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Introduction: Oral implants placed in the maxilla, especially the posterior region, have a lower success rate than those placed in the mandible. Poor bone quantity and quality have been suggested as a reason for this differential success rate. Objective: The purpose of this study was, therefore, to evaluate stress and strain distributions around loaded implants in the normal and atrophic maxilla by finite-element (FE) analyses. Material: FE models of a solitary implant were generated to determine stresses and strains in the bone adjacent to the implant surface under loading conditions. Study design: Different bony situations and implant lengths were used in a FE model. Static loads were applied axially and the resulting stresses and strains calculated. Results: Bone quality and quantity play a major role in decreasing bone strains adjacent to the implant surface under loading. It was found that stresses were more homogeneously distributed when more spongy bone was present. Decreased bone height was found to have less pronounced effects on strain and stress alterations than poor bone quality. Atrophic bony dimensions in combination with poor bone quality were associated with surface strains exceeding physiological levels (6000 microstrains). Conclusion: Our investigation indicates that supraphysiological bone strains adjacent to the implant surface should be expected under mechanical loading in the atrophic maxilla. Copyright 2001 European Association for Cranio-Maxillofacial Surgery.

Introduction In this study, we evaluated the pain and discomfort experienced by orthodontic patients by comparing how they rated the pain associated with microimplant placement, tooth extraction, and gingival tissue removal in preparation for implant placement. Methods Fifty-six microimplants were placed in 28 consecutive orthodontic patients for anchorage reinforcement in the maxilla for en-masse retraction. For all patients, extractions of maxillary, or maxillary and mandibular, premolars had been planned. The recruited patients were randomized into 2 groups according to the timing of the extractions. In group A, at least 1 extraction was performed during the evaluation period; the extractions in group B were after the evaluations. Furthermore, all patients had 2 different surgical procedures for placement. On 1 side, the gingival tissue was removed before placement. On the contralateral side, the implant was placed transgingivally. Each patient's perception of pain and discomfort was evaluated by a questionnaire before, immediately after, and 1 week after the intervention. Results The discomfort experienced during the extractions was described as very painful by 50% of the patients. It was significantly greater than during tissue removal and microimplant placement ( P P P Conclusions Microimplant surgery seems to be a well-accepted treatment option in orthodontic patients, with significantly lower pain levels than for tooth extractions. Furthermore, transgingival placement is clearly favored by patients who do not need tissue removed before placement.

The surface roughness of orthodontic archwires is an essential factor that determines the effectiveness of arch-guided tooth movement. Using the non-destructive techniques of atomic force microscopy (AFM) and of laser specular reflectance, the surface roughness of 11 nickel-titanium orthodontic wires, a stainless steel and a beta-titanium wire was measured. The results were compared with those obtained using surface profilometry. The smoothest wire, stainless steel, had an optical roughness of 0.10 micron, compared with 0.09 micron from AFM and 0.06 from profilometry. The surface roughness for the beta-titanium wire measured by all three methods was approximately 0.21 micron, while that of the NiTi wires ranged from 0.10 to 1.30 microns. As the surface roughness not only affects the effectiveness of sliding mechanics, but also the corrosion behaviour and the aesthetics of orthodontic components, the manufacturers of orthodontic wires should make an effort to improve the surface quality of their products.

Abutment angulation is one of the numerous biomechanical variables involved in implant dentistry that need scientific evaluation [Saab, 2007]. The aim of the present study was to investigate experimentally and numerically the influence of a fine threadedagainst a roughenedcervical region of immediately loaded dental implants in combination with straight and 20°angled abutments on the implant primary stability followed by a clinical validation of the results in a one year follow up study for immediately loaded and osseointegrated cases.

Unilateral and bilateral crossbites are a common malocclusion found in many orthodontic patients. One possible treatment method for a crossbite in the anterior dental arch uses a transpalatal arch (TPA) which is placed between the first molars of the upper jaw. It was the aim of this pilot study to simulate the biomechanical behaviour of 10 patients using a specialized experimental set-up as well as numerical methods and compare the results with the clinical outcome.

In recent years, Mini and Short dental implants became more and more popular as treatment alternatives in clinical cases with critical bony situations. So-called ‘Minis’ have a reduced diameter of about 2.5 mm and are designed to be inserted in the anterior region of the maxilla or mandible. Extremely short implants, called ‘Shorties’, have a length of 5 to 7 mm and are commonly used in the posterior region after severe bone atrophy. A profound scientific analysis of the mechanical and biomechanical impact of the reduced diameter and length of these implants has not been published yet. A combined experimental and numerical study was performed in order to determine whether ultimate dimensions with respect to length and diameter can be defined for dental implants.

In this study, we evaluated the pain and discomfort experienced by orthodontic patients by comparing how they rated pain associated with had microimplant placement, tooth extraction, and gingival tissue removal in preparation for implant placement.Fifty-six microimplants were placed in 28 consecutive orthodontic patients for anchorage reinforcement in the maxilla for en-masse retraction. For all patients, extractions of maxillary, or maxillary and mandibular, premolars had been planned. The recruited patients were randomized into 2 groups according to the timing of the extractions. In group A, at least 1 extraction was performed during the evaluation period; the extractions in group B were after the evaluations. Furthermore, all patients had 2 different surgical procedures for placement. On 1 side, the gingival tissue was removed before placement. On the contralateral side, the implant was placed transgingivally. Each patient's perception of pain and discomfort was evaluated by a questionnaire before, immediately after, and 1 week after the intervention.The discomfort experienced during the extractions was described as very painful by 50% of the patients. It was significantly greater than during tissue removal and microimplant placement (P0.05). Microimplant placement produced no pain in 30% of the patients and was described as the least painful procedure (P0.05). Transgingival microimplant placement was significantly preferred by all patients (P0.05).Microimplant surgery seems to be a well-accepted treatment option in orthodontic patients, with significantly lower pain levels than for tooth extractions. Furthermore, transgingival placement is clearly favored by patients who do not need tissue removed before placement.

An apparatus for the study of three-dimensional force systems and the resulting movements during orthodontic treatment is presented. The instrument consists of two force-torque transducers which are capable of recording both forces and torques simultaneously, in all spatial directions. Each sensor has a measuring range of 15N (450 Nmm) and a resolution of 0.02 N (0.5 Nmm) and is mounted on a set of three translational and three rotational stages driven by stepping motors. Positioning accuracy is in the range of 1 micron and 0.01 degrees respectively. The apparatus is computer controlled and supported by comprehensive software.

Aberration in the eruption process was found to be a prime etiologic factor in inducing impaction. Thus an ideal treatment approach should attempt to mimic the normal eruption modus. However, conventional traction methods have been found to be associated with gingiva inflammation, bone recession, reduced attached gingiva, periodontal pockets, exposed cementoenamel junction, and root resorption of the impacted and adjacent teeth. These side effects are the result of premature exposure of the impacted tooth to the oral cavity through a nonself-cleansing pathway and an uncontrolled force system. The present study introduces a new, magnetic attraction system, with a magnetic bracket bonded to an impacted tooth and an intraoral magnet linked to a Hawley type retainer. Vertical and horizontal magnetic brackets were designed, with the magnetic axis magnetized parallel and perpendicular to the base of the bracket, respectively. The vertical type is used for impacted incisors and canines, and the horizontal magnetic bracket is applied for impacted premolars and molars. A three-dimensional analysis of the magnetic force system, by means of the OMSS apparatus, found the small magnetic bracket combined with a large pole surface area of the intraoral magnet to exhibit the most efficient convergent guidance. For this report the magnetic eruption device was examined on one animal subject and four patients. The Nd2Fe14B magnets were coated with parylene and/or encapsulated in stainless steel housings. In deep impaction, the magnetic bracket was cold-sterilized before surgery, and the surgical mucoperiosteal flap was then sutured over the bonded magnetic bracket. Attraction was initiated 1 to 2 weeks after healing. Thus tooth emergence into the oral cavity replicated normal eruption conditioning. The system operated at an attractive force level of 0.2 to 0.5 N. Adjustment was accomplished by temporarily interposing a magnetic spacer between the two magnetic units. No side effects were observed in this restricted number of treated cases, and treatment time was reduced. The study recommends the application of magnets in the treatment of impaction on the grounds of less invasive surgical procedure, effective attractive forces at short distances, and controlled spatial guidance.

An orthodontic measurement and simulation system (OMSS) is introduced. The major component of the system consists of two force-moment sensors capable of measuring forces and moments in all three planes of space simultaneously. The two sensors are mounted on motor-driven positioning tables with full three-dimensional mobility. All mechanical components are built in a temperature-controlled chamber. A control programme executed by a personal computer performs various types of measurement which can be classified as absolute measurements (e.g. force-deflection diagrams) and simulations of orthodontic tooth movement. By using the OMSS any orthodontic problem at the level of a two-tooth model can be analysed statically and dynamically. Besides other applications, the study evaluates three mechanical systems available for uprighting molars, namely a straight wire, a conventional uprighting spring, and a modified Burstone uprighting spring. It was found that the force systems produced by the straight wire and by the conventional uprighting spring showed a severe extrusive force component which may lead to occlusal trauma. The uprighting performance of the straight wire was inadequate. The conventional uprighting spring produced a large uprighting moment (17.8 Nmm), but also a strong lingual tipping moment (1.5 Nmm). The modified Burstone loop showed the best static and dynamic performance. It produced a force system with substantial uprighting moments in both the sagittal (11.6 Nmm) and frontal plane (4.2 Nmm). A slight intrusive force (0.09 N) might prevent the development of occlusal trauma during treatment. However, concern should be addressed to the fact that intra-oral adjustment of this uprighting spring is difficult because of its high susceptibility to minor modifications of its geometry.

Implants of the types Ankylos® (DentsplyFriadent, Germany), Straumann® (Straumann, Switzerland) and Astra® (Astra Tech AB, Sweden) with different dimensions (diameters 3.5 to 4.5mm, lengths 9.5 to 12mm) were inserted into bovine rib segments. The specimens were loaded with occlusal forces of 50 to 100N in a opto-mechanical setup [Keilig, 2004], and the resulting deflections of the implants were registered. Subsequently the specimens were scanned using a μCT (μCT40, SCANCO Medical AG, Switzerland) and the geometry of each specimen was reconstructed three-dimensionally using a self-developed software (ADOR3D) [Rahimi, 2005]. The models were postedited using the remeshing options of the package 3Matic (Materialise, Belgium). The resulting models were imported into the FE package MSC.Marc/Mentat. The following material parameters were used: Young’s modulus of spongious bone 300MPa, cortical bone 20GPa, implant 110GPa, and Poisson’s ratio 0.3 for all materials. Simulation of the non-osseointegrated situation was realised by performing contact analyses.

A numerical model that calculates bone apposition and resorption around a tooth root on the basis of bone remodeling theories was developed to simulate orthodontic tooth movements. The model was used to calculate different kinds of orthodontic tooth movements, that were then compared with the expected movements based on clinical experience. For simulation of the movements the root of a canine was modeled in an idealized way in the form of an elliptical paraboloid and was processed with a finite element program. The finite element model was loaded with defined force systems. Two model assumptions were used to calculate the bone remodeling process. The mechanical loads firstly in the periodontal ligament and secondly in the alveolar bone were taken to simulate the following tooth movements: 1. mesial tipping around the center of resistance (force system at the bracket: isolated torque MY = 5 Nmm), 2. rotation around the long axis of the tooth (MZ = 5 Nmm), 3. uncontrolled tipping around the root tip (FX = 1 N, MZ = 5 Nmm), 4. canine retraction (FX = 1 N, MY = -9.5 Nmm, MZ = 5 Nmm), 5. and 6. extrusion/intrusion (FZ = +/- 0.5 N, MX = +/- 2.5 Nmm). Comparison with clinical experience was performed by calculating the orthodontic tooth movements based on the assumption of a fixed position of the center of resistance. It could be demonstrated that the numerical model of orthodontic bone remodeling can be used to calculate orthodontic tooth movements. However, the results are strongly dependent on the model assumptions. The model simulating the bone remodeling on the basis of the loading of the periodontal ligament delivers results that are in very good accordance with the biomechanical assumptions of the position of the center of resistance. However, marked side effects occurred with the second model, especially in the simulations of uncontrolled tipping, translation and intrusion/extrusion. Clinically, these side effects cannot be observed.

Guiding a tooth along an arch wire results in a counteracting frictional force. Clinically, a mesiodistally applied force must exceed the frictional force to produce a tooth movement. A friction-testing assembly simulating three-dimensional tooth rotations was constructed to study factors affecting friction magnitude. Five wire alloys (standard stainless steel, Hi-T stainless steel, Elgiloy blue, nitinol, and TMA) in five wire sizes (0.016, 0.016 x 0.022, 0.017 x 0.025, 0.018, and 0.018 x 0.025 inch) were examined with respect to three bracket widths (2.2, 3.3, and 4.2 mm) at four levels of retarding force (0, 1, 2, and 3 N). The following factors affected friction in decreasing order: retarding force (biologic resistance), surface roughness of wire, wire size (vertical dimension), bracket width, and elastic properties of wire. The study recommends the application of 0.016 x 0.022 inch stainless steel wire combined with a medium (3.3 mm) or wide (4.2 mm) bracket for an arch-guided mechanism with an 0.018 inch slot. The effective force of this arrangement has to increase twofold to overcome the friction. For TMA wire, however, the effective force must increase sixfold, resulting in a hazardous overload of the anchorage units.