The Tori of the Mouth and Ear: A Review
MARIOS LOUKAS,1,2* PAUL HULSBERG,1R. SHANE TUBBS,3THEODOROS KAPOS,4
CHRISTOPHER T. WARTMANN,5KITT SHAFFER,6AND BERNARD J. MOXHAM7
1Department of Anatomical Sciences, School of Medicine, St George’s University, Grenada, West Indies
2Department of Anatomy, Medical School Varmia and Masuria, Olsztyn, Poland
3Children’s Hospital, Pediatric Neurosurgery, Birmingham, Alabama
4Department of Restorative Dentistry and Biomaterials Sciences, Harvard School of Dental Medicine,
5Department of Otolaryngology/Head and Neck Surgery, University of Maryland Medical Center,
6Department of Radiology, Boston University, Boston, Massachusetts
7Cardiff School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
There is a great deal of literature regarding the tori of the mouth and ear. However,
there is controversy regarding the etiology and prevalence of each. The torus pala-
tinus is generally agreed to be the most common oral exostosis and is more fre-
quently found in females. The torus mandibularis is also quite common, is more
prevalent in males, and occurs bilaterally in 80% of cases. Far less data have been
presented regarding the torus maxillaries primarily due to the lack of consensus
regarding its nomenclature and classification. These oral tori are thought to be
inherited in an autosomal dominant manner with a relatively high penetrance;
however, environmental and functional factors have been postulated that may
account for a more complex etiology than simply genetics. The torus auditivus is
rarely acknowledged in clinical papers and most data are found in anthropological
journals. Although there is an abundance of literature that addresses these traits
individually, there is a lack of research that collectively acknowledges these.
Therefore, the aim of this study was to present a composite review of the tori with
regards to their anatomical features, prevalence, etiology and clinical relevance.
Clin. Anat. 00:000–000, 2013.
C2013 Wiley Periodicals, Inc.
An exostosis is generally defined as a nonpatho-
logic, localized protuberance arising from cortical bone
(Neville et al., 1995; Antoniades et al., 1998). Two
common forms of exostoses found in the oral region
are the torus palatinus and the torus mandibularis.
Additionally, two less common forms of tori also exist,
the torus auditivus and the torus maxillaris.
The torus palatinus is the most prevalent of these
exostoses of the head and similar to the other three,
is usually asymptomatic and does not warrant treat-
ment in most cases. It is classified as a benign osse-
ous outgrowth of the median raphe of the palatine
bone and can vary in shape and size (Kahn, 1977).
However, due to the fear of cancer, patients often
have these removed. Santorini reported the first
observations of exostoses of the hard palate (Sonnier
et al., 1999); however, the earliest article describing
these variationswaspublishedby Foxin 1814
*Correspondence to: Marios Loukas MD, PhD, Professor and
Chair, Department of Anatomical Sciences, St. George’s Univer-
Received 22 June 2011; Revised 16 March 2013; Accepted 28
Published online in Wiley Online Library
(wileyonlinelibrary.com). DOI: 10.1002/ca.22264
C 2013 Wiley Periodicals, Inc.
Clinical Anatomy 00:000–000 (2013)
(Antoniades et al., 1998). Kupffer and Bessel-Hagen
first coined the term torus palatinus in 1879, after the
Latin torus meaning “to stand out” or “lump” (Castro
Reino et al., 1990; Garc? ıa-Garc? ıa et al., 2010). Later,
the protuberance was claimed to be a characteristic of
East Prussian skulls. This led early 20th century
researchers to associate the torus palatinus with
tuberculosis, rickets, syphilis, scurvy, and cancer
(Dorrance, 1929; Woo, 1950; Anda, 1951; Lasker,
1952; Jorjensen, 1953; Antoniades et al., 1998). The
literature varies with regards to the prevalence of the
torus palatinus, especially among different popula-
tions, however it is found in about 20% of the US
population and more frequently among American
Indians and Eskimos (Larheim and Westesson, 2008).
The torus mandibularis was first reported by Dan-
ielli in 1884 (Antoniades et al., 1998). The term, how-
ever, was coined by F€ urst in 1908 to describe the
bony protuberance that developed in the premolar
area of the lingual surface of the mandible (F€ urst,
1908; Antoniades et al., 1998). In 1968, Goldman
and Cohen mentioned that high incidences of large
exostoses could be a factor in the delayed healing of
gingivectomy wounds in this area (Goldman and
Cohen, 1968; Antoniades et al., 1998). Most studies
show that the torus mandibularis is less common than
the torus palatinus with a general prevalence of about
6% with a bilateral presentation in about 80% of
cases (Laskaris, 2003).
The torus maxillaris is the least studied of the oral
exostoses. It is located in the region of the upper pre-
molars, and is made up of very compact bone (Broth-
well, 1981). It is seen in 2.5–17% of the population
and usually does not warrant removal (Brothwell,
1981). The torus palatinus is sometimes classified as
a “maxillary torus”; however, anthropologic studies
distinguish the two based on their relative location to
The torus auditivus is usually found on the floor of
the external acoustic meatus (Brothwell, 1981). It is
believed to be caused by trauma in the periosteum of
the ear canal, leading to osteogenesis (Mays, 1998).
Historically, cases of auditory tori have been found in
ancient skeletons worldwide, including ancient peoples
from the Balkans, Chileans from 7000 B.C., and indi-
viduals from Imperial Rome of the 1st century A.D.
(Frayer, 1988; Manzi et al., 1991; Sakalinskas and
Jankauskas, 1993; Standen et al., 1997; Gerszten
et al., 1998; Velasco-Vazquez et al., 2000; Okumura
et al., 2007).
Studies have been conducted on the prevalence as
well as the etiology of the tori, but with debate. With
the exception of the torus auditivus, it is almost uni-
versally accepted that genetic factors are involved
with the development of the tori, but environmental
aspects such as functional, nutritional, behavioral, and
climatological factors have also been studied to deter-
mine the causes of the tori (Hooton, 1918; Matthews,
1933; Schreiner et al., 1935; Hrdlicka, 1940; Towns-
ley, 1948; Archangeli, 1954; Johnson, 1959; Mayhall,
1968; Mayhall et al., 1970; King and Moore, 1971;
Mayhall and Mayhall, 1971; Haugen, 1992). Currently,
the cause of the tori is thought to be multifactorial
(Eggen, 1989), while most scholars consider the
inheritance as autosomal dominant (Castro Reino
et al., 1990; Donado, 1998; Kerdpon and Sirirungrojy-
Sonnier et al., 1999; Jainkittivong and Langlais, 2000;
Al-Bayaty et al., 2001; Bruce et al., 2004; Garc? ıa-
Garc? ıa et al., 2010). Because of the asymptomatic
nature of these bony excrescences, there has yet to
be a global study on their prevalence (Antoniades
et al., 1998). From the literature, however, it is appa-
rent that the existence of these tori varies depending
on racial groups, gender, and age. The aim of this
study is to review the literature on the torus palatinus,
mandibularis, maxillaris, and auditivus with regards to
gross and histological anatomy and also examine their
prevalence, etiology, and clinical relevance.
The torus palatinus is located along the longitudinal
ridge of the hard palate and can be flat, nodular, spin-
dle-shaped, and lobular (Kolas et al., 1953; Barnes,
2001) (Figs. 1 and 2). The flat type is the most com-
mon torus (49%) and is described as smooth and
symmetrically distributed on either side of the median
raphe (Kolas et al., 1953; Barnes, 2001). The nodular
variety, being the least common (6.5%), has multiple
prominences each protruding from its own base (Kolas
et al., 1953; Barnes, 2001). The spindle-shaped type
appears as a ridge divided by the longitudinal medial
groove and can be either confined to a limited area or
may extend to the posterior end of the hard palate
(Kolas et al., 1953; Barnes, 2001). The lobular form is
usually the largest and is characterized by a broad
base with multiple vertical and horizontal furrows
(Kolas et al., 1953; Barnes, 2001). The size varies
greatly among patients, as some individuals have a
torus that is barely discernible while others may have
a very large exostosis that may warrant removal,
especially if the patient is planning for denture con-
struction (Belsky et al., 2003).
nus. Reconstructed coronal CTscan shows highly calcified
lobulated mass growing from palatal bone (With permis-
sion from Yonetsu and Nakamura, 2001, AJR Am J Roent-
It depicts a 46-year-old man with torus palati-
2Loukas et al.
The torus palatinus is histologically characterized
as mature cortical and trabecular bone with minimal
osteoblastic activity (Regezi and Sciubba, 1989; Jain-
kittivong et al., 2000; Gnepp, 2001; Belsky et al.,
2003). It is encapsulated by a tight mucosal covering,
which makes it highly susceptible to trauma (Nash,
1972; Khan, 1977). With trauma to the area, ulcera-
tion, and inflammation often occur (Laskaris, 2003).
Unlike the mandibular torus, the incidence of torus
palatinus does not correlate with the presence or ab-
sence of teeth due to the fact that is formed on the
stable palatine bone and the palatine processes of the
maxilla, rather than the relatively labile alveolar man-
dibular bone (Sonnier et al., 1999).
The literature varies in regards to gender differ-
ences for prevalence of the torus palatinus but most
studies show that females are affected about 1.7
times as often as males in similar populations
(Eggen et al., 1994; Neville et al., 1995; Antoniades
et al., 1998). The torus palatinus seems to be most
prevalent between the third and fourth decade of
life, although it can occur at any age (K€ orner, 1910,
1924; Lachmann, 1927; Kolas et al., 1953; Baptista,
1957; Barnes, 2001). In the US, palatine tori seem
to be more prevalent in Caucasians (22.8%) than
African Americans (12.2%) (Sonnier et al., 1999).
Multiple studies have been done on various popula-
tions that allow for comparison of the incidence of
the torus palatinus across a variety of ethnic groups.
A study conducted by Reichart et al. (1988) com-
pared the prevalence of both torus palatinus and
torus mandibularis in German versus Thai popula-
tions. It was shown that the torus palatinus was
found in 23.1% of Thai patients but in only 13.5% of
the German patients.
showed that the spindle-shaped torus palatinus
occurred most frequently among German patients
(29.8%) (Reichart et al., 1988). A survey of four
studies performed on Turkish populations revealed
values of 45.4, 30.9, 20.9, and 4.1% (G€ ozil et al.,
1999; Cagirankaya et al., 2004; Yildiz et al., 2005;
Sisman et al., 2008).
It is generally accepted that inheritance plays a
major role in the incidence of the torus palatinus
(Sisman et al., 2008). The most common under-
standing is that the gene for torus palatinus is auto-
somal dominant (Gould, 1964). Because of the high
frequency of the trait, in some studies, it has been
suggested that the incidence is higher than would
be observed in predicted autosomal dominant inher-
itance because of a high rate of homozygous parents
(Gorsky et al., 1998). The trait is also described as
having variable expressivity and a penetrance of
85% (Barbujani et al., 1986; Barnes, 2001). Envi-
ronmental factors are also recognized as contribut-
ing to the incidence of the torus palatinus. Many
studies show that torus formation is influenced by
stress on the palatine bone due to masticatory
hyperfunction (Eggen and Natvig, 1986; Reichart
et al., 1988; Eggen, 1989; Haugen, 1992; Kerdpon
and Sirirungrojying, 1999; Yildiz et al., 2005). The
torus palatinus is less common (36.5%) in edentu-
lous patients than dentate or partially edentulous
patients (48%), which further suggests that masti-
cation plays a role in its presence (Chew and Tan,
1984; Antoniades et al., 1998).
The torus palatinus is usually benign, and there is
rarely a reason for removal. Many patients are
unaware of the presence of the exostosis (Pedlar and
Frame, 2001). It can, however, cause irritation when
the patient moves the tongue or masticates (Anto-
niades et al., 1998). The fragility of the thin mucosal
layer covering the torus palatinus can lead to abrasion
or laceration, exposing the bone (Goldman et al.,
2006). In a study performed by Goldman, it was
hypothesized that this can be a significant precursor
to osteonecrosis in postmenopausal women. This con-
dition can be exacerbated by the use of bisphonate
drugs, which inhibit osteoclastic repair of vulnerable
exostoses (Goldman et al., 2006). Dentures can
sometimes irritate the torus and cause ulceration of
the mucosa. This condition may warrant removal of
the torus if the dentures cannot be constructed to
avoid such an interaction (Pedlar and Frame, 2001).
The torus may be useful in some cases, due to its
ability to be harvested for grafting of periodontal or al-
veolar ridge defects (Sonnier et al., 1999). Sometimes
the torus may contain an air space, which, with sub-
sequent excision, could cause wound breakdown and
form an oronasal fistula. This is a serious condition
and can be very difficult to correct (Pedlar and Frame,
2001). General anesthesia is usually performed due to
the limited surgical access and poor pain control
involved with local analgesia (Pedlar and Frame,
2001). The incision into a palatal torus is through the
midline with flaps from a “double-Y” formation that
can be raised to expose the torus (Castro Reino et al.,
1990; Donado,1998; Pedlar
Garc? ıa-Garc? ıa et al., 2010). After removal with an
osteotome or destruction with a rotary bur, an acrylic
surgical stent is used to cover the wound and protect
the palate from hematoma formation (Pedlar and
palatal bone, maxilla, and mandible. Three-dimensional
CT image shows involvement of maxilla and palatal bone
(With permission from Yonetsu and Nakamura, 2001, AJR
Am J Roentgenol 177:937–943).
It depicts a 57-year-old woman with tori of
The Tori of the Mouth and Ear3
The torus mandibularis is found on the lingual sur-
face of the mandible, frequently in the canine to pre-
molar regions (Ruprecht et al., 2000) (Figs. 3 and 4).
It is always located above the mylohyoid line and, like
the palatinus, is made up of compact and cancellous
bone (Axelsson and Hedega ˚rd, 1981). Histopathologi-
cal findings of the torus mandibularis have revealed
decalcified dense bony tissue, the presence of lacu-
nae, normal osteocytes, and scattered areas of con-
(Antoniades et al., 1998). Similar to the torus palati-
nus, it has a limited amount of bone marrow and is
covered with a thin layer of poorly vascularized
mucosa (Garc? ıa-Garc? ıa et al., 2010). The torus mandi-
bularis can present unilaterally or bilaterally but is
most often (80%) found on both sides of the mandible
(Larheim and Westesson, 2008). It can appear as a
single elevation or as a group of fused tubercles
varying in size (Axelsson and Hedega ˚rd, 1981). Unlike
the torus palatinus, which is easily classified into well-
nodular), there exists no clear classification system
for the torus mandibularis. Some studies simply
classify the size of the torus as “palpable, visible, or
large” (Axelsson and Hedega ˚rd, 1981).
Most sources document the prevalence of the torus
mandibularis between 6 and 40% (Laskaris, 2003).
Like the torus palatinus, there seems to be gender
and ethnic related differences regarding its prevalence
in specific populations. Some literature claims there is
no gender predilection (Kolas et al., 1953; Eggen,
1992; Barnes, 2001) but some have found it slightly
more common in men (Garc? ıa-Garc? ıa et al., 2010). In
a study on the Norwegian population, Haugen cited
values of 8.53% prevalence in men and 6.36% preva-
lence in women (Haugen, 1992). The mandibular
torus seems to be more prevalent in African-Ameri-
cans (33.8%) than Caucasian Americans (24.8%)
(Sonnier et al., 1999). The mandibular torus was
rarely found in Chileans (0.05%), a feature shared by
the torus palatinus (Witkop and Barros, 1963; Barnes,
2001). Reichart’s study comparing the prevalence in
Germanand Thai populations
patients had a higher prevalence of the torus mandi-
bularis but a lower prevalence of the torus palatinus
than their German counterparts (Reichart et al.,
1988). The torus mandibularis is identified by patients
at a slightly later age (39.2 years) than the torus
palatinus (30.7 years) but data comparing ages of
onset vary due to the tori’s gradual growth and the
fact that patients will usually not notice the torus until
it is significantly proud (Garc? ıa-Garc? ıa et al., 2010).
Similar to the torus palatinus, the mandibular torus
has controversy concerning its etiology. Most litera-
ture cites genetics as having at least some effect on
its occurrence, but it is difficult to link this torus to a
simple autosomal dominant pattern of inheritance
(Gould, 1964). In comparison to the torus palatinus,
the mandibularis seems to have a higher functional
component due to stress placed on the jaw during
mastication. Research conducted by Eggen (1989) on
genetic determination shows that there is roughly a
30% genetic contribution, but that 70% of the inci-
dence of torus mandibularis is attributable to environ-
mental factors. Studies have shown that clenching
and grinding the teeth, a habit referred to as bruxism,
leads to a higher prevalence of the torus mandibularis
when compared to controls (Eggen, 1989). Other
sources link vitamin deficiency or calcium rich diets to
the presence of tori (Mart? ınez-Gonz? alez, 1998; Sirir-
ungrojying and Kerdpon, 1999; Al-Bayaty et al.,
2001; Bruce et al., 2004; Garc? ıa-Garc? ıa et al., 2010).
The functional relationship is supported by the high
frequencies of torus mandibularis among Eskimos.
This population is known for its consumption of dry,
raw, or frozen meat, all of which produce stress on
mastication (Eggen and Natvig, 1986). Studies also
show a correlation between the torus mandibularis
and the number of teeth in patients, suggesting that
the mandibular torus is protected from resorption
throughout life by the functional capacity of the teeth
mandibularis (arrows). [Color figure can be viewed in the
online issue, which is available at wileyonlinelibrary.com.]
It depicts a 42-year-old man with bilateral tori
palatal bone, maxilla, and mandible. Axial CT scan shows
symmetrical torus mandibularis composed of compact
bone (With permission from Yonetsu and Nakamura,
2001, AJR Am J Roentgenol 177:937–943).
It Depicts a 57-year-old woman with tori of
4Loukas et al.
(Eggen and Natvig, 1986). Alvesalo et al. (1996) have
shown that development of the torus mandibularis in
patients with Turner syndrome (45, X) occurs earlier
in life than in control groups of either sex. The authors
of this study suggest that the torus’s growth regula-
tion is found on the sex chromosome and that sexual
dimorphism could be due to the Y chromosome’s
effect on cell proliferation (Alvesalo et al., 1996).
The clinical relevance of a mandibular torus is usu-
ally quite minimal; due to its benign nature, most
patients do not recognize its existence and diagnosis
is found upon incidental observations during dental
visits (Castro Reino et al., 1990; Al Bayaty et al.,
2001; Garc? ıa-Garc? ıa et al., 2010). The torus is known
to bear clinical resemblance to a multitude of other
conditions, including an ossified subperiosteal hema-
toma, a non-resolved bony callus, and early osteosar-
coma, or single or multiple osteomas (Wood and
Goaz, 1985; Barnes, 2001). The torus mandiularis
can lead to disturbances in speech and mastication if
exceptionally large. Ulcerations of the mucosa are not
uncommon, and the pocket formed under the torus
can lead to food retention (Castro Reino et al., 1990;
Donado1998; Mart? ınez-Gonz? alez,
Garc? ıa et al., 2010). The most frequent reason for
removal is the delivery of a dental prosthesis in eden-
tulous patients (Garc? ıa-Garc? ıa et al., 2010). In some
cases the torus mandibularis has been used as a
bone graft for periodontal or alveolar ridge defects
(Schallhorn, 1977; Sonnier et al., 1999). The removal
of a mandibular torus is accomplished by raising a
lingual envelope flap to release the gingival margin
from the adjacent teeth. In edentulous patients, the
surgeon must be careful in avoiding the mental neuro-
vascular bundle when cutting along the alveolar ridge
(Pedlar and Frame, 2001). A high-speed drill cooled
with saline solution is recommended over an osteo-
tome and mallet to avoid iatrogenic injury (Castro
Reino et al., 1990; Garc? ıa-Garc? ıa et al., 2010). Follow-
ing removal, an acrylic stent is sometimes used to
hold the flap in place and prevent hematoma forma-
tion (Pedlar and Frame, 2001).
Literature on the torus maxillaris is limited, particu-
larly due to the varying names used to describe it.
Laskaris’ Color Atlas of Oral Disease does not use the
term “torus maxillaris” but rather classifies the ana-
tomical variant under “Multiple Exostoses” (Laskaris,
2003). The exostoses are described as “small nodular,
bony elevations below the mucco-labial fold covered
with normal mucosa” (Laskaris, 2003). Larheim and
“hyperostosis of normal cortical and medullary bone”
found on either the buccal or palatal aspects of the al-
veolar process. This text further classifies the tori as
“externus” or “internus” according to their location on
the buccal or palatal aspect, respectively (Larheim
and Westesson, 2008). The torus maxillaris is more
commonly found on the buccal aspect in the premolar
region, but can also be found in the anterior region of
the jaw on the labial aspect of the alveolar process
(Barnes, 2001) (Fig. 5). Based on these definitions,
one can find more examples of the torus maxillaris in
which the author(s) chose not to use the term. Raldi
et al. describe a case of a large palatal exostosis situ-
ated on the left lingual aspect of the palatal vault.
Because of its proximity to the maxillary jaw and its
deviation away from the midline, one would classify
this as torus maxillaris rather than a torus palatinus
(Raldi et al., 2008). Torus maxillaris is thus referred to
in the literature by several different names, including
palatal tubercles (Sonnier et al., 1999), palatal exos-
toses, buccal exostoses (Antoniades et al., 1998), or
as mentioned above, multiple exostoses (Laskaris,
2003). The latter term refers to the fact that maxillary
tori are frequently found as multiple nodules although
they can also be found as one (Larheim and Westes-
son, 2008). They are frequently bilateral and most of-
ten found in the premolar region (Larheim and
Westesson, 2008). Histopathological analysis of the
maxillary torus is similar to that of the torus palatinus
There have been very few clinical studies on the
prevalence of the torus maxillaris compared with the
aforementioned oral tori. Brothwell (1981) cites a
prevalence of 2.5–17% but acknowledges a lack of
data to warrant any further discussion on these fig-
ures (Brothwell, 1981). The torus maxillaris is more
commonly found in anthropological surveys than in
anatomical or clinical papers. One study conducted on
excavated skulls in England found 3 maxillary tori in a
total of 97 skulls (Connell and Rauxloh, 2007). Further
research shows that palatal exostoses have been
found in as high as 40.5% of certain populations,
while another study on buccal exostoses yields a prev-
alence rate of 0.9 per 1000 persons (Bouquot and
Gundlach, 1986; Antoniades et al., 1998). These data
are somewhat limited because they have been taken
from skulls rather than living subjects. Values taken
from skulls are most often higher due to the presence
palatal bone, maxilla, and mandible. Axial CT scan shows
marrow formation in torus maxillaris (With permission
from Yonetsu and Nakamura, 2001, AJR Am J Roentgenol
It depicts a 57-year-old woman with tori of
The Tori of the Mouth and Ear5
of small tori that would be obscured by mucosa in liv-
ing subjects (Woo, 1950; Haugen, 1992; Antoniades
et al., 1998). The previously mentioned studies were
conducted on either the buccal aspect or the palatal
aspect and were performed on separate populations,
but neither provided a full survey of maxillary torus
prevalence in the general population. In a study of a
Thai population, 26.9% of 960 patients exhibited ei-
ther palatal or buccal exostoses (Jainkittivong and
Langlais, 2000) with a higher frequency in men than
in women. The buccal torus was much more preva-
lent, appearing in 17.3% of patients compared to
2.2% of patients with a palatal exostosis. Patients
with both palatal and buccal exostoses were counted
separately and represented 5.9% of the surveyed
population. This study also yielded a torus mandibula-
ris prevalence of 5%, a value similar to other data in
the literature. The main purpose of Jainkittivong and
Langlais’ research was to examine the simultaneous
incidence of maxillary torus with the torus mandibula-
ris and/or the torus palatinus. The data show that
torus mandibularis is more often seen with the maxil-
lary exostosis than the torus palatinus and this sug-
gests that the torus mandibularis and the torus
maxillaris may share causative factors (Jainkittivong
and Langlais, 2000).
Most literature shows that the prevalence of maxil-
lary tori increases with age (Larato, 1972; Nery et al.,
1977; Jainkittivong and Langlais, 2000). A study done
on American skulls by Sonnier et al. (1999), however,
shows that the prevalence decreases after age 50.
This suggests a correlation with edentulism, a factor
common to the torus mandibularis but not necessarily
related to the torus palatinus (Sonnier et al., 1999).
Furthermore, one can anticipate a highly functional
component in the etiology of the torus maxillaris
(Jainkittivong and Langlais, 2000). One theory postu-
lates that stress causes the alveolar bone to grow
under the torus following a vector opposite to that of
occlusive forces (Burkes et al., 1985; Langlais et al.,
1995; Jainkittivong and Langlais, 2000). There are
probably genetic factors as well in regards to the inci-
dence of torus maxillaris. The 5.9% concurrence of
palatal and buccal exosotoses found in Jainkittivong
and Langlais’ (2000) study supports a conjecture
postulated by Nery et al. (1977) that suggests a syn-
drome of general multiple exostoses.
Similar to the other oral tori, maxillary exostoses
are relatively benign and usually do not warrant
removal. A maxillary torus can cause difficulty in mas-
tication and can lead to irritation or ulceration of the
(Antoniades et al., 1998). Some patients may be com-
pletely unaware of its presence, while others could
request its removal due to the fear of cancer (Anto-
niades et al., 1998). Other reasons for removal could
be difficulty in speech or interference with the delivery
of a prosthesis such as a complete full mouth denture
(Laskaris, 2003). In periodontal surgery, a maxillary
torus can interfere significantly with the repositioning
of a mucoperiosteal flap (Sonnier et al., 1999). Surgi-
cal intervention methods vary for the maxillary torus,
due to its imprecise location and variance in size. The
proximity to the greater palatine foramen should be
considered to avoid damage to the greater palatine
artery (Sonnier et al., 1999). In a rare case study con-
ducted by Raldi et al. (2008), the exostosis was large
enough to affect speech and feeding, and its removal
was conducted through two surgeries under local
anesthesia. This example contrasts with most litera-
ture and demonstrates that a palatal exostosis can
successfully be removed under local anesthesia given
the proper planning and careful examination through
CT scan and histopathology.
The torus auditivus is usually found on the floor of
the external acoustic meatus (Hauser and De Stefano,
1989; Okumura et al., 2007). These can be classified
as pedunculated or lobulated and can occur as single
or multiple protuberances (Ponzetta et al., 1997). It is
usually unilateral but can also be found bilaterally
(Barnes, 2001). It is important to distinguish the audi-
tory exostosis from an osteoma, which is a neoplastic
growth attached to a focal point of bone, contrasting
with the diffuseattachment
(Barnes, 2001). A defining histological feature of
osteomas not found in exostoses are the intraosseous
spaces filled with fibrous tissue, fat, or hematopoietic
elements (Barnes, 2001). The torus auditivus can
present as densely packed compact bone with irregu-
lar Haversian canals or it may be seen as spongy-cen-
tered protuberances (Broek, 1943; Brothwell, 1981).
Studies on the frequency of the torus auditivus
vary greatly depending on the location of the popula-
tion studied. For example, frequencies of 4.0–4.7%
can be found in coastal populations but widespread
frequencies are typically lower, ranging from 0.1 to
3.0% (Ponzetta et al., 1997). Other studies find an
even lower prevalence of the auditory torus, with fre-
quencies of 0.3% for inland populations and only
0.56% for coastal groups (Okumura et al., 2007). The
trait is slightly more common in males than females,
a feature similar to the torus palatinus and torus max-
illaris (Okumura et al., 2007).
Of the four tori discussed, the torus auditivus
seems to have the least amount of controversy sur-
acknowledge genetic predispositions leading to the
torus auditivus, it is thought to play a much smaller
role than that of the oral tori (Okumura et al., 2007).
The most widely accepted factor causing auditory
exostoses is exposure to cold water. In a study per-
formed by Kennedy (1986), it was shown that the
torusauditivus was most
between 30?and 45?, while anything lower would not
be cold enough to produce a torus and anything
higher would prevent the population from spending a
great amount of time in the water (Mays, 1998). Fur-
thermore, her study on Australians showed that
coastal regions yielded high frequencies of tori in male
but not in female skulls. This might be explained by
the technique used by aboriginal inhabitants to catch
freshwater fish. After casting a net into the water,
men dive into the cold river and retrieve the fish, thus
exposing their acoustic meati to the cold water.
6 Loukas et al.
Similarly, ethnographic evidence shows that Tasma-
nian women would dive into the cold water around the
island to retrieve shellfish. Kennedy linked this to the
higher prevalence of tori in Tasmanian women com-
pared to males (Kennedy, 1986; Mays, 1998). Van
Gilse explained the method of osteoblastic formation
of an auditory torus in 1938. His experiment showed
that cold exposure leading to vasodilation causes
increased tension in the periosteum, which results in
osteogenesis and exostosis formation (Van Gilse,
1938; Okumura et al., 2007).
The torus auditivus is usually asymptomatic, but if
enlarged, can obstruct the external acoustic meatus
and can lead to otitis externa or conductive hearing
loss (Barnes, 2001). This sometimes can be confused
with the complete absence of the external acoustic
meatus, which is thought to be congenital (Hrdlicka,
1935; Risdon, 1939; Brothwell, 1981). Although the
torus auditivus is strictly defined as an exostosis of
the external acoustic meatus, osteomas, and exosto-
ses can rarely occur in the middle and inner ear. Bony
growths in these locations can cause symptoms simi-
lar to acoustic neuromas, including unilateral hearing
loss, tinnitus,and vestibular
2001). The torus auditivus rarely causes symptoms
and does not usually require removal. However, due
to the ability of tori to continue to grow, patients and
clinicians should examine these exostoses periodically,
particularly if the patient is continually exposed to
cold water (Barnes, 2001).
Clinicians and anatomists are likely to encounter at
least one of the tori of the head. Although they are
typically asymptomatic, removal is sometimes war-
ranted in extreme cases; thus knowledge of these
structures and their anatomy is important. There is
still a lack of consensus as to the etiology of these
exostoses and there has yet to be a global study on
their prevalence. Because of the benign nature of
these osseous growths, however, unifying data on the
tori are doubtful to be presented in the near future.
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