This article reviews the literature on the outcome of flapless surgery for dental implants in the posterior maxilla. The literature search was carried out in using the keywords: flapless, dental implants and maxilla. A hand search and Medline search were carried out on studies published between 1971 and 2011. The authors included research involving a minimum of 15 dental implants with a follow-up period of 1 year, an outcome measurement of implant survival, but excluded studies involving multiple simultaneous interventions, and studies with missing data. The Cochrane approach for cohort studies and Oxford Centre for Evidence-Based Medicine were applied. Of the 56 published papers selected, 14 papers on the flapless technique showed high overall implant survival rates. The prospective studies yielded 97.01% (95% CI: 90.72–99.0) while retrospective studies or case series illustrated 95.08% (95% CI: 91.0–97.93) survival. The average of intraoperative complications was 6.55% using the flapless procedure. The limited data obtained showed that flapless surgery in posterior maxilla areas could be a viable and predictable treatment method for implant placement. Flapless surgery tends to be more applicable in this area of the mouth. Further long-term clinical controlled studies are needed.
The introduction of osseointegration in 1977 by Brånemark et al. revolutionized oral rehabilitation in partially and fully edentulous patients. This concept was based on the utilization of a mucoperiosteal flap. The flap was designed for the visualization of underlying bone by reflecting the alveolar crest soft tissue for placement and closure with suture on completion of the procedure. This concept implies that implants should be covered by soft tissue to warrant primary stabilization and decrease infection as a standard of care. For many practitioners, the flap technique has remained the mainstay of implant surgery as it allows better visualization, particularly in areas of inadequate bone quantity, and it permits the manipulation of soft tissue in aesthetic regions. Despite their popularity, flap techniques have disadvantages including gingival recession, bone resorption around natural teeth, soft tissue deficiency from flap raising, and negative implant aesthetic outcomes, especially in the anterior maxilla.
Over the last three decades, there have been many modifications to implant flap design, including the flapless surgical technique. In contrast to the flap technique, implant flapless surgery does not require reflection of a mucoperiosteal flap while perforating the alveolar mucosa and bone. Therefore, flapless surgery generates less postoperative bleeding, less discomfort for the patient, surgery time is shorter, and healing time is reduced. The patients heal with minor, or no, swelling. The flapless technique uses rotary burs or a tissue punch to gain access to bone without flap elevation, so the vascular supply and surrounding soft tissue are well preserved. The flapless technique has been well established in immediate extraction and site preservation with minimal complication. With the advance of flapless surgery, the traditional flap method is being challenged because it is being perceived as unnecessary.
Traditionally, flapless surgery has been regarded as having multiple limitations such as: poor control of precise drilling depth due to difficulty in observing the drilling direction of the alveolar bone; inability to preserve keratinized gingiva with a tissue punch perforation; and poor ability to assess the implant point of entry due to the lack of direct vision of the recipient bone. Therefore, it is difficult to correct intraoperative peri-implant defects. This implies that flapless surgery is mainly used for cases where there is sufficient quantity and quality of bone, as well as a decent quantity of keratinized gingiva. Maxilla posterior areas can satisfy these flapless surgery requirements.
Reviewing publications on animal studies aids understanding of flapless surgery and helps to improve the flapless technique. For example, the ‘biological width longitudinal dimension at the buccal aspect were higher in the flap group than in the flapless group’ in minipigs ; ‘flapless surgical implantation into freshly extracted sockets did not aid in the avoidance of alveolar bone resorption and had no influence in the dimensional differences of the alveolar process after tooth extraction in contrasted to the traditional implant placement using mucoperiosteal flaps’ ; and ‘flapless implant surgery can be utilized for the placement dental implants, and the application of a tissue punch larger than the diameter of the implants is not recommended, as it can endanger the result of the implantation process’.
The posterior maxilla is defined as the back part of the upper jaw, anteriorly bounded by the upper canine teeth, posteriorly by the maxillary tuberosities, bucally by buccal mucosa and medially by the palate. The supporting alveolar bone in this area is usually wide enough for implant placement, particularly in the molar region.
Following tooth loss, resorption has been shown to adhere to a predictable pattern: the alveolar labial aspect of the ridge is the main site of resorption, which diminishes first in width then in height. The posterior maxilla has different anatomy and bone quality, and distinctive buccal and palatal resorption patterns. When the maxilla becomes edentulous, its shape changes according to the extent of resorption. The cortical bone in the maxilla becomes thinner and more porous posteriorly in an aged population. Using computed tomography, trabecular bone density varies markedly with potential implant site in the anterior (516 ± 132 Hounsfield units, HU) and posterior (332 ± 136 HU) regions, which may compromise the clinical outcome of dental implants in the posterior maxilla. Fuh et al. indicated that female maxillae showed a smaller amount and a lower density of cancellous bone than male maxillae.
The literature reveals limited and conflicting information concerning dental implant treatment in poor quality bone of the posterior maxilla. Although there is a slightly lower osseointegration success rate, poor quality bone is not an absolute contraindication for dental implant treatment. The anatomical and structural features of the posterior maxilla, such as poor quality and quantity bone due to its proximity to the maxillary sinus, may compromise the clinical outcome of dental implants.
In recent years, the advance of three dimensional (3D) dental imaging, particularly cone beam computed tomography (CBCT), and the associated planning software, used in conjunction with computer generated surgical guides, has allowed more efficient results when using flapless techniques. This has turned flapless implant surgery into a predictable procedure with high success rates if patients are appropriately selected and an appropriate width of bone is available for implant placement. These studies mainly focus on anterior areas, in order to improve aesthetic results, to shorten in surgery time, and to decrease morbidity after surgery. Few studies focus on the posterior areas, especially posterior maxilla areas. There are some benefits for flapless surgery in this area, including: less aesthetic demand; bone resorption pattern resulting in wider width and less undercut; and minimal concern about nerve damage. Therefore, flapless surgery appears to have more applications in the posterior maxilla than in any other area. The difficulties in the posterior maxilla are: less bone density; the position of the sinus; and the difficult access to the mouth. The posterior maxilla has been described as the most difficult and problematic intraoral area confronting the implant practitioner, which may influence the results of flapless surgery.
This article reviews the contemporary literature relating to the outcome (efficiency and effectiveness) and surgical challenges of flapless dental implant surgery in the posterior maxilla and indicates that flapless implant surgery is an acceptable technique in the posterior maxilla.
Materials and methods
A search for English publications was carried out using Medline to search dental journals from 1971 to 2011. Major dental implant journals covering oral and maxillofacial surgery, dental implant, prosthodontics, and periodontics, for a similar period, were searched by hand to find relevant references. The reference search was conducted using a mixture of the following keywords: dental implants, flapless surgery, complications, maxilla, survival, success, efficacy, effectiveness, guided surgery, review.
Clinical human studies published in English in the last 40 years between 1971 and 2011 obtained through the Medline or the hand search were categorized by study types (case report, preclinical, cohort, control clinical trial, review and meta-analysis), and subjects (human versus animal). This review included only human studies of the posterior maxilla with 15 or more implants; expert and clinical opinion publications were excluded. In order to apply the best available evidence gained from the scientific method to clinical decision making, the Oxford Centre for Evidence-Based Medicine was used to weigh the level of evidence in clinical studies.
In this review, conventional implant surgery refers to flap surgical techniques that require elevation of a mucoperiosteal flap for the purpose of implant surgery and implant placement. Flapless implant surgery is defined as a surgical technique utilized to prepare the implant drilling site for surgical placement of the implant without the need to raise a mucoperiosteal flap.
The information was organized into a system of comparison in a table format similar to that suggested by Brodala containing type of study, number of participants, dropouts, follow-up time, mean age, implant case, outcomes (survival), complications and failures. It was assumed that these patients had no adverse medical conditions.
Statistical data management
The data retrieved from the selected papers was managed according to the following methods. The mean values of the survival rates were case weighted to have an even distribution. Ideally, one would limit the sample to studies that use Kaplan–Meier methods to estimate survival and include the results of the few studies that meet the new inclusion criteria. Owing to the limited number of publications available, retrospective studies were included in the review. To improve the validity of these studies, Oxford Centre for Evidence-Based Medicine’s 2001 classification of levels of evidence were used. The studies were organized, reported, and stratified by the levels of evidence.