Acrylic Crowns Research Articles

Examination of the effect of aging process on marginal fit and fracture strength of temporary crowns prepared from different materials

AimThe aim of this study is to investigate the effect of the aging process on the marginal fit and fracture resistance of temporary crowns prepared using different materials. Materials and methodThe steel die to represent the maxillary first premolar used in this study was produced on a CNC turning machine to include an anatomical occlusal surface. A total of 160 epoxy resin dies were obtained by taking impressions with conventional impression methods on the metal die. Epoxy resin dies were randomly divided into four groups. Temporary crowns were prepared for each group from poly acrylic resin (Vita CADTemp®), bis-acryl composite resin (Protemp 4), poly methyl methacrylate (PMMA; Imident) and poly ethyl methacrylate (PEMA; Dentalon Plus) restorative materials. Half of the specimens (n = 20) in each group (n = 40) were randomly separated and the aging process was applied 5000 times in the device. Marginal gap measurements on epoxy resin dies were made using a stereomicroscope. The fracture strength test of the specimens was performed by using the Instron Universal Test Device. Jamovi 2.2.5 statistical program was used for statistical analysis. ResultsWhen compared to temporary crowns prepared from all other materials, poly acrylic resin (Vita CADTemp ®) temporary crowns observed significantly lower marginal gap values (59,05 μm) regardless of the aging process, and a significantly higher fracture resistance (478,44 N) in the presence of aging process (p < .05 for each). While the highest marginal gap value was detected in PMMA (Imident) (120.36 μm) temporary crowns with aging process, the lowest marginal gap value was observed in poly acrylic resin (Vita CADTemp®) (59.05 μm) crowns without non-aging process. The marginal fit and fracture resistance of all temporary crowns were negatively affected by the aging process. ConclusionOur findings revealed the superiority of poly acrylic resin (Vita CADTemp®) crowns to the temporary crowns prepared from all other materials in terms of the significantly lower marginal gap in the absence of aging process, and the significantly higher fracture resistance in the presence of aging process. Marginal fit and fracture resistance values for all materials were found to be within clinically acceptable limits.

Clinical and immunological evaluation of peri-implant tissues around ultra-polished and conventional smoothness zirconia abutments. A 1-year follow-up randomized clinical trial.

This is a randomized clinical trial to compare the clinical and immunological performance of ultrasmooth versus regular-smooth zirconia abutments placed subgingivally after a period of 1 year. Sixty-two bone level platform-switched implants (NobelParallel CC) were placed epicrestally in the mandibular molar or premolar region in 62 patients. After osseointegration, implants were restored with auto polymerizing acrylic resin crowns and subsequently randomly allocated to 2 groups according to the type of screw-retained zirconia crown prescribed. The control group received custom zirconia restoration with the subgingival zirconia part conventionally polished, while the test group implants were restored with ultra-polished zirconia abutments. Periodontal parameters (PD, PI, BOP) and marginal bone level changes (MBLC) were recorded for each implant 2 months after insertion (T0), 1 month after final delivery of the crown (T2) and at the 1-year follow-up (T3). Immunological mediators from GCF (IL-1α, IL-1ra and TNF-α) were inspected at 1 month after provisional (T1) and accordingly at T2 and T3. Data was analyzed statistically, and significance level was set to α = 0.05. After 1-year, there were no significant changes in PD control - 2.18 ±0.89 mm and test - 2.5 ±0.72 mm (p = 0.073). PD between T2 and T3 dropped significantly in the test group (p = 0.037), and remained stable in the control group. PI was not different in both groups at T0 (p = 0.518) and T2 (p = 0.817). At T3, the test group (0.9 ±1.01) had a significantly lower PI than the control group (1.55 ±1.23) (p = 0.035). There was no difference in BOP positive cases between groups after 1 year (control - 61.3%, test - 51.7%, p = 0.455). The amount of IL-1ra decreased significantly in the test group (41.75 ±57.58) (p = 0.001) but not in the control group (59.59 ± 70.43) (p = 0.177). MBLC for the control and test groups after 1 year were 0.68 ±0.7 mm and 0.94 ±0.65 mm (p = 0.061). PD dynamics, PI, BOP and IL-1ra revealed better outcomes around ultra-polished zirconia abutments than around conventionally polished zirconia abutments. This article is protected by copyright. All rights reserved.

Evaluation of extra-narrow diameter implants in the oral rehabilitation of young patients after oral trauma: Aprospective study.

Oral trauma is a common event in young patients and can lead to tooth loss, especially after avulsion of a tooth. The aim of this study was to evaluate the survival, esthetic outcomes, ridge preservation, and patient satisfaction of extra-narrow diameter implants (NDIs) as a temporary rehabilitation treatment for young patients who had lost permanent maxillary incisors after an avulsion. This study comprised a prospective clinical and experimental study on a case series of 13 patients (age: 10-14 years) with a history of avulsion of one or more maxillary incisors. The patients received 19 mini-drive locks implants (Intralock) with acrylic resin crowns, divided into two evaluation arms: immediate implant placement (n=10) and delayed implant placement (n=9). The cases were followed up every 3months with an initial tomography (T0) before implant placement and after 1year (T1). The clinical stability of the implant in the bone and the retention of the provisional implant crown were evaluated, and the esthetic index was calculated at each follow-up. Intragroup and intergroup differences in alveolar ridge height and thickness were compared at T0 and T1, and a questionnaire was administered to assess the patient's perception of the treatment. The implant survival rate after 1year was 78.9%. Alveolar ridge height and thickness increased in all cases at T1 (p < .05). Patients who received immediate implants had greater initial and final alveolar ridge thickness. The esthetic index progressively increased over the investigated time period (p=.001). Only one female patient presented with crown infraocclusion after 1year. The patients' esthetic perceptions of their smiles significantly improved after treatment (p=.001). Extra-NDI had good survival rates, were effective at maintaining alveolar bone, and promoted aesthetic recovery and patient satisfaction with treatment during the period studied.

Polymethylmethacrylate (PMMA) Hosts Microbiome Associated with Oral Malodor

Previous study suggested that fixed dental prostheses (crowns) increase oral malodor production. There might be a role to temporary acrylic crowns contributing to oral malodor. In the current study, we analyzed the microbiome associated with malodorous temporary dental crowns. The study population comprised nineteen patients (mean age 45.8 ± 10.9, 8 females) who visited the Tel Aviv University dental clinic. Temporary crowns were scored by an odor judge using a 6-point malodor organoleptic scale (0–5) and temporary crowns that were scored 2 and above were assigned as malodor positive. Microbial DNA was extracted from the temporary dental crowns and analyzed using next generation 16S rDNA sequencing. Taxa identified could be classified into 11 phyla, 50 genera and 119 core species. Malodor positive samples demonstrated higher abundance of the phyla Proteobacteria and Actinobacteria and the genera Tannerella, Alloprevotella, Treponema, Olsenella and Bifidobacterium. Malodorous samples showed higher bacterial diversity and significant differences in microbial population. Taken together these results suggest a difference between the microbial populations of malodorous and non-malodorous temporary dental crowns both in composition and diversity.

Dental implants and the growing patient – A successful implant insertion and implant support prosthesis in a young boy

The case report included here describes a successful implant insertion and, six years later, the presentation of a permanent prosthesis case. A 13-year-old boy experienced a traumatic dental injury during a playful altercation with his classmate in the classroom. The boy was examined by a dentist, who took an OPG and recommended extraction of the fractured right maxillary central incisor. The dentist also suggested an implant prosthesis for both the right and left incisors, as they were avulsed as a result of the same injury. Since the fractured right central incisor was severely mobile, the decision was made to extract it and plan for an implant prosthesis for both central incisors. After thoroughly studying the recommendations and cautions outlined in the aforementioned articles, approximately a week later, two implants were inserted, one on each side. These implants had a diameter of 3.3mm and a length of 10mm. Although ensuring that the initial stability was satisfactory, one of the implant fixtures came loose, and a temporary crown was placed on the other one. However, it also came out because implants were ordered from a turner who manufactured them using a manual lathe. Subsequently, implants with a 3.4mm diameter were requested and affixed in the prepared osteotomy. A heatcured acrylic crown was fabricated and placed. The patient would visit regularly every six months, inquiring about the permanent crown. However, it was always postponed. Finally, when he turned 19 years old and was in his first year of engineering, he insisted on receiving the permanent crowns. Consequently, exactly six years after the initial insertion, the permanent Porcelain-Fused-to-Metal (PFM) crown was provided to him.

Gamut of tooth coloured opportunities to reinstate the paediatric smile: A review

Early Childhood Caries has been acknowledged as a root of severe decay in children at a global level. Most frequently we see involvement of upper incisors followed by the molars. This disturbs the phonetics and most importantly the aesthetics of the child. Over the years, there have been plenteous studies concerning the restoration of primary teeth. As the technology advanced, the level of parental satisfaction with the conventional stainless-steel crowns lowered, this made the Paediatric dentists to search for an aesthetic restoration for the decayed primary tooth. Treatment of decayed anterior teeth can be done by a variety of techniques which includes Strip crowns, Polycarbonate crowns, Cheng crowns, acrylic crowns, Zirconia crowns and the most recent is Figaro crowns. The advent of such advanced techniques and materials helps in creating beautiful restorations which help children to improve their self-image as the child aesthetics is the guide to the adult aesthetics. This article gives an overview of few of the aesthetic options for rehabilitation of ECC cases.

Anti-bacterial Efficacy of Probiotics used in Provisional Polymethyl Methacrylate Crowns against Porphyromonos gingivalis – an In vitro Study

Aim: To evaluate the effect of Probiotic used in PMMA Temporary restorations on gingival inflammatory response by its action on the marginal gingival epithelial cells.&#x0D; Materials and Methods: This is an in vitro Interventional pilot study using discs of PMMA ( Group A ) and PMMA incorporated with Probiotics (Group B . The effect of probiotics incorporated PMMA on strains of Porphyromonos gingivalis grown on culture plates will be assessed using zone of inhibition test and minimum inhibitory concentration was assessed . Data was recorded, tabulated and statistically evaluated using SPSS software.&#x0D; Results: The zone of Inhibition in the Group B was (Mean = 16.30mm) is comparatively higher than that of Group A with mean value 12.92mm. Results states that among the various concentration of Probiotic Lozenges (2.5, 5, 10, 15 and 20 µg/ml) used to determine the antibacterial activity , Highest mean zone of inhibition was observed with 20 µg/ml with 16 mm, followed by 15 µg/ml with 14mm , 10 µg/ml with 9mm, 5 µg/ml with 11 mm &amp; with the lowest inhibition observed in 2.5 µg/ml with 8mm. There is significant correlation between concentration of probiotics and its antibacterial efficacy. The increase in concentration of probiotics in the PMMA discs is directly proportional to its antibacterial efficacy against P. gingivalis.&#x0D; Conclusion: Thus the study proved a significant correlation between Probiotic used in PMMA Temporary crowns and reduction in gingival Inflammation at the margins of the restoration which will be beneficial when used in crowns used in patients undergoing Orthodontic treatment or Immediate Implant Loading with acrylic crowns.

Long-Term (> 15 Years) Postrestorative Outcomes of Surgical Crown Lengthening Associated with Early Postsurgical Physiologically Oriented Crevicular Repreparation (POCR) Technique in Esthetic Areas.

Surgical crown lengthening (SCL) is indicated to reestablish the biologic width and to increase the extent of supragingival tooth structure for restorative or esthetic purposes. The present study aimed to evaluate the postrestorative conditions and positional changes of the periodontal tissues following SCL 15 years or more after surgery. Moreover, an early postsurgical physiologically oriented crevicular tooth repreparation (POCR) approach for surgical and restorative phases of the SCL procedure is described. Eighteen patients who needed SCL to gain retention necessary for prosthetic treatment, or previous prosthetic margins, were included. During surgery, the bone level was reduced based on the future prosthetic margin and predetermined biologic width; flaps were placed at the bony crest. Relined temporary acrylic resin crowns were delivered 7 to 10 days postsurgery, and definitive crowns were delivered 9 months postsurgery. Patients were examined at baseline (BSL); at 3, 6, and 9 months postoperatively; and at each yearly recall visit. The following parameters were evaluated: Plaque and Gingival Indices, free gingival margin, width and thickness of the keratinized gingiva, probing depth, attachment level, bone level, direct bone level, and biologic width. Sixteen patients completed the study. No significant change in the position of the free gingival margin and periodontal parameters were seen from 9 months to > 15 years. Biologic width at 9 months was smaller compared to BSL (-0.06 ± 0.02 mm) and gradually increased during the follow-up period, almost reaching the initial levels at the examinations > 15 years later. The described SCL technique obtained a consistent 3-mm gain of coronal tooth structure and was successful in maintaining stable periodontal tissue conditions, reestablishing the biologic width to its original vertical dimension after 15 years.

A pilot study on immediate loading dental implants

Evolution in the field of dental implantology made the replacement of missing tooth easy and quick. During initial phase of evolution, there was a need of 3 to 6 months of healing period to get teeth on implants but with advancement of technology and research, immediate replacement of missing teeth without waiting period could become a possibility.To access the efficacy of immediate loading in dental implantology using Hexacone® (IHDE DENTAL - Switzerland) dental implant. The objectives were to evaluate pain, infection, recession, loosening of abutment, fracture of implant/crown, de-cementation, peri-implant radiolucency, and marginal bone loss.Five patients (3 male and 2 female) who needed teeth replacement were included in the study. Among 5 patients, 3 patients needed single tooth replacement and the remaining 2 needed segmental replacement. Out of 7 implants 6 implants were placed in the healed bone and 1 was placed in the extraction socket. In case of healed bone, permanent prosthesis were given on 3 day. In case of extraction site, temporary acrylic crown was given on 2 day, which was replaced by permanent prosthesis after 3 month. These patients were evaluated at 7 day, 1 month, 3 months, 6 months and 12 months clinically and radiographically.Infection, prosthetic problems, peri-apical radiolucency, and implant mobility were not observed and marginal bone loss was observed during follow-up periods. On 6 months follow up, 0.5mm and 0.45mm marginal mean bone loss was observed on mesial and distal aspect respectively whereas the same was 1.24mm and 1.14 mm on 12 months follow-up respectively.The immediate loading for dental implants is a successful procedure that decreases the time for the patients to obtain a final restoration satisfying both esthetical and functional problems. Immediately loaded implants survive equally well in extraction socket. No significant difference was seen in survival when implants were placed in healed bone and extraction socket.

Infiltration by Streptococcus mutans in provisional crowns fixed by two types of cementing agents – pilot double-blind randomized clinical trial

Objective : When provisional acrylic crowns are used for a long time, they become more susceptible to marginal leakage by cariogenic bacteria. The objectives of this pilot clinical study were to compare cement based on zinc oxide-eugenol and calcium hydroxide by contamination with Streptococcus mutans, and calculate the sample size for the continuation of this study. Methods : Individuals receiving provisional crowns and following inclusion/exclusion criteria, were randomly distributed into 2 groups: zinc oxide-eugenol (n=8); calcium hydroxide (n=9). The temporary crowns were made by a blind researcher and cemented by another. Patients were also blinded by the cement used inside their crowns. After 2 months, a cement sample from the crowns’ peripheral inner face was collected, placed in a tube containing 1 mL of sterile saline, serially diluted, plated on Mitis Salivarius Bacitracin agar, and incubated for 48 hours. Colony-forming units (CFU/mL) were counted. A statistical power analysis was performed to calculate sample size (1-β=80%) and the Mann Whitney test to compare both cements (α=0.05). Results : Both cements were contaminated with S. mutans, with an average of 166.6 x 102 CFU/mL for calcium hydroxide and 435.3 x 102 CFU/mL for zinc oxide-eugenol, with no significant difference (p=0.311). The sample size calculated for this study was 36 per group. Conclusion : This pilot study suggests that there is important contamination inside provisional crowns used for two months, independent of the cement. The continuation of this study is needed, with a bigger sample size, to enable a comparison between the cements.

Influence of occlusal anatomy on acrylic resin CAD/CAM crowns fracture load and stress distribution.

Objectives: This study compared the influence of occlusal anatomy on acrylic CAD/CAM crowns fracture load and stress distribution. The null hypothesis was that there would be no difference between the provisional crowns fracture load and stress according to different occlusal anatomy.Methods: A full-crown preparation was simulated using dentin analogue (G10, Protec, São Paulo, Brazil) totaling 20 identical preparations. Next, twenty acrylic crowns were milled using different occlusal design parameter (Young or Adult) available in the software database. The crowns were cemented (Temp-bond, NE Kerr Dental, Brea, CA, USA) and fractured using a compressive load (0.5 mm/min of cross-head speed). Data were analyzed by using one-way ANOVA and Tukey tests (p&lt; 0.05). A similar geometry was modeled and exported to the analysis software to perform a static structural analysis. The maximum principal stress was calculated using the finite element method with 300 N chewing load simulation.Results: The occlusal anatomy significantly influenced the load-to-fracture (p&lt;0.05). Young design showed lower fracture load (1139±132 N) than Adult design (2007±345 N). The tensile stress distribution showed a similar pattern for both groups however the highest stress peak was calculated for Young design (76 MPa) in the occlusal surface.Conclusion: The anatomy design with higher cusp angulation and occlusal sulcus more evident can increase the stress concentration and reduce the fracture load for acrylic resin CAD/CAM crowns.

Digital immediate tooth restoration: Fabricating acrylic resin interim crowns from CBCT scans for immediate implant-supported prostheses: A case series

Statement of problemAdjusting an interim screw-retained crown made of acrylic resin for maintenance of peri-implant soft tissues after immediate implant insertion requires accuracy and time. Assessments of these factors by using digital techniques are sparse. PurposeThe purpose of this clinical study was to describe a technique to fabricate an acrylic resin interim crown by using the data acquired from a cone beam computed tomography (CBCT) scan. The 3D tomography files were converted to a standard tessellation language (STL) file format used to print or to mill the interim crown with a technique called digital immediate tooth restoration (DITR). Additionally, the chair time spent during the prosthetic phase was evaluated in comparison with a protocol in which a standard interim crown (SIC) was fabricated with an indirect-direct technique. Material and methodsPatients who needed to replace a single nonrestorable tooth were treated from February to June 2018 with an immediately placed implant and an acrylic resin screw-retained interim prosthesis that was connected to the implant immediately after placement of the implant. The participants were divided into 2 groups according to the acrylic resin interim crown fabrication technique: group DITR and group SIC. The average time to finalize the prostheses was compared between the groups. The total chair time (TCT) taken for the adaptation of the interim crown was noted and distinguished in 3 different times corresponding to each phase of adaptation of the interim restoration of the interproximal contact areas (CT1), adaption of the postextractive alveolar bone walls (CT2), and adaption of the occlusal contacts (CT3). For each time, the number of changes (N-CT1, N-CT2, N-CT3, and TN) needed to complete each prosthetic phase was also marked and observed. Generalized linear mixed models and generalized linear models were used for data analysis. All the sites were definitively restored with a screw-retained crown after 6 months of healing, and the participants were provided with standard hygiene recall appointments for the next year. ResultsA total of 82 crowns at sites distributed across the mandible and the maxilla were included in the study. Thirty-five were restored with an SIC and 47 with a DITR interim crown. None of the implants were lost during the 18-month follow-up period. The analysis of the chair times registered for the adaptation of the interim crown to the implant healing abutment and to the neighboring teeth between the 2 groups showed a reduction if a DITR interim crown was used (average CT1 of 15 ±14 seconds, CT2 of 2 ±5 seconds, CT3 of 59 ±19 seconds, and TCT of 76 ±28 seconds for group DITR and average CT1 of 135 ±27 seconds, CT2 of 185 ±30 seconds, CT3 of 73 ±16 seconds, and TCT of 394 ±61 seconds for group SIC). The number of corrections to finalize the interim crown adaptations was lower for the group DITR (0.81 ±0.74 for N-CT1, 0.19 ±0.39 for N-CT2, and 2.81 ±0.74 for N-CT3) when compared with the number of corrections needed for the group SIC (4.37 ±0.81 for N-CT1, 5.57 ±0.77 for N-CT2, and 3.86 ±0.64 for N-CT3). ConclusionsThe data from CBCT scans led to interim acrylic resin crowns that needed fewer adjustments with the immediate implant placement and interim restoration approach, reducing chair time.

BRING BACK THE SMILE AND SELF-ESTEEM IN AN 11-YEAR-OLD CHILD: A CASE REPORT

Oligodontia is the congenital absence of six or more than six teeth in either permanent or primary dentition. Because of the missing teeth in these patient’s esthetic, functional and psychological problems may arise. Oral rehabilitation is recommended for the positive development of self-esteem as well as for improved speech, masticatory function and facial esthetics. Congenital absence of incisors may jeopardize the esthetic appearance of a child, especially during years of transition into adolescence. In such situations, interim restorations can be provided before any definitive treatment. This paper deals with the full mouth oral rehabilitation of an 11-year old child using a multidisciplinary approach involving acrylic crowns, 2*4 appliance, anterior functional space maintainer and direct composite restoration.

Hybrid Polyetheretherketone (PEEK)-Acrylic Resin Prostheses and the All-on-4 Concept: A Full-Arch Implant-Supported Fixed Solution with 3 Years of Follow-Up.

Background: The aim of this three-year prospective study was to examine the outcome of a solution for full-arch rehabilitation through a fixed implant-supported hybrid prosthesis (polyetheretherketone (PEEK)-acrylic resin) used in conjunction with the All-on-4 concept. Methods: Thirty-seven patients (29 females, 8 males), with an age range of 38 to 78 years (average: 59.8 years) were rehabilitated with 49 full-arch implant-supported prostheses (12 maxillary rehabilitations, 13 mandibular rehabilitations and 12 bimaxillary rehabilitations). The primary outcome measure was prosthetic survival. Secondary outcome measures were marginal bone loss, plaque and bleeding scores, veneer adhesion issues, biological complications, mechanical complications, and the patients’ subjective evaluation. Results: There were two patients (maxillary rehabilitations) lost to follow-up, while one patient withdrew (maxillary rehabilitation). One patient with bimaxillary rehabilitation fractured the mandibular PEEK framework, rendering a 98% prosthetic survival rate. Implant survival was 100%. Average (standard deviation) marginal bone loss at 3-years was 0.40 mm (0.73 mm). Veneer adhesion was the only technical complication (n = 8 patients), resolved for all patients. Nine patients (n = 11 prostheses) experienced mechanical complications (all resolved): fracture of acrylic resin crowns (n = 3 patients), prosthetic and abutment screw loosening (n = 4 patients and 3 patients, respectively), abutment wearing (n = 1 patient). One patient experienced a biological complication (peri-implant pathology), resolved through non-surgical therapy. A 90% satisfaction rate was registered for the patients’ subjective evaluation. Conclusions: Based on the results, the three-year outcome suggests the proposed rehabilitation solution as a legitimate treatment option, providing a potential shock-absorbing alternative that could benefit the implant biological outcome.

Immediately Loaded Single Unit Dental Implants: A Clinical Study.

ABSTRACTBackground:Immediate loading of dental implants is an obvious advantage. A long treatment period that involves the wearing of a temporary prosthesis may be of great inconvenience, and is sometimes the reason for not choosing implant-supported restorations at all.Aim:In our study, an attempt was made to immediately load single tooth implants in the aesthetic zone of the dentition.Materials and Methods:Patients were selected from Government Dental College, Patna. Twenty-four single tooth implants were placed in 24 patients; 12 male and 12 female patients desiring replacement of one or more missing teeth in anterior region were selected. Surgery for the placement of the implant was carried out, and implants of the Uniti Implant System were placed. The abutment was then attached and the flap was sutured. A temporary acrylic resin crown was fabricated and cemented on the same day. Permanent prosthesis was inserted on sixth month after implant placement.Results:A clinical study was performed to evaluate the treatment outcomes of dental implants installed according to a one-stage surgical procedure followed by immediate loading with prosthesis. Of the 24 implants, 23 showed signs of successful osseointegration over a 1-year follow-up.Conclusion:Within limits of the evaluated data, it was observed that immediately loaded implants osseointegrate, so this alternative was used over conventional procedures that take 6 months for osseointegration. This has advantages, both for patient and practitioner.

Influence of a Retentive Shoulder Design to Prevent Early Failure of Three Core Build-Ups.

This study evaluated the influence of a retentive shoulder design to prevent early failure of three resin composite build-ups on molars. Ninety-six intact extracted human maxillary third molars were assigned to two groups (n=48) based on occlusal, buccal cusps only and all cusps reduction. The groups were divided into two subgroups: pin retained and non-pin retained build-ups resulting in four groups (n=24), according the cusps reduction: pin retained/partial, pin retained/complete, non-pin retained/partial, non-pin retained/complete. Occlusal reduction was 3 mm with a semi-lunar retentive shoulder of 3 mm and an axial wall height of 1.5 mm. Groups were restored using a microhybrid, flowable or titanium reinforced resin composite. Modified self-curing acrylic resin provisional crowns were fabricated, cemented with non-eugenol temporary cement and thermal cycled. An instron machine applied tension to the provisional crowns parallel to the long axis of the tooth until dislodgement. A three-way analysis of variance was conducted on the influence of the variables on the retention of the core build-up. Ninety-three build-ups were retained under tensile load, while three core build-ups without pins were dislodged. Three-way analysis of variance showed no statistically significant difference between core build-ups using a retentive shoulder and pin retained core build-ups when tested under tensile load. With the advent of adhesive systems, increased surface area and retentive shoulder design can provide a retentive core foundation to prevent early failures of core build-ups during indirect restoration fabrication which will contribute to the longevity of final restorations.

IN VITRO STUDY ON MARGINAL MICROLEAKAGE OF FOUR TEMPORARY CEMENTS IN PROVISIONAL CROWNS

Background: Prolonged retention of provisional restoration is depends upon the long term affinity between restoration and teeth structures which depend upon the use of good mechanical characteristics, low solubility, and superior adhesion quality of luting cement which also resist bacterial and molecular penetration. Hence, assessment of marginal leakage of provisional restorative materials sealed with provisional cements using the standardized procedures is essential.&#x0D; Aim: This study aimed at in vitro study of microleakage of 4 provisional cements, a cavity base compound and a zinc-phosphate luting cement in provisional acrylic resin crowns fixed on extracted human teeth.&#x0D; Material &amp; Methods: The teeth with acrylic restorations were randomly divided into 6 groups of 6 specimens each. Each group received different types of temporary cement. Acrylic resin crowns were made and fitted on intact human premolars with the 4 cements. All restorations were applied in a standardized manner. Specimen were submerged in a 2% methylene blue solution, then sectioned and observed under a stereomicroscope for the detection of marginal microleakage. Obtained data were subjected to ANNOVA and Chi –square test to know statistical significant difference between different groups. P value less than 0.05 was considered significant.&#x0D; Results and observation: Mean frequency of microleakage was statistically significant among all the groups under study with Pvalue&lt;0.017.&#x0D; Conclusion: Among all the temporary cement, Zinc-phosphate cements has the best property with reduced microleakage. Even it is used as cavity base but can be used as good temporary cement as far as microleakage is concerned.&#x0D; Key words, Microleakage, provisional cement, restorations, crowns, in vitro

Impact of 0.5 mm vs 1.5 mm subcrestal implant placement on marginal bone loss and aesthetics ‐ 3‐year results of a multicenter RCT

Background Among the legends circulating in implant dentistry there is the belief that aesthetics can be improved by placing implants in a subcrestal position.In literature, there are only a few RCT evaluating the differences between crestal and subcrestal placement and their main outcome is limited to short term bone loss.The influence of implant depth in subcrestal placement on the mid-long term esthetic and biological outcomes remains poorly investigated, especially in conical connection implant. Aim/Hypothesis To evaluate if the placement of single dental implants either 0.5 or 1.5 mm subcrestally in healed bone crests has an impact on long term esthetic and biological outcomes. Material and Methods Sixty partially edentulous patients requiring two single implant-supported crowns were recruited from six centres. According to a split-mouth design , the two sites were randomly allocated either to 0.5 mm or 1.5 mm subcrestal implant placement. During the healing period of 3 months, surgical sites in aesthetic areas were closed while a one-stage approach with transgingival healing screw was followed in non-aesthetic areas . Provisional acrylic crowns were delivered and were replaced after 2 months by definitive metal-ceramic crowns. Patients were followed to 3 years after loading. Outcome measures were- crown and implant failures, complications, aesthetics assessed using the pink esthetic score (PES), peri-implant marginal bone level changes, and patient preference, recorded by blinded assessors. Results At delivery of definitive crowns, 2 months after loading, the mean pink aesthetic score was 11.2 ± 1.9 and 11.1 ± 1.5 for the 0.5 and 1.5 mm group, respectively. At 3 years after loading, the mean pink aesthetic score was 12 ± 1.9 and 12.2 ± 1.8 for the 0.5 and 1.5 mm group, respectively. There were no statistically significant differences between the two groups at 2 months (P = 0.626), at 1 year (P = 0.920) or at 3 years (P = 0.296). Three years after loading, patients of the 0.5 mm group lost on average 0.34 ± 0.87 mm and those of the 1.5 mm group 0.19 ± 0.54 mm, the difference being statistically significant (difference = 0.15 mm; 95% CI 0.00 to 0.30; P = 0.046). The implant placement was not reflected in patient preference. There were no differences in outcomes among centres. Conclusion and clinical implications Both surgical protocols resulted in very high esthetic outcome (PES > 12) and minimal bone resorption (<0.5 mm) after 3 years. A slightly lower bone resorption was measured with 1.5 mm subcrestal placement compared to 0.5 mm, with no impact on the esthetic score. This tends to show that deeper implant placement might be beneficial only regarding bone stability, which will be confirmed after 5 years of follow-up.

Effect of temporary cement removal methods from human dentin on zirconia-dentin adhesion

This study evaluated the effect of temporary cement residue removal methods from human coronary dentin on the bond strength of adhesively-luted zirconia on dentin. Forty non-carious human molars were embedded in acrylic resin and the dentin surfaces were exposed. Temporary acrylic crowns were provisionally cemented with zinc oxide cement without eugenol and stored in distilled water (37 °C/15 days). After crown removal, the excess temporary cement was removed from dentin according to one of the following cleaning methods: (n = 8 per group): (a) air-water rinse (AW), (b) pumice paste (PP), (c) air-abrasion with aluminum oxide particles (Al2O3) (AA), (d) sodium bicarbonate spray (SB) or (e) glycine powder (CP). Forty zirconia cylinders were made and each cylinder was adhesively luted onto each tooth after adhesive resin (Scotch Bond Universal, 3 M ESPE-SBU) application using resin cement (RelyX Ultimate, 3 M ESPE) and photo-polymerized from each surface for 20 s. The bonded specimens were stored in distilled water (37 °C) for 90 days. The bonded interface was loaded under shear (1 mm/min). Data (MPa) were analyzed using 1-way ANOVA and Tukey's test (α = 0.05). Mean bond strength was significantly affected by the cleaning method (p = 0.0289). Cleaning with AA method resulted in significantly higher bond strength than with SB (p < 0.05) but similar to CP, PP and AW (p > 0.05). All cleaning methods were effective in removing temporary resin cement from dentin surfaces. Air-abrasion with aluminum oxide particles was more effective than with sodium bicarbonate spray promoting adhesion between zirconia and dentin.

Multidisciplinary approach to the treatment of a complicated crown-root fracture

Complicated crown-root fractures are uncommon type of dental trauma but usually result in significant esthetic and functional problems to those affected. This case report demonstrates sequential endodontic, restorative, orthodontic, periodontal, and prosthodontic modalities for the conservative management of a complicated crown-root fracture of the maxillary left central incisor in a young patient. After root canal treatment and core buildup, the tooth was extruded using forced orthodontic eruption for 8 weeks and retention for 7 weeks. Zinc phosphate cement acrylic crown was used to preserve esthetics and function during the forced eruption and retention period.