Biomedical subjects

P W Major

Publications and source records attributed to P W Major.

At least 19 recordsLinked to original sources

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↗

PubMed2001

Evaluation of glucosamine sulfate compared to ibuprofen for the treatment of temporomandibular joint osteoarthritis: a randomized double blind controlled 3 month clinical trial.

OBJECTIVE: To compare the treatment potential of glucosamine sulfate (GS) and ibuprofen in patients diagnosed with temporomandibular joint (TMJ) osteoarthritis (OA). METHODS: Forty women and 5 men received either GS (500 mg tid) or ibuprofen (400 mg tid) for 90 days in a randomized double blind study. ASSESSMENT: TMJ pain with function, pain-free, and voluntary maximum mouth opening, Brief Pain Inventory (BPI) questionnaire and masticatory muscle tenderness were performed after a one week washout and at Day 90. Acetaminophen (500 mg) dispensed for breakthrough pain was counted every 30 days to Day 120. RESULTS: In total, 176 adults were interviewed, 45 (26%) qualified, 39 (87%) completed the study (21 GS, 18 ibuprofen). Four discontinued due to stomach upset (3 ibuprofen, one GS), one due to dizziness (GS), one due to inadequate pain control (ibuprofen). Within-group analysis revealed significant improvement compared to baseline of all variables in both treatment groups but no change in acetaminophen used. Fifteen GS (71%) and 11 ibuprofen (61%) improved, with positive clinical response taken as a 20% decrease in primary outcome (TMJ pain with function). The number of patients with positive clinical response was not statistically different between groups (p = 0.73). Between-group comparison revealed that patients taking GS had a significantly greater decrease in TMJ pain with function, effect of pain, and acetaminophen used between Day 90 and 120 compared with patients taking ibuprofen. CONCLUSION: GS and ibuprofen reduce pain levels in patients with TMJ degenerative joint disease. In the subgroup that met the initial efficacy criteria, GS had a significantly greater influence in reducing pain produced during function and effect of pain with daily activities. GS has a carryover effect.

Adult↗

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

Prevalence of TMJ disc displacement in a pre-orthodontic adolescent sample.

This study evaluated the prevalence of temporomandibular joint (TMJ) disc displacement in preorthodontic adolescents (75 boys, 119 girls) by means of magnetic resonance imaging (MRI). One hundred thirty-eight consecutive subjects were recruited regardless of TMJ signs or symptoms, whereas 56 other subjects were referred with associated signs or symptoms. Quantitative measurements of disc displacement and disc length were used to classify the degree of internal derangement into 6 categories on the basis of sagittal MRI slices of the joints. In addition, sideways disc displacement was determined from coronal MRI images of the joint. Unilateral and bilateral normal disc position was more prevalent in boys compared to girls. All forms of anterior and rotational disc displacement were more prevalent in the female sample than in the male. Sideways displacement was more prevalent in girls than boys and occurred more frequently in a lateral rather than a medial direction. This study supports previous studies in suggesting that disc displacements occur frequently in preorthodontic adolescents.

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↗

PubMed2000

Magnetic resonance imaging of the temporomandibular joint: interobserver agreement in subjective classification of disk status.

OBJECTIVES: To determine interobserver agreement in interpretation of magnetic resonance images of the temporomandibular joint by independent observers and to evaluate interobserver agreement within each subjectively assigned category. STUDY DESIGN: Sixty magnetic resonance images of adolescent temporomandibular joints were randomly drawn for evaluation by 4 observers who had not previously worked together. All observers independently classified disk position on sagittal magnetic resonance images according to written classification criteria consisting of 6 categories. RESULTS: Kappa statistics of agreement show moderate agreement among all observers for both medial (95% CI, 0.486-0.622) and lateral (95% CI, 0.450-0.566) components of the joint. Disk displacement without reduction was the category with the greatest agreement among all observers (kappa = 0.914). CONCLUSION: Moderate to substantial observer agreement across all defined categories of disk status may be achieved among a number of observers when standardized classification criteria are used. Interobserver agreement is, however, not uniform across all categories of disk position described.

Adolescent↗

PubMed1999

Female adolescent facial pattern associated with TMJ disk displacement and reduction in disk length: part I.

The aim of this study was to determine whether associations exist between temporomandibular joint (TMJ) disk displacement, and craniofacial morphology in an adolescent sample. Craniofacial lateral cephalometric radiographs and magnetic resonance images of the TMJs were obtained of 119 females between the ages of 10 and 17 years. Once the effects of age had been considered, associations between TMJ internal derangement and craniofacial morphology were studied in 5 facial regions making use of 5 separate multiple regression analyses. In females, associations between altered facial morphology and altered disk position were present within each of the facial regions investigated; the mandibular regions showed the strongest associations. This study shows that functional alteration in TMJ disk dynamics may be another factor to consider when craniofacial growth is forecasted for orthodontic treatment planning.

Adolescent↗

PubMed1999

Male adolescent facial pattern associated with TMJ disk displacement and reduction in disk length: Part II.

Dental practitioners continually strive to understand and determine which factors influence craniofacial morphology and how these factors may be controlled to provide the best treatment outcome for patients. Recently, an association between internal derangement of the TMJ and altered facial morphology was shown in an adolescent female sample by means of multiple regression techniques. The present study aims to determine whether similar associations are present between facial patterns exhibited by a preorthodontic male sample (n = 70) and varying degrees of TMJ internal derangement as assessed by magnetic resonance imaging. Multiple regression techniques were used to test the associations in 5 facial regions. Associations between internal derangement and craniofacial morphology differed in 3 of the facial regions when males and females were compared. However, associations between internal derangement and alteration in mandibular morphology and positioning were consistent in both gender groups.

Adolescent↗

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↗

PubMed1998

Interobserver reliability in quantitative MRI assessment of temporomandibular joint disk status.

OBJECTIVE: The purpose of this study was to investigate interobserver reliability of a new technique for quantification of magnetic resonance images of temporomandibular joint disk status. STUDY DESIGN: Sixty magnetic resonance images of adolescent temporomandibular joints were randomly drawn for analysis. Four experienced observers traced the articular disk and osseous structures on sagittal magnetic resonance slice images. Quantitative measurements of disk length and disk displacement were recorded for each slice of 57 joints traced by each observer through use of a new quantification technique. Intraclass correlation coefficients were computed to assess interobserver agreement in the tracing of joint structures. RESULTS: The calculated intraclass correlation coefficient was 0.681 for disk length and 0.830 for disk displacement. In addition, the mean variability among observers was 1.041 mm for measurement of disk length and 0.972 mm for measurement of disk displacement. CONCLUSIONS: Interobserver agreement is high when the new quantification technique is used to interpret magnetic resonance images.

Adolescent↗

PubMed1998

Quantitative assessment of temporomandibular joint disk status.

The purpose of this study was to quantify temporomandibular joint disk-slice information produced by magnetic resonance imaging by means of a stepwise discriminant analysis. One hundred ninety-four adolescents consented to magnetic resonance imaging evaluation of their temporomandibular joints. Sagittal magnetic resonance imaging slices of each joint were assigned to one of six subjective categories of disk position by an experienced maxillofacial radiologist. Standardized reference planes transferred to each magnetic resonance image from corresponding lateral cephalometric radiographics facilitated the measurement of disk length and disk displacement and the computation of ratio values of these measurements. Discriminant analysis revealed that all three quantitative variables were descriptive and discriminant for grouping slice data into pre-established subjective categories. Cross-validation and misclassification error calculations showed a 69.3% agreement between subjective and discriminant classification. Therefore quantification of disk displacement can be used in place of subjective evaluation. In addition, discriminant analysis disclosed a reduction in disk length associated with increased severity of disk displacement.

Adolescent↗

PubMed1998

Adolescent female craniofacial morphology associated with advanced bilateral TMJ disc displacement.

The aim of this study was to determine if cephalometric measurement differences occurred between two groups of similarly aged female adolescents which differed with respect to their diagnoses of temporomandibular joint disc position on magnetic resonance images (MRI). One group consisted of 17 female adolescents exhibiting complete bilateral disc displacement affecting the temporomandibular joints (TMJ), while the second group of 17 female adolescents was diagnosed as having bilateral normal disc position on MRI. Independent sample t-tests identified statistically significant differences in cephalometric measurements between the two groups, but no age difference between the two groups was evident. The group with bilateral total disc displacement exhibited the following significant angular differences from the group with normal disc position: an increased mandibular and palatal plane relative to sella-nasion; posterior rotation of the mandible as illustrated by an increased angle between the posterior border of the mandibular ramus and sella-nasion; and a decrease in Rickett's facial axis. Significant differences in linear cephalometric variables were also evident between the two groups. Total posterior facial height and ramus height were reduced in the totally disc displaced group. Furthermore, a slight increase in the middle anterior facial height was noted, with a decrease in the posterior cranial base vertical height in the totally disc displaced group.

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↗

PubMed1997

TMJ internal derangement and adolescent craniofacial morphology: a pilot study.

Intrinsic and extrinsic factors influence the growth of mandibular condylar cartilage. Local environmental factors, such as temporomandibular disc displacement, may alter condylar cartilage growth resulting in facial changes. The aim of this study was to determine if there was an association between identifiable altered craniofacial morphology and disc displacement. Magnetic resonance imaging (MRI) was employed to determine disc position in 25 preorthodontic adolescent patients (mean age 12.8 years, range 10 to 17 years). Magnetic resonance imaging and lateral cephalometric radiography were performed with the teeth held in centric occlusion by means of a polyvinylsiloxane bite registration. Radiographs were traced and variability between tracings within patients was insignificant for all variables (p > 0.04) except Co-Go, S-Go, and SN/Go-Me (p < 0.01). For each patient, 10 linear, 4 angular, and 3 ratio measurements were compared with an age- and sex-matched population in the Craniofacial Growth Series. Multiple regression analysis showed positive and negative associations between disc displacement and cephalometric variables. R-square value was .91 for the left TMJ and .82 for the right. Disc displacement in an adolescent population may be associated with altered craniofacial morphology.

Adolescent↗

PubMed1997

Use and effectiveness of splint appliance therapy: review of literature.

Interocclusal orthopedic appliances of varied design and application have been employed in the treatment of myofascial pain dysfunction (MPD) and temporomandibular joint disorders (TMD). These appliances provide the practitioner with a non-invasive, reversible form of intervention to manage the patient's symptoms. Literature on the use and effectiveness of these appliances has become readily available and now requires retrospective evaluation. However, comparison of results from studies making use of interocclusal orthopedic appliance therapy is difficult due to the employment of various outcome measurement scales, subjective evaluation of patient outcome, and variability in reporting of treatment outcomes. The aim of this paper is to review the effects and success rates of the various appliances reported in the literature and provide the practitioner with useful information that may be of assistance in the prediction of outcome and success of splint appliance therapy.

Electromyography↗

PubMed1996

Coupling electrical and mechanical outputs of human jaw muscles undertaking multidirectional bite-force tasks.

Previous studies have identified both linear and curvilinear relations between increasing bite-force magnitude and the integrated electromyogram (EMG) of jaw-closing muscles. In an attempt to explain the discrepancy, bite forces of incrementally increasing magnitude were produced on the right-hand side in five specified directions by eight humans. Linear regression lines were fitted to normalized EMG activities of the left and right masseter and temporalis muscles against increasing bite-force magnitude in each direction. The grand mean of linear correlation coefficients was 0.79 (+/- 0.11 SD), suggesting an overall linear relation. Each set of individual data was fitted with polynomial lines up to the third order. The best fit was selected by statistical significance of coefficients and the least-square analysis of the sum of residues for each fitted line; 62% of individual data-sets were best fitted with linear regression lines, 31% with quadratic lines and the remaining 7% with cubic lines. Repeated analysis of residue variance of the pooled data showed that either a linear or quadratic line fitted every data set except one, for which a cubic line had the best fit. Working-side muscles had significantly larger linear correlation coefficients than corresponding balancing-side muscles for most bite-force directions. Analysis of variance of linear correlation coefficients revealed that the degree of linearity often depended upon the roles played by a muscle in producing forces in different directions. It appears that linearity or non-linearity of the EMG force relation is a determinant, among other variables, of the direction of the resultant force.

Adult↗