A Comparison of the Accuracy Between a Digital Fabrication Workflow and a Conventional Fabrication Workflow for Occlusal Appliances: A Pilot Study.

PURPOSE: To compare the accuracy of occlusal stabilization appliances fabricated by digital workflows to those fabricated by conventional workflows. MATERIALS AND METHODS: In total, 10 volunteers were recruited in this single-blinded crossover study. All volunteers received two types of occlusal stabilization appliances: a digital additively manufactured stabilization splint (DS) and a conventionally fabricated splint (CS). The accuracy was assessed using a 4-point rating scale addressing two aspects of the occlusal appliances: occlusal contact and basic performance. In addition, silicone impression materials were used to assess the gap between the appliance and the maxillary arch to ensure an accurate fit. Differences were quantitatively assessed with Mann-Whitney U test and independent-sample t test. RESULTS: The occlusal contact rating of DS (15.90 ± 1.73) was significantly higher than that of CS (14.10 ± 1.10, P < .05). The basic performance rating of DS (8.70 ± 0.48) was also significantly higher than that of CS (7.20 ± 0.92. P < .05). Quantitative evaluation of fit accuracy revealed a statistically significant difference (P < .05), with DS (636.29 ± 268.51 µm) being superior to CS (704.2 ± 306.05 µm). CONCLUSION: The stabilization splints fabricated with a digital workflow showed better accuracy than the conventionally fabricated splints in terms of occlusal contact, basic performance, and fit accuracy. Because this is a pilot study, formal trials with a completely digital fabrication workflow will be conducted in the future.

Comparison of immediate response to four conservative treatment modalities for management of masticatory myalgia with limited mandibular movement: a retrospective study.

OBJECTIVE: Conservative treatment modalities are recommended for managing masticatory myalgia in individuals with temporomandibular disorders. The aim of this study was to retrospectively review and compare the effectiveness of four conservative treatments: counseling and occlusal splint therapy, counseling and manipulation integrated with electrophysiotherapy, the combination of the two treatments, and counseling only. METHOD AND MATERIALS: One hundred and sixty-eight patients who had myalgia with limited jaw movement were retrospectively observed in this study. Between January 2015 and December 2017, 63 patients received counseling and stabilization occlusal splint therapy (Group 1), 35 patients received counseling and manipulation integrated with electrophysiotherapy (Group 2), 33 patients received the combination of counseling, splint therapy, and manipulation integrated with electrophysiotherapy (Group 3), and 37 patients received counseling only (Group 4). All subjects were followed up for 12 weeks. The intensity of spontaneous pain, palpation pain, chewing pain in the masticatory muscles, and range of pain-free maximal mouth opening were recorded in the clinical assessments. Intragroup and intergroup differences were examined by using analysis of variance (ANOVA) and the Kruskal-Wallis test. RESULTS: Spontaneous pain in the masticatory muscles was relieved significantly in all groups at the 6-week visit (P < .05), and no significant difference was found among the groups (P > .05). Palpation pain was relieved significantly at the 9-week visit in the counseling + occlusal splint therapy group, counseling + manipulation + electrophysiotherapy group, and counseling + occlusal splint + manipulation + electrophysiotherapy group (P < .05). In the treatment group with counseling alone, significant palpation pain relief occurred at 12 weeks. Chewing pain was relieved significantly at the 6-week visit in the counseling + occlusal splint therapy group, counseling + manipulation + electrophysiotherapy group, and counseling + occlusal splint + manipulation + electrophysiotherapy group (P < .05), yet no significant difference compared to the baseline was observed in the counseling-only group (P > .05). A significant increase in the maximal range of pain-free mouth opening was observed at the 9-week visit in the counseling + occlusal splint therapy group, and at the 3-week visit in the counseling + manipulation + electrophysiotherapy group and counseling + occlusal splint + manipulation + electrophysiotherapy group (P < .05). Nevertheless, no significant change in the range of mouth opening was found throughout the follow-up period in the counseling-only group (P > .05). CONCLUSION: Each of the included treatment modalities relieved spontaneous pain and tenderness to palpation of the masticatory muscles during the follow-up intervals. Counseling alone did not help patients with chewing pain and limited mouth opening in the short term. Treatment protocols including counseling, occlusal splint therapy, and manipulation, integrated with electrophysiotherapy showed the best short-term outcomes for symptomatic improvement.

[Mechanical properties and cytotoxicity of three-dimensional printing polycarbonate for occlusal splints].

PURPOSE: To evaluate the mechanical properties and cytotoxicity of a 3D printing polycarbonate material used in digital occlusal splints, and to use this material to manufacture a splint with CAD/CAM technology. METHODS: Specimen of two different materials, 3D printing polycarbonate(PC-plus) and transparent base resin (PMMA) were processed. The flexural strength, elastic modulus, microhardness, hygroscopicity and water-solubility of these materials then were evaluated. According to the standard of GBT16886.5-2003, cell culture and cytotoxicity test in vitro were conducted to evaluate the target materials on the morphology, growth and proliferation of cultured cells (L929). By using 3D printing technology, a splint was made of this 3D printing polycarbonate material. Statistical analysis was performed using SPSS 24.0 software package. RESULTS: For the group of PC-plus, the flexural strength ranged from 89.4 to 109.8 MPa, the elastic modulus from 1939.4 to 2470.9 GPa, the microhardness from 15.6 to 24.7 MPa, hygroscopicity from 2.43 to 11.42 µg/mm3 and water-solubility from 0.11 to 0.30 µg/mm3. For PMMA group, the flexural strength ranged from 75.2 to 88.4 MPa, the elastic modulus from 1349.2 to 2470.2 GPa, the microhardness from 17.5 to 35.3 MPa, hygroscopicity from 12.80 to 16.16 µg/mm3 and water-solubility from 4.74 to 7.44 µg/mm3. The difference between 3D printing PC-plus group and PMMA base resin group was statistically significant (P<0.05). L929 cells showed normal morphology and proliferation increased with culture time. The toxicity grade of all groups was 0-1, and the 3D printing splint was made successfully. CONCLUSIONS: The polycarbonate material for 3D printing has adequate mechanical properties and biocompatibility to meet the requiement of clinical application.

[A preliminary study on the relationship between the wearing time of full denture and EMG in edentulous patients].

PURPOSE: This study was aimed to analyze the relationship between the periods of wearing time of full denture and function of mastication in edentulous patients. METHODS: Electromyogram (EMG) was done at an initial time of wearing full denture for 30 patients (Group A) and at an interval of wearing full denture for more than 3 months for 32 patients (Group B). EMG activities were recorded for 2 pairs of muscles (anterior temporalis, masseter) by means of Medelec Synergy Electromyography. Student's t test was used for statistical analysis. RESULTS: EMG amplitude of Group A was significantly lower than that of Group B (left anterior temporalis P < 0.05, bilateral masseter P < 0.05). Group A has larger area than Group B (P < 0.05); No significant difference was found in asymmetry index between Group A and Group B (P > 0.05). CONCLUSION: The function of mastication in patients who wore full denture for short time has not been achieved as expected.

[The influence of occlusion on the incidence of bruxism in 779 children in Shanghai].

PURPOSE: To explore the influence of occlusion on the incidence of bruxism in children. METHODS: The incidence of bruxism in children was investigated from the questionnaire of 779 children's parents. The occlusion of these children was checked by professionals. The influence of the occlusion on the incidence of bruxism in children was analysed. Chi-square test was used for statistical analysis. RESULTS: The occlusion of children with bruxism and children without bruxism had no significant difference (P>0.05). The incidence of bruxism did not increase in the children with mixed dentition(P>0.05). CONCLUSION: The occlusion does not affect the incidence of bruxism in children. The mixed dentition does not increase the incidence of bruxism in children.

[Epidemic investigation on 3 to 6 years children's bruxism in Shanghai.].

PURPOSE: The present investigation analyzed the states of children bruxism in Shanghai, aiming for early diagnosis and early treatments. METHODS: The investigation was conducted through questionnaising 779 3-to-6-years-old children's parents. The data were processed using Chi square test. RESULTS: (1)The prevalence of children bruxism in Shanghai was about 38.4%; (2)151 males (40.6%) and 148 females (36.4%) had bruxism, which indicated no statistic difference in two genders(X2=1.47, P>0.05);(3)There seemed to exist hereditary difference between children with or without bruxism(X2=102.98, P<0.01). CONCLUSION: There is a high bruxism prevalence among children aged from 3 to 6 years in Shanghai, which should be concerned about by the healthy care workers in order to make early diagnosis and treatment.