Crown and Bridge Anatomical Waxing 9780979740220, 0979740223

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Tech BODI< Crown &Bridge

Anatomical Waxing /'

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Crown and Bridge Anatomical Waxing John C. Ness CDT

Dedic ated to my friend and mento r: Richar d W. Walliser BS, MBA for all your encoura gement and for always helping me find the way through , no matter what the barrier.

John C. Ness, CDT

Edi r kLar on

Illustration Christopher Cross BA, MA Jeff Felson, BA

Photogra phy Christopher Cross BA, MA

Special Acknowledgment to James Mahan CDT

1his publication was adapted from methods developed by John C. Ness CDT

© 2009 JOHN C. NESS and PRODUCTIVI TY TRAINING CORPORATION

All worldwide rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, scanning or by any information storage and retrieval system, without prior written permission of Productivity Training Corporation. Printed in the USA. Revision 3.27.9 ISBN 10: 0-9797402-2-0 ISBN 13: 978-0-9797402-2-3 Published by

Productivity Training Corporation 360-A Cochrane Circle Morgan Hill CA 95037 Phone: 408-776-0433 • 800-448-8855 •Fax: 408-776-0145 E-mail: ptc@ptcdental. com.Web:www .ptcdental.com

Contents 07 I Introductory Reference I Full Arch Tooth Reference 13 I Introduction I The Basics of Fixed Crown and Bridge Waxing 15 The Basics of Pixed Crown and Bridge Waxing

17 Tooth Surfaces 18 Case Preparation

20 Function and Movement 23 Planning Cusp and Fossae Placement 24 Working with Wax

27 I Part One I Rough Waxing 39 IPart Two I Primary Anatomy 61 I Part Three I Secondary Anatomy 81 I Part Four I Waxing a Bridge with a Pontic 87 IAppendix I Individual Tooth Reference 103 I PTC Training Materials & Systems 111 I Glossary

Introductory Reference

Full Arch Tooth Reference

Full

rch Too th Reference

Maxillary Primary Anatomy

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11

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I Full Arch Tooth Reference I 9

Mandibular Primary Anatomy

Maxillary Secondary Anatomy

Mandibular Secondary Anatomy

Introduction

The Basics of Fixed Crown and Bridge Waxing

Introduction I Basics of Fixed Crown and Bridge I lj

The Basics of Fixed Crown and Bridge Waxing Before you proceed with the step-by-s tep procedure s that follow, you will need some important backgrou nd informati on. In this section, we will define some basic terms, show how the doctor prepares a case, show what happens in the laboratory before you receive a case, explain how teeth function, and show you how to work with wax.

Fig.

1 I crowns and

bridges

In some parts of the procedure s that follow, there are alternative methods that will achieve the same result. In those cases, we have selected the methods that are the easiest to learn and the quickest to perform. The procedure s used incorpora te all of the functional and esthetic objectives that you must achieve in the finished product. The fundamen tal procedure s you learn here will apply to every case you will work on in the future. Your ability to understan d and duplicate the steps accurately and efficiently will enable you to adapt the procedures to fit any situation you come across.

Basic Definitions 1here are a variety of restorations, or appliance , that take the place of natural tee th . Th ese are generally called cap , crown , or bridge . (Fig. 1) Crowns are re toration that r pl

on t

th.

Fig. 2 I Full Cast Crown

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~ d Crmn1

and B ·idge Intr dudi 1

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A crown fits over the preparation of a natural tooth that has been ground down by a doctor. Full cast crowns look exactly like natural teeth, except that they are usually metal. The crown is created in wax, and later cast in gold, semiprecious metal, a non-precious dental alloy or pressed in a ceramic material. (Fig. 2 previous

page) F:~. 1

Example of 3 Unit Bridge

A bridge replaces one or more missing teeth. If you are working with a bridge, you will have one or more panties, which replace the missing teeth. (Fig. 1) A coping is an understru cture for a single porcelain crown. A framewor k is the understructure for a porcelain bridge. A bridge framework consists of copings and panties. (Fig. 2) Frameworks can be made of metal or a rigid ceramic material.

Fig. 2 I Single Coping and Six Unit Bridge

A splint is a framework that consists of copings attached together, with no panties in between. There are many variations in coping and framework design. Most are initially created in wax and then reproduce d in metal or ceramic. They are then covered with porcelain, which is carefully contoured by the porcelain technician to form the fine anatomical details of the tooth. (Fig. 1 previous page)

Fig. 3 Waxed and cast crowns

Full metal or pressed ceramic crowns and frameworks go through a process called "lost wax" casting. First, the wax pattern is sprued. Then it is completely covered with investment material to make a mold. The mold is heated to vaporize the wax and create a void. Finally, the metal or ceramic material is ca t or pressed into the mold by centrifugal force or pressure. The re ult i a metal r ceramic casting that duplicates the original V\ a:'" pattern. (Fig. 3)

Introduction I Basics of Fixed Crown and Bridge I 17

The Tooth Surfaces Th m ial urfa e i the surface that faces the fr nt f the mouth, or toward the mid.line of th ar h. The distal surface faces away from the mid.line, or toward the back of the mouth. (Fig. 1) The urface facing the tongue is called the lingual surface. (Fig. 1) The urface facing the cheeks and lips has two names. On posterior teeth, it is called the buccal surface, because it faces the cheek. On anterior teeth, it is called the labial surface, because it faces the lips. (Figs. 1 and 2)

Fig. 1 I the surfaces

Finally, the surface of the posterior teeth with which we chew our food is called the occlusal surface. The perimeter of the occlusal surface is called the occlusal table. (Fig. 3) It is important to note that the teeth on one side of the mouth are mirror images of the teeth on the other side. (Fig. 2) Before you begin to work on a tooth, refer to the illustrations in the beginning of this manual to make sure you know exactly where the anatomical features are , on each tooth.

Crown and Bridge Anatomical H'axing

Fig. 2 I mirror image

Case Preparation In order to visualize how your work fits into the restorative process, you should have some basic understa nding of what the doctor does to prepare the case you will be working on. Also, you will want to know what the preparat ory departm ent of your laborato ry does to prepare the models you will be working on. In preparin g the decayed or broken tooth, the doctor uses abrasive burs and diamonds to reduce, or grind away, the enamel and part of the dentin of the tooth, leaving a stump, or preparation. (Fig. 1) When the crown is completed, the dentist will cement it in place over the prepared tooth. The doctor usually finishes the tooth preparation at or just below the gum line, or gingiva. The line around the tooth where the doctor stops preparin g is called the margin. The finished crown must seal perfectly at the margin so that no debris or fluid can get between the tooth and the crown after it is cemente d in place.

Fig. 3 negative imp ression

After the tooth is prepared, the doctor packs a retractio n cord around the preparation to keep the soft tissues clear of the margin. (Fig. 2) He then takes an impression that perfectly duplicates the preparation and the adjacent teeth. (Fig. 3) He also makes an impression of the opposing teeth, either separately or at the same time. In the case where separate impressions have been taken of the opposing arches, the doctor takes a bite registration of the upper and lower teeth in the closed position to assi~ in positioning the models correctly in the laboratory. (Fig. 4)

Fig. 4 : bite registration

Introduction I Basics of Fixed Crown and Bridge I 19

The impressions that the doctor makes are negatives. In the laboratory, a technician in the preparatory department pours die stone into the negative impressions to make the positive models of the upper and lower arches. Dowel pins are placed in the teeth that are to be worked on, to create dies that can be removed easily from the model and replaced in exactly the same location. (Fig. 1) Fig. 1 I dowel pins

Next, the preparatory technician mounts the upper and lower models together on a mechanical device called an articulator. (Fig. 2) The bite is used to position the models so that they come together correctly when the articulator is closed. In addition, the die is carefully trimmed (ditched) to clearly expose the margin line. (Fig. 3) At this point, your work begins. You will create the wax pattern for the all metal crown or bridge, or the ceramic framework. Fig. 2 I articulator with models

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a JSrid e I Introduction

Functi n nd Mo ment e crown and bridge you create mu t ork r ctly wit the patient natural teeth. Therefore, it i e entia l that you unde r tand the mov eme nt of the mandible (the lower jaw). You mu t ensure that the crown or bridge you build will function properly in relation to all the teeth it contacts. Fig. 1 I mandibular movements

You will be primarily concerned with the four directions of movement of the mandible. The e are the forward, back, left, and right movement (excursions). A forward shift of the mandible i called protrusive movement. The backward shift of the mandible is called retrusive movement. A shift to the right is called right lateral movement A shift to the left is called left lateral movement. (Fig. 1)

Occlusion

Fig. 2 I anterior centri c occlusion

Whe n the upper and lower teeth come together in max imum contact, they are in a po ition called centric occlusion. In normal centric occlusion, the incisal edges of the uppe r anterior exte nd over the labial surface of the lo er anteriors. (Fig. 2) The buccal cu p of the upper posteriors extend over the buccal urfa e of the lower posteriors. The lingual cu p f the I r posteriors are lingual to the uppe r p teri r and are out of contact with them. (Fi . ) Th upper buccal and lower lingual cu p are all nonfunctional cusp .

Fig. 3 I non-functional cusps Pmr111rti1Jitv Trainincr Co

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Introduction I Basics of Fixed Crown and Bridge I 21

Tue lingual cusps of the upper posteriors and buccal cu ps ofthe lower posteriors fit into fossae on the opposing teeth. These cusps are called functional or working cusps. (Fig. 1) Use the Ness TeethT>I and demonstrate this for yourself. Everything is fine when the teeth are in centric. However, when the teeth move out of centric, the issues of alignment and function become very important Ifall the cusps and ridges arent in just the right places, they are likely to create interferences or improper contact, causing damage to the teeth and the supportin g bone and tissue.

Fig. 1 I cusp-tojossa relationship

Therefore , when you work on crowns and bridges, the cusps and fossae must be placed in proper position, and must have the correct size and shape, so they will not interfere with opposing cusps and fossae when the teeth move in and out of centric.

Function Your work is the foundation that supports the work of the porcelain technician. You need to understand where porcelain cusps and fossae will eventually be placed, and wax accordingly. One way to understan d jaw function is to use an articulato r to simulate chewing motions. For instance, take the articulator and move the models into a protrusive position, where the lower teeth move forward. Notice how the incisal edges of the lower anteriors slide on the lingual surfaces of the upper anteriors in group contact, and the posteriors immediately move apart, or disclude. (Fig. 2)

Crnwn nnd Bridge Anatmnica/ V\ axing

Fig. 2 Iprotrusive movement

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Next, return the models to centric and move the 1 wer model to left lateral. The lower left cuspid slides on the lingual surface of the upper left cuspid. 1he posterio r teeth on the right side disclude. The teeth on the left side are in function and are said to be working. Those on the right are non-working. (Fig. 1)

Note: Mandibular movements are always described from the patient's point of view. Once again, return the models to centric. Move the lower model to right lateral. You will notice that the right teeth remain in contact and become the working teeth, while the left posterio rs disclude and become the non-wor king teeth. There must be no interference between cusps on the non-wo rking side. Even one misplaced cusp can cause interference with the other cusps or imprope r seating in the fossae of the opposing tooth, resulting in the occlusion being out of alignment. The unfortunate result may be trauma to the teeth in prematu re contact. (Fig. 2)

Fig. 2 I improper occlusion creates trauma

Note: In abnormal occlusions, the upper and lower teeth come together differently, and the teeth that slide together when the mandible moves from centric may be different. Nonetheless, the rule remains the same: There must be no interference among non-working cusps when the mandible moves.

Introduction I Basics of Fixed Crown and Bridge I 23

Planning Cusp and Fossa Placement To determine the proper placement of the cusps and fossae, close the articulator and note where the cusps and fossae are on the opposing teeth. Place the fossae where they will receive the opposing cusps, and place the cusps where they will enter the opposing fossae. (Fig. 1) The ideal cusp-to-fossa relationship will serve to stabilize the crown and the opposing teeth by directing the occlusal forces along the long axes of the teeth. If the stress is not aligned with the long axes of the teeth, there is risk of damage to the supporting bone and tissue, causing periodontal disorders and facial pain. (Fig. 2)

rown ond Brid._~c: Ant1tomical Hiuillg

Fig. 1

I cusps and fossae

I I11troducti

11

Working with Wax u will u e a va ~iety of in trume nt to carry molte n wax and to carve olid wax. (Fig. 1) ou will u e an electr ic waxe r or Bun en burne r to heat the instru ments for carrying wax> and po sibly a heate d wax reservoir pot to keep the wax at the optim um working temperature.

Warning! A prope rly adjusted electric waxer or Bunsen burne r flame is necessary. You must be very carefu l not to reach into the flame. Make sure there are no flammable objects near the burne r. Also> dont positi on your bench light above a Bunse n burner! The hottes t part of the flame is just above the faint blue cone in the center. Briefly hold your instru ment just above this cone when you want to heat it. (Fig. 2) A very impo rtant part oflearning to produce wax patterns has to do with learning to efficiently and comfortably work with molte n wax. When you apply wax to the die, it should be molten enough to flow smoo thly over the surface and adapt itself completely into the surface contours. (Fig. 3) Fig. 2 I heat center

Fig. ? adapti ng wax perfectly

Introduction I Basics of Fixed Crown and Bridge I 25

In order to achieve an even blend, any new wax that you add must be hot enough to melt the surface of the wax that is already on the die. Ifyou don't melt the existing wax, the newly added wax will not blend with the old. Air can be trapped between layers, which can cause voids or laminations in the wax. (Fig. 1) The wax in the heated wax reservoir should be heated to just above the melting point. If it is too hot, the wax will take too long to cool, making it difficult for you to control.

Fig. 1 I don't trap air

When the wax is the correct temperature, it will cool quickly when removed from the wax pot. Heat your instrument in the Bunsen burner, or adjust your electric waxer so the molten wax stays where you put it. To achieve complete control when placing large amounts of wax, manipulate the position of the die, using gravity in such a way that the wax is encouraged to flow where you want it. (Fig. 2)

Fig. 2 I controlling molten wax

With practice, you will learn to adjust the temperature ofyour electric waxer or instrument in order to control the molten wax.

Carving Wax When you are carving wax, especially on the lingual bands and on the buccal and lingual surfaces of full crowns, use light, short strokes and remove small amounts of wax with each stroke. (Figs. 3 and 4)

Note: Do not try to remove a large amount ofwax at one time, or you will lose control. You might even distort the wax, or break it.

Crown

1111d

Brid~c Anotomi al H axing

Fi(;. ~ I carve small amounts

d Bridge I Introduction

There are two ways to hold the carving instruments. The first way is to grasp the instrument as you would a pencil, and use your third or ring finger as a fulcrum. Your third or ring finger should always touch the die or model to steady your hand. (Fig. 1)

F( . 1 Ipencil grip with fulcrum

You will find that your control is best when you keep the die stationary and guide the instrument toward yourself. This method is usually used for applying wax and for light, precise carving. The second, and more commo n, way is to grasp the instrum ent in your fist between the thumb and index finger. Slide your thumb forward on the instrum ent and place it in contact with the surface being carved. Rock your thumb while keeping the pad of the index finger in contact with the instrum ent and your thumb. (Fig. 2)

Productivity Fig. 2 I underha nd fist grip

In the demon stration programs, we show you how to work on one bridge or crown at a time. In practice, however, when you become more familiar with the procedures, you will be able to increase your efficiency markedly by working on several cases at once. You will complete one step of the procedure on each case, then go on to the next step in the proced ure and complete it, and so on. (Fig. 3)

Fig. 3 I work in groups for efficiency

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Part One

Rough Waxing

}'..I f ( )lit' I Rough wax.mg I L 'j

Note: In Part 1 we ldll be showing the waxing of an upperjirst molar crovm. The same procedures 11 ould apply to any tooth. STEP

1

Read the work authorization or prescription.

If you have any questions, do not proceed until you get them answered.

Figure

Fig 1 I waxing instruments

1 shows each end of the PTC waxing

instrwnents you will use.

Note: Once you understand the process for doing one tooth, you will then work in groups of three teeth. Follow the identical procedure for each tooth. STEP

2

Block out all undercuts.

Remove the die from the model and examine it carefully. F(~. 2 I Survey the Undercut

Survey the die with a pencil to find all surface undercuts (indentations on the die). (Fig. 2)

Fill all under cuts and irregular areas with high- melti ng-po int under cut wax or block out resin. (Figs. 1 and 2)

When the wax is cool and hard, carefully carve away the excess. The wax should blend smoothly with the surface of the die.

STEP Fig. 1 I Fill the undercut

3

Mark the marg in on the die.

Using a red pencil, mark the margi n all the way aroun d the die. (Fig. 3) For easy identification, mark the case number on the die.

STEP

4

Fig. 2 I Fill the irregular areas

Fig. 3 I Marking the Margin

Surface hard en the die.

Coat the entire die with die harde ner to just below the margin line to fix the red mark permanently.

JJart Une

STEP

5

Coat the die with cement spacer.

Starting 1 to 2 millimeters up from the margin, coat the sides and occlusal surface of the die with cement spacer. (Fig. 1) Allow the spacer to dry. Repeat the procedure for the number of coats required for the die spacer you are using.

Note: Figure 2 shows a cutaway view ofthe spacer under the finished wax pattern.

Fig.

1

I Apply cement spacer

STEP

6

Coat the die with lubricant material.

When the cement spacer is dry, apply a lubricant to the die, the adjacent unprepared teeth, and anywhere else on the model that may come in contact with molten wax. Lubricate the occlusal surfaces of the opposing teeth. Blow excess lubricant off the die. Blot gently with tissue. The die should be moist, not wet.

Crown 11nd P.rid,~c Anl1tomi o/ 1\ tl.\ iJI,

Fig. 2 I Die spacer coverage

I .Kougn vvaxmg 1 J i

STEP

7

Coat the surfa ce of the die wax.

Exam ine the die for any uniqu e features such as retent ive groov es. (Fig. 1)

If there are no uniqu e features, hold the die b

Fig. 1 I Retention groove

the dowe l pin and dip it into the wax pot Coa the die to just below the marg in line. The thickness shoul d be no more than .5 mm. (Fig. 2) Go on to step 8.

Note: Some dip waxes are highly plastisised to avoid earring into the wax when carving occlusal anatomy. Use your carver to remove the occlusal of the dipped coping then flow carving wax to fill the occlusal. Proceed with the buildup.

Fig. 2 I dip the die

For dies requ iring preci si on attach ments , crown s with retent ive grooves, or other unusu ally prepa red teeth, start by flowm g wax into the specially prepa red areas on the die. Dip the end of the electr ic waxer or the PTC W C-2 spatu la into the soft wax. Flow the wax into the special prepa ration. ~ more wax u ntil the area is full, makincr ure e additi on ofwax is hot enoug h to melt the · tin a wax. (Fig. 3)

additi on into the exi ting until you have evenl y co ered th nti of the die down to it marITT.n. (Fi . 1 t Fig. 3 I Fill the special preparation

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8

Wax the contact areas.

Place the die back onto the model. Add wax between the mesial surface of the die and the distal surface of the adjacent unprepared tooth. (Fig. 2) Carefully fill the space between the two teeth by passing the waxed filled instrument between the die and the adjacent tooth. (Fig. 3)

Fig. 1 I coat the die

Do the same on the distal surface of the die.

Note: When working in groups ofthree to five units do all contacts on each case before going to the next step. at a time,

Fig. 2 I wax the contacts

Fig. 3 I contact areas done

Crown and Bridge Anatomical 1Vaxing

STEP

9

Ficr.

1

I applying buccal bead

Wax the buccal and lingual beads.

Place a bead of wax on the buccal surface along the uppe r part of the midd le third from the mesial to the distal of the crown. Keep adding wax by movi ng the instru ment back and forth along the bead until you have enoug h wax buccally. The bead shoul d extend slightly beyond the adjac ent unpre pared teeth as your guide. (Figs. 1 and 2) Blow on the bead to cool it. Close the articulator while the wax is still soft to ensure that the bead does not interfere with the oppos ing teeth. Create a lingual bead using the same procedure as the buccal bead.

STEP

10 Fig. 2 I buccal bead

Fill in under the buccal and lingual beads.

Apply wax on the mesial under the buccal bead, from the margin up to the bead. This is the beginning of the mesio-buccal surface. (Fig. 3) Apply wax under neath the bead at the distal from the marg in up to the bead to form the disto-buccal surface. (Fig. 1 next page) Add wax between these beads to create the form of the buccal surface. (Fig. 2 next page)

Fig. 3 I add m esial bead

Repeat these steps for the lingual surface, using the same sequence as the buccal. (Fig. 3)

Remember to make each buccal bead and lingual bead extend just beyond the adjacent unprepared teeth. In this way you will have enough wax to carve later on. (Fig. 3) When waxing the beads, rotate the model so the working surface is parallel to the floor, which allows you to use gravity to keep the molten wax where you want it. (Fig. 4) The purpose of the buccal and lingual beads is to establish the buccal and lingual heights of contour and to support the molten wax as you add it to the occlusal surface.

Fig. 2 fill between beads J

Fig. 3 Lingual view J

Fig. 1 add distal bead 1

Crown and Bridg Anatomical \~ nxin

Fig. 4 I Rotate model to control molten wax

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STEP

11 Wax the occlusal surface.

Add a large amount of wax to the occlusal surface. Continu e to add wax until the entire occlusal surface is overfille d with wax. It is common to misjudg e the amount of wax necessary to fill the occlusal. Be sure to add a sufficient amount. (Fig. 1) Allow the wax to cool until it is no longer shiny, but not until it begins to harden.

Fia. 1 I wax the occlusal

Close the articulat or and press the models firmly together to create a complet e impression of the opposin g teeth in the wax. (Fig. 2) Open the articulat or and examine the wax. If there are any voids or incompl ete areas in the surface, resoften the entire occlusal surface, add more wax, and close the articulat or again to create a complet e impression. (Fig. 3)

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Fig. 2 f opposing m odel space guides y ou

When working in groups of three to five units at a time, do all occlusal wax application on each case before going to the next step. By utilizing the entire space provided by the dentist, you now know you have established the five paramet ers of the wax pattern: 1. Mesial contact area; 2. Distal contact; 3. The buccal surface; 4. The lingual surface; and 5. The occlusal surface. At this point, all you have to do is accurate ly take away wax.

I

Fig. 3 utilize entire space provided

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12 Check your wax pattern. y u have created a rough wax pattern with the buccal lingual mesial and occlusal surfaces built

up. (Fig. 1) If this is your first time through the procedure, rough '~ax the remaining two crowns to this point. Keep your focus on the procedure, do three or more rough wax-ups at a time. This will help you to be very proficient and at the same time, produce higher and higher quality units.

Fig.

1 I completed

rough waxups

The five steps for rough waxing crowns: 1. Coat the dies perfectly on all units (area 1);

Add contacts on all units (area 2 ); 3. Add buccal and lingual beads on all units (area 3); 4. Add under buccal and lingual beads on all units areas 4 and 5); and 5. Add occlusal surface on all units (area

2.

6).

Crown and Bridge Anatomical H'axing

Fig. 2 I rough waxing steps 1 - 2

Part Two

Primary Anatomy

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TEP

13 Check for voids. Remove the die from the model and inspect all urface. Fill the voids under the contact areas with wax. (Fig. 1) Allow the wax to cool, then replace the die in the model.

STEP

14 Scribe the dissectional grooves.

Fig. J Ifill voids under contacts

Use the PKT end of the WC-1. For a beginning reference point, scribe the buccal dissectional groove, starting from the central pit over the occlusal table and down through the middle buccal third of each tooth. (Fig. 2) On a lower first molar, lightly scribe the extra buccal dissectional groove starting from the central groove. Lightly scribe the lingual dissectional groove on the upper and lower molars.

Fig. 2 I Scribe dissectional grooves

Using the central dissectional groove of the adjacent unprepared teeth as a guide, lightly scribe the central dissectional grooves on all teeth. (Fig. 3)

Fie,. 3 I Scribe dissectional

Crown and Bridge Anatomical H't1xi11g

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STEP

1 5 Carve the buccal and lingual planes.

Note: There are two 15 to 20° angles to be aware of One angle recreates the prominence of each of the buccal cusps. The second forms the 15 to 20° degree angle from the middle third bulge to the occlusal table. (Fig. 1) On the upper first molar, carve the distal side of the disto-buccal cusp plane from the contact area. Angle the blade toward the occlusal table. Hold the PTC WC-1 instrum ent at a 15 to 20° angle (Fig. 2) Carve the mesial plane of the disto-buccal cusp, cutting toward the buccal dissectional groove. Match the slope of the distal plane toward the occlusal table at 15°. (Fig. 1 next page) Carve the distal and mesial planes of the distobuccal cusp in the same way. Repeat the proced ure to carve the buccal planes on all teeth.

Fig. 2 upper molar buccal planes

Productivity Training Corporation

F ll :\"\ the rune t p t create the lingual planes n all teeth (Fi . )

STEP

16 Carve the buccal depression.

U e the rounded end of the WC-1 can er. With the "X' carver side o the WC-1 on its side, carve a sligh depression from the mesial to distal, just above the middle third bulge. Carve lightly and let the shape of the carver do the work. (Fig. 3)

Fig. 3 I rotate model for each plane

Fig.

Crown and Bridge Anatomical H'lvdng

2

I upper molar lingual planes

41:

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STEP

1 7 Carve the marginal ridges.

Start with the mesial marginal ridge. Mark the pit with the point of the half Holle nback end of the WC-1 carver.

Fig. 1 I make marginal ridges even

Carve the occlusal surface in the marginal ridge area to corre spond to the height of the adjacent unpre pared tooth. Carve until the edge of the carver almost touches the marginal ridge of the unpre pared tooth. (Figs. 1 and 2) Carve the distal marg inal ridge in the same way.

Fig. 2 I angle instrument 15°

Note: When carving marginal ridges, angle the carver down 15°, creating the planes ofthe mesial side of the mesial fossa and the distal side of the distal fossa. Three things are accomplished in this step: Proper height of the marginal ridges are achieved, the occlusal pits are established, and half of the planes of the mesial and distal fossae are done. The tip of the carver needs to be just inside the marginal ridge, in the area of the central dissectional groove.

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STEP

18 Carve the contacts.

Carefully remove the die from the model. Examine the wax pattern for concavities in the mesial and distal surfaces. You will create the contacts in these depressed areas. Use the Hollenback end of the WC1.

Carve away the excess wax on the outside perimeter of each depression, carving toward the the depressed contact area. Leave a small concave area where the crown contacts the adjacent tooth. (Fig. 1)

Fig. 1 I contact areas

On upper first molars the mesio lingual plane curves sharply into the contact area. You will need to remove more wax in this area. (Fig. 2) Complete all crowns to this point when working in groups of three or more.

Note: When carving contact areas you will always have afair amount ofexcess wax wrapping around the adjacent unprepared teeth. Because of this, you need to carve in a long sweeping motion to clear away all the excess wax from the outside perimeters of the contact areas until the crown gently curves into contact with the adjacent natural teeth.

Fig. 2 I upper molar mesio-lingual plane

Dissedional Groo e STEP

1 9 Carve the central dissectional grooves.

Use the carving tip end of the WCI.

Fig. 1 I central dissectional groove

Note: The angle ofthe instrument an the tooth must be positioned so that the groove being carved is smooth and follows the height of the ridges and the depth of each fossa. On molars, start on the mesial surface just o er the mesial margin al ridge (A). Carve a shallow groove down into the pit of the mesial fossa (B). From the mesial pit, go up over the oblique ridge, down into the pit ofthe central fossa (C), up o er ·the next oblique ridge, down into the pit of the distal fossa (D), and just breakth rough the distal margin al ridge (E). (Figs. 1and2 ) The central groove will be deeper in the pit of the fossae than where it goes over the ridge . (Fig. 2)

Fig. 2 I cutaway view

Piu ~ I rPtttrnl di