Odontodisplasia Regional y Agenesia de Premolares. Reporte de un Caso / Regional Odontodysplasia and Premolar Agenesis. Case Report

RESUMEN: La odontodisplasia regional (OR) es una alteración en el desarrollo, no hereditario y que afecta tanto la dentición temporal como la dentición definitiva. Involucra a los tejidos mesodérmicos y ectodérmicos de los dientes lo que es condescendiente con hallazgos clínicos, radiográficos e histológicos. Su etiología aun es desconocida y se presenta mayoritariamente en mujeres. Clínicamente puede afectar al maxilar, a la mandíbula o ambas arcadas pero generalmente solo se ve comprometida una ellas, principalmente el más afectado es el hueso maxilar. Radiográficamente se observa una pobre diferencia entre los tejidos del esmalte y la dentina, siendo tejidos menos radiopacos que su contraparte sana generando un aspecto descrito como "diente fantasma". Histológicamente se observan zonas hipocalcificadas del esmalte con un orden de prismas irregulares mientras que la dentina se observa con un número reducido de túbulos dentinarios y de consistencia más fibrosa en su zona coronal. El tratamiento de la OR es controversial ya que su incidencia es baja y la literatura al respecto no es clara. El objetivo de este manuscrito, fue reportar un caso de OR y revisar la literatura relacionada. Presentamos un caso de OR en una paciente de 12 años que presenta ausencia de los dientes 2.4, 2.5 y 2.6; restos radiculares y agenesia de los dientes 3.5 y 4.5. Se describirán sus aspectos clínicos, radiográficos e histológicos. Se realizó una búsqueda sistemática en las siguientes bases de datos: Clínical key, Science Direct, PubMed y SciELO.

ABSTRACT: Regional odontodysplasia (RO) is a variation in the development; it is not hereditary and it affects both deciduous and permanent dentition. It involves the mesodermal and ectodermal tissues of dental pieces, and coincides with clinical, radiographic and histological findings. Its etiology is still unknown and it reportedly occurs mostly in women. Clinically it can affect the maxilla, mandible or both arches but generally only one is compromised, mainly the maxilla which is affected the most. Radiographically there is limited difference between enamel and dentin tissue, which is less radiopaque than their healthy counterpart, generating an aspect described as "phantom tooth". Histologically hypocalcified areas of the enamel are observed with an irregular order of prisms while the dentine is observed with a reduced number of dentinal tubules and more fibrous consistency in the coronal area. RO treatment is controversial since its incidence is low and the literature on these events is not clear. The aim of this manuscript was to report a case of RO and review related literature. We present a case of RO in a 12-year-old patient who presents absence of parts 2.4.2.5 and 2.6; radicular remains and agenesis of parts 3.5 and 4.5. Its clinical, radiographic and histological aspects are described. A systematic search was carried out in the following databases: Clinical key, Science Direct, PubMed and SciELO.

Influence of non carious cervical lesions depth, loading point application and restoration on stress distribution pattern in lower premolars: a 2D finite element analysis / Influência da profundidade da lesão cervical não cariosa, ponto de aplicação de carga e restauração no padrão de distribuição de tensões em pré-molares inferiores: 2d-análise por elementos finitos

The aim of this study was to analyze the biomechanical behavior of lower premolars regarding the non-carious cervical lesion (NCCL) depth, load type and restoration status, using finite element analysis. Twodimensional virtual model simulating a healthy lower premolar were created using the CAD software. Based on this image, five models were generated: healthy (H), three types of NCCLs: small lesion (SL ­ 0.5 mm deep), medium lesion (ML ­ 1.0 mm), deep lesion (DL ­ 1.5 mm), and restored lesion (RL). The models were export to a CAE software (ANSYS Finite Element Analysis Software), the areas of all structures were plotted and each model was meshed using a control mesh device. All of the virtual models were subjected to two occlusal load types, (100N each): occlusal load (OL) and buccal load (BL) on buccal cusp. The magnitude and the stress distribution were obtained using the von Mises and maximum principal stress criteria (1), in MPa. The quantitative analysis of stress (MPa) was identified at three points of the NCCLs: enamel surface on its upper wall , dentin at the bottom wall and dentin on the lower wall. The results showed a direct relation between sequential removal of cervical structure and higher stress concentration for any groups and for both loads types. For OL the highest value of stress was 8.8 MPa for DL on upper wall of NCCLs.The BL exhibited higher stress values in comparison to the OL for all models.In addtion, the BL was responsible for providing the highest stress accumulation on the bottom wall, 38.2 MPa for DL. The restoration with composite resin was able to restore a stress distribution close to the healthy model, for both load types. In conclusion, the extent of non-carious cervical lesion and loading conditions influenced the stress distribution pattern of lower premolar. The outer load seems to be more critical in affecting the biomechanical behavior of lower premolars, regardless of the lesion size. The restoration of NCCLs with composite resin appears to recover the biomechanical behavior, similar to healthy model.

O objetivo desse estudo foi analisar o comportamento biomecânico de pré-molares inferiores em relação a profundidade da lesão cervical não cariosa (LCNC), tipo de carregamento e condição da restauração, utilizando a análise por elementos finitos. Modelo virtual bidimensional simulando um pré molar inferior hígido foi criado utizando o software de CAD.A partir dessa imagem, cinco modelos foram gerados: hígido (H), três tipos de LCNCs-lesão rasa (SL-0.5 mm de profundidade), lesão média (ML-1.0mm), lesão profunda (DL-1.5mm), e lesão restaurada (RL). Os modelos foram exportados para o software de CAE (ANSYS Software de Análise por Elementos Finitos), as áreas de todas as estruturas foram plotadas e cada modelo foi malhado utilizando um dispositivo controle de malha.Todos os modelos virtuais foram submetidos a dois tipos de carregamento oclusal (100N cada): carregamento oclusal (OL) e carregamento externo (BL) na cúspide vestibular. A intensidade e a distribuição das tensões foram obtidas utilizando os critérios de von Mises e tensão máxima principal (1),em Mpa. A análise quantitativa das tensões (MPa) foi identificada em três pontos das LCNCs: parede superior em esmalte, parede de fundo em dentina e parede inferior em dentina. Os resultados apresentaram uma relação direta entre a remoção sequencial de estrutura na região cervical e os maiores valores de concentração de tensões para todos os grupos e para os dois tipos de carga. Para OL, o maior valor de tensão foi 8.8 MPa para DL na parede superior da LCNCs. O BL exibiu maiores valores de tensão em comparação ao OL para todos os modelos. Além disso, BL foi responsável por promover o maior acúmulo de tensão na parede de fundo, 38.2 MPa para DL. A restauração com resina composta foi capaz de restaurar uma distribuição de tensões similar a do modelo hígido, para ambos os tipos de carga. Em conclusão, a extensão da lesão e o tipo de carregamento influenciaram no padrão de distribuição de tensões de pré-molares inferiores. A carga externa parece ser mais crítica para afetar o comportamento biomecânico de pré-molares inferiores, independente do tamanho da lesão. A restauração das LCNCs com resina composta, parece recuperar o comportamento biomecânico similar ao do modelo hígido.

Relación entre foramen apical, ápice anatómico y ápice radiográfico en premolares maxilares / Relationship between apical foramen, anatomic apex and radiographic apex in maxillary premolars

Objetivo: determinar la relación entre la localización del foramen apical, el ápice anatómico y el ápice radiográfico en premolares maxilares. Método: estudio descriptivo, transversal. La muestra fue de 106 dientes premolares maxilares con los ápices maduros y recién extraídos. El muestreo fue no probabilístico por criterio. Se seleccionaron los dientes según los criterios de inclusión y exclusión, se hicieron aperturas de acceso y tomas radiográficas, se midió la distancia del foramen apical y el ápice anatómico a través del microscopio óptico con la visualización del instrumento y una reglilla milimetrada. Para el análisis de la información se utilizaron pruebas de estadística descriptiva y el test Chi2. Se asumió un límite de decisión de 0,05. Resultados: en el 67 por ciento de los premolares evaluados el ápice radiográfico se encontró en posición apical y en el 50 por ciento de estos el ápice anatómico se encontró en esa misma posición. El foramen apical, con relación al ápice anatómico, se encontró en el 51 por ciento. En 30 dientes coincidió la posición del foramen y el ápice anatómico en apical y 11 dientes presentan una posición apical del ápice anatómico y en distal el foramen apical. En cuanto a la relación de la posición del ápice anatómico y el ápice radiográfico, 48 de los dientes evaluados coincidieron en apical y 19 en distal con un valor p < 0,05. Conclusiones: de acuerdo con los datos obtenidos en el presente estudio se puede afirmar que existe relación entre la posición del ápice anatómico y el foramen apical lo que debe ser tomado en cuenta por el odontólogo durante la determinación de la longitud de trabajo en dientes premolares maxilares(AU)

Objective: to determine the relationship between the location of the apical foramen and the anatomic and radiographic apex in maxillary premolars. Method: a descriptive study. Samples were 106 maxillary premolars with mature apices and freshly extracted. The sampling was not probabilistic criterion. Teeth were selected according to the inclusion and exclusion criteria, access openings were made and radiographs, we measured the distance from the apical foramen and anatomic apex through the optical microscope instrument display and a slide millimeter. For data analysis tests were used descriptive statistics and the Chi2 test. Statistical significance level was set at p < 0.05. Results: it was found that the radiographic apex was 67 percent in an apical position, also, the anatomic apex by 50 percent in the same position. The apical foramen was found in 51 percent compared to the anatomic apex. 30 teeth matched the position of the foramen and anatomical apex and 11 apical teeth have an apical position of the distal anatomic apex and apical foramen. As for the relationship of the position of the anatomical apex 48 and radiographic apex of the teeth coincide evaluated in the distal apical and 19 with a p < 0.05. Conclusion: according to data obtained in this study, we can say there is a relationship between the anatomical position of the apex and apical foramen which must be taken into account by the dentistry and the specialist during establishing the length of work in bicuspid teeth(AU)

The effect of overlaying titanium mesh with collagen membrane for ridge preservation

PURPOSE: The aim of this study was to determine the effect of overlaying titanium mesh (TM) with an adjunctive collagen membrane (CM) for preserving the buccal bone when used in association with immediate implant placement in dogs. METHODS: Immediate implant placements were performed in the mesial sockets of the third premolars of five dogs. At one site the TM was attached to the fixture with the aid of its own stabilizers and then covered by a CM (CM group), while the contralateral site received only TM (TM group). Biopsy specimens were retrieved for histologic and histomorphometric analyses after 16 weeks. RESULTS: All samples exhibited pronounced buccal bone resorption, and a high rate of TM exposure was noted (in three and four cases of the five samples in each of the TM and CM groups, respectively). A dense fibrous tissue with little vascularity or cellularity had infiltrated through the pores of the TM irrespective of the presence of a CM. The distances between the fixture platform and the first bone-implant contact and the bone crest did not differ significantly between the TM and CM groups. CONCLUSIONS: Our study suggests that the additional use of a CM over TM does not offer added benefit for mucosal healing and buccal bone preservation.

En-masse retraction with a preformed nickel-titanium and stainless steel archwire assembly and temporary skeletal anchorage devices without posterior bonding / 대한치과교정학회지

OBJECTIVE: To evaluate the therapeutic effects of a preformed assembly of nickel-titanium (NiTi) and stainless steel (SS) archwires (preformed C-wire) combined with temporary skeletal anchorage devices (TSADs) as the sole source of anchorage and to compare these effects with those of a SS version of C-wire (conventional C-wire) for en-masse retraction. METHODS: Thirty-one adult female patients with skeletal Class I or II dentoalveolar protrusion, mild-to-moderate anterior crowding (3.0-6.0 mm), and stable Class I posterior occlusion were divided into conventional (n = 15) and preformed (n = 16) C-wire groups. All subjects underwent first premolar extractions and en-masse retraction with pre-adjusted edgewise anterior brackets, the assigned C-wire, and maxillary C-tubes or C-implants; bonded mesh-tube appliances were used in the mandibular dentition. Differences in pretreatment and post-retraction measurements of skeletal, dental, and soft-tissue cephalometric variables were statistically analyzed. RESULTS: Both groups showed full retraction of the maxillary anterior teeth by controlled tipping and space closure without altered posterior occlusion. However, the preformed C-wire group had a shorter retraction period (by 3.2 months). Furthermore, the maxillary molars in this group showed no significant mesialization, mesial tipping, or extrusion; some mesialization and mesial tipping occurred in the conventional C-wire group. CONCLUSIONS: Preformed C-wires combined with maxillary TSADs enable simultaneous leveling and space closure from the beginning of the treatment without maxillary posterior bonding. This allows for faster treatment of dentoalveolar protrusion without unwanted side effects, when compared with conventional C-wire, evidencing its clinical expediency.

Three-dimensional finite element modeling of a maxillary premolar tooth based on the micro-CT scanning: a detailed description / 华中科技大学学报（医学）（英德文版）

This study describes the details of how to construct a three-dimensional (3D) finite element model of a maxillary first premolar tooth based on micro-CT data acquisition technique, MIMICS software and ANSYS software. The tooth was scanned by micro-CT, in which 1295 slices were obtained and then 648 slices were selected for modeling. The 3D surface mesh models of enamel and dentin were created by MIMICS (STL file). The solid mesh model was constructed by ANSYS. After the material properties and boundary conditions were set, a loading analysis was performed to demonstrate the applicableness of the resulting model. The first and third principal stresses were then evaluated. The results showed that the number of nodes and elements of the finite element model were 56 618 and 311801, respectively. The geometric form of the model was highly consistent with that of the true tooth, and the deviation between them was -0.28%. The loading analysis revealed the typical stress patterns in the contour map. The maximum compressive stress existed in the contact points and the maximum tensile stress existed in the deep fissure between the two cusps. It is concluded that by using the micro-CT and highly integrated software, construction of the 3D finite element model with high quality will not be difficult for clinical researchers.

Evaluación de la resistencia a la tracción de tres dispositivos ortodóncicos instalados con resina autopolimerizable en premolares: un estudio in vitro / Evaluation of the tensile strength of three orthodontic devices installed with self-curing resin in premolars: an in vitro study

Las tracciones orto-quirúrgicos son técnicas ampliamente utilizadas en odontología para la reposición en oclusión de dientes que incluidos. Nuestro objetivo fue evaluar la resistencia a la tracción de tres tipos de dispositivos de tracción. En este estudio in vitro fueron utilizados 45 premolares sanos, conservados inicialmente en suero fisiológico al 0,9%; fueron divididos en tres grupos, de los cuales 15 recibieron la instalación de brackets, 15 recibieron botones ortodóncicos y 15 recibieron la instalación de mallas. La adhesión fue realizada con resina de autocurado y en todos ellos se instaló un alambre ortodóncico de 0,30mm; los dientes fueron fijados con resina acrílica y almacenados en suero fisiológico al 0,9% por 72 horas. A continuación fueron sometidos a test de tracción mecánica, con una tracción máxima de 50N, siendo analizados con del programa Logger Pro®. Los brackets demostraron mayor resistencia a la tracción (44,6N), seguidos por los botones y finalmente por las mallas (32N). La principal área de falla fue la interface dispositivo/resina, siendo las mallas las que presentaron el mayor índice de fracaso (66%). Ningún alambre presentó ruptura en los análisis ejecutados. Las mallas presentan los resultados mecánicos más pobres cuando son comparados con botones y brackets; el área de ruptura más frecuente corresponde a la interface dispositivo/resina

Ortho-surgical tractions are techniques very used in dentistry for the reposition in occlusion of embedded teeth. The aim of this research was to evaluated the resistance to traction of three kind of devices used in a traction technique. In this in vitro research was used 45 bicuspid, initially maintained in saline solution (0,9%); were formed three groups, where 15 received brackets, 15 received button and 15 received mesh. The adhesion was do it with self-curing resin and in all of them was installed an orthodontics wire of 0,30 mm; the teeth was fixed with acrylic resin and maintained in saline solution (0,9%) for 72 hours. Follow that, the samples were submitted to mechanical traction test, with maximum traction of 50N, being analyzed with Logger Pro software. The brackets show more resistance to the traction (44,6N), follow that button and finally for mesh (32N). The principal areas of fracture was to device/resin interface, presented the mesh a more failure percentage (66%). Non wire presented fracture in the analyses. The mesh present poor results when compared to buttons and brackets; the more prevalent area failure was device/resin interface

Comparative evaluation of shear bond strength of different bracket base designs in dry and wet environments.

One hundred and thirty five extracted premolars were selected and bonded with three types of brackets with different bracket base designs viz. Gemini (foil mesh), Miniature twin (Laser etched) and Mini Dynalocks (Integral base). These brackets were bonded with Transbond XT adhesive using two types of primers viz. Conventional Transbond XT in dry conditions and M.I.P in dry and wet environments. The specimens were tested for SBS using Instron machine at C.I.P.E.T. (Amritsar), Punjab. Results were statistically analyzed. RESULTS AND DISCUSSION: The Miniature twin brackets revealed higher SBS values as compared to Gemini and Mini Dynalock in dry and wet conditions. All the groups showed higher SBS values in dry conditions as compared to wet conditions respectively. The Gemini and Mini Dynalock brackets showed very little difference of SBS values. CONCLUSION: Miniature twin brackets with laser etched bracket base in dry and wet environments have revealed the highest SBS values. All the groups have revealed clinically acceptable SBS value of above 8 MPa in moist conditions.

The influence of combining composite resins with different elastic modulus on the stress distribution of Class V restoration: a three-dimensional finite element study / 대한치과보존학회지

This study was to investigate the influence of combining composite resins with different elastic modulus, and occlusal loading condition on the stress distribution of restored notch-shaped non-carious cervical lesion using 3D finite element (FE) analysis. The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. A notch-shaped cavity was modeled and filled with hybrid, flowable resin or a combination of both. After restoration, a static load of 500N was applied in a point-load condition at buccal cusp and palatal cusp. The stress data were analyzed using analysis of principal stress. Results showed that combining method such that apex was restored by material with high elastic modulus and the occlusal and cervical cavosurface margin by small amount of material with low elastic modulus was the most profitable method in the view of tensile stress that was considered as the dominant factor jeopardizing the restoration durability and promoting the lesion progression.

The influence of occlusal loads on stress distribution of cervical composite resin restorations: A three-dimensional finite element study / 대한치과보존학회지

The purpose of this study was to investigate the influence of various occlusal loading sites and directions on the stress distribution of the cervical composite resin restorations of maxillary second premolar, using 3 dimensional (3D) finite element (FE) analysis. Extracted maxillary second premolar was scanned serially with Micro-CT (SkyScan1072; SkyScan, Aartselaar, Belgium). The 3D images were processed by 3D-DOCTOR (Able Software Co., Lexington, MA, USA). HyperMesh (Altair Engineering, Inc., Troy, USA) and ANSYS (Swanson Analysis Systems, Inc., Houston, USA) was used to mesh and analyze 3D FE model. Notch shaped cavity was filled with hybrid (Z100, 3M Dental Products, St. Paul, MN, USA) or flowable resin (Tetric Flow, Vivadent Ets., FL-9494-Schaan, Liechtenstein) and each restoration was simulated with adhesive layer thickness (40 microm). A static load of 200 N was applied on the three points of the buccal incline of the palatal cusp and oriented in 20degrees increments, from vertical (long axis of the tooth) to oblique 40degrees direction towards the buccal. The maximum principal stresses in the occlusal and cervical cavosurface margin and vertical section of buccal surfaces of notch-shaped class V cavity were analyzed using ANSYS. As the angle of loading direction increased, tensile stress increased. Loading site had little effect on it. Under same loading condition, Tetric Flow showed relatively lower stress than Z100 overall, except both point angles. Loading direction and the elastic modulus of restorative material seem to be important factor on the cervical restoration.

Stress distribution of Class V composite resin restorations: A three-dimensional finite element study / 대한치과보존학회지

This study was to investigate the influence of composite resins with different elastic modulus, cavity modification and occlusal loading condition on the stress distribution of restored notch-shaped noncarious cervical lesion using 3-dimensional (3D) finite element (FE) analysis. The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. A notch-shaped cavity and a modified cavity with a rounded apex were modeled. Unmodified and modified cavities were filled with hybrid or flowable resin. After restoration, a static load of 500N was applied in a point-load condition at buccal cusp and palatal cusp. The stress data were analyzed using analysis of principal stress. The results were as follows: 1. In the unrestored cavity, the stresses were highly concentrated at mesial CEJ and lesion apex and the peak stress was observed at the mesial point angle under both loading conditions. 2. After restoration of the cavity, stresses were significantly reduced at the lesion apex, however cervical cavosurface margin, stresses were more increased than before restoration under both loading conditions. 3. When restoring the notch-shaped lesion, material with high elastic modulus worked well at the lesion apex and material with low elastic modulus worked well at the cervical cavosurface margin. 4. Cavity modification the rounding apex did not reduce compressive stress, but tensile stress was reduced.

The influence of composite resin restoration on the stress distribution of notch shaped noncarious cervical lesion; A three dimensional finite element analysis study / 대한치과보존학회지

The purpose of this study was to investigate the effects of composite resin restorations on the stress distribution of notch shaped noncarious cervical lesion using three-dimensional (3D) finite element analysis (FEA). Extracted maxillary second premolar was scanned serially with Micro-CT (SkyScan1072; SkyScan, Aartselaar, Belgium). The 3D images were processed by 3D-DOCTOR (Able Software Co., Lexington, MA, USA). ANSYS (Swanson Analysis Systems, Inc., Houston, USA) was used to mesh and analyze 3D FE model. Notch shaped cavity was filled with hybrid or flowable resin and each restoration was simulated with adhesive layer thickness (40 microM). A static load of 500 N was applied on a point load condition at buccal cusp (loading A) and palatal cusp (loading B). The principal stresses in the lesion apex (internal line angle of cavity) and middle vertical wall were analyzed using ANSYS. The results were as follows 1. Under loading A, compressive stress is created in the unrestored and restored cavity. Under loading B, tensile stress is created. And the peak stress concentration is seen at near mesial corner of the cavity under each load condition. 2. Compared to the unrestored cavity, the principal stresses at the cemeto-enamel junction (CEJ) and internal line angle of the cavity were more reduced in the restored cavity on both load conditions. 3. In teeth restored with hybrid composite, the principal stresses at the CEJ and internal line angle of the cavity were more reduced than flowable resin.

Effects of occlusal load on the stress distribution of four cavity configurations of noncarious cervical lesions: a three-dimensional finite element analysis study / 대한치과보존학회지

The objective of this study was to investigate the effect of excessive occlusal loading on stress distribution on four type of cervical lesion, using a three dimensional finite element analysis (3D FEA). The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. Four different lesion configurations representative of the various types observed clinically for teeth were studied. A static point load of 500N was applied to the buccal and lingual cusp (Load A and B). The principal stresses in lesion apex, and vertical sectioned margin of cervical wall were analyzed. The results were as follows 1. The patterns of stress distribution were similar but the magnitude was different in four types of lesion. 2. The peak stress was observed at mesial corner and also stresses concentrated at lesion apex. 3. The compressive stress under load A and the tensile stress under load B were dominant stress. 4. Under the load, lesion can be increased and harmful to tooth structure unless restored.

Development and control of caries lesions on the occlusal surface using a new in vivo caries model

The aim of this study was to develop a new in vivo caries model for the occlusal surface and to describe the enamel features observed before and after dental plaque control (DPC). Four volunteers (12-15 years old) participated in the experiment, each of which was due to have 2 homologous first premolars extracted for orthodontic reasons. Test surfaces did not present visible signs of demineralization, opacities or fillings. A wire mesh was used to promote dental plaque accumulation on the occlusal surface. After 4 weeks, the wire mesh was removed and DPC was performed. In Groups 1 and 2, DPC was performed by the subjects daily and, in Groups 3 and 4, DPC was performed by the subjects daily and by the professional weekly. One tooth/pair of Groups 1 and 3 was extracted after 2 weeks. One tooth/pair of Groups 2 and 4 was extracted after 4 weeks. All test surfaces showed demineralization after the wire mesh was removed. The observed re-establishment of the enamel brightness was directly related to the increase of the DPC duration. In polarized light microscopy, interindividual differences varying from pseudoisotropic areas to enamel lesions were noted in specimens submitted to 2 weeks of DPC. Specimens submitted to 4 weeks of DPC showed less tissue porosity. It was concluded that the new in vivo caries model was effective since all occlusal surfaces presented clinical and microscopic signs of mineral loss in different stages after 4 weeks of cariogenic challenge. After DPC on the test surfaces, there was a reduction of mineral loss suggesting control of demineralization on these surfaces

Comparison of Resorbable and Nonresorbable Membrane for Guided Bone Regeneration in Implant Dehiscence Defects / 대한치주과학회지

The purpose of this study was to examine the frequency of dehiscence bone defect on peri-implant and to compare the difference between resorbable membrane and non-resorbable membrane in bone regeneration on peri-implant. Amomg the patients, 22 patientswho have recieved an implant surgery at the department of Periodontics in Dankook University Dental Hospital showed implant exposure due to the dehiscence defect and 27 implants of these 22 patients were the target of the treatment. Gore-Tex(R) and Bio-mesh(R) were applied to the patients and treated them with antibiotics for five days both preoperatively and postoperatively. Reentry period was 26 weeks on average in maxilla and 14 weeks on average in mandible. The results were as follows: 1. Dehiscence bone defect frequently appeared in premolar in mandible and anterior teeth in maxilla respectively. 2. Among 27 cases, 2 membrane exposures were observed and in these two cases, regenerated area was decreased. 3. In non-resorbable membrane, bone surface area 9.25+/-4.84 preoperatively and significantly increased to 11.48+/-7.52 postoperatively.(P<0.05) 4. In resorbable membrane, bone surface area was 14.80+/-8.25 preoperatively and meaningfully widened to 17.61+/-10.67 postoperatively.(P<0.05) 5. The increase of bone surface area in non-resorbable membrane was 2.23+/-3.38 and the increase of bone surface area in resorbable membrane was 2.80+/-3.00 ;therefore, there was no significant difference between these two membranes(P<0.05). This study implies that the surgical method using DFDB and membrane on peri-implant bone defect is effective in bone regeneration regardless the kind of the membrane, and a similar result was shown when a resorbable membrane was used.

Effects of thermal and mechanical fatigue stress on bond strength in bracket base configurations / 대한치과교정학회지

The purpose of this study is to evaluate the effects of mechanical and thermal fatigue stress on the shear, tensile and shear-tensile combined bond strengths(SBS, TBS, CBS) in various orthodontic brackets bonded to human premolars with chemically cured adhesive(Ortho-one, Bisco, USA). Five types of commercially available metal brackets with various bracket base configurations of Photoetched base(Tomy, Japan), Non-Etched Foil Mesh base(Dentaurum, Germany), Micro-Etched Foil Mesh base(Ortho Organizers, USA), Chessboard base(Daesung, Korea), and Integral base(3M Unitek, USA) were used. Samples were divided into 3 groups, the first group was acted with shear-tensile combined loads(45 degrees) of 200g for 4 weeks(mechanical fatigue stress), the second group was subjected to the 5,000 thermocycles of 15 second dwell time each in 5 degrees C and 55 degrees C baths(thermal fatigue stress), and the third group was the control. Bond strengths were measured at the crosshead speed of 0.5 mm/min. The cross-section of bracket base/adhesive interface and the fracture surface were examined with the stereoscope and the scanning electron microscope. The resin remnant on bracket base surface was assessed by ARI(Adhesive Remnant Index). The obtained results were summarized as follows; 1. In static bond strength, Photoetched base bracket showed the maximum bond strength and Integral base bracket showed the minimum bond strength(p<0.05). In all brackets, shear bond strength(SBS) was in the greatest value and shear-tensile combined strength(CBS) was in the least value(p<0.05). 2. After mechanical fatigue test, Photoetched base bracket showed the maximum bond strength and Integral base bracket showed the minimum bond strength(p<0.05). In Photoetched base bracket and Micro-Etched Foil Mesh base bracket, shear bond strength(SBS), tensile bond strength(TBS) and shear-tensile combined strength(CBS) were decreased after mechanical fatigue test(p<0.05). 3. After thermocycling, Integral base bracket showed the minimum bond strength. The SBS, TBS and CBS of Photoetched base, Chessboard base, and Micro-Etched Foil Mesh base bracket were decreased after 5,000 cycled thermocycling(p<0.05). 4. In static test, bond failure sites were mainly between bracket and adhesive. After thermocycling, ARI scores were greater than those in static test. 5. SEM micrographs of cross-section of bracket bonding site showed that many micro-cracks in bracket/resin interface and in enamel/resin interface were found in all brackets after thermocycling.

Alveolar Bone Formation in Dogs using Vicryl Absorbable Mesh(Polyglactin 910) and Decalcified Freeze-Dried Bone Grafting / 대한치주과학회지

The purpose of this study was to evaluate new bone formation following guided bone regeneration by resorbable and non-resorbable membrane. Six adult mongrel dogs were used. The first, second, third, fourth premolars in the mandible of each dog were extracted. Two months after tooth extraction, a buccal dehiscence defect was surgically created on each edentulous area. The experimental sites were divided into three groups according to the treatment modalities ; GroupI-a: surgical treatment only ; GroupI-b: allogenic decalcified freezed dried bone grafting ; Group II-a : e-PTFE membrane placement only ; Group II-b : allogenic decalcified freezed dried bone grafting and e-PTFE membrane placement ; Group III-a : Vicryl(R) mesh placement only ; Group III-b : allogenic decalcified freezed dried bone grafting and Vicryl(R) mesh placement. The animals were sacrificed at 8 weeks after operation and the specimens were prepared for histologic and histometric examination. The results were as follows: Clinically, all defect sites were healed without exposure of barrier membrane after the eight weeks. In Group I-a, dense connective tissues were impinged in the bony defect area. Well vascularized and fibrous bone marrow indicated that bone formation was still taking place was found. In Group I-b, in areas closer to the periphery, lamellation of the newly formed bone would found. In Group II-a, beneath the e-PTFE membrane a dense layer of connective tissue covering the most external portions of the regenerated tissue was seen. The new bone surfaces were lined with osteoid and osteoblast. In Group II-b, a dense layer of connective tissue covering the most external portions of the regenerated tissue was observed beneath the e-PTFE membrane. A notable amount of alveolar ridge regeneration was seen with new rigdes with well-contoured form. In Group III-a, the new bone surface were lined with osteoid and osteoblast, indicating active bone formation. A clear demarcation could not be noted between the host bone and new bone. In Group III-b, a notable amount of alveolar ridge regeneration was seen with new ridges assuming wellcontoured form. In areas closer to the periphery, lamellation of the newly formed bone would found. As histometric examination, the amount of bone formation was gained from 12.8mm2 to 26.3mm2. It was significantly greater in group II-b and group III-b compared to other groups(p<0.05). These results suggest that Vicryl(R) mesh after DFDB grafting used in guided bone regeneration could create and sustain sufficient space for new bone formation.

The effects of mechanical and thermal fatigue on the shear bond strength of orthodontic adhesives / 대한치과교정학회지

The purpose of this study was to examine the effects of mechanical and thermal fatigue on the shear bond strength(SBS) of stainless steel mesh brackets bonded to human premolar teeth with 3 no-mix adhesives. The stainless steel mesh bracket was Ormesh(Ormco, .022 slot) and three types of no-mix adhesives were Ortho-one(Bisco), Monolok2(RMO), System 1+(Ormco). The 10(6) loadcycles of 17.4x10(2)sin2piftlg . cm and the 1,000 thermocycles of 15 second dwell time in each bath of 5degrees C and 55degrees C were acturated as mechanical and thermal fatigue stress, and SBS were measured after each fatigue test. The fracture sites were analyzed by stereoscope and scanning electron microscope. The results obtained were summarized as follows; 1. Before thermocycles, Monolok2 showed the highest Knoop hardness number(KHN, 64.03kg/mm2) and System 1+ showed the lowest value(31.60kg/mm2). After thermocycling, Monolok2 also showed the highest KHN(38.03kg/mm2) and system 1+ showed the minimum(20.87kg/mm2). The KHN of Ortho-one, Monolok2, System 1+ significantly decreased after thermocycling(P<0.01).

Effects of chemically cured resin and light cured resin on shear bond strength of metal bracket and ceramic bracket / 대한치과교정학회지

This study was designed for comparison of shear bond strengths and failure patterns of four experimental groups which combinated mesh-backed metal brackets and texture based ceramic brackets (Transcend series 2000((TM))) with chemically cured resin (Mono Lok2((TM))) and visible light cured resin (Transbond((TM))). Brackets were bonded on the extracted human bicuspids, after etching them by manufacturer's recommand, and the shear bond strengths were measured on the Instron machine after 24 hrs passed in the 37degrees C water bath. The results were as follows. 1. Ceramic brackets, transcend series 2000((TM)), bonded with MonoLok2((TM)) showed statistically higher shear bond strength than mesh-backed metal brackets bonded with MonoLok2((TM)). 2. There was no significant difference in shear bond strengths between metal and ceramic brackets bonded with Transbond((TM)). 3. Ceramic brackets bonded with both Transbond((TM)) and MonoLok2((TM)) showed primarily fractures bet?ween brackets adhesive interface. 4. Enamel crack was not found in anyone specimen.

Effects of the different ceramic bracket bases on shear bond strength / 대한치과교정학회지

The purpose of this study was to evaluate the effects of different bases of ceramic brackets on shear bond strength and to observe failure patterns of bracket bondings. Lower bicuspid brackets whose bases designed for the macromechanical and silane treated chemical bon?ding, those for silane treated chemical bonding, those for micromechanical bonding, and those for macrome?chanical bonding were tested as experimental groups, and foil mesh-backed metal brackets as a control group. All the brackets were bonded with Mono-Lok 2((TM)) on the labial surface of extracted human lower bicuspids after etching the enamel with 38% phosphoric acid solution for 60 seconds. The shear bond strengths were measured on the universal test machine after 24 hours passed in the 37degrees C water bath. The gathered data were evaluated and tested by ANOVA and Duncan's multiple range test, and those results were as follows. The shear bond strengths of brackets for macromechanical and chemical bonding, those for chemical bonding, and those for micromechanical bonding were not different (p>0.05), but showed statistically higher than those of metal bracket and those of ceramic bracket for macromechanical bonding(p<0.05). The shear bond strengths of ceramic bracket for macromechanical bonding showed statistically lower than those of metal bracket(p<0.05). The enamel fractures and/or ceramic bracket fractures were observed in the cases of higher bond strength than that of metal bracket. These results supported that silane treated base of ceramic bracket show higher shear bond strength than that of metal bracket, and suggested that micromechanical form of ceramic bracket bases show higher shear bond strength than that of macromechanical form.