Immediately versus early placed bone-level-tapered implants supporting all-ceramic crowns on titanium base abutments: 1-year radiographic and pink esthetic outcomes of a multicenter pilot RCT.

OBJECTIVES: Aim of this study was to assess survival rates, radiographic, and pink esthetic outcomes of a bone-level-tapered (BLT) implant following immediate or early implant placement. MATERIALS AND METHODS: Patients in need of tooth extraction and one implant in the anterior or premolar area were recruited in five centers. Patients were randomly assigned to the immediate or early placement protocol. Implants were restored with all-ceramic crowns cemented to titanium-base-abutments. Radiographic bone levels, implant stability quotient (ISQ), and pink esthetic outcomes were assessed. Data were analyzed descriptively. Level of significance was set at 0.05. Differences between groups were tested using Wilcoxon-signed-rank and Mann-Whitney-U test as nonparametric tests. RESULTS: A total of 60 patients received 60 BLT implants (Institut Straumann). At 12-months, 59 implants (98.3%) were osseointegrated. The mean distance from implant shoulder to first bone-to-implant contact was 0.15 ± 0.59 mm without significant differences between the groups. Median ISQ values increased from 75.5 to 78.5. A mean buccal recession of 0.1 ± 0.70 mm occurred with no difference between groups. The mean papilla height gain in both groups was 0.5 ± 1.47 mm mesially and 0.4 ± 1.36 mm distally. CONCLUSIONS: After 1 year, immediately and early placed BLT implants exhibit similar bone level changes, ISQ values, and pink esthetic outcomes. CLINICAL SIGNIFICANCE: The present research contributes to the knowledge on clinical outcomes of immediately and early placed BLT implants restored with buccally microveneered ceramic single crowns out of two different ceramic materials. The research shows that similar esthetic and radiographic outcomes can be reached by means of immediate implant placement compared to the conventional early placement protocol. The improvement of esthetic soft-tissue parameters over time was shown for both implant placement protocols.

Two-piece zirconia versus titanium implants after 80 months: Clinical outcomes from a prospective randomized pilot trial.

OBJECTIVES: To prospectively evaluate, as part of an ongoing randomized pilot trial, the clinical outcomes of two-piece zirconia implants in comparison with titanium implants 80 months after delivery of all-ceramic (lithium disilicate) single-tooth restorations. MATERIAL AND METHODS: The original sample included 31 (16 zirconia and 15 titanium) implants in 22 healthy patients. In addition to evaluating implant survival and success, a number of clinical or radiographic parameters were statistically analyzed: plaque index (PI), bleeding on probing (BOP), pink esthetic score (PES), and marginal bone loss (MBL). Both implant groups were compared using a Mann-Whitney U test. RESULTS: Three implants (2 zirconia and 1 titanium) had been lost, so that 28 implants (14 zirconia and 14 titanium) in 21 patients could be evaluated after a mean of 80.9 (SD: 5.5) months. All surviving implants had remained stable, in the absence of any fixture or abutment fractures and without any chipping, fracture, or debonding of crowns. The zirconia implants were associated with PI values of 11.07% (SD: 8.11) and the titanium implants with 15.20% (SD: 15.58), the respective figures for the other parameters being 16.43% (SD: 6.16) or 12.60% (SD: 7.66) for BOP; 11.11 (SD: 1.27) or 11.56 (SD: 1.01) for PES; and 1.38 mm (SD: 0.81) or 1.17 mm (SD: 0.73) for MBL. CONCLUSIONS: No significant differences were found between the clinical outcomes of two-piece zirconia and titanium implants based on the aforementioned parameters after 80 months of clinical service. Our results should be interpreted with the limited sample size in mind.

Fit evaluation of cad/cam fabricated all-ceramic restorations based on direct and indirect digitalization in vivo: a systematic review.

The aim of this study was to compare the fit of all-ceramic restorations on natural teeth fabricated through a direct digital workflow or an indirect digital workflow. An electronic search of publications was established from three electronic databases: Cochrane, PubMed and Web of Science. The search strategy used a combination of controlled vocabulary and free-text words. The detailed search design and strategies, including keywords, are presented below. The authors used two filters to follow data for the research: papers written in English and published in the last 5 years. The search resulted in 3042 titles. Following the first stage of screening, after the records identification through database manual searching, 3047 potentially relevant studies were identified. After the second stage screening, 38 full text publications were obtained and analyzed and 17 were excluded. Afterwards, 22 articles resulted eligible after full text reading and a cross search of the articles references was accomplished and 5 articles were consequently added. At last, 6 articles were included in the quantitative analysis. This study was designed to compare the fit of restorations obtained by means of a direct or indirect digital workflow. The values reported on the maximum acceptable gap in scientific literature range from 50 to 200 µm, so there does not seem to be an objective limit based on scientific evidence. According to the most accepted marginal discrepancy in the literature, most of the values of the studies examined are in the 200 µm acceptability range. Within the limitations of this systematic review, computer-aided design and computer-aided manufacturing (CAD/CAM) fabricated restorations obtained by means of an intraoral scanner (IOS) showed better marginal and internal fit than restorations obtained through conventional impression and subsequent laboratory scanning. According to the results of this systematic review, the direct digital workflow resulted as a valid alternative to the indirect digital workflow to produce CAD/CAM all-ceramic restorations.

Comparative study of all-ceramic crowns obtained from conventional and digital impressions: clinical findings.

OBJECTIVE: To compare clinical aspects of all-ceramic crowns fabricated from conventional and digital impressions. METHODS: Thirty patients with 30 posterior teeth with the need of a crown restoration were selected. Zirconia-based ceramic crowns were made using an intraoral digital impression system (TRIOS®, 3shape) and two-step silicone impression technique. Two external blinded operators evaluated the all-ceramic crowns. Five selection items were assessed of which four were clinical: "marginal fit," "occlusal contacts," "interproximal contact points," and "primary retention." Then, the last selection item "final selection" was assessed when the operators considering all the variables had to select which of the digital or conventional crown had the best clinical conditions. Data was analyzed using Kappa index test and the Pearson's chi-square test (α = 0.05). RESULTS: For the items marginal fit and interproximal contact points, moderate agreement between the two operators was described and significant differences were found between the two study groups. Conversely, for the variables primary retention and occlusal contacts, the agreement between the operators was fair and no significant differences were found. For the final selection, a substantial agreement was reached between the two operators and significant differences were found between the two groups (p < 0.05). CONCLUSION: In most cases and in a significant way, the digital crowns had better clinical conditions according to both evaluators. The digital crowns were statistically superior for the interproximal contact points and marginal fit. For the variables occlusal contacts and primary retention, no difference between the two groups was observed. CLINICAL SIGNIFICANCE: Digital intraoral impressions can be used for manufacturing ceramic crowns, with the same or better clinical results as conventional impressions.

Fracture resistance of zirconia-based all-ceramic crowns after bur adjustment.

Intra-oral grinding is often required to optimize occlusion of all-ceramic restorations. The effect of burs of different grit size on the fracture resistance of veneered zirconia crowns was investigated in this study. Forty-eight standardized zirconia copings were produced. The ceramic veneer was designed with a positive ellipsoidal defect on the palatal aspect of the crowns. To simulate adjustment of dental restorations by burs, this palatal defect was removed by use of three different diamond-coated burs with grit sizes 46, 107, or 151 µm (fine, medium, or coarse, respectively). Each different grit size of bur was used to grind 16 crowns. All crowns were then polished and surface roughness was measured. Half of the specimens underwent thermomechanical aging (10,000 thermocycles between 6.5°C and 60°C) and 1.2 million cycles of chewing simulation (F = 108 N). A linear regression model was computed to test the effect of aging and grinding grit size at a level of significance of α = 0.05. Fracture loads increased with decreasing grit size. Grit size and aging had a significant effect on the fracture resistance of the crowns. Use of fine and coarse burs for intra-oral adjustments resulted in different fracture resistance of veneered zirconia crowns. Coarse burs should be avoided in the final stage of grinding before polishing.

Influence of conventional and digital intraoral impressions on the fit of CAD/CAM-fabricated all-ceramic crowns.

OBJECTIVES: To compare the fit of all-ceramic crowns fabricated from conventional silicone impressions with the fit of all-ceramic crowns fabricated from intraoral digital impressions. METHODS: Thirty patients with 30 posterior teeth with a prosthetic demand were selected. Zirconia-based ceramic crowns were made using an intraoral digital impression system (Ultrafast Optical Sectioning technology) (digital group, D) and 2-step silicone impression technique (conventional group, C). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation using ultra-flow silicone. Each crown was embedded in resin to stabilize the registered interface. Specimens were sectioned in buccolingual orientation, and internal misfit was measured at different areas using stereomicroscopy (×40). Data was analysed using Student's t test and Mann-Whitney test (α = 0.05). RESULTS: No statistically significant differences were found (P > 0.05) between two groups. The mean internal misfit and mean marginal misfit were 170.9 µm (SD = 119.4)/106.6 µm (SD = 69.6) for group D and 185.4 µm (SD = 112.1)/119.9 µm (SD = 59.9) for group C. CONCLUSION: Ceramic crowns fabricated using an intraoral scanner are comparable to elastomer conventional impressions in terms of their marginal and internal fits. The mean marginal fit in both groups was within the limits of clinical acceptability. CLINICAL SIGNIFICANCE: Impressions based on Ultrafast Optical Sectioning technology can be used for manufacturing ceramic crowns in a normal workflow, with the same results as silicone conventional impressions.

Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions.

OBJECTIVES: The aim of this study is to compare the fit of all-ceramic crowns fabricated from conventional silicone impressions with the fit of all-ceramic crowns fabricated from intraoral digital impressions. METHODS: Twenty patients with 26 posterior teeth with a prosthetic demand were selected for the study. Two crowns (Straumann-Zerion) were made for each preparation. One crown was fabricated from an intraoral digital impression system (IDI group; Cadent-iTero), and the other crown was fabricated from a conventional one-step silicone impression (CI group; Express Penta Putty and Body Light). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation with ultra-flow silicone (Express Ultra Light Body). Each crown was embedded in resin to stabilize the registered interface, cut in 2-mm-thick slices in a buco-lingual orientation. Internal misfit was measured in microns using stereomicroscopy with a magnification of ×40. Measurements were taken at different landmarks: margin, chamfer angle, axial, crest, and occlusal fosse. After checking for normality, data was analyzed using paired Student's t test (α = 0.05). RESULTS: Fit values were significantly affected by the impression technique (p = 0.000). Mean internal misfit and mean marginal misfit were 111.40 µm (SD = 54.04)/80.29 µm (SD = 26.24) for the crowns of the IDI group and 173.00 µm (SD = 92.65)/133.51 µm (SD = 48.78) for the CI group. CONCLUSION: All-ceramic crowns fabricated from intraoral digital impressions with parallel confocal technology demonstrated a clinically acceptable internal and marginal fit as conventional impression. CLINICAL SIGNIFICANCE: Intraoral digital impressions as initial step to the digital workflow could further improve the marginal adaptation of all ceramic single crowns. TRIAL REGISTRATION: http://www.isrctn.com/ISRCTN16111844.

All-ceramic restoration of zirconia two-piece implants--a randomized controlled clinical trial.

OBJECTIVES: Aim of this controlled prospective randomized study was to evaluate the outcome of two-piece zirconia implants compared to titanium implants over a period of up to 24 months. MATERIAL AND METHODS: A total of 31 implants (16 zirconia/Ziterion vario Z(®) + 15 titanium/Ziterion vario T(®) ) were inserted primary stable (>30 Ncm) in the maxilla (7) and mandible (24) of 22 patients (13 male, nine female) requiring neither bone nor soft tissue augmentation. After a healing period of 6 months in the maxilla and 4 months in the mandible, ceramic abutments were luted adhesively to the zirconia implants and definitive all-ceramic restoration was performed with high-density ceramics. Radiographic bone levels, condition of the peri-implant mucosa, aesthetic outcome, implant survival and success were recorded for up to 24 months. RESULTS: Measurements of mean marginal bone levels 24 months after surgery showed a significant bone loss (P < 0.001) in both groups (Ti: 1.43 (SD ± 0.67) vs. Zir 1.48 (SD ± 1.05). One zirconia implant was lost 8 months after restoration. No further complications were recorded, giving an overall survival and success rate of 93.3% for zirconia and 100% for titanium implants after a period of up to 24 months. CONCLUSIONS: After 24 months, success rates of the two-piece ceramic implants showed no significant difference compared to control two-piece titanium implants. The bonded zirconia implant abutment connection appears to be capable with clinical application over the observed period. However, further control measurements need to confirm the presented data.

Laser all-ceramic crown removal and pulpal temperature--a laboratory proof-of-principle study.

The objective of this proof-of-principle laboratory pilot study was to evaluate the temperature increase in the pulp chamber in a worst case scenario during Er:YAG laser debonding of all-ceramic crowns. Twenty extracted molars were prepared to receive all-ceramic IPS E.max CAD full contour crowns. The crowns were bonded to the teeth with Ivoclar Multilink Automix. Times for laser debonding and temperature rise in the pulp chamber using micro-thermocouples were measured. The Er:YAG was used with 560 mJ/pulse. The irradiation was applied at a distance of 5 mm from the crown surface. Additional air-water spray for cooling was utilized. Each all-ceramic crown was successfully laser debonded with an average debonding time of 135 ± 35 s. No crown fractured, and no damage to the underlying dentin was detected. The bonding cement deteriorated, but no carbonization at the dentin/cement interface occurred. The temperature rise in the pulp chamber averaged 5.4° ± 2.2 °C. During 8 out of the 20 crown removals, the temperature rise exceeded 5.5 °C, lasting 5 to 43 s (average 18.8 ± 11.6 s). A temperature rise of 11.5 °C occurred only once, while seven times the temperature rise was limited to 6.8 ± 0.5 °C. Temperature rises above 5.5 °C occurred only when the laser was applied from one side and additional cooling from the side opposite the irradiation. Er:YAG laser energy can successfully be used to efficiently debond all-ceramic crowns from natural teeth. Temperature rises exceeding 5.5 °C only occur when an additional air/water cooling from a dental syringe is inaccurately directed. To avoid possible thermal damage and to allow further heat diffusion, clinically temperature-reduced water might be applied.

Laser all-ceramic crown removal-a laboratory proof-of-principle study-phase 1 material characteristics.

BACKGROUND AND OBJECTIVES: The removal of all-ceramic crowns is a time consuming and destructive procedure in the dental office. The removal of all-ceramic crowns using Er:YAG lasers has not been previously described in the scientific literature. The objective of this laboratory proof-of-principle study was to evaluate whether with regards to absorption and transmission characteristics of bonding cements and ceramics all-ceramic crowns can be removed from natural teeth using an Erbium laser. STUDY DESIGN/MATERIALS AND METHODS: The Fourier Transform Infrared Spectroscopy (FTIR) was used on flat ceramic samples (IPS Empress Esthetic (EE), E.max CAD, and E.max ZirCAD) to assess which infrared laser wavelengths transmit through the ceramics. Additionally, FTIR spectra for four bonding cements (Variolink Veneer, Variolink II, Multilink Automix, and SpeedCEM) were obtained. The Er:YAG laser energy transmission (wavelength 2,940 nm, 10 Hz repetition rate, pulse duration 100 µs at 126 mJ/pulse to 300 µs at 508 mJ/pulse) through different ceramic thicknesses was measured. Ablation thresholds for bonding cements were determined. Cement samples were directly irradiated or laser light was transmitted through ceramic samples. RESULTS: While the ceramics did not show any characteristic water absorption bands in the FTIR, all bonding cements showed a broad H2 O/OH absorption band. Some cements exhibited a distinct absorption peak at the Er:YAG laser emission wavelength. Depending on the ceramic thickness, EE and E.max CAD ceramics transmitted between 21 and 60% of the incident Er:YAG energy, with E.max CAD transmitting more energy than EE at comparable thicknesses. In contrast, E.max ZirCAD transmitted only 5-10% of the incident energy. Initial signs of cement deterioration occurred at 1.3-2.6 J/cm(2) . Multilink Automix, SpeedCEM, and Variolink II started ablation at 4.4-4.7 J/cm(2) . Variolink Veneer needed 44% less energy for ablation. CONCLUSION: Er:YAG laser energy can be transmitted through all-ceramic materials and those transmitted energies are sufficient for ablation of bonding cements.

Laser all-ceramic crown removal-a laboratory proof-of-principle study-phase 2 crown debonding time.

BACKGROUND AND OBJECTIVES: The removal of all-ceramic crowns is a time consuming procedure in the dental office. Little research has been done in alternative removal techniques for all-ceramic crowns. The objective of the second phase of this proof-of-principle laboratory pilot study was to evaluate whether Ivoclar Vivadent all-ceramic crowns can be efficiently removed from natural teeth without damage to the underlying tooth structure using an Erbium laser. STUDY DESIGN/MATERIALS AND METHODS: The ceramic materials used were IPS E.max CAD Lithium-disilicate (LS2 ) (E.max CAD) and IPS E.max ZirCAD Zirconium-oxide (ZrO2 ) (ZirCAD) (Ivoclar, Vivadent, Liechtenstein). Molars, either as stand-alone teeth or placed in an artificial row of teeth, were prepared to receive all-ceramic crowns. Copings and full contour crowns with either featheredge or regular margins were produced. The all-ceramic crowns were bonded to the teeth with Ivoclar Multilink Automix. The time for Er:YAG laser debonding of each crown was then measured. The Er:YAG (LiteTouch, Syneron, Yokneam, Israel) was used with an 1,100 µm diameter fiber tip with energies up to 600 mJ per pulse (wavelength 2,940 nm, 10 Hz repetition rate, pulse duration 100 µs at 126 mJ/pulse, and 400 µs at 590 mJ/pulse). The irradiation was applied at a distance of 10 mm from the crown surface following a defined pattern. Air-water spray was applied to the crowns at a rate of 67 ml/minute. RESULTS: All of the all-ceramic crowns were successfully debonded with the laser. On average, an all-ceramic E.max CAD crown was debonded in 190 ± 92 seconds (average ± SD). The debonding time for ZirCAD featheredge crowns was 226 ± 105 seconds and for ZirCAD crowns with regular margins it was 312 ± 102 seconds. No crowns fractured and no damage to the underlying dentin was detected. The bonding cement deteriorated due to the Er:YAG irradiation. Additionally, no carbonization at the dentin/cement interface was observed. CONCLUSION: Er:YAG laser energy can successfully be used to efficiently debond all-ceramic full contour crowns from natural teeth without damage to the underlying tooth structure. Lasers Surg. Med. 46:636-643, 2014. © 2014 Wiley Periodicals, Inc.

A 3-year prospective study of implant-supported, single-tooth restorations of all-ceramic and metal-ceramic materials in patients with tooth agenesis.

OBJECTIVES: The purpose of this clinical study was to describe outcome variables of all-ceramic and metal-ceramic implant-supported, single-tooth restorations. MATERIALS AND METHODS: A total of 59 patients (mean age: 27.9 years) with tooth agenesis and treated with 98 implant-supported single-tooth restorations were included in this study. Two patients did not attend baseline examination, but all patients were followed for 3 years. The implants supported 52 zirconia, 21 titanium and 25 gold alloy abutments, which retained 64 all-ceramic and 34 metal-ceramic crowns. At baseline and 3-year follow-up examinations, the biological outcome variables such as survival rate of implants, marginal bone level, modified Plaque Index (mPlI), modified Sulcus Bleeding Index (mBI) and biological complications were registered. The technical outcome variables included abutment and crown survival rate, marginal adaptation of crowns, cement excess and technical complications. The aesthetic outcome was assessed by using the Copenhagen Index Score, and the patient-reported outcomes were recorded using the OHIP-49 questionnaire. The statistical analyses were mainly performed by using mixed model of ANOVA for quantitative data and PROC NLMIXED for ordinal categorical data. RESULTS: The 3-year survival rate was 100% for implants and 97% for abutments and crowns. Significantly more marginal bone loss was registered at gold-alloy compared to zirconia abutments (P = 0.040). The mPlI and mBI were not significantly different at three abutment materials. The frequency of biological complications was higher at restorations with all-ceramic restorations than metal-ceramic crowns. Loss of retention, which was only observed at metal-ceramic crowns, was the most frequent technical complication, and the marginal adaptations of all-ceramic crowns were significantly less optimal than metal-ceramic crowns (P = 0.020). The professional-reported aesthetic outcome demonstrated significantly superior colour match of all-ceramic over metal-ceramic crowns (P = 0.015). However, no significant differences in the other aesthetic parameters at various restoration materials were registered. After 3 years, the patient-reported outcome variables at different restoration materials were not significantly different. CONCLUSION: The biological outcomes at the zirconia and metal abutments were comparable. All-ceramic crowns demonstrated better colour match, but higher frequency of marginal discrepancy compared to metal-ceramic crowns. Generally, the patients noticed no difference in aesthetic outcome of all-ceramic and metal-ceramic restorations.

Prosthetic rehabilitation and management of an MTA-treated maxillary central incisor with root perforation and severe internal resorption.

Root canal perforation and root resorption are challenging clinical conditions to correctly diagnose and treat, especially when they occur in anterior teeth. This clinical report describes the computed tomography findings, endodontic treatment, prosthetic rehabilitation, and clinical outcome of an iatrogenic root perforation and internal resorption in a maxillary central incisor. The case management consisted of endodontic retreatment, periodontal surgery, and prosthetic rehabilitation. Gray mineral trioxide aggregate (MTA) was used to fill the resorption space and seal the perforation. The prosthetic treatment was performed with glass fiber-reinforced dowels and all-ceramic crowns. No signs or symptoms, including discomfort, pain, or esthetic defects were observed in 30 months of follow-up.

Pankey Mann Schuyler Philosophy-Based Prosthetic Rehabilitation for an Amelogenesis Imperfecta Patient: A Case Report.

This clinical case report presents the prosthetic rehabilitation of a 23-year-old male patient with generalized discolored and worn-out teeth, which were of aesthetic and functional concern. In collaboration with the Department of Oral Medicine and Radiology and Oral Pathology, this clinical condition was diagnosed as amelogenesis imperfecta (AGI). AGI is a genetic odontological disorder that is an epithelial derivative of the developed tooth bud with enamel malformation. AGI typically affects both deciduous and permanent teeth. Patients generally have aesthetic complaints and compromised chewing efficiency with loss of vertical dimension. Prosthetically rehabilitating an AGI patient is a multidisciplinary approach to regain aesthetics, phonetics, and mastication. This article describes the full mouth rehabilitation, following the Pankey Mann Schuyler philosophy, of the patient with AGI involving all teeth. Full mouth rehabilitation was planned to restore aesthetics, phonetics, and mastication in four phases. First was prosthetic rehabilitation of the mandibular anterior teeth, followed by the maxillary anterior, mandibular posterior, and, finally, maxillary posterior teeth.

Influence of Different Zirconia Coping Designs on the Fracture Resistance of All-Ceramic Crowns: An In Vitro Study.

BACKGROUND AND AIM: Increased demand for metal-free restorations in posterior areas has increased the focus on zirconia restorations because of its advantages in excellent mechanical properties, patient comfort, and acceptance. Although all-ceramic crowns have better biocompatibility and esthetic properties, there are some clinical reasons for the fracture of the veneer or the core materials in the posterior region. This study aims at comparing the influence of zirconia coping designs on the fracture resistance of all-ceramic crowns. MATERIALS AND METHODS: A total of 32 zirconia copings (n = 8 for each group) were designed and fabricated based on the marginal collar height of zirconia coping. The groups were the following: Group 1: 0.0 mm zirconia coping; Group 2: 0.5 mm collar; Group 3: 1.0 mm collar; and Group 4: 1.5 mm collar. All these zirconia copings were veneered with porcelain. Master die with cemented ceramic-layered zirconia copings was tested using Universal testing machine. Data obtained were statistically evaluated by one-way analysis of variance and post hoc test. RESULTS: There was statistically significant difference between the groups with P < 0.001. Group 4 has the highest strength (3318.89 ± 395.67) followed by Group 3 (2910.0 ± 219.22), then Group 1 (2320.02 ± 547.36) that is the control group and the least strength with Group 2 (2286.59 ± 496.66). CONCLUSION: On the basis of the results obtained from this study, it can be concluded that, the more the height of the zirconia collar, the higher the fracture strength of the all-ceramic crowns. Thus ceramic-layered zirconia coping design with 1.5 mm marginal collar height is recommended for functional long life, at least in the posterior higher load-bearing areas with lesser esthetic demands.

Hygroscopic expansion of self-adhesive resin cements and the integrity of all-ceramic crowns.

OBJECTIVE: Low pH neutralization and subsequent remnant hydrophilicity can lead to hygroscopic expansion of self-adhesive resin cements (SARCs) after water storage. The aim of this in vitro study was to investigate the effects of hygroscopic expansion of SARCs, used as luting and partial core build-up material, on integrity and cement gap thickness increase of all-ceramic CAD/CAM crowns. METHODS: Human third molars (n=48) were prepared and anatomical all-ceramic CAD/CAM crowns were manufactured (VITABLOCS Mark II, VITA Zahnfabrik). Crowns internal surfaces were HF etched and silanized. The prepared teeth with their respective crowns were divided into 6 groups (n=8). In groups 1, 3 and 5 the coronal dentin was removed to simulate a partial core build-up. Groups 1 and 2 were luted with iCEM (Heraeus Kulzer), 3 and 4 with RelyX Unicem 2 Automix (3M), 5 and 6 with Variolink Esthetic DC (Ivoclar Vivadent). All specimens were dual cured and stored in distilled water at 37°C. Crown integrity was controlled at baseline and in regular intervals until 180 days. Cement gap thickness was measured using an optical 3D scanner (ATOS Triple scan, GOM) at baseline and after 180 days. Crown integrity was statistically analysed using Kaplan-Meier survival analysis and cement gap thickness increase using two-way ANOVA (α=0.05). RESULTS: After 180 days storage, crack formation was observed in all specimens of group 1 (mean survival time of 85.5 days), in one specimen of group 2 and in two specimens of group 4. Two-way ANOVA analysis revealed a statistically significant interaction between material type and build-up on cement gap size increase for iCEM. SIGNIFICANCE: Within the limits of this study, the application of SARCs with low pH neutralization as partial build-up material under CAD/CAM crowns is not recommended for clinical use.

The effect of resistance grooves on the fracture toughness of zirconia-based crowns from mono and cyclic loading.

OBJECTIVE: Prosthetic molar crowns in service are subjected to chewing loads, which cause a shift or dislodgment. The objective of this study is to investigate whether the addition of resistance grooves to the proximal surfaces of the abutment teeth would enhance the fracture resistance of the zirconia crowns and to compare between the patterns of cracks development on the zirconia crowns after the application of mono loading versus cyclic loading forces. MATERIALS AND METHODS: Thirty-six all-ceramic zirconia cored crowns were prepared on the same abutment. Resistance grooves were added to the mesial and distal surfaces of 16 abutments. Before testing, all specimens subjected to thermal aging. Two groups of crowns were then subjected to cyclic axial and lateral forces for 1,250,000 cycles in aqueous conditions. Two groups of samples were also tested in monoloading fashion. RESULTS: The crack pattern between mono and cyclic loading were compared. The crown fracture resistance was compared in the two types of abutments, with and without grooves. The results confirmed that the grooves addition had no effect on critical conditions to initiate failure in the case of mono loading. In cyclic loading, grooves addition increased the critical loads in the order of two. Failure patterns and location were obtained. CONCLUSIONS: The results showed that the location of retention grooves halted the failure in the surfaces where it was located in all loading mechanisms used in this study.

Marginal fit of all-ceramic crowns fabricated using two extraoral CAD/CAM systems in comparison with the conventional technique.

OBJECTIVE: The purpose of this study was to determine the effect of two extraoral computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, in comparison with conventional techniques, on the marginal fit of monolithic CAD/CAM lithium disilicate ceramic crowns. STUDY DESIGN: This is an in vitro interventional study. PLACE AND DURATION OF STUDY: The study was carried out at the Department of Prosthodontics, School of Dentistry, Prince Sattam Bin Abdul-Aziz University, Saudi Arabia, from December 2015 to April 2016. METHODOLOGY: A marginal gap of 60 lithium disilicate crowns was evaluated by scanning electron microscopy. In total, 20 pressable lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) ceramic crowns were fabricated using the conventional lost-wax technique as a control group. The experimental all-ceramic crowns were produced based on a scan stone model and milled using two extraoral CAD/CAM systems: the Cerec group was fabricated using the Cerec CAD/CAM system, and the Trios group was fabricated using Trios CAD and milled using Wieland Zenotec CAM. One-way analysis of variance (ANOVA) and the Scheffe post hoc test were used for statistical comparison of the groups (α=0.05). RESULTS: The mean (±standard deviation) of the marginal gap of each group was as follows: the Control group was 91.15 (±15.35) µm, the Cerec group was 111.07 (±6.33) µm, and the Trios group was 60.17 (±11.09) µm. One-way ANOVA and the Scheffe post hoc test showed a statistically significant difference in the marginal gap between all groups. CONCLUSION: It can be concluded from the current study that all-ceramic crowns, fabricated using the CAD/CAM system, show a marginal accuracy that is acceptable in clinical environments. The Trios CAD group displayed the smallest marginal gap.

Zirconia in biomedical applications.

INTRODUCTION: The use of zirconia in medicine and dentistry has rapidly expanded over the past decade, driven by its advantageous physical, biological, esthetic, and corrosion properties. Zirconia orthopedic hip replacements have shown superior wear-resistance over other systems; however, risk of catastrophic fracture remains a concern. In dentistry, zirconia has been widely adopted for endosseous implants, implant abutments, and all-ceramic crowns. Because of an increasing demand for esthetically pleasing dental restorations, zirconia-based ceramic restorations have become one of the dominant restorative choices. Areas covered: This review provides an updated overview of the applications of zirconia in medicine and dentistry with a focus on dental applications. The MEDLINE electronic database (via PubMed) was searched, and relevant original and review articles from 2010 to 2016 were included. Expert commentary: Recent data suggest that zirconia performs favorably in both orthopedic and dental applications, but quality long-term clinical data remain scarce. Concerns about the effects of wear, crystalline degradation, crack propagation, and catastrophic fracture are still debated. The future of zirconia in biomedical applications will depend on the generation of these data to resolve concerns.

Replacement of Old Porcelain-Fused-to-Metal Crowns and Smile Rejuvenation Using All-Ceramic Restorations.

This case report points out the previous restorative breakdown of tooth #8. An interdisciplinary approach had to be applied to prepare the final treatment plan. All factors were taken into account when choosing the type of restorations and materials in this case. The ultimate treatment is presented with the final result. The objectives were to clinically assess patient's current chief complaint, address her aesthetic needs, apply an interdisciplinary approach, deliver treatment of utmost quality, and maintain oral health.