In quite young individuals where the teeth are newly erupting the proximal surfaces of the teeth meet at a contact point.This contact point gets converted into an area as it broadens and increases in size as a result of frictional wear of one proximal surface against another during physiologic movement of the teeth.
Properly located contact area allows normal healthy interdental papilla to fill the interproximal space.
The proximal contact of all the teeth in the same dental arch and their interdigitation through occlusal contact with the opposing teeth stabilizes and maintains the integrity of the dental arches.
It prevents the food from packing in between the teeth and thereby preventing the impingement to the gingival tissues.
CONTACT TAPERING SQUARE OVOID 1. Between incisors Contact starts at the incisal ridge incisally and a little towards the labial , labiolingually . Starts at incisal ridge incisally and in line with it labiolingually.
Slightly lingual to the incisual ridge , labiolingually .
Mesial contact start at 1/4 th of the crown inciso gingivally.
Distal contact start 1/3 rd to ½ of the crown inciso gingivally.
2.Canine 1. Mesial contact at the incisal ridge 2.Distal contact near the middle
Close to the incisal ridge incisally
Inline with them labiolingually.
Same as square type 3. Bicuspids
Buccal periphery almost at buccal axial angle of the tooth
Occlusal periphery at the junction of occlusal and middle third of the tooth
Contact is deviated buccally
Cusps form 1/4 th – 1/3 rd of the crown
Buccal periphery more towards buccal axial angle .
Occlusal periphery is at occlusal third
Convexity of marginal ridge carries occlusal periphery towards middle third
Buccal periphery at junction of buccal and middle third
4. Molars mesial contact 1.Buccal periphery almost at the buccal axial angle of the toot h 2.Occlusal periphery at junction of occlusal and middle third of the crown 3.Large cusps
Same as premolar
Extension lingually stops in the middle third(1-4mm)
Same as bicuspids 5.Molar distal contact
Buccal periphery of the middle third
Occlusal periphery at the middle third
Distal contact of first molar is variable due to position of distal cusps
More lingually deviated than the mesial but not to the extent of the tapering teeth. Buccal periphery in line with the central groove in the occlusal surface .
Incisal and labial are negligible
Gingival and lingual embrasures between anterior teeth are widest and longest in the mouth
Buccal embrasures are small
Lingual embrasures are long with medium width
Gingival embrasures between posterior teeth are broad and long
Incisal , lingual , occlusal and buccal embrasures are nil
Gingival embrasures are almost not noticable , if found they are very narrow and flat
Lingual embrasures are very narrow and long
Incisal , buccal , labial and occlusal embrasures are wider and deeper than the others
Gingival and lingual embrasures are short and broad
HAZARDS OF FAULTY CONTACTS
TOO BROAD CONTACT, BUCCO-LINGUALLY OR OCCLUSO-GINGIVALLY
a)The normal saddle area is broadened and the col area which is non-keratinized increases the susceptibility for periodontal diseases.
b)Improper shunting of food in buccal and lingual directions because of narrow embrasures ,hence chances of food impingement into the contact area resulting in inefficient mastication.
TOO NARROW CONTACT, BUCCO-LINGUALLY OR OCCLUSO-GINGIVALLY
a) food impaction vertically or horizontally on col area.
b) wide buccal and lingual embrasures in which normal hygiene measures are difficult to be accessed resulting to food retention and plaque accumulation in embrasure areas.
CONTACT PLACED TOO OCCLUSALLY
It will result in a flattened marginal ridge at the expense of occlusal embrasure.
CONTACT PLACED TOO BUCCALLY OR LINGUALLY It will result in a flattened restoration at the expense of buccal or lingual proximal walls.
CONTACTS PLACED TOO GINGIVALLY
It will increase the depth of the occlusal embrasure . Impingement on interdental col.
LOOSE (OPEN) CONTACT AREAS
Leading to food impaction.Accumulation of bacterial plaque.Periodontal and caries problem.
DEFINITION It is the term used to denote some degree of convexities and concavities on the facial/buccal and lingual surfaces of all the teeth that affords protection to the supporting tissues during mastication.
The greatest convexities are located generally at the gingival third of the crown on all facial and lingual surfaces of incisors and canines .
The lingual surfaces of the posterior teeth have greatest convexities at the middle third of the crown.
ROLE OF CONTOURS
FACIAL AND LINGUAL CONVEXITIES Convex contours on the facial and lingual surfaces of the teeth afford protection and stimulation to the supporting structures during mastication.
FACIAL AND LINGUAL CONCAVITIES Concavities occlusal to the height of contour are involved in the occlusal static and dynamic relations as they determine the pathways for teeth into and out of centric occlusion.
PROXIMAL CONTOURS ADJACENT TO THE CONTACT AREA Proximal contours adjacent to the contact areas are “V” shaped spaces also called as embrasures.Embrasures serve as a pathway for the passage of food which is passed to the occlusal surfaces by the movement of the facial tissues and tongue.
TYPES OF CONTOURS
According to their general shape ,teeth can be divided into three types:- 1) Tapering teeth contours The proximal contours of the tapering type of the teeth has one common feature:starting at the cemento-enamel junction , the surface presents a concavity almost to the contact areas and they are decidedly convex from there to the crest of the marginal ridges.The concavities are more pronounced on the mesial surface than on the distal surface.
2) Square type teeth contours The proximal contours of these type teeth have a tendency to become a plane instead of a curved surface.Bucco-lingual concavities are found occassionally on the mesial surface of maxillary first premolar,first and second molars.The distal surface are generally either flat or slightly convex from the buccal to lingual surface.The convexities which creates the marginal ridges disappear at the contact and the remainder of the surface is usually flat.
3)Ovoid type teeth contours
The proximal contours are decidedly convex from incisal angle to the cervix.Bicuspids of the ovoid type are frequently bell shaped with the convex surface running from the crests of the marginal ridges to the cervix and likewise convex from the buccal to the lingual axial angles . The mesial surface of this type of molars presents convex areas which are less extensive than those found on the distal . The distal surfaces are usually convex in all directions .
HAZARDS OF FAULTY CONTOUR
Overcontoured curvatures can create a favourable environment for the accumulation and growth of cariogenic and plaque bacteria at gingival margin , apical to the height of contour .This further results in chronic inflammation of gingiva . Fig
Deficient or dislocated concavities can lead to premature contacts during mandibular movements which could inhibit the physiologic capabilities of these movements .
Excessive concavities can invite extrusion , rotation or tilting of occluding elements into non - physiologic relation with opposing teeth . Fig
Too narrow the embrasures predispose the teeth and supporting structures to heavier stresses.
Too wide the embrasures offer little protection to the underlying soft tissue