Degeneration and regeneration of motor and sensory nerves: a stereological study of crush lesions in rat facial and mental nerves.

The aim of this study was to evaluate the degeneration and regeneration of a sensory nerve and a motor nerve at the histological level after a crush injury. Twenty-five female Wistar rats had their mental nerve and the buccal branch of their facial nerve compressed unilaterally against a glass rod for 30s. Specimens of the compressed nerves and the corresponding control nerves were dissected at 3, 7, and 19 days after surgery. Nerve cross-sections were stained with osmium tetroxide and toluidine blue and analysed using two-dimensional stereology. We found differences between the two nerves both in the normal anatomy and in the regenerative pattern. The mental nerve had a larger cross-sectional area including all tissue components. The mental nerve had a larger volume fraction of myelinated axons and a correspondingly smaller volume fraction of endoneurium. No differences were observed in the degenerative pattern; however, at day 19 the buccal branch had regenerated to the normal number of axons, whereas the mental nerve had only regained 50% of the normal number of axons. We conclude that the regenerative process is faster and/or more complete in the facial nerve (motor function) than it is in the mental nerve (somatosensory function).

Neurosensory function of the inferior alveolar nerve after bilateral sagittal ramus osteotomy: a retrospective study of 68 patients.

The aim of the present study was to report the incidence of neurosensory dysfunction in the lower lip and chin after bilateral sagittal split osteotomy at four postoperative time points, and the relation of impairment to factors connected with the operation. Sixty-eight patients who had undergone the procedure (at 136 operated sites) were reviewed, and neurosensory recovery was studied at 2, 6, 18 and finally 30 months postoperatively. A change in neurosensory recovery was seen over this period of time. Two months postoperatively, 84 sites had reduced sensitivity (62%). The incidence of disorder decreased to 52 sites (38%) at 6 months, 43 sites (32%) at 1.5 years and 32 sites (24%) at the final 2.5-year check up. The patient age at the time of surgery, the type of osteosynthesis and the perioperative position of the inferior alveolar nerve were variables that influenced the neurosensory outcome. In conclusion, this retrospective study shows that the most important factors influencing postoperative nerve function are patient age, fixation method and the perioperative position of the inferior alveolar nerve.

Complications associated with segmentation of the maxilla: a retrospective radiographic follow up of 82 patients.

The aim of the present study was to retrospectively examine the clinical and radiographic incidence and frequency of injuries to teeth and their surrounding tissues adjacent to interdental osteotomies in conjunction with segmentation of the maxilla. Vertical interdental osteotomies have been performed in combination with Le Fort I osteotomy for correction of various dento-facial deformities. All our orthognathic patients are followed prospectively in a standardized manner. Eighty-two consecutive patients who underwent dento-facial correction by segmented maxillary osteotomy alone or in combination with simultaneous mandibular surgery between 1992 and 1998 were included in the study. They were followed for up to 30 months postoperatively. A total of 158 interdental osteotomies were performed, involving a total of 316 teeth. Only a small number of complications such as osteolytic processes, marginal bone destruction, root resorption or mechanical injuries to the teeth were seen.

10-year follow-up of onlay bone grafts and implants in severely resorbed maxillae.

Thirty patients with extremely resorbed maxillae had reconstructive bone grafts from the ala iliaca and endosseous implants in a one-stage procedure. The first ten patients constituted a development group and the following 20 patients a routine group. The marginal bone level and implants success rate was evaluated in a prospective long-term follow-up for a minimum of 10 years (10-13 years). Clinical and radiographic examinations were performed at 6 months and then annually up to 5 years. The final examinations were performed at the 10-year follow-up. The bridges were removed at every clinical examination. Marginal bone loss was seen up to the 3-year examination, where it averaged 4.6 mm in the routine group. Between the 3- and 10-year follow-up no significant change was registered. The initial bone loss was probably due to the design of the 3.6 mm conical unthreaded marginal part of the implant. The implant success rate was 83.1% in the routine group. Failures mostly occurred during the first 2 years (14 out of 20). A substantial amount of bone can be gained in patients with extremely resorbed maxillae, when treated with bone graft according to the procedure described in this study.

Evaluation of hemorrhage depressors on blood loss during orthognathic surgery: a retrospective study.

PURPOSE: Correction of dentofacial deformities by orthognathic surgery may cause significant bleeding and therefore hypotensive anesthesia is often used to reduce the blood loss. The main objective of the present clinical study was to determine whether the addition of hemorrhage depressors to other medication during orthognathic surgery would further reduce the blood loss. PATIENTS AND METHODS: Thirty patients, consecutively operated on with standardized Le Fort I osteotomies in 1998 (n = 15, control group) and 1999 (n = 15, treatment group), were included in the study. Both groups received hypotension anesthesia during surgery and the treatment group received additional hemorrhage depressors; tranexamic acid and desmopressin. RESULTS: The mean blood loss was 740 +/- 410 mL (11.3 mL/kg) in the control group and 400 +/- 210 mL (5.7 mL/kg) in the treatment group. The results showed a statistically significant reduction of blood loss in the treatment group (P <.01). CONCLUSIONS: This study shows that blood loss during orthognathic surgery under hypotensive anesthesia can be significantly reduced when a combination of tranexamic acid and desmopressin is added.

Bone graft remodelling and implant success rate in the treatment of the severely resorbed maxilla: a 5-year longitudinal study.

A total of 30 patients, 10 in a developmental group and 20 in a routine group, with extremely resorbed maxillae were treated with bone grafting from the hip and implant placement in a one-stage procedure. All patients were followed for a minimum of 5 years and were examined regarding the long-term success rate of the implants and marginal bone level. The implant success rate was 74.6% for the whole patient group and 85.8% for the routine group, after 5 years. The marginal bone along the implant surface decreased continuously, up to 3 years and thereafter the bone level stabilized. In the routine group, changes in bone graft dimensions over time were also evaluated by computerized tomography. The mean height of the bone graft postoperatively at all implant sites was 8.3 mm. The total mean bone height, including bone graft and residual alveolar crest, was 12.4 mm. After 5 years the total bone height had decreased to a mean of 10 mm. The mean width of the bone graft was 12 mm postoperatively and 8.7 mm at the 5-year examination. A substantial amount of bone can be gained in patients with extremely resorbed maxillae, when treated with bone graft according to the procedure described in this study.

The adaptation of implant-supported superstructures to the alveolar crest: a follow-up of 49 cases.

A prospective clinical and radiographic study has been carried out in 49 patients with a total of 252 implants. In a mixture of 17 edentulous mandibles, 20 edentulous maxillas, nine partial edentulous cases, and three single-tooth cases, prosthetic treatments were aimed at getting as close an adaptation as possible between gingival tissues and superstructure. The shortest possible abutments were used, and the implants were surgically positioned subcrestally. The results during a 5-year follow-up showed a success rate of 98.9% for fixtures in the lower jaw and 96.3% for the upper jaw with a total success rate of 97.3%. The marginal bone reduction during five years with closely adapted superstructures was 0.11 mm in the mandible and 1.1 mm in the maxilla. Our results support the use of close gingivally adapted superstructures, although oral hygiene controls and instructions are regularly advisable.

Sinus lifting procedure. I. One-stage surgery with bone transplant and implants.

A prospective study of one-stage surgery with intrasinus bone transplant and implants has been performed in 26 patients (13 males and 13 females). The aim of the study was to evaluate the success rate with the one-stage sinus lifting procedure in patients with a need for bony augmentation of the alveolar process. Fifteen patients were partially dentate and 11 edentulous. The mean height of the alveolar ridge was 2.5 mm preoperatively (range 1-5.5 mm). 126 fixtures were inserted, 93 in grafted bone and 33 in alveolar bone. Twenty-two patients have been followed for three years, 21 for four years and 11 for five years. The clinical overall survival rate was 69.6% although only 61.2% in grafted bone. Ten of the patients had varying degree of sinusitis post-fixture installation. At the end of the study, 23 patients had permanent bridges. The survival rate was low for inlay supported implants when the one-stage surgical technique was applied. Two-stage surgery may be a safer method.

Effects of implant design and surface on bone regeneration and implant stability: an experimental study in the dog mandible.

BACKGROUND: Previous experimental studies have shown a higher degree of bone-implant contact for surface-enlarged implants compared with machined implants. Yet, there is insufficient evidence that such implants show higher stability and an increased survival rate. PURPOSE: The purpose of this investigation was to study the integration and stability of grit-blasted implants with retention elements on the implant neck, with and without marginal bone defects, compared with machined implants without retention elements. MATERIALS AND METHODS: After tooth extraction of the mandibular premolars in six dogs, two grit-blasted, partly microthreaded Astra Tech implants and one standard Brånemark implant were bilaterally placed in each dog. On one side, 3 x 3 mm large buccal defects were created, to expose three to four implant threads. The contralateral side served as control, and no defects were made. The animals were sacrificed after 4 months of healing. Implant stability was measured using resonance frequency analysis at implant installation and after 4 months of healing. Histologic and histomorphometric evaluation was made after 4 months of healing. RESULTS: Resonance frequency analysis indicated that all implants in the test and control groups were osseointegrated after 4 months, with a tendency toward higher implant stability for the Astra Tech implants. There was a statistically significant higher increase in resonance frequency for the Astra test implants compared with their corresponding controls. Histology and histomorphometry showed well-integrated implants with varying degrees of bone repair at the defect sites. The greater bone-implant contact for the Astra implants was statistically significant. No significant difference between the implants in amount of bone filling the threads was recorded. CONCLUSIONS: The Astra Tech implants tested showed a higher degree of bone-implant contact and higher level of bone regenerated at defect sites compared with the Brånemark implants. Resonance frequency analysis demonstrated a significantly higher increase in the Astra test implants compared with their control groups than did the Brånemark test implants versus their controls.

Tissue regeneration adjacent to titanium implants placed with simultaneous transposition of the inferior dental nerve: a study in dogs.

Transposition of the inferior alveolar nerve was performed in an experimental dog model. Four adult greyhounds were used in the study. Surgical transposition of the nerve was made bilaterally, and 3 implants were placed on each side while the nerve was lateralized. On one side, the nerve was repositioned in contact with the implants, while on the contralateral side a resorbable membrane was positioned between the implant surface and the neurovascular bundle. Histologic section after 4 months of healing showed an intimate contact between implants and nerve tissue in all cases without an interpositional membrane, in contrast to cases with membranes. Histomorphometric measurements of the distance between the implants and the nerve tissue showed that the membrane side had a considerably larger distance between the implant and the nerve, although not with concomitant bone formation.

Healing of titanium implants in onlay bone grafts: an experimental rabbit model.

An experimental rabbit bone graft model for the study of bone formation and remodeling around titanium implants is described. A 2.5-cm long radius bone segment served as an onlay graft. Two commercially pure (c.p.) titanium implants were inserted into the bone graft prior to fixation to the inferior border of the mandibular base with osteosynthesis titanium screws. Each animal was operated twice, allowing follow-up periods of 6 weeks on one side and 6 months on the contralateral side. In order to study bone remodeling by means of fluoroscopy the animals received single injections of tetracyclin and alizarine complexone 2 weeks and 1 week, respectively, prior to sacrifice by perfusion fixation with glutaraldehyde. The bone and implants were excized en bloc, postfixed and embedded in plastic resin. Stained and unstained thin ground sections as well as microradiographed thick sections were produced for light microscopic morphometry and fluoroscopy. After 6 weeks, osteoclastic/osteoblastic activity was primarily observed in the graft-recipient contact area and in the intracortical compartment of the graft bone. New bone formation observed on the implant surface originated from the recipient site. The bone formation was evident also in the implant-graft interface. At 6 weeks the average bone fill of the implant threads was 28.4% which increased to 36.4% after 6 months as measured by morphometry. An average of 17.6% bony contact was measured after 6 weeks which increased to 29.7% 6 months after surgery. The graft bone had reduced in size from an average of 39.5% after 6 weeks down to 24.8% after 6 months (P \lt 0.05). It is concluded that the described experimental model can serve as a useful method for the study of implant healing in onlay grafts.

Effects of barrier membranes on bone resorption and implant stability in onlay bone grafts. An experimental study.

The objective of the present report was to study the effects of barrier membranes on bone resorption and implant stability in a rabbit onlay bone graft model, using resonance frequency analysis, coordinate measurements on plaster models, removal torque measurements and histology. Disc-shaped bone grafts were harvested from the calvarium and placed with titanium implants in the proximal tibial metaphyses of 9 rabbits. On one side (test) the bone graft/implant was covered by an e-PTFE barrier, while the contralateral side was not covered by a membrane and served as control. Three animals were sacrificed after 8 weeks for histology. In 6 animals the membranes were removed after 8 weeks and the animals were followed for an additional period of 16 weeks. Implant stability and bone height around the implants was assessed for the test and control sides at Day 0 and 8, 16 and 24 weeks postoperatively. Removal torque tests were performed after 24 weeks. The results showed an increase in volume of the bone graft on the test side as long as the barrier membrane was in place. However, after removal of the membrane at 8 weeks the resorption rate was higher on the test side compared to the control side, resulting in a similar bone height after 24 weeks. There were no statistically significant differences in implant stability between the test and control sides at any time point, as measured with resonance frequency analysis. Additionally, no statistically significant differences were found between the test and control sides after 24 weeks, using removal torque measurements, coordinate measurements and histomorphometric evaluation. Thus, in this experimental model, the use of non-resorbable barrier membranes did not improve the stability of implants simultaneously placed with onlay bone grafts. Moreover, extensive resorption of the grafted bone was seen after barrier removal, which resulted in similar bone graft volume for the test and control sides at the end of the observation period.

Le Fort I osteotomy with interpositional bone grafts and implants for rehabilitation of the severely resorbed maxilla: a 2-stage procedure.

A surgical procedure for the rehabilitation of severely resorbed maxillae is described. Twenty-five patients, made up of a development group of 5 and a routine group of 20, were treated with Le Fort I osteotomy using interpositional bone grafts from the iliac crest and, in a second stage, titanium implants. Altogether, 181 Brånemark implants were placed, and the patients were followed for up to 5 years. The implant survival rate for the development group was 60.0% after 5 years. Life table analysis for the routine group showed a 5-year survival rate of 85.6%. Twenty-two patients received fixed prostheses and 2 received overdentures. One patient lost all implants and was rehabilitated with a prong denture.

Implant stability measurements using resonance frequency analysis in the grafted maxilla: a cross-sectional pilot study.

BACKGROUND: High failure rates have been presented for implants placed in grafted bone. The bone graft-implant interface constitutes a most complex healing situation, where the time scale for osseointegration and development of implant stability currently is not known. PURPOSE: The aim of the study was to measure the stability of implants placed in grafted bone after various follow-up periods. METHODS: Implant stability measurements by means of resonance frequency analysis were performed in 10 patients previously treated with a Le Fort I osteotomy and interpositional bone grafts. The implants were placed 3 to 4 months after the grafting procedure. Sixty-seven Brånemark implants were subjected to resonance frequency analysis measurements at fixture placement and up to 5.5 years after implant surgery. Periapical radiographs were used for assessment of marginal bone levels. RESULTS: The radiographic examinations showed marginal bone loss with time during the 5.5-year follow-up. The resonance frequencies varied from 5860 to 8440 Hz. When accounting for abutment length and marginal bone level, there was a tendency of increasing resonance frequency with time. Two implants with low resonance frequencies failed during the prosthetic phase. CONCLUSION: The results indicate an increased implant stability with time, which may reflect bone formation, remodeling, and maturation at the implant interface.

Prosthetic restoration following maxillary resection without an oroantral defect: a case report.

PURPOSE: The aim of this article was to present the oral rehabilitation of a patient with a large, created intraoral defect after the surgical extirpation of a pathologic process. MATERIALS AND METHODS: On osseointegrated oral implants, a bar was fabricated to support a partial overdenture by means of attachments. RESULTS: The treatment was successful and the construction has been in service for more than 5 years. CONCLUSION: In cases with large intraoral defects removable dentures may have clinical advantages over fixed partial dentures. In this patient the restoration of missing teeth, alveolar crest, and soft tissue was accomplished at the same time oral function was restored, and good oral hygiene access was obtained.

Stability assessments and histology of titanium implants placed simultaneously with autogenous onlay bone in the rabbit tibia.

A disc-shaped bone graft was harvested from the calvarium in ten rabbits and anchored as an onlay bone graft, using a titanium implant, at the proximal tibial metaphysis. The contralateral tibia served as the control, where an implant was placed without a graft with the implant head at a height corresponding to the thickness of the graft on the test side. Resonance frequency measurements were performed 4, 8, 16 and 24 weeks postoperatively and removal torque measurements were performed at 24 weeks. A statistically significant higher implant stability, as assessed by resonance frequency measurements (RFM), was measured from 4 weeks throughout the 24-week period. The mean peak removal torque for the test implants was 50.4+/-10.0 Ncm and 30.0+/-6.9 Ncm for the control implants, which was a statistically significant difference. Histologically, the grafted bone was well incorporated and morphometry revealed more bone around the test implants. Calculations of shear stresses indicated that the grafted bone had similar biomechanical properties to the cortical bone of the recipient site. It is concluded that the integration of titanium implants in autogenous onlay bone grafts results in an increased biomechanical support of the implant. The use of RFM may also serve as a useful instrument for noninvasive monitoring of implant stability in vivo.

An experimental rabbit model for studying the healing of onlay bone grafts.

An experimental rabbit model for studying the incorporation of onlay bone grafts is described. Bone grafts from radius served as the graft and were positioned beneath the mandibular basis. Six rabbits were used in the study and healing periods of 6 weeks and 6 months were used. Each animal was operated twice and in this way the grafts could be followed for six weeks on one side and for 6 months on the contralateral side of the mandible. Healing of the bone graft with bony union to the mandibular base with cortical bone in contact with cortical bone was encouraging. Remodelling of the graft was observed after 6 weeks but was even more pronounced after 6 months. After 6 weeks osteoclastic/osteoblastic activity was primarily observed in the graft-recipient contact area and in the intracortical compartment of the grafted bone. The resorption was most pronounced in the borderlines of the graft. It is concluded that the described experimental model can serve as a useful method for the study of onlay bone graft healing and interaction between implants and bone transplants.

Correction of maxillofacial asymmetry using orthognathic surgical methods.

A total of 20 patients with varying degrees of facial asymmetry were followed clinically and radiographically for at least 18 months after undergoing surgical correction. In 12 of the patients, the cause of asymmetry was hemifacial microsomia of varying severity. Infection of the TMJ in early childhood and irradiation damage were other causes of facial growth disturbance. Bimaxillary osteotomy was carried out in all cases and was often combined with resection of the coronoid process in order to lengthen the ramus. A postoperative jaw exercise programme has proved important as a means of maintaining or increasing mouth-opening capacity. The facial asymmetry cases are not easy to correct and are not always in line with expectations. However, they are an important part of maxillofacial reconstructive surgery.

Diskectomy in temporomandibular joints with internal derangement: a follow-up study.

OBJECTIVE: To follow up a series of patients treated consecutively who had undergone a diskectomy 2 years previously because of persistent pain and disk displacement in the temporomandibular joint. STUDY DESIGN: Sixteen subjects rated their current symptoms during 1 week and were systematically examined for signs of temporomandibular disorders clinically and radiographically by independent observers. RESULTS: Subjectively, all subjects were satisfied with the operation. Five rated their current pain as significant during masticatory function. Some signs of temporomandibular disorders, usually related to function, were registered in all subjects. Postoperative mandibular movements were improved but still below normal range. Signs and symptoms correlated significantly. Surgical complications were nonexistent, but radiographic changes were extensive. Erosion and flattening of the condyle were common. CONCLUSIONS: It was verified that subjects with persistent pain and disk displacement benefit subjectively and clinically from diskectomy. The radiographic outcomes appear less encouraging. Only prospective, randomized, and controlled studies can eventually clarify the effectiveness of diskectomy in relieving pain caused by displacements in the temporomandibular joint.

Structural alterations in the TMJ disk in patients surgically treated for internal derangements (ADD).

Twenty-eight patients with temporomandibular dysfunction problem have been subjected to diskectomy unilaterally. The diagnosis was in 23 patients ADD (anterior disk displacement) without reduction and in another five ADD with reduction. The disk was removed in total according to a routine procedure. Surgical observation of a firm connection between the inferior surface of the disk and the condylar head was noted in eighteen patients. The disk tissue was orientated on a cork sheet according to its position in the fossa and subjected to histological examination. Histopathological analysis showed that the posterior attachment was a considerable part of the specimen in 12 out of 28 disks. Splitting of the disk was confined to the inferior surface. Chondrocytes were found close to the inferior surface. Surface irregularities, tags, were noticed on the inferior surface in thirteen cases. However, cellular signs of inflammation were found in the retrodiskal tissue in eight cases.