Kenichi Kurita

Reliability of a negative clinical temporomandibular joint examination: Prevalence of disk displacement in asymptomatic temporomandibular joints☆

Unilateral temporomandibular joint arthrography was performed in 40 healthy volunteers with asymptomatic and clinically normal temporomandibular joints. Thirty-four joints (85%) showed superior disk position, and six joints (15%) were radiographically abnormal with displacement of the disk. Thus, two showed anterior displacement, one showed rotational anterolateral displacement, one showed rotational anteromedial displacement, one showed sideways lateral and one showed sideways medial displacement. Thus, a negative clinical examination for temporomandibular joint internal derangements may involve a risk of being false-negative. All but one of the joints showed normalization of disk position during opening, and it is suggested that lack of functional disturbances accounts for the freedom of symptoms.

Natural Course of Untreated Symptomatic Temporomandibular Joint Disc Displacement without Reduction

In some patients with disc displacement without reduction, the symptoms of pain and decreased range of motion have been observed to resolve spontaneously over time without treatment. The natural history of this condition, however, is not well-understood. Thus, to study the natural course of disc displacement without reduction, we followed 40 patients without treatment for a period of 2.5 years. The diagnosis was established by history and physical examination and confirmed with magnetic resonance (MR) imaging. After 2.5 years, 43% of the patients were asymptomatic, 33% had decreased symptoms, and 25% of the patients showed no improvement or had required treatment. MR evidence of osteoarthritis and advanced stages of internal derangement at the initial evaluation was associated with a poor prognosis. The result of this prospective cohort study indicated that approximately 40% of patients with symptomatic disc displacement without reduction will be free of symptoms within 2.5 years, one-third will improve, whereas one-quarter will continue to be symptomatic. This knowledge should be valuable for the treatment planning and evaluation of prognosis of patients with non-reducing symptomatic disc displacement.

Prevalence of temporomandibular joint internal derangement in patients with craniomandibular disorders

To determine the prevalence of temporomandibular joint internal derangement in patients with signs and symptoms of craniomandibular disorders, bilateral imaging was performed in a consecutive series of 115 patients with signs and symptoms of craniomandibular disorders. Ninety patients (78%) had different stages of unilateral or bilateral internal derangement, and 25 patients (22%) had normal temporomandibular joints bilaterally. Out of 230 joints, 60 showed disk displacement with reduction, 8 showed disk displacement without reduction, and 29 showed disk displacement without reduction associated with anthrosis. The study indicates that almost 80% of patients with signs and symptoms of craniomandibular disorders have different forms of internal derangement.

Histologic features of the temporomandibular joint disk and posterior disk attachment: Comparison of symptom-free persons with normally positioned disks and patients with internal derangement☆

To gain further knowledge about the differences between normal and pathologic anatomy of the temporomandibular joint disk, we examined histologically disks obtained at autopsy from 10 symptom-free persons and compared our findings with observations involving 17 surgically removed disks. The surgical patients had internal derangement and severe long-standing temporomandibular joint pain and dysfunction. The normal disks were biconcave, whereas the surgically removed disks were deformed and thicker than the normal disks. Chondrocytes (4 joints), a surface layer of proliferative connective tissue (4 joints), vessels (2 joints), and splitting (4 joints) were seen in the surgical specimens but not in the normal specimens. The surgical specimens also showed higher maximal density of fibroblasts and vessels. It was concluded that surgically removed temporomandibular joint disks demonstrated several histologic alterations that were not seen in normal disks. These characteristics may serve as the basis for development of a histologic grading of pathologic conditions of the temporomandibular joint disk and the posterior disk attachment.

Clinical evaluations of coronectomy (intentional partial odontectomy) for mandibular third molars using dental computed tomography: a case-control study.

PURPOSE Studies have suggested that coronectomy reduces the risk of inferior alveolar nerve injury (IANI) when a close relationship with the inferior alveolar canal is indicated on panoramic imaging. However, the relationship between the inferior alveolar canal and the root are unclear on panoramic imaging. Our aim was to compare coronectomy with traditional extraction for the treatment of mandibular third molars that had clear high IANI risks as evaluated by dental computed tomography. PATIENTS AND METHODS We designed a case-control study of subjects with high-risk signs of IANI on panoramic images evaluated by dental computed tomography before enrollment. The 220 patients enrolled were assigned to extraction (control group, n = 118) or coronectomy (case group, n = 102). RESULTS The mean follow-up time was 13 months in the extraction group and 13.5 months in the coronectomy group. Six IANIs (5%) were found in the extraction group. In the coronectomy group, 1 patient (1%) had symptoms of neurapraxia, which disappeared within 1 month. Four remaining roots had signs of postoperative infection, and the patients underwent extraction of the root. No nerve damage resulted in these patients after repeat extraction. CONCLUSIONS Coronectomy might reduce the risk of nerve injury for patients at true high risk of IANI as evaluated by dental computed tomography. A long-term postoperative review is needed to assess the incidence of root migration and the root extraction and infection rates after coronectomy.

The role of the disk in sheep temporomandibular joint ankylosis

OBJECTIVE The purpose of this study was to determine the role of the disk in intraarticular ankylosis of the temporomandibular joint. STUDY DESIGN Twelve adult sheep were divided into 2 groups. In group 1, removal of the temporal and condylar articular surfaces was performed on the right temporomandibular joint and the disk was maintained; in group 2, removal of the articular surfaces and diskectomy were performed on the right temporomandibular joint. One sheep from each group was killed just after surgery and 5 sheep from each group were killed at 3 months. The joints were examined radiologically, macroscopically, and histologically. The range of jaw movements was recorded preoperatively and at sacrifice. RESULTS Each of 2 sheep in group 2 had lost 4% of their body weight by 3 months; all of the other sheep maintained or increased their weight. The range of jaw motion to the right was significantly lower in group 2 than in group 1 (P<.01). In group 1, fibrous repair of the articular surface and regeneration of the condylar head was seen. In group 2, each of the joints showed a total fibrous ankylosis with some calcification. There was a statistically significant difference in radiologic score between the groups (P<.0001). Histologic scores for group 1 demonstrated significantly lower scores on the degree of ankylosis scale and degree of calcification scale (P<.0001). CONCLUSIONS This study showed that the presence of the disk prevented the development of fibrous intraarticular ankylosis of the temporomandibular joint.

Pain threshold and pain recovery after experimental stimulation in patients with burning mouth syndrome

Abstract The aim of the present study was to examine pain threshold and pain recovery in patients with burning mouth syndrome (BMS) and matched no‐pain controls. Twenty female patients diagnosed with BMS without organic gross changes were enrolled in the study. Twenty control subjects were chosen from age‐matched healthy female volunteers. We compared the thermal pain threshold using heat beam dolorimeter on the finger and tongue between patients and controls. Warm (at 50°C for 5 s), cold (at 0°C for 30 s) and mechanical (stimulation by electric tooth brush for 15 s) stimulation was applied to the tongue for both groups. Participants were asked to rate the subjective pain using a visual analogue scale (VAS). Although there was no significant differences between patients and controls in terms of the threshold on the finger, the threshold on the tongue was significantly higher in patients than in controls. We suggest there were peripheral dysfunction at the tongue, and/or central dysfunction in patients with BMS. Among the three types of stimulation, the patients perceived significantly the highest pain from the mechanical stimulation for the first 5 min after the stimulation. Furthermore, when patients with BMS perceived some pain, they continued to complain of the pain longer and more intricately than the controls. This indicates that the pain of the patients is strongly affected not only at a sensory component but also at an affective/motivational component than the controls. However, we should be cautious of simply advancing psychogenic theory in this etiology.

The use of granulocyte-colony stimulating factor induced mobilization for isolation of dental pulp stem cells with high regenerative potential.

Human dental pulp stem cells (DPSCs) contain subsets of progenitor/stem cells with high angiogenic, neurogenic and regenerative potential useful for cell therapy. It is essential to develop a safe and efficacious method to isolate the clinical-grade DPSCs subsets from a small amount of pulp tissue without using conventional flow cytometry. Thus, a method for isolation of DPSCs subsets based on their migratory response to optimized concentration of 100 ng/ml of granulocyte-colony stimulating factor (G-CSF) was determined in this study. The DPSCs mobilized by G-CSF (MDPSCs) were enriched for CD105, C-X-C chemokine receptor type 4 (CXCR-4) and G-CSF receptor (G-CSFR) positive cells, demonstrating stem cell properties including high proliferation rate and stability. The absence of abnormalities/aberrations in karyotype and lack of tumor formation after transplantation in an immunodeficient mouse were demonstrated. The conditioned medium of MDPSCs exhibited anti-apoptotic activity, enhanced migration and immunomodulatory properties. Furthermore, transplantation of MDPSCs accelerated vasculogenesis in an ischemic hindlimb model and augmented regenerated pulp tissue in an ectopic tooth root model compared to that of colony-derived DPSCs, indicating higher regenerative potential of MDPSCs. In conclusion, this isolation method for DPSCs subsets is safe and efficacious, having utility for potential clinical applications to autologous cell transplantation.

The effect of an intra-articular bone fragment in the genesis of temporomandibular joint ankylosis

The aim of this study was to examine the effect of an intra-articular bone fragment on the genesis of temporomandibular joint (TMJ) ankylosis. Twenty-two adult sheep had a unilateral operation of removal of the temporal and condylar articular surfaces, plus discectomy with or without insertion of an intra-articular bone fragment. Functionally, radiologically, macroscopically and histologically, in the group with the intra-articular bone fragment, the joints showed more advanced ankylosis both at one and three months after the operation, as compared to the group with no intra-articular bone. This study shows that the bone fragment increases the extent of ankylosis in the sheep model. The clinical significance of the various experimental findings of this study and others in the same series is presented.

Correlation between preoperative mouth opening and surgical outcome after arthroscopic lysis and lavage in patients with disc displacement without reduction

PURPOSE This study was designed to evaluate the efficacy of arthroscopic lysis and lavage for patients with limited mouth opening. The relationship between preoperative mouth opening and the surgical outcome was determined. METHOD Fourteen patients with 16 internally deranged joints were treated by arthroscopic lysis and lavage. All had received 10.4 (7 to 19) months of nonsurgical treatment before arthroscopy. The preoperative magnetic resonance images showed anterior disc displacement without reduction in all treated joints. RESULTS Twelve of the 14 patients (86%) showed good reduction in pain and improved range of jaw movement on average follow-up of 28.5 (13 to 66) months. Two patients showed no improvement after arthroscopy and required open surgical procedures. The preoperative mouth opening of the successful group averaged 29.4 (22 to 35) mm, whereas the two failed cases had 10- and 19-mm openings, respectively (P < .05). CONCLUSION Persistent limitation of mouth opening of more than 22 mm after nonsurgical treatment has a good prognosis when treated by arthroscopic lysis and lavage. However, those with greater limitation should probably have earlier surgical intervention.