Clinical assessment on application of Er:Cr:YSGG laser in dentinal hypersensitivity reduction

Objectives We aimed to evaluate the effectiveness of Er:Cr:YSGG laser therapy on the reduction of dentinal hypersensitivity while taking into account the length and depth of the cervical abrasion. Methods We included adults (age, 20-60 years) with at least 2 hypersensitive teeth. The hypersensitive teeth were stimulated with a pressure-indicating probe and an air syringe. The response of the subjects to this stimulation was quantified using a visual analog scale (VAS) and Schiff air sensitivity score. The patients were treated at baseline, immediately after laser treatment, and at 1, 2, and 4 weeks after the Er:Cr:YSGG laser therapy. The results were analyzed by repeated measure analysis of variance (ANOVA) and Bonferroni's post hoc test. Results The values of tactile test and air blast test showed statistically significant differences between the following time points: baseline and immediately after laser treatment, baseline and first week after treatment, and immediately after laser treatment and first week after treatment (P0.05). The depth and width of the cervical abrasion was not statistically significant in dentinal hypersensitivity reduction (P>0.05). Conclusions The use of Er:Cr:YSGG laser therapy reduced dentinal hypersensitivity, especially immediately after laser treatment. The depth and width of the cervical abrasion is not statistically significant in dentinal hypersensitivity reduction.ope

Accuracy in the Interface between Implant Components after a 5-year Functional Period; A Clinical Report

The reduction in the assembly accuracy of the implant complex could result from fatigue and micromovement during the functional phases and from the manufacturing process. The long-term functional integrity of implant prostheses can be ensured by accurate fit of the interfaces between the assemblies from a biomechanical perspective. A single implant restoration on the mandibular left first molar was removed after a 5-year functional period due to mobility, which was diagnosed as abutment screw loosening. The superstructure could not be retrieved, despite exceeding the torque value recommended by the manufacturer; therefore, the restoration was unscrewed and removed. The retrieved restoration, particularly the configuration of the abutment-gold cylinder and abutment-retaining screw interfaces, was analyzed with scanning electron microscopy. Moreover, the assembly accuracy of the old and new assemblies was compared. In the new specimen, a relatively an even linear gap was found between the threads of the abutment and screw and no vertical marginal gaps were found at the abutment-cylinder interface, wherein the horizontal and vertical contacts were incomplete. In the old specimen, an irregular pattern of screw-thread engagement, an irregular linear space at the abutment-cylinder interface, a partially worn-out screw configuration and remnants of the screw in the interface were observed.ope

Assessment of Age-Related Changes on Masticatory Function in a Population with Normal Dentition

This study aimed to investigate the influence of changes in age-related physiological muscular and dental factors on masticatory function. This study was conducted in 211 healthy participants divided into four different age groups: 20-45 years (Gr1); 45-60 years (Gr2); 61-70 years (Gr3); and ≥71 years (Gr4). For objective evaluation of masticatory function, the masticatory performance, bite force, posterior bite area (PBA), functional tooth units (FTUs), the number of remaining teeth, tongue pressure, masseter muscle thickness (MMT), and handgrip strength were examined. Food intake ability (FIA) and the Oral Health Impact Profile-14 score were assessed subjectively using questionnaires. A significant decrease in the number of remaining teeth, FTUs, handgrip strength, and FIA was found in Gr4, and a significant decrease in the tongue pressure, PBA, and bite force was found in those aged ≥61 years. In groups 1 and 3, an association of the PBA with masticatory performance was observed. However, there was no significant decreasing trend in the MMT with respect to masticatory performance with aging. With sufficient FTUs and posterior tooth support, although age-dependent decreases in the bite force, tongue pressure and handgrip strength were observed, masticatory performance was maintained. Establishing the PBA by improving occlusion through dental treatment is thought to be important for masticatory function.ope

Mechanical properties of CAD/CAM polylactic acid as a material for interim restoration

Statement of problem: Biomaterials, including polymethyl methacrylate (PMMA) and bisacrylate, have been widely used as conventional interim materials and may exhibit cytotoxicity or systemic toxicity. Purpose: This study was designed to compare the mechanical properties of polylactic acid (PLA) as an alternative to conventional dental polymers for computer-aided design and manufacturing (CAD/CAM). Material and methods: Four groups (n = 20 per group) of CAD/CAM polymers were assessed. Specimens of PLA (PLA Mill) and PMMA (PMMA Mill) for subtractive manufacturing, PLA for fused deposition modeling (PLA FDM), and bisphenol for additive manufacturing by stereo-lithography (Bisphenol SLA) were fabricated into 2-mm-wide, 2-mm-thick and 25-mm-long specimens using a milling machine, an FDM printer, and an SLA printer, respectively. The flexural strength (FS) and elastic modulus (EM) were calculated. The surface roughness and Shore D hardness were analyzed with a 3D optical surface roughness analyzer and a Shore durometer, respectively. Results: PLA Mill showed the lowest FS (64.9 ± 8.28), followed by PLA FDM (104.27 ± 4.42 MPa), PMMA Mill (139.2 ± 20.95 MPa), and Bisphenol SLA (171.56 ± 15.38 MPa), with statistically significant differences. PLA FDM showed the highest EM, followed by PLA Mill, Bisphenol SLA, and PMMA Mill. Significant differences were observed not only between PMMA Mill and Bisphenol SLA but also between PLA FDM and PLA Mill. The lowest Shore D hardness was observed for PLA FDM, followed by PLA Mill, PMMA Mill, and Bisphenol SLA, which showed the highest value among the 4 groups, with significance. The highest values for the surface roughness parameters were observed for PLA Mill, and the lowest were observed for Bisphenol SLA. Conclusions: Among the tested CAD/CAM polymers, Bisphenol SLA was the most durable material, and the mechanical properties of PLA FDM were within the clinically acceptable range.ope

Fracture strength analysis of titanium insert-reinforced zirconia abutments according to the axial height of the titanium insert with an internal connection

This study aimed to analyze fracture strength in vitro by varying the axial height of the titanium insert and the labial height of the zirconia abutment in an internal connection implant to identify the titanium insert axial height with optimal mechanical stability. Sixty implants with an internal connection system were used. Two-piece zirconia abutments were used with the titanium inserts. Combinations of different titanium insert axial heights (mm) and zirconia abutment labial heights (mm) constituted five groups: Gr1 (1-3), Gr2 (3-3), Gr3 (3-5), Gr4 (5-3), and Gr5 (5-5). After thermocycling, a fracture load test was performed with a universal testing machine. The initial deformation load and the fracture load were measured and analyzed. The fractured surface and cross-section of the specimens were examined by scanning electron microscopy (SEM). The groups of titanium inserts with axial heights of 3 mm and 5 mm showed significantly greater initial deformation load and fracture load than the group with an axial height of 1 mm (p < 0.05), but there was no significant difference between the two groups with axial heights of 3 mm and 5 mm. The labial height of the zirconia abutment had no significant influence on the initial deformation load and fracture load. In some specimens in Gr4 and Gr5, cracking or bending of the titanium insert and abutment screw was observed on SEM. The axial height of the titanium insert should be designed to not be less than 3 mm to increase the fracture strength and promote the long-term stability of implants.ope

Assessment of subjective and objective masticatory function among elderly individuals with mild cognitive impairment

Abstract Background : Masticatory function is known to be related to cognitive ability; therefore, factors for improving masticatory function should be identifed. Aims : This study aimed to identify factors infuencing masticatory function associated with mild cognitive mpairment (MCI) in elderly individuals. Methods : A total of 123 elderly participants [mean age: 76.5±6.5 years; 82 females (66.7%), 41 males (33.3%)] were included. Cognitive function was evaluated by the Korean version of the Mini-Mental State Examination (KMMSE). Questionnaires for subjective evaluation were administered, and dynamic objective masticatory function valuations, including chewing tests and bite force measurements, were performed. Intergroup diferences were evaluated by the Wilcoxon ranksum and chi-square test, and correlations between cognitive ability and masticatory function were evaluated by multilinear logistic regression. Results : The number of teeth, number of posterior teeth, bite force, masticatory ability index (MAI) and posterior support status showed signifcant diferences between the normal (KMMSE>23) and MCI (KMMSE≤23) groups. However, only the MAI, representing dynamic masticatory performance, was signifcantly associated with MCI regardless of age, sex and removable prostheses. The number of teeth and posterior teeth, bite force, subjective masticatory ability and posterior occlusal support showed no signifcant association with MCI. Discussion : These results suggested the importance of chewing function for preventing the progression of cognitive impairment. Conclusions : Considering that only the MAI was signifcantly associated with MCI, it is more important to improve chewing efciency by harmonizing therapeutic prosthetics with the surrounding masticatory system than simply increasing the number of teeth to prevent or delay cognitive impairment in elderly individuals.ope

컴퓨터를 이용한 속도 조절형 치과 국소마취 기구: 문헌고찰

Background: Today, there are computer controlled local anesthesia devices used clinically. The main principle is to control injection speed by computer aided system, and it relieves pain. However, there are few objective data considering this subject. In this literature review, we researched studies about computer controlled anesthetic delivery. We compared pain control effect of computer controlled to conventional local anesthetic syringe system. Methods: A bibliographic search in PubMed was performed and we reviewed original articles. Results: There were 18 publications that compared pain control effect of computer controlled to conventional system. There were 8 articles reported of children, similar pain control effect was found in 7 of them. One study showed superior pain control effect of computer controlled anesthetic delivery. For adults, 10 studies showed superior pain control effect in computer aided system. Conclusions: Computer controlled anesthetic delivery has similar or superior pain control effect compared to conventional local anesthetic syringe system. For both children and adults, computer controlled anesthetic delivery could be clinically useful, still it may be more effective for adults.ope

An esthetic appliance for the management of crown-root fracture; a case report

Orthodontic extrusion is usually performed by means of a fixed orthodontic appliance that utilizes arch wire attached to adjacent teeth and transfers the desired force by elastic from the wire to the root. However, clinicians often encounter cases where the bonding required for tooth traction is not possible because the adjacent teeth have been restored with ceramic or veneer. The purpose of this case report is to describe a modified orthodontic extrusion appliance that is useful when conventional orthodontic treatment is not possible. The modified appliance was fabricated using an artificial tooth, clear plastic sheeting, and a braided fiber-reinforced composite strip that covered adjacent teeth without bonding. It satisfied the esthetic and functional needs of the patient and established the optimal biologic width.ope

Accuracy evaluation of 3D printed interim prosthesis fabrication using a CBCT scanning based digital model

Objectives: This study aimed to evaluate the marginal and internal gaps in 3D-printed interim crowns made from digital models of cone-beam computed tomography (CBCT) conversion data. Materials and methods: Sixteen polyvinylsiloxane impressions were taken from patients for single crown restorations and were scanned using CBCT. The scanning data were converted to positive Standard Triangulation Language (STL) files using custom-developed software. The fabricated stone models were scanned with an intraoral optical scanner (IOS) to compare the surface accuracy with the STL data obtained by CBCT. The converted STL files were utilized to fabricate interim crowns with a photopolymer using a digital light-processing 3D printer. The replica method was used to analyze the accuracy. The marginal and internal gaps in the replica specimen of each interim crown were measured with a digital microscope. The Friedman test and Mann-Whitney U test (Wilcoxon-signed rank test) were conducted to compare the measurements of the marginal and internal gaps with a 95% level of confidence. Results: The root-mean-square values of the CBCT and IOS ranged from 41.00 to 126.60 μm; and the mean was 60.12 μm. The mean values of the marginal; internal; and total gaps were 132.96 (±139.23) μm; 137.86 (±103.09) μm; and 135.68 (±120.30) μm; respectively. There were no statistically significant differences in the marginal or internal gaps between the mesiodistal and buccolingual surfaces; but the marginal area (132.96 μm) and occlusal area (255.88 μm) had significant mean differences. Conclusion: The marginal gap of the fabricated interim crowns based on CBCT STL data was within the acceptable range of clinical success. Through ongoing developments of high-resolution CBCT and the digital model conversion technique; CBCT might be an alternative method to acquire digital models for interim crown fabrication.ope

Diplopia after Inferior Alveolar Nerve Block Anesthesia -A Case Report-

Inferior alveolar nerve block anesthesia is one of the most common procedures in dental clinic. Although it is well known as safe procedure, complications always can be occurred. Ocular complications such as diplopia, loss of vision, opthalmoplegia are very rare, but once it happens, dentist and patient can be embarrassed and rapport will be decreased between them. We experienced one diplopia case after inferior alveolar nerve block anesthesia and treated without any further complication. We report this case and describe the cause, diagnosis, and treatment objectives of diplopia caused by inferior alveolar nerve block anesthesiaope