Immediate Versus Delayed Loading

Five-Year Follow-up of Wide-Diameter Implants Placed in Fresh Molar Extraction Sockets in the Mandible: Immediate Versus Delayed Loading Loris Prosper, MD, DDS1/Roberto Crespi, MD, MS1/Edoardo Valenti, DDS2/ Paolo Capparé, MD2/Enrico Gherlone, MD, DDS, PhD3

Purpose: The aim of this study was to compare the long-term success rates of wide-diameter implants in the mandibular molar region placed immediately after extraction and loaded either immediately or after a 3-month healing period. Materials and Methods: In 71 patients, 120 implants were positioned immediately after tooth extraction; 60 implants (immediate loading group) were loaded immediately and 60 were loaded after 3 months (delayed loading group). Radiographic examinations were made at baseline and at 1, 2, 3, 4, and 5 years after implant placement. Results: After 5 years, a survival rate of 96.67% was reported for all implants (failure rate, 3.33%). Four implants were lost, two from the immediate loading group and two from the delayed loading group. There were no patient dropouts in either group. Conclusions: Wide-diameter implants placed in fresh extraction sockets and loaded immediately or after a delay showed no significant clinical or radiographic differences after 5 years. INT J ORAL MAXILLOFAC IMPLANTS 2010;25:607–612 Key words: extraction sockets, immediate loading, wide-diameter dental implants

o preserve alveolar bone from resorption during healing, various authors 1–3 have placed dental implants into fresh extraction sockets, with good results. Covani et al 4 analyzed bone remodeling around 20 implants placed immediately after extraction; they observed a healing pattern by new bone apposition around the implant neck, with horizontal and vertical bone resorption. The vertical bone resorption, observed at buccal sites, was not associated with any negative esthetic implications. Furthermore, to maintain an excellent esthetic profile of the soft tissues around an implant-prosthetic restoration, many authors5–8 have performed immediate loading (occlusal loading applied to provisional

T

1Clinical

Professor, Vita-Salute San Raffaele University and Department of Dentistry, San Raffaele Scientific Institute, Milan, Italy. 2Clinician, Department of Dentistry, San Raffaele Scientific Institute, Milan, Italy. 3Full Professor and Chairman, Department of Dentistry, San Raffaele Scientific Institute, Milan, Italy. Correspondence to: Dr Roberto Crespi, Department of Dentistry, San Raffaele Scientific Institute, Via Olgettina 58, 20132 Milano, Italy. Email: [email protected]

crowns positioned immediately on implants) on implants placed in fresh extraction sockets in anterior (premolar to premolar) regions. A survival rate of 100%, with minimal crestal bone loss, was reported.5–8 However, in mandibular molar sites, some anatomic limits, such as reduced bone height or width, can prevent implant placement in both edentulous ridges and in fresh sockets. Placement of implants in the interradicular bone of fresh molar sockets, gaps of different size within the confines of the residual alveolar margins may interfere with the bone remodeling process. Calibrated implant burs can be used to perform an osteotomy in the interradicular bone at the correct buccolingual width for ideal implant placement, but the mesiodistal dimensions of a mandibular molar exceed that of most standard implants (3.75 to 4 mm), inducing the possibility of functional overload that would result in implant failure. Another result of these dimensional discrepancies affecting the restoration of molars with standard implants is unfavorable marginal contours that may compromise hygiene maintenance and esthetic results. Although initially higher failure rates for wide-diameter implants were reported,9,10 recently improved surgical procedures, new implant designs, and new microsurfaces have demonstrated that wide implant diameter and lower survival rates are not related.11–14 The International Journal of Oral & Maxillofacial Implants 607

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Features related to wider implant platforms, such as stronger screws, higher torque forces applied to retaining screws, larger hex designs, and octagonal configurations, have helped improve component implant strength.15 The wide-diameter implant16 may better bear the occlusal loading in molar areas, allowing for higher mechanical stability, as compared to standard 3.75-mm-diameter implants. The use of larger-diameter implants in fresh molar sockets may reduce the anatomic discrepancy between the alveolus and implant diameter such that the implant almost completely fills the postextraction defect, with increased stability and prognosis as a result. Consequently, the aim of the present study was to compare the marginal bone levels around immediate and delayed loaded single wide-diameter (6.5 and 7.5 mm) implants placed in fresh extraction sockets in the mandibular molar region.

MATERIALS AND METHODS Patient Selection Between October 2003 and April 2004, 71 patients (36 women and 35 men with a mean age of 58.3 years [range, 26 to 72 years]) were included in this study. All selected patients required extractions of first or second mandibular molars for root fractures, caries, endodontic lesions, or periodontal disease and were randomly assigned to one of the two groups. One hundred twenty implants were positioned immediately after tooth extraction. Sixty implants were loaded immediately (immediate loading group [ILG]) and 60 implants were loaded after 3 months (delayed loading group [DLG]). The following inclusion criteria were adopted for each patient: all patients were in good health without chronic systemic disease, all bony walls of the alveolus were present, and the alveolar ridge was at least 10-mm high. Exclusion criteria were: presence of dehiscence or fenestration of the residual bony walls, coagulation disorders, presence of signs of acute infection around alveolar bone at the surgical site, heavy smoker (more than ten cigarettes per day), alcohol or drug abuse, bruxism. The local ethical committee approved the study, and all patients gave written informed consent for immediate implant loading. The patients included in this clinical study were treated by one oral surgeon and one prosthetic specialist in the Department of Dentistry, San Raffaele Hospital, Milan, Italy.

Surgical Protocol One hour prior to surgery the patients received 1 g amoxicillin; they continued taking amoxicillin 1 g 608 Volume 25, Number 3, 2010

twice a day for a week after surgery. Surgery was performed under local anesthesia (optocaine 20 mg/mL with adrenaline 1:80,000, Molteni Dental). One hundred twenty mandibular molars were extracted in 71 patients, with socket integrity carefully maintained. All mandibular multirooted molars to be removed were hemisected, the roots were removed carefully to preserve interradicular bone, and the sockets were debrided. No sites showed fenestration of dehiscence of the bone walls, with similar bone levels all around the socket. The trephine bur was inserted into the interradicular bone to engage the lateral wall of the most apical extent of the implant site preparation, according to the instructions provided by the manufacturer (Winsix)17,18 (Fig 1). After the osteotomy was completed, the implant was inserted to a depth that would ensure that the roughened surface was at or below the expected height of the alveolar bone and the platform was positioned at the level of the buccal bone crest. The threaded body flared in the bone walls to anchor the implant. All implants used in this study were of sandblasted commercially pure titanium (Bioactive Covering, Winsix) in the form of a self-threading cylindric screw (Magnum Implants, Winsix), with a length of 9, 11, or 13 mm and a diameter of 6.5 or 7.5 mm. A collagen sponge was positioned into any residual extraction socket defects. The buccal vertical releasing incisions were extended horizontally as necessary, in conjunction with the partial-thickness flaps, to provide greater flap mobility.

Prosthetic Protocol In the ILG, after surgery, single-tooth prefabricated provisional acrylic resin crowns were placed, adapted with acrylic resin along margins of the abutment, and attached with temporary cement (Temp Bond, Kerr Manufacturing). Provisional crowns were placed in full contact in centric occlusion, but the occlusal surfaces were flattened to avoid horizontal relations. The patients followed a soft diet for 2 months. The implants of both groups were restored with single porcelain metal crowns 3 months after placement (Fig 2a). The implants were followed for 5 years after loading and assessed by the criteria of Albrektsson et al.19

Follow-up Protocol Follow-up visits were performed by a dental hygienist two times a year after implant insertion. The following clinical parameters were checked: plaque scores,20 Bleeding Index (registered on four surfaces on each implant21), pain, occlusion, and prosthesis mobility. Success criteria for implant survival were: implant stability, absence of radiolucency around the implants, no mucosal suppuration, and no pain.

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Fig 1a Preoperative radiograph of the mandibular left first molar. A vertical radicular fracture was present.

Fig 1b Clinical aspect of the alveolar gingiva after tooth extraction.

Fig 1c  Preparation of implant site with trephine bur engaging inter radicular bone.

Fig 1d Clinical aspect of implant in the fresh socket.

Fig 1e Periapical radio graph of the implant immediately after placement into the fresh extraction socket.

Fig 2a Definitive restoration.

Fig 2b Postoperative periapical radiograph of implant after 2 months.

Fig 3a Postoperative periapical radiograph of implant after 2 years.

Fig 3b Postoperative periapical radiograph of implant after 5 years.

Intraoral digital radiographic examinations (Schick CDR, Schick Technologies) were made at baseline and at 1, 2, 3, 4, and 5 years after implant placement (Figs 2b and 3). The periapical radiographs were taken perpendicular to the long axis of the implant with a long-cone parallel technique using an occlusal template, so that the marginal bone levels could be measured. The radiographic template was customized to maintain the original angle of the film and beam. A blinded radiologist measured the changes in marginal bone height over time. The distance between the platform of the implant and the most coronal point of contact between the bone and the mesial and distal sites of implants was considered. The difference in bone levels was measured by software

(Schick CDR, Schick Technologies). For each implant, mesial, distal, and mean bone loss was calculated at baseline, 1 year, and 5 years after implant placement.

Statistics Computer software was used for all statistical analyses (SPSS 11.5.0, SPSS). All values are presented as means ± standard deviations. The mean values for marginal bone loss at 1 year and 5 years, between ILG and DLG, were compared. The implant was considered as a statistical unit. The comparisons were made for successful implant (58 for immediate loading and 58 for delayed loading group). A Student t test was performed, and P values < .05 were considered significant.

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Table 1 Implant Dimensions and Locations for Immediate Loading Group Implant dimensions L first (mm) molar 7.5 ⫻ 9 7.5 ⫻ 11 7.5 ⫻ 13 6.5 ⫻ 9 6.5 ⫻ 11 6.5 ⫻ 13 Total

2 8 1 4 2 0 17

Location L second molar 2 5 1 1 3 1 13

R first molar 4 4 2 2 4 2 18

R second molar Total 1 5 1 1 3 1 12

9 22 5 8 12 4 60

Table 3 Radiographic Bone Levels (Means ± SDs) at 5 Years After Implant Placement Implant protocol ILG DLG

1y

5y

–0.24 ± 0.12 mm –0.17 ± 0.11 mm

–1.31 ± 0.44 mm –1.01 ± 0.59 mm

Table 2 Implant Dimensions and Locations for Delayed Loading Group Implant dimensions L first (mm) molar 7.5 ⫻ 9 7.5 ⫻ 11 7.5 ⫻ 13 6.5 ⫻ 9 6.5 ⫻ 11 6.5 ⫻ 13 Total

3 6 0 3 4 1 17

Location L second molar 1 3 0 3 5 1 13

R first molar 4 4 0 4 3 3 18

R second molar Total 2 5 1 0 2 2 12

10 18 1 10 14 7 60

Radiographic Results Radiographic results were reported at 1 year and 5 years after implant placement (Table 3). No statistically significant differences between ILG and DLG for mean marginal bone loss were found (P > .05).

DISCUSSION RESULTS The positions and dimensions of all implants placed are shown in Table 1 for ILG and Table 2 for DLG. No regenerative procedures were performed in any sites, and no patients dropped out of the study.

Surgical and Prosthetic Results After 5 years, a survival rate of 96.67% was reported for all implants (failure rate 3.33%). Four implants were lost, two implants from the ILG and two from the DLG. For the ILG, two implants (6.5 ⫻ 11 mm and 7.5 ⫻ 11mm) were lost in the same patient, in the mandibular left first and second molar positions 30 days after placement. For the DLG, two implants (6.5 ⫻ 11 mm and 7.5 ⫻ 9 mm) were lost in different patients, in the right and left first molar positions; the first was lost 15 days after placement and the second was lost after placement of the provisional crown. There was suitable wound healing around the provisional abutments, with satisfactory adaptation to the provisional crown. Minor swelling of the gingival mucosa was apparent soon after the surgical procedures, but no mucositis or flap dehiscences with suppuration were found. The definitive ceramicfused-to-metal restorations were cemented 3 months after implant placement.

Clinical Findings Plaque accumulation at baseline was 5%; after 5 years, it was 8%. The Bleeding Index at baseline was 6%, and 5 years later a value of 8% was registered. No pain or mobility of the definitive prosthesis was registered. 610 Volume 25, Number 3, 2010

Because it has been hypothesized that dense bone in posterior mandibles might benefit from careful surgery and a longer remodeling time, the authors sought to examine the influences of surgical technique and healing time following placement of widediameter implants22 in fresh molar sockets in this study. The clinical and radiographic results were similar in both ILG and DLG, which both reported a survival rate of 96.67% for all implants after 5 years. These results may be explained by the careful assessment of residual alveolar bone for its ability to stabilize an implant of large dimensions in the desired prosthetic position. The positioned implant must achieve primary stability at the time of mandibular molar extraction in an ideal restorative position regarding force distribution and patient plaque control. In fresh extraction sockets, the width of the gap between the implant surface and bone walls at the time of implant placement represents a critical point for bone healing because, as the gap widens, the amount of bone-to-implant contact decreases and the point of the highest bone-to-implant contact shifts apically.23 Botticelli et al,24 in a study of the healing of marginal defects that occurred at implants placed in fresh extraction sockets in dogs, showed that, in sites in which teeth with an intact periodontium are present mesial and distal to the extraction socket, the height of the proximal socket walls may be retained since the reduction of the crestal bone will be limited to the buccal walls of the recipient site. Wide-diameter implants reduce the anatomic buccolingual discrepancies that would have evolved when

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substituting a molar with a standard-diameter implant in fresh sockets, since horizontal bone remodeling in the buccolingual direction was observed after immediate placement of implants.3 The coronal bone remodeling around immediate implants showed a healing pattern with new bone apposition around the neck of the implants and, at the same time, bone resorption with horizontal width reduction of the bone ridge. The use of 6.5- and 7.5-mm-diameter implants made it possible to increase stability and to almost completely fill postextraction defects. These wider implants can better withstand occlusal loading in molar areas, resulting in higher mechanical stability for immediate loading. Peñarrocha-Diego et al25 compared wide-diameter implants placed in mature bone versus implants placed in postextraction bone. The study examined 162 implants placed in 100 patients, with 130 placed in mature bone and 32 in postextraction bone. None of the implants placed in postextraction bone failed while, in mature bone, the success rate was 96.9%. The placement of wide-diameter implants in recent molar extraction sites has been shown to provide results similar to the placement of implants in healed mature bone after 12 months of follow-up. The ability to place implants in an ideal anatomic position at the time of mandibular molar extraction, with or without concomitant regenerative therapy, represents a key guideline for this treatment procedure.26 Schincaglia et al,27 in a prospective randomized controlled trial, compared single implant-supported mandibular molar restorations using either an immediate or a delayed loading protocol. No implants were lost in the delayed loading group, whereas one implant failed in the immediate loading group. No differences between groups were observed in relation to implant length or insertion torque. The mean radiographic bone level after 1 year of function was significantly less for immediately loaded implants. Cafiero et al 28 immediately placed 82 tapered implants with an endosseous diameter of 4.8 mm and a shoulder diameter of 6.5 mm into fresh molar sockets. All implants healed uneventfully, yielding a survival rate of 100% and healthy soft tissue conditions after 12 months. Statistically significant changes (P < .0001) in radiographic mesial and distal crestal bone levels were observed from baseline to the 12month follow-up. The success rate reported in clinical studies probably depends on an osseointegration process that occurs without initial bone contact, as observed in an in vivo study in mini-pigs.29 After tooth extractions, implants were immediately inserted, with a gap of 3 to 6 mm left circumferentially between bone and implant. At the coronal level, bone-implant contact

was close to 0% at day 7 but had increased to 60% at day 60 after surgery, and the epithelium never migrated more than 1.8 mm apical to the top of the alveolar bone level. Within the limits of the present study, the results showed no significant clinical and radiographic differences between immediate and delayed loading of wide-diameter implants placed in fresh extraction sockets after 5 years. However, further clinical studies are mandatory to improve the parameters of the surgical procedure and soft tissue management and to develop more suitable macrotextures and microtextures of dental implants for similar indications.

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14. Hulting-Mordenfeld M, Johansson A, Hedin M, Billstrom C, Fyrberg K. A retrospective clinical study of wide-diameter implants used in posterior edentulous areas. Int J Oral Maxillofac Implants 2004;19:387–392. 15. Schwartz-Arad D, Grossman Y, Chaushu G. The clinical effectiveness of implants placed immediately into fresh extraction sites of molar teeth. J Periodontol 2000;71:839–844. 16. Matsushita Y, Kitoh M, Mizuta K, Ikeda H, Suetsugu T. Twodimensional FEM analysis of hydroxyapatite implants: Diameter effects on stress distribution. J Oral implantol 1990;16:6–11. 17. Wong K. Immediate implantation of endosseous dental implants in the posterior maxilla and anatomic advantages for this region: A case report. Int J Oral Maxillofac Implants 1996; 11:529–533. 18. Prosper L, Gherlone EF, Redaelli S, Quaranta M. Four-year followup of larger-diameter implants placed in fresh extraction sockets using a resorbable membrane or a resorbable alloplastic material. Int J Oral Maxillofac Implants 2003;18:856–864. 19. Albrektsson T, Zarb G, Worthington P, Eiksson RA. The longterm efficacy of currently used dental implants: A review and proposed criteria of success. Int J Oral Maxillofac Implants 1986;1:11–25. 20. Mombelli A, Lang NP. Clinical parameters for the evaluation of dental implants. Periodontol 2000 1994;4:81–88. 21. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following single-tooth extraction: A clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent 2003;23:313–323. 22. Polizzi G, Rangert B, Lekholm U, Gualini F, Lindström H. Brånemark system wide platform implants for single molar replacement: Clinical evaluation of prospective and retrospective materials. Clin Implant Dent Relat Res 2000;2:61–69.

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23. Akimoto K, Becker W, Persson R, Baker DA, Roher MD, O’Neal RB. Evaluation of titanium implants placed into simulated extraction sockets: A study in dogs. Int J Oral Maxillofac Implants 1999;14:351–360. 24. Botticelli D, Persson LG, Lindhe J, Berglundh T. Bone tissue formation adjacent to implants placed in fresh extraction sockets: An experimental study in dogs. Clin Oral Implants Res 2006;17:351–358. 25. Peñarrocha-Diego M, Carrillo-Garcîa C, Boronat-Lopez A, García-Mira B. Comparative study of wide-diameter implants placed after dental extraction and implants positioned in mature bone for molar replacement. Int J Oral Maxillofac Implants 2008;23:497–501. 26. Fugazzotto PA. Implant placement at the time of mandibular molar extraction: Description of technique and preliminary results of 341 cases. J Periodontol 2008;79:737–747. 27. Schincaglia GP, Marzola R, Giovanni GF, Chiara CS, Scotti R. Replacement of mandibular molars with single-unit restorations supported by wide-body implants: Immediate versus delayed loading. A randomized controlled study. Int J Oral Maxillofac Implants 2008;23:474–480. 28. Cafiero C, Annibali S, Gherlone E, et al. Immediate transmucosal implant placement in molar extraction sites: A 12-month prospective multicenter cohort study. Clin Oral Implants Res 2008;19:476–482. 29. Rimondini L, Bruschi GB, Scipioni A, et al. Tissue healing in implants immediately placed into postextraction sockets: A pilot study in a mini-pig model. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;100:E43–E50.