Use of polyvinyl siloxane to maintain peri-implant submucosal contours on removal of screw-retained implant-supported restorations.

When submucosal screw-retained implant-supported restorations are removed for a short period, the soft-tissue contours collapse, which can affect treatment expediency and patient comfort when restorations are reinserted. This technique involves the fabrication of a polyvinyl siloxane submucosal template to help mitigate the soft-tissue collapse and its potential sequelae. This method of maintaining peri-implant soft-tissue contours is achieved through a quick succession of steps: removing the screw-retained implant prosthesis, drying the soft tissue thoroughly, injecting light-bodied fast-set polyvinyl siloxane directly into the implant fixture of the internal connection implants and the screw channel for external connection implants together with the remaining submucosal areas, allowing the polyvinyl siloxane submucosal template to polymerize undisturbed, and removing it when ready to replace the prosthesis.

Evaluation of Fracture Resistance of Zirconia Modification/Polishing Around Implant Abutments.

Subcrestal placement of implants may have interproximal bone proximity issues that interfere with the submucosal contour of implant-supported zirconia restorations during delivery of the restorations. Modification of the mesial distal submucosal areas may be necessary to fully seat the restoration without impingement of the interproximal bone. Our aim was to determine if modification of submucosal cervical contour of implant supported zirconia-titanium base (Zi-Ti base) restorations resulted in a significant change in fracture strength compared with Zi-Ti base restorations without any modification near the cervical submucosal area. Implant Zi-Ti base restorations designed in the form of a maxillary premolar were made for the Straumann implant lab analog. Zirconia samples were cemented onto the Ti-base and the test group (N = 20) underwent recontouring and polishing at the junction of the Zi-Ti base cervical areas. The control group (N = 20) did not undergo any modifications. All 40 samples underwent fracture testing with an Instron machine. We assessed differences between modified and unmodified implants restorations using a 2-tailed t test for independent samples. Fracture strength values (N) ranged from 4354.68 to 6412.49 in the test group (N = 20) and from 5400.31 to 6953.22 in the control group (N = 20). The average fracture strength in the control group (6154.84 ± 320.50) was higher than in the modified group (5593.13 ± 486.51; P < .001). Modification of submucosal contour significantly decreased fracture strength. However, the average fracture strength exceeded the masticatory forces of humans.

Stereographic analog application in implant-supported complete rehabilitation: A dental technique.

This article describes the application of stereographic analogs in complete mouth rehabilitation with implant-supported prostheses. The interarch restorative space and immobile support provided by dental implants allow the fabrication of a recording apparatus for the analysis of mandibular movement. An implant-supported fixed detachable recording apparatus was fabricated, and a stereographic tracing made to reproduce the patient's mandibular border movements.

CAD-CAM acrylic resin prosthesis superstructure: A technique for fabricating an implant-supported fixed complete denture.

The implant-supported fixed complete denture is a common treatment option in implant prosthodontics but has shortcomings that include the high wear rate of the acrylic resin denture material and the displacement of denture teeth from the denture base. This report describes a method for fabricating implant-supported fixed dental prostheses using computer-aided design and computer-aided manufacturing technology.

Biofilms in restorative dentistry: A clinical report.

This clinical report describes the structure and characteristics of the biofilm formed under a cemented restoration, confirming the need to develop new cementation protocols to disrupt and minimize the formation of biofilm before cementing definitive restorations.

Mandibular implant-supported fixed dental prosthesis with a modified design: a clinical report.

This clinical report describes the rehabilitation of a patient with a mandibular implant-supported fixed dental prosthesis. Because of the limited restorative space available in the posterior mandible and in considering the higher wear rate of acrylic resin in comparison with titanium when it opposes metal ceramic restorations, the treatment used a milled titanium bar with acrylic resin denture teeth, which replaced the anterior teeth with milled titanium for the posterior occluding surfaces.

Effects of setting under air pressure on the number of surface pores and irregularities of dental investment materials.

STATEMENT OF PROBLEM: Surface roughness and irregularities are important properties of dental investment materials that can affect the fit of a restoration. Whether setting under air pressure affects the surface irregularities of gypsum-bonded and phosphate-bonded investment materials is unknown. PURPOSE: The purpose of this study was to investigate the effect of air pressure on the pore size and surface irregularities of investment materials immediately after pouring. MATERIAL AND METHODS: Three dental investments, 1 gypsum-bonded investment and 2 phosphate-bonded investments, were investigated. They were vacuum mixed according to the manufacturers' recommendations, then poured into a ringless casting system. The prepared specimens were divided into 2 groups: 1 bench setting and the other placed in a pressure pot at 172 kPa. After 45 minutes of setting, the rings were removed and the investments were cut at a right angle to the long axis with a diamond disk. The surfaces of the investments were steam cleaned, dried with an air spray, and observed with a stereomicroscope. A profilometer was used to evaluate the surface roughness (µm) of the castings. The number of surface pores was counted for 8 specimens from each group and the means and standard deviations were reported. Two-way ANOVA was used to compare the data. RESULTS: Specimens that set under atmospheric air pressure had a significantly higher number of pores than specimens that set under increased pressure (P<.05). No statistically significant differences for surface roughness were found (P=.078). Also, no significant difference was observed among the 3 different types of materials tested (P>.05). CONCLUSION: Specimens set under positive pressure in a pressure chamber presented fewer surface bubbles than specimens set under atmospheric pressure. Positive pressure is effective and, therefore, is recommended for both gypsum-bonded and phosphate-bonded investment materials.

Design concepts of a removable partial dental prosthesis with implant-supported abutments.

A clinical report is presented that describes the restoration of a severe anterior maxillary ridge defect and pneumatized sinuses with a rotation-path partial removable dental prosthesis and implant-supported abutments. Other treatment options were considered and rejected based on patient preferences and limitations, which included avoiding invasive surgeries. The principles of integrating fixed and removable prosthesis design were applied. However, the clasp design was modified to take into account the direct bone-to-implant contact of the abutments. An esthetic and functional outcome was obtained without any overly invasive surgery.

A technique for retrieving fractured implant screws.

The use of dental implants as a source of support and retention for fixed restorations is common. This report describes the use of a fragment removal instrument together with the use of ultrasonic instrumentation to retrieve a screw fragment.

A multidisciplinary approach for the rehabilitation of a patient with an excessively worn dentition: a clinical report.

This clinical report describes a multidisciplinary approach to the diagnosis and treatment of a patient with a severely worn dentition. The treatment included osteotomy and immediate implant placement and loading in the mandible. The definitive restorations were implant- and tooth-supported metal ceramic restorations. These restorations were fabricated with metal occlusal surfaces at an increased occlusal vertical dimension, which provided acceptable esthetics and function.

Full mouth rehabilitation of a young patient with partial expressions of ectodermal dysplasia: a clinical report.

Ectodermal dysplasia (ED) is a hereditary disorder characterized by the abnormal development of specific tissues and structures of ectodermal origin. This clinical report describes the multidisciplinary approach to the diagnosis and treatment of a 24-year-old patient with partial expression of ED. The treatment plan used dental implants to support fixed prostheses and ceramic restorations to establish acceptable esthetics and provide function.

Treatment planning decisions: implant placement versus preserving natural teeth.

Dental implants are routinely used as a treatment modality for replacing missing teeth. An assessment of whether to extract teeth and place implants or preserve natural dentition can be a complex decision-making process. The purpose of this article is to review some of the factors that influence prosthetic planning of functional and esthetic rehabilitation for patients with diseased dentition either with conventional treatment options or with extractions and replacement with implant-supported prosthesis.

Evaluation of the amount of excess cement around the margins of cement-retained dental implant restorations: the effect of the cement application method.

STATEMENT OF PROBLEM: Complete removal of excess cement from subgingival margins after cementation of implant-supported restorations has been shown to be unpredictable. Remaining cement has been shown to be associated with periimplant inflammation and bleeding. PURPOSE: The purpose of this study was to investigate and compare the amount of excess cement after cementation with 4 different methods of cement application for cement-retained implant-supported restorations. MATERIAL AND METHODS: Ten implant replicas/abutments (3i) were embedded in acrylic resin blocks. Forty complete veneer crowns (CVCs) were fabricated by waxing onto the corresponding plastic waxing sleeves. The wax patterns were cast and the crowns were cemented to the implant replicas with either an interim (Temp Bond) or a definitive luting agent (FujiCEM). Four methods of cement application were used for cementation: Group IM-Cement applied on the internal marginal area of the crown only; Group AH-Cement applied on the apical half of the axial walls of the crown; Group AA-Cement applied to all axial walls of the interior surface of the crown, excluding the occlusal surface; and Group PI-Crown filled with cement then seated on a putty index formed to the internal configuration of the restoration (cementation device) (n=10). Cement on the external surfaces was removed before seating the restoration. Cement layers were applied on each crown, after which the crown was seated under constant load (80 N) for 10 minutes. The excess cement from each specimen was collected and measured. One operator performed all the procedures. Results for the groups were compared, with 1 and 2-way ANOVA and the Tukey multiple range test (α=.05). RESULTS: No significant difference in the amount of excess/used cement was observed between the 2 different types of cements (P=.1). Group PI showed the least amount of excess cement in comparison to other test groups (P=.031). No significant difference was found in the amount of excess cement among groups MI, AH, and AA. Group AA showed the highest amount of excess cement. The volume of cement used for group PI specimens was significantly higher than for those in the other groups (P=.001). With respect to the volume of cement loaded into the test crowns no statistically significant difference was observed among other test groups (groups IM, AH, and AA). Group MI used the least amount of cement, followed by group AH and AA. No correlation between the amount of used cement and the amount of excess cement was found in any of the tested groups. CONCLUSIONS: Within the limitations of this in vitro study, the least amount of excess cement was present when a cementation device was used to displace the excess cement before seating the crown on the abutment (Group PI). With this technique a uniform layer of the luting agent is distributed over the internal surface of the crown leaving minimal excess cement when the restoration is seated.

Properties of a proline-containing glass ionomer dental cement.

STATEMENT OF PROBLEM: Proline-containing glass ionomers are promising fast-set dental restorative materials with superior mechanical properties; however, little information is available on other physical properties of this type of glass ionomer. PURPOSE: The objectives of this study were to synthesize and characterize a polyacrylic acid terpolymer containing proline derivative (PD) and to investigate the physical properties of this glass ionomer cement (GIC) and its cytotoxicity in vitro. MATERIAL AND METHODS: A terpolymer of AA (acrylic acid), IA (itaconic acid), and proline derivative (MP) with an 8:1:1 molar ratio was synthesized and characterized. Experimental GIC specimens were made from the synthetized terpolymer with Fuji IX (GC America, Alsip, Ill) commercial glass ionomer powder as recommended by the manufacturer. Specimens were mixed and fabricated at room temperature and were conditioned in distilled water at 37°C for 1 day and 1 week. Vickers hardness was determined with a microhardness tester. The water sorption characteristics and fluoride releasing properties of the specimens were investigated. The in vitro cytotoxicity of the experimental glass ionomer was assessed by evaluating the C2C12 cell metabolism with methyltetrazolium (MTT) assay. Commercial Fuji IX was used as a control for comparison. The data obtained for the experimental GIC (PD) were compared with the control group by using 1- and 2-way ANOVA and the Tukey multiple range test at α=.05. RESULTS: Proline-modified GIC (PD) exhibited significantly higher surface hardness values (Vickers hardness number [VHN] 58 ±6.1) in comparison to Fuji IX GIC (VHN 47 ±5.3) after 1 week of maturation. Statistical analysis of data showed that the water sorption properties of the experimental cement (PD) were significantly greater than those of the control group (P<.05). The experimental GIC showed a significant increase in the amounts of initial fluoride release (P<.05) with continued fluoride release from the bulk of the material. The experimental group showed slightly reduced cell metabolism and cell number in comparison to the control group. However, the results were not statistically different (P>.05). CONCLUSIONS: An amino acid-containing GIC had better surface hardness properties than commercial Fuji IX GIC. This formulation of fast-set glass ionomer showed increased water sorption without adversely affecting the amount of fluoride release. Considering its biocompatibility, this material shows promise not only as a dental restorative material but also as a bone cement with low cytotoxicity.

Alginate hydrogel as a promising scaffold for dental-derived stem cells: an in vitro study.

The objectives of this study were to: (1) develop an injectable and biodegradable scaffold based on oxidized alginate microbeads encapsulating periodontal ligament (PDLSCs) and gingival mesenchymal stem cells (GMSCs); and (2) investigate the stem cell viability, and osteogenic differentiation of the stem cells in vitro. Stem cells were encapsulated using alginate hydrogel. The stem cell viability, proliferation and differentiation to adipogenic and osteogenic tissues were studied. To investigate the expression of both adipogenesis and ontogenesis related genes, the RNA was extracted and RT-PCR was performed. The degradation behavior of hydrogel based on oxidized sodium alginate with different degrees of oxidation was studied in PBS at 37 °C as a function of time by monitoring the changes in weight loss. The swelling kinetics of alginate hydrogel was also investigated. The results showed that alginate is a promising candidate as a non-toxic scaffold for PDLSCs and GMSCs. It also has the ability to direct the differentiation of these stem cells to osteogenic and adipogenic tissues as compared to the control group in vitro. The encapsulated stem cells remained viable in vitro and both osteo-differentiated and adipo-differentiated after 4 weeks of culturing in the induction media. It was found that the degradation profile and swelling kinetics of alginate hydrogel strongly depends on the degree of oxidation showing its tunable chemistry and degradation rate. These findings demonstrate for the first time that immobilization of PDLSCs and GMSCs in the alginate microspheres provides a promising strategy for bone tissue engineering.

Ultrasonically set novel NVC-containing glass-ionomer cements for applications in restorative dentistry.

The objective of this study is to investigate the effects of application of ultrasound on the physical properties of a novel NVC (N-vinylcaprolactam)-containing conventional glass-ionomer cement (GIC). Experimental GIC (EXP) samples were made from the acrylic acid (AA)-itaconic acid (IA)-NVC synthesized terpolymer with Fuji IX powder in a 3.6:1 P/L ratio as recommended by the manufacturer. Specimens were mixed and fabricated at room temperature and were conditioned in distilled water at 37°C for 1 day up to 4 week. Ultrasound (US) was applied 20 s after mixing by placing the dental scaler tip on the top of the cement and applying light hand pressure to ensure the tip remained in contact with cement without causing any deformation. Vickers hardness was determined using a microhardness tester. The working and setting times were determined using a Gillmore needle. Water sorption was also investigated. Commercial Fuji IX was used as control for comparison (CON). The data obtained for the EXP GIC set through conventional set (CS) and ultrasonically set (US) were compared with the CON group, using one-way ANOVA and the Tukey multiple range test at α = 0.05. Not only ultrasonic (US) application accelerated the curing process of both EXP cement and CON group but also improved the surface hardness of all the specimens. US set samples showed significantly lower water sorption values (P < 0.05) due to improved acid-base reaction within the GIC matrix and accelerated maturation process. According to the statistical analysis of data, significant increase was observed in the surface hardness properties of CS and US specimens both in EXP samples and the CON groups. It was concluded that it is possible to command set GICs by the application of ultrasound, leading to GICs with enhanced physical and handling properties. US application might be a potential way to broaden the clinical applications of conventional GICs in restorative dentistry for procedures such as class V cavity restorations.

Hallermann-Streiff syndrome patient treated with removable prosthesis: a clinical report.

Hallermann-Streiff syndrome is a rare congenital disorder characterized by bird-like facies and dental anomalies. A description of a 21-year-old Hispanic woman with Hallermann-Streiff syndrome, whose anterior open occlusal relationship and smile were improved with overdentures is presented. The treatment was satisfactory in terms of both esthetics and phonetics, excluding the need for aggressive surgical treatment.

Surface properties and bond strength measurements of N-vinylcaprolactam (NVC)-containing glass-ionomer cements.

STATEMENT OF PROBLEM: N-vinylcaprolactam (NVC)-containing glass ionomers are promising dental restorative materials with improved mechanical properties; however, little information is available on other physical characteristics of these types of modified glass ionomers, especially their surface properties. Understanding the surface characteristics and behavior of glass ionomers is important for understanding their clinical behavior and predictability as dental restorative materials. PURPOSE: The purpose of this study was to investigate the effect of NVC-containing terpolymers on the surface properties and bond strength to dentin of GIC (glass-ionomer cement), and to evaluate the effect of NVC-containing terpolymer as a dentin conditioner. MATERIAL AND METHODS: The terpolymer of acrylic acid (AA)-itaconic acid (IA)-N-vinylcaprolactam (NVC) with a molar ratio of 8:1:1 (AA:IA:NVC) was synthesized by free radical polymerization and characterized using nuclear magnetic resonance ((1)H-NMR) and Fourier transform infrared spectroscopy (FTIR). The synthesized terpolymer was used in glass-ionomer cement formulations (Fuji IX GP). Ten disc-shaped specimens (12 × 1 mm) were mixed and fabricated at room temperature. Surface properties (wettability) of modified cements were studied by contact angle measurements as a function of time. Work of adhesion values of different surfaces were also determined. The effect of NVC-modified polyacid on the bond strength of glass-ionomer cement to dentin was investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to t test and 2-way ANOVA (α=.05). RESULTS: NVC-modified glass-ionomer cements showed significantly (P<.05) lower contact angles (46 degrees) and higher work of adhesion (W(A)=60.33 erg/cm(2)) in comparison to commercially available Fuji IX GP (57 degrees and W(A)=53.01 erg/cm(2)). The wettability of dentin surfaces conditioned with NVC-containing terpolymer was significantly higher (P<.05) (22 degrees, WA=73.77 erg/cm(2)) than dentin conditioned with GC dentin conditioner (29 degrees, W(A)=70.52 erg/cm(2)). The experimental cement also showed significantly higher values for shear bond strength to dentin (8.7 ±0.15 MPa after 1 month) when compared to the control group (8.4 ±0.13 MPa after 1 month). CONCLUSIONS: NVC-containing terpolymers may enhance the surface properties of GICs and increase their bond strength to the dentin. Furthermore, NVC-containing polyelectrolytes are better dentin conditioners than a commercially available dentin conditioner (GC dentin conditioner).

Transitioning patients from teeth to implants utilizing fixed restorations.

The provisional phase of treatment can be the most challenging in implant dentistry. The choice of provisional restoration should be based on esthetic demands, functional requirements, duration, and ease of fabrication. One major obstacle to treatment with implants is the transitional phase between a tooth-supported occlusion and an implant-supported occlusion. This is of particular concern when a patient with a failing dentition has not worn a removable prosthesis before and is planned to have a reconstruction supported by implants.

Evaluation of Fracture Resistance of Varying Thicknesses of Zirconia Around Implant Abutment Cylinders.

Zirconia is becoming increasingly used as a restorative material for implant-supported restorations; however, information is lacking with respect to the minimum thickness of zirconia surrounding the implant components. The purpose of this study is to evaluate the resistance to fracture of different thicknesses of zirconia luted to implant components. Thirty cylinders of zirconia (Prettau, Zirkonzahn) with 13-mm height, designed with indented occlusal surface for loading, and varying wall thicknesses (0.5 mm, 1 mm, 1.5 mm; n = 10/group) were milled using a computer-aided design/computer-aided manufacturing system (Modellier, Zirkonzahn), after which they were sintered. Titanium temporary cylinders (ITCS41, Biomet3i) were attached to 30 implant analogs (ILA20, Biomet3i) that were embedded into polymethylmethacrylate blocks (Palapress Vario, Heraeus Kulzer) with dimensions of 4.5 × 1.8 × 2 cm. Zirconia specimens were cemented to the titanium cylinders using a self-adhesive, dual-cure resin cement (Panavia SA, Kuraray). Load to failure test was performed under compression until fracture using a universal testing machine (Instron5965, Instron) at a crosshead speed of 0.5 mm/min and measured in N (Newton). Statistical analysis was performed using 1-way analysis of variance and Tukey B test at α = .05 (SPSS19, IBM). Mean load to failure was 1059.94 N, 2019.46 N, and 4074.79 N for groups 0.5 mm, 1 mm, and 1.5 mm, respectively. Values were significantly different between the groups (P < .05). Study limitations are that it is in vitro, specimens do not replicate tooth dimensions, and forces are static and directed toward the occlusal portion of each specimen. Within these limitations and considering the average human bite force, a thickness of 0.5 mm to 1 mm of this particular type of zirconia around this type of implant component can avoid fracture with these dimensions.