Mandibular lateral side-shift and the need for gnathologic instrumentation

FUNCTION

CRANIOMANDIBULAR SECTION

AND DYSFUNCTION

EDITOR

GEORGE

A. ZARB

Mandibular pathologic Jerry Kenison University

lateral side-shift instrumentation

and the need for

Hart, D.D.S., M.S.,* and Joseph S. Sakumura,

of Missouri,

School

of Dentistry,

Kansas

City,

Ph.D.+*

MO.

C

omplete gnathologic instrumentation was originally devised to replicate human jaw movement and assist the dentist in restoring occlusion. As used in this article, the term complete gnathologic instrumentation includes both pantographic (recording) and adjustable articulator (playback) instrumentation. This approach is thought to result in a more accurate occlusion, which does not require extensive clinical occlusal correction. Although complete gnathologic instrumentation is widely used, controversy surrounds its time efficiency. Because of the time-efficiency controversy, one of us (JKH) believes that any systematic approach to occlusal rehabilitation requires quantification of (1) the range and directions of human jaw movement, (2) the effect of these movements on the occlusion, and (3) establishment of a minimum criterion for the occlusion attributable to each jaw movement. The minimum criterion would indicate time-efficient use of complete gnathologic instrumentation to attenuate occlusal error. Perhaps errors smaller than the minimum criterion are best managed by approximation on an adjustable articulator and/or clinical adjustment of the occlusion at the time of insertion. Although the focus of this study was on the immediate side-shift of the human mandible, it also included lateral displacement caused by an early or distributed type of progressive side-shift.’ The term lateral side shift (LSS) was selected as a more accurate description of the phenomenon under study because it focuses on that part of lateral mandibular excursions where tooth-to-tooth contact is more likely to occur. The specific purpose of this study was to quantify in a given population the effect of the mandibular LSS on posterior occlusion. Findings were compared with a criterion of 0.25 mm, which was an estimate as to when it would be time efficient to use complete gnathologic instrumentation techniques.

limited to (1) patient studies and/or personal opinions describing movements of the human jaw, (2) the subjective usefulness of this instrumentation, and (3) technique.‘.” Various movements of the human jaw and the gnathologic instrumentation used to record and reproduce these movements have been described.“-‘* One of the more notable efforts was Weinberg’s attempt to identify and describe human jaw movements and their simulation through gnathologic instrumentation; he also categorized the various gnathologic jaw movements and addressed his rationale in applying gnathologic instrumentation. Usefulness of the face-bow has also been evaluated.5.” However, the articles did not discuss the quantitative effect of the various gnathologic movements of the human mandible on the occlusion. Furthermore, quantification of the occlusal error controlled by use of such instrumentation was not discussed. Similar omission was noted in Lazzari’s’ study, which expressed personal opinions and listed advantages for using the face-bow in gnathologic instrumentation. The advantages reported, however, were not quantified in the occlusion or substantiated by evidence. Extensive literature exists concerning gnathologic techniques. The manual supplied with the Denar (Denar Corp., Anaheim, Calif.) pantograph and articulator* and Bauer’s9 text are good examples. However, neither these nor similar materials aid the dentist in making selective choices regarding the most time-efficient and product-effective applications of gnathologic instrumentation. Arstad” alluded to the need to quantify his work by such statements as “an error of 5 mm from the hinge-axis results in an error of 0.2 mm in the articulator.” Although Arstad’s attempt at quantification of gnathologic movements and instrumentation effects on occlusion is commendable, it was limited and should have been extended to be meaningful to the dentist.

REVIEW

MATERIAL AND METHODS Sample population

OF LITERATURE

The literature review revealed that current information on gnathology and gnathologic instrumentation was

*Associate

Professor,

and Director

of Preclinical

Fixed

Prosthodontir

Laboratories.

**Associate THE

Profrssor,

JOURNAL

and LXrector

OF PROSTHETIC

of Research DENTISTRY

Activities.

The sample population included 30 men, 21 to 35 years of age, whose condylar growth was completed.” All participants were screened to eliminate those with traumatic injury to the jaw and/or condylar region, a history of pathosis of the jaw or condylar regions (other than dental caries), myofascial pain-dysfunction syn415

HART

Fig. 1. Englarged tion X10.)

pantographic

tracings.

of LSS

The total LSS of the mandible within working range was estimated to include the first 4 mm of the progressive side-shift curve and was recorded for each subject using the Denar pantograph. The Denar pantographic tracings were found to reproduce images identical in size to the movements made by the condyles being recorded.2” On this basis, each subject’s pantographic tracings were photographically enlarged (X 10) to facilitate visibility and measurement. A calibration scale (a grid of fine wires spaced horizontally and vertically at 1 mm intervals and encased in thin plastic) was included to obtain accurate measurements. A vernier caliper was used to measure the enlarged image to an accuracy of kO.01 mm. Measurement of the LSS of the mandible in right and left excursive movements was made on the enlarged pantographic tracings (Fig. 1). A piece of matte acetate was initially placed over the enlarged pantographic tracings and a line (A/ drawn over the recording line representing protrusive movement of the mandible (Fig. 2). A second straight line (B) was drawn representing the best visual fit of the first 4 mm of the progressive side-shift curve. A line (C) perpendicular to the protrusive line from the point representing centric relation was 416

SAKAMURh

(Magnifica-

drome, growth or endocrine abnormalities that might effect condylar growth, and mutilated occlusions (other than tooth removal for orthodontic purposes).

Estimation

.AND

2. Tracing on matte acetate includes protrusive path (A), best visual fit of progressive side shift @I, and LSS (0.

Fig.

then scribed to intersect the line drawn through the progressive side-shift curve. The length of line C was measured as the amount of LSS. The average measurement for the combined left and right mandibular LSS was assumed to adequately assess the average lateral displacement of the mandible during lateral excursion. The degree of intrainvestigator consistency was determined by data on the best visual fit of lines. Two weeks lapsed between two measurement sessions and intraexaminer reliability was substantial (r = 0.98, r2 = 96%).

Geometric

representation

A geometric representation of the matte acetate tracing can easily be made (Fig. 3). Place a line, C-A, the fixed distance between the condyle (C) and canine (A), on one side of the mandible on the X axis of a two-spaee coordinate system with C located at the origin. Posterior teeth are positioned at their respective distances from the canine on the line C-A at point B,, B2, M,, and M> The LSS of the condyle is expressed as a Iinearmovement of point C to C’, establishing cord length (a). As point C SEPTEMBER

1985

VOLUME

54

NUMBER

3

LATERAL

SIDE-SHIFT

AND

GNATHOLOGIC

INSTRUMENTATION

moves to point C’, the positions assigned the posterior teeth move from B,, B, M,, and M, to B,‘, Bz’, M,‘, and M,‘, respectively. The distances between the respective points represent the effects of the condylar LSS on occlusion. To determine the lengths of lines a’, a”, a’ ’ ‘, and a ’ ’ ’ ’ for a triangle with known sides a, c, and c’, an equation

based on the law of cosines was used.

Time efficiency considerations LSS on occlusion

and effect of

Considerations to determine whether complete gnathologic instrumentation would be time efficient were based on the amount of movement of the posterior teeth associated with a given amount of mandibular LSS. When posterior tooth movement caused by mandibular LSS was larger than the selected criterion (0.25 mm), complete gnathologic instrumentation was considered time efficient and would provide clinically significant control of occlusal error. When posterior tooth movement was less than the criterion, pantographic techniques were not considered time efficient; approximation of LSS amounts on the articulator followed by occlusal correction clinically were considered more practical. The 0.25 mm criterion was selected for five basic reasons. 1. Acceptable occlusal tolerances based on periodontal ligament thickness. The periodontal ligament contains pressor sensors that detect pressure from occlusal prematurities resulting from occlusal error. This ligament has an average thickness of 0.25 mm t 0.10 mm.’ When compressed, the pressor sensors stimulate patient sensation and enable the patient to detect occlusal prematurities. Although individual patient differences influence the amount of compression on the periodontal ligament required to generate a nerve impulse from the pressor sensors, it appears that ligament compression from 0 to +0.25 mm results in patient sensation. 2. The limitation of procedures available to locate and measure small occlusal discrepancies. Occlusal waxes, marking pencils, silk or paper marking tapes, and sandblasting of the occlusal surface of a prosthesis are some of the methods used for occlusal adjustment. Such procedures are difficult to apply clinically for small discrepancies. 3. Inherent accuracy and operator consistency in the use ojgnathologic instrumentation. There is some difference of opinion as to the accuracy and consistency of use of gnathologic instruments.22-24 As noted by Jaarda and Clayton, 25the centric latch alone can have a variability of 0.12 mm in the centric mounting position on the Denar articulator. Although such studies demonstrate that both THE

JOURNAL

OF PROSTHETIC

DENTISTRY

C’-

MzM, B, B, A

-X

Fig. 3. Geometric representation of LSS when measured between condylar position (C) and canine (A). B,, B,, M,, and M, represent premolar and molar position in centric relation and B’,, B’*, M’,, and M’, represent premolar and molar positions following condylar LSS of distance a. Amount of posterior tooth movement is represented by a’, a’ ‘, a’ ’ ‘, and a’ ’ ’ ‘. Condyle-canine distance is represented by c and c’

operator consistency and instrumentation accuracy vary, the findings do not seem to negate the clinical usefulness of gnathologic instrumentation. However, operator and instrumentation variability do limit the degree of occlusal accuracy that can be expected when such procedures are used. 4. The ability of the dentist to correct small occlusal discrepancies. Motor and visual skills vary from one dentist to the next. It is believed, however, that without patient feedback, correction of occlusal prematurities smaller than 0.25 mm will tax the skill of most dentists. 5. The patient’s ability to sense occlusal discrepancies. Riis and Giddon*” reported that patients can detect occlusal discrepancies as small as 0.0125 mm. Because dentists have difficulty in finding and correcting such small occlusal discrepancies, fine occlusal adjustments would be best accomplished with accompanying patient direction. Correction for occlusal discrepancies of such small magnitude through applied gnathologic instrumentation should probably not be made.

RESULTS Direct measurement of face-bow records revealed that all 30 participants had a 90 + 5 mm distance between condyle and canine. In addition, each subject’s posterior 417

HART

Table I. Frequency distribution of lateral side shift (LSS) from the sample (N = 30) LSS intervals

f

f/n

Cum

1.35-1.50 1.20-1.34 1.05-1.19 0.90-1.04 0.75-0.89 0.60-0.74 0.45-0.59 0.30-0.44 0.15-0.29 0.00-0.14

I 0 1 2 3 4 5 4 9 1

0.03 0.00 0.03 0.07 0.10 0.13 0.17 0.13 0.30 0.23

f

Cum 1.00 0.47 0.47 0.03 0.87 0.77 0.63 0.47 0.33 0.03

30 29 29 28 26 23 19 14 10 1

/ = Frequcncy;//rL = frequency/number; cy; cum ,j/ll = cumulative frequency/numbel

cum,/

f/n

= cumulaCvc

Irrquen-

Table II. Amount of lateral side shift (LSS) required to produce effect of 0.25 mm at various positions of posterior teeth and sample (%) displaying at least this amount of LSS Occlusal position Second molar First molar Second premolar First premolar

Amount produce

of LSS required to effect of 0.25 mm

(mm) 0.56 0.75 1.12 2.25

76 of sample 41 23 5 0

teeth were positioned at approximately 10 mm intervals posterior to the canine as measured from center to center of the face-bow tooth wax imprints. Measurements of LSS ranged from 0 to 1.43 mm (mean = 0.53 mm, standard deviation = 0.33) (Table I). Most measurements were found at the lower end of the range (median = 0.48 mm). These findings indicated a 0.95 probability that the mean LSS among men aged 21 to 35 years ranges between 0.41 and 0.66 mm. The geometric model indicates that the average LSS (mean = 0.53) will result in lateral movement of each designated posterior tooth equal to (1) second molar, 0.22 mm; (2) first. molar, 0.17 mm; (3) second premolar, 0.11 mm; and (4) first premolar, 0.06 mm. If the effect at the level of each of these posterior teeth for the median LSS of this sample were computed, the respective effects would be less than those found for the mean side-shift. Use of the median as a more representative measure than the mean can be argued on the basis of the skewed nature of the distribution of LSS. In any event, identical decisions concerning the effects would be made. The maximal amount of LSS found in the sample produced an occlusal change of (1) second molar, 0.67 mm; (2) first molar, 0.50 mm; (3) second premolar, 0.33 418

AND

SAKAMURA.

mm; and (4) first premolar, 0.17 mm. l’he effects on occlusal change were compared with the criterion (ii.25 mm), which was determined as the minimum occlusal effect required to decide that complete gnathologir instrumentation would prove time-eflicient clinically. Comparisons indicate that complete gnathologic instrrimentation would not be time efficient for any position r)l the posterior occlusion with the sample mean LSS iO.53 mm) because no occlusal change was il.25 mm or more (Table II). However, for the sample maximum LSS (1.43 mm) complete gnathologic instrumentation would be time efficient in treating the second premolar (0.33 mm), first molar (0.5 mm), and second molar (0.67 mm). but not the first premolar (0.17 mmj. The amount of LSS needed to produce an effect greater than 0.25 mm at each occlusal position was calculated (Table II). For example, the centile rank of the LSS great enough to produce an effect of 0.25 mm at the level of the second molar is 0.59 (59%). This finding indicates that for 41% of the sample it would be time efficient to instigate complete gnathologic instrumentation of the second molar treatment site. At the first molar site and the second premolar sites it would be timr efficient to use complete gnathologic instrumentation 23% and 5% of the time, respectively. No benefit woutd accrue with use of gnathologic instruments at the first premolar site. DISCUSSION Given the finding that 41% of the sample possessedan LSS great enough to use complete gnathologic instcumentation, how can a dentist identify the four candidates of 10 on whom the pantographic process would prove to be time efficient? A dentist’s decision to apply pantographic recording instrumentation techniques to all or none would not be time efficient because of the need for either excessive instrumentation or difficult clinical adjustment of the final occlusion. A beneficial solution may result by estimating the presence, approximate degree, and ultimate significance of a patient’s LSS without applying pantographic procedures. Careful examination of a patient’s occlusion may suggest pronounced LSS by the presence of buccolingual wear facets on the posterior teeth with accompanying rounded central fossae. By noting such findings and instrumentation for these applying pantographic patients only, the use of gnathologic instrumentation will be made more time efficient. When clinical examination for a pronounced LSS is inconclusive, gnathologic estimations (based on the mean value of this study) used with an adjustable articulator can lead to the construction of a more accurate occlusion. The articulator can be set to an LSS slightly greater than the mean side-shift value of this study (0.53 mm). Slight occlusal overcorrection for LSS is not generally believed SEPTEMBER

1985

VOLUME

54

NUMBER

3

LATERAL

SIDE,-SHIFT

AND

GNATHOLOGIC

INSTRUMENTATION

to harm a patient’s occlusion. Overcorrection results in wider central fossae than needed but avoids lateral eccentric prematurities, which are one basis for occlusal pathoses. If the actual amount of LSS is underestimated by such a procedure, any clinical adjustments should be minimal because the estimation would have partially controlled the LSS affect. This process obviates recording of the precise amount of LSS with the pantograph and is thereby more time efficient. The amount of LSS for a given patient can also be estimated by mounting the working casts on the articulator with a face-bow and determining the LSS at the condyles from the occlusion present. One of us WKH) observed that most adult patients with a moderateto-large amount of LSS have posterior wear facets and rounded central fossae. Therefore, the mounted casts prior to corrective occlusal therapy can be used to project condylar movement by bringing the casts together in a lateral position. The condylar movement (LSS) can be measured on the articulator, and corresponding settings can be made for the occlusal reconstruction without applying pantographic instrumentation. This approach should provide the dentist with a more precise method to estimate the amount of LSS. By evaluating the presence of a significant LSS and by applying the mean value of this research project to the LSS phenomenon, the dentist can use gnathologic instrumentation in a more time-efficient manner. These suggestions are more applicable for the small-to-moderate rehabilitation for a mutually protected occlusal scheme. Because approximately 70% of the general population has a mutually protected occlusion, and because the need for single to three-unit fixed prostheses outnumbers full-mouth rehabilitations, the findings of this study are clinically useful. Additional studies are required to replicate the findings of this investigation and to determine and quantify the effects of the remaining gnathologic jaw movements on occlusion. Studies should also be conducted on populations that vary in age, sex, and race to determine the effect of these variables on the results. It is envisioned that through such studies a table could be compiled that would indicate a specific population average measurement and standard deviation for each of the various condylar movements and the associated effects on the posterior occlusion. Such a table would allow the dentist to use an adjustable articulator and pantographic techniques in the most time-efficient manner consistent with occlusal accuracy.

the use of gnathologic instrumentation to control for LSS during reconstruction of occlusion would not be clinically time efficient in any area of the posterior occlusion. 3. For 41% of the patients in this study, significant degrees of LSS were found. 4. Practical approaches to the management of patients with significant degrees of LSS were suggested for dentists confronted by the problem of time efficiency and gnathologic instrumentation. REFERENCES

I.

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

L/1:

concept

2.

An

Part

1063. Weinberg

evaluation

1: Basic

LA:

concepts.

An

Part

of

evaluaion

DEKI.

articulators

J PRo\ri{b:i of

11: Arbitrary,

tnrs. J P~oc-rtwr

basic

concept

basic

positional, 13:645,

arCculators

Weinberg

s

J PKOS.I.I~I. DEXI 11:32, Gaddock FW, Symmons

1961. HE‘.

J

1952.

PRO\I‘I1kX

evaluation

2:633,

DENT

of

the

Lwlualitrn

7.

Lazzari JB: Application J PROSI~HI:.,’ DEKT 5:626,

8.

GuicheL NF: Procedures for Occtusal ‘l‘reamwnc: Atlas. Anaheim. Calif, 1969, Drnar Corp.

9.

Bawl-

A:

IO.

Berlin, Gibbs

Die 1976, Quintessenz Cll, Messerman T, Reswick

II.

movements hlesscrman

12.

Introduction

mandibular

(;ihbs

Cl<,

mtrvemcn~s.

Reswirk

JB,

l’ossrl~ U An analyzer Dtw 7:386, 1957.

4.

l.nn,q Jr ,111

5.

“IC;I”S I’ossctl odo”cal

6.

1,undccn

17.

18.

Drnt

Lwatwn

Wirth

1lJ:

North

Am

13:629,

nwvcmcn~s

UnivrrsiLy, posItion\.

of the terminal

PracGre. Functitrnal

T: Functional

mandibular

CC;. Condyl;~r

A ~l‘rarhing

D1:w 26~604, I97 I. Investigation of func-

hingr

J 1’~oSl.llt.r L)ENl’ 23:l I, l’):O. I!: Studies in rhc mobilicy of Ihr S(~;t”d lO(Suppl IO): I, 1952. llC,

face-bow

and

Drrda

Clin

h1 esscrman ‘.

for

“C”

10 Theory JB,

late-bow.

01 an ear face-bow.

mandible. Case Weswrn Rrservc No. 4-69-24, p 159, 1969.

3.

thr

model

of the mandible. J PROS~F;~ T, Reswick JB, Gibbs Cll:

tional 1969. of the Report

accuracy llan;~u

moun~inp.

of

Teleruck WR, Lundeen I-IC The J PKosrIjI:.r Dtw l&1039, 1966 of the 1955.

and theil .J PKO\.I.HI,I

taw-bow

6.

Gnathotogy:

thril

arGrut;r-

1963.

4.

An

their

13:622. and

semi-adjuscabte

Weinberg LA: An evaluation of basic arCul;nors concep,s. Part III. Fully adjusmbtr arriculau~rs. DEN.I. 13:873. 1963. LA:

and DENY

3

moverncn~

J Ptx)srtII-

axi\

human

E.11.C I’

by ~nwaoral

mand~blr palierns

,\CM

engravrtt

in plasGv I)lwks. J PKO~~~~+.Y I)P.N I 30:866, 1973. l,w RI,: J‘IM movrments engr;lvcd in solid plastic, for ar~icula~ol con1rnl~. Part 1: Rwording apparatus. ,J I’M)\ I 11~1 111;~ I 22:209, 1969. 1,undccn ular

ll(:.

n~owncn~s:

Shryock 7‘hrir

El;, Gibbs c,har;wtrr

(:ll.

An cvalu;~~~on

and signilicancc.

01 nrandilr
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DMI 40:442, 1978. :1ruwd ‘I‘. ‘l‘hv Capsular

20.

Join1 and Retrusion I~;~ecs of the l)cntition hl;u~dihul;w Movcmen~s. Oslo, 1954. Oslo Bclt;inG ND. Rlartin KR: The signilicanw

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bility. Part II: The prrvalence of inlrnrdiate side-shifl. .J PROLI. u11:r 1)~s I’ 42:255, 1979 LlS Naval l)rnwl Shoal: Prriodonlics Syllabus. M’ashinqon,

CONCLUSIONS 1. The mean LSS of 30 men, aged 21 to 35 years, included in this study was 0.53 mm. In 95% of this sample, LSS ranged from 0.41 to 0.66 mm. 2. For most (59%) of the participants in this study,

Weinberg

22.

Ligaments

of Ihr

‘l‘~mptrromar~clit~ul;ll in Rcla~ionship IO University Press. of writ ulawr capa-

IX:, 1975, US Naval Dental School Lauritzen AC; Bodner GIH: VnriaCons in lwarion ot arbitrary and true hinge axis points. J PROSI~H~.I~ DEW 11:223, 1961.

419

HART

23.

24. 25.

Coye RB: A study of the variability of setting a fully adjustable gnathologic articulator to a pantographic tracing. J PROSTHET DENT 37:460, 1977. Winstanley RB: Observations on the use of the Denar pantograph and articulator. J PROSTHET DENT 38:660, 1977. Jaarda >IJ, Clayton JA: Measurement of cusp height and ridge and groove direction, using an electrical transducer. Part I: Instrumentation. J PROSTIIET DENT 39:678, 1978.

26.

Riis D, Giddon DB: Interdental discrimmation dill’erences. J PROSTHET DENT 24~324, 1970.

AND

SAKAMURA

of small thickness

Ke,b,rml w/Ut?,I.\ to: DR. JERRY KENNIWN HART UNIVERSITY OF MISS~UKI SCHOOL OF DENTISTRY, RM. 3- 104 KANSAS CITY, MO 64108

Factors influencing the outcome of treatment in patients referred to a temporomandibular joint clinic Anita

Wedel, L.D.S.,*

University

of Giiteborg,

and Gunnar

E. Carlsson,

Faculty of Odontology,

Giiteborg,

L.D.S., Odont.Dr.** Sweden

Ah e proposed multicausal etiology of temporomandibular joint (TMJ) disorders may explain the diverse treatment methods and their reported successes.‘-*While few carefully controlled comparative studies of treatment efficacy are available, a wide variety of specific and adjunctive therapies have been suggested, for example, biofeedback, hypnosis and other psychologic methods, acupuncture and electrical physical therapy, myofunctional therapy, and special techniques for TMJ surgery. + s,‘-I3 A multiprofessional approach in the management of patients with TMJ disorders has also been recommended.5~‘4~‘5While this might be necessary for a small group of patients, it is well documented that most TM J disorders can be successfully treated with counseling and simple dental methods.“,‘” It is difficult to perform comparative, studies of different treatment methods, and a wide disparity of thinking still exists in this field;9~‘0~“2” therefore, it is desirable to analyze the outcome of therapy in other ways. We chose to retrospectively study the number of visits, length of treatment period, and evaluation of clinical status at end of treatment in a relatively large group of patients who had been referred for treatment of functional disturbances of the masticatory system.

MATERIAL

AND

METHODS

Three hundred-fifty consecutive patients with functional disturbances of the masticatory system attending Supported by grants from Stiftelsen Handlanden Hjalmar Svenssons Forskningsfond, and the American Equilibration Society. *lIssistant Professor, Department of Stomatognathic Physiology. **Professor .~nd Chairman, Department of Stomatognathic Physiology. 420

the Department of Stomatognathic Physiology, University of Goteborg, were chosen for this study. The patients answered a self-administered questionnaire at their first visit. The design of the questionnaire study and results of analyses of the answers ,to the questions were reported elsewhere.“,‘(’ The patients were examined and treated at the clinic according to routine clinical procedures.‘6 Two and one-half years after the first visit, the records of the patients were examined for clinical findings, diagnoses, and observations related to treatment. A description of the main results of these observations were presented previously.2’ A series of variables were selected from the questionnaire and the patient records (Table I) for further statistical analyses with special respect to number of visits, length of treatment period, and evaluation of the patients’ signs and symptoms at the last clinic visit.

Statistical

methods

The variables listed in Table I were correlated one by one by means of Spearman’s nonparametric rank correlation test22 with each of the following three variables: (1) number of visits, (2) length of treatment in months, and (3) final evaluation of the signs and symptoms. Stepwise multiple regression analysis was then performed with the variables in Table I as independent variables and each of the three above-mentioned parameters as dependent variables. Subgroups of patients were also selected in different ways for comparison of the treatment results.

RESULTS The distribution of the number of visits and the length of treatment are shown in Figs. 1 and 2. There is a wide SEPTEMBER

1985

VOLUME

54

NUMBER

3