Introduction of equipment enabled acquisition of images under

Introduction

 

Teeth
are extremely resilient considering the constant change in environment they
encounter. However, teeth are subjected to physiological changes, which occur with
age, and in the development of caries. Both of these adaptive responses are
visible in the dental hard tissues. The aim is to investigate histological changes,
which have occurred as a result of these two processes.

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Materials and Methods

 

Two
different 2D oblique histological ground sections were examined: specimen 1
unstained presented as a molar (recorded as T1) and specimen 2 stained with
toluidine blue presented as a premolar recorded as T2. The sections were
observed using a Leica DM500 optical microscope equipped with an ICC50 HD
Camera. The combination of equipment enabled acquisition of images under
different magnifications: 40x, 100x and 200x. Measurements were added to images
using LAS EZ software and alternative
labelled added using Microsoft PowerPoint. Autostictch software allowed
production of collage images of each tooth using images at 40x magnification.

 

Results

 

Enamel
– Age changes

 

Enamel thickness in T1 measures 827.42?m, which is a reduction from the
expected average enamel tissue measurement of 2500?m, however, variation can
occur (Fig. 1c) (Berkovitz 2009). Tissue thickness of the right cusp of T1 is also significantly
reduced: 1365.72?m. Furthermore, flat wear facets are visible, confirming the
loss of enamel tissue and possibly signs of severe attrition (Fig. 1c). In
comparison, the enamel in the buccal cusp of T2 measures 2,375.54?m (Fig. 1d) however;
the enamel covering the lingual cusp of T2 has been completely lost (Fig. 1b). An enamel crack is
observable from the enamel surface to the dentinoenamel junction in T1. This is
suggestive of strong forces being applied to the outer enamel tissue coinciding
with severe tissue loss (Fig. 1e). In comparison, in T2, enamel lamellae are
visible proximally to the white spot lesion spanning the tip of enamel to
dentinoenamel junction (Fig. 1f).

 

Enamel – Caries changes

 

Amalgam restorative filling can be observed occlusally confirming
this tooth has been subjected to caries and required treatment (Fig. 1a).
Demineralisation and remineralisation regions can be detected on the buccal
cusp of T2 suggesting changes in mineralisation and possible initiation of
carious lesion development (Fig. 1d) (Berkovitz 2009). Furthermore, a white spot lesion is also visible measuring
788.10?m with distinctive zones; surface zone, body of lesion, dark zone and
translucent zone. White spot lesions are reversible if treated appropriately
(Fig. 1f) (Gugnani et al. 2012).

 

 

Dentine – Age Changes

 

Secondary
dentine can be observed around the coronal portion of T1 (Fig. 2c) and the root
portion of T2 (Fig. 2d) measuring 268.58?m and 367.49?m respectively. Secondary
dentine is distinguishable in both T1 and T2 from primary dentine by the presence
of contour line of Owen (Fig. 2c, Fig. 2d). Sclerotic dentine is visible in a
range of sections in both teeth: the roots in T1 and T2 measuring 257.16?m and
187.23?m respectively (Fig. 2e, Fig. 2f) and a larger segment visible in the
cusp region of T1 measuring 1,803.20?m bordered by dead tracks and
discolouration (Fig. 2g).

 

 

Dentine – Caries changes

 

The coronal section and lingual cusp of T2
displays toluidine blue-stained dentine (Fig. 2h) bound by and integrated with
dead tracks and sclerotic dentine: brown/yellow staining. These are suggestive indicators
of demineralisation and secondary caries (Nanci 2013). Toluidine blue is an acidophilic
dye staining acidic molecules and tissue components. It can be used to identifying
carious lesions by staining phosphoproteins and proteoglycans which are unmineralised
acidic dentine molecules (Sridharan and Shankar 2012; Nanci 2013). Reactionary dentine a form of tertiary dentine can be located
overlying the pulp horn in T1 measuring 721.41?m and spans almost the width of
the pulp head (Fig. 2j). Reactionary dentine can also be found in the pulp horn
of T2 measuring 209.28?m however on this occasion it is directly above
reparative dentine measuring 101.12?m (Fig. 2k).

Cementum – Age Changes

 

T1
exhibits large accumulation of cementum located in the apical and interradicular
regions measuring 1,168.03?m and 1,422.41?m respectively (Fig. 3c, Fig. 3e).
Measurements of this degree indicate increased stimuli on cementocytes and
exceed normal thickness: 50?m – 200?600?m (Berkovitz 2009). In contrast, apical thickness in T2 measured in the normal range
283.20?m (Fig.2d), whilst also displaying classical signs of cementum
deposition: cellular cementum overlying acellular cementum (Nanci 2013).

 

 

Discussion

 

Age changes

 

Enamel
is regarded as the hardest tooth tissue, consisting of ~97% inorganic substance
and measures ~2500?m (Berkovitz 2009; Kunin et al. 2015). However, in the two
specimens examined significant enamel tissue loss has occurred. T1 presents
reduced enamel thickness in both cusps, (Fig. 1c) while in T2, complete enamel
loss occurred in the lingual cusp indicative of enamel caries, yet buccally
there is minimal loss ~200?m. (Fig. 1b, Fig. 1d) Enamel loss is expected in
teeth during aging: ~20-38?m per annum (Murchie 2017).

 

Striae
of Retzius naturally parallel to the cementum-enamel junction pass over enamel
cusps without reaching the outer tooth surface unless positioned on the lateral
edges (Fig.1c) (Berkovitz 2009). Although they are not visible in T2, in T1 striae are exposed on
the upper enamel surface, further confirming the loss of enamel tissue. Tooth
wear is more pronounced in older people and presents as loss of tooth tissue
associated with repetitive physical or chemical dissolution: visible by sharp
or rough edges in cervical enamel as seen in T1 (Fig.1c) (Addy and Antonarakis 2005; Burke and McKenna 2011). Tooth wear of this nature is classified as attrition (e.g. Bruxism).
Attrition unlike abrasion will wear down the top surface of the tooth and can
be seen in cuspal and interproximal regions of a tooth (Burke and McKenna 2011).

 

Secondary
Dentine is a normal continuous process of dentine formation by Odontoblasts
lining pulp and canals after tooth completion. Often, secondary dentine is
irregularly distributed and produced slower that primary dentine ~0.5 um HM1 a day. It is distinguishable by the presence of contour line of Owen; marking a change in tubule direction passing from the visible primary
sinusoidal curvature to straight secondary direction (Fig 2c, Fig 2d) (Berkovitz 2009). With increasing age, secondary dentine can be linked to: reducing
size of pulp chamber, tubule sclerosis and presence of dental pulp calculi
(pulp stones), which also contribute to reducing the volume of the pulp chamber
(Carvalho and Lussi 2017). All this can clinically cause problems during endodontic
treatment.

 

Cementum:
a calcified connective tissue lines dentine of the root and small portion of
enamel at the cemento-enamel junction (CEJ) and connects the tooth to
surrounding tissues by being permeated by sharpey fibres of the surrounding periodontal
tissue (Berkovitz 2004). Cementum formation and age
are positively correlated, increasing in thickness through 20-60yrs of age (Gupta et al. 2014). T2 presents normal apical thickness of cementum (Fig.3d) compared
with T1, which exhibits more than double the normal range in both apical and
interradicular areas (Fig. 3c, Fig 3e). Cementum build-up of this nature could
be an indicator of compensation of vertical tooth drift, which occurs to keep
teeth in occlusal position following enamel tissue loss by attrition (Berkovitz 2009). Alternatively, a hypothetical conclusion could be drawn that T1 is
subjected to hypercementosis: idiopathic formation of excessive cementum beyond
necessary function resulting in modification of the root morphology, particularly
apically. (Alberto et al. 2012).

 

Caries changes

 

Dental
caries is a disease affecting a vast percentage of the population caused by
altered pH levels and cyclic demineralisation and remineralisation prompted by
an intake of food and drink (Gugnani et al. 2012; Greene and Bearn 2013). An early sign of
demineralisation is a white spot lesion (WSL) and can be seen on the buccal
cusp of T2 (Fig.1f): clinically WSL are reversible if remineralised or arrested
but they can  lead to cavitation (Gugnani et al. 2012). Physical regeneration of enamel cannot occur due to loss of
ameloblasts, however, remineralisation can occur by calcium, phosphate or fluoride
uptake. Histological zones of the WSL are visible in T2 (Fig.1f) and show the different
porosity levels of enamel: the surface, the body of lesions, dark zone, and
translucent zone. Porosity of enamel has a strong influence on the formation of
carious lesions.
(Berkovitz 2009)HM(2 

 

In
comparison, T1 presents with an amalgam restoration centrally, which confirms
this sample was subjected to occlusal caries: resulting in cavitation and
removal of damaged tissue. (Fig.1a*). Moliform teeth surface are susceptible
to caries occlusally as plaque can remain undisturbed if oral hygiene is inadequate
but also the dimensions/morphology of the pits and fissures (Ekstrand et al. 2001). Not all the fissure system is affected in occlusal caries and the spread
of an enamel lesion is guided by prism direction (Ekstrand et al. 2001). Amalgam restorations are more tolerant to a range of stresses due
to its high tensile, transverse and compressive strength, which can adequately
resist intra-oral abrasion and rarely fails (McCabe and Walls 2008). Properties of amalgam however, allow dimensional changes to occur
during or shortly after setting, resulting in cracks in the undamaged tooth or
microleakage due to its high diffusivity (McCabe and Walls 2008). A crack is visible lateral to the restoration in T1, penetrating from
enamel surface to tertiary dentine (Fig. 2j). Cracks can result in accumulation
of fluid, food debris and bacteria surrounding the restoration: increasing the possibility
of failure and development of secondary caries. Similarly, enamel lamellae
shown in T2 (Fig. 1f) can enable bacteria to penetrate areas of hard tissue: by
travelling through lamellae: resulting in caries (Berkovitz 2009; Kunin et al. 2015). Lamellae incidence can
increase due to various chemical or physical stimuli (Kunin et al. 2015).

 

Tertiary,
and sclerotic dentine formation are closely linked with a range of factors: attrition,
caries, restoration preparation, microleakage and trauma often associated dead
tracks. These protective responses to such stimuli provide barriers to the progression
of caries to the pulp (Berkovitz 2009). Reactionary dentine is noticeable by its irregular appearance and
is deposited by odontoblasts, which survive the injury. In T1 it is visible
overlying the pulp horn and spans almost the width of the pulp head (Fig. 2j).
This may have formed due to preparation of the cavity, or due to attrition. Reactionary
and reparative dentine is also distinguishable in pulp horn of T2 (Fig. 2k). Reparative
dentine is formed by odontoblast like-cells, which create a new calcified layer
of tissue after original odontoblasts have been destroyed due to a strong and
continuous stimulus (Berkovitz 2009). Although the quantity of tertiary dentine is low in T2, it can be suggested
the stimulus for its formation is the large carious lesion in the coronal
portion of the tooth. The reparative portion of dentine present in T2 will also
prevent hypersensitivity in the area (Carvalho and Lussi 2017).

Sclerotic
dentine can be found naturally in the roots and correlates with physiological ageing
(Fig.2e, Fig. 2f). It can also occur pathologically in response to caries
positioned between the pulp and carious lesions. The latter was observed in the
coronal section of both specimens (Fig 2g, Fig 2h).

 

Both
teeth portray different characteristics regarding changes that occur in
relation to hard tissues. It can be concluded that T1: has more age-associated
changes and was  subject to a chronic
level of attrition resulting vertical drift. T2 has severe loss of enamel and
dentinal tissues due to lack of treatment. Caries incidence can be
multifactorial including dietary habits and oral hygiene regimes. Treatment is
essential to save hard tissues when caries is irreversible and without action, pulpal
involvement is possible or even loss of the tooth.

 HM1Change it to the
u. I cant find the right one.

 HM(2Check
the paper on porosity see if I can get reference?

 

Wat paper??

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