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Applied Osseointegration Research - Vol ume 6, 2008 A One-Year Clinical, Radiographic and RFA Study of
Neoss Implants Used in Two-Stage Procedures
Peter Andersson1 , Damiano Verrocchi1, Rauno Viinamäki1, Lars Sennerby1,2
1Private Practice, Fiera di Primiero and Feltre, Italy2Dept Biomaterials, Inst Clinical Sciences, Sahlgrenska Academy, Gothenburg University, Sweden This study reports a survival rate of 98.1% for 102 Neoss implants in 44 patients with a mean bone loss of 0.7 mm after one year. The reduced component inventory and innovative designs enhancing primary stability and facilitating laboratory technology/prosthetics offer practical advantages whilst the clinical results with the implant system tested compare favourably with existing systems e use of implant-supported bridges is a routine treatment for oral surger y under local anaesthesia. modality for the edentulous patient with documented good long-term results (Albrektsson & Sennerby 1991, Esposito et al. 1998). From initial y a rather complicated and re- Patients were administered 2 gr of amoxicillin (Aug- stricted procedure, the techniques of implant-supported mentin , Roche, Milan, Italy) and sedation if required dentistry have improved and simplifi ed, at least from a (Valium®, Roche, Milan, Italy, 5 mg) prior to surgery. Anaesthesia was induced by infi ltration with articain/ and surface modifi ed implants, surgical guides, shortened epinephrine (Septocain™, Specialites Septodont, Saint- healing periods and immediate loading are some examples. Maur-Des-Fosses, France). Crestal incisions were used However, improvements could stil be made in dental labo- for fl ap elevation. Implant sites were prepared with a ratory and prosthetic techniques in order to reduce further 2.2 mm twist drill followed by a 3 mm (3.5 mm wide treatment times and the overall cost of the treatment. implant), 3.4 mm (4.0 mm wide implant) and 3.9 mm drills (4.5 mm wide implant) (Neoss ltd, Harrogate, The aim of the present study was to evaluate a new UK). Full countersink preparation was made for all implant system (Neoss) for one year using clinical implants. Implants were inserted with the torque driver and radiographic examinations and implant stability set to 40 Ncm and fi nal seating was performed with a measurements by resonance frequency analysis (RFA). hand wrench. Cover screws were applied and the fl aps were replaced and sutured. Bone quality and quantity according to Lekholm and Zarb (1985) were registered.
Abutment connection was performed 3 months Consecutive patients requiring implant treatment for later, usually with a punch technique and no sutures. total or partial loss of teeth were included in the study Bite registration and impressions were taken with until at least 100 implants had been inserted. Only closed tray and then healing abutments were con- two-stage procedures with 3 months of healing from nected. Neolink™ abutments (Neoss ltd, Harrogate, placement to abutment connection were performed. UK) of gold or titanium (to match the metal of the framework) were used. Abutments were either cast Preoperative examinations included intraoral and or welded into the metal frameworks. Porcelain panoramic radiographs. Computerized tomography was and acrylic veneers were used. Constructions were e implant sites should have suffi cient screw-retained if implant angulation permitted; bone for at least 7 mm long implants. Patients should otherwise, individual abutments (Neo Matrix, Ne- be over 18 years old and present no contraindications oss ltd, Harrogate, UK) were used for cementation.
Applied Osseointegration Research - Vol ume 6, 2008 Follow-upImplant stability was assessed by RFA (Mentor®, Integration Diagnostics AB, Gothenburg, Sweden) at implant surgery, abutment connection and after one year of loading (after unscrewing the construc-tions ). Cemented constructions were not removed.
Digital or conventional intraoral radiographs were taken at abutment connection and after one-year of service. Conventional radiographs were pho-tographed with a digital camera on a light desk. Measurements were made using a personal computer (Image J 1.34S, National Institutes of Health, USA) at mesial and distal aspects. Each radiograph was calibrated using the known width of the coronal cyl-inders of the implants. Th e upper platform was used as a reference point for measurements (Figure 1) .
Forty-four (44) patients (16 male and 28 female, mean age 54 years) were treated according to the protocol. Forty-eight (48) prosthetic construc-tions were delivered including fi ve full cross-arch bridges, 28 partial bridges and 17 single crowns. A total of 102 implants were placed, 34 in the max-illa and 68 in the mandible, in bone quality and quantity as presented in Table 1. Implant lengths a/ two implants in the posterior mandible after insertion, and diameters are presented in Tables 2 and 3.
b/ healing of soft tissues at the time of bridge delivery, c/ final bridge.
At writing all patients have completed one year in function. All constructions except one pa-tient with a cemented bridge on five im- plants were removed for stability checking.
All patients maintained a fi xed bridge or crown during the one year study. Two failures were experienced, giv-ing a survival rate of 98.1% after one year. One 13 mm long by 4.0 mm wide implant placed in a defect in a Table 1. Bone Quality and Quanitity encountered mandible was removed at impression due to mobility. In this case, a new implant was placed and a temporary bridge was made on the remaining three implants whilst awaiting healing. One 7 mm long by 4.5 mm wide im- plant in Q4 bone in the1st molar region in a maxilla was lost after one year. Th e implant was removed and the three-unit bridge was supported on the remain- ing two implants. No other prosthetic complications such as fractures or screw-loosening were experienced.
Applied Osseointegration Research - Vol ume 6, 2008 A total of 92 implants with readable radiographs at baseline and follow-up have been evaluated to date. On average, the marginal bone level was located 0.6 mm (SD 0.7) below the platform at baseline and 1.3 mm (SD 1.0) below after one year; giving an average bone loss of 0.7 mm (SD 1.0) at one year. X implants showed more than 3 mm bone loss.
Stability measures by RFA gave a mean of 75.0 (SD 6.5) ISQ at placement, 74.4 (SD 6.8) at abutment connection and 76.2 (SD 6.6) after one-year. Th ere seems to be a relation between bone quality and ISQ at implant placement (Fig. 4). Implant stability increased with time for implants in Q4 bone whilst stability decreased for implants in very dense bone, resulting in a similar stability for all implants after one year.
Early experience with the Neoss implant system used in a two-stage procedure with 3 months of healing in the present study shows satisfactory results. Two of 102 implants were lost during one year which compares well with the results reported from other implant systems (Albrektsson & Wennerberg 2004). From a surgical point of view, the implant was stable during Figure 2. Radiographs from a single tooth case at a/ baseline insertion and good primary stability was generally achieved. When poor primary stability was encoun-tered, a wider implant was used to enhance stability. is double the “apparent” thread spacing, so the implant Since the diff erent implant diameters have the same advances twice as far with one turn as for a single-helix prosthetic platform, an implant could be replaced thread. Th is feature reduces the insertion time and with a wider diameter without requiring changes to counteracts wobbling during insertion. Secondly, the the other prosthetic components, as is commonly implant has a positive tolerance, meaning that the necessary with other implant systems. Abutment implant is slightly conical in the coronal direction connection was easier with this implant than previ- and as the implant screws home its diameter increases ously experienced with external connection implants, slightly and there is a slight tendency to tighten the which often require a fl ap procedure and removal thread base against the bone. Previous research has of bone tissue in order to fi t an abutment. A punch shown higher stability for slightly tapered implants technique without suturing could frequently be used in soft bone than for parallel-sided implants, without in the present study and in most cases impressions jeopardizing the integration process (O’Sullivan et were taken in conjunction with abutment connection. al 2000, O´Sullivan et al 2004a, 2004b). Decreased Th e use of integrated abutments with the framework primary stability was seen with decreased bone den- facilitated prosthetics and reduced the overall costs . sity, which is in line with the fi ndings of Östman et al (2006). Implant stability increased slightly with time Th e RFA measurements revealed a high average pri- and was similar for all bone qualities after one year mary stability of these implants which is most probably of function, which indicates a favourable bone tissue due to the geometric features of the implant. Firstly, it response to the implants. Th e greatest increase of stabil- has a two-start thread, a twin helix, with two threads ity was seen for implants in Q4 bone which is in line running parallel but on diametrically opposite sides of with the fi ndings of Friberg et al. (1999). Th is can be the cylindrical substrate. Th us, the actual thread pitch explained by stiff ening of the bone-implant interface Applied Osseointegration Research - Vol ume 6, 2008 with time due to bone formation and remodelling. In contrast, decreased stability was observed in dense bone, which may be explained by mechanical relaxa-tion and/or bone remodelling as a response to the pre-sumably high stresses induced by implant placement. Th e radiographic analysis revealed that about 0.7 mm of bone was lost during the fi rst year of loading, which is in the range of previously reported results with other systems (Oh et al. 2002). X implants showed more than 3 mm bone loss during one year. Th e fact that the bone level was located 0.6 mm be-low the platform at abutment connection indicates some remodelling during healing as generally the implants were placed flush with the surrounding bone. Th is accords with the fi ndings of Engquist et al. (2001) who compared the marginal bone tissue response at Astra Tech and Brånemark system implants. It is concluded that prosthetic rehabilitation of the edentulous patient with the Neoss implant system results in good short-term clinical and radiographic outcomes. Th e innovative design solutions do seem to enhance primary stability and facilitate labora-tory technology/prosthetics, and with the reduced component inventory this system off ers advantages over our experiences with other implant systems.
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