1B Getting Ready for Instrumentation: Mathematical Principles and Anatomic Descriptors

Transcription

1 MODULE 1B Getting Ready for Instrumentation: Mathematical Principles and Anatomic Descriptors Module Overview This module contains a review of the mathematical principles and anatomic descriptors used in periodontal instrumentation. None of these concepts or terms is difficult; a brief review of these concepts will assure a clear understanding of each principle or descriptor. Module Outline Section 1 Mathematical Principles 3 Geometric Angles Parallel and Perpendicular Lines Cross Section Millimeter Measurements Section 2 Anatomic Descriptors 6 Midline Apical and Coronal Zones and Line Angles Aspect Sextant Section 3 Skill Application 8 Key Terms Angle 90-degree angle Right angle 45-degree angle Parallel Perpendicular Vertical Oblique Horizontal Cross section Millimeter Midline Apical Coronal Zones Line angle Aspects Facial aspect Lingual aspect Sextant 1

2 Learning Objectives Identify a 90-degree angle found in an everyday object. Create a 45-degree angle using two textbooks. Draw two parallel lines. Draw two perpendicular lines. Define the terms vertical, oblique, and horizontal. Define the term cross section. Select an object and describe its shape in cross section. Select a word from a page in a textbook. Measure the length of the word in millimeters. Define the term midline as it relates to an anterior tooth. Using a typodont tooth, demonstrate the terms apical to and coronal to. Define the terms midline, aspect, and sextant. Using a tooth model, name and identify (locate) the three zones on the tooth crown and the three zones on the tooth root. Using a tooth model, name and identify (locate) the four line angles. Using a tooth model, name and identify the three tooth surfaces included in the facial aspect of the tooth.

3 Module 1B Getting Ready for Instrumentation: Mathematical Principles and Anatomic Descriptors 3 Section 1 Mathematical Principles GEOMETRIC ANGLES angle Figure 1B-1. A 90-Degree Angle. The seat of this chair is at a 90-degree angle to the chair back. A right angle is another term for a 90-degree angle. Figure 1B-2. A 45-Degree Angle. This man is holding his arms at a 45-degree angle to the midline of his body. Face Figure 1B-3. Angulation for Calculus Removal. For effective calculus removal it is important to establish the correct angulation between the cutting edge and the tooth surface. The correct angulation for calculus removal is an angle that is greater than 45 degrees and less than 90 degrees.

4 4 Fundamentals of Periodontal Instrumentation & Advanced Root Instrumentation PARALLEL AND PERPENDICULAR Figure 1B-4. Parallel Lines. Parallel lines are lines that run in the same direction and will never meet or intersect one another. Line A is parallel to line B. A B C Figure 1B-5. Perpendicular Lines. Perpendicular lines are two lines that intersect (meet) to form a 90-degree angle. Line C is perpendicular to line D. D Shank Figure 1B-6. Shank Position. The shank of this periodontal instrument is positioned parallel to the facial surface of this molar tooth. LINES vertical oblique horizontal Figure 1B-7. Stroke Direction. During instrumentation, instrument strokes may be made across the tooth surface in a vertical, oblique, or horizontal direction. Horizontal instrumentation strokes also are referred to as circumferential strokes because these strokes are made around the circumference of the tooth.

5 Module 1B Getting Ready for Instrumentation: Mathematical Principles and Anatomic Descriptors 5 CROSS SECTION cross section Figure 1B-8. Hexagonal Cross Section. A typical lead pencil is hexagonal in cross section. MILLIMETER MEASUREMENTS Figure 1B-9. Triangular Cross Section. The working-end of certain periodontal instruments is triangular in cross section. Other periodontal instruments have working ends that are semicircular in cross section. millimeter mm. 3 mm 2 mm 1 mm 8 mm 7 mm 6 mm 13 mm 12 mm 11 mm 5 mm 4 mm 10 mm 9 mm 15 mm 14 mm Figure 1B-10. A Periodontal Probe. A probe is a periodontal instrument that is similar to a miniature ruler. The probe is marked in millimeter units and is used for making intraoral measurements. Figure 1B-11. Pocket Depth. Using a periodontal probe, the depth of a periodontal pocket is measured in millimeters. Periodontal pockets are 4 mm or greater in depth.

6 6 Fundamentals of Periodontal Instrumentation & Advanced Root Instrumentation Section 2 Anatomic Descriptors MIDLINE Midline Figure 1B-12. Midline. A midline is an imaginary line that divides a tooth into right and left halves. Anterior teeth are divided into right and left halves for instrumentation. APICAL AND CORONAL apical coronal 3 CEJ 4 Figure 1B-13. Apical and Coronal Apical. Point 3 is located apical to the cementoenamel junction (CEJ) on both illustrations. Coronal. Point 4 is coronal to the CEJ on both illustrations. For both teeth shown here, moving from Point 3 to Point 4 is moving in a coronal direction. When removing calculus with a hand instrument, the cutting edge is placed apical to the calculus deposit and the instrumentation stroke is made in a coronal direction. CEJ Crowns 4 3 ZONES AND LINE ANGLES zones Figure 1B-14. Zones. The crown of a tooth may be divided into three imaginary zones: (1) gingival third, (2) middle third, and (3) incisal or occlusal third. The root of a tooth may be divided into three imaginary zones: (1) cervical third, (2) middle third, and (3) apical third. Cervical third Middle third Apical third Incisal third Middle third Gingival third

7 Module 1B Getting Ready for Instrumentation: Mathematical Principles and Anatomic Descriptors 7 Distolingual line angle Distofacial line angle FACIAL Mesiofacial line angle MESIAL Mesiolingual line angle Figure 1B-15. Line Angle. A line angle is an imaginary line formed where two tooth surfaces meet. Instrumentation of a posterior tooth often is initiated at the distofacial or distolingual line angle of the tooth. Each tooth has four line angles: 1. Mesiofacial line angle 2. Distofacial line angle 3. Mesiolingual line angle 4. Distolingual line angle ASPECT Lingual Facial Figure 1B-16. Facial and Lingual Aspects. A tooth, sextant, quadrant, or dental arch may be divided into two aspects: (1) a facial aspect and (2) a lingual aspect. The facial aspect of a tooth is subdivided into three areas: (1) distofacial area, (2) facial surface, and (3) mesiofacial area. The lingual aspect of a tooth is subdivided into three areas: (4) distolingual area, (5) lingual area, and (6) mesiolingual area. SEXTANT Figure 1B-17. Sextants. For purposes of identification, the dentition may be divided into six areas. Each area is referred to as a sextant. There are two anterior sextants and four posterior sextants in the dental arch: 1. Maxillary right posterior sextant 2. Maxillary anterior sextant 3. Maxillary left posterior sextant 4. Mandibular left posterior sextant 5. Mandibular anterior sextant 6. Mandibular right posterior sextant

8 8 Fundamentals of Periodontal Instrumentation & Advanced Root Instrumentation Section 3 Skill Application A C Lingual B Facial Figure A Figure B Figure 1B-18 Figure 1B-19 Questions 1 to 5 refer to Figure A Figure B facial aspect lingual aspect