ABSTRACTS

THE FUNCTIONAL IMPACT
OF EXTRACTION AND
NON-EXTRACTION
TREATMENTS:
A LONG-TERM
COMPARISON IN
PATIENTS WITH
"BORDERLINE", EQUALLY
SUSCEPTIBLE CLASS II
MALOCCLUSION

John R. Beattie,
David E. Paquette and
Lysle E. Johnston Jr.

Discriminant analysis was used to identify in retrospect a sample of 63 patients who had presented initially with Class II malocclusions that, according to then prevailing standards of specialty practice, could have been treated either with or without the extraction of premolars. These "borderline" subjects (33 extraction, 30 non-extraction) were then recalled for a long-term evaluation (on average, about 14 years after treatment) of the functional status of both the head and the neck musculature and the temporomandibular joints. In terms of a menu of 62 signs and symptoms (muscle palpatation, joint function) that there are commonly thought to be characteristic of craniomandibular disorders, there were no significant differences between the extraction and non-extraction samples. The present data therefore fail to support the popular notion that "premolar extraction causes 'TMJ'".

Am J Orthod Dentofac Orthop
1994; 105: 444-9.

THE EFFECT OF TITANIUM
TETRAFLUORIDE (TiF₄)
APPLICATION AROUND
ORTHODONTIC BRACKETS

Tamer Büyükyilmaz,
Vivat Tangujsorn,
Bjørn Øgaard, Joop Arends,
Jan Ruben and Gunnar Rølla

In the present *in vivo* study, the cardiostatic potential of a titanium tetrafluoride (TiF₄) solution applied topically around orthodontic brackets was investigated with quantitative microradiography. Also characteristics of the TiF₄ treated enamel surface were examined with scanning electron microscopy (SEM). Ten pairs of premolars to be extracted for orthodontic treatment were used in the first part of this study. Brackets were bonded on all teeth with an orthodontic adhesive, and 10 randomly selected premolars served as controls, whereas a similar number were treated with 1% TiF₄ around brackets for 60 seconds. After 4 weeks with no topical fluoride supplementation, all teeth were extracted and stored for analysis. Results indicated the 1% TiF₄ solution reduced lesion depths and total mineral loss, at the bracket periphery, significantly during the 4-week period. The presence of a surface coating was demonstrated by SEM micrographs. It was concluded that TiF₄ may provide a high level performance as a prophylactic agent for orthodontic purposes.

Am J Orthod Dentofac Orthop
1994; 105: 293-6.

RISK FACTORS ASSOCIATED
WITH TEMPOROMANDIBULAR
JOINT SOUNDS IN CHILDREN
6 TO 12 YEARS OF AGE

Stephen D Keeling, Susan
McGorray, Timothy T Wheeler and
Gregory J King

The relationship between tempo-
romandibular joint (TMJ) sounds and a
person's dental and skeletal charac-
teristics is poorly understood. In this
study, data were obtained from 3428
grade school children (mean age = 9.0
years, SD = 0.8, range 6 to 12 years),
without a history of orthodontic treat-
ment. Each child had been examined
independently by one of six ortho-
dontists to assess: TMJ sounds (none,
click, crepitus), gender, age, race
(white/black), skeletal relations (con-
vexity, maxillary ad mandibular
positions), malocclusion (molar class,
overjet, overbite, anterior crowding,
posterior crossbite), maximum opening,
chin trauma (none, cut, scar) and
history of lower facial trauma. Temporo-
mandibular joint sounds were present in
344 children (10.0% of the sample); 276
(8.1%) had an isolated unilateral sound,
254 (7.4%) had unilateral clicking, 50
(1.5%) had bilateral clicking, 22 (0.6%)
had unilateral crepitus, and 11 (0.3%)
had bilateral creptius. Univariate
analyses compared children with and
without sounds for each variable;
logistic regression analyses examined
the relationship between groups of
variables and TMJ sounds. The preva-
lence of TMJ sounds was associated
with examiner (x² - 23.4, df = 5,
p<0.001); increased prevalence of TMJ
sounds occurred in children with
maxillary anterior crowding (t = 2.8,
p<0.006), mandibular anterior crowding
(t = 3.0, p < 0.002), and increased
maximum opening (t = 4.7, p > 0.001).
In contrast to other reports on children,
the prevalence of joint sounds was not
associated with age, race, gender, or
molar class. After accounting for
examiner differences and date of school
examination, we concluded that those
grade schoolchildren with larger
maximum opening, increased anterior
crowding, and deeper overbites had an
increased risk for having a TMJ sound.

Am J Orthod Dentofac Orthop
1994; 105: 279-87.
# ANATOMIC BASIS FOR DISK DISPLACEMENT IN TEMPOROMANDIBULAR JOINT (TMJ) DYSFUNCTION

Sasiwong Wongwatana,
Joseph H Kronman,
Ernest Clark, Sadru Kabani
and Noshir Mehta

This study was designed to investigate the site of lateral pterygoid muscle insertion into the temporomandibular joint (TMJ) disk, and the relationship between that attachment and the disk displacement. One hundred and ten TM joints from 78 cadavers were collected and sectioned in the sagittal plane. Sixty-two unilateral specimens were available and 16 additional specimens were selected randomly from the remaining cadavers in which both condyles were available. Thus statistical comparisons were not confounded by autocorrelation and were based on 78 independent specimens. The sites of muscle attachment in relation to the disk were identified histologically. Of the 78 joints, 49 had anterior disk displacement. In contrast, only 19 of the 36 disks without direction muscle insertion were displaced. This finding indicated a statistically significant relation between functional muscle attachment and disk displacement (x² = 9.28, df = 1, p = 0.006). However, the superior head of the lateral pterygoid muscle (SLP) may not be the precipitating factor for anterior disk displacement even though it does co-ordinate disk movement on closure. Since other factors (e.g. trauma) can result in disk displacement, the SLP can maintain disk displacement only when it inserts directly into the disk. In cases of normal disk displacement because disk attachment at the medial and lateral poles of the condyle allows the disk to move freely with the condyle. This movement of the condyle and the disk may overcome the pull of the SLP when normal disk attachment is maintained.

Am J Orthod Dentofac Orthop
1994; 105: 257-64.

# PROFILE ENHANCEMENT AND CEPHALOMETRIC LANDMARK IDENTIFICATION

HJ Burger, PE Rossouw
and I Stander

The reproducibility of two soft tissue landmarks (SN, V) and two anterior bony landmarks (A, ANS) was determined by three observers for three cephalometric techniques. The three techniques were aimed at soft tissue profile enhancement either by standard exposure control (technique 1), a handheld metal shield covering the profile (technique 2), or a brass wedge in the collimator (technique 3). For each technique, the sample was restricted to 20 subjects with a skeletal convexity greater than +4 mm. The four landmarks were identified three times with 7-day intervals between readings. The figure-of-merit (or mean radius) method was used to assess the probability of "hitting" a target (landmark) area. The mean radius from the sample mean point of impact (MPI) ranged from 0.585 mm to 1.758 mm. For a specific landmark, the difference was never greater than 0.5 mm when grouped by observer and technique. No technique excelled in overall consistency for the identification of anterior bony and soft tissue landmarks. Techniques 1 and 3 produced most consistent identification of points ANS and SN, but with no significant difference between the two techniques. Interacting factors prevented any recommendation regarding a preferential technique for the identification of points A and V. There is statistically no reason to recommend the use of a handheld, metal profile shield for more consistent landmark identification.

Am J Orthod Dentofac Orthop
1994; 105: 250-6

# THE VALIDITY OF THE PREDICTION OF SOFT TISSUE PROFILE CHANGES AFTER LEFORT I OSTEOTOMY USING THE DENTOFACIAL PLANNER (COMPUTER SOFTWARE)

Konstantina A Konstantos,
Maria T O'Reilly and John Close

The purpose of this study was to examine the validity of the prediction of soft tissue changes after LeFort I osteotomy with the DentoFacial Planner (DFP) (computer software). The preoperative and post-operative lateral cephalograms of 21 white adult orthodontic patients (10 males and 11 females) who underwent only LeFort I osteotomy as part of their overall treatment were digitized. A co-ordinate system of X and Y axes were used to assess the amount and direction of movement of the maxilla. The SN +7° was the X axis, and a perpendicular to this plane from nasion was the Y axis. The sample was divided into two groups depending on the amount of forward movement of the maxilla. More than 2 mm comprised the impaction group (8 patients). The selection criteria for the sample were (1) before and after cephalograms taken with lips in repose and in centric occlusion; (2) all preoperative records taken almost immediately before surgery; (3) postoperative records taken at least 6 months after surgery and checked by regional superimposition of the preoperative and post-operative lateral cephalograms onto the maxilla and the mandible. No tooth movement occurred between the time the records were taken. The following soft tissue landmarks were examined: pronasale, subnasale, stomion superior, middle upper lip, stomion inferior, middle lower lip, labrale inferior, labiomental fold, and pogonion. The results indicate that for some of these the actual surgical changes by LeFort I osteotomy. Differences between actual and predicted changes may be partially attributed to the variability of surgical procedures of previous studies that provided the data for the DFP computer software.

Am J Orthod Dentofac Orthop
1994; 105: 241-9.
MASTICATORY PERFORMANCE,
MUSCLE ACTIVITY AND
OCCLUSAL FORCE IN
PRE-ORTHOGNATHIC SURGERY
PATIENTS

Gregory S Tate,
Gaylord S Throckmorton,
Edward Ellis III and
Douglas P Sinn

Previous studies have indicated that patients scheduled for orthognathic surgery tend to have lower maximum bite forces and exert lower forces during mastication. The effect of these deficits on masticatory performance have not been previously assessed. Masticatory performance was analyzed in four groups: male and female orthognathic surgery patients prior to pre-surgical orthodontics (n = 12 and 23), and male and female controls (n = 27 and 31). Mastication performance was analyzed by having the subjects chew 5-g pieces of carrot for 20 cycles and measuring the resulting median particle size with a standard sieve method. Masticatory performance showed the same trends as maximum bite force and masticatory forces: male controls had the best and patients the poorest masticatory performance. There was a weak correlation between masticatory performance and maximum bite force at the molar positions. Masticatory performance also weakly correlated to electromyographic signals during mastication of a constant (gummy bears) for all muscles except the left posterior temporalis. Correlations were generally not present or were very weak between masticatory performance, estimated masticatory forces, and muscle efficiency, suggesting that muscle efficiency and forces generated during mastication are not the primary factors that determine masticatory performance. Other factors contributing to a person's ability to chew food might include occlusal relations and mechanical advantage.

J Oral Maxillofacial Surg
1994; 52: 476-81.

A 12-MONTH CLINICAL
EVALUATION OF A
LIGHT-ACTIVATED GLASS
POLYALKENOATE (IONOMER)
CEMENT FOR THE DIRECT
BONDING OF ORTHODONTIC
BRACKETS

John P Fricker

Glass polyalkenoate cements have the unique properties of physico-chemically bonding to enamel and base metals and to leach fluoride over prolonged periods. These cements have been modified to provide a dual setting with both light activation and chemical cure to produce a more rapid set. This article reports a 12-month clinical trial of a light activated glass polyalkenoate cement for the direct bonding of orthodontic brackets, compared with a standard composite bonding adhesive. There was no significant difference in failure rates of direct bonded orthodontic brackets cemented with Fuji II LC light-activated glass polyalkenoate cement (GC Industrial Co., Tokyo, Japan) (3.3%) compared with System 1+ composite bonding resin (Ormco Corp., Glendora, Calif.) (1.6%).

Am J Orthod Dentofac Orthop
1994; 105: 502-5.

COMPARATIVE STABILITY
STUDY OF WIRE
OSTEOSYNTHESIS VERSUS
RIGID FIXATION IN THE
TREATMENT OF CLASS III
DENTOSKELETAL
DEFORMITIES

Alessandro Silvestri,
Maurizio Ciaramelletti and
Giorgo Natali

The study analyzed two samples of 10 patients with Class III dentoskeletal deformities and maxillary and mandibular involvement. Surgery was performed on both jaws at the same time, using different techniques for the stabilization of bone. In one group, osteosynthesis by wire fixation was performed (WF); and in the other group, bicortical screws were used for the

mandible (RIF) and plates for the maxilla. At 20 and 40 days after the operation, radiocephalometric examinations were performed, and the differences in structural stability verified, by comparing the efficiency of the two methods of bone stabilization. Results indicate that in the post-operative period analyzed, dentoskeletal movements in the RIF group were inferior compared with the WF group. On the basis of these results, the advantages and the disadvantages offered by these two techniques of bone stabilization are analyzed.

Am J Orthod Dentofac Orthop
1994; 105: 477-82.

LONGITUDINAL CHANGES IN
THE ADULT FACIAL PROFILE

Walter A Formby, Ram S Nanda
and G. Frans Currier

Longitudinal growth changes in the adult craniofacial complex were studied for 24 white male and 23 white female subjects between the ages of 18 and 42 years who had Class I or end-to-end molar relations and no excessive protrusions or retrusions. The male profile straightened with age, and both lips became more retrusive. The males increased in all nose dimensions and in soft tissue thickness at pogonion, but decreased in upper lip thickness at labrale superius with a slight decrease in lower lip thickness at labrale inferius. The female profile did not become straighter with age, and the lips did not become more retrusive as with males. The females also increase in nose dimensions but decreased in soft tissue thickness at pogonion, decreased in upper lip thickness at labrale superius, and slightly increased in lower I lip thickness at labrale inferius. For males most changes in hard tissue measurements had been accomplished by age 25 years, whereas soft tissue changes in the nose, lips and chin occurred as much after age 25 years as from age 18 to 25 years than before. Those males how had high relative sagittal mandibular growth also experienced larger sagittal maxillary growth, and those who showed greater skeletal growth also had more soft tissue growth at the nose. The females also had good correlation between
sagittal growth in the mandible and the maxilla. Later maturing males had greater craniofacial skeletal growth in several dimensions.

Am J Orthod Dentofac Orthop
1994; 105: 464-76.

## OXYGEN TENSION REGULATES OSTEOBLAST FUNCTION

Orhan C Tuncay and
Melissa K Barker

Abrupt changes in oxygen availability within the periodontium have been suggested to have a regulatory role in alveolar bone remodelling during tooth movement; arguably, similar to that seen in bone growth or fracture healing. The purpose of this investigation was therefore to study the effects of ambient hypoxia and hyperoxia on osteoblast function in vitro. Osteoblast-enriched cultures from feral rat calvariae were exposed to atmospheres of hyperoxia (90% O₂) and hypoxia (10% O₂) and assayed for media pH, pO₂, pCO₂, cellular proliferation, alkaline phosphatase (AP) activity, and collagen synthesis. Results of this study who that in low ambient oxygen tension cellular proliferation increases, whereas the AP activity, collagen synthesis, media pO₂, pCO₂ decreases. In contrast, in hyperoxic conditions cellular proliferation is suppressed with concomitant increases in: AP activity, collagen synthesis, and partial pressures for oxygen and carbon dioxide. Media pH remained unaffected. In crossover experiments, where cells were initially grown in hypoxic conditions and were switched to hyperoxic conditions, their metabolic activities were abruptly reversed. These findings in conjunction with earlier reports, suggest a triggering role for oxygen tension (an environmental factor) in bone remodelling.

Am J Orthod Dentofac Orthop
1994; 105: 457-63.

## CLINICAL RAMIFICATIONS OF POSTERIOR AND ANTERIOR FACIAL HEIGHT CHANGES BETWEEN TREATED AND UNTREATED CLASS II SAMPLES

James L Vaden, Edward F Harris
and Peter M Sinclair

Some clinicians have suggested that one primary difference between successful and unsuccessful Class II treatment outcomes is the relative change of anterior and posterior facial heights. Successfully treated cases are claimed to exhibit greater increases in posterior facial height (PFH, articulare to gonion) than in the anterior facial height (AFH, menton to palatal plane). This conjecture was tested here by recalling a treated Class I sample and a treated Class II sample and by comparing the differences found in these samples to an untreated Class II sample at the same ages. The PFH/AFH ratio increased significantly more in the treated Class I and Class II samples during the active phase of treatment than in the untreated Class II sample at the same ages. During the years from post-treatment to recall (mean = 6 yrs), there was a significant increase in the PFH/AFH ratio in the treated Class II sample due to a greater increase in PFH than AFH. This ratio continued to improve after all appliance therapy had been discontinued, and it did not occur in the treated Class I sample nor in the untreated Class II sample. The conclusion was that the patient with a Class II malocclusion, if treated, continues to change favorably over time. This favorable change, in turn, helps maintain the Class II correction.

Am J Orthod Dentofac Orthop
1994; 105: 438-43.

## A PRELIMINARY COMPARISON OF THE DPB'S GRADING OF COMPLETED ORTHODONTIC CASES WITH THE PAR INDEX

Elizabeth A Turbill,
Stephen Richmond and
Mary Andrews

The PAR (Peer Assessment Rating) Index was compared to the grading system currently in use for completed orthodontic cases at the Dental Practice Board of England and Wales. Forty completed cases were graded by the two systems, which were compared for their intra- and inter-examiner reliability, as well as for their agreement and disparity in judging outcomes of cases. The implications of the results on the monitoring of standards in the General Dental Services are discussed.

Brit Journ Orthod
1994; 21: 279-85.

## EXTRACRANIAL VERSUS INTRACRANIAL REFERENCES IN INDIVIDUAL CEPHALOMETRIC ANALYSIS

### Murat Ozbek and Aysegul Koklu

This study was undertaken to determine whether angles SNA and ANB genuinely represent both the degree of maxillary prognathism and the intermaxillary relation in natural head position (NHP). Pearson's r correlation co-efficients were used to assess the associations between these angles, and variables based on NHP and extracranial reference lines. A large sample (n - 106) was used, comprising subjects with a variety of facial patterns. This was also divided into subgroups comprising subjects with similar facial configurations, determined by natural head position parameters.

For the subgroups, SNA and ANB were not associated with the variables based on NHP and showed high variations in subjects with similar facial patterns. SNA also showed statistically significant and high correlation with the inclination of the NSL to the true vertical.

Brit Journ Orthod
1994; 21: 259-63.