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.

Evaluating the relationship between tooth color and enamel thickness, using twin flash photography, cross-polarization photography, and spectrophotometer.

OBJECTIVES: To understand (a) the effects of labial enamel on tooth color (b) relationship of color data taken by nonpolarized (NP), cross-polarization photography (CP), and spectrophotometry (SP). MATERIALS AND METHODS: Fifty extracted human maxillary incisors were coated with resin on their palatal surfaces. Their color was measured with NP, CP, and SP and their dimensions were scanned by an intraoral scanner. The labial enamel was removed using a modified selective enamel demineralization technique. Tooth dimensions and color were recorded again. The differences in the labial enamel thickness (ΔT) and color (∆E*00 and ∆L*, ∆a*, ∆b*) were statistically analyzed with the Pearson correlation coefficient and simple linear regression. RESULTS: In CP and SP methods, ΔT and ∆E*00 were weakly to moderately positively correlated (r = .38 and .27). In NP, CP, and SP methods, ∆T and ∆b* are weakly positively correlated (r = .27, .27 and .29). The color data of three measuring methods were highly positively correlated (r > .8). A linear relationship between ∆E*00 and ∆T were found (CP and SP groups). CONCLUSIONS: (a) Thicker labial enamel has a greater impact on tooth color. (b) Reducing labial enamel thickness shifts the tooth color toward yellow. (c) Tooth color measured from the three methods were highly correlated. CLINICAL SIGNIFICANCE: Knowing the relationship between enamel thickness and tooth color, a clinician can better predict the stump shade before tooth preparation. Due to the highly correlated measuring outcomes, it is reasonable to combine these three methods during shade matching.

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.

Removal torque and force to failure of non-axially tightened implant abutment screws.

STATEMENT OF PROBLEM: Components have been introduced that allow the screw channel of an implant crown to be angled lingually and the screws to be tightened in a non-axial direction to the implant. Information is lacking as to how the removal torque value (RTV) and force to failure (FTF) of these components compare with those of conventional screws. PURPOSE: The purpose of this in vitro study was to evaluate and compare the RTV and FTF values of cyclically loaded implant-supported restorations. Specifically, values for conventional axially tightened gold screws were compared with those for non-axially tightened screws aligned at 3 different angulations. MATERIAL AND METHODS: A total of 28 external hexagon implants were embedded in acrylic resin and divided into 4 groups. Simulated restorations were fabricated on abutments capable of different screw channel angulations. Dynamic abutments (DA) were waxed at different angulations and then cast. Simulated restorations were placed on the implants and tightened: group 0GS: 0-degree angulation gold screw tightened to 35 Ncm (control group); group 0DAS, 0-degree angulation with dynamic abutment (DAS) screw; group 20DAS: 20-degree angulation with DA screw; group 28DAS: 28-degree angulation with DAS screw. In groups 0DAS, 20DAS, and 28DAS, the DAS screw was used and tightened to 25 Ncm. Screw removal torque values were recorded by using a digital torque gauge at baseline and, after reaching cyclic fatigue, by using a dual-axis mastication simulator for 1200000 cycles. The fracture strength (FS) of the implant restorations was tested under compression until failure by using a universal testing machine. Differences between baseline and removal torque (ΔRT) were calculated. Statistical analysis was performed by using 1-way ANOVA for ΔRT and FS separately (α=.05). RESULTS: ΔRT and FS values were not significantly different among the groups (P>.05). The screw fractured in 5 of 28 specimens (17.8%); the remaining specimens failed with fracture of the implant. CONCLUSIONS: The removal torque and FS values of the angulated abutment screw were comparable to those of the gold screw. Angulation of the abutment had no significant influence on the screw removal torque values.

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.

Single-unit implant-supported restoration adjacent to multiple lithium disilicate restorations, an approach to an esthetic challenge: A clinical report.

This clinical report describes a method for predictably shade matching a highly opaque yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) implant restoration adjacent to relatively translucent lithium disilicate veneers in the maxillary anterior region. To achieve a satisfactory outcome, the milled Y-TZP abutment was layered with low-fusing feldspathic porcelain to match the stump shade of the adjacent prepared teeth; this layer subsequently facilitated adhesive bonding of a veneer to the abutment before insertion.

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.

Force-to-failure of a simulated implant-supported complete fixed dental prosthesis reinforced with glass fiber.

STATEMENT OF PROBLEM: The joint adjacent to the cantilevered section of an implant-supported complete fixed dental prosthesis (ICFDP) undergoes the most stress because of force magnification in this area, making it more prone to mechanical failure. PURPOSE: The purpose of this in vitro study was to evaluate the ultimate force-to-failure distal to the terminal implant of a simulated ICFDP reinforced with glass fiber compared with that of a conventionally fabricated prosthesis. MATERIAL AND METHODS: Thirty ICFDPs with bilateral distal cantilevers were fabricated and divided into 3 groups: the not-reinforced (NR) group was processed without reinforcement, the glass-fiber-reinforced (GR) group was reinforced with glass fiber, and the titanium-reinforced (TR) group was fabricated with a titanium bar. The specimens were screw-retained onto a standardized mandibular model with 4-implant analogs embedded in acrylic resin. All groups were processed using heat-polymerized acrylic resin. After 24 hours, the cantilevers were loaded to fracture (in N) 10 mm away from the center of the most distal analog under compression at a crosshead speed of 1 mm/min. Statistical analysis of data was performed using a 1-way analysis of variance (ANOVA) model by using Tukey B post hoc comparison procedures (α=.05). RESULTS: Data revealed the mean fracture load of the NR group was 1073 ±108 N, 1400.75 ±123.53 N for the GR group, and 1652.78 ±274.14 N for the TR group. Statistically significant differences (P<.05) were found among all 3 groups. Comparison between the left and right side of the tested prostheses did not show any significant differences (P=.595). CONCLUSIONS: A fiber-reinforced ICFDP provides better biomechanical properties than an unreinforced one, which may allow its longer-term use as an interim ICFDP. However, the titanium bar ICFDP still provided the best resistance to fracture.

Two anterior wide-diameter implants using the All-on-4 concept in a predictable maxillary rehabilitation: A clinical report.

The quality of maxillary bone is generally lower than that of mandibular bone; consequently, complete arch immediate implant-loading treatment is not as predictable in the maxillary as in the mandibular arch. The All-on-4 concept has proven to be an effective and successful treatment protocol. However, the survival rate of All-on-4 implants in the maxilla is lower than of those in the mandible. In this report, 2 anterior wide-diameter implants were used with the All-on-4 concept for a maxillary rehabilitation to provide biomechanical benefits with better primary stability while still achieving a functional and esthetic result. The clinical challenges of using wide-diameter implants in the anterior region are also discussed and should be considered during treatment planning.

Biomechanical evaluation of one-piece and two-piece small-diameter dental implants: In-vitro experimental and three-dimensional finite element analyses.

BACKGROUND/PURPOSE: Small-diameter dental implants are associated with a higher risk of implant failure. This study used both three-dimensional finite-element (FE) simulations and in-vitro experimental tests to analyze the stresses and strains in both the implant and the surrounding bone when using one-piece (NobelDirect) and two-piece (NobelReplace) small-diameter implants, with the aim of understanding the underlying biomechanical mechanisms. METHODS: Six experimental artificial jawbone models and two FE models were prepared for one-piece and two-piece 3.5-mm diameter implants. Rosette strain gauges were used for in-vitro tests, with peak values of the principal bone strain recorded with a data acquisition system. Implant stability as quantified by Periotest values (PTV) were also recorded for both types of implants. Experimental data were analyzed statistically using Wilcoxon's rank-sum test. In FE simulations, the peak value and distribution of von-Mises stresses in the implant and bone were selected for evaluation. RESULTS: In in-vitro tests, the peak bone strain was 42% lower for two-piece implants than for one-piece implants. The PTV was slightly lower for one-piece implants (PTV = -6) than for two-piece implants (PTV = -5). In FE simulations, the stresses in the bone and implant were about 23% higher and 12% lower, respectively, for one-piece implants than those for two-piece implants. CONCLUSION: Due to the higher peri-implant bone stresses and strains, one-piece implants (NobelDirect) might be not suitable for use as small-diameter implants.

Biomechanical investigations of the expanded platform-switching concept in immediately loaded small diameter implants.

STATEMENT OF PROBLEM: Use of a small diameter implant may increase the stress on bone around the implant neck; however, an expanded platform design may mitigate these stress concentrations. To date, no study has compared the biomechanical effect of regular platform and extended platform designs on an implant. PURPOSE: The purpose of this in vitro study was to evaluate the biomechanical effects of an expanded platform-switching design for immediately loaded small diameter implants on bone strains. MATERIAL AND METHODS: Three groups of artificial jawbone models were prepared for small diameter (3.25-mm) and standard diameter (4.0-mm) implants with expanded or regular platform designs. Platform-switching implant design was implemented by assembling implants with a smaller connected abutment. Specimens were tested under both vertical and lateral static loads at 190 N. Peak values of the principal microstrain of bone were recorded and analyzed statistically with Kruskal-Wallis test and multiple comparisons Bonferroni test (α=.05). The initial stability of each implant was also measured for 3 types of implant. RESULTS: Under vertical loading, the bone strain was lowest for the regular type of immediately loaded small diameter implant. Under lateral loading, peak bone strain around the expanded platform small diameter implant with platform switched abutment was up to 74.9% lower than that of the regular type of small diameter implant. Increasing the implant diameter from 3.25 mm to 4.0 mm on the expanded platform implants reduced the bone strain by approximately 10% and 30% under lateral and vertical loading, respectively. The initial implant stability did not vary significantly among the implants tested. CONCLUSIONS: Using the expanded platform small diameter implant with a platform-switched abutment may decrease the marginal bone strains around immediately loaded small-diameter implants under lateral loading.

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.

Dynamic Abutment: A method of redirecting screw access for implant-supported restorations: Technical details and a clinical report.

The esthetic outcome of implant-supported restorations is affected by the implant position. A well-placed implant will allow appropriate contours of the restoration and together with an adequate volume of soft tissue will result in a functional and esthetic restoration. When a screw-retained restoration is anticipated, an implant that is angled too far facially would be esthetically unacceptable. In 2004, an abutment called the Dynamic Abutment (Talladium International Implantology) became commercially available. This abutment can allow a deviation of the restoration screw access angle to the implant angle of up to 28 degrees while allowing a screw-retained restoration to be connected directly to the platform of the implant. The purpose of this article was to describe the components, technique, and clinical use of this abutment.

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.

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 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.

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.

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.

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.