Long-term outcome of secondary alveolar bone grafting in patients with various types of cleft.

OBJECTIVE: To evaluate the results of secondary alveolar bone grafting in patients with various types of cleft. DESIGN: One hundred and seventy patients were classified as cleft lip and alveolar process alone (CLAP), complete unilateral cleft lip and palate (UCLP), and complete bilateral cleft lip and palate (BCLP). The Bergland criteria were used to assess the long-term outcome of alveolar bone grafting. RESULTS: In the UCLP and BCLP groups, the success rate was significantly better (P<0.05) when the cleft was grafted before the eruption of canines. When the operation was done after the eruption of canines, there was a significant difference in the success rate between CLAP and BCLP (P<0.05). CONCLUSION: The timing of the operation was the critical variable that affected the outcome in patients with complete cleft lip and palate. The severity of the deformity influenced the success rate when alveolar bone grafting was done after the eruption of canines.

Human periodontal ligament cells express osteoblastic phenotypes under intermittent force loading in vitro.

UNLABELLED: Mechanical strain applied to bone leads to bone remodeling. In the oral cavity, it is unclear how such mechanical force applied to move teeth orthodontically induces alveolar bone remodeling. It is known that osteoclasts are the only cells that are responsible for bone resorption, while the formation and activity of osteoclasts are regulated by osteoblasts. So it is believed that osteoblasts play an important role not only in bone formation but in bone remodeling as well. Therefore, the purpose of this study was to examine the effect of mechanical force on human periodontal ligament (PDL) cells and whether they express osteoblastic characters in vitro. METHODS: Human PDL cells cultured in vitro were loaded with intermittently stretching force for 24 hours. The expression of alkaline phosphatase (ALP), osteocalcin (OCN) and osteoprotegerin (OPG) were detected at mRNA and protein levels at 0, 2nd, 4th, 6th, 12th, 24th hours after intermittent force loading. RESULTS: Without any stimulation, ALP and OPG mRNA expressions were detected in human PDL cells by in-situ hybridization, but not that of OCN mRNA. ALP mRNA signal was up-regulated and that of OPG was down-regulated by mechanical force within 24 hours. OCN mRNA expression was induced by mechanical force in the late phase of the 24-hours loading cycle. The changes in secreted proteins showed similar results with those seen at the mRNA level. CONCLUSION: Human PDL cells express osteoblastic phenotypes under intermittent force loading and play a role in alveolar bone remodeling.

The expression of osteoprotegerin and the receptor activator of nuclear factor kappa B ligand in human periodontal ligament cells cultured with and without 1alpha,25-dihydroxyvitamin D3.

The receptor activator of nuclear factor kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG), are important bone metabolism molecules, which directly control osteoclastogenesis. Periodontal ligament (PDL) cells play a vital role in maintaining the homeostasis of periodontal tissues, releasing cytokines to affect bone metabolism. The purpose of this study was to investigate the expression of OPG and RANKL in cultured human periodontal ligament cells (hPDLCs) derived from permanent teeth and the expression change after stimulation by 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)vitD(3)), a kind of bone resorption promoter. HPDLCs were cultured in the presence or absence of 10(-8)M 1alpha,25(OH)(2)vitD(3) in vitro. The expression of mRNA for OPG and RANKL in hPDLCs during 6 days' culture was examined using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). The level of secreted OPG protein in the culture medium during 6 days' culture was detected by enzyme-linked immunoabsorbent assay (ELISA). The result showed that OPG and RANKL were expressed by hPDLCs. OPG expression was down-regulated by 10(-8)M 1alpha,25(OH)(2)vitD(3) in a time-dependent manner, while RANKL mRNA was up-regulated. The ratio of OPG/RANKL was decreased. In conclusion, our findings suggest that hPDLCs may regulate the alveolar bone metabolism through the OPG/RANKL system.

Magnetic resonance imaging of the upper airway in obstructive sleep apnea before and after oral appliance therapy.

OBJECTIVE: To determine the mechanism by which an oral appliance may be used to treat obstructive sleep apnea syndrome (OSAS). METHODS: Eleven OSAS patients (8 males and 3 females) were involved in the study. Mean age was 52.2 +/- 10.6 years; height was 166.6 +/- 7.2 cm, and weight was 75.6 +/- 9.3 kg; body mass index (BMI) was 27.2 +/- 2.9 kg/m2. Each patient underwent magnetic resonance imaging (MRI) and polysomnography before and after oral appliance therapy. Pharyngeal changes were measured and compared with the variation in sleep parameters. Also, Pearson's correlation and multiple linear regression were performed to investigate the relationship of sleep parameters and MRI items. RESULTS: Through oral appliance therapy, the sleep disorder decreased. Apnea/hypopnea index (AHI) decreased from 44.6 +/- 21.5 to 9.6 +/- 6.3 per hour of sleep. Lowest oxygen desaturation rose from 71.4 +/- 15.0% to 82.0 +/- 7.7%. Meanwhile, the upper airway increased at most levels, and especially at oropharynx. As measured by the correlation and regression analysis, the AHI changes had a negative association with tongue volume (R = -0.5730) and a positive association with the area alternation of high oropharynx (R = 0.5823); the change of the lowest oxygen desaturation (SaO2%) was positively associated with whole airway volume (R = 0.6554). CONCLUSION: The oral appliance works by enlarging the upper airway morphology and keeping the airway open, mainly at the back of soft palate. The effect of the oral appliance is associated with the degree of enlargement of the high oropharynx. Those who have a small tongue and a large pharynx may expect to have good results with the use of the oral appliance.

Effects of fluoride toothpaste on etched enamel of orthodontic patients.

OBJECTIVE: To investigate the effects of fluoride toothpaste on acid-etched enamel by means of a scanning electron microscope. METHODS: Permanent first premolars extracted for orthodontic reasons were etched with 37% H3PO4. They were divided into two groups in pairs of contralateral teeth. Group 1 was treated with fluoride toothpaste slurry; Group 2 was treated with deionized water. Treatment time was three weeks (one hour, 3 times a day). RESULTS: At the conclusion of the experiment, large amounts of precipitate were observed on the enamel surface of the teeth that were treated with fluoride toothpaste slurry. The etched structures were no longer evident and the enamel surface was smooth. The acid resistance of the teeth was significantly enhanced. However, clearly etched enamel structures were visible on the enamel surface of the teeth that were treated with deionized water. CONCLUSION: Fluoride toothpaste could promote the remineralization of etched enamel and enhance its resistance to acid attack.

Prevalence of temporomandibular joint dysfunction (TMJD) in Chinese children and adolescents. A cross-sectional epidemiological study.

The aim of this study was to investigate the prevalence of temporomandibular joint dysfunction (TMJD) in Chinese children and adolescents, and the relationship between TMJD and type of occlusion. The sample consisted of 3105 Chinese children, 3-19 years of age, divided into four groups by the stage of dental maturation. The prevalence of TMJD for the entir group was 17.9 per cent and there was no significant sex difference. TMJD increased in the mixed and early permanent dentitions, but decreased in the permanent and deciduous dentitions. In the subjects with TMJD, the most common sign was sound (87.7 per cent), followed by abnormal jaw movement (23.6 per cent), but pain was registered in 0.6 per cent only. A single sign was registered in 88.5 per cent, a combination of sound and abnormal jaw movement in 11.0 per cent, and combinations of other signs in less than 1.0 per cent. Sound as a single sign increased with the specific stages of dental development (P < 0.001).

Occlusal contact changes before and after orthodontic treatment of a group of child & adolescent patients with TMJ disturbance.

Occlusal contacts were examined before and after orthodontic treatment in 32 eight- to seventeen-years-old patients with temporomandibular joint disturbance. Add-Picture, a computer image system, was applied to a silicone occlusal record obtained in the intercuspal position (ICP) to assess the qualitative and quantitative changes of occlusal contacts. Comparing the two images before and after treatment, significant difference was noted in the number, size, location and type of contacts. After orthodontic treatment: the mean number of contacts on anterior teeth reduced, the mean area per contact decreased, the number of contacts on centric stops increased and type IV contacts (on the inclined plane) decreased. The present study indicates that orthodontic treatment has a positive effect, both qualitatively and quantitively, on the distribution of occlusal contacts in ICP and seems to contribute to the establishment of occlusal stability in ICP.

[Three dimensional finite element analysis of stress induced by orthodontic forces in the periodontal tissue].

The purpose of this study was to investigate the stress induced in the periodontal tissue of the upper central incisor by application of orthodontic forces. A three dimensional finite element model consist of tooth, periodontal ligament (PDL), cancellous and compact bone was established and the following results were obtained: (1) The highest stresses were observed on the root surface, the intermediate on the alveolar bone and the lowest in the PDL. (2) Stress condition on the surface of root and alveolar bone is very complex. The maximum, intermediate and minimum principle stresses on the same area are quite different, but the three principal stresses in the PDL are similar. (3) Regarding to tipping and torque movement, the stress value varied largely from the cervix to the apex, and there is stress concentration at the cervix and the apex. For bodily movement when M/F is -10.30, the stress induced is homogeneous and the difference of the stress values from the cervix to the apex is little, which seems to be more physiological.

[Electromyography of perioral muscles in the cleft lip and palate patients with crossbite].

In this study, twenty-nine cleft lip and palate patients with anterior crossbite were chosen as study group and twenty-eight normal children, twenty-seven patients with anterior crossbite as the control groups. All subjects were examined with EMG, and found some characters of the perioral muscles activity of the cleft patients. (1) The electromyographic amplitude of the upper lip and chin muscles was higher in cleft patients than that of other two groups during swallowing of saliva (2) Activity of chin muscle in cleft patients and crossbite patients in rest position were higher than that of normal occlusion (3) The Asymmetry index of the activity of upper lip muscle in every functional positions of the cleft patients are higher than ther groups. The abnormal activity of perioral muscles of the cleft patients demonstrate that functional repairment of cleft lip and needed lip bumper are necessary.

[A computerized system for image cephalometrics].

This system is composed of: (1) a perspective table, (2) TV camera, (3) a high-resolution image displayer, (4) a computer, (5) a laser printer The functions of this system are as follows: (1) It can perform cephalometries directly from image of X-ray film, (2) it can diagnose and analyse the deformity and provide treatment plan. This system is valuable for orthodontics and surgical orthodontics.

[Dental anthropological study of Mongoloid in China].

The purpose of this study was to evaluate the craniofacial and occlusal characteristics of the inhabitants in China. The material consisted of cephalograms, pantomograms, dental casts and anthropological measurements taken from 517 inhabitants: 416 Han Chinese in Beijing, Shanghai, Guangzhou and Changchun and 101 Mongolians in Hohhot. The data were compared among the above five regions and also with the Japanese data. The findings were summarized as follows: I. Craniofacial characteristics; a) The Han Chinese and the Mongolians showed brachycephaly. b) The inhabitants in Guangzhou showed a tendency of bimaxillary protrusion with a smaller facial height, and the inhabitants in Changchun showed a larger gonial angle with a larger facial height than those of the other regions. c) The Mongolians had a larger value of the saddle angle and of the bi-gonial breadth. d) Compared with the Japanese, their craniofacial complex was characterized by a larger facial angle, smaller mandibular plane angle and a smaller gonial angle. II. Occlusal characteristics; a) The inhabitants in China had a similar tendency in the dental arch form and in the dental trait frequency. b) The inhabitants in Beijing had a larger mesiodistal crown-diameter of the anterior teeth than those in the other regions. c) Compared with the Japanese, their teeth were characterized by a smaller mesiodistal crown-diameter (especially on the upper first molar), higher frequency of shovel-shape and lower frequency of Carabelli's tuberculum.

[The study and application of a direct bonding monoblock edgewise bracket].

The edgewise and light wire technics are the more advanced orthodontic appliance used widely in the world. Edgewise bracket is one of the important component of the edgewise technical materials. In this paper we indicate the manufacture, application and characteristics of direct bonding monoblock edgewise brackets. The bonding strength of four different base plate of brackets are studied and analysed. The results show that the strength of monoblock edgewise bracket is high enough to use in clinic.