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Biomedical subjects

M G Faulkner

Publications and source records attributed to M G Faulkner.

15 recordsLinked to original sources
PubMed2006

Predictive factors of vertical bone depth in the paramedian palate of adolescents.

OBJECTIVE: To determine whether a relationship exists between the vertical bone depth in the paramedian palate (PP) of growing patients and age, gender, and palatal morphology. Clinically detectable traits may decrease the need for further imaging prior to implant placement for orthodontic anchorage. MATERIALS AND METHODS: Cone beam computed tomagraphic scans (Newtom-9000, Verona, Italy) were acquired in 183 orthodontic patients (10-19 years old). Vertical bone depth was measured at nine unilateral locations in the PP of each subject. Measurements were analyzed with univariate and multivariate statistical tests. RESULTS: Significant variability in the bone thickness was found among locations and among subjects. Male subjects had significantly greater mean bone thickness in six of the nine locations measured, showing a mean of 1.22 mm more vertical bone than females showed at these locations. Age and palatal measurements did not demonstrate a clinically useful relationship with bone depth. CONCLUSIONS: Age and palatal morphology are not valid predictors of bone height in the PP. Because of the large variability of bone thickness in this region, computed tomographic imaging remains valuable prior to paramedian implant placement in growing individuals. The paramedian palate presents a promising region for palatal implant placements when the midpalatal suture is to be avoided.

Adolescent↗
PubMed2000

The friction and wear patterns of orthodontic brackets and archwires in the dry state.

Frictional resistance at the bracket-archwire interface has been demonstrated to impede tooth movement when sliding mechanics are used. Thus, the coefficients of friction of titanium and stainless steel brackets used in conjunction with stainless and ion-implanted beta-titanium archwires were investigated using a single contact interface between the brackets and archwires. The wear patterns between the brackets and the.016- in flat archwire surfaces were also examined using scanning electron microscopy and energy dispersive x-ray analysis. Stainless steel brackets tested with. 016-in flat stainless steel wire surfaces recorded the lowest coefficient of static friction mean (0.289), whereas titanium brackets paired with.016-in flat ion-implanted beta-titanium wire surfaces produced the highest mean (0.767). Stainless steel brackets had significantly (P <.05) lower coefficients of friction than titanium brackets for all wires except.020-in round stainless steel wires. Ion-implanted beta-titanium wires generally had significantly larger coefficients of friction than stainless steel wires. The increased friction of the titanium and ion-implanted beta-titanium alloys is also reflected in the severity of their wear patterns. An inverse relationship between friction and archwire surface dimension was generally found for ion-implanted beta-titanium wires. Round stainless steel wires demonstrated lower coefficients of kinetic friction than the flat stainless steel wire surfaces.

Analysis of Variance↗
PubMed1997

Three-dimensional effects in retraction appliance design.

The clinical importance of the three-dimensional effects of the force systems supplied by appliance designs used for retraction has long been appreciated. However, quantification of these force systems is not as well known. In this work, a numerical method is used to provide quantitative insight into three-dimensional effects for typical appliance designs. One problem that occurs clinically is the axial rotation of a single rooted tooth as a result of the forces being applied by the retraction device on the tooth's buccal surface. An out-of-plane preactivated bend can be used to counteract this rotation. The proposed numerical method can accurately determine the force systems resulting from this out-of-plane preactivation as well as the in-plane force systems. It is shown that the out-of-plane effects are independent of the in-plane behaviour so that the usual forces and moment to force ratios are maintained.

Elasticity↗
PubMed1996

Stroke normalized pressure: a useful parameter for the analysis of left ventricular outflow obstruction.

A new method of presenting the in vivo left ventricular pressure-flow data is developed in the present study. This separates left ventricle ejection into unrestricted, progressively restricted and severely restricted cases. This method uses ejection volume and time to define a normalizing 'stroke' pressure, which is successful in collapsing the large variability of in vivo data to a few curves with characteristic shapes, depending on the degree of obstruction. Hypertrophic cardiomyopathy is shown to fall into both unrestricted and progressively restricted categories. Normal hearts form the unrestricted case, while a severe aortic valvular stenosis is characteristic of the severely restricted case.

Aortic Valve Stenosis↗
PubMed1993

A comparison of various removable partial denture clasp materials and fabrication procedure for placing clasps on canine and premolar teeth.

There is no established protocol for selection among the different retentive material-attachment combinations for clasps other than tradition or laboratory preference. Various wrought-wire, cast-metal, and thermoplastic materials were subjected to several fabrication procedures and tested in a custom-designed force displacement apparatus. The wrought wires included ADA Spec. No. 7 type I and type II alloys and other precious and nonprecious alloys. A graphic means was devised to allow the rational selection of wrought-wire clasp-arm combinations for placing clasps on canine and premolar teeth. Guidelines for using straight wire data for curved wire applications are indicated.

Acrylic Resins↗
PubMed1992

Apparatus for the mechanical testing of maxillofacial prosthetic adhesives.

The use of adhesives to retain facial prosthesis remains controversial. This controversy arises in part from a lack of information on the biomechanical performance of this group of materials. No standard exists for maxillofacial prosthetic adhesives. This study describes the rationale for and design of an apparatus for testing maxillofacial and other skin adhesives. The apparatus provides for tensile, torsion, and combined tensile-torsion tests in a hard machine test. The results of the calibration studies of the apparatus are discussed.

Adhesiveness↗
PubMed1992

Mechanical behavior of three maxillofacial prosthetic adhesive systems: a pilot project.

The use of maxillofacial prosthetic adhesives remains controversial. A new machine for mechanical testing of adhesives was developed. This machine was used for in vivo testing of three adhesive systems to determine the adhesive joint strength of bonding silicone facial prosthetic elastomer to facial skin. Tensile, torsion, and combined tensile-torsion tests were carried out on two human subjects. The three adhesives tested were PSA1, Pros-Aide, and Dow Corning 355. All adhesives were applied according to the manufacturers' instructions. A 900 gm bonding load was applied for 20 seconds. The experimental design made use of two subjects, and the entire experiment was repeated on each subject. One test site on the cheek was used. Adhesive types were compared by means of the Student-Newman-Keuls method. Within the limitations of the design of this pilot study, the results showed that Dow Corning 355 adhesive was statistically significantly stronger than the other two adhesives evaluated by means of tensile and combined tensile-torsional tests. Although the results of the present pilot project are of interest, extrapolation to definitive conclusions of a clinical nature should be avoided.

Adhesives↗
PubMed1990

Large deformation analysis of orthodontic appliances.

The deformations of orthodontic appliances used for space closure are large so that any mathematical analysis will require a nonlinear approach. Existing incremental finite element and finite difference numerical methods suffer from excessive computational effort when analyzing these problems. An accurate segmental technique is proposed to handle these difficulties in an extremely efficient fashion. The segmental technique starts by assuming that an orthodontic appliance is composed of a number of smaller segments, the ends of which undergo small relative rotation. With an appropriate choice of local coordinate system the equilibrium equations for each segment are linearized and solved in a straightforward manner. The segments are then assembled using geometric and force compatibility relations similar to the transfer matrix method. Consequently, the original nonlinear boundary value problem is solved as a sequence of linear initial value problems which converge to the required boundary conditions. As only one segment need be considered at a time, the computations can be performed accurately and efficiently on a PC type computer. Although an iterative solution is used to match the boundary conditions, the time required to solve a given problem ranges from a few seconds to a couple of minutes depending on the initial geometric complexity. The accuracy of the segmental technique is verified by comparison with an exact solution for an initially curved cantilever beam with an end load. In addition, comparisons are made with existing experimental and numerical results as well as with a new set of experimental data. In all cases the segmental technique is in excellent agreement with the results of these other studies.

Equipment Design↗
PubMed1989

A parametric study of the force/moment systems produced by T-loop retraction springs.

This study considers the effects of several parameters on the force/moment systems produced by T-loop retraction springs. The springs are studied by using the finite element method and by experimentally measuring the forces and moments from the various designs. The results show that varying the spring height can produce larger moment to force ratios as the height increases. Changes in the preactivation bends result in unsymmetric moment characteristics and also produce large intrusive/extrusive forces. The addition of helices at the bends did little to alter the springs' mechanical characteristics.

Computer Simulation↗
PubMed1987

A three-dimensional investigation of temporomandibular joint loading.

A mathematical model of the muscle groups applied to the human mandible is developed to study the forces developed on the condyles during maximum unilateral occlusion. The results show that the reaction forces are in approximately a 2:1 ratio with the balancing side condyle carrying the greater load. Furthermore, the direction in which these condylar reactions occur is presented.

Biomechanical Phenomena↗
PubMedDate not supplied

Measuring abutment/implant joint integrity with the Periotest instrument.

Maintenance of the integrity of the abutment/implant interface is essential and is dependent on the abutment screw retaining a preload. Evaluation of this joint is usually done by manual assessment. The purpose of the current study was to determine whether the Periotest instrument could be used to evaluate abutment screw loosening. A custom-designed apparatus was constructed to measure abutment screw loosening. Abutment screws were torqued to 10, 20, 32, and 45 Ncm and then loosened. Objective assessment of screw loosening was carried out with the Periotest device. Subjective evaluation was done by 3 experienced clinicians. The Periotest was found to be more sensitive than manual detection of abutment screw loosening. With a change of 2 in the Periotest value, it was found that the tensile preload in the joint was lost. While the Periotest was more sensitive than manual evaluation, the instrument was not sensitive enough to indicate deterioration of abutment screw loosening prior to loss of tensile preload.

Dental Abutments↗
PubMedDate not supplied

The use and abuse of the Periotest for 2-piece implant/abutment systems.

While the Periotest continues to be used in assessing the integrity of implants, there are numerous reports of its inconsistencies. To understand more precisely what the Periotest is actually measuring, a mathematical model was developed that illustrates the effect that various geometric and clinical parameters have on the Periotest value (PTV). In addition, the model was validated with an in vitro experiment. Results of the mathematical model are shown to correlate with those obtained from the experimental test The PTV is very sensitive to the position at which the Periotest impacts the abutment and to angulation of the handpiece. It was shown that a change in position of 1 mm in striking height can produce a difference in PTV of between 1 and 2. Since the angulation of the handpiece can produce a difference in striking position of 2 mm, it must be controlled as well. The model also showed that the Periotest can detect changes in bone height of 0.5 mm.

Acceleration↗