Occlusion in implantology

Occlusion in implantology

INTRODUCTION

Many implant prosthesis failures are attributed to joint disorders.

dental. It is therefore logical, from the occlusal examination stage, to be able to anticipate a possible source of complication of an implant-supported reconstruction.

Study casts and the use of an articulator allow occlusal analysis to be completed, particularly in large reconstructions.

1. Definition of occlusion

Occlusion can be defined as the relationship established by the contact of the occlusal surfaces of two teeth or two groups of teeth of the maxilla and mandible.

Mechanism of dental occlusion:

2. Concepts on proprioception
3. Definition of proprioception

Proprioception (formed from proprio-, taken from the Latin proprius , “own”, and [re]ception) or deep sensitivity designates the perception of the position and movements of the different parts of the body.

• Proprioception provides information on the pressures experienced by the teeth, allowing the contraction of the masticatory muscles to be modulated.

2. Proprioceptors

These are the receptors specific to proprioception and are found in muscles, joints such as the TMJ and in ligaments such as the alveolar-dental ligament (ADL).

3. Comparison between natural tooth and implant

1. The desmodontal ligament and the bone/implant interface
2. The inter-occlusal detection threshold

A metal sheet interposed between natural teeth is detected from a thickness of 20μm, whereas between an implant and a natural tooth it is only detected at 48μm, between 2 implants at 64μm, and between natural teeth and a complete prosthesis on implants at 108μm.

Diagram showing the inter-occlusal detection thresholds according to Jacobs Van Steenberghe.

A! Even though the threshold is higher for an implant, it is interesting to note that it is still lower than that of conventional complete prostheses.

3. Under the effect of a lateral force

The center of rotation is located at the apical third of the natural root and the LAD absorbs part of the stress. Stress dissipation is observed along the root.

On an implant we observe very little displacement, the lateral forces are concentrated at the level of the neck (location of the center of rotation) with a transmission of the constraints directly towards the bone, explaining the bone losses in crater and the fractures at the neck of the implant.

4. Under the effect of an axial force

The axial mobility of the tooth is 25 to 100 μm. In contrast, a vertical force applied to an implant causes a depression of only 3 to 5 μm.

5. The benefits of the periodontal ligament
6. Occlusal requirements to be respected

Occlusal balance depends on stable contacts in centric occlusion, harmonious sliding in dynamic occlusion with a functional anterior guide, canine or group protection in lateralities and reliable periodontal support.

Natural teeth offer a degree of flexibility to compensate for any occlusal irregularities, which is not the case with implants.

1. The distance between the bone crest and the opposing tooth

It can be unfavorable for implant treatment if it is too low, or on the contrary too high. The height of the edentulous crest to the opposing tooth must be on average 7 mm.

2. The inter-arcade relationship

In malocclusion, in the horizontal direction (e.g. skeletal class III), there is a conflict between an acceptable arrangement of the teeth and the space available for the crowns.

prosthetics and the position and inclination of the implants.

Hence the interest in examining the casts mounted on an articulator, the temporary prosthesis and the radiological guide which allows the desired position and angulation of the implants to be assessed (validation of the prosthetic project).

3. Cusp tilt

In order to induce forces in the implant axis directed towards the apical area, it is necessary, during the prosthetic design, to consider an adequate occlusal form obtained by having a reduction in the cusp inclination with wider grooves and pits.

4. Occlusal area surface and crown height

• It has been suggested to reduce the surface area of ​​the occlusal area by 30 to 40% at the level of the

molars, depending on the diameter of the implant and therefore the bearing surface, so as not to generate harmful forces.

• The crown/implant ratio should not be greater than 1, in order to avoid a

vertical cantilever and therefore non-axial forces, and this is even more so if there is an angulation between the crown and the axis of the implant (angled abutment).

5. Contacts with antagonist teeth

In order to minimize lateral forces that are harmful to the durability of implant-supported restorations, particularly if the design includes risky features, an occlusal force whose impact is at the center of the central fossa and which corresponds, in

ideally, in the center of the implant axis and by a single point (and not tripod contacts) would favor this durability.

• Balancing is done taking into account the mobility differential between the tooth and the implant. It is done as follows:

• In non-tight OIM: the contacts of the prostheses on implants must not be marked.
• On the other hand, when the patient is asked to press hard on the marking paper with a thickness of at least 30 μm (minimum axial mobility of the tooth is 25 μm), distributed contacts should appear on both the teeth and the prostheses on implants.

6. Special cases
7. Distal extensions (cantilever bridge) = cantilevered Should be avoided as much as possible. If they are used, several implants should be joined together and the unsupported part should be of short span. Indeed, the occlusion on the extensions

causes non-axial stresses on the pillars, and can eventually lead to their loss.

These forces tend to be accentuated at distal cantilever pontics, which is why it is advisable to opt for a mesial cantilever rather than a distal one.

2. Implant-supported dento bridge: should be avoided for the same biomechanical reasons.
3. Implants and occlusal context

• Favorable occlusal context:

• Balanced occlusion
• No pathology at the level of the temporomandibular joints
• Regular mandibular excursion routes
• Low risk occlusal context:

• Presence of small abrasion facets
• Carbocalcic patient
• Unfavorable occlusion relationships without parafunctions (e.g., Class II Division 2 angle)
• Occlusal context with significant risk:

• Bruxism
• Parafunctions
• Posterior occlusal collapse
• Presence of significant abrasion facets
• History of cracks or fractures in natural teeth or dentures

• The more risky the occlusal context, the closer the number of implants must be to the number of root units to be replaced.
• It is essential to diagnose the patient’s functional habits, and to be very careful in cases of parafunctions.
• Bruxomaniacs are considered “at risk patients” in the same way as uncontrolled periodontitis and smoking.
• The contribution of occlusion in the etiology and/or maintenance of masticatory dysfunctions (MD) is not negligible. Therefore, caution is necessary before planning treatment of dental occlusion in patients with myofacial pain or any other signs of MD.

Conclusion

During the therapeutic phase, the correct recording of the inter-arch relationship is a key step in prosthetic reconstruction .

Balancing when fitting prostheses, as well as adjustments over time, allow us to anticipate failures due to occlusal overload and changes over time in the occluso-articular system.

Occlusion in implantology

  Untreated cavities can cause painful abscesses.
Untreated cavities can cause painful abscesses.
Dental veneers camouflage imperfections such as stains or spaces.
Misaligned teeth can cause digestive problems.
Dental implants restore chewing function and smile aesthetics.
Fluoride mouthwashes strengthen enamel and prevent cavities.
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A soft-bristled toothbrush protects enamel and sensitive gums.
 

Occlusion in implantology