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L Rasmusson

Publications and source records attributed to L Rasmusson.

At least 19 recordsLinked to original sources
PubMed2006

Osseointegration of oxidized and turned implants in circumferential bone defects with and without adjunctive therapies: an experimental study on BMP-2 and autogenous bone graft in the dog mandible.

The aim of the study was to compare the integration and implant stability of turned and oxidized titanium implants when placed in experimental bone defects with autogenous bone graft, BMP-2 or without adjunctive therapy. Four defects were prepared on each side of the mandible of 12 mongrel dogs five months after tooth extractions. Implants with turned and oxidized surfaces were placed in the defects. The circumferential gaps were filled with either autogenous bone grafts, a BMP-allogeneic dog mixture in a thermoplastic carrier, carrier alone or left without any treatment (control). There were no statistically significant differences between control and treated sites, neither for turned nor for oxidized implants with regard to histomorphometric measurements in ground sections and to implant stability as measured with resonance frequency analysis (RFA) after 4 and 12 weeks of healing. However, oxidized implants showed a significantly higher stability after 4 weeks and a tendency (p < 0.1) of that after 12 weeks. Histomorphometry showed more bone contacts for oxidized than for turned implants. It is concluded that oxidized implants gain stability more rapidly and integrate with more bone contacts than implants with a turned surface when placed in bone defects.

Animals↗
PubMed2005

Neurosensory function of the inferior alveolar nerve after bilateral sagittal ramus osteotomy: a retrospective study of 68 patients.

The aim of the present study was to report the incidence of neurosensory dysfunction in the lower lip and chin after bilateral sagittal split osteotomy at four postoperative time points, and the relation of impairment to factors connected with the operation. Sixty-eight patients who had undergone the procedure (at 136 operated sites) were reviewed, and neurosensory recovery was studied at 2, 6, 18 and finally 30 months postoperatively. A change in neurosensory recovery was seen over this period of time. Two months postoperatively, 84 sites had reduced sensitivity (62%). The incidence of disorder decreased to 52 sites (38%) at 6 months, 43 sites (32%) at 1.5 years and 32 sites (24%) at the final 2.5-year check up. The patient age at the time of surgery, the type of osteosynthesis and the perioperative position of the inferior alveolar nerve were variables that influenced the neurosensory outcome. In conclusion, this retrospective study shows that the most important factors influencing postoperative nerve function are patient age, fixation method and the perioperative position of the inferior alveolar nerve.

Adolescent↗
PubMed2001

Effects of implant design and surface on bone regeneration and implant stability: an experimental study in the dog mandible.

BACKGROUND: Previous experimental studies have shown a higher degree of bone-implant contact for surface-enlarged implants compared with machined implants. Yet, there is insufficient evidence that such implants show higher stability and an increased survival rate. PURPOSE: The purpose of this investigation was to study the integration and stability of grit-blasted implants with retention elements on the implant neck, with and without marginal bone defects, compared with machined implants without retention elements. MATERIALS AND METHODS: After tooth extraction of the mandibular premolars in six dogs, two grit-blasted, partly microthreaded Astra Tech implants and one standard Brånemark implant were bilaterally placed in each dog. On one side, 3 x 3 mm large buccal defects were created, to expose three to four implant threads. The contralateral side served as control, and no defects were made. The animals were sacrificed after 4 months of healing. Implant stability was measured using resonance frequency analysis at implant installation and after 4 months of healing. Histologic and histomorphometric evaluation was made after 4 months of healing. RESULTS: Resonance frequency analysis indicated that all implants in the test and control groups were osseointegrated after 4 months, with a tendency toward higher implant stability for the Astra Tech implants. There was a statistically significant higher increase in resonance frequency for the Astra test implants compared with their corresponding controls. Histology and histomorphometry showed well-integrated implants with varying degrees of bone repair at the defect sites. The greater bone-implant contact for the Astra implants was statistically significant. No significant difference between the implants in amount of bone filling the threads was recorded. CONCLUSIONS: The Astra Tech implants tested showed a higher degree of bone-implant contact and higher level of bone regenerated at defect sites compared with the Brånemark implants. Resonance frequency analysis demonstrated a significantly higher increase in the Astra test implants compared with their control groups than did the Brånemark test implants versus their controls.

Alveolar Bone Loss↗
PubMed2001

Maxillary implants loaded at 3 months after insertion: results with Astra Tech implants after up to 5 years.

BACKGROUND: To date, clinical studies have mainly focused on early loading of mandibular implants. Recently, there has also been considerable interest in early loading of maxillary implants. PURPOSE: The purpose of this article is to report the outcome of maxillary implants loaded after a 3-month healing period and followed up to 5 years. MATERIALS AND METHODS: Seventeen patients (11 males and 6 females) received 44 Astra Tech implants (Mölndal, Sweden) for treatment of single-tooth (13 cases) and partial edentulism (9 cases). The patients were followed up to 5 years after implant placement: 50% of the implants were followed for 3 years and 16% have been followed throughout the observation period. Preoperatively, bone height and width were assessed on radiographs. Marginal bone loss was recorded on intraoral radiographs annually. RESULTS: No implant was lost during the observation period. The average marginal bone loss was 0.5 +/- 0.7 mm after 1 year, 0.6 +/- 0.7 mm after 3 years, and 0.9 +/- 1.6 mm after 5 years. There were no soft-tissue or prosthetic failures recorded during the observation period. CONCLUSION: Early loading of Astra Tech implants was highly successful in maxillary partial and single-tooth cases followed up to 5 years in function.

Adult↗
PubMed2000

Healing of titanium implants in onlay bone grafts: an experimental rabbit model.

An experimental rabbit bone graft model for the study of bone formation and remodeling around titanium implants is described. A 2.5-cm long radius bone segment served as an onlay graft. Two commercially pure (c.p.) titanium implants were inserted into the bone graft prior to fixation to the inferior border of the mandibular base with osteosynthesis titanium screws. Each animal was operated twice, allowing follow-up periods of 6 weeks on one side and 6 months on the contralateral side. In order to study bone remodeling by means of fluoroscopy the animals received single injections of tetracyclin and alizarine complexone 2 weeks and 1 week, respectively, prior to sacrifice by perfusion fixation with glutaraldehyde. The bone and implants were excized en bloc, postfixed and embedded in plastic resin. Stained and unstained thin ground sections as well as microradiographed thick sections were produced for light microscopic morphometry and fluoroscopy. After 6 weeks, osteoclastic/osteoblastic activity was primarily observed in the graft-recipient contact area and in the intracortical compartment of the graft bone. New bone formation observed on the implant surface originated from the recipient site. The bone formation was evident also in the implant-graft interface. At 6 weeks the average bone fill of the implant threads was 28.4% which increased to 36.4% after 6 months as measured by morphometry. An average of 17.6% bony contact was measured after 6 weeks which increased to 29.7% 6 months after surgery. The graft bone had reduced in size from an average of 39.5% after 6 weeks down to 24.8% after 6 months (P \lt 0.05). It is concluded that the described experimental model can serve as a useful method for the study of implant healing in onlay grafts.

Journal Article↗
PubMed1999

Effects of barrier membranes on bone resorption and implant stability in onlay bone grafts. An experimental study.

The objective of the present report was to study the effects of barrier membranes on bone resorption and implant stability in a rabbit onlay bone graft model, using resonance frequency analysis, coordinate measurements on plaster models, removal torque measurements and histology. Disc-shaped bone grafts were harvested from the calvarium and placed with titanium implants in the proximal tibial metaphyses of 9 rabbits. On one side (test) the bone graft/implant was covered by an e-PTFE barrier, while the contralateral side was not covered by a membrane and served as control. Three animals were sacrificed after 8 weeks for histology. In 6 animals the membranes were removed after 8 weeks and the animals were followed for an additional period of 16 weeks. Implant stability and bone height around the implants was assessed for the test and control sides at Day 0 and 8, 16 and 24 weeks postoperatively. Removal torque tests were performed after 24 weeks. The results showed an increase in volume of the bone graft on the test side as long as the barrier membrane was in place. However, after removal of the membrane at 8 weeks the resorption rate was higher on the test side compared to the control side, resulting in a similar bone height after 24 weeks. There were no statistically significant differences in implant stability between the test and control sides at any time point, as measured with resonance frequency analysis. Additionally, no statistically significant differences were found between the test and control sides after 24 weeks, using removal torque measurements, coordinate measurements and histomorphometric evaluation. Thus, in this experimental model, the use of non-resorbable barrier membranes did not improve the stability of implants simultaneously placed with onlay bone grafts. Moreover, extensive resorption of the grafted bone was seen after barrier removal, which resulted in similar bone graft volume for the test and control sides at the end of the observation period.

Animals↗
PubMed1999

Implant stability measurements using resonance frequency analysis in the grafted maxilla: a cross-sectional pilot study.

BACKGROUND: High failure rates have been presented for implants placed in grafted bone. The bone graft-implant interface constitutes a most complex healing situation, where the time scale for osseointegration and development of implant stability currently is not known. PURPOSE: The aim of the study was to measure the stability of implants placed in grafted bone after various follow-up periods. METHODS: Implant stability measurements by means of resonance frequency analysis were performed in 10 patients previously treated with a Le Fort I osteotomy and interpositional bone grafts. The implants were placed 3 to 4 months after the grafting procedure. Sixty-seven Brånemark implants were subjected to resonance frequency analysis measurements at fixture placement and up to 5.5 years after implant surgery. Periapical radiographs were used for assessment of marginal bone levels. RESULTS: The radiographic examinations showed marginal bone loss with time during the 5.5-year follow-up. The resonance frequencies varied from 5860 to 8440 Hz. When accounting for abutment length and marginal bone level, there was a tendency of increasing resonance frequency with time. Two implants with low resonance frequencies failed during the prosthetic phase. CONCLUSION: The results indicate an increased implant stability with time, which may reflect bone formation, remodeling, and maturation at the implant interface.

Aged↗
PubMed1999

Simultaneous or delayed placement of titanium implants in free autogenous iliac bone grafts. Histological analysis of the bone graft-titanium interface in 10 consecutive patients.

The aim of the present study was to histologically analyse the bone graft-titanium implant interface after six and twelve months of healing for a simultaneous approach and after six months for a delayed approach. For this purpose, screw-shaped c.p. titanium microimplants, 2 mm in diameter and 5 mm long, were placed and retrieved at different time intervals in ten consecutive patients with severely resorbed maxillae and treated with iliac cortico-cancellous bone grafts and titanium implants in a two-stage procedure. The histomorphometrical analyses of ground sections of the specimens showed a higher degree of bone-implant contact and more bone filling the implant threads in the delayed approach microimplants. This was probably due to the partly revascularized grafted bone in the delayed approach being able to respond to the surgical trauma, resulting in interfacial bone formation. It is concluded that the results from the present study favour the use of a delayed approach when using free autogenous bone grafts and titanium implants for reconstruction of the severely atrophied maxilla.

Alveolar Process↗
PubMed1999

The influence of simultaneous versus delayed placement on the stability of titanium implants in onlay bone grafts. A histologic and biomechanic study in the rabbit.

A rabbit model was used to study the healing and stability of titanium implants in free bone grafts, placed simultaneously or after 8 weeks of healing and followed for 24 weeks. The skull bone was used as donor site and the tibial metaphysis as recipient site. Stability measurements were performed by using resonance frequency analysis (RFA) at implant placement and after 4, 8, 16 and 24 weeks of healing. Statistically significant higher resonance frequencies were measured at all time points for the delayed approach implants. Removal torque tests after 24 weeks revealed no differences between the two procedures. Histologic ground sections were prepared on specimens taken after 8, 16 and 24 weeks of healing. More bone-implant contacts were observed in the bone graft for the implants inserted in a delayed fashion, while there was no statistically significant difference in the degree of total bone-implant contact between the two groups. It is concluded that delayed implant placement in autogenous onlay bone grafts results in a better integration and stability of the implants.

Animals↗
PubMed1998

Stability assessments and histology of titanium implants placed simultaneously with autogenous onlay bone in the rabbit tibia.

A disc-shaped bone graft was harvested from the calvarium in ten rabbits and anchored as an onlay bone graft, using a titanium implant, at the proximal tibial metaphysis. The contralateral tibia served as the control, where an implant was placed without a graft with the implant head at a height corresponding to the thickness of the graft on the test side. Resonance frequency measurements were performed 4, 8, 16 and 24 weeks postoperatively and removal torque measurements were performed at 24 weeks. A statistically significant higher implant stability, as assessed by resonance frequency measurements (RFM), was measured from 4 weeks throughout the 24-week period. The mean peak removal torque for the test implants was 50.4+/-10.0 Ncm and 30.0+/-6.9 Ncm for the control implants, which was a statistically significant difference. Histologically, the grafted bone was well incorporated and morphometry revealed more bone around the test implants. Calculations of shear stresses indicated that the grafted bone had similar biomechanical properties to the cortical bone of the recipient site. It is concluded that the integration of titanium implants in autogenous onlay bone grafts results in an increased biomechanical support of the implant. The use of RFM may also serve as a useful instrument for noninvasive monitoring of implant stability in vivo.

Animals↗
PubMed1998

The use of a conical fixture design for fixed partial prostheses. A preliminary report.

A specially designed, TiO2-blasted titanium fixture, partially conical and microthreaded, the Astra Tech Fixture ST, was used for rehabilitation of partial edentulism in the posterior mandible. Superior to the mandibular canal 25 fixtures were placed in 10 patients. Fixed metal-ceramic bridges were then performed. After 1-year follow-up, all bridges were found to be clinically stable. The implant survival rate was 100% and the mean marginal bone resorption was 0.05 +/- 0.11 mm.

Aged↗
PubMed1998

An experimental rabbit model for studying the healing of onlay bone grafts.

An experimental rabbit model for studying the incorporation of onlay bone grafts is described. Bone grafts from radius served as the graft and were positioned beneath the mandibular basis. Six rabbits were used in the study and healing periods of 6 weeks and 6 months were used. Each animal was operated twice and in this way the grafts could be followed for six weeks on one side and for 6 months on the contralateral side of the mandible. Healing of the bone graft with bony union to the mandibular base with cortical bone in contact with cortical bone was encouraging. Remodelling of the graft was observed after 6 weeks but was even more pronounced after 6 months. After 6 weeks osteoclastic/osteoblastic activity was primarily observed in the graft-recipient contact area and in the intracortical compartment of the grafted bone. The resorption was most pronounced in the borderlines of the graft. It is concluded that the described experimental model can serve as a useful method for the study of onlay bone graft healing and interaction between implants and bone transplants.

Animals↗
PubMed1997

Morphological and dimensional changes after barrier removal in bone formed beyond the skeletal borders at titanium implants. A kinetic study in the rabbit tibia.

The aim of the present experimental investigation was to study the morphological and dimensional changes of bone, augmented at titanium implants by a membrane technique, taking place after membrane removal. In 12 rabbits, screw-shaped titanium implants were inserted in the tibial metaphyses in such a way that 5 threads became uncovered with bone. Surgery was performed on 2 occasions in order to retrieve specimens with different follow-up times. An e-PTFE barrier and a titanium device were used to provide space for bone formation. In 1 tibia of each rabbit, the membranes and spacers were removed after 8 weeks of healing, and the implants followed for 16 more weeks. Impressions were taken at day 0 and after 8 and 24 weeks of healing and plaster models were produced. In the contralateral tibiae, implants were inserted either 16 or 8 weeks prior to sacrifice. Measurements were made on the plaster models in 3 dimensions at 35 points around each implant in a coordinate measuring machine. Specimens taken 8, 16 and 24 weeks after insertion were analysed by means of light microscopical morphometry. The coordinate measurements showed that, in mean, 1.92 mm of bone had been formed during the first 8 weeks. A statistically significant loss of the height of the newly formed bone (0.70 mm) and thereby reduction of bone volume was found 24 weeks postoperatively. The volume decrease of the newly formed bone was more pronounced beside the implants than over the implant body. The histology showed that woven bone had been formed at the implants after 8 weeks. Further bone formation and remodelling and a net increase of mineralized bone were seen. The degree of bone-implant contact and bone area in the threads increased with time. The present study showed that coordinate measurements on plaster models, obtained from the experimental areas, in combination with histology, form a useful technique to study long-term changes of augmented bone. It was found that bone formed by a barrier membrane technique, decreased in volume during a 16-week follow-up period after barrier removal. Less dimensional changes were observed for the bone formed over the implant body, indicating that a solid surface may have a stabilizing effect on the augmented bone.

Animals↗
PubMed1997

Measurements of stability changes of titanium implants with exposed threads subjected to barrier membrane induced bone augmentation. An experimental study in the rabbit tibia.

The purpose of the present study was to evaluate in a rabbit model the changes in stability of implants that had been subjected to barrier membrane induced bone augmentation, as compared to untreated controls. One titanium implant was inserted in each proximal tibial metaphysis of 10 rabbits. The implants were placed in such a way that 4-5 threads on one side of the implant were left uncovered by bone. On the test side, the exposed implant surface was treated by means of a barrier membrane technique to provide for bone augmentation, while the contralateral side was untreated. The stability evaluations were made by means of resonance frequency measurements (RFM) at Day 0 and after 8, 16 and 24 weeks of healing. In addition, changes in the area of exposed implant threads were documented and measured on photographs. Removal torque measurements were performed at the day of sacrifice. In this study it was not possible to demonstrate a statistically significant better stability of implants subjected to barrier induced bone augmentation as compared to control implants still having exposed threads as evaluated by RFM and removal torque measurements.

Animals↗
PubMed1994

Knowledge among Swedish dentists about rules for patient records.

Some Swedish dentists chosen at random answered a questionnaire in 1992. The aim was to find out if the knowledge among dentists as a whole about patient record matters is as bad as patient records in disciplinary cases imply. The knowledge was good and better than expected. Specialists have a better knowledge than private practitioners and they also more often have a secretary to handle the patient records. Time of licensation and the dentist's age were of no importance. If the standard of knowledge in a few formal matters corresponds to a high standard in the observance of the rules will be investigated in the second part of this investigation (Rasmusson et al 1994), which will scrutinize patient records from the same dentists who answered the questionnaire.

Adult↗
PubMed1994

Quality evaluation of patient records in Swedish dental care.

The purposes of this study were to evaluate systematically five patient records each from randomly selected dentists in different regions of Sweden in 1992, and to see whether the good knowledge of some record-keeping rules, noted earlier, was reflected in practical observance of the rules as a whole. Observance was generally poor: in nearly 40% of the variables investigated, the documentation did not follow the rules. Patient history, status, diagnosis, therapy plans and other important information were often missing among the records from the general practitioners. The specialists' records, however, were in general very accurate. As a whole, Swedish dental patient records constitute poor antemortem material for forensic odontology. The dentist's age is related to the quality of the records. The standard of the patient records must be improved.

Adult↗
PubMedDate not supplied

Le Fort I osteotomy with interpositional bone grafts and implants for rehabilitation of the severely resorbed maxilla: a 2-stage procedure.

A surgical procedure for the rehabilitation of severely resorbed maxillae is described. Twenty-five patients, made up of a development group of 5 and a routine group of 20, were treated with Le Fort I osteotomy using interpositional bone grafts from the iliac crest and, in a second stage, titanium implants. Altogether, 181 Brånemark implants were placed, and the patients were followed for up to 5 years. The implant survival rate for the development group was 60.0% after 5 years. Life table analysis for the routine group showed a 5-year survival rate of 85.6%. Twenty-two patients received fixed prostheses and 2 received overdentures. One patient lost all implants and was rehabilitated with a prong denture.

Adult↗