The journal of PROSTHETIC AND IMPLANT DENTISTRY Official Publication of Indian Prosthodontic Society Kerala State Branch CONSIDERATIONS IN CANTILEVER FIXED DENTAL PROSTHESIS * Prasad Aravind, **Abdul Razak P, ***Nimisha Ramesh, ***Deepthi Venugopalan, ***Athira M *Professor, **Professor and HOD, ***Post graduate student, Department of Prosthodontics, MES Dental College, Perinthalmanna | Corresponding Author: Dr. Nimisha Ramesh, E-mail: [email protected] Criteria for abutment selection Abstract: The following factors by Ewing when using the The cantilever fixed dental prosthesis is a restoration cantilever principle are a good periodontal with one or more abutments at one end and attachment (covering maximum root surface, good unsupported at the other end. Forces transmitted alveolar bone support, favourable root length, through these cantilevered pontics results in tilting shape, and crown length, arch-to-arch relationship, and rotational movements of the abutments. The favourable tooth-to-tooth relationship. greatest strain in the distal cantilever fixed partial denture is recorded mesial to the most distal retainer Ante’s Law states that while selecting the number because most fractures occur in this region. There are of abutments for a fixed restoration, “the total various criteria and factors necessary for planning periodontal membrane area of the abutment teeth a cantilever fixed partial denture (FPD). This paper should equal or exceed that of the teeth to be discusses briefly various factors related to cantilever replaced.” fixed dental prosthesis. Varied clinical experience also becomes an important factor in treatment planning. Introduction Every dentist emphasizes on the correlations that Anterior cantilevered fixed dental exist between biology and mechanics in treating prosthesis patients with either fixed or removable partial Cantilevered fixed dental prosthesis shows more dentures. Distribution of stress within physiologic success in anterior than posterior because the limitations of supporting structures in both types forces are less in the anterior region than posterior of restorations plays a vital role resulting in a quadrants A cantilever fixed dental prosthesis successful outcome. requires at least two abutment teeth. The only documented indication for a single abutment is The cantilever fixed partial denture is a restoration the replacement of a maxillary lateral incisor with with one or more abutments at one end and the canine as an abutment3. Thus, the anterior unsupported at the other end1. A class I lever cantilevered fixed dental prosthesis can be system is created if vertical and oblique forces the ideal indication for cantilever fixed dental directed to the pontic result in forces on the prosthesis. abutment teeth greater than the applied stress2. JPID – The journal of Prosthetic and Implant Dentistry / Volume 4 Issue 2 / January–April 2021 / 85 The journal of Prasad Aravind, Abdul Razak P, Nimisha Ramesh, Deepthi Venugopalan, Athira M PROSTHETIC AND IMPLANT DENTISTRY Official Publication of Indian Prosthodontic Society Kerala State Branch Posterior cantilevers abutments to withstand the forces. In case of posterior region when a cantilever pontic Henderson et al. used a practical model and a is used to replace a missing tooth, forces applied laboratory model of a three-abutment posterior to the pontic have an entirely different effect on fixed dental prosthesis with strain gauges. the abutment teeth. The pontic acts as a lever that All the models, forces to the abutments through the tends to be depressed under the forces with strong cantilevered pontics were resisted by rotational occlusal vector. It also places maximum demands and tilting movements of the abutments on the retentive capacity of retainer. Even though the use of cantilevered restorations in these regions More than 5 hundredths of the force applied to the appears to be conservative the effect that it has cantilever pontic were absorbed by the abutment on the abutment teeth is detrimental. nearest the cantilever pontic, but the addition of abutment teeth lessened the Cross arch cantilever fixed dental prosthesis force on the distal abutment. It was all over that the abutment nearest the pontic of a cantilever style The cross-arch unilateral two-unit cantilever fixed of the mounted partial denture can assume over dental prosthesis were analysed by Lundgren and fifty per cent of the load placed against the pontic. Laurell4 to register occlusal forces throughout light tooth-tapping,chewing, swallowing, and maximal However, a three-abutment cantilever FDP can biting. reduce the “combined total resultant” forces to the distal abutment compared to a two-abutment They stated that in spite of functions the distal cantilever restoration. cantilevered fixed dental prosthesis was subjected to less stress than the contralateral posterior Patients restored with FDPs with bilateral terminal abutment with equal or smaller than local anterior abutments, an average of 26% of the muscular forces. capacity was activated during chewing compared with 37% in the bilateral terminal abutment group The diminished forces on the cantilever units fixed in study5. dental prosthesis attributed to a deflection of the cantilever units and to not the intrusion of the The variations were explained by the shortage connected abutments. of terminal abutments inflicting lateral bending forces that activate peripheral inhibitory feedback Forces and stress distribution reactions from the TMJ mechanoreceptors. Forces applied to the cantilevered pontic are Type of opposing dentition resisted through rotational and tilting movements 6 by the abutment teeth rather than those along Antonoff declared that cantilever FPDs were a the long axes. Single cantilevered pontics with at lot of often indicated once reduced stress was least two abutments are recommended, although inherent, like a whole denture in the opposing this may vary depending on the existing clinical dentition. conditions and the location of the pontic in the However, Randow et al.7 reported no major dental arch. The muscles of mastication exert the clinical significances between technical failures strongest forces in the posterior arch. Placement of cantilevered FPDs and also the kind of opposing of cantilever pontic posteriorly requires additional dentitions. The journal of Considerations in cantilever fixed dental prosthesis PROSTHETIC AND IMPLANT DENTISTRY Official Publication of Indian Prosthodontic Society Kerala State Branch They instructed that a well-supported, stable fixed prostheses appears with the first rule of complete denture might additionally generate not designing prosthetic cantilevers in the fixed high functional loading. prosthesis for partially edentulous patients of full- arch maxillary fixed restorations. This is because Role of occlusion of the fact that cantilevers are significant force magnifiers to the cement or prosthesis screws, 8,9 Studies concludes that dentition can be prosthesis superstructure, abutment screws, rehabilitated by use of FDPs with cantilever implant bone interface and the implants.12,13 pontic on specific, isolated abutments that are periodontally compromised. Stable FDPs were Cantilever options in esthetic zone, when two successful despite individual hypermobile adjacent teeth are missing anterior to canine and abutment teeth. Prolonged stability was achieved the intra tooth space is less than 12mm which by periodontal treatment and the development of usually occurs in the mandibular arch a cantilever a stable, nontraumatizing occlusion. Balancing may be an acceptable option. In the mandibular contacts were established to prevent migration, arch when a central incisor and a lateral incisor tilting, and increasing mobility when there was are missing, a larger diameter implant in the a possibility of FDP mobility during mandibular central incisor position and a cantilevered pontic movements. to replace the lateral incisor is indicated. In case of a maxillary arch the intratooth distance will be The forces of mastication declines with mostly greater than 12mm and hence two implants periodontally compromised teeth in dentitions with can be inserted. In a completely edentulous cross-arch unilateral posterior two-unit cantilever mandibles, a cantilever is often the most prudent FDPs. The quadrants with the cantilevers were treatment option. Pontics are cantilevered from never assigned as the preferred chewing side 10. anterior implants. When this option is considered, If the occlusion is stable and the cantilever is free the force factors of parafunction,crown height from premature contacts, the cantilever would be space, masticatory dynamics,implant location and only subjected to large forces. opposing arch are closely scrutinized.14 Biological features of cantilever FDPs Conclusion Axially directed force of mastication is influenced by It can be concluded from that the optimal treatment the periodontal support with cross-arch extension for replacing missing teeth is a fixed dental fixed dental prosthesis with unilateral cantilevers10. prosthesis secured at both ends. The cantilever is The periodontal tissues has less affect on the local considered a compromised solution especially for forces on the distal unit of the cantilever because of unilateral edentulous dentitions. Abutments should the deflection of the cantilever. Randow and Glantzs have suitable periodontal support, researchers stressed on the importance of mechanoreceptor have demonstrated that extensive