In this month’s Prosthodontips, Josh Sharpling and Zohaib Ali cover the thorny subject of occlusion and whether it should be restored with canine guidance or team work.
In recent columns, we have discussed treatment options for restoring patients with tooth decay. Today we are going to go very lightly into a huge dental topic, which can cause great controversy and huge controversy!
We’re going to talk about… occlusion.
Specifically, we will discuss whether to bring someone back to lead the dog or team mode.
The elephant in the room with any topic related to occlusion is temporomandibular disorders (TMD). Several systematic reviews (Manfredini Lombardo and Siciliani, 2017; Abduo, Tennant and McGeachie, 2013) show no relationship between lateral occlusive pattern and TMD.
Kahn et al (1999) also show that there is no relationship between TMD and non-functional lateral interference. This point may already be the beginning of controversy for some. However, hopefully the evidence will keep a lid on this can of worms for now.
Now that we’ve put the TMD to one side, we’ll focus on the decision-making process when designing lateral guidance. Situations where you may need to consider lateral guidance design include:
- Treating tooth wear (when adjusted or realigned)
- Broken restorations/fractured teeth
- Aesthetic restoration
- When restoring a tooth/teeth currently involved in lateral guidance
- Implant restorations
- Complete dentures.
Cynic guidance
Dog guiding is often considered the ideal form of lateral guidance. This is because guiding the canine will cause immediate blocking of the back teeth in excursions (an aspect of what is known as “reciprocally protected occlusion”).
Rejecting the posterior teeth will reduce the lateral forces on these teeth, reducing the chance of tooth breakage/restorations.
A heavily restored posterior dentition with a history of fractures may benefit from conversion to dog guidance. This will also limit the lateral forces on the weakened posterior teeth.
The patients in both photos below have largely restored posterior dentures. You could also make an argument that multiple capping restorations are indicated.
However, if the patient did not consent to this, but wished to limit the risk of future fractures, then restoring the canines and ensuring that the canine was guided (for example with canine lifts in the complex) would do so.
The occlusive reasoning behind guiding the dog is shown above. However, there is also a practical argument. it is relatively easy to design an occlusion with the guidance of the dog.
Steep slopes on the palatal surfaces of the maxillary canines (either in models in a dental lab/CAD software, or clinically) will almost always produce canine guidance.
Producing accurate group mode is much more difficult. Requires precise registrations on semi-adjustable articulator. Often alongside significant clinical adaptation.
Group mode
So far, we have said that canine guidance is easier to produce, reduces posterior lateral forces, and has the same effects on TMD as group work. So why would you ever want group mode?
There are a few specific reasons:
- Heavily restored cynic
- A dog that has undergone root canal treatment with a post may not be suitable for guidance. Therefore, it is better to share the guidance between other posterior teeth
- An implant replacing a canine may not be suitable for guidance
- Multi-unit implant restorations
- In full-arch restorations or restorations involving canine and premolar group function and shallow guidance is beneficial for sharing occlusal forces (Gross, 2008)
- Class III sectional relationship
- In patients with a class III incisal relationship, it is very difficult, if not impossible, to design a canine-guided occlusive scheme
- Anterior open bites
- Similar to those with class III relationships. It is impossible to design a canine-guided occlusive regimen in these patients (see Figure 3).
- Complete dentures
- It was conventionally believed that bilateral balanced occlusion benefited the complete dentition. However, this is not seen in the literature (Abduo, Tennant and McGeachie, 2013; Lemos et al, 2018; Zhao et al, 2013). Bilateral posterior balanced contacts in the maximum contact position are much more important for denture occlusion (see Figure 4).
Occlusion design with group mode
Obstructive records are required to accurately design an occlusion with group mode:
- Accurate displays (digital or analog)
- Accurate records of jaw relationships
- Retruded (see Figure 5 and Figure 6)
- It sticks out
- Mesolateral
- Facebow record.
Tooth records allow you to accurately assess and plan the anterior determinants of occlusion. Jaw relationship files allow you to program the articulator to more accurately reflect the posterior determinant of occlusion – the TMJ.
Question and answer section about prosthetics
This month we received the following questions.
When using BEWE (basic erosive wear examination) is the score for each tooth due to corrosion only or to all tooth wear?
This is a big question, and in this case, the term “erosive tooth wear” is confusing. Erosive tooth wear is another term for tooth surface loss and covers all forms of tooth wear. It is intended to cover the multifactorial nature of tooth wear and also to note the fact that tooth wear often has an element of erosion.
How do you know where to set the OVD when re-occluding a patient?
This is a very complex question and could take up a whole series of columns. However, in the very short term, there are several factors to consider when deciding how much to increase OVD by:
- Amount of recovery space required
- Planned position of incisal edges (guided by esthetics)
- Guidance section angle
- Scheduled tail tilts.
Please continue the questions. You can contact us on Instagram (@sharplingdental and @prostho_zo) and also email ([email protected]).
If there are specific topics you’d like us to cover in a column, please let us know.
Join us next month for the next installment of Prosthodontips, where we’ll then discuss how to prescribe a cosmetic wax.
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bibliographical references
Abduo J, Tennant M and McGeachie J (2013) Lateral occlusion designs in natural and minimally restored permanent dentition: a systematic review. Journal of Oral Rehabilitation 40(10): 788-802
Gross MD (2008) Occlusion in implant dentistry. A literature review of additive determinants and contemporary concepts. Australian Dental Journal 53(s1): S60-8
Kahn J, Talents RH, Katzberg RW, Ross ME and Murphy WC (1999) Prevalence of dental occlusal variables and intra-articular temporomandibular disorders: Molecular relationship, lateral guidance and non-functional lateral contacts. The Journal of Prosthetic Dentistry 82(4): 410-5
Lemos CA, Verri FR, Gomes JML, Santiago Júnior JF, Moraes SLD and Pellizzer EP (2018) Bilateral balanced occlusion compared with other occlusal schemes in complete dentures: A systematic review. Journal of Oral Rehabilitation 45(4): 344-54
Manfredini D, Lombardo L and Siciliani G (2017) Temporomandibular disorders and dental occlusion. A systematic review of correlational studies: end of an era? Journal of Oral Rehabilitation 44 (11): 908-23
Zhao K, Mai Q, Wang X, Yang W and Zhao L (2013) Occlusal designs on masticatory ability and patient satisfaction with complete dentures: a systematic review. Journal of Dentistry 41(11): 1036-42
