SciELO - Scientific Electronic Library Online

 
vol.22 issue5Quantification of intrusive/retraction force and moment generated during en-masse retraction of maxillary anterior teeth using mini-implants: A conceptual approachEffect of TiO2 nanoparticles incorporation on antibacterial properties and shear bond strength of dental composite used in Orthodontics author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand

Journal

Article

Indicators

Related links

Share


Dental Press Journal of Orthodontics

Print version ISSN 2176-9451On-line version ISSN 2177-6709

Dental Press J. Orthod. vol.22 no.5 Maringá Sept./Oct. 2017

http://dx.doi.org/10.1590/2177-6709.22.5.056-066.oar 

Original Article

Influence of the cranial base flexion on Class I, II and III malocclusions: a systematic review

Kélei Cristina Mathias de Almeida1 

Taísa Boamorte Raveli1 

Camila Ivini Viana Vieira2 

Ary dos Santos-Pinto1 

Dirceu Barnabé Raveli1 

1Universidade Estadual Paulista, Faculdade de Odontologia de Araraquara, Departamento de Ortodontia e Odontopediatria (Araraquara/SP, Brazil).

2Private practice (Araraquara/SP, Brazil).

ABSTRACT

Objective:

The aim of this study was to perform a systematic review on the morphological characteristics of the skull base (flexion, anterior length and posterior length) and the concomitant development of malocclusions, by comparing differences in dimorphism, ethnicity and age.

Methods:

The articles were selected by means of electronic search on BBO, MEDLINE and LILACS databases from 1966 to 2016. A qualitative evaluation of the methodologies used on the articles was also performed.

Results:

Although the literature on this topic is abundant, only 16 articles were selected for the present systematic review. The cranial base angle itself does not seem to play a significant role in the development of malocclusions. In fact, the cranial base angle is relatively stable at the ages of 5 to 15 years.

Conclusions:

A more obtuse angle at the skull base, in association or not with a greater anterior length of the cranial base, can contribute to the development of Class II division 1 malocclusions. On the other hand, a more acute angle at the skull base can contribute to a more anterior positioning of the mandible and to the development of Class III malocclusions.

Keywords: Malocclusion; Cephalometry; Growth; Skull base

RESUMO

Objetivo:

o objetivo desse estudo foi realizar uma revisão sistemática sobre as características morfológicas da base do crânio (flexão, comprimento anterior e comprimento posterior) e o desenvolvimento concomitante da má oclusão, comparando as diferenças do dimorfismo, etnia e idade.

Métodos:

os artigos foram selecionados por meio de busca eletrônica nas bases de dados BBO, MEDLINE e LILACS, de 1966 a 2016. Uma avaliação qualitativa da metodologia dos artigos também foi executada.

Resultados:

ainda que a literatura seja abundante nesse assunto, somente 16 artigos foram selecionados para a presente revisão sistemática. O ângulo da base do crânio, por si só, não parece desempenhar papel significativo no desenvolvimento das más oclusões. De fato, o ângulo da base do crânio é relativamente estável dos 5 aos 15 anos.

Conclusões:

um ângulo mais obtuso na base do crânio, associado ou não a um comprimento maior, pode contribuir para o desenvolvimento da má oclusão de Classe II, divisão 1. Por outro lado, um ângulo mais agudo na base do crânio pode contribuir para um posicionamento mais anterior da mandíbula e para o desenvolvimento da má oclusão de Classe III.

Palavras-chave: Má oclusão; Cefalometria; Crescimento; Base do crânio

INTRODUCTION

The skull base plays a key role in the craniofacial growth, thus helping to integrate different growth patterns both spatially and functionally, regarding several regions adjacent to the skull - such as brain components, nasal cavity, oral cavity and pharynx.1 In this way, the skull base supports the brain and allows the neurocranium and viscerocranium to adapt and develop during growth.2,3 It is reported that the first growth spurt of the skull base occurs between 14 and 32 weeks of intra-uterine life, and the second one occurs during the first year of life.4

The development of the skull base is closely related to both middle region of the face and mandibular positioning, with its anterior-posterior growth playing an important role in mandibular and nasomaxillary growth, thus directly contributing to the degree of facial prognathism.5 Based on geometrical relationships, it would be reasonable to say that any change in the skull base flexion might affect the positioning of maxilla and mandible, thus influencing skeletal pattern and occlusion as well.6

The literature is abundant, but controversial, regarding the influence of the skull base flexion on the development of malocclusions.6 Although there are studies supporting that the skull base flexion is not a factor in the etiology of malocclusions, others suggest the contrary.2,7 In fact, several authors2,8-12 showed evidence that the skull base has a considerable influence in the inter-maxillary relationships.

Ricketts9 reported that the skull base area has an important influence on total facial prognathism and development of anteroposterior relationship between maxilla and mandible. According to the same author, the Class II malocclusion worsens with age. To Hopkin et al,10 the skull base angle was lower in individuals with Class III malocclusions (males = 122.4o and females = 122.2o) and higher in those with Class II division 1 (males = 126.7o and females = 128.8o). By analyzing the craniofacial relationships in the mandibular prognathism and comparing them to Class I malocclusions, Horowitz and Converse11 found mean values of 119.3o for the BaSN angle in Class III malocclusions with horizontal growth pattern, 116.6o in Class III malocclusions with vertical growth pattern, and 124.1o in Class I malocclusions.

Among studies showing no influence of the skull base on malocclusions, Hildwein et al13 found no significant difference in the BaSN angle in individuals with Class II and Class I malocclusions. Kasai et al14 investigated the relationship between skull base and maxillofacial morphology in Japanese subjects and found no difference between Class I and Class II malocclusions. Similarly, Wilhelm et al15 observed no difference in the measurements of the skull base regarding Class I and Class II malocclusions.1

There are many studies corroborating the finding that skull base flexion has an influence on malocclusions, whereas others show no such evidence. Different factors can contribute to these divergent findings, such mixed samples - in terms of age and gender - as well as the use of chronological age instead of skeletal age. Other factors possibly contributing to these divergent findings include the following: lack of radiographic standardization, small sample size, and number of inter-group comparisons. In this way, the influence of the skull base flexion as an etiological factor influencing inter-maxillary relationships is still a matter of debate and investigation.16

The objective of the present study was to perform a systematic review on the relationship between skull base (flexion, anterior length and posterior length) and the development of malocclusions, by comparing differences in gender dimorphism, ethnicity and age.

METHODS

Search strategy

The articles selected for this systematic review of the literature were found by means of electronic search on BBO, MEDLINE and LILACS databases, from 1966 to 2016. The keywords used for this bibliographic search were the following: skull base, cephalometry, malocclusion, Class I malocclusion, Class II malocclusion, Class III malocclusion.

Next, a manual search was also performed by analyzing the bibliographic references of the articles according to the systematic review.

Criteria for study selection

The inclusion criteria were the following:

  • » Studies using lateral cephalometric radiography.

  • » Meta-analysis, randomized clinical studies, retrospective and prospective studies.

  • » Studies published from 1966 to 2016.

  • » Studies addressing non-treated Class I, Class II and Class II malocclusions.

  • » Studies with subjects aged between 6 and 12 years old (mixed dentition) and those aged between 12 to 18 years old (permanent dentition).

  • » Studies on skull base using linear (S-N, S-Ar, S-Ba) or angular (NSAr and NsBa) measurements.

  • » Articles written in Portuguese, English or Spanish idioms.

The exclusion criteria were the following:

  • » Clinical cases, descriptive studies, opinion articles or abstracts.

  • » Case studies.

  • » Adult studies (subjects over 18 years old).

  • » Animal studies or laboratory studies.

  • » Craniofacial syndromes.

  • » Dissertations.

Article selection

Four researchers have independently examined titles, keywords and abstracts of the articles found in the databases, according to the inclusion and exclusion criteria aforementioned. The articles were consensually selected and integrally considered, and after reading them a final decision was made regarding their inclusion or not in the present study. The articles were classified according to the criteria summarized in Table 1.

Table 1 Qualification of the methodology used by the articles selected for review. 

2 points 1 points
Clearly formulated objective (x) yes ( ) no
Study design (x) yes ( ) no
Description of the sample selection (x) yes ( ) no
Adequate sample size (x) yes ( ) no
Control group (x) yes ( ) no
Adequate measurement method (x) yes ( ) no
Adequate statistical analysis (x) yes ( ) no
Method error analysis (x) yes ( ) no
Blind study (x) yes ( ) no
Multiple comparison between Class I, II and III malocclusions (x) yes ( ) no
Total 20 points

RESULTS

A total of 315 articles were initially identified, 8 from BBO, 12 from LILACS and 295 from MEDLINE. After reading the abstracts, only 55 were selected: no article from BBO, 2 from LILACS and 53 from MEDLINE. These were fully considered and after applying the inclusion and exclusion criteria, 39 articles were excluded and 16 remained, all from the MEDLINE database (Table 2). Next, another article was excluded due to lack of the measurements considered for review.

Table 2 Evaluation of methodological quality of the 16 articles selected for review. 

Article Clear objective Study design Description of the sample selection Adequate sample size Control group Adequate measurement method Adequate statistical analysis Method error analysis Blind study Multiple comparison between Class I, II and III malocclusions Score
Dhoptkar et al.19 Yes No Yes Yes No Yes Yes Yes No Yes 17
Wilhelm et al.15 Yes Yes Yes Yes No Yes Yes No No No 16
Mouakeh21 Yes No Yes Yes Yes Yes Yes No No No 16
Alexander et al22 Yes Yes Yes Yes No Yes Yes Yes No No 17
Ishii et al.23 Yes No No Yes Yes Yes Yes Yes No No 16
Polat, Kaya1 Yes No Yes Yes No Yes Yes Yes No Yes 17
Singh et al24 Yes No Yes Yes Yes Yes Yes No No No 16
Johannsdottir et al.25 Yes No Yes Yes Yes Yes Yes No No No 16
Rothstein, Yoon-Tarlie16 Yes No Yes Yes Yes Yes Yes No No No 16
Ishii et al.26 Yes No Yes Yes Yes Yes Yes No No No 16
Kappor et al.27 Yes Yes Yes Yes Yes Yes Yes No No No 17
Singh et al.28 Yes No No Yes No Yes Yes No No No 14
Zeng et al.29 No Yes Yes No No Yes Yes Yes No No 15
Lau, Hagg30 No No No Yes Yes No No No No No 12
Chang et al.31 Yes Yes No Yes Yes Yes Yes Yes Yes No 18
Yoon, Chung37 Yes Yes Yes No No Yes Yes Yes Yes No 17

A qualitative evaluation of the methodology used by these articles was performed according to previous studies.17,18 The variables being considered for review are listed in Table 1, including corresponding values. Table 2 shows the articles presenting more accurate methodologies.

Each article was given points according to the items evaluated, as can be seen in Table 1. Each item had a maximum score of 2 points if there was a consensus on it, otherwise 1 point was given. This procedure was applied to each article.

Therefore, each article could reach a maximum score of 20 points, thus allowing the study quality to be ranked as follows: ≤ 10 points = low score; > 10 and ≤15 = average score; > 15 and ≤ 18 = moderately high score; and > 18 points = high score.

Table 3 shows the sample characteristics, including the objective of each article, and Table 4 lists the epitomes. In this last table, a study22 was excluded because it did not present total measures, but rather growth increments.

Table 3 Sample characteristics and objectives of the 16 articles selected for review. 

Article Type of study (T or L) n Control group Malocclusion Sex % Ethnicity Age Objective
Dhoptkar et al.19
(2002)
Transversal 200 No 50 with Class I
50 with Class II div 1
50 with Class II div 2
50 with Class III
50% Caucasian Class I: 10.4 yrs
Class II div 1: 10.1yrs
Class II div 2: 11.1yrs
Class III: 10.2 yrs
To compare the skull base
flexion to type of malocclusion as follows:
Class I to Class II div 1 to Class II div 2 and Class I to Class III
Wilhelm et al.15
(2001)
Longitudinal 43 No 22 with Class I
21 with Class II
50% European 1 month
2 yrs and
14 yrs old
To compare the longitudinal growth of the skull base (size and shape) to Class I and Class II malocclusions)
Mouakeh21
(2001)
Transversal 138 Yes; Paired by age, sex and ethnicity 69 with Class III
69 with Class I (control)
66.6% female Syrian 5 - 12 yrs old
Mean 8.4 ± 2 yrs old
To identify morphological characteristics of the craniofacial complex in Syrian patients with Class III malocclusion and compare them to controls
Alexander et al.22
(2009)
Longitudinal 103 No 103 with Class III 55 females
48 males
Caucasian 6-7; 7-8; 8-9; 10-11; 11-12; 12-13
13-14; 15-16; 16-17; 17-18 yrs old
To investigate changes in the craniofacial growth in untreated individuals with Class III malocclusion
Ishii et al.23
(2001)
Transversal 279 Yes 190 with Class II div 1
89 with Class I (control)
100% females Japanese 3 groups: Mixed dentition,
Delayed mixed dentition, Young permanent dentition
To compare the craniofacial characteristics of Japanese females with Class II division to those of controls
Polat, Kaya1
(2007)
Transversal 75 No 25 with Class I
25 with Class II
25 with Class III
CIass I: 13 F, 11 M
Class II: 14 F, 11 M
Class III: 13 M, 12 F
Not specified (patients treated at the Baskent University in Ankara, Turkey 15.74 yrs ± 4.28 To evaluate the difference in the skull base flexion between dental and skeletal Class I, Class II, and Class III malocclusions
Singh et al.24
(1997)
Transversal 142 Yes 73 with Class III
69 with Class I (control)
Approximately the same
number of males and females
European/American 7 groups of 5 to 11 yrs To differentiate the skull base between individuals with Class I malocclusion and those with Class III malocclusions
Johannsdottir et al.25
(1999)
Transversal 563 Yes 200 with Class I
363 with Class II
184 males
179 females
Icelanders 5 yrs 7 mo to 7 yrs 8 mo
Mean of 6 yrs 7 mo
To describe the craniofacial characteristics of Icelander children aged 6 years old with Class II malocclusion and compared them to Class II malocclusion
Rothstein, Yoon-Tarlie16
(2000)
Transversal 613 Yes 278 with normal occlusion
335 with Class II div 1
T1: 47 F and 48 M
T2: 47 F and 43 M
Caucasian 3 groups of subjects aged 10, 12 and 14 yrs old ± 6 years To investigate whether Class II malocclusion is characterized by a poorly developed mandible or by its retropositioning
Ishii et al.26
(2002)
Transversal 124 No Class II div 1 in Japanese females
Classe II div 1 in Caucasian females
100% females 49 Japanese and
75 Caucasian females
Japanese: 11 yrs 8 mo
British: 11 yrs 11 mo
To help define the craniofacial morphology of the Japanese with Class II malocclusion div 1 and to compare them with Caucasian individuals with the same malocclusion; and to elucidate craniofacial differences between ethnic groups
Kapoor et al.27
(2001)
Transversal 100 Yes 50 with Class II
50 with normal occlusion
50% Indian 9 to 12 yrs old
10.64 yrs old, males
9.8 yrs old, females
To understand and differentiate the skeletal-dental morphology of children with straight terminal plane and those with Class II pattern
Singh et al.28
(1998)
Transversal 141 No 72 with Class III, European/American
69 with Class III, Korean
50% European/American Korean 5 to 11 yrs old To compare Korean and European/American subjects with Class III malocclusion and provide data on ethnic diversity in individuals with Class III malocclusion
Zeng et al.29
(1998)
Transversal 160 No 40 with Class I Chinese;
40 with Class II Chinese (ch)
40 with Class I Swedish
40 with Class II Swedish (sw)
50% Chinese
Swedish
8 to 10 yrs old
9.1 ± 0.9 males (M) ch Class II
9 ± 0.8 females (F) ch Class II
9.4 ± 0.8 M/F ch Class I
9.3±0.9 M sw Class I
9.3 ± 0.8 F sw Class I
8.7±0.8 M sw Class II
8.9±1.0 F sw Class II
To assess craniofacial structures in two ethnic groups and two malocclusions by comparing Chinese and Swedish individuals with Class I and Class II malocclusions
Lau e Hagg30
(1999)
Transversal 416 No 105 Chinese with Class II div 1
107 Caucasians with Class II div 1
204 Chinese with normal occlusion
Approx. 50% Chinese
Caucasians
10 to 15 yrs old
11 to 13 yrs old
12 yrs old
To assess the craniofacial pattern of Chinese and Caucasian individuals with Class II div 1 malocclusion and those with normal occlusion;
Chinese with Class II x Chinese with normal occlusion;
Chinese with Class II div 1 x Caucasians with Class II div 1
Chang et al.31
(2005)
Transversal 200 Yes 100 with Class III
100 with normal occlusion (control)
50% No specification (radiographs from the Kaohsiung University, Taiwan) 9.4 to 11.5 yrs old To compare morphological characteristics
of the skull base in children with malocclusion
Class III with normal children and provide database for subsequent Class III studies
Yoon, Chung37
(2015)
Longitudinal 46 Yes 25 with Class I
21 with Class II
100% females Caucasian ages 9, 14, and 18 To investigate and compare the craniofacial growth of untreated Class I and Class II girls from ages 9 to 18 years

Table 4 Epitome of the articles selected for review. 

Article Flexion (NSBa or NSAr) Anterior length (N-S) Posterior length (S-Ba or S-Ar) Conclusion
Dhopatkar et al.19
(2002)
NSBa: non-significant / NSAr: more significant for Class II div 1 malocclusion than for Class I malocclusion. No difference was observed in the latter N-S: greater for Class II div 1 and 2 than in Class I malocclusion
Class I and Class II malocclusions no significant
S-Ba: greater in Class II div 1 and 2; than in Class I
Class I and Class III malocclusions no significant
S-Ar was not studied
The skull base angle itself has no key influence on the development of malocclusions
Wilhelm et al.15
(2001)
NSBa: not so obtuse in patients with Class II malocclusion, flexion decreases from 1 month to 2 years and 14 years.
NSAr was not studied
N-S: no difference was found between
Class I and Class II malocclusions
S-Ba: no difference between malocclusions
S-Ar was not used
Growth in skull base is similar to that in Class I and Class II malocclusions
Mouakeh21
(2001)
NSBa was not studied;
NSAr was smaller in Class III than in normal occlusion
N-S smaller in Class III than in normal occlusion S-Ba was not studied
S-Ar smaller in Class III than in normal occlusion
Flexion, anterior and posterior lengths are significantly smaller in Class III malocclusions
Alexander et al.22
(2009)
No measurement proposed was used N-S increased yearly in all age groups studied,
1 mm in boys and less than 1 mm in girls
S-Ba not studied
S-Ar not studied
No measurement proposed was used
Ishii et al.23
(2001)
NSBa was not studied
NSAr: not significant between age groups for Class II div 1 malocclusion
Not evaluated for Class I malocclusion.
N-S smaller in Japanese young permanent dentition with Class II div I malocclusion than in those with
normal occlusion
S-Ba not studied S-Ar: not significant between age groups for Class I div 1 malocclusion
Not evaluated between Class II div 1 malocclusion and Class I malocclusion
Class II div 1 malocclusion had an increase in facial angle in association with a shortened mandibular ramus, compared to Class I malocclusion
Polat, Kaya1
(2007)
NSBa not significant
NSAr not significant
N-S not significant SBa not different
S-Ar not significant
No difference was found in angle and dimensions of the skull base for Class I, II and III malocclusions
Singh et al.24
(1997)
NSBa was more acute in Class III at 8 to 9 yrs old
NSAr was not different between Class I and Class III malocclusions at 5-11 yrs old despite tending to be acute
N-S smaller in Class III than Class I malocclusions
at 8 and 9 yrs old
S-Ba: no difference between age groups
S-Ar not studied
Skull base angle tending to be more acute in Class III malocclusion than in normal occlusion
Johannsdottir et al.25
(1999)
NSBa not significant between men and women, being more obtuse in Class II than in Class I malocclusions
NSAr not significant between men and women, being more obtuse in Class II than in Class I malocclusions
N-S was greater in Class II than in Class I malocclusion, dimorphism; SN smaller in women; SN was significant S-Ba and S-Ar smaller in women Dimorphism was found at the skull base at 6 yrs old in Class II malocclusion
Rothstein, Yoon-Tarlie16
(2000)
NSBa greater in Class II div 1 malocclusion for girls at 10, 12, 14 yrs old (no difference); and boys at 10, 12, 14 yrs old.
NSAr not studied
N-S was significantly greater in Class II div 1 malocclusions
for girls at 10, 12, 14 yrs old and for boys at 14 yrs old compared to Caucasians with normal occlusion
S-Ba: no significant difference found in girls
Significant difference was found in boys at 10 and 12 yrs old only
S-Ar not studied
Anterior base is more protrusive in Class II malocclusions, with length being excessive at the skull base, maxillary and frontal sinuses increased (may contribute to Class II malocclusion increase)
Skull base flexion does not contribute to the retruded positioning of the mandible
Ishii et al.26
(2002)
NSBa not studied
NSAr smaller in Japanese than in Caucasian women despite the lack of significant difference
N-S was significantly smaller in Japanese than
in Caucasian women with Class II div 1 malocclusions
S-Ba not studied
S-Ar: no significant difference
Caucasian women have a more significantly longer anterior skull base
Kapoor et al.27
(2001)
NSBa not studied
NSAr: no significant gender difference was found despite being smaller in women. More acute for distal malocclusions
N-S not studied S-Ba not studied
S-Ar not studied
NSAr is one of the factors indicating a Class II pattern in association with a distal mandibular positioning and skull base rotation
Singh et al.28
(1998)
NSBa and NSAr are more acute in European/American individuals than in Korean ones with Class III malocclusion N-S greater in European/American individuals S-Ba and S-Ar greater in European/American individuals For European/American individuals with Class III malocclusions, the craniofacial morphology is affected by an orthocephalization of the skull base, exacerbated by prominent mandible and symphysis morphology
Zeng et al.29
(1998)
NSBa: no significant difference was found between Swedish and Chinese individuals with Class I and Class II malocclusions
NSAr not studied.
N-S greater in Chinese individuals with Class II
malocclusions than in Swedish ones, despite being
smaller in Chinese individuals with Class I malocclusion, compared to the Swedish ones
S-Ar not studied
S-Ba greater in Chinese individuals with Class II malocclusions than in Swedish ones
No significant difference was found in Class I malocclusion regarding both ethnic groups S-Ar not studied
Anterior and posterior lengths of the skull base were greater in Chinese than in Swedish individuals
Lau, Hagg30
(1999)
NSBa not studied
NSAr: no significant gender difference in Chinese individuals with Class II div 1; however, this angle was smaller when Class II div 1 malocclusion was compared to normal occlusion
S-N not studied S-Ba not studied
S-Ar not studied
No dimorphism was found between Chinese individuals with Class II div 1 malocclusion
Skull base angle is more acute in Chinese individuals with Class II div 1 malocclusion than in those with normal occlusion
Chang et al.31
(2005)
NSBa not significant
NSAr: more acute in Chinese individuals with Class III malocclusion
N-S smaller in Class III malocclusion than in
normal occlusion
S-Ba smaller in Class III malocclusion, but with no significant difference
S-Ar smaller in Class III malocclusion than in normal occlusion
The decreased flexion and length in Class III malocclusion may be related to the aetiology of this type of malocclusion
Yoon, Chung37
(2015)
NSAr ( Saddle angle) not significant N-S not significant S-Ba not studied
S-Ar not studied
In general, the Class I and Class II groups showed similar skeletal growth

Age

Seven studies have investigated the growth of the skull base by comparing the data obtained from different age groups16,20,22,23,24,28,37 with three22,24,28 of them using samples of individuals with Class III malocclusion and whose age ranged from 5 to 18 years old. These individuals were found22 to have a yearly increment in the length of the anterior skull base in all age groups (6 to 18 years old), which was smaller than 1 mm for women and approximately equal to 1 mm for men, similar to the growth estimated for individuals with Class I malocclusion. In another study24 comparing Class III malocclusion to Class I malocclusion in individuals aged 5 to 11 years old, it was found that NSBa angle was more acute in the latter at ages of 5, 8, and 9 years old, and that NSAr angle had the same trend; but no statistically significant difference was found at 8 years old. Researchers23 have reported that the skull base of Japanese individuals with Class II division 1 malocclusion had a significantly smaller anterior length at 10 years and 10 months to 15 years and 10 months old compared to other age groups, involving individuals with same malocclusion and race (Group 1: 7 years and 6 months to 13 years and 6 months old; and Group 2: 9 years and 1 month to 13 years and 6 months old). On the other hand, another study29 compared individuals with Class II division 1 malocclusion to controls and found that the length of the anterior skull base was statistically greater in all six age groups studied (females aged 10, 12, 14 years old, and males aged 10, 12, 14 years old). Two studies20,28 had samples with different age groups, but it was not possible to use all data because the first study20 had compared age groups of 1 month, 2 years and 14 years old, whereas the second study28 had assessed neither flexion nor the skull base length at different age groups. For Yoon and Chung,37 which compared Class I with Class II at three different ages (9, 14 and 18 years - all female), no difference was observed in the flexion or length of the anterior skull base.

Ethnic group

Three studies have assessed different ethnic groups,26,28,29 with Asian being compared to Caucasian individuals in most cases, and significant differences being found. The length of the anterior skull base was found to be greater for Japanese than for Caucasian females.26 However, a study28 reported a greater anterior skull base as well as a more acute NSAr angle in European/American than in Korean individuals. Similarly, with regard to the length of the anterior skull base, a study29 showed this measurement was smaller in Chinese than in Swedish individuals for both types of malocclusions (Class I and Class II), with the posterior length (S-Ba) being also smaller in Chinese individuals with Class II malocclusion. Another study24 evaluated two ethnic groups but no comparison was possible because of the lack of data on skull base structures regarding Caucasian individuals.

Dimorphism

Six studies have evaluated the relationship between sexual dimorphism and development of the skull base,22,25,27,30,16,29 but no significant difference was found in the angular measurements. However, one study25 showed that linear measurements (S-N, S-Ar and S-Ba) were significantly greater in Icelander male children compared to female ones with Class I and Class II malocclusions.

Malocclusion differences

Of the 16 articles selected, only one has not compared flexion or length of the skull base to some type of malocclusion.22 Two studies1,19 compared flexion or length of the skull base in individuals with Class I, Class II and Class III malocclusions. One of these studies19 found greater angular measurements for the skull base in Class II division 1 malocclusion, compared to Class I malocclusion. In this same study, no difference was found between Class I malocclusion and other ones, regarding such angular measurements, whereas the length of the anterior and posterior skull base were greater in the cases of Class II malocclusion. However, the other study1 reported significant differences in the skull base length between the three types of malocclusion. Studies21,24,31 have also compared Class III malocclusion to normal occlusion, whereas another one28 compared this condition between Caucasian and Korean individuals. All these studies found similar results, with the length of the anterior skull base being smaller in Korean individuals with Class III malocclusion and skull base flexion tending to be more acute in Caucasian individuals with the same condition.

Among these seven studies16,20,23,25,27,30,37 comparing Class II malocclusion to Class I malocclusion, similar results have been reported. For example, individuals with Class II malocclusion had greater anterior and posterior lengths and more obtuse angular measurements regarding the skull base. However, one study23 reported a smaller length of the skull base in Japanese girls with Class I malocclusion presenting permanent dentition, whereas another30 found no significant differences in the skull base flexion compared to normal occlusion. In the study, the compared groups (Class I and Class II) showed no differences in the length of the anterior skull base and flexion of the cranial base.

DISCUSSION

The skull base not only supports and protects the brain but also articulates the cranium with vertebral column, maxilla and mandible. One of its key functions has to do with adaptation and protection, including a shock-absorbing area between brain, face and pharyngeal region, whose growths occur differently. The growth of the skull base occurs by means of a complex balance between sutural growth, prolongation of synchondroses, extensive cortical sliding, and remodelling. This combination allows an increase in the differential growth between base and vault of the skull, expansion of the contours of the various endo-cranial fossae, maintenance of vessel and nerve pathways, and prolongation of the processes, such as hypophysis. Prolongation of the skull base occurs with the growth of synchondroses and direct cortical growth. The cortical sliding of the skull floor produces several degrees of growth movement at different regions, usually towards the ecto-cranial direction, with apposition proportional to the external surface.5

Enlow32 has shown that maxilla growth is influenced by the skull base, which in turn, is influenced by the growth of the brain. The mandible, because of its distant positioning, acts more independently, despite being articulated with glenoid fossa, thus being a potential factor influencing the skull base.

To better understand the cephalometric aspects, the skull base is divided into anterior and posterior lengths, the former extending anteriorly from sella turcica (S) to nasofrontal suture (N), and the latter extending from sella turcica to the anterior edge of the foramen magnum, defined as Ba.21 There is a consensus that the length of the anterior skull base corresponds to the linear N-S distance, but the same cannot be said about the posterior region, which corresponds to either S-Ba or S-Ar linear distances.19

Björk2 supported the use of the latter, as it is more easily visualized, with most studies using this measurement. Verjanne and Koski33 suggested the use of Ba to measure the skull base angle as they considered the S-Ar measurement too distant; Kerr and Adams34 used Ba to measure the skull base angle. Bhatia and Leighton35 used N-S-Ba, N-S-Art as well as S-Ba and S-Art, and found similar measurements.

According to the other authors,19 the skull base follows a neural (anterior region) and somatic (posterior region) growth pattern despite its cartilaginous origin (chondrocranium). After birth, especially in the early childhood, the growth of the anterior portion occurs mainly due to the increase in frontal sinus and remodelling of the nasal region, whereas the growth of the posterior region is related to the interstitial growth occurring in the spheno-occipital synchondrosis.

The two segments of the base of the skull form an flexion of 130-135 degrees at the angle formed at the Sela point (center of the sella turcica). This angle (NSBa) has approximately 142 degrees at birth, but decreases to 130 degrees at 5 years old.19 From 5 to 15 years old, the skull base angle is relatively stable.23 Other studies suggest that there are no differences in this angle of the skull base during childhood, puberty and adult phase.1,23

There is evidence showing that the skull base angle (N-S-Ba) is greater in Class II division 1 malocclusion than in Class I malocclusion or normal occlusion, with this angle not differing between Class II division 2 and Class I malocclusions.19 In addition, studies comparing Class II malocclusions to normal occlusion or Class I malocclusion16,20,23,25,27,30,37 found similar results.16,25,27 However, two studies30,37 compared such malocclusions and reported a smaller flexion of the skull base in individuals with Class II malocclusion. This can be explained by the fact that the posterior region of the skull base (S-Ba) forming the S-N-Ba angle might be anteriorly or posteriorly inclined, whereas the anterior region (S-N) might also be inclined anteriorly upwards or downwards, thus causing a variation in either S or N points vertically.36 Therefore, variable lengths of the anterior and posterior regions of the skull base can compensate any cranial flexion, that is, a posterior acute angle anteriorly positioned in relation to the mandible can neutralize the cranial flexion through the greater posterior length, thus positioning Ba and mandible posteriorly and vice-versa.20 However, the skull base length was not assessed.30 Despite these findings, the skull base flexion is thought to have no influence on malocclusions,1,19 whereas there is no consensus among other studies regarding this issue.21,23-27,30-31

With regard to the Class III malocclusion, it has been reported that linear and angular measurements of the skull base are smaller when compared to other types of malocclusion.1 These findings are corroborated by some studies,21,31 although one study1 had found smaller angular measurements for Class III malocclusions, despite not being significant.

Asian individuals present a smaller anterior length and a more obtuse angle of the skull base, compared to Caucasians, with this finding comprising the both ethnic and morphological characteristics, according to some authors.23,26,28

CONCLUSIONS

After evaluating all these articles selected for the present systematic review, one can state the following:

  1. The skull base angle itself does not seem to play a key role in the development of malocclusions.

  2. The skull base angle is relatively stable at the ages of 5 to 15 years old.

  3. A more obtuse skull base flexion, in association or not with a greater length of the anterior skull base, can contribute to the development of Class II division 1 malocclusion. A more acute skull base flexion can contribute to a more anterior positioning of the mandible and to development of Class III malocclusion as well.

REFERENCES

1 Polat OO, Kaya B. Changes in cranial base morphology in difference malocclusions. Orthod Craniofac Res. 2007 Nov;10(4):216-21. [ Links ]

2 Björk A. Cranial base development. Am J Orthod. 1955 Mar;41(3):198-255. [ Links ]

3 Ford EHR. Growth of the human cranial base. Am J Orthod. 1958 July;44(7):498-506. [ Links ]

4 Scott JH. The cranial base. Am L Phys Anthropol. 1958 Apr;16(3):319-48. [ Links ]

5 Moyers RE. Ortodontia. 4ª ed. Rio de Janeiro: Guanabara Koogan; 1991. [ Links ]

6 Santos-Pinto A, Martins JCR, Uetanabaro T, Sakima T, Mendes AJD. Influência do grau de deflexão da base craniana no relacionamento ântero-posterior dos maxilares. Ortodontia. 1983;16:5-9. [ Links ]

7 Björk A. The nature of facial prognathism and its relation to normal occlusion of the teeth. Am J Orthod. 1951 Feb;37(2):106-24. [ Links ]

8 Björk A. The face in profile. An Anthropological X-ray Investigation on Swedish Children and Conscripts. Svensk Tandläkare-Tidskrift. 1947;40(5B Suppl):1-180. [ Links ]

9 Ricketts RM. A foundation for cephalometric communication. Am J Orthod. 1960 May;46(5):330-57. [ Links ]

10 Hopkin GB, Houston WJ, James GA,et al. The cranial base as an aetiological, factor in malocclusion. Angle Orthod. 1968 July;38(3):250-5. [ Links ]

11 Horowitz SL, Converse JM. Craniofacial relationships in mandibular prognathism. Arch Oral Biol. 1969 Jan;14(1):121-31. [ Links ]

12 Dibbets JMH. Morphological associations between the Angle classes. Eur J Orthod. 1996 Apr;18(2):111-8. [ Links ]

13 Hildwein M, Bacon W, Turlot JC, Kuntz M. Spécificités et discriminants majeurs dans une population de Classe II division 1. Revue d'Orthopédie Dento-Faciale. 1986 June;20(2):197-208. [ Links ]

14 Kasai K, Moro T, Kanazawa E, Iwasawa T. Relationship between cranial base and maxillofacial morphology. Eur J Orthod. 1995 Oct;17(5):403-10. [ Links ]

15 Wilhelm BM, Beck FM, Lidral AC, Vig KWL. A comparison of cranial base growth in Class I and Class II skeletal patterns. Am J Orthod Dentofacial Orthop. 2001 Apr;119(4):401-5. [ Links ]

16 Rothstein T, Yoon-Tarlie C. Dental and facial skeletal characteristics and growth of males and females with Class II, division 1 malocclusion between the ages of 10 and 14 (revisited)-Part I: characteristics of size form, and position. Am J Orthod Dentofacial Orthop. 2000 Mar;117(3):320-32. [ Links ]

17 Antczak AA, Tang J, Chalmers TC. Quality assessent of randomized control trials in dental research. I: Methods. J Periodontal Res. 1986 July;21(4):305-14. [ Links ]

18 Flores-Mir C, Major MP, Major PW. Search and selection methodology of systematic reviews in orthodontics. Am J Orthod Dentofacial Orthop. 2006 Aug;130(2):214-7. [ Links ]

19 Dhoptkar A, Bhatia S, Rock P. An investigation into the relationship between the cranial base angle and malocclusion. Angle Orthodontist. 2002 Oct;72(5):456-63. [ Links ]

20 Andria LM, Leite LP, Prevatte TM, King LB. Correlation of the cranial base angle and its components with other dental /skeletal variables and treatment time. Angle Orthod. 2004 June;74(3):361-6. [ Links ]

21 Mouakeh M. Cephalometric evaluation of craniofacial pattern of Syrian children with Class III malocclusion. Am J Orthod Dentofacial Orthop. 2001 June;119(6):640-9. [ Links ]

22 Alexander AEZ, McNamara JA, Franchi L, Baccetti T. Semi longitudinal cephalometric study of craniofacial growth in untreated Class III malocclusion. Am J Orthod Dentofacial Orthop. 2009 June;135(6):701-14. [ Links ]

23 Ishii N, Deguchi T, Hunt N. Craniofacial morphology of Japanese girls with Class II division 1 malocclusion. J Orthod. 2001 Sept;28(3):211-5. [ Links ]

24 Singh GD, McNamara JA Jr, Lozanoff S. Morphometry of the cranial base in subjects with Class III malocclusion. J Dent Res. 1997 Feb;76(2):694-703. [ Links ]

25 Johannsdottir B, Thordarson A, Magnusson TE. Craniofacial morphology in 6-year-old Icelandic children. Eur J Orthod. 1999 June;21(3):283-90. [ Links ]

26 Ishii N, Deguchi T, Hunt NP. Morphological diferences in the craniofacial structure between Japanese and Caucasian girls with Class II division 1 malocclusion. Eur J Orthod. 2002 Feb;24(1):61-7. [ Links ]

27 Kapoor S, Kapoor DN, Jaiswal JN. Cephalometric evaluation of Class II malocclusion in transitional dentition. J Indian Soc Pedo Dent. 2001 Dec;19(4):127-33. [ Links ]

28 Singh GD, McNamara JA Jr, Lozanoff S. Craniofacial heterogeneity of prepubertal Korean and European-American subjects with Class III malocclusions: procrustes, EDMA, and cephalometric analyses. Int J Adult Orthod Orthognath Surg. 1998 Jan;13(3):227-40. [ Links ]

29 Zeng XL, Forsberg CM, Aronson SL. Craniofacial morphology in Chinese and Swedish children with Angle Class I and Class II occlusal relations. Australian Orthod J. 1998 Oct;15(3):168-76. [ Links ]

30 Lau JWP, Hagg U. Cephalometric morphology of Chinese with Class II division 1 malocclusion. Br Dental J. 1999 Feb;186(4):188-90. [ Links ]

31 Chang HP, Hsieh SH, Tseng YC, Chou TM. Cranial-base morphology in children with Class III malocclusion. Kaohsiung J Med Sci. 2005 Apr;21(4):159-65. [ Links ]

32 Enlow DH. Crescimento facial. 3ª ed. Rio de Janeiro: Artes Médicas; 1993. [ Links ]

33 Varjanne I, Koski K. Cranial base, sagittal jaw relationship and occlusion. A radiological: craniometric appraisal. Proc Finn Dent Soc. 1982 Jan;78(4):179-83. [ Links ]

34 Kerr WJS, Adams CP. Cranial base and jaw relationship. Am J Phys Anthropol. 1988 Oct;77(2):213-20. [ Links ]

35 Bathia SN, Leighton BC. A manual of facial growth. Oxford: Oxford University Press; 1993. [ Links ]

36 Kerr WJS. A method of superimposing serial lateral cephalometric films for the purpose of comparison: a preliminary report. Br J Orthod. 1978 Jan;5(1):51-3. [ Links ]

37 Yoon SS, Chung CH. Comparison of craniofacial growth of untreated Class I and Class II girls from ages 9 to 18 years: a longitudinal study. Am J Orthod Dentofacial Orthop. 2015 Feb;147(2):190-6. [ Links ]

» The authors report no commercial, proprietary or financial interest in the products or companies described in this article.

Received: June 02, 2016; Accepted: August 27, 2017

Contact address: Dirceu Barnabé Raveli Rua Humaitá, 1680, Araraquara/SP - CEP: 14.801-903 E-mail: draveli@foar.unesp.br

Author contributions

Conception or design of the study: KCMA, TBR, CIVV, ASP. Data acquisition, analysis or interpretation: KCMA, TBR, CIVV, ASP, DBR. Writing the article: KCMA, TBR, CIVV, ASP, DBR. Critical revision of the article: KCMA, TBR, ASP, DBR. Final approval of the article: KCMA, TBR, ASP.

Creative Commons License This is an open-access article distributed under the terms of the Creative Commons Attribution License