The understanding of TMJ anatomy as well as its function is very important to generate stable as well as healthy intercuspation. TMJ consists of condyle, disk, muscles and ligaments. It connects the lower jaw to the temporal bone in the skull in both sides and has two movements (Rosenstiel and Land, 2001). The TMJ along with muscles stabilization is the starting point to get the ideal maxilla-mandibular relationship in the centric relation. There is no way to register and transfer an accurate interocclusal record if patient has TMJ or muscles dysfunction. The patient with this dysfunction should be treated first before final restoration, cementation or construction. The conservative management of unstable joints and muscles via appliance therapy is the most common modality of management (Capp and Clayton, 1985).
4.2 Occlusal vertical dimension:
Perhaps one of the toughest and most intricate recuperative experiments for dentists in today's world is directly related to the occlusal vertical dimension (OVD). However, dentists have realized over the years that for the recuperation to work appropriately and the patients to get a good long-term solution to their needs, changes have to be made in the overall OVD structure (Guertin and Prostho, 2003).
The OVD is normally described as the space between the two points that exist when the occlusal surfaces come in contact with each other. Hence, it is important to note that the OVD is a phenomenon that appears with the overall positioning of the teeth.
Hence, it is important to note here that the decision to change or alter the OVD at any stage cannot be a hasty or careless decision. This is so because any level of change, minor or major will require an appropriate recuperation plan for one arc, and at times, even both (Guertin and Prostho, 2003).
4.2.2 Vertical dimension at rest:
One of the biggest questions that people ask is whether or not dental wear and tear can directly lead to the overall deficiency of OVD? There are two different ideologies that emerge as an answer to this question (Guertin and Prostho, 2003).
Niswonger came up with the first concept after making observations and analyses of his personal experiences with his patients. His analyses helped him assert that that it was nature's course to preserve a consistent level of distance in the constant inter-occlusal space of nearly 3mm throughout an individual's life span. The methodology used to sustain this distance over the years is through the extrusion of the dento-alveolar composite which can help balance any natural or man-ensued dental wear that occurs. However, over the years, the advocates of this particular theory have concluded that the dental, muscular and articular spheres can possibly face sever damages with the alterations made in the VD of an individual (Guertin and Prostho, 2003).
The other ideology that was brought forth in response to the query of whether OVD was a direct result of dental wear has been supported by numerous cephalometric researches that have been conducted over the years. This ideology focuses on the impact of various scopes of facial structures, movements and expressions. The main idea that this particular phenomenon promotes is that the OVD undergoes changes at times after the dental wear process is finished or after the posterior teeth have been lost. The followers and advocates of this particular concept assert that the individual's natural neuromuscular structure is strong enough to adapt to the alterations that happen in the dento-alveolar construct (Guertin and Prostho, 2003).
However, it is important to note here that the deficiency or decrease of the OVD levels is nearly impossible to determine if the original location of the steady bony points of reference is not known i.e. before any dental alterations have taken place. This raises the important question of how, then, can an appropriate diagnosis be made? This is why dental history records play an important role. Furthermore, the methods mentioned in the prior paragraphs are all extremely helpful in allowing dentists to make an appropriate diagnosis. All of the methods mentioned here are established methods; none of them are new or experimental. Even though, all of these methods single-handedly might not be very helpful to a dentist but combining them together can also help a dentist make an informed diagnosis (Guertin and Prostho, 2003).
4.2.3 Increasing Occlusal Vertical Dimension:
The sculpturer Phidias explains that the shapes that are agreeable to the human eye are formed when two separate entities are joined together respecting the proportions that each entity has. These, he calls, the golden number and the principle under which these shapes are formed, he calls, the golden rule. Hence, if we were to consider the golden rule in the dynamics of dentistry, we must understand the scope of the facial proportions. Looking at figure 2, we can clearly see that the golden rule exhibits the association between the pupil-commissure of the lips and the commissure of the lip-chin measures 1.618:1. It is important to note here that the space between the chin and the inside edge of the nose is mostly equivalent to the space between the commissure of the lips and the pupil (Dawson, 2007). Figure 2:
4.3 Centric Relation:
In the realm of dentistry, centric relation is the mandibular jaw location which holds the top of the condyle in place far more superior and anterior then anything else inside the mandibular fossa. According to the prosthodontic glossary, the centric relation can defined as an anterior and superior braced position that is placed along the articular eminence of the glenoid fossa, with the articular disc interposed between the condyle and eminence (Dawson, 2007). It is the relationship between the upper and lower jaws when the mandibular condyles are in their transverse horizontal axis, regardless of the teeth contact (Krishan 1957).
The use of centric relation is mostly in situations when the recuperations of edentulous patients is needed, specifically those patients who have either the implant-braced hybrid or fixed and detachable prostheses. This process is used mainly because the dentist aims to reproducibly connect the individual's mandible and maxilla. However, alternate methods have to be at times used because the individual might not always have the teeth to clearly ascertain his own vertical dimension of the occlusion. This is why the condyle has to be placed in the same position every time if the consistency of its placement nearest to the most superior and anterior location inside the fossa has to be maintained (Dawson, 2007).
4.3.2 Philosophy of centric relation:
Maxillomandibular relationship in centric relation is the most controversial point in dentistry (Silverman, 1956). Centric relation is the essential key and factor in the study of the occlusion stability, so the determination of occlusal problem and TMJ evaluation are highly dependent upon the position of the lower jaw in the centric relation (Krishan, 1957). The centric relation exists irrespective of the presence or absence of teeth because it is essentially the relationship between the upper and lower jaw (Davies and Gray, 2001).
Moreover, the basic uses of an accurate Centric Relation recording should be made to reduce time spent, and then all the intraoral adjustments can be made at delivery. Some of the applicable situations include (Davies and Gray, 2001):
a. MI that is not clearly defined due to restored dentition.
b. Changing VDO
c. Occlusal scheme - group function rather than mutual protection.
d. TMJ disorder patients with occlusal discrepancies, as part of the etiology of the TMD (Davies and Gray, 2001).
Furthermore, in the picture used of the skull on the previous instance (FIG 2), the TMJ has been shaded a lighter shade so that the overall anatomy becomes more obvious to see. When analyzing the centric relation, the condyle has to be placed as centered within the glenoid fossa as possible, closer to the highest part and the back of the fossa. This particular placement is known as the centric relation. If and when the TM Joints are more or less healthy then they usually display this placement when the teeth have a slight space between them and the overall muscles of the mastication are in a calmed state. Preferably, this particular centric relation should exist when the overall teeth placement is close, with minimal to no space in between, within the individual's centric occlusion (Dawson, 2007).
4.3.3 Systems for recording Centric Relation:
The first step needs to be taken when the individual's wax rims start hitting the anterior. This happens when there is an obvious distance between the occlusion rims distal to the canines; this usually permits a normal recording. The procedure in this case must be to get the individual close, but to make sure that the patient is not tensed but relaxed, and then blot in the midline on the wax, making sure that both of the rims on the occlusion are marked or blotted distinctly. This is followed by a…