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PubMed2004

Dynamic frictional behaviour of orthodontic archwires and brackets.

The aim of this study was to evaluate the frictional behaviour of 15 different archwires and 16 different brackets using small oscillating displacements when opposed to a standard stainless steel bracket or a standard stainless steel wire. Tests were run according to a pilot study at a frequency of 1 Hz and with a reciprocating tangential displacement of 200 microm, while the wire remained centred in the bracket slot under a load of 2 N. The results indicated a significant difference between the evaluated wires and brackets. The mean coefficient of friction (COF) of the wires varied from 0.16 for Imagination NiTi tooth-coloured wire to 0.69 for the True Chrome Resilient Purple wire, while for the brackets it ranged from 0.39 for Ultratrimm to 0.72 for the Master Series. The fact that in this study, a large number of different commercially available archwires and brackets were evaluated with the same apparatus according to the same protocol, allows a direct comparison of the different archwire and bracket combinations, and can assist in the choice of the optimal bracket-wire combination with regard to friction.

Analysis of Variance↗
PubMed1998

[Glassman palatine expansion. Experiences with mono- and bimaxillary dysgnathia operations].

The median palatine suture has long been regarded as having the greatest resistance to dilatation of the maxilla. In 1984 Glassman [3] presented a conservative-surgical method of division of the palatineal suture in which only the lateral and anterior support of the maxilla is debilitated surgically. An orthodontic apparatus cemented in place preoperatively is already used intraoperatively for dilatation of the maxilla. In the period from 1991 to 1997, 16 patients with a leptomaxilla and various dysnathic findings have been operated on at our clinic by the method described by Glassman. Sometimes the maxilla was dilated intraoperatively using the apparatus cemented in place by the method of Derichsweiler and dilatation was continued post-operatively until the described result was achieved. After successful dilatation of the maxilla and a stabilizing phase, a mono- or bimaxillary operation was performed. The use of this method led to the desired result in 15 patients. Dilatation of the maxilla was objectivized by determining the pre- and postoperative width of the anterior and posterior dental arch using models and X-ray of the occlusal overlay of the maxilla. In one patient who was operated on at the age of 38 years, a fracture of the alveolar process of the maxilla occurred unilaterally due to the completed ossification of the median palatine suture. The method of surgically aided dilatation of the maxilla at the level of Le Fort I plane is suitable for patients up to the age of 30. In older patients, the median palatine suture should be transsected as well.

Adult↗
PubMed1989

Reduction and fixation of jaw fractures using acrylic splints.

This paper proposes the criteria for application of acrylic splints in the treatment of various types of maxillofacial fractures. These were based mainly on the number of remaining teeth that are important for the restoration of occlusion. The acrylic splints studied consisted of intermaxillary, lingual and labiolingual types that hold a dental arch and a cap type that covers a dental arch. It was found that the intermaxillary type was best indicated for the loss of multiple teeth, the lingual type for the predicted intraversion of bone fragments and the labiolingual as well as cap types for the deciduous or mixed dentition. Clinical application based on the above standard, which was attempted in our 60 patients, produced successful results. In addition, the usefulness of these acrylic splints as an intraoral apparatus was discussed.

Acrylic Resins↗
PubMed2005

Asthma and the diver.

Self-contained underwater breathing apparatus (scuba) diving has grown in popularity, with nearly 9 million sport divers in the United States alone. Approximately 7% of the population has been diagnosed with asthma, which is similar to the percentage of divers admitting they have asthma. Numerous concerns exist regarding subjects with asthma who choose to participate in recreational diving. Among these concerns are pulmonary barotrauma, pneumomediastinum, pneumothorax, arterial gas embolism, ear barotrauma, sinus barotrauma, and dental barotrauma. Despite these concerns, a paucity of information exists linking asthma to increased risk of diving complications. However, it has long been the norm to discourage individuals with asthma from participating in recreational scuba diving. This article examines the currently available literature to allow for a more informed decision regarding the possible risks associated with diving and asthma. It examines the underlying physiological principles associated with diving, including Henry's law and Boyle's law, to provide a more intimate understanding on physiological changes occurring in the respiratory system under compressive stress. Finally, this article offers a framework for guiding the patient with asthma who is interested in scuba diving. Under the right circumstances, the patient with asthma can safely participate in recreational diving without apparent increased risk of an asthma-related event.

Asthma↗
PubMed1978

Scanning electron microscopy of epithelial cells grown on enamel, glass and implant materials.

The purpose of the present study was to examine with scanning electron microscopy gingival epithelial cells grown in cell culture on tooth enamel, glass, Vitallium, titanium and vitreous carbon. SGL (Smulow-Glickman) gingival epithelial cells were grown for 5 days and processed using a critical point drying apparatus. Scanning electron microscopy carried out at X 1500 magnification revealed that the gingival epithelial cells gres equally well on all materials on either smooth or rough (sand-blasted) surfaces.

Carbon↗
PubMed1996

Fate of demineralized freeze-dried bone allografts in human intrabony defects.

Demineralized freeze-dried bone (DFDBA) is the most widely used allograft in periodontics. Little information exists, however, on the fate of DFDBA matrix or on the effects of residual particles within grafted defects. The purpose of this study was to histologically examine the fate of DFDBA used for regeneration in intrabony defects. A secondary objective was to compare the amount of new attachment apparatus formation, including component tissues, in relation to the presence or absence of residual graft material. Histologic data were obtained from earlier studies in which intrabony defects grafted with DFDBA were removed at 6 months en bloc and submitted for histologic examination. Histologic sections (1,120) from 12 patients with 32 grafted defects revealed that 72% of the grafted defects exhibited residual DFDBA particles. When present, DFDBA appeared amalgamated within the new viable bone. Data from 5 patients with 14 grafted sites permitted a within-subject comparison of the amount of regeneration in relation to the presence or absence of residual graft material. Defects harboring residual graft particles exhibited significantly greater amounts of new attachment apparatus formation (1.72 mm vs. 0.20 mm), including new bone (2.33 mm vs. 0.23 mm), cementum (1.74 mm vs. 0.23 mm), and associated periodontal ligament than sites without evidence of graft matrix (P < or = 0.05). No apparent differences were seen in the nature of the new attachment apparatus or component tissues, other than in amount of formation. Inflammation and graft containment appear to be important factors influencing the fate of DFDBA and the regenerative response.

Alveolar Bone Loss↗
PubMed2002

[Early contributions for the development of nitrous oxide-oxygen anesthesia in central Europe].

The American dentist Horace Wells was the first to administer nitrous oxide for pain relief during painful tooth extractions. Since, however, an official demonstration of the pain-relieving properties of the gas at Massachusetts General Hospital in Boston ended in failure, use of the drug was abandoned. A few years later, Gardner Quincey Colton, a former coworker of Wells, took up Wells' idea to use nitrous oxide for pain relief and this was instrumental in its reintroduction into daily practice. Colton's publications on the advantageous use of nitrous oxide caused Stanislav Klikovitch from St. Petersburg, Russia, to administer the drug for pain relief during labour. In order to minimize the risk of asphyxia during the inhalation of the gas, he used an anaesthetic mixture consisting of 80% nitrous oxide and 20% oxygen. Moreover, it is to Klikovitch that we owe the first description of effective self-administration of nitrous oxide mixtures for pain relief. He recommended that inhalation should start 30-60 seconds before the expected pain and said between 2 and 6 inhalations would give the expected effect. Additionally, he suggested taking deep breaths and doing so at the beginning of subsequent pains. This is the first description of patient-controlled analgesia. Klikovitch reported his experiences with the new anaesthetic method in several German-language publications. Among those who were fascinated by his pain-relieving concept was Paul Zweifel from Leipzig, one of the leading obstetricians of his time in Germany. Together with numerous of his pupils, he popularized the method, using new apparatus for a safer kind of administration. Further technical developments in the early twenties, such as the introduction of the circle system or the clinical use of oxygen-monitoring devices, were additional milestones in nitrous oxide/oxygen anaesthesia.

Analgesia, Obstetrical↗
PubMedDate not supplied

[Stomatological amalgam mixer].

For preparing silver amalgam an amalgam mixer AC-01 has been constructed with a time relay. This is a table apparatus in whose body and oscillating movement mechanism with an electric drive and a time relay are arranged. Mixing the amalgam is done in capsules. The set is made up together with proportioners for mercury, powder and capsules for the preparation of the amalgam.

Dental Amalgam↗
PubMed1991

[Quantitative profilometric surface analyses to verify the accuracy of reproduction of elastic impression material].

The optical fine scanner RM 600 Laser Stylus (Rodenstock) allows in combination with the perthometer S 8P (mechanical scanner, Feinprüf/Perthen) a direct quantitative analysis of elastic impression materials. We verified with this apparatus the accuracy of surface reproduction of thirty-three various impression materials. The mean roughness values (Rz) of the originals and the reproductions showed no significant differences. This result suggests that all materials used have a high surface reproduction and they can be used unrestrictly.

Dental Impression Materials↗
PubMed2004

A clinical investigation of the morphological changes in the posterior mandible when implant-retained overdentures are used.

OBJECTIVES: The widespread use and broad acceptance of osseointegrated dental implants as a means of retaining and supporting mandibular overdentures provide potentially stable three-dimensional reference structures, which have been used to examine the morphological changes of the surface contours of the mandibular ridges distal to implants. Unlike traditional methods that tended to measure changes in ridge morphology and quantity radiographically, this prospective study investigated the changes in the sagittal surface contours of the posterior residual ridges over a 1-year period by an alternative, non-radiographic method using serial casts of residual ridges of a group of patients. MATERIAL AND METHODS: The residual ridges of the serial casts produced were examined using a profiling apparatus and computer software programs that allowed the orientation, digitised recording and measurement of the sagittal surface contours of the posterior residual ridges of mandibular casts in terms of area (cm(2)). RESULTS: Statistical analysis revealed that the detected reductive changes in the surface contour of the posterior residual ridges following the wearing of an implant-retained mandibular overdenture over a 1-year period were highly significant (P<0.001). CONCLUSION: It is concluded that the methodology presented in this study can be used reliably as an alternative to radiographical examination for detecting changes that occur in the distal residual alveolar ridges of the implant containing edentulous mandible when implant-retained overdentures are used. Thus, the method presented may be used to contribute to a reduced exposure to ionising radiation for patients wearing implant-retained overdentures.

Adult↗
PubMed2001

High-resolution immunocytochemistry of noncollagenous matrix proteins in rat mandibles processed with microwave irradiation.

The mineral phase in calcified tissues represents an additional factor to be considered during their preservation for ultrastructural analyses. Microwave (MW) irradiation has been shown to facilitate fixative penetration and to improve structural preservation and immunolabeling in a variety of soft tissues. The aim of the present study was to determine whether MW processing could offer similar advantages for hard tissues. Rat hemimandibles were immersed in 4% formaldehyde + 0.1% glutaraldehyde buffered with 0.1 M sodium cacodylate, pH 7.2, and exposed to MWs for three periods of 5 min at temperatures not exceeding 37C. They were then decalcified in 4.13% EDTA, pH 7.2, for 15 hr, also under MW irradiation. Osmicated and non-osmicated samples were dehydrated in graded concentrations of ethanol and embedded in LR White resin. Sections of incisor, molars, and alveolar bone were processed for postembedding colloidal gold immunolabeling using antibodies against ameloblastin, amelogenin, bone sialoprotein, or osteopontin. Ultrastructural preservation of tissues was in most cases comparable to that obtained by perfusion-fixation, and there was no difference in distribution of labeling with those previously reported for the antibodies used. However, the immunoreactivities obtained were generally more intense, particularly at early stages of tooth formation. Amelogenin was abundant between differentiating ameloblasts and labeling for osteopontin appeared over the Golgi apparatus of odontoblasts after initiation of dentine mineralization. We conclude that MW irradiation represents a simple method that can accelerate the processing of calcified tissues while yielding good structural preservation and antigen retention. (J Histochem Cytochem 49:1099-1109, 2001)

Amelogenin↗
PubMedDate not supplied

Evaluation of vertical accuracy of interocclusal records.

PURPOSE: The aim of this study was to evaluate four recording materials (polyether, polyvinyl siloxane, acrylic resin, and wax) for their ability to accurately record, maintain, and reproduce the vertical interocclusal relationship. MATERIALS AND METHODS: A metallic apparatus was used to represent the opposing arches; its epoxy resin duplicate represented the working casts. The vertical discrepancies produced because of the presence of the records were measured both after repositioning them on the metal apparatus and after transferring them onto the casts. Two-way ANOVA was performed. RESULTS: Closure through the interocclusal recording materials produced small vertical discrepancies ranging from 24 to 74 microm. When repositioned on the apparatus, the vertical discrepancies were greater. The lowest discrepancy was displayed by polyvinyl siloxane (101 microm) and polyether (107 microm), and the greatest was displayed by wax (168 microm). When records were transferred onto casts, the discrepancies were approximately 0.5 mm, without significant differences among materials. CONCLUSION: Closure through interocclusal recording materials and removal and repositioning of the records on the apparatus produced small vertical discrepancies with clinically insignificant differences between the materials tested. When records of all materials tested were transferred onto casts, vertical discrepancies of approximately 0.5 mm were found, which is of clinical concern.

Acrylic Resins↗
PubMed1989

[Measurement of orthodontic appliance force using prototype sensors].

In introductory remarks the most important biomechanical principles, which are relevant for the research, and conditions which must be satisfied presented in intraoral measuring of orthodontic forces were pointed out. First the aim of the research was defined, and then the investigation of mechanical properties of acrylics as a material for orthodontic appliances were carried out. The type of strain gauges, bonds and measuring system configurations, as well as measuring amplifiers and recording instruments were discussed. Some of measuring sensors, their principles and applicability were discussed. The calibration apparatus was modified for the sensor developed, and the calibration results were analysed by means of statistical methods (linear regression). The behaviour of all used sensors were found to be linear, which enables their application and reduces the measuring results interpretation.

Acrylic Resins↗
PubMed1979

Alveolar bone mass using 125I absorptiometry.

Small changes in alveolar bone mass are very difficult to detect using radiograms. A method is described for registering minute changes in bone mass in restricted parts of the jaw. The method is based on the use of collimated monenergetic radiation from 125I and replacement of the roentgen film by a non-image forming detector. As the apparatus also can be used for measuring the object thickness, the attenuation formula can be used for calculating the alveolar bone mass. The radiation dose can be kept an extremely low level and the reproducibility of the measurements is high. The technique therefore may be used for long-term studies of changes in alveolar bone mass. The alveolar bone mass responds rapidly to changes in the neighboring tissues. The reaction following gingivectomy or dental trauma is characterized by a significant loss of alveolar bone mass initially. After 4 weeks an increase in the alveolar bone mass is noted and found to continue during the subsequent months.

Absorptiometry, Photon↗
PubMed2000

Occlusal considerations in determining treatment prognosis.

To function in occlusal harmony, the masticatory apparatus--composed of the teeth and its supporting structures, temporomandibular joints, and associated neuromusculoskeletal structures--must operate in an integrated and dynamic manner. Loss of integrated function, or of homeostasis in response to functional demand, may generate problems in occlusion. In health, adaptive changes occur with the teeth and periodontium in response to functional occlusal forces. With periodontal and endodontic disease, this adaptive capacity diminishes. The ability to foresee how these changes may influence dental treatment is important in the art of determining treatment prognosis.

Adaptation, Physiological↗
PubMed1989

Ultrastructural and histochemical study of beta-tricalcium phosphate resorbing cells in periodontium of dogs.

beta-TCP was implanted in surgically prepared alveolar bone defects on the mesial side of the upper canine. The dogs that we used were sacrificed after 5 weeks, fixed by perfusion, and the beta-TCP resorbing cells were examined ultrastructurally and histochemically, with the following results: (1) beta-TCP was resorbed by macrophages and multinucleated giant cells. (2) Mitochondria, vacuoles and Golgi apparatus were abundant in beta-TCP-resorbing multinucleated giant cells that possessed neither ruffled borders nor clear zones. (3) The addition of tartric acid inhibited acid phosphatase activity in the cytoplasm of the multinucleated giant cells and macrophages.

Acid Phosphatase↗
PubMed1989

Histologic evaluation of new attachment apparatus formation in humans. Part I.

Part I of this three-part human study evaluated the formation of a new attachment apparatus (bone, cementum, and periodontal ligament) on pathologically exposed root surfaces in an open and closed environment. The most apical level of calculus on the root served as a histologic reference point to measure regeneration on root surfaces exposed to the oral environment. Attempts were made to initiate the formation of a new attachment apparatus by flap curettage, root planing, coronectomy, and submersion of vital roots beneath the mucosa. Nonsubmerged defects were treated by the same surgical technique and served as controls. Biopsies were obtained at 6 months and regeneration was evaluated histometrically by two investigators who were unaware of the treatment performed. Data from 9 patients with 25 submerged and 22 nonsubmerged defects were submitted for statistical analysis. Results indicate that a new attachment apparatus did not form in any of the 22 nonsubmerged teeth; a new attachment apparatus did form in a submerged environment (0.75 mm); significantly more new attachment apparatus (P less than 0.05), new cementum (P less than 0.01), new connective tissue (P less than 0.05), and new bone (P less than 0.02) formed in submerged defects; new cementum was cellular in nature and formed equally well on old cementum and dentin. Greater percent positive regeneration of the attachment apparatus and all component tissues occurred in submerged defects and no extensive root resorption, ankylosis, or pulp death was observed on submerged or nonsubmerged roots.

Analysis of Variance↗
PubMed1999

[Prevention of dental trauma].

Dental trauma is for people under 25 years of age a larger threat than caries and periodontal diseases. Protrusion of the upper front teeth in youth should therefore be corrected by orthodontic treatment. By doing contact-sports the use of the mouth guard is necessary. Since several different types are available, one has to make a correct choice specified by the kind of sport. The statement that it is more important to use an apparatus than just to own it sounds logically, but is often not followed in daily live.

Age Distribution↗