OCCLUSION IN IMPLANT-AT A GLANCE Khushboo Mishra1, Divya Hegde2,, Sajan Shetty3, Sanjana Shah1, Sneha Sreeram1, Sree Lakshmi Reddy1

1 PG Student, Department of 2 Professor and Head of the Department, Department of Prosthodontics 3 Senior Lecturer, Department of Prosthodontics 5 PG Student, Department of Prosthodontics 6. PG Student, Department of Prosthodontics

CORRESPONDING AUTHOR: [email protected]

ABSTRACT

Objectives: is a critical and very important component for the clinical success and longevity of dental implants. This review article focuses on the various aspects of implant protective occlusion. Our scientific literature regarding implant occlusion, particularly in implant-supported fixed dental prostheses remains controversial. Materials and methods: A search strategy was performed in MEDLINE/PubMed, Scopus and Google Scholar with keywords – ‘implants’ and ‘occlusion’, ‘implants’ and ‘fixed , ‘implants’ and ‘fixed dental prostheses’, ‘implants’ and ‘partial edentulism’, ‘implants’ and ‘complications’, ‘implants’ and ‘failures’, ‘implants’ and ‘cantilever’, ‘implants’ and ‘occlusal load’. Results: 135 articles were retrieved. After hand search a total of 290 articles were identified. Ultimately, 30 articles were selected and summarized and discussed as they met the selection criteria. Conclusion: Most of the available clinical data are controversial. Implant-protected occlusion can be accomplished by decreasing the width of the occlusal table and improving the direction of force. By doing these things, we can minimize overload on bone-implant interfaces and implant prostheses, to maintain an implant load within the physiological limits of individualized occlusion, and ultimately provide long-term stability of implants and implant prostheses. Current clinical practices rely heavily on principles extracted from the natural dentition or removable dental prostheses on complete edentulous patients and on expert opinions.

KEYWORDS: Dental implants, Dental occlusion, Fixed partial denture, Implant-supported dental prosthesis, Review. http://dx.doi.org/10.19177/jrd.v8e2202021-27

INTRODUCTION osseointegration, mechanical stresses This review discusses the beyond the physical limits of hard tissues implant-protected occlusion for implant Determining an occlusal have been suggested as the primary longevity and to provide clinical scheme for the restoration of implants cause of initial and long-term bone loss guidelines for optimal implant occlusion requires careful consideration. This around implants[1,2]. based on the currently available stems from the fact that after literature.

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depth and peri-implant disease states prostheses, despite the lack of the STUDY SELECTION [3,4]. I.Naert et al concluded in his study periodontal ligament as an integral that the location of the fixtures, the component of the neuromuscular This review was based on occlusal design and fixed prostheses in coordination. However, an eccentric articles searched through the both jaws influence prosthetic and function, such as maximal occluding MEDLINE/PubMed, Scopus and google implant complications [5]. The choice of force, could potentially induce abnormal Scholar databases. The search was occlusal scheme for implant-supported muscle reaction in the implant patients. augmented by hand search of the prosthesis is broad and often According to him, occlusal concepts relevant journals unavailable through controversial. developed from the natural dentition can electronic database and the list of Judith L. Gartner conducted a be implemented to implant support references of the included studies. The pilot study on effect of osseointegrated systems without any modifications, main keywords keywords – ‘implants’ implants on the coordination of because mandibular movement, velocity, and ‘occlusion’, ‘implants’ and ‘fixed masticatory muscles in which he and chewing patterns are the same for prosthesis, ‘implants’ and ‘fixed dental concluded Patients with implant- patients with natural teeth and implants prostheses’, ‘implants’ and ‘partial supported prostheses appeared to be [6]. edentulism’, ‘implants’ and well adapted to perform habitual Occlusion is the critical process ‘complications’, ‘implants’ and ‘failures’, masticatory functions. The results of this for implant longevity because of the ‘implants’ and ‘cantilever’, ‘implants’ and study suggest that habitual masticatory nature of the attachment of the bone to ‘occlusal load’were used. function can be restored with the implant surface. In 1954, Beyron put Total of 135 articles were osseointegrated implant-supported forward characteristics of functionally retrieved. After hand search a total of 290 articles were identified. Ultimately, 30 articles were selected and summarized and discussed as they met the selection criteria.

INCLUSION CRITERIA

1. Peer reviewed articles in English only. 2. Full text articles-Reviews, reports and studies.

EXCLUSION CRITERIA

1. Abstracts only on the Databases searched. 2. Unpublished reports or abstracts or case reports as well as reports that did not cover both conventional and digital impression techniques.

Occlusal overload is often regarded as one of the main causes of peri-implant bone loss and implant prosthesis failure because it can cause crestal bone loss, thus increasing the anaerobic sulcus

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Mishra et al • Journal of Research in Dentistry 2020, 8(2):21-27 optimal occlusion and principles of occlusal loading and occlusal scheme movement in single unit implant- occlusal rehabilitation and he design was of minor or no importance to supported prostheses [16,17,18] emphasized about the concept of marginal bone loss, and (b) the key 5. The reduced cuspal inclination can therapeutic occlusion. THERAPEUTIC confounding variables were smoking decrease the bending moment, OCCLUSION is one in which and poor plaque control, which were increase the axial loading force of arrangement of teeth and their opposing directly associated with marginal bone implants, and reduce stress on the occlusal surfaces satisfies function and loss. Best practice guidelines for implant implant and the implant/abutment esthetic requirements while distributing superstructure design have been interface [19] the forces of occlusion over as many developed by extrapolation from (a) Kim Y et al in Occlusal teeth during functions of mandible [7]. biomechanical studies on implant considerations in implant therapy has cantilevers and (b) design features used put forward implant occlusion Occlusal goals for implant supported for tooth-supported superstructures that guidelines: [13] restorations:

1. bilateral simultaneous contacts and equal distribution of occlusal forces [7] 2. no occlusal prematurities [8] 3. Smooth, even lateral excursive movements with no non-working interferences [9]

Difference between natural tooth and implant supported prosthesis have been found to be effective to Implant-protected occlusion has minimise effects of loading and been suggested for implant-supported Kim et al. [10] and Misch [11], achieving desirable patient outcomes prostheses [2]. Earlier in the literature compared natural teeth and implants [12]. In addition, occlusal scheme design bilateral balanced occlusion for complete and main differences between these two has minor or no importance to marginal denture fabrication [20], group-function structures: bone loss of implant-supported occlusion, and mutually protected prostheses [13]. occlusion for the natural dentition with and without fixed prostheses [21,22] have Occlusal Design and morphology Recommendation for occlusal been mentioned and are holding the consideration : morphology: great importance till day.

Iven Klineberg in a study named 1. shallow occlusal anatomy, a narrow Implant Protected Occlusion the bases for using a particular occlusal occlusal table, and reduced cuspal design in tooth and implant-borne inclination[14] Occlusal design is a primary reconstructions and complete denture, requirement for the success of long term 2. flat fossa and grooves for wide within the limits of contemporary survival of implant. freedom in centric [15] clinical outcome studies, based on their Implant-protective occlusion 3. size of the occlusal table be 30% to design and population size, data (IPO) is an occlusal scheme suggested to 40% smaller for molars [16,17,18] suggested that long-term clinical decrease overload on the implant outcome studies on implant-supported 4. Widths greater than the implant fixed partial in the mandible diameters may generate cantilever have indicated that (a) the association of effects and some bending

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than the initial breakage force for the 0- degree cuspless occlusal design specimen. 2. No significant differences were demonstrated in maximum breakage forces or maximum strains between the 33-degree cusped and the 0- degree cuspless occlusal design specimens. 3. The occlusal configuration and cusp angulation of implant-retained prostheses played a significant role in force transmission and the stress-strain relationship in bone.

No premature occlusal contact

Premature contacts are defined as occlusal contacts that divert the mandible from a normal path of closure, interfere with normal, smooth, gliding mandibular movement, and/or deflect the position of the condyle, teeth, or supported prosthesis and enable its prosthesis. Several animal studies successful functioning in the oral set-up. Jamie A. Kaukinen in 1996 demonstrated that excessive lateral The IPO concept addresses several conducted a study on The influence of forces from premature occlusal contact conditions to decrease stress to the occlusal design on simulated can cause excessive marginal bone loss implant interface. masticatory forces transferred to or even osseointegration failure[24]. Misch has put forward in Occlusal implant-retained prostheses and Occlusal prematurity between considerations for implant-supported supporting bone [23]. and centric prosthesis factors affecting implant This pilot study used a method to relation occlusion should be taken into protected occlusion [2] apply quantified vertical forces to a food consideration especially on an implant substance and record the forces and supported prostheses. This is because, • No premature occlusal contacts or strain transmitted through cusped 33- non-mobile implants bear the entire load interferences: timing of occlusal degree and cuspless 0-degree occlusal of the prosthesis when it comes in contacts design specimens to a simulated contact with the mobile natural teeth, • Influence of surface area implant-retained prosthesis and the hence during the occlusal adjustment • Mutually protected articulation supporting bone. The data were analyzed between implants and natural teeth, • Implant body angle to occlusal load to compare the forces required to cause premature occlusal contacts on the • Cusp angle of crowns (cuspal initial breakage of the food, the implants can occur as the natural teeth inclination) maximum breakage forces applied can move away from the centric during • Cantilever or offset distance before cycle termination, and the function [1]. (horizontal offset) maximum strain registered by strain Occlusal adjustment can be • height (vertical offset) gauges at the bone level. The following done by using a thin articulating paper • Occlusal contact positions conclusions were drawn within the which is less than 25 μm to evaluate the • Implant crown contour limits of this pilot study. 1. The initial of the occlusal contact. • Protect the weakest component breakage force for the 33-degree cusped This is done to relieve the implant crown • Occlusal materials occlusal design specimen was greater which leads to heavier contact on the

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Mishra et al • Journal of Research in Dentistry 2020, 8(2):21-27 adjacent natural tooth. A greater occlusal and wide grooves and fossae may be Crown height force is then applied to the articulating beneficial when constructing implanted paper, establishing equal contact regions prostheses due to the axial loading Implant crown height is often on both the implant-supported crowns induced. It is especially critical when the greater than the natural anatomical and natural teeth. Tooth might not intensity and duration of the force crown. As the implant crown height return to its original position for several increase. becomes greater, the crestal moment hours after application of a heavy with any lateral component of force also occlusal force. Following this, light forces Influence of surface area becomes greater [30]. Therefore any on adjacent natural teeth are first harmful effect of any feebly selected cusp equilibrated. Occlusal adjustment of Sufficient surface area is angle, angled implant body, or angled implants and teeth in the opposing arch required to withstand the load load to the crown will be magnified by should also be compensated for the transmitted to the prosthesis therefore the crown height measurements. primary tooth movement [1]. when an implant of decreased surface area, subjected to increased load in CONCLUSION Cusp inclination magnitude, direction or duration, the stress and strain in the interfacial tissue Occlusal overload is regarded as Kaukinen et al. [23] determined will increase. This can be minimized by one of the main causes for peri-implant the difference of the force transmission placing additional implants in the region bone loss and implant/implant between 33° and 0° cusps. The mean of concern, ridge augmentation, reduce prosthesis failure. Many clinical initial breakage force of 33°-cusped crown height or by increasing the complications may be attributed to specimens was 3.846 kg, while the implant width [26]. Bidez et al have implant overload. Most of the available corresponding value of the 0° cuspless reported a study showing that, forces clinical data are controversial. Implant- occlusal designed specimens was 1.938 distributed over 3 abutments results in protected occlusion can be accomplished kg. So they suggested that the cusp less stress on the crestal bone compared by decreasing the width of the occlusal inclination affects the magnitude of to 2 abutments [27]. table and improving the direction of forces transmitted to implanted force. By doing these things, we can prostheses. Anterior guidance minimize overload on bone-implant Weinberg and Kruger [25] interfaces and implant prostheses, to evaluated the torque of a gold screw, According to Weinberg and maintain an implant load within the abutment screw, and implant and Kruger[25], with every 10° change in the physiological limits of individualized concluded that cuspal inclination angle of disclusion, there is a 30% occlusion, and ultimately provide long- produces the most torque, followed by difference in load. They suggested that term stability of implants and implant maxillary horizontal implant offset, the anterior guidance of prostheses.Current clinical practices rely while implant inclination and apical implantsupported prostheses should be heavily on principles extracted from the implant offset produce minimal torque. as shallow as possible to avoid greater natural dentition or removable dental Weinberg [15] also claimed that forces on the anterior implants by prostheses on complete edentulous cusp inclination is 1 of the most steeper incisal guiding angles. patients and on expert opinions. significant factors in producing bending Anterior bite force moments. Because the angle of force to measurements and electromyographic REFERENCES the implanted body may be influenced by studies also reported that the cusp inclination, a reduction in cusp stomatognathic system elicits 1. Y Y Chen, C L Kuan, Y B Wang, inclination can decrease the resultant significantly less force when the Implant occlusion: biomechanical bending moment with a lever-arm posterior segments are not in contact in considerations for implant reduction and improvement of the axial the lateral mandibular position[28,29]. supported prostheses, J Dent Sci, loading force. Therefore a reduced cusp 3(2), 2008, 65 -74. inclination, shallow occlusal anatomy,

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