Temporomandibular joint and occlusal considerations in periodontics

Occlusion plays an important role in the pathogenesis of periodontal diseases. A faulty occlusion may induce traumatic lesions in the supporting periodontal structures, thereby adversely affecting the long-term prognosis of tooth/teeth. Occlusion may also indirectly affect the periodontal health status by interfering with the plaque elimination and by influencing periodontal defense mechanism. Sometimes, occlusal problems are difficult to diagnose and if diagnosed, they may be difficult to treat. Presently, most of the dentists overlook the occlusal disturbances even after they have been recognized. Reason being, most of the occlusal disturbances involve the function of the entire dentition rather than a single tooth or segment.  It must be understood that most of the occlusal problems require full mouth treatment and a dentist should be well trained to recognize them and treat them appropriately.

There are many controversies regarding the relationship of occlusal trauma and progression of periodontal inflammatory diseases. Can occlusal trauma initiate gingivitis or periodontitis? Can it modify the response of periodontium to local irritants which are considered as primary etiological factors for periodontal inflammation or their occurrence together is just coincidental? A thorough knowledge of normal occlusion is essential to answer the above questions.

Rationale for comprehensive occlusal examination

A detailed history of the patient and thorough clinical examination are the most fundamental steps in comprehensive periodontal treatment.  It must be remembered that occlusal problems are not always associated with pain. It has been demonstrated that individuals with malocclusion have no more pain than those with an ideal occlusal scheme 1-3. It is commonly seen that patients who have severe malocclusion have negligible clinical symptoms. Parafunctional habits are more responsible for causing occlusal and temporomandibular joint problems than a bad occlusion. Lytle et al. (1990, 2001a, 2001b) 4-6 have categorized parafunctional activity, according to the severity of the condition (Table 34.1). So, carefully identifying any sign or symptom which is related to occlusal disharmony is the primary rationale of comprehensive occlusal examination.

Table 34.1 Categories of parafunctional activity

Category
Parafunctional activity
TYPE 1Almost no parafunction, no evidence of wear, mobility, tooth migration, muscle
soreness, fractures, cracks, craze lines, or abfractive lesions.
TYPE 2Moderate parafunction, evidence of slight wear, mobility, tooth migration, muscle soreness, fractures, cracks, craze lines, or abfractive lesions.
TYPE 3Destructive parafunction, evidence of excessive wear, mobility, tooth migration, muscle soreness, fractures, cracks, craze lines, or abfractive lesions

Physiology of temporomandibular joint (TMJ)

TMJ is one of the most complex joints in the human body. It is a ginglymoarthrodial joint, a term that is derived from ginglymus, meaning a hinge joint, allowing motion only backward and forward in one plane, and arthrodia, meaning a joint of which permits a gliding motion of the surfaces 7. Its compound articulation is formed by the articular surfaces of the temporal bone and the mandibular condyle. Both the articulating surfaces are covered by a dense articular fibrocartilage (Figure 34.1). The right and left TMJs make a bicondylar articulation and an ellipsoid variety of synovial joints.

Figure 34.1 Diagrammatic representation of longitudinal section through temporomandibular joint demonstrating its components

Longitudinal section of temporomandibular joint showing its components

Components of the temporomandibular joint:

TMJ consists of,

  • 2 bones: Temporal and mandibular bone
  • A disk that divides the joint into 2 spaces: Upper and lower compartments
  • A joint capsule
  • Ligaments: The lateral ligament, sphenomandibular ligament, and stylomandibular ligament.
  • 4 main muscles that create 5 motions: Temporalis, masseter, medial pterygoid, lateral pterygoid

Bones:

The TMJ is formed by mandibular and temporal bones. The cranial end of ramus of the mandible has two processes: the coronoid process, anteriorly and the condylar process, posteriorly which has a head on top and a distinct neck below. The head of the condyle articulates with the articular surface in the squamous portion of temporal bone. The squamous portion of temporal bone has a concave articular fossa posteriorly and a convex articular tubercle anteriorly.

Intra-articular meniscus or disk:

The articular disc of the TMJ is a strong fibroelastic oval disc that is concave inferiorly and concavoconvex above. It consists of strong collagen fibers with a blend of elastic fibers, especially in its anterior and posterior aspects. Unlike other joint discs, it does not have any cartilage in its composition. The disc is attached peripherally to the joint capsule and completely separates the capsule into superior and inferior spaces. It is strongly bound to the lateral and medial aspects of the mandibular condyle and closely tracks the movement of the condyle. The articular disk has 3 bands: ………………..

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The joint capsule:

The joint capsule completely covers the joint and is wide and loose on the upper aspect around the mandibular fossa and funnel-shaped near the neck of the mandible.

Ligaments:

The TMJ is stabilized by three ligaments: collateral (discal), capsular, and temporomandibular. The lateral ligaments attach the medial and lateral borders of the disc to the condyle. They divide the condyle into two cavities and restrict movement of the disc away from condyle. The capsular ligament surrounds the joint space and disc and acts to contain the synovial fluid within the joint space. The two extracapsular ligaments, sphenomandibular and stylomandibular ligaments act as “guiding” restraints to keep the condyle, disc, and temporal bone firmly opposed. The stylomandibular ligament is, in fact, a specialized band of deep cerebral fascia with thickening of the parotid fascia.

Muscles:

Muscles that are involved in the mandibular movement are masseter, temporal and pterygoid muscles (Table 34.2). The masseter muscle has superficial and deep fibers. The superficial fibers originate from anterior 2/3 of the lower border of the zygomatic arch whereas deep fibers originate from posterior 1/3 and medial surface of the zygomatic arch. Insertion of superficial fibers is at the angle of the mandible and of deep fibers is at the ramus of the mandible. The temporalis muscle originates from entire temporal fossa and gets inserted into the coronoid process of the mandible. We have two pterygoid muscles: medial and lateral. The medial pterygoid muscle originates from pterygoid fossa of the sphenoid bone and gets inserted at the angle of the mandible on the medial side of the ramus. The lateral pterygoid has two origins. The superior head originates from the greater wing of the sphenoid bone and the inferior head originates from the lateral surface of the lateral pterygoid plate of the sphenoid bone. Insertion of the superior head is at the neck of the condyle and of the inferior head is into the capsule of the TMJ.

Table 34.2 Various mandibular movement and muscles involved in those movements

Actions
Muscles
Depression (Open mouth)Lateral pterygoid
Suprahyoid
Infrahyoid
Elevation (Close mouth) Temporalis
Masseter
Medial pterygoid
Protrusion (Protrude chin)Masseter (superficial fibers)
Lateral pterygoid
Medial pterygoid
Retrusion (Retrude chin)Temporalis
Masseter (deep fibers)
Side-to-side movements (grinding and chewing) Temporalis on the same side
Pterygoid muscles of opposite side
Masseter

What is occlusion?

Dental occlusion is defined by the Glossary of Prosthodontic Terms as “the static relationship between the incising or masticating surfaces of the maxillary and mandibular teeth or tooth analog” 8. Many books have been written solely on occlusion. Readers are advised to go through these books for a detailed knowledge on occlusion. In the present discussion, we shall discuss normal occlusion in brief, and occlusal interferences in detail. We must know some terminologies before we go ahead with our discussion. These are,

Centric occlusion (CO):

It refers to the relationship of the mandible to the maxilla when the teeth are in maximum occlusal contact, irrespective of the position or alignment of the condyle-disk assemblies.

Centric relation (CR):

It is the position of the mandible when the condyles are in an orthopedically stable position. This occurs when the condyles are in their most superoanterior position, resting on the posterior slopes of the articular eminences with the disks properly interposed.

or

It is the maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior-superior position against the slopes of the articular eminences. This position is independent of tooth contact and is also referred to as retruded contact position (RCP).

Working side:

The side towards which the mandible moves in a lateral movement. Working side condyle pivots within the socket and is better supported.

Balancing side:

It is the non-functioning side from which the mandible moves during the working bite. Balancing side condyle has a downward orbiting path. It is traveling a greater distance in ‘space’ and is more prone to injury or damage.

Terminal hinge position:

It is the most retruded physiological position of the condyle in the glenoid fossa that the patient can achieve with his/her own musculature. In this movement, the mandible turns without any translator component in an arc whose axis lies in the condyle. The importance of this position is that the patient who is edentulous or deprived of cuspal guidance can be trained to repeatedly go through this movement so that patient can duplicate the movement again and again. During the movement, the repeatable reference points can be established and can be used for mounting the casts on articulators.

Static occlusion:

Static occlusion refers to the contact between teeth when the jaw is closed and stationary.

Dynamic occlusion:

Dynamic occlusion refers to the occlusal contacts made when the jaw is moving, as while chewing.

Incisal guidance:

The guidance provided by the surfaces of the maxillary incisors in protruive movements of the mandible.

Canine guidance:

The guidance provided during the movement of the mandibular canines over the palatal surfaces of the maxillary canines.

Group function:

Multiple contacts between the maxillary and mandibular teeth on the working side during lateral movements.

Christensen’s phenomenon:

A gap which appears between the posterior teeth of opposing dental arches when the mandible is protruded and the incisors are placed in edge-to-edge position.

The curve of Monson:

The curve of occlusion of natural teeth in which each cusp and incisal edge touches or conforms to a segment of the surface of a sphere with its center in the region of glabella.

The curve of Spee:

An arc of a circle that touches the tips of all the mandibular teeth when the skull is viewed laterally; when continued it touches the anterior surface of the condyles.

Normal functional occlusion

Before we start discussing the occlusal abnormalities and interferences, let us first know what all clinical findings are present in normal occlusion. There is a disagreement over defining a normal functional occlusion. Most of the researchers have agreed on the fact that a wide range of malocclusions may be considered normal if they do not possess any subjective symptom or any pathological change due to occlusal disharmony. Further, an occlusion which is otherwise having characteristics of normal occlusion can be considered abnormal if signs and symptoms of occlusal disharmony are present. It is essential for us to know the characteristics of normal occlusion. Andrews (1972) reported six significant characteristics of normal occlusion 9. These are,

1. Molar relationship:

The mesiobuccal cusp of the upper first molar should occlude in the buccal groove of the lower first molar and the teeth are arranged in a smoothly curving line of occlusion. The distal surface of the distobuccal cusp of the upper first permanent molar should make contact and occluded with the mesial surface of the mesiobuccal cusp of the lower second molar.

2. Correct crown angulation (mesiodistal tip of the crown):

The angulation of the facial axis of every clinical crown should be positive i.e. the gingival portions of long axis of all crowns are more distal than the incisal portions. The extent of angulation varies according to tooth type.

3. Correct crown inclination (labiolingual or buccolingual torque):

In upper incisors, the gingival portion of the crown’s labial surface is lingual to the incisal portion. In all other crowns, including lower incisors, the gingival portion of the labial or buccal surface is labial or buccal to the incisal or occlusal portion. In upper posterior crowns (cuspids through molars), the lingual crown inclination of the buccal surfaces is slightly more pronounced in the molars than it is in cuspids and bicuspids. In lower posterior crowns (cuspids through molars), lingual inclination progressively increases.

4. Absence of rotations:

Teeth should be free of undesirable rotations.

5. Tight proximal contacts:

In the absence of abnormalities such as genuine tooth size discrepancies, contact point should be tight.

6. Occlusal plane:

The plane of occlusion varies from generally flat to a slight curve of Spee.

To understand occlusion, the first step is to understand the border movements of the mandible and its physiologic functional movements. This is a very vast topic for discussion; however, in the following section, we shall discuss these movements briefly.

Functional movements of the mandible

The movement of the mandible during mastication follows a path which is specific for every individual because every individual has a specific occlusal scheme. Posselt in 1957 10 described the extreme or border movements of the mandible as an “envelope of motion”. The positions of the mandible during these border movements are constant and can be reproduced for each individual in both sagittal and horizontal plane. All the mandibular movements which constitute the normal function are within this envelope (Figure 34.2 a,b).

Figure 34.2 The border movements of the mandible in sagittal (a) and horizontal (b) plane.

Border movement of the mandible in (a) segittal and (b) horizontal plane

In the facial skeleton, the mandible is the only bone which is movable. The border movements of the mandible are recorded as the movement of the tip of the lower incisor when viewed in the sagittal or frontal plane. When the mandible is opened, the initial movement that occurs along the TMJ is hinge movement. During this movement, the condyles are in retruded and most superior position in their fossae.

When the mandible is moved to make tooth contact, the mandibular position when the first tooth the first tooth contact occurs is referred to as retruded contact position (RCP). Following this contact, the mandible moves……………..

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Mandibular border movement during maximum mouth opening:

While moving the mandible to the maximum mouth opening position, the mandibular movement starts from RCP. Initially, mandible moves in an arc of a circle around the terminal hinge axis. This movement is approximately up to 2-2.5 cm of opening. After this limit, lateral pterygoid muscle is activated which initiates forward translatory movement of the mandible. During translatory movement, condyles slide downwards and forwards along the articular eminences of the glenoid fossae to a point of maximum opening. The most common error done by the dentists during identification of occlusal interferences is the inability to accurately recognize RCP and transferring this registered position to an articulator. 

Protrusive mandibular border movement:

When the mandible is moved anteriorly from ICP, it s known as protrusion. The path of this movement is primarily determined by articulating surfaces of anterior teeth. It is referred to as anterior guidance. The anterior guidance is absent if maxillary and mandibular anterior teeth do not come in contact at all (open bite) or if they are in an edge to edge relation. In these cases, the anterior guidance is obtained from the posterior teeth that glide on each other during protrusion. The angle of anterior guidance depends on overbite and overjet i.e. the incisal relationship. For example, in case of class II division II malocclusion, the anterior guidance is almost vertical as the lower incisors are almost locked under the upper incisors and to bring them forward, almost vertical movement of the lower teeth is required. Posselt’s anterior guidance tracing, in this case, is completely different as compared to teeth with normal overbite and overjet. 

Lateral mandibular border movements:

To understand the lateral mandibular border movements we must know about supporting and non-supporting cusps in the maxillary and mandibular arch. When in ICP, the palatal cusps of the maxillary teeth and buccal cusps of mandibular teeth are referred to as supporting cusps because these contact the cuspal inclines and fossae of the teeth in opposite arch. On the other hand, the buccal cusps of maxillary teeth and lingual cusps of mandibular teeth are referred to as non-supporting cusps. This relationship is reversed in cross bite. To perform lateral mandibular border movement, the mandible is moved to one side by performing lateral excursion and moving it to maximum lateral position without producing any pain. The side to which the mandible is moved is called as working side and the another side is referred to as the balancing side. During registration of lateral movement, the dentist should manipulate the mandible in such as way that any anterior translation of the working condyle is prevented.

 While performing this movement; if only canines come in contact on the working side, the occlusion is referred to as canine guided occlusion. On the other hand, if two or more pairs of teeth contact during this movement, the occlusion is referred to as group function occlusion.

Various concepts of mandibular positions

Various authors have different views concerning centric occlusion (CO) and centric relation (CR) positions during mandibular movement. Some authors say that the CO and CR position should coincide 12 while others say that CR and CO positions in natural dentition should not coincide 13. Many researchers believe that the mandibular shift from CO to CR position can be ignored if it is less than 1 mm 11. Presently, most of the researchers believe that CR and CO positions of the mandible should coincide. However, most of the individuals have a slight shift of the mandible from CR to CO position. If this movement is slight (less than 1 mm) with no lateral shift, it should be considered normal. While making occlusal contacts, there should be no deflecting interferences. If these interferences are present, they should be removed. In natural dentition, cuspids should most preferably cause slight disocclusion of both the working and the non-working sides during the lateral mandibular excursion. While doing the protrusive movement, preferably no posterior teeth should come in contact or there should be no deflective contacts.

Indications for occlusal adjustment

It must be remembered that occlusal adjustments result in changes in occlusal scheme. It is an irreversible treatment so should only be planned with great care. Even minor mistakes made during the occlusal adjustment may result in worsening of the situation.  Following are the indications for occlusal adjustment,

  1. The presence of parafunctional habits in conjunction with occlusal disharmony.
  2. Signs of occlusal trauma, excessive occlusal attrition, and/or TMJ dysfunction.
  3. The presence of multiple restorations on posterior or anterior teeth, which require occlusal adjustment to achieve a harmonious occlusion.
  4. To eliminate occlusal interferences after the orthodontic treatment is finished.
  5. Some clinicians also recommend prophylactic occlusal adjustments in the absence of any periodontal or TMJ symptom to prevent future problems.

Evaluation of TMJ and occlusion

A precise occlusal history should be recorded before any occlusal examination is done. The details of the history depend on the type of occlusal symptoms and their severity. The patient’s problems and their duration should be recorded in a chronological order. The patients usually cannot relate the occlusal problems with their symptoms. So, appropriate questions should be asked to establish any relation between the patient’s symptoms and occlusal abnormalities. Parafunctional habits are the most common cause of occlusal problems. So, the patient should be asked questions about the history of pain in teeth, periodontium or TMJ and associated musculature. The patient should be asked questions like: “Do you have your teeth in tight contact when you wake up? Do you feel tiredness in the jaws on waking up?” Any positive answer indicates parafunctional habit. The patients usually do not know about night grinding. So, any other person sleeping with the patient should be asked about night grinding of teeth. Another important point to remember is that parafunctional habits are commonly associated with psychological disorders. Hence, if the patient is having psychological stress, its reason should be identified and appropriate stress management should be done.   The occlusal examination consists of extra-oral and intra-oral examination. 

Extra-oral examination:

The patient should be made to sit in a semi-recline position with head slightly tipped back. The head should be supported by the headrest. Any facial asymmetry should be noted and the cause of abnormality should be detected. The patient should be asked to open and close the mouth slowly. Any deviation during mouth opening or closing should be noted. The TMJ examination should be done by lateral palpation of the joint and auscultation of the joint should be done (For more detail, see chapter 39 “Art of history taking in periodontics”). The muscles of mastication should be palpated for any tenderness. 

Intra-oral examination:

The intra-oral examination of the patient should be done to identify any occlusal interference. It must be emphasized here that any single positive sign should not be considered as diagnostic of the occlusal problem, but should be related carefully to other findings. The following steps are followed while recording functional occlusion,

  • The static relation between maxillary and mandibular teeth i.e., centric occlusion (CO) position should be determined first.
  • Overjet, overbite and freeway space should be determined.
  • Any occlusal variation in the occlusion plane, cross-bite, open bite, extrusion etc. should be recorded.
  • Wear facets and their distribution should be recorded. It should be remembered that the presence of wear facets is related to patient’s age. The presence of wear facets is not always pathognomonic of traumatic occlusion. So, it must be correlated with other findings.
  • Tooth/teeth with increased mobility should be identified. Along with increased tooth mobility, increased tooth sensitivity to thermal changes and to percussion should also be checked because these findings can also be due to occlusal trauma.
  • Any tooth migration should be recorded. Tooth migration associated with an occlusal abnormality is usually associated with wear Tooth migration without wear facets is usually associated with abnormal tongue habits or atypical swallowing habits.
  • Radiographic examination of teeth with mobility or migration should be done. Loss of bone support or changes in periodontal ligament space is indicative of trauma from occlusion.
 

Know more…………

Physiological tooth mobility:

All the teeth with normal periodontal support exhibit physiological tooth mobility. It occurs in two stages: initial intra-socket tooth movement and later tooth movement which occurs due to elastic deformation of the alveolar bone. The initial movement of a tooth in the socket is the result of viscoelastic deformation of periodontal ligament in the socket. The physiological tooth mobility ranges from 0.05 to 0.1 mm when forces up to 100 lbs are applied 14. The degree of mobility varies according to patient’s age, gender, state of the systemic condition (pregnancy) and tooth type. The physiological tooth mobility is greater in children and young adults and is slightly increased in females during pregnancy. Tooth mobility is greatest immediately after arising and it progressively reduces during working hours.

 

Diagnosis of occlusal interferences

An “occlusal interference” is any tooth contact that inhibits the remaining occluding surfaces from achieving stable and harmonious contacts 15. Very small interferences up to 15 µm can trigger an untoward response such as tooth pain or mobility 16, 17. Hence, these interferences must be eliminated to achieve a stable and harmonious occlusion.  In a harmonious occlusion without any interference, the occlusal contact time simultaneity by definition implies that a time of 0 seconds elapses between the first and the last occlusal contact 18. In other words, we can say that all the occluding surfaces of the mandibular teeth come in contact with the maxillary teeth at the same instant during the mandibular closure.

There are four types of occlusal interferences:

  • Centric
  • Non-working
  • Working

Armamentarium required for diagnosing and correcting occlusal interferences:

The armamentarium used to record functional occlusion includes occlusion indicators (described below), cotton rolls, dental mirror, hand mirror, abrasive disks, and wheels, cutting and abrasive burrs, polishing burs and rubber polishing cones. The findings of the occlusal examination should be recorded on a chart which consists of columns for recording all the significant occlusal parameters (Figure 34.3).

Figure 34.3 Sample chart for recording occlusal interferences

Sample chart for recording occlusal interferences

Occlusal indicators are essential components of recording functional occlusion. Occlusal indicators can be divided as qualitative and quantitative indicators. The primary difference between the qualitative and quantitative indicators is that quantitative indicators are capable of recording the tooth contact events.

Figure 34.3 Sample chart demonstrating occlusal interferences in a 56 years old patient

Sample chart demonstrating occlusal interferences

Qualitative indicators:

  • Articulating paper
  • Articulating silk
  • Articulating film
  • Waxes
  • Metallic shim stock film
  • High spot indicator

Quantitative indicators

  • T-Scan occlusal analysis system
  • Virtual dental patient

Qualitative indicators:

Articulating papers:

Articulating papers are the most commonly used occlusal indicators (Figure 34.5). These consist of a coloring agent and a bonding agent between the two layers of the film. On making tooth contact, the coloring agent is expelled from the film and the bonding agent binds it onto the tooth surface. In areas with heavy contact, the dye spreads peripheral to the actual location of the occlusal contact making a central area that is devoid of the colorant surrounded by a peripheral rim of the dye. The central area of the contact indicates interference and requires correction. Articulating papers are available with different width, thickness and the type of the dye impregnated. The disadvantages of the articulating paper include their thickness (40 µm) which is well above the thickness perception level of the patient; these are easily spoiled in saliva so require a dry field and a relatively inflexible base material which commonly results in the formation of pseudo-markings.

Figure 34.5 Occlusal indicator foil (Coltene)

Occlusal indicator foil

Articulating silk:

A better way to avoid pseudo-markings is to use an articulating silk. It is made up of micronized color pigment, embedded in a wax-oil emulsion. However, it should be remembered that its marking capability is lost if the staining components are dried. Secondly, contamination of the field by saliva spoils the markings. Hence, it should be used in a dry field and should be stored in a cool and closed environment. It can be used on highly polished surfaces which is its important advantage over articulating papers.

Articulating films:

These are made up of emulsion which is hydrophobic and contained a polyester film inside. The thickness of the film is 6 µm which is well below the perception level of the patient. The film has to be used with special holders in a dry environment.

Waxes:

Thin sheets of dark-colored wax are available which can be placed over the occlusal surfaces of the teeth in one arch. The opposing teeth are tapped gently into the wax until it perforates. The perforation represents interfering contacts. These are then marked with pencil and reduced. Waxes are very useful in identifying interferences on sharp line angles.

Metallic shim stock films:

These contain metallic surface on one side and coloring agent on the other side of the film. These are primarily used to accurately mark the contacts on the soft splint.

High spot indicators:

These are also used in the laboratory to check the proximal contacts of crowns, inlays, onlays, telescopic crowns and clasps. These are supplied in the form of a liquid which is applied over the proximal areas where it forms a thickness of 3 µm.

Quantitative indicators:

T-Scan occlusal analysis system:

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Virtual dental patient:

This is a recently introduced technology wherein patient’s dentition casts are scanned and a three-dimensional virtual occlusion is established. The functional movements on this virtual model provide us the quantitative information regarding the occlusal interferences. Similar to the T-scan, the sequence of the occlusal contacts, enables us to eliminate the initial contacts and hence the interferences.

Determination and recording of CR and CO position

The patient should be seated in a reclined and comfortable position in the dental chair with the head properly supported by the headrest. The patient should be asked to take a deep breath and relax the body as much as possible. The patient is asked to look in front and to keep the head stable during manipulation of the lower jaw.

Now, the little figure is placed slightly behind the angle of the jaw and remaining three fingers on the border of the mandible. The thumb is placed over the notch over the symphysis. The patient is asked to open and close the mouth and the hinge movement of the mandible is felt. A firm pressure is then applied with fingers in an upward direction and with the thumb in a downward and backward direction to position the condyle of the mandible in terminal hinge position. It must be made sure that the manipulation of the mandible in the terminal hinge position should be totally free of any muscular influence. The position is then again verified by repeating the procedure. While the terminal hinge position is verified repeatedly, the patient is asked to gently close the mouth.

Sometimes, the patient complains of pain or discomfort while positioning the mandible in terminal hinge position. It indicates that the condyle meniscus assembly has not been braced against the bone. In such a situation repositioning of the mandible is done by placing cotton rolls between anterior teeth or by placing Hawley’s bite plane.

Once the CR position is well established, an articulating paper (preferably blue) is placed with the help of Miller’s forceps between the occlusal surfaces of teeth on the side making initial contacts. To avoid pseudo markings, thin articulating paper such as GHM occlusion foil (Hanel-GMH Dental GMBH, Nurtingen, Germany) which has 19 μm thickness should be used. The patient is then asked to slowly close the mouth to make contact of maxillary and mandibular teeth.  The pair of teeth, making initial contacts is noted on the occlusal chart. The patient is then asked to position the teeth slowly in maximum intercuspation position (CO). Any anterior or lateral movement of the mandible from CR to CO position is recorded in mm. It should be noted here that a slight anterior slide from CR to CO is less significant than lateral slide component. Teeth which are making the last contacts should also be recorded because they are generally more traumatized than teeth providing the initial sliding path.

Registration of lateral and protrusive excursions

The lateral excursive movements are preferably recorded with a different color (such as red) than used for recording CR and CO. A dental tape is placed between the teeth of the patient on the right side and with the help of hand pressure mandible is moved to the right. Teeth with red marks are recorded on the occlusal chart. A similar procedure is then repeated on the left side and markings are recorded on the occlusal chart (Figure 34.3). A hand mirror can be given to the patient if he/she faces difficulty in performing lateral excursions. The protrusive excursion movements are recorded by gliding the teeth forward from the CO position without any lateral movement.

Now, the dental tape used to record CO and CR position is placed between the teeth and the patient is asked to bring teeth in CO position. The CO points of contact will superimpose on the lateral and protrusive contacts. The CO contact points (blue) can be differentiated from the lateral and protrusive contacts (red) by their color difference.

Impression making and articulator analysis

Although the information gathered from contact point markings in CR, CO, lateral and protrusive positions are sufficient to identify the occlusal interferences; but for accurate diagnosis and treatment planning, the impressions are made and casts are mounted on a semi-adjustable articulator. All the parameters in relation to the TMJ and occlusion are accurately transferred on an articulator and interferences are first removed on the articulated cast models and are then duplicated on the patient.

Types of occlusal therapy

Occlusal therapy is any treatment that alters a patient’s occlusal condition. It can be used to improve the function of the masticatory system through the influence of occlusal contact patterns and by altering the functional jaw position. Occlusal therapy can be reversible or irreversible. Reversible therapy temporarily alters the occlusal condition, the joint position, or both. The example of this therapy is occlusal splints. The disadvantage of reversible occlusal therapy is that the original condition might return after the therapy is discontinued. On the other hand, irreversible therapy permanently alters the occlusal condition so that the original condition cannot be recovered. The examples of irreversible occlusal therapy include selective grinding, fixed prosthetic procedures, and orthodontic therapy. In the following sections, we shall discuss in detail the irreversible occlusal therapy (selective occlusal grinding). 

Principles of selective grinding:

The clinical procedure to eliminate occlusal interferences consists of three procedures, namely grooving, spheroiding and pointing 19. Grooving is done to re-establish the depth of developmental grooves. Spheroiding is done to restore the original tooth contour in areas with supra-contacts. Once the supra-contacts have been identified,…………………..

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Steps in the correction of occlusal interferences:

Once the occlusal interferences have been identified, the clinician must determine the extent of occlusal adjustments required. As already stated these adjustments should be first performed on the articulated casts and then should be duplicated on the patient.  Another important factor to be considered while doing occlusal adjustment is the age of the patient. In younger patients, usually conservative approach is adopted because they have a developing dentition which may have many unpredictable mechanisms for occlusal harmonization. Only minor occlusal adjustment, interceptive in nature is adopted in these patients. On the other hand, in older patients extensive occlusal adjustment can be planned.

Basic principles followed to eliminate occlusal interferences:

The selective occlusal grinding is done to eliminate the occlusal interferences in a stepwise manner. These are,

Step 1:  Elimination of retrusive supra-contacts and deflective occlusal interferences from CR to CO.

Step 2: Adjust CO to achieve stable, simultaneous, multi-pointed, widely distributed contacts. The unbalanced cuspal inclines and contacts should be eliminated to maintain or move the force vectors along the long axis of the tooth.

Step 3: Test for excessive contact (fremitus) on the incisal teeth.

Step 4: Remove posterior protrusive supra-contacts and establish contacts that are bilaterally distributed on the anterior teeth.

Step 5: Remove all interferences to lateral excursions.

Step 6: Eliminate gross occlusal disharmonies. Improve the occlusal anatomy by maintaining the cusp form, by creating correct marginal ridge relationships, cusp-fossa relationships, elimination of broad facets and narrow occlusal tables.

Step 7: Recheck tooth contact relationships.

Step 8: Polish all rough tooth surfaces.

Following is the detailed description of these steps, 

Step 1:

The first step in the elimination of occlusal interferences is to remove these interferences in retrusive and CR to CO position. The primary objective here is to remove the supra-contacts and remove interferences that interfere with posterior border closure of the mandible to a stable bilateral RCP. The clinician should try to achieve following objectives by removing these interferences,

  • A maximum number of centric holding contacts are achieved in CR position.
  • Vertical dimension in CR should be same or a little more than in CO position.
  • Removal of interferences from CR to CO position, thereby facilitating smooth gliding movement in the horizontal plane from CR to CO.

The interferences are identified by placing blue marking tape between the teeth and asking the patient to “Squeeze” once the initial contact is made (Figure 34.6 a, b). Most commonly the mesial inclines of the maxillary lingual cusps and their opposing tooth surfaces are typical sites for supra-contacts. The mesial inner incline of the lingual cusp of the maxillary first premolars is the most common initial supra-contact at the RCP.

Figure 34.6 Recording of occlusal interferences in centric relation to centric occlusion position

Recording of interferences in centric relation to centric occlusion position

Step 2:

The second step is to achieve stable centric contacts in CO position. The occlusal contacts in the CO position should be planned in such a way that maximum stability of occlusion in this position is achieved. The primary objectives of clinician during this step are,

  • Achieving a cusp to fossa relationship wherever possible as compared to cusp to marginal relationship. The cusp should contact, preferably at the center of the fossae so that occlusal forces are directed along the long axis of the tooth. However, it should be remembered that in unworn teeth (young patients), the cusp tips do not reach the base of the fossa. In such situation, multiple contacts on the inclined planes are considered as stable centric holding contacts.
  • There should be no cusp contacts with the inclined planes except for the lingual surfaces of the maxillary anterior teeth.

The patient is asked to tap the teeth together on both sides at the same time. This is CO position where the maxillary and mandibular teeth are in maximum contact. Now, the wax is placed on the occlusal and incisal surfaces of the mandibular teeth and patient is then asked to open and close again as before (Figure 34.7). The supra-contacts will appear as translucent areas which are then removed.

Figure 34.7 Recording of supra-contacts in centric occlusion after adapting the wax sheet on occlusal surfaces of teeth and then asking the patient to close in centric occlusion

Recording of supra-contacts in centric occlusion

Step 3:

The third step is to remove excessive contacts from incisal surfaces. The objectives of this step are,

  • Making the incisors slightly out of contact or in light contact over the maximum number of teeth.
  • Eliminating supra-contact and hence trauma from occlusion on anterior teeth.

The firmness of the occlusal contact can be detected by placing a Mylar occlusal strip between the maxillary and mandibular anterior teeth held with a hemostat. The strip should just slip through the incisor teeth when the patient clenches teeth firmly in centric occlusion. If teeth are contacting, the degree of fremitus should be determined. A moistened forefinger should be placed on the labial aspect of maxillary anterior teeth and vibration or displacement of teeth should be felt when patient taps the upper and lower teeth. The supra-contacts can then be identified using occlusal tape of wax and are eliminated.

Step 4:

Protrusive excursion refers to the path of the mandible as it moves anteriorly between the CO and the edge to edge relationship of the anterior teeth (Figure 34.8). In this step, adjustment in protrusive excursions is done. The primary objectives of the dentist during this step are,

  • Even distribution of contacts during protrusive excursions over as many teeth as possible. During the protrusive excursion, there should be no contact between the posterior teeth, except between the mesial slope of the buccal cusp of mandibular first premolar and the distal slope of maxillary cuspid.
  • Reduction of the incisal edges of the extruded anterior teeth if they are interfering with the smooth protrusive excursion.
  • Elimination of deep overbite by reduction of crown length of the anterior teeth. However, it must be remembered that it does not eliminate the requirement of orthodontic treatment. Only slight overbite can be eliminated by selective grinding. Moderate to severe cases require orthodontic treatment for deep bite correction.

Figure 34.8 Recording of protrusive interferences

Recording of protrusive interferences

The patient is asked to protrude the mandible slowly from CO position to edge to edge position of anterior teeth. Ideally, there should be bilateral contacts between maxillary and mandibular anterior teeth during this movement with little or no deviation of the mandible. The deviation usually is caused by a molar interference or an asymmetric incisal plane. Now, marking ribbon or articulating paper or wax strip is placed between the anterior teeth and the patient is again asked to perform the same movement. Selective grinding of the marks on maxillary and mandibular teeth eliminates the interferences. However, it should be preferred that wherever possible the adjustment is confined to the maxillary teeth to protect mandibular functional cusp height. Mandibular incisors should be ground only when the limit of grinding of the maxillary teeth has been reached because of pain, proximity to the pulp, or aesthetic reasons. Following selective grinding, all the marks are removed and the patient is again asked to perform the protrusive movement. If posterior teeth are interfering with the protrusive movement, tooth structure is removed from the offending cusps until all articulating contacts between the posterior teeth have been eliminated.

Step 5:

This step deals with the removal or lessening of all interferences in lateral excursions. The mediotrusive interferences usually manifest as oblique facets on the first and second molar teeth on the inner inclines of the mandibular buccal cusps and the inner inclines of maxillary lingual cusps. The objectives of dentist while eliminating lateral interferences are,

  • A slight cuspid mediated disocclusion of the posterior teeth during the lateral excursion except in situations where cuspid is already worn and group function occlusion is present or cuspid is malposed and adjustment to group function of posterior teeth is necessary.
  • Elimination of interferences on working side and balancing side.
  • Elimination of interferences on central and lateral incisors which hinder the cuspid function during the lateral excursion except when both central and lateral incisors are in group function with cuspid and show no sign of trauma from occlusion.

While registering the lateral interferences,…………………..

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To remove interferences, only undesirable red marks are removed (Figure 34.8 a, b). The inner inclines of maxillary buccal cusps or lingual surfaces of the upper anterior teeth are adjusted.

Figure 34.8 Recording of lateral interferences

Recording of lateral interferences

For registering interferences on the balancing side, a strip of adhesive occlusal registration wax is placed over the mandibular quadrant in question and another strip of folded occlusal registration wax is given to the patient that is placed on the opposite side and the patient is asked to chew this wax bolus up to five times. If there are significant lateral interferences or supra-contacts, oblique perforations of the applied wax strip will be observed. After adjustment of these interferences, the procedure is repeated and re-evaluation is done.

It should be remembered that while adjusting interferences on lateral excursion, reshape the inner inclines of the maxillary buccal cusps and mandibular lingual cusps. This is because grinding of the mandibular buccal cusps jeopardizes the functional cusps in CO position. Grinding should not result in the formation of flat surfaces and vertical stops should be preserved during the procedure.

Step 6:

This step deals with the elimination of undesirable gross occlusal features. Once all the interferences have been removed, there may be some remaining gross undesirable occlusal features which are harmful to the periodontal structures, and require modification. These include,

Extruded teeth:

These teeth are reduced to the level of the occlusal plane by grinding and reshaping within the limits permitted by proximity to the pulp.

Plunger cusps:

Plunger cusps are responsible for wedging of food in the interdental areas. Distolingual cusps of maxillary molars often are plunger cusps. These cusps should be rounded off and reshaped to eliminate food impaction.

Uneven adjacent marginal ridges:

These may also cause food impaction and should be corrected by either reducing the height of a comparatively high marginal ridge or increasing the height of a lower one with a restoration.

Rotated malposed and tilted teeth:

The most preferred treatment for rotated teeth is orthodontic de-rotation. However, minor rotations which interfere with the functional movement of the mandible or are causing food accumulation and impaction can be re-shaped by selective grinding.

Facets and flat occlusal wear:

The wear facets are the result of the tooth to tooth wear. These can be easily detected by drying the tooth surface and viewing under a regular dental chair lamp. These should be corrected because the periphery of these facets may produce lateral or tipping forces which are deleterious to the periodontium.

Flat occlusal wear:

Sometimes excessive wear of the occlusal surfaces of the posterior teeth results in the formation of the flat occlusal surface. Similar to facets, the margins of the occlusal wear creates force component which causes lateral and tipping forces deleterious to the periodontium. The anatomy of the occlusal surfaces should be restored by selective grinding.

Step 7:

All the occlusal adjustments done are re-investigated in this step. All possible movements are done to check retrusive, protrusive and lateralotrusive interferences.  In cases where occlusal equilibration can be better achieved by prosthodontic, restorative or orthodontic treatment, these treatments should be considered.

Step 8:

 All the surfaces which have been selectively reduced are then polished to achieve smooth tooth surfaces and patient is instructed regarding the maintenance of teeth.

Conclusion

A comprehensive TMJ and occlusal examination is an inseparable part of the complete periodontal examination. The neuromuscular harmony is the prime requirement for appropriate TMJ function and functional mandibular movements. However, it should be remembered that a thorough knowledge of occlusion is required to treat the condition otherwise the situation may worsen after the treatment. Therefore,  clinical  examination,  which  consists  of  examination  of  the  TMJ, teeth, soft tissue as well as the periodontium, should be carried out before the commencement  of  dental  treatment. The occlusal examination and identification of the interferences should be done and in a stepwise manner, all the interferences should be eliminated.

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References:

References available in the hard copy of the website

Periobasics: A textbook of periodontics and implantology

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