Design and Biomechanical Analysis of Customized Angled Abutment Based on Tooth Inclination Angle for Immediate Implant Placement on Maxillary Anterior Region.

PURPOSE: Finite element analysis and an in vitro experiment were employed to investigate the loading effects of angled abutments, comparing various customized angled abutments derived from the average angle of incisors in patients with a commercial 15°∆ angled abutment, on both the implant and surrounding bone. METHODS: Four customized angled abutment models (21.9°∆, 24.15°∆, 20.22°∆, 33°∆) were developed using cone-beam computed tomography (CBCT) images of incisor inclination from various age groups of patients. 3D maxillary bone models were created from CBCT images of four individual patients. Finite element analysis and in-vitro strain gauge experiments were conducted, applying 100N or 50N of axial or oblique force, to assess the differences in stress/strain between the customized and the commercial 15°∆ angled abutments in both the implants and surrounding bone. RESULTS: Under axial loading, the stress values in the dental implant and surrounding bone were elevated due to the relatively higher angles of the customized angled abutments (21.9°∆, 24.15°∆, 20.22°∆, 33°∆) when compared to the commercial 15°∆ angled abutment; however, under oblique loading the commercial 15°∆angled abutment exhibited higher stress values in both the implant and surrounding bone. For in vitro experiment, there is no statically difference in bone strain between the customized (21.9°∆) and the commercial 15°∆ angled abutments in axial loading. Nevertheless, in oblique loading using a commercial 15°∆ angled abutment induced the higher bone strains. CONCLUSION: Customized angled abutments offer lower stress/strain under oblique loads but higher stress/strain under axial loads compared to commercial ones. Therefore, in the design and application of angled abutments, careful consideration of the occlusal load direction is paramount for achieving biomechanical success of dental implant.

Biomechanical analysis of plate versus K-wire fixation for metacarpal shaft fractures with wedge-shaped bone defects.

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.

Preoperative assessment of bone density for dental implantation: a comparative study of three different ROI methods.

BACKGROUND: Dental cone beam computed tomography (CBCT) is commonly used to evaluate cancellous bone density before dental implant surgery. However, to our knowledge, no measurement approach has been standardized yet. This study aimed to evaluate the relationship between three different regions of interest (ROI) methods on cancellous bone density at the dental implant site using dental CBCT images. METHODS: Patients' dental CBCT images (n = 300) obtained before dental implant surgery were processed using Mimics (Materialise, Leuven, Belgium). At the potential implant sites, the rectangle, cylinder, and surrounding cylinder ROI methods were used to measure bone density. Repeated measures one-way analysis of variance was performed to compare the three ROI methods in terms of measurement results. Pearson correlation analysis was performed to identify the likely pair-wise correlations between the three ROI methods. RESULTS: The density value obtained using the surrounding cylinder approach (grayscale value [GV],523.56 ± 228.03) was significantly higher than the values obtained using the rectangle (GV, 497.04 ± 236.69) and cylinder (GV,493 ± 231.19) ROI methods in terms of results. Furthermore, significant correlations were noted between the ROI methods (r > 0.965; p < 0.001). CONCLUSIONS: The density measured using the surrounding cylinder method was the highest. The choice of method may not influence the trends of measurement results. TRIAL REGISTRATION: This study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH111-REC3-205. Informed consent was waived by the Institutional Review Board of China Medical University Hospital, CMUH111-REC3-205, owing to the retrospective nature of the study.

Effects of diameters of implant and abutment screw on stress distribution within dental implant and alveolar bone: A three-dimensional finite element analysis.

Background/purpose: Few studies have investigated the effects of abutment screw diameter in the stress of dental implants and alveolar bones under occlusal forces. In this study, we investigated how variations in implant diameter, abutment screw diameter, and bone condition affect stresses in the abutment screw, implant, and surrounding bone. Materials and methods: Three-dimensional finite element (FE) models were fabricated for dental implants with external hex-type abutments measuring 4 and 5 mm in diameter. The models also included abutment screws measuring 2.0 and 2.5 mm in diameter. Each implant model was integrated with the mandibular bone comprising the cortical bone and four types of cancellous bone. In total, 12 finite element models were generated, subjected to three different occlusal forces, and analyzed using FE software to investigate the stress distribution of dental implant and alveolar bone. Results: Wider implants demonstrated lower stresses in implant and bone compared with standard-diameter implants. The quality of cancellous bone has a minimal impact on the stress values of the implant, abutment screw, and cortical bone. Regardless of occlusal arrangement or quality of cancellous bone, a consistent pattern emerged: larger abutment screw diameters led to increased stress levels on the screws, while the stress levels in both cortical and cancellous bone showed comparatively minor fluctuations. Conclusion: Wider implants tend to have better stress distribution than standard-diameter implants. The potential advantage of augmenting the abutment screw diameter is unfavorable. It may result in elevated stresses in the implant system.

Effects of an augmented reality aided system on the placement precision of orthodontic miniscrews: A pilot study.

Background/purpose: Augmented reality (AR) is gaining popularity in medical applications, which may aid clinicians in achieving improved clinical outcomes. The purpose of this study was to determine the positional and angle errors of orthodontic miniscrew placement by using a self-developed AR aided system. Materials and methods: Cone beam computed tomography (CBCT) and patient printed models were used in in vitro experiments. The participants were divided into a control group and an AR group, in which traditional orthodontic methods and the AR-aided system were used respectively. After the information obtained from the CBCT images and navigation system was combined on the display device, the AR-aided system indicated the planned miniscrew position to guide the clinicians during the placement of miniscrews. Both methods were compared by a senior and a junior dentist, and the position and angle of miniscrew placement were statistically analyzed using Wilcoxon's signed-rank and Mann-Whitney U tests. Results: When the AR-aided system was used, the accuracy of miniscrew placement in the mesiodistal position considerably increased (83%) when the procedure was performed by a senior clinician. In addition, the accuracy of miniscrew placement in the mesiodistal position and the angle of miniscrew placement considerably increased by approximately 67% and 72%, respectively, when the procedure was performed by a junior clinician. The position error of miniscrew placement was smaller for the junior clinician when the AR-aided system was used than for the senior clinician. Conclusion: The AR-aided system improved the accuracy of miniscrew placement regardless of the clinician's level of experience.

Analysis of mandibular molar anatomy in Taiwanese individuals using cone beam computed tomography.

Background/purpose: Before periapical surgery in the mandibular posterior teeth is performed, the thicknesses of the buccal alveolar bone wall and buccolingual root might be a critical issue. This study aimed to assess the anatomical structure of the posterior region of the mandible in Taiwanese individuals using cone-beam computed tomography (CBCT). Materials and methods: The CBCT images of 96 Taiwanese individuals (51 male and 45 female), which included 192 mandibular first molars and 192 mandibular second molars, were imported into medical imaging software to measure the buccal alveolar bone thickness and buccolingual root thickness at 3 mm above the root apex. Statistical analysis was conducted to examine the impact of tooth position, gender, and age on the anatomical position of mandibular molars. Results: The buccal alveolar bone thickness at 3 mm above the root apex of the mandibular second molar demonstrates a significantly higher value when compared to that of the first molar. Nonetheless, concerning the buccolingual root thickness, no significant differences were observed between these two teeth. In addition, the buccal alveolar bone thickness and buccolingual root thickness at 3 mm above the root apex may not be influenced by gender and age. Conclusion: The anatomical structures of the posterior region of the mandible in Taiwanese individuals exhibited variations between the mandibular first and second molars. However, these differences were not influenced by gender or age.

Influence of implant length and insertion depth on primary stability of short dental implants: An in vitro study of a novel mandibular artificial bone model.

Background/purpose: Dental implants are a mainstream solution for missing teeth. For the improvement of dental implant surface treatment and design, short dental implants have become an alternative to various complex bone augmentation procedures, especially those performed at the posterior region of both the maxilla and mandible. The objective of this study was to evaluate the effect of various insertion methods on the primary stability of short dental implants. Materials and methods: Commercial dental implants were inserted into artificial mandibular bone specimens using various insertion methods (equicrestal position, subcrestal position 1.5 mm, and lateral cortical anchorage) in accordance with an implant surgical guide. Insertion torque value (ITV) curves were recorded while implant procedures were performed. Both maximum ITVs (MITVs) and final ITVs (FITVs) were evaluated. Subsequently, Periotest values (PTVs) and implant stability quotients (ISQs) were measured for all specimens. A Kruskal-Wallis test was conducted to analyze the results for four primary stability parameters, and the Dunn test was used for a post hoc pairwise comparison when a difference was identified. Results: For all groups, their mean MITVs ranged from 33.6 to 59.4 N cm, whereas their mean FITVs ranged from 17.5 to 43.5 N cm. Insertion torque value, ISQ, and PTV decreased significantly when implants were inserted into subcrestal positions. When implants were inserted in the lateral bicortical position, the four aforementioned parameters yielded greater values. Conclusion: When 6-mm short implants were inserted in a lateral cortical anchorage position, high primary stability was yielded.

Biomechanical study of the fixation ability of the dorsal and volar locking plate for transverse metacarpal neck fractures.

Metacarpal neck fracture is one of the most common types of hand fractures; the literature suggests that applying a bone plate on the dorsal side provides higher fixation strength than that provided by other fixation methods. However, bone plate fixation on the dorsal side may result in postoperative tendon adhesion. So far, no studies have investigated the fixation of metacarpal neck fractures on the volar side by using a bone plate. The objective of this study was to investigate the differences in the fixation results between bone plate fixation on the dorsal side and bone plate fixation on the volar side of the metacarpal in the case of a metacarpal neck fracture. A saw blade was used to create a transverse metacarpal neck fracture on 14 artificial metacarpal bone specimens. The specimens were divided into 2 groups depending on the fixation method: a volar locking plate (VLP) group and a dorsal locking plate (DLP) group. All specimens were subjected to a cantilever bending test on a material testing system, and a force-displacement curve was used to measure the yield force and stiffness, which served as an indicator of the fixation ability of the 2 fracture fixation methods. For the experimental results, the Mann-Whitney U test was used to compare the fixation abilities of the 2 fixation methods. In terms of yield force, the DLP group (266.9 ± 68.3 N) scored significantly higher than the VLP group (32.6 ± 2.7 N) (P < .05); expressed in terms of median, the DLP group scored 8.2 times higher than the VLP group. Similarly, in terms of stiffness, the DLP group (69.0 ± 13.4 N/mm, median ± interquartile range) scored significantly higher than the VLP group (12.9 ± 1.4 N/mm) (P < .05); expressed in terms of median, the DLP group scored 5.3 times higher than the VLP group. The fixation strength of volar bone plates is only about one-third of that of dorsal bone plates.

Comparison sealing ability in three bioceramic sealers applied in hydraulic condensation technique by using micro-computed tomography.

Background/purpose: Sealing ability in root canal obturation has always been a key concern for endodontic success. The purpose of this study was to analyze the percentage of voids in root canal space obturated by using single cone hydraulic condensation with different root canal sealers and to compare those with AH Plus sealer. Materials and methods: Experiments were conducted using twenty 3D-printed upper first premolars. After the buccal root canals were prepared using Ni-Ti rotary instruments, the teeth were divided into four groups: the AH Plus, BC sealer, BC sealer HiFlow, and Endoseal MTA groups. All buccal canals were obturated by single-cone hydraulic condensation. All specimens were scanned using micro-computed tomography and the percentage volume of the voids inside and outside the filled materials (Vin and Vout) at three different canal depth intervals were calculated by a Bruker micro-CT software. Differences according to root canal sealers were evaluated statistically using the Kruskal-Wallis test and the Wilcoxon Rank Sum test at a significance level of 0.05. Results: The results indicated that most of the voids were presented near the interface (Vout), the Vin is very small and not significant different between groups. The Vout decreased in the following order: AH Plus(1.837% ± 1.226%)≅BC sealer (1.225% ± 0.836%)>BC sealer Hiflow(0.349% ± 0.071%)>Endoseal MTA(0.203% ± 0.049%). Conclusion: For the percentage volume of voids between the root canal filling material and root canal surface, though the BC sealer Hiflow is slightly larger than Endoseal MTA, which is still much less than BC sealer and AH Plus.

Assessment of sagittal root position, alveolar bone concavity, and labial bone perforation in the mandibular anterior tooth region for immediate implant placement.

Background/purpose: Immediate implant placement in the mandibular anterior tooth region requires a thorough understanding of the alveolar bone anatomy for determining the ideal implant position and preventing labial bone perforation. The anatomical characteristics of the jaws are closely related to the sagittal root position (SRP) and labial concavity of the alveolar bone. This study evaluated SRP, labial concavity, and labial bone perforation in the mandibular anterior tooth region. Materials and methods: Cone-beam computed tomography images of 116 participants (696 teeth) were uploaded to medical imaging software. SRP classification, labial concavity of the alveolar bone, and labial bone perforation were analyzed. A t-test was performed to compare measurements between the central and lateral incisors, central incisors and canines, and lateral incisors and canines. Results: The results revealed that the frequency of SRP Class I (88.20%) was the highest, and that of SRP Class III was the lowest (0.53%). Central incisors had the highest mean labial concavity (144.5°), followed by the canines (143.9°) and lateral incisors (143.3°), and the differences were significant between any two of the tooth groups (all P < 0.05). The frequency distribution of labial bone perforation was the highest in central incisors (69.9%), followed by the canines (40.5%) and lateral incisors (10.8%). Conclusion: The majority of mandibular anterior teeth had SRP Class I, with Class III being the least prevalent. Central incisors had the highest mean alveolar bone concavity angle and the most frequent labial bone perforations.

New classification for bone type at dental implant sites: a dental computed tomography study.

OBJECTIVE: This study proposed a new classification method of bone quantity and quality at the dental implant site using cone-beam computed tomography (CBCT) image analysis, classifying cortical and cancellous bones separately and using CBCT for quantitative analysis. METHODS: Preoperative CBCT images were obtained from 128 implant patients (315 sites). First, measure the crestal cortical bone thickness (in mm) and the cancellous bone density [in grayscale values (GV) and bone mineral density (g/cm3)] at the implant sites. The new classification for bone quality at the implant site proposed in this study is a "nine-square division" bone classification system, where the cortical bone thickness is classified into A: > 1.1 mm, B:0.7-1.1 mm, and C: < 0.7 mm, and the cancellous bone density is classified into 1: > 600 GV (= 420 g/cm3), 2:300-600 GV (= 160 g/cm3-420 g/cm3), and 3: < 300 GV (= 160 g/cm3). RESULTS: The results of the nine bone type proportions based on the new jawbone classification were as follows: A1 (8.57%,27/315), A2 (13.02%), A3 (4.13%), B1 (17.78%), B2 (20.63%), B3 (8.57%) C1 (4.44%), C2 (14.29%), and C3 (8.57%). CONCLUSIONS: The proposed classification can complement the parts overlooked in previous bone classification methods (bone types A3 and C1). TRIAL REGISTRATION: The retrospective registration of this study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH 108-REC2-181.

Effect of Implant Length and Insertion Depth on Primary Stability of Short Dental Implant.

Purpose: To evaluate the effect of insertion depth, bone type, and implant diameter on the primary stability of short implants. Materials and Methods: Commercial dental implants with different lengths (6 and 8 mm; BLX, Straumann) were inserted into artificial bone specimens of good and poor quality at three different depth positions: equicrestal, 1-mm subcrestal, and 2-mm subcrestal. Insertion torque values were recorded spontaneously during the implant procedure. Both maximum insertion torque values (MITVs) and final insertion torque values (FITVs) were recorded. Subsequently, Periotest values (PTVs) and implant stability quotients (ISQs) were measured for all specimens. Results: The mean MITVs of all groups ranged from 31.8 to 46.2 Ncm. However, the mean FITVs of all groups ranged from 8.8 to 29 Ncm. Torque values decreased significantly when the implants were inserted into their final positions. When insertion depth was increased, the PTV and ISQ decreased. Long implants and implants inserted into good-quality bone yielded greater primary stability, and bone quality appeared to have a greater effect on primary stability. Conclusion: When 6-mm short implants are inserted in a subcrestal position, low primary stability may be yielded, particularly in poor-quality bone.

Evaluation of sagittal root position and labial alveolar bone concavity in the maxillary anterior tooth area for immediate implant placement.

BACKGROUND: The anatomical characteristics of the maxillary labial alveolar bone play a crucial role in the treatment planning of immediate implant placement. The sagittal root position (SRP) and alveolar bone concavity are closely related to anatomical characteristics in determining the ideal implant position. This study evaluated the SRP and labial alveolar bone concavity in the maxillary anterior teeth area. METHODS: Cone-beam computed tomography images of 120 samples involving 720 teeth were uploaded to the medical imaging software. The SRP was classified as Class I, II, III, or IV, and the concavity of labial alveolar bone was measured. A T test was performed to compare measurements between the central and lateral incisors, between the central incisors and canines, and between the lateral incisors and canine. RESULTS: The majority of the SRPs of the maxillary anterior teeth were class I (engaging the labial cortical plate) with frequencies of 98.3%, 85.8%, and 81.7% for the canines, lateral incisors, and central incisors, respectively. In terms of concavity of labial alveolar bone in maxillary tooth area, canines also had the largest mean value (139.5°), followed by lateral incisors, whereas central incisors has the smallest mean value (131.7°). The results of the T test revealed a significant difference ( p < 0.001) in labial alveolar bone concavity between central and lateral incisors, between central incisors and canines, and between lateral incisors and canines. CONCLUSION: Most maxillary anterior teeth were classified as Class I SRP, Class III SRP was the least prevalent, and the concavity of the labial alveolar bone significantly differed between the central and lateral incisors, between the central incisors and canines, and between the lateral incisors and canines. In addition, the canines had the highest mean alveolar bone concavity angle, indicating that less concavity in the canines area.

Biomechanical study on fixation methods for horizontal oblique metacarpal shaft fractures.

OBJECTIVE: To investigate differences in the effectiveness of two lag screws, a regular bone plate, and locking bone plate fixation in treating horizontal oblique metacarpal shaft fractures. MATERIALS AND METHODS: Horizontal oblique metacarpal shaft fractures were created in 21 artificial metacarpal bones and fixed using one of the three methods: (1) two lag screws, (2) a regular plate, and (3) a locking plate. All the specimens were subjected to the cantilever bending test performed using a material testing machine to enable recording of the force-displacement data of the specimens before failure. The Kruskal-Wallis test was used to compare failure force and stiffness values among the three fixation methods. RESULTS: The mean failure force of the two lag screw group (78.5 ± 6.6 N, mean + SD) was higher than those of the regular plate group (69.3 ± 17.6 N) and locking plate group (68.2 ± 14.2 N). However, the mean failure force did not significantly differ among the three groups. The mean stiffness value of the two lag screw group (17.8 ± 2.6 N/mm) was lower than those of the regular plate group (20.2 ± 10.5 N/mm) and locking plate group (21.8 ± 3.8 N/mm). However, the mean stiffness value did not significantly differ among the three groups. CONCLUSION: The fixation strength of two lag screw fixation did not significantly differ from that of regular and locking bone plate fixation, as indicated by the measurement of the ability to sustain force and stiffness.

Patients with periodontitis are at a higher risk of stroke: A Taiwanese cohort study.

BACKGROUND: This study aimed to investigate the risk of stroke incidence in patients with periodontitis. METHODS: Data on patients diagnosed with periodontitis were collected from Taiwan's National Health Insurance Research Database and were matched (1:1) with patients without periodontitis between 2001 and 2010. A multivariable Cox survival model was used to predict stroke between patients with and without periodontitis, and the possibility of confounders. Hazard ratios (HRs) with 95% confidence intervals (CIs) were used to explore the risk of stroke in the case and control groups. Diseases found during the follow-up period were analyzed to determine possible effects on the study. A total of 282 560 periodontitis and nonperiodontitis patients were enrolled, with most subjects aged 40 to 59 years. RESULTS: The overall cumulative incidence of stroke was 2.14 times higher in periodontitis than in nonperiodontitis, and the highest HR was in the more than 80 years age group (HR = 9.30; 95% CI, 7.06-12.26). The multivariate Cox model indicated that the adjusted HR (aHR) between the case and control was 2.03 (95% CI, 1.99-2.08), and a higher aHR was associated with hypertension. Atherosclerosis, atrial fibrillation, obesity, kidney disease, anxiety, and gout discovered during follow-up also showed a potential risk of stroke in patients with periodontitis. CONCLUSION: Therefore, this study suggests a high risk of stroke in patients with periodontitis.

Maximum standardised uptake value is prognostic in patients with early-stage squamous cell carcinoma of the tongue.

The aims of this paper were to evaluate the relation between the preoperative primary tumour maximum standardised uptake value (SUVmax, tSUVmax) and clinicopathological features, including depth of invasion (DOI), recurrence factors, and survival outcomes, and to compare the prognostic value of tSUVmax with that of other factors associated with the recurrence of early-stage oral squamous cell carcinoma (OSCC) of the tongue. We retrospectively analysed data from 155 patients. All patients were treated and regularly monitored at the Changhua Christian Hospital (CCH). Only those who had undergone 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in the 14 days before surgery were included. A tSUVmax of >5.2 was found to be the sole strong predictor of a DOI of >4 mm. A tSUVmax of >7.6 was strongly associated with pT2 SCC of the tongue, more aggressive DOI, and perineural invasion. DOI and tSUVmax could be used to predict disease-free survival (DFS) for early-stage SCC of the tongue, and they showed stronger predictive power than the traditional American Joint Committee on Cancer (AJCC) T stage. Therefore tSUVmax could be a prognostic tool for DFS in AJCC early-stage SCC of the tongue.

Survival and clinicopathological characteristics of cT4b oral squamous cell carcinoma based on different treatment modalities: A single-center retrospective study.

INTRODUCTION: Primary surgical treatment for oral squamous cell carcinoma (OSCC) is reserved for T1 to T4a tumors, but not for T4b tumors, according to the present National Comprehensive Cancer Network clinical practice guidelines. In this retrospective study, we aimed to determine the association between the clinicopathological characteristics and different treatment modalities for T4b OSCC based on whether patients received primary surgical treatment. Therefore, we conducted a survival analysis based on different treatment modalities. METHODS: This retrospective cohort study enrolled 125 patients with clinical stage T4b OSCC who received treatment and were followed up at Changhua Christian Hospital between January 1, 2008 and December 31, 2018. RESULTS: Overall, 81 patients received primary surgical treatment and 44 received primary nonsurgical treatment. Comparison of the clinicopathological characteristics between those who did and did not undergo surgery revealed no significant differences in age at tumor diagnosis, tumor location, clinical N stage, and involved tumor area based on computed tomography or magnetic resonance imaging, or stratified Charlson Comorbidity Index scores. In the survival analysis, Kaplan-Meier curves revealed that patients who received treatment modalities including surgery exhibited better survival than those who received treatment modalities that did not include surgery. CONCLUSIONS: In the present study, patients with T4b OSCC treated with primary surgery had a better overall survival rate than those who received nonsurgical treatment. In the future, it will be necessary for clinicians worldwide to report the treatment outcomes of patients with T4b OSCC based on the common criteria.

Biomechanical Evaluation of Bone Atrophy and Implant Length in Four Implants Supporting Mandibular Full-Arch-Fixed Dentures.

Residual alveolar ridge resorption often occurs after tooth extraction, which causes issues requiring further prothesis rehabilitation. A treatment concept referred to as all-on-four, involving fixed dentures supported with four implants, was recently developed. The current study aimed to determine the effect of changing bone atrophy and implant length in all-on-four treatments on stress and strain in the surrounding bone of the implant. A three-dimensional finite element method was used in this research. The stress analysis was conducted with von Mises stress values. Two types of synthetic jawbone models with mild and moderate atrophy were used. Furthermore, two different implant lengths with a similar implant design and diameter were selected, and they were classified into eight models. Then, the bone model was assessed via a computed tomography (CT) scan and was transformed into a virtual model in Geomagic and SolidWorks with implant rebuilding. After modifying bone atrophy, the von Mises stresses in the surrounding bone of the implant were as follows: mild type 2 < mild type 3 < moderate type 3 < moderate type 4. The bone quantity change rate increased more than when bone conditions were limited. Compared with changes in implant lengths, the stresses in the peri-implant surrounding bone were generally higher in the 9 mm implant length group than in the 11.5 mm group. However, the results did not significantly differ. In conclusion, the von Mises stress and strain increased in the models with moderate atrophy and low-density trabecular bone. Hence, bone atrophy and its presurgical diagnosis in long-term implant prognosis are crucial.

Comparison of the Efficacies of Direct-Acting Antiviral Treatment for HCV Infection in People Who Inject Drugs and Non-Drug Users.

Background and Objectives: Hepatitis C virus (HCV) is a major cause of liver disease worldwide. People who inject drugs (PWIDs) constitute the majority of patients with HCV infection in the United States and Central Asia. There are several obstacles to treating HCV infection in PWIDs because PWIDs are often accompanied by concurrent infection, low compliance, substance abuse, and risky behavior. The aim of the study is to compare the efficacies of direct-acting antiviral (DAA) therapy for HCV infection in PWIDs and those without opioid injection. Materials and Methods: In this retrospective cohort study, we included 53 PWIDs with HCV infections treated on site in a methadone program and 106 age- and sex-matched patients with HCV infections who had no history of opioid injection (ratio of 1:2). All eligible subjects received anti-HCV treatment by DAA agents in our hospital from March 2018 to December 2020. The charts of these patients were carefully reviewed for demographic data, types of DAA agents, and treatment outcomes. The primary outcome measure was sustained virological response (SVR). Results: PWIDs and non-drug users had different HCV genotype profiles (p = 0.013). The former had higher proportions of genotype 3 (18.9% vs. 7.5%) and genotype 6 (24.5% vs. 14.2%) than the latter. The two patient groups had comparable rates of complete drug refilling (100.0% vs. 91.1%) and frequency of loss to follow-up (3.8% vs. 0.9%). However, PWIDs had a lower SVR rate of DAA treatment than non-drug users (92.2% vs. 99.0%; p = 0.04). Further analysis showed that both human immunodeficiency virus (HIV) coinfection and history of PWID were risk factors associated with treatment failure. The subjects with coinfection with HIV had lower SVR rates than those without HIV infection (50.0% vs. 96.5%; p = 0.021). Conclusions: PWIDs with HCV infections have higher proportions of HCV genotype 3 and genotype 6 than non-drug users with infections. DAA therapy can achieve a high cure rate (>90%) for HCV infection in PWID, but its efficacy in PWID is lower than that in non-drug users.

Comparison of the fixation ability between lag screw and bone plate for oblique metacarpal shaft fracture.

BACKGROUND: For oblique metacarpal shaft fracture, if anatomical reduction is achieved through conservative cast immobilization rather than stable fixation, bone malrotation can easily occur, resulting in severe loss in hand prehensile function. However, whether bone plate fixation or only lag screw fixation is more preferable remains unclear. Few studies have evaluated whether screw fixation can provide biomechanical fixation strength similar to bone plate fixation. OBJECTIVE: We assessed the difference in fixation strength between fixtation with two lag screws and bone plate for oblique metacarpal shaft fractures. MATERIALS AND METHODS: We created oblique metacarpal shaft fractures on 21 artificial bones and fixated them using (1) double lag screw (2LS group), (2) regular plate (RP group), or (3) locked plate (LP group). To obtain the force-displacement data, a cantilever bending test was conducted for each specimen through a material testing machine. One-way analysis of variance and a Tukey test were conducted to compare the maximum fracture force and stiffness of the three fixation methods. RESULTS: The maximum fracture force of the 2LS group (mean + SD: 153.6 ± 26.5 N) was significantly lower than that of the RP (211.6 ± 18.5 N) and LP (227.5 ± 10.0 N) groups (p < 0.001). However, no significant differences were discovered between the RP and LP groups. The coefficient of variation for the maximum fracture force of the 2LS group (17.3%) was more than twice as high as that of the RP (8.7%) and LP (4.4%) groups. In addition, the stiffness of the three fixation methods was similar. CONCLUSION: Compared with bone plate fixation, double lag screw fixation yielded slightly lower maximum bearable fracture force but similar stiffness. Therefore, this technique could be used for treating oblique metacarpal shaft fractures. However, using double lag screw fixation alone is technically demanding and requires considerable surgical experiences to produce consistent results.