Evaluation of the clinical efficacy of implant-supported overdenture with edentulous mandible in elderly patients / 华西口腔医学杂志

The aging society of the global population has led to an increase in the number of patients with edentulous jaw, a common multiple disease. Given the developments in implant techniques, the method of implant denture has received a positive and good response in terms of the quality of life and psychological well-being of patients. Implant-supported overdenture in mandible has two main advantages. 1) It has better retention and chewing efficiency than those of mandibular conventional denture. The required implant site of implant-supported overdenture is less than that of fixed implant-supported denture and can repair more defect tissues to help restore beauty and pronunciation. The price of the former is more acceptable than that of the latter. Therefore, this article aimed to systemically analyze and further discuss the clinical effect of implant-supported overdenture in elderly patients; combine existing related studies on the selection of number, site, and upper restoration of implants; and illustrate the advantages of removable implant-supported protheses in the repair of toothless mandible.

Effect of removable partial dentures restoration on oral health-related quality of life of patients with shortened dental arch / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To assess the effect of removable partial dentures (PRD) restoration on oral health-related quality of life (OHRQOL) of subjects with shortened dental arches (SDA) using the Chinese version of the Oral Health Impact Profile (OHIP-14).</p><p><b>METHODS</b>Consecutive patients with shortened dental arches were recruited from the Department of Prosthodontics, Foshan Chancheng Hospital of Stomatology. The Chinese version of OHIP-14 was administered to each subject before treatment and after treatment. The subjective outcomes of removable partial dentures therapy on SDA were collected and the pre- and post-treatment scores of the Chinese version of OHIP-14 were compared.</p><p><b>RESULTS</b>After treatment, significant decrease in patients' total score of OHRQOL [before: 9 (6, 12) ; after: 4 (2.25, 6)] was detected, as well as physical pain subscale, physical disability subscale and handicap subscale; and the score of OHRQOL in function limitation subscale increased [before: 0(0,0); after: 2(1, 2)].</p><p><b>CONCLUSIONS</b>The main impacts of shortened dental arch with intact anterior region affecting patients' OHRQOL are physical disability.From a quality-of-life perspective, patients with SDA can perceive benefits from RPD.</p>

The surface roughness analysis of the titanium casting founding by a new titanium casting investment material / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the surface roughness property of the titanium castings cast in a new investment for titanium casting.</p><p><b>METHODS</b>Six wax patterns (20 mm × 20 mm × 0.5 mm) were invested using two investments: three in a new titanium investment material and three in the control material (Rematitan Plus). Six titanium specimens were obtained by conventional casting. After casting, surface roughness of the specimens were evaluated with a surface profilometer.</p><p><b>RESULTS</b>The surface roughness of the specimens cast in new titanium investment material was (1.72 ± 0.08) µm, which was much smaller than that from Rematitan Plus [(1.91 ± 0.15) µm, P < 0.05].</p><p><b>CONCLUSIONS</b>The surfaces of titanium cast using these two investment materials are both smooth enough to fulfill the demand of the titanium precision-casting for prosthodontic clinical use.</p>

Finite element contact stress analysis of simulating teeth with wedge shaped defects in the cervical region / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the distribution of stress of simulating teeth with wedge shaped defects in the cervical region.</p><p><b>METHODS</b>The models of anisotropic enamel of the mandibular first premolar and the opposite maxillary first premolar crown were created. A defect was introduced into the model of mandibular premolar in the buccal cervical region along the enamelo-dentinal junction (DEJ). The stress distribution in the cervical region of the mandibular premolar was investigated considering lateral condition simulating working micromotions. In this case, the stroke was applied to the maxillary first mandibular in a stepping procedure using nonlinear contact analysis.</p><p><b>RESULTS</b>The stresses were concentrated in the defect of the enamel and dentin at the DEJ in the condition of lateral loading. As the defect length increased in size, the peak maximum principal stress (MPS) value and the magnitude of the stress field along the DEJ both increased.</p><p><b>CONCLUSION</b>Undermined cervical DEJ had a significant effect on the stress distribution in the buccal cervical region.</p>

Relationship between occlusal plane and masticatory path in youth with individual normal occlusion / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the characteristics of and relationship between occlusal plane and masticatory path in young adults with individual normal occlusion, and to provide clinical implications on both morphological and functional reference of occlusal plane location.</p><p><b>METHODS</b>Forty-three young adults with individual normal occlusion were included. Lateral projections of cephalometric radiographs were taken. The parameters of anatomical landmarks were analyzed. The BioEGN mandibular kinesiography analyzer was used to record the path of incisal edge of mandibular central incisor movement during mastication. The Pearson's linear correlation analysis was performed to analyze the relationship of inclination of occlusal plane and data mentioned above with SPSS13.0 software.</p><p><b>RESULTS</b>The inclination of occlusal plane (the angle between occlusal plane and Camper's line OP-CP) was (2.1 ± 3.8)° in youth with normal occlusion. Means of maximal distances of 3-dimensional masticatory mandibular movement paths were as follow: the vertical length was (20.22 ± 4.28) mm, the anterior-posterior width was (11.42 ± 2.45) mm, and the lateral width was (8.62 ± 1.52) mm. The inclination of occlusal plane was negatively correlated to the lateral width of masticatory path in frontal plane (r = -0.39, P < 0.05). Occlusal plane was approximately vertical to the opening and closing path in the vicinity of intercuspal position during mastication. The inclination of occlusal plane was positively related to occlusal plane-closing angles in the upper segments of closing path during mastication (P < 0.05). Masticatory axis angle was (66.50 ± 7.98)° with no significant correlation to the inclination of occlusal plane (P > 0.05).</p><p><b>CONCLUSIONS</b>These results suggest that the sagittal inclination of occlusal plane can influence 3-dimensional morphology of masticatory path.The inclination of occlusal plane has a guiding effect on masticatory movement in the upper segments of closing path.</p>

The characteristics of masticatory muscle activity in bruxers / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effects of bruxism on masticatory muscle electromyographic (EMG) activity.</p><p><b>METHODS</b>Twenty-four bruxers and sixteen asymptomatic control subjects were included through questionnaire and clinical examination. EMG activity was recorded by placing surface electrodes on bilateral anterior temporalis (TA), masseters (MM), anterior digastrics (DA) and sternocleidomastoid (SCM) muscles. EMG activities at rest, during maximal voluntary clenching in intercuspal position and swallowing were recorded by means of Bio PAK system.</p><p><b>RESULTS</b>EMG activities of TA and MM at rest were significantly higher in bruxism group than in control group (P<0.05). When subjects clenched their teeth in intercuspal position, the activities of TA and MM were much lower in bruxism group than in control one (P<0.05). EMG activity during swallowing was no significant difference between the two groups. The asymmetry index of bilateral TA and MM in bruxism group was a little higher than the control group, but there was no significant difference between the two groups (P>0.05).</p><p><b>CONCLUSION</b>Masticatory muscle dysfunction of bruxers is mainly represented as higher potential in postural position and lower potential during maximal voluntary clenching in intercuspal position of anterior temporalis and masseters.</p>

Investigation on relationship between wedge-shaped defects and occlusal interference / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the relationship between wedge-shaped defects and occlusal interference.</p><p><b>METHODS</b>Following examination from 46 patients, a total of 157 teeth were identified to have the criteria set for wedge-shaped defects and regarded as the experiment group. Also, 157 adjacent teeth exhibiting no such noncarious cervical lesions were randomly selected from the same group of patients and regarded as the control group. The distribution of occlusal force and time were examined with T-Scan II system in 46 patients with wedge-shaped defects in intercuspal occlusion position, protrusive movement and lateral movement. Occlusal interference and premature contact were evaluated and compared between the two groups.</p><p><b>RESULTS</b>The proportion of the teeth with premature contact in experiment group was 6.37%, while the control group was 2.55%, there was no significant difference between the two groups (P > 0.05). The total proportion with occlusal interferences in experiment group was 23.57%, which was significantly higher than that of the control group (10.19%, P < 0.05), in experiment group the proportion with working side interferences was 15.92%, and in control group, the proportion was 3.82%, there was significant difference between the two groups (P < 0.01). At the same time, the teeth with occlusal interferences had more serious degree of the wedge-shape defects than those with no occlusal interference.</p><p><b>CONCLUSION</b>The increased occlusal force has relation to the formation as well as severity of wedge-shaped defects.</p>