that technical problems, such as extended fracture of the veneering ceramic, tended to occur more frequently in the zirconia-ceramic FDP groups. The difference in the frequency of failure was statistically significant only in the comparison of groups C and P. CONCLUSIONS: Even if no statistically significant difference in the clinical outcome of zirconia-ceramic FDPs of both groups (P and L) considered together and metal-ceramic posterior single FDPs was found at 5 years of function, clinical data showed that the two zirconia-ceramic FDP groups tended to have more frequent clinical problems: for this reason all the clinical and technical variables related to the use of zirconia-ceramic FDPs generated with CAD/CAM systems should be carefully considered prior to all treatment procedures.

Clinical evaluation of marginal bone level change of multiple adjacent implants restored with splinted and nonsplinted restorations: a 5-year prospective study.

PURPOSE: The success of single-tooth implant restorations has resulted in an increased use of nonsplinted implants to replace adjacent missing teeth; however, this may result in excessive force transmission to the implant and bone, causing bone loss. The purpose of this prospective study was to compare the marginal bone level change of adjacent splinted implants and of nonsplinted implants functionally loaded with cemented restorations up to 5 years in maxillae. MATERIAL AND METHODS: Between 2002 and 2004, all patients who received three consecutive adjacent implants in a private office and a university implant dentistry department were included in this study. All implants were placed in posterior maxillae. Maxillary left implants were restored with splinted cemented restorations, and maxillary right implants were restored with nonsplinted cemented restorations. Marginal bone resorption was measured with intraoral radiographs annually for 5 years. The data were analyzed statistically with the Mann-Whitney U test and the two-sample Kolmogorov-Smirnov test to identify differences between splinted and nonsplinted implant restorations. RESULTS: One hundred thirty-two implants were placed in 44 patients. Two subjects (6 implants in total) did not complete the study. Three implants failed at stage-two surgery. Of the remaining 123 implants, 63 were restored with splinted cemented restorations and 60 were restored with nonsplinted cemented restorations. The mean marginal bone level changes at the 5-year recall were -0.7 ± 0.2 mm for splinted restorations and -0.8 ± 0.2 mm) for nonsplinted restorations. CONCLUSIONS: Peri-implant marginal bone loss around nonsplinted implants in the present study was statistically equivalent to that observed in splinted implants. Multiple nonsplinted implants can be successfully included in many clinical situations in an effort to optimize esthetics and circumvent the problem of nonpassively fitting frameworks.

Evaluation of rotational freedom of In-Ceram ceramic blank abutments before and after infiltration.

PURPOSE: Laboratory processing of implant-supported prostheses may alter the surface of the abutment in contact with the corresponding surface and thus the interface fit. This study assessed changes in the rotational freedom (R) at the interface of 1 implant ceramic abutments before and after preparation and glass infiltration processes. MATERIALS AND METHODS: The abutment R was assessed for 20 as-received In-Ceram Ceramic Blanks over synOcta abutments and after both preparation and infiltration procedures. RESULTS: Compared with the as-received blanks, there was a statistically significant (P < 0.009) increase of 0.8 minutes in the R after preparation and glass infiltration processes. CONCLUSION: The results of this investigation suggest that, if all laboratory steps are observed carefully, changes at the abutment interface of Ceramic Blanks do not occur.

An in vitro evaluation of zirconia surface roughness caused by different scaling methods.

STATEMENT OF PROBLEM: Plaque control is essential for the prevention of inflammatory periodontal disease. Ultrasonic scaling and hand scaling have been shown to be effective for the removal of plaque. However, routine periodontal prophylactic procedures may alter the surface profile of restorative materials. PURPOSE: The purpose of this study was to assess in vitro the changes in roughness of zirconia surfaces treated by various scaling procedures. MATERIAL AND METHODS: One hundred forty identical disks (10 mm in diameter, 2 mm thick) were made. The specimens were divided into 7 groups of 20 each; the surfaces of the specimens were exposed to different types of scaling methods simulating standard clinical conditions. In the control group (C), no scaling procedures were performed; in the other groups, a steel curette (SC), a plastic curette (PC), a titanium curette (TC), a piezoelectric ultrasonic scaler (PUS), an ultrasonic scaler (US), and a magnetostrictive ultrasonic scaler (MUS) were used. The surface texture was analyzed quantitatively and qualitatively with a profilometer and a scanning electron microscope (SEM). A 1-way ANOVA was performed to assess whether roughness profile (Ra) differed among groups, while pairwise comparisons between groups were evaluated by the Tukey HSD test (alpha=.05). RESULTS: The 1-way ANOVA revealed significant differences among groups (P<.001); the Tukey HSD test demonstrated that all methods achieved different results. Analysis of zirconia surfaces treated by different ultrasonic scaling systems demonstrated some deeper scratches, whereas zirconia instrumented with various types of periodontal curettes exhibited smaller scratches. Scaling with a steel curette produced the least alteration of zirconia surfaces. CONCLUSIONS: All instrument types evaluated altered the smoothness of zirconia surfaces. Follow-up in vivo studies are indicated to assess potential clinical problems associated with increased roughness at the margin of zirconia restorations following routine dental prophylaxis.

Platform-switched restorations on wide-diameter implants: a 5-year clinical prospective study.

PURPOSE: The purpose of the present investigation was to clinically assess and compare crestal bone changes, over a 5-year period, around external-hexagon wide-diameter implants restored with either matching wide-diameter prosthetic components or with platform-switched prosthetic components. MATERIALS AND METHODS: During the years 2000 to 2002 all patients who received a single 5-mm-diameter implant with an external hexagon in a private office setting were included in this study. All implants were placed in the posterior areas of the jaws. Maxillary left molars (group A1) and mandibular right molars (group A2) were restored with matching wide-diameter prosthetic components; maxillary right molars (group B1) and mandibular left molars (group B2) were restored with platform-switched prosthetic components. Marginal bone resorption was measured via intraoral radiographs each year after abutment and crown insertion. Statistical analyses were used to determine whether there was a significant difference in marginal bone levels with respect to the width of prosthetic components used. RESULTS: In all, 182 single 5-mm-diameter implants were placed in 144 patients and all implants survived. Eighty-five implants were restored with matching wide-diameter prosthetic components (group A), and 97 implants were restored with platform-switched prosthetic components (group B). A significant difference in marginal bone levels was found between group A and group B implants after 1 year. The mean marginal bone resorption was 0.9 mm (SD 0.3 mm) for group A implants and 0.6 mm (SD 0.2 mm) for group B implants. Marginal bone resorption observed at the second, third, fourth, and fifth years after abutment and crown insertion did not show any significant change. CONCLUSION: Statistically significant differences in marginal bone loss were observed between study groups. The 85 implants restored with matching wide-diameter prosthetic components showed more bone loss than the 97 implants restored with platform-switched prosthetic components.

Dimensional accuracy of an epoxy die material using different polymerization methods.

PURPOSE: Shrinkage of resinous die materials during setting reaction limits their acceptance, even though these materials show several advantages compared to stone die materials with respect to strength, abrasion resistance, and detail reproduction. The purpose of this study was to determine if retarding the setting reaction during polymerization and altering the base-to-catalyst ratio, as suggested by previous studies, can be recommended for resinous die materials to reduce the inaccuracy in transferring the spatial position of teeth or implants from the oral cavity to the master cast. MATERIALS AND METHODS: A Blue Star Type E epoxy resin die material was tested. A reference triangular metal master die was fabricated. Forty medium-consistency polyether impressions of this model were made. Four groups (S, M, N, P) were compared, and ten dies were fabricated for each group. In the S group, the epoxy resin die material was manipulated according to the manufacturer's instructions; in the other three groups, the epoxy resin die material was manipulated by retarding the setting reaction and by modifying the epoxy resin base/activator ratio. RESULTS: One-way ANOVA revealed significant differences between the four groups of the epoxy resin die material (p < 0.0001). Tukey's multiple comparisons test (p < 0.05) revealed that none of the resin groups was similar to the metal master die for each of the tested dimensions (A, B, and C). For the specific dimension C, however, the P group was statistically closer to the metal master die than the S group. CONCLUSION: The epoxy resin die material tested in this research did not improve its dimensional accuracy following retarding polymerization or modifying the epoxy resin base/activator ratio. The epoxy resin material exhibited higher contraction variability across all tested groups. This shrinkage can significantly affect the dimension of the master cast.

Titanium and Zirconia External Connection Abutments Produced Following a Digital Protocol: An In Vitro Study.

PURPOSE: To assess the quality of precision at the implant-abutment interface of single-tooth restorations with titanium and zirconia abutments with hexagonal external connections produced using a digital protocol. MATERIALS AND METHODS: A total of 20 abutments were produced with commercially pure titanium, and 20 abutments with zirconia, both following a necessary digital protocol. Rotational freedom of all the abutments was assessed. All data were analyzed according to procedures established by software package STATA 14.2. RESULTS: No significant differences relative to rotational freedom emerged between the two groups. CONCLUSION: This study showed that both types of abutments constantly demonstrated approximately 2 degrees of rotational freedom between implant and abutment where the hexagonal external connection was concerned.

Randomized Clinical Trial on Single Zirconia Crowns with Feather-Edge vs Chamfer Finish Lines: Four-Year Results.

The objective of this study was to evaluate the influence of two finish lines on the fracture resistance and periodontal response of porcelain zirconia crowns. Ethical committee approval was obtained, and 50 zirconia single crowns were placed in posterior regions. Abutments were randomly distributed into two groups: Group 1 (feather-edge preparation) and Group 2 (chamfer preparation). Patients were recalled after 1 month, 6 months, and 1, 2, 3, and 4 years. The function, esthetics, and marginal adaptation of the restorations were evaluated. Bleeding on probing (BoP) and distance of margins from the bone crest were recorded. Statistical analyses were performed for survival and success rates. Group 1 had an 80% success rate (21/25 crowns) and a 96% survival rate (24/25 crowns; 1 encountered irreparable fracture of ceramic layer); Group 2 had a 76% success rate (20/25 crowns) and a 100% survival rate (25/25 crowns). Chippings were noticed on 4 crowns in Group 1 (one crown replacement). Five chippings occurred in Group 2, without any replacement. There were no statistically significant differences between the two groups. BoP was found in 18 of the 25 crowns in Group 1 (72%) and in 12 of the 25 crowns in Group 2 (48%). A statistically significant correlation between BoP and the distance of the margin to the bone crest was found. It was concluded that: (1) clinical survival and success rates of the two preparation methods on crowns are not significantly different; (2) due to the statistically significant correlation between BoP and the distance of the margin to the bone crest, margins should be placed at least 3 mm from the bone crest; and (3) higher probability of BoP is expected in cases with feather-edge preparation.

Full arch digital scanning systems performances for implant-supported fixed dental prostheses: a comparative study of 8 intraoral scanners.

PURPOSE: Compare the accuracy of intraoral digital impression in full-arch implant-supported fixed dental prosthesis acquired with eight different intraoral scanner (Ios). METHODS: A polymethyl methacrylate acrylic model of an edentulous mandible with six scan-abutment was used as a master model and its dimensions measured with a coordinate measuring machine. Eight different Ios were used to generate digital impression: True Definition, Trios, Cerec Omnicam, 3D progress, CS3500, CS3600, Planmeca Emelard and Dental Wings. Fifteen digital impressions were made. A software called "Scan-abut" was developed to analyse and compare the digital impression with the master model, obtaining the scanning accuracy. The three-dimensional (3D) position and distance analysis were performed. RESULTS: Mean value of the 3D position analysis showed that the True Definition (31 µm ± 8 µm) and Trios (32 µm ± 5 µm) have the best performance of the group. The Cerec Omnicam (71 µm ± 55 µm), CS3600 (61 µm ± 14 µm) have an average performance. The CS3500 (107 µm ± 28 µm) and Planmeca Emelard (101 µm ± 38 µm) present a middle-low performance, while the 3D progress (344 µm ± 121 µm) and Dental Wings (148 µm ± 64 µm) show the low performance. The 3D distance analysis showed a good linear relationship between the errors and scan-abutment distance only with the True Definition and CS3600. CONCLUSIONS: Not all scanners are suitable for digital impression in full-arch implant-supported fixed dental prosthesis and the weight of the output files is independent from the accuracy of the Ios.

Influence of Crown-to-Implant Ratio on Long-Term Marginal Bone Loss Around Short Implants.

PURPOSE: To evaluate the influence of the crown-to-implant ratio (CI) on marginal bone loss (MBL) around short dental implants placed in the posterior mandible. MATERIALS AND METHODS: All patients treated with short implants (7 mm length) in the posterior mandible between 1994 and 2003 at the Dental Clinic of the Department of Neuroscience of the University of Padua (Italy) were retrospectively included in the analysis. MBL and clinical CI (cCI) were measured on the radiographs. Implant characteristics including implant diameter, prosthetic type, retention mode, antagonist type, veneering material, and implant surfaces were retrieved from local medical records. A generalized linear mixed model was estimated to identify the predictors of MBL. RESULTS: A total of 108 dental implants placed in 51 patients were included in the analysis. Mean follow-up was 16 years (range: 11 to 20 years). Mean cCI was 2.21 (SD = 0.31) with a mean crown height of 10.86 mm (SD = 0.99). Mean MBL was 1.42 mm (SD = 0.38). At multivariable analysis, cCI ≥ 2 was associated with higher MBL (regression coefficient: 0.27; 95% CI: 0.15 to 0.40), while implant characteristics, follow-up, and site were not associated with MBL. The effect of a cCI ≥ 2 was estimated in an increase of 0.28 mm in MBL (95% CI: 0.14 to 0.43 mm). CONCLUSION: Higher cCI was associated with greater MBL of implant-supported fixed dental prostheses in short dental implants placed in the posterior mandible, while implant characteristics, follow-up, and site were not associated with MBL. However, the increase of 0.28 mm of MBL in patients with a cCI ≥ 2 may be not clinically relevant.

Evaluation of gold-machined UCLA-type abutments and CAD/CAM titanium abutments with hexagonal external connection and with internal connection.

PURPOSE: The purpose of this study was to assess the precision at the implant interface of gold-machined UCLA-type abutments and computer-assisted design and manufacture (CAD/CAM) titanium abutments with both external-hexagonal connection and internal-hexagonal connection. MATERIALS AND METHODS: Fifteen gold-machined UCLA-type abutments with external-hexagonal connection, 15 gold-machined UCLA-type abutments with internal-hexagonal connection, 15 CAD/CAM titanium abutments with external-hexagonal connection, and 15 CAD/CAM titanium abutments with internal-hexagonal connection were produced. The rotational freedom of all the abutments was assessed to detect the precision of fit of each abutment on the top of the implant platform. Measurements of rotational freedom were compared among groups. The quantitative differences among groups were assessed using 1-way analysis of variance (alpha = .05). RESULTS: Significant differences relative to rotational freedom were not found among the 4 groups (P > .19). CONCLUSION: Both types of abutments (gold-machined UCLA-type and CAD/CAM titanium) consistently showed 1 degree of rotational freedom between the implant and abutment in both cases of external-hexagonal connection and internal-hexagonal connection.

An in vitro evaluation of fit of zirconium-oxide-based ceramic four-unit fixed partial dentures, generated with three different CAD/CAM systems, before and after porcelain firing cycles and after glaze cycles.

PURPOSE: The purpose of this study was to assess in vitro the marginal fit of four-unit fixed partial dentures (FPDs) produced using three different computer aided design/computer aided manufacturing (CAD/CAM) all-ceramic systems before and after porcelain firing cycles and after glaze cycles. MATERIALS AND METHODS: An acrylic resin model of a maxillary arch was fabricated. Teeth #6 and 9 were prepared; teeth #7 and 8 were absent. Forty-five four-unit zirconium-oxide-based ceramic FPDs were made following conventional impression and master cast techniques: 15 were made with the Everest system, 15 with the Procera system, and 15 with the Lava system. Marginal gaps along vertical planes were measured for each bridge before (Time 0) and after (Time 1) porcelain firing cycles and after glaze cycles (Time 2) using a total of 8 landmarks (4 for tooth #6 and 4 for tooth #9) by means of a microscope at a magnification of x50. MANOVA was performed to determine whether the 8 landmarks, jointly considered, differed between CAD/CAM systems and time phases. Two-way ANOVA was performed to investigate in detail, for each landmark, how gap measurements were related to CAD/CAM systems and time phases. Differences were considered to be significant at p < 0.05. RESULTS: The mean values of the Everest system (microm) were: 63.37 (Time 0), 65.34 (Time 1), and 65.49 (Time 2); the mean values of the Lava system (microm) were: 46.30 (Time 0), 46.79 (Time 1), and 47.28 (Time 2); the mean values of the Procera system (microm) were: 61.08 (Time 0), 62.46 (Time 1), and 63.46 (Time 2). MANOVA revealed quantitative differences of the 8 landmarks, jointly considered, between the three CAD/CAM systems (p < 0.0001), but it did not reveal any quantitative differences among the three time phases (p > 0.4). Two-way ANOVA revealed that the Lava system produced gap measurements statistically smaller than the Everest and Procera systems (p < 0.0001 for each landmark). CONCLUSIONS: Within the limitations of this study, it was concluded that the three zirconium-oxide-based ceramic CAD/CAM systems demonstrated a comparable and acceptable marginal fit; however, the Lava system produced gap measurements statistically smaller than the Everest and Procera systems. The porcelain firing cycles and the glaze cycles did not affect the marginal fit of the zirconium-oxide-based ceramic CAD/CAM systems.