Karl Martin Lehmann

Four color-measuring devices compared with a spectrophotometric reference system

OBJECTIVES The objective of this study was to compare the L*C*h° color coordinates of dental color-measuring devices with those of a spectrophotometric reference system. METHODS The International Commission on Illumination (CIE) L*C*h° color coordinates of ceramic samples, matching the colors of the VITA Linearguide, were recorded using four color-measuring devices (VITA Easyshade (A), VITA Easyshade compact (B), Degudent Shadepilot (C), X-Rite Shadevision (D)) and a spectrophotometric reference system under standardized test conditions. The intraclass correlation coefficients, regression lines with coefficients of determination, and mean deviations of the dental color-measuring devices from the spectrophotometric reference system were calculated. RESULTS All of the devices had high intraclass correlation coefficients, between 0.979 and 1.000. Nearly all measurements, except the hue values of devices A, B, and D, showed coefficients of determination close to 1.0 over the range of measurements for L*C*h° color coordinates. Similarly, all of the devices had coefficients of determination near the optimum value of 1.0. Devices C and D produced regression line slopes near the optimum value of 1.0 and intercepts close to the optimum value of zero. Only the L* coordinate measurements of devices A and B and the h° coordinate measurements of device B differed not significantly from the spectrophotometric reference values. CONCLUSIONS The electronic dental color-measuring devices tested showed excellent repeatability, but some devices showed substantial deviations in color coordinate values from the spectrophotometric reference system. Devices C and D showed higher precision than devices A and B.

Fracture Strength of Monolithic All-Ceramic Crowns on Titanium Implant Abutments.

PURPOSE The fracture strengths of all-ceramic crowns cemented on titanium implant abutments may vary depending on crown materials and luting agents. The purpose of this study was to examine differences in fracture strength among crowns cemented on implant abutments using crowns made of seven different monolithic ceramic materials and five different luting agents. MATERIALS AND METHODS In total, 525 crowns (75 each of Vita Mark II, feldspathic ceramic [FSC]; Ivoclar Empress CAD, leucite-reinforced glass ceramic [LrGC]; Ivoclar e.max CAD, lithium disilicate [LiDS]; Vita Suprinity, presintered zirconia-reinforced lithium silicate ceramic [PSZirLS]; Vita Enamic, polymer-reinforced fine-structure feldspathic ceramic [PolyFSP], Lava Ultimate; resin nanoceramic [ResNC], Celtra Duo; fully crystallized zirconia-reinforced lithium silicate [FcZirLS]) were milled using a CAD/CAM system. The inner surfaces of the crowns were etched and silanized. Titanium implant abutments were fixed on implant analogs, and airborne-particle abrasion was used on their exterior specific adhesion surfaces (Al2O3, 50 μm). Then, the abutments were degreased and silanized. The crowns were cemented on the implant abutments using five luting agents (Multilink Implant, Variolink II, RelyX Unicem, GC FujiCEM, Panavia 2.0). After thermocycling for 5,000 cycles (5 to 55°C, 30 seconds dwell time), the crowns were subjected to fracture strength testing under static load using a universal testing machine. Statistical analyses were performed using analysis of variance (α = .0002) and the Bonferroni correction. RESULTS No significant difference among the luting agents was found using the different all-ceramic materials. Ceramic materials LiDS, PSZirLS, PolyFSP, and ResNC showed significantly higher fracture strength values compared with FSC, FcZirLS, and LrGC. The PSZirLS especially showed significantly better results. CONCLUSION Within the limitations of this study, fracture strength was not differentially affected by the various luting agents. However, the fracture strength was significantly higher for PSZirLS, PolyFSP, ResNC, and LiDS ceramics than for the FSP, LrGC, and the FcZirLS ceramic with all luting agents tested.

A New Method for Volumetric Evaluation of Gingival Recessions: A Feasibility Study

BACKGROUND This preliminary in vitro study, presented at the General Session of the International and American Association for Dental Research in 2010 (Barcelona, Spain), evaluates whether three-dimensional (3D) optical scanning and subsequent superimposing procedures could be used for reproducible volumetric evaluation of gingival recession. METHODS Silicone impressions were taken of mandibular and maxillary master casts, and eight stone replicas of each master cast were produced. Each replica was scanned 10 times with a 3D optical system, and 3D datasets representing the computer-aided design reference models were calculated using a triangulation method. Marks designating gingival recession were scratched into the anterior segments of the replicas. The modified replicas were then scanned 10 times, and 3D datasets were calculated and subsequently superimposed. Differences in the volume of the gingival recession were recorded with reference to the initial data. RESULTS The determination of gingival recession volume was highly reproducible. For all replicas, the 3D optical method showed small standard deviations and intraclass correlation coefficients between 0.997 and 0.999. CONCLUSIONS This new method allows the reproducible volumetric evaluation of gingival recession marks on stone replicas. Additional clinical trials are necessary to confirm these in vitro findings. This method allows the operator to control the volumetric progression of periodontal soft tissue, for example, after root coverage procedures and to detect relapses at an early stage.

Counting touching cell nuclei using fast ellipse detection to assess in vitro cell characteristics: a feasibility study

In this article, we describe a new image analysis software that allows rapid segmentation and separation of fluorescently stained cell nuclei using a fast ellipse detection algorithm. Detection time ranged between 1.84 and 3.14 s. Segmentation results were compared with manual evaluation. The achieved over-segmentation rate was 0.11 (0.1 double counts and 0.01 false positive detections), and the under-segmentation rate was of 0.03 over all images. We demonstrate the applicability of the proposed algorithm to automated counting of fluorescent-labeled cell nuclei and to tissue characterization. Moreover, the performance of the proposed algorithm is compared with preexisting automated image analysis techniques described by others.

Long-term effect of overdenture bar design on peri-implant tissues.

PURPOSE To evaluate factors promoting mucositis and peri-implantitis (plaque accumulation, poor peri-implant soft tissue health, bone loss) with regard to prosthetic attachment systems consisting of implant-supported bar-retained overdentures. MATERIALS AND METHODS Patients who received TiOblast implants to support overdentures retained by either (1) prefabricated bars with or without extensions or (2) cast bars were recalled and examined clinically and radiographically. Plaque Index (PI), Sulcus Bleeding Index (SBI), probing pocket depth (PPD), and peri-implant bone loss were measured. Peri-implant tissue health was assessed, and the presence of mucositis and peri-implantitis was recorded. One-way analysis of variance with the Bonferroni adjustment was used to compare groups (α = .05). RESULTS Five to 10 years after prosthetic loading, 107 patients who received 516 TiOblast implants were evaluated; 31 of these patients were treated with 131 implants to support bar-retained overdentures. PI, SBI, PPD, and pathologic bone loss were least common in the group with prefabricated bars, followed by the group with prefabricated bars with extensions, and were most common in the group with cast bars. Plaque accumulation and pathologic bone loss values were higher with implants that supported mandibular bar-retained overdentures than with those supporting maxillary bar-retained overdentures. However, these differences among attachment systems or between maxillary and mandibular implants were not significant (P > .05). Mucositis was observed in one implant in the group with prefabricated bars, four implants in the group with prefabricated bars with extensions, and four implants in the group with cast bars. Peri-implantitis was observed in one implant of the cast bar group. CONCLUSIONS Five to 10 years after prosthetic loading, no significant difference in PI, SBI, PPD, pathologic bone loss, or peri-implant tissue conditions among the different bar designs tested was observed.

Primary Stability of Cylindrical and Conical Dental Implants in Relation to Insertion Torque—A Comparative Ex Vivo Evaluation

Introduction: The aim of this ex vivo study was to investigate the influence of different insertion torques on primary stability of a conical and a cylindrical implant system. Materials and Methods: Thirty-two dental implants (Astra Tech OsseoSpeed 5.0 S × 11 mm cylindrical [n = 16] and 5.0 × 11 mm conical [n = 16]) were inserted with 20, 30, 40, and 45 N·cm into fresh porcine bone of mixed trabecular-cortical quality. Before insertion, bone quality was assessed via cone beam tomography. After insertion, resonance frequency analysis was reported using the implant stability quotient (ISQ). Implant insertion depths were evaluated, and the implants were pushed out of the bone by force (measured in N). All experiments were done with n = 4 per group. Results: The highest ISQ (mean 78.25 ± 2.9) and pushout values (mean 675 N ± 5.8) were measured for the cylindrical implant after insertion using 30 N·cm. The conical implant showed the highest primary stability by means of ISQ (mean 76.25 ± 2.2) and pushout force (mean 502.5 N ± 9.6) after an insertion torque of 40 N·cm. If more insertion force was used, primary stability was reduced in all cases. Conclusion: The data indicate that different forms of an implant system need different insertion torques to obtain an optimal primary stability. These results have to be verified clinically.

Dental color matching: A comparison between visual and instrumental methods

The aim of this study was to compare the agreement rate (%) and color difference (ΔE*ab) of three dental color-measuring devices, with the visual shade identification. The tooth color were determined by two operators, which were advised to select a VITA classic shade tab in each others agreement. The Shadepilot (SP), CrystalEye (CE) and ShadeVision (SV) were used to measure tooth color. Statistically analyses include agreement rate (%), color difference (ΔE*ab), McNemar test (p=0.05), Students t-test (p=0.05) and Bland Altman scatterplots. The SP had an agreement of 56.3% with the visual shade determination, the CE 49.0% and SV 51.3%. ΔE*ab of the visually and instrumentally selected shade tabs and natural teeth were frequently above the threshold for acceptability. Comparing both methods, for SP ΔE*ab values differ in a range of clinical acceptability.

Interdevice agreement of eight equivalent dental color measurement devices.

ObjectivesThe reproducibility of electronic color-measuring devices used in dentistry refers to the consistency of measurements of a single device and also that between identical devices. This in vitro study evaluated the short-term interdevice agreement of eight equivalent dental measurement devices.MethodsThe short-term repeatability of eight identical VITA Easyshade Advance color measurement devices was evaluated. Each device was used to quantify the Commission Internationale de l’Eclairage (CIE) L*a*b* color coordinates of ceramic disks, designed in accordance with guidelines set by the VITA Toothguide 3D-Master shade tab organization. Statistical analysis involved calculating the intraclass correlation coefficients (ICCs) and color differences (ΔE*) for corresponding measurements taken by the devices. In addition, the mean color difference from the mean (MCDM) was calculated for each color.ResultsAll devices showed high ICCs for the color coordinates (L = 0.996, a = 0.993, b = 0.999). The ΔE* by shade ranged from 0.62 to 1.67. The MCDM by color-measuring device ranged from 0.11 to 0.23.ConclusionThis in vitro study showed that the color-measuring devices used were suitable for determining shade with high repeatability.Clinical relevanceThe high interdevice agreement of the VITA Easyshade Advance means that dental professionals can use this device independently, without compromising the consistency and quality of color measurements.

Preload, Coefficient of Friction, and Thread Friction in an Implant-Abutment-Screw Complex

PURPOSE To examine the screw preload, coefficient of friction (COF), and tightening torque needed to overcome the thread friction of an implant-abutment-screw complex. MATERIALS AND METHODS In a customized load frame, 25 new implant-abutment-screw complexes including uncoated titanium alloy screws were torqued and untorqued 10 times each, applying 25 Ncm. RESULTS Mean preload values decreased significantly from 209.8 N to 129.5 N according to the number of repetitions. The overall COF increased correspondingly. There was no comparable trend for the thread friction component. CONCLUSION These results suggest that the application of a used implant-abutment-screw complex may be unfavorable for obtaining optimal screw preload.

Polygonal Area of Prosthesis Support with Straight and Tilted Dental Implants in Edentulous Maxillae.

PURPOSE The aim of this in vitro study was to assess the increase in the polygonal area of implant-retained prosthesis supports in edentulous maxillae with the use of tilted distal implants compared with the use of straight distal implants, using a variety of implant lengths. MATERIALS AND METHODS A total of 25 DICOM datasets of atrophic edentulous maxillae were provided. Bone augmentations in the molar region had to be avoided. Two straight reference implants were virtually inserted in the anterior region. Two additional implants were placed far distally on both sides (4 groups: [1] straight, 12-mm length; [2] straight, 10 mm; [3] straight, 8 mm; [4] tilted, 12-16 mm). The resulting implant-supported polygon was measured for each of the 4 groups using three-dimensional planning software. RESULTS The mean sagittal depth of the supported polygon in Group 1 was 9.9 mm (standard deviation [SD] 4.4) on the right and 10.2 mm (SD 4.4) on the left, and it was 33.7 mm (SD 5.8) in width. For Group 2, the mean sagittal depth was 11.5 mm (SD 5.0) on the right and 11.9 mm (SD 4.7) on the left, and the width was 35.2 mm (SD 5.6). The measurements for Group 3 were 13.8 mm (SD 4.9) deep on the right, 13.8 mm (SD 5.1) deep on the left, and 37.0 mm (SD 5.4) in width. For Group 4, the depth was 15.8 mm (SD 4.9) on the right and 16.4 mm (SD 5.8) on the left, and the width was 39.0 mm (SD 5.1). CONCLUSION The area of implant-retained prosthesis support can be enlarged by the use of tilted implants (12 to 16 mm in length, 42 to 45 degrees) compared to the use of straight 8-mm implants (resulting increase: about 15%).