Self-assessment skills of undergraduate dental students in the preclinical course of complete removable prosthodontics at Tehran University of Medical Sciences.

INTRODUCTION: This study evaluated the self-assessment skills of third-year dental students regarding their performance in complete removable prosthodontics (CRP) preclinical course. METHODS AND MATERIALS: This cross-sectional study was conducted on all third-year dental students attending the International Dental College of Tehran University of Medical Sciences. The students were requested to self-assess their performance in primary impression making, custom tray fabrication, border moulding, final impression making, master cast fabrication, record-base fabrication and tooth arrangement in CRP preclinical course. The performance of dental students in each step was scored by themselves and their mentors. Data were analysed by the Mann-Whitney U, Pearson's correlation and t-tests (α = 0.05). RESULTS: Totally 25 male (55.6%) and 20 female (44.4%) dental students were evaluated. Significant differences were noted between male and female dental students in self-assessment scores regarding adequate extension of the custom tray (p = .027), the correct position of tray handle (p = .020), visibility of vestibular width and depth on the cast (p = .011), the coincidence of upper and lower midlines (p = .005) and correct orientation of maxillary and mandibular planes in the articulator (p = .036). The mean self-assessment score of female students was significantly higher than that of male students (p = .01). The scores given by the mentors were not significantly different for male and female students (p = .975). The difference between the self-assessment score of students and the mentor score was not significant (p = .067) either in males or in females (p > .05). CONCLUSION: Undergraduate dental students favourably self-assessed their performance in all steps of the preclinical course of CRP, comparable with their mentor assessment.

Fracture strength and three-dimensional marginal evaluation of biocompatible high-performance polymer versus pressed lithium disilicate crowns.

STATEMENT OF PROBLEM: Despite the acceptable physical properties of biocompatible high-performance polymer (BioHPP), little is known about the marginal accuracy and fracture strength of restorations made from this material. PURPOSE: This in vitro study assessed the marginal and internal adaptation and fracture strength of teeth restored with lithium disilicate (LD) ceramics and BioHPP monolithic crowns. MATERIAL AND METHODS: Twenty-four extracted premolars were prepared for complete coverage crowns and divided into 2 groups to receive pressed IPS e.max LD, or computer-aided design and computer-aided manufacturing (CAD-CAM) BioHPP monolithic crowns. After adhesive cementation, the marginal and internal adaptations of the restorations were evaluated by microcomputed tomography at 18 points for each crown. Specimens were subjected to 6000 thermal cycles at 5 °C and 55 °C and 200 000 load cycles of 100 N at a frequency of 1.2 Hz. The fracture strength of the restorations was then measured in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed via an independent-sample t-test (α=.05). RESULTS: The mean ±standard deviation of marginal gap was 138.8 ±43.6 µm for LD and 242.1 ±70.7 µm for BioHPP groups (P=.001). The mean ±standard deviation value of absolute marginal discrepancy was 193.8 ±60.8 µm for LD and 263.5 ±97.6 µm for BioHPP groups (P=.06). The internal occlusal and axial gap measurements were 547.5 ±253.1 µm and 197.3 ±54.8 µm for LD (P=.03) and 360 ±62.9 µm and 152.8 ±44.8 µm for BioHPP (P=.04). The mean ±standard deviation of internal space volume was 15.3 ±11.8 µm³ for LD and 24.1 ±10.7 µm³ for BioHPP (P=.08). The mean ±standard deviation of fracture strength was 2509.8 ±680 N for BioHPP and 1090.4 ±454.2 MPa for LD groups (P<.05). CONCLUSIONS: The marginal adaptation of pressed lithium disilicate crowns was better, while BioHPP crowns displayed greater fracture strength. Marginal gap width was not correlated with fracture strength in either group.

Bacterial Leakage at Implant-Abutment Interface With Different Intermediate Materials.

A gap exists at the implant-abutment interface in two-piece implants and can serve as a reservoir of bacteria and compromise the health of peri-implant tissue. This study aimed to compare the effect of different intermediate materials on bacterial leakage at the implant-abutment interface. A total of 75 implants were divided into 5 groups (n = 15) based on the material applied at the implant-abutment connection: (1) Atridox, (2) chlorhexidine, (3) Gapseal silicone, (4) saliva, and (5) no material. All the implants were inoculated with 0.1 µL of Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) suspension, and then the respective material was applied. The abutments were connected to the implants, and appropriate torque was applied as recommended by the manufacturer (Implantium, Dentium, Korea, Seoul). Bacterial leakage was determined by evaluating the turbidity of the broth. Bacterial contamination was found in all samples at different times; in groups 1, 2 and 3, contamination was noted after 7, 5, and 6 days, respectively, on average. Contamination occurred averagely after 4 days in groups 4 and 5. The present study showed that Atridox applied at the implant-abutment interface significantly delayed bacterial leakage.

Mandibular Overdentures Supported by Two vs Four Endosteal Implants: A Retrospective Cohort Study.

AIM: Documentation of marginal bone resorption caused by implant-supported mandibular overdentures is scarce. This study sought to evaluate marginal bone resorption, survival rate, patient satisfaction, peri-implant soft tissue status, and prosthetic aftercare of mandibular overdentures supported by two vs four implants. MATERIALS AND METHODS: This retrospective cohort study evaluated 92 edentulous patients presented to the Implant Center of Tehran University of Medical Sciences; out of which, 46 patients received overdentures supported by two Implantium implants (group A), while the remaining 46 received overdentures supported by four Implantium implants (group B). Standard radiographic indices were assessed following the delivery of overdenture and after 2 years of functional loading. Clinical evaluation was performed after 2 years of function. Data were analyzed using the t test (for continuous variables) and the Mann-Whitney test (for ordinal variables). RESULTS: In group A, two implants were lost in one patient. The groups were not significantly different in terms of clinical or radiographic parameters (p > 0.05). Patient satisfaction and prosthetic aftercare were not significantly different in groups A and B (p > 0.05). CONCLUSIONS: During the 2-year evaluation period, the clinical and radiographic parameters were the same in patients who received overdentures supported by two or four implants. CLINICAL SIGNIFICANCE: Successful results may be obtained by the use of mandibular overdentures supported by two or four implants.

Fracture Strength of Posterior Crowns made of Adoro and Gradia Fiber-reinforced Composites.

Aim: The aim of this study was to assess the fracture strength of posterior crowns made of Adoro and Gradia fiber-reinforced composites (FRCs). Materials and methods: In this in vitro, experimental study, extracted sound 37 maxillary first and second premolars were selected. A celluloid index was taken from teeth and the teeth received crown preparation. Impressions were made and poured. Composite crowns were fabricated of Adoro and Gradia composite resins. After curing, the teeth were immersed in distilled water for 24 hours and thermal cycled for 6,000 cycles between 5 and 55°C. Load was applied at a crosshead speed of 1 mm/minute and the fracture strength was measured. Specimens were inspected under a stereomicroscope to determine the mode of failure. Results: The fracture strength was 1,631.77 N for Gradia and 1,569.84 N for Adoro. The difference between the fracture strength of the two groups was not significant (p > 0.05). The mode of failure was cohesive in composite in 7 specimens and adhesive between composite and fiber in 12 specimens in the Gradia group. In the Adoro group, the mode of failure was cohesive within composite in 11 specimens and adhesive between composite and fiber in 7 specimens. Complete tear of fiber did not occur in any group. Conclusion: The fracture strength of Gradia and Adoro composites is not significantly different. Clinical significance: Cohesive fracture within the fiber did not occur in any case in our study and the mode of failure was adhesive at the fiber-composite interface or cohesive within the composite in most specimens. Keywords: Composite resin, Crown, Gradia, Laboratory.

Fabrication of a mandibular implant-retained overdenture using an existing subperiosteal implant: A clinical report.

A 64-year-old edentulous woman with a mandibular fracture received a subperiosteal implant for fracture fixation and dental rehabilitation. However, the ball abutments were submerged by the soft tissue because they were too short. Therefore, we designed a connector to lengthen the attachment and achieve adequate stability and retention for the overdenture.

Comparative study of the effect of different exposure parameters of 635nm diode laser and toluidine blue O in eliminating Aggregatibacter actinomycetemcomitans biofilm from titanium implant surfaces.

BACKGROUND: The aim of this study was to investigate the effects of antimicrobial photodynamic therapy (PDT) using 635 nm diode laser irradiation with an energy density of 6 to 30 J/cm2 and toluidine blue O (TBO) as a photosensitizer on the viability of Aggregatibacter actinomycetemcomitans attached to the surface of titanium implants. MATERIALS AND METHODS: Titanium implants contaminated with A. actinomycetemcomitans were treated with TBO alone or in combination with different exposure parameters (light doses of 6 - 30 J/cm2 at 635 nm) and 0.2 % chlorhexidine (CHX). After treatment, colony forming units (CFUs)/ml were determined to assess PDT efficacy. The structure of the biofilm of A. actinomycetemcomitans was analyzed by field emission scanning electron microscopy (FESEM). RESULTS: Under optimal conditions, the colony count was reduced by ∼90 %. Treatment with CHX was somewhat more effective (colony formation was reduced by ∼95 %), but this agent has adverse effects that can be avoided with PDT. CONCLUSION: This study confirms the efficacy of PDT against A. actinomycetemcomitans depending on the light dose. Treatment with TBO + 635 nm diode laser has an effect that may be equivalent to that of CHX, but perhaps with fewer adverse effects.

Simultaneous Dual-Wavelength Laser Irradiation against Implant-Adherent Biofilms of Staphylococcus aureus, Escherichia coli, and Candida albicans for Improved Antimicrobial Photodynamic Therapy.

The efficiency of antimicrobial photodynamic therapy (PDT) might be improved by using multiple wavelengths. This study investigates the sensitivity of implant-adherent biofilms of Staphylococcus aureus, Escherichia coli, and Candida albicans to indocyanine green (ICG)-808 nm diode laser, toluidine blue O (TBO)-635 nm diode laser, and hydrogen peroxide (HP)-980 nm diode laser and their combination when irradiated with dual-wavelength laser irradiation (simultaneously 980-635 nm or 980-808 nm). After an incubation period of 72 h, the infected implants were randomly divided into seven different treatment modalities: Control, HP, HP-PDT, TBO-PDT, HP-TBO-PDT, ICG-PDT, and HP-ICG-PDT. After the treatments, the colony-forming units (CFUs)/mL and reactive oxygen species (ROS) generation were determined. All evaluated disinfection methods were significantly effective against the three investigated bacteria compared to the control. The combined treatment of HP-ICG-PDT or HP-TBO-PDT had the greatest antibacterial effect compared to each treatment alone. There were statistical differences between HP-ICG-PDT and ICG-PDT or HP-TBO-PDT and TBO-PDT for all three bacteria studied. PDT with simultaneous dual-wavelength laser irradiation is an efficient strategy to improve the therapeutic effect of PDT.

Effect of Internal, Office, and Home Bleaching on Shear Bond Strength of Enamel to Porcelain Laminate Veneers

PURPOSE: To compare the effect of office, home, and internal bleaching on the shear bond strength (SBS) of enamel to porcelain laminate veneers. MATERIALS AND METHODS: A total of 36 extracted maxillary central incisors were randomly assigned to four groups: (1) no bleaching (control); (2) office bleaching with 40% hydrogen peroxide (HP); (3) home bleaching with 15% carbamide peroxide; and (4) intracoronal bleaching with sodium perborate (SP) using the walking bleaching technique. All teeth were separately immersed in artificial saliva for 14 days. The enamel surface was then reduced by 0.5 mm, and IPS e.max Press ceramic discs were bonded using a resin cement. After 24 hours, all specimens were thermocycled (5,000 cycles, 5°C to 55°C). The SBS was measured using a universal testing machine, and the failure mode was determined using a stereomicroscope. One-way ANOVA and Tukey honest significant difference tests were used for data analysis (P < .05). RESULTS: A significant difference was noted among the groups (P < .001). The highest SBS was noted in the control group (15.71 ± 5.39 MPa). The mean SBS in the office bleaching group (12.30 ± 4.64 MPa) was almost the same as the control. The lowest mean SBS belonged to the home bleaching group (5.39 ± 3.99 MPa). The mode of failure was adhesive in all four groups. CONCLUSION: If bleaching is intended to be followed by porcelain veneers, the office bleaching technique with 40% HP is recommended. Delaying the bonding procedure for 2 weeks does not appear to be effective with home or intracoronal bleaching.

Additively custom-made 3D-printed subperiosteal implants for the rehabilitation of the severely atrophic maxilla (a case report).

Key Clinical Message: Subperiosteal implants might be the future first-line treatment in patients with compromised alveolar ridges, although the use of proper techniques and pre-surgical imaging is required to ensure treatment success. Abstract: Severe bone loss puts the success of endosseous implants at risk. This technical report aims to introduce the subperiosteal implants (SPIs) created through additive manufacturing. A case study is presented, outlining the process and strategies employed to fully restore a maxillary structure using a customized subperiosteal implant. The patient, who had previously faced disappointment with traditional endosseous implants, received a customized SPI. A detailed 3-year follow-up is also provided. The design of the subperiosteal framework and abutments is based on digital records of the patient's jaw structure and a radiographic stent during occlusion. This ensures optimal placement within the dental arch. The implant and abutments are then three-dimensional (3D) printed using a titanium alloy, while a provisional denture is 3D-printed using polymer materials. SPIs offer a viable alternative for individuals with severe jaw bone degeneration, as demonstrated in this report detailing their application in complete maxillary restoration. This patient-specific, prosthesis-driven approach avoids the need for bone grafting and enables immediate functional recovery through a single surgical procedure.

Composite Resin Bond Strength to Zirconia and Base Metal Alloys Using Two Types of Intraoral Porcelain Repair Systems.

Objectives: This study aimed to evaluate the shear bond strength (SBS) of two repair composites (Crea.lign vs. PermaFlo) to a base metal alloy and zirconia ceramic. Materials and Methods: Sixty-four discs (12mm diameter, 1mm thickness) were fabricated using Wirobond base metal alloy and zirconia. They were then bonded with their respective composite resins (N=16) in each of the two porcelain chipping repair kit subgroups consisting of PermaFlo and Crea.lign. All specimens were stored in 37°C distilled water for 24 hours. Half of them were subjected to 10,000 thermal cycles (5-55°C, 30s). All specimens were tested for SBS with a universal testing machine. Failure types were analyzed using a digital camera. Analysis of the data was done by two-way ANOVA and Bonferroni post-hoc tests. Results: SBS was significantly affected by the type of composite resin. PermaFlo had a significantly higher SBS than Crea.lign to base metal alloy (P<0.001) and zirconia ceramic (P<0.001). Thermocycling decreased the SBS of both composites to base metal alloy (P<0.001) and zirconia (P<0.001). Conclusion: A universal adhesive could provide higher shear bond strength of zirconia and base metal alloy to composite resin than Crea.lign composite and the MKZ primer supplied by its manufacturer.

Effect of Implant Angulation on the Rotational Displacement of a 3-Unit Bridge after Digital Impression.

OBJECTIVES: This study aimed to assess the effect of implant angulation on the rotational displacement of a 3-unit bridge following a digital impression. MATERIALS AND METHODS: This in vitro experimental study evaluated 3 master models of the maxilla with Kennedy's class III partial edentulism and bilateral three-unit implant-supported fixed partial dentures. Two implants were placed with 0° (first model), 15° (second model), and 30° (third model) interimplant angles. The implants were placed bilaterally at the sites of first premolars and first molars from the posterior towards the anterior region and coded A (posterior) and B (anterior) in the left, and C (posterior) and D (anterior) in the right side. Next, their position was recorded using a coordinate measuring machine to serve as a reference. The models were then scanned by both 3Shape and Sirona digital scanners (12 times by each scanner). The obtained data were compared with the reference data three-dimensionally using GOM Inspect software to determine the rotational displacement of the implants. Data were analyzed by repeated-measures ANOVA, one-way ANOVA, paired sample t-test, and independent sample t-test (P < 0.05). RESULTS: Since repeated-measures ANOVA showed that the interaction effect was significant (P = 0.010), the data were analyzed by subgroup analysis. The 3Shape scanner showed significantly higher accuracy for C-D region in model 2 (P = 0.001), and A-B region in model 1 (P ≤ 0.01). In the use of the 3Shape scanner, model 3 showed a lower error rate in the A-B region, compared with models 1 and 2. Model 1 showed higher error rate than models 2 and 3 in the C-D region (P ≤ 0.01). In the use of the Sirona scanner, model 1 showed a higher error rate than models 2 (P = 0.031) and 3 (P = 0.004) in the C-D region. CONCLUSION: In digital impressions of angulated implants in 3-unit bridges by using 3Shape and Sirona scanners, the rotational error decreases as the interimplant angle increases.

Effect of prophylactic application of doxycycline at the implant-abutment interface on the outcomes of implant therapy: a split-mouth randomized clinical trial.

OBJECTIVES: Doxycycline hyclate is a controlled-release doxycycline polymer which can locally be applied. This study aimed to assess the effects of the prophylactic application of doxycycline hyclate at the implant-abutment interface on the short-term outcomes of implant therapy. METHOD AND MATERIALS: The present split-mouth randomized clinical trial included 20 subjects who received two mandibular implants bilaterally (40 implants in total). In the test side (n = 20), doxycycline hyclate was injected at the implant-abutment interface at the time of delivery of final prosthesis. No intervention was performed for the control side (n = 20). The marginal bone level on mesial and distal implant surfaces, bleeding on probing, pocket probing depth, and incidence of peri-implant mucositis were recorded at baseline and after 3, 6, and 12 months. RESULTS: Significant differences were found between the test and control sites, all favoring the test group, for marginal bone level changes at mesial and distal implant surfaces as well as for changes in pocket probing depth after 6 and 12 months. Furthermore, the numbers of implants with bleeding on probing and risk of developing peri-implant mucositis were significantly greater in the control group compared to the test group at 3-months, 6-months, and 12-months following baseline. CONCLUSIONS: Within the limitations of this study, it can be concluded that prophylactic application of doxycycline hyclate at the implant-abutment interface results in reduced crestal bone resorption and pocket probing depth levels. In addition, it reduces the risk of developing peri-implant mucositis.

Effect of Light-Emitting Diode Phototherapy on Allograft Bone After Open Sinus Lift Surgery: A Randomized Clinical Trial (Concurrent Parallel).

Introduction: Phototherapy with a light-emitting diode (LED) is used in medicine due to its potential bio-stimulatory effects on the human body. However, controversy still exists regarding the efficacy of low-level laser therapy (LLLT) and phototherapy with LED. This in vivo study aimed to quantitatively and qualitatively assess the newly formed bone following LED phototherapy of the human maxillary sinuses. Methods: This randomized clinical trial (concurrent parallel) was conducted on 44 patients in two groups (n=22) at the Implant Department of Tehran University of Medical Sciences. Randomization was done by a random sequence generator program. The inclusion criteria were absence of chronic sinusitis and chronic bone marrow conditions, no history of surgery at the site, absence of diabetes mellitus, no history of chemotherapy or radiotherapy, maxillary premolar edentulism, and signing informed consent forms. Group A underwent LED phototherapy with 620 ± 2 nm wavelength for 20 minutes daily for a total of 21 days after sinus lift surgery. Group B served as the control group and did not receive phototherapy. After 6 months, the grafted sites were re-opened for implant placement, and bone biopsy samples were obtained using a trephine bur. The samples were stained with hematoxylin and eosin and inspected under a light microscope. The results were statistically analyzed using the Mann-Whitney U test. Both the surgeon and pathologist were blinded to the group allocation of patients. Results: Forty tissue specimens were analyzed. Insignificant differences existed between the two groups in terms of the degree of inflammation, bone quality, and maturity of collagen. Histological analyses revealed no significant difference in the mineralized areas of bone between the two groups (P >0.05). Conclusion: The results indicated that LED phototherapy cannot significantly enhance osteogenesis after sinus lift surgery. No side effects were observed in the experimental group.

Effect of Application of a Bio-Adhesive on the Removal Torque Value and Rotational Misfit at the Implant-Abutment Junction: An In Vitro Study.

The aim of this study was to assess the effect of application of a recently developed bio-adhesive (Impladhesive) to abutment screw threads on the removal torque value and rotational misfit at the implant-abutment junction. This in vitro study evaluated 20 implant fixtures and 20 straight abutments. Specimens were randomly divided into two groups (n = 10) with/without adhesive application. In the adhesive group, the abutment was dipped in Impladhesive before torquing. In the control group, the abutment was torqued conventionally without adhesive application. The removal torque value was recorded after completion of the cyclic loading of 500,000 cycles with 2 Hz frequency and 75 N load. Rotational misfit was recorded using a video measuring machine. After applying the torque, the change in the bisector angle on the abutment hex was recorded for each implant. The biocompatibility of Impladhesive was evaluated using a MTT cell vitality assay. Normal distribution of data was assessed using the Kolmogorov-Smirnov test. Data were analyzed using a t-test and Pearson's correlation coefficient The application of Impladhesive at the implant-abutment interface resulted in significantly greater mean removal torque value compared to the control group (p = 0.008). In addition, the mean rotational misfit at the implant-abutment interface was significantly lower in the use of Impladhesive compared to the control group (p = 0.001). In addition, the cell vitality was found to be greater than 80% at all evaluated time points. It can be concluded that the application of Impladhesive on the abutment screw significantly decreased rotational misfit and increased the removal torque value. Future studies are needed to evaluate the efficacy of this bio-adhesive an in vivo setting.

Dental rehabilitation of a cleft lip and palate patient by implant-supported overdenture: A case report.

Our patient was a 27-year-old male with a unilateral cleft lip and palate. Considering the mobility of bone segments around the cleft, an implant-supported removable overdenture (obturator) was fabricated, which improved the function and esthetics and led to patient satisfaction. The treatment results are still satisfactory after 5 years of follow-up.

Finite Element Analysis of Stress in Bone and Abutment-Implant Interface under Static and Cyclic Loadings.

OBJECTIVES: The success of implant treatment depends on many factors affecting the bone-implant, implant-abutment, and abutment-prosthesis interfaces. Stress distribution in bone plays a major role in success/failure of dental implants. This study aimed to assess the pattern of stress distribution in bone and abutment-implant interface under static and cyclic loadings using finite element analysis (FEA). MATERIALS AND METHODS: In this study, ITI implants (4.1×12 mm) placed at the second premolar site with Synocta abutments and metal-ceramic crowns were simulated using SolidWorks 2007 and ABAQUS software. The bone-implant contact was assumed to be 100%. The abutments were tightened with 35 Ncm preload torque according to the manufacturer's instructions. Static and cyclic loads were applied in axial (116 Ncm), lingual (18 Ncm), and mesiodistal (24 Ncm) directions. The maximum von Mises stress and strain values were recorded. RESULTS: The maximum stress concentration was at the abutment neck during both static and cyclic loadings. Also, maximum stress concentration was observed in the cortical bone. The loading stress was higher in cyclic than static loading. CONCLUSION: Within the limitations of this study, it can be concluded that the level of stress in single-unit implant restorations is within the tolerable range by bone.

Restoration of endodontically treated cracked maxillary teeth: A case series.

Cracks adversely affect the prognosis and survival of the teeth. Thus, the possibility of presence of crack should be considered after endodontic treatment and before the initiation of periodontal/prosthetic treatments. Attempts must be made to restore cracked teeth with efficient restorative materials to increase their survival and prevent additional costs.

A novel technique to retrieve cold-welded implant abutment: A case series.

Abutment fracture is a complication of dental implant treatment. When an abutment breaks, the remaining part should be retrieved without damaging the implant hex. In many cases, the implant-abutment connection is cold-welded, which makes it difficult to remove the remaining part. The aim of the present study was to describe a simple technique to retrieve the remaining part of a broken abutment.

Rehabilitation of a patient with amelogenesis imperfecta and severe open bite: A multidisciplinary approach.

Amelogenesis imperfecta (AI) is typically associated with anterior open bite and a number of other dental problems, which require complex treatments such as orthognathic surgery. This case report describes management of a patient with AI and severe open bite via a multidisciplinary approach.