Biomedical subjects

J C Maltha

Publications and source records attributed to J C Maltha.

At least 19 recordsLinked to original sources

PubMed2006

CMT-3 inhibits orthodontic tooth displacement in the rat.

OBJECTIVE: Orthodontic tooth movement requires extensive remodeling of the periodontal ligament (PDL) and the alveolar bone. Osteoclasts resorb bone, allowing teeth to migrate in the direction of the force. Matrix metalloproteinases (MMPs) are able to degrade the extracellular matrix of the periodontal tissues. Chemically modified tetracyclines (CMTs) can inhibit MMPs, but lack antimicrobial activity. We hypothesize that CMT-3 will decrease the rate of orthodontic tooth movement in the rat. DESIGN: Eighteen Wistar rats received a standardized orthodontic appliance at one side of the maxilla. During 14 days, three groups of six rats received a daily dose of 0, 6 or 30mg/kg CMT-3, and tooth displacement was measured. Thereafter, osteoclasts were counted on histological sections using an ED-1 staining. Multi- and mononuclear ED-1-positive cells in the PDL were also counted. In addition, sections were stained for MMP-9. RESULTS: CMT-3 significantly inhibited tooth movement (p=0.03) and also decreased the number of osteoclasts at the compression sides in the 30mg/kg group (p<0.05). Significantly more mono- than multinuclear ED-1-positive cells were present in the PDL, but no significant differences were found between the dosage groups. Osteoclasts in the 30mg/kg group seemed to contain less MMP-9 than in the control. CONCLUSIONS: CMT-3 inhibits tooth movement in the rat, probably by reducing the number of osteoclasts at the compression side. This might be due to induction of apoptosis in activated osteoclasts or reduced osteoclast migration. Reduced MMP activity by CMT-3 might also directly inhibit degradation of the organic bone matrix.

Alveolar Process↗

PubMed2006

Biomechanical behaviour of the periodontal ligament of the beagle dog during the first 5 hours of orthodontic force application.

The aim of this study was to describe the mechanical behaviour of the periodontal ligament (PDL) in response to loading with different forces for a period of 5 hours. Seven young adult male beagle dogs (age 1.0-1.5 years) were used. After extractions and placement of implants, custom-made appliances on both sides of the mandible were used to measure the displacement of the second premolars. Tooth displacement was measured during 5 hours of force application. Each dog underwent two measurement sessions. One premolar was moved with a force of 100 cN in the first session and with 50 cN in the second. The contralateral premolar was moved with forces of 100 and 300 cN, respectively. Time-displacement curves showed a rapid instantaneous response lasting only a few seconds followed by a slowly decreasing creep displacement. The instantaneous response demonstrated a large individual variability, caused by both a dog and a force effect. Differences in tooth and PDL anatomy and in the orientation of the periodontal fibres are probably important in this respect. The individual variability faded after the first seconds of tooth displacement, when the viscoelastic properties of the periodontal fibres became more pronounced. The force effect was non-linear for the first minute. Higher forces did not lead to proportionally larger displacements. The non-linearity decreased in the second response. The PDL is a complex material that might be considered as a non-linear fibre-reinforced poroviscoelastic material.

Analysis of Variance↗

PubMed2006

Objective measures as indicators for facial esthetics in white adolescents.

The objective of this study was to examine the contribution of objective measures representing anterior-posterior and vertical characteristics, dental esthetics, or their combination that are used in daily orthodontic practice in the assessment of facial esthetics. A panel of 78 laymen evaluated facial esthetics of 32 boys and 32 girls, stratified over the four Angle classes, on a visual analogue scale. The relation between the objective parameters and facial esthetics was evaluated by backward multiple regression analysis. Dental esthetics as expressed by the Aesthetic Component of the Index of Orthodontic Treatment Need (AC/IOTN) appeared to be the most important indicator for facial esthetics. A new parameter, the "horizontal sum" was found to be a reliable variable for the anterior-posterior characteristics of the patient. Addition of this newly defined parameter to the AC/IOTN improved the prognostic value from 25% to 31%.

Adolescent↗

PubMed2006

Fluid shear stress inhibits TNFalpha-induced osteocyte apoptosis.

Bone tissue can adapt to orthodontic load. Mechanosensing in bone is primarily a task for the osteocytes, which translate the canalicular flow resulting from bone loading into osteoclast and osteoblast recruiting signals. Apoptotic osteocytes attract osteoclasts, and inhibition of osteocyte apoptosis can therefore affect bone remodeling. Since TNF-alpha is a pro-inflammatory cytokine with apoptotic potency, and elevated levels are found in the gingival sulcus during orthodontic tooth movement, we investigated if mechanical loading by pulsating fluid flow affects TNF-alpha-induced apoptosis in chicken osteocytes, osteoblasts, and periosteal fibroblasts. During fluid stasis, TNF-alpha increased apoptosis by more than two-fold in both osteocytes and osteoblasts, but not in periosteal fibroblasts. One-hour pulsating fluid flow (0.70 +/- 0.30 Pa, 5 Hz) inhibited (-25%) TNF-alpha-induced apoptosis in osteocytes, but not in osteoblasts or periosteal fibroblasts, suggesting a key regulatory role for osteocyte apoptosis in bone remodeling after the application of an orthodontic load.

Adaptation, Physiological↗

PubMed2006

[Dissertations 25 years after date 9. How is tooth eruption regulated?].

A lot of attention has been paid to the questions of how and why teeth erupt. In the past many theories were developed, all of which showed mechanistic characteristics and suggested that a certain structure exerts force on the tooth germ to initiate its eruption. The dominant theory considered the collagenous fibres or the fibroblasts within the periodontal ligament to be the primary moving force in the eruption process. However, most research was done on continuously erupting incisors of rodents or lagomorphs, an experimental model with serious drawbacks. Because dogs, like humans, have teeth with limited eruption, 25 years ago research was carried out on tooth eruption in beagles. One of the most important conclusions of this study was that the periodontal ligament is not the primary moving force in tooth eruption, as its development only begins at the end of the eruption process. In subsequent years several others have focused their research on tooth eruption in beagles. The current state of knowledge in this field can be summarized as follows: the reduced enamel epithelium and the dental follicle control bone deposition and resorption around an erupting tooth germ, enabling its occlusal movement; the periodontal ligament develops only after its emergence in the oral cavity, and is thus not important in the eruption process; the tooth itself does not play a role in the regulation of its eruption.

Animals↗

PubMed2005

A measuring system for facial aesthetics in Caucasian adolescents: reproducibility and validity.

A new measuring system to judge facial aesthetics in young Caucasians is presented. The system uses sets of three photographs (one frontal, one three-quarter smiling, and one lateral) as a stimulus. Scores are performed on a visual analogue scale (VAS) with separate sets of reference photographs for girls and boys. The choice of the reference photographs was based on a panel evaluation of facial aesthetics of 40 boys and 40 girls from the archive of the orthodontic department. Reproducibility of the new measuring system was tested on a series of photographic sets (one frontal, one three-quarter smiling, and one lateral view) of 64 patients, using a panel of 78 adult laymen and 89 professionals. The panel members assessed these sets of photographs on a VAS, in relation to the reference sets. The system was shown to be reproducible. Although the intra-observer reproducibility was low, the reliability coefficient was excellent (Cronbach's alpha > or = 0.98). Validity was tested by comparing the scores on the new scales with those of the three-quarter smiling photographic views on an earlier published scale. The correlation between the ratings on the new measuring system and the earlier published scale was 0.82 for laymen and 0.77 for professionals. The new system is simple and flexible in its use, and reproducible and valid for assessing facial aesthetics in young Caucasians. The system can be used in further investigations on the evaluation of facial aesthetics.

Adolescent↗

PubMed2005

Myofibroblasts in palatal wound healing: prospects for the reduction of wound contraction after cleft palate repair.

The surgical closure of orofacial clefts is considered to impair maxillary growth and dento-alveolar development. Wound contraction and subsequent scar tissue formation, during healing of these surgical wounds, contribute largely to these growth disturbances. The potential to minimize wound contraction and subsequent scarring by clinical interventions depends on the surgeon's knowledge of the events responsible for these phenomena. Fibroblasts initiate wound contraction, but proto-myofibroblasts and mature myofibroblasts are by far the most important cells in this process. Myofibroblasts are characterized by their cytoskeleton, which contains alpha-smooth-muscle actin. Additionally, their contractile apparatus contains bundles of actin microfilaments and associated contractile proteins, such as non-muscle myosin. This contractile apparatus is thought to be the major force-generating element involved in wound contraction. After closure of the wound, the myofibroblasts disappear by apoptosis, and a less cellular scar is formed. A reduction of contraction and scarring might be obtained by inhibition of myofibroblast differentiation, stimulation of their de-differentiation, stimulation of myofibroblast apoptosis, or impairment of myofibroblast function. In this review, we will discuss all of these possibilities, which ultimately may lead to a better outcome of cleft palate surgery.

Animals↗

PubMed2004

Growth stimulation of mandibular condyles and femoral heads of newborn rats by IGF-I.

Primary and secondary cartilage differ in embryonic origin and are generally considered to have a different mode of growth. However, few experimental studies exist that directly compare the two types of cartilage and their growth regulation. The regulation of cartilage growth is a complex mechanism involving growth factors like insulin-like growth factor-I (IGF-I). The purpose of this study was to compare the growth of mandibular condyles of 4-day-old rats with that of femoral heads in vitro and to analyze the effects of IGF-I. Explants were cultured for up to 2 weeks with 0, 5, and 25 ng/ml IGF-1. Both, 5 and 25 ng/ml IGF-I significantly stimulated growth of the mandibular condyles while only 25 ng/ml IGF-I stimulated growth of the femoral heads. IGF-I increased glycosaminoglycan synthesis of both condylar and femoral cartilage. However, only the DNA synthesis of the mandibular condyles was significantly increased by IGF-I while that of the femoral heads was not affected. It is concluded that IGF-I stimulates growth of both secondary condylar cartilage and primary femoral cartilage. The mandibular condyle appears to be more sensitive to IGF-I than the femoral head, which may partly be due to the different developmental stage.

Animals↗

PubMed2004

Incidence and severity of root resorption in orthodontically moved premolars in dogs.

OBJECTIVES: To study treatment-related factors for external root resorption during orthodontic tooth movement. DESIGN: An experimental animal study. SETTING AND SAMPLE POPULATION: Department of Orthodontics and Oral Biology, University Medical Centre Nijmegen, The Netherlands. Twenty-four young adult beagle dogs. EXPERIMENTAL VARIABLE: Mandibular premolars were bodily moved with continuous or intermittent controlled orthodontic forces of 10, 25, 50, 100, or 200 cN according to standardized protocols. At different points in time histomorphometry was performed to determine the severity of root resorption. OUTCOME MEASURE: Prevalence of root resorptions, defined as microscopically visible resorption lacunae in the dentin. Severity of resorption was defined by the length, relative length, depth, and surface area of each resorption area. RESULTS: The incidence of root resorption increased with the duration of force application. After 14-17 weeks of force application root resorption was found at 94% of the root surfaces at pressure sides. The effect of force magnitude on the severity of root resorption was not statistically significant. The severity of root resorption was highly related to the force regimen. Continuous forces caused significantly more severe root resorption than intermittent forces. A strong correlation (0.60 < r < 0.68) was found between the amount of tooth movement and the severity of root resorption. CONCLUSIONS: Root resorption increases with the duration of force application. The more teeth are displaced, the more root resorption will occur. Intermittent forces cause less severe root resorption than continuous forces, and force magnitude is probably not decisive for root resorption.

Analysis of Variance↗

PubMed2003

Assessment of the value of anorganic bone additives in sinus floor augmentation: a review of clinical reports.

In order to objectively assess the value of anorganic bone additives in sinus floor augmentation, a review of the English literature till May 2002 was carried out. The studies or parts of studies had to include at the least two patients, with a follow-up of at least 3 months, whilst histomorphometric data ought to be available of biopsies taken from the core of the graft. Only 12 studies fulfilled these criteria. Firm conclusions could not be drawn because there were substantial differences in histomorphometric techniques, healing periods and ratio autogenous bone anorganic additives, but it seemed that autogenous bone without anorganic additives resulted in the highest amount of bone after a 4-6 months healing period, while hydroxyapatite and bovine bone mineral, used as a bone substitute, gave the lowest amount of bone. No correlation between bone volume and time of graft healing could be found. The consequences, however, for implant placement and survival are at present, not fully understood. A plea is made for systematic prospective clinical and experimental studies to assess the various bone additives and ratios of autogenous bone to bone additives in composite grafts analysed with an adequate histomorphometric technique. Part of this study was presented at the 15th ICOMS, Durban, South Africa, 19-24 May 2001.

Alveolar Ridge Augmentation↗

PubMed2003

Soft tissue reaction to microgrooved poly-L-lactic acid implants loaded with transforming growth factor beta(3).

In both normal and disturbed wound healing, the generation of large, contracting scars can raise serious functional and cosmetic problems. A possible strategy to minimize or avoid the generation of scar tissue surrounding an implant is to apply transforming growth factor-beta(3) (TGF-beta(3)) to the implant. TGF-beta(3) (0, 1, or 2.5 microg) was freeze-dried onto poly-L-lactic acid (PLA) microgrooved substrates (width, 10 microm; depth, 1 microm) and implanted subcutaneously on the backs of rats for 2 and 8 weeks. After sacrifice, implants and surrounding tissue were histologically processed. Light microscopic and histomorphometric evaluation of capsule thickness, capsule quality, and implant-tissue interface was performed. In addition, we stained for alpha-smooth muscle actin (SMA), collagen, and ED-1 (a monocyte-macrophage marker). All implants were surrounded by a fibrous capsule. Capsules of the implants loaded with 1 or 2.5 microg of TGF-beta(3) showed significantly higher capsule quality. This meant that capsules were more mature compared with implants without TGF-beta(3). However, no significant differences were found in terms of thickness of the capsules or quality of the interface. Finally, apparently significant differences were also found in the expression of alpha-SMA, when comparing the various growth factor concentrations at both implantation points. In conclusion, the use of microgrooved PLA substrates with TGF-beta(3) did not lead to an overall improvement of periimplant tissue healing.

Actins↗

PubMed2003

Age effect on orthodontic tooth movement in rats.

Orthodontic procedures seem to be more time-consuming in adults than in juveniles. This might be related to delay in the initial tissue response or to a slower turnover of the bone and periodontal ligament in adults. To study this problem, we studied orthodontic tooth movement in two groups of 30 rats, aged 6 wks and 9-12 mos, respectively. At one side of the maxilla, 3 molars together were moved mesially with a standardized orthodontic appliance delivering a force of 10 cN. The other side served as a control. The results showed a faster initial tooth movement in juvenile than in adult animals. However, once tooth movement had reached the linear phase, the rate of tooth movement was the same in both groups. The results indicate that, besides a delay in the onset of tooth movement in adult animals, tooth movement could be equally efficient in adults once it had started.

Aging↗

PubMed2002

Soft-tissue response to silicone and poly-L-lactic acid implants with a periodic or random surface micropattern.

Tissue reaction to biomaterials is dependent on properties such as surface topography. The aim of this study was to evaluate the tissue reaction around implants with different surface topographies. We made coin-shaped silicone and poly-L-lactic acid (PLLA) implants with double-sided parallel microgrooves (depth 1.0 microm; width 10.0 microm) and random roughness on a micrometer scale. The control implants were smooth. These implants were inserted into subcutaneous pockets created on the flanks of goats. After 1, 3, or 12 weeks, the goats were sacrificed and the implants retrieved and histologically processed. Light microscopic evaluation revealed the formation of fibrous tissue capsules around all implant materials. The PLLA did not visibly degrade during the study period. Histomorphometric analyses were performed on capsule thickness, capsule quality, and on the implant-tissue interface quality. Compared with the silicone implants, the capsules around the PLLA implants showed significantly better capsule quality. Compared to the smooth implants, the capsules around the microgrooved implants were thicker, but the capsules around the roughened implants were thinner. However, randomly roughened implant surfaces generally elicited a stronger and more prolonged inflammatory reaction compared to smooth and microgrooved implant surfaces. We conclude that the application of microgrooves or random surface roughness to polymer implants apparently does not have beneficial effects on peri-implant tissue healing.

Animals↗

PubMed2002

Soft tissue response to microtextured silicone and poly-L-lactic acid implants: fibronectin pre-coating vs. radio-frequency glow discharge treatment.

From in vitro studies it is known that a plasma-treatment can enhance cell spreading. Similar effects can be observed after pretreatment of the surface with a protein coating, to mediate cell adhesion. The aim of the current study was to evaluate the in vivo effects of these surface modifications, in a three-month experiment in a goat model. We made silicone and poly-L-lactic acid implants with double-sided parallel micro-grooves (depth 1.0 microm, width 10.0 microm), a random surface roughness, or a smooth surface. Implants either received a radio-frequency glow discharge (RFGD) treatment, a fibronectin (Fn) pre-coating, or no pre-treatment. Subsequently, they were inserted into subcutaneous pockets created on the flanks of goats for 1, 3 or 12 weeks. Histological analysis showed that a fibrous tissue capsule had formed around all implants. Histomorphometrical analysis was performed on capsule thickness, capsule quality and the implant-tissue interface quality. Fn-treated surfaces showed a considerable early inflammatory reaction. Besides this, RFGD treatment or Fn pre-coating did not further influence any of the measured parameters. In conclusion, pre-treatment of polymer implant surfaces with Fn or RFGD treatment did not significantly influence tissue reaction around implants with micro-grooved, roughened or smooth surfaces.

Animals↗

PubMed2002

The effect of bone anchoring and micro-grooves on the soft tissue reaction to implants.

Here we aimed to compare the tissue reaction to smooth and micro-grooved implants, at different implantation sites. We hypothesised that subperiosteally less mobility is to be expected between an implant and the surrounding tissue, which can lead to a more subdued tissue response. In addition, we hypothesised that a similar effect can be reached when substrata are equipped with micro-grooves. Poly-L-lactic acid smooth or micro-grooved surfaces (width 2 or 10 microm, depth 1 microm) were implanted subperiosteally on the frontal bone of the skull, or subcutaneously in the flanks of goats for 2, 4 and 12 weeks. After sacrifice, implants and surrounding tissue were histologically processed. Light microscopical and histomorphometrical evaluation of the histomorphometrical analyses, capsule thickness, capsule quality and implant-tissue interface was performed. In addition, we stained for alpha-smooth muscle actin. collagen and CD-68 expression. All implants were surrounded by a fibrous capsule. Capsules around subperiosteal implants were more matured than around subcutaneous implants. In time, capsule thickness significantly decreased around subperiosteal implants, but increased around subcutaneous implants. Also, nowhere differences were found in the presence of collagen or alpha-smooth muscle actin. The interfacial cells around all implants frequently showed staining for the monocyte-macrophage marker CD-68. We concluded that in this model, decreased mobility of an implant relative to the surrounding tissue did positively influence the peri-implant tissue response, but the applied surface topography did not.

Actins↗

PubMed2002

Effects of locally injected interferon-beta on palatal mucoperiosteal wound healing.

BACKGROUND: Wound contraction and scar formation in the palatal mucoperiosteum after cleft palate surgery impair maxillary growth. The aim of this study was to determine the effects of IFN-beta on palatal mucoperiosteal wound healing in growing rats. METHODS: Standardized wounds were made in the palatal mucoperiosteum of young rats. Either IFN-beta or vehicle were injected at the wound site between 4 and 29 days after wounding. The results were compared with control wounds. Tissue samples were collected at 8, 15, 30, and 60 days PW for biochemical and microscopic analysis. RESULTS: IFN-beta stimulated re-epithelialization but did not reduce the number of myofibroblasts or scar tissue formation. Surprisingly, the injection of vehicle alone delayed the healing process. CONCLUSION: IFN-beta might be suitable to stimulate re-epithelialization but it does not reduce scar tissue formation in rat palatal wound healing. The injection of agents into palatal wounds might severely impair the healing process.

Analysis of Variance↗

PubMed2002

Release of bioactive transforming growth factor beta(3) from microtextured polymer surfaces in vitro and in vivo.

Transforming growth factor beta(3) (TGF-beta(3)) has been under investigation with the objective of improving wound healing. Yet, little experimental knowledge exists about applications of TGF-beta(3) in implantology and tissue engineering. The aims of this study were to determine the release kinetics and bioactivity of TGF-beta(3) released from microtextured silicone and poly-L-lactic acid (PLA) surfaces in vitro and in vivo. We loaded surfaces with 100 ng of TGF-beta(3). An in vitro assay showed that TGF-beta(3) was released in a burstlike manner. Released TGF-beta(3) was capable of inhibiting the proliferation of mink lung epithelial cells, indicating that released TGF-beta(3) had remained at least partly active. Subsequently, an in vivo experiment (1 h-3 days) was performed with implants loaded with TGF-beta(3). In cryosections, TGF-beta(3) activity was assessed by an in situ bioassay. We found that active TGF-beta(3) was released for up to 24 h. Furthermore, released TGF-beta(3) could be detected up to 320 microm from the implant. On the basis of these observations, we conclude that TGF-beta(3) loaded onto microtextured polymer membranes remains functional when released in vitro and in vivo and, therefore, may represent an alternative for introducing a growth factor into a wound to achieve long-term and long-range biological effects.

Animals↗

PubMed2000

Incorporation of composite bone implants in the facial skeleton.

The purpose of this study was to evaluate the capacity of composite grafts consisting of either particulated cancellous or particulated cortical bone and anorganic bovine bone mineral (BBM) (Bio-Oss) to induce regeneration in standardized critical size bony defects overlying the frontal sinus. Four full thickness critical size bone defects were made in the frontal bone in each of 8 skeletally mature female goats. These defects were filled at random with composite cancellous bone/BBM grafts or composite cortical bone/BBM grafts. Control defects were not included but could be evaluated using data from a previous study in which the same experimental setting was used (Merkx et al. 1999a). Fluorochrome bone markers were injected subcutaneously 1 and 5 weeks after implantation, and 1 week before the animals were killed. Two animals were killed at 3, 6, 12 and 24 weeks after surgery respectively. The results were evaluated by histological means including fluorescence microscopy. In conclusion, composite grafts consisting of autogenous cancellous bone/BBM yield good results, combining the advantages of each material alone and reducing the disadvantages of each when used separately. Critical size defects in the maxillofacial area, overlying a paranasal sinus, filled with this material heal uneventfully within 12 weeks. Composite grafts consisting of cortical bone and BBM show less favorable results. These grafts induce osteoclasts, probably by the presence of non-functional BBM, resulting in resorption of the cortical bone chips.

Animals↗