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BACKGROUND: Metacarpal shaft fracture is a common type of hand fracture. Numerous studies have explored fixing transverse fractures in the midshaft of the metacarpal bone. However, this section of the metacarpal bone is often susceptible to high-energy injury, resulting in comminuted fracture or bone loss. In such cases, wedge-shaped bone defects can develop in the metacarpal shaft, increasing the difficulty of performing fracture fixation. Notably, the research on this type of fracture fixation is limited. This study compared the abilities of four fixation methods to fix metacarpal shaft fractures with wedge-shaped bone defects. METHODS: In total, 28 artificial metacarpal bones were used. To create wedge-shaped bone defects, an electric saw was used to create metacarpal shaft fractures at the midshaft of each bone. The artificial metacarpal bones were then divided into four groups for fixation. The bones in the first group were fixed with a dorsal locked plate (DP group), those in the second group were fixed with a volar locked plate (VP group), and those in the third group were fixed by combining dorsal and volar locked plates (DP + VP group), and those in the fourth group were fixed with two K-wires (2 K group). Cantilever bending tests were conducted using a material testing machine to measure yielding force and stiffness. The four groups' fixation capabilities were then assessed through analysis of variance and Tukey's test. RESULTS: The DP + VP group (164.1±44.0 N) achieved a significantly higher yielding force relative to the 2 K group (50.7 ± 8.9 N); the DP group (13.6 ± 3.0 N) and VP group (12.3 ± 1.0 N) did not differ significantly in terms of yielding force, with both achieving lower yielding forces relative to the DP + VP group and 2 K group. The DP + VP group (19.8±6.3 N/mm) achieved the highest level of stiffness, and the other three groups did not differ significantly in terms of stiffness (2 K group, 5.4 ± 1.1 N/mm; DP group, 4.0 ± 0.9 N/mm; VP group, 3.9 ± 1.9 N/mm). CONCLUSIONS: The fixation method involving the combined use of dorsal and volar locked plates (DP + VP group) resulted in optimal outcomes with respect to fixing metacarpal shaft fractures with volar wedge bone defects.

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Objective @# To investigate the effects of different occlusal veneer preparation designs and fiber posts on the fracture load and failure mode of endodontically treated maxillary premolars with pulp-piercing wedge-shaped defect．@*Methods @# 60 maxillary first premolars were randomly divided into group A and group B after Root Canal Therapy (RCT) and severe defects(n = 30) ．Group A was filled with glass fiber post and resin core，and group B was filled with resin core only．Then the occlusal veneer( G2) ，buccal-occlusal veneer( G3) and buccal-proximal-occlusal veneer ( G4 ) were applied to the isolated teeth．The teeth filled with composite resin ( G1 ) and full crown ( G5) were set as negative and positive control respectively，with 6 samples in each group．The sample was subjected to 5 000 hot and cold cycles and 20 000 vertical compression load aging．Finally，all the samples were loaded with static load until the sample broke at the speed of 0．5mm / min．The fracture load and failure mode of each sample were recorded. @*Results @# Both the fracture load in group A and B was G5 ＞G3 ＞G2 ＞G4 ＞G1，and the fracture load in G2，G3，G4，G5 was significantly higher than that in G1 (P＜0. 05) ，and there was no significant difference between group A and B (P＞0. 05) ．The fracture form of G3 was mostly unbonding of the repair body，which was conducive to re-repair．@*Conclusion @#Buccal ( occlusal) veneer is the most effective in repairing pulp-piercing wedge-shaped defects．The fiber post could not significantly enhance the fracture load of the pulp-piercing wedge- shaped defects teeth.

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OBJECTIVE: The aim of this research is to study the influence of size and location of wedge-shaped defects of teeth on stress and strain state of restorative material on the basis of biomechanical analysis. PATIENTS AND METHODS: Materials and methods: Biomechanical analysis of the stress-strain state was performed on a jaw bone fragment with canine and premolar inclusion. RESULTS: Results: Tangential stress increase both in the adhesive layer and in restorative material with depth and width (medial-distal size) of restored wedge-shaped defects of teeth,.The most unfavorable loading on a tooth is a joint action of vertical and horizontal loading in lingual- vestibular or vestibular-lingual direction, depending on localization of the restored wedge-shaped defects of teeth. The formation of retention grooves in wedge-shaped defects of teeth reduces the value of the maximum tangential stress in the adhesive layer of restorative material to 25% and extends the longevity of restorations. CONCLUSION: Conclusions: The difference in maximal values of tangential stress increases in adhesive layer of restorative material with or without retention grooves with increasing depth of defect. Thus, it is advisable to form retention grooves in cases of wedge-shaped teeth defects that exceed 1.5 mm. In case of restoration of subgingival wedge-shaped defects of teeth of small height it is recommended to create one retention groove on the gingival or incisal planes of a carious cavity due to significant inconveniences, and sometimes impossibility of formation of traditionally located retention grooves.

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Non-carious cervical lesion is a common dental disease, which not only affects the aesthetic and function of the teeth, but also leads to dentin sensitivity, pulpitis and other consequences. The main causes of lesions are abrasion, abfraction, acid erosion and so on. The treatment design should depend on the etiology, defect size, location, symptoms and presence or absence of gingival recession.

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This study was to compare the influence of glass fiber post placement and crown restoration on endodontically treated maxillary first premolars with severe NCCLs using three-dimensional finite element analysis and fracture resistance testing. G1, intact teeth. G2, teeth with artificial defect. G3, composite resin (CR). G4, CR and fiber post in buccal canal (FPB). G5, CR and fiber post in palatal canal (FPP). G6, CR and fiber posts in buccal and palatal canals (FPBP). G7, CR and crown (C). G8, CR, FPB, C. G9, CR, FPP, C. G10, CR, FPBP, C. Teeth in G2, G3, and G5 showed a similar stress concentration at the tip of the defect. The fracture resistance of G2 did not differ significantly from G3 and G5 (p>0.05) but differed significantly from that in other groups (p<0.05). The fractures in G4 were more favorable, and the difference of those in G1 from those in G7, G8, G9, and G10 was statistically significant (p<0.05). Restoration of root-filled maxillary premolars with severe NCCLs using fiber post in the buccal canal may be more efficacious than other restoration methods.

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Wedge-shaped defects are frequently observed on the cervical region of the human tooth. Previously, most studies explained that improper tooth-brushing causes such defects. However, recent clinical observation suggested that the repeated stress due to occlusal force may induce the formation of these wedge-shaped defects. In this study, therefore, two-dimensional human tooth models are considered with and without a wedge-shaped defect by applying the finite element method. To evaluate large stress concentrations accurately, a method of analysis is discussed in terms of the intensity of singular stress fields appearing at the tip of the sharp wedge-shaped defect. The effects of the position and direction of occlusion on the intensity of singular stress fields are discussed before and after restoration with composite resins.

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OBJECTIVE: The objective of this paper is to analyze the stress distribution in the deep wedge-shaped defective mandibular first premolars restored with different methods. METHODS: Three-dimensional finite element models of mandibular first premolar with deep wedge-shaped defect were created. The model, which was untreated after root canal treatment, served as the control group. Then, according to different treatment designs, four experimental groups were established as follows: resin filling (A), post restoration after resin filling (B), crown restoration after resin filling (C), and post and crown restoration after resin filling (D). Four different post materials were then chosen for establishing the subgroup models: fiber post (B1, D1), AuPd post (B2, D2), pure Ti post (B3, D3), and CoCr post (B4, D4). A force of 100 N was applied at a 30° angle on the buccal-inclined surface near the top of the buccal cusp. The maximum principal stress and Von Mises stress were investigated using finite element analysis software. RESULTS: 1) For the control group, the maximum principal stress and Von Mises stress of the residual dentine were the same as those of the tip of the defect. 2) Compared with the control group, the maximum principal stress and Von Mises stress of groups A, B, C, and D decreased greatly (P<0.05). The maximum principal stress and Von Mises stress of groups C and D with crowns were similar. The maximum principal stress and Von Mises stress of the post-dentine surface of groups B and D with fiber post were less than those in the cast metal post models (P<0.05). 3) The displacement of the buccal cusp of group A was similar to that of the control group (P>0.05) and larger than those in groups B, C, and D (P<0.05). CONCLUSIONS: It is necessary for deep wedge-shaped defective teeth to be treated with full crowns, but a post is not necessary. If a post is used, fiber post with elastic modulus closer to the dentine is more suitable than metal post.
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OBJECTIVES: To investigate the application value of resin filling device in the repair of wedge-shaped defects. METHODS: 126 cases of wedge-shaped defect patients, a total of 178 teeth, were randomly divided into control group, repaired with ordinary resin filler, study group repaired with Kerr resin filler. Observe two groups of repair time, effect and shaping ability. RESULTS: Study group's filling time, shaping ability filling were significantly better than those of control group, P<0.05. There is statistically significant difference. And the work head has not sticking phenomenon of filling material. CONCLUSIONS: Kerr resin filler can use of repairing wedge-shaped defect, has obviously clinal effect.

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Objective To observe the effect of glass fiber post combined with gingival retraction in the treat-ment of teeth with severe wedge -shaped defect.Methods 53 patients with 120 teeth treated for severe wedge -shaped defect were selected.All the teeth were given root canal treatment,glass fiber post was applied after root canal prepared and resin was applied to fill wedge-shaped defect after gingival retraction.All the teeth were followed up for 2-3 years.Results In 2-3 years follow-up after treatment,there was no adverse outcome such as crown fracture or root fracture,neither filling material falling off in all the 53 patients with 120 teeth.The effect was good and satis-fied.Conclusion The indication should be strictly grasped and then it is convenient to apply glass fiber post com-bined with gingival retraction to treat premolar with severe wedge -shaped defect,and complete coronal restoration should be avoided to reduce the cost of health care.

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302 teeth with wedge-shaped defect in 168 patients were restored by SDR(smart dentin replacement,n =112),glass ionomer (n =98) and light-cured composite resin(n =92) respectively.12 to 15 month follow-up showed the success rate was 96.2％,84.8％ and 86.2％ respectively(P ＜ 0.01).SDR is an ideal material in restoring wedge-shaped defect.

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@#The mandibular first premolar has complicated morphology of root canal, it has more variation which increases the incidence of multiple root canals. A successful root canal therapy not only need strict cleaning, disinfection and filling, but also need a correct understanding of root canal morphology and anatomy. Otherwise there might be a risk of missing canals that resulting the failure of the therapy. Also crown closure is one of the successful elements of root canal therapy. This is a case report accompanied by a review of the literature that shows the unusual anatomy of the mandibular first molar with three roots and three root canals.

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<p><b>OBJECTIVE</b>The objective of this paper is to analyze the stress distribution in the deep wedge-shaped defective mandibular first premolars restored with different methods.</p><p><b>METHODS</b>Three-dimensional finite element models of mandibular first premolar with deep wedge-shaped defect were created. The model, which was untreated after root canal treatment, served as the control group. Then, according to different treatment designs, four experimental groups were established as follows: resin filling (A), post restoration after resin filling (B), crown restoration after resin filling (C), and post and crown restoration after resin filling (D). Four different post materials were then chosen for establishing the subgroup models: fiber post (B1, D1), AuPd post (B2, D2), pure Ti post (B3, D3), and CoCr post (B4, D4). A force of 100 N was applied at a 30° angle on the buccal-inclined surface near the top of the buccal cusp. The maximum principal stress and Von Mises stress were investigated using finite element analysis software.</p><p><b>RESULTS</b>1) For the control group, the maximum principal stress and Von Mises stress of the residual dentine were the same as those of the tip of the defect. 2) Compared with the control group, the maximum principal stress and Von Mises stress of groups A, B, C, and D decreased greatly (P<0.05). The maximum principal stress and Von Mises stress of groups C and D with crowns were similar. The maximum principal stress and Von Mises stress of the post-dentine surface of groups B and D with fiber post were less than those in the cast metal post models (P<0.05). 3) The displacement of the buccal cusp of group A was similar to that of the control group (P>0.05) and larger than those in groups B, C, and D (P<0.05).</p><p><b>CONCLUSIONS</b>It is necessary for deep wedge-shaped defective teeth to be treated with full crowns, but a post is not necessary. If a post is used, fiber post with elastic modulus closer to the dentine is more suitable than metal post.
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Objective:To observe the effect of “bulk-fill”flowable resin in filling deep wedge-shaped defects.Methods:50 pa-tients with totally 85 pairs of premolars with deep wedge-shaped defects(depth >2 mm)were included.Each pair of the defects was randomly divided into the test group and the control group,the defects were treated by “bulk-fill”flowable resin with single cure tech-nique and conventional flowable resin with incremental layering technique respectively,the tooth sensitive rate 1 week after filling,the filling failure rate,the edge coloring and secondary caries rate 2 years after filling of the 2 groups were compared.Results:There was no significant difference between the 2 groups in the sensitive rate 1 week after filling,the failure rate and the edge coloring and sec-ondary caries rate 2 years after filling(P >0.05).Conclusion:The “bulk-filled”flowable resin using single cure technique can ac-quire the same clinical effect as conventional flowable resin using incremental layering technique in filling deep wedge-shaped defects.

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Objective To study the main factors of young people the wedge-shaped teeth defect.Methods Random sampling way,746 middle-aged and young people in 20-50 years old with the wedge-shaped teeth defect patients status were checked,the oral examination and questionnaire survey was used to surveyed the factors on the young people of wedge-shaped defects.Results The young people of wedge-shaped defects in the reason,the most common was the mechanical friction 576 cases accounted for 75.4％,followed by etching 422 cases accounted for 56.6％,in addition to bite force fatigue in 112 cases accounted for 15.0％,other 46 cases,accounting for 6.7％.Conclusion The young people oral care has many defects,but also exposed many problems,the wedge-shaped teeth defectand oral care,using habit has the very big relations,and the prevention was the mainly measure for the wedgeshaped teeth defect.

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PURPOSE: To evaluate the efficiency of digital retinal nerve fiber layer (RNFL) photographs converted from a non-mydriatic digital fundus camera for detecting RNFL defects. METHODS: Ninety-five eyes were evaluated with both a non-mydriatic digital fundus photograph and a digital RNFL photograph by two glaucoma specialists independently. The red-free, monochrome modified digital fundus photograph was acquired from non-mydriatic digital fundus photographs using Photoshop 7.0. Whether a localized wedge-shaped or diffuse RNFL defect existed or not was evaluated on a non-mydriatic digital fundus photograph and a modified digital fundus photograph, and inter- and intraobserver agreement were also evaluated. Regarding the use of digital RNFL photographs as a standard method, we calculated the sensitivity, specificity, and positive and negative predictive values of the two types of photographs. RESULTS Interobserver agreement (Cohen's kappa values) about localized RNFL defects observable on digital RNFL photographs, non-mydriatic digital fundus photographs, and modified digital fundus photographs were 0.749, 0.634, and 0.793, respectively, but all were 0.417 or less with regard to diffuse RNFL defects. Regarding localized RNFL defects, the sensitivity, specificity, and positive and negative predictive values of modified digital fundus photographs were 85.7%, 95.5%, 85.7% and 94.1%, respectively, showing superiority to those of non-mydriatic digital fundus photographs. But, in cases of diffuse RNFL defect, the sensitivity and specificity of modified digital fundus photographs were 60.0% and 97.8%, respectively, indicating no superiority to non-mydriatic digital fundus photographs. CONCLUSIONS: The localized RNFL defect can be detected more efficiently with modified digital fundus photographs than non-mydriatic digital fundus photographs, but the diffuse RNFL defect cannot.

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PURPOSE: To evaluate the efficiency of digital retinal nerve fiber layer (RNFL) photographs converted from a non-mydriatic digital fundus camera for detecting RNFL defects. METHODS: Ninety-five eyes were evaluated with both a non-mydriatic digital fundus photograph and a digital RNFL photograph by two glaucoma specialists independently. The red-free, monochrome modified digital fundus photograph was acquired from non-mydriatic digital fundus photographs using Photoshop 7.0. Whether a localized wedge-shaped or diffuse RNFL defect existed or not was evaluated on a non-mydriatic digital fundus photograph and a modified digital fundus photograph, and inter- and intraobserver agreement were also evaluated. Regarding the use of digital RNFL photographs as a standard method, we calculated the sensitivity, specificity, and positive and negative predictive values of the two types of photographs. RESULTS Interobserver agreement (Cohen's kappa values) about localized RNFL defects observable on digital RNFL photographs, non-mydriatic digital fundus photographs, and modified digital fundus photographs were 0.749, 0.634, and 0.793, respectively, but all were 0.417 or less with regard to diffuse RNFL defects. Regarding localized RNFL defects, the sensitivity, specificity, and positive and negative predictive values of modified digital fundus photographs were 85.7%, 95.5%, 85.7% and 94.1%, respectively, showing superiority to those of non-mydriatic digital fundus photographs. But, in cases of diffuse RNFL defect, the sensitivity and specificity of modified digital fundus photographs were 60.0% and 97.8%, respectively, indicating no superiority to non-mydriatic digital fundus photographs. CONCLUSIONS: The localized RNFL defect can be detected more efficiently with modified digital fundus photographs than non-mydriatic digital fundus photographs, but the diffuse RNFL defect cannot.

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Objective To study the effect of CEREC CAD/CAM ceramic inlay on repair of wedge-shaped defects of teeth and test its anti-fracture properties. Methods Extracted teeth were divided into control group ( n = 16) and experimental group ( n = 16) ,and prepared into imitating teeth with wedge-shaped defects. Teeth in experimental and control groups were repaired with CEREC CAD/CAM ceramic inlay and light-cured composite resin,respectively. Anti-fracture strength of teeth with wedge-shaped defects repaired with CEREC CAD/CAM was assayed on a universal testing device with its maximal loading recorded. The anti-fracture strength was compared between the 2 groups. Results The anti-fracture strength of teeth with wedge-shaped defects repaired with CEREC CAD/CAM ceramic inlay was significantly higher in experimental group than in control group ( 3. 56 ? 0. 27 vs 2. 43 ? 0. 15,P

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We investigated differences in clinical findings among normal-tension glaucoma(NTG)patients between those with wedge-shaped nerve fiber layer(NFL)defect and with diffuse atrophy. Forty-one eyes of patients with NTG having diurnal intraocular pressure < 21mmHg, glaucomatous visual field defect, optic disc analysis with Heidelberg Retina Tomograph(HRT), and brain magnetic resonance imaging were divided into wedge-shaped defect group and diffuse atrophy group according to the types of NFL atrophy. We found no difference between two groups in the mean deviation of visual field, area of peripapillary atrophy measured with HRT, and presence of peripapillary atrophy. The patients with diffuse atrophy were older than those with wedge-shaped defect(p=0.01). The intraocular pressure was slightly higher (p=0.02)and maximal cup depth was larger(p=0.03)in patients with wedge-shaped defect compared with diffuse atrophy. Cerebral small vessel disease was more frequent in patients with diffuse atrophy than with wedge-shaped defect(p=0.02). This study suggests that cerebral small vessel disease is more common in patients with diffuse atrophy and potentially suggests indirectly ischemia may cause more diffuse damage than localized damage in patients with NTG.

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