Dental Asia Jul/Aug 2018

56 Behind the Scenes DENTAL ASIA JULY / AUGUST 2018 T he edentulous state affects many essential aspects of a patient’s life, their masticatory and phone t i c f unc t i ons , their appearance and even their social relationships. Although the edentulous patient’s rehabilitation can be successfully met thanks to a complete dental prosthesis, in some cases, however, problems of instability and poor retention can appear, primarily concerning the lower denture. The use of osseointegrated implants allows successfully managing all these inconveniences, even though implant rehabilitations may also present functional and aesthetic problems or requiring frequent maintenance interventions. It is therefore recommended to perform, right from the preliminary stages, an accurate surgical andprosthetic evaluation inorder to intercept and reduce possible complications of the Ƥnal restorations. To this intent, the basic principles of the complete dental prosthesis can be a valuable support in planning future rehabilitations on implants. The case reported in this paper describes the rehabilitation of an edentulous patient with a complete upper prosthesis and a lower implant-supported overdenture. Introduction The functional and aesthetic restoration of edentulous patients is still nowadays a contemporary theme in prosthetics. In recent decades, the phenomenon of tooth loss has been greatly reduced thanks to the important achievements in the field of prevention of caries and periodontal disease. However, the marked tendency towards population ageing keeps the demand for this kind of rehabilitation constant in absolute terms 1-2 . For many years already, the complete prosthesis has allowed to successfully treat most edentulous patients 3-6 . However, the management of the lower denture is often di ƥ cult due to lack of retention and poor stability 7-8 . The adaptation to this type of rehabilitation is a very complex process inƪuenced by various anatomical, functional and psychological aspects, and this is why it is not routine in all patients, as has been well-documented 9 . Therefore, the instability of the complete prosthesis a ơ ects not only the chewing function but also the patient’s social life 10 ; this greatly reduces the satisfaction of people more interested in their social life, and especially of women 11 . The advantages of mandibular implant-supported overdenture have been widely highlighted by many clinical studies 12-19 . This type of prosthesis can be planned on a variable number of implant abutments (one to four) ontowhich can be positioned di ơ erent retentive components. The overdenture on two intraforaminal implants with attachments is currently the most scientifically validated solution on an international level. The advantages of this type of rehabilitation are mainly linked to the improvement it determines in the quality of life of edentulous patients 20 , as well as the very favourable price-e ƥ ciency ratio of the treatment. Several authors at the Consensus Conference at McGill University 21 in 2002 had already identiƤed this rehabilitation mode as a “potential treatment standard” for the edentulous mandible. However, the scientiƤc literature has often reported problems related to themaintenance of the retentive components and to the fracture of the prosthesis itself 22-24 . The attachments are exposed to stress, distortion and wear, which determine a premature loss of retention 25-26 ; this is why a great number of solutions are offered on the market. Furthermore, the fracture risk of the product increases when the prosthesis is thin; to overcome this drawback, in addition to the use of non-voluminous attachments and the insertion of reinforcing structures, it may be necessary to schedule a resective plastic surgery of the alveolar ridge to be performed during implant surgery 27-28 . It has been reported that about 10-12 mm of space are required between the soft tissues and the occlusal table 29 ; in this evaluation it is necessary to not only consider the occlusal planes, but also to respect the neutral zone in order not to invade the necessary functional spaces of the tongue and cheeks 30 . Some studies have also pointed out that in the case of rehabilitations with complete upper prostheses combined with lower implant overdenture or Ƥxed rehabilitations with reduced posterior occlusal support, one can recreate the underlying mechanisms of the combined syndrome 31-32 . This e ơ ect seems to promote an excessive anterior occlusal contact that affects the pre-maxilla 33 . It is not uncommon toƤnd some conditionswherein the anchorage structures impose an overexposure of the anterior teeth, which not only creates an aesthetic discomfort, but also a dramatic loss of functionality of the upper prosthesis 34 . The realisation of an implant-supported or implant-anchored prosthesis must therefore comply with the construction aspects of a full prosthesis in order to intercept and reduce the maintenance and functionality problems of future implant restorations. It is therefore essential to determine parameters such as the occlusal plane, the correct allocation of spaces between the upper and the lower jaw, the vertical dimension of occlusion (VDO), to establish a stable and repeatable centric relation (CR) and to properly set up the mounting of the teeth according to phonetic and aesthetic criteria. This preliminary analysis is ultimately functional to the correct setting of the treatment plan and to e ƥ cient communication with the patient. The aim of this paper is to describe the diagnostic and rehabilitation pathway of an edentulous patient treated with a complete upper prosthesis and an overdenture on two implants. Case report A 68-year-old patient, edentulous upper and lower arches restored with prostheses for about three years, requested a new rehabilitation. The patient did not show any significant pathology (Figs. 1-3). Part I: Indispensable Guide for Implant-Supported Overdentures By Dr. Alessio Casucci and Mr. Rodolfo Colognesi