Journal of Prosthetic Dentistry最新文献

Statement of problem: Removal of a ceramic veneer may become necessary, but whether a noninvasive method for debonding ceramic veneers using ultrafast laser technology is effective is unclear.

Purpose: The purpose of this in vitro study was to investigate the effects and mechanisms of ultrafast laser technology in the removal of ceramic veneers.

Material and methods: An in vitro model for the ceramic veneer-abutment complex was constructed involving the precise deposition of ultrafast laser beams into both the ceramic veneer and adhesive layer. The temperature of the dental pulp was monitored during this process. Shear strength was evaluated, and both surface and cross-sectional morphologies of the specimens were examined with a 3-dimensional (3D) digital microscope and a scanning electron microscope. A Raman spectrometer was used to analyze changes in components within the abutment and ceramic veneers. Data were statistically analyzed with 1-way analysis of variance (ANOVA) (α=.05).

Results: Carbonization and micro-explosion were 2 typical reactions in the adhesive layer, resulting in the reduction of bond strength (P<.05). Under carbonization conditions, the shear strength was typically diminished, falling as low as 1.2 MPa; therefore, veneers can be easily removed from the surface of the teeth. The temperature within the dental pulp can be regulated by adjusting laser parameters and scanning strategies; the shear strength in carbonization mode was significantly less than that in micro-explosion mode, indicating that the carbonization mode was more efficient for veneer removal. Detailed structural characterization further confirmed that the internal dentin was unaffected, suggesting that bioactivity was preserved.

Conclusions: Ultrafast laser technology offers a convenient, rapid, and safe method of removing ceramic veneers and has potential as a noninvasive procedure.

Statement of problem: Limited information is available regarding the accuracy of computer-aided design and computer-aided manufacturing (CAD-CAM) zirconia implant-supported restorations in relation to tool wear under standardized repeated milling conditions.

Purpose: The purpose of this in vitro study was to evaluate the correlations of milling tool wear with changes in tool morphology and the external surface characteristics and marginal adaptation of zirconia implant restorations during repeated milling cycles.

Material and methods: A mandibular premolar implant-supported restoration was designed using a CAD software program. Zirconia restorations were repeatedly milled with a Ø1-mm cutting tool until 1 additional specimen was fabricated after the software program indicated tool replacement. Tool deterioration was quantified, and the cutting edge width measured 0.2 mm from the tool tip for each cycle. Pre- and post-processing scans of each restoration were superimposed with a surface-matching program to calculate deviations. Marginal discrepancies between the zirconia restoration and implant abutment were assessed by image analysis. The Kruskal-Wallis test was used for statistical comparisons; Spearman correlation coefficients (ρ) were calculated to assess relationships between tool wear and test variables (α=.05).

Results: Progressive wear was observed on the milling tools. The cutting-edge width increased from 776.4 µm at 0% to 20% deterioration to 797.5 µm at 81% to 100% deterioration, indicating a strong correlation (r=.802). Digital superimposition revealed slight increases in surface deviations of the zirconia restorations with successive milling cycles. Marginal discrepancies substantially increased: horizontal gaps rose from 17.9 µm at 0% to 20% deterioration to 52.3 µm at 81% to 100% deterioration, also indicating a strong correlation (r=.664).

Conclusions: As milling cycles increased, tools became progressively wider and blunter. Although the external surfaces of zirconia implant-supported restorations remained largely consistent, marginal discrepancies increased significantly.

Statement of problem: Root-analog implants (RAIs) aim to replicate natural tooth root morphology, potentially enhancing the outcomes of immediate implant placement. However, clinical evidence on their survival, success, and long-term reliability is limited and varied.

Purpose: This systematic review aimed to evaluate the clinical survival and success of RAIs fabricated using different biomaterials and digital fabrication methods.

Material and methods: A systematic search of the PubMed, Scopus, Web of Science, and Cochrane databases was conducted by following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Clinical trials, case series, and clinical reports on human RAIs were included. The risk of bias was assessed using the Cochrane Risk of Bias Tool (RoB 2), ROBINS-I, Newcastle-Ottawa Scale (NOS), and JBI tools. Primary outcomes were survival and success rates; secondary outcomes included marginal bone loss (MBL), esthetics, prosthetic performance, and patient satisfaction.

Results: Twenty-eight studies (432 RAIs) were included. RAIs were made from titanium, zirconia, or hybrid titanium-zirconia materials using CNC milling, selective laser melting (SLM), or direct laser metal sintering (DLMS). Most studies reported survival rates ranging from 71% to 100% and success rates from 64.5% to 100%. Titanium and hybrid RAIs were more predictable than zirconia, which showed higher failure and fracture rates. RAIs demonstrated favorable esthetic and soft-tissue outcomes, as well as high patient satisfaction. Evidence was limited by small cohorts, heterogeneous protocols, and scarce long-term follow-up.

Conclusions: RAIs show promising short-term survival, stability, and esthetics, particularly with implants using titanium or combined titanium-zirconia materials. However, variability in outcomes highlights the need for well-designed multicenter trials with larger cohorts and longer follow-up to confirm long-term clinical reliability.

The accurate alignment of digital scan data is a critical step in providing a complete arch implant-supported prosthesis, mainly because of the lack of stable and repeatable reference points in edentulous arches. This limitation poses a significant challenge when attempting to align multiple surface geometry datasets precisely. This clinical report describes a practical and efficient procedure that enhanced the accuracy of digital dataset alignment and facilitated a fully digital workflow for the design, fabrication, and conversion of interim prostheses into definitive complete arch implant-supported prostheses.

Immediate implant placement in the anterior maxilla is indicated for patients with an intact labial plate to achieve esthetics and predictability. This clinical report describes the use of the immediate dentoalveolar restoration (IDR) protocol with a digitally designed tuberosity adjustment guide (TAG) to restore a compromised socket in the esthetic zone. A 47-year-old patient presented with a missing lateral incisor with loss of the labial wall. The tooth had been lost because of trauma. A tuberosity bone graft was shaped using a computer-aided design and computer-aided manufactured (CAD-CAM) TAG and placed simultaneously with the implant and a screw-retained interim crown. At 2 years, soft and hard tissue stability was maintained.

Oral squamous cell carcinomas result in significant impairment of oral function as they tend to invade bone. Bone invasion often mandates partial mandibular resection, such as hemimandibulectomy, which reduces overall quality of life. To rehabilitate such patients, fixed functional guide flanges position the mandible, improving overall masticatory ability. Custom fixed functional prostheses using digitally assisted dentistry are highly accurate. This technique uses digital technology and a digital workflow to fabricate an open-frame fixed functional guide flange prosthesis.

This clinical report describes a digital workflow to fabricate digital tooth reduction guides for the esthetic rehabilitation of severely malformed and misaligned teeth by referencing the contours established during digital esthetic planning. For accurate trial restorations, primary reduction guides with reserved windows were fabricated to identify areas of tooth structure protruding beyond the planned contours. The secondary reduction guide enabled visualization of the intended restorative form and real-time assessment of tooth reduction. The combined use of both guides provided a predictable, efficient, and conservative approach for restoring severely malformed and misaligned teeth.