Biomedical subjects

P W Major

Publications and source records attributed to P W Major.

At least 19 recordsLinked to original sources

PubMed2006

Dental and skeletal changes following surgically assisted rapid maxillary expansion.

The aim of this study was to evaluate skeletal and dental changes after surgically assisted rapid maxillary expansion (SARME). Clinical trials were carried out that assessed skeletal and dental changes through cephalograms, computer tomographs or dental casts. No other simultaneous treatment during the active expansion period was accepted. Electronic databases (Pubmed, Medline, Medline In-Process & Other Non-Indexed Citations, All Evidence-based Medicine Reviews, Embase, Web of Science and Lilacs) were searched. Abstracts which appeared to fulfil the selection criteria were selected by consensus. The original articles were then retrieved and evaluated with a methodological checklist. Their references were hand searched for possible missing articles. Only 12 articles fulfilled the selection criteria. All presented methodological flaws. An individual methodological analysis of these articles was made. Expansion was greater at the molars and diminished progressively to the anterior part of the dental arch in all the evaluation periods. Vertical and sagittal skeletal changes were nil or not clinically significant. The nasal portion of the maxillary complex showed an increase in dimensions thereby improving nasal patency. An overall dental relapse of 0.5-1 mm is reported after 1 year of orthodontic treatment. The conclusions should be considered with caution because only a secondary level of evidence was found.

Cephalometry↗

PubMed2006

Mandibular kinematics associated with simulated low-velocity rear-end impacts.

Rear-end-impact motor vehicle accidents may result in cervical and temporomandibular-related pain complaints. Head kimematics in simulated low-impact rear-end impacts have been investigated but mandibular kinematics have not been described. Thirty healthy adult subjects underwent three impacts (4.5 m s(-2) expected, 10.0 m s(-2) unexpected, and 10.0 m s(-2) expected). Onset time and peak magnitude of angular head acceleration, angular mandibular acceleration and angular mandibular displacement were measured. Significant mandibular opening acceleration was not identified with rearward head rotation. The peak magnitude of mandibular closing angular acceleration approximately doubled with increased impact magnitude. No differences in peak angular mandibular acceleration regarding expectation were identified. Gender differences were detected in the fast unexpected impact. The peak time for the angular mandibular acceleration (mandibular closure) was approximately 84-120 ms later than peak rearward angular head acceleration for all impacts. Onset and peak times for angular mandibular acceleration (mandibular closure) were similar to the onset and peak times for forward head acceleration. There was also a positive correlation between the magnitude of the forward angular acceleration of the head and angular acceleration of the mandible for the slow (0.65, P = 0.015) and fast expected (0.844, P = 0.001) impacts. The average angular mandibular angular displacement (mandibular closure) was approximately 6 degrees . The hyperextension hypothesis regarding mechanism of temporomandibular joint injury in low-impact rear-end collisions cannot be supported.

Acceleration↗

PubMed2006

Prevalence of xerostomia in population-based samples: a systematic review.

The consequences of xerostomia on oral health have been studied for decades; however, the actual prevalence of this disorder on the general population remains controversial. The purpose of this systematic review was to determine the prevalence of xerostomia in population-based samples. Electronic databases were screened for relevant articles and reference lists of pertinent articles were also hand-searched. Thirteen articles meeting the final inclusion criteria were identified. Based on the definition of xerostomia used in this review, only publications including a subjective diagnosis of the disorder were included. All of the self-reported diagnoses were achieved through a questionnaire either by mail, telephone, interview or self-administered by the patient. There was a variation across papers regarding number and content of the questions as well as guidelines for the diagnosis of xerostomia (i.e. answer yes to one or more than one question). The prevalence of xerostomia in the selected articles ranged from 0.9% to 64.8%. The majority of these studies were performed in Scandinavia. In 9 of the articles, the studied samples were 50 years and older. None of the studies evaluated the prevalence xerostomia among individuals younger than 18 years. Based on these observations, it can be concluded that there is a need for population-based studies on prevalence of xerostomia in regions other than Scandinavia. A standardized protocol to diagnose xerostomia needs to be developed. Patient-perceived treatment needs and impact on quality of life should be included to have a complete picture of public health implications of the disease.

Age Distribution↗

PubMed2006

Density conversion factor determined using a cone-beam computed tomography unit NewTom QR-DVT 9000.

OBJECTIVE: The purpose of this study was to determine a conversion coefficient for Hounsfield Units (HU) to material density (g cm(-3)) obtained from cone-beam computed tomography (CBCT-NewTom QR-DVT 9000) data. METHODS: Six cylindrical models of materials with different densities were made and scanned using the NewTom QR-DVT 9000 Volume Scanner. The raw data were converted into DICOM format and analysed using Merge eFilm and AMIRA to determine the HU of different areas of the models. RESULTS: There was no significant difference (P = 0.846) between the HU given by each piece of software. A linear regression was performed using the density, rho (g cm(-3)), as the dependent variable in terms of the HU (H). The regression equation obtained was rho = 0.002H-0.381 with an R2 value of 0.986. The standard error of the estimation is 27.104 HU in the case of the Hounsfield Units and 0.064 g cm(-3) in the case of density. CONCLUSION: CBCT provides an effective option for determination of material density expressed as Hounsfield Units.

Humans↗

PubMed2005

Temporary loss of plasma membrane integrity in orthodontic tooth movement.

In these studies, a rat model of orthodontic tooth movement was used to support the premise that periodontal ligament (PDL) cells experience plasma membrane disruption and resealing events upon application of mechanical stress. Immunoelectron microscopy, showed albumin in the cytoplasm of PDL and bone lining cells in the tension side of moved molars. The intracellular localization of this large molecule (60 KDa) suggests that these cells have undergone plasma membrane disruption and resealing. To further assess these and previous findings, fluorescent dyes (FITC-dextran and rhodamine-dextran) were delivered into the vascular system followed by application of 50 g of static load. These large dextran molecules (10 KDa) were preferentially taken up by PDL cells of the buccal (tension side) of moved molars. These cells were determined to be viable since dead cells do not retain these diffusible tracers. These studies provide evidence of a novel cellular mechanism for uptake and release of molecules and suggest a potential role for plasma membrane disruption in the mechanotransduction of orthodontic tooth movement.

Animals↗

PubMed2004

Self-perceived orthodontic treatment need evaluated through 3 scales in a university population.

OBJECTIVE: To evaluate the self-perceived orthodontic treatment need in a university population evaluated through 3 scales that used different approaches. DESIGN: Cross-sectional survey. SETTING: University dental clinic, Lima, Peru, 2001. MATERIALS AND METHODS: Questionnaires that gathered perceptions on dentofacial aesthetic perception and orthodontic treatment need were applied to a randomly selected sample (329) of first year university students (729). Subjects undergoing orthodontic treatment at the time of examination were excluded. MAIN OUTCOME MEASURES: Aesthetic component (AC) of the Index of Orthodontic Treatment Need (IOTN), Oral Aesthetics Subjective Index Scale (OASIS) and a visual analogue scale (VAS) were used. STATISTICAL ANALYSIS: Descriptive statistics, Spearman correlation test, Kruskall-Wallis test and Mann-Whitney U-test were used. RESULTS: For the AC, 87.5% were in the "without treatment need" category, 10.6% in the "borderline need" category and 1.8% in the "treatment need" category. The mean AC score was 3.02 (+/-1.49). The mean OASIS score was 11.81 (+/-4.84), and the VAS score was 40.16 (+/-18.16). Correlations between the 3 self-assessment scales were moderate (AC-OASIS 0.416, AC-VAS 0.541 and OASIS-VAS 0.457). Gender or previous orthodontic treatment had no influence (p<0.05) on the scales. CONCLUSIONS: Differences in the approaches used by each scale to evaluate the self-perception of the aesthetical arrangement of the front teeth may explain the moderate correlation values.

Adolescent↗

PubMed2004

Lay person's perception of smile aesthetics in dental and facial views.

OBJECTIVE: To compare the aesthetic perception of different anterior visible occlusions in different facial and dental views (frontal view, lower facial third view and dental view) by lay persons. DESIGN: Cross-sectional survey, Lima, Peru, 2002. SUBJECTS: The different views were rated by 91 randomly selected adult lay persons. MAIN OUTCOME MEASUREMENT: Visual Analogue Scale (VAS) ratings of aesthetic perception of the views. RESULTS: Anterior visible occlusion, photographed subject and view (p<0.001) had a significant effect on the aesthetic ratings. Also gender (p=0.001) and the interaction between gender and level of education (p=0.046) had a significant effect over the aesthetic rating. CONCLUSIONS: A lay panel perceived that the aesthetic impact of the visible anterior occlusion was greater in a dental view compared with a full facial view. The anterior visible occlusion, photographed subject, view type are factors, which influence the aesthetic perception of smiles. In addition, gender and level of education had an influence.

Adolescent↗

PubMed2003

Prediction of mesiodistal canine and premolar tooth width in a sample of Peruvian adolescents.

OBJECTIVES: To compare the predicted tooth width measurements of permanent canine and premolars from Tanaka-Johnston regression equations and Moyers probability tables with the in situ measurements in a sample of Peruvian adolescents. DESIGN: Cross-sectional. SETTING AND SAMPLE POPULATION: Trujillo, Peru; 248 dental casts were measured using a sliding caliper with a Vernier scale rounded to 0.1 mm. RESULTS: Tanaka-Johnston regression equations were not precise, except for the upper arch in the male sample. For females, the Moyers 95th percentile in the upper arch and the 65th percentile in the lower arch predicted the sum precisely. For males, the Moyers 65th percentile for the lower arch predicted the sum precisely, but none of the Moyers percentiles provided precise prediction in the upper arch. CONCLUSIONS: Using tooth width prediction methods from a different racial origin could create an under- or overestimation of the actual combined canine and premolar tooth width, although their clinical significance is disputable.

Adolescent↗

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↗

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↗