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Biomedical subjects

K E Glover

Publications and source records attributed to K E Glover.

14 recordsLinked to original sources
PubMed2001

Identification and structural characterization of nucleus-encoded transfer RNAs imported into wheat mitochondria.

Despite its large size (200-2400 kilobase pairs), the mitochondrial genome of angiosperms does not encode the minimal set of tRNAs required to support mitochondrial protein synthesis. Here we report the identification of cytosolic-like tRNAs in wheat mitochondria using a method involving quantitative hybridization to distinguish among three tRNA classes: (i) those encoded by mitochondrial DNA (mtDNA) and localized in mitochondria, (ii) those encoded by nuclear DNA and located in the cytosol, and (iii) those encoded by nuclear DNA and found in both the cytosol and mitochondria. The latter class comprises tRNA species that are considered to be imported into mitochondria to compensate for the deficiency of mtDNA-encoded tRNAs. In a comprehensive survey of the wheat mitochondrial tRNA population, we identified 14 such imported tRNAs, the structural characterization of which is presented here. These imported tRNAs complement 16 mtDNA-encoded tRNAs, for a total of at least 30 distinct tRNA species in wheat mitochondria. Considering differences in the set of mtDNA-encoded and imported tRNAs in the mitochondria of various land plants, the import system must be able to adapt relatively rapidly over evolutionary time with regard to the particular cytosolic-like tRNAs that are brought into mitochondria.

Base Sequence↗
PubMed2001

The effect of vertical and horizontal head positioning in panoramic radiography on mesiodistal tooth angulations.

The purposes of this study were to examine the effect of potentially common patient positioning errors in panoramic radiography on imaged mesiodistal tooth angulations and to compare these results with the imaged mesiodistal tooth angulations present at an idealized head position. A human skull served as the matrix into which a constructed typodont testing device was fixed according to anteroposterior and vertical cephalometric normals. The skull was then repeatedly imaged and repositioned five times at each of the following five head positions: ideal head position, 5 degrees right, 5 degrees left, 5 degrees up, and 5 degrees down. The images were scanned and digitized with custom software to determine the image mesiodistal tooth angulations. Results revealed that the majority of image angles from the five head positions were statistically significantly different than image angles from the idealized head position. Maxillary teeth were more sensitive to 5 degrees up/down head rotation, with 5 degrees up causing mesial projection and 5 degrees down causing distal projection of maxillary roots. Mandibular anterior teeth were more sensitive to 5 degrees right/left head rotation, with the projected mesiodistal angular difference between 5 degrees right and 5 degrees left rotation ranging from 4.0 degrees to 22.3 degrees. Maxillary teeth were relatively unaffected by 5 degrees right/left head rotation, and mandibular teeth were relatively unaffected by 5 degrees up/down head rotation. It was concluded that the clinical assessment of mesiodistal tooth angulation with panoramic radiography should be approached with extreme caution with an understanding of the inherent image distortions that can be further complicated by the potential for aberrant head positioning.

Cephalometry↗
PubMed2001

Factors that relate to treatment duration for patients with palatally impacted maxillary canines.

The objectives of this study were to determine the relationship between the initial position of a palatally impacted maxillary canine (as seen on a panoramic radiograph) and the duration of orthodontic treatment and to determine whether a difference in treatment duration existed between patients with bilateral palatally impacted canines and patients with unilateral impaction. A total of 47 adolescent subjects were chosen (9 subjects with unilateral impactions and 18 subjects with bilateral impactions). All subjects had full fixed orthodontic appliances placed. The treatment duration of this group was compared with that of a control group with similar characteristics but without the impacted canine. The results showed that the average duration of treatment was 22.4 months for the control group, 25.8 months for the unilateral-impacted group, and 32.3 months for the bilateral-impacted canine group. The length of treatment for the impacted canine sample was related to the age of the patient at the start of treatment; younger patients required a longer treatment. The younger the patient, the more severely impacted the canine. The bilateral-impacted canine group had at least 1 canine that was more severely impacted than the impacted canine in the unilateral-impacted group. If the canine was impacted less than 14 mm from the occlusal plane, treatment duration averaged 23.8 months; if the canine was impacted more than 14 mm from the occlusal plane, treatment duration averaged 31.1 months.

Adolescent↗
PubMed2000

Osseous morphology and spatial relationships of the temporomandibular joint: comparisons of normal and anterior disc positions.

The objective of this study was to determine differences in spatial relationships and osseous morphology between temporomandibular joints with normal and anterior disc positions. Magnetic resonance imaging was employed to determine disc position in 335 temporomandibular joints in 175 subjects (106 female and 69 male) between the ages of 7.27 years and 20.0 years (mean age: 13.08 years). Twelve tomographic variables were measured from preorthodontic tomograms of the same individuals. Tomographic data were cross-referenced with MRI data for those with normal and full anterior disc displacement. Independent sample t-tests revealed significant differences for all measures of joint space, condylar position, and morphology of the articular eminence (P < .05) between joints with normal disc position and with full anterior disc displacement. This study indicated that measures of joint space and eminence morphology might provide diagnostic information for the assessment of joint status in the adolescent population.

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↗
PubMed1999

Horizontal condylar angulation and condyle position associated with adolescent TMJ disk status.

The purpose of this research was to examine the relationship between horizontal condylar angulation and position and joint status in an adolescent population. Submentovertex (SMV) radiographs and MRI (magnetic resonance images) of 95 subjects (56 females and 39 males) between the ages of 10-17 years (mean age 13.3 years) were used for this study. Horizontal condylar angulation as well as A-P and transverse condyle position were determined in relation to a cranial base reference (a line formed between the two foramina spinosa) from SMV images. Joint status variables consisted of disk length and disk displacement measurements taken from medial, central and lateral sagittal MRI slices of each joint. Additional joint status variables were derived through a principal component analysis which was used to calculate a single disk length, disk displacement, and internal derangement variable for each joint. The results were: 1. No significant correlations (p = .05) were found between any of the joint status variables and horizontal condylar angulation; 2. Statistically significant correlations (r = .14 to .22, p = .05) were observed between certain joint status variables (anterior disk displacement in medial and central joint slices, disk displacement variable, and TMJ internal derangement variable) and transverse condyle position; and, 3. Statistically significant correlations (r = -.22 to .25; p = .05) were observed between condylar angulation and both A-P and transverse condyle position.

Adolescent↗
PubMed1998

Orthodontists' views of justification for cost of orthognathic surgery.

PURPOSE: This study evaluated whether orthodontists' treatment of patients was influenced by their perception of the justification for the cost of orthognathic surgery. MATERIALS AND METHODS: A survey of 334 Canadian orthodontists was used to determine what factors influenced views of cost justification. RESULTS: Approximately 80%, 49%, and 9% of orthodontists perceived cost of surgery to be justified for severely, moderately, and mildly compromised patients, respectively. Whether the compromise was functional or aesthetic did not particularly affect their views. Least experienced orthodontists were more likely than more experienced orthodontists to perceive cost of surgery as justified for patients with moderate functional compromise (P < .01). Most experienced orthodontists were more likely than less experienced orthodontists to perceive cost of surgery as unjustified for patients with moderate aesthetic compromise (P < .01). Orthodontists who did not believe cost of surgery to be justified for patients with mild or moderate compromise tended to recommend orthognathic surgery less frequently than camouflage orthodontics for borderline surgery patients (P < .05). CONCLUSIONS: The findings suggest that costs may be contained by orthodontists rationing surgery on the basis of severity of facial skeletal malrelationship and perception of justification of cost. Less experienced orthodontists are less likely to contain costs for patients with moderate functional and aesthetic compromise. Most experienced orthodontists are less likely to contain costs for patients with severe functional compromise. Patient satisfaction may be affected by rationing, which affects the treatment approach and thus the outcome.

Adult↗
PubMed1998

Landmark identification error in submentovertex cephalometrics. A computerized method for determining the condylar long axis.

The purpose of this study was to examine the identification error of certain submentovertex landmarks and to compare three different methods of determining horizontal condylar angulation in submentovertex radiographs. To determine landmark identification error, a random sampling of 12 submentovertex radiographs from preorthodontic patients between the ages of 10 and 17 years was used to determine both intraexaminer and interexaminer reliability. The error associated with the identification of each of 11 landmarks varied between specific landmarks, between the same landmarks bilaterally, and between the vertical and horizontal components of the same landmark. In general, intraexaminer data showed less landmark identification error in both vertical and horizontal directions than did interexaminer data. The foramen spinosum landmarks demonstrated the lowest identification error in both horizontal and vertical direction (intraexaminer), whereas greater identification error was associated with the condylar lateral poles and posterior condylar points (both intraexaminer and interexaminer). A comparison of three different methods of condylar angulation determination was undertaken through the use of two tracings of each of 101 submentovertex radiographs. A computer-derived method representing the principal axis of minimum moment of inertia of the condyle was shown to be more reliable (p < 0.05) with respect to describing condylar angulation than both a method that used a best-fit line through the anterior condylar border and an interpolar axis method.

Adolescent↗
PubMed1997

Mechanical and electrothermal debonding: effect on ceramic veneers and dental pulp.

This study compared the ability of three orthodontic debonding techniques for the removal of brackets from ceramic veneers without creating veneer damage. Three experimental groups included metal brackets debonded by either Howe pliers, lift off debonding instrument (LODI, 3M Unitek), or electrothermal debonder (ETD, "A" Company), as well as a group of electrothermally debonded ceramic brackets. It also evaluated and compared the intrapulpal temperature changes produced by electrothermal debonding metal and ceramic brackets. A sample of 95 extracted maxillary first premolars were prepared and restored with Mirage ceramic veneers (Chameleon Dental Products, Inc.). Veneer buccal surfaces were treated with 2.5% hydrofluoric acid, before silane application and bracket bonding with a no-mix resin. Specimens were thermocycled before debonding. All debonded specimens were examined under x20 magnification for veneer damage. A thermocouple was positioned at the pulp chamber buccal wall to record temperature increases (due to ETD activation) through a digital thermometer. Results suggest that ETD provides predictable debonding to ceramic brackets with no veneer damage and minimal risk to the pulp. Removal of metal brackets through electrothermal debonding produced ceramic damage in 13% of cases, and elevated temperatures beyond the threshold of irreversible pulpal damage (5.5 degrees C) in 46% of cases. Howe plier and LODI bracket removal are associated with ceramic damage incidence of 21% and 35%, respectively.

Analysis of Variance↗
PubMed1996

Stability of maxilla downgrafting after rigid or wire fixation.

PURPOSE: This article compares the long-term outcomes of rigid internal fixation with wire fixation. PATIENTS AND METHODS: In this retrospective study, nine cases of vertical midface augmentation in which rigid fixation was used were compared with 11 cases with wire fixation. One surgeon completed all cases for the rigid fixation group, and another surgeon completed the cases in the wire fixation group. RESULTS: Follow-up was 16 +/- 11 months for the rigid fixation group and 20 +/- 12 months for the wire fixation group. Inferior movement at the anterior portion of the maxilla was 7.0 +/- 2.9 mm with rigid fixation and 4.5 +/- 3.6 mm with wire fixation (P < .05). Postsurgical superior movement (relapse) was 0.4 +/- 0.4 mm with rigid fixation and 2.4 +/- 2.4 mm with wire fixation (P < .01). Inferior movement at the posterior maxilla was 3.1 +/- 0.2 mm with rigid fixation and 2.8 +/- 2.3 mm with wire fixation. Postsurgical superior movement (relapse) was 0.8 +/- 0.4 mm with rigid fixation and 0.5 +/- 2.3 mm with wire fixation, which was not significantly different. CONCLUSION: This comparison showed downgrafting of the maxilla using autogenous bone harvested from the iliac crest and rigid internal fixation to be a predictable and stable procedure.

Adolescent↗
PubMed1996

Effect of head orientation on posterior anterior cephalometric landmark identification.

This study examined the effect of head rotation about the vertical and transverse axes on posterior anterior cephalometric landmarks. Radiographs were taken on 25 skulls, first in a normal position, then in four positions each rotated 5 degrees from normal. The identification errors of 52 bilateral and midline landmarks were determined in the horizontal and vertical dimensions. The landmark identification errors for each of the five orientations were compared and those landmarks affected by 5 degrees rotation were identified. Landmarks with significantly larger identification error in a rotated position were: nasal cavity, mandible/occiput, foramen rotundum and orbitale. Best fit vertical and horizontal reference lines were determined, and the effect of head rotation on the choice of best fit reference lines was assessed. Rotation about the transverse axis did not affect the relationship of landmarks to the best vertical or horizontal lines. Rotation about the vertical axis did not affect the relationship of landmarks to the best horizontal line but did affect their relationship to the best vertical line.

Adult↗
PubMed1996

Orthodontists' perceptions of need for jaw surgery.

Treatment recommendations in borderline orthognathic surgery cases were examined for influence of orthodontists' traits and orthodontist's perceptions of patients', surgeons', and psychologists' traits. A mail questionnaire consisted of 23 case vignettes describing borderline surgical candidates with certain physical, psychological, attitudinal, and support system traits, as well as demographic and attitudinal items. The response rate from 512 licensed Canadian orthodontists was 65%. Seventy-four percent of orthodontists preferred camouflage for themselves. Recommendation of camouflage predominated in 12 of 23 vignettes and surgery in only four, although the cost of surgery was considered justified. Psychological referral was recommended highly for certain patients: those hoping to improve negative life events through positive facial change, those having low self-esteem, and those wanting to opl out of surgery in the middle of orthodontic treatment. Certain patient traits appeared to influence orthodontists' treatment recommendations. The availability, expertise, and receptiveness to case discussion of oral surgeons and psychologists did not influence orthodontists' treatment recommendations.

Adult↗
PubMed1994

Landmark identification error in posterior anterior cephalometrics.

This study was designed to quantify the intraexaminer and interexaminer reliability of 52 commonly used posterior anterior cephalometric landmarks. The horizontal and vertical identification errors were determined for a sample of 33 skulls and 25 patients. The results show that there is a considerable range in the magnitude of error with different horizontal and vertical values. Interexaminer landmark identification error was significantly larger than intraexaminer error for many landmarks. The identification error was different for the skull sample compared to the patient sample for a number of landmarks. The relevance of knowing the identification error for each landmark being considered in a particular application was discussed.

Adult↗