The International Journal of Oral & Maxillofacial Implants, 01/2006

Purpose: This study was proposed to analyze histologically the process of repairing bone defects created surgically in the cranial vaults of rabbits. Materials and Methods: Thirty adult male rabbits (Oryctolagus cunilicus) received, under general anesthesia, bilateral parietal osteotomies by means of a 6-mm-diameter trephine. The bony defects were divided into 4 groups. In group 1 the defect did not receive any treatment; in group 2 the defect was filled with lyophilized bovine bone (Biograft); in group 3 it was filled with bovine bone and covered with a bone matrix membrane (Bioplate); in group 4 it was covered with a bone matrix membrane. Animals were sacrificed in 3 equal groups at 15, 30, and 60 days. The specimens were subjected to routine laboratory procedures to evaluate the degree of bone repair. Results: After 60 days, new bone formation in group 2 was not satisfactory when compared to that of group 3. Large amounts of new bone formation in maturation were seen in group 3. In the defects covered with a membrane the results were similar to those of group 1 (ie, the cavity was filled with fibrous connective tissue). The implanted bone and membranes were totally resorbed. Discussion and Conclusions: The use of a membrane served as a barrier against the migration of cells from the adjacent tissue and the bone graft/membrane preserved the cavity space, resulting in an enhanced osteogenic effect. Keywords: bone grafting, bone regeneration, cranial vault reconstruction, resorbable membranes, xenografts

Purpose: Patterns of von Mises stress values surrounding implants supporting fixed prostheses in the posterior edentulous maxilla were evaluated using 3-dimensional finite element analysis. Materials and Methods: Implants were placed in maxillary bone in 2 different configurations. In the first configuration, implants were placed in the first premolar, second premolar, and second molar regions; in the second configuration, implants were placed in the second premolar and second molar regions, and a mesial cantilever was extended to the space of the first premolar tooth on the superstructure. On the implant placed in the socket of the second molar, 3 different inclinations were used (0, 15, and 30 degrees). Loading was applied in the vertical, oblique, and horizontal axes. Results: Inclination of the implant in the molar region was found to result in increased stress. Significant increase in stress on the implant embedded in the premolar region was also seen in the design with the cantilever as compared to the conventional prosthesis design. Discussion: The stress concentrations observed at the neck of the implant were similar to results reported in the literature. Conclusion: The highest stress value obtained in the study was 194.2 MPa with oblique loading. This value did not exceed the endurance limit of pure titanium, which is 259.9 MPa. Keywords: finite element analysis, fixed partial dentures, implant inclination, implant-supported prostheses, stress distribution

Purpose: The purpose of this study was to evaluate in dogs the area between implants after prosthetic restoration within 5 mm distance between the contact point (CP) between crowns and the bone crest (BC). Materials and Methods: The mandibular premolars of 6 dogs were extracted bilaterally. After 12 weeks of healing, each dog received 8 implants. On each side, 2 implants were separated by 2 mm (group 1) and 2 by 3 mm (group 2). After a healing period (3 months), the implants were restored with temporary acrylic resin prostheses and after 4 more weeks, with definitive metallic prostheses. After 8 weeks, the distance between the CP and the papilla (P) was measured. The distance between a line extending from the CP and the gingival height at the distal extension of the prosthesis (DE) was also measured. Digital radiographic images were obtained for evaluation of the CP-BC and BC-P distances and the analysis of bone resorption adjacent to the implant surfaces. Results: The median CP-P distances were 1.75 mm and 1.98 mm for groups 1 and 2, respectively; the median CP-DE distances were 2.60 and 2.69, respectively. The mean CP-BC distances were 5.64 mm and 6.45 mm, for groups 1 and 2, respectively; mean BC-P distances were 3.07 mm and 3.55 mm, respectively. Discussion and Conclusions: The differences in distances of 2 and 3 mm between implants did not present significant differences in the formation of papillae or in crestal resorption. The CP-BC distances for prostheses should be different from those of natural teeth because in natural teeth, the biologic width is already present, and in the case of implant-supported prostheses, it will develop following second-stage surgery. Keywords: bone crest, bone resorption, contact point, gingival papilla, interimplant distance

Purpose: To analyze the bone graft-implant interface of titanium microimplants (MIs) placed at the time of bone grafting or after a healing period of 6 months and retrieved after another 6 to 14 months of healing. Integration of MIs placed in interpositional bone grafts (IBGs) in conjunction with a Le Fort I osteotomy was compared with the integration of those placed in onlay/inlay bone grafts (OBGs). Materials and Methods: The severely atrophied edentulous maxillae of 23 patients (14 women, 9 men) were restored with autogenous bone grafts (either IBG [n = 8] or OBG [n = 15]) and titanium implants. Six-month periods were allowed between grafting, implant placement, and abutment connection. The bone-implant interface was studied histologically with the use of unloaded titanium MIs. Results: Sixty-eight MIs were either (1) placed simultaneously with grafting and retrieved after 6, 12, or 14 months or (2) placed after 6 months of healing and retrieved after another 6 to 8 months. Histomorphometry indicated equal degrees of osseointegration for the 2 intraoral reconstruction techniques when looking at bone-implant contact, bone area in threads, and newly formed bone (NFB) (Student t test for unpaired observations). There was a significant difference between simultaneous and delayed implant placement with respect to BIC and NFB (Student t test for paired observations). Three additional MIs placed in the nongrafted residual alveolar ridge and retrieved after 6 months showed significantly more bone in threads and NFB (Student t test for paired observations; P = .003 and P = .009, respectively) compared to MIs placed at graft placement (6 months' healing). Discussion: Timing of implant placement appeared more important than healing time or surgical technique. The delayed approach resulted in better implant integration, probably because of the initial revascularization of the graft. Conclusions: Implant integration was similar in the IBG and OBG groups. Placement of MIs after an initial healing period of 6 months resulted in better integration than placement simultaneously with grafting. Keywords: autogenous bone grafts, atrophic maxilla, edentulous maxilla, interpositional bone graft, microimplants, onlay/inlay bone grafting

Purpose: The aim of this article was to evaluate the survival and success of Straumann implants after immediate loading. A new method for fabricating effective definitive prostheses to immediately load implants in edentulous patients was presented. Materials and Methods: Nine patients received 4 implants each, and resin-metal prostheses were installed less than 48 hours after implant placement. Mobility was evaluated immediately after the surgical procedures and 3 months subsequently using the Periotest. Clinical evaluation of soft peri-implant tissues was conducted monthly after the sutures were removed, and radiographs were obtained 6, 12, and 24 months after the surgery. Results: The Periotest revealed statistical values that were stable, with no mobility. No signs of inflammation and/or bleeding were observed. The radiographs did not reveal any continuous areas of radiolucency beyond the first thread of the 36 implants after 24 months. None of them failed, and the success rate was 100%. Discussion: It is possible to submit implants to immediate load without jeopardizing osseointegration if parameters are met, such as suitable bone quality and quantity, lack of unfavorable systemic and psychologic factors, lack of parafunctional habits, strict maintenance of prosthetic requirements, minimization of micromotion, and use of an appropriate surgical protocol. Conclusion: Under immediate load, osseointegration of implants is possible, and the method presented for the fabrication of resin-metal prostheses has been reliable and predictable. Keywords: dental implants, immediate loading of implants, implant-supported prostheses

Purpose: The purpose of the present study was to evaluate implant survival rates with immediate implant placement (IIP) into fresh extraction sockets and to determine risk factors for implant failure. Materials and Methods: A retrospective chart review was conducted of all patients in whom IIP was performed between January 1988 and December 31, 2004. Treatment required atraumatic tooth extraction, IIP, and mineralized freeze-dried bone allograft with an absorbable barrier to cover exposed implant threads. Implant failure was documented along with time of failure, age, gender, medical history, medications taken, postsurgical antibiotic usage, site of implant placement, and reason for implant failure. Statistical analysis was performed using chi-square and logistic regression analysis methods. Results: A total of 1,925 IIPs (1,398 machined-surface and 527 rough-surface implants) occurred in 891 patients. Seventy-one implants failed to achieve integration; a total of 77 implants were lost in 68 patients. The overall implant survival rate was 96.0% with a failure rate of 3.7% prerestoration and 0.3% postrestoration. Machined-surface implants were twice as likely to fail as rough-surface implants (4.6% versus 2.3%). Men were 1.65 times more likely to experience implant failure. Implants placed in sites where teeth were removed for periodontal reasons were 2.3 times more likely to fail than implants placed in other sites. Patients unable to utilize postsurgical amoxicillin were 3.34 times as likely to experience implant failure as patients who received amoxicillin. Conclusions: With a 1- to 16-year survival rate of 96%, IIP following tooth extraction may be considered to be a predictable procedure. Factors such as the ability to use postsurgical amoxicillin and reason for tooth extraction should be considered when treatment planning for IIP. Keywords: age factors, dental implants, gender, implant surfaces, implant survival, penicillin allergy, smoking

Purpose: The aim of this study was to evaluate the rate of complications in maxillary sinus augmentation surgery and the impact of complications on subsequent implant treatment in a patient population with severe maxillary atrophy scheduled for treatment under general anesthesia. Materials and Methods: The study population consisted of 70 patients (124 sinuses) with severe maxillary atrophy who underwent maxillary sinus augmentation. Sixteen patients were scheduled to have a unilateral procedure and 54 patients a bilateral procedure. Sinus augmentation was performed with autogenous bone alone in 93 sinuses; in 31 sinuses, a 1:1 mixture of autogenous bone and corticocancellous pig bone particles was used. Twenty-six of 124 procedures involved both sinus augmentation and autogenous block grafting for the treatment of severely atrophic maxillae. Results: The most common intraoperative complication was the perforation of the sinus membrane, which was observed in 31 sinuses (25%). Seven (5.6%) sinuses in 7 patients exhibited suppuration of the maxillary sinus. Five of the 7 patients with sinus infection were smokers, showing a prevalence of complications significantly greater in smokers compared to nonsmokers. Moreover, the use of an onlay bone graft in conjunction with sinus augmentation appeared to significantly increase the rate of infective complications. Infections were treated by drainage and the administration of systemic antibiotics. Two clinical cases showing persistent signs of infection required an endoscopic inspection of the maxillary sinus. Discussion and Conclusion: In the present study sinus membrane perforation was not shown to be a significant factor in the rate of implant complications. However, the combination of smoking and onlay bone grafting could significantly increase the rate of postoperative infection following sinus grafting. Keywords: maxillary sinus complications, maxillary sinus grafts, maxillary sinus surgery

Purpose: The purpose of this study was to consider the therapeutic decision whether to use advanced surgery or short implants based on data concerning the use of these implants found in follow-up studies. Materials and Methods: The MEDLINE database was consulted for follow-up studies published between the years 1980 and 2004. For those studies that met the inclusion and exclusion criteria, data concerning the number of implants 7, 8.5, or 10 mm long placed and lost, the time at which the failure occurred, and related risk factors were gathered for 33 studies arranged in tables and subjected to analysis. The studies included 16,344 implant placements with 786 failures (4.8%). Implants were analyzed according to the time of failure (ie, before or after prosthesis seating) and risk factors implicated in the failures. Results: The total rate of failures was 4.8%. Implants 3.75 mm wide and 7 mm long failed at a rate of 9.7%, compared to 6.3% for 3.75 3 10-mm implants. It was found that 54.9% of failures occurred before the prosthesis connection. Finally, 66.7% of all failures were attributed to poor bone quality, 45.4% to the location (maxilla or mandible), 27.2% to occlusal overload, 24.2% to location within the jaw, and 15.1% to infections (an implant could be associated with multiple risk factors). Discussion: The analysis revealed that among the risk factors, poor bone quality in association with short implants seemed to be relevant to failure. The use of implants 4 mm in diameter appeared to minimize failure in these situations. The 3.75 3 7-mm implant presented the highest failure rate (9.7%) of 1,894 implants analyzed (excluding implant designs with higher failure rates but few total implants). Conclusion: Short implants should be considered as an alternative to advanced bone augmentation surgeries, since surgeries can involve higher morbidity, require extended clinical periods, and involve higher costs to the patient. Keywords: bone quality, risk factors, short implants

Purpose: One-stage implant placement in the grafted maxillary sinus has traditionally been limited to patients with at least 5 mm of residual bone to ensure complete implant stabilization. The aim of this prospective study was to determine the long-term survival rates of implants with roughened surfaces placed immediately into maxillary sinus grafts in patients with 1 to 5 mm of residual bone. Materials and Methods: A total of 2,132 microtextured screw-type (n = 1,374) or hydroxyapatite-coated cylinder-type (n = 758) implants were immediately placed into the grafted sinuses of 731 patients. The implants were restored and monitored for up to 9 years of clinical follow-up. Results: Cumulative survival at 9 years was 97.9% (n = 2,091 implants); 20.4% of the implants were placed in 1 to 2 mm of residual bone. Discussion: Initial implant stability and parallelism were achieved through a combination of meticulous condensation of the particulate bone graft material around the implants, the frictional interface of the roughened implant surfaces and the host tissues, and selection of an appropriate graft material. Conclusions: Simultaneous implant placement into sinus floor grafts can be a predictable treatment option for patients with at least 1 to 2 mm of vertical residual bone height when careful case planning and meticulous surgical techniques are used. (More than 50 references) Keywords: bone graft, implants, sinus lift, subantral augmentation

Purpose: The marginal bone loss (MBL) around implants placed in maxillary sinus grafts was evaluated. Materials and Methods: The study consisted of 70 patients who had undergone 81 sinus-graft procedures (total 212 screw-type implants). Complete radiographic records were available for 160 implants, which were used to calculate MBL (follow-up 6 to 56.5 months). Habits (smoking, bruxism), surgical phase parameters (preoperative residual bone, grafting material, implant characteristics, and complications), and prosthetic parameters (crown-implant ratio, marginal fit, and opposite-arch restoration) were recorded for each patient and statistically analyzed regarding MBL. Results: Cumulative survival and overall radiographic success rates were 95.5% and 83.7% for 4.5 years, respectively. Smoking, small implant surface area, and a delayed implantation approach were related to enhanced MBL, with mean MBL values of 0.24 mm/y (P .011), 0.21 mm/y (P .031), and 0.31 mm/y (P = .052), respectively. In residual bone of = 4 mm, the relation to enhanced MBL was stronger (P .018) for delayed implantation. Discussion: Survival and radiographic success rates compare well with other reports. However, most studies modify success criteria regarding MBL. Smoking may be a primary risk factor regarding implant success. Implants with greater surface area values could compensate for problematic bone characteristics (eg, in grafted maxillary sinuses). The effect of delayed implantation on MBL was surprising and may prompt simultaneous implantation whenever primary stability can be achieved. Conclusions: Smoking and implant surface area affected MBL in this patient population. Criteria for long-term implant success should be revised to a standard. Keywords: implant success, implant survival, marginal bone loss, radiographic success, sinus graft

Endosseous mandibular implant placement can result in injuries to the peripheral branches of the trigeminal nerve even with the most careful preoperative planning and intraoperative technique. In the past, many patients have been discouraged from seeking repair for such injuries because of the unreliability of the techniques for correcting the injury. It is now possible to perform microneurosurgical repair of such injuries. If the repair is done in a timely fashion, sensation can be improved or restored and painful nerve dysesthesia can be relieved. This article reviews the different types of nerve injuries, their symptoms and diagnosis, and provides information for clinicians to manage their implant patients with neurosensory disturbance. Keywords: dysesthesia, mandibular implants, trigeminal nerve injury

Prefabricated composite grafts were introduced in reconstructive oral and maxillofacial surgery in the mid-1990s. The purpose of this report is to introduce a novel technique - the iliac prefabricated composite graft-for reconstruction of the alveolar ridge simultaneously with masticatory attached gingiva and integrated implants in a single procedure. Clinical and immunohistologic results are reported and reveal this technique to be an attractive alternative in dentoalveolar surgery and implant dentistry. Keywords: dentoalveolar reconstruction, iliac crest, keratinized attached gingiva, prefabricated composite grafts, severe maxillary atrophy

Eosinophilic granuloma is the localized and most benign form of Langerhans' cell histiocytosis. The disease shows a particular predilection for the head and neck region and usually involves the skull bones, where it manifests as well-defined lytic lesions on standard radiographs. The case of an extensive lesion involving the body of the mandible in a 52-year-old man is reported. Operative procedures consisted of enucleation of the lytic lesion and follow-up with clinical examinations and computerized tomographic studies of the mandible at 2, 12, and 18 months postoperatively. Reconstructive surgery without radiotherapy was performed with an autologous bone graft from the iliac crest and implant placement to provide support for a dental restoration. Keywords: bone grafting, dental implants, eosinophilic granuloma, Langerhans' cell histiocytosis

Bone matrix derived from mandibular periosteal cells and cultivated by tissue engineering on a polymer fleece has recently been used for sinus floor elevation and augmentation. This case report focuses on clinical and histologic results after lateral ridge augmentation of a localized non-space-maintaining defect in the right posterior area of the mandible using tissue-engineered bone. Implant-supported prosthetic rehabilitation of a partially edentulous 32-year-old woman was planned involving a fixed partial denture. Preoperative investigations revealed a transversely reduced alveolar ridge width on the right side of the posterior mandible. Lateral augmentation was performed using tissue-engineered bone obtained by autogenous periosteum cells from the same area. Six months after augmentation 2 implants were placed and a bone biopsy was obtained from the augmented area. Transverse ridge dimensions were found to be enhanced. Histologic examination of the biopsy revealed dense lamellar bone. Wound healing was uneventful after all surgical interventions. This case report demonstrates the successful clinical application of tissue-engineered bone for lateral augmentation of the transversely reduced alveolar ridge. The results suggest that periosteum-derived tissue-engineered bone can be used to create a sufficient implant site not only for the sinus floor elevation and augmentation procedure for vertical bone enhancement but also for lateral augmentation. Keywords: alveolar ridge augmentation, bone biopsy, dental implants, tissue engineering

The present case report depicts the management of a patient with persistent idiopathic facial pain following the placement of 2 dental implants in the mandibular anterior alveolar ridge. After 15 months of unsuccessful diagnosis and management, the patient was seen at the Orofacial Pain Unit of the Oral Surgery and Implantology master's degree program of the University of Barcelona. Seven months after treatment onset, a combination of nortriptyline, clonazepam, and relaxation procedures has successfully controlled the patient's facial pain symptoms. Keywords: atypical facial pain, dental implants, idiopathic facial pain

Distraction osteogenesis (DO) can provide predictable bone regeneration without grafting procedures but requires long treatment time and forms less bone transverse to the direction of distraction. To promote 3-dimensional bone formation and shorten the consolidation period, tissue-engineered osteogenic material (injectable bone) was applied in a patient who was being treated with vertical DO with an osteocutaneous fibular flap to reconstruct the mandible. The material, which comprised autologous mesenchymal stem cells culture-expanded then induced to be osteogenic in character and platelet-rich plasma (PRP) activated with thrombin and calcium chloride, was infiltrated into the distracted tissue at the end of distraction and injected into a space created labially with a titanium mesh at implant placement. The infiltration contributed to full consolidation of the regenerate for 3 months, and the injection thickened the regenerated ridge and bridged a gap between the native mandible and distracted fibula. The reconstructed mandible was expanded from 10 mm to 25 mm in height despite a lacerated and opened labial periosteum in the distracted area. Six implants 18 mm in length were placed and subsequently achieved osseointegration. The cutaneous flap covering the implants was trimmed, and the palatal mucosa was transplanted to the regenerated ridge for vestibuloplasty. These raw surfaces were covered with PRP; within 3 weeks, they had attained an epithelium. The implants have supported a fixed prosthesis with adequate surrounding bone and attached mucosa. DO was assisted by tissue engineering and became effective in restoring the compromised mandible. Keywords: distraction osteogenesis, injectable bone, platelet-rich plasma, stem cells, tissue engineering