Vertical distraction of the severely resorbed edentulous mandible: an assessment of treatment outcome

PURPOSE: To assess the treatment outcome (implant survival, surgical complications, patient satisfaction) of vertical distraction of the severely resorbed edentulous mandible. MATERIALS AND METHODS: Forty-six patients with severe resorption of the edentulous mandible (bone height 5 to 8 mm, median 6 mm) participated in this study. The anterior segment of the mandible was vertically augmented using the Groningen distraction device. One or 2 months after the last day of distraction, 2 implants (n = 92) were placed. Standardized clinical and radiographic assessments were performed annually, and patient satisfaction was scored on a 10-point rating scale (0 = completely dissatisfied; 10 = completely satisfied). RESULTS: Three implants were lost during the healing phase, but none were lost for the rest of the follow-up period (72 +/- 10.3 months), resulting in an implant survival rate of 97%. One patient developed a fracture of the mandible 3 days after the last day of distraction; it healed uneventfully. The mean mandibular bone resorption during follow-up as measured on radiographs in the midline and distal of the implants was 9.8% +/- 0.6% and 10.2% +/- 0.8%, respectively. In 4 patients radiolucency in the distracted area persisted during the follow-up period. Four patients reported a slight sensory disturbance at the final evaluation visit. All patients functioned well with their prostheses. The mean patient satisfaction score after treatment was 8.1 +/- 1.2. CONCLUSION: Vertical distraction of the anterior segment of a severely resorbed alveolar ridge of the mandible can provide a proper basis for insertion and osseointegration of endosseous load-bearing implants with good implant survival, few surgical complications, and good patient satisfaction.     

Implant treatment without bone grafting in edentulous severely resorbed maxillas: a long-term follow-up study.

PURPOSE: To evaluate retrospectively the surgical outcome of tilted implants in severely resorbed edentulous maxillas as an alternative to bone grafting and the prosthodontic outcome of posterior extension bridges on tilted implants. PATIENTS AND METHODS: A total of 33 consecutive patients with severely resorbed edentulous maxillas participated in the study. In these patients, the maxillary bone volumes were insufficient for conventional placement of implants to support a fixed prosthesis. As an alternative to bone transplantation, a surgical technique with fenestration of the maxillary sinus to visualize the total amount of maxillary bone was used, followed by implant placement in a tilted manner along the anterior maxillary sinus wall. Thus, 4 to 6 implants of optimal length could be installed in each patient. Nineteen patients were included in this long-term follow-up study and were eligible for clinical evaluation at 8 to 12 years (mean, 10 years) after second-stage surgery. Each patient was examined clinically and radiographically. RESULTS: The 19 patients had a total of 103 implants. In 2 of these patients, 3 fixtures were lost during the first year after second-stage surgery. All other patients had all implants intact with functionally fixed dental prostheses, corresponding to a success rate of 97%. Radiographic examination showed bone resorption in 10% of the implants (10 implants in 5 patients with a total number of 27 implants), with a mean bone loss of 1.2 mm. Mucositis was seen in 47% of the patients. CONCLUSIONS: This long-term follow-up study (mean time, 10 years) demonstrates that patients with a severely resorbed maxilla can be treated successfully with conventional implant treatment. This simplified surgical technique can be an alternative to the more resource-demanding technique with bone grafting.     

Immediate loading of dental implants placed in severely resorbed edentulous mandibles reconstructed with autogenous calvarial grafts

OBJECTIVE: The aim of this prospective study was to present the clinical outcome of immediately loaded dental implants placed in edentulous, severely atrophied mandibles, after reconstruction with autogenous multilayered calvarial grafts. MATERIALS AND METHODS: Six patients, two males and four females, aged 40-67 years (mean: 56 years) presenting with severely atrophied edentulous mandibles (Cawood and Howell class VI), were reconstructed with multilayered calvarial bone grafts placed in the intraforaminal area of the mandible. Five to 8 months afterwards, 23 dental implants were placed in the reconstructed areas (three to four implants per patient) and immediately loaded with implant-supported overdentures. Patients were followed with clinical and radiographic controls annually. RESULTS: Recovery after the reconstruction was uneventful in all patients. All 23 implants were osseointegrated 1-3 years after the start of immediate loading. The survival and success rates of implants were 100% and 95.7%, respectively. CONCLUSION: Results from this study showed that immediate loading of dental implants placed in severely atrophied edentulous mandibles reconstructed with calvarial bone grafts is a predictable procedure, which permits a successful dental rehabilitation with a shortening of treatment times.     

Maxillary alveolar ridge reconstruction with nonvascularized autogenous block bone: clinical results.

PURPOSE: The purposes of this study were to evaluate the clinical success of bone reconstruction of the severely atrophic maxilla using autogenous bone harvested from the anterosuperior edge of iliac wing and to analyze the clinical success and the marginal bone level of dental implants placed 4 to 5 months after bone grafting and before prosthetic rehabilitation. PATIENTS AND METHODS: Fifty-six patients (18 men, 38 women) aged 27 to 63 years were included in the study and required treatment for maxillary atrophy. All patients selected were scheduled for onlay bone graft and titanium implants in a 2-stage procedure. The dental implants were inserted 4 to 5 months after grafting. RESULTS: No major complications were observed from the donor sites. A total of 129 onlay bone grafts were used to augment 56 severely resorbed maxillas. Three out of 129 bone grafts had to be removed because of early exposure occurring with bone grafts placed to increase the vertical dimension of the alveolar ridge. One hundred sixty-two implants were placed in the area of bone augmentation. Seven implants failed to integrate and were successfully re-placed without any need for additional bone grafting. The clinical measurements for bone resorption around implants revealed a mean bone loss of 0.05 mm (+/- 0.2); the marginal bone level evaluated with periapical radiographies was 0.3 mm (+/- 0.4) at implant placement and 0.1 mm (+/- 0.3) 6 months after placement. CONCLUSION: The success rate of the block grafts was very good. The clinical and radiographic bone observations showed a very low rate of resorption after bone graft and implant placement. Therefore, on the basis of this preliminary study, iliac bone grafts (from the anterosuperior edge of the iliac wing) can be considered a promising treatment for severe maxillary atrophy.     

Reconstruction of the severely resorbed mandible prior to vestibuloplasty or placement of endosseous implants. A 2 to 5 year follow-up.

Ninety-two patients underwent augmentation of the severely resorbed mandible using corticocancellous bone grafts in the symphysis and a mixture of autogenous cancellous bone chips and hydroxylapatite particles in the posterior area. This study, extending from 2 to 5 years, shows that predictable and stable results were achieved. The average loss of height measured at 3 reference points was approximately 20%. Slight sensory disturbance was present in 19 patients (23%). Benefits derived from augmentation of the atrophic mandible include: improvement of facial form due to the renewed support of the collapsed circumoral muscles, a decrease in the intermaxillary distance, and restoration of mandibular bone bulk that will accommodate endosseous implants of maximum size.     

Immediate dental implant placement in calvarial bone grafts to rehabilitate the severely resorbed edentulous maxilla: A prospective pilot study

Purpose

The aim of this study was to describe the surgical technique of immediate dental implant placement in calvarial grafts for augmentation of the severely resorbed maxilla and to assess the treatment results.

Mandibular ridge augmentation with simultaneous onlay iliac bone graft and endosseous implants: a preliminary report.

Mandibular onlay composite grafts (autogenous iliac bone and titanium cylindrical threaded endosseous dental implants) were placed in seven patients with advanced bone resorption. All seven patients have experienced uncomplicated healing and continuous, uninterrupted prosthesis use without soft tissue or mechanical complications for 1 to 4 years. This preliminary report includes a discussion of the indications for the procedure, potential alternative management of the severely resorbed mandible, and details of the surgical procedure illustrated by two patients who received this treatment modality.     

Vertical distraction of the severely resorbed mandible. The Groningen distraction device

In this paper, both the surgical procedure and the clinical results of a novel distraction device to augment a severely resorbed anterior edentulous mandible are described. The distraction device is non-voluminous, and consists of two distraction screws and one guide screw. Two months after the last day of distraction, both distraction screws are replaced by endosseous implants and the guide screw is removed. Three months after implantation, the prosthetic treatment can be started. So far three patients have been treated. In all patients, the severely resorbed mandible (mandibular height in the canine region: 5, 6 and 7 mm, respectively) could be sufficiently enlarged to enable reliable insertion of endosseous implants with a length of at least 12 mm. No complications occurred. Biopsies taken from the distraction site revealed formation of lamellar bone parallel to the distraction vector. From this preliminary study it is concluded that the Groningen vertical distraction device has the potential for reliable augmentation of the anterior segment of a severely resorbed edentulous mandible to enable insertion of endosseous implants with adequate length and primary stability.     

Implant-retained mandibular overdentures: 6-year results of a multicenter clinical trial on 3 different implant systems.

PURPOSE: The goal of this multicenter prospective clinical trial was to compare clinical outcome and post-treatment care and patient satisfaction with different implant systems used for mandibular overdenture treatment during a 6-year follow-up period. PATIENTS AND METHODS: A total of 87 edentulous patients with a severely resorbed mandible (bone height, 8 to 15 mm) received treatment involving either 2 Intra Mobiele Zylinder implants (IMZ group, n = 41) (Friedrichsfeld AG, Mannheim, Germany), 2 Br?nemark implants (Br? group, n = 17) (Nobel Biocare AB, Gothenburg, Sweden) or a Transmandibular Implant (TMI; Krijnen Medical, Beesd, The Netherlands) (TMI group, n = 29). The evaluation involved clinical parameters, radiographs, surgical and prosthetic post-treatment care, clinical implant performance (CIP scale), and patient satisfaction. RESULTS: After 6 years, there was a significant difference in the mean plaque index:the mean plaque index of the TMI group was significantly higher than that of the IMZ and Br? groups. Other clinical parameters showed no significant differences. The implant survival rate of 97.5% was noted in the IMZ group, 97.1% in the Br? group, and 72.0% in the TMI group. The CIP scale were significantly worse for the TMI group. CONCLUSION: It was concluded that the IMZ and the Br?nemark implant systems have a better survival rate and clinical implant performance than the TMI system. Based on these data, these systems should be the choice for the edentulous mandible with a height between 8 and 15 mm.     

Clinical, histologic, and histomorphometric evaluation of mineralized solvent-dehydrated bone allograf (Puros) in human maxillary sinus grafts

Demineralized freeze-dried bone allografts (DFDBA) have been successfully used alone or in composite grafts for many decades. Little research has been done on the effect of retaining the mineral content of bone allografts. This study histologically and histomorphometrically evaluated a new mineralized bone allograft material placed in human atrophic maxillary sinuses. Seven partially edentulous patients requiring sinus grafts before implant placement were selected for this study Their age range was 56 to 81 years (mean 67.7 years). Test grafts consisted of a mineralized solvent-dehydrated cancellous bone allograft, and control grafts were a composite of DFDBA and deproteinized bovine bone xenograft (1:1). Bilateral cases (n = 3) received both test and control grafts on opposite sides, and unilateral cases received either a test (n = 3) or control (n = 1) graft only. At 10 months, core biopsies were taken from each graft site, and dental implants were placed into the augmented bone. All bone grafts resulted in new bone formation and all implants osseointegrated. Test grafts resorbed and were replaced by newly formed bone significantly faster and in greater quantities than were control grafts. No complications with grafts or implants were noted. Both test and control grafts achieved excellent results. The faster bone formation observed with the test graft may be due, in part, to its smaller particle size compared with the bovine portion of the control graft. Test grafts were either replaced by new bone or displayed new bone-to-particle surface contact in higher percentages than did control grafts. No differences in osseointegration or graft stability were noted 2 years after the study.     

Implant treatment without bone grafting in severely resorbed edentulous maxillae.

PURPOSE: This article describes the surgical technique for implant treatment in severely resorbed edentulous maxillae without any alveolar reconstruction before or combined with implant placement. PATIENTS AND MATERIAL: Fifteen patients with severely resorbed edentulous maxillae were treated with osseointegrated implants and fixed dental prostheses. All patients were initially considered to be treated with bone grafting because of a lack of sufficient bone volume for conventional treatment. Preoperative radiographic examinations showed that the height of the alveolar crest was on average 7.4 mm at the 4-mm-width level (Classes V to VI). RESULTS: By fenestration of the maxillary sinus and uncovering the nasal floor, the maxillary bone could be visualized and used maximally for installation of implants. By angulation of the implants and permitting two to five uncovered fixture threads on the palatal aspect, implants of optimal length could be installed. Eighty-six implants were placed (four to six implants in every patient). One implant was lost during the observation time (range, 36 to 54 months; mean, 45 months). All patients had stable fixed prostheses at the end of the observation time. CONCLUSION: This cost-effective surgical technique may be considered as an alternative to more resource-demanding techniques such as bone grafting in patients with severely resorbed edentulous maxillae. However, further prospective comparative studies are necessary for full evaluation.     

Management of a patient with a failed transmandibular implant

The Transmandibular Implant System (TMI) had been developed in order to provide a patient with a severely resorbed mandible with a stable and retensive implant-supported overdenture. Failure of the transmucosal posts may necessitate removal of the transmandibular implant in total and treatment with an implant-supported prosthesis. The purpose of this paper is to describe overcoming failure of a transmandibular implant without removal and synchronous placement of endosseous dental implants in the interforaminal region, providing an implant-retained overdenture to the patient. CLINICAL RELEVANCE: Transmandibular implants are rarely used nowadays and management of a failed transmandibular implant is reported even less often. Where bone height is adequate, dental implants may be placed in the anterior mandible, even when the failed transmandibular implant is not completely removed.     

The outcome of intraoral onlay block bone grafts on alveolar ridge augmentations: A systematic review

Aim: The purpose of this study was to systematically review clinical studies examining the survival and success rates of implants placed with intraoral onlay autogenous bone grafts to answer the following question: do ridge augmentations procedures with intraoral onlay block bone grafts in conjunction with or prior to implant placement influence implant outcome when compared with a control group (guided bone regeneration, alveolar distraction, native bone or short dental implants.)? Material and Method: An electronic data banks and hand searching were used to find relevant articles on vertical and lateral augmentation procedures performed with intraoral onlay block bone grafts for dental implant therapy published up to October 2013. Publications in English, on human subjects, with a controlled study design –involving at least one group with defects treated with intraoral onlay block bone grafts, more than five patients and a minimum follow-up of 12 months after prosthetic loading were included. Two reviewers extracted the data. Results: A total of 6 studies met the inclusion criteria: 4 studies on horizontal augmentation and 2 studies on vertical augmentation. Intraoperative complications were not reported. Most common postsurgical complications included mainly mucosal dehiscences (4 studies), bone graft or membrane exposures (3 studies), complete failures of block grafts (2 studies) and neurosensory alterations (4 studies). For lateral augmentation procedures, implant survival rates ranged from 96.9% to 100%, while for vertical augmentation they ranged from 89.5% to 100%. None article studied the soft tissues healing. Conclusions: Survival and success rates of implants placed in horizontally and vertically resorbed edentulous ridges reconstructed with block bone grafts are similar to those of implants placed in native bone, in distracted sites or with guided bone regeneration. More surgical challenges and morbidity arise from vertical augmentations, thus short implants may be a feasible option. Key words:Alveolar ridge augmentation, intraoral bone grafts, onlay grafts, block grafts, dental implants.     

Safety of zygomatic bone harvesting: a prospective study of 32 consecutive patients with simultaneous zygomatic bone grafting and 1-stage implant placement

PURPOSE: The purpose of this prospective study was to evaluate the safety of zygomatic bone harvesting and to determine whether a particulated zygomatic bone graft can be used simultaneously with 1-stage dental implants to reconstruct resorbed edentulous alveolar ridges. MATERIALS AND METHODS: Altogether, 82 dental implants were placed in 32 patients. Particulated bone grafts harvested from the zygomatic process were used in 72 of the implant sites. The volume of bone harvested, intraoperative complications, morbidity, and complications on follow-up visits were recorded. Implant survival was examined prospectively. RESULTS: As a harvest site, the zygoma yielded enough bone to complete the reconstructions in each case. The average zygomatic bone graft volume was 0.90 mL (SD 0.30). Perforation of the maxillary sinus occurred at 11 zygomatic sites. None of these perforations led to postoperative problems. No paresthesias or other complications were noted during follow-up examinations. Mean duration of postoperative swelling was 4.5 days, and patients used pain medication for a mean duration of 4 days. After the mean follow-up period of 26.9 months postplacement, 80 of 82 implants were osseointegrated (survival rate 97.6%). DISCUSSSION: Zygomatic bone is an alternative donor site for bone harvesting with low morbidity. The bone graft yielded is sufficient for use in 2 to 3 implant sites. CONCLUSIONS: The zygoma was a safe intraoral bone harvesting donor site in this patient population. Further, the use of simultaneous particulated zygomatic bone grafts and 1-stage implant placement appears to be an effective procedure.     

Severely resorbed mandible treated with iliac crest autogenous bone graft and dental implants: 17-year follow-up

Severe bone atrophy in the mandible may result in weakening of the jaw, unstable dentures, and dysfunction of the inferior alveolar nerve. These conditions were diagnosed in a 65-year-old woman who presented with a severely resorbed mandible. The interforaminal region of the mandible was augmented with an onlay graft harvested from the iliac crest. Four dental implants stabilized the graft by anchoring it inferiorly to the residual mandibular basal bone. Implants later served as abutments for a fixed 12-unit implant-supported prosthesis. The patient was followed for 17 years, during which the mandibular prosthesis was replaced twice. Despite the initial questionable prognosis, oral rehabilitation was successful, with no detectable clinical signs of bone loss over the 17-year follow-up period.     

Use of rhBMP-2 to reconstruct a severely atrophic mandible: a modified approach

This study reports the case of a patient with a severely resorbed mandible who was treated without a bone graft, using short implants, internal rigid fixation, rhBMP-2 and β-tricalcium phosphate. A 76-year-old woman, with a severely resorbed mandible (less than 3 mm), reported a history of nearly 25 years of complete edentulism and consecutive treatment failures, with total bilateral exposed inferior alveolar nerves and complete bone resorption of the inferior border in some areas. The treatment of choice was the placement of a 2.0 mm thick unilock bone plate (MatrixMandible, Synthes Maxillofacial, Paoli, PA, USA), to reinforce the mandible. Eight short implants with a regular platform (Nobel Biocare, Goteborg, Sweden) were placed: three on the external oblique line on both sides and two on the symphysis. In order to augment mandible height and coat the exposed thread of the anterior implants, rhBMP-2 (Infuse Bone, Meditronic Sofamor Danek, Memphis, TN, USA) and β-tricalcium phosphate (Cerasorb; Curasan, Kleinostheim, Germany) were used. Four 1.3 mm L miniplates were placed to support the graft. 14 months after surgery, the patient was satisfied and had excellent function without complications.     

Staged reconstruction of the severely atrophic mandible with autogenous bone graft and endosteal implants.

PURPOSE: Vastly different surgical techniques have been advocated for osseous reconstruction of the severely atrophic mandible. Endosseous implants placed in autologous bone grafts have been proposed to minimize graft resorption and restore function; however, sufficient bone must exist to support the implants and prevent pathologic fracture. The purpose of this retrospective analysis was to assess the efficacy of autologous bone grafting and the subsequent placement of endosteal implants as a staged procedure in patients with severely atrophic mandibles. MATERIALS AND METHODS: The records of all patients presenting to The University of North Carolina for treatment from 1997 to 1999 with atrophic mandibles (vertical mandibular height <7 mm as measured on panoramic radiographs in at least 1 site at the mandibular midline and at the thinnest portion of the mandibular body) were reviewed. Bone height was assessed preoperatively, immediately postoperatively, at the time of implant placement (4 to 6 months), and again at 12 and 24 months after bone grafting from posterior iliac crest to the mandible via an extraoral approach. Five endosteal implants were subsequently placed in each patient as a delayed procedure 4 to 6 months after bone grafting, and prosthetic rehabilitation was completed with implant supported prostheses. RESULTS: Fourteen consecutive patients were identified with a median preoperative bone height of 9 mm (interquartile range, 25th to 75th percentile [IQ], 7 to 10 mm) in the mandibular midline and 5 mm (IQ, 2 to 5 mm) in the body region. There were no perioperative complications. Median estimated blood loss during the bone graft procedure, as estimated by the surgeon and the anesthesiologist, was 300 mL (IQ, 150 to 1,100 mL), and 1 patient required blood transfusion secondary to symptomatic anemia. The mean loss of vertical bone height after grafting and during the 4 to 6 months before implant placement was 33%. After implant placement and at 12 months, the vertical bone loss was negligible in the implant-supported region and less than 11% in the body region. CONCLUSION: Reconstruction of the severely atrophic mandible using autogenous corticocancellous bone grafts followed by placement of osseointegrated implants in 4 to 6 months can restore and maintain mandibular bone sufficient to support implants and facilitate successful restoration of occlusion. A prospective study is planned to identify predictors of successful outcomes compared with other surgical/prosthetic treatment.     

Implant placement and simultaneous ridge augmentation using autogenous bone and a micro titanium mesh: a prospective clinical study with 20 implants

This prospective clinical study evaluated bone regeneration around 20 dental implants placed in 15 patients (mean age 39.7 years). Peri-implant bone defects were augmented with autogenous bone grafts harvested intraorally from the mandible (chin or retromolar area). Augmented sites were covered with an individually trimmed micro titanium mesh which was rigidly affixed with microscrews to the residual jaw bone. Height of implant exposure (mean 6.5 mm), i.e. dehiscencies (80%) or fenestrations (20%), and graft height (mean 6.2 mm) were measured in an apico-coronal direction using a periodontal probe. At re-entry (mean interval 6.6 months) the titanium mesh and microscrews were removed and bone regeneration assessed. The mean height of the integrated bone graft was 5.8 mm corresponding to a mean bone fill of 93.5%. The overall postop healing course was excellent with only one site developing a soft tissue dehiscence with subsequent mesh exposure (complication rate 5%). This study demonstrated that a micro titanium mesh in combination with autogenous bone grafts is effective for treatment of peri-implant bone defects.     

Ultrasound to stimulate early bone formation in a distraction gap: a double blind randomised clinical pilot trial in the edentulous mandible

OBJECTIVE: In a double blind randomised clinical pilot trial, it was investigated whether low intensity pulsed ultrasound therapy stimulates early bone formation in a distraction gap created in a severely resorbed mandible. DESIGN: Eight patients underwent a mandibular vertical distraction over an average distance of 6.6+/-1.1mm. Ultrasound self-therapy or placebo therapy was started on the first day of distraction and continued daily until the implants were inserted. After 31+/-3.8 days of consolidation, the distraction device was removed, a transmandibular biopsy was taken, and two endosseous implants were inserted. RESULTS: All patients complied well with ultrasound therapy. During an average of 30.1+/-4.1 months follow-up, no complications did occur. Microradiographic examination of the biopsies revealed a comparable mean area of mineralised tissue in the distraction gap of 1.9+/-1.7mm(2) in the ultrasound treatment group and 1.9+/-1.3mm(2) in the placebo treatment group. Histological examination indicated that active woven bone was present within the distraction gap just adjacent to the osteotomy plane, with no apparent differences between the treatment groups. The lamellar bone formation outside the distraction gap appeared to have started as well. CONCLUSION: During a 31-day consolidation period, ultrasound treatment does not appear to stimulate bone formation in the severely resorbed vertical distracted mandible and it seems that this period is too short to evaluate properly if there is an effect. Therefore, a longer consolidation period has to be studied.     

Bone resorption and complications in alveolar distraction osteogenesis

Distraction osteogenesis presents an alternative procedure for augmentation of atrophic alveolar bone prior to inserting dental implants. The aim of this retrospective study was to evaluate complications of this method with specific focus on bone resorption during the consolidation period and the follow-up period after dental implant insertion into distracted bone. Thirty partially edentulous patients underwent a total of 36 vertical alveolar distractions with an extraosseous distraction system. Eleven devices were placed in the maxilla and 25 in the mandible. Eighty-two dental implants were inserted after a mean consolidation period of 4.5 months. Treatment results were evaluated by means of panoramic radiographs for distraction follow-up and periapical radiographs for implant follow-up. The mean length of the transport segment was 19 mm. The average alveolar height achieved was 6.4 mm with a mean resorption of 1.8 mm (21.1%) at the time of dental implant insertion. Main problems comprised oral displacement of the transport segment (n = 15) and inadequate soft tissue extension (n = 13). Eighty-two dental implants were inserted with an overall survival rate of 95.1% after 45.8 months. For periimplant marginal bone, an average resorption of 3.5 mm was recorded 50.4 months after implant insertion. Although alveolar distraction osteogenesis seems to be an effective tool to treat vertical defects of the alveolar ridge, it is not an uncomplicated procedure. A combination with vestibular augmentation of autogenous bone grafts should be considered. Overcorrection of 20% may compensate bone relapse during the consolidation period of the distracted alveolar bone. Further bone resorption after dental implantation is common.