The effect of experimental occlusal interferences on nerve growth factor levels in periodontal tissues.

OBJECTIVE: To test the hypothesis that experimental occlusal interferences increase the nerve growth factor (NGF) levels in periodontal tissues and cause an up-regulation of preprotachykinin-A (PPTA) mRNA. BACKGROUND: NGF is related to hyperalgesia and inflammation. PPTA mRNA, a primer of substance P, is a possible factor in the aetiology of pain. METHODS: Experimental interferences were created by placing inlays in the right maxillary molars of 15 dogs. The right side molars formed the experimental group. The left side molars served as controls. Three dogs with cavities prepared without changing the occlusion formed a sham group. The dogs in the first group were sacrificed, 3 at each time, after 3, 7, 14, 30, and 60 days. The sham group was sacrificed after 14 days. The levels of NGF in periodontal tissues and PPTA mRNA in the trigeminal ganglions were detected by ELISA and TR-PCR. Comparisons were made with paired t-tests and a multivariate MANOVA test. RESULTS: On all measurement days, there were higher levels of NGF mRNA, PPTA mRNA, and NGF on the experimental than on the control side in 14 of 15 comparisons and in the sham group. NGF production in periodontium was time-dependent. No differences in NGF protein levels were observed between the control and the sham groups. CONCLUSION: The results which need confirmation in further tests are of clinical interest. They indicate that occlusal experimental interferences may be an etiologic factor in oral facial pain by increasing mRNA and NGF protein levels in the periodontal tissues.

Histological evaluation and surface componential analysis of modified micro-arc oxidation-treated titanium implants.

The objective of this study is to investigate soft tissue and bone tissue reaction to titanium implants treated by a modified micro arc oxidation (MAO) technique, and analyze the surface components and implant-bone contact ratio by animal experiments to evaluate the osseointegration condition of implants with this modified MAO surface. MAO titanium plates were installed subcutaneously in rabbits. Tissue reaction was evaluated by HE sections. MAO titanium implants designed for endosseous examination were installed in Beagles' femurs. Bone tissue surrounding implants was analyzed histologically. Surfaces of retrieved implants were observed and examined by SEM and EDX. All procedures were performed under the control of untreated pure titanium implants. Thin homogeneous fibrous envelope could be found without apparent inflammation cells infiltration around the subcutaneously imbedded MAO titanium plates, which was almost same as control group. Fast osteoid deposition comprising high content of calcium, phosphor, carbon, and nitrogen elements was found on the retrieved MAO implant surfaces, while comparatively less amount of carbon and nitrogen elements were found on the retrieved implants of control group. Matured bone tissue comprising bone trabeculae and Haversian canals appeared in 8 weeks, while it took 12 weeks needed to form matured bone tissue in control group. In conclusion, MAO titanium materials shows good biocompatibility and calcium phosphate inducement capability in vivo and could accelerate bone tissue growth and shorten the osseointegration time.

[A study of mandible chewing movement in patients with developmental lateral jaw deformity].

OBJECTIVE: The purpose of the present study was to investigate effects of developmental lateral jaw deformity (DLJD) on masticatory movement. METHODS: Three coordinates of mandibular movement signals were recorded in 35 young healthy adults with normal occlusion and 28 patients with DLJD by means of a Sirognathography System during gum chewing movement. Paired and unpaired t-tests were used to compare significant difference of intra-group and inter-groups in displacement and speed. P < 0.05 was chosen as significance level. RESULTS: (1) The rhythm and directional sequence of chewing trajectory in both frontal and sagittal planes were normal in control group, while anomalies of rhythm and distribution (n = 9) and reversed sequencing (n = 7) were found in DLJD group. (2) The maximum magnitude of jaw retrusion and average speed were significant higher in DLJD group than those in control group (P < 0.01). The spatial displacement and average speed in horizontal plane and in chewing phase were also higher in DLJD group compared with control group (P < 0.05). CONCLUSIONS: DLJD patients showed anomalies in chewing pattern as well as chewing speed and displacement in horizontal plane.

[The expression of PPTA and c-fos mRNA in dog caudal spinal trigeminal nucleus induced by traumatic occlusion].

OBJECTIVE: PPTA and c-fos mRNA expression were detected in dog caudalis subnucleus of trigeminal spinal tract nucleus (VC) induced by trauma occlusion in order to investigate orofacial pain mechanism. METHODS: The occlusal surface of the first and second maxillary right molars in 15 dogs were unilaterally raised 1.5 mm with casting Ni-Cr inlay which were fixed in Class I hole. On days 3, 7, 14, 30 and 60 after teeth operation, the VC of right and left sides were removed. PPTA and c-fos mRNAs were detected in experimental and control groups with reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: (1) The basal levels of PPTA and c-fos mRNAs were extremely low and poorly detectable in VC in control animals. (2) The expression of PPTA mRNA in VC of traumatic side was up regulated from 3 days after inlay was fixed in molar and reached peak level during 14 to 30 days and then down-regulated gradually and no significant difference was noted between 60 days group and control group. (3) c-fos mRNA expression was more intense during 3 to 7 days compared with the control group but undetectable in the other experimental period. (4) Both PPTA and c-fos mRNAs expression in VC of trauma occlusal side were more intense than that in the contralateral side. CONCLUSIONS: The present results show that both PPTA and c-fos mRNA expression are elevated in dog's VC induced by traumatic occlusion. The primary afferent terminal of orofacial area is sensitized, which suggest one kind of mechanism of orofacial pain in the condition of traumatic occlusion.