Effect of maxillary premolar extraction on transverse arch dimension in Class III surgical-orthodontic treatment / 대한치과교정학회지

Collective changes caused by orthodontic tooth movement evaluated in a specific treatment modality could give suggestive information on the specific treatment strategy. The aim of this study was to investigate retrospectively the characteristics of the orthodontic tooth movement during surgical-orthodontic treatment in order to provide an effective presurgical orthodontic treatment planning for the maxillary premolar extraction modality in the skeletal Class III malocclusion patient. Pre- and posttreatment dental casts of skeletal Class III malocclusion patients with nonextraction (N=24) and the maxillary premolar extraction (N=31) were collected. The angulation and inclination measuring gauge (Invisitech Co. Seoul, Korea) was used to evaluate the orthodontic tooth movement. The changes in the maxillary and mandibular dental arch widths were also measured from the canines to the second molars. As a result, more palatal inclination change in the maxillary dentition was found with the premolar extraction modality than with the nonextraction modality. Linear regression analysis showed that the inter-arch width coordination was mainly due to the inclination changes of maxillary posterior teeth. We conclude that the indications and proper treatment planning for surgical-orthodontic treatment in skeletal Class III malocclusion with maxillary premolar extraction could depend partly on the magnitude of the transverse inter-arch coordination especially in the maxillary dentition.

Locus of control of surgical-orthodontic patient / 대한치과교정학회지

Surgical-orthodontic treatment is an increasingly more common dental procedure whose unique psycho-social or psychological feature has not been fairly quantified objectively. Since the treatment of a surgical-orthodontic (or orthodontic) patient is part science and part art, a subjective recognition of a patient about his or her own treatment may be more important than technical success during and after treatment. Therefore, the knowledge of the patient's underlying psychological status could be useful in the prediction of patient's response to surgical-orthodontic (or orthodontic) treatment. The purpose of this study was to investigate and evaluate the psychological difference between conventional orthodontic patient and surgical-orthodontic patient by using locus of control (LOC) examination. Locus of control scale has been proven to be extremely useful in the prediction of a variety of human behaviors. Two types of locus of control data (I-score, Internal locus of control score; E-score, External locus of control score) were obtained for 42 surgical-orthodontic patients and randomly selected 42 conventional orthodontic patients (as a control group) matched for age and gender. No statistically significant difference was observed in the scale of internal and external locus of control between the groups of surgical-orthodontic patients and conventional orthodontic patients. However, in the group of surgical-orthodontic patients, males showed lower E-score (external locus of control score, higher internal locus of control tendency) than females. The results of this study suggested that the psychological background of surgical-orthodontic patients, in contrast with that of cosmetic surgery patients, has a similar disposition with that of orthodontic patients.

Differential approaches in the maloclusion with canine impaction / 대한치과교정학회지

During diagnostic process of the orthodontic patients, it is not unusual to find canine impaction. Generally, the chief complaint of the patients is crowding or antetior crossbite which is not related with canine impaction, but sometimes they complainted delayed eruption of the canine or deviation of the adjacent teeth caused by canine impaction. Orthodondists have to make the proper treatment plan according to final treatment goals. On the following cases, two patients were diagnosed as a malocclusion with canine impaction, and were treated by different accesses, one by extraction, and the other by non-extraction each.

Three dimensional finite element analysis for reaction to molar uprighting spring / 대한치과교정학회지

The purpose of this study was to investigate the stress distribution and tooth displacement at the initial phase produced by 5 types of molar uprighting springs using finite element method. The three dimensional finite element model of lower dentition, bone and springs was composed of 5803 elements and 2071 nodes. The results were as follows: 1. In case of helical spring and root spring, intrusion of lower canine and first premolar were observed and distal tipping, translation and extrusion of lower second molar were observed. 2. In case of T-loop, modified T-loop and box loop, intrusion and distal translation of lower second premolar were observed, and the largest crown distal tipping and translation of lower second molar were observed in T-loop and the smallest were observed in box loop. 3. In case of T-loop with cinch-back, crown distal tipping and translation of lower second molar were decreased, but extrusion was also decreased. 4. With increase of activation in T-loop, mesial translation and crown distal tipping of lower second molar were increased and edentulous space was closing, but distal translation of second premolar was also increased. 5. With increase of tip-back bend in T--loop, distal tipping and translation of lower second molar were increased, but extrusion was also increased more largely.

Effects of acid etching times on enamel surface morphology and shear bond strength of orthodontic attachment to enamel / 대한치과교정학회지

The porpuse of this in vito study was to evaluate the effects of different acid etching times on the enamel srface morphology, shear bond strength and debinding failure mode of orthodontic attachment. Ninety six extracted human mandibular premolars were divided into eight groups of twelve teeth. The buccal surfaces were etched with 37% phosphoric acid 5, 10, 15, 30, 45, 60, 90 and 120 seconds, respectively. Two teeth from each group were used for scanning electron mocroscope examination. On the etched buccal aurfaces of remaining teeth, orthodontic attachments(lingual buttons) were bonded with light cured orthodontic adhesive. Twenty four hours after bonding, a Instron universal testing machine was used to determine shear bond strength of orhtodontic attachment to enamel. After debonding, bases of orthodontic attachments and enamel surfaces were examined under stereoscopic microscope to determine failure mode. Statistical analysis of the data was carried out with one way ANOVA and Duncan';s multiple range test. The results were as follows : 1. There was no statistically significant difference in shear bond strengths between the various etching times(p<0.05). 2. The failure modes of orthodontic attachments had some differences. In 5, 10 and 15 seconds etching groups, the percentage of adhesive/ enamel interface failure was higher than that of adhesive/attachment interface failure. On the contrary, 30, 45, 60, 90 and 120 seconds etching groups, the recults were reersed. 3. The etching parerns of enmel surfaces had a great variation. So, we could not find any correlation between etching pattern and bond strength. 4. The findings in this study indicate that in vito reduction of the etching time to 5 seconds maintains clinically acceptable bond strength. However, further study is required to determine the cause of failure mode in 5, 10 and 15 seconds groups.

An evaluation on the indications of bionator in Class II division 1 malocclusion / 대한치과교정학회지

The purpose of this study was to evaluate the indications of bionator in Class II division 1 malocclusion. The 48 subjects were classified into good result group(groupl) and poor result group(group2) in reference to posttreatment molar relation, posttreatment overbite and overjet, posttreatment profile, and relapse. Pretreatment lateral cephalograms were calculated and evaluated by t-test and stepwise discrminant analysis. The results were as follows; 1. In jaw bone relationship, ANB, facial convexity angle, AB to facial plane angle were significantly different between two treatment groups. In denture pattern, Ll to facial plane, Ll to A-Pog, FMIA, and Ul to facial plane were significantly different and in soft tissue profile, protuberance of lower lip and upper lip were significantly different between two treatment groups. 2. The results in according to discriminant analysis stated that Ll to facial plane, ANB, FMIA and protuberance of lower lip help prediction of treatment result of bionator. 3. 3 major influential variables were obtained by stepwise discriminant analysis - Ll to facial plane, articular angle and ANB difference. And Fisher discriminant function was made by these three major variables.

A study on the mandibular movement changes after orthognathic surgery in skeletal Class III patients / 대한치과교정학회지

The purpose of this study was to evaluate changes in mandibular movement patterns after orthognathic surgery in skeletal Class III patients. The sample consisted of 20 Class III malocclusion patients(9 males, 11 females). Just before and after(2-7months) surgery, maximum opening & closing movement, mandibi3 ar border movement on sagittal, frontal and horizontal planes were recorded using Sirognathograph & BioPak EGN. On each record, 21 items were measured and statistically analyzed. The results were as follows 1. Angle of protrusive movement on sagittal plane showed greatest change after surgery. Also, as the incisal guidance was established by surgery, straight path of protrusive movement became curved line. 2. Maximum opening distance and maximum antero-posterior distance on maximum opening & closing movement, maximum opening distance on sagittal plane, angle of left lateral excursion on frontal plane were statistically significant after snrgery(p<0.01). 3. Maximum width of lateral excursion on frontal plane, distane of right lateral excursion and angle of maximum left lateral excursion on horizontal plane were statistiraily significant after surgery(p<0.05). 4. Maximum opening distance and maximum antero-posterior distance on maximum opening & closing movement showed significant differences according to post-surgical time(p<0.05). More recovery of range of movement occured in 5-7month group than in 2-3month group. 5. As the occlusal interferences were removed by orthognathic surgery, irregular opening & closing path became smooth curve.

Evaluation of internal derangement of TMJ by analyzing TMJ sounds / 대한치과교정학회지

The purpose of this study was to evaluate the diagnostic value of SONOPAK* in internal derangement of TMJ by comparing the spectral analysis data of TMJ sounds recorded by SONOPAK with the results of MRI. From the patients who came to Department of Orthodontics, Seoul National University Dental Hospital for treatment of malocclusion, eighteen adult patients (five males and thirteen females) with TMD symptoms were selected. After joint sounds were checked by a pediatric stethoscope, they were recorded and analyzed by the SONOPAK. The spectral analysis of the SONOPAK provided SONOPAK INTERPRETATION data about the stage of internal derangement, which were compared with the results of MRI. Among the patients whose disc positions were diagnosed as 'normal' by MRI, there were no false positive diagnosis by the SONOPAK INTERPRETATION. But in the cases of anterior disc displacements(reducible and/or nonreducible), most of SONOPAK INTERPRETATION data did not coincide with MRI results. In conclusion, it is not adequate to try to differentiate reducible and non-reducible anterior disc displacements on the basis of joint sounds. And it is recommended not to determine the stage of internal derangement according to the nature of sounds. We suggest that the diagnostic value of the SONOPAK will be enhanced when clinicians combine some other informations such as clinical signs/symptoms and other supplementary diagnostic tools), and that more data be incoporated into the SONOPAK INTERPRETATION software.

Application of genioplasty in malocclusion with chin deformity / 대한치과교정학회지

The chin is one of the factors which express human character, and appropriately protruding chin is very important to harmonious profile. the purpose of genioplasty is to reshape the chin and improve the facial esthetics which is one of the purposes of orthodontic treatment. It can be classified as augmentation genioplasty which enlarge the chin vertico-horizontally and reduction genioplasty which smallen it. The examples to apply this procedure are as follows. 1. advancement of retruded chin 2. reduction of chin prominence 3. control of chin vertical dimension 4. correction of asymmetry

An evaluation of treatment effects of bionator in Class II division 1 malocclusion by finite element method / 대한치과교정학회지

The purpose of this study was to evaluate treatment effects of bionator in Class II division 1 malocclusion by FEM(Finite Element Method). The 73 subjects were classified into good result group and poor result group in reference to posttreatment molar relation, posttreatment overbite and overjet, posttreatment profile, and relapse. Pretreatment and posttreatment lateral cephalograms were taken and FEM was performed. The results were as follow; 1. There was no statistical significance in treatment changes between the sexes, and between the treatment result groups. 2. Treatment changes were not significantly different among the age groups. 3. The effect of treatment period groups on skeletal and dentoalveolar changes were analyzed using ANOVA. Body of maxilla, upper incisor, anterior face, ramus, upper anterior face, lower anterior face and treatment effect were correlated with the treatment period, but correlation coefficients were low. 4. The results of present investigation confirm that Class II bionator can assist in the correction of Class II division 1 malocclusion, mainly due to dentoalveolar changes. 5. There is significant difference in skeletal and dentoalveolar pattern between good result group and poor result group. In poor result group, maxilla was relatively downward and backward rotated, mandible was relatively backward rotated, upper incisor was in relatively lingual position, lower incisor was in relatively labial position.

Three-dimensional finite element analysis of the phenomenon produced during retraction of four maxillary incisors / 대한치과교정학회지

This study was designed to investigate force systems and tooth movements produced by retraction archwire during retraction of four maxillary incisors after the maxillary canine retraction into the maxillary first premolar extraction space using the computer-aided three-dimensional finite element method. A three-dimensional finite element model, consisting of 2248 elements and 3194 nodes, was constructed. The model consisted of maxillary teeth and surrounding periodontal membranes, .022" x .028" -slot brackets, and 5 types of retraction archwires(.019" x .025" stainless steel archwire) modeled using the beam elements. The contact between the wire and the bracket slot was modeled using the gap elements because of the non-linear elastic behaviors of the contact between them. The forces and moments, and displacements produced by retraction archwire were measured at various conditions to investigate the difference according to types of loops, magnitudes of activation force, gable angle, and anterior lingual root torque. The results were expressed quantitative and visual ways in the three-dimensional method. The following conclusions can be drawn from this study: 1. When the tear-drop loop archwire was activated, the mesio-distal and lingual translational movements of the teeth helped to close the extraction space, but unwanted movements of the teeth including intrusions and extrusions, and rotational movements in each direction occurred. 2. Activation of T-loop archwire compared with those of other types of retraction archwires produced the least translational movements of the teeth helped to space closure and also the least unwanted movements of the teeth. 3. Increasing amount of activation in the tear-drop archwire led not only to increase of translational movements of the teeth helped to space closure, but also to increase of unwanted movements of the teeth. 4. Addition of gable bend in the tear-drop archwire helped anterior teeth to translational movements in the mesio-distal direction, but increased unwanted movements of the teeth. 5. Addition of anterior lingual root torque in the tear-drop archwire helped central and lateral incisor to improve their facio-lingual inclination, but increased unwanted movements of the teeth.

Study of craniocervical posture and craniofacial morphology in Korean young adults / 대한치과교정학회지

The purpose of this study was to estimate correlations of craniocervical posture and craniofacial morphology in Korean young adults. The sample consisted of 50 young adults (25 males and 25 females) who had good profile and Class I molar relationship. The analysis of craniocervical posture and craniofacial morphology was performed on lateral cephalograms taken in natural head position. The results were as follows; 1. The mean and the standard deviation of postural and morphologic variables were obtained. 2. Korean young adult had cervical lordosis of which degree between OPT and CVT shows 3.55+/-2.58degrees 3. Craniocervical posture and each of vertical ratio, facial prognathism, mandibular rotation showed high correlation. 4. Correlation coefficients between postural variables and each of intermaxillary relation, anteroposterior ratio were low. 5. The head positioning error of natural head position was smaller than the inter-individual variability of postural variables.

Recognition of malocclusion and orthodontic treatment need of 7~18 year-old korean adolescent / 대한치과교정학회지

The purpose of this study was to evaluate self perception of occlusal status and recognition for ortho?dontic treatment as well as the prevalence of orthodontic treatment need objectively and subjectively. 3979 (male 2107, female 1872) school students of age 7~18 were analyzed by questionnaire and clinical examination and the results were as follows. 1. Perception of occlusal status on one's own was more generous than that of orthodontist's and it was affected by the factors such as age, patterns of malocclusion. 2. Recognition of subjective need for orthodontic treatment was more generous than that of objective need for the treatment, and factors such as age and sex of patient, parents' age and rate of education, income, occupation, classification of malocclusion and regional discrepancy were influenced. 3. Negative aspect of orthodontic treatment was influenced by the environmental factors. 4. A survey of want for orthodontic treatment showed one's alteration in recognition of the occlusal status with age and esthetic component was much more emphasized than functional component. 5. The multivariate discriminanat analysis for orthodontic treatment group showed that mother's rate of education, classification of malocclusion, demographic characteristics were critical in the determination of treatment group. 6. Test of inter-examiner reliability showed moderate coincidence.

Effect of various cytokines on the production of prostaglandin E2 leukotriene B4 and collagenase in human periodontal ligament fibroblasts in vitro / 대한치과교정학회지

This experiment was designed to study possible roles of interleukin-1beta, interleukin-6 and tumor necrosis factor-alpha in bone remodeling by measuring their effects on PGE2, LTB4 and collagenase production when they were administered to human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were collected from first premolars extracted for orthodontic treatment. They were incubated in the environment of 37degrees C, 5% CO2, and 100% humidity. They were treated with 0.25% trypsin-EDTA solution and centrifuged. PDL cells in the fifth to seventh passage were used for the experiment. Cells were seeded onto the culture dishes and when they were successfully attached, human recombinant interieukin-lbeta, interleukin-6, and tumor necrosis factor-alpha were administered, alone or in combination. They were incubated for 4, 8 and 24 hours and the levels of PGE2, LTB4 and collagenase released into the culture media were assessed by enzymeimmunoassay and collagenase activity assay. The conclusions are as follows: 1. IL-1beta and TNF-a were very active in stimulating the production of PGE2 and collagenase by human periodontal ligament fibroblasts, while IL -6 increased LTB4 production. 2. IL-1beta significantly increased PGE2 , but LTB4 production was not increased. IL-1beta is thought to act mainly via the cyclooxygenase pathway of arachidonic acid metabolism. 3. IL-6 tended to inhibit IL- 1beta in the production of PGE2 and collagense whereas IL-6 and TNF-alpha showed additive effect in the level of PGE2. The above cytokines increased the release of at least one of PGE2, L TB4 and collagenase. It suggests that cytokines are involved in bone remodeling process by stimulating PDL fibroblasts to produce various bone-resorptive agents. The roles of cytokines in bone remodeling as a whole would need further study.

Three-dimensional finite element analysis on reciprocal action by torque application in maxillary archwire / 대한치과교정학회지

This study was designed to investigate the reciprocal movement which was derived form application of active torque in ideal arch wire by computer-aided three-dimensional finite element analysis of maxillary teeth and surrounding periodontal ligament composed of 2617 elements and 3725 nodes. Ideal arch wire model was also made using the beam elements and the contact between the wire and the bracket slot was made using the gap element. In this study non-linear elastic behaviors of contact between the wire and the bracket slot were considered on. We put the active torque between the lateral and central incisor and between the second premolar and the first molar with/without cinch-back. The results were expressed by quantitative and visible ways. The findings of this study were as follows: 1. Reciprocal actions to active torque were complex system consisting of a combination of counter-torque, bucco-lingual linear displacement and tipping, rotation of the teeth, occluso-gingival linear displacement. 2. When active anterior crown labial torque was applied, crown labial tippings of the lateral were the greatest, and those of the central incisor was the next. Crown lingual tippings of the canine and the first premolar, mesial rotations and extrusion of the lateral and distal rotations and intrusion of the canine occurred. When anterior torque with the cinch-back was applied, amount of crown labial tippings of the lateral and central incisor were reduced. Amount of crown lingual tipping of the canine and the first premolar were increased. Mesial tippings and mesial rotations of the second molar occurred. 3. When active posterior crown lingual torque was applied, crown lingual tippings of the first molar were the greatest, and crown labial tippings of the second premolar and the first premolar were the next, the crown lingual tipping of the second molar were a little. Mesial rotations of the second premolar occurred but those of the first premolar didn't occurred.

Analysis of skeletal facial asymmetry with submentovertex cephalometric radiograph / 대한치과교정학회지

This study was performed to investigate the midline having the least difference between the right and left structure among the lines that had been used in the submentovertex analysis and secondarily to know the distribution of asymmetry and it's degree existed normal persons and asymmetric patients. The subjects consisted of 40 normal adult patients and 40 asymmetric adult patients. The computerized anaylses from submentovertex cepholometric radiograph were carried out. The results were as follows; 1. The right and left difference of the perpendicular bisecting line between right and left foramen spinosum was larger than the other midlines in the anterior area and it was decreased gradually as it progressed posteriorly. Specially the difference of this line was the smallest in the area where there was foramen spinosum. 2. The right and left difference of the perpendicular line through crista gali to the line between right and left foramen spinosum was smaller than the other midlines in the anterior area and it was increased gradually as it progressed posteriorly. 3. The right and left difference of the line between crista gali and anterior process of atlas was constant and smaller than the other midlines. 4. Asymmetry was a common finding in both normal and asymmetry group and left or right dominance of asymmetry was not statistically significant. 5. When the analyses were undertaken after submentovertex radiogram was divided into cranial base, upper face and lower face, the more inferior part showed relative asymmetry than the more superior part.

Study of recognition of malocclusion and orthodontic treatments / 대한치과교정학회지

In this study, in order to survey the effect on public recognition in malocclusion and orthodontic treatment by brochures made by Korean orthodontic association, sample were divided into control and experimental group and a questionnaire was inguired and the results were as follows: 1. In the experimental group, frequency of recognition for the need of orthodontic treatment was high, and this indicates dental health behavior and recognition can be inspired by adequate giving of information. 2. Between the control and the experimental group, patterns of the negative opinion was different, and especially the demand for specific orthodontic treatment can be influenced by the content of brochures. 3. The brochures used in this study can call attention to develop the orthodontic aspect for the malocclusion, hereafter more systemic and active measures for development of public dental behavior and recognition should be needed.

Change in concentration of salivary streptococcus mutans following the application of varnish containing chlorhexidine in orthodontic patients / 대한치과교정학회지

Dental caries is one of the most prevalent dental diseases in Korea and its prevention is very important in orthodontic therapy. For the cleansing action of saliva itself and/or tooth-brushing is lowered in patient with fixed orthodontic appliance, oral hygiene of the patient becomes worse, which provides more favorable environment for micro-organisms. Chlorhexidine, one of the series of bisguanide, has been reported to be strong antimicrobial agent and very effective on Streptococcus mutans. The purpose of this study is to evaluate the possibility of chlorhexidine as a anticariogenic agent in fixed orthodontic therapy. We used the varnish containing chlorhexidine as a main ingredient for the chemical control of salivary S.mutans in patients with fixed appliance therapy. We applied the varnish containing chlorhexidine on the labial and interproximal surface of the teeth before bonding and banding teeth of our patients(N=20) and compared to control group patients(N=20). Before the application of chlorhexidine varnish and four times periodically after the completion of fixed appliance set-up, we sampled saliva of both group patients and incuvate S.mutans for 24 hours. In the culture study of sampled saliva, counting the number of S.mutans colonies, we founded as follows: 1. In patients with fixed appliance therapy, the risk of dental caries increase when it compared to that of preorthodontic treatment; The number of salivary S.mutans increase in patient's oral cavity. 2. The experimental agent that contain chlorhexidine is effective to reduce the number of salivary S.mutans. 3. For the effect of this agent is not ever-lasting, periodical application is needed, and additional study for economical interval and number of application is needed.

Hard and soft tissue changes after orthognathic surgery of mandibular prognathism / 대한치과교정학회지

The purpose of the study is to estimate hard and soft tissue changes after orthognathic surgery for the correction of the mandibular prognathism and to describe interrelationship and ratios of soft and hard tissue changes. The presurgical and postsurgical lateral cephalograms of 31 treated patients(17 males and 14 females) was used ; these patients had received combined orthodontic-surgical treatment by means of a bilateral sagittal split ramus osteotomy. Their ages ranged from 16 to 31 years and mean age was 21.4 years. A computerized cephalometric appraisal was developed and used to analyse linear and angular changes of skeletal and soft tissue profile. The statistical elaboration of the data was made by means of SPSS/PC+. The results of the study were as follows: 1. The correlations of soft and hard tissue horizontal changes were significantly high and the ratios were 97% at LI, 107% at ILS, and 93% at Pog'. 2. The correlations of vertical changes at Stm, LI and horizontal changes at Pog were high (26 %) and at the other areas were not statistically high. 3. The correlations of soft ad hard tissue vertical changes were not significantly high in all areas except Gn' (30%) and Me' (56%). 4. The soft tissue thickness was significantly decreased in upper lip and increased in lower lip, and the amount of changes after surgery was reversely correlated with initial thickness. 5. The facial convexity was increased and relative protrusion of upper lip was increased and that of lower lip was decreased. 6. The upper to lower facial height(G1-Sn/Sn-Me') was increased and upper to lower jaw height(Sn-Stms/Stmi-Me') was increased.

A study of the software on scheduling, diagnosis, growth and treatment analysis / 대한치과교정학회지

It is prerequisite of orthodontists to diagnose malocclusion correctly and make treatment plans accurately for treating maloccluded patients efficiently and earning more stable and better results. Recently computers were introduced in orthodontic diagnosis steps, which enabled orthodontists to get more precise diagnosis, to make more accurate treatment planning and to provide better orthodontic cares for more patients. The authors studied on the diagnostic analysis methods which have been used frequently in Korea and made a diagnostic computer program including the horizontal and/or vertical measurement of length, degrees and proportions in lateral cephalometric radiographs, the analysis of the skeletal and soft-tissue features and the evaluation of the treatment results. We also made a scheduling program for arrangement and management of patients. 40 skeletal and 24 soft-tissue landmarks were selected in a lateral cephalometric radiographs. The available analysis methods in this program are Angular analysis, Linear analysis, Ricketts analysis, Profilogram , Steiner analysis, Tweed analysis, MacNamara analysis, Open bite analysis, Kim's diagnosis, Skeleto-dental cephalometric analysis and Height & weight analysis. We suggested that this diagnostic computer program make it possible for orthodontists to get more rapid and accurate diagnostic analysis and treatment planning and for patient to earn better and more efficient orthodontic service.