Volumetric analysis of artifacts from fiducial markers under cone beam computed tomography.

Abstract Background/purpose: Computer aided implant surgery has been widely adopted in modern implant dentistry. However, absence of reliable anatomic landmarks for superimposing digital data sets for patients with terminal dentition or complete edentulism remained challenging. Utilization of additional fiducial markers intraorally as the reference points for the improvement of accuracy became crucial in implant digital workflow. Nevertheless, the choice of the material for fiducial markers should present the least radiographic artifacts under cone beam computed tomography (CBCT) for better accuracy. The aim of this in vitro study was to investigate the volume of radiographic artifacts generated through different materials under the image of CBCT. Materials and methods: Fifteen dental materials were selected and configured into cubic shape. All the materials were scanned initially with the laboratory scanner as the control groups. The samples were scanned by CBCT machine as test groups and the volume of artifact generated under CBCT images were compared and analyzed using 3D modeling software. Results: Eleven out of fifteen materials could be recognized under CBCT images. Volumetric analysis reported that statistically significant differences among the materials could be noted, and the flowable composite resin presented the least volumetric difference. Lithium disilicate glass-ceramic, flowable composite resin, and gutta-percha presented the least deformation and maintained their cubic shapes. Conclusion: The results of the present study may imply that flowable composite resin compared to all ceramic materials, amalgam and gutta-percha may be a preferable choice when utilized as fiducial markers under CBCT images.

Immediate implant placement with and without provisionalization: A comparison of a one-year longitudinal study.

Background/purpose: Immediate implant placement (IIP) with and without immediate provisionalization (Ipro) may yield satisfactory results in appropriate indications and treatment, especially in the esthetic zone. The aim of this study was to compare implant stability, marginal bone loss (MBL), survival rates, and patient satisfaction between IIP with Ipro and IIP without Ipro. Materials and methods: Seventy patients, each with a failed maxillary anterior tooth, were randomly assigned to IIP with Ipro (Group A: n = 35) or IIP without Ipro (Group B: n = 35). Implant stability quotient (ISQ) and standardized periapical radiographs were performed at surgery and at 3, 6, 9, and 12 months postoperatively to investigate implant stability and MBL, respectively. Survival was assessed 1 year after surgery. Patient satisfaction was evaluated with a visual analogue scale (VAS). Results: Primary ISQ and MBL were not significantly different between groups A and B immediately after surgery (P ＞ 0.05). Implant survival was 100% in both groups, and only one mechanical complication was observed. Patient satisfaction was good at definitive crown delivery and postoperatively 1-year in both groups. However, the immediate postoperative VAS score in Group A was significantly higher than that in Group B (P < 0.05). Conclusion: Group A revealed significantly higher secondary ISQ than Group B at postoperatively 3, 6, 9, and 12 months. There were no significant differences between groups A and B in terms of MBL and survival. Notably, patient satisfaction in Group A was significantly higher than in Group B immediately after surgery.

Implant stability and marginal bone level changes: A 2-year prospective pilot study.

Background/purpose: Implant stability is crucial for successful osseointegration. Marginal bone level is considered an important indicator of long-term implant success and stability. The purposes of this study were to investigate 1) the effect of age, gender, bone density, implant length, and implant diameter on insertion torque (IT), primary implant stability quotient (ISQ), and secondary ISQ, 2) the impact of age, gender, bone density, implant length, implant diameter, IT, and ISQ on marginal bone loss (MBL). Materials and methods: Ninety patients who needed implant therapy were enrolled and overall 156 implants were installed to support single crowns. IT and ISQ were recorded for all implants during surgery and ISQ measurements were performed at follow-up visits. Age, gender, bone density, implant length and diameter were also registered. Radiographic evaluation of MBL was performed postoperative immediate (baseline), 3, 6, 9, 12, 18, and 24 months using digital periapical radiographs. Results: Age had little effect on IT and primary ISQ (P > 0.05). Generally, males had higher IT and primary ISQ, but no significant differences between genders were detected. Bone density showed significant effects on IT and primary ISQ. Correlation analysis revealed high positive correlations between IT/bone density and primary ISQ/implant diameter. Significant impacts of bone density and IT on MBL were found. Conclusion: Implant diameter had a more profound impact than length on IT/primary ISQ. Bone density played a considerable role in IT/primary ISQ determination. Bone density and IT had more impacts than primary ISQ on MBL.

Total solution of a smart shade matching.

Background/purpose: The simulated color of restorations plays an important role in improving patient satisfaction. The aim of this study was to test a new intelligent colorimetric solution using the Advanced Reflectionless Technology (ART) monitor and compare them using commercially available shade systems. Materials and methods: Six participants' right maxillary central incisors were tested with three devices, including the AUO Display Plus (Group A), a Canon single-lens reflex camera with eLAB's polar eyes filter (Group E), and the VITA Easyshade V (Group V). Each porcelain tooth was divided into three areas, and was assigned a CIELAB L∗a∗b∗ value by using the VITA Easyshade V. The original data were compared with the CIELAB L∗a∗b∗ obtained using the VITA Easyshade V. A prosthodontist compared the color of the porcelain veneers by eyes and gave the scores from 1 to 3. Results: For the ΔE, the three areas of Group A had the smallest differences between the color of the fabricated teeth and that of the original teeth. Colorimetric analysis indicated that Groups A and V did not differ much in the color of the three areas of the tooth. Groups E and A exhibited significant differences between the cervical third and middle third of the tooth, and Groups E and V exhibited significant differences between the middle third and incisal third of the tooth. Conclusion: Compared with traditional monitors, ART is closer to real images in terms of color, contrast, and detail grayscale. Technicians are able to produce realistic and pleasing colors.

Investigation on the effect of recasting palladium-silver alloy by argon arc vacuum pressure casting process.

Background/purpose: Palladium-silver (Pd-Ag) alloys are important as an alternative to gold-based alloys. The purpose of this study was to investigate the effect of an argon-arc vacuum pressure casting process on the recasting of the Pd-Ag alloy. Materials and methods: The recasting Pd-Ag alloys were compared with conventional horizontal centrifugal (HC) casting to an argon (Ar)-arc vacuum pressure (Ar-arc/VP) casting. The first-generation castings were made from a Pd-Ag alloy purchased from a supplier. Next-generation castings were made from 50 wt% Pd-Ag alloy before casting and 50 wt% from previous castings. This sequence was repeated over three generations to form the 2nd, 3rd and 4th recasting ingots. The ingots were then measured for marginal accuracy, interfacial oxidation, hardness and phase identification. Results: The recasting success rate of recastibility reached 100%. Compared with the HC group, the Ar-arc/VP group had better edge precision, smaller oxide layer thickness and lower hardness. The comparison of X-ray diffraction intensity showed that the relative intensities of Pd and Ag in the first, second and third generations recasting of the Ar-arc/VP group were significantly higher than those of the HC group. Phase analysis showed that the trace elements of indium and tin contents in the Pd-Ag recasting ingots of the Ar-arc/VP group were higher than those of the HC group. Conclusion: The results showed that the casting process used for recasting affected the quality of the Pd-Ag alloy. Therefore, Ar-arc/VP casting process could improve the effect of Pd-Ag recasting and maintain the alloy properties in comparison with HC casting.

Preliminary comparison of the remineralization and desensitization effects of a novel mineralized ion-releasing toothpaste and commercially available competitive products.

Background/purpose: Toothpaste plays an important role in brushing teeth to maintain oral hygiene and health. The purpose of this study was to develop a new toothpaste containing surface nanocrystal-rich dicalcium phosphate anhydrous (DCPA) powder and to investigate its effect on tooth samples. Materials and methods: The innovative toothpaste (REALCaP®/Group R) was compared with two commercial toothpastes (BioRepair®/Group B and Sensodyne®/Group S). Brushing cycle tests were performed on bovine tooth slices coated with individual toothpaste and a control group without toothpaste (Group C). Microhardness, roughness, surface structure observation, and X-ray diffraction (XRD) were performed on cycle days 4, 7, and 14 to analyze the impact of the toothpastes on tooth samples. Reults: Microhardness in the Group R was higher than that of the other groups regardless of the cycle days. Roughness in the Group R increased on days 4 and 7 but decreased on day 14. Roughness in the groups S and B increased with days. Microstructural observation revealed that most exposed dentinal tubules had been sealed in the Group R on day 14. Overlay thickness in the Group R was significantly higher than that in the groups S and B on days 4, 7, and 14. XRD analysis showed no hydroxyapatite (HA) peak in the Group S. The HA peak in the Group R was higher than that in the Group B on day 14. Conclusion: The innovative toothpaste has better properties than the commercially available products in terms of microhardness, roughness, and effectiveness in sealing dentinal tubules.

The influence of cone beam computed tomography on IRIS-100 implant navigation system.

Background/purpose: Cone beam computed tomography (CBCT) is frequently used in dental diagnosis and treatment. Comparative studies of the effects of CBCT on implant navigation, however, are still limited. The objective of this study was to evaluate whether the computed tomography images of the four commercial brands will affect the accuracy of the new version of IRIS implant navigation system. Materials and methods: In the first part, the accuracy of the IRIS implant navigation system was evaluated by a precision confirmation jig whose position is confirmed. In the second part, the IRIS implant navigation system was used in conjunction with 4 brands of CBCT scans analyzed by its effect on accuracy. Results: The results showed that the mean deviation of the new version of IRIS-100 system accuracy was less than 1 mm. Among the four groups, the overall average deviation caused by CBCT images showed that the 3D eXam group had the smallest error of approximately 0.94 ± 0.12 mm and the AZ 3000 CT group had the largest error of approximately 1.34 ± 0.10 mm. Conclusion: Based on the study, the accuracy of the IRIS implant navigation system will vary with the CBCT image resolution and the status of the CBCT machine.

Biodegradable Hydrogel Beads Combined with Calcium Phosphate Bone Cement for Bone Repair: In Vitro and In Vivo Characterization.

This study evaluated the in vitro characterizations of biodegradable hydrogel beads with calcium phosphate bone cement (CPC). Commercial fast-setting CPC and hydrogel beads were compared with 25%-volume hydrogel in CPC (C/0.25) in vivo. The histological behaviors and absorption rates of CPC only, hydrogel beads, and hydrogel/CPC composite were measured and compared at 4, 8, and 12 weeks. The results indicated that the C/0.25 composite can be molded and does not disintegrate when immersed in the solution, but this delays the phase transition of the CPC into the product in the early reaction process. The osteoprogenitor D1 cell affinity of the C/0.25 composite was equally competitive with that of the CPC-only. Adding hydrogel beads to CPC did not inhibit cell proliferation as well as differentiation of osteoprogenitor cells. In vivo histological evaluations did not indicate any significant difference in the CPC-only, hydrogel-only, and C/0.25 composite after 4 weeks of implantation; however, significantly less residue was observed in the C/0.25 composite relative to the CPC-only after 8 weeks. After 12 weeks of hydrogel beads implantation, the hydrogel degraded substantially, creating vacancies that were subsequently occupied by a large amount of soft tissue. New bone was formed in large quantities in the C/0.25; therefore, the C/0.25 composite is a promising option for a wide range of dental, craniofacial, and orthopedic applications.

Comparison of optical and crystal properties of three translucent yttria-stabilized tetragonal zirconia polycrystals with those of lithium disilicate glass-ceramic material.

BACKGROUND/PURPOSE: Among the ceramic materials used for all-ceramic crowns, zirconia has high biocompatibility and favorable mechanical properties, but its main drawbacks include low translucency and stress-induced phase transformation. To stabilize high-strength tetragonal zirconia polycrystal (TZP), 3-5 mol% yttria is usually added to prepare yttria-stabilized TZP (Y-TZP). In this study, the optical properties of three commercial Y-TZP ceramics were compared with those of the clinically available glass-ceramic material of lithium disilicate, and the relationship between translucency and crystal properties was analyzed in vitro. MATERIALS AND METHODS: Twelve 5-mm-thick standardized disks were prepared from three Y-TZP ceramics and one lithium disilicate block. Absolute translucency was measured using a spectrophotometer with an integrating sphere. X-ray diffraction was used to quantify the main structural parameters (i.e., preferred plane, quantitative phase, and grain size) of Y-TZP crystals. RESULTS: The product-dominated phase of Y-TZP exhibited a tetragonal lattice pattern, and the preferred planes had minor variations. The diffraction patterns of the three Y-TZP ceramics demonstrated minor effects on translucency, without significant differences (p > 0.05). The grain size of 54-70 nm was negatively related to translucency in Y-TZP. Lithium disilicate specimens had significantly higher translucency than the three Y-TZP specimens (p < 0.001). CONCLUSION: Grain size reduction played an essential role in developing highly translucent Y-TZP ceramics. The three Y-TZP ceramics were essentially opaque but exhibited poorer translucency than lithium disilicate in terms of esthetics.

Effects of Gamma Radiation on the Sterility Assurance, Antibacterial Ability, and Biocompatibility of Impregnated Hydrogel Macrosphere Protein and Drug Release.

Devices and medicines used in the medical field must be sterile. Gamma (γ)-irradiation is commonly used for sterilization because its high rate of penetration ensures uniform sterilization. To confirm that hydrogel macrosphere carriers inherit excellent liquid absorption with no cytotoxicity after γ-irradiation sterilization, investigating whether the physiochemical properties of hydrogel macrospheres differ before and after sterilization is essential. The present study evaluated the influence of the recommended 25-kGy γ-irradiation dose on the physicochemical characteristics and in vitro release of bovine serum albumin and vancomycin (an antibiotic medication) from alginate/gelatin with a w/w ratio of 1/4 crosslinking gel macrospheres. Gel macrosphere properties before and after sterilization were compared according to optical and scanning electron microscopy, infrared spectroscopy analysis, the amino residual crosslinking index, water absorption, degradation, sterility assurance, in vitro drug release, antibacterial ability, and cytotoxicity. The crosslinking index was almost unchanged; however, the γ-irradiation caused in situ hydrogel debonding and recrosslinking, which led to a decrease in the water absorption and increase in the degradation rate of the macrospheres after immersion. The release of gel macrospheres carrying vancomycin did not significantly affect antibacterial ability or biocompatibility after γ-irradiation. Accordingly, we conclude that γ-irradiation is suitable for macrospherical formulation.

Effect of different firing atmospheres on debonding strength of dental porcelain fused to commercially pure titanium.

An in vitro investigation was performed to evaluate the bonding characteristics of porcelain fused to metal (PFM)/commercially pure titanium (cp Ti, grade II) in three firing atmospheres of under vacuum and using two noble gases argon (Ar) and helium (He). Three groups of porcelain veneers firing under vacuum, Ar, and He were prepared to evaluate the bonding of porcelain fused to the cold-rolled cp Ti. The bond strength of PFM durability by a three-point bending test, phases, microhardness of cp Ti after firing processes, and fractures were measured and evaluated. Results show the microhardness of cp Ti in group of porcelain firing under He atmosphere was significantly lower than that of the two other groups, which were in vacuum and Ar (P < .05). X-ray diffraction showed the He group produced in relatively small amounts of TiO2 and TiO oxides than other groups but featured relatively high quantity of airhole defects in the porcelain body leading to the lowest bond strength. The Ar group presented the highest bond strength of comparing with the groups under vacuum and using He (P < .05). Although the firing processes in He could efficiently prevent the diffusion of oxygen into Ti, the porcelain-cp Ti bond strength using Ar protective atmosphere presented the advantage to achieve clinical requirement because porcelain firing under He revealed prominent voids and defects within the body of porcelain.

The possibility of recasting of pure titanium.

BACKGROUND/PURPOSE: Pure titanium (Ti) has many advantages, such as high corrosion resistance and excellent biocompatibility. The mechanical properties of pure Ti are like those of type IV gold alloys. Furthermore, gold alloys can be successfully recast in dental clinics. The aim of this study was to investigate the possibility of recasting pure Ti. MATERIALS AND METHODS: Magnesium oxide (MgO)-based investment that contained a 5 wt. % zirconium dioxide (ZrO2) additive was used. An argon-casting machine (Castmatic-S, Iwatani) was used to recast pure Ti. The first generation and second generation pure Ti (50 wt. % new Ti + 50 wt. % surplus Ti) were used. Five specimens were fabricated and tested. The data were evaluated using two-sample t-test analysis (P < 0.05). RESULTS: The experimental results showed that recasting the Ti did not decrease the marginal accuracy, average surface roughness, Vickers hardness value of the superficial surface, and the thickness of the reaction layer. CONCLUSION: This study clearly showed Ti could be recast when a 5 wt. % ZrO2 additive MgO-based investment was used. This modified investment has the potential for use in clinical applications.

Unilaterally impacted maxillary central incisor and canine with ipsilateral transposed canine-lateral incisor.

Concurrent impaction and transposition of maxillary anterior teeth is uncommon and poses a challenge for dentists. Early diagnosis and management of eruption disturbances benefits esthetic and functional outcomes. This article describes the treatment of a teenager who had impactions of the left maxillary central incisor and canine as well as ipsilateral canine-lateral incisor transposition. Treatment alternatives and effective orthodontic techniques are delineated. To optimize the treatment results, the impacted maxillary canine was surgically exposed and orthodontically distalized with an innovative cantilever. Subsequently, the deeply impacted maxillary central incisor was uncovered and orthodontically mesialized into the arch. Finally, the displaced maxillary lateral incisor was brought into its normal position. The combined surgical-orthodontic approach resolved a difficult clinical issue and avoided additional restorations. An esthetic, functional outcome was achieved and satisfied the patient.

Optimizing anterior esthetics of a single-tooth implant through socket augmentation and immediate provisionalization: a case report with 7-year follow-up.

Tooth extraction inevitably accompanies alveolar ridge resorption with loss of pre-existing tissue morphology. Replacing missing teeth with dental implants has become popular, but restoring anterior teeth with implant-supported restorations is a technique-sensitive task and poses challenges for dentists. With the progress of implant dentistry, the demand for optimal esthetics has become linked with the desire for faster, easier techniques that shorten treatment time and also satisfy patients. Immediate provisionalization of a single-tooth implant provides significant benefits compared with traditional delayed protocols, such as aiding the contouring of peri-implant soft tissue and enhancing patient comfort and satisfaction. This article describes a meticulous approach to a hopeless maxillary central incisor with root fracture. The defect in the extraction socket was reconstructed using autogenous bone harvested from the chin. Four months later, an implant was installed and immediately restored. After another healing period of 6 months, the peri-implant soft tissue had been shaped and matured according to the contours of the provisional restoration. The emergence profile was used to duplicate the definitive restoration. Peri-implant esthetics was achieved through socket augmentation and immediate provisionalization of the implant. This treatment modality attained predictable and maintainable outcomes, both functionally and esthetically.

Evaluating the accuracy of tooth color measurement by combining the Munsell color system and dental colorimeter.

As we pay increasing attention to dental aesthetics, tooth color matching has become an important part of daily dental practice. This aim of this study was to develop a method to enhance the accuracy of a tooth color matching machine. The Munsell color tabs in the range of natural human teeth were measured using a tooth color measuring machine (ShadeEye NCC). The machine's accuracy was analyzed using an analysis of variance test and a Tukey post-hoc test. When matching the Munsell color tabs with the ShadeEye NCC colorimeter, settings of Chroma greater than 6 and Value less than 4 showed unacceptable clinical results. When the CIELAB mode was used, the a* value (which represents the red-green axis in the Commission Internationale de l'Eclairage color space) made no significant difference (p=0.84), the L* value (which represents the lightness) resulted in a negative correlation, and the b* value (which represents the yellow-blue axis) resulted in a positive correlation with ΔE. When the Munsell color tabs and the Vitapan were measured in the same mode and compared, the inaccuracies showed that the Vitapan was not a proper tool for evaluating the stability and accuracy of ShadeEye NCC. By knowing the limitations of the machine, we evaluated the data using the Munsell color tabs; shade beyond the acceptable range should be reevaluated using a visual shade matching method, or if measured by another machine, this shade range should be covered to obtain more accurate results.

Impacted mandibular second molars.

OBJECTIVE: To determine the prevalence and severity of impacted permanent mandibular second molars (MdM2s) in the general population of Taiwan as well as to evaluate treatment outcomes with an innovative method for impacted MdM2s. MATERIALS AND METHODS: Dental records of 21,580 patients were retrospectively screened in this study. The impactions of MdM2s were registered. The chosen study population consisted of 96 patients with 125 impacted MdM2s who received orthodontic treatment in our clinics. Standardized periapical radiographs were taken to measure the angles and depths of the impacted MdM2s. In addition, the initial uprighting periods of the impacted MdM2s were recorded. RESULTS: The prevalence of MdM2 impaction in the Taiwanese population was 0.65%. Most of the angles and depths of the MdM2s were 31-60° and 9-12 mm, respectively. The mean initial uprighting period of the impacted MdM2 was 3.6 months. There were no significant differences between genders in the initial uprighting period based on patient ages, impacted angles, or impacted depths (P > .05). Correlation analysis revealed that the impacted depth was highly and positively correlated with the initial uprighting period (r > .75). CONCLUSIONS: The prevalence of MdM2 impaction in this study was low but slightly higher than previous reports investigating whites. Although such impactions are rare, it is recommended to diagnose early for an optimal treatment time and reduction of complications. In addition, the effective molar uprighting appliance used in this study has displayed good treatment outcomes with natural improvement of the adjacent infrabony defects of the first molars.

Management of unilaterally deep impacted first, second, and third mandibular molars.

Simultaneous impactions of first, second, and third permanent molars comprises a very rare clinical situation with diverse therapeutic approaches and is a difficult challenge for dentists. Early diagnosis and treatment of eruption disturbances contributes to optimal outcomes. This article reports the treatment of a teenager with severe impaction of right mandibular first, second, and third molars, which hinders the masticatory function and dental arch integrity. A decision-making process and a simple orthodontic technique are described. To shorten the treatment time and simplify the procedures, the impacted right mandibular third and second molars were orthodontically uprighted with an innovative tip-back cantilever. Subsequently, the deeply impacted right mandibular first molar was extracted with minimal obstacles. The combined surgical-orthodontic approach resolved a challenging clinical problem and eliminated the need for prosthetic or dental implant replacement of the impacted molars. Good occlusion, normal function, and a healthy periodontium of the patient were also achieved.

Using a spectrophotometric study of human gingival colour distribution to develop a shade guide.

OBJECTIVES: For dental prostheses, colour choice is a main concern. The present spectrometric study analyzes healthy gingiva to develop a shade guide for pink aesthetics. METHODS: A reflectance spectrometer and an external light source were set up in a 45/0-degree optical configuration to measure the colour of gingiva over the maxillary anterior area. A total of 362 human subjects with healthy gingiva were divided into groups according to sex and age. The Commission Internationale de l'Eclairage L*, a*, and b* (CIELAB) values and differences in colour (ΔE) were measured. A two-way analysis of variance (ANOVA) test and cluster analyses were used to analyse the data. RESULTS: There are significant differences in the gingival colour by sex (ΔE > 3.7). The mean CIE L* value of female gingiva is significantly higher than that of male gingiva (p < 0.05). No significant differences were found between age groups. 10 categories for gingival colour are established. CONCLUSION: The gingival colour of females is lighter than that of males. The proposed colour classification can be used as a gingival shade guide reference by dental laboratory technicians.

Immediate implant placement following minimally invasive extraction: a case report with a 6-year follow-up.

Single tooth replacement with a dental implant has become an increasingly favored treatment option in the anterior maxilla; however, bone resorption following maxillary anterior tooth extraction is very common and often compromises gingival tissue for the implant restoration. Achieving predictable peri-implant esthetics requires a proper understanding and preservation of the osseous and gingival tissue surrounding the failing tooth. Therefore, the key to maintaining the interproximal papillae is to preserve the osseous support with minimally invasive extraction. An immediate implant insertion after tooth extraction may maintain the crest bone and the interdental papillae, thus achieving peri-implant esthetics. This article describes the detailed treatment planning and meticulous techniques in immediate implant placement that reduce treatment time and maintain functional as well as esthetic results through a 6-year follow-up.