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Biomedical subjects

J A Staggers

Publications and source records attributed to J A Staggers.

8 recordsLinked to original sources
PubMed1994

Vertical changes following first premolar extractions.

Orthodontic treatment involving the extraction of first premolars has been implicated in the dental literature as an etiologic factor in the development of temporomandibular joint (TMJ) disorders. Authors have proposed that the extraction of first premolars causes a decrease in the vertical dimension of occlusion. The purpose of this study was to investigate the validity of this claim. Records of 45 Class I, nonextraction cases and 38 Class I, first premolar extraction cases were obtained. The pretreatment and posttreatment cephalographs were digitized, and several cephalometric variables were examined to evaluate the vertical changes occurring as a result of orthodontic treatment. Statistical analysis of the data revealed no significant differences between the vertical changes occurring in the extraction and nonextraction groups. On average, orthodontic treatment in both groups produced an increase in the cephalometric vertical dimensions that were examined.

Adolescent↗
PubMed1993

The effects of sterilization on the tensile strength of orthodontic wires.

The purpose of this study was to evaluate the effect of sterilization on the tensile strength of 0.016" beta-titanium, nickel titanium and stainless steel wires. Three common methods of sterilization--autoclaving, dry heat and ethylene oxide--were evaluated in three test trials involving zero, one and five sterilization cycles. For each of the test trials, five pieces each of 0.016" TMA, 0.016" Sentalloy and 0.016" Tru-chrome stainless steel wires were sterilized using a standard autoclave. Five other pieces of each of the same wires were sterilized in a dryclave, while an additional five pieces of each of the three wire types were sterilized using ethylene oxide. The ultimate tensile strengths of the wires were then determined using an Instron Universal Testing Machine. The data were compared for statistical differences using analysis of variance. The results showed that dry heat sterilization significantly increased the tensile strength of TMA wires after one cycle, but not after five cycles. Autoclaving and ethylene oxide sterilization did not significantly alter the tensile strength of TMA wires. Dry heat and autoclave sterilization also significantly increased the tensile strength of Sentalloy wires, but the mean strength after five sterilization cycles was not significantly different than after one cycle. Ethylene oxide sterilization of Sentalloy wires did not significantly alter the tensile strengths of that wire. There were no significant differences in the tensile strengths of the stainless steel wires following zero, one or five cycles for any of the sterilization methods.

Humans↗
PubMed1992

Arch length considerations due to the curve of Spee: a mathematical model.

Arch length analysis should consider discrepancies not only within the sagittal plane but also within the vertical and transverse planes. The vertical deviation of the occlusal plane from a flat plane is known as the curve of Spee. The purpose of this study was to produce a mathematical model of the mandibular arch form in three planes of space and to determine the effect that the curve of Spee has on arch circumference. Two mandibular arch forms, the catenary and the Bonwill-Hawley, were examined. The curve of Spee was modeled as a cylinder perpendicular to the midsagittal plane centered on the arch anteroposteriorly. A mathematical distance formula was used to calculate arch circumferences from the central fossa of the first molars for 10 arches with curves of Spee ranging from 0 to 10 mm. This procedure was repeated for arch circumferences extending from the central fossa of the second molars. Plots for the difference in arch circumferences verses depth of the curve of Spee showed that the relationship between these two variables is not linear and is less than one to one. This model showed that clinical practice of allowing 1 mm of arch circumference for leveling each millimeter of curve of Spee overestimates the amount of arch circumference needed to flatten the curve of Spee.

Child↗
PubMed1992

A comparison of the effects of first premolar extractions on third molar angulation.

The effect of third molars on the stability of orthodontic treatment has been studied extensively. Yet the effect of orthodontic treatment, particularly premolar extractions, on third molars has not been substantially studied. The purpose of this investigation was to compare the changes in third molar angulation in patients treated with and without extractions. Records of 45 Class I, nonextraction and 33 Class I, first premolar extraction patients were examined. The pretreatment and posttreatment pantographs were digitized, and the angles between the third molar long axes and the occlusal plane were measured. Changes in third molar angulation from pretreatment to posttreatment for the two groups were compared for statistical differences using a Student's t-test. Statistical analysis revealed there were no significant differences in the change in third molar angulation in either group. On average, the maxillary and mandibular third molars showed an improvement in angulation relative to the occlusal plane. The results suggest that factors other than first premolar extractions may influence third molar angulation.

Adolescent↗
PubMed1990

A comparison of results of second molar and first premolar extraction treatment.

The purpose of this study was to examine treatment results of maxillary and mandibular second molar extraction cases and compare them with treatment results of maxillary and mandibular first-premolar extraction cases. Records of 22 maxillary and mandibular second-molar extraction cases and 22 maxillary and mandibular first-premolar extraction cases were evaluated. For each case, pretreatment and posttreatment lateral cephalograms were traced and several cephalometric parameters were compared. From the pretreatment and posttreatment panoramic radiographs, angulations of the maxillary and mandibular third molars were evaluated. Average treatment time, in months, was recorded for both groups. The data obtained from each group were analyzed for statistical difference. The results showed that the two groups had fewer differences than indicated by advocates of second-molar extractions. Analysis of the cephalometric data demonstrated only a few statistical differences between the groups. The maxillary and mandibular incisors in the premolar group were retracted a significantly greater amount than in the second-molar group. The maxillary and mandibular first molars were protracted a greater amount in the premolar group than in the second-molar group. The lower lips in the premolar group were retracted a greater amount than in the second-molar group. The resulting facial profile after extraction of second-molars appears to be no different from that obtained after extraction of first premolars. The pantographic evaluation of the changes in third-molar angulation were not statistically different. In both groups, the maxillary third molars showed an improvement in third-molar angulation, while the mandibular third-molars showed an undesirable increase in angulation. The average treatment time for both groups was not statistically different.

Adolescent↗