implant supported

Statement of the Problem:

 The satisfaction of patients with dentures on implants has different points of view that become fundamental aspects for the development of research on the quality of life of these patients, the eventual biomechanical complications to which these prostheses and implants can be subjected, and design considerations for cantilever extensions.

The objective of research was to assess the implants and prosthesis survival rates, biomechanical complications relative to the length of the distal extensions (cantilevers), and the satisfaction of the patients with a fixed implant-supported full-arch fiber-reinforced composites prosthesis.

A retrospective clinical and radiographic cohort study was developed. Clinical records of a selected cohort were analyzed according to inclusion and exclusion criteria. Data on a patient who underwent to fixed implant-supported full-arch fiber-reinforced composites prosthesis at least of five years of function were collected. Data analysis was performed using Kaplan-Meier curves and Fisher's Exact Test. P values less than 0.05 were considered statistically significant.

After insertion, 1 of 29 prostheses failed, the overall prosthetic survival rate observed at 5 years was 96.5%. Of the 120 implants placed in 28 patients, only 4 patients experienced loss of an implant during the 5 years of observation; the implant survival rate throughout the observation period was 86.2%. Distal extension seems to negatively affect the prognosis of implant-supported rehabilitation. Regarding the level of satisfaction of the patient with the prosthesis, none reported being uncomfortable or dissatisfied neither with their appearance nor with the taste of food throughout the studied period.

No relevant associations were found between the variables involved. The study found the improvement in quality of life following the installation of fixed rehabilitation on the patients. Once the potential benefits of patients are obtained, controlled clinical trials are encouraged.

This study aimed to investigate the aesthetic aspect of screw-retained restorations by examining three different types of filling materials used for the access cavity, highlighting the significance of aesthetics in implant restorations.

In this laboratory investigation, simulation samples of screw-retained restorations were filled with flowable composite resin (group F), opaque and flowable composite resin (group O) and porcelain plug (group P) at baseline (T0). The samples were subjected to thermocycling twice (T1 and T3), undergoing 1000 cycles in coffee, orange juice, and distilled water, followed by washing performed after each thermocycling (T2 and T4). Colorimetric analysis and surface roughness measurements were conducted, and the data were statistically analyzed using. two-way analysis of variance (ANOVA), Tukey post hoc, two-way analysis of covariance (ANCOVA), and paired-t test. P<0.05 was considered significant.

The type of filling material had a significant effect on the color difference observed between the restoration and filling materials (P<0.05). Notably, samples from group P exhibited a more pronounced color difference at T4, despite showing a lower color difference at T0, when compared to group O.

The use of porcelain plugs did not provide a notable advantage over the combination of flowable and opaque composite resins, particularly given the difficulties in fabricating and positioning porcelain plugs within the access cavity. Therefore, it is recommended to utilize flowable composite resins in conjunction with an opaque composite resin layer beneath, to effectively conceal any dark shades from the underlying metal

This study aimed to do a comprehensive systematic review on the comparison of digital and conventional workflows regarding prosthetic outcomes, accuracy of implant impressions, framework passivity and fit, and clinical fabrication of multi-unit implant-supported fixed restorations.

The EMBASE, PubMed, Scopus, and Cochrane Library databases were searched for relevant articles published up until April 2020.

No in-vivo article was found to compare full digital and conventional workflows regarding the accuracy of implant impressions, passivity and fit of frameworks, and prosthetic outcomes. There was no study to investigate full digital and conventional workflows for clinical fabrication of multi-unit implant-supported fixed restorations.

This empty review highlights the need for further research to compare full digital and conventional workflows for implant-supported restorations.

Statement of the Problem: 

Some components of implant treatment are reusable. Therefore, possible changes during fixation, removal, and sterilization process should be tested. Many studies have examined the reuse of implant parts, but the impact of repeated use of scan bodies on the accuracy of implant position has not been well investigated.

The aim of this in vitro study was to compare the effect of repeated use of two different types of scan bodies on the accuracy of implant position.

In this in vitro experimental study, two acrylic resin maxillary models, each with two implant analogues inserted at the site of missing first and second molars were used. Two types of scan bodies including titanium and polyetheretherketone (PEEK) were used for digital impression. Then they were ten times removed and autoclaved for sterilization. The first scan was considered as a reference to be compared with the other next nine scans. Values of linear distance between two scan bodies, diameter changes of each scan body, and three-dimensional linear displacement (ΔR) were measured. These values were compared between the two types of scan bodies using t-test (α=.05). 

There was significant difference between titanium and PEEK scan bodies regarding inter-implant distance variation (p=.006) and diameter change (p< .001) in repeated use. However, for the ΔR, there was no significant difference between them (p= 0.759).

The results demonstrated that type of scan body could affect the accuracy of implant position transfer after repeated use. PEEK scan body performed better after 9 cycles of reuse in comparison with titanium scan body.

Attachments are used for connections between overdentures and dental implants. The maintenance of attachment components plays an important role in optimal clinical service of overdentures. This study aimed to compare the effects of overdenture insertion by hand pressure versus placement by clenching the jaws on the retention and diameter of resilient attachments. Thirty patients with mandibular overdentures participated in this study. First, the patients were instructed to insert the overdentures with hand pressure. After 6 months, patients were recalled, the nylon matrix components of the attachments were replaced, and the patients were instructed to place the overdentures by clenching for the next 6 months. The retention and internal diameter of matrices were measured at baseline and at 6 and 12 months later. A universal testing machine was used to measure the residual retention, and a coordinate measuring machine was used to assess the matrix diameter. The retention loss and changes in matrix diameter were compared between the two techniques, using paired samples t-test. The results showed that retention loss was lower in the hand placement method than in the clenching method (P<0.001). The two insertion methods were not significantly different regarding the amount of diameter increase (P=0.074). The residual retention of the matrices was significantly greater in the hand placement of overdentures along the longitudinal attachment axis, which may result in greater efficacy and longevity of implant overdentures.

 This study compared the amount of residual cement at the margin of implant-supported crowns cemented using the polytetrafluoroethylene (PTFE) tape, replica technique, and conventional cementation technique.

 In this in vitro experimental study, a mandibular model underwent full-arch scanning. The right first molar tooth was eliminated on the scan using Exocad software, and a regular implant analog was modelled using the Exocad model creator. The designed abutment was then printed. The implant analog was fixed in place with acrylic resin and scanned using a scan body. A full-zirconia custom abutment was then designed by Exocad. Abutments were fabricated using zirconia and sintered. Twenty-seven resin crowns were fabricated for the abutments, and their fit was assessed. Nine crowns were conventionally cemented by filling half of the crown space with cement, 9 crowns were cemented using PTFE tape, and the remaining 9 were first placed on a resin replica and then cemented on the abutments. The residual cement was weighed using a digital scale, and the groups were compared by one-way ANOVA and LSD test (α=0.05).

 The amount of residual cement was significantly different among the three groups, indicating that the amount of residual cement was the highest in conventional cementation, and the lowest in the replica group (P < 0.05). Pairwise comparisons showed significant differences between all groups (P < 0.05).

 The replica technique followed by the PTFE tape resulted in the minimum amount of residual cement at the margin of implant-supported cement-retained crowns and are preferred for use in the clinical setting.

Statement of the Problem: 

In most cases, insertion of single implants with a standard diameter is used to replace a molar tooth but placing two implants with a narrow diameter seems to be a viable treatment modality to withstand functional and biomechanical forces.

This study aimed to evaluate and compare stress distribution in the bone surrounding a single molar area rehabilitated by a single implant versus two implants with a narrow diameter.

The study was conducted by computer-aided in vitro modeling. The initial model used a single implant, 4.8 mm wide in diameter, inserted with a 3.9-mm distance from both sides and 12.6-mm mesiodistal space. The second model used two 3.3-mm narrow-sized implants with a 3-mm distance from one another, 1.5 mm from both sides, and a 12.6-mm mesiodistal space. Following the completion of these models, a 100-N force was exerted obliquely, once in three locations and once in the mesial aspect of the implant-supported crown. Stress distribution was then measured using finite element analysis (FEA) with ANSYS Workbench software package in both models.

The maximum stress in the bone around the single implant was less than that around double implants. The maximum stress of cortical bone in three-point loading was lower than mesial loading either in one (146.7 vs. 126.72 MPa) or two implants model (186.8 vs. 139.24).

According to the results, because of more cortical bone contact area, the stress of surrounding bone in wide implant was decreased.

This report details the successful prosthetic rehabilitation of a 25-year-old male patient with Papillon Lefèvre Syndrome (PLS) using an implant-supported hybrid prosthesis. Six implants were placed in the maxilla, and four were placed in the mandibular arch. All implants were inserted axially (non-tilted) and were planned to be loaded after a healing period of 6 months. One implant failed due to graft loss during the healing phase, which was removed and the remaining implants were restored with a hybrid prosthesis after 6 months, using the delayed loading protocol. The patient was followed-up for four years and all the remaining implants successfully integrated and remained fully functional during this period. The prosthesis significantly improved the functional, aesthetic, and psychological well-being of the patient. This case report is the first of its kind to use only four axially placed implants for rehabilitation of a PLS patient with a successful four-year follow-up.

Reconstruction of functional occlusion in case of a large surgical defect of the mandible involving partial mandibulectomy remains a significant challenge to the maxillofacial surgeon and prosthodontist. Removable appliances and the conventional implant‑supported prosthesis are precluded in this case due to the absence of normal anatomical contours of the bone. In recent years, due to the advancement of technology, bone graft reconstruction with computer‑guided rehabilitation of the functional occlusion has been advocated to reverse the debilitating effects of the hemimandibulectomy defect. This clinical report describes the prosthodontic management of fibular graft reconstructed mandible by computer‑aided design–computer‑aided manufacturing guided implant‑supported prosthesis.

Reconstruction of functional occlusion in case of a large surgical defect of the mandible involving partial mandibulectomy remains a significant challenge to the maxillofacial surgeon and prosthodontist. Removable appliances and the conventional implant‑supported prosthesis are precluded in this case due to the absence of normal anatomical contours of the bone. In recent years, due to the advancement of technology, bone graft reconstruction with computer‑guided rehabilitation of the functional occlusion has been advocated to reverse the debilitating effects of the hemimandibulectomy defect. This clinical report describes the prosthodontic management of fibular graft reconstructed mandible by computer‑aided design–computer‑aided manufacturing guided implant‑supported prosthesis

The quality of dental treatment is one of the factors that affects life satisfaction in the elderly. Patients expect optimal function, esthetics, and speech from their prosthesis, while durability and technical considerations are also important for clinicians. In addition, social and psychological factors as well as costs can affect patient satisfaction. This study aimed to evaluate the relationship of life sat-isfaction with satisfaction with implant treatment.

In this cross-sectional study, a total of 67 partially edentulous patients (molars and premolars) who had undergone prosthetic treatment 2-6 months earlier were recruited by convenience sampling in Isfahan, Iran. Data were collected by a questionnaire and analyzed using SPSS version 24 via t-test, ANOVA, and Pearson’s correlation test.

The mean score of satisfaction with implant treatment was 33.70 ± 5.15 while the mean score of satisfaction with old age was 24.28 ± 4.75 out of 45. There was a significant correlation (r=0.748) between life satisfaction and satisfaction with implant treatment (P=0.001). Patients with higher level of education were more satis-fied with their treatment (r=0.407, P=0.023). There was a significant difference between satisfaction with single crowns and bridges, and the use of single crowns was associated with greater level of satisfaction with treatment (P=0.004).

Satisfaction with implant treatment is significantly correlated with life satisfaction among the elderly. Gender and surgical history were not correlated with treatment satisfaction, but higher educational level and having a single crown were as-sociated with greater patient satisfaction.

Statement of the Problem: 

Retrieval of cement-retained implant-supported restorations is challenging in cases of screw loosening or periodontal problems.

The purpose of this study was to evaluate the effect of the screw access hole on the fracture resistance of zirconia-based cement-retained restorations with and without an access opening.

In this in vitro study thirty-three cement-retained implant-supported zirconia-based molar crowns were fabricated and divided into 3 groups (n=11). As the control group, group 1 consisted of conventional cement-retained crowns. Group 2 comprised conventional cement-retained crowns in which a hole was created in the location of the screw. Group 3 consisted of cement-retained crowns in which a ledge was created in the location of the screw access channel. The specimens were cemented to their abutments and their access openings were filled with composite resin. A compressive load was applied to the specimens using a universal testing machine until they fractured. The mean fracture resistance values of the samples were compared by using the one-way ANOVA and Tamhane post-hoc test (a=0.05).

The mean fracture resistance values were 1270.18± 12.67 N in group 1 (the control group), 960.09±210.67 N in group 2 (conventional), and 1357.81±361.68 N in group 3 (the special design). The fracture resistance value was higher in the special design group than that of the conventional design (p= 0.018) and the fracture resistance value of the conventional design group was less than that of the control group (p= 0.042). No statistically significant difference was detected between the control group and the special design group in fracture resistance values.

Preparing a screw access hole in cement-retained implant-supported zirconia-based crowns decreased the fracture resistance of the restoration. Designing a ledge in the zirconia framework around the access hole may increase the fracture resistance of the restoration.

This study aimed to compare the oral health related quality of life (OHRQoL) of patients using conventional dentures versus implant-supported overdentures.

This study evaluated the OHRQoL of 90 patients between 35 to 75 years who were selected from several public and private dental clinics in Tehran in 2018. Of all, 45 had conventional dentures of both jaws, and 45 had a mandibular overdenture supported by two implants at the site of mandibular canine teeth and a conventional maxillary denture. The OHRQoL of patients was determined using the Oral Health Impact Prfile-20 (OHIP-20). The questionnaire was translated to Persian, and its content validity and internal consistency were confirmed. Data were analyzed by one-way ANOVA, Mann-Whitney test, and independent t-test.

In the conventional denture group, 46.7% had good, 46.7% had moderate, and 6.6% had poor OHRQoL. These values were 55.6%, 37.8% and 6.6% in the overdenture group, respectively. Level of education had a significant correlation with the total score of OHIP-20 in both groups (P<0.05). But no significant association was noted between the residential status and gender of patients with different domains of OHRQoL (P>0.05) except for the psychological disability domain, which had a higher mean value in males with conventional dentures (P<0.05).

Patients with a mandibular overdenture supported by two implants at the site of canine teeth and a conventional maxillary denture had higher OHRQoL than patients with conventional dentures of both jaws.

Local or systemic issues may prevent the installation of a sufficient number of dental implants for fixed prosthetic rehabilitations. Splinting dental implants and natural teeth in fixed dentures could overcome such limitations. Therefore, this study aimed to evaluate the influence of the number of dental abutments in the biomechanics of tooth-implant supported fixed partial dentures. Null hypothesis was that increasing the number of abutment teeth would not decrease the stress over abutments and surrounding bone.

Left mandibular lateral incisor, canine, premolars, and molars were reconstructed through computed tomography and edited using image processing software to represent a cemented fixed metal-ceramic partial denture. Three models were set reducing the number of abutment teeth: 1) lateral incisor, canine, and first premolar; 2) canine and first premolar; 3) first premolar. Second premolar and first molar were set as pontics and second molar was set as implant abutment in all models. Finite element analyses were performed under physiologic masticatory forces with axial and oblique loading vectors.

After simulation of axial loads, the stress peaks on bone around the implant, bone around the first premolar, and prosthetic structures did not experience major changes when the number of abutment teeth was reduced. However, under oblique loads, decreasing the number of abutment teeth led to increased stress peaks on the surrounding bone and denture.

Increasing the number of dental abutments in tooth-implant supported cemented fixed partial denture models led to the reduction of stress on its constituents, favoring the prosthetic biomechanics.

Internal fit of implant frameworks is an important factor determining the long-term success of dental implant restorations. This in-vitro study aimed to evaluate dimensional changes of implant-supported zirconia frameworks fabricated by two computer-aided design/computer-aided manufacturing (CAD/CAM) systems from scanning to sintering.

A master model of a three-unit fixed partial denture was fabricated with two implant abutments. In each CAD/CAM system (AmannGirrbach and Zirkonzahn), the master model was scanned 12 times, and data were saved as Standard Transformation Language files (scanning groups). Using semi-sintered zirconia, 12 real-size frameworks (milling groups) and 12 enlarged frameworks, were sintered (sintering groups) and made by each system. Dimensions of the master model and frameworks in each phase were measured. Dimensional changes (compared to the master model) were calculated. Data were analyzed using repeated measures analysis of variance, independent t-test, and paired sample t-test (α=0.05).

Comparison of the two CAD/CAM systems revealed that although dimensional changes were greater in the Zirkonzahn system in the milling phase, they were greater in the AmannGirrbach system in the sintering phase. Evaluation of fabrication phases in each system revealed greater dimensional changes in the milling phase compared to other phases in the Zirkonzahn system (P<0.05). However, in the AmannGirrbach system, the values were not significantly different between the milling and sintering phases (P>0.05).

Within the limitations of this study, the results showed that fabrication phases, type of CAD/CAM system, and abutment size had significant effects on dimensional changes.

Progressive loading protocol is a high-demanding procedure suggested to increase the quality of bone when the implant is inserted in D3 or D4-typed bone. The purpose of this study was to present a case report regarding simultaneously progressive and immediately loading implants in the anterior position of the maxilla.
Case report: One patient whose implants in the anterior maxilla (in site of teeth #7, #9, #11) had questionable to poor prognosis who was treated immediate and delayed progressive loading protocol and was followed up for 2 years.
Although the number of studies in this field is limited, it can be concluded that the progressive loading protocol can predictably enhance the treatment success in immediate-loaded implants with poor prognosis and when inserted in low quality bone such as the present case.

Because of compromised angulations of implants, the abutments are sometimes prepared. The purpose of this study was to investigate the effect of removing one wall of the implant abutment on the retention of cement-retained crowns. Four prefabricated abutments were attached to analogues and embedded in acrylic resin blocks. The first abutment was left intact. Axial walls were partially removed from the remaining abutments to produce abutments with three walls. The screw access channel for the first and second abutments were completely filled with composite resin. For the third and fourth abutments, only partial filling was done. Wax-up models were made by CAD/CAM. Ten cast copings were fabricated for each abutment. The copings of fourth abutment had an extension into the screw access channel. Copings were cemented with Temp Bond. The castings were removed from the abutment using an Instron machine, and the peak removal force was recorded. A one-way ANOVA was used to test for a significant difference followed by the pairwise comparisons. The abutments with opened screw access channel had a significantly higher retention than the two other abutments. The abutment with removed wall and no engagement into the hole by the castings exhibited the highest retention. Preserving the opening of screw access channel significantly increases the retention where one of the axial walls of implant abutments for cement-retained restorations is removed during preparation.