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implants international magazine of oral implantology

I research Fig. 1_Peri-implant (mesial and distal) bone level around short implants six months (0.5 years) and two years after implant insertion. The implant shoulder is included to visualise the periapical bone level also in relation to the implant geometry. generation)implantsinarandomisedparallelgroup study.16 They concluded that in cases with limited residualboneof7–8mmoverthemandibularcanal short implants are a viable alternative to vertical augmentation. The treatment is faster, cheaper and associated with reduced morbidity. It is to be noted that implant insertion into pris- tine bone was compared with implants placed after preliminary sinus lift elevation.17 In this prospective study, which included 393 implants and 155 pa- tients treated in two groups, the implants placed into augmented sinuses had a lower survival rate compared with implants placed into pristine bone. Crown-implantratio Excessive crown–implant ratios have been hy- pothesised to be detrimental to long-term with- drawal.Forobviousreasons,thisratiomustbegiven particular attention when using short implants. Birdi et al. determined the crown–implant ratios of 309 single-tooth implant-supported restorations on short implants.18 The mean follow-up time was 21 months and the mean crown–implant ratio was 2,thatis,ratherunfavourableforatooth.Nostatis- tically significant relationship was found between thecrown–implantratioandimplantsuccess,orthe mesial or distal periapical bone level. Shortimplantsinposteriorregions DeSantisetal.studiedshortimplants(≤8.5mm) placed in edentulous posterior regions, predomi- nantly in the mandible, that were affected by high bone resorption.3 After one- to three-year follow- up,theyfoundasurvivalrateof98.1%(i.e.only2of 107implantswerelost)andasuccessrateof96.3% (i.e.only4of107implantsfailedthepredefinedsuc- cesscriteria).Theresultsofthisstudythereforealso support the use of short implants in posterior re- gionswithhighlyresorbedbone.Inthiscontext,itis important to be aware that the implant length used byBrånemarketal.intheiroriginalprotocolwases- tablished empirically.19 The implants at that time had a machined (smooth) endosteal surface. Current implants with microstructured endosteal surfaces are charac- terisedbyimprovedosseointegrationandincreased bone–implant contacts. Together with optimised geometry, contemporary implants are superior in maintaining implant stability.3 This in turn should allowtheuseofshorterimplants.Shortimplantsare typicallydescribedas<10mmlong,20 butHagietal. have described short implants as < 7 mm long.21 A European Association for Osseointegration con- sensus conference defined short implants as ≤8mm.Thisismorepracticable,asimplants>8mm had been commonly used for a long time without any particular problem related to their length.22 Survivalratesinstudiesreviewed In a recent review on the meta-analysis of short implant survival studies,20 it was found that the cu- mulative survival rate in the majority of the studies was similar to that of longer implants (92.5% and 98.4% for implants with machined and rough sur- faces,respectively)andconcludedthatrehabilitation using short implants is a reliable treatment.23 This conclusionistobeunderstoodwithinthelimitations ofameta-analysisandthelackofwell-designedran- domised trials. A similar conclusion was drawn by Tellemanetal.fromtheirsystematicliteraturereview of the survival rate of 2,611 short implants that were placedinpartiallyedentulouspatients.24 Nevertheless,Tellemanetal.foundanincreasein implantsurvival(from93.1to98.6%)thatwasasso- ciated with increasing implant length (from 5.0 to 9.5 mm).24 The authors believe that there is fair evi- dence that short implants can be placed in partially edentulous patients, but with a tendency towards an increasing survival rate according to implant length and a better prognosis in the mandibles of non-smokers.MorandandIrinakisintheirearlierlit- erature review also concluded that, even though short implants are commonly used in the areas of themouthunderincreasedstress(posteriorregion), the success rate of short implants is similar to that of longer implants when careful case selection cri- teria have been applied.25 Annibali et al. too con- cluded in their systematic review on short implants that prostheses retained by short implants in pa- tients with atrophic alveolar ridges appears to be a successful treatment option in the short term, but recommended further studies to determine its suc- cess in the long term.26 _Clinical study Patients This prospective case series included 56 consec- utivepatients(35femalesand21males)referredfor dental implantation to three different practices (JNH, JH and DA). Patients were entered into the study consecutively, that is, with no specific selec- 08 I implants4_2014 Fig. 1

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