The aim of this study was to compare success rates in immediate and delayed dental implant placement following guided bone regeneration or onlay bone block ridge augmentation. A systematic review of all studies on this topic was performed. For inclusion, studies had to involve at least five patients, report specific success criteria, and have a minimum follow-up period of 6 months. Studies reporting only the survival rate of implants were excluded. From 287 studies identified, 79 were screened and 13 were included in the analysis. Six studies provided data on simultaneous (immediate) positioning of implants, five studies on delayed positioning, and two studies provided data on both of these approaches. Success rates for implants placed using a simultaneous approach ranged from 61.5% to 100%; success rates for implants placed using a staged approach ranged from 75% to 98%. Even though the current review revealed that there are not many studies reporting data relevant to the analyzed topic, the data obtained suggest that the delayed positioning of implants should be considered more predictable than the immediate positioning. Studies presenting a control group and adopting standardized success criteria are required, and data from this review must be considered indicative.
The dental rehabilitation of partially or totally edentulous patients with osseointegrated oral implants is nowadays one of the most successful methods to restore oral aesthetics and function, with predictable results. However, a minimum amount of bone width and height is an essential prerequisite for the correct placement of oral implants. Thus, unfavourable local conditions due to atrophy, trauma, and periodontal disease, may result in insufficient bone volume or an unfavourable inter-arch relationship, which will not allow the correct and prosthodontically guided positioning of dental implants. For such cases, many different techniques have been developed to reconstruct the deficient alveolar jaws for the placement of dental implants.
Further, the ideal timing of implant placement after dental extraction has been extensively discussed in the literature, and advantages and disadvantages have been attributed to the different protocols : (1) immediate or type 1,when the implant is placed during the same surgical intervention as the dental extraction; (2) early implant placement or type 2, when implants are placed during the early stages of healing (from 4 to 8 weeks); and (3) delayed implant placement or type 3, when implants are placed when the ridge has healed (from 3 to 6 months). The timing of implant placement after reconstruction of atrophic alveolar ridges instead, also remains a controversial topic.
In fact implants can be positioned in conjunction with grafting procedures (one-stage surgery or immediate implant placement) or after a consolidation period (two-stage surgery or delayed implant placement). Although it is difficult to determine a clear indication for immediate or delayed implant placement, the majority of authors suggest immediate implant placement when the residual alveolar bone presents adequate quality and quantity . In fact, the primary stability of dental implants, which is considered to be the essential condition for osseointegration, is closely related to these parameters.
Through the years, many studies proposing the two different approaches have appeared in the scientific literature. According to the authors who support immediate implant placement, the reason is that the resorption of grafted bone over time is not a linear process but most pronounced soon after its transplantation. Those who advocate delayed placement instead, affirm that immediate placement of implants exposes the patient to some risks, such as partial or total loss of the graft in the case of wound dehiscence, membrane or onlay graft exposure and/or infection, and non-integration of implants related to the immediate placement into avascular bone. In fact, when a delayed protocol is performed, it would be possible to place implants in a revascularized graft. Since the regenerative capacity of bone is determined by the presence of vessels, bone marrow, and vital bone surfaces, a delayed approach would permit a better integration of implants (higher values of bone–implant contact) and stability of implants as compared with immediate implant placement.
The aim of this study was to compare, in a systematic manner, publications reporting the success rate of dental implants placed simultaneously or as a second surgery following ridge augmentation by means of guided bone regeneration (GBR) or onlay graft regeneration technique.
Materials and methods
Inclusion and exclusion criteria were defined by the authors, before beginning the study, according to the protocol outlined below.
For inclusion, publications had to be based on human subjects and written in English, and had to analyze the success rate of endosseus implants placed in augmented jaws by means of GBR or onlay graft technique, specifying the type of implant surgery (simultaneous or staged) with the respective results. Every study design (prospective and retrospective) was accepted, but studies had to involve more than five healthy patients and report on implant success with at least 6 months of loading, in order to observe biological complications during function rather than early implant failures.
Publications that reported the same data as reported in later publications by the same authors were not considered. Studies describing only the results of bone augmentation, only the survival rate of implants, and those without any specified success criteria, were excluded. Studies on major maxillofacial reconstruction following tissue resection in the case of tumours and bone defects related to congenital malformations (such as cleft lip and palate or major craniofacial malformations), as well as socket preservation techniques or the treatment of peri-implantitis were not included.
The following augmentation procedures were considered: (1) GBR, according to the biological principle of a protected space, created with a resorbable or non-resorbable barrier membrane over the area to be augmented, in order to stabilize the blood clot and to exclude soft tissue penetration ; and (2) bone block grafts, according to an onlay graft technique, used alone or associated with particulate bone, and covered or not by a resorbable membrane.
Even if studies did not adopt the same criteria, implant success was the main outcome, and it had to be well-specified in the publications for inclusion. However, when possible, the following clinical and radiographic criteria were utilized to define implant success based on a combination of the success criteria previously defined by Albrektsson et al. and adapted by Buser et al. : absence of mobility, absence of persistent subjective complaints (pain, foreign body sensation and/or dysesthesia), absence of recurrent peri-implant infection with suppuration, absence of a continuous radiolucency around the implant, and absence of a pocket probing depth (PPD) >5 mm. Even if during the first year of function 1.5 mm of vertical bone resorption was accepted, after that time, the annual vertical bone loss should not exceed 0.2 mm (mesially or distally).
The search strategy incorporated a search of electronic databases, supplemented by cross-checking of the bibliographies of relevant review articles. A search on MEDLINE and EMBASE was conducted up to January 2010 in accordance with the Preferred Reporting Items Systematic review and Meta-Analyses (PRISMA) statement, using a combination of medical subject heading (MeSH) terms and text words: “Implants”, “Dental Implants”, “Osseointegrated Implants”, “Oral Implants”, “Implant Supported Prosthesis”, “Transmucosal Implants”, “Alveolar Ridge Augmentation”, “Lateral Ridge Augmentation”, “Alveolar Ridge Atrophy”, “Regeneration”, “Bone Regeneration”, “Guided Bone Regeneration”, “Guided Tissue Regeneration”, “Barrier Membranes”, “Membranes”, “Bone Substitutes”, “Autogenous Bone Grafts”, “Allograft”, “Xenograft”, “Calvarial Bone Graft”, “Iliac Crest Graft”, “Chin Bone Grafts”, “Onlay Bone Grafts”, “Implant Outcomes”, “Success Rate”, “Simultaneous Positioning”, “Staged Approach”, “Immediate”, “Delayed”. To exclude some non-relevant studies, “NOT (“trauma” OR “tumour” OR “injuries” OR “cancer” OR “animal”)” was added to the search.
A three-stage ( Fig. 1 ) screening process was performed independently by two reviewers (MC and AM).
At first, all the titles were screened to eliminate irrelevant publications, review articles, and animal studies; then, all abstracts of publications selected during the first screening were analyzed, and studies were excluded on the basis of the number of patients, the intervention, and the outcome characteristics. In the last stage, through an analysis of the whole selected full texts, study eligibility was based on the predetermined inclusion and exclusion criteria. Any disagreements between the two reviewers were resolved after additional discussion with a third reviewer (CA). The inter-reviewer reliability of the data extraction was calculated by determining the percentage of agreement and the correlation coefficients with a kappa analysis.
A table was created to organize the data from all the included studies ( Table 1 ) and the results were discussed.
|Ref.||Study design||Year||City||Type of augmentation||Number of patients (smokers)||Mean age, years||Implants (number/type/surface)||Area of implants||Post-loading follow-up||Restorative design||Approach||Success rate of implants||Survival rate of implants|
|Onlay from calvaria||6 (>15 cigarettes/day excluded)||56||23/ITI (Nobel Biocare)/surface not reported||Mandible||1–3 years||Overdentures||Delayed||95.7%||100%|
|Onlay from mandibular ramus||8 (>15 cigarettes/day excluded)||41||19/Straumann/surface not reported||Mandible||24–48 months||Single crowns||Delayed||89.5%||100%|
|Vertical GBR||11 (all but one <10 cigarettes/day)||48||32/Osseotite (BIOMET 3i)/surface not reported||Mandible||1 year||NR||Immediate||93.75%||93.75%|
|Vertical GBR||17 (>10 cigarettes/day excluded)||39.6||20/Osteofix/surface not reported||NR||5 years||Single crowns||Immediate||90%||100%|
|Van der Meij||CS||2005||Alkmaar
|Onlay from iliac crest||17 (no data about smoking)||56||34/Frialit/surface not reported||Mandible||From 6 months to 7 years||Overdentures||Immediate||88.2%||–|
|Vertical GBR||11 (>15 cigarettes/day excluded)||NR||25/Brånemark/surface not reported||10 maxilla
|From 29 to 41 months||NR||13 immediate
|Onlay from iliac crest||30 (no data about smoking)||53||177/NR/surface not reported||Maxilla||10 years||Full arch screw bridges||Immediate||72.8%||–|
|Horizontal GBR||40 (no data about smoking)||NR||61/ITI/surface not reported||NR||5 years||Single crowns or fixed partial dentures||Delayed||98.3%||100%|
|GBR||14 (no smokers)||48||14/NR/surface not reported||13 maxilla
|GBR and onlay from intra-oral sites, calvaria, iliac crest||15 (heavy smokers excluded)||NR||30/18 ITI; 12 Brånemark/surface not reported||21 maxilla
|From 18 to 36 months||NR||Delayed||93.3%||100%|
|GBR||82 (no data about smoking)||21–61||85/Frialit/surface not reported||39 maxilla
|24 months||Single crowns cemented
Single crowns screw
|Onlay from ilium and cranium||NR (no data about smoking)||NR||175/NR/surface not reported||Maxilla and mandible||From 12 months||NR||65 immediate
|Isaksson||CS||1992||NR||Onlay from iliac crest||8 (all heavy smokers apart from one patient)||NR||46/Brånemark/surface not reported||Maxilla||32–64 months||Implant supported partial dentures||Immediate||83%||–|