Chapter 4-Treatments considering the occlusal form
Professor emeritus of Okayama University
Director of Yamashita Dental Clinic
Atsushi Yamashita
A case where occlusal correction was also conducted with implantation
The advantage of implant prosthetics is that it does not affect the teeth positioned adjacent to the missing
tooth. With good prognosis of the neighboring teeth, life of the remaining teeth has been shown to be
prolonged by implant treatment1). Meanwhile, the recovery of the masticatory functions by the implant
prosthetics can subsequently subject mechanical pressure to the implant body themselves2). As theimplant body must bear the large masticatory force, the substantial pressure can result in the fracturing,screw loosening and its fracture, and the acceleration of the bone resorption3). For a long-term prognosisof implant treatment, it can be said that the extensive understanding of the maxillofacial physiology andof the functional occlusion system4) (Fig. 1) that forms the basis of dental articulation are essential.
There are a number of factors that are known to affect the prognosis of implant treatments such as:edentulous arch, bone quantity/ quality, infection, and load bearing. The most frequently arisingcomplication is the peri-implantitis, followed by the load exertion from the dental articulation5), which inturn affects both the superstructures and the body.
In the recent years with the ease in the bonding of the implant with the bone, less weighting has beenplaced on matters such as the occlusal analysis and the means to bestow an occlusion. However, for a goodlong-term prognosis, occlusions after the implantation must not be taken lightly.
Patient: 34 year-old female
Main complaint: Does not in which region of the mouth she can chew with.
Present disease history: Strains on the back of her neck, stiff shoulders, physical body strain and dryeyes.

Functional Occlusion System
Brain and the central
nervous system

The Masticatory muscles
Occlusion

Teeth・Dentition

Temporomandibular joint(1972, Yojiro Kawamura)Fig. 1 Occlusion is the interaction between the teeth/ dental arch, masticatory muscles, and thetemporomandibular joint components that receive nervous supplies from the central nervous system(CNS) and the brain and are controlled by these. The failure of any one of these components cansubsequently affect other factors, resulting in dysfunctional occlusion.

23Fig. 2 Image of the oral cavity at the first clinical evaluation
Fig. 3 Dental and panoramic radiograph at the first examination
1. Analysis of occlusion with CMS
For an implant prosthetic treatment, each components of the functional occlusion system are required tobe evaluated to achieving a state in which a sufficient amount of pressure is exerted. Out of thefunctional occlusion system, occlusion components were examined using computerized mandibular
scanning (CMS), K7 Evaluation system6).
1)

Rapid movement of opening and closing of the mouth

Fig. 4 features patient’s velocity graph (Velocity) recorded while undergoing maximum mouth opening
movements at the normal and at rapid rates, and the movement of the frontal plane (right) that wasrecorded simultaneously. Along with the opening and closing of the mouth motor pathway, a slight fault
can be observed. Regarding the motor pathway during rapid opening and closing of the mouth, since thegraph is showing a smooth lissajous curve that is indicative of a coordinated action of the massetermuscle, it appears that the articular disc dislocation has not occurred. Nevertheless, the recordings of themotor pathway of the right frontal plane with the jaw opening and closing displays a disorderly pattern ofthe centric point of the curve (indicated with red arrows). This is reflective of the patient’s main complaintof not knowing with which part of the mouth to chew.

Fig. 4 – The occlusal position is highly

Fig. 5 – A left shift in the posterior occlusal

unstable during the recording of opening

position can be observed in the transfer fromand closing mouth exercise.

mandibular rest position to the occlusal position.

2)

Biting from the mandible rest position to the centric occlusion

Fig. 5 shows the kinesiograph recorded while tapping twice at the centric occlusion after shifting from themandible rest position. The three graphs show the up-down movements on the top, the front-backmovement in the middle and left-right movement at the bottom. If there is no displacement of themandible in relation to the cranium, the free-way space from the position of the muscles are usuallyaround 1.0 mm (±0.5 mm) that shows a ratio of vertical and longitudinal movements to be from 1:1 to 3:1,
should not show horizontal displacement.
In this patient, in the shift from the mandible rest position to the occlusal position, the longitudinal
movement was found to be more significant than the vertical movement that had a relatively small
free-way space, with a particularly unstable centric. With regard to the horizontal movement, there is acuspal interference on the left undergoing unsteady tapping movement. These recordings suggested thatthe mandibular position was displaced in both longitudinal and horizontal axis, relative to the skull.
2. Temporomandibular joint examination
At the medical examination conducted ten years ago, an arthrosound was presented. However as there
were no pain symptoms, it was left untreated. From this, the disc displacement was suspected. Frompalpation, a clicking was heard in the right temporomandibular joint during the mouth opening andclosing therefore a MRI scan was conducted for further examination.
Fig 6, top right image shows a non-restorative articular disc anterior dislocation, bottom left image showsa restorative articular disc anterior dislocation. Taking into consideration, the absence of subjective
symptoms, the age, and the degree of deformation, it was decided that the correction of the articular joint
was not practical, and with consent from the patient, the mandibular position (muscular contact position)that was best for the functional occlusion in this state was attempted to be achieved.

Left intercuspal position

Left open mouth position

A non-articular disc with reduction
Right intercuspal position

Right open mouth positionAn articular disc with reduction

Fig. 6 – The MRI scan of the temporomandibular joint region shows the transition and modification of thearticular disc.
3. Masseter muscle examination
Fig. 7 is the electrocardiogram of the left and right masseter muscles and the anterior belly of thetemporal muscle at the mandible rest position. The presence of abnormal electrical discharge of the left
temporal muscle can be observed indicating the shift in the mandibular position. Fig. 8 features therecording after the patient had undergone a treatment of transcutaneous electrical nerve stimulation(TENS) for a period of 40 minutes muscle relaxation, and shows the muscle tone to have improved 7).

78Fig. 7 – Abnormal electrical discharge of the left temporal muscle
Fig. 8 – Recording of the state after undergoing TENS treatment where the tension in the muscles toshow a vast improvement.

Examination and treatment plan
The analysis of above results confirmed the symptom to have arisen from the shift in the mandibular
position relative to the skull, the instability in occlusion, and sense of discomfort in the craniocervicalregion. The most important consideration that has to be paid in conducting implant treatment is toprevent exertion of excessive lateral force and the occlusal rotary moment on the implant at the time ofchewing. The shift in the mandible position in relation to the skull can manifest as shown in Fig. 10, suchthat the lateral force is exerted on the implant with chewing. Where there is no shift in the position of themandible relative to the skull, there are no excessive pressure exerted on the implant body, as shown inFig.9 8).
The planned treatment is shown below:a) Extraction of No. 2 toothb) Endodontic care of the anterior maxilla teeth as well as No. 5 and 21 teethc) Correction of the mandibular position (muscular contact position9)) with removable orthosis.
d) Refabrication of crown for: No. 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 21, 30, 31.
e) Placement of unilateral distal extension bar removable partial denture (RPD) with attachmentf)Perioperative examination of the occlusion with K7 Diagnostic system (for confirmation of thecorrection of occlusal position and re-evaluation of functional occlusion).

g) Implant treatment for No. 19 and 20.
Having completed the endodontic treatment, carefully adjust the removable orthosis, for which theocclusal impression was taken at the muscular contact position, to ensure that the occlusion can beachieved at the muscular contact position (Fig.11).

Muscular
contact
positionIntercuspal
PositionIntercuspal
Position
Muscularcontact
position

Small openand-close
movement
without
contact of
teeth

9

MandibleslidesTapping at
intercuspal
position

Small open-andclose movement
without contact ofteeth

10Fig. 9 – With the absence of any shift in the mandibular position relative to the skull, implant is not
subjected to excess lateral pressure.
Fig.10 – If there is a shift in the mandibular position relative to the skull, the implant body becomessubjected to excessive lateral pressure, and rotary masticatory moments with chewing, and subsequently
damaging the bone structures surrounding the implant body.
Fig. 11 – Left showing the occlusal
impression taking; and on the right,
shows the removable orthosis that has
been fabricated at the muscular contact
position.
Perioperative examination of the occlusion (for confirmation of the correction of occlusal position andre-evaluation of functional occlusion)
The orthosis was adjusted till occlusion was achieved with the mandible positioned at the muscular
contact position, and to confirm that the shift in the mandibular position had been corrected in relation
with the skull.
Fig. 12 is a record of the mouth opening and closing exercise after the removable orthosis was adjusted tothe muscular contact position. It shows the recovery of the shift in the mandibular position in relation to
the skull, a motor pathway similar to that of a healthy individual.
Since the shift in the mandibular position was able to be corrected, even though there was still a notch, asmooth lissajous curve in the velocity graph was recorded as shown in Fig. 13, thus confirming astabilized occlusion to have been set at the muscular contact position.
Fig. 14 shows the recording with the placement of the crown bridge, or unilateral distal extension bar
RPD. The ratio of the lateral and longitudinal movements were shown to have improved close to normal,
but possibly owing to the fact that the superstructure had only recently been placed, the longitudinal
movement was shown to be rather unstable and the muscular contact position to have been displaced to
the left side by approximately 0.2 mm. The patient’s complaints of the strain at the back of the neck, stiffshoulders, physical strain, and dry eyes were all solved.

Fig. 12 – The maximal open-close

Fig. 13 – The velocity graph of theFig. 14 – The record of thepathway after treating therapid opening and closing of thetransition from the mandibular

occlusion has been corrected tomouth exercise pathway shows arest position to the occlusion

the pathway of a normalsmooth lissajous curve, indicating

position after the occlusionindividual.

that the position of the mandible

treatment have shown thehad been restored at the muscularocclusion to have been correctedcontact position.

to the norm.

Examining the temporomandibular joint
Fig. 15 shows the TMJ radiograph taken with standardized technique, the individualized anatomic X-ray
aligner “condyray”, after the occlusal correction with orthosis.
Although the left articular disc is shown to have been dislocated, the mandibular condyles on both sides
are positioned at the centre of the temporomandibular fossa in the occlusal position as well as in the restposition. The articular joint spaces are also evenly distributed longitudinally.
The left two images of Fig. 16 features the electrical discharge of the anterior bellies of the temporalmuscles and the masseter muscles on the left and right, recorded at the time of strong masticatory force
application with the natural teeth without any mediators. The images on the right shows the recordingwith the application of strong masticatory force in the presence of roll of cotton placed in between theteeth. The amount of electrical discharge and the ratio both indicate its recovery to the norm. The results
confirmed the mandibular position to have been corrected to the position of the muscles, and that themasseter muscle group to be functioning in a coordinated manner.
From these findings it was concluded that the mandibular position in relation to the skull had beencorrected, and that unwarranted occlusal pressure would not be exerted onto the implant body installed.
The implant prostodontic treatment was conducted with the objective of long-term functional
maintenance. Fig. 17 and 18 show images with the placement of implant prosthesis, placed after thecorrection of functional occlusion system. Functional recovery was able to be achieved. The width of theocclusal plane of the implant in the molar region was constructed to be the same as that of the premolarregion. The occlusal conditions are checked every three months in the regular follow-up of the oral
hygiene conditions.

1516

Image-15 – The TMJ radiogram taken by a standardized technique, the individualized anatomic X-ray
aligner “condyray”, after the occlusal correction with orthosis.
Image-16 – The examination of the dislocation of the mandibular position relative to the skull shows theabsence of the mandibular dispositioning, and the co-ordinated action of the masseter muscle group canbe observed.

1718

Fig.17 - The image after the placement of superstructure.
Fig.18 – The image at the time of follow-up, five years after the implant installation.