Alteration of the Occlusal Vertical Dimension for Prosthetic Restoration Using a Target Tracking System

Clinicians and researchers have used various methods to reproduce the maxillomandibular relationship and mandibular movement of individual patients using an articulator, with efforts being made to reduce errors associated with the conventional technique. When a change to a vertical dimension is required during the conventional prosthesis construction process, the maxillary and mandibular casts are mounted on the mechanical articulator using a facebow and bite registration and the elevation of the anterior guide pin of the articulator is used. However, this can inevitably cause errors due to differences between the articulator hinge movement and the actual trajectory of the patient. There has recently been increasing interest in tracking the trajectory of jaw motion of a patient, and this paper presents a new technique for altering the vertical dimension based on the measured trajectory. Target materials for performing tracking are attached to the maxillary and mandibular anterior teeth to record opening and closing movements of the patient’s mouth in real time and align the patient’s scanned intraoral data or cast data. The movements of the targets are replaced with the movement of the patient’s oral scan data. Additionally, then the occlusal vertical dimension is set to a new position based on the obtained trajectory. After determining the optimal vertical dimension with consideration of the space required for restoration, maxillary and mandibular STL files are exported and the designed cast is created using a 3D printer. The printed cast is mounted on an articulator for subsequent procedures. This approach maintains the patient’s actual maxillomandibular relationship at various vertical heights and can also reduce the chair time required when adjusting for errors.ope

Three-dimensional morphometric analysis of the trabecular bone in the human mandible using microcomputed tomography

Dept. of Dental Science/박사[한글] 하악골은 신체의 다른 부위와 비교하여 여러 가지 형태적 기능적특징을 가지고 있다. 하지만 가장 큰 특징은 치아가 존재하는 것이다. 이러한 치아의 존재로 인하여 교합력과 같은 외력이 소주골에 직접전달이 되어 골량이나, 골 구조등에 영향을 미친다. 신체의 골 구조에 대해서는 많은 학자들이 연구하였고 그 중요성에 대하여 언급을 하였으나 하악골에서는 치조골흡수, 치아상실이나 Implant성공률등에 대하여 골량이나 골 밀도에 관계하여 연구를 했지만 골 구조와 관계하여서는 거의 관심을 기울이지 않은 것이 사실이다. 따라서 본 실험은 하악소주골의 3차원적인 구조를 분석하여 저작기능과의 관련성을 살펴보고 보다 정확한 생체역학연구를 위한 기초자료를 제시하여 Micro-CT의 치의학분야에 대한 응용가능성을 위하여 소구치 및 대구치시편을 Skyscan 1072( SKYSCAN, Antwerpen, Belgium)를 이용하여 치조골부위와 하치조신경을 기준으로 한 상,하 두 부분의 기저골부위를 촬영 및 분석하여 다음과 같은 결과를 얻었다. 1.치조골부위에 존재하는 소주골이 기저골부위보다 골량 및 골 소주가 많았으며 골 소주의 간격이 좁아서 치조골부위가 보다 치밀한 구조로 이루어져 있었다. 2.하치조신경을 기준으로 한 상방 과 하방의 기저골의 비교에 있어서는 상방의 기저골에서 높은 골량 및 골 소주의 개수를 나타내고 있으며 낮은 소주간 거리 및 이방성을 나타내어 하방의 기저골보다 치밀한 구조를 보이고 있었다. 3.치조골에 대한 소구치와 대구치의 비교에 있어서는 대구치의 치조골부위에서 소구치의 치조골부위보다 골량 및 골 소주의 개수가 많았고 낮은 골 소주간의 거리, 이방성의 정도와 낮은 구조형태지수를 나타내어 보다 판상의 형태로서 치밀하게 연결이 되어 교합력을 비롯한 외력에 보다 잘 저항할 수 있는 구조로 되어 있음을 알 수 있었다. 4.기저골에 대한 소구치와 대구치의 비교에 있어서는 모든 계측항목들이 차이가 없었다. 5.골량과 다른 계측항목 들과의 상관관계에서는 골 소주간의 거리, 골 소주 개수와 구조형태지수가 비교적 높은 상관관계를 나타내었다. 이와 같은 결과로 볼 때, 하악의 소주골은 치아를 통한 외력에 잘 견딜 수 있는 기능적인 구조로 적절하게 배열이 되어 있는 것으로 여겨지며 대구치 부위에서 보다 명확하였다. 또한 이와 같은 사실은 생역학적 분석을 비롯한 하악골의 연구 시에 고려되어야 할 사 항으로 생각된다. [영문] The mandible has unique functional and structural characteristics when compared with other skeletal bones of the body. Especially the presence of dentition is considered as the most characteristic features of the mandible. Through the dentition, any external forces such as occlusal force can be transmitted to the bone and effect on the bone mass and structure. There have been numerous studies of the bone structure in the other parts of the body and emphasized on its importance. On the mandible, there have been studies on bone mass and density regarding alveolar bone resorption, tooth loss and implant success rate, however little has been studies on the bone structure. The purpose of this study is to analyze any correlation between trabecular bone structure of the mandible and masticatory function, and the efficacy of micro-CT in biomechanical analysis in dentistry. Skyscan 1072 (SKYSCAN, Antwerpen, Belgium) was used in scanning alveolar and basal bone of premolar and molar regions of the mandible and following results were obtained. 1.In intrasite comparison, the alveolar bone had higher values of bone volume fraction and trabecular number but lower in trabecular separation than the basal trabecular bone. A compacted with a large portion of trabecular bone in alveolar bone could be concluded. 2.When the basal bones superior and inferior to mandibular canal were compared, bone volume fraction and trabecular number at superior region had higher values that were statistically significant. Trabecular separation and degree of anisotropy on the other hand were low, which implies that the basal bone in superior region were more compact in structure. 3.When the same site of molar and premolar regions were compared, a higher bone volume fraction and trabecular number were found in molar alveolar region which implies a compact structure. Trabecular separation, degree of anisotropy and structural model index in molar regions had lower values and it could be concluded that this area had trabecular bone which has more plate-like structure and less polarity of trabecular bone than premolar region, indicating adequately remodeling zone against the external forces. 4.In basal bone, all parameters between premolar and molar regions were statistically not significant. 5.In the relationships between bone volume fraction and other parameters, a linear correlation was found with other parameters and some relationships appear strong such as trabecular separation, trabecular number and structure model index. In reference to the results above, it can be concluded that the structure of mandible is appropriately designed to perform and withstand occlusal forces and masticatory function. It is more clearly noted in the molar regions and these facts should be considered in biomechanical analysis of the mandible.ope

The Transmandibular Implant System

Many of problems which are faced to the edentulous patients are related to a minimal amount of available mandibular bone volume and height. Most of the patients with mild atrophy of mandible are treated using endosseous implant prosthodontics. TMI(Transmandibular Implant) can be used in case of severe mandibular atrophy of the mandible with exposed of inferior alveolar nerve, osteoporosis and the fracture of the atrophic mandible.Also it can eliminate the need for bone grafting and vestibuloplasty. The TMI is a rigid box frame structure which controls and distribute the masticatory force over the severely resorbed mandile. The box frame structure consist of a superstructure, baseplate, 4 transosseous posts, and 5cotical screws. This is a case report that also describes about the transmanibular implant reconstruction system.ope

Improving Bone Formation by Guided Bone Regeneration Using a Collagen Membrane with rhBMP-2: A Novel Concept

We examined whether recombinant human bone morphogenetic protein-2 (rhBMP-2) when applied to collagen membranes, would reinforce them during guided bone regeneration. Four critical cranial bone defects were created and treated in 30 New Zealand white rabbits, including a control group, critical defect only; group 1, collagen membrane only; group 2, biphasic calcium phosphate (BCP) only; group 3, collagen membrane + BCP; group 4, collagen membrane with rhBMP-2 (1.0 mg/mL); group 5, collagen membrane with rhBMP-2 (0.5 mg/mL); group 6, collagen membrane with rhBMP-2 (1.0 mg/mL) + BCP; and group 7, collagen membrane with rhBMP-2 (0.5 mg/mL) + BCP. After a 2-, 4-, or 8-week healing period, the animals were sacrificed. The combination of collagen membranes with rhBMP-2 and BCP yielded significantly higher bone formation rates compared to the other groups (control group and groups 1–5 < groups 6 and 7; p < 0.05). A 2-week healing period yielded significantly lower bone formation than that at 4 and 8 weeks (2 < 4 = 8 weeks; p < 0.05). This study proposes a novel GBR concept in which rhBMP-2 is applied to collagen membranes outside instead of inside the grafted area, thereby inducing quantitatively and qualitatively enhanced bone regeneration in critical bone defects. © 2023 by the authors.ope

Evaluation methods of occlusal vertical dimension and their clinical applications: A narrative review

In an extensive oral rehabilitation, determining a proper occlusal vertical dimension is a critical step and the starting point for successful treatment. Since changing the occlusal vertical dimension could be time-consuming, financially challenging, and physically demanding for both clinicians and patients, multi-faceted analysis and careful consideration are essential in the diagnosis and further treatment process. The purpose of this narrative review is to discuss the occlusal vertical dimension and its current issues, and to summarize previous methods of evaluating occlusal vertical dimension to propose clinical guidance for determining a viable occlusal vertical dimension for full-mouth rehabilitation.ope

Maxillary Implant-supported Hybrid Prosthesis Fabricated using a Polyetherketoneketone Framework: A Case Report

This clinical report describes a case involving a 74-year-old woman with maxillary edentulism who was successf ully treated using an implant-supported hybrid prosthesis. The f ramework of the prosthesis was fabricated using polyetherketoneketone (PEKK), which is a high-performance polymer, and individual lithium disilicate ceramic crowns were cemented for optimal esthetics. No mechanical or biological complications were observed during a 3-year follow-up period. Further clinical studies and long-term clinical data regarding the usef ulness of PEKK as a f ramework material for dental prostheses are necessaryope

Accuracy of Additively Manufactured Dental Casts Compared with That of Virtual Scan Data Obtained with an Intraoral Scanner: An In Vitro Study

The study aimed to evaluate the time-related accuracy of additively manufactured dental casts and to compare it with scan data obtained with an intraoral scanner in vitro. Twenty-eight markers were attached to a set of dentiforms as reference model, and the distances between the markers were measured using a digital caliper. An intraoral scanner was used to obtain the virtual scan data of the reference model with a total of 30 scans per arch. The distances between markers were measured using a three-dimensional inspection software for all scans (group IOS). Scan data were additively manufactured using a 3D printer, and the distances between markers were measured as in the reference model immediately after post-polymerization (group PPIA), 1 day (group PP1D), 7 days (group PP7D), and 30 days after post-polymerization (group PP30D). The linear deviation in group IOS was 199.74 ± 11.14 μm, PPIA was 242.88 ± 49 μm, PP1D was 259.9 ± 42.59 μm, PP7D was 289.82 ± 39.74 μm, and PP30D was 315.8 ± 33.28 μm, in comparison with the reference model, with significant differences among all groups (all p < 0.05). When additively manufacturing casts from scan data to verify the quality of dental prostheses designed virtually, the prostheses should be adapted to casts manufactured within one week.ope

Clinical Acceptability of the Internal Gap of CAD/CAM PD-AG Crowns Using Intraoral Digital Impressions

The purpose of this study was to compare the internal gap between CAD/CAM palladium-silver crowns and cast gold crowns generated from intraoral digital versus conventional impressions and to determine the clinical acceptability. Nickel-chrome master dies were made from the prepared resin tooth with the conventional impression method (n = 40). For ICC (Intraoral, CAD/CAM) group, 10 intraoral digital impressions were made, and 10 CAD/CAM crowns of a PD-AG (palladium-silver) machinable alloy were generated. For IC (Intraoral, Cast) group, 10 gold crowns were cast from ten intraoral digital impressions. For CCC (Conventional, CAD/CAM) group, 10 CAD/CAM PD-AG crowns were made using the conventional impression method. For CC (Conventional, Cast) group, 10 gold crowns were fabricated from 10 conventional impressions. One hundred magnifications of the internal gaps of each crown were measured at 50 points with an optical microscope and these values were statistically analyzed using a two-way analysis of variance (α = 0.05). The internal gap of the intraoral digital impression group was significantly larger than in the conventional impression group (P 0.05). Within the limitations of this in vitro study, crowns from intraoral digital impressions showed larger internal gap values than crowns from conventional impressionsope

Effects of ultraviolet treatment and alendronate immersion on osteoblast-like cells and human gingival fibroblasts cultured on titanium surfaces

In this study, we evaluated the effects of ultraviolet (UV) treatment and alendronate (ALN) immersion on the proliferation and differentiation of MG-63 osteoblast-like cells and human gingival fibroblasts (HGFs) cultured on titanium surfaces. MG-63 cells were used for sandblasted, large grit, and acid-etched (SLA) titanium surfaces, and HGFs were used for machined (MA) titanium surfaces. SLA and MA specimens were subdivided into four groups (n = 12) according to the combination of surface treatments (UV treatment and/or ALN immersion) applied. After culturing MG-63 cells and HGFs on titanium discs, cellular morphology, proliferation, and differentiation were evaluated. The results revealed that UV treatment of titanium surfaces did not alter the proliferation of MG-63 cells; however, HGF differentiation and adhesion were increased in response to UV treatment. In contrast, ALN immersion of titanium discs reduced MG-63 cell proliferation and changed HGFs into a more atrophic form. Simultaneous application of UV treatment and ALN immersion induced greater differentiation of MG-63 cells. Within the limitations of this cellular level study, simultaneous application of UV treatment and ALN immersion of titanium surfaces was shown to improve the osseointegration of titanium implants; in addition, UV treatment may be used to enhance mucosal sealing of titanium abutments.ope

Digital Workflow to Fabricate Complete Dentures for Edentulous Patients Using a Reversing and Superimposing Technique

This technical procedure demonstrates a 4-step completely digital workflow for the fabrication of complete dentures in edentulous patients. The digital scan data of the edentulous arches were obtained using an intraoral scanner, followed by the fabrication of modeless trial denture bases using additive manufacturing. Using the trial denture base and a wax rim assembly, the interarch relationship was recorded. This record was digitized using an intraoral scanner and reversed for each maxillary and mandibular section individually. The digital scan data directly obtained using the intraoral scanner were superimposed over the reversed data, establishing a proper interarch relationship. The artificial teeth were arranged virtually and try-in dentures were additively manufactured. Subsequently, the gingival and tooth sections were additively manufactured individually and characterized. Thus, fabrication of digital complete dentures can be accomplished using digital data characteristics. The workflow includes data acquisition using an intraoral scanner, data processing using reverse engineering and computer-aided design software programs, and additive manufacturing.ope