Impact of loading protocol of two-implant bar-retained mandibular overdentures on oral health-related quality of life – a randomized controlled trial

Tooth loss is the final outcome of most common dental diseases, i.e. dental caries and periodontitis.1 It is highly relevant with a prevalence of 56.8% in adults (35 – 44 yrs) and 96.3% in seniors (65 – 74 yrs) in 2014 in Germany.2 Even though the prevalence of edentulism decreased in recent years and is expected to further decrease in the future,3 in 2015 about 4.1% of the global population still was edentulous.4 Edentulism impacts the patients by reducing not only masticatory function and esthetics, but also by increasing pain during chewing and eventually by its psychosocial impacts.5,6 These impacts can be summarized as oral health-related quality of life (OHRQoL), the most important dental patient-reported outcome (dPRO).7 Other outcomes, for instance due to reduced masticatory function, might be related to general health (e.g. dementia).8,9 For many years, the only treatment option for edentulism was a conventional complete denture. Even though these dentures can substantially increase patients’ OHRQoL over a substantial period, a still considerable impairment in OHRQoL remains.10,11 Furthermore, not all patients benefit from conventional complete dentures, basically due to problems in adaption, high requirements on function, or insufficient anatomical conditions.12 Accordingly, many edentulous patients can only insufficiently be helped by conventional complete dentures.

Dental implants can be the solution to increase dPROs in edentulous patients.13 They can be used to support either removable dental protheses (RDP) or fixed dental protheses (FDP). Modern implant concepts suggest that only four implants are required for implant-supported FDP.14 However, four implants still represent a substantial intervention with related biological and financial costs. To reduce costs and potential risks, a lower number of implants might be beneficial. And indeed, guidelines suggest two implants as first choice for the edentulous mandible.15 Implants can be provided with different types of attachments including balls or bars to support of a RDP.16,17 When considering dPROs and patients’ choice, implant-supported RDP are superior than implant-supported FDP in many aspects, e.g. esthetics, ability to speak, and ease of cleaning.18,19.

However, to help the patients as soon as possible, when to load the implants becomes an important issue. When implants are loaded immediately, patients potentially benefit from implants basically at the time of implant placement and do not have to wait several months until implant exposure and provision of the final restoration. Furthermore, during the healing period in the delayed loading approach, the present conventional complete denture needs to be modified to ensure the implant location is without contact and not load-bearing. Obviously, this can substantially decrease denture stability with all the related negative effects on the patients during this period. Therefore, immediate loading might not only provide the patients directly with the implant-related benefits but also decreases impairments during the healing period. One important issue was whether immediate loading affects complication rates and survival of implants. With exception of a single implant with significant inferiority of survival rates for immediate than conventional loading,20 current evidence suggests that in edentulous mandibles the loading protocol of implant-supported RDP does not significantly affect clinical outcomes.21, 22, 23

Another issue is the long-term effect on patients, i.e. on dPROs. Even though it has been shown that OHRQoL significantly increases after immediate loading of two implants for bar-retained overdentures in the edentulous mandible,24 evidence on the specific effect of loading protocol on OHRQoL is limited. A recent study investigating this effect of loading protocol in patients with a single implant in the middle of the mandible to support an overdenture concluded that there is no short-term difference in OHRQoL with respect to loading protocol.25 However, this study investigated only short-term effects four months after treatment and only a single implant with ball-attachment was provided. Since guidelines suggest at least two implants and follow-up periods should be substantially longer than only four months, there is a need for further studies.

Aim of this study was to assess whether immediate loading is more effective than delayed loading for two-implant bar-retained mandibular overdentures in terms of OHRQoL improvement over a period of 24 months.

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