original papers - Advances in Clinical and Experimental Medicine

original papers
Adv Clin Exp Med 2012, 21, 5, 637–643
ISSN 1899–5276
© Copyright by Wroclaw Medical University
Krzysztof Woźniak1, A–F, Hubert Teichert2, A–F, Dagmara Piątkowska1, A, D–F,
Mariusz Lipski3, A, D–F
An Assessment of Relationships Between the Five-Factor
Personality Model and the Morphology and Function
of the Stomathognatic System
Ocena zależności między pięcioczynnikowym modelem osobowości
a morfologią i czynnością układu stomatognatycznego
Department of Orthodontics, Pomeranian Medical University, Szczecin, Poland
Teichert & Partners: Psychology and Business, Szczecin, Poland
3
Department of Preclinical Conservative Dentistry and Preclinical Endodontics, Pomeranian Medical University,
Szczecin, Poland
1
2
A – research concept and design; B – collection and/or assembly of data; C – data analysis and interpretation;
D – writing the article; E – critical revision of the article; F – final approval of article; G – other
Abstract
Background. The personality as a system of genetically predetermined features is responsible for modifying relations between an individual’s genotype and phenotype. The key element linking personality with facial morphology
is the muscular system.
Objectives. The aim of this study was to investigate the association between facets of the five-factor personality
model (FFM) domains and both the morphology and function of the stomathognatic system.
Material and Methods. Two hundred volunteers (100 female and 100 male) aged 20 to 25 (mean age: 23.4) underwent anthropometric measurements to calculate the anterior face height ratio N-Sn/Sn-Gn. For cephalometric
analysis, standard right-profile images of the face were used. Calibration was performed with a 100-mm metal
ruler placed next to each photographed individual. The Revised NEO Personality Inventory (NEO-PI-R), which
includes 240 statements, was used for personality assessment in order to investigate the five main personality
domains: neuroticism, extraversion, openness to experience, agreeableness, conscientiousness and six facets within
each domain.
Results. The results show significant correlations between factors of the personality such as neuroticism (r = 0.3488;
p = 0.0000) and extraversion (r = –0.3405; p = 0.0000) and the inclination angle (FH/HOR) as the predictor of the
function of the stomathognatic system. Additionally, the correlation analysis revealed a significant positive association between the anterior face height ratio and anxiety (r = 0.3952; p = 0.0000).
Conclusions. The results of this study indicate a selective association between personality and both the morphology and function of the stomathognatic system (Adv Clin Exp Med 2012, 21, 5, 637–643).
Key words: personality, anxiety, NEO-PI-R, face morphology.
Streszczenie
Wprowadzenie. Osobowość jako zespół cech zdeterminowanych genetycznie, jest odpowiedzialna za modyfikowanie relacji zachodzących między genotypem człowieka a jego fenotypem. W obrębie głowy elementem łączącym
osobowość z morfologią twarzy jest układ mięśniowy.
Cel pracy. Określenie związku między aspektami pięcioczynnikowego modelu osobowości (PMO) a morfologią
i czynnością układu stomatognatycznego.
Materiał i metody. Dwustu ochotnikom (100 kobiet i 100 mężczyzn) w przedziale wiekowym 20–25 lat (średnia
23,4) wykonano pomiary antropometryczne w celu obliczenia indeksu przedniej wysokości twarzy (N-Sn/Sn-Gn).
Pomiary cefalometryczne wykonano na standardowych zdjęciach prawego profilu twarzy. Do kalibracji zdjęć wyko-
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K. Woźniak et al.
rzystano 100 mm metalową linijkę umieszczoną w pobliżu twarzy każdej fotografowanej osoby. Oceny osobowości
dokonano, używając inwentarza osobowości NEO-PI-R. Inwentarz ten składa się z 240 twierdzeń umożliwiających
pomiar 5 głównych obszarów osobowości: neurotyzmu, ekstrawersji, otwartości na doświadczenia, sumienności,
ugodowości oraz 6 składników w obrębie każdego z nich.
Wyniki. Uzyskane wyniki wskazują na statystycznie istotną korelację czynników osobowości i kąta inklinacji (FH/
HOR) jako predykatora czynności układu stomatognatycznego w aspekcie Neurotyczności (r = 0.3488; p = 0.0000)
i Ekstrawertyczności (r = –0,3405; p = 0,0000). Ponadto analiza korelacji wykazała pozytywną zależność między
indeksem przedniej wysokości twarzy a lękiem (r = 0,3952; p = 0,0000).
Wnioski. Wyniki badań wskazują na wybiórczy związek osobowości z morfologią i czynnością układu stomatognatycznego (Adv Clin Exp Med 2012, 21, 5, 637–643).
Słowa kluczowe: osobowość, lęk, NEO-PI-R, morfologia twarzy.
Numerous long-term studies on the five-factor personality model (FFM), implementing multivariate analysis, have resulted in the creation of
the five-factor theory of personality (the “big five”)
[1–3]. In this model, the personality is described
by certain unique traits. A primary stipulation of
this theory is that features of the personality are
endogenous basic qualities of the inheritable type
with little environmental influence [4]. These
qualities tend to develop from early childhood
up to adulthood, when their ultimate shape is acquired. The features are organized hierarchically,
from strictly determined and specific ones to general ones.
The topmost part of this hierarchy is shaped
by the traits constituting the “big five”: neuroticism, extraversion, openness, agreeableness, and
conscientiousness. The validity of the five-factor
personality model has been ascertained by the
intercultural convergence of its principles with
roots in lexical hypotheses [5]; by the association between self-descriptions and descriptions of
studied individuals by their relatives and friends;
by internal correlations between indicators related
to personality traits and indicators of motivation,
emotion and interpersonal contact; by diagnoses
of personality disturbance related to the dimensions and facets of personality factors rather than
categories [6]; and by genetic evidence and evolution theory [7].
Neuroticism is one of the best investigated
traits among the “big five”. It is also known as
emotional sensitivity, or emotional instability/
reactivity. It reflects emotional adaptation as opposed to emotional instability. It refers directly
to the tendency to experience negative emotions
such as anger, sadness, fear, embarrassment, guilt
and disgust. These emotions commonly impair the
process of adaptation, therefore neurotic individuals may be more prone to accept irrational ideas
and fantasies, and may tend to present worse impulse control and difficulty to cope with stress effectively. It is also related to nervousness, excessive
emotional reactions, a feeling of endangerment
and an inclination to be hypochondriac. Other
facets of this domain include excessive unnecessary worrying and low self-esteem [8].
Neuroticism is comprised of angry hostility,
depressiveness, overt criticism, impulsiveness and
hypersensitivity to anxiety. Anxiety is often confused with fear, which occurs only in the situation
of natural, immediate and real danger. Anxiety is
experienced in the context of imaginary situations,
which might or might not appear, and in most cases is not linked with any observable reason [9].
In dentistry, fear as a psychological factor is
addressed as a basic feature influencing the shape
and function of the stomatoghathic system, along
with psychiatric illnesses, disturbances of occlusion, orthopedic dysfunctions, isometric muscle
work, the influence of physical factors (cold, humidity, the climate), hormonal and metabolic influences, the proprioceptive reflex from dysfunctional and improperly or overly loaded joints, or
joint microinjuries.
Difficulties with controlling aggression and
fear lead to functional body changes – for example, excessive muscular tension and hyperactivity
cause a long-term, non-physiological load on the
supportive tissues [10]. This process may result in
morphological changes of the face.
The aim of this study was to investigate the association between the facets of the five-factor personality model domains and the morphology and
function of the stomathognatic system.
Material and Methods
Two hundred volunteers (100 female and
100 male) aged 20 to 25 (mean age: 23.4) participated in this study. Cephalometric measurements
were done on the basis of standard right-profile
images of the face, stored in Adobe Photoshop
software. Prior to conducting the vertical linear
measurements, verification and calibration of the
true image size was performed, using a 100-mm
metal ruler placed near each of the photographed
individuals. Each picture was taken at a distance
of one meter from the photographed individual,
639
FFM and the Stomathognatic System
using a Canon IXY Digital 800 IS camera in the
same lighting conditions. Study participants were
seated on a chair in an upright position with the
head in its natural position (NHP), with teeth in
maximum intercuspidation and lips in repose.
First, two anthropometric linear measurements – nasion to subnasale (N-Sn) and subnasale
to gnathion (Sn-Gn) were measured on each of the
lateral photographs, and were used to estimate the
anterior face height ratio N-Sn/Sn-Gn (in %). One
angular measurement was also made: the inclination angle (FH/HOR), between the Frankfort horizontal (FH) line and the extracranial horizontal
(HOR) line with the head in the NHP. If the Frankfort horizontal line is formed over the extracranial
horizontal line passing through the Tragus point,
the angle is read in positive degrees. If the Frankfort horizontal is formed below the extracranial
horizontal line passing through the Tragus point,
the angle is read in negative degrees [11].
The survey comprised the second part of the
research. The Revised NEO Personality Inventory
(NEO-PI-R), which included 240 statements, was
used. The inventory allows the five main personality domains to be investigated: neuroticism, extraversion, openness to experience, agreeableness
and conscientiousness, with six facets within each
of them. The analyzed facets include:
– for neuroticism: anxiety, angry hostility, depression, self-consciousness, impulsiveness and
vulnerability;
– for extraversion: warmth, gregariousness,
assertiveness, activity, excitement seeking and experience of positive emotions;
– for openness to experience: fantasy, esthetics, feelings, actions, ideas and values;
– for agreeableness: trust, straightforwardness,
altruism, compliance, modesty and tenderness;
– for conscientiousness: competence, order,
dutifulness, achievement striving, self-discipline
and deliberation.
To complete the NEO-PI-R study, the participants recorded their responses using the five-point
Likert scale, ranging from “strongly disagree” (0)
to “strongly agree” (4). The time allowed for completing the inventory was from 35 to 45 minutes
[12, 13].
Linear regression analysis was used to check
the association between the dependent variable of
the anterior face height ratio and the independent
variables of the facets. The significance level for all
statistical comparisons was predetermined at the
threshold of p ≤ 0.05. The data analysis was performed with Statistica 7.0 software (Stat Soft. Inc.).
Results
Table 1 presents results of the anterior face
height ratio N-Sn/Sn-Gn (in %). The anterior face
height ratio varied from 65.91% to 119.60% (mean:
80.70%). Female participants tended to present
a larger inclination (mean: 81.02%) than the males
(meanL 80.38%). There were no significant differences between the male and female subjects (p =
0.8679).
The results in Table 2 show significant correlations between the factors of the personality such as
neuroticism (r = 0.3488; p = 0.0000) and extraversion (r = –0.3405; p = 0.0000) and the inclination
angle (FH/HOR) assesed in NHP as a predictor of
the function of the stomathognatic system.
Table 3 presents the Pearson correlation coefficients of the anterior face height ratio at each of
the personality domains. Among the volunteers,
modestly significant positive correlations were
found between the anterior face height ratio and
anxiety (r = 0.3952; p = 0.0000).
Table 1. The anterior face height ratio (N-Sn/Sn-Gn). Mean, median and standard deviations as well as min-max values are
presented in percentages
Tabela 1. Indeks przedniej wysokości twarzy (N-Sn/Sn-Gn). Wartości średniej, mediany, odchylenia standardowego i wartości min-max zostały wyrażone w procentach
N-Sn/Sn-Gn
N
Mean
(Średnia)
Median
(Mediana)
SD
Minimum
Maximum
p-value
Female
(Kobiety)
100
81.02
79.46
8.98
65.91
119.6
0.8679
Male
(Mężczyźni)
100
80.38
80.08
5.99
68.75
100.00
Total
(Razem)
200
80.70
80.00
7.63
65.91
119.60
640
K. Woźniak et al.
Table 2. Correlations between the five-factor model and the inclination angle FH/HOR in NHP
Tabela 2. Wyniki analizy korelacji między pięcioma głównymi czynnikami osobowości a kątem inklinacji FH/HOR w NHP
NEO-PI-R domain scale
(Czynniki NEO-PI-R)
Inclination angle FH/HOR
(Kąt inklinacji FH/HOR)
r
p-value
Neuroticism (Neurotyczność)
  0.3488
0.0000*
Extraversion (Ekstrawertyczność)
–0.3405
0.0000*
Openness to experience (Otwartość na doświadczenie)
  0.0812
0.2787
Agreeableness (Ugodowość)
–0.0373
0.6051
Conscientiousness (Sumienność)
  0.0770
0.3013
* p-value ≤ 0.05.
* istotność statystyczna ≤ 0,05.
Discussion
Alongside Sheldon’s theory, the most popular
classification based on constitutional personality
types was created by Kretschmer, who associated
the body type with temperament and psyche. Each
of the constitutional types was described by characteristic features. The leptosomic type (thin and
weak) was associated with a schizothymic temperament and a tendency to develop schizophrenia
in adult life, and to suffer more frequently from
tuberculosis and gastritis. Pyknic people were
supposed to present a cyclothymic temperament,
a tendency for depression, cardiovascular disease,
arteriosclerosis, arthritis, cholelithiasis, pancreatitis and diabetes. People of athletic type tended to
be predisposed to epilepsy, vasomotor head disturbance (migraine) and asthma. Further studies
on personality traits as a factor influencing human
functioning have confirmed these relationships
[14–16].
The personality as a system of genetically predetermined features is responsible for modifying
relations between an individual’s genotype, which
provides background developmental capabilities,
and the external environmental factors that influence phenotypic variability. For the head, the key
element linking genetically determined personality with facial morphology is the muscular system.
If it is assumed that function is superior to shape,
changes in the muscular part of the stomatoghathic system during the developmental stages of life
induce alterations in morphology.
Individuals with a strong element of anxiety
presenting in the personality structure experience
strong and overwhelming feelings of tension and
concern. They are filled with insecurity, timidity,
feelings of misadaptation, personal unattractiveness and low self-esteem [8]. At a somatic level, this
results in a constant state of overload, manifesting
as an increase in muscular tension not only within
the stomathoghatic system but also within the individual’s whole motor system. Moreover, a craving for acceptance and recognition with increased
sensitivity to criticism and rejection enhances the
tendency to withdraw from social contacts, with
fear of being criticized resulting in additional feelings of self-worthlessness.
Importantly, restraint from verbal expression (“teeth clenching”) is intensified, for fear of
being judged by the social sphere when expressing unpopular personal opinions or feelings (e.g.
of discontentment). Other reason for an increase
in muscular tension is constant anticipation of
an imaginary attack from the people around one.
Continuous control over one’s personal reactions
and analysis of behavior are other reasons for
muscle tensing, along with the raising of a psychological barrier preventing the expression of natural
and spontaneous reactions. A permanent increase
in muscular tension results in impairment of vertical facial growth, manifesting morphologically in
lower face height.
The influence of psychological factors on the
stomathonathic system is also present after growth
has concluded. This is especially important for patients with temporomandibular disorders (TMDs)
– a group of conditions characterized by pain
or dysfunction in the temporomandibular joint
(TMJ) and/or the muscles of mastication. TMD
can include myofascial pain, internal derangement
and/or degenerative changes of the temporomandiblular joint. TMD pain is a common and costly
problem affecting approximately to 15% of the
adult population [17, 18]. These patients also have
a lower pain threshold and increased response to
experimental pain stimuli. There are many theories attempting to explain the cause of these dif-
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FFM and the Stomathognatic System
Table 3. Correlations between the domains and facets of the personality and the anterior face height ratio
Tabela 3. Wyniki analizy korelacji między czynnikami i składnikami osobowości a indeksem przedniej wysokości twarzy
NEO-PI-R domain and facet scale
(Czynniki i składniki NEO-PI-R)
Anterior face height ratio
(Indeks przedniej wysokości twarzy)
r
p-value
N
neuroticism (neurotyczność)
  0.0182
0.0573
N1:
anxiety (lęk)
  0.3952
0.0000*
N2:
angry hostility (agresywna wrogość)
  0.0843
0.2376
N3:
depression (depresyjność)
  0.1043
0.1416
N4:
self-consciousness (nadmierny samokrytycyzm)
  0.1016
0.1525
N5:
impulsiveness (impulsywność)
  0.1141
0.1075
N6:
vulnerability (nadwrażliwość)
  0.0291
0.6851
E
extraversion (ekstrawertyczność)
  0.0207
0.7797
E1:
warmth (serdeczność)
  0.0504
0.4781
E2:
gregariousness (towarzyskość)
  0.0960
0.1851
E3:
assertiveness (asertywność)
  0.0807
0.2827
E4:
activity (aktywność)
  0.0594
0.4060
E5:
excitement seeking (poszukiwanie doznań)
  0.0854
0.2318
E6:
positive emotions (emocje pozytywne)
  0.0311
0.6615
O
openness to experience (otwartość na doświadczenie)
  0.0069
0.9226
O1:
fantasy (wyobraźnia)
–0.0528
0.4576
O2:
aesthetics (estetyka)
  0.0097
0.8917
O3:
feelings (uczucia)
  0.0995
0.1611
O4:
actions (działanie)
  0.1030
0.1468
O5:
ideas (idee)
–0.0943
0.1864
O6:
values (wartości)
  0.0517
0.4669
A
agreeableness (ugodowość)
–0.0101
0.8875
A1:
trust (zaufanie)
–0.0233
0.7436
A2:
straightforward (prostolinijność)
–0.1042
0.1421
A3:
altruism (altruizm)
  0.0899
0.2054
A4:
compliance (ustępliwość)
–0.0514
0.4724
A5:
modesty (skromność)
  0.0438
0.5382
A6:
tender-minded (skłonność do rozczulania się)
  0.1083
0.1269
C
conscientiousness (sumienność)
–0.0780
0.2746
C1:
competence (kompetencja)
–0.0077
0.9133
C2:
order (skłonność do porządku)
–0.0899
0.2099
C3:
dutifulness (obowiązkowość)
–0.0261
0.7133
C4:
achievement striving (dążenie do osiągnięć)
–0.0300
0.6727
C5:
self-discipline (samodyscyplina)
–0.1112
0.1169
C6:
deliberation (rozwaga)
–0.0484
0.4997
* p-value ≤ 0.05.
* istotność statystyczna ≤ 0,05.
642
K. Woźniak et al.
ferences, but psychological theories are among the
most credible [17, 18].
The current authors’ review of papers by
Turner and Dworkin [19] related to TMD and
psychological factors, published from1995 to 2002,
provided some interesting insights. There was
substantial empirical evidence that psychosocial
factors play an important role in the symptoms,
symptom impact and treatment response of patients with TMD. Depression, somatization and
anxiety are prevalent among patients with TMD.
These factors in particular have been indicated to
influence the expression of the signs and symptoms of TMD.
Anxiety is a negative emotional condition
linked to the expectation of external or internal
danger, often reflected as uneasiness, a feeling of
tension, embarrassment or a sense of being threatened. In contrast to fear, it is an internal process, not directly linked to any immediate threat
or pain. Anxiety becomes pathological, when it
dominates personal behavior, restricts freedom
and in consequence leads to various disturbances.
Anxiety reactions lose their adaptative function
and become inadequate to the stimuli, often exacerbated by situations in which there is no threat. It
is often accompanied by vegetative components of
various types, such as tremors, increased muscular
tension, tingling, heart pain, breathing problems,
diarrhea and/or nycturia. Anxiety is associated
with a number of psychopathological reactions,
especially when it is perceived as a cognitive risk
factor for panic disorders [9].
Somatization has been defined by Sherman
et al. as “the tendency to experience numerous
physical symptoms for which no apparent organic
cause can be determined. Alternatively, if a medical cause is present, somatization is said to occur
when complaints about the bodily disturbance and
dysfunction are in excess of the pathology. Barsky
suggests that somatization is related to an amplification of bodily signals” [20, 21]. It is necessary to
refer patients to an appropriately trained psychologist or psychiatrist if one or more of the following
symptoms is noted in their history: disability (in
daily work, household maintenance, recreational
and social activities) out of proportion to objective findings; symptoms of psychological disorders (most commonly depression, anxiety or somatization); prolonged or excessive use of opiates,
benzodiazepines, alcohol or other drugs. It must
also be emphasized here that patients qualified as
moderately or severely disabled should undergo
multidisciplinary treatment, aiming at reducing
the psychological factor in TMD etiology.
The relationship between mood and somatic
ailments requires a thorough assessment of the
psychometric point of view. The axis that best
describes the character of the symptoms is neuroticism. It may be assumed that complaints are
more related to a real ailment and symptoms in
people with a low level of neurotism, in comparison to individuals with a higher level of this factor.
Generally, neurotism is of such importance in the
research on the psychological aspects of health, especially stress-related aspects, that it should always
be measured and controlled [4].
Clinical research, health-related psychology
and behavioral medicine are three branches of
research where psychometric tools, including the
NEO Personality Inventory (NEO-PI-R) are used.
The choice of this tool is justified by the strong association between health status and lifestyle, which
in turn is a sum of personality facets. It is clear
that in every aspect of human life, from one’s professional and recreational interests to one’s reactions to stress, personality determinants play a key
role, becoming a cognitive filter that enhances or
reduces the interaction of environmental factors
with the body. It must be emphasized that personality features, as the most basic and permanent
tendencies, have a wide range of influence on an
individual’s acquired interactions with the environment.
The results of this study indicate that there is
a selective association between the personality and
both the morphology and function of the stomathognatic system.
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Address for correspondence:
Dagmara Piątkowska
Department of Orthodontics
Pomeranian Medical University
Al. Powstańców Wlkp. 72/6
70-111 Szczecin
Poland
Tel.: +48 504 012 262
E-mail: [email protected]
Conflict of interest: None declared
Received: 18.04.2012
Revised: 13.08.2012
Accepted: 8.10.2012