Intraoral wear of PICN CAD-CAM composite restorations used in severe tooth wear treatment: 5-year results of a prospective clinical study using 3D profilometry.

OBJECTIVES: To evaluate, in a prospective clinical study over 5 years with ex vivo 3D profilometry analyses, the intraoral wear of Polymer-Infiltrated Ceramic Network (PICN) CAD-CAM composite restorations used in severe tooth wear treatment with the One-Step No-Prep technique. METHODS: 192 PICN (Vita Enamic) restorations on molars and premolars were included in a prospective clinical study involving patients treated according to the One-step No-prep protocol (n = 7). All patients showed clinical signs of bruxism. Replicas of restorations on molars and premolars were realized at each evaluation time (baseline and then every year up to 5 years) and scanned to perform 3D profilometry. Baseline and recall scans were superimposed with Geomagic Control software. The mean material wear was calculated for the full occlusal area (FOA) and for the occlusal contact area (OCA), respectively. Clinical evaluation of restorations was performed at recall. RESULTS: At 5 years, the estimated mean material wear for FOA was inferior to the accuracy threshold of the profilometry measurement chain. For OCA, the estimated mean wear of the material was - 27.97 µm. This material wear was shown to be significantly influenced by time (p < 0.0001) and patient (p = 0.026), while the type of tooth (molar or premolar) had no influence. At 5 years, the survival and the success rates of restorations were 99.48% and 90.62%, respectively. SIGNIFICANCE: The PICN material exhibits a low wear process in the treatment of severe tooth wear despite the presence of clinical signs of bruxism, and it constitutes a suitable material for the One-step No-prep technique.

Risk factors of tooth wear in permanent dentition: A scoping review.

BACKGROUND: Tooth wear (TW) prevalence is high and increasing and has important consequences on the patient's quality of life. Knowledge of risk factors is crucial to promote diagnosis, prevention strategies and timely interceptive treatment. Many studies have identified TW risk factors. OBJECTIVE: This scoping review aims to map and describe suspected available factors associated with TW in permanent dentition based on quantitative measurement. METHODS: The scoping review was conducted using the PRISMA extension of the Scoping Reviews checklist. The search was conducted in October 2022 from the Medline® (PubMed® interface) and Scopus® databases. Two independent reviewers selected and characterised the studies. RESULTS: 2702 articles were identified for assessment of titles and abstracts, and 273 articles were included in the review. The results show a need to standardise TW measurement indices and the study design. The included studies highlighted various factors, classified into nine domains: sociodemographic factors, medical history, drinking habits, eating habits, oral hygiene habits, dental factors, bruxism and temporomandibular disorders, behavioural factors, and stress. Results related to chemical TW (erosion) risk factors underline the importance of eating disorders, gastroesophageal reflux and lifestyle, particularly drinking and eating behaviours, which supports developing public health information campaigns and interventions. Besides chemical, this review identifies evidence of several mechanical TW risk factors, such as toothbrushing and bruxism; the influence of this last factor needs to be further explored. CONCLUSIONS: TW management and prevention require a multidisciplinary approach. Dentists are in the first line to detect associated diseases such as reflux or eating disorders. Consequently, practitioners' information and guideline diffusion should be promoted, and a TW risk factors checklist (the ToWeR checklist) is proposed to help diagnostic approaches.

Photobiomodulation Therapy vs. Corticosteroid for the Management of Erosive/Ulcerative and Painful Oral Lichen Planus. Assessment of Success Rate during One-Year Follow-Up: A Retrospective Study.

Photobiomodulation (PBM) therapy is a promising approach for the management of inflammatory conditions and autoimmune lesions, such as oral lichen planus (OLP). The aim of this retrospective study was to assess the effectiveness of PBM in the management of painful and erosive/ulcerative OLP and to compare it with the standard of care that is the topical application of corticosteroids. 96 patients were included with erosive and painful OLP. 48 patients received PBM therapy and 48 received corticosteroids. Data was collected retrospectively on pain using the visual analogue scale; clinical aspects of lesions were assessed with the REU score, and the recurrence rate was noted. One session of PBM therapy with a helium-neon red light (635 nm) was carried out every 48 h for 6 weeks. Treatments were mainly made in contact mode, using a fiber with a diameter of 600 µm (0.6 mm). The output power of the laser beam was calibrated by a power meter. A delivered power of 0.1 W was used for 40 s in a continuous wave (CW), corresponding to a delivered energy of 4 J. The delivered energy density related to the fiber diameter was 1415 J/cm2. Each treated point was considered as 1 cm2 of diameter. PBM therapy within these parameters was carried out on each point until the totality of the lesion was covered, including the non-erosive OLP area. Furthermore, healthy mucosa within 5 mm of the lesion was also irradiated with the same conditions. This PBM treatment was performed during 6 consecutive weeks. The topical corticosteroid treatment consisted of cortisone application to cover the OLP 3 times/day for 6 weeks. Follow-up was made at 6 weeks and at 3, 6 and 12 months. After 6 weeks, both groups showed complete absence of pain, and a complete disappearance of ulcerative/erosive areas. No significant difference was found for both groups concerning the recurrence rate of erosive OLP during the follow-up period; values were 0% at 6 weeks for both groups and 79% and 87.5% for the corticosteroid and PBM group, respectively, at 12 months of follow-up. PBM is effective for managing OLP and is significantly similar to topical corticosteroids without any need for the use of medication and with no reported side effects.

Aesthetic Treatment Outcomes of Capillary Hemangioma, Venous Lake, and Venous Malformation of the Lip Using Different Surgical Procedures and Laser Wavelengths (Nd:YAG, Er,Cr:YSGG, CO2, and Diode 980 nm).

Different approaches with different clinical outcomes have been found in treating capillary hemangioma (CH), venous lake (VL), or venous malformations (VM) of the lips. This retrospective study aims to assess scar quality, recurrence rate, and patient satisfaction after different surgeries with different laser wavelengths. A total of 143 patients with CH or VM were included. Nd:YAG laser was used for 47 patients, diode 980 nm laser was used for 32 patients (treatments by transmucosal photo-thermo-coagulation), Er,Cr:YSSG laser was used for 12 patients (treatments by excision), and CO2 laser was used for 52 patients (treatments by photo-vaporization). The Manchester scar scale was used by practitioners to assess the scar quality. The recurrence rate and patients' satisfaction were noted at different follow-ups during 12 months. Our retrospective study showed that laser-assisted aesthetic treatment of vascular lesions (CH, VL, and VM) of the lips can be considered effective regardless of the wavelength used (Er,Cr:YSGG, CO2, Nd:YAG, and diode 980 nm) or the treatment procedure (transmucosal photo-thermo-coagulation, photo-vaporization, and surgical excision). There was no significant difference in patient and practitioner satisfaction with aesthetic outcome at 6 months follow-up. Furthermore, the treatments of lip vascular lesions performed using Er,Cr:YSGG and CO2 lasers did not show any recurrence during the 12 months of follow-up, while recurrence rates of 11% ± 1.4% and 8% ± 0.9% were seen in the diode and Nd:YAG groups, respectively.

Decontamination of Dental Implant Surfaces by the Er:YAG Laser Beam: A Comparative in Vitro Study of Various Protocols.

Oral rehabilitation with dental implants has revolutionized the field of dentistry and has been proven to be an effective procedure. However, the incidence of peri-implantitis has become an emerging concern. The efficacy of the decontamination of the implant surface, by means of lasers, is still controversial. Previous studies have revealed a reduction in osteoblast adhesion to carbon-contaminated implant surfaces. This in-vitro study aimed to evaluate the decontamination of failed implants by assessing the carbon proportion, after irradiation by low-energy erbium yttrium-aluminum-garnet laser (Er:YAG) (Fotona; 2940 nm, Ljubljana, Slovenia) for a single and for multiple passages, until getting a surface, free of organic matters; to find the appropriate procedure for dental-implant surface-decontamination. Ninety implants were used. Thirty sterile implants were kept as a negative control. Thirty failed implants were irradiated by the Er:YAG laser, for a single passage, and the other thirty, for multiple passages. The parameters used in our experiments were an irradiation energy of 50 mJ, frequency of 30 Hz, and an energy density of 3.76 J/cm². A sapphire tip, with a length of 8 mm, was used with concomitant water spray irrigation, under air 6 and water spray 4. Super short pulse mode (SSP) was of 50 µs; irradiation speed being 2 mm/s. We used energy-dispersive X-ray spectroscopy (EDX) to evaluate the carbon proportion on the surfaces of the sterile implants, the contaminated, and the lased implants, with one (LX1) and with three passages (LX3). Statistical analysis was performed by ANOVA. Results showed mean difference between the three groups (contaminated, LX1, and LX3) with p < 0.0001, as between LX1 and Group A (p < 0.0001), while the difference between LX3 and the control group was not statistically significant. The decontamination of the implant surfaces with a low-energy Er:YAG laser with three passages, appeared to be an encouraging approach.

No post-no core approach to restore severely damaged posterior teeth: An up to 10-year retrospective study of documented endocrown cases.

OBJECTIVES: The objectives of the present study were to (1) retrospectively evaluate documented cases of ceramic and composite endocrowns performed using immediate dentin sealing (IDS); (2) correlate failures with clinical parameters such as tooth preparation characteristics and occlusal parameters. METHODS: 99 documented cases of endocrowns were evaluated after a mean observation period of 44.7±34.6months. A classification of restorations was established in function of the level of damage of residual tooth tissues after preparation, from 1 to 3. Evaluation was performed according to FDI criteria and endodontic outcomes were analyzed. Occlusal risk factors were examined and fractographic analysis was performed in case of fracture. RESULTS: 48.4% of patients were shown to present occlusal risk factors. 75.8% of restorations were Class 3 endocrowns. 56.6% were performed on molars, 41.4% on premolars and 2.0% on canines. 84.8% were performed in lithium-disilicate glass-ceramic and 12.1% in Polymer-Infiltrated Ceramic Network (PICN) material. The survival and success rates of endocrowns were 99.0% and 89.9% respectively, while the 10-year Kaplan-Meier estimated survival and success rates were 98.8% and 54.9% respectively. Ten failures were detected: periodontal disease (n=3), endocrown debonding (n=2), minor chipping (n=2), caries recurrence (n=2) and major fractures (n=1). Due to the reduced amount of failures, no statistical correlation could be established with clinical parameters. CONCLUSIONS: Endocrowns were shown to constitute a reliable approach to restore severely damaged molars and premolars, even in the presence of extensive coronal tissue loss or occlusal risk factors, such as bruxism or unfavorable occlusal relationships. CLINICAL SIGNIFICANCE: Practitioners should consider the endocrown instead of the post and core approach to restore severely damaged non-vital posterior teeth. This minimally invasive solution reduces the risk of catastrophic failures and is easily performed. The use of IDS procedure and lithium-disilicate glass-ceramic as prosthesis material gave very good results.

Evaluation of Different Laser-Supported Surgical Protocols for the Treatment of Oral Leukoplakia: A Long-Term Follow-Up.

PURPOSE: The aim of this study was to evaluate the long-term success rate of oral leukoplakia treatments by using different laser-supported surgical protocols. PATIENTS AND METHODS: Overall, 2347 diagnosed homogeneous oral leukoplakias were treated with CO2 laser and were included in this study. Different surgical protocols (P) were used: P1 (SV = superficial scanning) was a complete superficial vaporization of the leukoplakia by a scanning mode in two passages respecting an overlapping. Only the visible white area was treated in one surgical session independently of the lesion size. P2 (CR1x1) was a complete excision of the lesions until a tissular depth of 1 mm and 1 mm of surrounding healthy-like tissue were attained. The visible white area was treated in one surgical session independently of the lesion size. P3 (CR1x3) was a complete excision of the lesions until a minimum tissue depth of 1 mm and 3 mm of surrounding healthy-like tissue were obtained. The visible white area was treated in one surgical session independently of the lesion size. P4 (PR1x3) was similar to the third one, but for patient comfort, the large lesions of leukoplakias (lesion size higher than 20 mm), the complete surgical excision of the leukoplakia was performed in multiple sessions that were spaced by 1 month (partial surgical removal of 10 mm per session). All patients were recalled at 2 and 8 weeks after surgery, and then every 2 months during the first year, every 4 months during the second year, and once a year for the follow-up period of 6 years. A biopsy was done once a year during the follow-up period in the surgical site when needed. The control consisted of checking the nature and the aspect of the healed mucosa to exclude an eventual recurrence of leukoplakia. RESULTS: The percentage of permanent success after 6 years of follow-up was 5.7%, 69.7%, 97.8%, and 71.9%, respectively, for the first surgical protocol (SV), the second (CR 1 × 1), the third (CR 1 × 3), and the fourth (PR 1 × 3). The appearance of malignant transformation after laser treatment (during the follow-up period of 6 years) was 20%, 1%, and 0.2%, respectively, for the groups treated by the following protocols: 1 (SV), 2 (CR 1 × 1), and 4 (PR 1 × 3). Only in the third group CR1x3, no dysplasia or malignant transformation was noted. On the contrary, the appearance of malignant transformation in failed treated cases was 21.21% for the protocol 1 (SV), 3% for the protocol 2 (CR 1 × 1), and 0.6% for the protocol 4 (PR 1 × 3). CONCLUSIONS: The results of this long-term follow-up of treated patients with oral homogeneous leukoplakias pointed out that the surgical laser protocol respecting the complete excision of leukoplakias, in one session, by the removal of a minimum of 1 mm in lesion depth and 3 mm of surrounding healthy-like tissues (CR 1 × 3) offers significantly the highest success rate.

Biocompatibility of polymer-infiltrated-ceramic-network (PICN) materials with Human Gingival Keratinocytes (HGKs).

OBJECTIVE: Biocompatibility of polymer-infiltrated-ceramic-network (PICN) materials, a new class of CAD-CAM composites, is poorly explored in the literature, in particular, no data are available regarding Human Gingival Keratinocytes (HGK). The first objective of this study was to evaluate the in vitro biocompatibility of PICNs with HGKs in comparison with other materials typically used for implant prostheses. The second objective was to correlate results with PICN monomer release and indirect cytotoxicity. METHODS: HGK attachment, proliferation and spreading on PICN, grade V titanium (Ti), yttrium zirconia (Zi), lithium disilicate glass-ceramic (eM) and polytetrafluoroethylene (negative control) discs were evaluated using a specific insert-based culture system. For PICN and eM samples, monomer release in the culture medium was quantified by high performance liquid chromatography and indirect cytotoxicity tests were performed. RESULTS: Ti and Zi exhibited the best results regarding HGK viability, number and coverage. eM showed inferior results while PICN showed statistically similar results to eM but also to Ti regarding cell number and to Ti and Zi regarding cell viability. No monomer release from PICN discs was found, nor indirect cytotoxicity, as for eM. SIGNIFICANCE: The results confirmed the excellent behavior of Ti and Zi with gingival cells. Even if polymer based, PICN materials exhibited intermediate results between Ti-Zi and eM. These promising results could notably be explained by PICN high temperature-high pressure (HT-HP) innovative polymerization mode, as confirmed by the absence of monomer release and indirect cytotoxicity.

Biocompatibility of polymer-infiltrated-ceramic-network (PICN) materials with Human Gingival Fibroblasts (HGFs).

OBJECTIVES: Polymer-infiltrated-ceramic-network (PICN) materials constitute an innovative class of CAD-CAM materials offering promising perspectives in prosthodontics, but no data are available in the literature regarding their biological properties. The objective of the present study was to evaluate the in vitro biocompatibility of PICNs with human gingival fibroblasts (HGFs) in comparison with materials typically used for implant prostheses and abutments. METHODS: HGF attachment, proliferation and spreading on discs made of PICN, grade V titanium (Ti), yttrium zirconia (Zi), lithium disilicate glass-ceramic (eM) and polytetrafluoroethylene (negative control), were evaluated using a specific insert-based culture system (IBS-R). Sample surface properties were characterized by XPS, contact angle measurement, profilometry and SEM. RESULTS: Ti and Zi gave the best results regarding HGF viability, morphology, number and coverage increase with time in comparison with the negative control, while PICN and eM gave intermediate results, cell spreading being comparable for PICN, Ti, Zi and eM. Despite the presence of polymers and their related hydrophobicity, PICN exhibited comparable results to glass-ceramic materials, which could be explained by the mode of polymerization of the monomers. SIGNIFICANCE: The results of the present study confirm that the currently employed materials, i.e. Ti and Zi, can be considered to be the gold standard of materials in terms of HGF behavior, while PICN gave intermediate results comparable to eM. The impact of the present in vitro results needs to be further investigated clinically, particularly in the view of the utilization of PICNs for prostheses on bone-level implants.

A new method using insert-based systems (IBS) to improve cell behavior study on flexible and rigid biomaterials.

In vitro studies about biomaterials biological properties are essential screening tests. Yet cell cultures encounter difficulties related to cell retention on material surface or to the observation of both faces of permeable materials. The objective of the present study was to develop a reliable in vitro method to study cell behavior on rigid and flexible/permeable biomaterials elaborating two specific insert-based systems (IBS-R and IBS-F respectively). IBS-R was designed as a specific cylindrical polytetrafluoroethylene (PTFE) system to evaluate attachment, proliferation and morphology of human gingival fibroblasts (HGFs) on grade V titanium and lithium disilicate glass-ceramic discs characteristics of dental prostheses. The number of cells, their covering on discs and their morphology were determined from MTS assays and microscopic fluorescent images after 24, 48 and 72 h. IBS-F was developed as a two components system to study HGFs behavior on guided bone regeneration polyester membranes. The viability and the membrane barrier effect were evaluated by metabolic MTS assays and by scanning electron microscopy. IBS-R and IBS-F were shown to promote (1) easy and rapid handling; (2) cell retention on biomaterial surface; (3) accurate evaluation of the cellular proliferation, spreading and viability; (4) use of non-toxic material. Moreover IBS-F allowed the study of the cell migration through degradable membranes, with an access to both faces of the biomaterial and to the bottom of culture wells for medium changing.

Evaluation of a New Method for the Treatment of Invasive, Diffuse, and Unexcisable Lymphangiomas of the Oral Cavity with Defocus CO2 Laser Beam: A 20-Year Follow-Up.

OBJECTIVE: The aim of our study is to evaluate the efficiency of a new therapeutic method using CO2 laser to avoid mutilation or total excision for the treatment of invasive, large and unexcisable oral lymphangiomas. BACKGROUND DATA: Cystic lymphatic malformations, or lymphangiomas, are mature lymphatic malformations, consisting of abnormal lymphatic vessels. Surgical excision is considered by most surgeons to be the treatment of choice for lymphangioma. Laser beam has been used to treat superficial or small lymphatic malformations by excision or by photocoagulation, and to excise or photocoagulate small lymphangiomas. PATIENTS AND METHODS: Seventeen patients with diffuse and unexcisable lymphangiomas were treated using a CO2 laser with specific settings: beam was 2 W in noncontact and defocus mode, power density was 0.63 W/cm2 for irradiation time in the range of 3-5 min, and the estimated energy density range was 114.65-191.02 J/cm2. The beam diameter at the tissular impact point was ±2 cm. The laser beam was defocused to provoke a deep heat generation that would dry up the lymphatic tissues and induce deep tissue necrosis that heals by fibrous tissue process. RESULTS: The results were satisfactory and stable, with localized recurrence in three cases. The recurrent areas were re-treated using the same technique successfully and with no further recurrence. CONCLUSIONS: The use of CO2 laser under the suggested irradiation conditions can be considered a useful technique for the treatment of invasive lymphangiomas.

Aging of monolithic zirconia dental prostheses: Protocol for a 5-year prospective clinical study using ex vivo analyses.

BACKGROUND: Recent introduction of computer-aided design/computer-aided manufacturing (CAD/CAM) monolithic zirconia dental prostheses raises the issue of material low thermal degradation (LTD), a well-known problem with zirconia hip prostheses. This phenomenon could be accentuated by masticatory mechanical stress. Until now zirconia LTD process has only been studied in vitro. This work introduces an original protocol to evaluate LTD process of monolithic zirconia prostheses in the oral environment and to study their general clinical behavior, notably in terms of wear. METHODS/DESIGN: 101 posterior monolithic zirconia tooth elements (molars and premolars) are included in a 5-year prospective clinical trial. On each element, several areas between 1 and 2 mm2 (6 on molars, 4 on premolars) are determined on restoration surface: areas submitted or non-submitted to mastication mechanical stress, glazed or non-glazed. Before prosthesis placement, ex vivo analyses regarding LTD and wear are performed using Raman spectroscopy, SEM imagery and 3D laser profilometry. After placement, restorations are clinically evaluated following criteria of the World Dental Federation (FDI), complemented by the analysis of fracture clinical risk factors. Two independent examiners perform the evaluations. Clinical evaluation and ex vivo analyses are carried out after 6 months and then each year for up to 5 years. DISCUSSION: For clinicians and patients, the results of this trial will justify the use of monolithic zirconia restorations in dental practice. For researchers, the originality of a clinical study including ex vivo analyses of material aging will provide important data regarding zirconia properties.Trial registration: ClinicalTrials.gov Identifier: NCT02150226.

Clinical risk factors related to failures with zirconia-based restorations: an up to 9-year retrospective study.

OBJECTIVES: The first objective of this study was to retrospectively evaluate zirconia-based restorations (ZBR). The second was to correlate failures with clinical parameters and to identify and to analyse chipping failures using fractographic analysis. METHODS: 147 ZBR (tooth- and implant-supported crowns and fixed partial dentures (FPDs)) were evaluated after a mean observation period of 41.5 ± 31.8 months. Accessorily, zirconia implant abutments (n=46) were also observed. The technical (USPHS criteria) and the biological outcomes of the ZBR were evaluated. Occlusal risk factors were examined: occlusal relationships, parafunctional habits, and the presence of occlusal nightguard. SEM fractographic analysis was performed using the intra-oral replica technique. RESULTS: The survival rate of crowns and FPDs was 93.2%, the success rate was 81.63% and the 9-year Kaplan-Meier estimated success rate was 52.66%. The chipping rate was 15% and the framework fracture rate was 2.7%. Most fractographic analyses revealed that veneer fractures originated from occlusal surface roughness. Several parameters were shown to significantly influence veneer fracture: the absence of occlusal nightguard (p=0.0048), the presence of a ceramic restoration as an antagonist (p=0.013), the presence of parafunctional activity (p=0.018), and the presence of implants as support (p=0.026). The implant abutments success rate was 100%. CONCLUSIONS: The results of the present study confirm that chipping is the first cause of ZBR failure. They also underline the importance of clinical parameters in regards to the explanation of this complex problem. This issue should be considered in future prospective clinical studies. CLINICAL SIGNIFICANCE: Practitioners can reduce chipping failures by taking into account several risk parameters, such as the presence of a ceramic restoration as an antagonist, the presence of parafunctional activity and the presence of implants as support. The use of an occlusal nightguard can also decrease failure rate.

Influence of zirconia framework thickness on residual stress profile in veneering ceramic: measurement by hole-drilling.

OBJECTIVES: Framework design is reported to influence chipping in zirconia-based restorations, which is an important cause of failure of such restorations. Residual stress profile in the veneering ceramic after the manufacturing process is an important predictive factor of the mechanical behavior of the material. The objective of this study is to investigate the influence of framework thickness on the stress profile measured in zirconia-based structures. METHODS: The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 1.5 mm thick veneering ceramic layer. Six different framework thicknesses from 0.5 mm to 3 mm were studied. Two different cooling procedures were also investigated. RESULTS: Compressive stresses were observed in the surface, and tensile stresses in the depth of most of the samples. The slow cooling procedure was found to promote the development of interior tensile stresses, except for the sample with a 3mm thick framework. With the tempering procedure, samples with a 1.5 mm thick framework exhibited the most favorable stress profile, while thicker and thinner frameworks exhibited respectively in surface or interior tensile stresses. SIGNIFICANCE: The measurements performed highlight the importance of framework thickness, which determine the nature of stresses and can explain clinical failures encountered, especially with thin frameworks. The adequate ratio between veneering ceramic and zirconia is hard to define, restricting the range of indications of zirconia-based restorations until a better understanding of such a delicate veneering process is achieved.

Influence of veneer thickness on residual stress profile in veneering ceramic: measurement by hole-drilling.

OBJECTIVES: The veneering process of frameworks induces residual stresses and can initiate cracks when combined with functional stresses. The stress distribution within the veneering ceramic as a function of depth is a key factor influencing failure by chipping. This is a well-known problem with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objective of this study is to investigate the influence of veneer thickness on the stress profile in zirconia- and metal-based structures. METHODS: The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. The stress profile was measured in bilayered disc samples of 20 mm diameter, with a 1 mm thick zirconia or metal framework. Different veneering ceramic thicknesses were performed: 1 mm, 1.5 mm, 2 mm, 2.5 mm and 3 mm. RESULTS: All samples exhibited the same type of stress vs. depth profile, starting with compressive at the ceramic surface, decreasing with depth up to 0.5-1.0 mm from the surface, and then becoming compressive again near the framework, except for the 1.5 mm-veneered zirconia samples which exhibited interior tensile stresses. Stresses in the surface of metal samples were not influenced by veneer thickness. Variation of interior stresses at 1.2 mm from the surface in function of veneer thickness was inverted for metal and zirconia samples. SIGNIFICANCE: Veneer thickness influences in an opposite way the residual stress profile in metal- and in zirconia-based structures. A three-step approach and the hypothesis of the crystalline transformation are discussed to explain the less favorable residual stress development in zirconia samples.

Influence of cooling rate on residual stress profile in veneering ceramic: measurement by hole-drilling.

OBJECTIVES: The manufacture of dental crowns and bridges generates residual stresses within the veneering ceramic and framework during the cooling process. Residual stress is an important factor that control the mechanical behavior of restorations. Knowing the stress distribution within the veneering ceramic as a function of depth can help the understanding of failures, particularly chipping, a well-known problem with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objective of this study is to investigate the cooling rate dependence of the stress profile in veneering ceramic layered on metal and zirconia frameworks. METHODS: The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. The stress profile was measured in bilayered disc samples 20 mm in diameter, with a 0.7 mm thick metal or Yttria-tetragonal-zirconia-polycrystal framework and a 1.5mm thick veneering ceramic. Three different cooling procedures were investigated. RESULTS: The magnitude of the stresses in the surface of the veneering ceramic was found to increase with cooling rate, while the interior stresses decreased. At the surface, compressive stresses were observed in all samples. In the interior, compressive stresses were observed in metal samples and tensile in zirconia samples. SIGNIFICANCE: Cooling rate influences the magnitude of residual stresses. These can significantly influence the mechanical behavior of metal-and zirconia-based bilayered systems. The framework material influenced the nature of the interior stresses, with zirconia samples showing a less favorable stress profile than metal.

Fit of single tooth zirconia copings: comparison between various manufacturing processes.

STATEMENT OF PROBLEM: Various CAD/CAM processes are commercially available to manufacture zirconia copings. Comparative data on their performance in terms of fit are needed. PURPOSE: The purpose of this in vitro study was to compare the internal and marginal fit of single tooth zirconia copings manufactured with a CAD/CAM process (Procera; Nobel Biocare) and a mechanized manufacturing process (Ceramill; Amann Girrbach). MATERIAL AND METHODS: Abutments (n=20) prepared in vivo for ceramic crowns served as a template for manufacturing both Procera and Ceramill zirconia copings. Copings were manufactured and cemented (Clearfil Esthetic Cement; Kuraray) on epoxy replicas of stone cast abutments. Specimens were sectioned. Nine measurements were performed for each coping. Over- and under-extended margins were evaluated. Comparisons between the 2 processes were performed with a generalized linear mixed model (α=.05). RESULTS: Internal gap values between Procera and Ceramill groups were not significantly different (P=.13). The mean marginal gap (SD) for Procera copings (51(50) µm) was significantly smaller than for Ceramill (81(66) µm) (P<.005). The percentages of over- and under-extended margins were 43% and 57% for Procera respectively, and 71% and 29% for Ceramill. CONCLUSIONS: Within the limitations of this in vitro study, the marginal fit of Procera copings was significantly better than that of Ceramill copings. Furthermore, Procera copings showed a smaller percentage of over-extended margins than did Ceramill copings.

Residual stress measurement in veneering ceramic by hole-drilling.

OBJECTIVES: Mismatch in thermal expansion properties between veneering ceramic and metallic or high-strength ceramic cores can induce residual stresses and initiate cracks when combined with functional stresses. Knowledge of the stress distribution within the veneering ceramic is a key factor for understanding and predicting chipping failures, which are well-known problems with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objectives of this study are to develop a method for measuring the stress profile in veneering ceramics and to compare ceramic-fused-to-metal compounds to veneered Yttria-tetragonal-zirconia-polycrystal ceramic. METHODS: The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. Because of the high sensitivity needed in comparison with industrial applications, a high sensitivity electrical measurement chain was developed. RESULTS: All samples exhibited the same type of stress vs. depth profile, starting with compressive at the ceramic surface, decreasing with depth and becoming tensile at 0.5-1.0mm from the surface, and then becoming slightly compressive again. The zirconia samples exhibited a stress depth profile of larger magnitude. SIGNIFICANCE: The hole drilling method was shown be a practical tool for measuring residual stresses in veneering ceramics.

[Posterior ceramic bonded partial restorations]. / Les restaurations partielles collées postérieures en céramique.

Posterior ceramic bonded partial restorations are conservative and esthetic approaches for compromised teeth. Overlays constitute a less invasive alternative for tooth tissues than crown preparations. With inlays and onlays they are also indicated in case of full arch or quadrant rehabilitations including several teeth. This article screens indications and realization of this type of restorations.

[Ceramic posts]. / Les piliers en céramique.

As a result of ceramics and all-ceram technologies development esthetic inlay core and abutments flooded the market. Their tooth-colored appearance enhances restoration biomimetism principally on the marginal gingiva area. This article reviews indications and types of cores designed for natural teeth and implants.