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T w o i m p l a n t s s u p p o r t i n g a m a n d i b u l a r o v e r d e n t u r e for successful treatment of patients presenting with Cawood and Howell Class V or VI mandibular atrophy. After a short period of accommodation, it is recommended to replace the conventional retention caps with stronger ones to improve overdenture stability and thus patient satisfaction. K e y w o r d s Dental implant, overdenture, retention system, atrophic mandible, edentulous. Introduction Edentulism can lead to significant functional im- pairment and unfavorable esthetic and psycho- logical changes in patients. Problems include restrictions in diet, speech impairment, loss of soft-tissue support and decreased vertical dimen- sion.1 The conventional method for treating eden- tulism is to provide complete dentures. However, progressive and irreversible loss of basal bone may lead to incrementally increasing difficulties for the denture patient, especially in relation to the mandible, creating problems like loss of re- tention and stability, hyperplasia and ulceration of the underlying mucosa, discomfort and pain, and impaired psychosocial functioning.2 A remov- able implant-supported prosthetic design offers better retention and improves oral function and patient satisfaction compared with a convention- al complete denture.3, 4 Furthermore, in the man- dible, it is possible to load implants immediately without increasing the risk of implant failure.5-7 Implant overdentures have been the subject of several clinical trials and systematic reviews, which have demonstrated them to be an effective and clinically predictable approach to obtaining improved retention and hence masticatory func- tion and patient satisfaction.8, 9 Implant overdentures can be divided into two subcategories:1 implant-retained, mucosa- supported overdentures (retained by different abutment or bar designs); and overdentures fully supported by implants.10, 11 In contrast to a mucosa- supported overdenture, an overdenture that is rigidly anchored to a milled bar support- ed by four interforaminal implants prevents rotational movement of the prosthesis, reducing possible jaw resorption and consequently pos- sibly also the incidence of prosthodontic main- tenance.10 In patients with an altered skeletal maxillomandibular relationship and severe bone atrophy (Cawood and Howell Class V and VI),12 an overdenture fully supported by four implants has been shown to be a predictable method for long-term treatment of edentulous patients.10 Nevertheless, limitations such as financial restrictions sometimes prevent the placement of a sufficient number of implants to accommo- date a fixed dental prosthesis and therefore an alternative for edentulous patients with com- promised oral function is required. The purpose of this proof- of- concept study was to present the preliminary results one year after loading for a single cohort of Cawood and Howell Class V and VI1 patients rehabilitated with a mandibular overdenture supported by two implants using a novel low-profile retention system. This study followed the Strengthening the Reporting of Observational Studies in Epi- demiology reporting guidelines.13 Materials and methods This prospective case series study was carried out in accordance with the Declaration of Helsinki of 1975, as revised in 2008. All of the participants were consecutively enrolled and treated in two private centers after being informed about the nature of the study and providing their written consent. Any healthy edentulous individual aged 18 years or older at the time of implant placement with Class V or VI mandibular atrophy according to Cawood and Howell,1 assessed by a cone beam computed tomography scan (Fig. 1), was consid- ered eligible for the study. Exclusion criteria were general contraindications to oral surgery, preg- nancy or nursing, intravenous bisphosphonate therapy, alcohol or drug abuse, heavy smoking (≥ 20 cigarettes/day), radiation therapy to the head or neck region within the last five years, parafunctional activity, untreated periodontitis, and allergy or adverse reactions to the restorative materials. All of the patients received a new conven- tional removable denture before implant place- Journal of Oral Science & Rehabilitation Volume 3 | Issue 2/2017 53