Reduced mesiodistal tooth dimension in individuals with osteogenesis imperfecta: a cross-sectional study.

OBJECTIVE: Osteogenesis imperfecta (OI) is a rare, hereditary disease affecting collagen type-1 in connective tissue. Collagen type-1 is a substantial component of dentine, and it is speculated, whether affected dentine could cause altered mesiodistal tooth dimension possibly affecting restorative treatment regimen. Therefore, the aim of the present study was to measure mesiodistal tooth dimensions in individuals with OI and compare them with healthy controls. MATERIALS AND METHODS: Fifty-seven individuals aged 20-77 years with OI type 1-4 were included and 70 control patients aged 11-34 years were drawn from an orthodontic database. Mesiodistal tooth dimensions of all tooth types, except third molars, were measured in mm (two decimals) on digital 3 D-models of the tooth-bearing arches. RESULTS: Multilevel mixed-effects linear regression analysis showed that mesiodistal tooth dimension on average was 0.17 mm (95% CI = (-0.33; -0.01)) reduced for the OI group compared to controls. The analysis revealed variation between tooth types; incisors and first premolars were most affected and molars minimally affected. CONCLUSIONS: The mesiodistal tooth dimension in individuals diagnosed with OI is significantly smaller compared to healthy controls, which should be taken into consideration in the restorative treatment planning of individuals with OI, although the magnitude of the deviation is relatively small. The results on mesiodistal tooth dimensions of the present controls may be used as a standard for comparisons in future studies on tooth dimensions.

Drifting of teeth in the mandible studied in adult human autopsy material.

OBJECTIVES: Increase in lower anterior crowding is a general problem among adult Caucasians. The tooth movement responsible for this phenomenon, however, is not fully elucidated. Aim of this study was to describe signs of ongoing tooth movement reflected in the thickness of the bundle bone around mandibular teeth and the distribution of eroding surfaces of the alveolar wall in human autopsy material. MATERIAL AND METHODS: The distribution of bundle bone and eroding surfaces was assessed histomorphometrically on 106 mandibular teeth, and the surrounding bone obtained at autopsy from 35 deceased persons ranging from 19 to 55 years of age. By examining the mesio-distal and bucco-lingual aspects at the cervical and apical levels of the roots, a pattern of tooth movements could be established. RESULTS: The distribution of the bundle bone thickness and the vectors of eroding surfaces enabled the direction of tooth movement to be reconstructed. Mesial and lingual displacement was prevalent for the anterior teeth. CONCLUSION: The signs of ongoing displacement of lower teeth support the concept of crowding occurring in adult individuals and support the maintenance of retainers, even following cessation of growth.

Influence of a titanium mesh on the management of segmental long bone defects. An experimental study in a canine ulnar model.

OBJECTIVES: To evaluate the influence of titanium mesh on guided bone regeneration when used, either alone or in combination with autogenous bone block graft, in a canine ulnar model. METHODS: Thirty-two, purpose bred, adult, castrated male Beagles were used, divided into four equal-size groups. A unilateral mid-diaphyseal ulnar critical-size defect was created in each dog. The ulnar segments were stabilized with a stainless-steel plate and screws. Each defect was managed by: no further treatment (Group A) or by placement of a bone block graft taken from the ipsilateral iliac crest (Group B), or titanium mesh wrapped around the ulna (Group C), or a bone block graft and titanium mesh (Group D). After six months, bone block biopsies were performed and the samples were scanned using micro-computed tomography. Qualitative histological evaluation was performed on two non-decalcified longitudinal sections from each block. RESULTS: No significant differences in terms of mineralized bone volume were detected between the grafted sites (Groups B and D) or between the non-grafted ones (Groups A and C). The histological evaluation indicated good integration of the bone blocks irrespective of the use of titanium mesh. CLINICAL SIGNIFICANCE: The use of titanium mesh does not influence the amount of bone formation. The canine ulnar critical-size defect model seems to be a reliable model to use in experimental studies.

Multi-level synchrotron radiation-based microtomography of the dental alveolus and its consequences for orthodontics.

Multilevel synchrotron radiation-based microtomography has been performed on a human jaw segment obtained at autopsy by cutting increasingly smaller samples from the original segment. The focus of this study lay on the microstructure of the interface between root, periodontal ligament (PDL) and alveolar bone in order to find an answer to the question why alveolar bone remodels during orthodontic loading, when the associated stress and strain levels calculated with finite element analyses are well below the established threshold levels for bone remodeling. While the inner surface of the alveolus appears to be rather smooth on the lower resolution scans, detailed scans of the root-PDL-bone interface reveal that on a microscopical scale it is actually quite rough and uneven with bony spiculae protruding into the PDL space. Any external (orthodontic) loading applied to the root, when transferred through the PDL to the alveolar bone, will cause stress concentrations in these spiculae, rather than be distributed over a "smooth surface". As osteocyte lacunae are shown to be present in these spiculae, the local amplified stresses and strain can well be registered by the mechano-sensory network of osteocytes. In addition, a second stress amplification mechanism, due to the very presence of the lacunae themselves, is evidence that stresses and strains calculated with FE analyses, based on macroscopical scale models of teeth and their supporting structures, grossly underestimate the actual mechanical loading of alveolar bone at tissue level. It is therefore hypothesized that remodeling of alveolar bone is subject to the same biological regulatory process as remodeling in other bones.

Alveolar bone preservation subsequent to miniscrew implant placement in a canine model.

OBJECTIVE: To assess the effects of transcortical screws on alveolar (bone) ridge preservation following extraction. DESIGN: Four adult beagle dogs had mandibular premolars extracted bilaterally. After 6 weeks, using a split-mouth design, two transcortical screws were inserted unilaterally below the alveolar crest on the experimental side in the region of the extraction. The dogs were killed after 12 weeks. The bone at the extraction sites was analyzed using µCT and 3D analysis. A cylindrical core was placed around the actual and a virtual screw placed in the identical location on the control side. The bone volume within the cylinders was quantified. An insertion of a dental implant was simulated bilaterally at the insertion site. The height of the clinical crown and the alveolar crest were determined on both sides. The bone turnover was assessed histomorphometrically on un-decalcified bucco-lingual sections stained with basic fuchsine and toluidine blue. RESULTS: Comparison of the two sides revealed a significant difference both with regard to the bone volume and morphology. The transcortical screw caused an increase in bone density and less ridge atrophy. When simulating a dental implant placement on both sides, the bone preservation on the experimental side led to a need for a shorter clinical crown compared to the control side. A higher activity level of the bone in the experimental side was demonstrated histologically. CONCLUSION: In this dog model the insertion of a mini-implant across the healing alveolar process results in increased density not only adjacent to the screws, but also in the region where a potential dental implant would be inserted. In humans, the insertion of transcortical screws may maintain bone when for various reasons insertion of a permanent dental implant has to be postponed.

A rat model for orthodontic translational expansive tooth movement.

OBJECTIVES: To present the development of an experimental model in rats for translational expansive tooth movement. SETTING AND SAMPLE: Section of Periodontology at Department of Dentistry Aarhus University. Twenty male Wistar rats in two pilot experimental settings plus seven animals without any intervention serving as controls. MATERIAL AND METHODS: The second molar (group P1) or the second and third molar (group P2) in the maxillae of the animals were moved buccally using transpalatal ß-titanium springs. In the group P2, two spring types (high force and low force) and two preangulations (0° passive or 30° torsion moment) were tested. The amount and type of tooth movement achieved and the resulting skeletal effect were assessed on microCT images, histological analysis was performed on few selected specimens. RESULTS: Expansive translational root movement amounting half a tooth width was achieved. Comparison of the amount of tooth movement at the right and left side of the maxilla showed that the expansion was rather symmetrical in the P2 group. Skeletal widening of the maxilla contributed in the P2 group to approximately one-third of the total root movement, whereas two-thirds were dental movement. CONCLUSION: With the model used in the P2 group, further research on translational expansive tooth movement and its effect on the periodontium can be pursued. In models for orthodontic expansion, it is strongly recommended to separately evaluate skeletal and dental effects.

Mechanical stability of the femoral fixation for single- and double-bundle ACL reconstruction in an in vitro experimental model.

Anterior cruciate ligament ACL reconstruction using the double-bundle (DB) technique is gaining popularity. A possible weak link in the DB technique could be that two tendon grafts of smaller diameters are used. The purpose of this study was to test different femoral fixation methods and graft diameters representing single-bundle (SB) and DB ACL reconstructions and compare their biomechanical properties. We hypothesized that SB 6-mm graft constructs had inferior biomechanical properties than SB 9-mm grafts or DB 2 × 6-mm grafts. Furthermore, we hypothesized that interference (IF) screw fixation would demonstrate less elongation and a higher stiffness than Endobutton (Smith & Nephew®, Inc., Andover, Massachusetts, USA) fixation (EBF). We performed an in vitro study using porcine knees and extensor tendons. The mechanical test consisted of a cyclic test followed by a load-to-failure test. We found that 6-mm graft constructs had an ultimate failure load that was up to 40% less than both the 9-mm and 2 × 6-mm graft constructs, despite the fixation method (P-values ≥ 0.004). Comparing fixation methods, EBF was superior to IF concerning maximum load to failure (P < 0.001); IF resulted in a higher stiffness of the femur/graft complex than the EBF (P < 0.001) but no significant difference in elongation between fixation methods. Since the two graft strands are subjected to different loads in different knee flexion angles, the reduced strength of the individual graft strands in DB ACL reconstruction could be a concern.

Micro-CT analyses of apical enlargement and molar root canal complexity.

AIM: To compare the effectiveness of two rotary hybrid instrumentation techniques with focus on apical enlargement in molar teeth and to quantify and visualize spatial details of instrumentation efficacy in root canals of different complexity. METHODOLOGY: Maxillary and mandibular molar teeth were scanned using X-ray microcomputed tomography. Root canals were prepared using either a GT/Profile protocol or a RaCe/NiTi protocol. Variables used for evaluation were the following: distance between root canal surfaces before and after preparation (distance after preparation, DAP), percentage of root canal area remaining unprepared and increase in canal volume after preparation. Root canals were classified according to size and complexity, and consequences of unprepared portions of narrow root canals and intraradicular connections/isthmuses were included in the analyses. One- and two-way anova were used in the statistical analyses. RESULTS: No difference was found between the two techniques: DAP(apical-third) (P = 0.590), area unprepared(apical-third) (P = 0.126) and volume increase(apical-third) (P = 0.821). Unprepared root canal area became larger in relation to root canal size and complexity, irrespective of the technique used. Percentage of root canal area remaining unprepared was significantly lower in small root canals and complex systems compared to large root canals. The isthmus area per se contributed with a mean of 17.6%, and with a mean of 25.7%, when a narrow root canal remained unprepared. CONCLUSIONS: The addition of isthmuses did not significantly alter the ratio of instrumented to unprepared areas at total root canal level. Distal and palatal root canals had the highest level of unprepared area irrespective of the two instrumentation techniques examined.

An analysis of different approaches to the assessment of upper airway morphology: a CBCT study.

BACKGROUND: Upper airway morphology and respiration have been assigned an important role in the development of the craniofacial complex. Several studies advocate lateral cephalograms to evaluate the upper airway. Although this method has been widely used, a two-dimensional projection of a three-dimensional anatomical structure is questionable. OBJECTIVE: To correlate linear measurements (sagittal and transversal), cross-sectional areas, and volumes of the upper airway determined on Cone Beam CT (CBCT) data sets. MATERIAL AND METHODS: CBCT-scans of 34 patients were used to perform a 3D evaluation of the upper airway. Linear sagittal measurements reproducing those usually performed on lateral cephalograms, linear transversal measurements, cross-sectional areas, partial and total volumes (TV) were computed. RESULTS: The analysis showed a weak correlation (r < 0.8) between most of the linear measurements. The correlations between sagittal, transversal, and cross-sectional area with partial volumes were weak, except for the lower part of the nasopharynx which was highly correlated (r > 0.9) with sagittal measurement and with area. The upper part of the velopharynx presented a good correlation (0.8 < r < 0.9) between area and volume. Good correlation between most transversal measurements and the corresponding areas was found. Minimal sagittal, minimal transversal, and minimal area were weakly correlated with TV. CONCLUSIONS: Upper airway cannot be accurately expressed by single linear measurements as performed on cephalograms. The TV alone does not depict the morphology of the airway. A CBCT-based 3D analysis gives a better picture of the anatomical characteristics of the upper airways and therefore can lead to an improvement of the diagnosis.

Strains in periodontal ligament and alveolar bone associated with orthodontic tooth movement analyzed by finite element.

INTRODUCTION: Orthodontic tooth movement (OTM) is achieved by applying an orthodontic force system to the brackets. The (re)modeling processes of the alveolar support structures are triggered by alterations in the stress/strain distribution in the periodontium. According to the classical OTM theories, symmetric zones of compression and tension are present in the periodontium, but these do not consider the complex mechanical properties of the PDL, the alveolar structures' morphology, and the magnitude of the force applied. MATERIALS AND METHODS: Human jaws segments obtained from autopsy were microCT-scanned and sample-specific finite element (FE) models were generated. The material behavior of the PDL was considered to be nonlinear and non-symmetric and the alveolar bone was modeled according to its actual morphology. A series of FE-analyzes investigated the influence of the moment-to-force ratio, force magnitude, and chewing forces on the stress/strain in the alveolar support structures and OTM. RESULTS: Stress/strain findings were dependent on alveolar bone's morphology. Because of the nonlinear behavior of the PDL, distinct areas of tension, and compression could not be detected. Secondary load transfer mechanisms were activated and the stress/strain distribution in the periodontium was concealed by occlusal forces. CONCLUSIONS: We could not confirm the classical ideas of distinct and symmetrical compressive and tensile areas in the periodontium in relation to different OTM scenarios. Light continuous orthodontics forces will be perceived as intermittent by the periodontium. Because roots and alveolar bone morphology are patient-specific, FE-analysis of orthodontic loading regime should not be based on general models.

Bioactive glass granules as extender of autogenous bone grafting in cementless intercalary implant of the canine femur.

BACKGROUND AND AIMS: Ceramic bone graft substitutes have a potential to be used as replacement of allogeneic bone grafting and, under optimal distribution of particle size, they may even provide mechanical support. The current study examined the efficacy of bioactive glass granules as an extender of autogenous bone grafting in a segmental bone replacement model of the canine femur. MATERIAL AND METHOD: A 16 mm long segment of the femur shaft was bilaterally replaced with an intercalary titanium implant in eight animals. The implant had cementless grooved proximal and distal stems. In one leg, the peri-implant space was packed with composite graft consisting of a mixture of bioactive glass granules and autogenous bone graft in proportion of 50:50. In the opposite leg, the peri-implant space was treated with autogenous bone graft alone. After surgery, unlimited functional loading was allowed. The outcome was evaluated at three months. RESULTS: Eight out of sixteen autografted implants and seven out of sixteen composite-grafted implants were radiographically incorporated and clinically stable at three months. In the paired comparison, the proximal components of composite-grafted implants showed lower maximum load under torsional testing (p = 0.068), less new bone in the longitudinal grooves of the stems (p = 0.036) and lower affinity of new bone to implant surface (p = 0.046). The distal components of the two sides showed a similar trend for less new bone in the grooves and lower bone affinity of new bone in the distal composite-grafted components. CONCLUSIONS: The current study suggests that supplementation of periprosthetic bone graft with bioactive ceramic particles may not help to promote healing of cementless implants under high dynamic loading conditions.

Synchrotron radiation-based microtomography of alveolar support tissues.

OBJECTIVES: To study the alveolar support structures using synchrotron radiation (SR)-based microtomography with particular focus on the alveolar surface. DESIGN: High-resolution microtomography of jaw segments of various species and subsequent three-dimensional (3D) reconstruction. SETTING AND SAMPLE POPULATION: Microtomography was performed at the DORIS-ring of the synchrotron facility of HASYLAB/DESY in Hamburg, Germany. The samples consisted of human, simian and porcine jaw segments. RESULTS: With SR being monochromatic, no beam-hardening artifacts could occur and the grey values in the scans were therefore directly related to the local tissue densities. Apart from the mineralized tissues, the beam energy was low enough to allow for the visualization of soft tissues like the fibers of the periodontal ligament (PDL) and blood vessels. 3D reconstructions of the alveolar bone showed that it can be rough and sharply edged. Furthermore, an intricate network of marrow cavities and blood vessels penetrates its surface. Differences in the local grey value distribution in the alveolar bone pointed to remodeling activity in the close vicinity of the PDL. CONCLUSION: The assumption that the alveolar bone surface is smooth and continuous is not correct. This means that even small orthodontic loads can already give rise to high local stresses and strains in the bone and thus initiate remodeling processes.

The finite element method: a tool to study orthodontic tooth movement.

Orthodontic tooth movement is achieved by (re)modeling processes of the alveolar bone, which are triggered by changes in the stress/strain distribution in the periodontium. In the past, the finite element (FE) method has been used to describe the stressed situation within the periodontal ligament (PDL) and surrounding alveolar bone. The present study sought to determine the impact of the modeling process on the outcome from FE analyses and to relate these findings to the current theories on orthodontic tooth movement. In a series of FE analyses simulating teeth subjected to orthodontic loading, the influence of geometry/morphology, material properties, and boundary conditions was evaluated. The accurate description of alveolar bone morphology and the assignment of non-linear mechanical properties for the PDF elements demonstrate that loading of the periodontium cannot be explained in simple terms of compression and tension along the loading direction. Tension in the alveolar bone was far more predominant than compression.

Changed morphology and mechanical properties of cancellous bone in the mandibular condyles of edentate people.

Since edentate subjects have a reduced masticatory function, it can be expected that the morphology of the cancellous bone of their mandibular condyles has changed according to the altered mechanical environment. In the present study, the morphology of cylindrical cancellous bone specimens of the mandibular condyles of edentate subjects (n = 25) was compared with that of dentate subjects (n = 24) by means of micro-computed tomography and by the application of Archimedes' principle. Stiffness and strength were determined by destructive mechanical testing. Compared with dentate subjects, it appeared that, in edentate subjects, the bone was less dense and the trabecular structure was less plate-like. The regression models of stiffness and strength built from bone volume fraction and the trabecular orientation relative to the axis of the specimen were similar for both dentate and edentate subjects. This indicates that, under reduced mechanical load, the fundamental relationship between bone morphology and mechanical properties does not change.

Architectural measures of the cancellous bone of the mandibular condyle identified by principal components analysis.

As several morphological parameters of cancellous bone express more or less the same architectural measure, we applied principal components analysis to group these measures and correlated these to the mechanical properties. Cylindrical specimens (n = 24) were obtained in different orientations from embalmed mandibular condyles; the angle of the first principal direction and the axis of the specimen, expressing the orientation of the trabeculae, ranged from 10 degrees to 87 degrees. Morphological parameters were determined by a method based on Archimedes' principle and by micro-CT scanning, and the mechanical properties were obtained by mechanical testing. The principal components analysis was used to obtain a set of independent components to describe the morphology. This set was entered into linear regression analyses for explaining the variance in mechanical properties. The principal components analysis revealed four components: amount of bone, number of trabeculae, trabecular orientation, and miscellaneous. They accounted for about 90% of the variance in the morphological variables. The component loadings indicated that a higher amount of bone was primarily associated with more plate-like trabeculae, and not with more or thicker trabeculae. The trabecular orientation was most determinative (about 50%) in explaining stiffness, strength, and failure energy. The amount of bone was second most determinative and increased the explained variance to about 72%. These results suggest that trabecular orientation and amount of bone are important in explaining the anisotropic mechanical properties of the cancellous bone of the mandibular condyle.

Reduced mechanical load decreases the density, stiffness, and strength of cancellous bone of the mandibular condyle.

OBJECTIVE: To investigate the influence of decreased mechanical loading on the density and mechanical properties of the cancellous bone of the human mandibular condyle. DESIGN: Destructive compressive mechanical tests were performed on cancellous bone specimens.Background. Reduced masticatory function in edentate people leads to a reduction of forces acting on the mandible. As bone reacts to its mechanical environment a change in its material properties can be expected. METHODS: Cylindrical bone specimens were obtained from dentate and edentate embalmed cadavers. Mechanical parameters were determined in the axial and in the transverse directions. Subsequently, density parameters were determined according to a method based on Archimedes' principle. RESULTS: The apparent density and volume fraction of the bone were about 18% lower in the edentate group; no age-related effect on density was found. The decrease of bone in the edentate group was associated with a lower stiffness and strength (about 22% and 28%, respectively). The ultimate strain, however, did not differ between the two groups. Both groups had similar mechanical anisotropy; in axial loading the bone was stiffer and stronger than in transverse loading. CONCLUSIONS: Reduced mechanical load had affected the density and herewith the mechanical properties of condylar cancellous bone, but not its anisotropy. RELEVANCE: The change in material properties of the cancellous bone after loss of teeth indicate that the mandibular condyle is sensitive for changes in its mechanical environment. Therefore, changes in mechanical loading of the condyle have to be accounted for in surgical procedures of the mandible.

Mechanical properties of cancellous bone in the human mandibular condyle are anisotropic.

The objective of the present study was (1) to test the hypothesis that the elastic and failure properties of the cancellous bone of the mandibular condyle depend on the loading direction, and (2) to relate these properties to bone density parameters. Uniaxial compression tests were performed on cylindrical specimens (n=47) obtained from the condyles of 24 embalmed cadavers. Two loading directions were examined, i.e., a direction coinciding with the predominant orientation of the plate-like trabeculae (axial loading) and a direction perpendicular to the plate-like trabeculae (transverse loading). Archimedes' principle was applied to determine bone density parameters. The cancellous bone was in axial loading 3.4 times stiffer and 2.8 times stronger upon failure than in transverse loading. High coefficients of correlation were found among the various mechanical properties and between them and the apparent density and volume fraction. The anisotropic mechanical properties can possibly be considered as a mechanical adaptation to the loading of the condyle in vivo.

A three-dimensional finite element model from computed tomography data: a semi-automated method.

Three-dimensional finite element analysis is one of the best ways to assess stress and strain distributions in complex bone structures. However, accuracy in the results may be achieved only when accurate input information is given. A semi-automated method to generate a finite element (FE) model using data retrieved from computed tomography (CT) was developed. Due to its complex and irregular shape, the glenoid part of a left embalmed scapula bone was chosen as working material. CT data were retrieved using a standard clinical CT scanner (Siemens Somatom Plus 2, Siemens AG, Germany). This was done to produce a method that could later be utilized to generate a patient-specific FE model. Different methods of converting Hounsfield unit (HU) values to apparent densities and subsequently to Young's moduli were tested. All the models obtained were loaded using three-dimensional loading conditions taken from literature, corresponding to an arm abduction of 90 degrees. Additional models with different amounts of elements were generated to verify convergence. Direct comparison between the models showed that the best method to convert HU values directly to apparent densities was to use different equations for cancellous and cortical bone. In this study, a reliable method of determining both geometrical data and bone properties from patient CT scans for the semi-automated generation of an FE model is presented.

Growth hormone treatment promotes guided bone regeneration in rat calvarial defects.

This study evaluated the biomechanical strength and bone formation in calvarial critical size bone defects covered with expanded polytetrafluoroethylene (e-PTFE) membranes in rats treated systemically with recombinant human growth hormone (rhGH). A full-thickness bone defect, 5 mm in diameter, was trephined in the central part of each parietal bone in 40 one-year-old female Wistar rats, which were randomly assigned to two groups of 20 animals each. The bone defects were covered with an exocranial and an endocranial e-PTFE membrane. From the day of operation, the rhGH-treated animals were given 2.7 mg rhGH/kg/day and the placebo-injected rats were given isotonic sodium chloride. The animals were killed 28 days after operation. The biomechanical test was performed by a punch out test procedure placing a 3.5-mm diameter steel punch in the centre of the right healed defect. After mechanical testing, the newly formed tissue inside the defect was removed and the dry and ash weights were measured. The left healed defects were used for three-dimensional (3D) reconstruction by means of micro-computer tomography (micro-CT). Ultimate load, ultimate stiffness, and energy absorption at ultimate load were significantly increased in the rhGH-treated group (P < 0.003). Also, tissue dry and ash weights were significantly augmented in the rhGH-treated group (P < 0.001). The 3D reconstruction of newly formed bone showed that there was almost twice as much bone volume present in the rhGH-treated defects compared with the placebo group. The experiment demonstrated that rhGH administration enhances bone deposition and mechanical strength of healing rat calvarial defects, covered with e-PTFE membranes.

Statin given perorally to adult rats increases cancellous bone mass and compressive strength.

Recently, it has been shown that statins increased cancellous bone formation and volume in 3-month-old rats and induced a minor decrease in osteoclast number. In the present study, one-year-old female rats were given simvastatin (10 mg/kg) or placebo daily for 3 months by a gastric tube. Specimens, 2.0 mm high, were cut transversely from the 5th lumbar vertebral body. The cancellous bone core diameters within the cortical shell of each specimen were delineated by a micro-CT scanner and then the cancellous bone was compressed in a materials testing machine between an upper and a lower platen with a diameter corresponding to the diameter of the cancellous bone core of each specimen. The cancellous bone volume was determined histomorphometrically on transverse sections. The cancellous bone volume in the simvastatin group (52.7 +/- 1.6%, mean value +/- SEM) was increased by 23% compared with the placebo group (42.8 +/- 1.7%). The compressive stress of the cancellous bone from the simvastatin group (31.8 +/- 2.7 MPa) was increased by 24% compared with the placebo group (24.1 +/- 1.9 MPa). No changes were found in cortical bone mass and strength after the statin treatment. In conclusion, statin given perorally to adult rats increased cancellous bone mass and increased cancellous bone compressive strength. The cancellous bone was found to possess normal biomechanical competence after the statin treatment.