Volumetric analysis of spontaneous bone formation after segmental mandibulectomy in patients with MRONJ.

OBJECTIVE: The purpose of this study was to quantify the spontaneous new bone formation and bony bridge formation by 3-dimensional analysis of cone-beam computed tomography (CBCT) after segmental mandibulectomy reconstruction using an R-plate without any graft material in patients with medication-related osteonecrosis of the jaw (MRONJ). STUDY DESIGN: 15 MRONJ patients (13 females and 2 males) were selected based on the inclusion criteria. Data on new bone formation, bony bridge formation, R-plate fracture, patient age, and type and duration of medication were collected. Panoramic and CBCT scans were obtained at 1 day, 6, 12, and 24 months postoperatively. CBCT images of each period were transferred to a personal computer using MIMICS 21.0 for volumetric analysis. After quantifying the volume of new bone formation, we calculated the percentage of the volume of new bone to the segmentally resected necrotic bone volume (%NB). RESULTS: All patients showed spontaneous new bone formation with the average of 20.69% within a year and 28.52% within 2 years, and 80.0% showed bony bridge formation within a year. CONCLUSIONS: The R-plate reconstruction in patients with MRONJ showed significant amount of spontaneous new bone formation within 2 years after segmental mandibulectomy.

Reliability of a Trapezium Miniplate with Endoscope-Assisted Internal Fixation in Mandibular Subcondylar Fractures: A Three-Dimensional Analysis.

This study aimed to evaluate the reliability of a trapezium plate for open reduction and internal fixation (ORIF) of mandibular subcondylar fractures with the simultaneous use of an endoscope. We selected and retrospectively studied 18 patients (12 males and 6 females) with unilateral mandibular subcondylar fractures who visited the Wonju Severance Christian Hospital. The mean age of the patients was 43.43 ± 15.76 years. Patients underwent ORIF with trapezium miniplate application through an intraoral incision under general anesthesia. The clinical and radiographic findings of the fractured side were compared with those of the non-operated side at 6 months follow-up. All occlusions became stable, and transient functional disturbances disappeared within 6 months of periodic follow-up. Functional mandibular movement recovered within the normal range, with an average mouth opening of 41.5 mm, protrusion of 7.5 mm, and lateral excursion of 7 mm at 6 months. Radiographic controls and statistical analysis confirmed a decent anatomical reduction in all 18 cases. In conclusion, the use of a trapezium miniplate with endoscope-assisted ORIF in mandibular subcondylar fractures can be useful for fixation and functional recovery.

Immediate nonfunctional loading of implants placed simultaneously using computer-guided flapless maxillary crestal sinus augmentation with bone morphogenetic protein-2/collagen matrix.

BACKGROUND: Immediate loading has shown positive results for total, partial, or single edentulism. The effects of BMP-2 addition to graft materials on bone formation and implant stability in the early stages of healing have rarely been studied, especially in patients with severely atrophic maxillae. PURPOSE: To evaluate the effects of simultaneously placed immediate non-functional loaded implants and bone morphogenetic protein-2 (BMP-2)-loaded Bio-Oss collagen, on bone formation and implant stability during the early healing stages of patients with a severely atrophic posterior maxilla using crestal approach. MATERIALS AND METHODS: Thirty-three cases presenting posterior maxillary residual alveolar bone height of 1-3 mm were evaluated. Flapless crestal sinus augmentation surgery was performed using BMP-2-loaded Bio-Oss collagen, with non-functional implants immediately loaded after surgery. The bone height was assessed using preoperative and postoperative cone beam computed tomography (CBCT). Bone density of the sinus graft sites and implant stability (after 3 months) were evaluated using postoperative CBCT scans and Periotest, respectively. The periodontal parameters and marginal bone loss around the implant were checked after 37.3 months of final prosthesis. RESULTS: The survival rate of the implants was 100% and the gingiva around the implants remained healthy. All implants remained integrated, and all sinus grafts showed radiographic bone formation. The results indicated high level of bone density and good implant stability, showing minimal marginal bone loss after 37.3 months. CONCLUSION: This technique could be used in the posterior maxillary region exhibiting poor bone quantity.

Accuracy of computer-guided implant placement in anterior regions.

STATEMENT OF PROBLEM: Implant placement in the anterior regions is often challenging because of limited space and bone volume availability. PURPOSE: The purpose of this clinical study was to investigate the accuracy of computer-guided surgery with a long drill key to place implants in the anterior regions. MATERIAL AND METHODS: Computer-guided implant surgery was performed for 32 participants requiring implants in anterior regions. The procedure involved using a 12-mm-long drill key to guide the 2.0-mm-diameter drill. Deviations between the planned and actual implant positions were evaluated by using cone beam computed tomography (CBCT) scans obtained before and after surgery. A t test was used for comparisons between the planned and placed implants and to determine the influence of the arch (maxilla/mandible) and time (immediate/delayed) on accuracy. RESULTS: A total of 40 implants (20 implants in the maxilla and 20 implants in the mandible) were placed. The mean linear deviation was 0.46 mm (range, 0 to 1.15 mm) for the implant shoulder and 0.67 mm (range, 0.14 to 1.19 mm) for the implant apex. The mean angular deviation was 1.40 degrees (range, 0.30 to 2.57 degrees). The mean depth deviation was 0.15 mm (range, 0.10 to 0.82 mm). CONCLUSIONS: This clinical study showed that the accuracy of computer-guided implant placement may be enhanced by using a long drill key and may thus enable more accurate implant placement in anterior regions.

A Technique for Digital Impression and Bite Registration for a Single Edentulous Arch.

Few studies have reported the application of digital technology for the process of impression and interocclusal recordings in edentulous patients. This article describes a digitizing system for generating digital edentulous models with a jaw relationship by taking direct digital impressions and a virtual bite registration using intraoral digital scanning. A specialized scan retractor was used to make digital impressions of edentulous jaws in patients' mouths using an intraoral scanner. Virtual bite registration was obtained with optical scanning of the buccal surfaces of both jaws at the occlusal vertical dimension. The registration was then used as a reference for aligning both jaws. Digital edentulous models that include the jaw relationship would be clinically beneficial for the fabrication of complete dentures in edentulous patients.

Crestal Sinus Augmentation in the Presence of Severe Sinus Mucosal Thickening: A Report of 3 Cases.

PURPOSE: In the presence of severe sinus mucosal thickening, the ostium can be blocked when the sinus membrane is lifted, causing drainage disturbances and sinusitis. Here, we present 3 cases in which maxillary sinus floor elevation was performed using a crestal approach in the presence of severe sinus mucosal thickening (>10 mm). MATERIALS AND METHODS: The effects of maxillary sinus floor elevation using the crestal approach technique on sinus mucosal thickening and bone formation in the sinus were evaluated using cone beam computed tomography. RESULTS: None of the patients exhibited an increase in sinus membrane thickness. No complications were encountered during the follow-up periods, and bone formation was observed around the implants at the sinus floor. All implants were functioning successfully. CONCLUSIONS: Maxillary sinus floor elevation using the crestal approach technique in the presence of severe sinus mucosal thickening allows for minimally invasive sinus grafting and simultaneous implant placement and does not increase sinus membrane thickness.

The effect of low-speed drilling without irrigation on heat generation: an experimental study.

OBJECTIVES: In this study we evaluated heat generation during the low-speed drilling procedure without irrigation. MATERIALS AND METHODS: Ten artificial bone blocks that were similar to human D1 bone were used in this study. The baseline temperature was 37.0℃. We drilled into 5 artificial bone blocks 60 times at the speed of 50 rpm without irrigation. As a control group, we drilled into an additional 5 artificial bone blocks 60 times at the speed of 1,500 rpm with irrigation. The temperature changes during diameter 2 mm drilling were measured using thermocouples. RESULTS: The mean maximum temperatures during drilling were 40.9℃ in the test group and 39.7℃ in the control group. Even though a statistically significant difference existed between the two groups, the low-speed drilling did not produce overheating. CONCLUSION: These findings suggest that low-speed drilling without irrigation may not lead to overheating during drilling.

Vertical ridge augmentation using xenogenous bone blocks: a comparison between the flap and tunneling procedures.

PURPOSE: Previous studies have shown that the subperiosteal tunneling procedure in vertical ridge augmentation accelerates healing after grafting and prevents graft exposure, with minor postoperative complications. It is conceivable that new bone formation would be greater with the tunneling procedure than with the flap procedure, because the former is minimally invasive. This hypothesis was tested in this study by comparing new bone formation between the flap and tunneling procedures after vertical ridge augmentation using xenogenous bone blocks in a canine mandible model. MATERIALS AND METHODS: Two Bio-Oss blocks were placed on the edentulous ridge in each side of the mandibles of 6 mongrel dogs. The blocks in each side were randomly assigned to grafting with a flap procedure (flap group) or grafting with a tunneling procedure (tunneling group). RESULTS: The mean percentage of newly formed bone within the block was 15.3 ± 6.6% in the flap group and 46.6 ± 23.4% in the tunneling group. CONCLUSION: Based on data presented in this study, when a tunneling procedure is used to place xenogenous bone blocks for vertical ridge augmentation, bone formation in the graft sites is significantly greater than when a flap procedure is used.

Simultaneous sinus lift and implantation using platelet-rich fibrin as sole grafting material.

Recently, several authors have shown that simultaneous sinus lift and implantation using autologous platelet-rich fibrin as the sole filling material is a reliable procedure promoting bone augmentation in the maxillary sinus. The aim of this study was to examine the effect of simultaneous sinus lift and implantation using platelet-rich fibrin as the sole grafting material on bone formation in a canine sinus model. An implant was placed after sinus membrane elevation in the maxillary sinus of six adult female mongrel dogs. The resulting space between the membrane and sinus floor was filled with autologous platelet-rich fibrin retrieved from each dog. The implants were left in place for six months. Bone tissue was seen at the lower part of the implants introduced into the sinus cavity. The height of the newly formed bone around the implants ranged from 0 mm to 4.9 mm (mean; 2.6 ± 2.0 mm) on the buccal side and from 0 mm to 4.2 mm (mean; 1.3 ± 1.8 mm) on the palatal side. The findings from this study suggest that simultaneous sinus lift and implantation using platelet-rich fibrin as sole grafting material is not a predictable and reproducible procedure, especially with respect to the bone formation around the implants in the sinus cavity.

The effect of guided flapless implant procedure on heat generation from implant drilling.

The objective of this study was to evaluate the heat generation in vitro during the flapless drilling procedure using surgical drill guides. Ten resin models with bilateral edentulous tooth spaces in the first and second molars in the mandible were used in this study. On one side of the mandible, drilling was performed with a flapless approach using a surgical drill guide. On the other side of the mandible, drilling was performed with a flap approach. The temperature changes were measured during final drilling by thermocouples. The mean maximum temperatures during drilling with guided flapless procedures were 29.5 °C and 32.6 °C at the depths of 3 and 6 mm, respectively, whereas for flap procedures they were 29.4 °C and 31.3 °C. There was no statistically significant difference between the groups. These findings suggest that drilling with external irrigation in an up-and-down pumping motion may not lead to a significant increase the bone temperature during a flapless procedure using surgical drill guides.

[Change of coagulation and fibrinolysis in rabbit model with acute decompression sickness and its mechanism].

This study was purposed to investigate the changes in coagulation and fibrinolysis pathways in rabbits suffered from the acute decompression sickness(DCS). Model of DCS in rabbits was established. Survival rate and symptoms of DCS in animal model was monitored. The prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen (Fib), fibrinogen degradation product (FDP) and D-dimers were measured before compression and at 0, 3, 24 hours after decompression by latex agglutination semiquantitative methods. The changes of plasmin-antiplasmin complex (PAP), fibrinopeptide A (FPA), plasminogen activator inhibitor 1 (PAI-1) and thrombomodulin (TM) were measured by ELISA at different time points after decompression. The results showed that the model of DCS in rabbits was successfully established. There was a statistically significant extension in APTT, TT, increase of Fib concentration at 15 minutes after decompression, the changes were peaked at 3 hours and recovered at 24 hours after decompression. The concentration of FDP significantly decreased at 3 hours after decompression. The concentration of D-dimers significantly increased at 24 hours after decompression in rabbits model with DCS. FPA concentration was significantly increased at 15 minutes and recovered at 24 hours after decompression. PAP concentration was increased after decompression, but had no significant changes. PAI-1 could not be detected. TM significantly increased after decompression. It is concluded that the acute DCS significantly impacts on blood coagulation system in rabbit model. It is shown that hypocoagulation occurred at initial time and hyperfibrinolysis subsequently, which varied with time. The damage of blood vessel endothelium may be one of the causes of these variations.