Year : 2008 | Volume
: 19 | Issue : 4 | Page : 320--325
In vivo evaluation of crestal bone heights following implant placement with 'flapless' and 'with-flap' techniques in sites of immediately loaded implants
Shibu Job, Vinaya Bhat, E Munirathnam Naidu
Department of Prosthodontics, Meenakshi Ammal Dental College, Chennai, India
Department of Prosthodontics, Meenakshi Ammal Dental College, Chennai
Purpose: To evaluate and compare the changes in crestal bone height around implants placed with flapless surgery and with-flap surgery.
Materials and Methods: Ten implants were placed in six patients - five using flapless and five using with-flap techniques. Single-piece root-form implants and a one-stage approach with immediate nonfunctional loading protocol were used. The change in heights of crestal bone was measured on standardized digital periapical radiographs taken at 0, 1, and 3 months.
Results: On mesial side, the mean change from months 0-1, months 1-3, and months 0-3 for flapless method was significantly lower than with-flap method [0.01-0.06 mm for flapless and 0.13-0.40 mm for with-flap ( P = 0.01)]. On the distal side, the mean change from months 0-1, months 1-3, and months 0-3 for flapless method was significantly lower than with-flap method [0.02-0.05 mm for flapless and 0.09-0.30 mm for with-flap ( P = 0.01)].
Conclusions: During the three-month period, reduction of crestal bone height around the implants placed with flapless surgery (0.06 mm) was not statistically significant, while the reduction of crestal bone height around the implants placed using with-flap surgery (0.4 mm) was statistically significant. Comparitively, flapless approach showed lesser crestal bone height reduction, which was statistically significant.
|How to cite this article:|
Job S, Bhat V, Naidu E M. In vivo evaluation of crestal bone heights following implant placement with 'flapless' and 'with-flap' techniques in sites of immediately loaded implants.Indian J Dent Res 2008;19:320-325
|How to cite this URL:|
Job S, Bhat V, Naidu E M. In vivo evaluation of crestal bone heights following implant placement with 'flapless' and 'with-flap' techniques in sites of immediately loaded implants. Indian J Dent Res [serial online] 2008 [cited 2021 Oct 18 ];19:320-325
Available from: https://www.ijdr.in/text.asp?2008/19/4/320/44535
Recently, single-stage, immediate loading of implants are done using flapless surgery.  Single-stage system involves one-piece implant, comprising of implant and abutment manufactured as one-piece or placement of two-piece implant system in one surgical procedure.  Immediate loading suggests delivering a prosthesis at the time of implant placement, or within 48 hours following surgery. 
In the flapless surgical technique, a round tissue punch is used to remove the soft tissue on the crestal bone at the implant site, ,,, or the osteotomy is directly initiated through the soft tissue. , Roman  recommended this technique to minimize interproximal crestal bone loss and possible loss of papillae, but Campelo and Camara  advocated elevating a flap, when the esthetic appearance of the soft tissue is critical, since it can be manipulated to its final desirable position. However, it has been found that implants placed with flap reflection, often lead to bone resorption. 
Recently, one experimental study on animals showed that the flapless implant placement had positive response on bone height and osseointegration compared to with-flap method.  However, there is no documentation on such studies carried out on human subjects.
The aim of this study was to evaluate and compare the changes in crestal bone heights around implants placed with flapless and with-flap surgeries. The hypothesis was that flapless surgery results in lesser crestal bone reduction compared to with-flap surgery, and that it is clinically a predictable procedure.
Materials and Methods
Patients, aged between 35 and 55 years, were selected and their informed consents were obtained. A total of ten implants were placed - five using flapless and five using with-flap techniques. One-stage, single-piece root-form implants were selected considering the available bone measurements. The implants were indigenously manufactured in various dimensions [Figure 1]. The implants were of lengths 10 mm, 12 mm, and 15 mm (from crest module to apex), and diameters of 3.3 mm at the apex and 3.8 mm at the first-thread area. The surface of the fixture was treated by sandblasting and consisted of standard V threads, the number of which ranged from 5-8 depending on the length of the implant. The abutment was cylindrical in shape with a length of 5.5 mm and width of 3.5 mm at the implant-abutment junction and 2.5 mm at the coronal end. A flat surface was present on one side of the abutment as antirotational feature. The crest module was funnel shaped with the widest diameter of 4.7 mm.
Routine pre-surgical protocol was followed for each patient. The site for flapless placement of the implant was selected based on bone width of at least 4.5 mm without undercuts of >15 o , and keratinized tissue of at least 5 mm.  Initial penetration into the bone was achieved with no. 6 round bur directly through the soft tissue [Figure 2]. Drilling was done using progressively larger drills. The implants were placed using a wrench.
The control site implants were placed after elevating a full thickness flap [Figure 3]. Nonresorbable silk sutures (3-0) were used to approximate the flaps.
All the abutments were prepared. The provisionals were cemented for immediate loading. 
Crestal bone height was evaluated with a series of digital periapical radiographs at 0, 1, and 3 months. Radiovisiograph (RVG) with software, SOPRO, was used for this purpose including measurement of crestal bone height to resolution level up to 0.00 mm. The methodology of obtaining radiographs was standardized with long cone paralleling technique using film holder customized for each patient using putty indices [Figure 4]. The patient's position was standardized with the upper arch parallel to, and midsagittal plane perpendicular to the floor. The finish line of the abutment was taken as the reference point. The distance from the finish line to the crest of the bone where it contacted the implant on the proximal sides was measured [Figure 5A-C] and [Figure 6A-C]. Magnification factor was calculated using the standard formula.
To determine the accuracy of standardization, three radiographs were printed on separate transparent sheets [Figure 7]. Two points were marked on the implant outline on all the prints. Sheets were superimposed to check the outlines of each implant for accuracy [Figure 8].
Values were subjected to statistical analyses using Mann-Whitney U-test and Wilcoxon matched-pairs signed ranks test. Also, the rate of change of bone height, if any, within each design study was calculated.
Results and Discussion
For implant placement, several flap designs have been published in the past. Han et al.,  described two types of incisions - crestal and remote - and Sclar AG  advocated three designs such as resective contouring, papilla regeneration, and lateral flap advancement to maintain adequate keratinized tissue around implants. Roman  compared the effect of two flap designs namely: widely mobilized flap and limited flap design, on interproximal crestal bone loss. Rosenquist  advised excision using punch technique, cervical folding of the flap, and apically repositioned flap for the second-stage surgery. Also, coronally repositioned flap, multiple C incisions and a large coronally repositioned flap, and buccally repositioned flap with approximal pedicles were used to save or create papilla. Cranin , advised that incision be made at the crest within the linea alba. Takei et al.,  presented flap design for preserving interdental papilla.
Flap elevation permits easy access by the operator and visibility of the planned site. It is considered advantageous when esthetics of the soft tissue is critical, since it can be manipulated to a desirable position.  Tissue augmentation can be predictably achieved around a healing abutment at the time of implant placement or second-stage surgery.
However, when the implants are placed with flaps, there generally is bone resorption that is related to its thickness at the site.  Van der Zee et al.,  in their study on effect of flap reflection on gingiva and bone, following guided bone regeneration found that there was statistically significant gingival recession and bone resorption 12 months after surgery.
The flapless procedure involves either accessing the bone by punching out a small amount of soft tissue required for osteotomy preparation ,,, or preparing the osteotomy directly through soft tissue. ,
In this approach, surgical trauma is minimal; hence, related postoperative pain and discomfort are greatly minimized. Study by Fortin et al.,  showed that pain decreased faster with the flapless procedure and the number of patients who felt no pain was higher with the same procedure. Furthermore, the intact periosteum maintains a better blood supply reducing the likelihood of early bone resorption. ,
In addition, it maintains the soft tissue architecture and hard tissue volume, decreases the surgical time, and accelerates recuperation, allowing the patient to resume normal oral hygiene procedures immediately.  Also, a second surgical procedure to place the abutment and for adjusting the mucosa is eliminated. Possibility of using the abutment as a temporary device to aid in supporting the prosthesis during the initial healing phase is enhanced. In effect, the total management time, number of visits, and the materials required are reduced. 
In the past, several studies indicating resorption of bone following elevation of mucoperiosteal flap have been done. But literature lacks studies comparing the crestal bone height using flapless and with-flap surgical techniques. As the amount and quality of bone are critical for osseointegration, it was appropriate to study the change in crestal bone height with these techniques.
Bone height was evaluated using standardized digital periapical radiographs in conformation with other studies. ,,,, Even though histometry serves as the gold standard, a study by Hermann et al.,  has shown that the precision of the radiographs was within 0.1 mm of the histometry in 73.4% and between 0.1 and 0.2 mm in 15.9% of the evaluations.
The present study showed that on both proximal sides, the mean change from months 0-1, months 1-3, and months 0-3 for flapless method was significantly lower than with-flap method (0.01-0.06 mm against 0.09-0.40 mm) [Table 1] and [Table 2]. This indicates that the loss of bone during the three-month period was significantly lower with flapless method compared to with-flap method. Therefore, the results of the present study confirms the hypothesis that flapless surgical procedures result in lesser crestal bone reduction compared to surgeries where mucoperiosteal flap is elevated. Wood et al.,  reported bone loss ranging from 0.23-1.60 mm four to six months following flap elevation.
Present study also showed that among different time intervals, the mean change from months 0-1, months 1-3, and months 0-3 for flapless method was not statistically significant [Table 3] and [Table 4]. This means that the rate of loss of bone around implants placed using flapless method was not clinically significant.
However, the mean change in crestal bone height at different time intervals from months 0-1, months 1-3, and months 0-3 for with-flap method was statistically significant [Table 5] and [Table 6]. This shows that there was significant loss of bone around implants placed using with-flap technique unlike in flapless method wherein it remained stable over a period of 3 months. This significant reduction is clinically relevant when considering the amount of bone required for initial stability and support of the soft tissue.
When teeth are present, blood supply to the bone comes from three different paths: from the periodontal ligament, from the connective tissue above the periosteum, and from within the bone.  When a tooth is lost, periodontal supply disappears; blood comes only from soft tissue and bone. When soft tissue flaps are reflected, supply from the soft tissue is removed, leaving poorly vascularized cortical bone without a part of its vascular supply, resulting in bone resorption. This may lead to long-term esthetic compromise by the effect of the distance from the contact point to the crest of the bone in the absence of interdental papillae.  Following loss of the interdental papillae, the interproximal root surface of the tooth adjacent to implants may become exposed causing sensitivity and the implant itself may get exposed. This indicates the significance of maintenance of the soft tissue configuration around the implants.
In a flapless technique, the intact blood supply from soft tissue facilitates maintenance of nutrition, which is a critical factor in preventing initial bone loss around the implant. This helps in maintaining the soft tissue contour for esthetic emergence profile.
However, flapless implant placement generally is a 'blind' procedure and care must be taken during surgery. , Angulation of the implants is critical to avoid perforation of cortical plates, especially the lingual in mandibular molar area and the labial in maxilla.
Another concern regarding flapless technique is the presumption that some amount of epithelial tissue could be carried to the osteotomy site affecting osseointegration. But an animal study by Becker et al.,  showed no epithelial or connective tissue residues within the histologic sections in implant sites placed with flapless technique.
Even though the flapless technique is a 'blind' procedure, accurate implant placement and angulations could be achieved with the help of sound knowledge of the anatomy of the site, meticulous diagnostic procedures, and a diligent surgical technique. Jeong et al.,  in 2007 conducted a study in six mongrel dogs to explain the effect of flapless technique on the crestal bone loss and osseointegration. This study, claimed to be the first of its kind in this subject, supported the advantages of flapless surgery over with-flap implant placement. Flapless technique improved both, the osseointegration and the bone height around the implants.
The present study involved human subjects, which to our knowledge, is a unique experimental design to determine the effect of flapless surgery on crestal bone loss. Data obtained in this study also support that flapless method is more effective than with-flap surgery in improving the implant anchorage. Considering the advantages of this technique regarding the initial stable crestal bone level, it can be recommended as the method for all single-stage implant placements with suitable bone dimensions in future. However, the limitations of the study include small number of samples and short observational period. Therefore, long-term studies with more number of samples are suggested.
Within the limitations of the study, it can be concluded that reduction of crestal bone height was seen in both flapless and with-flap techniques. The change in crestal bone height observed in flapless group was not statistically significant, while the reduction in crestal bone height found in with-flap group was statistically significant; And when the change in crestal bone height was compared, the flapless approach showed statistically significant lesser reduction.
We would like to express our deepest gratitude to Dr. G. Sivagami, Professor and Head, Department of Prosthodontics, Meenakshi Ammal Dental College, Chennai, and Dr. K. Chandrasekharan Nair, Professor, Department of Prosthodontics, AECS Maaruti College of Dental Sciences, Bangalore, for their critical evaluation, unwavering guidance, and immeasurable encouragement.
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