Stock price movement prediction based on Stocktwits investor sentiment using FinBERT and ensemble SVM

Investor sentiment plays a crucial role in the stock market, and in recent years, numerous studies have aimed to predict future stock prices by analyzing market sentiment obtained from social media or news. This study investigates the use of investor sentiment from social media, with a focus on Stocktwits, a social media platform for investors. However, using investor sentiment on Stocktwits to predict stock price movements may be challenging due to a lack of user-initiated sentiment data and the limitations of existing sentiment analyzers, which may inaccurately classify neutral comments. To overcome these challenges, this study proposes an alternative approach using FinBERT, a pre-trained language model specifically designed to analyze the sentiment of financial text. This study proposes an ensemble support vector machine for improving the accuracy of stock price movement predictions. Then, it predicts the future movement of SPDR S&P 500 Index Exchange Traded Funds using the rolling window approach to prevent look-ahead bias. Through comparing various techniques for generating sentiment, our results show that using the FinBERT model for sentiment analysis yields the best results, with an F1-score that is 4-5% higher than other techniques. Additionally, the proposed ensemble support vector machine improves the accuracy of stock price movement predictions when compared to the original support vector machine in a series of experiments.

An Osteotomy Tool That Preserves Bone Viability: Evaluation in Preclinical and Clinical Settings

The main objectives of this work were to assess the efficiency, ease-of-use, and general performance of a novel osseoshaping tool based on first-user clinical experiences and to compare these observations with preclinical data generated in rodents using a miniaturized version of the instrument. All patients selected for the surgery presented challenging clinical conditions in terms of the quality and/or quantity of the available bone. The presented data were collected during the implant placement of 15 implants in 7 patients, and included implant recipient site (bone quality and quantity) and ridge evaluation, intra-operative handling of the novel instrument, and the evaluation of subsequent implant insertion. The instrument was easy to handle and was applied without any complications during the surgical procedure. Its use obviated the need for multiple drills and enabled adequate insertion torque in all cases. This biologically driven innovation in implant site preparation shows improvements in preserving vital anatomical and cellular structures as well as simplifying the surgical protocol with excellent ease-of-use and handling properties.

A Novel Osteotomy Preparation Technique to Preserve Implant Site Viability and Enhance Osteogenesis

The preservation of bone viability at an osteotomy site is a critical variable for subsequent implant osseointegration. Recent biomechanical studies evaluating the consequences of site preparation led us to rethink the design of bone-cutting drills, especially those intended for implant site preparation. We present here a novel drill design that is designed to efficiently cut bone at a very low rotational velocity, obviating the need for irrigation as a coolant. The low-speed cutting produces little heat and, consequently, osteocyte viability is maintained. The lack of irrigation, coupled with the unique design of the cutting flutes, channels into the osteotomy autologous bone chips and osseous coagulum that have inherent osteogenic potential. Collectively, these features result in robust, new bone formation at rates significantly faster than those observed with conventional drilling protocols. These preclinical data have practical implications for the clinical preparation of osteotomies and alveolar bone reconstructive surgeries.

On Implant Prosthodontics: One Narrative, Twelve Voices - 10

No abstract available.

Clinical reliability of CAD/CAM cross-arch zirconia bridges on immediately loaded implants placed with computer-assisted/template-guided surgery: a retrospective study with a follow-up between 3 and 5 years

PURPOSE

The purpose of this study is to retrospectively evaluate the implant and prosthetic survival and success rates of zirconia-based, implant-supported, screw-retained, cross-arch restorations up to 5 years after placement.

MATERIALS AND METHODS

Twenty-two consecutive edentulous patients (11 males and females, each; mean age 68.3 years) received 26 CAD/CAM cross-arch zirconia implant bridges (NobelProcera™ Implant Bridge Zirconia; Nobel Biocare AG, Zurich, Switzerland) supported by 4 to 10 implants each. All patients were followed for at least 3 years (range 36-60 months, mean 42.3 months). Clinical assessments were scheduled every 4 months during hygiene maintenance. Outcomes were implant and prosthetic survival rates, prosthetic success rate, any observed clinical complications, patient satisfaction, and soft tissue parameters. Fisher's exact test was used to assess associations between categorical variables.

RESULTS

No dropouts occurred. The overall implant and prostheses survival rate up to 5 years was 100%. Three out of 26 restorations (five out of three hundred forty eight dental units) showed an adhesive chip-off fracture of the veneering ceramic, scoring a cumulative prosthetic success rate of 88.5% at the prosthetic level and 98.6% at the unit level. All 22 patients were functionally and aesthetically highly satisfied with their restorations. Successful soft tissue parameters were found around all implants.

CONCLUSIONS

Industrially manufactured, zirconia-based, implant-supported, screw-retained, cross-arch restorations are a viable alternative to conventionally manufactured porcelain-fused-to-metal restorations for rehabilitating the edentulous patient.

Influence of attachment and bone loss on the mobility of incisors and canine teeth

OBJECTIVE

The purpose of this clinical study was to evaluate the correlation between tooth mobility (TM), crown-to-root ratio (CRR) and clinical attachment loss (CAL) in periodontally-compromised participants.

MATERIALS AND METHODS

While slowly biting on a load cell, the mobility of the upper incisors and canine teeth of 20 volunteers was measured using a photogrammetric measurement technique. An automated software program recorded the force-related three-dimensional TM at 3-N intervals. CAL was assessed clinically and CRR values were assessed radiographically. For each contralateral pair of teeth (central, lateral incisor, canine) and for each main level of force, the Pearson product-moment correlation coefficient between TM and CRR and between TM and CAL was computed. Correlations were considered statistically significant at p < 0.05.

RESULTS

Statistically significant positive correlations were found between TM and CRR for incisors and canines for each main level of force, whereas canines had the lowest correlation. Statistically significant positive correlations were also found between TM and CAL for the central and lateral incisors at each main level of force. Canines showed no significant correlation between CAL and TM, regardless of force level.

CONCLUSION

The loss of attachment and bone seem to have more influence on the mobility of incisors than canines.

Correlations between tooth mobility and the Periotest method in periodontally involved teeth

OBJECTIVE

The aim of this clinical study was to evaluate whether a correlation exists between three-dimensional tooth mobility (TM) and Periotest values for maxillary anterior periodontally involved teeth (pocket depth > 3 mm) before and after periodontal therapy.

METHOD AND MATERIALS

Force-related TM was measured in 3 N intervals in 19 participants as they bit down on a load cell. Periotest values were evaluated at reproducible measurement points. Both measurement techniques were performed on maxillary central and lateral incisors and canine teeth before periodontal treatment and after a healing period of 3 months. The Pearson product-moment correlation coefficient was calculated to determine exploratory associations.

RESULTS

The comparison between TM and Periotest values indicated "high" and "optimum" correlations for maxillary central incisors before and after periodontal therapy. Lateral incisors exhibited "moderate" and "high" correlations, whereas canines exhibited "weak" and "moderate" correlations before and after periodontal therapy.

CONCLUSION

Periotest values may provide valuable information about quantitative metric tooth mobility in periodontally involved teeth. In future investigations, the study design can expand on various dental fields, such as implantology and traumatology.

Retrieval analysis of different orthodontic brackets: the applicability of electron microprobe techniques for determining material heterogeneities and corrosive potential

Objective

The objective of this study was to investigate the applicability of micro-analytical methods with high spatial resolution to the characterization of the composition and corrosion behavior of two bracket systems.

Material and methods

The surfaces of six nickel-free brackets and six nickel-containing brackets were examined for signs of corrosion and qualitative surface analysis using an electron probe microanalyzer (EPMA), prior to bonding to patient's tooth surfaces and four months after clinical use. The surfaces were characterized qualitatively by secondary electron (SE) images and back scattered electron (BSE) images in both compositional and topographical mode. Qualitative and quantitative wavelength-dispersive analyses were performed for different elements, and by utilizing qualitative analysis the relative concentration of selected elements was mapped two-dimensionally. The absolute concentration of the elements was determined in specially prepared brackets by quantitative analysis using pure element standards for calibration and calculating correction-factors (ZAF).

Results

Clear differences were observed between the different bracket types. The nickel-containing stainless steel brackets consist of two separate pieces joined by a brazing alloy. Compositional analysis revealed two different alloy compositions, and reaction zones on both sides of the brazing alloy. The nickel-free bracket was a single piece with only slight variation in element concentration, but had a significantly rougher surface. After clinical use, no corrosive phenomena were detectable with the methods applied. Traces of intraoral wear at the contact areas between the bracket slot and the arch wire were verified.

Conclusion

Electron probe microanalysis is a valuable tool for the characterization of element distribution and quantitative analysis for corrosion studies.

Circumferential fit assessment of CAD/CAM single crowns--a pilot investigation on a new virtual analytical protocol

OBJECTIVE

Techniques currently applied to determine the marginal accuracy of dental crown restorations yield inadequate information. This investigation aimed to test a new virtual approach for determining the precision of fit of single-crown copings.

METHOD AND MATERIALS

Zirconia single crown copings were manufactured on 10 gypsum, single-tooth master casts with two different established computer-aided design/computer-assisted manufacture (CAD/CAM) systems (groups A and B). After cementation, the circumferential fit was assessed with an industrial noncontact scanner and virtual 3D analysis, following a triple-scan protocol. Marginal fit was determined by virtual sectioning; each abutment-coping complex was digitally sliced in 360 vertical sections (1 degree per section). Standardized measurement distances for analyzing the marginal fit (z, xy, xyz) were selected, and a crosshair alignment was utilized to determine whether crowns were horizontally and/or vertically too large or small. The Mann-Whitney test was applied to test for differences between groups.

RESULTS

Significant differences in the xy direction (P = .008) were measured between groups. Group A showed a greater number of horizontally overextended margins and a higher frequency of xy distances greater than 150 Μm, in addition to a tendency for excessive z distances (P = .095).

CONCLUSION

The mean marginal gap values were clinically acceptable in the present investigation; however, a full circumferential analysis revealed significant differences in marginal coping quality.

A technique for in vitro fit assessment of multi-unit screw-retained implant restorations: Application of a triple-scan protocol

Recent advances in industrial non-contact scanners offer unprecedented opportunities for quality assessment of dental restorations. The majority of investigations published to date are limited to local two-dimensional results. A triple-scan protocol for virtual fit assessment of multi-unit screw-retained implant restorations is presented in this technical report. The advantages for application in biomechanical research include detailed three-dimensional information on internal component congruence in implant superstructures to be used in mathematical models.

Strain development of screw-retained implant-supported fixed restorations: procera implant bridge versus conventionally cast restorations

The aim of this study was to quantify the strain development of screw-retained three-unit implant-supported Procera Implant Bridge restorations. Two groups of screw-retained implant-supported restorations (n = 10) were fabricated by means of casting or computer-aided design/computer-assisted manufacture (CAD/CAM) to fit an in vitro cast situation with two implants. During fixation of the restorations, the emerging strains were recorded using strain gauges attached to the cast material mesially and distally adjacent to the implants. Absolute mean strain development ranged from 29.35 Μm/m to 2,665.80 Μm/m at the different strain gauge locations. Fabrication method had a significant effect on strain development (multivariate analysis of variance, P = .000), with the cast restorations showing significantly higher strain levels compared to the CAD/CAM-fabricated superstructures. CAD/CAM fabrication of screw-retained implant-supported restorations provides greater passivity of fit compared to conventional fabrication methods such as casting.

Correlations between photogrammetric measurements of tooth mobility and the Periotest method

OBJECTIVE

The purpose of the present study was to investigate whether or not the quantitative Periotest values of anterior teeth correlate with quantitative metric values of tooth mobility under vertical (VL) and horizontal load (HL) in periodontally healthy subjects.

MATERIALS AND METHODS

Thirty-one subjects with good periodontal conditions were included and subjected to two different tooth mobility measurement techniques. Periotest values were measured at reproducible measurement points in the vertical (vPT) and horizontal (hPT) dimensions of upper central and lateral incisors and canine teeth. Using the optical measurement technique (photogrammetry), tooth mobility was measured under load in the horizontal (HL) and vertical loading directions (VL) at different load forces. Pearson's correlation coefficients were used to determine exploratory associations.

RESULTS

The comparison between hPT and HL showed no correlations between the two measurements except for 'weak' and 'moderate' correlations for teeth 21 and 23. The analysis of correlations between vPT and VL data showed statistically significant correlations for both the left and right canine teeth that ranged from 'weak' to 'high'. Comparisons between hPT values and VL and between vPT and HL showed significant correlations at a few loading forces only.

CONCLUSION

Quantitative Periotest values cannot be used to draw conclusions about the metric assessment of tooth mobility. For this purpose, the photogrammetric technique could be an additional tool for scientific questions.

Digitizing implant position locators on master casts: comparison of a noncontact scanner and a contact-probe scanner

PURPOSE

Although several investigations of the fit of computer-aided design/computer-assisted manufactured implant restorations have been reported in the literature, very limited information is available on the accuracy of dental scanners for surface data acquisition. The objective of this research project was to investigate the accuracy and repeatability of a three-dimensional noncontact laser scanning system based on conoscopic holography recording the spatial orientation of an implant in vitro.

MATERIALS AND METHODS

One master cast containing five nonparallel implant replicas with scan abutments (implant position locator [IPL], Nobel Biocare) was repeatedly digitized by two commercially available dental scanners and an industrial highprecision coordinate measuring machine as a reference. Repeated measurements of the center point and vector analysis were applied to determine the accuracy and repeatability of IPL orientation. The Wilcoxon signed rank test modified for equivalence was applied to determine whether the systems were equally accurate based on given threshold limits of 0.010, 0.005, and 0.001 mm.

RESULTS

All between-system tests identified significant differences, although most differences were very small in absolute terms. Tests for equivalence based on difference windows were exploratorily significant for 0.010 and 0.005 mm.

CONCLUSION

Conoscopic holography scan technology is a valid option to supplement dental touch-probe scanners for laboratory digitization of implant master casts.

A new triple-scan protocol for 3D fit assessment of dental restorations

OBJECTIVE

Assessing the level of precision entailed by the virtual fit of dental restorations is a very challenging issue. A cement space between an abutment tooth and a dental restoration is a clinical requisite that precludes the application of conventional best-fit registration protocols routinely applied in industrial precision measurements. Since two-dimensional fit assessment techniques currently used in dentistry miss important information about the third dimension, a new protocol was developed to provide three-dimensional information for the virtual registration of the digitized restoration with respect to the abutment.

METHOD AND MATERIALS

CAD/CAM was used to produce 10 titanium single crown copings for five gypsum master casts each, representing a molar prepared for a full crown. An industrial noncontact scanner was used for digitizing the components. Registration of surface data sets was achieved by a new triple-scan protocol. For statistical analysis and repeatability testing of the triple-scan protocol, mean distances of the cement space of all copings on their respective abutments were measured three times.

RESULTS

The validity of the approach is verified by intraclass correlation coefficients that revealed an almost perfect coefficient for repeatability (ICC = 0.981, P < .001) with a 95% confidence range between 0.970 and 0.989.

CONCLUSION

The triple-scan protocol represents a reliable registration approach for surface data sets in dental applications and eliminates the limitations of conventional best-fit registration protocols when a cement space or gap is present between a restoration and its underlying abutment. Future fit assessment investigations can implement this approach of obtaining detailed information of component precision in all spatial orientation.

Effect of geometric parameters on finite element analysis of bone loading caused by nonpassively fitting implant-supported dental restorations

OBJECTIVE

Finite element analysis (FEA) has been frequently used to study the loading situation of dental implants and bone resulting from the fixation of nonpassively fitting restorations. The goal of the present investigation was to demonstrate the effect of geometric model parameters and mesh size on FEA results.

METHOD AND MATERIALS

Five three-dimensional FEA models representing a three-unit fixed dental prosthesis (FDP) supported by two terminal implants were constructed. The models differed in terms of mesh size, bone geometry, implants, and restoration and were created either by joining virtual free-form objects or utilizing optical scans of existing components. By applying thermal changes in volume of specific elements in the area of the FDP pontic, a horizontal misfit of 10 Μm between implants and the restoration was introduced. The resulting loading situation of the bone around the implants was recorded as von Mises equivalent stress.

RESULTS

Maximum stress magnitudes ranging from 13.1 to 24.9 MPa occurred in the cortical part of the implant site where the neck of the implant penetrates bone. In trabecular bone, loading magnitudes were lower by a factor of 20. Modeling implant threads did have a remarkable effect on the stress situation as well as different span lengths of the restorations modeled. All other parameters led only to small variations in maximum loading magnitudes.

CONCLUSION

Simplistic FEA models based on virtual free-form objects with limited level of mesh refinement seem to allow for a basic evaluation of peri-implant bone loading resulting from the fixation of misfitting superstructures.

Student attitudes towards computer-aided testing

INTRODUCTION

  Computer-aided learning (CAL) is a viable alternative to traditional teaching methods. While CAL is used for teaching only, computer-aided testing (CAT) can be applied as a computer-based examination method. The aim of the present study was to evaluate students' attitude towards CAT as compared to written multiple choice tests.

MATERIALS AND METHODS

  Forty-one undergraduate dental students underwent a mock examination consisting of 15 written multiple choice questions and 15 questions delivered using the interactive MobiTed® system. A questionnaire based on an eight-item seven-point Likert scale was used to evaluate the students' attitude towards CAT. The students' performance in both tests was analysed using paired t-tests. Correlations between test performance and questionnaire were expressed by Pearson correlation coefficients.

RESULTS

  Despite study-design-related differences, students' test performance between written multiple choice and MobiTed® was comparable. No correlations between test results and questionnaire could be set up. Students rated MobiTed® to be equivalent to written multiple choice and had no difficulties with the CAT set up. The pre-defined sequence of questions with each question being shown only once was considered to be a major disadvantage of the CAT system. Complex questions should be displayed longer compared to short questions.

DISCUSSION

  Computer-aided testing appeared to be equivalent to written multiple choice tests not only in terms of student performance but also to their perception. This is consistent with previous studies.

CONCLUSIONS

  Interactive multiple choice tests may provide an alternative to written tests, but should allow examinees to have control over the sequence, as well as the length of time the questions are displayed.

Five-year clinical follow-up of prefabricated precision attachments: a comparison of uni- and bilateral removable dental prostheses

OBJECTIVES

To evaluate the clinical long-term success of prefabricated precision attachments in retaining uni- or bilateral removable dental prostheses.

METHOD AND MATERIALS

Twenty-three patients with uni- or bilateral shortened dental arches received removable dental prostheses attached to the residual dentition with two types of precision attachments.

RESULTS

After 5 years, 70% of bilateral and 25% of unilateral removable dental prostheses remained clinically functional. The most frequent cause of clinical failure was fracture of the abutment teeth for bilateral partial dentures and irreversible wear of the precision attachment for unilateral prostheses. Oral hygiene status significantly improved, and the mean pocket depth of the abutment teeth did not increase after 5 years.

CONCLUSION

Removable partial denture prostheses, retained bilaterally with precision attachments, are a reliable treatment modality without negative long-term effects on periodontal health, whereas unilateral removable dental prostheses cannot be recommended because of high clinical failure rates.

The effect of axial and oblique loading on the micromovement of dental implants

PURPOSE

To quantify implant displacement upon axial and oblique force application and compare the effects of bone quality using an in vitro experimental setup.

MATERIALS AND METHODS

One hundred ninety-two implants were inserted into artificial bone block specimens using a drill guide. Ninety-six implants were placed in soft cancellous bone and loaded in 10-N increments up to 80 N in axial and oblique (30-degree angle) directions (n = 48 in each group). The other 96 implants were inserted in dense artificial bone and loaded in axial and oblique directions in the same force increments. Three-dimensional displacement data were recorded for all implants using a noncontact optical image correlation technique based on photogrammetric principles, and the absolute displacement vector was calculated.

RESULTS

There were significant differences in the absolute implant displacement in the different bone densities over all load increments. Implant displacement was significantly higher in soft cancellous bone than in dense bone. Axial and oblique loading revealed significant differences in implant displacement in the cancellous specimens, whereas oblique loading showed increased displacement (339 ± 47 Μm at 80 N) compared to axial loading (266 ± 39 Μm at 80 N). However, axial and oblique loading showed no significant differences over all load increments when implants were inserted in dense specimens (absolute displacement with an 80-N load: 147 ± 10 Μm axial and 126 ± 17 Μm oblique).

CONCLUSIONS

Bone density influenced implant displacement. The loading character (axial versus oblique) significantly influenced implant displacement in soft cancellous bone block specimens only. However, the limitation of the measured displacement values to an in vitro application that did not represent the complexity of vital bone has to be considered.

Surface characteristics of zirconia-based posterior restorations: clinical and scanning electron microscopic analysis

AIM

The aim of this prospective clinical trial was to evaluate the performance of zirconia-based all-ceramic posterior fixed partial dentures (FPDs) after 4 years of clinical use.

MATERIALS AND METHODS

Fifteen patients who needed 3- or 4-unit posterior FPDs were enrolled in the study. One manufacturer fabricated all restorations, following established clinical protocols and using computer-aided design/computer-aided manufacturing technology and one veneering material. Survival and success were evaluated clinically. Impressions were taken immediately after definitive cementation and after 48 months. Gold-coated epoxy replicas of the restorations were analyzed with scanning electron microscopy (SEM). Surface alterations were also evaluated clinically.

RESULTS

After 48 months, the survival rate for the FPDs was 100%. Three restorations exhibited minor chipping, for a fracture rate of 20% after 4 years. Thirty (59%) of the 51 individual restoration units revealed clinically rough occlusal surfaces, a finding that was confirmed by SEM.

CONCLUSION

The placement of 3- and 4-unit zirconia-based posterior FPDs can be considered a reliable treatment modality for medium-term clinical use. However, surface alterations of the veneering ceramics were observed after 4 years and are of notable clinical concern.

Bone loading caused by different types of misfits of implant-supported fixed dental prostheses: a three-dimensional finite element analysis based on experimental results

PURPOSE

To show, by comparison of horizontal, vertical, and angular misfit in a three-dimensional finite element model, that clinical methods for the evaluation of implant framework fit cannot provide objective results.

MATERIALS AND METHODS

Two three-dimensional finite element models were designed for the simulation of experimentally determined strain values of three-unit fixed dental prostheses supported by two implants. Horizontal, vertical, and angular misfits between implants and restorations were used to create predetermined strain levels. The magnitudes of misfit and resulting bone loading were recorded as von Mises equivalent stresses for the different types of misfit.

RESULTS

A horizontal misfit of 36 μm and a vertical misfit of 79 μm had to be modeled to simulate the experimentally determined strain values. An angular misfit of 0.083 degree (equivalent to a gap of 3 μm on one aspect of the implant) resulted in comparable strain levels. Bone loading in the cortical area around both implants ranged from 50 to 90 MPa for horizontal and vertical misfit. In trabecular bone, loading of 2 to 5 MPa was found. For the angular misfit, bone loading up to 20 MPa in the cortical layer and 1 MPa in the cervical part of the trabecular bone occurred at the implant where the misfit had been introduced. Horizontal and vertical misfits led to comparable loading patterns around both supporting implants. Under angular misfit, bone loading mainly occurred around the implant where the misfit had been introduced. Almost no loading was observed in the circumference of the contralateral implant.

CONCLUSIONS

Minimal angular misfits between implant abutments and restorations, which cannot be detected clinically, may lead to substantial bone loading.

Bond strength of different veneering ceramics to zirconia and their susceptibility to thermocycling

PURPOSE

To evaluate the bond strength of recently developed feldspathic veneering ceramics to zirconium-oxide ceramic core material (Y-TZP). In addition, the effect of thermocycling on the bond strength was investigated.

METHODS

90 square Lava framework Y-TZP specimens were randomly assigned to three groups (n = 30) and veneered with one of the three zirconia veneering ceramics Cerabien ZR (CZR), GC Initial (GCI), or Lava Ceram (LC). 30 additional metal-ceramic specimens served as the control (VO). 15 specimens per group were stored in a saline solution for 3 days. To test the durability of the bond, 15 specimens per group were thermocycled for 10,000 cycles between 5 degrees to 60 degrees C with a 15-second dwell time. Shear strength was tested with an Instron universal testing system. A two-way ANOVA model and Tukey's HSD were applied for statistical analyses (alpha = 0.05).

RESULTS

The different material combinations revealed significantly different shear bond strength values (CZR > GCI > LC > VO). All veneering ceramic/zirconia combinations showed significantly higher bond strength than the metal-ceramic control VO. Bond strength values were not affected by thermocycling, except for CZR, which had significantly higher bond strength after thermocycling. Microscopic evaluation of failure modes revealed 100% cohesive failures in the veneering ceramic for all specimens.

Photogrammetric measurement of initial tooth displacement under tensile force

The purpose of this study was to quantitatively measure tooth displacement under low horizontal tensile force (≤18 N) and to test the reproducibility of measurements. Anterior tooth mobility was measured using a photogrammetric measurement technique in 23 periodontally healthy subjects. While slowly increasing the tension on each tooth, an automated software program recorded three-dimensional tooth displacement at 3 N intervals, up to 18 N. Measurements were repeated three-times for each tooth. The vector of absolute tooth mobility in the buccal direction was calculated. Intra-class correlations of the three repeated measurements of each tooth were calculated and ranged between "good" and "optimal". The agreement of measurements was significant (p≤0.05). The analysis of differences between the deviation vectors of contralateral teeth revealed that most differences emerged to be statistically non-significant. The combination of a mechanical loading approach with the optoelectronic system allowed the measurement of three-dimensional tooth mobility in vivo.

Dental aspects in patients with DiGeorge syndrome

DiGeorge syndrome, which is caused by a microdeletion of 1.5 to 3.0 megabases on the long arm of chromosome 22, has an incidence of approximately 1:4,000 to 1:5,000 live births. The phenotypic spectrum of this disorder includes congenital heart defects, immunodeficiency due to thymic hypoplasia or aplasia, transient or permanent hypocalcemia due to parathyroid hypoplasia or aplasia, developmental retardation, and psychiatric disorders. Dental aspects in these patients include skeletal malformations, velopharyngeal insufficiency with or without cleft palate, small mouth, and hypotonus orofacial musculature, as well as impaired salivary flow. Enamel aberrations related to hypocalcemia may result in a higher frequency of dental caries. Based on a series of five patients, the medical and dental aspects that have to be considered in the care of patients with DiGeorge syndrome are presented.

Prosthodontic treatment of a patient with bisphosphonate-induced osteonecrosis of the jaw using a removable dental prosthesis with a heat-polymerized resilient liner: a clinical report

Bisphosphonate-induced osteonecrosis of the jaws (BONJ) is reported frequently in patients receiving oral or intravenous bisphosphonates. To minimize potential complications, dental treatment must be performed with care. There are invasive and noninvasive treatment options for patients with active BONJ or a history of this complication. This clinical report describes the prosthodontic treatment of a patient who developed BONJ after receiving intravenous bisphosphonates (pamidronate). Because of the recurrent incidence of BONJ, noninvasive prosthetic therapy with telescopic overdentures and a heat-polymerized resilient liner was provided. After 2 years, there were no biological or technical complications.

Parameters of implant stability measurements based on resonance frequency and damping capacity: a comparative finite element analysis

PURPOSE

Contradictory results have been reported on the comparability of implant stability measurements performed with the Periotest and the Osstell Mentor devices. The purpose of the present finite element analysis was to simulate the influence of the parameters implant length, bone quality (cortical thickness and damping factor), bone loss, and quality of transducer fixation on resonance frequency analysis (RFA) and damping capacity measurements.

MATERIALS AND METHODS

Three-dimensional finite element models of implants placed in human mandibular bone were designed for the simulation of Periotest (Periotest value; PTV) and RFA (implant stability quotient) measurements. Three values for each of the parameters implant length, damping capacity of cortical and trabecular bone, thickness of cortical bone, bone loss, and quality of transducer fixation were obtained. Measurements were simulated at four stages of osseointegration.

RESULTS

For all parameters, an increase in implant stability was found with increasing levels of osseointegration. Implant stability was positively correlated with implant length and thickness of cortical bone, with slightly converging values at increased levels of osseointegration. Varying the damping factor of bone had no significant effect. Implant stability was negatively correlated with bone loss, with slightly converging values at increased levels of osseointegration. Linear changes in implant length and bone loss caused nonlinear effects in implant stability values. Stiffness of transducer fixation had an impact on RFA measurements when values below 10 GPa were applied.

CONCLUSION

Although both measuring devices reacted similarly when different parameters of implant stability were changed, good correlation between Periotest values and implant stability quotients was observed only when measurement values of implants without bone loss were considered.

Restoring severely compromised anterior teeth with zirconia crowns and feather-edged margin preparations: a 3-year follow-up of a prospective clinical trial

This prospective clinical trial sought to evaluate the 3-year clinical results of anterior teeth restored with 0.3-mm-thick zirconia copings and feather-edged marginal preparations. Ten patients received 19 single-tooth restorations in the anterior maxilla to restore severely decayed teeth. After a mean observation period of 39.2 months, no material fracture occurred and all crowns had acceptable surfaces. A survival and success rate of 100% was recorded, which suggests that the clinical method may be a reliable treatment modality for restoring severely compromised anterior teeth.

Quantitative assessment of orthodontic mini-implant displacement: the effect of initial force application

OBJECTIVE

Primary stability and micromovement of orthodontic mini-implants depends on a number of factors and influences clinical success or failure. The purpose of this study was to assess the behavior of orthodontic mini-implants upon initial load application.

METHOD AND MATERIALS

Orthodontic mini-implants (n = 39) were inserted in the alveolar process of maxillary human cadaver specimens (n = 10). Increasing horizontal forces (up to 2.5 N) were applied, and triggered images were taken in 0.5-N load intervals. Additionally, peri-implant parameters based on micro-CT volume data were recorded. Data were subjected to a two-sided nonparametric Wilcoxon signed rank test, and between-group comparisons were assessed with a Mann-Whitney test (alpha = .05).

RESULTS

Initial load application led to displacement beyond elastic recovery of the surrounding bone after force release (P < .001). Cortical thickness and insertion depth, despite numeric differences, did not reveal any statistical differences, while displacement of mini-implants was significantly affected by contact to neighboring teeth (P < .001).

CONCLUSIONS

Insertion technique and initial load application on orthodontic mini-implants may be regarded as two crucial factors for success, while repeated application of orthodontic force does not seem to increase screw mobility.

Zirconia posterior fixed partial dentures: a prospective clinical 3-year follow-up

PURPOSE

The aim of this prospective clinical trial was to evaluate the reliability of three- and four-unit posterior fixed partial dentures (FPDs) with zirconia frameworks after 3 years of clinical function.

MATERIALS AND METHODS

Thirty patients, each needing a posterior FPD to restore one or two missing teeth, were included in the study. Preparation guidelines were: occlusal reduction of 1.5 to 2 mm, axial reduction of 1.5 mm, and circumferential chamfer preparation placed 0.5 mm subgingivally. Frameworks were fabricated using a computer-aided design/computer-assisted manufacture technique. All FPDs were cemented with glass-ionomer cement. At baseline and 12, 24, and 36 months after cementation, survival and success of the zirconia framework and the ceramic veneer were evaluated. To analyze the effect of placement of an all-ceramic restoration on the gingival tissue, Gingival Index, Plaque Index, sulcus bleeding index, and pocket depth at abutment (test) and contralateral analogous teeth (control) were assessed. Data were analyzed by descriptive statistics, the Wilcoxon test, and the McNemar test.

RESULTS

Of the 30 initial subjects, 27 patients with 27 zirconia FPDs were examined after a mean testing period of 34.2 months. All FPDs were still in use and unfractured, resulting in a 100% survival rate for the frameworks. One FPD exhibited a major chip after 36 months. The cumulative success rate was 96.3%. No significant differences between the periodontal parameters of the test and control teeth were observed. The Plaque Index revealed significantly higher scores for mesial and distal control teeth at baseline and after 12 and 24 months for distal control teeth.

CONCLUSION

Posterior zirconia-based three- and four-unit FPDs present a reliable treatment modality after medium-term clinical use.

Vertical and Sagittal Growth in Patients with Unilateral and Bilateral Cleft Lip and Palate—A Retrospective Cephalometric Evaluation

Objective:

To investigate whether the craniofacial vertical and sagittal jaw relationship in patients with cleft lip and palate (CLP) differed from that of age-matched noncleft controls, before and after the pubertal growth spurt.

Design:

Retrospective observational study.

Patients:

The study group comprised 126 patients with CLP, subdivided according to gender and cleft type, and the control group comprised 53 age-matched skeletal class I patients.

Methods:

Angular and linear measurements were taken from prepubertal and postpubertal lateral cephalograms of all patients.

Results:

In patients with cleft lip and palate, the maxillary retrognathism became more remarkable with increasing age; whereas, the retrognathic position of the mandible became less pronounced as compared with controls. Reduced posterior midfacial height, a common prepubertal finding in patients with cleft lip and palate, was significant in postpubertal girls and young women with unilateral cleft lip and palate (p  =  .002). The total anterior facial height in male patients with bilateral cleft lip and palate was larger than in control patients (p  =  .002) after the pubertal growth spurt due to an increased anterior midfacial height. In male patients with unilateral cleft lip and palate, this finding was due to an increased anterior lower facial height (p < .001).

Conclusions:

Patients with cleft lip and palate treated according to a standardized treatment concept had adequate craniofacial jaw relationships after puberty. Despite a measured skeletal class I in both male and female patients with cleft lip and palate regardless of cleft type, there was a slight tendency toward a skeletal class III. Findings were similar for all groups of cleft lip and palate patients irrespective of the type of orthodontic treatment performed.

Biomechanical methods applied in dentistry: a comparative overview of photoelastic examinations, strain gauge measurements, finite element analysis and three-dimensional deformation analysis

The aim of this article is to illustrate and discuss current methods applied in the analysis of biomechanical components in dental applications. For illustration purposes, the strain development of a non-passively fitting implant supported fixed restoration was evaluated using the four techniques: photoelastic examination, strain gauge measurements, finite element analysis, and three-dimensional deformation analysis. Photoelastic analysis only allowed for a raw estimation of the strains evoked by superstructure fixation. Quantitative results could be derived from both strain gauge measurements and three-dimensional deformation analysis which could then be used to simulate the loading situation around the supporting implants.

Prosthetic screw detorque values in implants retained as cast bar superstructures or bars modified by the Cresco Ti Precision technique--a comparative in vivo study

PURPOSE

This prospective clinical trial investigated the effect of different fabrication techniques on screw-joint stability in implant-retained frameworks.

MATERIALS AND METHODS

Seventy-nine dental implants (39 Brånemark System and 40 Straumann) were inserted into 20 patients with an edentulous mandible. One of two fabrication techniques was randomly chosen as a definitive restoration, either a cast bar or a bar superstructure modified with the Cresco Ti Precision (CTiP) technique. The patients were divided into four groups depending on the type of implant and prosthetic superstructure: Straumann-conventional (Sc), Straumann-Cresco (SCr), Brånemark-conventional (Bc), and Brånemark-Cresco (BCr). Initial torque values and removal torque values were recorded with a custom-made digital torque controller both 1 week (T1) and 3 months (T2) after clinical function.

RESULTS

Statistical analysis revealed significant differences in absolute detorque values at T1 (P = .002) with 4.51 Ncm (SD = 3.80) for the Sc group, 10.65 Ncm (SD = 4.42) for SCr, 11.24 Ncm (SD = 4.00) for Bc, and 9.02 Ncm (SD = 3.81) for BCr. At T2 (P = .000) the median values of lost torque were 5.08 Ncm (SD = 4.05) for the Sc group, 10.51 (SD = 3.00) for SCr, 7.50 (SD = 5.86) for Bc, and 9.41 Ncm (SD = 4.54) for BCr. However, when correlation of detorque values to initial torque values was performed, no statistical differences were found between groups or time points. The percentage of lost torque at T1 (P = .849) and T2 (P = .058) was 28.60% (SD = 21.80) and 32.85% (SD = 24.65), 30.04% (SD = 12.49) and 30.80% (SD = 8.66), 32.11% (SD = 11.37) and 21.03% (SD = 16.53), and 25.33% (SD = 10.69) and 27.83% (SD = 12.57) for the Sc, SCr, Bc, and BCr groups, respectively.

CONCLUSIONS

The screw-joint stability of passivated bars is not superior to cast superstructures. A general decrease of approximately 30% of initial torque values can be expected in clinical situations, independent of the implant system used.

Updated implant-retained restorative solutions in patients with hypodontia

Hypodontia is often found during orthodontic screening and occurs with a prevalence of between 5% and 10%. One or more congenitally missing permanent teeth is a clinical finding that affects both male and female patients. Although maintaining deciduous teeth is an option in a few cases, the majority of patients with agenesis of teeth require extraction and orthodontic space closure or restorative treatment. Depending on the number and location of missing teeth, implant-supported fixed single-tooth restorations provide excellent long-term results. Choosing appropriate treatment techniques and materials will result in long-term clinical function, stability, and esthetic success.

Effects of topographical surface modifications of electron beam melted Ti-6Al-4V titanium on human fetal osteoblasts

The aim of the study was to assess the suitability of different Ti-6Al-4V surfaces produced by the electron beam melting (EBM) process as matrices for attachment, proliferation, and differentiation of human fetal osteoblasts (hFOB 1.19). Human osteoblasts were cultured in vitro on smooth and rough-textured Ti-6Al-4V alloy disks. By means of cell number and vitality and SEM micrographs cell attachment and proliferation were observed. The differentiation rate was examined by using quantitative real-time PCR analysis for the gene expression of alkaline phosphatase (ALP), type I collagen (Coll-I), bone sialoprotein (BSP) and osteocalcin (OC). After 3 days of incubation there was a significant higher vitality (p < 0.02) and proliferation (p < 0.02) of hFOB cells on smooth surfaces (R(a) = 0.077 microm) and compact surfaces with adherent partly molten titanium particles on the surface (R(a) </= 24.9 microm). On these samples cells spread over almost the whole surface. On porous surfaces with higher R(a) values, cell proliferation was reduced significantly. Quantitative real-time PCR analysis showed that the expression of osteogenic differentiation markers was not influenced by surface characteristics. Gene expression did not differ more than twofold for the different samples. Compact titanium samples with adherent partly molten titanium particles on the surface (R(a) </= 24.9 microm) fabricated by the EBM process turned out to be best suited for cell proliferation, while highly rough surfaces (R(a) >/= 56.9 microm) reduced proliferation of hFOB cells. Surface characteristics of titanium can easily be changed by EBM in order to further improve proliferation.

Comparative study on interactive computer-aided-learning and computer-aided-testing in patient-based dental training in maxillofacial surgery

AIM

The objective of this comparative study was to validate, through empirical data, the use of interactive, problem-oriented computer-aided-learning (CAL) and computer-aided-testing (CAT) in dental studies by directly comparing these methods with conventional teaching.

METHOD

A total of 95 students from the third and fourth clinical semesters participated in an interdisciplinary seminar on oral maxillofacial implantology; 47 of these were taught using conventional teaching methods, while the remaining 48 students were taught using mobiTED, a CAL/CAT-based interactive communication system that can be used patient- and problem-oriented. An examination was given at the end of the course to evaluate student learning. A student's interest/attentiveness, involvement, knowledge gain, and the course attractiveness and quality were evaluated with visual analogue scales (VAS) in a subjective experience protocol.

RESULTS

The study group taught using the CAL/CAT-based interactive communication system showed statistically significant better results in the examination, with a median score of 89.2%, while the conventional teaching study group achieved a median score of 76.0%. A VAS-based analysis of subjective experiences also revealed statistically significant differences between the two study groups.

CONCLUSION

Use of the CAL/CAT system for interactive, problem-oriented learning in patient-based dental training led to increased levels of attentiveness, of student acceptance and of the perceived attractiveness of the seminar. CAL/CAT-mediated instruction also led to increased communication, with a subsequent improvement in the qualitative and quantitative parameters of knowledge transfer and cognitive knowledge assimilation. Use of CAL/CAT also facilitated the acquisition, appraisal, and understanding of complex medical data.

Influence of cementation technique on fracture strength and leakage of alumina all-ceramic crowns after cyclic loading

OBJECTIVE

To compare in vitro the influence of 3 cementation techniques on leakage and fracture strength of alumina all-ceramic crowns after cyclic loading in an artificial chewing simulator.

METHOD AND MATERIALS

Forty-eight extracted molars were mounted in a way that simulates natural tooth mobility. Crowns (Procera Alumina, Nobel Biocare) were fabricated and inserted with either conventional cementation with zinc phosphate cement without pretreatment (group ZOP); cementation with a universal adhesive resin cement without pretreatment (group HYB); or adhesive bonding with composite resin after pretreatment of the tooth (dentin bonding agent) and the crown (airborne-particle abrasion and a special ceramic priming agent containing adhesive monomers that bond to metal-oxide ceramics) (group ADH). All specimens were stored in artificial saliva and subjected to 1.2 million load cycles in a dual-axis chewing simulator (Willytec). Eight specimens per group were subjected to compressive load until failure, while the remaining 8 specimens were stained and sectioned for measuring of dye penetration. One-way ANOVA and Tukey HSD were used for statistical analyses (alpha = .05).

RESULTS

Cementation techniques were significantly different (P = .009) in regard to mean load at failure. Fracture strength was significantly greater for ADH (mean load at fracture, 2,782 +/- 419 N) as compared to HYB (1,980 +/- 270 N) or ZOP (1,788 +/- 242 N). All groups differed significantly for leakage values (P < .001), with ADH showing the lowest mean leakage (0.04 +/- 0.07 mm), followed by HYB (0.96 +/- 0.16 mm) and ZOP (2.44 +/- 0.19 mm).

CONCLUSION

Cementation technique affects fracture strength and leakage of all-ceramic molar crowns. Fracture strengths were well above natural chewing forces for all cementation methods. However, adhesive bonding significantly increased fracture strength and improved marginal seal of alumina crowns.

CAD/CAM and telescopic technology: design options for implant-supported overdentures

There are many options with respect to materials, construction methods, and design concepts for the technical implementation of implant-supported dental prostheses. Different methods of anchorage can be used to attach removable superstructures to implants. Telescopic crowns make it possible to fabricate inexpensive superstructures with precise and passive fit. Computer-aided design/computer-assisted manufacture (CAD/CAM) technology allows copings to be fabricated from materials such as zirconia or titanium. Moreover, CAD/CAM crown copings can serve as a base for fabricating customized ceramic replacement teeth. Different veneering techniques, such as pressed-on ceramics for zirconia cores, ensure a fast and economic work process. With the use of electroforming it is possible to manufacture highly precise secondary structures that ensure passive seating of the prosthesis in a stable position. This article demonstrates a restorative treatment option using current techniques with the aim of rehabilitation with an esthetic and functional implant-supported removable denture.

[Psychological and dental considerations in the prosthetic rehabilitation of children. Child prothesis--part I]

The fabrication of a prosthesis for a child requires an extensive diagnostic process together with a detailed medical and dental history. The treatment modalities for children and adults are different. By young patients attention must be paid in order to establish a feeling of trust and close cooperation between the dentist and the patient. The aim of the treatment with removable denture prosthesis is the re-establishment of aesthetic, phonetic and function while assuring at the same time a high standard of oral hygiene and periodontal maintenance. The continuous jaw growth and the dentition changes of a child must be closely monitored. Therefore, frequent (3-6 months recall intervals) follow-up examinations and denture adjustments are needed.

[Technical treatment considerations in making prostheses for children. Child prostheses--Part 2]

The rehabilitation of a child's dentition with a removable prosthesis is more complex and time consuming, when comparing it to the one of adults. Prerequisite for a successful treatment is a careful consideration of age-related, technical, functional and psychological aspects. The aesthetic and functional replacement of the missing teeth using a removable prosthesis results in an increased self-esteem for the young patients. This case report describes the management of a young child as well as the treatment planning and the prosthetic rehabilitation process.

Diagnostic potential of 3D-data-based reconstruction software: an analysis of the rare disease pattern of cherubism

Cherubism is an autosomal-dominant syndrome characterized by bilateral maxillomandibular bony degeneration, fibrous connective tissue hyperplasia, and displacement of permanent tooth germs. Reossification of the cystic lumen occurs spontaneously, but dislocated teeth must be realigned orthodontically. Advancements in virtual 3D reconstruction of anatomic structures based on computed tomography (CT) or cone beam CT data have provided for more predictable individual treatment planning. We evaluated two software programs for making densitometry and volume measurements of cystic areas in the mandibles, and for 3D visualization of permanent tooth germs within the cystic lumen, in two siblings with cherubism.

Influence of surface treatment and simulated aging on bond strengths of luting agents to zirconia

OBJECTIVE

To evaluate short- and long-term shear bond strengths of 4 luting agents to zirconia following different surface treatments.

METHOD AND MATERIALS

A total of 320 ceramic specimens fabricated from a commercial zirconium oxide ceramic (Lava) were randomly divided into 4 groups: left untreated (NOT), airborne-particle abraded (SND), Rocatec tribochemical silica/silane coated (ROC), or ground and polished (GRD). Resin composite cylinders were bonded to the zirconia specimens with resin composite luting agent RelyX ARC (ARC), universal adhesive resin composite RelyX Unicem (UNI), adhesive-phosphate-monomer-containing resin composite Panavia F (PAN), or the hybrid glass-ionomer cement RelyX Luting (LUT). Subgroups of 10 specimens were stored in distilled water (37 degrees C) for 3 days (ST) or stored for 180 days and thermocycled for 12,000 cycles (LT/TC) before shear bond strength was tested. Statistical analyses included Kruskal-Wallis and Wilcoxon 2-sample rank sum test (alpha = .01).

RESULTS

Short-term shear bond strengths were higher with ROC than with SND, which were both greater than GRD or NOT. UNI revealed higher shear bond strengths than PAN, ARC, and LUT. LT/TC significantly decreased shear bond strength values. GRD and NOT produced the lowest shear bond strengths. SND and ROC significantly increased bond strength. ROC generally yielded the highest long-term shear bond strength, especially with UNI, PAN, or ARC. These were similar to SND and PAN, which revealed the highest long-term shear bond strengths.

CONCLUSIONS

Surface treatment, luting agent, and storage conditions significantly influence shear bond strengths to zirconia. Artificial aging significantly reduces shear bond strengths. Airborne-particle abrasion combined with a resin composite containing adhesive phosphate monomers or tribochemical silica/silane coating combined with any of the tested resin composite luting agents provides superior long-term shear bond strength values.

Clinical study on the correlation between psychogenic dental prosthesis incompatibility, oral stereognosis, and the psychologic diagnostic tools SCL-90-R and CES-D

PURPOSE

The objective of this study was to use an oral stereognosis test to evaluate possible intraoral/sensorimotor causes in patients with a psychologic diagnosis of psychogenic prosthesis incompatibility, and to evaluate possible correlations between oral stereognosis and the psychologic diagnostic tools Symptom Checklist-90-R (SCL-90-R) and Center of Epidemiological Studies Depression Scale (CES-D).

MATERIALS AND METHODS

The study cohort comprised 83 patients with complete dentures fabricated according to a standardized protocol. Twelve patients diagnosed with psychogenic prosthesis incompatibility (11 women, 1 man) using the SCL-90-R and CES-D scales in a previous study and a group of 24 randomly selected control subjects (14 women, 10 men) underwent an oral stereognosis test with 10 neutral-tasting plastic test specimens with a maximum edge length of 8 mm in 2 test cycles.

RESULTS

The results revealed no significant differences in oral stereognostic ability between patients with diagnosed psychogenic dental prosthesis incompatibility and the control patients. The patients in the test group expressed clear dissatisfaction with their dentures. No correlation was found between oral stereognostic ability and the SCL-90-R or CES-D values.

CONCLUSIONS

This study is the first to use oral stereognosis tests for patients with psychologically diagnosed psychogenic dental prosthesis incompatibility. The diagnosis of psychogenic prosthesis incompatibility by the SCL-90-R and CES-D scales is affirmed by the lack of correlations between the functional/anatomic aspects of oral stereognostic ability, psychologic diagnostic tools, and the clinical picture of psychogenic prosthesis incompatibility. Thus, psychogenic prosthesis incompatibility can be classified more explicitly as a psychosomatic disorder.