Tracking Accuracy of a Stereo Camera-Based Augmented Reality Navigation System for Orthognathic Surgery.

PURPOSE: Tracking accuracy is critical to successful augmented reality (AR) in the diagnosis and surgical correction of maxillofacial deformities. The present study investigated the tracking accuracy of an AR navigation system combined with a stereo camera during repositioning of the maxilla after a Le Fort I osteotomy using a 3-dimensional skull model and compared the tracking accuracy with that of an existing infrared (IR)-based optical tracking system (OTS). MATERIALS AND METHODS: Five maxillary surgery plans were designed using a 6 degrees-of-freedom articulator that allowed maxillary movement to be set up quantitatively (target distance, 5 mm). To evaluate the accuracy of the stereo camera AR navigation system, it was compared with a commercially available and commonly used IR-based OTS. RESULTS: The mean error was 0.0584 mm in the IR-based OTS and 0.0596 mm in the AR navigation system. The mean accuracy was 98.83% in the IR-based OTS and 98.81% in the AR navigation system. CONCLUSIONS: In this study, the stereo camera-based AR navigation system fabricated and analyzed by the authors was designed for accuracy. The experiments showed its reliability and accuracy. The hardware developed for this AR navigation system displayed accuracy similar to that of existing high-cost imported devices at a substantially lower cost. In addition to surgery, potential applications of the AR navigation system include patient communication and training for novice clinicians.

Are Three-Dimensional Monitors More Appropriate Than Two-Dimensional Monitors in the Three-Dimensional Analysis?

In orthognathic surgery, three-dimensional (3D) program-based analysis of 3D reconstructions of computed tomography (CT) images is commonly used, and images viewed on a monitor. The authors compared the coordinates of facial landmarks on images in a 3D program displayed on a two-dimensional (2D) (standard) or 3D monitor. Facial bone CT data from 30 patients were reconstructed in 3D. Four researchers identified 33 facial landmarks, 3 times each on 2D and 3D monitors, for each patient, by their x-, y-, and z-coordinates. The time taken to complete these identifications was measured.For each set of coordinates, the average intraclass coefficient was >0.8 for 2D and 3D analyses, as well as among 4 readers. It took on average of 2 minutes 46 seconds to identify the landmarks on the 2D monitor, compared with 2 minutes 25 seconds on the 3D monitor. The variance of individual coordinates differed when measured on 2D or 3D monitor. The landmarks affected were located near the median region of the facial area, and are important for setting the reference sagittal plane during diagnosis for orthognathic surgery. Therefore, identifying facial landmarks using 3D monitors may be helpful for conducting accurate facial diagnoses.

Fatal Progression of Gorham Disease: A Case Report and Review of the Literature.

Gorham disease is an idiopathic massive osteolysis, and maxillofacial involvement is rare. This report describes a case of a 12-year-old boy with severe progressive osteolysis in the mandible, hyoid bone, mastoid process, and cervical spine. Radiation therapy and interferon-α therapy were followed by bisphosphonate therapy. The patient died of respiratory failure. To describe the clinicopathologic features of Gorham disease of the jaws with an emphasis on the fatal types, 64 cases in the literature were reviewed (female-to-male ratio, 1:1.78; average age, 33.02 ± 19.38 yr). Most lesions were located only in the mandible or in other locations in combination with the mandible, except for 3 cases. During follow-up, there were 7 cases of disease-specific death, resulting in a mortality rate of 10.94%. The main causes of death were chylothorax, rib fractures secondary to osteolysis, or spinal fractures. Although most patients received surgical treatment (43.75%), the type of treatment was not related to prognosis.

Is Three-Dimensional Soft Tissue Prediction by Software Accurate?

The authors assessed whether virtual surgery, performed with a soft tissue prediction program, could correctly simulate the actual surgical outcome, focusing on soft tissue movement. Preoperative and postoperative computed tomography (CT) data for 29 patients, who had undergone orthognathic surgery, were obtained and analyzed using the Simplant Pro software. The program made a predicted soft tissue image (A) based on presurgical CT data. After the operation, we obtained actual postoperative CT data and an actual soft tissue image (B) was generated. Finally, the 2 images (A and B) were superimposed and analyzed differences between the A and B. Results were grouped in 2 classes: absolute values and vector values. In the absolute values, the left mouth corner was the most significant error point (2.36 mm). The right mouth corner (2.28 mm), labrale inferius (2.08 mm), and the pogonion (2.03 mm) also had significant errors. In vector values, prediction of the right-left side had a left-sided tendency, the superior-inferior had a superior tendency, and the anterior-posterior showed an anterior tendency. As a result, with this program, the position of points tended to be located more left, anterior, and superior than the "real" situation. There is a need to improve the prediction accuracy for soft tissue images. Such software is particularly valuable in predicting craniofacial soft tissues landmarks, such as the pronasale. With this software, landmark positions were most inaccurate in terms of anterior-posterior predictions.

Quantitative biomechanical analysis of the influence of the cortical bone and implant length on primary stability.

AIM: The aim of the study was to investigate the influence of cortical bone and increasing implant fixture length on primary stability. Further investigation considered the correlation between the presence of cortical bone at the marginal bone and implant stability measured by insertion torque (IT) and resonance frequency analysis (RFA), as well as implant length, were determined. MATERIALS AND METHODS: Two different types of polyurethane bone models were compared. (Group 1: with cortical and cancellous bone; Group 2: with cancellous bone only). A total of 60 external type implants (∅ 4.1, OSSTEM(®), US II(®)) with different lengths (7, 10, and 13 mm) were used. IT was recorded automatically by a computer which was connected to the Implant fixture installation device during the placement. RFA was conducted to quantify the primary implant stability quotient (ISQ). All two measurements were repeated 10 times for each group. RESULTS: All these differences were statistically significant between the two groups (P < 0.001) and intragroups (P < 0.001). Upon comparing the IT, cortical bone appears to have a greater influence on implant stability than implant lengths, whereas the RFA value strongly affects implant length rather than the presence of the crestal cortical bone. CONCLUSIONS: The quantitative biomechanical evaluations clearly demonstrated that primary implant stability seems to be influenced by the presence of a cortical plate and total surface area of the implant fixture appears to be the decisive determinant for ISQ value.

Morphologic evaluation and classification of facial asymmetry using 3-dimensional computed tomography.

PURPOSE: A systematic classification is needed for the diagnosis and surgical treatment of facial asymmetry. The purposes of this study were to analyze the skeletal structures of patients with facial asymmetry and to objectively classify these patients into groups according to these structural characteristics. PATIENTS AND METHODS: Patients with facial asymmetry and recent computed tomographic images from 2005 through 2009 were included in this study, which was approved by the institutional review board. Linear measurements, angles, and reference planes on 3-dimensional computed tomograms were obtained, including maxillary (upper midline deviation, maxilla canting, and arch form discrepancy) and mandibular (menton deviation, gonion to midsagittal plane, ramus height, and frontal ramus inclination) measurements. All measurements were analyzed using paired t tests with Bonferroni correction followed by K-means cluster analysis using SPSS 13.0 to determine an objective classification of facial asymmetry in the enrolled patients. Kruskal-Wallis test was performed to verify differences among clustered groups. P < .05 was considered statistically significant. RESULTS: Forty-three patients (18 male, 25 female) were included in the study. They were classified into 4 groups based on cluster analysis. Their mean age was 24.3 ± 4.4 years. Group 1 included subjects (44% of patients) with asymmetry caused by a shift or lateralization of the mandibular body. Group 2 included subjects (39%) with a significant difference between the left and right ramus height with menton deviation to the short side. Group 3 included subjects (12%) with atypical asymmetry, including deviation of the menton to the short side, prominence of the angle/gonion on the larger side, and reverse maxillary canting. Group 4 included subjects (5%) with severe maxillary canting, ramus height differences, and menton deviation to the short side. CONCLUSION: In this study, patients with asymmetry were classified into 4 statistically distinct groups according to their anatomic features. This diagnostic classification method will assist in treatment planning for patients with facial asymmetry and may be used to explore the etiology of these variants of facial asymmetry.

Efficacy and safety of rhBMP/ß-TCP in alveolar ridge preservation: a multicenter, randomized, open-label, comparative, investigator-blinded clinical trial.

BACKGROUND: The aim of this multicenter, randomized, open-label, comparative, investigator-blinded study was to investigate the efficacy and safety of recombinant human bone morphogenetic protein 2 (rhBMP-2) combined with ß-TCP (rhBMP-2/ß-TCP) in alveolar ridge preservation. MATERIALS AND METHODS: Eighty-four subjects from three centers were enrolled in this clinical trial. After tooth extraction, rhBMP-2/ß-TCP (n = 41, test group) or ß-TCP (n = 43, control group) were grafted to the extraction socket with an absorbable barrier membrane for alveolar ridge preservation. Using computed tomography images obtained immediately after and 12 weeks after surgery, changes in the alveolar bone height and width were analyzed for each group and compared between the two groups. RESULTS: Both the test and control groups showed a significant decrease in alveolar bone height in the 12 weeks after surgery (both groups, p < 0.0001). However, the test group exhibited a significantly lower decrease in alveolar bone height than the control group (p = 0.0004). Alveolar bone width also showed significantly less resorption in the test group than in the control group for all extraction socket levels (ESL) (p = 0.0152 for 75% ESL; p < 0.0001 for 50% ESL; p < 0.0001 for 25% ESL). There were no statistically significant differences in the incidence of adverse events between the two groups. No severe adverse events occurred in either group. CONCLUSIONS: The results of this study suggest that rhBMP-2/ß-TCP is a safe graft material that provides a high alveolar bone preservation effect in patients receiving dental extraction. TRIAL REGISTRATION: Clinicaltrials.gov , NCT02714829 , Registered 22 March 2016.

Change of lip cant after bimaxillary orthognathic surgery.

PURPOSE: The purpose of the present study was to investigate the correlations between lip cant change after bimaxillary orthognathic surgery and the ratio of lip cant change and occlusal cant change after surgery. PATIENTS AND METHODS: The subjects for the present study were obtained from a group of 25 patients who underwent bimaxillary orthognathic surgery for occlusal cant correction at the Department of Oral and Maxillofacial Surgery, Samsung Medical Center (Seoul, South Korea) from January 2000 to December 2005. To be included, a patient's chart had to contain a resting frontal facial photograph in the natural head position and a corresponding posteroanterior cephalogram in occlusion on the same day before surgery and postoperatively 6 months later. The lip cant change was assessed by the angle of each labial commissure and the bi-pupillary reference line. The occlusal canting change in the frontal plane was assessed with the angle between each maxillary first molar occlusal surface and the bi-frontozygomatic suture reference line. RESULTS: With the angular measurement, the average occlusal cant change was 3.09 degrees (standard deviation [SD] 1.05 degrees), and the average lip cant change was 1.56 degrees (SD 1.05 degrees). With the linear measurement, the average occlusal cant change was 2.41 mm (SD 2.75), and the average lip cant change was 1.18 mm (SD 0.43). The lip cant correction ratio to occlusal cant correction was 51.5% +/- 8.4% in the angular measurement and 48.8% +/- 9.1% in the linear measurement. With Pearson's correlation analysis, the Pearson correlation coefficient was 0.869 for the angular measurement and 0.887 for the linear measurement. A high correlation was shown between the occlusal cant change and lip cant change. CONCLUSIONS: Bimaxillary orthognathic surgery can correct lip cant and occlusal cant. The average amount of lip cant correction and occlusal cant correction in our study was 51.5% +/- 8.4% and 48.8% +/- 9.1%, respectively.

Retrospective analysis of the factors influencing mesiodentes eruption.

AIM: This study aimed to evaluate the factors that predict the spontaneous eruption of mesiodens. DESIGN: From the records of 431 patients (346 boys and 85 girls, average age 8.8 years) who visited Samsung Medical Center from January 2002 to December 2006, 471 mesiodentes were reviewed. The eruption rate was investigated according to the width/length ratio, angulation, location, and shape determined from periapical or panoramic radiographs. RESULTS: The regression model showed that the width/length ratio and angulation were important determinants influencing the eruption of mesiodentes (P < 0.001, Pearson's r = 0.619). The location of the mesiodentes also affected their eruption (P < 0.01). However, no significant relationship was detected between the shape and eruption rate of mesiodentes (P > 0.05). CONCLUSIONS: A lower probability of spontaneous eruption existed when the tooth had a greater angulation, shorter length, and wider width. Spontaneous eruption occurs more often when the mesiodens is located between the permanent incisors.

Acoustic analysis of vowel sounds before and after orthognathic surgery.

The purpose of this study was to compare the articular structures and vowel sounds of patients with mandibular prognathism before and after bilateral sagittal split ramus osteotomy (BSSRO). Eight patients who underwent BSSRO to correct mandibular prognathism were selected for inclusion in this study. All patients were asked to read short words (vowels), and these sounds were recorded. Every utterance was repeated twice in four different sessions before the operation and at 6 weeks, 3 months, and 6 months after the operation. The data were analysed using Praat (ver. 5.1.31), and the formant frequencies (F1, F2) of the eight vowels were extracted. PlotFormant (ver. 1.0) was used to draw formant diagrams. The F1 and F2 of front-low vowels were reduced after BSSRO, and the articulating positions of the patients shifted in a posterior-superior direction after the procedure. Additionally, the area of vowel articulation was dramatically reduced after BSSRO but increased slowly over time.

The Effects of Defect Type and Depth, and Measurement Direction on the Implant Stability Quotient Value.

The purpose of this study was to evaluate the effect of defect type and depth as well as measurement direction on implant stability in an ex vivo peri-implant bovine rib bone model. Six kinds of defects (3-wall 2.5 mm, 3-wall 5 mm, 1-wall 2.5 mm, 1-wall 5 mm, circumferential 2.5 mm, circumferential 5 mm), and control (no defect) were prepared in 14 bovine rib bones. A total of 84 defects and 14 controls were created. The same type and size of implants (4 × 10 mm) were placed in each group. The thickness of cortical bone and the insertion torque were measured for each defect, and the implant stability quotient (ISQ) value was measured 3 times from 4 different directions. The thickness of cortical bone ranged from 2.71-3.18 mm. Insertion torque decreased as the defect size increased. As the defect size for the same defect depth increased, the ISQ value decreased (P < .001). There were significant differences between the ISQ values obtained with different measurement directions only between the control and 3-wall 5 mm defect (P < .0001). The ISQ value opposite to the defect direction was higher than that in the defect direction in all 3 directions of the 3-wall and 1-wall 5 mm defects. ISQ values were influenced by defect type and depth. Loss of cortical bone reduced the stability of implants and reduced the ISQ value. Measurement direction also influenced ISQ values.

Bone cement grafting increases implant primary stability in circumferential cortical bone defects.

PURPOSE: Implant beds with an insufficient amount of cortical bone or a loss of cortical bone can result in the initial instability of a dental implant. Thus, the objective of this study was to evaluate the effect of bone cement grafting on implant initial stability in areas with insufficient cortical bone. METHODS: Two different circumferential defect depths (2.5 mm and 5 mm) and a control (no defect) were prepared in six bovine rib bones. Fourteen implants of the same type and size (4 mm×10 mm) were placed in each group. The thickness of the cortical bone was measured for each defect. After the implant stability quotient (ISQ) values were measured three times in four different directions, bone cement was grafted to increase the primary stability of the otherwise unstable implant. After grafting, the ISQ values were measured again. RESULTS: As defect depth increased, the ISQ value decreased. In the controls, the ISQ value was 85.45±3.36 (mean±standard deviation). In circumferential 2.5-mm and 5-mm defect groups, the ISQ values were 69.42±7.06 and 57.43±6.87, respectively, before grafting. These three values were significantly different (P<0.001). After grafting the bone cement, the ISQ values significantly increased to 73.72±8.00 and 67.88±10.09 in the 2.5-mm and 5.0-mm defect groups, respectively (P<0.05 and P<0.001). The ISQ value increased to more than double that before grafting in the circumferential 5-mm defect group. The ISQ values did not significantly differ when measured in any of the four directions. CONCLUSIONS: The use of bone cement remarkably increased the stability of the implant that otherwise had an insufficient level of stability at placement, which was caused by insufficient cortical bone volume.

Determination of specific interactions between glucose ligand carrying polymer and glucose transporter type-1 (GLUT-1) using different cell types.

In order to develop a biomimetic polymer for cell recognition, poly [3-O-(4'-vinylbenzyl)-D-glucose] (PVG) and different types of glucose transport (GLUT)-carrying cells, namely, HepG2 cells (GLUT-1), 3T3-L1 fibroblast cells (GLUT-1 and GLUT-4), and MIN6 cells (GLUT-2), were tested for specific interaction. To clarify the nature of interaction between PVG and the different cell types, rhodamine-B isothiocyanate (RITC)-labeled polymers were used to prove and visualize the interactions. In this study, we found that labeled polymer strongly binds to HepG2 cells. The fluorescence intensity of PVG with in the presence of HepG2 cells was found to be stronger than that of 3T3-L1 fibroblast cells (0.11 +/- 0.05) and MIN6 cells, which carry GLUT-2 (0.028 +/- 0.01); a confocal laser microscopic study confirmed this interaction. To confirm the specificity of the interaction mediated by GLUT, the cells were pretreated with phloretin, an inhibitor of GLUT-1, before adding RITC-labeled PVG polymer to the cell culture medium. This treatment suppressed the interaction of PVG with HepG2 cells and partially suppressed its interaction with 3T3-L1 fibroblast cells.

A comparative study between data obtained from conventional lateral cephalometry and reconstructed three-dimensional computed tomography images.

OBJECTIVES: The aim of this study was to verify the concordance of the measurement values when the same cephalometric analysis method was used for two-dimensional (2D) cephalometric radiography and three-dimensional computed tomography (3D CT), and to identify which 3D Frankfort horizontal (FH) plane was the most concordant with FH plane used for cephalometric radiography. MATERIALS AND METHODS: Reference horizontal plane was FH plane. Palatal angle and occlusal plane angle was evaluated with FH plane. Gonial angle (GA), palatal angle, upper occlusal plane angle (UOPA), mandibular plane angle (MPA), U1 to occlusal plane angle, U1 to FH plane angle, SNA and SNB were obtained on 2D cephalmetries and reconstructed 3D CT. The values measured eight angles in 2D lateral cephalometry and reconstructed 3D CT were evaluated by intraclass correlation coefficiency (ICC). It also was evaluated to identify 3D FH plane with high degree of concordance to 2D one by studying which one in four FH planes shows the highest degree of concordance with 2D FH plane. RESULTS: ICCs of MPA (0.752), UOPA (0.745), SNA (0.798) and SNB (0.869) were high. On the other hand, ICCs of gonial angle (0.583), palatal angle (0.287), U1 to occlusal plane (0.404), U1 to FH plane (0.617) were low respectively. Additionally GA and MPA acquired from 2D were bigger than those on 3D in all 20 patients included in this study. Concordance between one UOPA from 2D and four UOPAs from 3D CT were evaluated by ICC values. Results showed no significant difference among four FH planes defined on 3D CT. CONCLUSION: FH plane that can be set on 3D CT does not have difference in concordance from FH plane on lateral cephalometry. However, it is desirable to define FH plane on 3D CT with two orbitales and one porion considering the reproduction of orbitale itself.

Frankfort horizontal plane is an appropriate three-dimensinal reference in the evaluation of clinical and skeletal cant.

OBJECTIVES: In three-dimensional computed tomography (3D-CT), the cant is evaluated by measuring the distance between the reference plane (or line) and the tooth. The purpose of this study was to determine the horizontal skeletal reference plane that showed the greatest correlation with clinical evaluation. MATERIALS AND METHODS: The subjects were 15 patients who closed their eyes during the CT image taking process. The menton points of all patients deviated by more than 3 mm. In the first evaluation, clinical cant was measured. The distance from the inner canthus to the ipsilateral canine tip and the distance from the eyelid to the ipsilateral first molar were obtained. The distance between the left and right sides was also measured. In the second evaluation, skeletal cant was measured. Six reference planes and one line were used for the evaluation of occlusal cant: 1) FH plane R: Or.R - Or.L - Po.R; 2) FH plane L: Or.R - Or.L - Po.L; 3) F. Ovale plane R: Rt.F.Ovale - Lt.F.Ovale - Or.R; 4) F. Ovale plane L: Rt.F.Ovale - Lt.F.Ovale - Or.L; 5) FZS plane R: Rt.FZS - Lt.FZS - Po.R; 6) FZS plane R: Rt.FZS - Lt.FZS - Po.L, and; 7) FZS line: Rt.FZS - Lt.FZS. RESULTS: The clinical and skeletal cants were compared using linear regression analysis. The FH plane R, FH plane L, and FZS line showed the highest correlation (P<0.05). CONCLUSION: The FH plane R and FH plane L are the most appropriate horizontal reference plane in evaluation of occlusal cant on 3D-CT.

Segregation analysis of mandibular prognathism in Korean orthognathic surgery patients and their families.

OBJECTIVE: To investigate the existence of genetic influences on the incidence of mandibular prognathism (MP) in Korean Class III patients. MATERIALS AND METHODS: The probands consisted of 100 Class III patients with MP (51 men and 49 women; mean age, 22.1 ± 5.2 years; SNA, 81.2° ± 3.2°; SNB, 84.1° ± 3.9°) who underwent orthognathic surgery. Using three-generation pedigree charts, questionnaires, and clinical examinations, general information and information regarding MP for a total of 3777 relatives of the probands (1911 men and 1866 women) was ascertained. Familial correlations of MP between possible pairs in the pedigree were estimated. Heritability (h(2)) of MP under various models was estimated. Segregation analysis was conducted under the assumption of the nonpolygenic multivariate logistic model and finite polygenic mixed model. One-, two-, and three-susceptibility-type models were evaluated. RESULTS: Among 3777 relatives, 199 (97 men and 102 women) were affected with MP (5.3%). Correlation coefficients of MP incidence in full siblings and in parent-offspring were .2003 and .2036, respectively (all P < .001). The h(2) of MP was estimated as 21.5% after adjusting for sex and founder effects. Two- and three-susceptibility-type models showed that the general model fit better than the other models. MP incidence did not have a major gene transmission model and was influenced by numerous minor effect genes and their additive effects. CONCLUSION: These results suggest that the inherited susceptibility to MP in Korean Class III patients might be due to the summation of minor effects from a variety of different genes and/or influence of environmental factors, rather than Mendelian transmission of major genes.

Comparative study of skeletal stability between bicortical resorbable and titanium screw fixation after sagittal split ramus osteotomy for mandibular prognathism.

INTRODUCTION: Resorbable screw fixation for orthognathic surgery is widely used in oral and maxillofacial surgery and has several advantages. However, surgeons are concerned about using resorbable screws in orthognathic surgery because of possible postoperative complications such as relapse, screw fracture, and infection. The purpose of this study was to evaluate the skeletal stability of bicortical resorbable screw fixation after sagittal split ramus osteotomies for mandibular prognathism. MATERIALS AND METHODS: This study included 25 patients who underwent mandibular setback surgery fixed with resorbable screws after sagittal split osteotomy at the Department of Oral and Maxillofacial Surgery at Seoul National University Dental Hospital. Five resorbable screws (Inion CPS(®), Inion Ltd., Finland) were applied bicortically at each osteotomy site via a transbuccal approach. No rigid intermaxillary fixation was applied on the first postoperative day. Passive mouth opening exercises were allowed, using two light, rubber elastics for guidance. The control group was 25 patients fixed with four titanium screws. The follow-up period was 12-22 months (mean 17.8 months). Postoperative skeletal changes on lateral cephalometric radiographs were analyzed and compared between the two groups preoperatively, immediately postoperatively, and 6 months postoperatively. RESULTS: The average setback was 6.9 mm and no major intraoperative complications occurred. One patient experienced infection immediately after surgery that was controlled uneventfully. The data did not demonstrate any significant difference in postoperative skeletal stability between the two groups. Differences between the immediate postoperative state and 6 months after surgery were not significant. In earlier cases, especially for patients with severe mandibular prognathism, immediate postoperative elastic traction was needed for stable occlusal guidance. CONCLUSIONS: The results of this study indicate that bicortical resorbable screws offer a clinically stable outcome for the fixation of mandibular sagittal split osteotomies in mandibular prognathism. However the resorbable screws showed less stable results vertically than the titanium screws.

The effect of peri-implant bone exposure on soft tissue healing and bone loss in two adjacent implants.

PURPOSE: The purpose of this study was to evaluate the soft tissue and bone change around two adjacent implants in one-stage implant surgery. METHODS: Eleven subjects (7 males, 4 females) who were needed placement of 2 adjacent implants in the molar area were included. The two implants were placed with the platform at the level of the alveolar crest. The interproximal bone between the 2 implants was not covered with gingiva. After surgery, an alginate impression was taken to record the gingival shape and radiographs were taken to evaluate implant placement. Using a master cast, the gingival height was measured at baseline, 4 weeks, and 12 weeks. In the radiograph, the alveolar bone level was measured at the mesial and distal side of both implants at baseline and 12 weeks. RESULTS: The exposed bone was covered with gingiva at both 4 and 12 weeks. Loss of alveolar bone around implants was found in all areas. The alveolar bone level in the exposed bone area did not differ from that in the non-exposed area. CONCLUSIONS: This study showed that the alveolar bone level and gingival height around 2 adjacent implants in the exposed bone area did not differ from that in unexposed bone area.

Correlation study between distal caries in the mandibular second molar and the eruption status of the mandibular third molar in the Korean population.

OBJECTIVES: The purpose of this study was to analyze the correlation parameters between the distal caries of the mandibular second molars (M2Ms) and the eruption status of the mandibular third molars (M3Ms). STUDY DESIGN: The records of 786 patients who had their M3Ms extracted from 2002 to 2007 at Samsung Medical Center were reviewed. The distal caries of M2Ms, age, gender, angulations, impaction degree, and distance between M2M and M3M were assessed. RESULTS: Among 883 M2Ms, 152 had distal caries (17.2%, caries group). In the caries group, 79.6% of M3Ms exhibited mesial angulation between 40 degrees and 80 degrees and 82.2% of M3Ms exhibited an impaction level in which the most coronal aspect of the M3M was located superior to the occlusal surface of the M2M. The distance between M2M and M3M (between cemontoenamel junctions) was 7-9 mm for 57.2% of the caries group. CONCLUSIONS: The M3Ms under eruption status as described here could be considered for preventive extraction.

Immediate implant placement into infected and noninfected extraction sockets: a pilot study.

OBJECTIVE: This study compared the osseointegration of immediate implants in dogs in infection-free sites and in sites with periradicular lesions which were removed by simulated periradicular surgery. STUDY DESIGN: Periradicular surgeries were performed to remove intentionally induced periradicular lesions, followed by teeth extraction and immediate implant placement with (experimental group 1) or without (experimental group 2) membranes. In the control group, implants were placed at healthy extraction sockets. After 12 weeks, the animals were killed and the results of histomorphometric study were analyzed by Kruskal-Wallis test. RESULTS: Both the control and the experimental implants were clinically acceptable. The control group showed significantly higher bone-implant contact (BIC; 76.03 +/- 7.98%) than the experimental groups 1 (59.55 +/- 14.21%) and 2 (48.62 +/- 20.22%) (P < .05). CONCLUSIONS: Despite the lower BIC of the experimental groups, this pilot study showed the possibility that immediate implant placement might be successful in extraction sockets with periradicular lesions. Further studies with larger sample sizes are required.