Evaluation of the pattern of fracture formation from trauma to the human mandible with finite element analysis. Part 2: The corpus and the angle regions.

BACKGROUND/AIMS: Although the mandible is the largest and strongest bone of the facial skeleton, it is frequently broken. The fracture location in the mandible depends on the biomechanical features, direction and angle of the trauma, and masticatory muscles. This study aimed to evaluate the stresses caused by trauma to the corpus and angle regions from different angles. MATERIALS AND METHODS: After computer-based mandible models were created using finite element analysis, a force of 2000 Newton(N) was simulated with the mouth open or closed to the corpus and the angle. To the corpus: at 90° (Model 1) in the lateromedial direction, 45° (Model 2) in the lateromedial-inferosuperior direction, and 90° (Model 3) in the inferosuperior direction. To angle: 90° (Model 4) in the lateromedial direction and 45° (Model 5) in the lateromedial-inferosuperior direction. The resulting stress intensity was assessed using FEA. RESULTS: Following the simulated forces, the maximum stress in the mandible occurred in the condylar region, except in Model 3 (Left(L)Corpus2[36 megapascals(MPa)]) in the mouth-closed condition. After traumas in Model 1 (open-mouth: LCondyle2[547 MPa]) and Model 4 (closed-mouth: LCondyle2[607 MPa]), higher stress values occurred in the condyle. In the mouth open-closed state, there was no significant stress change in the condyle region in Model 1 (open-mouth: LCondyle2[547 MPa], closed-mouth:LCondyle2[546 MPa]) or in Model 2 (open mouth: Right(R)Condyle2[431 MPa], closed-mouth:LCondyle2[439 MPa]). In Model 3, lower stress values occurred in the closed-mouth rather than the open-mouth (LCondyle1[167 MPa]) state. In Models 4 and 5, the stress values increased in the mouth-closed condition compared with the mouth-open condition. CONCLUSIONS: Stress in the mandible is affected by the location of the trauma and the angle of incidence of the blow. In trauma to both the corpus and the angle, the most common area to be fractured is the condyle.

Evaluation of the pattern of fracture formation from trauma to the human mandible with finite element analysis. Part 1: Symphysis region.

BACKGROUND/AIM: The mandible is the largest, strongest bone in the maxillofacial region. When a fracture occurs in the mandible, its location depends on several factors: the direction of the trauma, the angle of the trauma, masticatory muscles and the quality of the bone. The aim of this study was to evaluate the stresses caused by trauma to the symphysis region from different angles. MATERIALS AND METHODS: Computer-based mandible models were created, and a 2000 N force was applied to the symphysis at three different angles using finite element analysis. Six trauma situations were simulated with the mouth open or closed. Forces were applied to the symphysis at 90° (Model 1) in the anteroposterior direction, 45° (Model 2) in the anteroposterior-inferosuperior direction and 90° (Model 3) in the inferosuperior direction, when the mouth was open or closed. The resulting stress intensity was assessed using finite element analysis. RESULTS: As a result of trauma applied to the symphysis region, maximum stresses were found where the impact originated and at the condyle region (Model 2, open mouth: condyle 1 [1172 MPa]). The open mouth position caused higher stress values than the closed mouth position (Model 2, open mouth: condyle 1 [1172 MPa]; closed mouth: symphysis 4 [82 MPa]). The Model 2, open-mouth state (Model 2, open mouth: condyle 1 [1172 MPa]) sustained higher stresses than all the other models. CONCLUSION: The stress values in the mandible were affected by the force applied to the symphysis region, the angle of impact arrival and the open or closed state of the mouth. Keeping the mouth closed at the time of trauma reduced the stress value. A closed mouth during trauma directed at the symphysis reduced the possibility of mandible fractures.

Evaluation of metal concentrations in hair and nails after dental implant placement.

STATEMENT OF PROBLEM: The accumulation of the elements contained in Ti6Al4V, the mostly used titanium alloy for dental implants, in epithelial extensions requires investigation. Studies evaluating the metals in dental implants in the hair and nails of patients with dental implants are lacking. PURPOSE: The purpose of this clinical research was to measure the levels of titanium (Ti), aluminum (Al), and vanadium (V) in the hair and nails of patients treated with grade 5 Ti alloy dental implants. MATERIAL AND METHODS: Ti, Al, and V elemental levels in the hair and nail samples of 33 participants treated with grade 5 Ti alloy dental implants were measured by using an inductively coupled plasma mass spectrometer. RESULTS: The results revealed a statistically significant increase in the amount of Ti in nail samples after implant surgery (P=.01), but no statistically significant increases in the amounts of Al or V in nail samples (P=.48, P=.645). In hair samples, the increase in Ti, Al, and V was not statistically significant (P=.728, P=.221, P=.376). The correlation between the amount of change in the elements in implants and the contact areas was weak for hair (Al, r=0.114; Ti, r=0.361; V, r=0.377) and for nails (Al, r=0.127; Ti, r=0.116; V, r=0.058). CONCLUSIONS: After the placement of dental implants made of grade 5 Ti alloy, minimal Al and V accumulated in hair and nails.

In Vitro Evaluation of the Effects of Different Fixation Methods on Stabilization of Mandibular Body Fractures.

PURPOSE: Mandibular body fractures are considered to be one of the most affected fracture sites in the maxillofacial region. Although the rates of fracture in this region are high, biomechanical evaluations related to this region are rare. The purpose of this investigation was to reveal the effects of different treatment methods onmandibular body fractures. METHOD: Twenty-five synthetic polyurethane hemi-mandibles were used in this study. The hemi-mandibles, which simulated simple unfavorable mandibular body fractures, were divided into 5 groups (n = 5/group) according to the treatment method. The bone segments were fixed using different osteosynthesis methods and 2.0 mm miniplate/screw systems. The groups consisted of locking or conventional systems, 5 or 11 mm long screws and 4 or 6 holes. The hemi-mandibles were loaded vertically with compressive strength until they reached 120 N. RESULTS: The results were analyzed using Tamhane's T2 post hoc test, and the significance level was 0.05. Group 1 had the lowest mechanical resistance of all groups and group 5 had the highest. No significant differences were observed in group 2 or 3. CONCLUSION: The locking system miniplate group showed better fixation stability than the conventional systems for the same screw length, and the number of holes and screw length seemed to be effective for stabilization.

Evaluation of Blood Titanium Levels and Total Bone Contact Area of Dental Implants.

The purpose of this study was to evaluate the effect of total implant-bone surface contact area of dental implants applied on partial or total edentulous patients on the increase in the level of blood titanium level. Changes of the blood titanium levels were evaluated after placement of the dental implants in 30 patients including 15 females and 15 males. Patients were divided into 3 groups as dental implants were applied on only maxilla, only mandible, or both of them. Taking into the consideration anatomic formation and prosthetic indication, dental implant-bone total contact area was calculated and saved for each patient after dental implants placement. Blood samples of the patients taken preoperatively and postoperatively at 12 weeks were analyzed by ICP-MS device. Blood titanium levels of preoperative and postoperative blood samples were analyzed for each patient and results were evaluated statistically. In the evaluation after analyzing blood titanium level changes, while a statistically significant decrease was observed in Group 1 patients, a statistically significant increase was observed in Group 2 and Group 3 patients to blood titanium level. A statistically significant difference was observed between Group 1 and Group 2 and between Group 1 and Group 3 patients of blood titanium levels. The change of the blood titanium level was not related to total implant-bone surface area, number of the implants, and gender. In our study, no correlation was found between change of blood titanium level and total contact area with bone of dental implants. We believe that more accurate results can be obtained with biopsy of tissues and organs on animal studies.

A comparison of diode laser and Er:YAG lasers in the treatment of gingival melanin pigmentation.

OBJECTIVES: This study compared the use of diode and Er:YAG lasers in treating gingival melanin pigmentation (GMP) in terms of gingival depigmentation, local anesthesia requirements, postoperative pain/discomfort, depigmentation effectiveness, and total treatment duration. STUDY DESIGN: Twenty patients (13 female, 7 male) referred with GMP were enrolled in the study. Patients were randomly divided into 2 groups. Group 1 was treated with a gallium aluminum arsenide diode laser with a continuous wavelength of 808 nm, and group 2 was treated with an Er:YAG laser with a continuous wavelength of 2,940 nm. Gingival depigmentation was performed by applying the laser at 1 W. Treatment was administered on a weekly basis until a normal pink gingival color was observable in clinical examination and photographs. In addition, patients were asked to evaluate the procedure by using a self-administered questionnaire. RESULTS: Procedures were carried out without the need for any topical or local anesthetic, and no unpleasant events occurred during the actual procedure or the healing period. The total length of treatment was significantly shorter with the diode laser (group 1) than with the Er:YAG laser (group 2; P < .05). No melanin recurrence was detected during any follow-up session. CONCLUSIONS: Diode and Er:YAG lasers administered at 1 W both result in satisfactory depigmentation of GMP.

Local treatment of chronic osteomyelitis with surgical debridement and tigecycline-impregnated calcium hydroxyapatite: an experimental study.

OBJECTIVE: The aim of this study was to determine the efficacy of tigecycline-impregnated hydroxyapatite in the local treatment of chronic osteomyelitis experimentally induced in rat tibias with methicillin-resistant Staphylococcus aureus. STUDY DESIGN: Monocortical defects were established in the left tibias of 32 adult Wistar albino rats. Five rats were randomly selected and injected intramedullarly with saline solution (group 1), whereas chronic osteomyelitis was induced in other rats by intramedullary injection of S. aureus. Infected rats were then randomized and divided into 4 groups: group 2, no further treatment; group 3, debridement only; group 4, debridement followed by implantation of calcium hydroxyapatite; and group 5, debridement followed by implantation of tigecycline-impregnated calcium hydroxyapatite. On day 21 after induction, all rats in groups 2-5 showed signs of osteomyelitis. Rats in groups 1 and 2 were killed on day 21 after induction, whereas rats in groups 3, 4, and 5 underwent debridement surgery on day 21 after induction and were killed 21 days after debridement surgery. Tibias were analyzed histopathologically and cultured for S. aureus. RESULTS: Compared with group 2, histopathologic disease severity scores in groups 3, 4, and 5 were 37%, 44%, and 83% lower, respectively. Nontreated infected rats had the highest bacteria count (mean 5 × 10(5) colony-forming units/g bone), and bacterial count was 26%, 29%, and 79% lower in groups 3, 4, and 5, respectively, compared with group 2. CONCLUSIONS: Tigecycline-impregnated hydroxyapatite can have a potential in the treatment of chronic osteomyelitis of methicillin-resistant S. aureus origin, which may be considered as a therapeutic alternative by surgeons dealing with osteomyelitis.

Soft tissue pathosis associated with asymptomatic impacted lower third molars.

OBJECTIVE: The aim of this study was to identify the prevalence of pathological changes in the pericoronal tissue of asymptomatic impacted lower third molars and to assess the correlation between pathological changes and patient demographic, radiographic and morphological characteristics. STUDY DESIGN: Follicles associated with fully impacted lower third molars were submitted for histological examination after surgical extraction from 50 patients. The correlation between pathological changes in the dental follicle and age, gender, depth of impaction, angular position, and coverage and tooth development was analyzed. RESULTS: Cystic changes were observed in 10% of specimens and inflammatory changes in 62%. Incidence of pathological changes was significantly higher in Class B impacted teeth when compared to Class C impacted teeth. A significant correlation was found between epithelial cell activity and the completion of tooth development. CONCLUSION: We recommend monitoring all third molars whether or not they are symptomatic and conducting histopathological analyses on all surgically extracted follicle tissue.

Prevalence of impacted premolars in a Turkish population and considerations for surgical treatment.

OBJECTIVE: The aim of this study was to identify the prevalence, associated pathology and symptoms, and treatment of impacted premolars in a Turkish population. STUDY DESIGN: This retrospective study examined panoramic radiographs and clinical records of 9,000 patients who presented consecutively at our oral and maxillofacial surgery clinics between January 1998 and January 2009. In addition to demographic data (patient sex and age), data was compiled on the number and location of impacted missing maxillary and mandibular premolars, retained deciduous molars, associated pathologies and symptoms, and treatment methods. RESULTS: A total of 105 impacted maxillary or mandibular premolars were observed in 93 patients (1.03%). Of these, 48 (51.6%) were female (age range: 13-57 years) and 45 (43.4%) were male (age range: 13-58 years). Impacted mandibular second premolars accounted for 55.2% (n=58) of all impacted premolars. Migration was observed in only 11.83% of patients (n=11). Pathological changes and symptoms were noted in 15.05% of patients. CONCLUSION: Our results suggest that the prophylactic extraction of non-migrated impacted premolars may not be necessary. If the patient is cooperative, a "wait and see " approach may be preferable. Orthodontic or prosthetic treatment options should also be considered when planning treatment of non-migrated impacted premolars. Migrated impacted premolars should be kept under observation and should only be removed if they are associated with pathology or if extraction is required for prosthetic or orthodontic treatment.

Non-syndromic supernumerary premolars.

OBJECTIVE: The objective of this study was to estimate the incidence of non-syndromic supernumerary premolars, to classify them and to identify the complications related to them. STUDY DESIGN: This retrospective cohort study was composed of 8400 panoramic radiographs of patients who presented at our Oral and Maxillofacial Surgery Services from January 1998 to May 2008. The number of supernumerary premolars, their localization, the ages and the sex of the patients, any associated complications and treatment methods were estimated. RESULTS AND CONCLUSION: A total of 20 supernumerary premolar teeth were found in 10 of the 8400 patients (0.24%) with 7 of those being females and three males. Three patients had pain localized to the mental foramen and one patient had resorption in the root of the adjacent tooth. In these series, 18 supernumerary premolar teeth were extracted. In contrast with previous studies, this study suggested that this phenomenon is more frequently encountered in females than in males. The presence of complications associated with the supernumerary premolars in 4 patients necessitated consideration of surgical intervention as a treatment choice for these teeth. Otherwise, they should be kept under observation.

Review of biomechanical experimental studies on different plating techniques of mandibular condyle fractures.

Mandibular condyle fractures are one of the most frequent injuries of the facial skeleton. The option for open treatment of mandibular condyle fractures has become more favorable since osteosynthesis materials were developed in the past few decades. However, the rigid fixation techniques of treating condyle fractures remain one of the controversial issues in maxillofacial trauma. These injuries are currently treated by plate-screw osteosynthesis and, depending on the case, the bone segments are fixed by one or two miniplates. Several techniques and plate types like adaption miniplates, minidynamic compression plates, resorbable plates and double plates have been evaluated biomechanically in various experimental and clinical studies. The biomechanical and physical behavior of mandibles have been investigated by different approaches. It can be divided into computer biomodels (e.g., finite element analysis) and physical models. Physical models allow testing on a gross level to give fatigue performance and fracture strength. The aim of this article is to carry out a review of the literature which deals with biomechanical evaluation made with physical models of plating techniques of mandibular condyle fracture. Based on the results of these studies, osteosynthesis with two miniplates seems to be the most stable way of treating mandible subcondylar fractures, and PLLA plates were not strong enough compared with metal plates.

Transmigrant maxillary canines.

OBJECTIVE: The objective of this study was to investigate the incidence and pattern of transmigrant maxillary canines. PATIENTS AND METHODS: The records of 6000 patients who were presented to our oral and maxillofacial surgery services between January 1998 and January 2007 were reviewed. Observations were made as to the right/left localization and number of transmigrant canines; sex and age of patients; retained deciduous canines; and any other associated pathology. RESULTS: A total of 12 patients presented with transmigrated maxillary canines with 6 females (age 15 to 37) and 6 males (age 17 to 57) in 6000 individuals (0.2%). All transmigrant canines were unilateral. The numbers of left and right transmigrant maxillary canines were equal. Ten individuals in 12 patients had not retained deciduous canines. None of these patients had any pathology associated with impacted canines. CONCLUSION: The canine transmigration can occur not only in the mandible but also the maxilla. Further studies are necessary to examine this rare phenomenon to allow classification of transmigrant canines in the maxillary arch. Thus, the incidence, demographic factors, and etiology of this phenomenon can be clarified. How transmigrant maxillary canines pass on the contralateral side of the mid palatal suture must be completely clarified.

The effect of hyaluronic acid-supplemented bone graft in bone healing: experimental study in rabbits.

Hyaluronic acid (HA) is one of the essential components of extracellular matrix, which plays a predominant role in tissue morphogenesis, cell migration, differentiation, and adhesion. Bone allografts are frequently used to repair and reconstruct bone defects. In this study, two cavities of 3 mm diameter and depth have been created in the right tibia of 30 mature rabbits in accordance with the principles of general surgery. One of the cavities in the tibia is filled with HA and bone graft and the other is filled with only spongiosal bone graft, for the purpose of control. On the 20th, 30th, and 40th days, rabbits have been sacrificed in equal numbers and defective regions have been extracted. The Kruskal-Wallis test was applied to the data obtained in the result of histopathologic survey of specimens. In conclusion, the cavities that have been filled with HA and bone graft have shown higher scores than the control group during every period of the study.

Guided bone regeneration (GBR) on healing bone defects: a histological study in rabbits.

In this study, the effects of guided bone regeneration (GBR) on the healing of bone defects were evaluated. Resorbable membranes were placed in experimentally formed cavities in the right posterior tibia of 30 rabbits. Decalcified histological sections were evaluated using optical microscopy at 10, 20, and 30 days after GBR. Osteocondrial bone union, active bone formation and spongiosal bone formation values of the GBR group are higher than the control group. It was found that GBR technique had a positive and accelerating influence in all phases of bone healing.

Flow-cytometric analysis of T-lymphocyte subsets after different treatment methods in patients with pericoronitis.

PURPOSE: The aim of this study was to determine whether there was any change in T-lymphocyte subsets in patients with periocoronitis after the application of different treatment methods. PATIENTS AND METHODS: Twenty-six patients with acute pericoronitis were included in the study. In every phase of the treatment (pretreatment, postcurettage, and postextraction), the biopsy samples were taken from the gingival tissues at sites of pericoronitis. Then, CD4(+) and CD8(+) lymphocyte and CD4(+)/CD8(+) ratio values were determined using flow cytometry in the biopsy samples. At the same time, gingival index (Löe-Silness) and plaque index (Silness-Löe) scores were recorded to assess the periodontal status in patients. To determine the correlation between the clinical measurements and the laboratory results obtained before the treatment, after curettage, and after extraction, we conducted an analysis using a paired t-test. RESULTS: The normal values in peripheral blood of CD4(+) and CD8(+) lymphocytes are 25% to 29% and 19% to 48%, respectively. However, the CD4(+) and CD8(+) lymphocyte values in the patients with acute pericoronitis were found to be 22.12% +/- 6.15% and 7.69% +/- 4.12%, respectively. These values are lower than the normal values. The CD4(+) lymphocyte value increased to 31.06% +/- 7.09% postcurettage and to 32.24% +/- 3.11% postextraction. The CD8(+) lymphocyte value increased to 16.21% +/- 5.27% postcurettage and to 18.25% +/- 3.13% postextraction. The CD4/CD8 ratio increased postcurettage and postextraction. This increase was statistically significant (P <.001). Postcurettage, there was decrease in clinical indexes, which was statistically significant (P <.001). A significant correlation between CD4(+) lymphocyte and ginigival index values and also between CD8(+) lymphocyte and plaque index values was determined postcurettage (P <.05). CONCLUSION: CD4(+) and CD8(+) T-lymphocytes could play a significant role in pericoronitis pathobiology.

Predictability of hand skill and cognitive abilities from craniofacial width in right- and left-handed men and women: relation of skeletal structure to cerebral function.

Recently, a family of homeobox genes involved in brain and craniofacial development was identified. In light of this genetic background, we hypothesized that some functional characteristics of human brain (hand skill, cognition) may be linked to some structural characteristics of human skull (e.g., craniofacial width) in humans. Hand preference was assessed by Oldfield's Handedness Questionnaire. Hand skill was measured by Peg Moving Task. Face width was measured from the anteroposterior cephalograms (x-ray) using right (R) and left (L) zygomatic points. Intelligence "g" was assessed by Cattell's Culture Fair Intelligence Test; the perceptual-verbal ability was assessed by "Finding A's Test"; the spatial ability was assessed by the mental rotation task, in right- and left-handed men and women. The percentages of right-, left-, and mixed-faced subjects were close to those found for paw preference in cats. Women tended to be more right-faced (R--L > 0) and less left-faced (R--L < 0) than men, who tended to be more left-faced and less right-faced than women. R--L face width inversely correlated with L--R PMT (peg moving time) in left-handers; there was a direct relation between these variables in right-handers. Cattell IQ linearly increased with R--L face width in left-handers, negatively correlated in right-handed men and women. Verbal ability inversely related to R--L face width in right- and left-handed men, but directly correlated in right-handed women. The number of correct response on mental-rotation task positively and linearly correlated with R--L face width in left-handers and right-handed women. It was concluded that the structural-functional coupling revealed in the present work may have its origins in parallel development of the craniofacial skeleton and brain under the influence of homeobox genes.