Implantology and the Severely Resorbed Edentulous Mandible

Microbiological Aspects of Human Mandibular Subperiosteal Dental Implants

Clinical, microbiological, and biochemical features of human mandibular subperiosteal dental implants exhibiting peri-implantitis were compared with those experiencing long-term peri-implant health. After evaluation of clinical parameters, submucosal plaque samples were obtained from permucosal implant abutment posts exhibiting probing depths ≥5 mm and bleeding on probing in subjects with peri-implantitis (n = 3) and from posts with peri-implant health in subjects with long-term subperiosteal implant health (n = 8). The microbial specimens were transported in VMGA III and plated onto enriched Brucella blood agar and Hammond's selective medium with anaerobic incubation, and onto selective TSBV with 5% CO2 incubation. Total anaerobic viable counts and selected bacterial species were identified using established phenotypic methods and criteria. In vitro resistance to doxycycline (2 μg/mL), amoxicillin (2 μg/mL), or metronidazole (4 μg/mL) was recorded per subject when bacterial pathogen growth was noted on antibiotic-supplemented isolation plates. Interleukin (IL)–1β levels were measured with an enzyme-linked immunosorbent assay in peri-implant crevicular fluid samples from 5 study subjects. Significantly higher Plaque Index scores, higher total anaerobic viable counts, more red complex species, and lower proportions of gram-positive facultative viridans streptococci and Actinomyces species were detected on peri-implantitis–affected subperiosteal implants as compared with subperiosteal implants with long-term peri-implant health. No in vitro resistance to the 3 test antibiotic breakpoint concentrations studied was found, except a Fusobacterium nucleatum strain resistant to doxycycline at 2 μg/mL from 1 peri-implantitis subject. Subperiosteal implants with peri-implantitis tended to yield higher peri-implant crevicular fluid IL-1β levels. The level of peri-implant supramucosal plaque control and the composition of the peri-implant submucosal microbiome may be important determinants of the long-term clinical status of mandibular subperiosteal dental implants.

Effect of chronic kidney disease on the healing of titanium implants

Chronic kidney disease (CKD) has become a worldwide public health problem. However, its effect on osseointegration of dental implants is largely unknown. The aim of this study is to investigate whether CKD impairs the quality of the osseointegration of titanium implants. Uremia was induced by 5/6 nephrectomy in mice, and serum levels of BUN, FGF23, PTH and ALP were significantly increased. For in vitro tests, bone marrow mesenchymal stem cells (BMMSCs) were obtained and cultured on titanium discs. There was no significant difference in term of expression of osteogenic marker genes including Osx, Col-1, Ocn, and Opn, as quantified by qPCR. Moreover, Alizarin Red S staining showed comparable mineralized nodules formation. Histomorphometrical analysis of experimental implants inserted in the femurs of CKD mice revealed a trend of decreased BIC ratio at 2-week healing. The strength of bone-implant integration, as measured by a push-in method, was significantly lower for the CKD group at 2 weeks, although a comparable level was reached at 4 weeks. These results demonstrated that CKD only negatively affects the osseointegration of titanium implants at the early stage.

Outcome of treatment of implant-retained overdenture in patients with extreme mandibular bone resorption treated with bone grafts using a modified tent pole technique

PURPOSE

To evaluate the outcome (prosthetic maintenance, survival of implants, patient satisfaction, and quality of life) of prosthetic treatment using an implant-retained overdenture and a modified tent pole procedure for severe mandibular resorption.

MATERIAL AND METHODS

Seventeen edentulous patients (mean age, 68 yr; range, 54 to 77 yr) with severely resorbed mandibles were treated with autogenous bone grafts using a modified tent pole technique and implant overdentures. A bar was used to splint the implants and the final prostheses with implant connection were completed approximately 7 months after surgery. The mean follow-up time was 5 years (1.5 to 7.4 yr). Patients filled out the Oral Health Impact Profile-14 questionnaire concerning their oral health-related quality of life, and then panoramic radiographs were taken during clinical examination.

RESULTS

The stability of the overdenture was good in 58.8% of cases and retention was good in 64.7%. The most usual prosthetic complication was loosening of the attachment component, which occurred in 7 cases (41.2%). The amount of plaque and bleeding was more remarkable on the lingual surface of the implants and less remarkable on the buccal surface. Pocket depth around the implants seemed to correspond to intraoral implantation. The radiographs depicted excellent grafted bone survival. The patients' oral health-related quality of life was found to be good after treatment.

CONCLUSIONS

Implant placement with bone grafting using a modified tent pole technique enables the achievement of a good prosthetic solution and the rehabilitation of occlusion, thereby improving the functionality of the prostheses and quality of life.

Implants in bone: part I. A current overview about tissue response, surface modifications and future perspectives

PURPOSE

The aim of study paper is to present an overview of osseointegration of dental implants, focusing on tissue response, surface modifications and future perspective.

DISCUSSION

Great progress has been made over the decades in the understanding of osseous peri-implant healing of dental implants, leading to the development of new implant materials and surfaces. However, failures and losses of implants are an indicator that there is room for improvement. Of particular importance is the understanding of the biological interaction between the implant and its surrounding bone.

CONCLUSION

The survival rates of dental implants in bone of over 90 % after 10 years show that they are an effective and well-established therapy option. However, new implant materials and surface modifications may be able to improve osseointegration of medical implants especially when the wound healing is compromised. Advanced techniques of evaluation are necessary to understand and validate osseointegration in these cases. An overview regarding the current state of the art in experimental evaluation of osseointegration of implants and implant material modifications will be given in Part II.

Implants Inserted in Mandible: A Case Series

It is generally accepted that the mandible (especially in the interforaminal region) has better bone quality than the maxilla, and this fact is probably the reason why several reports are available regarding implants inserted into the mandible. Since no report is available on a new type of implants, a retrospective study was performed. A total of 185 two-piece implants (FMD srl, Rome, Italy) were inserted in mandible, 102 in female and 83 in males. The median age was 58 ± 13 (min-max 25–80 years). Implants replaced 14 incisors, 7 cuspids, 49 premolars and 115 molars. Implant' length was x ≤ 10 mm, 10,30 ≤ x ≤ 12.30, equal to 13 mm and x ≥14 mm in 80, 90,13 and 2 cases, respectively. Implant' diameter was narrower than 3.5 mm, equal to 3.8 mm and wider than 4.0 mm in 25, 17,143 cases, respectively. There were 36,41,106 and 2 Elisir, I-fix, Shiner, and Storm implant types, respectively. One implant was lost, survival rate = 98.15%. Among the studies variables immediate loaded implants on single tooth rehabilitations (p=0.017) have a worse clinical outcome. Then peri-implant bone resorption (i.e. delta IAJ) was used to investigate SCR. Among the remaining 184 implants, 20 fixtures have a crestal bone resorption greater than 1.5 mm (SCR = 89.13). Statistical analysis demonstrated signifiance only for surgeon (p=0.001). In conclusion FMD implants are reliable devices for oral rehabilitation with a very high SCR and SVR.

Reliability of Short Implants in Oral Rehabilitation

Implant prostheses are often used to restore partially or completely edentulous patients but limited bone height, especially in the posterior mandible, may restrict the use of dental implants. Short implants (i.e. x ≤ 10 mm) may be selected in these situations. They have several advantages: 1 - restricting the need for sophisticated and expensive surgical procedures like sinus lifting, bone grafting and mandibular nerve transposition, 2 - placing short-span dentures and 3 - avoiding cantilevers in the posterior sextants. The limited surface area of SIs, conversely, can be a potential disadvantage as it has less resistance to occlusal forces. Since no report is available on a new type of implants, a retrospective study was performed. A total of 148 short (i.e x ≤ 10 mm) two-piece implants (FMD srl, Rome, Italy) were inserted, 91 in female and 57 in males. The median age was 58 ± 12 (min-max 25–80 years). Implants were inserted 68 in the maxilla and 80 in the mandible. One implant was lost, survival rate = 98.52%. Among the studies variables post-extractive implants on single tooth rehabilitations (p=0.043) was the only significant variable. Then peri-implant bone resorption (i.e. delta IAJ) was used to investigate SCR. Among the remaining 147 implants, 18 fixtures have a crestal bone resorption greater than 1.5 mm (SCR = 87.75). Statistical analysis demonstrated that only diabetes has a negative impact on peri-implant crestal bone resorption (p=0.016). In conclusion FMD implants are reliable devices for oral rehabilitation with a very high SCR and SVR.

Implants in the severely resorbed mandibles: whether or not to augment? What is the clinician's preference?

Introduction

The aim of this study is to inventory in the Netherlands which therapy is the clinician’s first choice when restoring the edentulous mandible.

Material and methods

A questionnaire was sent to all Dutch Oral and Maxillofacial surgeons. As part of this, the surgeons were invited to treat five virtual edentulous patients, differing only in mandibular residual height.

Results

In cases of a sufficient residual height of 15 mm, all surgeons were in favour to insert solely two implants to anchor an overdenture. In case of a residual height of 12 mm, 10% of the surgeons choose for an augmentation procedure. If a patient was presented with a mandibular height of 10 mm, already 40% of the OMF surgeons executed an augmentation procedure. Most (80%) surgeons prefer the (anterior) iliac crest as donor site. The choice of ‘whether or not to augment’ was not influenced by the surgeon’s age; however, the hospital, where he was trained, did. Surgeons trained in Groningen were more in favour of installing short implants in mandibles with reduced vertical height.

Discussion

As the option overdenture supported on two interforaminal implants is reimbursed by the Dutch health assurance, this treatment modality is very popular in the Netherlands. From a point of costs and to minimize bypass comorbidity, surgeons should be more reluctant in executing augmentation procedures to restore the resorbed edentulous mandible as it is dated in literature that also in mandibles with a residual height of 10 mm or less, solely placing implants, thus without an augmentation procedure in advance, is a reliable treatment option.

Electronic supplementary material

The online version of this article (doi:10.1007/s10006-011-0285-6) contains supplementary material, which is available to authorized users.

Impact of dental implant length on early failure rates: a meta-analysis of observational studies

AIM

To test the null hypothesis of no difference in failure rates of short (minimum length: 7 mm) and longer dental implants (≥ 10 mm), a meta-analysis was performed on prospective observational trials.

MATERIALS AND METHODS

A systematic electronic and hand search was performed to identify eligible studies. Having additional data supplied by the authors, 54 publications were included (19,083 implants).

RESULTS

In case of mandibular implants, the null hypothesis of no impact of reduced implant length on failure within the first year of prosthetic loading could not be rejected. A significant impact of implant length could be substantiated for short machined implants in the anterior [odds ratio (OR) 5.4] and posterior maxilla (OR 3.4), while short rough-surfaced implants demonstrated increased failure rates in the anterior maxillary sites. No influence of implant diameter and denture type on the failure rate of short implants could be revealed.

CONCLUSION

In areas of reduced alveolar bone height the use of short dental implants may reduce the need for invasive bone augmentation procedures.

Fracture of the atrophic mandible: case series and critical review

PURPOSE

Atrophic mandible fracture is common among elderly patients. Such fractures present management difficulties related to anatomic and physiologic alterations in this population. The purpose of this study was to evaluate the results of this type of fracture treatment and to realize a critical review of literature on the subject.

PATIENTS AND METHODS

The sample was obtained from records of patients of Restauração Hospital (Recife, Brazil) who underwent surgical treatment of atrophic mandible fracture between 2006 and 2009. Data, such as etiology, location, and degree of displacement of the fractures, as well as access, type of fixation used, and the presence of postoperative complications, were analyzed.

RESULTS

Successful bone union was achieved in 100% of cases. Complications were related to those patients treated with reconstruction plates (2.4 mm).

CONCLUSIONS

Open reduction and internal fixation with miniplates seem a feasible option for primary treatment of atrophic mandible fractures without comminution or loss of substance. The level of scientific evidence for the treatment of atrophic mandible fractures is low.

Short implants in maxillae and mandibles: a retrospective study with 1 to 8 years of follow-up

BACKGROUND

The aims of this study are to evaluate the long-term survival rates of short dental implants in posterior areas in both jaws and analyze the influence of different factors on implant survival.

METHODS

A retrospective cohort study design was used. Six hundred and sixty-one patients received 1,287 short implants (<8.5 mm) between 2001 to 2008 in Vitoria, Spain. All implant installations were performed by two experienced surgeons and rehabilitations were done by three prosthodontists. Each implant failure was carefully analyzed. The potential influence of demographic factors, clinical factors, surgery-depending factors, and prosthetic variables on implant survival was studied. Implant survival was analyzed using a life table analysis (Wilcoxon [Gehan] test).

RESULTS

The overall survival rates of short implants were 99.3% and 98.8% for the implant and subject-based analysis, respectively. The mean follow-up period for the implants was 47.9 +/- 24.46 months. A total of 9 out of 1,287 implants were lost during the observation period. None of the variables studied resulted in statistical association with implant failure because of the low number of failures.

CONCLUSION

Results of the present retrospective study show that treatment with short implants can be considered safe and predictable if used under strict clinical protocols.

A new approach for reconstruction of a severely atrophic mandible

PURPOSE

The purpose of this study is to report a case of a patient with a severely atrophic mandible (less than 5 mm) who was treated without bone graft using short implants and internal rigid fixation.

PATIENT AND METHODS

A 61-year-old woman was referred to a private clinic in the city of Recife (Brazil) with a severely resorbed mandible (less than 5 mm). The patient reported a history of nearly 15 years of complete edentulism and consecutive treatment failures. Cone beam tomography was performed and severe atrophy was confirmed, revealing total bilateral exposed inferior alveolar nerves. There was a high risk of pathologic mandible fracture, since bone density in critical areas was very low. Treatment of choice was the placement of 4 Shorty (3.75 x 5.5 mm) implants (Nobel Biocare, Göteborg, Sweden) at the symphysis for immediate functional reasons and a 2.0-mm large profile Unilock bone plate (Synthes Maxillofacial, Paoli, PA) to reinforce the mandible. A rapid prototype model was made to help precontour the plate, enabling the insertion of the plate through the transoral approach.

RESULTS

A week after surgery, a Brånemark prosthesis protocol was performed and the patient was satisfied with the result. At 29 months after surgery, the patient was still satisfied and had excellent function without complications.

CONCLUSIONS

Because of the reported advances in implantology and internal rigid fixation, more patients would be able to improve their severe dental condition without the use of more invasive techniques.

Mandibular fractures associated with endosteal implants

PURPOSE

The purpose of this study is to report four cases of mandibular fractures associated with endosteal implants and to discuss prevention and treatment of these types of fractures.

DISCUSSION

To evaluate whether the patient's anatomy allows insertion of implants, radiological exams that demonstrate the height and the labial-lingual width are needed. To reduce the potential fracture problem, the mandible can be restrengthened with bone grafting techniques. The treatment of a fracture in an atrophic mandible is always a challenge because of the diminished central blood supply, the depressed vitality of the bone, and the dependence on the periosteal blood supply. The basic principles in fracture treatment are reduction and immobilization of the fractured site for restoration of form and function.

CONCLUSIONS

If implants are placed in severe atrophic mandible, iatrogenic fracture of the mandible may occur during or after implant surgery because implant placement weakens the already-compromised mandible. A few millimeters of cortical bone should remain on both the labial and the lingual sites after the hole for insertion of an implant has been drilled. A 3-D surgical planning should be recommended at least in severe atrophic mandibles in order to prevent a severe reduction of bone tissue.

What is the quality of the evidence base for pre-implant surgery of the atrophic jaw?

This review aimed to evaluate the level of evidence for bone augmentation preimplant surgery for atrophic jaws in studies which measure outcome. Medline, Embase, Cochrane library and online journal searches were performed with a defined search strategy and the abstracts screened against selection criteria. The resultant papers were sorted by study design using the Cochrane study design algorithm, analysed for clinical/statistical homogeneity and graded with the Oxford Centre of Evidence-based Medicine levels of evidence. The initial online Medline search yielded 1194 results and the Embase search yielded 490 results. Using the selection criteria, 10 studies were identified. Additionally, 5 articles were identified from bibliography and online searches, giving a total of 15 studies for grading. All 15 studies were graded as level 4 evidence. No meta-analysis of outcomes was possible with the low level of evidence and degree of heterogeneity found. The best grade of recommendation that can be made for a particular preimplant surgical bone augmentation procedure, from these level 4 studies, is Grade C. Benchmarking studies by assessing quality of evidence can be helpful to inform future study designs with respect to reporting study outcomes with a higher level of evidence.

Rehabilitation of severely resorbed edentulous mandible using the modified visor osteotomy technique

The prosthetic rehabilitation of an atrophic mandible is usually unsatisfactory due to the lack of support tissues, mainly bone and keratinized mucosa for treatment with osseointegrated implants or even conventional prosthesis. The prosthetic instability leads to social and functional limitations and chronic physical trauma decreasing the patient's quality of life. A 53-year-old female patient sought care at our surgical service complaining of impairment of her masticatory function associated with the instability of the lower total prosthetic denture. The clinical and complementary exams revealed edentulism in both arches, while the mandibular arch presented severe reabsorption resulting in denture instability and chronic trauma to the oral mucosa. The proposed treatment plan consisted in the mandibular rehabilitation with osseointegrated implants and fixed Brånemark's protocol prosthesis after mandibular reconstruction applying the modified visor osteotomy technique. The proposed technique offered predictable results for reconstruction of the severely resorbed edentulous mandible and posterior rehabilitation with osseointegrated implants.

Histologic study of the cellular events during rat mandibular distraction osteogenesis

OBJECTIVE

The cellular events, underlying bone regeneration through rat mandibular distraction osteogenesis (DO) was examined using micro computerized tomography (microCT), histology, and histochemistry.

STUDY DESIGN

After 5-day latency, mandibles were distracted at 0.2 mm/12 h for 10 days, and fixed at latency 5 days (L5D), distraction 3, 6, 10 days (D3D, D6D, D10D), and consolidation 1, 3, 6, 10 weeks (C1W, C3W, C6W, C10W).

RESULTS

The microCT demonstrated radiopacity at the distraction gap (DG) during C1W, which was filled with new bone at C6W and C10W. At D3D, collagen fibers were aligned along the axis of the distraction vector. At D6D, alkaline phosphatase-positive osteoblasts and intramembranous ossification was observed. Collagen bundles became thicker with new bony trabeculae at D10D. Type II collagen-immunopositive areas first appeared at C1W. At C3W, cartilage tissue and endochondral ossification were found. By C6W, the entire DG had been bridged by new bone. The C10W specimens showed mature lamellar bone.

CONCLUSION

Mandibular DO produces bone through both intramembranous and endochondral ossification.

Short Implants Placed One-Stage in Maxillae and Mandibles: A Retrospective Clinical Study with 1 to 9 Years of Follow-Up

BACKGROUND

The use of short implants (7-8.5 mm) has historically been associated with lower survival rates than for longer implants. However, recent clinical studies indicate that short implants may support most prosthetic restorations quite adequately, but still clinical documentation is sparse.

PURPOSE

The purpose of this study was to report on the placement of short Brånemark implants, testing the hypothesis that short implants in atrophied jaws might give similar long-term implant survival rates as longer implants used in larger bone volumes.

MATERIALS AND METHODS

This retrospective clinical study included 237 consecutively treated patients with 408 short Brånemark implants supporting 151 fixed prostheses. One hundred thirty-one of the implants were 7-mm long, and 277 were 8.5-mm long. Final abutments were delivered at the time of surgery, and final prostheses were delivered 4 to 6 months later.

RESULTS

One hundred and twenty six of the 7-mm implants (96%) have passed the 1-year follow-up; 110 (84%), the 2-year follow-up; and 88 (67%), the 5-year follow-up. Five implants failed in four patients before the 6-month follow-up, giving a cumulative survival rate of 96.2% at 5 years. The average bone resorption was 1 mm (SD=0.6 mm) after the first year and 1.8 mm (SD=0.8 mm) after the fifth year of function. Two hundred sixty nine of the 8.5-mm implants (97%) have passed the 1-year follow-up; 220 (79%), the 2-year follow-up; and 142 (51%), the 5-year follow-up. Eight implants failed in seven patients before the 6-month follow-up, giving a cumulative survival rate of 97.1% at 5 years. The average bone resorption was 1.3 mm (SD=0.8 mm) after the first year and 2.2 mm (SD=0.9 mm) after the fifth year of function.

CONCLUSIONS

The cumulative survival rates of 96.2 and 97.1% at 5 years for implants of 7.0- and 8.5-mm length, respectively, indicate that one-stage short Brånemark implants used in both jaws is a viable concept.

Assessment of cell proliferation during mandibular distraction osteogenesis in the maturing rat

INTRODUCTION

The cellular mechanisms controlling distraction osteogenesis are not well understood. The purpose of this study was to examine the role of cell proliferation in the regulation of mandibular distraction osteogenesis.

METHODS

Unilateral mandibular ramus osteotomies were performed on 125 3-month-old Sprague-Dawley rats. The rats were randomized into 4 distraction rate groups and distracted for 5 days after 3-day latency. Rats (7 or 8 from each rate group) were killed at 4 time points. The rats received 5-bromo-2-deoxyuridine (BrdU) injections (40 mg per kilogram, i.p.) at day 3 (end of latency).

RESULTS

Both intramembranous and endochondral ossification was seen in the osteogenesis area. BrdU+ mesenchymal progenitor cells were significantly higher at day 10 (P <.05) and were found most numerously around the sagittal middle portion of the gap (P <.01). The greatest numbers of BrdU+ osteocytes were seen at day 38 (P <.05). Both BrdU+ osteoclasts and chondrocytes peaked at day 24.

CONCLUSIONS

Mesenchymal progenitor cells are mostly recruited in the early consolidation period, but they decrease in the middle and late consolidation periods during mandibular distraction osteogenesis. The rapid rate might suppress or sustain the proliferation and differentiation of mesenchymal progenitor cells during mandibular distraction osteogenesis. BrdU+ cells can survive throughout the entire experimental period of 5 weeks.

Reconstruction of the severely atrophic mandible using calvarial split bone grafts for implant-supported oral rehabilitation

OBJECTIVES

This article describes reconstruction of the severely atrophic mandible using calvarial bone grafts for implant-supported prosthetic oral rehabilitation. The study aim was to evaluate the efficacy of the treatment by determining implant survival and complication rates, and the extent of the postoperative graft resorption.

STUDY DESIGN

Ten patients who underwent the treatment were followed clinically and radiologically using panoramic radiographs and CT scans during a mean postoperative period of 30 months.

RESULTS

Good bone healing was observable 6 months postoperatively. The height reduction measured on panoramic radiographs was insignificant (mean 0.68 mm). Only minor complications occurred. Implant survival was 95%. Prosthodontic treatment was successfully performed in all cases, resulting in an improvement of oral function. Histological analysis of 1 bone biopsy showed minimal resorptive changes in otherwise very dense bone.

CONCLUSION

Augmentation using calvarial grafts is a promising treatment alternative for the severely atrophic mandible.

Piezosurgery: Basics and Possibilities

Useful in a variety of oral surgery procedures, piezosurgery has therapeutic features that include a micrometric cut (precise and secure action to limit tissue damage, especially to osteocytes), a selective cut (affecting mineralized tissues, but not surrounding soft tissues), and a clear surgical site (the result of the cavitation effect created by an irrigation/cooling solution and oscillating tip). Because the instrument's tip vibrates at different ultrasonic frequencies, since hard and soft tissues are cut at different frequencies, a "selective cut" enables the clinician to cut hard tissues while sparing fine anatomical structures (e.g., schneiderian membrane, nerve tissue). An oscillating tip drives the cooling-irrigation fluid, making it possible to obtain effective cooling as well as higher visibility (via cavitation effect) compared to conventional surgical instruments (rotating burs and oscillating saws), even in deep spaces. As a result, implantology surgical techniques such as bone harvesting (chips and blocks), crestal bone splitting, and sinus floor elevation can be performed with greater ease and safety.

Permucosal implants combined with iliac crest onlay grafts used in extreme atrophy of the mandible: long-term results of a prospective study

Thirteen patients received an onlay bone-graft augmentation to their severely atrophic mandible in combination with simultaneous implant insertion. This treatment modality was studied in a long-term prospective clinical and radiographic study. A reproducible measurement method, consisting of oblique lateral cephalometric radiographs, in combination with an image analysis system, was used to accurately assess the graft resorption rate. On average, 51% (95% confidence interval 42-61%) of the grafted bone height remained after 10-11 years. Resorption of the graft occurred mainly during the first years and showed a marked degree of individual variance. In the following years, the resorption rate followed a predictable pattern in most of our patients. Ventral and dorsal sites exhibited a similar degree of resorption. Peri-implantitis occurred in nine patients. Ten muco-gingival surgical interventions were necessary in four of these nine patients. No implants were lost and 12 patients indicated that they were satisfied. It is concluded that the described surgical technique should be used on stringent indication only, and alternative techniques are discussed.