NUMBERING SYSTEMS?
There are more than 12 systems available for tooth numbering but most commonly used systems are as follow:
Universal System of Tooth Numbering
It has been approved by American Dental Association. It is as follows.
Deciduous (Primary) Dentition
Consecutive uppercase letters (A through T moving clockwise) are assigned to identify the deciduous dentition. The deciduous dentition is divided into quadrants as follows.
Maxillary
A B C D E F G H I J
Patient’s right side ______________________ Patient’s left side T S R Q P O N M L K
Mandibular
A denotes maxillary right second deciduous molar and J denotes maxillary left second deciduous molar. K denotes the mandibular left second deciduous molar and T denotes mandibular right second deciduous molar. Permanent Dentition
Tooth numbering of permanent dentition presented by universal system is as follows.
Maxillary arch
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Patient’s —————————————————————— Patient’s right side 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 left side
Mandibular arch
Number 1 denotes permanent maxillary right third molar and 16 denotes permanent maxillary left third molar. Moving clockwise permanent mandibular left third molar is denoted by 17 and permanent mandibular right third molar is represented by 32. Significance of this system is that each tooth has its unique letter or number.
Zsigmondy or Palmer System
It is the oldest and the most widely used system. Here numbering of teeth starts from the mid-line, moves distally in both maxillary and mandibular arches. Deciduous Dentition
In deciduous dentition quadrants and the teeth are designated as follows:
Maxillary arch E D C B A A B C D E
Patient’s right side ——————————————— Patient’s left side E D C B A A B C D E
Mandibular arch
Permanent Dentition
In permanent dentition quadrants and the teeth are designated as follows:
Maxillary arch 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8
Patient’s right side —————————————— Patient’s left side 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 Mandibular arch ○○○ ○ ○○○ ○ ○○○ ○ ○○○ ○
Federation Dentaire Internationale (FDI) or Two-digit System
FDI has adopted the two-digit system for designating teeth. In the two-digit system, the first digit indicates the quadrant and the second digit specifies tooth within that quadrant. In permanent dentition quadrants are denoted by the digits 1 to 4 and in deciduous quadrants are denoted by 5 to 8. This system has the following advantages:
i. Easy to pronounce in conversation ii. Simple in teaching and understanding
iii. Easy to make standard charts used in practice. Federation Dentaire Internationale presents tooth numbering as follows:
Permanent teeth Maxillary
18 17 16 15 14 13 12 11 21 22 23 24 25 26 27 28
Patient’s ————————————————————— Patient’s
right side 48 47 46 45 44 43 42 41 31 32 33 34 35 36 37 38 left side Mandibular
Deciduous Teeth Maxillary 55 54 53 52 51 61 62 63 64 65
Patient’s right side ____________________________ Patient’s left side 85 84 83 82 81 71 72 73 74 75
Mandibular
WHAT ARE DIFFERENT TOOTH SURFACES?
Coronal portion of each tooth is divided into surfaces that are designated according to their related anatomic structures and landmarks (Fig. 28.1).
Buccal — Towards the cheek.
Facial — refers to either buccal or labial or both.
Labial — Towards the lip
Mesial — Towards the anterior midline
Distal — Foremost (most distant or distal) from
anterior midline
Lingual/ — Towards the tongue, in maxillary teeth
Palatal the surface towards the palate are also
called palatal
Occlusal — Masticating surfaces of premolars or
molars (posterior teeth)
Incisal — Cutting edges of anterior teeth (incisors
and canines)
Gingival — Nearest and towards the gingiva
Cervical — Nearest and towards the cervix or neck
of the tooth
WHAT IS SIGNIFICANCE OF PHYSIOLOGY OF TOOTH FORM? Contours
There is small degree of convexity on buccal and lingual surfaces of all the teeth, known as contours. On facial surfaces of all the teeth contours are present at cervical third of crown. On lingual surface of posterior teeth contours are present at the middle third of crown. Importance
• It permits and provides an adequate stimulation for supporting tissues during mastication (Fig. 28.2). • Maintains the health of gingiva.
• Make the area self cleaning.
• Maintains normal mesiodistal relationship between teeth.
• Overcontour causes under-stimulation of gingiva. • Under contouring of teeth causes direct impact of
food on supporting tissues.
Fig. 28.1: Maxillary arch showing different tooth surfaces
Figs 28.2A to C: (A) Normal contour of tooth helps in
physiological stimulation of gingiva, (B) Undercontoured surfaces causing food impaction and injury to interdental papilla, (C) Overcontoured surface causes deflection of food without touching gingiva, so no gingival stimulation
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122 Review of Endodontics and Operative Dentistry
Proximal Contact Area
Physiological significance of properly located and properly formed proximal contacts is to provide normal healthy interdental papillae filling the interproximal space. The improper proximal contact is the cause of impaction of food, movement of teeth, periodontal diseases, caries and halitosis.
Embrasures
Embrasures are spillway V-shaped spaces that originate at the proximal contact areas between adjacent teeth. If embrasures are too large they can damage the supporting tissues as food is forced into the interproximal space by the opposing cusp, and if too small or absent, additional stress is created on teeth and supporting tissues, during mastication.
Importance
• Makes spillway for escape for food • Reduce loads of occlusal forces • Provides stimulation to gingiva
Marginal Ridges
They are rounded borders of enamel which form mesial and distal margins of occlusal surfaces of posterior teeth and lingual surfaces of anteriors.
Form and Functions of Teeth
Teeth perform four main functions: (1) Mastication, (2) Esthetics, (3) Speech and (4) Protection.
Proper alignment of the teeth and their normal form ensure efficiency in their functions.
WHAT ARE PERIODONTAL ASPECTS BEFORE DOING ANY RESTORATION?
Before doing any restoration the gingiva should be healthy. Rubber dam should be applied prior to any restorative procedure so that any kind of trauma to the gingiva can be prevented. If the cavity is being prepared subgingivally the epithelium gets totally separated from the tooth surface. But the epithelium gets attached to the tooth surface within 7 days.
Effects of Faulty Restorations on Periodontium
Level of Restoration
Subgingivally placed restoration often causes gingival irritation. Rough surface of the restoration facilitates the deposition of plaque.
Margins of the Restoration
If margin of the restoration is placed subgingivally, it can result in food impaction and gingival irritation which is due to:
• If the restoration attaches plaque on its surface. • If the restoration and tooth do not contact evenly.
The degree of inflammation depends on the material and the contouring and finishing of the restoration.
As far as possible the restoration should not be placed more than 0.5 to 1 mm below the gingival margin. Contour
• If the contour of the restoration is flat the gingiva becomes thicker.
• Overcontoured and undercontoured, both resto- rations are harmful to periodontium. Overcontoured restorations are much more harmful compared to the restorations that are very slightly undercontoured. • Undercontour restorations can result in food impac-
tion and area which is difficult to clean. Contact
• If the occlusal contacts are not functionally acceptable then it may lead to accumulation of food and periodontal trauma
• If food gets accumulated it will cause irritation of the periodontal tissues
• Contact placed too occlusally causes flattened marginal ridges
• Contact placed too gingivally causes increased depth of occlusal embrasure and injury to col area
• Open contact can result in continuity of embrasure with each other and with interdental papilla. Post-restorative Care
If a patient is having high caries index the patient should be instructed for regular dental check up and oral prophylaxis once in 3 months. During oral prophylaxis the following should also be done.
a. Patient should be reinstructed about the oral hygiene measures.
b. Polishing of the tooth surface.
c. Plaque and calculus below the gingival margin should be removed by a curette.
d Pockets around the tooth should be probed with a periodontal probe.
HOW IS PERIODONTIUM AFFECTED WHILE DOING OPERATIVE PROCEDURES?
Separation of Teeth
When separators are used, the width of the periodontal ligament should be greater than the amount of separation to be achieved. But if reverse is true, the periodontal ligament will be excessively compressed on one side and get torn on the other side.
Rubber Dam
Carelessness in application of rubber dam can harm the periodontium as following:
a. The rubber dam which is applied between the two septa can cause ischemia.
b. When clamps are not used properly.
c. When the dental floss is forced injudiciously. Instrumentation
During instrumentation the following can damage the periodontium.
a. Excessive vibration causes tearing of the fibers of the periodontal ligament.
b. Care must be taken while preparing gingival cavo- surface margin to avoid laceration of the tissues. Placement of Matrix Band
Matrices and bands should not be irritating to the tissues. They should be:
a. Well contoured for the mesial and distal as well as buccolingual sides.
b. Well contoured on occlusal and gingival sides.
c. On or after fitting, should never slip, apically and laterally. The slipping can cause tearing of the gingiva and contusion of gingiva as well as other periodontal tissues.
Procedures involved in Impression Taking
While making cast restorations, the impression procedures, and the materials used in that procedure may irritate the periodontal tissues. Such situations are the following:
a. When hydrocolloid and heat producing are used for impression making.
b. In some conditions where catalyst and derivatives of rubberbase elastomeric impression material cause allergy.
c. Impression taking can also cause trauma to the surrounding periodontium.
Fabrication of Interim Restorations
Periodontium may be injured due to following:
a. If self-curing resin is used, excess monomer and heat production can cause irritation.
b. The cement used may be of irritating nature. c. During cementation of restoration irritation may
occur. Restorations
The periodontium is affected by restorations in the following ways:
1. The facial and lingual surfaces if are overcontoured may act as a reservoir for food particles.
2. Overhanging restorations or underhanging restora- tions can cause irritation to the gingiva.
3. If two dissimilar metals are used then galvanism may cause atrophy of the surrounding gingiva.
4. Various restorative materials if in contact of gingiva may cause inflammatory changes.
5. Some of the restorative materials or their constituents may cause allergy, redness and ulcers in the surrounding gingiva.
6. During the excess material removal from the gingival margin of the restoration the periodontium can be traumatized.