The effect of wavelet and discrete cosine transform compression of digital radiographs on the detection of subtle proximal caries. ROC analysis.

The study compared diagnostic performances of 2 different image compression methods: JPEG (discrete cosine transform; Joint Photographic Experts Group compression standard) versus JPEG2000 (discrete wavelet transform), both at a compression ratio of 12:1, from the original uncompressed TIFF radiograph with respect to the detection of non-cavitated carious lesions. Therefore, 100 approximal surfaces of 50 tooth pairs were evaluated on the radiographs by 10 experienced observers using a 5-point confidence scale. Observations were carried out on a standardized viewing monitor under subdued light conditions. The proportion of diseased surfaces was balanced to approximately 50% to avoid bias. True caries status was assessed by serial ground sectioning and microscopic evaluation. A non-parametric receiver operating characteristic analysis revealed non-significant differences between the 3 image modalities, as computed from the critical ratios z not exceeding +/-2 (JPEG/JPEG2000, z = -0.0339; TIFF/JPEG2000, z = 0.251;TIFF/JPEG, z = 0.914). The mean area beneath the curve was highest for TIFF (0.604) followed by JPEG2000 (0.593) and JPEG (0.591). Both intra-rater and inter-rater agreement were significantly higher for TIFF (kappa(intra) = 0.52; kappa(inter) = 0.40) and JPEG2000 images (kappa(intra) = 0.49; kappa(inter) = 0.38) than for JPEG images (kappa(intra) = 0.33; kappa(inter) = 0.35). Our results indicate that image compression with typical compression algorithms at rates yielding storage sizes of around 50 kB is sufficient even for the challenging task of radiographic detection of non-cavitated carious approximal lesions.

Effect of digital noise filters on diagnostic radiographs for the diagnosis of experimental root fractures.

This article discusses basic concepts of noise suppression for digital radiographs, and shows how false application of algorithms available can lead to a loss of information. Noise suppression realized with low pass convolution filters are designed to decrease strong grey level changes of neighboring pixels. Sixty-two extracted fully intact premolars were selected and treated usingthe crown-down technique to prepare them for experimental fractures. A total of 358 radiographs were taken, of which 312 images were selected with clearly visible root fractures. The selected radiographs were stored as uncompressed images and manipulated with 8 different convolution filters. A total of 2496 raw and filtered images were inspected for visible root fractures. Only the arithmetic mean filter with 5 x 5 kernel size led to a deletion of the visible fracture line in 33.3% of the inspected cases. The other filters proved to be useful for noise reduction without loss of any necessary diagnostic information. None of the filters improved the diagnostic outcome in the 46 remaining radiographs which did not show clearly visible root fractures before application of the filters.

Fast algorithm for real-time detection of root canal orifices in video images.

Real-time image analysis in endodontics opens new options of treatment support in dentistry. Imaging software was developed to detect the root canal orifices in video sequences of trepanated teeth acquired by a digital video microscope, the Motic DM 143. The software developed is capable of communicating with any video camera connected to it and can automatically detect almost all root canal orifices in trepanated teeth. To recognize the root canal orifices we used the so-called Minimum-Distance Classification. The Minimum-Distance Classification provides a color-based pattern recognition algorithm, which is directly implemented in the function accessing the video stream, and is therefore very fast. Processing speed varied between 30 and 64 ms per image with an input image resolution of 352 x 288 pixels on the Pentium 4 computer (2 GHz). The developed software was tested in this study on 78 trepanated teeth. The mean detection sensitivity of the software found for all 78 teeth is 97.01%.

Development and functionality of isoelastic dental implants of titanium alloys.

Two types of isoelastic endosseous dental implants were produced and their functionality was tested. One type consisted of a porous sintered TiTa30 alloy, the other had a special surface structure consisting of titanium wire loops. Their mechanical properties were optimized by the production parameter (sintering and diffusion bonding, respectively). The functionality was tested after insertion into an artificial jaw which had properties corresponding to the natural mandibular. The elastic properties of both implants were similar to the properties of the bone. In addition the implants have a safe anchorage bone ingrowth. In animal experiments using the implant with surface loops it was observed that the bone entered the loops and even extremely small surface cavities in the wire loops.

Effect of diode laser irradiation on the attachment rate of periodontal ligament cells: an in vitro study.

BACKGROUND: The present study is part of a basic research program investigating the cellular effects of an 810 nm GaAlAs-diode laser on human periodontal tissues. The aim of the investigation was to evaluate the effects of laser treatment of root surface specimens on the attachment of periodontal ligament (PDL) cells in vitro. METHODS: Root specimens were prepared from periodontally diseased teeth. PDL cells were obtained from human third molar ligaments. Cells were cultured under simple, standardized, and reproducible experimental conditions. One hundred fifty root specimens were scaled and root planed with curets followed by air-powder abrasive treatment; 75 were then lased and 75 served as controls. The irradiation time was 20 seconds at a power output of 1 W. The root segments were placed into culture dishes, covered with a solution of PDL cells, and incubated for 72 hours. The specimens were then washed with phosphate buffer to remove cells not attached to the surface, and the adherent cells were stained with methylene blue. Cells were counted using a reflected light microscope and the cell density per mm2 was calculated. RESULTS: The analysis of 150 specimens revealed no significant differences between the groups (P = 0.347, Wilcoxon test). The cell numbers, however, were slightly higher on laser specimens. The mean was 66 cells/mm2 in the laser group and 63.7 cells/mm2 in the control group. CONCLUSIONS: The application of the diode laser at the parameters used did not have a substantially positive effect on the new attachment of PDL cells on the tooth specimens. It remains to be investigated whether the difference detected is really clinically relevant.

Effects of various hygiene procedures on the surface characteristics of titanium abutments.

The use of cleaning instruments on titanium implants may cause undesired surface alterations. In a qualitative and quantitative assessment of these alterations, 5 titanium implant abutments were treated with a steel curet, a prototype pure titanium curet, an air abrasive polishing system, and an ultrasonic system. Custom-made polymer templates, used to secure the curet to a vertical guide bar and a spring scale to maintain a constant instrument pressure, guaranteed a standardized procedure and reproducible results. The ultrasonic and the air abrasive polishing method were also standardized. Evaluation by scanning electron microscopy (SEM) revealed surface alterations for all instruments and systems except the plastic curet, which did not roughen the surface at all. The confocal laser-scanning microscope allows a 3-dimensional reproduction of these surface alterations and their direct measurement. The profilometric tracing was not sensitive enough to register the minor effects caused by the titanium curet and the air abrasive polishing system. Dimensions of the resulting surface microstructure could be determined with the laser-scanning microscope. Since the influence of such surface defects on the peri-implant tissue reaction is unpredictable, the titanium curet and the air abrasive system can only be recommended with restrictions. The steel curet and the ultrasonic system proved to be totally unsuitable for cleaning titanium implants.

A comparative study of results with various endosseous implant systems.

The results of regular follow-up of various endosseous titanium implant systems are presented together with an overview of the results with Tübingen Frialit aluminum oxide ceramic implants. Using ITI implants, pathological findings for sulcus depth and peri-implant bone degradation were found significantly more frequently than with the other titanium implants. Clinical mobility was present significantly more frequently with TPS implants than with the IMZ system, whereas an increase in the depth of the peri-implant sulcus alone occurred significantly more frequently with the IMZ and ITI than with the TPS implant system. The observation period for Brånemark implants is too short to permit final evaluation. However, pathological findings have not occurred to date.

The longitudinal clinical effectiveness of ITI solid-screw implants in partially edentulous patients: a 5-year follow-up report.

A total of 114 ITI solid-screw implants was consecutively placed in 55 partially edentulous patients and restored with 68 fixed prostheses. The patients were followed for at least 5 years in a prospective study that focused on implant success and longitudinal reactions of the peri-implant hard and soft tissues. During the study period, 5 implants failed and 15 implants were lost to follow-up, resulting in a cumulative survival rate of 95.3% after 5 years of loading. The success analysis included additional strictly defined events ("first occurrence of marginal bone loss > or = 4 mm," "first occurrence of pocket depth > or = 4 mm," and "first occurrence of crevicular fluid volume > or = 2.5 mm") and resulted in a cumulative 5-year success rate of 89.0%. Median loss of marginal bone, as observed on radiographs, was 0.7 mm between implant placement and prosthetic treatment and 0.5 mm between prosthesis placement and the 5-year evaluation. Compared to the previous year's value, the annual increase in marginal bone loss did not reach a level of statistical significance between 1 and 5 years of function, so that a steady state prevailed. The incidence of lingual-palatal surfaces affected with remarkable plaque deposits increased from 13% after prosthesis placement to 23% after 5 years. Sulcus Bleeding index, probing depth, attachment level, and crevicular fluid volume were used to describe the health of the peri-implant soft tissues. The research parameters remained almost unchanged and indicated a soft tissue response within physiologic levels. Most mechanical complications were experienced during the first year of loading and were related to loosening of occlusal screws, which occurred in 8 (12%) of 68 restorations.

Treatment of peri-implantitis defects with autogenous bone grafts: six-month to 3-year results of a prospective study in 17 patients.

As part of an ongoing prospective study, the treatment of peri-implantitis defects using autogenous bone grafts was evaluated. This present report is based on data from 25 ITI screw implants in 17 patients with progressive peri-implant tissue destruction during the maintenance phase. Treatment of these lesions included raising flaps, removal of the surrounding granulation tissue, and air-polishing of the implant surface. Subsequently, corticocancellous bone grafts or particulate bone were placed into the peri-implant osseous defects, and the flaps were sutured around the cervical segment of the implants, allowing for transmucosal healing. Two of the 25 cases resulted in a negative outcome of the procedure. One of the transplants had to be removed 40 days after augmentation because of flap dehiscence and graft mobility. In another patient, the healing period was uneventful until the re-entry surgery, but when the site was reopened, the total graft volume was resorbed. The primary therapeutic success at re-entry surgery evaluated by intraoperative measurements resulted in a median defect depth reduction of 6.9 to 0.7 mm (P = .001), corresponding to a bone repair of 90%. The change in defect width was 1.9 mm (P = .002, repair 100%). A positive result of the reconstructive therapy has been observed during a re-evaluation time of up to 3 years. Median marginal bone loss was reduced from 6.2 to 2.3 mm after 2 and 3 years, respectively. The median vertical bone resorption of 4.5 mm was completely repaired. The crevicular fluid volume, a parameter of the level of marginal inflammation, along with probing depths and attachment levels, were reduced to a physiologic rate. The implant observation period until the first appearance of the lesion seems to be crucial to the effectiveness of the therapy. Early failures appearing within the first 2 years after implant placement showed a more stable therapeutic result over time.

Contribution to the functional surface structure of endosseous implants.

An endosseous implant that should allow osseointegration as well as fixation by connective tissue has been developed. A special surface structure consisting of titanium wire loops on a titanium implant was produced by diffusion bonding. The mechanical properties of this implant are investigated.

Hard and soft tissue reactions to ITI screw implants: 3-year longitudinal results of a prospective study.

Between November 1988 and July 1992, a total of 320 ITI screw implants were consecutively placed in 109 patients. The patients were observed in a prospective longitudinal study focusing on implant success and clinical proof. Radiologic and clinical parameters were established at specific time intervals to examine hard and soft tissue reactions. Clinical parameters and the measured bone resorption were analyzed for possible correlation. Seventy-five percent (n = 82) of patients were edentulous, and 16% (n = 17) had distal extensions or extended edentulous spaces. Nine percent (n = 10) of the implants were for single-tooth replacement. During the follow-up period, a total of 10 patients with 29 implants dropped out, and 6 implants were lost as a result of failed osseointegration. The cumulative implant survival rate was 98.1%, and the cumulative implant success rate, using strict criteria for success, was 97.1% after 3 years. The mean bone loss between implant placement and prosthetic restoration was 0.8 mm. For the period between prosthetic treatment and the 3-year examination, a mean annual bone resorption of approximately 0.1 mm was observed. The periodontal parameters indicated a healthy soft tissue response during the time of observation. The statistical correlation analysis showed a definite relationship between the crevicular fluid volume and bone resorption. The results of this 3-year study indicate that ITI screw implants, with their nonsubmerged healing characteristic, can serve as a reliable foundation for implant-supported restorations.

The Frialit-2 implant system: five-year clinical experience in single-tooth and immediately postextraction applications.

In an observational study of 696 Frialit-2 implants in 376 patients that was carried out between 1990 and 1995, implants of varying diameters and lengths were delivered for a range of indications in the maxilla and mandible. Single-tooth replacement was performed in 42% of cases; of these, 22.4% were placed immediately following extraction. Study parameters (Plaque Index, Gingival Index, probing depth, Periotest value, and peri-implant bone loss) are reported in detail. Statistical analysis is based on a 97.6% rate of recall. The overall success rate was found to be 96% using the Kaplan-Meier statistical analysis. No difference was apparent between single-tooth applications and prosthesis restorations.

The influence of fine surface structures on the osseo-integration of implants.

The availability of inert materials like dense, pure Al2O3-ceramic or titanium allows the study of purely biomechanical influences of surface modulations or lacune on the osseo-integration of implants at different locations of the skeleton. The discovery of the "load-line-shadow" phenomenon in lacune of dental implants and the observation of the same effect in the grooves of hip sockets (Lindenhof type) indicate the general validity of the rules controlling the remodelling ability of bony tissue. Their application to the problems concerned with load transmission via surfaces which are mainly loaded by shear can contribute to achieve a well defined anchorage of implants.

The modulation transfer function and signal-to-noise ratio of different digital filters: a technical approach.

OBJECTIVES: The aim of this study was to illustrate the influence of digital filters on the signal-to-noise ratio (SNR) and modulation transfer function (MTF) of digital images. The article will address image pre-processing that may be beneficial for the production of clinically useful digital radiographs with lower radiation dose. METHODS: Three filters, an arithmetic mean filter, a median filter and a Gaussian filter (standard deviation (SD) = 0.4), with kernel sizes of 3 × 3 pixels and 5 × 5 pixels were tested. Synthetic images with exactly increasing amounts of Gaussian noise were created to gather linear regression of SNR before and after application of digital filters. Artificial stripe patterns with defined amounts of line pairs per millimetre were used to calculate MTF before and after the application of the digital filters. RESULTS: The Gaussian filter with a 5 × 5 kernel size caused the highest noise suppression (SNR increased from 2.22, measured in the synthetic image, to 11.31 in the filtered image). The smallest noise reduction was found with the 3 × 3 median filter. The application of the median filters resulted in no changes in MTF at the different resolutions but did result in the deletion of smaller structures. The 5 × 5 Gaussian filter and the 5 × 5 arithmetic mean filter showed the strongest changes of MTF. CONCLUSIONS: The application of digital filters can improve the SNR of a digital sensor; however, MTF can be adversely affected. As such, imaging systems should not be judged solely on their quoted spatial resolutions because pre-processing may influence image quality.

Software for automated application of a reference-based method for a posteriori determination of the effective radiographic imaging geometry.

OBJECTIVES: Presentation and validation of software developed for automated and accurate application of a reference-based algorithm (reference sphere method: RSM) inferring the effective imaging geometry from quantitative radiographic image analysis. METHODS: The software uses modern pattern recognition and computer vision algorithms adapted for the particular application of automated detection of the reference sphere shadows (ellipses) with subpixel accuracy. It applies the RSM algorithm to the shadows detected, thereby providing three-dimensional Cartesian coordinates of the spheres. If the three sphere centres do not lie on one line, they uniquely determine the imaging geometry. Accuracy of the computed coordinates is investigated in a set of 28 charge-coupled device (CCD)-based radiographs of two human mandible segments produced on an optical bench. Each specimen contained three reference spheres (two different radii r1=1.5 mm, r2=2.5 mm). True sphere coordinates were assessed with a manually operated calliper. Software accuracy was investigated for a weighted and unweighted algebraic ellipse-fitting algorithm. RESULTS: The critical depth- (z-) coordinates revealed mean absolute errors ranging between 1.1+/-0.7 mm (unweighted version; r=2.5 mm) and 1.4+/-1.4 mm (weighted version, r=2.5 mm), corresponding to mean relative errors between 5% and 6%. Outliers resulted from complete circular dense structure superimposition and one obviously deformed reference sphere. CONCLUSIONS: The software provides information fundamentally important for the image formation and geometric image registration, which is a crucial step for three-dimensional reconstruction from > or =2 two-dimensional views.

Mathematical analysis of projection errors in "paralleling technique" with respect to implant geometry.

"Standardized" radiographs acquired in paralleling technique serve for monitoring of marginal bone levels around endosseous implants. Under clinical conditions, parallel adjustment of the film to the implant is beset with great difficulties. A mathematical model matching clinical conditions was developed to evaluate projection geometry within an interval of clinically relevant angulations (+/- 10 degrees from parallel position). Radiographs of two implants (Frialit 2, Friadent AG, Mannheim, Germany; Implant No. 1: 3.8 mm, length 10 mm; Implant No. 2: 6.5 mm, length 13 mm) were separately produced per angulation (2 degrees increments) at one focus-object distance (FO=322.9 mm). Implant images were repeatedly measured along their midline/vertical edge, local magnification (MF) was calculated and the values were compared to the computed ones. Projected dimensions of the implants were calculated for a second distance (232.3 mm). The experimentally acquired data were in agreement with the mathematical calculation. MF calculated for assessment along the vertical edge varied less (+/-1.94% from mean value) than along the midline (+/-2.74%), with a range of 1.037-1.068 (FO=322.9 mm) and 1.061-1.099 (FO=232.3 mm) for implant No.1, and 1.060-1.101 (FO=232.3 mm) and 1.037-1.069 (FO=322.9 mm) for Implant No. 2. Magnification revealed a mean variation of 4%. Radiographic evaluation of periimplant bone level should not exceed a precision of 0.5 mm, when parallelism between film and implant is not guaranteed and FO is less than 380 mm.

Precision and accuracy of measurements in digital panoramic radiography.

OBJECTIVES: To evaluate the precision and accuracy of digital measurements in digital panoramic radiography. METHODS: A series of 70 digital panoramic radiographs were obtained of a dry skull in seven different positions with metallic pins and spheres fixed to the mandible. Three replicate measurements were performed with the mouse-driven cursor by one reader at 1:1 and 2:1 magnification. Precision was assessed with the reliability index (R) and Malony/Rastogi test and the effect of magnification on accuracy by paired Wilcoxon test. RESULTS: Vertical measurements were less reproducible than horizontal measurements. There were significant differences in assessments between images at 1:1 and 2:1 magnification (P < 0.05). The maximum variation in mean difference was 0.4% of actual object length for pins and 1.2% for spheres. The difference did not exceed 0.1 mm. R was lower for 2:1 magnification and consistently lower for spheres compared with pins. CONCLUSION: The most reliable measurements were obtained of linear objects in the horizontal plane. Digital measurements are sufficiently accurate for clinical use.

A method to calculate angular disparities between object and receptor in "paralleling technique".

OBJECTIVE: To develop an image analysis method for calculation of angular disparities between an object, temporarily equipped with a reference system, and a radiographic receptor. MATERIALS AND METHODS: A mathematical method based on a reference system containing two metallic spheres is developed, allowing calculation of inclination between the inter-spherical axis and the digital image receptor using image features. Experimental evaluation was done in standardized projection geometry for two sphere sizes at four randomly chosen inclinations per size, with each radiograph assessed three times. Truth was assessed threefold from photographs obtained at each inclination. RESULTS: Mean standard deviation between single assessments was 2.6 degrees. Significant differences (P Maloney/Rastogy=0.00) were found between absolute values of truth and calculated values (mean: -0.9 degrees; range: -6.0 degrees; 3.6 degrees), indicating a significant lack of accuracy. CONCLUSIONS: Although so far not sufficiently accurate, the method yields information relevant for correction of distortion in intra-oral radiology.

[The Tübingen implant within the scope of adult orthodontic treatment]. / Das "Tübinger Implantat" im Rahmen der kieferorthopädischen Erwachsenenbehandlung.

Prior to the replacement of a missing tooth with an implant the adult dentition, orthodontic treatment can be carried out to widen the space mesio-distally, correct the axial inclination of the neighbouring teeth and safeguard the anterior overbite. Implantation is not possible if, as a result of orthodontic treatment the gap cannot be widened to a minimum of at least 6 mm, if the alveolar bone is not thick enough in the vertical dimension or if the implant does not have sufficient space in the oro-vestibular direction.