Journal of Prosthetic Dentistry最新文献

Statement of problem: Speed sintering techniques have been introduced to shorten the sintering time of zirconia ceramics, yet their impact on multilayered zirconia properties remains understudied.

Purpose: The purpose of this in vitro study was to assess the effect of speed sintering on the optical properties and the mechanical flexural strength of multilayered zirconia materials.

Material and methods: A total of 360 disks (Ø14 ±2 mm ×1.2 ±0.02 mm) were fabricated by following the International Organization for Standardization (ISO) 6872:2015 standard using 2 types of Vita A2 shade multilayered zirconia materials: IPS e.max ZirCAD Prime (ZP) and IPS e.max ZirCAD Prime Esthetic (ZPE). Each material comprised translucent (Tr), gradient l (Gr), and dentin (De) layers, with 60 disks per layer. Half were sintered using a standard sintering protocol and half using a speed sintering protocol. Biaxial flexural strength was accessed using a universal testing machine equipped with the Blue Hill Universal software program by following the ISO 6872:2015 standard, with 20 disks per subgroup. The spectrophotometric analysis of optical properties (contrast ratio [CR], translucency parameter [TP], and total transmittance [Tt%]) was performed using a dual-beam spectrophotometer (Ultrascan VIS) in accordance with the ISO 7491:2000 standard, with 10 disks per subgroup. The comparison of the optical properties and the mechanical flexural strength between the speed and standard protocol was analyzed using an unpaired t test (α=.05).

Results: Speed sintering reduced biaxial flexural strength in all ZP layers (P<.05) and in ZPE-Gr (P<.05). A statistically significant difference in the CR was observed in the ZP-Tr, ZP-Gr, and ZPE-Gr layers (P<.05). The TP of the ZP-Gr, ZP-De, and ZPE-Gr layers was significantly lower when using the speed sintering protocol. Tt% was significantly lower with speed sintering for both materials (P<.05).

Conclusions: Speed sintering statistically changed both the optical (CR, TP, Tt%) and mechanical (flexural strength) properties of multilayered zirconia materials, but the differences may not be clinically relevant.

Statement of problem: Characterizing interim restorations promotes esthetics. However, studies on the effects of characterization materials on the surface roughness and gloss of interim materials after toothbrushing are lacking.

Purpose: The purpose of this in vitro study was to evaluate the surface roughness and gloss of 5 different interim materials with different surface treatments after 1 year of simulated toothbrushing.

Material and methods: Cuboid specimens (10×12×2 mm) were fabricated from each interim material: autopolymerized polymethyl methacrylate (UNIFAST Trad), autopolymerized bis-acryl composite resin (Protemp 4), light-activated composite resin (REVOTEK LC), milled polymethyl methacrylate block (DD provi P HI), and 3-dimensionally printed methacrylate oligomer (Nextdent C&B MFH). Each material was divided into 3 groups based on surface treatment (n=10): polishing, application of Lite Art and Resin Glaze, and application of OPTIGLAZE color. The specimens were subjected to 5000 and 10 000 cycles of toothbrushing. The surface roughness and gloss were measured and separately analyzed by using 3-way repeated measures ANOVA (α=.05).

Results: Significant interactions of the surface roughness and gloss among interim materials, surface treatments, and toothbrushing durations were found (P<.001). After 5000 and 10 000 cycles, each polished material showed no significant difference in surface roughness compared with baseline: Protemp 4 (P>.999), REVOTEK LC (P>.999, P=.922), and Nextdent C&B MFH (P>.999), except for UNIFAST Trad and DD provi P HI (P<.001). Coating with Lite Art and Resin Glaze, as well as OPTIGLAZE color, significantly reduced surface roughness after both 5000 and 10 000 cycles for all materials (application of Lite Art and Resin Glaze with UNIFAST TRAD (P<.001), Protemp 4 (P<.001), REVOTEK LC (P<.001), DD provi P HI (P<.001), and Nextdent C&B MFH (P<.001, P=.002), and application of OPTIGLAZE color with UNIFAST TRAD (P<.001), Protemp 4 (P<.001), REVOTEK LC (P<.001, P=.002), DD provi P HI (P<.001), and Nextdent C&B MFH (P<.001, P=.008)). Specimens with these treatments also exhibited significantly better gloss compared with the polished specimens (P<.001).

Conclusions: After 5000 to 10 000 cycles of toothbrushing, Protemp 4, REVOTEK LC, and Nextdent C&B MFH, interim materials containing fillers, exhibited smoother surfaces compared with UNIFAST Trad and DD provi P HI, interim materials without fillers. Coating of all materials reduced surface roughness and increased gloss. After 5000 to 10 000 cycles of toothbrushing, the surface roughness of each material remained stable; while the gloss decreased slightly, it remained within clinically acceptable levels.

Statement of problem: The effects of nonaxial forces on peri-implant bone loss have been investigated, mostly in reference to buccal mesiodistal implant angulations as potential risk indicators. However, when implant angulations are multidirectional, including the buccolingual aspect, evaluations of peri-implant bone loss based solely on mesiodistal measurements may skew the correlation.

Purpose: The purpose of this retrospective study was to evaluate the correlation between the magnitudes of multidirectional implant angulations and peri-implant crestal bone loss.

Material and methods: Data were retrospectively collected and analyzed from clinical records, periapical radiographic images, and computer-aided design (CAD) files of custom abutments. The study included 288 patients with 506 dental implants, and the mean follow-up duration after the placement of definitive prostheses was 5.1 years. Patients with uncontrolled systemic disease were excluded. Variables such as age, sex, type of unit (single-unit or multi-unit), location (maxillary or mandibular and anterior, premolar, or molar), and antagonist (natural tooth, implant-supported prosthesis, or removable prosthesis) were evaluated. The angulation of the implant (mesiodistal and buccolingual) and status of attrition (normal, localized, or generalized) were assessed using the CAD file. The angulation of the implant was then derived from the mesiodistal and buccolingual angle measurements by using a mathematical formula. Peri-implant bone loss was measured from periapical radiographs. A comparison of peri-implant bone loss between axial and nonaxial implants was performed using the Student t test (α=.05). Additional comparative evaluations were performed according to the type of unit, location, antagonist, and status of attrition in reference to the angulation categories.

Results: The mean ±standard deviation peri-implant bone loss over 5 years was 0.10 ±0.39 mm in the axial implants and 0.22 ±0.48 mm in the nonaxial implants. Statistical analysis showed that nonaxial implants had a significantly greater bone loss (P<.05), which was more pronounced when the antagonists were implant-supported prostheses (P<.05) and when the implants were located in the mandible (P<.05).

Conclusions: A significant correlation was observed between implant angulation and peri-implant bone loss. Nonaxially positioned implants exhibited greater bone loss compared with axially positioned implants. Additionally, the location of the implant and the type of antagonist were found to influence the extent of bone loss. These findings suggest that careful consideration of implant angulation, as well as the position and type of antagonist, is crucial in minimizing peri-implant bone loss.

Statement of problem: As part of the growing digitization of the dental field, clinicians are looking for ways to simplify digital workflow, reduce chairside time, and provide new work patterns for future applications. Whether scanning with a multifunctional apparatus (MFA) scan body results in improved scanning is unclear.

Purpose: The purpose of this in vitro study was to compare the horizontal, vertical, and angular deviations with the MFA scan body with a commercially available scan body (SBIO).

Material and methods: Sixteen identically printed edentulous maxillary models were used to plan two Ø3.8×11.5-mm implants in the right maxillary first molar and left maxillary central incisor locations. Two implants in each model were installed using a surgical guide. The models were scanned using an intraoral scanner with MFA and then rescanned twice, with SBIO using the intraoral scanner and a laboratory 3D scanner. The implants were digitally positioned according to the scanned MFA and SBIO locations in standard tessellation language (STL) files. These STL files were superimposed on the reference laboratory 3D scanner STL files. Linear measurements included implant apex/cervical horizontal/vertical deviations, as well as implant axis angular deviations. Normality was evaluated with the Shapiro-Wilk test. Paired samples t tests (2 sided) were used for the mean SBIO-MFA deviation difference. To compare the molar/incisor sites, paired samples Wilcoxon tests were used (α=.05 for all tests).

Results: No statistically significant differences were found between the MFA/ SBIO deviations, for each of the 10 sites × deviation combinations (P>.05). Overall, the lowest endpoint of the 95% confidence intervals among the 8 linear measurement comparisons was -0.107 mm (coronal vertical deviation, right maxillary first molar site) and -0.30 degrees between the 2 angular measurement comparisons.

Conclusions: The current in vitro study demonstrated high accuracy for the novel MFA device, similar to that of the standard SBIO scan body. Furthermore, the current study offers an alternative technique to evaluate the accuracy of implant placement by using scanning and back programming over the traditional postplacement cone beam computed tomography (CBCT) scanning.

Fabricating a crown to fit both a tooth and an existing removable partial denture (RPD) using many different techniques has been described. However, in the event of abutment loss, information regarding the clinical and laboratory steps used to fabricate a crown that fits both an implant and an RPD is lacking. This report describes the use of either an impression coping or an interim abutment attached to the implant to which a composite resin interim restoration material is flowed and the RPD then seated to form a resin pattern of the required crown form. The process allows the implant crown to be made without retaining the patient's RPD during crown fabrication.

The steady rise in cocaine consumption, particularly in its snorted form, has led to the increased incidence of cocaine-induced midline destructive lesions (CIMDLs), a severe condition resulting from chronic cocaine use that leads to significant tissue destruction in the nasal and palatal regions. Four patients with CIMDLs are presented, all characterized by nasopalatine perforation. Each patient reported a spontaneous onset of tissue loss in the hard palate near the midline, with the affected area ranging from 2.3 to 5.1 cm². All patients had a history of psychiatric conditions, including depressive episodes but without other significant medical conditions, which contributed to an average delay of 9 months before seeking initial medical consultation. Treatment, which included the use of palatal obturators to improve quality of life, remains nonstandardized and, combined with the patients' continued cocaine use and refusal of addiction care, led to poor follow-up and persistent tissue damage. This clinical report underscores the need for a paradigm shift in managing CIMDLs, emphasizing the integration of addiction treatment and psychological support with prosthetic rehabilitation to optimize long-term outcomes and prevent relapse.