A critical review of interpositional grafts following temporomandibular joint discectomy with an overview of the dermis-fat graft

A guide for temporomandibular joint surgery using a simple surgical classification - A narrative-style review

The aim of this narrative style review is to clarify the role of TMJ surgery in the management of specific TMJ disorders by introducing a simple and practical surgical classification. A decade ago, a new surgical classification was published which, like the Wilkes classification, included the five escalating degrees of joint pathology, but with more practical definitions and proposed surgical options for each of the disease categories. The classification begins with Category 1 - painful but otherwise structurally normal joints, which are largely managed nonsurgically. Categories 2 and 3 denote reducing and nonreducing disc displacement of the TMJ, respectively, with the former treated by TMJ arthrocentesis or level 1 arthroscopy and the latter best managed with disc repositioning or discopexy. Category 4 describes degenerative changes to the disc itself, where the disc cannot be salvaged and is thus removed with TMJ discectomy. Lastly, Category 5 refers to end-stage joint disease, where none of the joint components can be salvaged; both the disc and condylar head are sacrificed, and the TMJ is reconstructed with a prosthetic total joint replacement. In the decade since its publication, various studies have served to validate the usefulness of the TMJ surgical classification, and how it can be applied to better understand the role of TMJ surgery in everyday clinical practice.

Superficial musculoaponeurotic system interpositional graft after temporomandibular joint discectomy

Arthroplasty with discectomy is a proven treatment for internal derangement of the temporomandibular joint (TMJ), however there is no consensus on the type of interpositional graft that should be used after the disc is removed. While an ideal graft should be easy to obtain and provide an adequate buffer between the articular surfaces, the authors suggest that it should also minimize donor site morbidity. This Technical Note highlights the technique for harvesting and utilizing the superficial musculoaponeurotic system (SMAS) as an interpositional graft. Three patients were treated with a SMAS graft after TMJ arthroplasty with discectomy. The average pain score decreased from 9/10 preoperatively to 2/10 at 6 weeks postoperatively, while the average maximum incisal opening increased from 31 mm to 36.7 mm. Since these patients were concurrently treated with a facelift, they were asked about their esthetic outcome on a scale of 1-10, with 1 representing extremely dissatisfied and 10 representing extremely satisfied. The average esthetic rating at 6 weeks postoperatively was 9.3/10. The SMAS interpositional graft technique eliminates a second surgical site, improves function, reduces pain, and provides the opportunity for concurrent esthetic facial rejuvenation if desired.

Consensus Report and Recommendations on the Management of Late-stage Internal Derangement of the Temporomandibular Joint

Introduction: This report investigates late-stage internal derangement (ID) of the temporomandibular joint (TMJ) with the aim of establishing a more effective and personalized treatment protocol to improve patients' quality of life (QoL). Material and methods: A consensus was reached among maxillofacial surgeons specializing in LSID, based on a literature research and collective expert experience following the Delphi method. Consensus was considered to be achieved when a response received at least 80% of votes. Results: Four expert groups were established, respectively, focusing on diagnosis, minimally invasive surgery (MIS), open surgery and joint replacement. A comprehensive approach to late-stage ID of the TMJ requires a consensus report. This underscores the need for a personalized treatment plan, considering the variability in clinical presentations and progression of this pathology. Our recommendations aim to optimize clinical outcomes and enhance patient QoL.

Management of paediatric ankylosis

Temporomandibular joint ankylosis (TMJa) is one of the most crippling craniomaxillofacial pathological conditions characterized by replacement of normal architecture of temporomandibular joint (TMJ) with fibrous or bony tissue. The incidence of TMJa is most common in the paediatric population [first and second decades of life] and is commonly associated with maxillofacial trauma. Comprehensive management entails a thorough evaluation of the associated anatomy of the ankylotic mass and other pertinent details like the presence or absence of obstructive sleep apnoea. Categorizing patients based on these variables helps in selecting an appropriate surgical intervention. Various resective and reconstructive surgical techniques are discussed; along with their merits and demerits. Long-term physiotherapy, long-term clinical follow-up and appropriate family counselling are the essential pillars for success. In this review, the authors present an algorithmic approach to evaluation and management of paediatric TMJa. Appropriate recommendations are made based on evidence to select optimum surgical intervention.

Surgical Treatment of Temporomandibular Joint Derangement: 30-Year Follow-Up of Temporomandibular Joint Discectomy, a Case Report and Literature Review

The improvement in diagnostic accuracy, improvement of the endoscopic equipment, better selection of patients for open TMJ surgery, and increased focus on research and education are promising for the treatment of the group of patients with TMJ derangements. In the future, prospective randomized clinical trials need to be performed to give the clinician guidelines as to which type of intervention should be chosen in a particular patient base on accepted criteria for diagnosis and treatment of TMJ derangement.

Decellularized small intestine submucosa device for temporomandibular joint meniscus repair: Acute timepoint safety study

Temporomandibular joint (TMJ) Meniscus removal is an option for the patient to regain full range of motion if the disc is irreversibly damaged or unable to be reduced. However, this procedure leaves the joint vulnerable to condylar remodeling and degeneration. We have shown that extracellular matrix (ECM) scaffolds remodel into a tissue with near native TMJ meniscus in previous studies. The next step towards clinical translation is to manufacture the ECM scaffold as a device under good manufacturing practices (GMP) and test it in a pre-clinical animal study under good laboratory practices (GLP). The primary objective of this study was to evaluate the in-vivo histopathological response to a Prototype GMP manufactured device made of decellularized porcine small intestinal submucosa (SIS), by observing for signs of surrounding tissue reaction to the device that are indicative of an adverse host response in comparison to an empty control at 21 days post-surgical implantation in a canine TMJ meniscus removal and implant model in a GLP setting. The conclusive findings were that the ECM device is safe for placement in the TMJ. After 21 days post implantation, histology of tissue surrounding the device and draining lymph nodes showed that the Prototype GMP device had no negative effects compared to the empty site (as evaluated by the board-certified veterinary pathologist). Furthermore, there was a lack of negative findings for clinical pathology (hematology and clinical chemistry), mortality, and body weight/weight change. Future studies will go to one year after implantation to show that the remodel device remains as a viable tissue with near native mechanical properties.

Advances in Tissue Engineering of the Temporomandibular Joint Disc: An Overview of Current Status and Future Directions

Advances in tissue engineering have progressed to potentially offer a solution to temporomandibular joint disc (TMJ) disorders not amenable to conservative therapies. Conclusive treatment options for patients with end-stage disc disorders requires discectomy and reconstruction of the articular disc with various materials. Tissue engineering TMJ disc is a promising alternative to the limited and sometimes inadequate clinical options in the management of such disorders. However, tissue engineering is far from completion for the TMJ disc regeneration. This review briefly discusses the properties of native disc, the mechanism by which TMJ disorders manifest, and how a tissue engineered disc could assuage the problems inherent in the management of such disorders. Furthermore, the review addresses and provides updates to relevant themes of tissue engineering in regards to the TMJ disc, namely, the scaffolds, cells and biomarkers, hurdles in tissue engineering of the disc, and its application in translation to the clinical practice and future directions.

Use of the Temporalis Myofascial Flap in Internal Derangement of the Temporomandibular Joint - An Evaluative Study

Introduction

Internal derangement is an abnormal relationship between the articular disc and the mandibular condyle. The most common cause is trauma. Various classifications have been given for internal derangement. Initial management is done conservatively and if the disease is progressed, surgery is the option. Various surgical methods and interpositional materials following discectomy have been given in the literature.

Materials and Methods

Over the past 15 years, we selected a group of 30 patients, Wilkes Class IV and V where conservative therapy had failed and were candidates for surgery. The patients had their disc repositioned, the damaged part of the disc was excised and disc was reinforced using the temporalis myofascial flap (TMF). In cases where the disc was non-salvageable, discectomy was done and TMF was placed between condyle and glenoid fossa, sutured with Prolene. The follow-up period was 3 years.

Results

Of the 30 patients, there were 9 male and 21 female. Range of mouth opening was 3.3-3.8 cm with improvements in 1 year. The jaw relations gradually improved and were restored after 3 weeks. Patients were totally pain free in 6 months.

Discussion

For the cases where surgery is the line of treatment, we strongly suggest disc repositioning and reinforcement with TMF as the flap is bulky, locally available and easy to harvest and causes no deformity at the donor site.

Current Treatment Strategies for the Management of the Internal Derangements of the Temporomandibular Joint: A Global Perspective

Internal joint derangement is a disruption of the internal aspects of the TMJ-disc displacements/adhesions/impingements, causing alterations in the normal dynamic motions of the joint. Clinicians must be diligent in establishing the correct diagnosis and cause of TMJID, which ultimately leads to the appropriate management of such patients. While many patients adapt over time or with non-surgical treatment, surgery may be indicated for those with ongoing problems. The surgical pyramid provides a stepwise progression for TMJ surgical patients. This paper aims to review TMJID and its management with special emphasis on arthroscopic minimally invasive surgery, as practised in other countries around the world, and compare this to current education, understanding and practice in India. Currently, India is lagging behind in providing the full scope of TMJ services as there are very few surgeons trained in the skill of arthroscopic techniques. There needs to be continued expansion of our understanding of TMJID treatment in India to bring it level with the rest of the world.

Reasons for failure of total temporomandibular joint replacement: a systematic review and meta-analysis

The aim of this study was to evaluate the revision rate after total alloplastic temporomandibular joint replacement (TMJR) and determine whether there is a higher risk of revision surgery with stock or custom-fitted prostheses (the two most current TMJR prosthesis types). A systematic review was performed, with a search of PubMed, Google Scholar, and the Cochrane Library in November 2020. Overall, 27 articles were included in this study, describing Biomet and TMJ Concepts prostheses and including postoperative data on complications requiring a return to the operating room. A total of 2247 prostheses were analysed: 1350 stock Biomet prostheses and 897 custom-fitted TMJ Concepts and custom-fitted Biomet prostheses. The global revision rate was 1.19 per 100 prosthesis-years. The most common reason for revision was heterotopic bone formation. Stock prostheses appeared to have a lower risk of revision compared to custom prostheses: rate ratio 0.52 (95% confidence interval 0.33-0.81, P-value 0.003). Regarding causes of revision, the only significant difference between the types of devices was a higher rate of heterotopic bone formation for custom-made prostheses (P = 0.001). The results of this study revealed a low revision rate post TMJR revision, with stock devices even less prone to such risk. Nevertheless, these results can be explained by the fact that custom-made prostheses are more likely to be used for cases in which the anatomy is significantly abnormal or there is a history of multiple joint surgeries, which carry a greater risk of complications and heterotopic bone formation.

Autogenous Fat as an Ideal Interpositional Material in Temporomandibular Joint Surgery

Interpositional gap arthroplasty has established itself as the the standard surgical treatment of Temporomandibular joint (TMJ) ankylosis. The autogenous tissue has replaced the alloplastic and other xenografts materials owing to its bioavailability, easy uptake, and no additional cost. Commonly used autogenous tissue has been temporalis muscle and fascia, fascia lata, skin graft, auricular and costal cartilage, the masseter and/or medial pterygoid muscle. With the turn of the century, TMJ surgeons started using autogenous fat from the lower abdomen and today it has taken over as the most favored autogenous filler material in TMJ ankylosis surgery or total joint replacement (TMJ-TJR). The use of buccal fat pad (BFP) has increased in the last decade due to its local availability and pedicled nature. This paper will discuss various autogenous tissues used in interposition and bring forth the journey of the autogenous fat as the preferred interpositional material now and rest the case in its favor.

3D printed gelatin-genipin scaffolds for temporomandibular joint cartilage regeneration

Gelatin has emerged as a biocompatible polymer with high printability in scaffold-based tissue engineering. The aim of the current study was to investigate the potential of genipin-crosslinked 3D printed gelatin scaffolds for temporomandibular joint (TMJ) cartilage regeneration. Crosslinking with genipin increased the stability and mechanical properties, without any cytotoxic effects. Chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSC) on the scaffolds were compared to cell pellets and spheres. Although hBMSC seeded scaffolds showed a lower expression of chondrogenesis-related genes compared to cell pellets and spheres, they demonstrated a significantly reduced expression of collagen (COL) 10, suggesting a decreased hypertrophic tendency. After 21 days, staining with Alcian blue and immunofluorescence for SOX9 and COL1 confirmed the chondrogenic differentiation of hBMSC on genipin-crosslinked gelatin scaffolds. In summary, 3D printed gelatin-genipin scaffolds supported the viability, attachment and chondrogenic differentiation of hBMSC, thus, demonstrating potential for TMJ cartilage regeneration applications.

Biological Treatments for Temporomandibular Joint Disc Disorders: Strategies in Tissue Engineering

The temporomandibular joint (TMJ) is an important structure for the masticatory system and the pathologies associated with it affect a large part of the population and impair people's lifestyle. It comprises an articular disc, that presents low regeneration capacities and the existing clinical options for repairing it are not effective. This way, it is imperative to achieve a permanent solution to guarantee a good quality of life for people who suffer from these pathologies. Complete knowledge of the unique characteristics of the disc will make it easier to achieve a successful tissue engineering (TE) construct. Thus, the search for an effective, safe and lasting solution has already started, including materials that replace the disc, is currently growing. The search for a solution based on TE approaches, which involve regenerating the disc. The present work revises the TMJ disc characteristics and its associated diseases. The different materials used for a total disc replacement are presented, highlighting the TE area. A special focus on future trends in the field and part of the solution for the TMJ problems described in this review will involve the development of a promising engineered disc approach through the use of decellularized extracellular matrices.

Risk Factors Associated With Poor Outcomes Following Temporomandibular Joint Discectomy and Fat Graft

PURPOSE

Temporomandibular joint (TMJ) discectomy is performed for patients with degenerative joint disease with an unsalvageable disc, but with a salvageable condylar head and glenoid fossa. The purpose of this study was to estimate the incidence and risk factors associated with poor postoperative outcomes following TMJ discectomy and abdominal fat grafting.

METHODS

A retrospective cohort study was conducted on patients who underwent TMJ discectomy. Included in this study were patients who had complete data sets with a minimum of 1-year follow-up. Potential risk factors included demographics, preoperative findings (mouth opening, pain levels, previous TMJ surgery), operative findings (disc degeneration, state of TMJ components), and postoperative outcomes (pain levels, mouth opening). Failed outcomes were those who had return of pain postoperatively, no improvement in mouth opening following TMJ discectomy, and/or those who progressed to TMJ total joint replacement (TJR). Statistical methods included Kaplan-Meier curves and Cox proportional hazards regression time to event analyses.

RESULTS

This study included 129 patients who had undergone 132 TMJ discectomies. Most patients were female (89.9%), with a mean age of 43.2 years, standard deviation 14.2. The success rate for discectomy was 75.2% and the conversion rate of TMJ discectomy to TJR was 11.7%. A total of 32 patients (24.8%) experienced return of pain. The median time to return of pain or second surgery was 94.4 months (95% CI = 88.3 to 101.8). No risk factors were statistically significant, although mouth opening improvement of less than 10% was associated with higher risk of poor outcome (P = .77).

CONCLUSION

The findings of this study suggest that lower improvement in mouth opening at 1 year following surgery is likely to result in failure of the TMJ discectomy procedure although the result was not statistically significant. This outcome may ultimately necessitate a TJR.

Role of Custom-Made Prosthesis for Temporomandibular Joint Replacement in Unilateral Ankylosis - An Evaluative Study

Introduction

Ankylosis is a physically and psychologically distressing condition to a patient. The aim of this study was to evaluate the efficiency of custom-made temporomandibular joint (TMJ) prosthesis (fossa-condyle component) in patients with unilateral ankylosis in restoring the form and functions of the TMJ.

Materials and Methods

This retrospective study was conducted in ten patients with unilateral TMJ ankylosis who had undergone TMJ reconstruction with custom-made TMJ prosthesis. Clinical parameters assessed were maximal mouth opening, lateral movements, improvement of the pain levels, and dietary efficiency of the patient. The data were analyzed using SPSS version 20 (IBM Corporation, SPSS Inc.; Chicago, IL, USA).

Results

The mean preoperative mouth opening was 5.70 ± 3.62 mm. After gap arthroplasty, it was 32.50 ± 3.31 mm. The postoperative mouth opening after the reconstruction of TMJ using alloplastic joint prosthesis was 34.90 ± 2.69 mm, and after a mean follow-up period of 4 years, the mean postoperative mouth opening was 34.60 ± 2.50 mm. The mean preoperative movement toward the right and left side was 0.9 ± 1.2 mm and 1.3 ± 1.25 mm, respectively. The mean right and left lateral movements of the TMJ after reconstruction were 3.5 ± 0.97 mm and 3.70 ± 1.06 mm, respectively. There was decrease in deviation of the unaffected jaw during mouth opening and closure. Functional occlusion was maintained postoperatively. There was no appreciable change in the visual analog pain scales. The dietary efficiency improved from a scale of 10 (liquids) to a scale of 0 (no restriction to diet) in eight patients and 1 in two patients. The dietary score improved significantly after alloplastic reconstruction (P = 0.000). No evidence of facial nerve paralysis or foreign body reactions was noted in the patients during the follow-up period. Radiographic assessment revealed good positioning and adaptation of the fossa component and the condylar ramal component both postoperatively and after a mean 4-year follow-up period. There was no evidence of screw loosening or prosthesis breakage during the follow-up period.

Discussion and Conclusion

The custom-made TMJ-total joint replacement (TJR) devices provide stable, improved long-term results, thereby increasing the quality of life of the patient. The custom-made alloplastic TMJ-TJR prosthesis proves to be the optimal surgical procedure to reconstruct the TMJ in comparison to the autogenous grafts (to avoid complications) in severe degenerated and ankylosed joints. However, long-term clinical and radiological studies on a larger sample size are imperative to establish the versatility of this procedure.

Angiostatin-functionalized collagen scaffolds suppress angiogenesis but do not induce chondrogenesis by mesenchymal stromal cells in vivo

Tissue engineering for fibrocartilage regeneration using mesenchymal stromal cells (MSC) and biomaterial scaffolds is emerging as a promising strategy, but inhibiting vascularization to prevent endochondral ossification is important to develop stable implants. The objective of this study was to investigate the effect of angiostatin on inhibition of angiogenesis and promotion of chondrogenesis by collagen scaffolds with or without MSC implanted subcutaneously in rats. One scaffold from the following groups was implanted in each animal: Collagen scaffolds only, scaffolds functionalized with angiostatin, scaffolds loaded with MSC and scaffolds functionalized with angiostatin and loaded with MSC. The various scaffolds were harvested after 2 and 8 weeks for histological analysis, Real-time quantitative polymerase chain reaction (RT-qPCR) and immunofluorescence quantification. Results demonstrated significantly decreased expression of inflammatory (interleukin 1 alpha and beta) and angiogenic genes (platelet and endothelial cell adhesion molecule 1) in scaffolds functionalized with angiostatin after 2 weeks in vivo. Histologically, after 8 weeks, the scaffolds with angiostatin had less inflammatory cells and more collagen matrix formation, but no fibrocartilage formation was detected. Thus, although angiostatin suppressed angiogenesis, it did not stimulate ectopic chondrogenesis in tissue engineered constructs in vivo.

Discectomy with Subsequent Free Fat Flap Insertion in Disc Perforation Therapy of Temporomandibular Joint. Assessment of Results 24 Months after Operation

Discectomy with replacement of disc is one possibility for treating disc perforation where conservative, mini-invasive therapy and arthroscopy has had no effect. Allogenic or autologous materials are used to replace the disc. The authors assess the use of a free fat flap (FFF) in 19 patients who in 2015-2016 underwent a unilateral discectomy with disc replacement. In the retrospective 24-month follow-up study a total of 16 patients (84%) were free of difficulties. 24 months after the operation mouth opening was on average 39.3 mm, pain (VAS - visual analog scale (0-10) was assessed on average at 0.3). Crepitus was present after 24 months in 37.5% of patients (6 patients). An assessment of changes in joint structures on cone beam computed tomography (CBCT) for these patients 24 months after the operation showed the progression of flattening of the joint head, in one case unevenness of the joint head. In 3 cases (16%) there was a recurrence of the state within 24 months - in all cases with clinical manifestations of pain and limited mobility, for these patients on the CBCT significant unevennesses of the joint head, subchondral cysts were noted. The authors find discectomy with use of FFF to be an effective method of treatment with a minimum of complications. However, one should take into account the relatively short time of monitoring after the operation (2 years) and limited number of patients in the cohort (19 patients).

Outcome of eminectomy combined with discectomy and silastic interpositional graft for temporomandibular joint dysfunction: a retrospective study of 20 years

Internal derangement of the temporomandibular joint (TMJ) is usually treated conservatively, but about 5% require surgical treatment. We designed a retrospective study to assess the long-term outcomes of eminectomy combined with discectomy and silastic interpositional graft in 44 patients who had chronic TMJ dysfunction that had not responded to traditional conservative treatment and arthrocentesis. The maximum mouth opening, pain score, Wilkes stage, and clinical dysfunction index were measured before, and two years after, operation. All the patients showed significant improvement in mouth opening and reduced pain scores (p<0.0001 in each case). There were no long-term operative complications, and postoperative magnetic resonance scans showed that the silastic interpositional graft was in a stable position with no evidence of degenerative changes on the surfaces of the joint and no lymphadenopathy.

Key points in surgical management of mandibular condylar fractures

Mandibular condylar fractures are among the most common facial fractures and some of the most difficult to manage. Opinions about the management of mandibular condylar fractures differ among surgeons. With the implementation of new technology, an increased understanding of fracture management, and better functional and morphological outcomes reported in the literature, open reduction and internal fixation is becoming many surgeons' preferred choice for the treatment of condylar fractures. Because surgical treatment of such fractures is complex, certain factors must be considered to achieve satisfactory outcomes. In this article, we summarise six key points in the management of mandibular condylar fractures: virtual evaluation of condylar fracture, a suitable surgical approach, good reduction, stable internal fixation, repair of the articular disc, and restoration of the mandibular arch width. We believe that these points will help to improve the prognosis of mandibular condyle fractures.

Clinical assessment of acellular dermal matrix (AlloDerm©) as an option in the replacement of the temporomandibular joint disc: A pilot study

BACKGROUND

There is limited data available in the literature describing the utility of acellular dermal matrix (AlloDerm©) in the replacement of the temporomandibular joint disc. Few reports of clinicians using implantable AlloDerm to replace the disc do exist, however, this has been described for reconstruction after surgical resection of the entire temporomandibular joint complex to treat pathology, as opposed to isolated articular disc disorders. Moreover, there is a lack of description in the literature regarding associated perioperative outcomes after such a procedure. We sought to assess the immediate perioperative outcomes in the form of a pilot study, to determine whether this technique warrants further investigation in the form of prospective clinical studies.

METHODS

The study team conducted a retrospective review of medical records for patients who underwent temporomandibular joint discectomy and replacement with AlloDerm© at a single tertiary care center, from 2011 to 2016. Perioperative outcomes of interest including pain levels and range of motion were recorded and descriptive statistics were utilized for statistical analysis.

RESULTS

15 patients met the inclusion criteria, of which 87% were females and 13% males. The mean age was 47.27±15.93 years. Preoperatively, 74% of the patients reported severe pain (VAS scores of 7-10); in contrast, 73% of the patients reported only mild pain (VAS scores of 1-3) during the postoperative visits, suggesting an overall reduction in pain intensity. Range of motion also improved from an average of 27.73±13.04mm, to an average of 38.60±6.08mm (P<0.01).

CONCLUSIONS

Based on our preliminary data, patients with advanced TMJ articular disc disorders showed clinical improvement from discectomy and replacement with acellular dermal matrix (AlloDerm©). Further longitudinal studies evaluating long-term outcomes need to be conducted to validate this technique, in the form of larger sample sizes with a control group, as well as radiographic assessment of long-term clinical outcomes.

Tissue engineering toward temporomandibular joint disc regeneration

Treatments for temporomandibular joint (TMJ) disc thinning and perforation, conditions prevalent in TMJ pathologies, are palliative but not reparative. To address this, scaffold-free tissue-engineered implants were created using allogeneic, passaged costal chondrocytes. A combination of compressive and bioactive stimulation regimens produced implants with mechanical properties akin to those of the native disc. Efficacy in repairing disc thinning was examined in minipigs. Compared to empty controls, treatment with tissue-engineered implants restored disc integrity by inducing 4.4 times more complete defect closure, formed 3.4-fold stiffer repair tissue, and promoted 3.2-fold stiffer intralaminar fusion. The osteoarthritis score (indicative of degenerative changes) of the untreated group was 3.0-fold of the implant-treated group. This tissue engineering strategy paves the way for developing tissue-engineered implants as clinical treatments for TMJ disc thinning.

Guidelines for Single-Stage Correction of TMJ Ankylosis, Facial Asymmetry and OSA in Adults

Introduction

Treatment for TMJ Ankylosis aims at restoring joint function, improving the patient's aesthetic appearance and quality of life and preventing re-ankylosis. Mouth opening is achieved by gap arthroplasty with various options of interpositional materials. Ramus-condyle unit (RCU) reconstruction maintains the height of the ramus and prevents secondary occlusal problems. Advancement genioplasty corrects chin deformities as well as increases the posterior airway space (N-PAS) by the forward pull exerted on geniohyoid and genioglossus.

Materials and Methods

This prospective single-centre study on 43 joints in 25 adult patients with TMJ Ankylosis aimed at providing a single-staged management plan of ankylosis release, RCU reconstruction and extended advancement centering genioplasty. Interpositional arthroplasty was done using temporalis myofascial flap, abdominal dermis fat or buccal fat pad. RCU reconstruction was done either by vertical ramus osteotomy or L osteotomy.

Observations and Results

Follow-up ranged from 12 to 20 months (mean 14.4). Average mouth opening at maximum follow-up was 34.36 mm with re-ankylosis in no case. Cephalometric parameters showed increase in point P to Pog, decrease in N perpendicular to Pog, angle N-A-Pog, Cg-ANS to Cg-Menton, neck-chin angle and labiomental angle. N-PAS increased, and average 50% improvement in AHI was seen in all patients with OSA. Most common complications involved transient paraesthesia of temporal and zygomatic branches of facial nerve.

Conclusion

Based on the findings of the above study, we propose treatment guidelines for treatment of TMJ ankylosis in adult patients with AHI < 20.

Temporomandibular Joint Discectomy Followed by Disc Replacement Using Viable Osteochondral and Umbilical Cord Allografts Results in Improved Patient Outcomes

PURPOSE

The ideal surgical solution to reconstruct the temporomandibular joint (TMJ) disc after it has been removed has remained elusive. The major obstacle has been identifying a durable biocompatible material that will provide for restoration of TMJ function. The present study evaluated the outcomes of the interpositional implantation of a cryopreserved viable osteochondral allograft (CVOCA) combined with a viable cryopreserved umbilical cord tissue (vCUT) allograft after TMJ discectomy in patients with internal derangement and/or degenerative joint disease (DJD).

PATIENTS AND METHODS

We implemented a retrospective case series study and enrolled patients with DJD or disc displacement diagnosed using the Diagnostic Criteria of Temporomandibular Disorders, who had undergone interpositional CVOCA and vCUT implantation after TMJ discectomy. The primary outcome variable was pain, measured using a visual analog scale (VAS). The secondary outcomes variables included maximal incisal opening (MIO) and Glasgow Benefit Inventory (GBI) general subscale scores. The primary analysis compared the preoperative measures with those at the last follow-up visit. Descriptive and analytic statistics were computed to summarize the sample's characteristics and assess the pre- and postoperative differences.

RESULTS

The study sample included 9 patients with a mean age of 36 years, and 44% were men. The VAS scores had decreased significantly from 9.0 ± 2.0 to 3.0 ± 3.0 postoperatively (P = .001). The MIO had increased from 31 ± 5 to 36 ± 5 mm (P = .178). The average GBI general subscale score of 13 ± 46 for the 9 patients showed a trend toward improved quality of life and patient satisfaction with the surgery. The median postoperative follow-up at the time of our report was 15 months (interquartile range, 10; range, 2 to 27) without treatment-related complications.

CONCLUSIONS

The reported outcomes suggest that the interpositional implantation of CVOCA and vCUT after TMJ discectomy could be a solution for reducing TMJ-related pain and restoring TMJ function. Longer follow-up and prospective multicenter studies are warranted.

Tissue Engineering for the Temporomandibular Joint

Tissue engineering potentially offers new treatments for disorders of the temporomandibular joint which frequently afflict patients. Damage or disease in this area adversely affects masticatory function and speaking, reducing patients' quality of life. Effective treatment options for patients suffering from severe temporomandibular joint disorders are in high demand because surgical options are restricted to removal of damaged tissue or complete replacement of the joint with prosthetics. Tissue engineering approaches for the temporomandibular joint are a promising alternative to the limited clinical treatment options. However, tissue engineering is still a developing field and only in its formative years for the temporomandibular joint. This review outlines the anatomical and physiological characteristics of the temporomandibular joint, clinical management of temporomandibular joint disorder, and current perspectives in the tissue engineering approach for the temporomandibular joint disorder. The tissue engineering perspectives have been categorized according to the primary structures of the temporomandibular joint: the disc, the mandibular condyle, and the glenoid fossa. In each section, contemporary approaches in cellularization, growth factor selection, and scaffold fabrication strategies are reviewed in detail along with their achievements and challenges.

Pre-arthroplastic mandibular distraction osteogenesis for the correction of OSA in TMJ ankylosis: a prospective observational study of 25 cases

INTRODUCTION

In severe TMJ ankylosis cases, the lack of growth of the mandible creates an anatomically narrow airway with a reduced pharyngeal airway space [PAS] which predisposes these patients towards obstructive apnoea [OSA]. There is evidence in the literature that such patients experience severe discomfort during physiotherapy if such airway abnormalities are not corrected prior to ankylosis release. This eventually leads to non-compliance towards physiotherapy and increases the risk of re-ankylosis.

OBJECTIVE

In our study, pre-arthroplastic mandibular distraction osteogenesis [DO] was used to increase the PAS and resolve the underlying OSA prior to releasing the ankylosis.

MATERIALS AND METHODS

Twenty-five cases of TMJ ankylosis with micrognathia and OSA were included in this prospective observational sleep study. They were further divided into a paediatric group [14 subjects] and an adult group [11 subjects]. All cases presented with a history of onset of ankylosis during childhood [before the completion of craniofacial growth] as result of which there was a lack of forward growth of the mandible. Subjects included in our study underwent initial DO of the mandible followed by a second procedure for distractor removal and ankylosis release. Questionnaires, lateral cephalograms and sleep studies were taken pre-operatively (T0), immediate post-distraction to the desired length (T1) and 12 months post the distractor removal and ankylosis release (T2). The parameters studied were PAS width, apnoea hypopnea index [AHI], O₂ saturation, mouth opening and mandibular advancement.

RESULTS

The paediatric group variables were as follows: mean PAS width which increased from 3.5 mm [T0] to 9 mm [T2], mean AHI which decreased from 48.04 [T0] to 3.60 [T2], mouth opening which increased from 4.5 mm [T0] to 34 mm [T2] and mean O₂ saturation which increased from 89.86% [T1] to 96.88% [T2]. The adult group variables were as follows: mean PAS width which increased from 5 mm [T0] to 11 mm [T2], mean AHI which decreased from 31.45 [T0] to 1.43 [T2], mouth opening which increased from 5 mm [T0] to 34 mm [T2] and mean O₂ saturation which increased from 92.01% [T0] to 96.84% [T2]. Statistical analysis revealed that DO of the mandible significantly improved OSA by increasing the PAS which was evident by the lower AHI score. Mouth opening was also significantly improved post ankylosis release and maintained at the T2 interval. Ten subjects followed up beyond the T2 interval [mean 28 months post ankylosis release] and their data also revealed positive compliance towards physiotherapy, adequate mouth opening and maintenance of normal AHI.

CONCLUSION

Pre-arthroplastic mandibular DO has proved to be a successful modality for treatment of OSA in TMJ ankylosis patients with stable results at 12 months. By resolving the narrow airway and OSA, compliance towards physiotherapy was improved thus reducing the risk of re-ankylosis in the long term.

Fibro/chondrogenic differentiation of dental stem cells into chitosan/alginate scaffolds towards temporomandibular joint disc regeneration

Tissue engineering (TE) may provide effective alternative treatment for challenging temporomandibular joint (TMJ) pathologies associated with disc malpositioning or degeneration and leading to severe masticatory dysfunction. Aim of this study was to evaluate the potential of chitosan/alginate (Ch/Alg) scaffolds to promote fibro/chondrogenic differentiation of dental pulp stem cells (DPSCs) and production of fibrocartilage tissue, serving as a replacement of the natural TMJ disc. Ch/Alg scaffolds were fabricated by crosslinking with CaCl2 combined or not with glutaraldehyde, resulting in two scaffold types that were physicochemically characterized, seeded with DPSCs or human nucleus pulposus cells (hNPCs) used as control and evaluated for cell attachment, viability, and proliferation. The DPSCs/scaffold constructs were incubated for up to 8 weeks and assessed for extracellular matrix production by means of histology, immunofluorescence, and thermomechanical analysis. Both Ch/Alg scaffold types with a mass ratio of 1:1 presented a gel-like structure with interconnected pores. Scaffolds supported cell adhesion and long-term viability/proliferation of DPSCs and hNPCs. DPSCs cultured into Ch/Alg scaffolds demonstrated a significant increase of gene expression of fibrocartilaginous markers (COLI, COL X, SOX9, COM, ACAN) after up to 3 weeks in culture. Dynamic thermomechanical analysis revealed that scaffolds loaded with DPSCs significantly increased storage modulus and elastic response compared to cell-free scaffolds, obtaining values similar to those of native TMJ disc. Histological data and immunochemical staining for aggrecan after 4 to 8 weeks indicated that the scaffolds support abundant fibrocartilaginous tissue formation, thus providing a promising strategy for TMJ disc TE-based replacement.

Scaffold-Based Temporomandibular Joint Tissue Regeneration in Experimental Animal Models: A Systematic Review

Reconstruction of degenerated temporomandibular joint (TMJ) structures remains a clinical challenge. Tissue engineering (TE) is a promising alternative to current treatment options, where the TMJ is either left without functional components, or replaced with autogenous, allogeneic, or synthetic grafts. The objective of this systematic review was to answer the focused question: in experimental animal models, does the implantation of biomaterial scaffolds loaded with cells and/or growth factors (GFs) enhance regeneration of the discal or osteochondral TMJ tissues, compared with scaffolds alone, without cells, or GFs? Following PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analysis) guidelines, electronic databases were searched for relevant controlled preclinical in vivo studies. Thirty studies reporting TMJ TE strategies in both small (rodents, rabbits; n = 25) and large animals (dogs, sheep, goats; n = 5) reporting histological and/or radiographic outcomes were included. Twelve studies reported ectopic (subcutaneous) implantation models in rodents, whereas 18 studies reported orthotopic, surgically induced defect models in large animals. On average, studies presented with an unclear-to-high risk of bias. In most studies, mesenchymal stem cells or chondrocytes were used in combination with either natural or synthetic polymer scaffolds, aiming for either TMJ disc or condyle regeneration. In summary, the overall preclinical evidence (ectopic [n = 6] and orthotopic TMJ models [n = 6]) indicate that addition of chondrogenic and/or osteogenic cells to biomaterial scaffolds enhances the potential for TMJ tissue regeneration. Standardization of animal models and quantitative outcome evaluations (biomechanical, biochemical, histomorphometric, and radiographic) in future studies, would allow more reliable comparisons and increase the validity of the results.

Temporomandibular joint arthroplasty for osteoarthrosis: A series of 24 patients that received a uni- or bilateral inter-positional silicone sheet

PURPOSE

To evaluate mid-term results from using a silicone sheet for inter-positional arthroplasty in moderate or severe cases of osteoarthrosis of the temporo-mandibular joint (TMJ). To also determine any remaining indications from this method.

PATIENTS AND METHODS

This retrospective study included patients that underwent surgery between 2008 and 2016. Pre- and post-operative mouth opening (MO), according to inter-incisal distance (mm) and pain score (PS: 0=no pain to 4=very severe pain) were recorded for 24 patients. Patients were divided according to thickness of the silicone sheet (group A: 1.0 mm, group B: 1.5 mm).

RESULTS

The cohort included 22 females (92%). Mean age at surgery was 55 years±13 (26-80). Mean length of follow-up was 26 months±24 (6-80). Mean improvement in MO was 8.2 mm (+33%) and of PS was 1.7 (-68%). MO was not improved for two patients and worsened for one. PS score improved for all patients. No statistical difference was found between groups A and B. There was also a tendency for degradation of outcomes over time.

CONCLUSION

The poor reputation of prosthetic discoplasty was not as evident in our series, even though anatomical and functional status seemed to deteriorate over time. This is because total-joint prosthetic replacement is often proposed instead. However, for elderly or fragile patients that have severe pain, and regarding cost-benefit aspects, conventional arthroplasty can still be discussed, especially since French national health-care insurance does not yet support TMJ prosthetic replacement for osteoarthrosis.

Regionally variant collagen alignment correlates with viscoelastic properties of the disc of the human temporomandibular joint

OBJECTIVE

To determine the regionally variant quality of collagen alignment in human TMJ discs and its statistical correlation with viscoelastic properties.

DESIGN

For quantitative analysis of the quality of collagen alignment, horizontal sections of human TMJ discs with Pricrosirius Red staining were imaged under circularly polarized microscopy. Mean angle and angular deviation of collagen fibers in each region were analyzed using a well-established automated image-processing for angular gradient. Instantaneous and relaxation moduli of each disc region were measured under stress-relaxation test both in tensile and compression. Then Spearman correlation analysis was performed between the angular deviation and the moduli. To understand the effect of glycosaminoglycans on the correlation, TMJ disc samples were treated by chondroitinase ABC (C-ABC).

RESULTS

Our imaging processing analysis showed the region-variant direction of collagen alignment, consistently with previous findings. Interestingly, the quality of collagen alignment, not only the directions, was significantly different in between the regions. The angular deviation of fiber alignment in the anterior and intermediate regions were significantly smaller than the posterior region. Medial and lateral regions showed significantly bigger angular deviation than all the other regions. The regionally variant angular deviation values showed statistically significant correlation with the tensile instantaneous modulus and the relaxation modulus, partially dependent on C-ABC treatment.

CONCLUSION

Our findings suggest the region-variant degree of collagen fiber alignment is likely attributed to the heterogeneous viscoelastic properties of TMJ disc that may have significant implications in development of regenerative therapy for TMJ disc.

Interleukin-6 expression in disc derangement of human temporomandibular joint and association with osteoarthrosis

The inflammatory process is a coordinated response that protects host after infection or trauma, involving several molecular reactions. Once the inflammation is closely linked to the process of destruction of the temporomandibular joint, this study aims to examine, by immunohistochemistry, the expression of interleukin-6 (IL-6), an important inflammatory marker, in temporomandibular articular discs of patients with anterior disc displacement with (ADDwR) and without reduction (ADDwoR) and its association with osteoarthrosis (OA). Thirty-eight (n = 38) articular discs were divided into two cutoffs: 1) analysis 1: 4 control (acute pathology), 17 ADDwR, 17 ADDwoR; and 2) analysis 2: without OA (n = 21) and with OA (n = 17). The area of immunostaining was compared statistically between groups (p < 0.05). In the disc samples, no significant differences were observed between the groups ADDwR and ADDwoR, and with and without OA, in respect to the expression of IL-6 by immunohistochemical examination. Future studies should be conducted with a larger sample size, which could clarify the association of the inflammatory mediator IL-6 with temporomandibular joint dysfunction.

Engineering Human TMJ Discs with Protein-Releasing 3D-Printed Scaffolds

The temporomandibular joint (TMJ) disc is a heterogeneous fibrocartilaginous tissue positioned between the mandibular condyle and glenoid fossa of the temporal bone, with important roles in TMJ functions. Tissue engineering TMJ discs has emerged as an alternative approach to overcoming limitations of current treatments for TMJ disorders. However, the anisotropic collagen orientation and inhomogeneous fibrocartilaginous matrix distribution present challenges in the tissue engineering of functional TMJ discs. Here, we developed 3-dimensional (3D)-printed anatomically correct scaffolds with region-variant microstrand alignment, mimicking anisotropic collagen alignment in the TMJ disc and corresponding mechanical properties. Connective tissue growth factor (CTGF) and transforming growth factor beta 3 (TGFβ3) were then delivered in the scaffolds by spatially embedding CTGF- or TGFβ3-encapsulated microspheres (µS) to reconstruct the regionally variant fibrocartilaginous matrix in the native TMJ disc. When cultured with human mesenchymal stem/progenitor cells (MSCs) for 6 wk, 3D-printed scaffolds with CTGF/TGFβ3-µS resulted in a heterogeneous fibrocartilaginous matrix with overall distribution of collagen-rich fibrous structure in the anterior/posterior (AP) bands and fibrocartilaginous matrix in the intermediate zone, reminiscent of the native TMJ disc. High dose of CTGF/TGFβ3-µS (100 mg µS/g of scaffold) showed significantly more collagen II and aggrecan in the intermediate zone than a low dose (50 mg µS/g of scaffold). Similarly, a high dose of CTGF/TGFβ3-µS yielded significantly higher collagen I expression in the AP bands compared with the low-dose and empty µS. From stress relaxation tests, the ratio of relaxation modulus to instantaneous modulus was significantly smaller with CTGF/TGFβ3-µS than empty µS. Similarly, a significantly higher coefficient of viscosity was achieved with the high dose of CTGF/TGFβ3-µS compared with the low-dose and empty µS, suggesting the dose effect of CTGF and TGFβ3 on fibrocartilage formation. Together, our findings may represent an efficient approach to engineering the TMJ disc graft with anisotropic scaffold microstructure, heterogeneous fibrocartilaginous matrix, and region-dependent viscoelastic properties.

Advancing biomaterials of human origin for tissue engineering

Biomaterials have played an increasingly prominent role in the success of biomedical devices and in the development of tissue engineering, which seeks to unlock the regenerative potential innate to human tissues/organs in a state of deterioration and to restore or reestablish normal bodily function. Advances in our understanding of regenerative biomaterials and their roles in new tissue formation can potentially open a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multi-component construction of native extracellular matrices (ECMs) for cell accommodation, the synthetic biomaterials produced today routinely incorporate biologically active components to define an artificial in vivo milieu with complex and dynamic interactions that foster and regulate stem cells, similar to the events occurring in a natural cellular microenvironment. The range and degree of biomaterial sophistication have also dramatically increased as more knowledge has accumulated through materials science, matrix biology and tissue engineering. However, achieving clinical translation and commercial success requires regenerative biomaterials to be not only efficacious and safe but also cost-effective and convenient for use and production. Utilizing biomaterials of human origin as building blocks for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural tissue with regard to its physical and chemical properties for the orchestration of wound healing and tissue regeneration. In addition to directly using tissue transfers and transplants for repair, new applications of human-derived biomaterials are now focusing on the use of naturally occurring biomacromolecules, decellularized ECM scaffolds and autologous preparations rich in growth factors/non-expanded stem cells to either target acceleration/magnification of the body's own repair capacity or use nature's paradigms to create new tissues for restoration. In particular, there is increasing interest in separating ECMs into simplified functional domains and/or biopolymeric assemblies so that these components/constituents can be discretely exploited and manipulated for the production of bioscaffolds and new biomimetic biomaterials. Here, following an overview of tissue auto-/allo-transplantation, we discuss the recent trends and advances as well as the challenges and future directions in the evolution and application of human-derived biomaterials for reconstructive surgery and tissue engineering. In particular, we focus on an exploration of the structural, mechanical, biochemical and biological information present in native human tissue for bioengineering applications and to provide inspiration for the design of future biomaterials.

The fate of autogenous free fat grafts in the human temporomandibular joint using magnetic resonance imaging

OBJECTIVE

Autologous fat grafts in the temporomandibular joint (TMJ) has achieved positive clinical effects in preventing adhesion after surgery. However it still remains indeterminate about the survival rate of grafted fat. The purpose of this study was to evaluate the long-term survival rate of free fat grafts in the TMJ using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

89 patients (117 joints) with free fat grafts placed into TMJs following modified TMJ disc anchor were included in our study. They were divided into the following groups according to the time lapse between TMJ surgery and the latest MRI investigation: 1-3 months, 4-6 months, 7-12 months, 13-24 months, and >24 months. The signal intensity changes and volume retention were evaluated by MRI.

RESULTS

The volume retention rate of grafted free fat showed that the size was hovering right around 50% although it reduced very slowly with a long-term follow-up. Nearly half joints showed lower signal intensity of the grafted fat on MRI within 6 months and it recovered to normal compared with that of the day after surgery 6 months later.

CONCLUSIONS

Free fat grafted into TMJ cavity could be alive for a long time with the survival rate about 48.44%. However the survival mechanism has still been unknown, which need us to explore and study in the future.

Ultrasonography for the volumetric analysis of the buccal fat pad as an interposition material for the management of ankylosis of the temporomandibular joint in adolescent patients

The aim of this study was to analyse preoperatively with ultrasound the minimum volume of buccal fat that would be required for interposition of a pad after gap arthroplasty, and to emphasise the value of such a pad in the management of ankylosis of the temporomandibular joint (TMJ) during a short term follow up. Nineteen patients with ankylosis of the TMJ (22 joints) were selected, whose mean (SD) mouth opening was 4.9 (3.7) mm. In 10 joints in which the mean (SD) volume of the buccal fat pad was 0.7 (0.2) ml, the harvested buccal fat was inadequate for interposition, so they were treated with other materials. The remaining 12 joints had a mean (SD) volume of 1.1 (0.3) ml, which gave enough fat for interposition after gap arthroplasty. Investigation with ultrasound at 15 days and 6 months postoperatively showed that the fat pad was viable and the volume had shrunk by 28%. The 6-month postoperative computed tomographic (CT) scan showed little or no heterotopic calcification. We conclude that a buccal fat pad with a preoperative mean (SD) volume of 1.1 (0.3) ml is easy to harvest as interposition material. At a mean follow up of the 12 joints after 31 (range 24-36) months there was progressive improvement in mouth opening with a mean (SD) of 32.5 (5.0) mm, which established that a pedicled buccal fat pad is a stable, efficient, viable soft tissue barrier in the management of ankylosis of the TMJ.

Tissue engineering of the temporomandibular joint disc: current status and future trends

INTRODUCTION

Temporomandibular joint disorders are extremely prevalent and there is no ideal treatment clinically for the moment. For severe cases, a discectomy often need to be performed, which will further result in the development of osteoarthritis. In the past thirty years, tissue engineering has provided a promising approach for the effective remedy of severe TMJ disease through the creation of viable, effective, and biological functional implants.

METHODS

Although TMJ disc tissue engineering is still in early stage, unremitting efforts and some achievements have been made over the past decades. In this review, a comprehensive summary of the available literature on the progress and status in tissue engineering of the TMJ disc regarding cell sources, scaffolds, biochemical and biomechanical stimuli, and other prospects relative to this field is provided.

RESULTS AND CONCLUSIONS

Even though research studies in this field are too few compared to other fibrocartilage (e.g., knee meniscus) and numerous, difficult tasks still exist, we believe that our ultimate goal of regenerating a biological implant whose histological, biochemical, and biomechanical properties parallel native TMJ discs for clinical therapy will be achieved in the near future.

Temporomandibular disorders: evaluation and management

Temporomandibular disorders remain a common cause of visits to primary care physicians, internists, pediatricians, and emergency departments. Advances in the clinical diagnosis, radiographic imaging, and classification of these disorders have improved long-term management. There are several types of disorders of the masticatory muscles and the temporomandibular joint as well as associated structures and each may have a complex cause, clinical course, and response to therapy. Host susceptibility plays a role at several stages of these disorders. Future research offers greater possibility in defining this heterogeneous group of disorders and providing more focused and effective treatment strategies.

Comparing calvarial transport distraction with and without radiation and fat grafting

The purpose of this study is to: a) assess transport distraction to reconstruct cranial defects in radiated and non-radiated fields b) examine adipose grafting's effect on the bony regenerate and overlying wound, and c) elucidate sources of bone formation during transport distraction osteogenesis. Twenty-three male New Zealand white rabbits (3 months; 3.5 kg) were used, 10 non-irradiated and 13 irradiated (17 treatment, 6 control) with a one-time fraction of 35 Gy. A 16 × 16 mm defect was abutted by a 10 × 16 mm transport disc 5 weeks after irradiation, and 11 animals were fat grafted at the distraction site. Latency (1 day), distraction (1.5 mm/day), and consolidation (4 weeks) followed. Fluorochromes were injected subcutaneously and microCT, fluorescence, and histology assessed. In distracted animals without fat grafting, bone density measured 701.87 mgHA/ccm and 2271.95 mgHA/ccm in irradiated and non-irradiated animals. In distracted animals with fat grafting, bone density measured 703.23 mgHA/ccm and 2254.27 mgHA/ccm in irradiated and non-irradiated animals. Fluorescence revealed ossification emanating from the dura, periosteum, and transport segment with decreased formation in irradiated animals. Transport distraction is possible for cranial reconstruction in irradiated fields but short-term osseous fill is significantly diminished. Adipose grafting enhances wound healing in previously irradiated fields but does not enhance ossification.