Michel Dalstra - Academia.edu (original) (raw)

Papers by Michel Dalstra

Journal of Clinical Medicine, 2020

The aim of this cohort study was to quantify the morphological changes in the palatal cleft and t... more The aim of this cohort study was to quantify the morphological changes in the palatal cleft and true cleft areas with passive plate therapy using a new analysis method based on three-dimensional standardized reproducible landmarks. Forty-five casts of 15 consecutive patients with complete unilateral cleft lip and palate were laser scanned and investigated retrospectively. The landmarks and the coordinate system were defined, and the interrater and intrarater measurement errors were within 1.0 mm. The morphological changes of the cleft palate area after a period of 8 months of passive plate therapy without prior lip surgery are presented graphically. The median decrease in cleft width was 38.0% for the palatal cleft, whereas it was 44.5% for the true cleft. The width of the true and palatal cleft decreased significantly over a period of 8 months. The true cleft area decreased by 34.7% from a median of 185.4 mm2 (interquartile range, IQR = 151.5–220.1) to 121.1 mm2 (IQR = 100.2–144.6)...

The Angle Orthodontist, 2019

Objectives: To compare a fluorescence-aided identification technique (FIT) with a conventional li... more Objectives: To compare a fluorescence-aided identification technique (FIT) with a conventional light source (CLS) for removing composite during debonding of brackets with respect to time needed, composite remnants, and tooth substance loss. Materials and Methods: Twelve maxillary models with 10 bovine teeth each were digitally surface-scanned and metal brackets were bonded on each tooth with Opal Seal and Opal Bond. Two operators: an experienced orthodontist (A) and an undergraduate student (B) received six models each and were asked to remove the composite remnants with a tungsten carbide bur and Sof-Lex discs by both a conventional light source (CLS group, n = 3), and fluorescent inducing light (FIT group, n = 3). The time taken was recorded, and a postoperative scan was digitally superimposed on the preoperative scan to quantify number of teeth with composite remnants and volume and thickness of enamel loss and composite remnants. Chi-square test and independent t-tests were perf...

Advances in Experimental Medicine and Biology, 2001

It is a well-known fact that denser materials appear brighter in radiographic images than less de... more It is a well-known fact that denser materials appear brighter in radiographic images than less dense materials. The reason for this is that denser materials absorb more photons.

Skeletal Anchorage in Orthodontic Treatment of Class II Malocclusion, 2015

European Journal of Morphology, 2005

Bone remodelling has been associated with microdamage. The aim of this study was to investigate t... more Bone remodelling has been associated with microdamage. The aim of this study was to investigate the presence of microdamage in the alveolar bone and its potential role in the initiation of bone remodelling following the application of an orthodontic load. The three-dimensional morphology of the alveolar bone was investigated by means of high resolution micro-CT scanning. In 25, 3-month-old, male Danish land-race pigs, the alveolar bone around the lower right and left first molars was analysed. The right first molar was moved buccally with a force of 130 cN by means of a custom-made cantilever made of a TMA 0.017 6 0.025 inch wire. The left molar was left untreated. After 1, 2, 4, 7 and 15 days of treatment the regions containing the right and left molars were excised and en bloc stained in basic fuchsin and the presence of microdamage detected. Diffuse damage was present in the alveolar bone of both the treated and the untreated teeth on both sides. On the lingual sides, diffuse damage showed the same orientation as the periodontal fibres. Bone microcracks were also detected on both the treated and untreated teeth. On the buccal surfaces they where often observed in close proximity to scalloped resorption surfaces. After 1 day of treatment, the presence of microcracks on the buccal-treated side was particularly marked. To conclude, bone microdamage is present in porcine alveolar bone in form of both microcracks and diffuse damage, suggesting that microdamage-driven remodelling also occurs in the alveolar bone. The presence of bone microcracks in the direction of the orthodontic force at day 1 suggests that they could represent the first damage induced by the orthodontic load that has to be repaired.

Het is reeds menigmaal gezegd: "Promoveren doe je niet alleen!" Maar het is toch vaak pas bij het... more Het is reeds menigmaal gezegd: "Promoveren doe je niet alleen!" Maar het is toch vaak pas bij het schrijven van het dankwoord van het proefschrift, dat je dit ten volste realiseert en apprecieert. In de eerste plaats is daar mijn promotor Rik Huiskes. Beste Rik, ik ben jou erg dankbaar dat jij mij indertijd in staat hebt gesteld om na mijn afstuderen en militaire dienst terug te keren naar Nijmegen voor promotie onderzoek. Als leermeester had ik mij geen betere dan jou kunnen wensen. Jouw verblijf in Ann Arbor was voor mij zo in het laatste jaar van mijn onderzoek niet altijd even gemakkelijk, maar toch kon ik altijd rekenen op een vlotte en gedegen reactie op mijn manuscripten per fax. Juist nu ik binnenkort het honk ga verlaten, blijf ik jou beschouwen als mijn grote voorbeeld. Voor de geweldige werksfeer tekenden mijn collega-(oud-)promovendi: Leendert Blankevoort, Jan Herman Kuiper, Dorethé Mommersteeg, Margriet Mullender, Bert van Rietbergen, Nico Verdonschot en Harrie Weinans. Jongens, bedankt voor jullie bijdrage, zij het groot of klein. Ik zal jullie straks missen. Een deel van het werk voor Hoofdstuk I heb ik uitgevoerd bij het Biomekanisk Laboratorium van het Ortopoedisk Hospital van de Universiteit van Aarhus. Ik wil speciaal Anders Odgaard en Prof. Sneppen bedanken voor de fijne samenwerking. Voor het verkrijgen van de heupbeenderen voor de verschillende experimenten was ik aangewezen op de vakgroep Anatomie. Dank aan Prof. Kauer en zijn medewerkers, die behulpzaam zijn geweest bij het uitprepareren van de botten. De CT-scans konden worden gemaakt dankzij de faciliteiten van de afdeling Radiodiagnostiek. Ik wil bij deze Leon van Erning bedanken voor het extra werk dat ik hem hiermee bezorgde. Binnen de eigen gelederen gaat mijn dank uit naar Willem van de Wijdeven voor zijn technische assistentie bij de experimenten. Verder ben ik Huub Peeters en René van der Venne zeer erkentelijk voor hun hulp wanneer een computer het weer eens niet deed zoals ik wilde. Wie ik ook niet onvernoemd wil laten zijn de leden van de manuscriptcommissie. Ik wil Prof. Gabreëls, Prof. Grootenboer (Universiteit Twente), Dr. Jansen en Prof. van der Linden (Rijks Universiteit Limburg) bedanken voor het nemen van de moeite om in hun vrije tijd mijn werk te bestuderen. Tenslotte nog een woord aan al mijn vrienden. Ik realiseer mij dat ik jullie de afgelopen tijd niet de aandacht heb gegeven die jullie verdienen. Ik hoop dat wij de oude draad gauw weer op kunnen pakken. Chapter VI Differences in pelvic load transfer due to variations in acetabular cup design Chapter VII Towards a mechanically optimized acetabular cup? Summary and conclusion Samenvatting en conclusie Curriculum Vitae introduction to maximize a realistic representation of the material properties throughout the pelvic bone. Validation of this model was done by simulating an in vitro loading experiment and comparing the numerical and the experimental results. The model is then used in Chapter III to study the load transfer in a natural pelvic bone under normal loading. Using physiological data for the hip-joint force and the most important muscle forces, stress distributions throughout the pelvic bone are analyzed for several phases of a walking cycle. Chapter IV describes the mechanical consequences of the placement of an acetabular cup for the pelvic load transfer. The model is adjusted to account for both a relatively flexible and a relatively stiff acetabular reconstruction. The stress distributions in both implant and bone are investigated, as well as the changes in load transfer relative to the normal situation. One of the possibilities for acetabular reconstruction is fixation with screwed cups. The prestrcsses these cups generate upon insertion are important for the initial stability of the implant, yet no quantitative data on these stresses exists. Chapter V describes in vitro experiments in which these prestresses are determined for two different designs of screwed cups. The effect of the prestresses on the stress distributions due to normal loading are assessed as well. In Chapter VI the three-dimensional pelvic finite element model is used again, this time to study the influences of various design features of acetabular cups on the load transfer across the pelvic bone and on the stress distributions in the various materials. These design features include the presence of a metal backing, the use of bone cement and the thickness of the polyethylene liner. Finally, in Chapter VII, the model is used in combination with a numerical optimization procedure. By varying the local stiffness of the backing of an acetabular cup, this procedure searches for the most optimal design for a cup with regard to loading of the cement mantle and the subchondral bone.

The Angle Orthodontist, 2017

Objective: To evaluate the effect of diameter and orthodontic loading of a screw-type implantable... more Objective: To evaluate the effect of diameter and orthodontic loading of a screw-type implantable device on bone remodeling. Materials and Methods: Screw-shaped devices of four distinct diameters, 1.6, 2, 3, and 3.75 mm, were placed into edentulous sites in five skeletally mature beagle dogs (n = 14/dog) following premolar extraction. Using a split-mouth design, devices on one side were loaded using calibrated 2N coil springs. Epifluorescent bone labels were administered intravenous prior to sacrifice. Bone-implant sections (∼ 70 μm) were evaluated to quantify bone formation rate (BFR), and other histomorphometric variables were assessed in the implant supporting bone. Results: The mean BFR ranged from 10.93 percent per year to 38.91 percent per year. BFR in the bone adjacent to the device was lower for the loaded 1.6-mm screws when compared with the nonloaded 1.6-mm screws (P < .01) and the loaded 2.0-, 3.0-, and 3.75-mm diameter screws (P < .01). No significant differences i...

Chinese medical journal, 1999

To investigate the differences in bone interface between titanium and stainless steel pedicle scr... more To investigate the differences in bone interface between titanium and stainless steel pedicle screws in the lumbar spine. Eighteen adult mini-pigs that underwent total laminectomy, posterolateral spinal fusion (L4-L5) were randomly selected to receive stainless steel (9) or titanium pedicle screw devices (9). In both groups, the devices were CCD (Sofamore Danek) type with the same size and shape. The postoperative observation time was 3 months. Screws from L4 were harvested along their long axis of pedicle for histomorphometric study. Bone-screw interface and bone volume from thread were examined using linear intercept techniques. Mechanical testing (torsional test and pull-out test) was performed on the screws from L5. The titanium screw group had a significantly higher maximum torque (P < 0.05) and angle related stiffness (P < 0.05) measured by torsional test. In the pull-out tests, no differences were found between the two groups in relation to the maximum load, stiffness a...

Journal of Biomechanics, 1987

European Spine Journal, 2000

Bone, 1996

It is usually assumed that architectural and mechanical main directions are aligned in cancellous... more It is usually assumed that architectural and mechanical main directions are aligned in cancellous bone. but this has not been demonstrated experimentally. Architectural anisotropy (fabric) has almost exclusively been quantified using the mean intercept length (MIL) method'. Volume based anisotropy measures2-3 were introduced as an alternative to the MIL method, which may have theoretical shortcomings. The purpose of this study was 1) to examine the agreement between architectural and mechanical main directions, and 2) to compare architectural main directions determined by different fabric measures.

Developments in X-Ray Tomography V, 2006

In this study the structure of the adult human dentoalveolar process is examined using convention... more In this study the structure of the adult human dentoalveolar process is examined using conventional and synchrotron radiation-based microtomography (SRµCT). Mandibular and maxillary segments containing two to five adjacent teeth were harvested at autopsy from 49 adult donors. These segments were embedded in blocks of methylmetacrylate and scanned using a conventional table-top µCT-scanner at a pixel size and slice thickness of 35 µm. A few segments were also scanned at a synchrotron facility at an initial pixel size of 16.4 µm, which was binned by a factor 2 to result in an effective voxel size of almost 32.8 µm. The three-dimensional reconstructions revealed how intricately the teeth are supported by the alveolar bone. Furthermore, this support is highly inhomogeneous with respect to the buccal, mesial, lingual and distal quadrants. Reflecting their various degrees of mineralization, tissues like bone, dentine, enamel and cementum, could well be identified, especially in the scans made with SRµCT. Despite comparable voxel sizes, the reconstructed data-sets obtained with conventional µCT were less detailed and somewhat fuzzy in appearance compared to the data-sets of SRµCT. However, for quantification of macroscopical features like the thickness of the alveolar wall or the presence of dehiscences/fenestrations this seemed sufficient.

Parathyroid hormone induces formation of new cancellous bone with substantial mechanical strength... more Parathyroid hormone induces formation of new cancellous bone with substantial mechanical strength at a site where it had disappeared in old rats

European Journal of Endocrinology, 2002

OBJECTIVE: The present study addresses the question--can PTH induce formation of trabeculae in ar... more OBJECTIVE: The present study addresses the question--can PTH induce formation of trabeculae in areas where cancellous bone has disappeared? Two-year-old male rats were chosen, because in this aged animal model the distal femurs have almost no cancellous bone, and the marrow cavity has reached a substantial dimension. DESIGN: The rats were injected for 56 days with either PTH(1-34), 15 nmol/kg/day (62.5 microg/kg/day), or vehicle. METHODS: Transverse specimens, 2-mm high, were cut from the distal femoral metaphysis. Marrow cavity diameters and cancellous bone trabeculae were analysed by a micro-computerized tomography scanner. The cancellous bone within the cortical and endocortical rim of each specimen was submitted to a biomechanical compression test. Furthermore, the cancellous bone was studied by dynamic tetracycline labelling and histomorphometry. RESULTS: In the vehicle-injected group the trabecular bone volume was 0% (0-1.4), median (range). All PTH-injected rats had trabecula...

Journal of Biomechanics, 2008

Dentistry Journal

This review aims to discuss and illustrate various uses of cantilevers to solve multiple clinical... more This review aims to discuss and illustrate various uses of cantilevers to solve multiple clinical issues and prove their versatility. Cantilevers are commonly used in the segmented arch technique, and they can be designed to solve various clinical problems with highly predictable results. Its design and shape can modify the various combinations of vertical and horizontal forces. The novel trend is to combine cantilevers with skeletal anchorage. Cantilevers offer a very simple and statically determined force system. The advantage is the control over side effects, which normally occur on the anchor teeth and the occlusion. The disadvantages include possible side effects on the anchorage unit, when the anchorage is poorly controlled. The review highlights the clear benefits of cantilever use in complex corrections of single teeth, segments, and entire arch with a diminished effect on the dentition, also with the use of skeletal anchorage. With their simple and easily tailored design, t...

Materials

Intrusion with a three-piece arch is routinely achieved during orthodontic treatment. This study ... more Intrusion with a three-piece arch is routinely achieved during orthodontic treatment. This study aimed to experimentally determine how the cantilever design influences the generated force system. Both straight and arch-formed cantilever designs: tip-back (TB), flat curve (FC) deep curve (DC), and 3 mm and 6 mm high utility arch (UA3; UA6) were activated for 5 mm and 10 mm. Force systems were determined by a hexapod. Typodonts simulating a three piece-intrusion arch were scanned using an intraoral scanner (3Shape, TRIOS, Denmark) before (T0) and after (T1) the experiment and superimposed with Mimics software (Materialise, Leuven, Belgium). Data were analyzed. All straight designs displayed an extrusive force in the vertical plane, and all arch-formed an intrusive force. DC and TB showed a retrusive force in the sagittal plane and UA6 a protrusive. For the medial/lateral forces, DC and TB displayed a medial, and UA6 a lateral force. Configurations can be distinctively ranked from DC, ...

The Angle orthodontist, Jan 22, 2016

To evaluate three-dimensional (3D) condylar and mandibular growth in patients with juvenile idi... more To evaluate three-dimensional (3D) condylar and mandibular growth in patients with juvenile idiopathic arthritis (JIA) with unilateral temporomandibular joint involvement treated with a distraction splint. Cone-beam computed tomography (CBCT) scans were taken for 16 patients with JIA with unilateral TMJ involvement before treatment (T0) and 2 years after treatment (T1). All patients received orthopedic treatment with a distraction splint. Eleven patients without JIA who were undergoing orthodontic treatment without a functional appliance or Class II mechanics and who had taken CBCT scans before and after treatment, served as controls. Reconstructed 3D models of the mandibles at T0 and T1 were superimposed on stable structures. Intra- and intergroup growth differences in condylar and mandibular ramus modifications and growth vector direction of the mandibular ramus were evaluated. In all patients with JIA there were asymmetric condylar volume, distal and vertical condylar displ...

Orthodontics & Craniofacial Research, 2009

Authors-Cattaneo PM, Dalstra M, Melsen B Introduction-Orthodontic tooth movement (OTM) is achieve... more Authors-Cattaneo PM, Dalstra M, Melsen B 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 FEanalyzes 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 patientspecific, FE-analysis of orthodontic loading regime should not be based on general models.