International Journal of Oral Implantology, 04/2010

Purpose: The aim of this randomised clinical trial was to evaluate the influence of restoration on marginal bone loss (MBL) using immediately definitive abutments (one abutment-one time concept) versus provisional abutments later replaced by definitive abutments. Materials and methods: In three private clinics, 32 patients with 32 hopeless maxillary premolars were selected for post-extractive implant-supported immediate restoration and randomised to provisional abutment (PA) and definitive abutment (DA) groups, 16 sites in each group. After tooth extraction, 7 patients had to be excluded for buccal wall fracture at tooth extraction or lack of sufficient primary implant stability ( 35 Ncm). The remaining 25 patients (10 PA, 15 DA) received a post-extractive wide-diameter implant. Immediately after insertion, the PA group were immediately restored using a platform-switched provisional titanium abutment. In the DA group, definitive platform-switched titanium abutments were tightened. In both groups, provisional crowns were adapted, avoiding occlusal contacts. All implants were definitively restored after 3 months. In the PA group, a traditional impression technique with coping transfer was adopted, dis/reconnecting abutments several times; in the DA group, metal prefabricated copings were used and final restorations were seated, avoiding abutment disconnection. Digital standardised periapical radiographs using a customised film holder were recorded at baseline (T0 = implant insertion), final restoration (T1 = 3 months later), and at 18-month (T2) and 3-year (T3) follow-ups. The MBL was evaluated with a computerised measuring technique and digital subtraction radiography (DSR) software was used to evaluate radiographic density. Results: At the 3-year follow-up a success rate of 100% in both groups was reported. In the PA group, peri-implant bone resorption was 0.36 mm at T1, 0.43 mm at T2, and 0.55 mm at T3. In the DA group, peri-implant bone resorption was 0.35 mm at T1, 0.33 mm at T2, and 0.34 mm at T3. Statistically significant lower bone losses were found at T2 (0.1 mm) and T3 (0.2 mm) for the DA group. At T3, significantly higher DSR values around implant necks were recorded in the DA group (72 ± 5.0) when compared with the PA group (52 ± 9.5). Conclusions: The current trial suggests that the 'one abutment-one time' concept might be a possible additional strategy in post-extraction immediately restored platform-switched single implants to further minimise peri-implant crestal bone resorption, although a 0.2 mm difference may not have any clinical effect. Additional clinical trials with larger groups of patients should be performed to better investigate this hypothesis. Keywords: bone preservation, definitive abutment, dental implant, immediate loading, platform switching

Purpose: To compare the efficacy of two different techniques for maintaining the space beneath a maxillary lining lifted using a lateral window approach: rigid synthetic resorbable barriers versus granular anorganic bovine bone. Materials and methods: Ten partially edentulous patients having bilaterally 1 to 5 mm of residual bone height and at least 5 mm bone width below the maxillary sinuses, were randomised in a split-mouth study design, to receive a rigid Inion GTR Biodegradable Membrane System barrier without any graft on one side and 100% loosely packed granular Bio-Oss on the contralateral side following a lateral window, two-stage, sinus lift procedure. After 6 months, two or three implants were inserted at each side and submerged for 4 months. Implants were loaded with provisional acrylic prostheses and replaced, after 4 months, by definitive metal-ceramic prostheses cemented with provisional cement. Outcome measures were implant and prosthetic failures, any complication and peri-implant marginal bone level changes assessed by a blinded outcome assessor. All patients were followed up to 1 year after loading. Results: One patient dropped out after implant placement. One distal implant failed at the Inion side just before delivery of the definitive prosthesis, which was cut and maintained as a single crown. Four complications occurred in three patients at Inion sites (two sinus lining perforations, one fracture of the ceramic cusp of the definitive prosthesis, one iatrogenic peri-implantitis) versus two complications at Bio-Oss sites (one sinus lining perforation and one iatrogenic peri-implantitis). There were no differences for failures or complications between groups; however, in one of the patients where a perforation occurred at the Inion site, at implant placement, the sinus was filled two-thirds with soft tissue and the site was retreated with Bio-Oss. There were no statistically significant differences in bone loss between groups. One year after loading, Inion sides lost an average of 1.5 mm of periimplant bone and Bio-Oss sides about 1.7 mm. Conclusions: A bone graft may not be needed to augment atrophic maxillary sinuses since it is sufficient to keep space with a rigid barrier; however, it may be simpler to fill sinuses with a bone substitute than positioning a rigid barrier to maintain space. Keywords: anorganic bovine bone, resorbable barrier, sinus lift

Aim: To evaluate the outcome of dental implants placed in patients with a history of periodontitis. Patients with no or mild history of periodontitis served as controls. Materials and methods: A total of 1727 patients were consecutively treated in four private practices. Patients were divided into three groups according to their initial periodontal conditions assessed with a modified periodontal screening and recording (PSR) index: 630 patients were in the severe periodontitis (SP) group, 839 in the moderate periodontitis (MP) group, and 258 had no periodontitis (NP). Patients requiring periodontal treatment were treated prior to implantation. Various implant systems and procedures were used. In total, 3260 implants and 1707 implantsupported prostheses were placed in the SP group, 2813 implants and 1744 implant-supported prostheses in the MP group, and 647 implants and 424 implant-supported prostheses in the NP group. Mixed implant-tooth supported prostheses (98 prostheses in 89 patients) were not considered. Outcome measures were prosthesis and implant survival. Results: Two-hundred and fifty patients were lost to follow-up 5 years after loading. Regarding prosthesis failures, 13 prostheses could not be placed or failed in 13 patients of the SP group (0.8%), 11 prostheses could not be placed or failed in 9 patients of the MP group (0.7%), and 3 prostheses failed in 3 patients of the NP group (0.9%). For implant failures, 130 (4.5%) implants failed in the SP group, 74 (3.1%) implants failed in the MP group, and 15 (3.0%) implants failed in the NP group. Most of the implant failures (90%) occurred before implant loading. Fitting a logistic regression for early implant failures and total implant failures, taking into account the clustering of implants in patients, there were no statistically significant differences between the three PSR groups (P > 0.05). Conclusions: Owing to the retrospective nature of this study, conclusions need to be interpreted with caution. A previous history of periodontal disease may not have a significant impact on implant failures up to 5 years after loading. Keywords: dental implants, periodontitis, prognosis

Aim: The aim of the present study was to assess retrospectively the survival of narrow-diameter implants (2.5 and 3 mm in diameter) in patients with insufficient bone ridge thickness for placement of standard-diameter implants. Material and methods: Fifty-one patients with 89 inserted narrow-diameter implants (2.5 and 3.0 mm) were included. Patients were treated with one or more narrow-diameter implants between June 2004 and December 2005. The observation period for all included implants was at least 3 years after implant loading. Outcome measures were implant survival, complications and marginal bone level changes evaluated on panoramic radiographs. Results: The mean follow-up period for all implants was 48 months. Only one implant was lost, yielding survival rates of 98.9% and 98.0% for the implant- and subject-based analyses, respectively. Six complications were reported. Twenty-four months after implant insertion, mean bone loss was 1.26 mm (SD 0.51). Conclusions: Narrow-diameter implants can be successfully used to treat narrow bone ridges up to 3 years after loading. Keywords: failure, long-term follow-up, narrow-diameter implants, narrow implants, plasma rich in growth factors (PRGF), survival analysis

Purpose: To evaluate the clinical outcome of maxillary prostheses supported by four immediately loaded zygomatic implants after 1 year of function. Materials and methods: Seventeen patients were consecutively included and followed up to 1 year after prosthetic loading. Patients had severely atrophic maxillae (Cawood and Howell classification C-VI and D-V or D-VI) and were rehabilitated using four immediately loaded zygomatic implants, two in each zygoma bone. Outcome measures were success rates of the prostheses, of the zygomatic implants, complications and oral health-related quality of life (OHRQoL). Results: No patients dropped out. No zygomatic implants were lost, although one implant could not be used because it was placed in an unfavourable position. The orbital cavity was penetrated during the drilling procedure in one patient with no relevant clinical consequences. One patient experienced an infection followed by a fistula in one zygomatic implant, which was successfully treated. The average score from the OHIP-14 questionnaire was 3.4, which is similar to that of the general population. Conclusions: The present study suggests that four immediately loaded zygomatic implants can be used to rehabilitate patients with severely atrophied maxillae. Keywords: atrophic maxilla, immediate loading, zygomatic implants