World journal of orthodontics最新文献

Aim: The size and shape of the jaws are related to occlusion and masticatory muscle function. Consequently, teeth and muscles are considered the functional matrix for the two jaws. Existing studies did not focus on the relationship between maxillary and mandibular base but on just their absolute dimensions. As the relationship between the two is of interest to orthodontists, the aim of this study was to calculate the maxillary-mandibular ratio (m-m ratio) in individuals from Central Italy and to compare it to that of ancient skulls from the same geographic area.

Methods: Forty individuals from Opi, a small, isolated mountain village in Central Italy, and 40 ancient skulls from the same region were the sample of this study. The lengths of the maxillary and mandibular base were assessed on lateral cephalograms, the m-m ratio was calculated, and the measurements between the groups were compared.

Results: Due to a significantly shorter maxillary base in the modern human sample, the m-m ratio was significantly lower in these subjects.

Conclusion: This finding supports the hypothesis that growth of the skull is strongly modulated by the functional matrix, within which a morphologic unit develops.

An adult woman with amelogenesis imperfecta, a skeletal Class III relationship, long face syndrome, and a severe anterior open bite received interdisciplinary treatment (orthodontics, orthognathic surgery, and prosthodontics). Presurgical orthodontic treatment was followed by a maxillary posterior impaction with anterior advancement and a mandibular setback. After surgery, the patient received ceramic crowns. Function and esthetics were successfully re-established.

Internal derangement of the temporomandibular joint (TMJ) is characterized by an abnormal disc-condyle relationship. Of all the various treatment modalities used in the management of disc displacements, flat occlusal and anterior repositioning splints are the most commonly used. Myofunctional appliances (such as bite-jumping appliances) are also advocated to treat anterior disc displacements. The present study compares the efficacy of twin blocks with conventional flat occlusal splints in patients with anterior disc displacement with reduction using clinical examination, MRI, and EMG. The sample consisted of 20 subjects between 12 and 20 years of age, who were randomly divided into two groups of 10 patients each: Group 1 was treated with twin blocks, while group 2 was treated using maxillary flat occlusal splints. The twin block is more effective in relieving joint pain, diminishing joint dysfunction, reducing joint clicking, and eliminating muscle tenderness in patients with anterior disc displacement with reduction as compared to the occlusal splint.

Aim: To evaluate the amount of initial force and to compare the amount of force decay between the elastomeric chain and tie-back method over a period of time.

Methods: Twenty five-unit elastomeric chains (15 mm) stretched 100%, and twenty elastic modules in tie-back method stretched twice their original diameter were held in place by a series of pins 30-mm apart in acrylic blocks. The blocks were stored in 37 °C distilled water. The force of all samples was measured at baseline, 24 and 48 hours, and once a week thereafter for 4 weeks with a force gauge. The groups were tested with a multivariate analysis of repeated measurement at the 95% confidence level.

Results: The tie-back method with mean force of 577.50 grams (standard deviation [SD] 28.63) had a lower initial force than the elastomeric chain with mean force of 650.00 grams (SD 34.47). The elastomeric chain showed a substantial force decay of 355.50 grams (SD 53.2) at 24 hours, but the force decay in the tie-back method was less (mean 154 grams, SD 56.50). The force decay of the elastomeric chain and tie-back at 48 hours were 446.50 grams (SD 35.4) and 209 grams (SD 57.1), respectively. The difference between the force decay of the two groups at both 24 and 48 hours was statistically significant (P<.05).

Conclusion: Using the tie-back method of space closure, which has more appropriate initial force and slower force decay, may have a clinical value, approaching a more light and continued force. However, more studies are required to test these findings in vivo.

Aim: To determine whether there is sexual dimorphism regarding Bolton ratios within four ethnic groups and to compare them against Bolton standards.

Methods: The sample consisted of 140 dental study casts of untreated normal occlusion subjects, derived from four racial groups: black, white, Afro-Mediterranean, and Japanese. Anterior and overall Bolton ratios were calculated for each cast. The Kolmogorov-Smirnov test, t test, and one-way ANOVA were used.

Results: No statistically significant sexual dimorphism in anterior or total tooth-size ratios were found within any group. Only the Japanese anterior ratio (75.09) was statistically less than the Bolton standard (77.2; P<.001).

Conclusion: The Bolton ratio can be applied to the investigated ethnic groups except for the anterior ratio in Japanese patients.

This study investigated the prevalence of signs and symptoms of temporomandibular disorders (TMD) in 1,134 orthodontically untreated children and adolescents (593 boys, 541 girls; age range 5 to 15 years) with and without crossbites. The sample with crossbites was further grouped according to the type (anterior, posterior, unilateral, or bilateral). The TMD symptoms bruxism (obvious active attrition/myalgia), joint sounds (clicking/crepitation), deviation during opening, reduced functional movements (maximum opening <40 mm), and myopain (originating in the masticatory muscles/related to masticatory functions) were evaluated based on the standardized RDC/TMD protocol (Research Diagnostic Criteria for Temporomandibular Disorders) and compared among the various groups. Girls had a significantly higher prevalence of myopain than boys (x(2)=3.882, P<.05). Furthermore, individuals with posterior unilateral crossbites showed a significantly higher prevalence of TMD symptoms (x(2)=33.877, P<.001) and reduced functional movements (x2 = 10.800, P<.05) than any other group. In conclusion, sex and type of crossbite play a role in the prevalence of TMD signs and symptoms.