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Calcified lesions of the temporomandibular joint discs obtained from 135 human cadavers were studied. Calcifications were observed in 92 of 250 discs by soft x-ray radiography. Studies by light and electron microscopy and x-ray diffraction revealed that there were two different types of calcification in the discs: apatite crystal deposition with or without ossification, and calcium pyrophosphate dehydrate (CPPD) crystal deposition. Calcifications were recognized more frequently posteriorly than anteriorly, and were related to disc perforation. The results of this investigation suggest that disc degeneration, which may occur as a result of aging or mechanical stress, causes calcifications.

This report describes a case of localized Langerhans' cell histiocytosis which occurred in the maxilla of a 23-year-old male. The lesion was treated by an injection of corticosteroids. Corticosteroid treatment for Langerhans' cell histiocytosis of the maxilla is considered to be beneficial because no sequelae remain following the treatment.

Keratocystic odontogenic tumor commonly occurs in the posterior body and ramus of the mandible. Rarely, however, it develops in the attached gingiva or alveolar mucosa and exhibits the same histopathologic features. The lesion clinically resembles a gingival cyst in adults. Differential diagnosis is therefore difficult. We encountered a case of keratocystic odontogenic tumor arising in the mandibular gingiva and report it as a peripheral keratocystic odontogenic tumor.A 53-year-old man was referred to our department because of an asymptomatic swelling measuring 6 mm in diameter at the gingiva attached to the labia near teeth 2 3. The swelling was covered with normally appearing mucosa and had a whitish hue. The lesion was fluctuant on palpation and had neither spontaneous pain nor tenderness. The teeth adjacent to the lesion were noncarious, and confirmed pulp vitality by electrical stimulation. The lesion was totally excised with a 1-mm margin of normal gingiva under local anesthesia. The alveolar bone adjacent to the lesion had undergone pressure resorption. Exposure of the root surface of 2 3 was noted intraoperatively. Histopathologically, a cystic space was located within the gingival soft tissue. It was lined by parakeratotic stratified squamous epithelium composed of several cell layers and lacking rete pegs. No recurrence was noted for 6 years.

Mediastinal emphysema is a relatively rare complication of dental treatment. This paper reports a case of mediastinal emphysema arising after CO2 laser irradiation. A 48-year-old woman underwent irradiation with a CO2 laser to treat an alveolar abscess at a dental clinic. On the same day, the patient was referred to our hospital because of difficult breathing and swelling extending from the face to neck. A CT examination revealed mediastinal emphysema. The patient was hospitalized and received anti-inflammatory therapy. The swelling subsided by the 5th day, and she was discharged on the 10th day. We have to master the proper technique for treatment and recognize this complication of CO2 laser irradiation.

The percentages of healthy subjects carrying ampicillin- and cefaclor-resistant streptococci in saliva were 52% (27 of 52 subjects) and 100%, respectively. From the sequencing results of pbp1a, 2x, 2b genes, Streptococcus mitis including both ampicillin-resistant and -susceptible strains (a total of 13 strains) were divided into 5 groups. The highly resistant strains had multiple mutations in all pbp genes. By competitive assay using a fluorescent penicillin derivative, affinity of the PBPs for both ampicillin and cefaclor in the ampicillin-resistant strain reduced significantly, compared to that in the susceptible strain. These results suggest that the accumulation of the mutations in pbp genes might contribute to the beta-lactam resistance by means of coding PBPs with a low affinity for the antibiotics. Furthermore, an ampicillin-resistant strain was not completely killed even after 24 h incubation with the MIC of ampicillin against the strain (8 μg/ml) in vitro, and cefaclor at the same concentration never influenced the growth of this bacteria. Therefore, we should be aware of the increase of beta-lactam resistant streptococci in oral flora as the causative agents of penicillin-insensitive infective endocarditis.

Primary intraosseous squamous cell carcinoma was reported in a 76-year-old Japanese woman. The patient exhibited bone expansion of the premolar-molar region of the left mandible with unilocular radiolucency surrounded by indistinct margins. Biopsy revealed a cystic cavity lined by non-carcinomatous squamous epithelium focally exhibiting epithelial dysplasia and distinct basal cell palisading. However, the overlying oral mucosa was normal in appearance. Under the provisional diagnosis of carcinoma arising in odontogenic cyst, segmental resection of the mandible and supraomohyoid neck dissection was performed. The resected mandible had a unicystic lumen lined by papillary or verrucous proliferation characteristic of welldifferentiated squamous cell carcinoma. However, invasion of the malignant cells along the displaced inferior alveolar nerve was not seen. There was no trace of unicystic ameloblastoma. No lymph node metastasis was confirmed. From these clinical, radiographic and histological findings, the present carcinoma was strongly suspected to be derived from a pre-existing keratocystic odontogenic tumor.

Glandular odontogenic cyst (GOC), first described in 1988 by Gardner et. al, is a comparatively rare jawbone cyst of odontogenic origin, which shares some features with both botryroid odontogenic cysts and mucous-producing salivary gland tumors. Although GOC has a high rate of recurrence, cases of recurrence have not been reported in the Japanese literature.This paper describes a case of GOC arising in the mandible of a 58-year-old man. The cyst recurred 12 years after primary treatment. Diagnosis and treatment of the lesion are discussed.

Myoepithelioma is a rare salivary gland tumor that appears mainly in the parotid gland and palate. We report a case of myoepithelioma originating from the buccal gland. A 19-year-old woman presented with a painless elastic hard mass beneath the left buccal mucosa. The mass was well defined and showed no ulcer. The mass was surgically removed under the clinical diagnosis of a benign minor salivary gland tumor. Macroscopically, the tumor was solid and nodular, surrounded by a thin fibrous capsule. Histopathologically, the tumor consisted of spindle-shaped and/or stellate cells with scanty cytoplasm. These tumor cells formed a trabecular structure and small nests in some regions; however a tubular structure was not seen. Immunohistochemistry showed positive staining for cytokeratin, S-100 protein, actin, and GFAP.The tumor was diagnosed as a myoepithelioma arising from the buccal gland.

Reports of iatrogenic foreign bodies in the jaw are rare. Two cases of accidental insertion of broken extracting instruments into the mandible are reported. These accidents occurred during removal of impacted mandibular third molars. One patient was referred on the day of the accident, and the other was referred 2 months after the accident. Radiographs revealed metal foreign bodies in the mandible, separate from the tooth sockets. The objects were removed by enlargement of the tooth sockets. They were a broken elevator and a broken root tip elevator. Healing was uneventful, but one patient had prolonged sensory nerve disturbance of the lower lip.

口腔癌の病理組織学的予後因子としての脈管侵襲 (VI) と神経周囲浸潤 (PNI) の意義を評価するために, 一次治療で切除術を施行した48例51病変における舌扁平上皮癌の全割標本を検索した。脈管腔を正確に同定し, アーティファクトによる偽陽性を除くため, VIの検索については脈管内皮細胞を検知できる第皿因子関連抗原とCD31に対する抗体を用いた免疫組織化学を行った。加えて, 血管への腫瘍塞栓同定のために弾性線維染色も行った。VIとPNIはそれぞれ9病変 (17.6%) , 7病変 (13.6%) に認めた。VIを認めた9病変の内訳は, 4病変にリンパ管侵襲 (ly) を, 9病変すべてに静脈侵襲 (v) を認めた。すべてのT1病変と深達度4mm以下の病変ではVIもPNIも認めなかった。しかし深達度10mm以上の病変では, それ以下の病変よりVIの頻度が有意に高かった (p

Lipoma is a common tumor found anywhere on the body. However, reports of large lipoma of the submandibular region, particularly extending into the parapharyngeal space, are rare. To remove tumor of the parapharyngeal space, many authors recommend a transcervical or transparotid-cervical approach. We report a case of lipoma of the submandibular region that extended into the parapharyngeal space which was removed with small invasion using a transmandibular approach.

根治手術後に即時再建手術を行った口底癌19症例の術後の構音機能と手術との関連性を分析した。評価方法は日本語100語音による発語明瞭度検査である。対象症例の内訳を軟組織の再建方法別にみると, 遊離前腕皮弁移植症例が12例, 大胸筋皮弁移植症例と腹直筋皮弁移植症例がそれぞれ3例, 前腕皮弁と大胸筋皮弁の併用症例が1例であった。舌の切除範囲別では, 舌部分切除症例が14例, 可動部半側切除症例が1例, 半側切除症例が1例, 亜全摘出症例が3例であった。これらの症例について原発腫瘍の大きさ, 切除範囲, 切除様式, 軟組織の再建方法, 下顎骨の再建方法と術後の構音機能の関連について検討した。その結果, 原発腫瘍の大きさによる術後の構音機能の差は少なかったが, 舌の切除範囲が大きくなると構音機能は低下していた。切除様式については側方型の切除を受けた症例の明瞭度は前方型の切除を受けた症例よりも明らかに高く, 切除様式による発音機能の差異が明らかであった。前方型の切除を行った症例の術後の発音障害を防ぐためには, 手術法の改善が必要であり補綴物の応用が有用であることが示唆された。

Hyaluronidase (HAase) activity was detected in both a human pus sample and the culture supernatant of the only bacterial isolate from the pus, Streptococcus intermedius, using a zymographic technique. The optimum pH range for HAase activity was similar for both samples. Although the bands showing the strongest HAase activity of these samples differed from each other with respect to molecular size, both samples were equally inhibited by an antiserum raised against HAase of S. intermedius. These results suggest that S. intermedius may produce HAase in vivo as well as in vitro, and that this enzyme and/or its fragments may play an important role in host tissue degradation.

Fifty-two patients with squamous cell carcinomas of the oral cavity, oropharynx, and maxillary sinus who underwent neck dissection were clinico-pathologically reviewed. Maxillary sinus and tongue carcinomas showed high incidences of lymph node metastases. In contrast, carcinomas of the lower gum and oropharynx had low incidences of lymph node metastases. Of the 36 cases with histologically positive nodes, level 2 was the most frequent site of metastases followed by level 3, level 1, and level 4 at the affected side. Metastasis contralateral to level 2 was not infrequently observed. Non-contiguous nodal sites were observed in 2 patients with bilateral metastases. The largest number of metastatic nodes was 18, but the largest proportion of cases in this series had only one positive node. There was some correlation between the number of involved nodes and the level of metastasis. In relation to T category, many of the T 1 cases had only one affected node, but the numbers of involved nodes varied considerably in T2, T3 and T4 cases. The cumulative 5-year survival rate was 86.7% in pN (+) cases, versus 62.4% in pN (-) cases, and this difference was significant (P

MR imaging is useful in the diagnosis of bilateral internal derangement of the temporomandibular joint. This study was performed to investigate the correlation between clinical symptoms and displacement of the bilateral articular disk in patients with temporomandibular joint disorders (TMJD). A series of 170 patients who had signs and symptoms of TMJDs (TMJ pain, TMJ sound, trismus) were examined bilaterally by MR imaging. One hundred twenty-six patients had only unilateral symptoms, but 55 (44%) of them showed bilateral disk displacement. Among 93 patients with unilateral TMJ pain, 89% showed disk displacement (22 TMJs with reduction, 61 TMJs without reduction) on the symptomatic side, and 44% showed disk displacement on the asymptomatic side. Among 53 patients with unilateral TMJ sound, 96% showed disk displacement (28 TMJs with reduction, 23 TMJs without reduction) on the symptomatic side, and 53% showed disk displacement on the asymptomatic side. In patients with severe trismus (interincisal opening distance

15症例の急性歯性感染症の細菌学的検索の結果, Streptococcus milleri groupの分離頻度が高かった。本菌群分離株について, 菌群内の鑑別性状となり, かつ病原因子となりうる酵素を中心に検討を行った。DNase は全株で陽性であり, hyaluronidase (HAase) は80%以上の株で陽性であった。S.constellatus, S.intermedius はともにHAase産生性であったが, substrate gelを用いたzymogramでは, バンドパターンに菌種間で差異が見られた。また, S.intermediusのHAaseはchondroitin sulfate Aの分解 (Chase) 活性を持つことが示唆されたが, S.constellatusではChase活性は検出されず, 両菌種のHAaseは性状的に異なる可能性が考えられた。

根尖病巣より発生したと思われる下顎骨中心性癌の1例を報告する。症例は48歳の日本人女性で, 左下唇の知覚異常を主訴に紹介来科した。左下顎小臼歯部から大臼歯部歯肉頬移行部に硬い腫瘤を触知するも, 口腔粘膜に異常は認めない。X線写真では5の根尖を中心に境界不明瞭な透過像を認める。紹介医にて撮影された6年4か月と3年4か月前のオルソパントモX線写真では, 同歯に根尖病巣と思われる境界明瞭な小透過像を認める。生検により扁平上皮癌の診断を得た。全身精査の結果, 他に原発巣が見あたらないため, 左下顎骨区域切除と全頸部郭清術を施行した。術後1年3か月で再発や転移の兆候はない。切除物の病理検索にて, 腫瘍は5の根尖周囲から頬側皮質骨を破壊して頬部軟組織に及んでいた。しかし粘膜上皮はまったく正常で, 深部の腫瘍と接している部分も認めなかった。組織学的には歯根嚢胞が存在した証拠は得られず, リンパ節転移はなかった。

Clinically, more reliable methods of estimating tenderness are needed. A pressure pain meter is an investigative tool for the measurement of tenderness. The purpose of this research was to measure the pressure pain threshold (PPT), and to compare topographic variability in PPT in the maxillofacial regions of normal subjects. PPT is the minimum pressure inducing pain or discomfort. The pressure pain meter consists of a force gauge to which a resin disc with a 1-cm diameter surface is attached. Normal threshold values were established in 22 volunteers (11 women and 11 men), at 6 different sites of the facial skin, including the mental protuberance (surface of the mandible), mental foramen and infraorbital foramen, lateral pole of the condyle, and the temporal and masseter muscles.The results indicated mean PPT in the mental protuberance (surface of the mandible) to be 2144g in women and 2349g in men. PTT at the mental foramen and infraorbital foramen, pole of the condyle (mouth opening phase), and masseter muscle (relaxation phase) were significantly lower than the values measured at the mental protuberance (surface of the mandible) in both sexes.PTT at the pole of the condyle when the mouth was open was significantly lower than that measured when the mouth was closed.PTT at the masseter muscle region in relaxation phase was significantly lower than that measured in contraction phase.

In spite of extensive research, the nature and origin of oral lichen planus (OLP) are still unknown. A clinical examination of 111 cases of OLP is presented. OLP predominantly occurred in middle-aged and elderly patients ranging in age from 40-60 years; 69.4% of the patients were women. The chief complaints of the patients were a sore or burning sensation or white lesions. Many patients seeked consultation after more than 3 month from the onset of disease. Some type of systemic disease was noted in 77 cases (69.4%), and 45 cases (40.5%) used some form of medication. A history of allergy was present in 19 cases (17.1%) and skin lesions were noted in 11 cases (9.9%). The distribution of OLP by site of occurrence was as follows; buccal mucosa 83.8%, upper and lower gingivae 32.4%, tongue 24.3%, lips 19.8%, floor of mouth and palate, less than 10%.These lesions were distributed in a symmetrical or multiple pattern, but OLP predominantly found on the mucous membrane of the vestibule oris. The size of the lesions was often more than 3 cm in diameter. Reticular lesions were most common, followed by atrophic red lesions. Many factors have been reported to cause lichen planus. However, the present clinical study suggests that OLP is caused by other local factors than skin lichen planus.

A case of acinic cell tumor of accessory parotid gland associated with “crystalloid” is presented. The patient was a 69-year-old female who was aware of a small mass of right buccal mucosa for 12 years. She consulted our clinic complaining of repeated swelling of the right parotid region. Oral examination revealed a submucosal elastic hard nodule beneath the right papilla parotidea. The lesion exhibited scattered radiopacity on roentgenogram. Under the clinical diagnosis of infected sialolithiasis in Stensen's duct, curettage was performed intra-orally. After two weeks, the submucosal nodule remained unchanged, then the lesion was excised along with the papilla parotidea under local anesthesia. Stensen's duct involved with the capsulated spheroid tumor was sacrificed and the proximal stump of the duct was sutured to the buccal mucosa. The patient recovered well after surgery.The excised tumor was 15 mm in diameter, and histologically composed of eosinophilic cuboidal cells organizing tubular or acinar structure with poor fibrous stroma. Capsular structure with thin fibrous connective tissue was evident. Characteristic “crystalloid”, which is occasionally found confined in the parotid gland and the origin of which is not known, as well as psammorna body were scattered throughout tumor, and some of the crystalloids had cores consisting of psammoma body. But, there was no sialolith in the specimen. Histopathological diagnosis was acinic cell tumor.The origin of the tumor in tins case was speculated to be accessory parotid gland rather than buccal minor salivary gland upon consideration of findings such as the anatomical relationship between the tumor and Stensen's duct, and identified crystalloid in the tumor. This is the first case reporting the existence of crystalloid in acinic cell tumor.

A case of pseudogout occurring in the temporomandibular joint of a 76-year-old man is reported. The diagnostic work-up and its differential diagnosis is discussed.

We describe two unusual cases of necrotizing sialometaplasia of the hard palate in which the lesions were caused by self-induced vomiting. The first patient, a 35-year-old woman, pressed her palate with a spoon to induce vomiting 2 weeks before presentation to our department. The second patient, a 16-year-old girl, was suffering from bulimia and chronic self-induced vomiting. Clinical and pathological findings and causative factors are discussed.

Optimal dose of N-22 (Mofezolac), a new non-steroidal anti-inflammatory agent, was evaluated in a double-blind comparative study on post-exodontic pain, at 3 single dosing levels of 100 mg, 150 mg and 200 mg, respectively. The results are summarized as follows.1) A total of 197 cases subjected for analysis are broken down into a group of 68 cases with a 100mg dose, that of 64 eases with a 150mg dose and that of 65 cases with a 200mg dose, respectively. No significant deviation in clinical background factors of all cases was recognized.2) A total of 189 cases (67 cases-100mg, 60-150mg arid 62-200mg) were subjected for analysis of its efficacy. Analysis by U-test proved both 150 mg and 200mg groups to be significantly superior (P

To overcome the operational diffficulty of TMJ arthroscopy, and to reduce injury during the examination a fine needle fiber arthroscope was developed and clinically applied. The equipment is composed of a fine needle arthroscopic probe and a television monitor system with an output for a videorecorder and camera. The characteristics of this optical system are as follows:1) The fine needle arthroscope (0.8mm in diameter, 20 G) can be inserted into the narrow or tiny TMJ spaces, such as the lower joint compartment and also reduced iatrgenic injury to the joint tissues.2) There is no distortion of the picture or breakage of the scope by bending. The picture is clear enough for diagnostic purpose.3) Using this system it is possible to examine the joint both arthrographically, arthroscopically and to treat TMJ diseases, by means of pumping manipulation technique and injection of appropriate medicines. All of these manipulations are possible using only one insertion of the cannule (18 G) for each articular cavity under local anesthesia. 17 patients (19 TMJ) were examined by this system, and the results obtained are as follows:1) Adhesions were generally seen below the articular tubercle, and they were mostly white membrane like fibrous adhesion without blood vessel, similar lesions with debris were also seen in the lower articular cavity. It was possible to perform arthroscopic detachment by using this approach.2) Two types of disk perforation were observed, one without tissue reaction, the other with fibrous adhesion and granulation tissue.As mentioned above, very favorable results were obtained without any complications.

Clinical usefulness of N-22 (Mofezolac; N), a new non-steroidal antiinflammatory agent, on post-exodontic pain was evaluated at a single dose level of 150mg/time, in a double-blind comparative study, in comparison with Mefenamic acid; M also at a single dose level of 500 mg/time; results are summarized as follows.Of a total of 228 cases, 33 with no onset of post-exodontic pain took neither of the agents and were therefore removed, meaning that 195 cases were subjected for analysis, in comparison with M put under previously well controlled studies. No significant difference in patient background factors between N and M groups was found. Based on the protocol, either N or M was administered alone for evaluation at a single dose level/time. Double dummy method was used in allotment for administration of 4 kinds of test agents-N, NI, N's placebo and M's placebo.Of a total of 193 efficacy evaluable cases (N-96 & M-97), 25.0% of N group and 11.3% of M were rated “Remarkably improved” in final global improvement rate, with N group found significantly superior (P

Clinico-statistical observations on 104 cases of bilateral TMJ disorders are presented. The proportion of bilateral TMJ disorders (BTMJD) to the total patients of TMJ disorders was 23.1 percent. BTMJD occurred most frequently in the twenties and was predominant among female patients. The most common chief complaint was TMJ pain or TMJ sound. There were no significant differences in the age and sex distribution and the chief compaint between BTMJD and unilateral TMJ disorders. Among the initial symptoms of BTMJD, muscle symptoms mostly occurred bilaterally, but TMJ pains occurred unilaterally. TMJ sounds occurred equally in the bilateral and unilateral groups. The period from the onset of BTMJD symptoms to the initial visit to a clinic was longer than that for unilateral TMJ disorders. As for the present condition, most patients of BTMJD had several composit symptoms, TMJ pains+TMJ sounds or TMJ pains muscle symptoms. They rarely presented a similar symptom on both sides. Bilateral TMJ pains and bilateral TMJ sounds were concurrently recognized only in 11 cases. Bilateral TMJ pains and bilateral muscle symptoms were simultaneously recognized only in 11 cases as well. Most of the unilateral TMJ pains were accompanied with TMJ sound on the other side, but many of unilateral TMJ pains were recognized on the same side as that showing unilateral muscle symptoms. Difficulty in opening the mouth wide (

Purpose The purpose of the present study was to determine whether panoramic radiographs could predict physical contact between the mandibular third molar and the mandibular canal on limited cone-beam computed tomography, known as dental 3D-CT (3-dimensional computed tomography [3D-CT]). Patients and Methods The association of images between the panoramic radiograph and the dental 3D-CT was investigated in a cross-sectional study. Seventy-three lower third molars in 65 patients were examined. Findings of absence or presence of the white line of the mandibular canal wall on panoramic radiographs and contact or separation between the tooth and the mandibular canal on dental 3D-CT were compared. Results Absence of a superior white line on panoramic radiography was associated with an increased risk of contact between the third molar and the mandibular canal on dental 3D-CT, even when the effects of tooth position, age, and gender were taken into account. The multivariate adjusted odds ratio was 10.79. Women were more likely to have contact between the 2 structures on dental 3D-CT when their panoramic radiograph showed absence of the white line. Conclusions Panoramic radiography is useful for predicting to a limited extent physical contact between the mandibular third molar and the mandibular canal on dental 3D-CT.

A case of peripheral osteoma in the mandible of a 56-year-old man is described. He noticed a hard mass of the mandible while he was in junior high school. The mass grew gradually, but there were no other symptoms, and he did not consult a doctor for 43 years. Radiographic examination revealed a hen-egg-sized ovoid, radiopaque mass in the floor of the mouth. The mass was removed surgically, and the histopathological diagnosis was osteoma spongiosum characterized by delicate cancellous bone with yellow bone marrow.

Three isolates of beta-lactam-resistant streptococci from the saliva of healthy adults were identified as Streptococcus mitis. Minimum inhibitory concentrations (MICs) were 2 to 4 micro g/ml for ampicillin (ABPC) and 64 to more than 128 micro g/ml for cefaclor (CCL). To determine the position of base alterations of the penicillin-binding protein 2b ( pbp2b) gene, upstream primers containing possible mutation points were designed, and used for polymerase chain reaction (PCR), together with a downstream primer. Alterations adjacent to the conserved motifs of the pbp2b gene were apparent. DNA sequencing data indicated replacements in deduced amino acid sequences in all resistant isolates: from threonine to alanine just after the serine-serine-asparagine (SSN) motif, and from alanine to glycine two residues downstream of the lysine-threonine-glycine (KTG) motif. These changes were the same as those in penicillin-resistant Streptococcus pneumoniae (PRSP), suggesting importance for the enzymatic activity of the protein. Thus, Beta-lactam susceptibility of S. mitis may be partially predicted by PCR using our primer set for pbp2b.

So-called static bone defects are usually situated in the molar or angular regions of the mandible. A rare case of a so-called static bone defect which existed in the ascending ramus of the mandible of a 25 year-old female is reported. X-ray findings showed a cyst-like radiolucent lesion in the ascending ramus but computed tomography and magentic resonance imaging proved that the lesion was a defect on the lingual ramus with anomaly of the mandible. Histopathological examination revealed the lesion to contain fatty tissue.

No published study on synaptogenesis in masseter muscle has focused on the shift of nicotinic acetylcholine receptors (nAChRs) from the embryonic type (alpha(2)-, beta-, gamma- and delta-subunits) to the adult-type (alpha(2)-, beta-, epsilon- and delta-subunits) and the elimination of nAChRs outside the neuromuscular junction. To identify the time course of the nAChR transitions in rat masseter muscle between 1 and 63 days of age, the expression of delta-, epsilon- and gamma-subunit mRNAs was analysed by competitive polymerase chain reaction in combination with reverse transcription. The expression of the delta-subunit was high between 1 and 7 days of age, then decreased by 95% (P0.0001) between 7 and 28 days, suggesting that the nAChR elimination occurs during this period. The quantity of the epsilon-subunit increased by approximately 600% (P0.0001) between 1 and 21 days of age, whereas the quantity of the gamma-subunit decreased by 85% (P0.0001) during the same period. This result indicates that the nAChR type shift is terminated at 21 days of age. The feeding behaviour of the rats inevitably changed from suckling to biting after 19 days of age, because they were weaned at that age. As the nAChR type shift was terminated soon after weaning, the termination could be related to the change in feeding behaviour. However, it might also be the case that nAChR elimination is not directly related to the change in feeding behaviour, as the elimination continued at the same rate for 9 days after weaning (from 19 to 28 days of age).

A case of oral lichen planus (lichenoid lesions) caused by a dental nickel alloy isreported. Patch test and X-ray microanalyser (XMA) were useful in distinguishing the causa-tive metal from other dental alloys because many teeth of the patient had been repaired byvarious dental materials.