The effect of reduced thickness in different regions on the fracture resistance of monolithic zirconia crowns / 대한치과보철학회지

Purpose@#. This study aims to evaluate the combined effect of reduced thickness in different regions on the fracture resistance of monolithic zirconia crowns. @*Materials and methods@#. Seven nickel-chromium dies were generated from a 3D model of mandibular first molar using the digital scanner with the following geometries:1.5 mm occlusal reduction, 1.0 mm deep chamfer. Based on the abutment model, Zirconia blocks (Luxen Zirconia) were selected to fabricate Sixty-three zirconia crowns with occlusal thicknesses of 0.3 mm, 0.5 mm, and 1.5 mm, and different axial thicknesses of 0.3 mm, 0.5 mm, and 1.0 mm. All crowns were cemented by resin cement. Next, the crowns were subjected to load-to-fracture test until fracture using an electronic universal testing machine. In addition, fracture patterns were observed with a scanning electron microscope (SEM). Two-way ANOVA and the Tuckey HSD test for post hoc analysis were used for statistical analysis (P < .05). @*Results@#. The mean values of fracture resistancerecorded was higher than the average biting force in the posterior region. The two-way ANOVA showed that the occlusal and axial thickness affected the fracture resistance significantly (P < .05). However, the effect of axial thickness on fracture resistance did not show a statistical difference when thicker than 0.5 mm. The observed failure modes were partial or complete fracture depending on the severity of crack propagation. @*Conclusion@#. Within the limitations of the present study, the CAD-CAM monolithic zirconia crown with extremely reduced thickness showed adequate fracture resistance to withstand occlusal load in molar regions. In addition, both occlusal and axial thickness affected the fracture resistance of the zirconia crown and showed different results as combined.

A new rationale for preservation of the mandibular third molar in orthognathic patients with missing molars

Controversies exist regarding the need for prophylactic extraction of mandibular third molars in patients who plan to undergo orthognathic surgery.An 18-year-old male patient was diagnosed with mandibular prognathism and maxillary retrognathism with mild facial asymmetry. He had a severely damaged mandibular first molar and a horizontally impacted third molar. After extraction of the first molar, the second molar was protracted into the first molar space, and the third molar erupted into the posterior line of occlusion. The orthognathic surgery involved clockwise rotation of the maxillomandibular complex as well as angle shaving and chin border trimming. Patients who are missing or have damaged mandibular molars should be monitored for eruption of third molars to replace the missing posterior tooth regardless of the timing of orthognathic surgery.

Angioedema of the Left Maxillary Area

Osteogenic potential of adult stem cells from human maxillary sinus membrane by Simvastatin in vitro: preliminary report

OBJECTIVES: The objective of this study is to determine the adequate concentration and to evaluate the osteogenic potential of simvastatin in human maxillary sinus membrane-derived stem cells (hSMSC). MATERIALS AND METHODS: Mesenchymal stem cells derived from the human maxillary sinus membrane were treated with various concentrations of simvastatin. The adequate concentration of simvastatin for osteogenic induction was determined using bone morphogenetic protein (BMP-2). The efficacy of osteogenic differentiation of simavastatin was verified using osteocalcin mRNA, and the mineralization efficacy of hSMSCs and simvastatin treatment was compared with alkaline phosphatase and von Kossa staining. RESULTS: Expression of BMP-2 mRNA and protein was observed after three days and was dependent on the concentration of simvastatin. Expression of osteocalcin mRNA was observed after three days in the 1.0 microM simvastatin-treated group. Mineralization was observed after three days in the simvastatin-treated group. CONCLUSION: These results suggest that simvastatin induces the osteogenic potential of mesenchymal stem cells derived from the human maxillary sinus membrane mucosa.

The Vertical Changes of Lip and Perioral Soft Tissue Following Orthognathic Surgery in Skeletal Class III Patients by a Cephalometric Analysis of Cone Beam Computed Tomography

Three-dimensional finite element analysis of the stress distribution and displacement in different fixation methods of bilateral sagittal split ramus osteotomy

OBJECTIVES: This study evaluated a range of fixation methods to determine which is best for the postoperative stabilization of a mandibular osteotomy using three-dimensional finite element analysis of the stress distribution on the plate, screw and surrounding bone and displacement of the lower incisors. MATERIALS AND METHODS: The model was generated using the synthetic skull scan data, and the surface model was changed to a solid model using software. Bilateral sagittal split ramus osteotomy was performed using the program, and 8 different types of fixation methods were evaluated. A vertical load of 10 N was applied to the occlusal surface of the first molar. RESULTS: In the case of bicortical screws, von-Mises stress on the screws and screw hole and deflection of the lower central incisor were minimal in type 2 (inverted L pattern with 3 bicortical repositioning screws). In the case of plates, von-Mises stress was minimal in type 8 (fixation 5 mm above the inferior border of the mandible with 1 metal plate and 4 monocortical screws), and deflection of the lower central incisor was minimal in types 6 (fixation 5 mm below the superior border of the mandible with 1 metal plate and 4 monocortical screws) and 7 (fixation 12 mm below the superior border of the mandible with 1 metal plate and 4 monocortical screws). CONCLUSION: Types 2 and 6 fixation methods provide better stability than the others.

Three-dimensional analysis of pharyngeal airway change of skeletal class III patients in cone beam computed tomography after bimaxillary surgery

INTRODUCTION: To evaluate the 3-dimensional changes in the pharyngeal airway of skeletal class III patients after bimaxillary surgery. MATERIALS AND METHODS: The study sample consisted of 18 Korean patients that had undergone maxillary setback or posterosuperior movement and mandibular bilateral sagittal split osteotomy setback surgery due to skeletal class III malocclusion (8 males, 10 females; mean age of 28.7). Cone beam computed tomography was taken 1 month before and 6 months after orthognathic surgery. Preoperative and postoperative volumes of the nasopharyngeal, oropharyngeal, and laryngopharyngeal airways and minimum axial areas of the oropharyngeal and laryngopharyngeal spaces were measured. Moreover, the pharyngeal airway volume of the patient group that had received genioplasty advancement was compared with the other group that had not. RESULTS: The nasopharyngeal and laryngopharyngeal spaces did not show significant differences before or after surgery. However, the oropharyngeal space volume and total volume of pharyngeal airway decreased significantly (P<0.05). The minimum axial area of the oropharynx also decreased significantly. CONCLUSION: The results indicate that bimaxillary surgery decreased the volume and the minimum axial area of the oropharyngeal space. Advanced genioplasty did not seem to have a significant effect on the volumes of the oropharyngeal and laryngopharyngeal spaces.

A comparison of fixation methods using three-dimensional finite element analysis following anterior segmental osteotomy

OBJECTIVES: This study sought to evaluate fixation methods and determine the best method for the postoperative stabilization of maxillary osteotomy. For our analysis we performed a three-dimensional finite element analysis of stress distribution on the plate, screw, and surrounding bone, as well as displacement onto the plate. MATERIALS AND METHODS: We generated a model using synthetic skull scan data; an initital surface model was changed to a solid model using software. Modified anterior segmental osteotomy (using Park's method) was made using the program, and four different types of fixation methods were used. An anterior load of 100 N was applied on the palatal surface of two central incisors. RESULTS: The Type 1 (L-shaped) fixation method gave stresses of 187.8 MPa at the plate, 45.8 MPa at the screw, and 15.4 MPa at the bone around the plate. The Type 2 (I-shaped) fixation method gave stresses of 186.6 MPa at the plate, 75.7 MPa at the screw, and 13.8 MPa at the bone around the plate. The Type 3 (inverted L-shaped) fixation method gave stresses of 28.6 MPa at the plate, 29.9 MPa at the screw, and 15.3 MPa at the bone around the plate. The Type 4 (I-shaped) fixation method gave stresses of 34.8 MPa at the plate, 36.9 MPa at the screw, and 14.9 MPa at the bone around the plate. The deflection of the plates for the four fixation methods was 0.014 mm, 0.022 mm, 0.017 mm, and 0.018 mm, respectively. CONCLUSION: The Type 3 (inverted L-shaped) fixation method offers more stability than the other fixation methods. We therefore recommend this method for the postoperative stabilization of maxillary osteotomy.

Soft tissue changes of upper lip and nose following posterosuperior rotation of the maxilla by Le Fort I osteotomy

INTRODUCTION: This study evaluate the soft tissue changes to the upper lip and nose after Le Fort I maxillary posterosuperior rotational movement. MATERIALS AND METHODS: Twenty Skeletal class III patients, who had undergone bimaxillary surgery with a maxillary Le Fort I osteotomy and bilateral sagittal split ramus osteotomy, were included in the study. The surgical plan for maxilla was posterosuperior rotational movement, with the rotation center in the anterior nasal spine (ANS) of maxilla. Soft and hard tissue changes were measured by evaluating the lateral cephalograms obtained prior to surgery and at least 6 months after surgery. For cephalometric analysis, four hard tissue landmarks ANS, posterior nasal spine [PNS], A point, U1 tip), and five soft tissue landmarks (pronasale [Pn], subnasale [Sn], A' Point, upper lip [UL], stomion superius [StmS]) were marked. A paired t test, Pearson's correlation analysis and linear regression analysis were used to evaluate the soft and hard tissue changes and assess the correlation. A P value <0.05 was considered significant. RESULTS: The U1 tip moved 2.52+/-1.54 mm posteriorly in the horizontal plane (P<0.05). Among the soft tissue landmarks, Pn moved 0.97+/-1.1 mm downward (P<0.05), UL moved 1.98+/-1.58 mm posteriorly (P<0.05) and 1.18+/-1.85 mm inferiorly (P<0.05), and StmS moved 1.68+/-1.48 mm posteriorly (P<0.05) and 1.06+/-1.29 mm inferiorly (P<0.05). The ratios of horizontal soft tissue movement to the hard tissue were 1:0.47 for the A point and A' point, and 1:0.74 for the U1 tip and UL. Vertically, the movement ratio between the A point and A' point was 1:0.38, between U1 tip and UL was 1:0.83, and between U1 tip and StmS was 1:0.79. CONCLUSION: Posterosuperior rotational movement of the maxilla in Le Fort I osteotomy results in posterior and inferior movement of UL. In addition, nasolabial angle was increased. Nasal tip and base of the nose showed a tendency to move downward and showed significant horizontal movement. The soft tissue changes in the upper lip and nasal area are believed to be induced by posterior movement at the UL area.

Eagle's Syndrome Presenting Unilateral Facial Nerve Palsy: Case Report

A clinical evaluation of efficacy of an office bleaching gel containing 30% hydrogen peroxide / 대한치과보존학회지

This study evaluated the efficacy of an office bleaching gel (RemeWhite, Remedent Inc., Deurle, Belgium) containing 30% hydrogen peroxide. 31 volunteers were recieved office bleaching with the RemeWhite for 3 times at one visit, total 2 visits. As control group, the same gel in which hydrogen peroxide was not included was applied to 31 volunteers with the same protocol. The shade change (DeltaE*, color difference) of 12 anterior teeth was measured using Colorimerter and Vitapan classical shade guide. The shade change of overall teeth in the experimental group was significantly greater than that in the control group which was measured using Colorimeter. There was also a significant difference between baseline and 14 weeks or 26 weeks though color rebounding phenomenon occurred as time went by. Small shade change difference can be measured accurately using Colorimeter than using Vitapan classical shade guide.

A clinical evaluation of safety of an office bleaching gel containing 30% hydrogen peroxide / 대한치과보존학회지

This study evaluated the safety of an office bleaching gel (RemeWhite, Remedent Inc., Deurle, Belgium) containing 30% hydrogen peroxide. 37 volunteers were recieved office bleaching with the RemeWhite for 3 times at one visit, total 2 visits. As control group, the same gel in which hydrogen peroxide was not included was applied to 34 volunteers with the same protocol. There was no difference between experimental group and control group using electric pulp test. In the result of gingival inflammation index and tooth sensitivity test, there was mild pain response in experimental group but it disappeared as time went by. Therefore, safety of the office bleaching gel containing 30% hydrogen peroxide was confirmed.

Soft tissue changes associated with ASO/BSSRO and Le Fort I/BSSRO in skeletal Class III malocclusion with upper lip protrusion / 대한치과교정학회지

OBJECTIVE: The objective of this study was to compare maxillary soft tissue changes and their relative ratios to hard tissue changes after anterior segmental osteotomy (ASO)/bilateral sagittal split ramus osteotomy (BSSRO) and Le Fort I/BSSRO in skeletal Class III malocclusion with upper lip protrusion. METHODS: The study sample comprised the ASO/BSSRO group (n = 14) and the Le Fort I/BSSRO group (n = 15). The Le Fort I/BSSRO group included cases of maxillary posterior impaction only. Lateral cephalograms were taken 2 months before and 6 months after surgery. Linear and angular measurements were performed. RESULTS: The anterior maxilla moved backward in both groups after surgery, however the amount of change was significantly larger in the ASO/BSSRO group (p < 0.01). The ratios of hard to soft tissue change were 79% (SLS to A point), 80% (LS to A point) in the ASO/BSSRO group, and 15% (SLS to A point), 68% (LS to A point) in the Le fort I/BSSRO group. In addition, there was a 3.23degrees increase of the occlusal plane in the Le Fort I/BSSRO group. CONCLUSIONS: When two-jaw surgery is indicated in skeletal Class III patients with protrusive lips, ASO may be a treatment of choice for cases with more severe upper lip protrusion, while Le Fort I with posterior impaction may be considered if an increase of occlusal plane angle is required.

Soft tissue changes in skeletal class II patients treated with bilateral sagittal split osteotomy advancement surgery

The purpose of this study was to examine the soft tissue changes in skeletal class II patients after mandibular advancement by bilateral sagittal split ramus osteotomy (BSSRO). In Asian population, the incidence of skeletal class II malocclusion is lower than that of skeletal class III malocclusion unlike the caucasians. This study was conducted to figure out the ratio at which hard tissue and soft tissue changes after mandibular advancement by analyzing cephalograms of 13 patients that have undergone the mandibular advancement surgery. As a result, change ratios of Li, B', Pog' according to the movement of li, B, Pog were found to be 0.59, 1.06, 0.82. Also, vertical height of vermilion zone (Si-Vb) and lower lip and chin (Si-Me') were measured to evaluate vertical changes. Vermilion zone showed tendency to decrease by 1.02 mm on the average postoperatively, whereas vertical length of lower lip and chin showed tendency to increase by 3.57 mm on the average.

A Study on Bone-Contact to Inter-Segmental Length Ratio of Rigid Fixation Screws used in Bssro for Mandibular Setback

OBJECTIVE: To evaluate the ratio between bone-contact length and inter-segmental length of the rigid fixation screw used in bilateral sagittal split ramus osteotomy (BSSRO) for mandibular setback. MATERIAL AND METHODS: Records of 40 patients with Class III malocclusion were selected. 20 of them had BSSRO, while the other 20 had BSSRO with maxillary LeFort I osteotomy. All of the patients had three noncompressive bicortical screws inserted at the gonial angle through transcutaneous approach. Two screws were inserted antero-posteriorly above inferior alveolar nerve and one screw was inserted below. The lengths of bone-contact and that of inter-segmental part were measured using cone-beam computed tomography. Ratio between these two measured lengths was calculated. RESULTS: Both bone-contact and inter-segmental lengths were longer in BSSRO group than in BSSRO with maxillary LeFort I osteotomy group. Ratio of bone-contact to inter-segmental length was lower in BSSRO group than in BSSRO with Lefort I group. Both bone-contact and inter-segmental lengths were longer at the antero-superior position than at the inferior position. However, their ratio showed little difference. CONCLUSION: This study suggest that stability of screws in BSSRO group was greater than in BSSRO with Lefort I group. Stability of screws at the antero-superior position was greater than at the inferior position. Ratio of bone-contact to inter- segmental lengths was 0.2 in average.

Cone-beam computed tomography measurement of the position of the inferior alveolar nerve canal in mandibular prognathism

BACKGROUND AND OBJECTIVES: To determine the anatomic position of the inferior alveolar nerve (IAN) canal in patients with mandibular prognathism using the cone-beam CT (CBCT). MATERIALS AND METHODS: Fifty rami from 25 patients were evaluated. The images were taken by i-CAT and reconstructed 3-dimensionally using the Simplant 11 program. The linear distances between the IAN canal to the buccal cortex (a, a* and a**), from the IAN canal to the alveolar crest (b and b*) and the anterior margin (b**) and finally the buccal cortical thickness (c, c* and c**) were measured at three reference planes (VP, OP and HP). RESULTS: On the left side, the average distance of a, b and c were 7.12, 15.96 and 3.60 mm on the VP plane, respectively. On the OP, the distance of a*, b* and c* was 6.11, 8.83 and 2.63 mm. For the HP, the distance of a**, b** and c** was 4.84, 10.11 and 2.30 mm. On the right side, the distance of a, b and c, on the VP, was 7.10, 16.13 and 3.42 mm, respectively. On the OP, the distance of a*, b* and c* was 4.77, 8.75 and 2.68 mm. On the HP, the distance of a*, b* and c** was 4.55, 9.84 and 2.38 mm. Regarding the difference between genders, the distance in male's was longer than female's on the VP (p=0.019), and was thicker in males than females on the HP (p=0.002). CONCLUSION: The CBCT data provided accurate information about the location and course of the IAN.

Cone-beam computed tomography measurement of the position of the inferior alveolar nerve canal in mandibular prognathism

BACKGROUND AND OBJECTIVES: To determine the anatomic position of the inferior alveolar nerve (IAN) canal in patients with mandibular prognathism using the cone-beam CT (CBCT). MATERIALS AND METHODS: Fifty rami from 25 patients were evaluated. The images were taken by i-CAT and reconstructed 3-dimensionally using the Simplant 11 program. The linear distances between the IAN canal to the buccal cortex (a, a* and a**), from the IAN canal to the alveolar crest (b and b*) and the anterior margin (b**) and finally the buccal cortical thickness (c, c* and c**) were measured at three reference planes (VP, OP and HP). RESULTS: On the left side, the average distance of a, b and c were 7.12, 15.96 and 3.60 mm on the VP plane, respectively. On the OP, the distance of a*, b* and c* was 6.11, 8.83 and 2.63 mm. For the HP, the distance of a**, b** and c** was 4.84, 10.11 and 2.30 mm. On the right side, the distance of a, b and c, on the VP, was 7.10, 16.13 and 3.42 mm, respectively. On the OP, the distance of a*, b* and c* was 4.77, 8.75 and 2.68 mm. On the HP, the distance of a*, b* and c** was 4.55, 9.84 and 2.38 mm. Regarding the difference between genders, the distance in male's was longer than female's on the VP (p=0.019), and was thicker in males than females on the HP (p=0.002). CONCLUSION: The CBCT data provided accurate information about the location and course of the IAN.

Chondrosarcoma in the mandibular condyle: Case report

Chondrosarcoma is an uncommon neoplasm originated from cartilage cells. This occurs less than 10% in the head and neck region. Chondrosarcoma of the condyle affects mainly women. The most common symptom is swelling in the preaucricular region, limited mouth opening and pain on chewing. This report describes a case of chondrosarcoma, which occurred in the mandibular condyle.

Post-extubation acute respiratory distress syndrome occurred in the orthognathic surgery patient : a Case Report

Multiple myeloma in the mandible manifested as oral lesion of plasmacytoma: a Case Report