Dental Update - Technique tips (1)

Article

The Manchester bite block is a modified lower occlusal rim that was first described by McCord and Grant in 2000.¹ The Manchester bite block (Figure 1) has two pillars of wax situated bilaterally in the region of the mandibular second premolar-first molar tooth positions. It provides the clinician with a simplified lower rim to record the jaw registration stage of complete denture construction.

Figure 1. Manchester bite block (modified lower occlusal rim).

The aim of this paper is to revisit the Manchester bite block jaw registration technique and to introduce clinicians to a further modification that can be made to outline the position of the lower anterior teeth to the technician.

Jaw registration

A jaw registration record can be made by the mandible closing in its retruded arc of closure with occlusal rims separating the maxilla and mandible at the selected occlusal vertical dimension (OVD).¹

The use of conventional upper and lower wax rims (Figure 2) is one of the most common jaw registration techniques. In this technique, the lower wax rim is placed in the mouth and trimmed until it contacts the upper rim evenly in the retruded contact position (RCP) at the selected OVD. This is done by selectively removing points of first contact bilaterally. It can be difficult to detect these premature contacts and accurately remove them along the entire length of the rims bilaterally.¹ Furthermore, prior to securing a jaw registration, the lower wax rim should be adjusted in bucco-lingual width until within the ‘neutral zone space’.² This is important to provide tongue space, facial tissue support and lower complete denture stability.^3,4 One of the disadvantages of this technique is that it can be difficult to identify this space accurately and adjusting the wax bucco-lingually can be a time consuming process to carry out.

Figure 2. Conventional upper and lower wax rims.

Conventional wax rim technique

The upper occlusal rim is customized to prescribe the aesthetic component of the maxillary denture;

The conventional lower occlusal rim is placed in the mouth and trimmed until it contacts the upper rim evenly in RCP at the selected OVD;

This is achieved by selectively removing points of first contact from the entire length of the lower rim;

Once this position can be reproduced, the bucco-lingual width of the lower occlusal rim is adjusted to identify ‘the denture space’ (neutral zone space);

The occlusal rims are then sealed at the selected OVD in RCP with a suitable registration medium.

Manchester bite block technique

This technique is based on the principle of occlusal pivots which are well established as occlusal adjustments for a worn complete denture dentition.⁵ The clinical and laboratory stages of this technique are outlined below:

The upper occlusal rim is customized to prescribe the aesthetic component of the maxillary denture as in the conventional technique;

The two pillars of wax situated bilaterally in the Manchester bite block are trimmed until they contact evenly at the selected OVD in RCP (Figure 3);

A suitable registration medium is interposed between the rims and the patient is instructed to close in RCP. This seals the conventional upper wax rim and lower Manchester rim, completing the jaw registration;

The technician sets the mandibular anterior teeth perpendicular to the crest of the alveolar ridge^6,7 as dictated by the OVD and RCP record indicated by the registration medium and the mandibular Manchester bite block.

Figure 3. The Manchester bite block pillars contacting the conventional upper occlusal rim bilaterally at the selected OVD in RCP.

Care must be taken in this technique that the mandibular anterior teeth are not set excessively labially, as this may compromise lower lip muscle activity, leading to an antero-posterior rock in function.⁸ Equally, care must also be taken not to set mandibular anterior teeth too far lingually as this may encroach upon tongue space, resulting in a lisp.⁹

Modified Manchester bite block technique

McCord and Grant described a further modification that can be made to the Manchester bite block involving the use of carding wax to outline the position of the lower anterior teeth to the technician.¹ A variation of this technique using poly-vinyl siloxane (PVS) in a putty or medium-bodied consistency attached to the anterior aspect of the rim can provide a functional registration of the space which the anterior polished surfaces of the mandibular denture will occupy. The clinical and laboratory stages for the use of this modification are outlined below:

The Manchester bite block technique described above to record RCP at the selected OVD is first completed;

The Manchester rim is removed from the oral cavity and poly-vinyl siloxane (PVS) adhesive is placed on the anterior aspect of the rim;

Poly-vinyl siloxane (PVS) in a putty or medium body consistency is attached to the anterior aspect of the rim;

The mandibular modified Manchester bite block is then seated and the patient is instructed to carry out functional movements, including pursing their lips, licking their lips, swallowing and sipping water (Figure 4);

In the laboratory, the Manchester rim is lubricated with vaseline and putty indices are placed around the modified Manchester bite block by the technician (Figure 5);

The putty indices are then used to set the prosthetic teeth into the space indicated, guiding the technician to the position of the lower anterior teeth (Figure 6).

Figure 4. PVS putty attached to the anterior aspect of the Manchester bite block molded by the patient carrying out functional movements.

Figure 5. Putty indices placed around the lubricated modified Manchester bite block.

Figure 6. The technician setting the mandibular teeth into the space indicated by the putty indices.

Figure 7 shows a case completed using the modified Manchester bite block technique in the management of a patient with a Class II skeletal relationship.

Figure 7. A case completed using the modified Manchester bite block technique in the management of a patient with a Class II skeletal relationship.

Advantages

Provides a RCP record that can be easily returned to the mouth to verify its accuracy;

Control over the OVD as the pillars of wax can be readily trimmed evenly bilaterally;

Ensures a stable relationship between the bases and the underlying tissues;

The ‘modification’ to the Manchester bite block technique allows a clinician to record a functional registration of the space which the entire anterior polished surfaces of the mandibular denture will occupy. This is analogous to a neutral zone registration⁸ of the anterior mandibular denture space but with the further benefit that it can be completed at the same visit as the remainder of the jaw registration.

Conclusion

The modified Manchester bite block provides the clinician with a simplified technique to record the jaw registration stage of complete denture construction whilst also providing scope to outline the anterior polished surfaces of a mandibular denture in the same visit. It is the authors' experience that this modification is particularly useful in patients with Class II skeletal patterns. This technique can also save a clinician time during the jaw registration visit and may reduce the number of ‘re-tries’ in complete denture construction. The materials used in this technique are readily available in general dental practice and do not increase a practitioner's laboratory bill.

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References

Technique tips

Authors

Kasim Butt

Wouter Leyssen

David Attrill