Knockout of hyaluronidase Spam1 reduces age-related bone and cartilage changes in mouse knee.

OBJECTIVE: To investigate the role of Spam1 hyaluronidase in age-related bone and cartilage changes in the mouse knee. DESIGN: Spam1-/- and WT mice were euthanised at different ages from 10 to 52 weeks. The right hindlimbs were dissected, scanned with peripheral Quantitative Computed Tomography (pQCT) and then decalcified for histological analysis (modified Mankin score). In other mice, cartilages of both tibiae were sampled at 10, 30 and 52 weeks of age for RNA extraction and qPCR analysis. We assessed the expression of hyaluronidases Hyal1 and Hyal2, hyaluronan synthase HAS2, extracellular matrix proteases Mmp13 and Adamts-5, and type 2 collagen. RESULTS: Spam1-/- mice did not exhibit specific morphological characters up to 52 weeks of age. From 20 weeks, the proximal tibia of Spam1-/- mice had a significantly lower bone mineral density than WT mice. At 52 weeks, the modified Mankin score was significantly lower in Spam1-/- than WT mice. Spam1-/- chondrocytes expressed significantly less Hyal2 than WT ones at all ages and less Mmp13 at 52 weeks. Through all the experiment, the Hyal1 expression of Spam1-/- chondrocytes remained similar as that of WT chondrocytes. CONCLUSION: Spam1 knockout reduced significantly cartilage degradation in mouse knee whereas the chondrocyte expression of Hyal 1, Hyal 2 and Mmp13 was modified, suggesting a role of this hyaluronidase in cartilage metabolism.

Mineral features of connective dental hard tissues in hypoplastic amelogenesis imperfecta.

OBJECTIVE: To explore the mineral features of dentin and cementum in hypoplastic Amelogenesis imperfecta AI teeth. MATERIALS AND METHODS: Forty-four (44) teeth cleaned and free of caries were used: 20 control and 24 affected by hypoplastic amelogenesis imperfecta. Thirty-two teeth were studied by pQCT, cut in sections, and analyzed under microradiography, polarized light microscopy, and confocal Raman spectroscopy. Eight teeth were observed under scanning electron microscope. Four teeth were used for an X-ray diffraction. The mineral density data were analyzed statistically with the Mann-Whitney U test, using GraphPad InStat software. RESULTS: Both coronal dentin and radicular dentin were less mineralized in AI teeth when compared to control (respectively 6.2% and 6.8%; p < .001). Root dentinal walls were thin and irregular, while the cellular cementum layers were thick, reaching sometimes the cervical region of the tooth. Regular dentinal tubules and sclerotic dentin areas were noticed. Partially tubular or cellular dysplastic dentin and hyper-, normo-, or hypomineralized areas were noticed in the inter-radicular areas of hypoplastic AI teeth. The main mineral component was carbonate hydroxyapatite as explored by Raman spectroscopy and X-ray diffraction. CONCLUSIONS: Dentin and cementum in hypoplastic AI teeth are (i) hypomineralized, (ii) constituted of carbonate hydroxyapatite, and (iii) of non-homogenous structure.

Management of Root Perforations Using MTA with or without Er:YAG Laser Irradiation: An In Vitro Study.

The aim of this in vitro study is to compare the microleakage of a root perforation sealed with MTA (mineral trioxide aggregate) (group M) to that sealed with MTA following Er:YAG laser irradiation (group ML). Forty-two recently extracted human monoroot teeth were used. Two cavities were prepared on each root surface. Randomly, on each root, the exposed dentine of one cavity was irradiated prior to MTA filling using an Er:YAG laser with the following settings: 200 mJ/pulses under an air water spray, 10 Hz, pulse duration of 50 µsec, and 0.7 mm beam diameter. All cavities were then sealed with MTA. submitted to thermocycling and immersed in 2% methylene blue dye solution for 12 h. The penetration of methylene blue in the microleakage of cavity was observed and recorded. The mean value dye penetration in cavities sealed with MTA following Er:YAG laser irradiation (23.91 ± 14.63%) was lower than that of unlased cavities sealed only with MTA (25.17 ± 17.53%). No significant difference was noted. The use of an Er:YAG laser beam for dentinal conditioning prior to MTA filling of perforated roots did not decrease significantly the microleakage of MTA sealing when compared to the conventional use of MTA filling.

Effect of low fluency dentin conditioning on tensile bond strength of composite bonded to Er:YAG laser-prepared dentin: a preliminary study.

Several studies in the literature have previously shown that the bond strength of a composite bonded to dentin is almost equivalent as when dentin is prepared by either bur or Er:YAG laser. The aim of this preliminary study is to assess the hypothesis that dentin conditioning at low fluency by means of Er:YAG laser can improve the value of adhesion of composites resin to dentin. Sixty surfaces of caries-free human third molars extracted for orthodontic purposes were randomly divided into five groups of 12 teeth. The bur group was the control, prepared using bur, group L was prepared using Er:YAG 200 mJ, SSP (50 µs), 20 Hz, 15 seconds of sweeping, for groups L80, L100, L120, they were prepared first, with the same parameters of the group L 200, and then they received a conditioning, which is, respectively, 15 s of irradiations at: 80 mJ (SSP, 10 Hz), 100 mJ (SSP, 10 Hz), and 120 mJ (SSP, 10 Hz). All samples were restored in a single-component adhesive system: Xenon (DENTSPLY), and ceramX (DENTSPLY) as the resin composite. The specimens were submitted to tensile bond strength test using a universal testing machine. Data were submitted to statistical analysis using ANOVA coupled to a Tukey-Kramer test at the 95% level. The mean values in MPa were 33.3 for group B, 36.73 for group L 200, 41.7 for group L80, 37.9 for group L100, and 39.1 for group L120. Our results showed that dentin conditioning at a low fluency of 12.58 J/cm(2) per pulse, with 80 mJ output energy and 50-µs pulse duration can significantly improve tensile bond strength of a composite bonded to Er:YAG laser-prepared dentine.

Does orthodontic loading influence bone mineral density around titanium miniplates? An experimental study in dogs.

OBJECTIVES: To evaluate whether orthodontic loading has an effect on miniplate stability and bone mineral density (BMD) around the screws supporting those miniplates. SETTING AND SAMPLE POPULATION: Two miniplates were inserted in each jaw quadrant of 10 dogs. MATERIAL AND METHODS: Two weeks later, coil springs were placed between the miniplates of one upper quadrant and between those of the contralateral lower quadrant. The other miniplates remained non-loaded. The dogs were sacrificed 7 or 29 weeks after surgery, and the jaws were scanned with peripheral Quantitative Computed Tomography (pQCT) to assess BMD. RESULTS: The success rate was not significantly different for the loaded and the non-loaded miniplates, but was significantly higher for the maxillary compared to the mandibular ones. Mobility, associated with local inflammation, most often occurred during the transition between primary and secondary stability. pQCT showed higher BMD around mandibular vs. maxillary screws, without significant difference between loaded and non-loaded ones. Furthermore, load direction did not lead to any significant difference in BMD. CONCLUSION: Miniplate stability and BMD of the adjacent bone did not appear to depend significantly on orthodontic loading, but rather on the receptor site anatomy.

Effect of acid etching duration on tensile bond strength of composite resin bonded to erbium:yttrium-aluminium-garnet laser-prepared dentine. Preliminary study.

The purpose of this study was to compare the tensile bond strength of composite resin bonded to erbium:yttrium-aluminium-garnet (Er:YAG) laser-prepared dentine after different durations of acid etching. The occlusal third of 68 human third molars was removed in order to expose the dentine surface. The teeth were randomly divided into five groups: group B (control group), prepared with bur and total etch system with 15 s acid etching [37% orthophosphoric acid (H(3)PO(4))]; group L15, laser photo-ablated dentine (200 mJ) (laser irradiation conditions: pulse duration 100 micros, air-water spray, fluence 31.45 J/ cm(2), 10 Hz, non-contact hand pieces, beam spot size 0.9 mm, irradiation speed 3 mm/s, and total irradiation time 2 x 40 s); group L30, laser prepared, laser conditioned and 30 s acid etching; group L60, laser prepared, laser conditioned and 60 s acid etching; group L90, laser prepared, laser conditioned and 90 s acid etching. A plot of composite resin was bonded onto each exposed dentine and then tested for tensile bond strength. The values obtained were statistically analysed by analysis of variance (ANOVA) coupled with the Tukey-Kramer test at the 95% level. A 90 s acid etching before bonding showed the best bonding value (P < 0.05) when compared with all the other groups including the control group. There is no significance difference between other groups, nor within each group and the control group. There was a significant increase in tensile bond strength of the samples acid etched for 90 s.

[Comparative study on dogs between CO2 laser and conventional technique in direct pulp capping]. / Etude comparative concernant l'apport du laser CO2 dans le coiffage pulpaire direct vs technique conventionnelle chez le chien.

UNLABELLED: Three dogs have been used in this experiment. Class V cavities were made in sixty teeth. A pulpal communication was provoked intentionally in these cavities. Teeth were randomly split in 2 groups (30 teeth for each). On first group, the pulp bleeding was stopped until appearance of coagulum on exposed pulp surfaces by means of CO2 laser irradiation (Output Power: 3 W, Pulse duration: 0.1 sec, frequency: 1 Hz, spot size diameter: 0.3 mm, Energy density: 425 J/cm2). Calcium Dihydroxide was deposited followed by a temporary filling (IRM, Dentsply, De Trey, Germany). In the second group, the calcium Dihydroxide was deposited directly on exposed bleed pulp (conventional technique) followed by the same temporary filling. Ten weeks later, all teeth were extracted and prepared for histological study. RESULTS: 93% of treated teeth preserved their pulp vitality in the group treated with CO2 laser for direct pulp capping versus 82% in the group treated by conventional technique. The average of the thickness of the dentinal bridge newly formed was 391.5 +/- 33 microm for teeth irradiated with laser and 294.1 +/- 28 microm for teeth treated by conventional technique. The thickness of the dentinal bridge newly formed in teeth treated by means of CO2 laser was 33% more important than in those treated by the conventional technique. Statistical analysis showed a significant difference between the averages of values in all groups (p < 0.05). To conclude, CO2 Laser use in the direct pulp capping increases significantly the percentage of pulp vitality preservation and the thickness of the dentinal bridge newly formed after pulp exposition.

Orthodontic loading of titanium miniplates in dogs: microradiographic and histological evaluation.

OBJECTIVES: The objectives of this animal study were to evaluate if orthodontic loading has an impact on osseointegration of screws supporting miniplates, and to describe the histological components of the bone-screw interface. MATERIALS AND METHODS: Eighty orthodontic miniplates were placed in the jaws of 10 dogs. After 2 weeks, a 125 g force was applied between the miniplates of one upper quadrant of each dog and between those of the controlateral lower quadrant. The others, nonloaded miniplates, were considered as controls. Five dogs were sacrificed 7 weeks after implantation and the remaining five dogs after 29 weeks [Short Term (ST) and Long Term (LT) groups, respectively]. Fluorochromes were injected at implantation and at sacrifice. Jaw quadrants were dissected, embedded, cut into undecalcified transverse sections through the screws and finally submitted to microradiographic analysis to allow assessment of bone-implant contact (BIC) and bone volume/total volume (BV/TV). The sections were observed under UV light and stained in order to examine them under ordinary light. RESULTS: Osseointegration occurred around 90/160 screws and consisted mainly in limited repair and remodelling processes of lamellar bone, without inflammation. Wide variations were observed in BIC and BV/TV, but without any significant difference, neither between the loaded and the nonloaded screws, nor according to the direction of load, whereas they were significantly higher in the LT than in the ST group. Nonosseointegrated screws were surrounded by fibrous tissue. Osteoblastic activity, when present in front of these screws, was not sufficient to achieve stability. CONCLUSIONS: Osseointegration underlying orthodontic anchorage was not affected by loading. BIC increased with time and varied according to implantation site. Particularly the tight-fitting screw insertion appeared crucial in determining the appropriate bone healing response.

Effects of irradiation on bone remodelling around mandibular implants: an experimental study in dogs.

This research focuses on the effects of radiotherapy on bone remodelling around mandibular implants in dogs. After bilateral extraction of the mandibular premolars and first 2 molars, each of 11 beagles received 8 mandibular implants. Four animals were irradiated 4 weeks after implantation and 4 others 8 weeks before implantation; the remaining 3 did not receive radiotherapy. Irradiation consisted of 10 daily fractions of 4.3Gy (60)Co. Fluorochromes were given at implantation and irradiation to allow the measurement of bone apposition. The dogs were killed 6 months after implantation. Each hemi-mandible was processed according to bone-specific histological techniques. New bone formation was visible around 85 of the 88 implants. Stimulated mandibular remodelling was attested in both irradiated groups by increased porosity and numerous labelled osteons. Resorption was more pronounced in the group irradiated after implantation, but osteon formation appeared unvarying. Osseointegration was thus shown to be compatible with bone irradiation as bone turnover activities were maintained throughout the experiment. As the apposition stage of the remodelling cycle appears crucial to achieve optimal osseointegration, its normal completion should be taken into account in clinical practice by respecting a 6-month period between irradiation and implantation.

The deep belly of the temporalis muscle: an anatomical, histological and MRI study.

In order to achieve a better functional and clinical knowledge of a masticatory muscle called the sphenomandibularis that is suspected to be responsible for headaches by compressing the maxillary nerve, bilateral dissections of the infratemporal fossa were performed on ten human cadavers and completed by histological and radiological studies of the same areas. Both macroscopic and microscopic observations obviously showed that the so-called sphenomandibularis muscle corresponds to the deep portion of the temporalis muscle, since there is no epimysial septum between these two structures, which previously have been described as being completely independent from each other. In spite of the close topographic relationship between the deep belly of the temporalis and the lateral pterygoid muscle, as well as their similar innervation pattern, the sphenomandibularis in fact has to be considered functionally as an original but non-isolated positional fascicle of the temporalis muscle itself. Our observations, correlated with MR images, suggest indeed that the deep belly of the temporalis muscle is of functional importance in the masticatory movements, but is not involved by its neurovascular vicinity in the genesis of specific headaches. Its surgical release, however, should be discussed in the case of a temporal myoplasty.

Anatomical and radiological correlation of Lequesne's "false profile".

Lequesne introduced a radiological projection, which is an oblique view of the edge of the acetabulum, to diagnose arthrosis affecting the anterior part of the joint and to measure the anterior coverage of the femoral head. In this study, we attempted to determine the anatomical correlation of his technique. Fifteen in vitro hemipelvises underwent radiography according to Lequesne's description, using metallic markers and wires to mark physical landmarks. According to geometric laws, the points used by Lequesne do not correlate anatomically. Although Lequesne's technique allows a diagnosis of acetabular dysplasia, measurements are on average 5.5 degrees less than those made anatomically.

Postmenopausal osteoporosis: microradiographic aspects.

A comparative microradiographic and histologic analysis of undecalcified bone samples was performed in men and women aged 18-98 years. These morphological methods showed that besides usual lamellar bone remodelling, all the so-called inert surfaces, namely both haversian and vascular canals as well as trabecular surfaces, were involved in weathering alterations of the superficial lamellae, resulting in eroded outlines devoid of osteoclast. These aspects, recorded in all pieces of our material, were visible from the earliest adult age and were randomly distributed. Except the grade of osteoporosis at a given age, the microradiographic and histologic aspects were similar in both aged men and women and did not allow sex distinction. These observations were consistent with the hypothesis of a particular destructive process affecting all the quiescent lamellar bone surfaces without osteoclast or cell participation. This kind of erosion, termed delitescence, could be at least partially responsible for the age-related and postmenopausal bone loss. In order to explain the increasing osteoporosis after menopause, it has been suggested that the estrogen deficiency could increase the percentage of dead osteocytes. Thereby the reduced cellular control on the bone surface could impair the remodeling process and fail to adapt the bone structure by repairing the microscopic lesions.

Structural changes with aging in cortical bone of the human tibia.

Structural modifications are considered to play a significant role in the age-related alterations of bone quality and strength. Senescent compact bone is characterized by an increasing heterogeneity of aspects, including high numbers of lowly mineralized osteons as well as the presence of osteons with hypermineralized lamellae or with a notched haversian canal wall, and of double-zone osteons. These latter three types of osteons are different from the structures involved in the haversian remodeling. In the present study, blocks of midshaft tibia from 7 young men (18-39 years), 14 aged men (50-92 years) and 15 aged women (57-96 years) were embedded in methyl methacrylate in order to perform microradiographic and histomorphometric analysis of undecalcified sections. The intracortical porosity was higher in the aged men than in the young ones, as were the numbers of haversian structures and, to a lesser extent, the diameters of the haversian canals. The aged women showed the same tendency, with cortical porosity still higher than in the men. The osteons with hypermineralized lamellae, those with a notched canal and the double-zone osteons appear to constitute large subgroups of the total haversian population, even in the early adult life. Among them, only the osteons with a notched canal wall increased in frequency with age. The 3 types are much more numerous than the structures involved in the typical haversian remodeling. The correlations between their frequencies as well as their significant topographic association corroborates the hypothesis that the hypermineralized lamellae may crumble down because of their excessive brittleness, giving rise to the haversian canals with notched walls. These enlarged canals could be refilled by bone apposition and result in the double-zone osteons. The 3 types of osteons could constitute different steps of one mechanism of bone desintegration and repair occurring very progressively, which might contribute to modify the bone quality and to increase the intracortical porosity.

A new familial short stature syndrome: Brussels type.

A new association of congenital familial short stature with facial dysmorphism and osteochondrodysplastic lesions is described in two siblings. Clinical abnormalities include severe prenatal and postnatal growth failure and facial dysmorphism. Radiographs show osteochondrodysplastic lesions with a narrow thorax, short ribs, epiphyseal maturation delay and slightly deformed metaphyses. Microscopic analysis of the skeleton shows pathological features.

Aging effect on inductive capacity of human demineralized bone matrix.

Demineralized bone powder (DBP) prepared from human cortical bone was implanted into subcutaneous pouches of athymic Nu/Nu mice for 28 days. The osteoinductive capacity was evaluated by histomorphometry of the induced cartilage and bone, and by alkaline phosphatase activity in the implant. Very small amounts of new bone and cartilage were found at histological analysis, confirming that human DBP is much less osteoinductive than that from other species. Whereas the morphometric data of the implants from the young and aged donors were not significantly different, the alkaline phosphatase activity was significantly lower in the implants from the old donors than from the younger ones. This difference between the morphometric and biochemical results could reflect the fact that the enzymatic activity is already present in the osteoprogenitor cells. At 28 days, the osteoblastic activity in contact with DBP from the aged group is characterized by a decrease in the enzymatic amount which is not yet visible at the tissue level. This tendency to a decrease in the osteoinductive capacity of bone matrix is an additional aspect of the age-related alterations which occur in bone tissue and could be attributed to modifications of different proteins of the bone matrix, including bone morphogenetic protein.

Microradiography and fluorescence microscopy of bone remodeling on the basal crypt of permanent mandibular premolars in dogs during eruption.

Alveolar bone of erupting teeth was studied in order to define the types of calcified tissues deposited as well as the rate of tooth growth. The third (P3) and fourth (P4) mandibular premolars of 30 dogs aged 12-24 weeks were analyzed by microradiography and microscopy in fluorescent and ordinary light. The bone plate separating P3 and P4 from the mandibular canal presented a complex arrangement of lamellar and woven bone, and even of chondroid tissue. During the pre-eruptive phase, this plate shifted towards the base of the mandible by means of selective resorption and apposition activities. As soon as the furcation was formed, bone apposition appeared on the alveolar side and became the main activity under P3 at the outset of eruption. Under the roots of P4 it occurred 4 weeks later. Dynamic morphometry in fluorescence microscopy showed that eruption progressed faster than the radicular growth. The formation of interradicular bone underwent the same acceleration as the eruption. However, though the tissues were formed at a high rate, it cannot be inferred therefrom that they are responsible for tooth shifting. They might just fill the space left by the erupting tooth.

Cancellous bone in human acetabulum: microradiographic and histomorphometric aspects.

The acetabular cancellous bone of 18 subjects aged 57-88 years was characterized by low mass and a poorly ramified pattern according to microradiographic analysis. There was no correlation between the histomorphometric data of this region and those of the iliac crest. Microcalluses were visible in 13 acetabular samples, whereas they were absent from the iliac crest. As the acetabular trabeculae appeared decidedly longitudinal, age-related bone rarefaction is suggested to occur in two different ways: uniform thinning of the trabeculae and selective disappearance of transverse elements. The remaining longitudinal trabeculae are considered to be most useful for the weight-bearing function of the hip joint.

Hypermineralized lamellae below the bone surface: a quantitative microradiographic study.

Hypermineralized lamellae similar to interstitial resting lines were identified by microradiography beneath haversian, endocortical, and trabecular resting surfaces in 42 subjects aged 18-96 years. In cross-sectioned osteons, this hypermineralized lamella appeared as a circle showing the same high microdensity as the inner margin of the haversian canal. Bone tissue separating this circle and the margin was more mineralized than the peripheral lamellae of the osteon. In the tibia, 13.7 +/- 0.9% (Mean +/- SE) of Haversian canals exhibited a hypermineralized circle, localized at a distance of 20 +/- 0.4 microns from the canal wall. The scalloped haversian canals, different from osteoclastic resorption cavities, represented 9.9 +/- 0.7% of the haversian canals. There was a significant correlation between both types of haversian canals. Therefore, hypermineralized lamellae can appear at the end of bone apposition, whatever the bone surface. Their high mineral content may secondarily lead to an increased brittleness of the most superficial lamellae and even to their disaggregation.

The fate of the quiescent surfaces of lamellar bone.

Microradiographic and histologic analysis of undemineralized bone was performed in 62 subjects aged 18-97 years. Ten of these samples were also submitted to scanning electron microscopy. Besides the usual lamellar bone remodeling, all types of bone surfaces, namely both haversian and vascular canals and the endosteal and trabecular surfaces, were involved in weathering alterations of the superficial lamellae, resulting in eroded outlines, less deeply notched than the Howship lacunae and devoid of osteoclast. Present as soon as early adult life and randomly distributed, these aspects were recorded in all the bone pieces examined. These observations were consistent with the hypothesis of a particular destructive process in all the quiescent lamellar bone surfaces without osteoclast participation, termed delitescence, which could be partly responsible for age-related bone loss.