The validity of different display monitors in the assessment of dental implant site dimensions in cone beam computed tomography images

Abstract

Objective. To determine if the differing contrast resolution of various LCD monitors affects the reliability or accuracy of measurements of proposed implant sites. Materials and methods. Edentulous areas of human dry skulls were marked with radiopaque markers in order to standardize the plane of the transverse cross-sections of the ridges and path of measurements. The skulls were imaged by a CBCT device and the images stored in proprietary format on the workstation. The data sets were then transferred, with the proprietary reformatting software, to two different laptops using CDs. Transverse cross-sectional images of the ridges were reformatted on all three computers and ridge dimensions were recorded using the linear measurement tool of the proprietary software. Ridge dimensions were recorded directly from the three different monitors by two observers and compared to measurements recorded directly from the bone. The measurement errors and intra- and inter-examiner reliability were calculated for each monitor and compared with each other. Results. Intra- and inter-examiner reliability scores for the measurements recorded from all three devices were very high and ranged between 0.993–0.999. The mean of the absolute errors was 0.55 mm for the workstation, 0.61 mm for laptop 1 and 0.68 mm for laptop 2. The absolute errors were statistically significant for all three monitors (p-value < 0.001), but there was no statistically significant difference between the absolute errors obtained from the three monitors. Conclusions. No differences in the reliability or accuracy of measurements of implant site dimensions were obtained using color LCD monitors with different contrast resolution capabilities.     

Digital replacement of the distorted dentition acquired by cone beam computed tomography (CBCT): a pilot study

During cone beam computed tomography (CBCT) scanning, intra-oral metallic objects may produce streak artefacts, which impair the occlusal surface of the teeth. This study aimed to determine the accuracy of replacement of the CBCT dentition with a more accurate dentition and to determine the clinical feasibility of the method. Impressions of the teeth of six cadaveric skulls with unrestored dentitions were taken and acrylic base plates constructed incorporating radiopaque registration markers. Each appliance was fitted to the skull and a CBCT performed. Impressions were taken of the dentition with the devices in situ and dental models were produced. These were CBCT-scanned and the images of the skulls and models imported into computer-aided design/computer-aided manufacturing (CAD/CAM) software and aligned on the registration markers. The occlusal surfaces of each dentition were then replaced with the occlusal image of the corresponding model. The absolute mean distance between the registration markers in the skulls and the dental models was 0.09 ± 0.02 mm, and for the dentition was 0.24 ± 0.09 mm. When the method was applied to patients, the distance between markers was 0.12 ± 0.04 mm for the maxilla and 0.16 ± 0.02 mm for the mandible. It is possible to replace the inaccurate dentition on a CBCT scan using this method and to create a composite skull which is clinically acceptable.     

Validity of three-dimensional computed tomography measurements for Le Fort I osteotomy

The purpose of this study was to test the precision and accuracy of three-dimensional (3D) linear measurements for Le Fort I osteotomy, obtained from multi-slice computed tomography (MSCT) and cone beam computed tomography (CBCT) scans. The study population consisted of 11 dried skulls submitted to 64-row MSCT and CBCT scans. Three-dimensional reconstructed images (3D-CT) were generated, and linear measurements (n = 11) based on anatomical structures and landmarks of interest for Le Fort I osteotomy were performed independently by two oral and maxillofacial radiologists, twice each, using Vitrea software; this allows true 3D measurement on 3D-CT images. The results demonstrated no statistically significant differences between the inter-examiner and intra-examiner analyses, and physical and true 3D linear measurements using MSCT and CBCT images. Regarding examiner accuracy, no statistically significant differences were found for the comparisons among the physical and the MSCT and the CBCT linear measurements by either examiner. For examiners 1 and 2, the analysis intra-examiner correlation coefficient ranged from 0.87 to 0.96 and 0.82 to 0.98, respectively, using MSCT, and from 0.84 to 0.98 and 0.80 to 0.98, respectively, using CBCT, indicating almost perfect agreement for all analyses performed. 3D linear measurements obtained from MSCT and CBCT images were considered precise and accurate for Le Fort I osteotomy and thus accurate and helpful for Le Fort I osteotomy planning.     

Accuracy of implant position when placed using static computer-assisted implant surgical guides manufactured with two different optical scanning techniques: a randomized clinical trial

Data from cone beam computed tomography (CBCT) and optical scans (intraoral or model scanner) are required for computer-assisted implant surgery (CAIS). This study compared the accuracy of implant position when placed with CAIS guides produced by intraoral and extraoral (model) scanning. Forty-seven patients received 60 single implants by means of CAIS. Each implant was randomly assigned to either the intraoral group (n = 30) (Trios Scanner, 3Shape) or extraoral group (n = 30), in which stereolithographic surgical guides were manufactured after conventional impression and extraoral scanning of the stone model (D900L Lab Scanner, 3Shape). CBCT and surface scan data were imported into coDiagnostiX software for virtual implant position planning and surgical guide design. Postoperative CBCT scans were obtained. Software was used to compare the deviation between the planned and final positions. Average deviation for the intraoral vs. model scan groups was 2.42° ± 1.47° vs. 3.23° ± 2.09° for implant angle, 0.87 ± 0.49 mm vs. 1.01 ± 0.56 mm for implant platform, and 1.10 ± 0.53 mm vs. 1.38 ± 0.68 mm for implant apex; there was no statistically significant difference between the groups (P > 0.05). CAIS conducted with stereolithographic guides manufactured by means of intraoral or extraoral scans appears to result in equal accuracy of implant positioning.     

Age-related changes in anatomic bases for the insertion of zygomatic implants

The objectives of this study were to verify whether Chinese patients are well-suited for zygomatic implantation and to observe age-related changes in the linear and angular anatomic bases of the maxilla and zygoma. Using three-dimensional images selected from maxillofacial cone beam computed tomography (CBCT) scans generated by SimPlant, linear and angular measurements were obtained by simulating zygomatic implantation. The edentulous group comprised 40 subjects aged between 62 and 65 years. A total of 120 dentate cases were divided into three groups based on age: the established occlusion group (n = 40; 12–15 years old), the adult group (n = 40; 37–40 years old), and the elderly group (n = 40; 62–65 years old). The mean potential insertion length of the ordinary and additional zygomatic implants became longer with age in the dentate groups. For both zygomatic implant insertion areas, the anteroposterior lengths of the maxilla and zygoma were thicker in the older dentate groups (P < 0.05). Significant differences were verified in the installation direction among the dentate groups. Gender was not a significant factor. The zygomatic skeleton changes with age, which results in linear and angular variations in the zygomatic implant insertion area. Therefore, the anatomic bases in Chinese adults are suitable for zygomatic implants.     

Comparative study of the accuracy of CBCT implant site measurements using different software programs

PurposeTo measure and compare the accuracy of the linear dimensions of implant sites recorded from cone beam computed tomography (CBCT) images using Blue Sky Plan, coDiagnostiX, and RadiAnt.Materials and MethodsFive human dry skulls were imaged with a CBCT device then sectioned to obtain sample transverse cross-sections of the edentulous ridges, and the height and width of the ridge were measured with a digital caliper to provide the gold standard measurements. The CBCT datasets were exported in DICOM format and imported into the three test software programs which were used to obtain reformatted sectional images corresponding to the sample transverse cross-sections, and the height and width of the edentulous ridge was recorded using the linear measurement tool. Reliability of the measurements were measured using the intraclass correlation coefficient. One-sample t-test (test value: zero) was used to test the statistical significance of the mean of the absolute errors for each software program. Analysis of Variance with Repeated Measures was used to test the statistical significance of the difference between the means of the absolute errors obtained by the different software programs. Statistical significance was set at a p-value of 0.05.ResultsThe reliability of the gold standard and image measurements were excellent. All three software programs demonstrated a statistically significant mean absolute measurement error of between 0.43 and 0.56 mm (p-value < 0.01), but no significant difference in error values was found between any of the tested programs (p- value = 0.18).ConclusionsThere was no statistically significant difference in accuracy of linear CBCT measurements of implant sites recorded using Blue Sky Plan, coDiagnostiX, and RadiAnt.     

Texture analysis of cone beam computed tomography images reveals dental implant stability

The aim of this study was to characterize the alveolar bone of edentulous maxillary sites using texture analysis (TA) of cone beam computed tomography (CBCT) images and to correlate the results to the insertion torque, thus verifying whether TA is a predictive tool of final implant treatment. This study was conducted on patients who had received single implants in the maxilla (46 implants) 1 year earlier and whose torque values were properly recorded. Three cross-sections of the sites were selected on CBCT scans. Two regions of interest (ROIs) corresponding to the implant bone site and peri-implant bone were also outlined, according to virtual planning. The CBCT scans were exported to MaZda software, where the two ROIs were delimited following the previously demarcated contours. Values for the co-occurrence matrix were calculated for TA. With regard to the insertion torque value, there was a direct correlation with the contrast of the peri-implant bone (P < 0.001) and an inverse correlation with the entropy of the implant bone site (P = 0.006). A greater contrast indicates a greater torque value for insertion of the implants, and there is a possible association with a lower entropy value of the implant–bone interface.     

Immediate dental implant placement with a horizontal gap more than two millimetres: a randomized clinical trial

The purpose of this study was to evaluate the horizontal dimensional changes in buccal alveolar bone immediately after dental implant placement in the upper premolar area with horizontal gaps >2 mm. A total of 48 patients were enrolled in this randomized clinical trial and were randomly assigned to one of three groups. Group I (flap with graft; n = 16) patients received an immediate implant with bone graft, membrane, and primary flap closure. Group II (flap without graft; n = 16) patients received an immediate implant with primary flap closure only. Group III (flapless without graft; n = 16) patients received an immediate implant without graft, membrane, or primary closure. Cone beam computed tomography (CBCT) scans were obtained preoperatively, immediately after implant placement, and at 6 months postoperative to evaluate horizontal dimensional changes in the buccal alveolar bone. Pain intensity was measured using a numerical rating scale. CBCT examinations revealed that bone had filled the horizontal gap in all three groups. Group II showed the greatest horizontal dimensional changes in the buccal alveolar bone, followed by group I. The least amount of change was recorded for group III. Furthermore, significantly less postoperative pain was recorded in group III when compared to the other groups. Short-term results suggest that the ‘flapless without graft’ technique shows similar results to the ‘flap with graft technique’ for immediate implant placement in the maxillary premolar extraction site with a horizontal gap >2 mm, when the bone plate is intact.     

Influence of implant scanbody material,position and operator on the accuracy of digital impression for complete-arch: A randomized in vitro trial

PurposeTo evaluate the influence of implant scanbody (ISB) material, position and operator on the accuracy of a confocal microscopy intraoral scanning (IOS) for complete-arch implant impression.MethodsAn edentulous maxillary model with 6 internal hexagonal connection analogues was scanned with an extraoral optical scanner to achieve a reference file. Three ISBs made of different materials (polyetheretherketone (Pk), titanium (T) and Pk with a titanium base (Pkt)) were scanned with IOS by 3 operators. The resulting 45 test files were aligned to the reference file with a best fit algorithm. Linear (ΔX, ΔY and ΔZ-axis) and angular deviations (ΔANGLE) were assessed. Absolute values of the linear discrepancies were summed up to obtain a global measure of linear absolute error (ΔASS). Influence of ISB material, position and operator was statistically assessed using the mixed general linear model.ResultsAt multivariate analysis, whenΔASS was considered as response variable, it was identified a significant influence of material (p < 0.0001) and position (p = 0.0009) while no significant operator effect was detected.When ΔANGLE was considered as response variable, material and position significantly influenced the expected ΔANGLE (p = 0.0232 and p < 0.0001) and no operator effect was identified.ConclusionsThe investigated IOS for complete-arch digital impression was influenced by the ISB material with peek reporting the best results on both linear and angular measurements followed by titanium, peek-titanium resulting as the less accurate. Implant angulation affected significantly the linear deviations while implant position the angular deviations. Operator did not show any significant effect on the IOS accuracy.     

Comparison of the accuracy for three dental impression techniques and index: An in vitro study

ObjectivesThis in vitro study compared the dimensional accuracy of stone index (I) and three impression techniques: tapered impression copings (T), squared impression copings (S) and modified squared impression copings (MS) for implant-supported prostheses.MethodsA master cast, with four parallel implant abutment analogs and a passive framework, were fabricated. Vinyl polysiloxane impression material was used for all impressions with two metal stock trays (open and closed tray). Four groups (I, T, S and MS) were tested (n = 5). A metallic framework was seated on each of the casts, one abutment screw was tightened, and the gap between the analog of implant and the framework was measured with a stereomicroscope. The groups’ measurements (80 gap values) were analyzed using software (LeicaQWin – Leica Imaging Systems Ltd.) that received the images of a video camera coupled to a Leica stereomicroscope at 100× magnification. The results were statistically analyzed with Kruskal–Wallis One Way ANOVA on Ranks test followed by Dunn's Method, 0.05.ResultsThe mean values of abutment/framework interface gaps were: Master Cast = 32 μm (SD 2); Group I = 45 μm (SD 3); Group T = 78 μm (SD 25); Group S = 134 μm (SD 30); Group MS = 143 μm (SD 27). No significant difference was detected among Index and Master Cast (P = .05).ConclusionUnder the limitations of this study, it could be suggested that a more accurate working cast is possible using tapered impression copings techniques and stone index.     

In-vitro accuracy and reproducibility evaluation of probing depth measurements of selected periodontal probes

AimThe purpose of the present in vitro study was to measure the accuracy and reproducibility of three periodontal probes. To eliminate environment- or examiner-related probing errors, two aluminum blocks with predrilled holes of varying depths were examined by participants who had been trained in probing before the study. This methodology improved the likelihood that any probing errors identified were generated by the probes themselves.Materials and methodsThree probes, Williams 14 W (Hu-Friedy Mfg. Co., LLC, UK), Chapple UB-CF-15 (Implantium, Shrewsbury, UK), and Vivacare TPS (Ivoclar Vivadent, Enderby, UK), were randomly distributed to 23 participants (9 males and 14 females; mean age: 31.35 years). Participants measured 30 holes in two aluminum blocks, average 20 days, SD = 341.05. For each hole, the mean measured depth was calculated for each participant and compared to the true depth. Intra- and inter-examiner accuracy and reproducibility for each of the duplicate measurements were calculated. Data were analyzed by paired-samples t-test with the SPSS 18 software package (IBM Portsmouth, UK). A p-value <0.05 indicated statistical significance. Tables were constructed from the data.ResultsWhen used by participants, the Williams 14 W probe was reproducible but not necessarily accurate; Vivacare TPS was neither accurate nor reproducible; and Chapple UBCF-15 was both accurate and reproducible.ConclusionDepth measurements with the Chapple UB-CF-15 probe were more accurate and reproducible compared to measurements with the Vivacare TPS and Williams 14 W probes. This in vitro model may be useful for intra-examiner calibration or clinician training prior to the clinical evaluation of patients or in longitudinal studies involving periodontal evaluation.     

The virtual human face: Superimposing the simultaneously captured 3D photorealistic skin surface of the face on the untextured skin image of the CBCT scan

The aim of this study was to evaluate the impact of simultaneous capture of the three-dimensional (3D) surface of the face and cone beam computed tomography (CBCT) scan of the skull on the accuracy of their registration and superimposition. 3D facial images were acquired in 14 patients using the Di3d (Dimensional Imaging, UK) imaging system and i-CAT CBCT scanner. One stereophotogrammetry image was captured at the same time as the CBCT and another 1 h later. The two stereophotographs were individually superimposed over the CBCT using VRmesh. Seven patches were isolated on the final merged surfaces. For the whole face and each individual patch: maximum and minimum range of deviation between surfaces; absolute average distance between surfaces; and standard deviation for the 90th percentile of the distance errors were calculated. The superimposition errors of the whole face for both captures revealed statistically significant differences (P = 0.00081). The absolute average distances in both separate and simultaneous captures were 0.47 and 0.27 mm, respectively. The level of superimposition accuracy in patches from separate captures was 0.3–0.9 mm, while that of simultaneous captures was 0.4 mm. Simultaneous capture of Di3d and CBCT images significantly improved the accuracy of superimposition of these image modalities.     

Effect of different composite modulation protocols on the conversion and polymerization stress profile of bulk-filled resin restorations

ObjectiveThe aim of this in vitro study was to test the effect of different composite modulation protocols (pre-heating, light-curing time and oligomer addition) for bulk filling techniques on resin polymerization stress, intra-pulpal temperature change and degree of conversion.MethodsClass I cavities (4 mm depth × 5 mm diameter) were prepared in 48 extracted third molars and divided in 6 groups. Restorations were completed with a single increment, according to the following groups: (1) Filtek Z250XT (room temperature – activated for 20 s); (2) Filtek Z250XT (at room temperature – activated for 40 s); (3) Filtek Z250XT (pre-heated at 68 °C – activated for 20 s); (4) Filtek Z250XT (pre-heated at 68 °C – activated for 40 s); (5) Filtek BulkFill (at room temperature – activated for 20 s); (6) Filtek Z250XT (modified by the addition of a thio-urethane oligomer at room temperature – activated for 40 s). Acoustic emission test was used as a real-time polymerization stress (PS) assessment. The intra-pulpal temperature change was recorded with a thermocouple and bottom/top degree of conversion (DC) measured by Raman spectroscopy. Data were analyzed with one-way ANOVA/Tukey's test (α = 5%).ResultsPre-heating the resin composite did not influence the intra-pulpal temperature (p = 0.077). The thio-urethane-containing composite exhibited significantly less PS, due to a lower number of acoustic events. Groups with pre-heated composites did not result in significantly different PS. Filtek BulkFill and the thio-urethane experimental composite presented significantly higher DC.SignificanceResin composite pre-heating was not able to reduce polymerization stress in direct restorations. However, thio-urethane addition to a resin composite could reduce the polymerization stress while improving the DC.     

Biocompatibility of resin composites subcutaneously implanted in rats with experimentally induced arthritis

ObjectiveTo evaluate the biocompatibility of resin composite specimens with different curing efficiency, subcutaneously implanted in rats with experimentally induced arthritis.MethodsThe amount of remaining CC bonds (%RDB) of hybrid resin composite specimens photopolymerized for 10 s and 40 s exposure time (n = 3) was measured by micro-attenuated total reflectance Fourier transform infrared spectroscopy. Male Wistar rats (n = 36) were classified in two groups (n = 18) of healthy animals and of animals with experimentally induced arthritis. Resin composite specimens irradiated for 10 s and 40 s and calcium hydroxide control specimens were implanted subcutaneously in each animals’ dorsum. Following 2-, 4- and 9-week periods the animals were sacrificed. The development of arthritis was defined by biochemical analysis and the changes in the relative weight of animals’ organs (spleen, thymus, adrenals). Tissue reactions were examined histologically.Results%RDB per site and exposure time showed statistically significant differences. Lowest %RDB values were recorded on 40 s exposed specimens. Biochemical indices and relative organ weights demonstrated statistically significant differences between healthy animals and animals with arthritis. The health status of the animals and the materials used did not influence tissue response. First and second periods of sacrifice showed reduced propensity of connective tissue development in comparison to the third period. The same applied for the second period regarding the presence of giant cells.SignificanceThe materials tested and the animals’ health status did not result in altered tissue response compared to control group. The period of sacrifice was associated with different tissue responses.     

Microhardness of resin composite materials light-cured through fiber reinforced composite

ObjectivesTo compare polymerization efficiency of resin composite basing materials when light-cured through resin composite and fiber reinforced composite (FRC) by testing microhardness.MethodsSimulated indirect restorations were prepared by application of resin composite (Clearfil AP-X) or FRC (EverStick) to nylon rings with 1.5 mm thickness and 8 mm diameter, followed by light-curing. Resin composite basing material (Clearfil Majesty Flow or Clearfil AP-X) was applied to identical rings and light-cured through the simulated indirect restorations with exposure times of 20, 40, or 60 s. Light-curing though a ring without resin material (=no indirect restoration) served as control. For each combination of basing material and indirect restoration 10 specimens were prepared for each exposure time. Top and bottom surface Vickers microhardness numbers (VHNs) of basing materials were recorded after 24 h.ResultsAfter 60 s exposure time, VHNs with indirect FRC were not different from control VHNs, while VHNs with indirect resin composite were significantly lower (p < 0.001). Linear regression analysis revealed that resin composite basing material used had the greatest effect on top and bottom VHNs (p < 0.001). The presence of an indirect restoration resulted in decreased VHNs (p < 0.001), with resin composite resulting in lower VHNs when compared to FRC. Moreover, a longer exposure time resulted in increased VHNs (p < 0.001).SignificanceResults suggest that polymerization of resin composite basing materials is more effective when light-curing through an FRC than through a resin composite indirect restoration. Prolonging of exposure time, however, is necessary when compared to light-curing without presence of indirect restoration material.     

Evaluation of tooth root surface area using a three-dimensional scanning technique and cone beam computed tomographic reconstruction in vitro

ObjectiveTo study the feasibility of measuring root surface area (RSA) by 3D scanning technique and cone beam computed tomography (CBCT) reconstruction in vitro.DesignTwenty extracted teeth (10 single-rooted teeth and 10 multi-rooted teeth) were collected in this study. The RSA of the extracted teeth was measured by the membrane technique, 3D scanning technique, and CBCT reconstruction. A standard part was also designed to check the accuracy of each method. All statistical analyses were performed using the SPSS software.ResultsAccording to the results of one-way ANOVA, there was no significant difference among the values of RSA measured by the three techniques (p > 0.05). The results of Wilcoxon matched-pairs signed-rank test further demonstrated that there was no significant difference among the values of RSA in both single- and multi-rooted teeth measured by the three techniques (p > 0.05).ConclusionsThe membrane technique, the 3D scanning technique, and CBCT reconstruction are novel reliable techniques for measuring the RSA in both single- and multi-rooted teeth, which will provide wide clinical applications in the future.     

The reliability of cone-beam computed tomography (CBCT) – Generated frontal cephalograms

BackgroundThe purpose of this study was to evaluate the reliability of measurements from cone-beam computed tomography (CBCT)-generated frontal cephalogram.Materials and methodsCBCT and conventional posteroanterior (PA) cephalograms were taken from 30 adult patients. CBCT image was set according to the Frankfurt-Horizontal (FH) plane as the horizontal plane and the midsagittal reference (MSR) plane. The CBCT frontal cephalograms were generated using the orthogonal Raycast method (group CT_raycast), the orthogonal maximum intensity projection (MIP) method (group CT_MIP) after the head reorientation according to the reference planes, and the generator tool provided by the employed 3-dimensional (3D) imaging software (group CT_generator), respectively. The differences between the CBCT-generated frontal cephalograms and conventional PA cephalograms (group PA_ceph) were compared by paired t-test (p < 0.05).ResultsThe significant differences were shown in two measurements for group CT_raycast, in 12 measurements for group CT_MIP, and in eight measurements for group CT_generator. It was confirmed that the CBCT frontal cephalograms, generated by means of the Raycast method (Group CT_raycast), were more comparable to the conventional PA cephalograms in their measurements than were the others (Groups CT_MIP, CT_generator).ConclusionThis study may well suggest that frontal cephalograms derived by 3D CBCT reorientation can be effectively employed in clinical applications.     

Assessment of gingival biotype and facial hard/soft tissue dimensions in the maxillary anterior teeth region using cone beam computed tomography

ObjectiveThis study sought to assess the relationship between facial gingival and bone dimensions in maxillary anterior teeth region using cone beam computed tomography (CBCT).DesignThis study assessed 621 maxillary anterior teeth in 144 patients. In the sagittal plane, facial bone thickness (BT) and gingival thickness (GT) were measured at the crestal level and at 2, 4 and 6 mm apical to the cementoenamel junction (CEJ). The dentogingival complex (DGC) dimensions and the distance from the CEJ to bone crest were also measured on CBCT scans. To determine the gingival biotype, GT at 2 mm apical to the gingival margin was measured and GT <1.5 mm was categorized as thin while GT ≥1.5 mm was categorized as thick. The data were analyzed using SPSS version 21 via repeated measures ANOVA and the Cochrane’s Q, chi-square and independent samples t-tests.ResultsThe BT around the maxillary central and lateral incisors and canine teeth at 4 and 6 mm apical to the CEJ was significantly different in thick and thin gingival biotypes (P < 0.05). The mean GT at 2 and 4 mm apical to the CEJ was significantly different around central and lateral incisors (P < 0.05). Thickness of crestal bone was significantly different between the two gingival biotypes around central and lateral incisors (P < 0.05).ConclusionThe two gingival biotypes had significantly different mean BT; different biotypes and their relationship to BT varied around anterior maxillary teeth.     

Effects of different abutment material and surgical insertion torque on the marginal adaptation of an internal conical interface: An in vitro study

PurposeTo evaluate the marginal adaptation at implant–abutment connection of an implant featuring a conical (45° taper) internal hexagonal abutment with a connection depth of 2.5 mm, comparing the performance of two identical abutments of different material (titanium grade-4 and Co-Cr-alloy).MethodsTwenty implants (3.75 mm × 15 mm) were connected to non-matching abutments (5.5 mm × 10 mm) of two different materials (titanium grade-4: n = 10; Co-Cr-alloy: n = 10). The specimens were separately embedded in epoxylite resin, inside copper cylinders, and submerged without covering the most coronal portion (5 mm) of the fixture. Five specimens per group were stressed simulating a surgical 100 Ncm insertion torque, while the others had no torque simulation. All specimens were subjected to a non-axial static load (100 N) in a universal testing machine, under an angle of 30° with respect to the implant axis. Once 100 N load was reached, low shrinkage self-curing resin was injected inside the cylinders, and load was maintained until complete resin polymerization. Specimens were cut and analyzed with optical and scanning-electron-microscope (SEM) to evaluate the marginal adaptation at the implant–abutment connection. Statistical analysis was performed using one-way ANOVA (p = 0.02).ResultsNone of the 20 samples failed. The implant–abutment connection was able to guarantee a good optical seal; SEM analysis confirmed the absence of microgaps.ConclusionsWithin the limits of this study (small sample size, limited time) the marginal adaptation of the implant–abutment connection was not affected by the abutment material nor by the application of surgical insertion torque.     

Effect of exposure parameters on the radiopacity of root canal sealers

BackgroundThe aim of this study was to test the effect of different kilovoltage, milliampere, and exposure time settings on the radiopacity of two endodontic sealers using an image plate system.Materials and methodsMM-Seal (MicroMega, Besancon, France) and Diaket (3M Espe, Seefeld, Germany) were packed into a polytetrafluoroethylene ring mold with an internal diameter of 10 mm and a depth of 1 mm. Five discs of each material were imaged alongside an aluminum step-wedge. Sets of radiographs were obtained using storage phosphor plates (SPPs). The SPPs were exposed at 60, 65, or 70 kVp, 7 or 8 mA for 0.12 or 0.16 s. Radiographic densities of the sealers and each step of the step-wedge were analyzed with Image Tool 3.0 SDK software (University of Texas Health Sciences Center, TX, USA). Three readings were made for each image. The mean was calculated to give the radiographic density expressed as mean gray values. Three-way ANOVA was used to test the differences in radiopacity of sealers with respect to kilovoltage, milliampere, exposure time, and the interaction of the three factors.ResultsNo significant difference in sealers’ radiopacity was found with change in three exposure parameters (p > 0.05). However, standard deviations of the measurements for lower exposures were greater; MM-Seal was significantly more radiopaque than Diaket (p < 0.0001) at any parameter.ConclusionsDifferences in kilovoltage, milliampere, and exposure time do not affect the radiopacity measurements of sealers on SPP images. However, choosing the proper exposure parameters may optimize the gray value range of the sealers allowing for better discrimination of the sealer and surrounding structures thereby providing better clinical guidance.