Introduction
Physiological tooth form analysis usually has four major functions
1- mastication
normal shape of the tooth and proper alignment ensure mastication efficiency,
2-Esthetics
form and alignment of anterior teeth- physical appearance,
3-speech
shape and alignment of anterior and posterior teeth assist in the
articulation of certain sounds,
4-Supporting tissue protection
form and alignment of teeth assist in
sustaining the teeth in dental arches, The shape of the teeth and their
arrangement are presumed to be related to incising or crushing food
without causing damage to their supporting tissues (Periodontium).
The periodontium it’s the system that supporting, investing, attachment
and covering of teeth, It is involve soft tissue ( gingiva and periodontal
ligament ) and hard tissue (cementum and alveolar bone) .
Generally There are direct and indirect Factors that protecting
periodontium .
Direct factors protect the periodontium
1-Proximal Contact Relation
The proximal (mesial or distal) teeth
contact areas are the areas on the teeth ‘s surfaces where the proximal
surfaces meet each other, the contact area between two teeth prevents the
food from accumulating between them, the contact surface created in a
healthy mouth is small enough to prevent large quantities of bacteria, food or surrounding debris from building up, But wide enough to be an efficient
barrier and to prevent food from packing between the teeth, this offers
protection to the underlying gum tissue between the teeth, Lastly, when the
teeth touch slightly, they provide mutual support and anchorage and
resistance to traumatic forces displacement, Finally, we must note that two neighboring teeth share the same interproximal bone, The same bone that
supports the distal root portion of the first tooth also supports the second
tooth’s mesial root part. If something causes the loss of this boney, it affects
both teeth, and periodontally involved tooth is often removed to protect a
neighboring tooth; By removing the tooth with the most bone damage , the
periedontium of the adjacent tooth has a chance to heal, the proximal contact
areas are located at the widest portion on the mesial and distal surfaces of
each tooth and the greatest curvature to spread the chewing forces between
adjacent teeth(1).
2-Inter Proximal Space And Form
Interproximal spaces are triangular
spaces between the bone-formed teeth on one side and the proximal surfaces
on the other side and their contact area on the other side. The contact area
forms the apex of the triangle, the proximal surfaces form the sides, and the alveolar bone forms the base.
Such gaps are normally filled with gingival tissue, called papillary gingiva
or papilla interdental.
The interdental papilla prevents food from accumulating cervically to the areas of contact between the teeth by its
presence. The interdental area (the area between the teeth) provides a
position for a bulk of bone, thus providing stronger anchoring and supported, This area is wider cervical than occlusally to allow the vascular help more access to nourish the interdental bone and papillary tissue. This provides a stronger bony foundation too, The interdental papilla and bone no longer
occupy the entire interproximal space when gingival recession occurs
between the teeth; a gap exists cervically to the contact point. This gap is
called a cervical embrasure (2).
3-Embrasures Or Spillways
an opening that stretches outwardly or
inwardly; specifically, the space adjacent to the interproximal area of contact
the spreads towards the facial, gingival, lingual, occlusal, or incisal part, also
it’s Continuous space with an interproximal space, created by contact
curvatures of teeth in the same arch; it provides a passage through which
food escapes from the occlusal surfaces during chewing , protect the
gingival tissues from undue frictional trauma by proper sliding of food thus
food provide massage for gingiva and it reduction occlusal forces by
decreasing occlusal table (3)
4-Facial Contours (At The Cervical Thirds) And Lingual Contour (At The Middle Thirds )Of Crown
it’s much development in primary teeth
than secondary teeth , it has great importance as The proper maximum
curvature of contour provides and autogenic dental hygiene, This is decided
as it keeps the gingival under definite stress, making the chewed food
deflects along the gingival advantageously, thus fulfilling
1-self-cleaning of the teeth,
2– prevents harmful frictional rubbing of the gingiva by hard food
by deflecting it comparatively away from the gingiva ,
3– allows the
deflected food to be massages rather than injurious over the gingiva.
Due to its reduced development, individual variation or malocclusion of
teeth, the slight or absence of the maximum curvature contour causes food
deflection to be traumatic to the gingival margin and food and bacteria
stagnation between the tooth surface and gingiva , Gingival trauma causes or
accelerates gingival recession and destroys the periodontium while the
stagnation of food and bacteria initiates and maintains the pathological
changes in the periodontium unless controlled .
Instead of the excessive growth, or when passively occurring with the rapid
physiological gingival recession, the great maximum curvature contour
protects the gingiva too much. This state leads to the creation of an
unsanitary environment by means of first the loss of tissue tone, caused by
the continuous gingival stimulation provided by the physiological massage
of the food as it properly deflects on the gingiva; second the accumulation
of food debris around the gingiva in areas unavailable for the cleansing of
food friction or tongue, lip and cheek movements. This triggers pathological
changes that ultimately destroy the periodontium(4).
5- Curvature Of Cervical Line: (Dentogingival junction)
The curvature of the cervical line depends on the contact area height and the buccolingual diameter of the crown, The value of the curvature of the cervical line is due to the fact that it is the location where the gingiva is connected to the tooth by means of a structure called the epithelium of the dentogingival junction,
Where the teeth are in natural alignment and contact, the epithelium connection matches the curvature of the cervical line but not always at the
same point(5).
refernces
1-Brand R, Isselhard D. Anatomy of Orofacial Structures – Enhanced 7thE dition – E-Book.
2-Themes U.3: Fundamental and Preventive Curvatures: Proximal
Alignment of the Teeth and Protection of the Periodontium [Internet].
Pocket Dentistry. 2020 [cited 13 May 2020]. Available from:
https://pocketdentistry.com/3-fundamental-and-preventive-curvatures-
proximal-alignment-of-the-teeth-and-protection-of-the-periodontium/
3- Flanagan D. Gingival Embrasure Fill In Fixed Implant-Supported
Prosthetics: A Review. Journal of Oral Implantology. 2015;41(6):e297-
e300.
4-Nelson S. Wheeler’s Dental Anatomy, Physiology and Occlusion: 1st
SAE – E-book.
5-direct factors and their significeance in protection of periodontium
[Internet]. Slideshare.net. 2020 [cited 13 May 2020]. Available from:
https://www.slideshare.net/mobile/mahmod3mmar/direct-factors-and-
their-significeance-in-protection-of-periodontium
