Biomedical subjects

K Gröndahl

Publications and source records attributed to K Gröndahl.

At least 19 recordsLinked to original sources

PubMed2006

Diagnostic value of computed tomography in re-treatment of root fillings in maxillary molars.

AIM: To compare the diagnostic information and radiation dose between intraoral radiography and computed tomography (CT) in re-treatment decision making concerning root fillings in maxillary molars. METHODOLOGY: Thirty-nine root-filled maxillary molars with suspected apical periodontitis were examined with two intraoral periapical radiographs and CT. Presence of periapical lesion/s per tooth and root were analysed for both techniques. In addition, in the CT images, the number of root canals, erosion, or perforation of cortical bone plates, and the distance between palatal root and cortical bone plates were evaluated. Radiation dose for CT was registered and calculated; and that of periapical radiographs used as reported previously (Ekestubbe et al. 2004). RESULTS: Periapical radiographs revealed periapical lesions in 33 teeth compared with 38 on CT images. A lesion of any root was detected more often with CT. The mesiobuccal root had two root canals in 30 teeth of which 27 of the MB2 canals were not filled, and 22 roots with an unfilled canal were associated a periapical lesion. Distances to palatal root, from the buccal and palatal cortex were measured in CT and varied between 5.0-12.0 mm and 0-4.0 mm, respectively. Based on the radiographic information, a variety of treatment alternatives were suggested. Mean effective dose of periapical radiographs was 0.02 mSv and that of CT 0.055 mSv. CONCLUSIONS: Computed tomography may give important information in re-treatment decision when considering root fillings in maxillary molars. The radiation dose should be considered individually.

Adult↗

PubMed2004

A digital subtraction radiography scheme based on automatic multiresolution registration.

OBJECTIVES: To establish a digital subtraction radiography scheme for aligning clinical in vivo radiographs based on the implementations of an automatic geometric registration method and a contrast correction technique. METHODS: Thirty-five pairs of in vivo dental radiographs from four clinical studies were used in this work. First, each image pair was automatically aligned by applying a multiresolution registration strategy using the affine transformation followed by the implementation of the projective transformation at full resolution. Then, a contrast correction technique was applied in order to produce subtraction radiographs and fused images for further clinical evaluation. The performance of the proposed registration method was assessed against a manual method based on the projective transformation. RESULTS: The qualitative assessment of the experiments based on visual inspection has shown advantageous performance of the proposed automatic registration method against the manual method. Furthermore, the quantitative analysis showed statistical difference in terms of the root mean square (RMS) error estimated over the whole images and specific regions of interest. CONCLUSIONS: The proposed automatic geometric registration method is capable of aligning radiographs acquired with or without rigorous a priori standardization. The methodology is pixel-based and does not require the application of any segmentation process prior to alignment. The employed projective transformation provides a reliable model for registering intraoral radiographs. The implemented contrast correction technique sequentially applied provides subtraction radiographs and fused images for clinical evaluation regarding the evolution of a disease or the response to a therapeutic scheme.

Algorithms↗

PubMed2001

Sinus lifting procedure. I. One-stage surgery with bone transplant and implants.

A prospective study of one-stage surgery with intrasinus bone transplant and implants has been performed in 26 patients (13 males and 13 females). The aim of the study was to evaluate the success rate with the one-stage sinus lifting procedure in patients with a need for bony augmentation of the alveolar process. Fifteen patients were partially dentate and 11 edentulous. The mean height of the alveolar ridge was 2.5 mm preoperatively (range 1-5.5 mm). 126 fixtures were inserted, 93 in grafted bone and 33 in alveolar bone. Twenty-two patients have been followed for three years, 21 for four years and 11 for five years. The clinical overall survival rate was 69.6% although only 61.2% in grafted bone. Ten of the patients had varying degree of sinusitis post-fixture installation. At the end of the study, 23 patients had permanent bridges. The survival rate was low for inlay supported implants when the one-stage surgical technique was applied. Two-stage surgery may be a safer method.

Adult↗

PubMed2000

Periapical status of root-filled teeth exposed to the oral environment by loss of restoration or caries.

OBJECTIVE: Studies in vitro carried out on extracted teeth have demonstrated that bacterial elements may penetrate root fillings from the coronal to the apical end after a period of exposure to artificial saliva or bacterial culture. To address the clinical significance of this so-called issue of coronal leakage, a retrospective cohort analysis was conducted of 55 patients with root fillings that had been exposed to the oral environment because of caries or absent restorations. STUDY DESIGN: Cases were matched 1-to-1 with regard to initial pulpal and periapical diagnosis, period after completion of endodontic therapy, tooth type, age of the patient, and the technical quality of the root filling. Only cases with a follow-up period of 3 years or more were included. Radiographs taken at the last follow-up examination were subjected to a masked evaluation. RESULTS: A total of 14 osteolytic lesions were recorded. In 43 of the 55 matched pairs (78%), there were identical periapical conditions. In 9 pairs, a periapical lesion was present in the "open" tooth category, whereas in 3 pairs, a periapical lesion was seen exclusively in the "intact" tooth. Though the odds-ratio for a lesion to be present in the "open group" was 3. 0, this was not a statistically significant result (P >.10). CONCLUSIONS: Data suggest that the problem of coronal leakage may not be of such a great clinical importance as implicated by numerous studies in vitro, provided instrumentation and root fillings are carefully performed.

Adolescent↗

PubMed2000

Marginal bone level around implants assessed in digital and film radiographs: in vivo study in the dog.

BACKGROUND: One of the objectives of postoperative radiographic examinations of implants is to evaluate the marginal bone height and its changes over time. PURPOSE: The purpose of this study was to assess the influence of digital image processing on measurements of the marginal bone level around implants. MATERIAL AND METHODS: Implants in beagle dogs, used to study the development of peri-implantitis and subsequent healing following treatment, were monitored with conventional radiography and a digital image plate system. Five observers measured the distance between a reference point and the bone level. Measurements in conventional radiographs were made with the use of an x-ray viewer (2x) and a magnifying lens (7x). For the digital images, the system's built-in measuring function was used together with five image processing techniques: edge enhancement (matrixes set on 5 and 25), inverted grey scale, single color highlight, and color intensity mapping together with the brightness and contrast control. From the time of maximum breakdown and the end of the experiment, histologic values were available. RESULTS: Differences between techniques and observers increased toward the end of the healing period. Measurements made at maximum breakdown did not differ significantly from the histologic value. Measurements made after healing all methods, except that using edge enhancement and a 25 x 25 kernel, differed significantly from the histologic value by underestimating the bone level. CONCLUSIONS: Measurements of bone level around implants from digital radiographs are as accurate and precise as those from film images. In particular cases, the use of specific image processing algorithms may improve both accuracy and precision. After healing, the histologic specimens showed an incomplete bone fill in the crater with a remaining thin layer of connective tissue in contact with the fixture, and in such situations, the morphology of the bone will give a more complicated diagnostic task.

Algorithms↗

PubMed2000

Long-term follow-up of severely atrophic edentulous mandibles reconstructed with short Brånemark implants.

BACKGROUND: Oral implant treatment (Brånemark System) of edentulous mandibles has been presented in numerous studies. However, with regard to the severely atrophic lower jaw, no long-term follow-up studies with solely short implants are available. PURPOSE: The purpose of the present investigation was to retrospectively follow the long-term treatment outcome of patients with severely resorbed edentulous mandibles being subjected to oral implant placement with short (6-7 mm) Brånemark implants. MATERIALS AND METHODS: A total of 247 standard (7 mm long, Ø 3.75 mm) and 13 wide (6 mm long, Ø 5 mm) implants were inserted in 49 patients, all of whom exhibited severe resorption of edentate mandibles. Fixed implant-supported prostheses were manufactured for 45 patients, whereas 4 patients received overdentures. The patients were followed for a mean period of 8 years (range, 1-14 yr). RESULTS: Seventeen implants failed during the study period (cumulative implant survival rate 95.5% at 5-yr and 92.3% at 10-yr follow-up). Implant-supported constructions were worn continuously throughout the investigation by all study subjects. Marginal bone loss, measured after 1, 5, and 10 years of function, concurred with studies of Brånemark implants placed in more voluminous mandibles. No major clinical or construction complications occurred in the followed patients. CONCLUSIONS: The outcome of the present study showed that placement of short Brånemark implants without the use of bone grafting procedures for reconstruction of severely atrophic edentulous mandibles is a highly predictable treatment procedure.

Adult↗

PubMed1999

Quality of preimplant low-dose tomography.

OBJECTIVES: The aim of this study was to test the influence of radiation dose on image quality in mandibular preimplant computed tomographic examinations and to compare the quality of computed and conventional spiral tomographic images. STUDY DESIGN: Cross-sectional images were obtained on 17 patients with conventional spiral tomography (Scanora technique) and reformatted computed tomography at 40 and 80 mAs. Observers graded the acceptability of images for implant planning and traced the contour of the mandibular body and canal. RESULTS: Conventional spiral tomographic images scored significantly higher than computed tomographic images whereas mean score differences between computed tomographic techniques were not statistically significant. Anatomic structures, in particular the mandibular canal, were more frequently untraceable in high-dose than in low-dose computed tomography but always traceable in conventional tomograms. CONCLUSION: Conventional spiral tomograms were subjectively preferred over computed tomographic images. For mandibular implant planning, computed tomography examinations can be performed with lower-than-standard mAs. Quantum noise seems to contribute to the visibility of anatomic structures in reformatted computed tomographic images.

Adult↗

PubMed1999

Resolution of peri-implantitis following treatment. An experimental study in the dog.

The aim of the present experiment was i) to study the effect of anti-microbial therapy of experimentally induced peri-implantitis lesions and ii) to assess features of bone regrowth following treatment. Four beagle dogs were used. Three titanium fixtures (Brånemark System) were installed in each quadrant of the mandible (premolars previously extracted). Abutment connection was performed 5 months later and ligature induced breakdown was initiated. The ligatures were removed when approximately 50% of the initial bone support was lost. A 3-week antibiotic regimen (amoxicillin and metronidazole) was initiated 1 month later. Two days after the start of the antibiotic administration, the experimental implant sites were exposed to local therapy. The abutments were removed and the exposed fixture surfaces were treated with an abrasive (pumice) administered via a rotating brush (left side) or cleaned with cotton pellets soaked in saline (right side). Cover screws were attached to the fixtures and the implants were submerged. Fluorochromes were injected intravenously 2 weeks, 4 weeks and 12 weeks after surgery. The animals were killed 7 months after surgery and block biopsies of each implant site were dissected and prepared for histological analysis. The findings of the examinations disclosed that the inflammatory lesion was resolved and new bone formation had occurred in the previous defect following antimicrobial and local therapy. The amount of "re-osseointegration" that had taken place, however, was small. Indeed, at all experimental implant sites, a thin connective tissue capsule was found to separate the implant surface from the newly formed bone.

Administration, Oral↗

PubMed1999

Brånemark Novum: a new treatment concept for rehabilitation of the edentulous mandible. Preliminary results from a prospective clinical follow-up study.

BACKGROUND: Brånemark fixtures were originally prescribed to be placed in two surgical stages. During the past years, reports on the placement of machined titanium implants in a one-stage procedure have been published, and the results have been encouraging. Recently there has been considerable interest in early or immediate loading. PURPOSE: The purpose of this article is to report the preliminary clinical results of a new method for implant treatment of the edentulous mandible. The new protocol involves prefabricated components and surgical guides, elimination of the prosthetic impression procedure and attachment of the permanent fixed bridge on the day of implant placement. METHODS: Fifty patients (26 males, 24 females) received 150 Brånemark Novum implants and were followed from 6 months to 3 years after implant placement. Bone width and height were determined preoperatively with the use of radiographs. The jaw was reduced in height to accommodate three special 5-mm wide implants. Precise implant positioning was accomplished with special drilling templates. Drill guides were placed over the drilling templates during site preparation using a series of specially designed drills. After the mucosa had been sutured back into position, a prefabricated titanium lower bar was connected with titanium screws to the transmucosal fixture. Another titanium bar was then attached by the prosthodontist, and a bite registration was performed. The bridge was attached to the upper bar. The permanent reconstruction was provided to the patient later the same day. RESULTS: Three implants were lost to follow-up and three failed, resulting in an overall survival rate of 98%. One prosthesis failed, leaving a prosthetic survival rate of 98%. The average treatment time was approximately 7 hours. At the baseline examination, the marginal bone level was 0.72 mm below the reference point. The average marginal bone loss was 0.2 mm per year and 0.26 mm between the 3-month and 1-year control visits. The accumulated mean bone loss, including baseline, was -1.25 mm. A patient questionnaire demonstrated that 94% of the patients did not experience any discomfort during treatment and all patients would recommend the procedure to others. CONCLUSION: The results of this study indicate that the precise surgical and prosthetic protocol allows successful prosthetic rehabilitation of mandibular edentulism and that the permanent reconstruction can be provided to the patient on the day of fixture surgery.

Aged↗

PubMed1999

Astra Tech and Brånemark System implants: a prospective 5-year comparative study. Results after one year.

BACKGROUND: Endosseous dental implants are used frequently, and many implant systems are available. The scientific documentation of the implant system presents a great variation, and it is often difficult to compare studies of different systems. PURPOSE: The aim of this study was to compare two Swedish implant systems (Astra Tech and Brånemark System implants), in a prospective randomized study. MATERIALS AND METHODS: Sixty-six patients were equally distributed between the two implant systems; 184 Astra Tech and 187 Brånemark System implants were used. The patients have been followed annually with clinical and radiographic examinations. The results after 1 year are reported. RESULTS: The abutment procedure was found to be easier and less time-consuming with Astra Tech than with Brånemark implants. The operation times in minutes (mean +/- SEM) were for the respective implant 35 +/- 4.0 and 51 +/- 4.8 in the maxilla and 32 +/- 3.8 and 43 +/- 2.4 in the mandible. The differences in both cases were significant: p < .02 and p < .05, respectively. The failure rate for Astra Tech implants was 0.5% and for Brånemark implants 4.3%. The difference was significant (p < .05); however, taking into account that five of the eight implant losses in the Brånemark implant group occurred in one patient, an intraindividual correlation cannot be excluded. Therefore, this result should be interpreted with caution. The marginal bone level changes were examined already from the fixture installation. The major bone loss was found between fixture installation and baseline. This bone loss was several times greater than the bone loss between the baseline and the 1-year follow-up. The total bone loss during the observation period did not differ significantly between the systems, but they had different resorption patterns. The bone loss in the upper jaw between baseline and 1-year follow-up was 0.22 +/- 0.14 and 0.03 +/- 0.09 mm for the Astra Tech and Brånemark implants, respectively. In the lower jaw, the loss was -0.31 for both systems. The frequency of plaque accumulation and bleeding on probing did not differ between the implant systems. CONCLUSIONS: Abutment connection with Astra Tech implants was simpler than the corresponding surgery with Brånemark System implants and the survival rate of Astra Tech implants was higher than that of Brånemark system implants.

Adult↗

PubMed1999

On cutting torque measurements during implant placement: a 3-year clinical prospective study.

BACKGROUND: Evaluation of jaw bone quality at implant placement is mainly based on preoperative radiographic assessments and subjective hand registrations during implant site preparation. An objective technique with cutting torque measurements has been introduced, presenting an objective bone quality or bone hardness value of individual implant sites. PURPOSE: The purpose of this study was to evaluate cutting torque measurements during implant placement and to compare these values in different regions in mandibles and maxillae. The objective was to identify implants at risk for failing at implant placement. MATERIAL AND METHODS: Cutting torque measurements were performed during placement of Mk II self-tapping implants (Brånemark System) in 105 patients, comprising 72 edentulous (40 maxillae) and 34 partially edentulous (22 maxillae) jaws. A total of 523 implants were inserted, of which 420 were of the Mk II design and of which 412 were subjected to cutting torque measurements. Statistical analyses were performed by comparing cutting torque values of maxillae and mandibles and of different jaw regions. Cutting torque values were also correlated with radiographically and clinically assessed bone quality scores. Patients were followed clinically for a minimum of 3 years. RESULTS: A statistically significant difference in cutting torque values of maxillae and mandibles was seen, although not when comparing anterior and posterior regions within the same jaws or of different jaws. Significant correlations were found between values of cutting torque and bone quality. The majority of failures were seen in bone of medium to high density, whereas implants inserted in bone of poor density presented a better outcome, perhaps due to an adapted surgical protocol and an extended healing period. The overall implant survival rate at 3 years was 95%, and when analyzing different jaw categories, survival rates of 92.0% and 99.4% were seen for edentulous maxillae and mandibles, respectively. The corresponding figures for partially edentulous jaws were 95.4% and 97.6%. CONCLUSION: It was not possible to identify sites at risk for future implant losses or to determine a lower limit value of cutting torque in order to achieve successful implant integration.

Adolescent↗

PubMed1999

Stability measurements of one-stage Brånemark implants during healing in mandibles. A clinical resonance frequency analysis study.

Using a one-stage surgical protocol, 75 implants ad modum Brånemark of three different designs were inserted in 15 edentulous mandibles of high bone density. All implants were followed with repeated stability measurements by means of resonance frequency analysis (RFA) from implant placement to connection of the fixed prostheses (3-4 months), in order to evaluate possible stability changes during healing. It was shown that the resonance frequency (RF) values slightly decreased for the majority of the implants during the study period independent of design. Consequently, the results of the present study indicated that the implants were as stable at time of placement as when measured at 3-4 months post-surgery, i.e. when the prostheses were attached. The available data support the concept of direct loading of implants when inserted between the mental interforaminal regions. One implant failed during healing and the corresponding RF measurement disclosed, at six weeks post-surgery, a value being far below the one registered at implant placement. The lowered RF value indicated the failure several weeks before the mobility was clinically diagnosed. The presence or absence of a fixture/abutment junction did not exert any influence on the marginal bone level, as determined radiographically at the end of the short investigation period.

Aged↗

PubMed1998

Film and digital radiography for detection of simulated root resorption cavities.

OBJECTIVES: The purpose of this study was to evaluate observers' ability to detect simulated root resorption cavities in conventional radiographs and digital radiographs from a charge-coupled device system and a storage phosphor system and to determine whether the detectability was influenced by resorption size and exposure. STUDY DESIGN: In teeth from dry mandibular jaw specimens, resorptive defects 1.2 mm in diameter and two different depths (0.6 and 0.9 mm) were prepared in the buccal root surface. Each tooth was radiographed at a number of different exposure settings. Observers were asked to rate their confidence that a resorption was or was not present using a five-graded confidence scale. Receiver operating characteristic analysis was used to evaluate the results. RESULTS AND CONCLUSION: Given optimal exposures, all systems reached what might be considered clinically acceptable Az values (> 0.75). The storage phosphor system reached this value at considerably lower exposures than those required for both the film and charge-coupled device systems. There was a tendency to better detect the deeper lesions and to identify them at lower exposures.

Confidence Intervals↗

PubMed1998

Inter- and intraobserver variability in radiographic bone level assessment at Brånemark fixtures.

The aim was to determine inter- and intraobserver variability in radiographic bone level assessments at Brånemark fixtures and to study the influence of various factors (radiographic density; projection geometry; jaw in which the fixtures were inserted; degree of bone loss; time after fixture loading; and number of radiographs of each fixture) on the variability. Intraoral radiographs from bridge connection and 1- and 3-year check-ups from 15 upper and 15 lower jaws (172 fixtures) were assessed by 6 observers. Measurements were taken from a reference point on the fixture to the marginal bone level, and some were repeated by all observers after 1 months. Results showed a small interobserver variation (0.14 mm) with the intraobserver variation (0.08 mm) as its largest component. The radiographic density and the degree of bone loss showed the strongest influence on the interobserver variation. The only variable with a significant effect on the intraobserver variation was the number of radiographs of each fixture. Calculated confidence values showed that measurement reliability can be improved by letting one observer or preferably more make several, independent readings, allowing for the demonstration of minor differences in bone height over time or between implant systems.

Alveolar Bone Loss↗

PubMed1998

Observer-independent registration of perspective projection prior to subtraction of in vivo radiographs.

OBJECTIVES: To prove that the model of perspective projection allows precise registration of intra-oral radiographs regardless of whether they have been acquired with or without individual adjustment aids and independent of the human observer or computer algorithm marking corresponding landmarks in the images and, based on in vivo radiographs, to introduce and evaluate a model-based registration method. METHODS: Five observers (three experts and two non-experts) were asked to define corresponding points in 24 pairs of in vivo dental radiographs from the same region of the same patient. The landmarks were used to fit the model of perspective projection applying the least squares method. Misplaced landmarks were detected and suppressed by analysing the quality of all subsets of landmarks with respect to the minimal residual (leaving one out method). In addition, local correlation was used to optimize the quality of registration as well as observer independence. RESULTS: Using six or more corresponding landmarks in both radiographs the correlation of the images registered was > 0.95 (S.D. < 0.063) irrespective of the observers' expertise. CONCLUSIONS: Perspective projection is a reliable model for sequentially acquired intra-oral radiographs. The co-ordinates of anatomical landmarks are useful for determining the parameters of perspective projection. Local correlation and leaving one out techniques improve the geometrical adjustment as well as observer independence. Registration is nearly independent of the actual position of the landmarks and hence independent of the observer. Our algorithm will also be useful for registration techniques based on automatically detected landmarks.

Humans↗

PubMed1998

Impact of endodontic conditions on marginal bone loss.

This study was undertaken to examine the extent to which the marginal alveolar bone may be influenced by the condition of the dental pulp. A total of 115 pairs of contralateral teeth were observed in 87 patients (25 to 45 years old) in which the test tooth, but not the control tooth, was either endodontically treated or not treated but with a periapical radiolucency. The distance from the cemento-enamel junction to the marginal bone level was measured using intraoral radiographs. The condition of the endodontic filling, the periapical status, and the presence of root canal post were also assessed. With clinical parameters similar between teeth in the two groups in terms of visible plaque, bleeding on probing, probing depth, and attachment level, the results showed a somewhat (mean value 0.1 mm; SD 0.7) larger reduction of the alveolar bone support in test than control teeth. This difference was not statistically significant on a patient level. Hence, this study failed to demonstrate a correlation between a reduced marginal bone support and endodontic status.

Adult↗

PubMed1997

Glandular odontogenic cyst. Report of seven cases.

This study describes the clinical, radiographic and histopathological features of seven glandular odontogenic cysts. These cysts comprised 0.012% of 5800 jaw cysts diagnosed in a 19-year period. There was strong predilection for the mandible (five of the seven cases). Both clinical and radiographic features were nonspecific. The main histological findings were a nonkeratinized, stratified squamous epithelium lining to the cyst cavity which varied in thickness with superficial eosinophilic cuboidal cells and mucous pools within the spinous cell layer. Daughter cysts were found in the wall of 2 cysts. At surgery, most walls were found to be thin and lumen to contain a serous, low viscosity exudate. Because of the high rate of recurrence found in three cases out of the seven after conservative surgical treatment, careful clinical and radiographic follow-up is recommended.

Adult↗

PubMed1997

The use of tomography for dental implant planning.

OBJECTIVES: To examine the use of tomography for dental implant planning. METHODS: A questionnaire was sent to oral radiology clinics in Sweden and to implantology clinics in different parts of the world with questions on selection criteria and techniques for, and frequency of, pre-implant tomography. Differences between mean values were assessed by t-test. A new method developed by the Swedish Radiation Protection Institute was used to assess radiation absorbed dose from CT. RESULTS: Tomography was used by 93.4% of the clinics, but there was marked variation both between and within different clinical situations. It was performed in all cases by 21% and the majority used it for the evaluation of the maxilla, the posterior mandible and in single implant cases. Small clinics (< 100 patients per year) used tomography frequently and clinics in Sweden significantly more often than those in other countries. The majority had changed their policy recently, using tomography more often. CT was used by 73% of respondents, mainly the small clinics. The majority of the large clinics (> 500 patients per year) used conventional tomography. The mean absorbed dose for CT scanning protocols was 65 mGy. The variation within and between different makes of CT was considerable. CONCLUSIONS: There are large variations in frequency of use of both conventional and computed tomography for dental implant planning by different clinics who also vary in the indications for their choice. A substantial factor influencing the technique chosen was its availability rather than clinical need.

Dental Implantation, Endosseous↗