|Year : 2018 | Volume
| Issue : 2 | Page : 41-42
Thinking big about small contacts: Is occlusion being ignored?
Editor-in-Chief, Journal of Dental Implants; ProSmile Dental Clinic and Implant Centre, Dr. L. H. Hiranandani Hospital, Mumbai, Maharashtra, India
|Date of Web Publication||17-Dec-2018|
Dr. Sharat Shetty
Editor.in.Chief, Journal of Dental Implants, ProSmile Dental Clinic and Implant Centre, Dr. L. H. Hiranandani Hospital, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Shetty S. Thinking big about small contacts: Is occlusion being ignored?. J Dent Implant 2018;8:41-2
Rehabilitation of missing dentition with dental implants are significantly rising in routine dental practices and there is huge expectation that the implant restorations perform similar to or better than natural teeth restoration. This is logical and desired but an unrealistic expectation, considering the vast differences between implant-osseointegration and natural tooth-to-bone connection. Besides, natural teeth offer defense to the occlusal forces through proprioception, single-piece designs, excellent anatomy, favourable modulous of elasticity and good repair and adaptability mechanism in adverse conditions and hence can tolerate great occlusal loads. And implants, due to their inherent designs and material limitations, are more vulnerable to large and unfavourable occlusal loads. This is clearly evident from the proliferating reports of increasing incidences of post-insertion failures like the peri-implant bone loss, soft tissue inflammatory changes and superstructure breakdowns including loosening, fractures of various mechanical components and wear and breakdowns of occlusal materials.
Though there have been significant improvements on the surgical outcomes of implant placement leading to very high implant survival and success rates, there has been slow to no paradigm shift in strategies to manage the said postinsertion failures amongst majority of the practicing clinicians. This stems from the fact that:
- Natural teeth are more tolerant to imperfections in delivered occlusal therapies
- Nonreinforced training on occlusion in dental schools and lack of training later too
- Efforts are directed to solving the problem, most of the time mechanically rather than preventing them knowing the current limitations of implant prosthesis
- Poor understanding that occlusal relationships are not static but dynamic
- There are also the patient factors of normal, paranormal and abnormal functional loadings which are constantly changing in one's lifetime.
General dentists are more in distress and with the patients expressing their displeasures over the recurrences, they seek quick fixes to tide over these problems. Persistent failure rates and unforgiving responses to implant imperfections lead to disillusionment among dentists due to the high stakes of procedural complexities, costs, time and expectations often leading to altered approaches to future management of edentulous spaces without implants, depriving the patients of optimum oral efficiencies. Even most reported cases in literature have little mention on the correlation of selected therapy and occlusion and lack significant long-term follow-ups. Short-term success stories easily find mention in most digital media except indexed journals and the readers/viewers are impressed but no further reports are found to assess their successes or failures, which are essential for growth of scientific legitimacy.
So, there is an urgent need for awareness among practicing clinicians about this important contributing factor of occlusal loading on implants and customize every treatment plan with a protocol of regular appraisals throughout life which are more frequent than natural teeth supported restorations. The foundation of any implant therapy planning should be based on the following considerations:
- Consistent upgrading of knowledge and skills by the clinicians based on scientific norms of learning and implement and evaluate them to the core. This allows for judicious and customized planning of the whole case both restoratively and surgically, in that order
- Patient's desires and expectations: This should primarily drive the choice of possible options and all established procedures should be discussed and undertaken to achieve predictable outcomes. Often removable implant prosthesis performs better for favourable occlusal load distribution. They are also indicated in cases of nocturnal parafunctions
- Understand the patient's current occlusal scheme and evaluate whether they are favourable in static and dynamic situations. Institute changes for favorable force distribution. Also retain and maintain healthy natural teeth for their proprioceptive advantages
- Evaluate prosthetic space (both vertical and horizontal) first rather than bone for implant placement. Remember teeth meet first and then load is transferred to implants. One could make them favorable by making implant choices after understanding how they will tolerate the loads and not vice versa. Mounted casts are key for this decision. This will also help to decide on the suitability of cement or screw retained prosthesis
- The location and direction of implants are significant when there are single, or fewer implants as axial loading is more favourable. Nonaxial forces act in a non-perpendicular direction to the occlusal plane and lead to progressive disruption of the bone-implant interface or component failures. This is can be easily achieved by use of properly constructed surgical splints rather than free-hand implant placement. Two-dimensional radiographs do not reveal bucco/labio-lingual discrepancies. Virtual three-dimensional planning is a useful tool and can be used to fabricate fully or partially guided surgical stents
- Local bone and soft tissue morphology should be modified for choice of implant size (diameter and length) for optimum results with enough hard and short tissues around them. Long-term studies have shown progressive loss even under good conditions and hence need early compensation. Smallest diameter and shortest length should be used individually only when loads are not significantly high or can be splinted with other neighbouring implants
- Splinted non-parallel implants are acceptable but not ideal as this increases the complexity of the prosthesis fabrication
- Loading protocols should be planned for every patient based on many factors, micromotion being the most significant one. Early loading, though always desirable, must be chosen when high initial primary stability can be achieved and maintained with passive splinted prosthetic fabrication and immediate postinsertion maintenance care. Non-loaded prosthesis should be given only for reasons of esthetic gratification and gingival contouring
- Passivity of definite prosthesis is essential to prevent any additional load on the bone-implant-prosthesis entity. Occlusal loading magnifies this active force leading to early failures. Hence, precision in intermediate clinical steps and accurate laboratory fabrications are paramount
- Cantilevers are silent destroyer of bone and many times of components too as they excessively bend the unsupported prosthesis. They are more significant when a narrower implant supports a larger restoration leading to bigger circumferential horizontal cantilever or a shorter implant leads to longer vertical cantilever. Opposing dentition are also important while deciding the cantilever extent
- Minimizing occlusal loading of implant prosthesis should be the goal to reduce the biomechanical failures of the whole implant-prosthesis complex. Besides axial loading, narrow the occlusal width bucco-lingually and make occlusal table shallower. Also, cross-arch splinting provides resistance to lateral vectors of functional and parafunctional loading
- Recruit good natural teeth for major load sharing in centric/MIP position and guidance teeth for posterior disclusion of natural teeth and implant prothesis
- Posterior implant restorations should always have smooth protrusive and lateral excursive movements without any working or nonworking interferences
- Presence of parafunction should be identified and appropriate occlusal splints for fixed implant prosthesis should be designed and evaluated for efficacy periodically. Consider progressive loading in these situations. Also, retrievable design of implant prosthesis should be considered for ease of removal and repair if needed
- Tissue surface of implant prosthesis should have favorable emergence and gingival contact profiles for ease of maintenance as they influence health of peri-implant tissues, which are easily susceptible to breakdowns to occlusal overloads
- Regular appraisals of the existing scheme should be done for potential unforeseen events and detection of early complications and due corrections.
After many years of clinical practice of implant dentistry, I have learnt that occlusal contact relationship has the most meaningful impact on the incidence and recurrences of complications or failures and once implants are placed, an uncorrectable handicap has set in. So “Plan the occlusion prior to surgical phase”. This will inadvertently increase both the implant and its prosthesis survival and success rates.
“False facts are highly injurious to the progress of science, for they often endure long: but false views, if supported by some evidence, do little harm, for everyone takes a salutary pleasure in proving their falseness: and when this is done, one path towards error is closed and the road to truth is often at the same time opened.”