Comparison of surface micro-roughness and adaptation of titanium and cobalt chrome implant abutment fabricated by selective laser melting and conventional techniques.

PURPOSE: The objective of this study was to assess the surface micro-roughness and abutment adaptation of selective laser melting (SLM) implant abutments in comparison to cast and machined implant abutments. METHODS: Forty abutment specimens were divided equally into four groups according to the fabrication technique as follows (n = 10), Machined Ti alloy abutments (Control), Cast CoCr abutments, SLM-CoCr abutments, and SLM-Ti alloy abutments. Forty internal connection implants (Ø 4.0 ×10 mm, Superline™, Dentium Co., Seoul, Korea) were mounted in clear acrylic resin. Fabricated abutments were assessed for surface micro-roughness using a 3D optical noncontact surface microscope. Vertical and horizontal adaptation of the abutment with implant interface was assessed by using Bruker micro-CT. Data was assessed using analysis of variance and Tukey post hoc comparison tests for all the variables except vertical misfit was assessed using Kruskal-Wallis test. Pearson correlation was used to assess dependence between independent variable (surface roughness) and dependent variables (Horizontal misfit and vertical misfit). RESULTS: SLM-Ti abutments showed significantly rougher surface (p < 0.05) among the study groups. While SLM-CoCr abutments were smoother than Cast abutments with mean Ra of 1.30 ± 0.11 and 1.58 ± 0.17 µm, respectively (p < 0.05). For abutment adaptation, SLM-Ti abutments showed the highest horizontal misfit among the groups (p < 0.05). While, SLM-CoCr abutments (29.24 ± 11.11 µm) showed comparable (p > 0.05) horizontal misfit results with Cast (26.08 ± 3.93 µm) and machined (26.45 ± 7.33 µm) abutments. Comparable (p > 0.05) vertical misfit values between Cast CoCr (487.01 ± 40.34 µm), SLM-CoCr (358.38 ± 114.93 µm) and SLM-Ti (299.85 ± 172.88 µm) abutments were observed. A positive correlation was found between the surface roughness of the mating surfaces and abutment adaptation. CONCLUSION: SLM CoCr abutments exhibited low roughness and comparable abutment adaptation (vertically and horizontally) than cast (control) abutments. Therefore, SLM CoCr abutments should be clinically investigated as potential implant abutments for clinical use.

Considerations for using a removable prosthesis with attachments for a staged approach to a failing implant reconstruction.

Full-arch implant reconstructions are being utilized in clinical practice today. Very often these prostheses are prosthetically driven, but not periodontally maintainable. Often the patient presents to the general practitioner with a failing implant reconstruction, where several fixtures need to be removed and others are maintainable. The article presents a case report where a removable prosthesis is used as a transitional appliance during the retreatment of the case. A removable complete overdenture prosthesis using attachments was used to establish proper occlusion and function, prevent loading on the guided bone regeneration sites, and to assist in fabrication of a stable guide for implant placement. The staged approach facilitated laser periodontal therapy on the remaining fixtures, and allowed proper oral hygiene instruction and assessment of the patient's ability to clean the remaining fixtures properly. Although the potential to treat this case with transitional implants or immediate load fixtures was discussed, the risk versus benefit scenario favored a removable prosthesis with attachments. Success required proper communication between the surgeon, restorative dental practitioner, laboratory, and patient. (Quintessence Int 2023;54:126-132; doi: 10.3290/j.qi.b3648969).

In vitro Assessment of Clasps of Cobalt-Chromium and Nickel-titanium Alloys in Removable Prosthesis.

BACKGROUND: It has been since a long time that the use of base-metal alloys has significantly increased in the area of prosthetic science. One of the factors contributing for the increasing use of base-metal alloys is the increasing and high cost factor of noble metals. Although numerous materials have been tried since the recent past, Cobalt-Chromium (CoCr) alloys still form the most commonly used ones because of the numerous advantages they offer. Titanium alloys are also significantly being used in this field because of their high resistance strength and high corrosion resistance. Therefore, we aimed to evaluate the flexure strength and fatigue resistance of clasps made up of CoCr alloys and Nickel-titanium (NiTi) alloys. MATERIALS AND METHODS: We evaluated the retentive forces of CoCr and NiTi clasps two different sizes engaging retentive undercuts of different depths (0.25 and 0.50 mm). Mandibluar second premolar was prepared to frame the prosthesis for missing mandibular first and second molar. A total of 50 clasps were included in the study out of which 30 were NiTi clasps and 30 CoCr clasps. We evaluated the loading of the force at the rate of half Newton(N)/second at the central part of the specimen until fracturing of the specimen occurred and finally measurement of the modulus of elasticity was also done. Statistical analysis was carried out; unpaired "t" test was used for evaluating the level of significance. RESULTS: The mean load needed for CoCr clasps was 0.7450 and for NiTi clasp was 0.6140 Kgf for producing a deflection of 0.25 mm. As far as flexibility is concerned, more value was seen in NiTi group than CoCr group. For deflecting the clasp up to 0.50 mm, the mean load needed for CoCr clasps was 1.4102 and for NiTi clasp was 0.8260 Kgf. The results were statistically significant. While measuring the flexibility, more value (p < 0.05) was seen in NiTi group than in CoCr group. NiTi alloy clasps had mean flexural strength of 1640 MPa and modulus of elasticity of 32 GPa. CONCLUSION: For producing deflection of 0.25 and 0.50 mm, the mean loading force was higher for NiTi alloys. Although being increasingly used these days, NiTi alloys have limited use as compared with CoCr alloys due to high cost of titanium and certain other limitations.

Color stability and force decay of clear orthodontic elastomeric chains: An in vitro study.

OBJECTIVE: To compare the percentage force decay of clear and semi-clear elastomeric chain products from eight different manufacturers and to evaluate the amount of discoloration after immersion in colored dietary media of the same elastomeric chain products. MATERIAL AND METHODS: An in vitro study was designed using an electronic force gauge to measure six samples from each of 19 types of elastomeric chains stretched for a period of four weeks. A spectrophotometer was used to measure the color of each specimen (10 of each type) at baseline and after being soaked in a dietary medium (coffee, tea, cola, and wine in 250 ml amounts) for 72 h. RESULTS: There was a significant difference in the percentage of the lost initial force between all the tested E-chains (P<0.001). ANOVA shows a significant difference in the amount of discoloration between the E-chain types (P<0.001). Semi-clear (tooth-color/pearl/obscure) E-chain types (TP-ToothC, OrthO-Pearl, GAC-SiliPearl, 3M-Obscure) present significantly less change in color than clear E-chains of the same brand (TP-Clear, OrthoO-Clear, GAC-SiliClear, 3M-Clear). CONCLUSIONS: Significant differences in the mean percentage force decay between the 19 studied clear elastomeric chain types were present. AO-Memory and Ormco maintained most of their original force at the end of the four-week interval. Significant differences in discoloration also exist between the various types of E-chains. TP Orthodontics (Tooth-Colored, SuperSlick, Clear) and Ortho Organizers (Pearl) showed the least discoloration.