Adhesion of Conventional, 3D-Printed and Milled Artificial Teeth to Resin Substrates for Complete Dentures: A Narrative Review.

BACKGROUND: One type of failure in complete or partial dentures is the detachment of resin teeth from denture base resin (DBR). This common complication is also observed in the new generation of digitally fabricated dentures. The purpose of this review was to provide an update on the adhesion of artificial teeth to denture resin substrates fabricated by conventional and digital methods. METHODS: A search strategy was applied to retrieve relevant studies in PubMed and Scopus. RESULTS: Chemical (monomers, ethyl acetone, conditioning liquids, adhesive agents, etc.) and mechanical (grinding, laser, sandblasting, etc.) treatments are commonly used by technicians to improve denture teeth retention with controversial benefits. Better performance in conventional dentures is realized for certain combinations of DBR materials and denture teeth after mechanical or chemical treatment. CONCLUSIONS: The incompatibility of certain materials and lack of copolymerization are the main reasons for failure. Due to the emerging field of new techniques for denture fabrication, different materials have been developed, and further research is needed to elaborate the best combination of teeth and DBRs. Lower bond strength and suboptimal failure modes have been related to 3D-printed combinations of teeth and DBRs, while milled and conventional combinations seem to be a safer choice until further improvements in printing technologies are developed.

Impact of maxillofacial growth on implants placed in adults: A narrative review.

OBJECTIVE: To determine the effect of lifetime maxillofacial changes on dental implants placed in adults, analyze the clinical implications of these changes, identify prognostic factors, and offer possible solutions. OVERVIEW: The relationship between implant placement and maxillofacial changes, occurring during not only the active growth period but also the entire span of adulthood, has not been extensively examined. Vertical differences between implants and adjacent teeth due to the ankylotic behavior of the former might be observed at any age and endanger restoration biologically, functionally, and esthetically. Regarding interproximal contacts, firm contact loss may occur within a few months after restoration, resulting in food impaction. Many prognostic factors have been reported, but most do not exhibit a statistically significant association with implant infraocclusion and interproximal contact loss. Incorporation of alternative solutions, accurate treatment planning, strict recall protocols, and retrievability of implant-supported restorations can facilitate efficient management of complications. CONCLUSION: Maxillomandibular changes throughout adulthood may lead to complications such as implant infraocclusion and interproximal contact loss. Rehabilitation of edentulism should be characterized by well-designed and flexible treatment plans to resolve long-term complications efficiently. Further long-term clinical studies are needed to identify other risk factors. CLINICAL SIGNIFICANCE: Treatment plans for implant therapy should be reconsidered for adults. Careful patient monitoring and early intervention are essential for securing treatment outcomes.

Effectiveness of prosthetic rehabilitation and quality of life of older edentulous head and neck cancer survivors following resection of the maxilla: a cross-sectional study.

PURPOSE: To evaluate the effectiveness of prosthetic rehabilitation, as well as the quality of life (QOL) of older edentulous maxillectomy patients. METHODS: Effectiveness of the complete denture obturator prosthesis and QOL of N = 44 older edentulous patients who had resection of the maxilla and were restored with a definitive prosthesis that was in use for a minimum of 1 year was assessed using three instruments: European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Core Questionnaire (QLQ-C30), Head and Neck Cancer Module (QLQ-HN35), and Obturator Functioning Scale (OFS). Data analysis was performed by one-way analysis of variance (ANOVA) on ranks, Spearman rank-order correlation, and hierarchical multivariable rank regression at α = .05 level of significance. RESULTS: Participants' gender (P < .001), adjuvant treatment (P = .016), surgical approach (P = .017), size of the maxillary defect (P = .028), participants' prosthetic history (P = .047), and dental status of the mandible (P = .038) were significantly related to the self-reported effectiveness of the complete denture obturator prosthesis. Perceived functioning of the prosthesis (P = .001), participants' gender (P = .002), the American Society of Anesthesiologists (ASA) physical status (P = .027), and surgical approach (P = .039) were significant predictors of QOL. CONCLUSION: Restoration of the edentulous maxillectomy defect is challenging. An effective definitive complete denture obturator appeared to be the strongest predictor for advanced quality of life in older maxillectomy patients. The physical status of the older participants significantly affected the overall QOL, but did not influence the self-reported functioning of the complete denture obturator prosthesis.

A Thorough Analysis of the Endocrown Restoration: A Literature Review.

AIM: The aim of this literature review is to determine whether endocrowns are a reliable alternative for endodontically treated teeth with extensive loss of tooth structure, the indications and contraindications of this restorative choice, the principles that should be followed for tooth preparation and which material is most appropriate for endocrown fabrication. BACKGROUND: Rehabilitation of endodontically treated teeth with severe coronal destruction has always been a challenge for the dental clinician. Until recently, the fabrication of a metal-ceramic or all-ceramic full-coverage crown along with a metal or glass fiber post has been the "gold standard" proving its efficacy via numerous clinical studies. With the development of CAD/CAM technology and the evolution of dental materials, new minimally invasive techniques have been introduced with less need for adjustments and less incorporation of structural defects. One of them, the "monoblock technique," proposed by Pissis in 1995, was the forerunner of endocrown restoration, a term used by Bindl and Mörmann to describe an all-ceramic crown anchored to the internal portion of the pulp chamber and on the cavity margins, thus obtaining macromechanical retention provided by the axial opposing pulpal walls and microretention attained with the use of adhesive cementation. REVIEW RESULTS: Endocrowns require a decay-oriented preparation taking advantage of both the adhesion and the retention from the pulp-chamber walls, they are strongly indicated in endodontically treated molars in cases where minimal interocclusal space and curved or narrow root canals are present and they should be manufactured from materials that can be bonded to the tooth structure. CONCLUSION: Endocrowns are a reliable alternative to traditional restorative choices, given that the clinicians respect the requirements and indications describing this technique. CLINICAL SIGNIFICANCE: Traditional restorative techniques demanding tooth substance removal and minimizing the opportunity for reinterventions should be reconsidered.

Immediate Dentin Sealing: A Literature Review.

PURPOSE: The immediate application of a dentin-bonding agent after tooth preparation and before impression-taking (immediate dentin sealing [IDS]) has been suggested to provide several advantages concerning bacterial microleakage, hypersensitivity, and bonding quality. We reviewed the literature and clarified certain aspects related to each step of IDS application. MATERIALS AND METHODS: The search strategy comprised an electronic research in MEDLINE, Cochrane, Ovid and Scopus for studies published from January 1990 to December 2020 regarding the IDS technique and including both in vitro and clinical studies. RESULTS: After exclusion of irrelevant or duplicate articles, 88 articles focusing on aspects of the IDS technique were assessed. IDS seems to be advantageous with regard to bond strength, gap formation, bacterial microleakage, and dentin hypersensitivity. However, issues arising from interaction with impression materials, the provisional phase, and conditioning methods before cementation require further investigation. CONCLUSION: There are no documented reasons preventing clinicians applying IDS in their everyday practice. On the contrary, the presented technique seems to be beneficial in certain aspects regarding indirect restorations.

Surface Characteristics and Color Stability of Gingiva-Colored Resin Composites.

The purpose of this study was to investigate the surface characteristics and color stability of gingiva-colored composite restorative materials (Anaxgum-ANG, Ceramage-CMG and Gradia Gum-GRG). The microstructure, composition, degree of conversion (DC %) and 3D roughness (Sa, Sz, Sdr, Sc) were examined by LV-SEM/EDS, ATR-FTIR and optical profilometry, respectively. For the color stability (CIE L*, a*, b* system) and hardness (HV), measurements were performed at baseline and after 30 days storage in distilled water, coffee and red wine. The ANG and GRG contain prepolymerized particles in aromatic and aliphatic resin matrices, respectively, whereas CMG contains inorganic zirconia silicate/silica particles, in an aromatic resin matrix, with a smaller particle size and a higher surface area fraction. Urethane monomers were mainly identified in CMG and GRG. The DC% showed statistically insignificant differences between the materials. The same applied for the roughness parameters, except for the greatest Sdr in CMG. ANG showed a color difference (ΔE) of > 3.3 after immersion in all media, CMG in coffee and wine and GRG only in coffee. Sc was the only roughness parameter demonstrating correlations with the ΔL*, Δb* and ΔE*. The HV values showed insignificant differences between the storage conditions per material. There are important differences in the color stability of the materials tested, which were mostly affected by the roughness parameters due to variations in their microstructure.

The influence of impression coping splinting on the accuracy of the open-tray technique.

The objective of this study was to examine the effect of splinting of the impression copings on the accuracy of the cast when the open-tray technique is used. An epoxy master cast with 3 implants was fabricated. The first 2 implants were parallel to each other and perpendicular to the horizontal plane (implants A and B), and the third implant (implant C) had a 25-degree inclination. A passively fitting metal framework that was fabricated over this master cast was used to measure accuracy of fit. Ten casts were fabricated from this epoxy resin master cast with the use of polyether material and the open-tray technique. For the first 5 casts, the impression copings were splinted with dental floss and autopolymerizing acrylic resin; in the next 5 casts, the impression copings were not splinted. The metal framework in the master cast was fixed in the new specimens, and the microgap between this prosthesis and the implant analogs was evaluated. The specimens were observed under an optical microscope, and microgap measurements were made on photographs taken at a standardized magnification of 40×. The inclined implant C had the smallest mean microgap among the 3 implants, but the differences were not statistically significant. Microgaps for all 3 implants were smaller when they were splinted, but the difference from the mean of the nonsplinted counterpart was statistically significant only for the inclined implant. The results suggest that there is no clinical advantage in splinting the impression copings for parallel implants. On the other hand, when the implants are not parallel, splinting of the impression copings can result in greater accuracy of the fabricated cast.

The Influence of Thermocycling on the Flexural Strength of a Polyamide Denture Base Material.

OBJECTIVE: The aim of the present study was to evaluate the influence of thermocycling on the flexural strength of a polyamide base denture material. MATERIALS AND METHODS: A polyamide denture base material (Valplast) was tested, whereas a PMMA material (Vertex) was used as a control. Thirty specimens of each material were fabricated for flexural strength testing according to ISO 1567. They were prepared and stored in water at 37°C for 48 hours. The specimens of each material were divided into three equal groups (n=10). Flexural strength testing was performed immediately after water storage and after thermocycling (5°C / 55°C, 2 c/min) for 3000 and 5000 cycles. A three point flexural test was performed on a universal testing machine at a crosshead speed of 5 mm/min. The final flexural strength was calculated using the formula: FS = 3 PL/2 bd2. A two-way ANOVA with post-hoc analysis using Tukey's procedure was applied at .05 level of statistical significance. RESULTS: A statistically significant reduction in flexural strength was recorded after thermocycling at 3000 cycles for PMMA and at 5000 cycles for both materials. The flexural strength of PMMA was significantly higher compared to polyamide for all the conditions tested (p<0.05). CONCLUSION: Thermocycling had a significant adverse effect on the flexural strength of polyamide and PMMA denture base materials.

A Case Series Treatment Outcome Report Following 5 Years of Implant Overdenture Treatment.

PURPOSE: To assess clinical performance of bar-retained implant overdentures (IOs) with distally placed ERA attachments on four implants, and patient satisfaction after a follow-up period of 5 years in a convenience selection of 15 patients. MATERIALS AND METHODS: Bar-retained IOs with distally placed ERA attachments were placed and clinically monitored. Encountered complications during a 5-year follow-up period were recorded; and a modified OHIP-14 questionnaire was used to assess patient satisfaction. RESULTS: Implant and restoration survival rates of 97.5% and 100%, respectively, were recorded. The most common maintenance requirement was the replacement of ERA retentive elements. A high degree of patient satisfaction was reported. CONCLUSIONS: The proposed IO design is a reliable clinical treatment protocol associated with a high degree of patient satisfaction and minor prosthetic complications.

Matching repeatability and interdevice agreement of 2 intraoral spectrophotometers.

STATEMENT OF PROBLEM: The visual determination of tooth color with standard shade guides is a subjective method of color communication, depending on variables such as the light source, the operator, and the tooth. The assessment of tooth color may be improved by the use of special devices such as colorimeters or spectrophotometers. However, the repeatability and the interdevice agreement of these devices have not been thoroughly investigated. PURPOSE: The purpose of this study was to evaluate the effect of different illuminants (natural daylight, dental unit lamp, and daylight lamp) on the matching repeatability of 2 intraoral spectrophotometers (Easyshade and SpectroShade). MATERIAL AND METHODS: The maxillary right central incisor and canine and the mandibular left central incisor of each of 10 dental students were measured by a single operator using both devices. The color of each tooth was assessed 3 times with each device under each of the 3 different illuminants (natural daylight, a dental unit lamp, and a daylight lamp). The device readings were expressed in Vitapan 3D-Master shade codes. Statistical analysis was performed and the level of agreement was assessed with the Spearman Correlation Coefficient. RESULTS: A particularly high to moderate level of agreement among the readings made under natural daylight, a dental unit lamp, and a daylight lamp was observed for both devices (P<.01), suggesting that their matching repeatability was not completely satisfactory for clinical practice. A moderate and a moderate to high level of agreement was found among Easyshade readings when the 3 different illuminants were used. The level of agreement for the respective SpectroShade readings was particularly high to high (P<.001). A particularly low level of agreement was found among the respective Easyshade and SpectroShade readings performed under any of the illuminants tested (P<.05), suggesting poor interdevice reliability. CONCLUSIONS: The matching repeatability of both devices under natural daylight, a dental unit lamp, and a daylight lamp was not completely satisfactory for clinical practice. The effects of different illuminants seem to be more pronounced for Spectroshade than for Easyshade. The interdevice agreement between the 2 devices tested was poor, suggesting that the 2 devices were not compatible.

Colour stability of veneering composites after accelerated aging.

OBJECTIVES: To investigate the colour stability of four indirect composite restorative materials after accelerated aging. METHODS: Four indirect composites (Gradia, Signum+, HFO and Adoro) were used. For each material, six specimens were prepared and subjected to accelerated aging (Suntest CPS+, Atlas, Chicago, IL, USA) according to ISO 7491. A Dr. Lange Microcolor Data Station colorimeter (Braive Instruments, Liege, Belgium) was used to measure specimen colour before and after aging. Measurements were performed according to the CIE L*a*b* system, and the mean L*, a* and b* values for each material were calculated. The equation DeltaE = [(DeltaL*)2 + (Deltaa*)2 + (Deltab*)2](1/2) was used to measure the total colour change (DeltaE), where DeltaL*, Deltaa* and Deltab* are the differences in the respective values before and after aging. One-way ANOVA were used to determine statistically significant differences in DeltaL*, Deltaa*, Deltab* and DeltaE. RESULTS: No statistically significant differences were found in DeltaL*, Deltaa*, Deltab* and DeltaE among the materials tested (PDeltaL*=.063; PDeltaa*=.521; PDeltab*=.984 and PDeltaE=.408). After aging, Gradia specimens showed an increase in lightness (DeltaL*=0.36) and a green-yellow shift (Deltaa*=-1.18, Deltab*=0.6), while Signum+ specimens exhibited an increase in lightness (DeltaL*=0.5) and a green-blue shift (Deltaa*=-0.9, Deltab*=-0.45). HFO specimens exhibited an increase in lightness (DeltaL*=0.75) and a green-yellow shift (Deltaa*=-1.3, Deltab*=0.06), and Adoro specimens exhibited an increase in lightness (DeltaL*=2.07) and a green-yellow shift (Deltaa*=-1.3, Deltab*=0.68). CONCLUSIONS: Colour changes were found to be within accepted values of perceptibility and clinical acceptance after accelerated aging, and no statistically significant differences were found in DeltaL*, Deltaa*, Deltab* and DeltaE among the materials tested.

Effectiveness of different adhesive primers on the bond strength between an indirect composite resin and a base metal alloy.

STATEMENT OF PROBLEM: There is a need for achieving reliable chemical bond strength between veneering composites resins and casting alloys through the use of simplified procedures. PURPOSE: The purpose of this study was to examine the shear bond strength of an indirect composite resin to a Ni-Cr alloy, using 4 primers and 2 airborne-particle-abrasion procedures. MATERIAL AND METHODS: Fifty-six Ni-Cr (Heraenium NA) discs, 10 mm in diameter and 1.5 mm in height, were fabricated. Twenty-four discs were airborne-particle abraded with 50-microm Al2O3 particles, while another 24 were airborne-particle abraded with 250-microm Al2O3 particles. The following primers were applied on 6 discs of each airborne-particle-abrasion treatment group: Solidex Metal Photo Primer (MPP50, MPP250), Metal Primer II (MPII50, MPII250), SR Link (SRL50, SRL250), and Tender Bond (TB50, TB250). The Rocatec system was used on another 6 discs, airborne-particle abraded according to the manufacturer's recommendations, which served as the control group (R). Two more discs were airborne-particle abraded with 50-microm and 250-microm Al2O3 particles, respectively, to determine the Al content on their surfaces, without any bonding procedure. The indirect composite resin used was Sinfony. Specimens were thermally cycled (5 degrees C and 55 degrees C, 30-second dwell time, 5000 cycles) and tested in shear mode in a universal testing machine. The failure mode was determined with an optical microscope, and selected specimens were subjected to energy dispersive spectroscopy (EDS). Mean bond strength values were analyzed using 2-way ANOVA followed by Tukey's multiple comparison tests (alpha=.05) and compared to the control group using 1-way ANOVA followed by Tukey's multiple comparison tests (alpha=.05). RESULTS: The groups abraded with 50-microm particles exhibited significantly higher bond strength compared to the groups abraded with 250-microm particles. Group MPII50 exhibited the highest mean value (17.4 +/-2 MPa). Groups MPP50, MPP250, and TB50, TB250 showed adhesive failures and significantly lower bond strength compared to group R. Groups MPII50, MPII250, and SRL50, SRL250 showed combination failures and no significant difference compared with group R. EDS revealed interfacial rather than adhesive failures. CONCLUSIONS: Airborne-particle abrasion with 50-microm Al2O3 particles may result in improved bond strength, independent of the primer used. The bond strength of Metal Primer II and SR Link specimens was comparable to that of specimens treated with Rocatec.

The use of dental implants in combination with removable partial dentures: a case report.

UNLABELLED: Implant treatment protocols for fully edentulous patients include implant-supported fixed restorations with a minimum of five to six implants or overdentures on two to four implants. However, implant placement in the posterior areas is sometimes not permitted by anatomic and/or financial restraints, or patients' unwillingness to have extensive surgical procedures. The purpose of this case report is to present a treatment option where bilateral distal extension removable partial dentures (RPDs) are used in combination with anterior fixed implant prostheses with semi-precision attachments. The initial treatment plan of a 65-year-old female with failing dentition involved the fabrication of overdentures supported by four implants placed in the interforaminal area in both arches. Because of inadequate space for the retentive elements of the overdenture and the patient's objection to surgical procedures for the placement of additional implants to support a fixed restoration, the treatment plan was modified. Fixed ceramometal cement-retained implant restorations with semi-precision attachments adjacent to the distal abutments were fabricated in the maxilla and the mandible. Bilateral distal extension RPDs were placed in both arches. The patient's benefits were increased comfort, good esthetics in the anterior area, improved phonetics, and masticatory function. Retentive element maintenance requirements were similar to conventional RPDs. More extended controlled clinical studies are needed to establish the long-term success of this treatment option. CLINICAL SIGNIFICANCE: Removable partial dentures may offer an attractive treatment option for an edentulous patient, as they may combine an FPD in the anterior segment with a removable appliance in the posterior areas. A satisfying restoration can be achieved with fewer implants.

Color stability and degree of cure of direct composite restoratives after accelerated aging.

PURPOSE: This study evaluated the color changes and amount of remaining C = C bonds (%RDB) in three dental composites after hydrothermal- and photoaging. METHODS AND MATERIALS: The materials tested were Estelite sigma, Filtek Supreme and Tetric Ceram. Specimens were fabricated from each material and subjected to L* a* b* colorimetry and FTIR spectroscopy before and after aging. Statistical evaluation of the deltaL,* deltaa,* deltab,* deltaE and %deltaRDB data was performed by one-way ANOVA and Tukey's test. The %RDB data before and after aging were statistically analyzed using two-way ANOVA and Student-Newman-Keuls test. In all cases an alpha = 0.05 significance level was used. RESULTS: No statistically significant differences were found in deltaL*, deltaa*, deltaE and %deltaRDB among the materials tested. Tetric Ceram demonstrated a significant difference in deltab*. All the materials showed visually perceptible (deltaE >1) but clinically acceptable values (deltaE < 3.3). Within each material group, statistically significant differences in %RDB were noticed before and after aging (p < 0.05). Filtek Supreme presented the lowest %RDB before aging, with Tetric Ceram presenting the lowest %RDB after aging (p < 0.05). The %deltaRDB mean values were statistically significantly different among all the groups tested. No correlation was found between deltaE and %deltaRDB.