OBJECTIVETo clarify the related factors of marginal bone loss (MBL) around tissue level implants in the posterior part of the mandible.

METHODSA total of 116 tissue level implants were implanted in the mandibular posterior region of 76 patients. Patients' information, including general characteristics, implant characteristics, implant site characteristics, and prosthesis characteristics, was recorded. Their cone beam computed tomography data were measured immediately after implant placement, 3 months later, and 3 and 12 months after prosthesis loading. The measurement of MBL was conducted by One Volume Viewer software. SPSS 20.0 was used for statistic analysis.

RESULTSSmoking, cortical bone thickness (CBT), collum angle (CA), and implant local sanitation showed significant differences with body mass loss (P<0.05). No significant differences were found among sex, age, length of implant, diameter of implants, implant systems, bone height, prosthesis type, and MBL (P>0.05).

CONCLUSIONThe risk factors that caused MBL were smoking, thicker CBT, larger CA, and poor implant local sanitation. Among them, poor implant local sanitation had the highest correlation with MBL.

Alveolar Bone Loss ; epidemiology ; etiology ; Cone-Beam Computed Tomography ; Dental Implants ; adverse effects ; Dental Prosthesis Design ; Dental Prosthesis, Implant-Supported ; Follow-Up Studies ; Humans ; Mandible ; Mandibular Prosthesis ; statistics & numerical data ; Oral Hygiene ; Postoperative Complications ; Smoking ; adverse effects ; Treatment Outcome

Objective:To compare the clinical efficacy between our first generation and second generation dynamic anterior plate-screw system for quadrilateral area (DAPSQ) in the treatment of T-shaped acetabular fractures.Methods:A retrospective study was conducted of the 28 patients with T-shaped acetabular fractures who had been treated at Department of Orthopaedics, General Hospital of Central Theater Command from January 2008 to December 2019. They were divided into 2 groups according to fixation methods. Group A [15 patients, 11 males and 4 females, an age of (43.5±9.1) years] were treated with the first generation DAPSQ while Group B [13 patients, 8 males and 5 females, an age of (42.5±7.0) years] with the second generation DAPSQ. Operation time, intraoperative bleeding, fracture reduction, function of the affected hip and postoperative complications were recorded and compared between the 2 groups.Results:The 2 groups were comparable because there was no significant difference between them in the preoperative general data ( P>0.05). The 28 patients were followed up for 12 to 60 months (average, 35.0 months). The operation time [(193.9±33.3) min] and intraoperative bleeding [(830.8±177.4) mL] for Group B were significantly less than those for Group A [(231.3±40.0) min and (1,043.3±190.7) mL] ( P<0.05). In Group A, according to the Matta scoring, the fracture reduction was rated as excellent in 8 cases, good in 5 and poor in 2; in Group B, the fracture reduction was rated as excellent in 8 cases, good in 4 and poor in one. According to the modified Merle d'Aubigné & Postel scoring at the final follow-up, the function of the affected hip was rated as excellent in 9 cases, as good in 3, as fair in 2 and as poor in one in Group A while as excellent in 9 cases, as good in 2 and as fair in 2 in Group B. There were no statistically significant differences between the 2 groups in reduction quality or in the function of the affected hip ( P>0.05). Follow-up observed hip traumatic arthritis in 2 cases in Group A and in one in Group B. Conclusion:In the treatment of T-shaped acetabular fractures, compared with the first generation DAPSQ, the second generation DAPSQ can shorten operation time and decrease intraoperative bleeding significantly, though both achieve comparable functional outcomes.

Objective:To introduce the standard screw implantation methods and to analyze the biomechanical stability of the second-generation dynamic anterior plate-screw system for quadrilateral area (DAPSQ).Methods:Six adult formalin-preserved corpses were selected to make a complete pelvic specimen. Further, the left high double-column fracture models were made and randomly fixed with second-generation DAPSQ or anterior reconstruction titanium plate and 1/3 tube buttress-plate (ARTPB). The specimens of intact pelvis (IP) group, DAPSQ group and ARTPB group were fixed on a Zwick Z100 material machine and loaded vertically with 200 N, 300 N, 400 N, 500 N, 600 N, 700 N, and 800 N in a simulated sitting position, respectively. The axial displacement and strain changes in the anterior and posterior columns were tested in the three groups. The stiffness was calculated accordingly.Results:The axial compression displacement in the three groups showed an increase trend as well with the vertical load increased from 200 N to 800 N ( F=68.581, P<0.001; F=91.795, P<0.001; F=33.819, P=0.002). The axial displacement in ARTPB group was significantly larger than that in DAPSQ group and IP group ( P<0.05), while the difference between DAPSQ and IP groups was not significant ( P>0.05). Under the vertical load of 600 N, the pelvic axial stiffness of IP group, DAPSQ group, and ARTPB group were 220.72±70.33 N/mm, 185.68±48.49 N/mm and 135.83±60.58 N/mm, respectively. The axial stiffness of ARTPB group was significantly lower than that in DAPSQ group and IP group ( t=5.345, P=0.003; t=6.443, P=0.001), while the difference between DAPSQ and IP groups was not significant ( t=2.138, P=0.086). There were no significant differences of the strain values in anterior column among the three groups during the load increasing from 200 N to 800 N ( P>0.05). With the load increasing from 500 N to 800 N, the strain values of the posterior column in ARTPB group were significantly greater than those of IP and DAPSQ groups ( P<0.05). However, the differences between IP and DAPSQ groups were not statistically significant in strain values of the posterior column ( P>0.05). Conclusion:Compared with anterior reconstruction titanium plate and 1/3 tube buttress-plate, acetabular double-column fracture model fixed with the second-generation DAPSQ has less axial compression displacement but with greater axial stiffness. The stress change in the posterior columns of the acetabulum is like in IP. Therefore, the second-generation DAPSQ has reliable biomechanical stability.

Objective: To investigate the clinical efficacy of dynamic anterior plate-screw system (DAPSQ) assisted by preoperative digital design in the treatment of acetabular bi-column fractures. Methods: A retrospective case-control study was conducted to analyze the clinical data of 34 patients with acetabular bi-column fractures admitted to the General Hospital of Central Theater Command from January 2012 to January 2018. There were 24 males and 10 females, aged 21-65 years[(43.0±14.2)years]. According to the treatment method, the patients were divided into Group A treated with DAPSQ assisted by preoperative digital design and Group B treated with conventional DAPSQ.Group A was consisted of 17 patients, including 11 males and six females aged 22-64 years [(42.7±12.4)years]. Group B consisted of 17 patients, including 13 males and four females aged 21-65 years[(43.2±14.6)years]. The operation time, intraoperative blood loss, hospitalization time, fracture healing time, Matta radiological standard score of fracture reduction, Merle d'Aubignre-Postel score and complications were recorded and compared between the two groups. Results: All patients were followed up for 12-62 months [(32.8±9.1)months]. The operation time [(160.8±38.5)minutes] and intraoperative bleeding [(455.6±190.4)ml] in Group A were significantly less than those in Group B [(216.9±59.5)minutes] and [(780.2±211.6)ml] (P<0.05). There were no significant differences in hospitalization time, fracture healing time, Matta radiological standard score, modified Merle d'Aubignre-Postel score at the last follow-up between the two groups (P>0.05). In Group A, four patients had traumatic arthritis, with one patient receiving total hip replacement. In Group B, three patients were found with traumatic arthritis, and one with avascular necrosis of femoral head who underwent total hip replacement. None of the two groups had complications such as screws' entry into articular cavity, failure of internal fixation, and incision infection. Conclusions For acetabular bi-column fractures, DAPSQ can effectively maintain the stability of the fracture, without the risk of screws entering the joint cavity, and obtain satisfactory clinical effect. Compared with conventional DAPSQ, preoperative digital design can significantly shorten the operation time and reduce intraoperative bleeding.