This series describes step-by-step wax carving guides, developed over a 14-year period, to teach three dimensional tooth anatomy to undergraduate students at the University of Birmingham's school of dentistry. The carving sequences have also been extensively used in postgraduate training courses, designed to help experienced clinicians master dental anatomy for practical application in restorative procedures.
CPD/Clinical Relevance: Knowledge and understanding of posterior tooth anatomy is a key skill in dentistry.
Article
Detailed knowledge and understanding of posterior tooth anatomy enables the accurate restoration of form, function and aesthetics of damaged teeth. While the anatomy of individual teeth is complex and infinitely variable, learning the fundamental anatomical patterns common to human dentition is of great use clinically, especially for the shaping and carving of direct restorative materials.
Wax is a material commonly used in dentistry for manufacturing and diagnostic procedures. It has also been widely used by dental technicians and dentists who aim to develop and refine practical skills in reproducing the anatomical forms of natural teeth via additive or reductive shaping exercises.
Learning tooth anatomy
Most undergraduate curricula teach tooth anatomy as a compulsory component of pre-clinical training.
Although anatomical complexity and variation make it a challenging subject to learn, most undergraduate programmes aim to teach basic shapes and predictable patterns so that students can recognise individual teeth and compare them to one another. The teaching modules of tooth anatomy and clinical training are often separated by many months, making it challenging for students to apply previously learned anatomical principles to restorative procedures.
If tooth anatomy is not mastered during undergraduate training, there is a risk that students may graduate with limited skills in the accurate shaping of direct restorations and in designing fixed and removable prosthodontic restorations so that they integrate biologically, functionally and aesthetically with the residual dentition.
In 2009, a review of the undergraduate curriculum at the University of Birmingham School of Dentistry provided the opportunity to redesign tooth anatomy teaching with a greater restorative focus. This article is the first of a two-part series describing wax carving exercises designed to teach the 3D coronal anatomy of posterior teeth. These exercises may be carried out following completion of 2D tooth drawing exercises previously described in Dental Update.1
This article illustrates wax carvings for posterior teeth from the right hand side of the mouth only, as the skills developed can be easily mirrored when repeated on contralateral teeth. The wax carving exercises also focus on the permanent dentition only, as the majority of restorative procedures are carried out on these teeth.
Care was taken not to overcomplicate the wax carving designs and to interpret the salient anatomical features in simplified, stylised formats, rather than relying on exact duplicates of specific natural teeth (Figure 1).
Figure 1.
Intracoronal wax carvings of (a) maxillary and (b) mandibular molars and premolars.
Wax carving
Wax is a dental material commonly used in manufacturing and diagnostic procedures. Wax also possesses ideal properties for practical exercises designed to teach tooth anatomy (Table 1).
Table 1.
Advantages of using wax for tooth anatomy training.
Easy to use and reuse Easy to repair by reheating May be used with identical carving instruments to those used clinically Available with different handling properties and colours Inexpensive, sustainable protocol with minimal waste
Classical publications described sequential additive techniques that use coloured waxes to build up the individual anatomical features of teeth.2 Wax may also be used successfully in reductive carving exercises designed to teach practical skills that may be used clinically in the shaping and carving of direct resin composite and dental amalgam restorations.3
Table 2 lists the materials and equipment described in this article, but these may be replaced with suitable alternatives (see the second article in this series), and natural teeth mounted in a die stone may be used instead of plastic tooth models.
Table 2.
Recommended materials and equipment.
Product Supplier Maxillary jaw and plastic teeth OKV16 KaVo Dental; Amersham. UK Mandibular jaw and plastic teeth OKV16 KaVo Dental; Amersham. UK Carving wax. Neon green recommended for fissure clarity Yeti IQ Ash-Free sculpturing wax, Bracon dental laboratory products; East Sussex, UK Discoid-Cleoid carver (LM 731-732) LM instruments; J&S Davis, UK Flameless induction heater NoFlame Plus; Amann Girrbach, Austria Ash 5 carver (for heating wax) Various suppliers Frahms carver Half Hollenback carver Right angled probe Silicone impression material Scalpel (10 blade)
Step-by-step wax carving guides
The following step-by-step guides describe waxing-up protocols and carving techniques for eight posterior teeth, which were designed to simulate the carving of dental amalgam and the shaping of direct resin composite intracoronal restorations.
First, use silicone impression material to form buccal and lingual pre-operative matrices (Figure 2).
Prepare cavities in the mandibular and maxillary molars and premolars (Figure 3). Table 3 shows the cavity configurations that are recommended for these exercises.
Adapt and firmly hold the buccal and palatal/lingual matrices. Add pieces of unheated wax to the cavities. Apply heat and encourage complete adaptation to the cavity floor (Figure 4), e.g. using the heated beaver tail tip of an Ash 5 instrument (Figure 4b). Add wax until the wax-ups are slightly overbuilt (Figure 4c).
Add and heat further increments of wax to create homogeneous, slightly overbuilt wax-ups of eight mandibular and maxillary posterior teeth. Remove the matrices, inspect for voids/deficiencies and repair accordingly (Figure 5).
Figure 2.
(a,b) Silicone matrix construction.
Figure 3.
(a,b) Cavity preparation for four mandibular and maxillary teeth.
Table 3.
Tooth preparation.
Tooth Cavity LR7 Occlusal LR6 MOD LR5 MO LR4 Occlusal UR6 MODP UR7 MO UR5 MOD UR4 Occlusal
Figure 4.
(a) Waxing-up by adding wax, (b) heating and (c) building wax up.
Figure 5.
(a,b) Posterior wax-ups ready for carving.
Complete the carvings using the following progressive sequence. Errors may be easily corrected by localised re-heating and/or repairing with small increments of wax.
Mandibular right second molar
Carve the midline fissure (Frahm's carver or equivalent) slightly lingual to the middle of the occlusal surface. Ensure that the fissure is carved to anatomical depth, using contralateral teeth as a guide (Figure 6).
Carve the lingual lateral fissure and the buccal lateral fissure, extending to the buccal and lingual axial grooves. Carve the lateral fissures perpendicular to the midline fissure to create a cruciform (cross-shaped) fissure pattern (Figure 7).
Carve the mesial and distal marginal fissures (Figure 8).
Outline the four individual cusps using a probe. Then carve four convex/rounded cusp ridges using a half Hollenback carver (or equivalent). The four oblique cusp ridges should be orientated towards the centre of the tooth at approximately 45° (Figure 9).
Carve the mesial and distal triangular marginal fossae using the cleoid (claw-shaped) tip of a discoid-cleoid carver (or equivalent) (Figure 10).
Carve the mesial and distal marginal grooves orientated towards the lowest aspect at the centre of the marginal ridges (Figure 11).
Remove marginal excess, e.g. using the discoid (disc) tip of a discoid-cleoid carver. The completed the LR7 carving should comprise:
Carve the mesial part of the midline and mesio-buccal lateral fissures (Frahm's carver). The midline fissure should be placed slightly to the lingual of the middle of the occlusal surface and the lateral fissure should extend into the mesial axial groove on the buccal surface (Figure 13).
Carve the lingual lateral fissure in the centre of the tooth, parallel and slightly distal to the mesio-buccal lateral fissure. Stop the carving short of the midline as shown and extend into the lingual axial groove (Figure 14).
Carve the disto-buccal lateral fissure extending into the distal axial groove on the buccal surface. Carve a Y-shaped central fossa as shown. This is described as dryopithecus fissure pattern, which is unique to mandibular first molars (Figure 15).
Carve the mesial and distal marginal fissures. The mesial marginal fossa is a triangular shape (Figure 16a). The distal fossa is similar but is orientated towards the lingual surface as shown (Figure 16b).
Carve five individual convex/rounded cusps using a half Hollenback carver. The mesio-lingual and mesio-distal cusps should be similar in size. The centro-buccal cusp should be the largest and the disto-buccal cusp (hypoconus) the smallest.
The five oblique cusp ridges should all be orientated towards the centre of the tooth (~45°) (Figure 17).
Carve the mesial and distal triangular marginal fossae, as with the LR7 carving (Figure 18).
Carve the mesial and distal marginal grooves (Figure 19).
(a) Mesial and (b) distal marginal fissures/fossae.
Figure 17.
Five cusps.
Figure 18.
Marginal fossae.
Figure 19.
(a,b) Marginal grooves.
Figure 20.
LR6 carving complete.
Mandibular right second premolar
Carve the midline (and lingual-lateral fissures as shown (Frahm's carver) (Figure 21).
Carve the mesial and distal marginal fissures (Figure 22).
Carve the convex buccal cusp. This cusp ridge should be perpendicular to the midline as it is a transverse rather than an oblique cusp ridge (Figure 23).
Carve the mesio-lingual and disto-lingual oblique cusp ridges (the latter is the smaller of the two).
Lower second premolars are the only posterior teeth to have oblique as well as transverse cusp ridges. 60% of lower second premolars display this Y-form fissure pattern, while the remaining 40% have an H-form fissure pattern, similar to that of all other premolars.
Carve the mesial and distal marginal grooves (Figure 24).
Y-form lower second premolar carving complete (Figure 25).
Figure 21.
(a) Midline and (b) lingual-lateral fissure.
Figure 22.
Marginal fissures.
Figure 23.
Y-form fissure pattern.
Figure 24.
Marginal grooves.
Figure 25.
LR5 carving complete.
Mandibular right first premolar
Carve midline fissure and mesial and distal marginal fissures (H-form fissure pattern; Figure 26).
Carve the mesial and distal marginal fossae (discoid-cleoid carver). The distal fossa should be larger than the mesial (Figure 27).
Lower right first premolar carving is then complete (Figure 28).
This completes the mandibular carvings. Refine carvings or reheat and re-wax-up as required until optimal anatomical shapes are acheived (Figure 29).
Figure 26.
(a,b) H-form fissure pattern.
Figure 27.
Marginal fossae.
Figure 28.
LR4 carving complete.
Figure 29.
Mandibular carvings complete.
Carving maxillary posterior teeth
Carve the mesial midline fissure and buccal lateral fissure (Frahm's carver or equivalent) to create ‘L-shape’ fissures. Carve to anatomical depth (use contralateral teeth as a guide) (Figure 30).
Carve distal midline and palatal fissures into a second ‘L-shape’ (Figure 31).
Carve the mesial and distal marginal fissures (Figure 32).
Carve an oblique fissure between mesio-palatal and disto-buccal cusps. Note, this fissure should be shallower than the preceding ‘L-shape’ fissures (Figure 33).
Carve four individual cusps with a half Hollenback carver (or equivalent) used at different angles to create convex/rounded cusp ridges.
The mesio-buccal and disto-buccal cusps should be similar in size. The mesio-palatal cusp is the largest and the disto-palatal (Hypoconus) is the smallest cusp.
All cusp ridges should be orientated towards the centre of the occlusal surface at about 45° (Figure 34).
Carve the mesial and distal triangular marginal fossae, e.g. with the cleoid tip of a discoid-cleoid carver (Figure 35).
Carve the mesial and distal marginal grooves (Figure 36).
Carve away excess marginal wax to create an obvious demarcation between wax and adjacent ‘tooth’. This completes the first maxillary molar wax carving (Figure 37).
Figure 30.
Mesial and buccal fissures.
Figure 31.
Distal and palatal fissures.
Figure 32.
(a,b) Marginal fissures.
Figure 33.
Oblique fissure.
Figure 34.
Cusp ridges.
Figure 35.
Marginal fossae.
Figure 36.
Marginal grooves.
Figure 37.
UR6 carving complete.
Maxillary right second molar
Copy the preceding carving sequence for the UR7.
Mesio-buccal and disto-buccal cusps of similar size.
Large mesio-palatal cusp.
Small disto-palatal cusp.
Note that all maxillary molars (first, second and third) have similar anatomy. Moving distally, the teeth tend to become smaller and more triangular owing to the progressively diminishing size of the disto-palatal cusp.
The buccal lateral fissure may also be orientated more distally on second and third upper molars (Figure 38).
Figure 38.
UR7 carving.
Maxillary second premolar
Carve the midline fissure (Frahm's carver) to anatomical depth (Figure 39).
Carve the distal marginal fissures to complete the H-form fissure pattern typical of premolar teeth (Figure 41).
Shape the buccal and palatal cusps. Note, upper premolars have transverse (rather than oblique) cusp ridges that are orientated perpendicular to the midline fissure (Figure 42).
Shape the mesial and distal triangular fossae (discoid-cleoid carver) (Figure 43).
Carve the marginal grooves across the mesial and distal marginal ridges to complete the maxillary second premolar carving (Figure 44).
Figure 39.
Midline fissure.
Figure 40.
Mesial marginal fissures.
Figure 41.
H-form fissure pattern.
Figure 42.
Transverse cusp ridges.
Figure 43.
Marginal fossae.
Figure 44.
UR5 carving complete.
Maxillary first premolar
Use the same technique to carve the H-form fissure pattern of the maxillary first premolar. The only difference being the slight palatal orientation of the mesial marginal groove (Figure 45).
Maxillary first premolar carving is then complete (Figure 46).
This completes the maxillary carvings. Refine carvings and reheat as required until optimal anatomical shapes are achieved. (Figure 47).
Photograph and study the carvings. Refine or reheat and re-wax-up as required until opimal anatomical outcomes are acheived.
These carving exercises may be also be repeated (as ‘mirror images’) on the maxillary and mandibular left posterior teeth (Figure 48).
Figure 45.
Mesial marginal groove.
Figure 46.
UR4 carving complete.
Figure 47.
Complete axillary posterior carvings.
Figure 48.
(a,b) Wax carvings repeated on the maxillary and mandibular left posterior teeth.
