Cepharanthine and Oral Lichen Planus Efficacy (COLE) study: protocol for a multicentre randomised controlled study assessing the efficacy and safety of cepharanthine with topical corticosteroids in oral lichen planus.

INTRODUCTION: Oral lichen planus (OLP) is a chronic, inflammatory oral condition leading to a range of symptoms from mild discomfort to severe pain, affecting patients' quality of life. Standard therapy involves the use of topical corticosteroids, although some patients respond insufficiently or develop resistance to therapy. We aim to explore if adding cepharanthine, an herbal extract from Stephania cepharantha Hayata, can enhance the efficacy of corticosteroid therapy in symptomatic OLP. METHODS AND ANALYSIS: This open-label, parallel-group, multi-centre, randomised controlled study will be conducted at three Japanese hospitals. It will compare safety and efficacy of integrated oral cepharanthine and corticosteroid therapy versus standard corticosteroid therapy. 50 symptomatic OLP patients will be randomised 1:1 to receive cepharanthine (30 mg/day) plus topical dexamethasone, or topical dexamethasone alone for 8 weeks. The primary outcome will be changed in pain intensity while drinking room-temperature water, measured on a visual analogue scale. The primary outcome is the change in pain intensity from baseline when drinking room-temperature water, evaluated using a visual analogue scale. Secondary outcomes are changes in the longest diameter of the target lesion from baseline to weeks 4 and 8, improvement and deterioration rates according to appearance and severity criteria at weeks 4 and 8, change in pain intensity when drinking room-temperature water from baseline to week 4, changes in pain intensity at rest from baseline to weeks 4 and 8, and the rates of adverse events. ETHICS AND DISSEMINATION: This protocol was approved by the Certified Review Board of Nara Medical University (CRB5200002). Participants will provide informed consent. Results will be disseminated in peer-reviewed journals and conferences. TRIAL REGISTRATION NUMBER: Japan Registry of Clinical Trials (jRCTs051220130).

Buccal Silicone Granuloma Caused by the Dental Infection.

The facial injection of liquid silicone is performed for cosmetic purposes. The use of injectable fillers in facial procedures has become extremely popular over the past decade. Most procedures are performed in the perioral, periocular, and cheek areas of middle-aged women. Even though silicone is biologically inert, its injection can result in the formation of granulomas. Silicone granulomas can result from an inflammatory or autoimmune tissue response. However, the development of silicone granulomas secondary to dental infection has not yet been reported. We report a case of a 73-year-old woman with a right buccal silicone granuloma that developed following a dental infection. Ultimately, this case healed completely after the surgical removal of all lesions. Silicone in the facial region may become infected by a dental infection, and infective silicone develops granulomas and cellulitis. In the context of cosmetic facial silicone injections, it is necessary to improve oral hygiene prior to dental treatment and to maintain a healthy oral environment after surgery. In some cases, surgical treatment using an intraoral approach is effective.

Study of Treatment Methods for Surrounding Soft Tissues of Implants Following Mandibular Reconstructions with Fibula-Free Flaps.

In maxillofacial reconstruction implant treatment, unsatisfactory soft tissue treatment of the area around the implant may lead to inflammation. As a result, appropriate soft tissue treatment is critical. To the best of our knowledge, there are no studies that compare the different tissue treatment methods available. Hence, in this study, we compare three soft tissue treatment methods around implants after mandibular reconstruction is achieved with a fibula-free flap. Out of 33 patients who underwent mandible reconstruction using fibula-free flaps between 2006 and 2015, 5 were selected for this study. A total of 17 implants were used for treatment by the final prosthetics of the five patients. Three soft tissue treatment methods with free gingival graft (FGG) were evaluated, namely, installing a splint in a modified abutment to protect the wounded area during a palatal mucosa transplant (method 1), installing a splint or dentures to a locator abutment (method 2), and the use of screw-in fixed dentures (method 3). The method that could guarantee the widest keratinized mucosa was the screw-in fixed denture method. The results of our study indicated that employing screw-in fixed dentures for FGG may be a useful soft tissue treatment for mandible reconstruction implants.

Maxillofacial Fractures Associated With Interpersonal Violence.

Interpersonal violence is a major cause of maxillofacial fractures. The aim of this study was to analyze the characteristics of these fractures associated in an effort to develop more effective management. The clinical records and radiographs of 272 patients with maxillofacial fractures associated with interpersonal violence collected during a 36-year period were retrospectively analyzed. Two hundred and nineteen patients were male (80.5%) and 53 (19.5%) were female. The patients ranged in age from 1 to 77 years. Two hundred and two patients (74.3%) were aged 10 to 29 years. The injury was the result of impact by a fist/hand/elbow in 224 patients (82.3%). The fracture site was the mandible in 191 patients (70.2%), the midface in 78 (28.7%), and both sites in 3 (1.1%). One hundred and eight (39.6%) of 273 mandibular fractures were in the angle, 75 (27.5%) were in the symphysis, and 90 (33.0%) were at other sites. Forty-three (53.1%) of 81 fractures in the midface were in the zygoma, 19 (23.5%) were in the maxilla, and 19 (23.5%) were at other sites. Fractures were more common on the left side. Nine patients (3.3%) also had injuries at other body sites. Ninety-five patients (34.9%) were treated by maxillomandibular fixation, 84 (30.9%) by open reduction and internal fixation, 59 (21.7%) by observation, 14 (5.1%) by intramaxillary splinting, 14 (5.1%) by transcutaneous reduction, and 6 (2.2%) by other procedures. Interpersonal violence-related maxillofacial fractures have characteristic features, especially with regard to site and laterality.

Evaluation of Primary Stability of Cylindrical and Tapered Implants in Different Bone Types by Measuring Implant Displacement: An In vitro Study.

AIMS: The purposes of this study were to investigate the primary stability of cylindrical and tapered implants in different bone types by measuring implant displacement and to examine the relationship between insertion torque value (ITV) and implant displacement. MATERIALS AND METHODS: Four different polyurethane bone models consisted of low-density or low-to-medium-density cancellous bone with or without a cortical bone layer. A total of 120 cylindrical and tapered implants were placed into bone blocks (n = 15 in each group), and the ITV was measured. A lateral load of 15 N was applied to the top of the abutment, and implant displacement was recorded. RESULTS: Implant displacement was significantly affected by cancellous bone density and to a lesser degree by cortical bone thickness. The displacement of tapered implants was significantly smaller than that of cylindrical implants in the presence of cortical bone. However, both implant groups showed similar ITV in the low-density cancellous bone model with the cortical bone layer. There was a correlation between ITV and displacement in the cylindrical and tapered implants. However, no correlation was observed between ITV and displacement within each bone type. CONCLUSIONS: Implant stability depended mainly on the bone type, whereas implant design had a limited influence on primary stability. The use of tapered implants may be advantageous for improving primary stability in patients with low-density cancellous bone only when crestal cortical bone exists. The same ITV of cylindrical and tapered implants did not necessarily represent similar primary stability in the bone type.

Odontogenic deep neck space infection in a patient with hyper-IgE syndrome: A case report.

Hyperimmunoglobulin E syndrome is a primary immunodeficiency state that is characterized by eczema, recurrent skin and lung infections, and markedly increased levels of IgE. Odontogenic infection can spread to vital and deep structures in such immunocompromised patients. We report a case of a 19-year-old man with hyperimmunoglobulin E syndrome presenting deep neck space infection that had spread from periapical periodontitis of the lower molars. A computed tomography scan showed an area of bony destruction in the left mandible and abscess formation in the submandibular and submental spaces. The patient was successfully treated by cervical drainage, extraction of the causative teeth, and antibiotic therapy. The present case highlights the importance of adequate treatment of dental infections in immunocompromised patients. Key words:Hyperimmunoglobulin E syndrome, odontogenic infection.

Immune Thrombocytopenic Purpura Detected with Oral Hemorrhage: a Case Report.

Immune thrombocytopenic purpura (ITP) is an immune-mediated acquired disease found in both adults and children. It is characterized by transient or persistent decreases in the platelet count. We report a case of ITP detected based on oral hemorrhagic symptoms. The patient was a 79-year-old female with no significant past medical history. She presented with sudden onset of gingival bleeding and hemorrhagic bullae on the buccal mucosa. Gingival bleeding was difficult to control. Laboratory tests revealed severe thrombocytopenia with a platelet count as low as 2000/µL. Under a provisional diagnosis of a hematological disorder, she was referred to a hematologist. A peripheral smear showed normal-sized platelets. A bone marrow examination revealed increased numbers of megakaryocytes without morphologic abnormalities. The patient was diagnosed with ITP and treated with a combination of pulsed steroid therapy and high-dose immunoglobulin therapy. However, her severe thrombocytopenia was refractory to these treatments. Then, a thrombopoietin receptor agonist was begun as a second-line treatment. Her platelets rapidly increased, and no bleeding complications were reported. Because oral symptoms can be one of the initial manifestations of ITP, dentists should be familiar with the clinical appearance of ITP, and attention must be paid to detect and diagnose unidentified cases.

Spindle Cell Hemangioma in the Mucosa of the Upper Lip: A Case Report and Review of the Literature.

Spindle cell hemangioma (SCH) is a unique benign vascular lesion. We present a case of SCH in the upper lip of a 41-year-old woman. A submucosal nodular mass 30 × 20 mm in size was observed in the left upper lip. The mass developed 5 years earlier and enlarged after repeated ethanol injections. The mass was elastic firm, mobile, bluish in color, and well demarcated in magnetic resonance imaging. Under the clinical diagnosis of hemangioma, surgical excision was performed under local anesthesia. Microscopically, the lesion was composed of irregular cavernous spaces and multiple solid cellular areas. Cavernous spaces were filled with a mix of erythrocytes and organizing thrombi. The solid areas showed proliferation of spindle-shaped cells arranged haphazardly or in short interlacing fascicles. Immunohistochemically, most cells strongly reacted with vimentin. CD31, CD34, factor VIII, smooth muscle actin, and Wilms tumor-1 reacted with endothelial cells lining the cavernous spaces. The cells within solid areas consisted of mixed cell population with variable reaction for the markers except for factor VIII. From these findings, the diagnosis of SCH was made. Two years after surgery, no recurrence was noted. A review of SCH in the head and neck region is made.

Trends and characteristics of maxillofacial fractures sustained during sports activities in Japan.

BACKGROUND/AIM: Sports activity increases the risk of maxillofacial fractures. The aim of this study was to analyze trends and characteristics of maxillofacial fractures sustained during sports activity to develop more effective treatments and possibly to prevent injury. MATERIALS AND METHODS: Data of 248 patients with maxillofacial fractures sustained during sports activity were retrospectively analyzed based on their clinical records and radiographs. RESULTS: The patients were 226 males (91.1%) and 22 females (8.9%). Their ages ranged from 6 to 70 years and the majority were in their second decade. The fractures were sustained in various sports which included baseball in 85 patients (34.3%), rugby in 40 (16.1%), soccer in 30 (12.1%), softball in 22 (8.9%), golf in 10 (4.0%), hockey in 8 (3.2%), combat sports in 28 (11.3%), and others in 29 (11.7%). The cause of injuries was collision with another player in 97 patients (39.1%), hit by a ball in 89 (35.9%), intended attack in 20 (8.1%), hit by equipment of another player in 15 (6.0%), a fall in 14 (5.6%), and collision with ground equipment in 13 (5.2%). The site of fractures was the mandible in 145 patients (58.5%), midface in 100 (40.3%), and both in 3 (1.2%). Among 210 fracture sites in the mandible, 77 (36.6%) were in the angle, 68 (32.4%) in the symphysis, and 65 (30.9%) in others. Among 103 fractures in the midface, 58 (56.3%) were in the zygoma, 26 (25.2%) in alveolar bone, and 19 (18.4%) in others. Treatment was observation in 67 patients (27.0%), maxillomandibular fixation in 64 (25.8%), open reduction and internal fixation in 63 (25.4%), intramaxillary splinting in 40 (16.1%), transcutaneous reduction in 10 (4.0%), and other procedures in 4 (1.6%). CONCLUSION: Maxillofacial fractures sustained during sports activity showed characteristic features dependent on the type of sport and cause of injury.

Micromotion analysis of different implant configuration, bone density, and crestal cortical bone thickness in immediately loaded mandibular full-arch implant restorations: A nonlinear finite element study.

BACKGROUND: Excessive micromotion may cause failure of osseointegration between the implant and bone. PURPOSE: This study investigated the effects of implant configuration, bone density, and crestal cortical bone thickness on micromotion in immediately loaded mandibular full-arch implant restorations. MATERIALS AND METHODS: A finite element model of the edentulous mandible was constructed. Four implants were inserted in two different configurations, which were four parallel implants or tilted distal implants according to the all-on-four concept. Different cancellous bone densities and crestal cortical bone thicknesses were simulated. The framework was made of acrylic resin. A vertical load of 200 N was applied at the cantilever or on the distal implant (noncantilever loading). RESULTS: The maximum extent of micromotion was significantly influenced by the density of cancellous bone and to a lesser extent by implant configuration and the crestal cortical bone thickness. The all-on-four configuration showed less micromotion than the parallel implant configuration in some circumstances. The maximum micromotion detected with noncantilever loading was less than 1/3 of that with cantilever loading. CONCLUSIONS: Implant configuration had a limited influence on micromotion. Avoiding cantilever loading during the healing period should effectively reduce the risk of excessive micromotion in patients with low-density cancellous bone and thin crestal cortical bone.

Effects of implant tilting and the loading direction on the displacement and micromotion of immediately loaded implants: an in vitro experiment and finite element analysis.

PURPOSE: The purpose of this study was to investigate the effects of implant tilting and the loading direction on the displacement and micromotion (relative displacement between the implant and bone) of immediately loaded implants by in vitro experiments and finite element analysis (FEA). METHODS: Six artificial bone blocks were prepared. Six screw-type implants with a length of 10 mm and diameter of 4.3 mm were placed, with 3 positioned axially and 3 tilted. The tilted implants were 30° distally inclined to the axial implants. Vertical and mesiodistal oblique (45° angle) loads of 200 N were applied to the top of the abutment, and the abutment displacement was recorded. Nonlinear finite element models simulating the in vitro experiment were constructed, and the abutment displacement and micromotion were calculated. The data on the abutment displacement from in vitro experiments and FEA were compared, and the validity of the finite element model was evaluated. RESULTS: The abutment displacement was greater under oblique loading than under axial loading and greater for the tilted implants than for the axial implants. The in vitro and FEA results showed satisfactory consistency. The maximum micromotion was 2.8- to 4.1-fold higher under oblique loading than under vertical loading. The maximum micromotion values in the axial and tilted implants were very close under vertical loading. However, in the tilted implant model, the maximum micromotion was 38.7% less than in the axial implant model under oblique loading. The relationship between abutment displacement and micromotion varied according to the loading direction (vertical or oblique) as well as the implant insertion angle (axial or tilted). CONCLUSIONS: Tilted implants may have a lower maximum extent of micromotion than axial implants under mesiodistal oblique loading. The maximum micromotion values were strongly influenced by the loading direction. The maximum micromotion values did not reflect the abutment displacement values.

Computed Tomography-Based 3-Dimensional Finite Element Analyses of Various Types of Plates Placed for a Virtually Reduced Unilateral Condylar Fracture of the Mandible of a Patient.

PURPOSE: This study was performed to evaluate stresses in various types of plates placed for a virtually reduced unilateral condylar fracture of the mandible using computed tomography-based 3-dimensional finite element (FE) models of a patient to select the optimal plate system. MATERIALS AND METHODS: A computed tomography-based FE model of the mandible of a patient with a unilateral condylar fracture was constructed. The fracture was virtually reduced and fixed with 1 straight titanium plate; 2 straight titanium plates; 2 straight poly-L-lactic acid plates; and 4-hole (box), 5-hole (strut), and 7-hole (lambda) condylar plates. Stresses developing in these plates were analyzed by applying 478.1 N of bite force at the first molar of the contralateral side of the mandible. RESULTS: The magnitudes of tensile stress were within the tensile strength in all types of plates. However, the magnitudes of compressive stress in 1 straight titanium plate and 2 straight poly-L-lactic acid plates were beyond the compressive strength. The tensile and compressive stresses of the 5-hole (strut) plate were the smallest among the 3 types of condylar plates. CONCLUSIONS: Fixation by 2 straight titanium plates or any type of condylar plate was biomechanically indicated for the condylar fracture of this patient. Among these plates, the 5-hole (strut) plate was considered optimal. FE analysis is useful in selecting the optimal fixation method in the individual patient.

Tetanus: A Report of Two Cases and Review of Literature - A Continuing Threat to the Elderly in Japan.

Tetanus has become rare in industrialized countries, largely due to the effectiveness of immunization. However, the elderly are susceptible to tetanus because many have not received primary immunization; the incidence of tetanus in Japan is still 120 cases/year. The initial symptoms of tetanus, such as trismus and dysphagia, are observed in the orofacial region. However, because of the disease's rarity, the clinician may be unfamiliar with the clinical presentation and may not suspect tetanus. We report two cases of elderly patients with generalized tetanus. Both patients presented trismus and/or dysphagia and consulted three different departments before the diagnosis of tetanus. Japanese clinicians will encounter tetanus more frequently than practitioners in other countries. Dental surgeons should be familiar with the clinical appearance of tetanus and should consider this disease in a nonimmunized patient presenting as an atypical case of trismus and dysphagia.

Biomechanical analysis of immediately loaded implants according to the "All-on-Four" concept.

PURPOSE: The purpose of this study was to investigate the biomechanical behavior of immediately loaded implants in an edentulous mandible according to the "All-on-Four" concept. METHODS: A 3D-finite element model of an edentulous mandible was constructed. Four implants were placed between the bilateral mental foramen according to "All-on-Four" concept. A framework made of titanium or acrylic resin between the bilateral first molars was modeled. Immediate loading and a delayed loading protocol were simulated. A vertical load of 200N was applied at the cantilever or on the abutments region of the distal implants, simulating the absence of a cantilever. RESULTS: The peak principal compressive strains in the immediate loading models resulted in 24.0-35.8% and 26.4-39.0% increases compared with the delayed loading models under non-cantilever loading and cantilever loading, respectively. The loading position greatly affected the principal compressive and tensile strain values. The peak principal compressive strains in non-cantilever loading resulted in a 45.3-52.6% reduction compared with those in cantilever loading. The framework material did not influence the peak compressive and tensile strain. The maximum micromotion at the bone-implant interface in the immediate loading models was 7.5-14.4µm. CONCLUSIONS: Mandibular fixed full-arch prostheses without cantilevers may result in a favorable reduction of the peri-implant bone strain during the healing period, compared with cantilevers. The maximum micromotion was within the acceptable limits for uneventful implant osseointegration in the immediate loading models. Framework material did not play an important role in reducing the peri-implant bone strain and micromotion at the bone-implant interface.

Chronic Maxillary Sinusitis Caused by Denture Lining Material.

We report a case of chronic maxillary sinusitis caused by denture lining material entering through an oroantral fistula after tooth extraction. The patient was an 80-year-old female who visited us with a complaint of pus discharge from the right posterior maxilla. She had extraction of the upper right second molar and had her upper denture relined with silicone lining material. The patient noticed swelling of the right cheek and purulent rhinorrhea 20 days before her first visit to our clinic. Oral examination showed an oroantral fistula with a diameter of 3 mm in the posterior alveolar ridge of the right maxilla. Computed tomography revealed a hyperdense foreign body in the right maxillary sinus and thickening of the mucosal lining. Under diagnosis of maxillary sinusitis caused by a foreign body, endoscopic maxillary surgery was performed simultaneously with the removal of the foreign body. The foreign body removed was 12 × 6 mm in size, oval in shape, light pink in color, and compatible with silicone denture lining material. During the follow-up it was observed that the oroantral fistula closed spontaneously after the removal of the foreign body. The maxillary sinus was in a good shape without recurrence of sinusitis seven months after surgery.

The effects of bone density and crestal cortical bone thickness on micromotion and peri-implant bone strain distribution in an immediately loaded implant: a nonlinear finite element analysis.

PURPOSE: This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions. METHODS: A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment. RESULTS: The maximum extent of micromotion was approximately 100 µm in the low-density cancellous bone models, whereas it was under 30 µm in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness. CONCLUSIONS: Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading.

Trend and Characteristics of 2,636 Maxillofacial Fracture Cases over 32 Years in Suburban City of Japan.

Trend and characteristics of maxillofacial fractures in 2,636 patients over 32 years were analyzed retrospectively. Patients comprised 1,764 males and 872 females with ages ranging from 0 to 99 years. Patients younger than 30 years consisted of 60% maxillofacial fractures in the early period but decreased to 40% in the late period. In contrast, patients older than 60 years gradually increased to 30%. In terms of cause, traffic accidents consisted of more than 50%, predominantly motorcycle accidents, but gradually decreased to 40%. In contrast, falls markedly increased from less than 10 to 30%. Fractures occurred in the midface in 938 patients, in the mandible in 1,490, and in both in 208. In the midface, zygoma fractures consisted of 50% throughout the period. In the mandible, condyle fractures were observed in 40%, followed by fractures of the symphysis and angle. The ratio of condylar fractures slightly increased. Open reduction and internal fixation (ORIF) were performed in 782 patients, followed by observation in 716, maxillomandibular fixation (MMF) in 605, intramaxillary splinting (IMS) in 294, transcutaneous reduction (TCR) in 126, and others in 113. MMF markedly decreased from more than 30 to less than 5% and observation increased from 20 to 40%.

Routine removal of the plate after surgical treatment for mandibular angle fracture with a third molar in relation to the fracture line.

PURPOSE: The purpose was to analyze the clinical course of surgically treated mandibular angle fractures from the viewpoint of routine removal of the plate because these fractures are associated with high rates of complications and plate removal. SUBJECTS AND METHODS: The subjects were 40 patients with unilateral mandibular angle fracture, which was intraorally reduced and principally fixed with a single miniplate on the external oblique ridge. The third molar in relation to the fracture line was extracted in seven patients during the surgery. Clinical course was evaluated in terms of removal of the plate, preservation of the third molar and complications. RESULTS: One patient showed a wound infection postoperatively, and two patients developed pericoronitis during the follow-up. These were managed with medication and local irrigation. One patient with a preserved third molar did not make a required visit and was lost from the follow-up. Removal of the plates was performed in 39 patients after confirmation of good fracture healing, mostly within a year. Twenty-four of 32 preserved third molars were simultaneously extracted. These procedures were generally performed under local anesthesia on an outpatient basis, and they did not cause any complications. CONCLUSIONS: Routine removal of the plate after surgical treatment for mandibular angle fractures, simultaneously with extraction of the third molar if indicated, may be beneficial to avoid complications related to the plate and the third molar later in life.

Biomechanical analysis of poly-L-lactic acid and titanium plates fixated for mandibular symphyseal fracture with a conservatively treated unilateral condylar fracture using the three-dimensional finite element method.

The purpose of this study was to investigate stress on poly-L-lactic acid (PLLA) plates with a thickness of 1.4 mm and titanium plates with a thickness of 1.0 and 1.4 mm placed for mandibular symphyseal fractures with or without conservatively treated, unilateral condylar fractures using finite element analysis. The symphyseal fracture region was defined by the following three conditions: the defect, the callus, and the contact condition. Stress on the plates was analyzed by an applying occlusal force of 478.1 N on the first molar of the non-condylar fracture side. In the model of isolated symphyseal fracture, the maximal stresses were below the material strength in all plate types and conditions. In the models with condylar fracture, the maximal stresses on these plates were much higher than those in the models of isolated symphyseal fracture, especially for the defect condition. Although the maximal stresses on all types of plates in the contact condition were below the material strengths, some of those in the defect condition were higher than these strengths. These results suggest that a PLLA plate can theoretically withstand stress under good reductions of symphyseal fractures, even for condylar fractures; however, both the PLLA plate and titanium miniplate may be at risk of fracture under poor reduction.

Influence of bone parameters on peri-implant bone strain distribution in the posterior mandible

OBJECTIVES: The success rate of dental implants depends on the type of bone at the implant site. The purpose of the present study was to investigate the effects of the bone parameters at the implant-placement site on peri-implantbone strain distributions. Study DESIGN: The morphologies and bone densities of seventy-five potential implant sites in the posterior mandible were measured using computed tomography (CT). Based on the CT data, we defined bone parameters (low and high in terms of cancellous-bone density and crestal-cortical bone density, and thin and thick in terms of crestal-cortical bone thickness), and we constructed finite-element models simulating the various bone types. A buccolingual oblique load of 200 N was applied to the top of the abutment. The von Mises equivalent (EQV)strains in the crestal-cortical bone and in the cancellous bone around the implant were calculated. RESULTS: Cancellous-bone density greatly affected the maximum EQV strain regardless of the density and thickness of the crestal cortical-bone. The maximum EQV strains in the crestal cortical-bone and the cancellous bone in the low-density cancellous-bone models (of 150 Hounsfield units (HU) were 1.56 to 2.62-fold and 3.49 to 5.31-fold higher than those in the high-density cancellous-bone models (of 850 HU), respectively. The crestal cortical bonedensity affected the maximum EQV strains in the crestal cortical-bone and in the cancellous bone in the low-density cancellous-bone models. The crestal cortical-bone thickness affected the maximum EQV strains in the cancellous bone and in the crestal cortical-bone in the low-density cancellous-bone models. CONCLUSIONS: Our results confirm the importance of bone types for the peri-implant bone strain distribution. Cancellous-bone density may be a critical factor for peri-implant bone strain