Influence of additive and subtractive zirconia and lithium disilicate manufacturing on tensile bond strength and surface topography.

STATEMENT OF PROBLEM: Although bonding is important for long-term clinical success, studies on the bonding of additively manufactured ceramics are sparse. PURPOSE: The purpose of this in vitro study was to determine the influence of manufacturing methods, additive (LCM) versus subtractive (CAM). and ceramic materials, zirconia (ZrO2) and lithium disilicate (LiSi), on the tensile bond strength (TBS), failure mode, and surface roughness of ceramics. MATERIAL AND METHODS: A total of 240 ceramic specimens (n=60/group; 2×2×10 mm) were prepared. Two additively manufactured (LCM-printed) ceramics, LiSi and ZrO2 (Lithoz), subtractively manufactured LiSi (IPS e.max CAD), and subtractively manufactured ZrO2 (KATANA Zirconia HTML PLUS) were evaluated. From each material, 40 specimens were bonded together (n=20 ceramic-ceramic specimens/group), and 20 specimens were bonded to equally sized human dentin specimens (n=20 ceramic-dentin specimens/group). The ZrO2 specimens were airborne-particle abraded (Al2O3, 50 µm, 0.1 MPa), and the LiSi specimens were etched with hydrofluoric acid. Then, a universal primer (Monobond Plus) was applied. After the dentin was coated with an etch-and-rinse adhesive (Syntac Classic), the specimens were bonded with luting composite resin (Variolink Esthetic DC), light polymerized for 40 seconds, thermally aged (10 000 cycles between 5 °C and 55 °C), tested for TBS, and statistically analyzed (1- and 3-way ANOVA and Weibull analysis). The ceramic surface was examined with scanning electron microscopy, and surface roughness was measured with digital microscopy before and after surface pretreatment. RESULTS: TBS varied between 5.88 ±2.22 MPa and 6.34 ±2.26 MPa in the ceramic-dentin groups and 12.40 ±1.56 MPa and 18.82 ±5.92 MPa in the ceramic-ceramic groups. No significant difference was observed regarding the manufacturing method and material for different bonding conditions (P>.05). Additive and subtractive LiSi showed the highest reliability with m=18.27. The ceramic-ceramic specimens failed cohesively in the luting composite resin, whereas the ceramic-dentin specimens failed adhesively. CONCLUSIONS: The manufacturing method and material used had little effect on bond strength values or surface properties. The recently introduced printed materials performed similarly to conventionally milled materials.

Influence of Immediate Dentin Sealing on Marginal Gaps of Laminate Veneers: Machinable Monolithic Zirconia Versus Pressable Lithium Dislocate. An In Vitro Study.

PURPOSE: To investigate the influence of immediate dentin sealing (IDS) vs delayed dentin sealing (DDS) on the marginal gaps of machinable monolithic zirconia (MMZ) vs pressable lithium disilicate (PLD) laminate veneers. MATERIALS AND METHODS: A total of 40 maxillary lateral incisors were used and received butt-joint laminate veneer preparation. The samples were divided into two groups (n = 20 each) according to ceramic material: PLD ceramic was used in the first group, and MMZ was used in the second. Each group was then divided into two subgroups according to the bonding protocol: IDS was employed in one, and DDS in the other (n = 10 each). The marginal gap widths were measured using digital microscopy and statistically analyzed. RESULTS: The smallest marginal gaps were observed in MMZ-DDS (57.2 ± 8.4 µm), followed by PLD-DDS (62.4 ± 2.7 µm) and MMZ-IDS (63.5 ± 1.9 µm). The largest marginal gaps were observed in PLD-IDS (81.5 ± 6.3 µm). Two-way ANOVA revealed that the bonding technique (P < .001) and ceramic material (P < .001) both showed significant differences. CONCLUSIONS: MMZ produced beIer marginal accuracy than PLD. IDS seems to have a predisposition to significantly wider marginal gaps than DDS, but these gaps are within the clinically acceptable range. The marginal accuracy of ceramic veneers appears to be related to the bonding technique as well as the material of construction.

Proximal Caries Detection Using Short-Wave Infrared Transillumination at Wavelengths of 1050, 1200 and 1300 nm in Permanent Posterior Human Teeth.

This in vitro study aimed to investigate the diagnostic potential of short-wave infrared transillumination (SWIRT) at 1050, 1200 and 1300 nm for the detection of proximal caries in molars and premolars. It was compared to the diagnostic performance of bitewing radiography (BWR) and micro-computed tomography (µCT) as the reference standard. 250 sound or decayed proximal surfaces of permanent posterior extracted teeth were examined using (1) SWIRT at 1050, 1200 and 1300 nm with two camera systems of different resolutions, (2) BWR and (3) µCT. Thresholds were defined for both test methods and the reference standard for caries in general, enamel caries and dentin caries. All images were assessed by two examiners twice, at an interval of two weeks. SWIRT at wavelengths of 1050, 1200 and 1300 nm achieved sensitivity values more than 2.5 times higher than BWR (enamel caries 3.2-4.4 times; dentin caries 3.25-4.25 times) for the detection of proximal caries. Sensitivity values of SWIRT improved with the higher wavelength. No significant difference was found in diagnostic quality between the two camera systems. SWIRT at 1300 nm imaged proximal enamel caries with the highest accuracy, while the physical optimum for transillumination in dentin was located at a lower wavelength (<1000 nm).

Chairside oral prophylaxis for people with profound intellectual or multiple disabilities-a retrospective feasibility study.

OBJECTIVES: People with severe intellectual or multiple disabilities (PIMD) have been receiving dental care in a specialized unit offering special care dentistry. For most of these adult patients, the initial consultation is complaint driven. In addition, the limited ability to cooperate due to their disabilities often means that dental treatment for these patients is usually carried out under general anesthesia (GA). Chairside treatment attempts are the exception rather than the rule. This retrospective study evaluated whether consistent practice of behavioral management principles and techniques embedded in a specific dental environment enables successful dental treatment of PIMD. MATERIALS AND METHODS: The feasibility of chairside dental prophylaxis in PIMD (n=36) was analyzed: specific behavioral management techniques were applied, and professional tooth cleaning (PTC) was performed in the dental chair. Clinical data obtained from medical records and a questionnaire were analyzed. RESULTS: All patients had severe intellectual or multiple disabilities and had previously undergone at least one dental treatment under GA. Of these patients, 55.6% never had their teeth professionally cleaned before. Applying different behavioral techniques, all patients were compliant with receiving PTC in the dental chair. CONCLUSIONS: An individualized and disability-specific treatment strategy using various noninvasive and nonpharmacological behavioral guidance techniques resulted in a higher compliance rate in PIMD, which allowed chairside PTC and reduced the need for treatment under GA. CLINICAL RELEVANCE: Consistent implementation of various behavioral guidance techniques and communication strategies in a supportive environment enabled all patients to receive chairside PTC and be involved in a lifelong recall program.

Simulating the shrinkage-induced interfacial damage around Class I composite resin restorations with damage mechanics.

OBJECTIVES: To investigate the shrinkage-induced damage at the composite-tooth interface by finite element analysis (FEA) using the cohesive zone model (CZM). METHODS: Axisymmetric models of Class I restorations were created to illustrate the interfacial damage around composite resin restorations of different dimensions, with polymerization shrinkage modeled analogously to thermal shrinkage. The damage to the adhesive interface was determined using a CZM based on the fracture strength and fracture energy. To show the effects of damage, conventional models with perfectly bonded composite resin restorations were created as controls. RESULTS: The results indicated interfacial damage at the butt-joint cavosurface margin, dentinoenamel junction, and internal line angle. The percentage of damaged interfacial area was found to increase with decreasing diameter for restorations of the same height. For a given diameter, the damage was more severe for restorations of greater depth. The effects of the damage were further illustrated in the model with a restoration of 2-mm diameter and height. The interfacial damage occurred primarily at the internal line angle (83.3 % of all the damaged interfacial area), leading to local stress relief (from 18.3 MPa to 12.8 MPa), but also higher stress at the damage fronts. Greater local shrinkage was found in composites adjacent to the damage. SIGNIFICANCE: The damage mechanics-based CZM is an essential refinement of the FEA to predict interfacial damage and its implications. The extent of damage was found to be greater around restorations with smaller diameters and greater depths. The entire simulation is available via an open-source platform to facilitate further applications in adhesive dentistry.

Oral health in patients with neurodegenerative and cerebrovascular disease: a retrospective study.

PURPOSE: This retrospective study investigates oral health and oral care in patients with neurodegenerative and cerebrovascular diseases (CVDs) treated in a dental facility for people with disabilities. METHODS: Oral health indices decayed, missing, and filled teeth (DMFT), periodontal screening index (PSI), treatment spectrum, and oral hygiene were evaluated in 152 patients with multiple sclerosis, Parkinson's disease, dementia, and CVD and 30 controls. Regression analyses identified group differences and influencing factors on DMFT. RESULTS: Patients with neurodegenerative or CVD had a significantly higher DMFT (21.2 ± 5.8 vs. 18.3 ± 5.9), more decayed teeth (4.3 ± 4.8 vs. 1 ± 1.9), fewer filled teeth (7.9 ± 5.5 vs. 11 ± 5.6), and a higher number of surgical (39.5% vs. 20%) treatments but significantly less conservative (49.3% vs. 73.3%) and prosthetic (15.1% vs. 56.7%) treatments than the control group (p< 0.05). The frequency of toothbrushing and the use of an electric toothbrush were related to lower DMFT in patients with neurodegenerative and CVD. Smoking was associated with higher DMFT. CONCLUSIONS: Poor oral health was found in all individuals with disabilities, suggesting that limitations in oral care attributed to aging and neurological disorders negatively affect oral health. Oral rehabilitation of patients with disabilities requires awareness of oral health limitations and early intervention through dental care. Implications for rehabilitationPoor oral health and oral hygiene is common among older people with disabilities.To optimize oral rehabilitation of patients with disabilities, early intervention, individualized treatment plans and an adapted time frame for dental treatment are required.Education of dentists, caregivers, and family members is essential for oral rehabilitation and improvement of oral hygiene in patients with disabilities.

Current Strategies to Control Recurrent and Residual Caries with Resin Composite Restorations: Operator- and Material-Related Factors.

This review addresses the rationale of recurrent and/or residual caries associated with resin composite restorations alongside current strategies and evidence-based recommendations to arrest residual caries and restrain recurrent caries. The PubMed and MEDLINE databases were searched for composite-associated recurrent/residual caries focusing on predisposing factors related to materials and operator's skills; patient-related factors were out of scope. Recurrent caries and fractures are the main reasons for the failure of resin composites. Recurrent and residual caries are evaluated differently with no exact distinguishment, especially for wall lesions. Recurrent caries correlates to patient factors, the operator's skills of cavity preparation, and material selection and insertion. Material-related factors are significant. Strong evidence validates the minimally invasive management of deep caries, with concerns regarding residual infected dentin. Promising technologies promote resin composites with antibacterial and remineralizing potentials. Insertion techniques influence adaptation, marginal seal, and proximal contact tightness. A reliable diagnostic method for recurrent or residual caries is urgently required. Ongoing endeavors cannot eliminate recurrent caries or precisely validate residual caries. The operator's responsibility to precisely diagnose original caries and remaining tooth structure, consider oral environmental conditions, accurately prepare cavities, and select and apply restorative materials are integral aspects. Recurrent caries around composites requires a triad of attention where the operator's skills are cornerstones.

Influence of Immediate Dentin Sealing on the Marginal Gaps of Laminate Veneers: Machinable Monolithic Zirconia Versus Pressable Lithium Disilicate: An in vitro study.

PURPOSE: To investigate the influence of immediate dentin sealing (IDS) vs delayed dentin sealing (DDS) on the marginal gaps of machinable monolithic zirconia vs pressable lithium disilicate laminate veneers. MATERIALS AND METHODS: A total of 40 maxillary lateral incisors were used and received butt-joint laminate veneer preparation. The samples were divided into two groups (n = 20 each) according to ceramic material: pressable lithium disilicate ceramic (PLD) was used in the first group, and machinable monolithic zirconia (MMZ) was used in the second. Each group was then divided into two subgroups according to the bonding protocol: IDS was employed in one, and DDS in the other (n = 10 each). The marginal gap widths were measured using digital microscopy and statistically analyzed. RESULTS: The smallest marginal gaps were observed in MMZ-DDS (57.2 ± 8.4 µm), followed by PLD-DDS (62.4 ± 2.7 µm) and MMZ-IDS (63.5 ± 1.9 µm). The largest marginal gaps were observed in PLD-IDS (81.5 ± 6.3 µm). Two-way ANOVA revealed that the bonding technique (P < .001) and ceramic material (P < .001) both showed significant differences. CONCLUSIONS: MMZ produced better marginal accuracy than PLD. IDS seems to have a predisposition to significantly wider marginal gaps than DDS, but these gaps are within the clinically acceptable range. The marginal accuracy of ceramic veneers appears to be related to the bonding technique as well as the material of construction.

Matrix Metalloproteinases in Dental and Periodontal Tissues and Their Current Inhibitors: Developmental, Degradational and Pathological Aspects.

OBJECTIVES: This review article aims to describe some of the roles of Matrix metalloproteinases (MMPs) in enamel, dentine, dental caries, hybrid layer degradation, pulp and periodontal tissues, throwing light on their current inhibitors. The article addresses the potential of MMPs to serve as biomarkers with diagnostic and therapeutic value. DESIGN: The sections of this review discuss MMPs' involvement in developmental, remodeling, degradational and turnover aspects of dental and periodontal tissues as well as their signals in the pathogenesis, progress of different lesions and wound healing of these tissues. The literature was searched for original research articles, review articles and theses. The literature search was conducted in PubMed and MEDLINE for articles published in the last 20 years. RESULTS: 119 published papers, two textbooks and two doctoral theses were selected for preparing the current review. CONCLUSIONS: MMPs are significant proteases, of evident contribution in dental and periapical tissue development, health and disease processes, with promising potential for use as diagnostic and prognostic disease biomarkers. Continuing understanding of their role in pathogenesis and progress of different dental, periapical and periodontal lesions, as well as in dentine-pulp wound healing could be a keystone to future diagnostic and therapeutic regimens.

Tooth whitening with an experimental toothpaste containing hydroxyapatite nanoparticles.

BACKGROUND: The aim of this study was to evaluate the postbrushing tooth-whitening effect of toothpaste containing hydroxyapatite nanoparticles (nano-HAPs). The impact of the concentration on the whitening performance of nano-HAP toothpaste was also investigated. METHODS: Two concentrations of nano-HAP (10 wt% and 1 wt%) were incorporated in nonabrasive toothpastes. Forty bovine incisors were randomly assigned into four groups: 10 wt% nano-HAP, 1 wt% nano-HAP, toothpaste without nano-HAP as a negative control and water as a blank control. Each tooth was treated with the toothpaste three times and hydrodynamic shear force (HSF) once. The teeth surfaces were observed by SEM after each application. Tooth color (L*, a* and b* values) was measured by a spectrophotometer, and color changes (△E, △L, △a and △b values) were calculated. Two-way mixed ANOVA was performed to evaluate the influence of the concentration and repeated application on the tooth-whitening effect of nano-HAP. RESULTS: We found that nano-HAP-treated enamel exhibited higher L* values and lower a* and b* values than the control groups (P < 0.05). The 10 wt% nano-HAP group showed significantly higher △E values than the 1 wt% nano-HAP group (P < 0.05). After three applications, the △E mean value of the 10 wt% nano-HAP group was 4.47. The △E and △L values were slightly reduced after HSF (P < 0.05). For both nano-HAP groups, HAP single crystallites and agglomerates were identified, and their sizes grew with nano-HAP reapplication. CONCLUSIONS: In conclusion, nano-HAP toothpaste has a satisfying postbrushing whitening effect and good resistance to mechanical forces. The whitening effect seemed to be concentration-dependent.

Treatment Plan and Challenges in Full-Mouth Rehabilitation of a Quadriplegic Patient: A Clinical Report.

Spinal cord injuries lead to physical limitations, and the resulting levels of dependency and emotional distress have devastating consequences on individuals' oral health. A 46-year-old patient with incomplete quadriplegia due to a complicated medical history presented for prosthetic rehabilitation. The patient's ability and tolerance to be treated in the dental chair was assessed. Prosthetic treatment options were discussed considering his dependency on alternating caregivers. The final treatment plan involved restorative treatment, implant-supported crowns, an implant-supported fixed dental prosthesis and, in the upper jaw, an implant-supported overdenture to allow proper oral hygiene. The dental treatment sessions were performed with frequent interruptions in the dental chair, whereas the implants were placed under general anesthesia in the maxillo-facial surgery department. The final treatment plan resulted in a compromise between the prosthetic recommendation and the patient's wish. The decisive factor for choosing an implant-supported overdenture rather than an implant-supported fixed dental prosthesis in the upper jaw was the inability of the patient to maintain adequate hygiene measures by himself and his dependence on the caregivers. This clinical report demonstrates how special care dentistry can improve quality of life, even in people with severe physical and/or mental impairments. We would like to encourage dental professionals to provide high-quality care for patients with disabilities in particular, and this practice is in line with the requirements of the UN convention on the rights of persons with disabilities.

Diagnostic validity of early proximal caries detection using near-infrared imaging technology on 3D range data of posterior teeth.

OBJECTIVES: This in vitro study analysed potential of early proximal caries detection using 3D range data of teeth consisting of near-infrared reflection images at 850 nm (NIRR). MATERIALS AND METHODS: Two hundred fifty healthy and carious permanent human teeth were arranged pairwise, examined with bitewing radiography (BWR) and NIRR and validated with micro-computed tomography. NIRR findings were evaluated from buccal, lingual and occlusal (trilateral) views according to yes/no decisions about presence of caries. Reliability assessments included kappa statistics and revealed high agreement for both methods. Statistical analysis included cross tabulation and calculation of sensitivity, specificity and AUC. RESULTS: Underestimation of caries was 24.8% for NIRR and 26.4% for BWR. Overestimation was 10.4% for occlusal NIRR and 0% for BWR. Trilateral NIRR had overall accuracy of 64.8%, overestimation of 15.6% and underestimation of 19.6%. NIRR and BWR showed high specificity and low sensitivity for proximal caries detection. CONCLUSIONS: NIRR achieved diagnostic results comparable to BWR. Trilateral NIRR assessments overestimated presence of proximal caries, revealing stronger sensitivity for initial caries detection than BWR. CLINICAL RELEVANCE: NIRR provided valid complement to BWR as diagnostic instrument. Investigation from multiple angles did not substantially improve proximal caries detection with NIRR.

Effects of application method on shrinkage vectors and volumetric shrinkage of bulk-fill composites in class-II restorations.

OBJECTIVES: Upon initial proximal wall construction, the favorable C-factor of class-II cavities may become unfavorable. This study investigated the application method on bulk-fill resin composite polymerization shrinkage. METHODS: Occluso-proximal class-II cavities were prepared in 40 molars and bonded with a self-etch adhesive (Adhese Universal). The study groups varied according to the resin composite application: group-1: bulk application, Tetric EvoCeram Bulk Fill (TBF); group-2: proximal wall construction (TBF) and occlusal cavity filling (TBF); group-3: thin flowable liner layer, Tetric EvoFlow Bulk Fill (TEF) and bulk filling (TBF); group-4: flowable liner (TEF), proximal wall (TBF), occlusal cavity (TBF); and group-5: bulk application, SDR (3 mm) and capping layer (TBF, 1 mm). Each resin composite increment was scanned twice using micro-CT (uncured, cured 40 s) at a resolution of 16 µm. Shrinkage vectors and volumetric polymerization shrinkage were evaluated and statistically analyzed (one-way ANOVA). SEM images were used to investigate the tooth-restoration interface. RESULTS: Shrinkage vectors differed significantly among the groups and were greatest in gp5-fl/SDR (47.6 µm), followed by gp1-TBF (23.8 µm) and least in gp5-fl/SDR+TBF (11.1 µm). Volumetric shrinkage varied significantly with the use of SDR (gp5-fl/SDR: 2.6%) and TEF (gp4-fl/TEF: 2.5%) to TBF (gp4-fl/TEF+wl/TBF: 0.6%) in the incremental application. SIGNIFICANCE: Building a proximal resin composite wall yielded smaller shrinkage vectors than the bulk application. Applying a thin flowable liner decreased the shrinkage vectors, even more when building a proximal wall. A thin flowable liner is recommended when building a proximal resin composite wall.

Effects of flowable liners on the shrinkage vectors of bulk-fill composites.

OBJECTIVES: This investigation evaluated the effect of flowable liners beneath a composite restoration applied via different methods on the pattern of shrinkage vectors. METHODS: Forty molars were divided into five groups (n = 8), and cylindrical cavities were prepared and bonded with a self-etch adhesive (AdheSe). Tetric EvoCeram Bulk Fill (TBF) was used as the filling material in all cavities. The flowable liners Tetric EvoFlow Bulk Fill (TEF) and SDR were used to line the cavity floor. In gp1-TBF, the flowable composite was not used. TEF was applied in a thin layer in gp2-fl/TEF + TBF and gp3-fl/TEF + TBFincremental. Two flowable composites with a layer thickness of 2 mm were compared in gp4-fl/TEF + TBF and gp5-fl/SDR + TBF. TEF and SDR were mixed with radiolucent glass beads, while air bubbles inherently present in TBF served as markers. Each material application was scanned twice by micro-computed tomography before and after light curing. Scans were subjected to image segmentation for calculation of the shrinkage vectors. RESULTS: The absence of a flowable liner resulted in the greatest shrinkage vectors. A thin flowable liner (gp2-fl/TEF + TBFbulk) resulted in larger overall shrinkage vectors for the whole restoration than a thick flowable liner (gp4-fl/TEF + TBF). A thin flowable liner and incremental application (gp3-fl/TEF + TBFincremental) yielded the smallest shrinkage vectors. SDR yielded slightly smaller shrinkage vectors for the whole restoration than that observed in gp4-fl/TEF + TBF. CONCLUSIONS: Thick flowable liner layers had a more pronounced stress-relieving effect than thin layers regardless of the flowable liner type. CLINICAL RELEVANCE: It is recommended to apply a flowable liner (thin or thick) beneath bulk-fill composites, preferably incrementally.

A cross-sectional multicenter survey on the future of dental education in the era of COVID-19: Alternatives and implications.

PURPOSE: The coronavirus disease 2019 (COVID-19) pandemic has significantly challenged dental education. This study investigated the procedures outlined by dental faculty members to maintain quality dental education in a safe bioenvironment and adequately control the risk of cross-infection METHOD: Dental educators from dental schools around the world were invited to join an online survey considering different demographic factors. The survey consisted of 31 questions that were classified into separate sections, including academic characteristics, college size and facilities, action taken after announcement of the COVID-19 pandemic, perception of the pandemic, opinion regarding teaching, patient flow, possible facilities to implement for short- and long-term plans, and actions suggested to deal with the COVID-19 pandemic RESULTS: Two hundred-twelve responses were received. Respondents commonly agreed that COVID-19 will have major negative effects on dental education, adversely affecting all clinical disciplines. Shifting to virtual curricula, simulation labs, and distant learning were the prevailing actions taken in different dental colleges during the pandemic. Special attention was raised by the majority of respondents regarding dental aerosolizing procedures, preferring to postpone their training to a postpandemic/later phase. Coinciding opinions suggested adopting a future dynamic hybrid strategy analysis that combines online distant learning, virtual simulation, and haptic labs together with traditional direct clinical training on real patients CONCLUSION: The future of dental education will have far-reaching changes in strategies and tools to cope with COVID-19 pandemic and the postpandemic requirements of an effective, yet safe, dental learning environment. Dental colleges need to invest in infection precautions and in modern virtual education and training facilities.

Shrinkage vectors in flowable bulk-fill and conventional composites: bulk versus incremental application.

OBJECTIVES: Sufficient depth of cure allows bulk-fill composites to be placed with a 4-mm thickness. This study investigated bulk versus incremental application methods by visualizing shrinkage vectors in flowable bulk-fill and conventional composites. MATERIALS AND METHODS: Cylindrical cavities (diameter = 6 mm, depth = 4 mm) were prepared in 24 teeth and then etched and bonded with OptiBond FL (Kerr, Italy). The composites were mixed with 2 wt% radiolucent glass beads. In one group, smart dentin replacement (SDR, Dentsply) was applied in bulk "SDR-bulk" (n = 8). In two groups, SDR and Tetric EvoFlow (Ivoclar Vivadent) were applied in two 2-mm-thick increments: "SDR-incremental" and "EvoFlow-incremental." Each material application was scanned with a micro-CT before and after light-curing (40 s, 1100 mW/cm2), and the shrinkage vectors were computed via image segmentation. Thereafter, linear polymerization shrinkage, shrinkage stress and gelation time were measured (n = 10). RESULTS: The greatest shrinkage vectors were found in "SDR-bulk" and "SDR-increment2," and the smallest were found in "SDR-increment1-covered" and "EvoFlow-increment1-covered." Shrinkage away from and toward the cavity floor was greatest in "SDR-bulk" and "EvoFlow-increment2," respectively. The mean values of the shrinkage vectors were significantly different between groups (one-way ANOVA, Tamhane's T2 test, p < 0.05). The linear polymerization shrinkage and shrinkage stress were greatest in Tetric EvoFlow, and the gelation time was greatest in "SDR-bulk." CONCLUSIONS: The bulk application method had greater values of shrinkage vectors and a higher debonding tendency at the cavity floor. CLINICAL RELEVANCE: Incremental application remains the gold standard of composite insertion.

Adhesion and whitening effects of P11-4 self-assembling peptide and HAP suspension on bovine enamel.

OBJECTIVES: This study evaluated the adhesion and whitening effects of a combination of P11-4 self-assembling peptide and hydroxyapatite (peptide-HAP) on bovine enamel. METHODS: Forty-six caries-free bovine teeth were selected, and 40 teeth were randomly allocated to one of five groups (n = 8). First, the effects of application frequency, exposure time, and storage in saliva on the whitening effects of an experimental low-concentrated peptide-HAP suspension (0.5 wt% HAP; Curodont, Credentis) were evaluated and compared with a commercial bleaching agent (VivaStyle Paint on Plus, VS, Ivoclar Vivadent). Tooth color was measured using a spectrophotometer (Gretag MacBeth), and color changes ΔE were statistically analyzed. Second, the effects of peptide-HAP concentration (low versus high: 6.25% HAP; Curodont Protect), and its interactions with saliva and postapplication restaining, were investigated. Third, enamel surfaces (n = 2) were treated with low concentration peptide-HAP and high-concentration peptide-HAP in polymeric and monomeric forms (Curodont Protect & Curodont Repair, Credentis) and analyzed by SEM. RESULTS: The ΔE of the low-concentration peptide-HAP suspension did not differ from that of VS. Application frequency, exposure time, and storage in saliva did not have any significant impact on whitening efficacy of the peptide-HAP suspension. Increasing the concentration of the suspension did not promote overall ΔE. SEM observations confirmed the presence of the newly generated peptide and HAP on the enamel surface. CONCLUSIONS: The peptide-HAP suspension is a mild tooth whitener, and the adhesion of peptide-HAP to enamel is concentration dependent. CLINICAL RELEVANCE: This peptide-HAP suspension is effective in offsetting discoloration caused by restaining after treatment.

Remineralization, Regeneration, and Repair of Natural Tooth Structure: Influences on the Future of Restorative Dentistry Practice.

Currently, the principal strategy for the treatment of carious defects involves cavity preparations followed by the restoration of natural tooth structure with a synthetic material of inferior biomechanical and esthetic qualities and with questionable long-term clinical reliability of the interfacial bonds. Consequently, prevention and minimally invasive dentistry are considered basic approaches for the preservation of sound tooth structure. Moreover, conventional periodontal therapies do not always ensure predictable outcomes or completely restore the integrity of the periodontal ligament complex that has been lost due to periodontitis. Much effort and comprehensive research have been undertaken to mimic the natural development and biomineralization of teeth to regenerate and repair natural hard dental tissues and restore the integrity of the periodontium. Regeneration of the dentin-pulp tissue has faced several challenges, starting with the basic concerns of clinical applicability. Recent technologies and multidisciplinary approaches in tissue engineering and nanotechnology, as well as the use of modern strategies for stem cell recruitment, synthesis of effective biodegradable scaffolds, molecular signaling, gene therapy, and 3D bioprinting, have resulted in impressive outcomes that may revolutionize the practice of restorative dentistry. This Review covers the current approaches and technologies for remineralization, regeneration, and repair of natural tooth structure.

Effect of fiber incorporation on the contraction stress of composite materials.

OBJECTIVES: This study aimed to assess the effects of fiber incorporation on the contraction stress (CS), time to gelation (TG), and temperature rise (TR) features of two experimental resin-based composites (RBCs) in comparison to those of bulk-fill RBCs and conventional RBCs in simulated, clinically relevant cavities. MATERIALS AND METHODS: CS over 300 s, TG and TR were assessed by a stress-strain analyzer (SSA T80) in two cavity configurations (2 × 4 × 4 mm3/4 × 4 × 4 mm3/configuration value [Formula: see text] and [Formula: see text]) for two experimental RBCs, eight bulk-fill RBCs (EverX Posterior, Filtek Bulk Fill, SDR, SonicFill, Tetric EvoCeram Bulk Fill, Venus Bulk Fill, X-tra base, and X-tra Fill) and one RBC (Filtek Supreme XTE) by light curing (1200 mW/cm2) (n = 10). The experimental materials used were based on EverX Posterior with modifications made to the fiber and filler content. Statistical analyses were performed via ANOVA; multiple pair-wise comparisons were performed via Tukey's test, and homogeneous subsets were identified ("multcomp" package, R). RESULTS: CS values ranged from 1.00 to 4.07 MPa (2 × 4 × 4 mm3) and from 0.97 to 2.49 MPa (4 × 4 × 4 mm3); TG values ranged from 1.31 to 4.05 s (2 × 4 × 4 mm3) and from 1.39 to 3.84 s (4 × 4 × 4 mm3). SDR values showed lowest stress values in both cavity configurations. The experimental composite with fibers presented significantly higher stress values than did the experimental composite without fibers. CONCLUSION: Bulk-fill RBCs showed lower levels of stress than did conventional RBCs. The incorporation of fibers had no positive impact on the CS and TG. CLINICAL RELEVANCE: Appropriate material selection may be essential to clinical success because certain RBCs exhibit higher CS, TG, and TR values.

Effects of boundary condition on shrinkage vectors of a flowable composite in experimental cavity models made of dental substrates.

OBJECTIVES: Bond strength to enamel and dentin depends on the bonding approach or condition. This study investigated the effects of the boundary conditions, in terms of the bonding substrate and the bonding condition, on the shrinkage vectors of a flowable composite. MATERIALS AND METHODS: An experimental cylindrical cavity (diameter = 6 mm, depth = 3 mm) consisting of the enamel floor and the surrounding dentin cavity walls was prepared for the "enamel-floor" group. Cylindrical cavities of the same dimensions were prepared with access from the occlusal enamel into dentin and served as controls. Each cavity model group was divided and bonded with two bonding conditions (n = 9): a self-etch (Adper Easy Bond, 3M ESPE) and a total-etch approach (OptiBond FL, Kerr). The composite (Tetric EvoFlow, Ivoclar Vivadent) was mixed with glass beads, applied to the cavity, scanned twice by micro-CT (uncured and cured states). The scans were evaluated by rigid registration, sphere segmentation, and registration for computing shrinkage vectors. RESULTS: The free surface of all restorations moved downward. The shrinkage vectors in the experimental cavity model pointed downward towards the enamel cavity floor, and the net axial movement was downward. In the control group, shrinkage vectors additionally moved upward, away from the cavity floor. The effect of the bonding substrate and the bonding condition was investigated for the shrinkage vectors and the axial movement (univariate ANOVA). CONCLUSION: The bonding substrate, enamel, influenced the shrinkage vectors' direction, while the bonding condition caused only variations in the magnitude. CLINICAL RELEVANCE: Bonding to enamel influences shrinkage vectors' direction, while the bonding condition plays only a minor role. Graphical abstract ᅟ.