The application of occlusion in clinical practice part 2: the taking of occlusal records

The fabrication of appropriate study casts and records to enable occlusal analysis

In order to ensure the accuracy of the study casts, impressions should be taken using rigid impression trays such as metal rim-lock trays (Figure 1) or a custom tray (as opposed to the use of plastic stock trays, where errors may become introduced as a result of any flexion of the tray). Rim-lock trays do not require the use of a tray adhesive; furthermore, the retentive feature offered by the rim-lock design will permit excess material beyond the edges of the tray to be readily cut away to ensure that the set material does not flex (which can occur when the set impression material and tray are placed on a flat table top surface when pouring the casts. Trimming away of excess impression material (Figure 2) will also allow the operator to check easily that the material has not pulled away from the tray.³ The latter is a risk associated with the use of impression trays where an adhesive may have been ineffectively applied, however, the deficiency may not have become immediately noticeable (for instance at the central portion of the tray).

Although alginate can be used as a suitable impression material, it is preferable to use a high quality, dimensionally accurate form of alginate or, as an alternative, an appropriate polyvinyl silicone (PVS) based material. In either case, it is important to ensure that the manufacturer's instructions are carefully followed. Whilst the use of a silicone material will also allow the pouring of duplicate casts, when a more rigid material such as silicone is being used, any dental undercuts must be appropriately blocked out (using a material such as soft red ribbon wax) and the presence of a sufficient amount of space ensured between the anatomical structures and the inner surface of the tray to help avoid the impression material and tray from becoming locked in the patient's mouth.

Vacuum mixed Type III gypsum stone should be used to pour the impressions.⁶ On receipt of the casts, they should be inspected for the absence of any obvious distortions (which may be noticeable upon the verification of the individual casts and/or upon simple hand-articulation, assuming that the intercuspal position is stable and readily identifiable). Any marked defects (such as from the casting of airblows and/or heel contacts) should be carefully eased away (Figure 3). However, if this process results in an erroneous occlusal recording, new impressions should be taken. Sometimes, an error with the casts may not be noticed until the process of attempting to fit the cast to an appropriate type of occlusal record (taken using a relatively rigid and accurate material), such as those used on the bite fork when taking a facebow record or an inter-occlusal record,⁶ as discussed further below.

Dental articulators

According to The Glossary of Prosthodontic Terms, the dental articulator is defined as, ‘a mechanical instrument that represents the temporomandibular joints and jaws, to which maxillary and mandibular casts may be attached to simulate some or all mandibular movements’.⁷ The use of the dental articulator will allow for the relationship of the teeth during static and dynamic movements of the mandible to be crudely imitated (to varying levels of accuracy) in the extra-oral setting. There is of course a diverse variety of dental articulators available in the market place, traditionally referred to as being either; hinge, plane line, average value, semi-adjustable, fully-adjustable and/or fossa-moulded/stereographic.⁸ For a more detailed account, please refer to Milosevic, 2003. ⁸ However, as per The Glossary of Prosthodontic Terms such devices may broadly fall into one of four classes:⁷

The use of a dental articulator is not essential, or indeed by any means a guarantee of success, when providing dental care. However, their use when trying to study and reproduce mandibular movements should be given due consideration.⁹ The selection of an appropriate device will depend on the level of reproducibility of mandibular movement required. In general, when planning care for a patient likely to include a prescribed change to the existing occlusal scheme, or where there is the need to copy the dynamic movements of the mandible crudely, the use of an Arcon (Articulated Condyle) type of semi-adjustable device (where the condylar elements are positioned on the lower member of the articulator), akin to the anatomical arrangement (such as with the Denar Mark II, Kavo Protar Evo or Whip Mix articulator), as opposed to a non-arcon semi-adjustable device (such as the Dentatus and Hanau) is generally considered acceptable (Figure 4).⁸ The taking of a facebow record and appropriate intra-occlusal records, as discussed in depth below, are required to permit the further programming of the semi-adjustable articulator in order to enable the setting of the:

The above measurements in the situation of using an average value articulator would be pre-set (usually at 110 mm for the intercondylar width, 30° for the condylar guidance angle, between 7°–15° for the progressive side shift and 15° for the incisal guidance angle).^5,8

The use of an average value articulator may be sufficient for cases where a limited number of restorations are planned (with existing stable occlusal reference points which are not going to be altered). The semi-adjustable device will offer further scope to help determine a more appropriate occlusal morphology of any dental restoration or appliance. This would minimize the level of adjustment that may be required during the time of trial and fitting and help improve overall patient experience and acceptance.^3,8

The semi-adjustable articulator does, however, have a clear limitation over that offered by a fully adjustable device, as the former can only simulate straight-line movements at the level of the condylar housing. However, from a true anatomical perspective, condylar movements against the fossa tend to adopt a curved/non-linear pathway. Thus, the straight-line arrangement (as per the semi-adjustable device) only represents the starting-point and end-point of the mandibular movements, whilst a fully adjustable device will allow for a wider array of the patient's border movements to be replicated.⁴ However, the financial and time costs incurred, together with the technical skills and experience required for the effective use of a fully adjustable articulator will serve as important limitations to their routine use. The use of predictable methods of undertaking restorative rehabilitation using adjustable materials to establish and confirm the occlusal prescription can also help to overcome some of the limitations offered by the semi-adjustable device, as discussed in the third part of this series.

The facebow record

The facebow recording is often the first procedure undertaken when mounting study casts on a (semi-adjustable) dental articulator. The facebow (also referred to as a hingebow) is a rigid but adjustable device that relates the maxillary occlusal surface to an anatomical reference point.⁴ The primary purpose of the facebow record is to permit mounting of the maxillary cast on the articulator. In addition, the facebow also provides a guide to the width between the condyles, referred to as the inter-condylar width, which has further practical significance in relation to the morphology of the posterior restorations, as alluded to in part 1.

Typically, two reference points are chosen when attaining a facebow record:

Both anterior and posterior reference points should be reproducible during further subsequent appointments. Typical anterior reference points include; Nasion (Whip Mix), the inferior orbital notch (Dentatus) or a set distance from the incisal level of a designated tooth (Denar). The use of the anterior reference point will also allow the casts to be centrally located within the confines of the articulator.³

Facebows generally fall into the category of being either of the arbitrary variety or kinematic variety.⁴ Arbitrary facebows are less accurate by the manner in which they relate themselves to the terminal hinge axis. They are, however, suitable for most routine restorative dental procedures. The latter effectively approximate the position of the terminal hinge axis typically to the position external auditory meatus (which is erroneous by definition). Facebows that utilize the external auditory meatus as the reference point are commonly referred to as earbows.

In contrast, the use of kinematic facebows requires the terminal hinge axis to be more accurately determined. Kinematic facebows may be more relevant where there is a need to copy the precise opening and closing movements of the mandible on the dental articulator, such as with a case of a complex restorative reconstruction involving an alteration of the existing vertical and horizontal occlusal relations.

The facebow fork or bite fork (Figure 5) is an item of equipment that is used to record the maxillary occlusal surfaces using a variety of different media/materials. These materials should offer dimensional stability, a suitable working time and ease of use. Typically applied recording materials include, Brown impression compound, Green Stick, polyvinyl siloxane bite registration materials (such as Stonebite, Dreve Dentamid GmbH, Germany and Blue Mousse, Parkell Inc, USA) or extra hard wax, such as Moyco beauty wax (Moyco Industries, USA) (Figure 6). The record attained using the bite fork is then inserted into the facebow, thus permitting the attainment of the registration required.

The procedure for the taking of a facebow record described below relates to the use of the Denar® Mark II System (Whipmix, KY, USA), utilizing the Denar® Slidematic Facebow.¹⁰ The latter is an example of an arbitrary facebow, where the articulator is of the Arcon, semi-adjustable variety. This system is widely used in clinical practice.

The facebow recording procedure would usually commence by using the reference point indictor that is contained within the Denar® Slidematic Facebow kit, whereby the anterior reference point for facebow transfer should be identified and marked up. For dentate patients, this will be 43 mm from the patient's incisal edge of either the right central or lateral incisor towards the inner canthus (corner) of his/her right eye; for edentulous patients the measurement is taken from the incisal edge in the area of the lateral incisor of a trimmed upper wax block.

The chosen material for recording the occlusal surface of the maxillary arch should then be applied onto the correct surface of the bite fork. When using a thermoplastic material such as wax or impression compound, the temperature of the material should be carefully checked to avoid unwanted scalding of the patient's lips and face.

The bite fork is then inserted into the patient's mouth and carefully centred over the maxillary cusp tips, lightly compressing the bite fork, thus forming an impression. Some protocols advocate instructing the patient to bite down gently into the recording medium. The midline indicator of the bite fork should be aligned to the midline of the maxillary arch, which can be indicated by the midline anterior frenal attachment. The overall objective (according to the manufacturer) is to produce a ‘slight impression’ of the cusp tips, primarily avoiding fossae.¹⁰ It is not essential to record every cusp; the level of detail required should be enough to permit the seating of an accurate maxillary cast in a stable manner. A record that is very shallow will not permit accurate and reproducible seating of the cast; in contrast, a record that is too deep will not permit accurate repositioning (Figure 7). The detail of the record should be sufficient in order visually to confirm the accurate seating of the cusp into the indentation made by it.

When using a wax-based material or impression compound (such as Brown impression compound or Green Stick composition, Kerr, USA), the cooling of the material using a 3 in 1 airgun is advisable, followed by the subsequent removal of the record from the patient's mouth. The registration material may then be chilled under cold water. Clearly, this stage will not be necessary when using PVS recording materials. The record should then be carefully assessed and re-seated in the patient's moth to assess for distortion and stability. Distortion may be indicated by the presence of a ‘rocking motion’ when the bite fork is re-positioned and is supported by the index fingers on either side of the bite fork. Where the record may reveal unwanted details, such as pits and fissures, the recording medium should be carefully trimmed prior to re-seating of the model using a scalpel. If there are any perforations through the registration medium (with metallic display) the cast will not seat accurately. Under such circumstances (as well as with the case of known/likely distortion), there is the need to take a new record.

It is also good practice to have the maxillary cast at the operator's disposal prior to the facebow recording. This will allow the clinician to check that the cast seats accurately and positively into the record in the bite fork, whilst concomitantly verifying the accuracy of the study cast. In the event of an error, it is advisable to take new impressions. Patel and Alani have, in fact, described the use of a separate bite fork to take the record of the mandibular arch to verify the accuracy of this cast.⁶

For the next stage, patients may assist by supporting the bite fork in situ by placing their thumbs on either underside of the bite fork or, alternatively, the dental assistant can support the bite fork. Another method involves the placement of cotton wool rolls against the occlusal surfaces of the mandibular posterior teeth and instructing the patient to bite together (care should be taken to ensure the accurate positioning of the bite fork and that the patient does not bite too hard).

The reference pin should then be fastened to the sidearm of the facebow and all of the toggles and clamps on the Denar Slidematic facebow subsequently loosened. The clamp marked ‘2’ should then be slid over the protruding end of the bite fork towards the patient's face. The clamp should be positioned over the shaft on the right side of the patient. Each of the calliper ends are then placed into the patient's external auditory opening (similar to a stethoscope). It can be helpful to have the dental assistant guiding the positioning of the calliper end on the side from which the operator is facing away. Where the choice is taken to use cotton wool roll to help support the fork in situ, the patient may be requested to position the earpieces themselves, particularly if placement appears to be proving to be difficult and/or uncomfortable, typically for instance where both ears are at slightly different level, which may sometimes be associated with the presence of facial asymmetry.

The anterior reference pointer should now be carefully released and positioned such that it is pointing towards the anterior reference point marked earlier. The facebow is then slid upwards or downwards, such that the tip of the reference pointer contacts the reference point; at this point the bow will be horizontal to the Frankfort plane. The screw on clamp ‘1’ should then be tightened (which is the vertical reference pin), whilst the screw on clamp ‘2’ serves as the horizontal reference pin. At this point, the digits ‘1 and 2’ on the clamps should be facing in the direction of the operator. The toggles and clamps should next be tightened until the recording apparatus is secure.

On the superior surface of the facebow is a scale. It is relevant to make a note of this measurement, which serves as an indication as to the inter-condylar width. The latter can also be used to position the condylar pillars of the articulator.

Finally, the calliper screw should be slackened, the facebow carefully removed from the patient's ears and the entire device taken out of the patient's mouth and appropriately disinfected. The facebow and bite fork assembly can be separated, disinfected and then carefully transported. For this purpose, it is helpful to wrap the bite fork in bubble wrap and place it in a hard container.⁵

The assembly (Figure 8) is then transferred to the articulator (in part or whole), depending on the apparatus being used. The maxillary cast is positioned onto the occlusal record, which has been related to the terminal hinge axis on the articulator and the cast attached to a mounting plate on the articulator using a suitable mounting stone/plaster (Figure 9).

The taking of inter-occlusal records

Accurate inter-occlusal records of the selected variety can be used to relate the occlusal surfaces of the mandibular cast to those of the maxillary cast, thereby permitting the mounting of a set of casts against each other on the articulator. Interocclusal records generally take the form of an:

The intercuspal record by definition records the position where the antagonistic occlusal surfaces are maximally meshed together. The centric relation record, however, aims to record the relationship of the mandibular arch to that of the maxillary arch when the condyles are seated in their most anterior-superior positions in the glenoid fossae. In the latter position (as discussed in Part 1), the opening and closing movements of the mandible will take place in a rotational manner (as opposed to translation) for the first few millimetres, and would correspond to rotational movements occurring at the dental articulator's condylar housing.

Lateral excursive and/or protrusive mandibular records may also be taken in conjunction with the CR record in order to programme the condylar guides on the semi-adjustable articulator, which would relate to the anatomical limits of the movements of the condyles in their glenoid fossae, respectively.

The Intercuspal (ICP) Record

An intercuspal record is generally taken when mounting a set of working casts where the occlusal scheme is stable, often where relatively simple restorations are being considered; hence a need to conform to the existing occlusal scheme. The use of casts mounted in CR for this purpose may culminate in undesirable occlusal interference.

For a dentate patient, where the occlusal surfaces inter-relate in a manner where the intercuspal position is readily determined, there may be no need to fabricate any type of record to help the process of cast mounting; this is in fact the ideal scenario, as it would avoid the obvious risk of introducing further potential sources of inaccuracy. However, where an ICP record is required, it should be as minimal as necessary, to help accurately locate the casts (Figure 10).³

Intercuspal records are perhaps most frequently taken following the preparation of a tooth/teeth to receive an indirect restoration involving the occluding surfaces. Such an intercuspal record may be attained by placing a suitable quantity of recording material, such as polyvinyl siloxane-based bite registration paste onto the dried occlusal surface (such as that of a tooth preparation) avoiding, where possible, the unprepared surfaces of the adjacent teeth. More extensive ICP records may, however, be required where the adjacent teeth may not allow the ICP to be readily established where, for instance, multiple teeth may be absent or an anterior open bite be present. Where PVS materials are used, the bite registration attained should be carefully trimmed to permit effective mounting.

Other materials, such as Moyco beauty wax or cold-cured acrylic resins, may also be used for the above purpose; typical examples being Duralay (Reliance Dental Manufacturing Co, Worth, Illinois, USA) Palavit G (Kulzer) or Trim (Bosworth, USA). However, where possible, the record should be as thin as possible in key areas. Once the chosen recording material has been placed evenly onto the patient's occlusal surface, patients should be asked to bring their teeth together into the position ‘of best fit’; a process that can prove difficult for some patients. Once set, the record is carefully removed, examined, disinfected, trimmed (if required) and subsequently used to mount the mandibular casts on the articulator against the maxillary casts (that will have been mounted against the upper member using the facebow record provided).

The accuracy of the mounting can be verified by using ultra-thin foil articulating paper. Holding contacts identified intra-orally should be congruent with those on the dental casts. If not, this may be indicative of an error. As discussed above, it is important to appraise the casts for any casting nodules or incorrectly trimmed models, especially in the heel areas.

For partially dentate patients, there may be a need to fabricate a wax occlusal rim, ideally supported by an acrylic baseplate.³

With advances in digital dentistry, a T-Scan Occlusal Analysis System (Tekscan) may be used to record ICP, and further analyse the relative hardness of the contacts between the teeth in this position.

The centric relation record

The centric relation record (unlike that of the intercuspal record) is attained regardless of any given position of tooth contact. The CR record, as discussed in Part 1, is often referred to as being a fixed and relatively reproducible record in the literature, as it is relatively reproducible in the patient between successive attempts and is one that is fixed between that of the patient's condyles and the condylar housing of the dental articulator (where rotational movements of the condyles will take place against the corresponding articular eminences).

The centric relation record is advocated when fabricating study/diagnostic casts, thereby permitting the evaluation of the retruded contact position which may otherwise be difficult in the presence of the soft tissues and protective neuromuscular reflexes of the patient. The taking of such records for the mounting of study casts is advised when attempting to perform occlusal adjustments and when aiming to carry out a re-organization of the occlusal scheme (inclusive of cases such as that of a patient with tooth wear (TW), where there is a need to increase the occlusal vertical dimension – OVD).³ As discussed in Part 1, approximately 90% of adult patients have a slide between RCP and ICP (with ICP being anterior and superior to CR by 1.25 mm +/- 1.0 mm).¹¹ Casts mounted in CR can readily elucidate this feature, if present, which may prove valuable to help accommodate the chosen dental material to restore the worn surfaces without the need for any further significant tooth preparation. Any premature tooth contacts (also termed deflective contacts) that will guide the patient's mandible from RCP to ICP may also be noted at this stage, as well as the need for any occlusal correction determined (prior to embarking upon complex prosthodontics treatment plans).

Centric relation records may also be used to mount working casts. There are a number of clinical circumstances where this becomes likely: these can include the scenario when providing removable partial dentures where the ICP may not be readily identifiable/recordable or is unstable; when constructing a set of complete dentures; when providing restorative treatment for a patient with tooth wear, especially where adhesively retained restorations are to be placed in a supra-occlusal position, as may often be the case when treating a case of localized anterior maxillary wear utilizing the Dahl Concept/phenomenon of Relative Axial Movement (as discussed further in Paper 3);^3,12,13,14 or when attempting to provide an indirect restoration at a tooth which in fact also contains the first point of tooth contact in CR (RCP), where there may be an indication to copy this feature into the definitive restoration. Again, the technical means for achieving this have been discussed further in Part 3.

Centric relation would also be chosen when for the construction of full coverage occlusal stabilization splints. The latter may not only be used for the management of parafunctional habits (that may lead to TW), but also for the protection of heavily restored dentitions and also to plan restorative rehabilitation of patients with generalized tooth wear whereby the prescription a temporary removable ‘ideal occlusal scheme’ (which represents the desired end point of the restorative process) can be reversibly ‘tried-out’ for tolerance.^15,16

In Part 1, the frequently applied technique of bimanual manipulation as described by Dawson to locate CR was described.^17,18 However, for many patients (especially those who present with occlusal dysfunction and/or with protective neuromuscular reflexes), the location of CR by the latter means will prove difficult. To assist with more challenging cases, the use of an anterior de-programming device may prove helpful. The latter aim to overcome the neuromuscular reflexes, which are initiated by tooth contact, by causing tooth separation and providing an anterior reference point/stop to help stabilize the mandible during the act of taking the record.¹⁸

Many practitioners often resort to the simple process of initially asking the patient to bite on some cotton wool rolls, ensuring that all of the teeth are separated (by a minimal distance that permits the effective use of the recording medium). Alternatively, the use of wooden spatulas (‘tongue blade method’) has been described, where it has been suggested that the teeth should be discluded for a period of 10 to 20 minutes (to allow the proprioceptive input to be lost) prior to taking the registration.¹⁸

Commercially available products to the above may, however, provide a better option for the above purpose. An example of a commonly used device is the Leaf Gauge (Huffman Dental Products LLC, OH, USA). The Leaf Gauge is composed of thin plastic strips of 0.1 mm width which are placed in the anterior region; further layers sequentially being added until there is evidence of posterior tooth separation when the patients bite down lightly. Once CR has been located, occlusal stops can be prepared using direct resin composite to record and relocate this position (Figures 11, 12, 13 and 14). This technique is frequently used by the authors.

For some patients, however, it may still remain difficult to locate CR. Under such circumstances it is appropriate to fabricate an anterior de-programming device, such as a Lucia Jig.

The Lucia Jig, is effectively an anterior bite plane/platform deprogrammer, first described by Lucia in the 1960s, traditionally constructed using cold-cured acrylic resins (such as Duralay, Palavit G or Trim, Bosworth) (Figure 15). The Jig should be sculpted such that it just covers the palatal soft tissues and has a slope of approximately 50° and be of a level of thickness that allows for the introduction of the recording medium, avoiding any unnecessary separation of the opposing arches, where possible. An additional merit of the Jig, in improving the efficacy of the device in determining CR, is by enabling the undertaking of a gothic arch tracing. In the latter instance, the patient is advised to make lateral excursive and protrusive movements with the Lucia Jig in situ and a piece of articulating paper imposed between the Jig and the mandibular incisor teeth. A point is selected from the lower dentition to form the pattern on the Jig by removing the influence of the other teeth by undertaking selective adjustment of the Jig (Figure 16). This process can, however, sometimes end up being a very time consuming and cumbersome experience. A method to assist with the aforementioned process (often used by the authors) involves the preparation of a small stylus made by bonding on a small amount of flowable resin composite to one of the lower incisor teeth, making sure to remove the stylus prior to discharging of the patient. Regardless of the chosen method to undertake the tracing, it would be hoped that the tracing produced on the Jig will result in a gothic arch pattern, with the apex of the arch used to indicate the retruded mandibular relationship.

Other techniques that have been described by Wilson and Banerjee to help locate CR include:¹⁸

The use of digital pantograph machines;

The use of an electric jaw muscle stimulating device to assist with the attainment of muscle relaxation – ‘Myomonitor’.

For patients who continue to fail to permit manipulation of the mandible after having placed the Jig in situ for more than 30 minutes, the use of an appropriate form of full coverage acrylic-based occlusal stabilization splint may be indicated.¹⁹

Having located CR, there is of course a need to record it. Commonly used materials for this purpose are PVS-based bite registration pastes or extra hard dental wax such as Moyco beauty wax. When planning the use of the latter form of material (wax record), it is helpful to prepare the inter-occlusal records prior to the patient's arrival. For such records, the outline should extend approximately 5 mm beyond the buccal cusp tips, and should comprise a minimum of two sheets of wax sealed together. Some operators choose to support the wax record with a section of shellac placed between the two layers of wax.

Where the use of a Lucia Jig (or an alternative device) may be required, a relief can be cut into the anterior portion of the wax record to permit concurrent placement of both the record and jig, respectively. Upon patient arrival, the wax record should be re-softened and placed over the maxillary occluding surfaces. The record should be lightly pressed against the cusp tips to produce shallow indentations and the patient's mandible subsequently guided into CR, such as to develop shallow indentations of the mandibular teeth cusps. The wax record should then be cooled using a 3 in 1 air and water gun. On removal, the record should be carefully inspected and verified for the absence of any signs of perforation. The record should be chilled using cold water and re-positioned to verify the accuracy of the record. Some operators choose the use of a material such as Temp-Bond™ (Kerr, Orange, CA, USA) to refine the occlusal contacts. It has also become increasingly popular to elect to use preformed wax wafers for this purpose, such as the Denar® Bite Registration Wax material, which in fact features a pre-cut notch to help accommodate an anterior de-programmer.

The fit of the CR record should next be checked on the dental casts, avoiding the temptation to squeeze the record to make it fit. An obvious drawback to the use of a thermoplastic material such as wax is distortion on cooling. To help indicate the presence of possible unwanted distortion on cooling and/or transfer to the dental laboratory, the application of a stripe of zinc-oxide eugenol paste, such as Temp-Bond™, across a portion of the record may be helpful; cracking of this in due course may be indicative of unwanted distortion. For a patient who may be partially dentate or edentulous, wax rims mounted on a stable (ideally rigid) baseplate will be needed, which should locate accurately onto the casts.

The CR record may then be used to mount the maxillary cast against the mandibular cast, which in turn can be attached to the lower member of the articulator. Where possible, the lower cast should be mounted as soon as possible to avoid the risks of deformation; indeed, many clinicians carry out this phase immediately after taking the record in the operatory.⁶

Lateral and protrusive records

Lateral excursive and protrusive occlusal records can be used to programme the settings on a semi-adjustable articulator as per the movements and dimensions discussed above, thereby providing further information on how best to deliver dental care.

There does, however, appear to be an element of inconsistency relating to the manner by which lateral and protrusive occlusal records are clinically obtained. Whilst some experts advocate the manipulation of the patient's dentition into a spatial position where the incisor teeth and canine teeth meet at an edge-to-edge location (deemed to be representative of the protrusive position and lateral excursion, respectively), in the opinion of the authors, given that these records represent condylar movement within the glenoid fossae (and are independent of guidance offered by the teeth), lateral excursive and protrusive records should strictly be taken independent of a tooth contacting position.

The technical execution of the procedure used by the authors would initially involve the preparation of a wax record analogous to one described above for the recording of CR with an additional layer of wax on the working side (to take account of the extra level of tooth separation when making dynamic movements) or, alternatively, the use of prefabricated wax wafer.⁴ With the patient supine in a comfortable position in the dental chair and with his/her mandible relaxed, the lower jaw is then guided in lateral excursion without any influence of the dentition. Supporting the mandible into the lateral position, some resin composite can then be placed between antagonistic teeth in the canine region on the side of excursion so as to ‘locate’ this position (without any preparation of the enamel with etching or bonding agents), ensuring the lack of tooth-to-tooth contact during any of the aforementioned stages. Subsequently, using the set composite as a guide, the patient can be asked to close, and the chosen recording material be placed to capture this ‘open lateral position’ of the mandible. The process is repeated on the contralateral side. These left and right lateral records can also be used to determine the condylar guidance angle during protrusion of the mandible (Figures 17 and 18).

A Leaf Gauge and/or Lucia Jig can also be used to assist with the process of taking dynamic records, which some clinicians may find helpful in attaining consistency with the taking of these records.

Having mounted the maxillary and mandibular casts using the facebow record and either the chosen ICP/CR record (or indeed no inter-arch record of either of the latter positions), the lateral excursive and protrusive records can then be used to programme the settings on the semi-adjustable articulator accordingly, as described by Sharpling.⁵

Finally, it is important to verify the accuracy of the mounting process. This is typically done by comparing the clinical observations to those seen on the mounted casts using Shimstock bite foil (which should have a thickness of 8 μm). In the event of disparity, there may be a need to re-check the occlusal scheme clinically and, if required, to repeat the process of taking the CR record followed by remounting of the mandibular cast. Some authors indeed advocate the taking of multiple (3–5) CR records to permit comparison and allow the mounting of the record they feel most appropriate.⁶

Conclusions

There are some situations in restorative dentistry where further occlusal records will be indicated; the individual circumstances will be discussed in further depth in Part 3. Whilst there may be limited evidence to support the necessity for the taking of such records (especially given the lack of significant supportive evidence in the scientific literature to endorse these measures),²⁰ this should by no means form the basis to ignore some of the Guidelines for Good Occlusal Practice completely,²¹ especially when planning and prescribing invasive and/or complex dental treatment, as discussed in Part 1.

It is important that the clinical operator has a good understanding of the forms of occlusal records that may be appropriate to the given circumstances, as well as the skills and knowledge to execute the procedures needed to ensure a suitable standard and clinical accuracy technically.