In Vitro Analysis of the Removability of Fractured Prosthetic Screws within Endosseous Implants Using Conventional and Mechanical Techniques.

STATEMENT OF PROBLEM: The extraction of fractured abutment screws can be a difficult challenge to overcome. PURPOSE: To compare the removal capacity, dental implant connection damage, and time required to remove the fractured abutment screws between three drilling techniques and a conventional method. MATERIALS AND METHODS: A total of 180 prefabricated screw-retained abutments were intentionally fractured in internal connection dental implants after being subjected to a cyclic load and a static compression load. Afterwards, three operators randomly removed the fractured abutment screws with the following drilling techniques and a conventional method: A: a conventional technique using an exploration probe and ultrasonic appliance (n = 45), Rhein83® (n = 45); B: Sanhigia® (n = 45); C: Phibo® (n = 45). Two-way ANOVA models were estimated to evaluate the mean time according to the method and operator used. RESULTS: The probability of removal of the screws with mobility was twelve times higher than that of the screws without mobility (OR = 12.4; p < 0.001). The success rate according to the operators did not show statistically significant differences (p = 0.371). The location of the fractured screw did not affect removal success (p = 0.530). The internal thread of the implant was affected after the removal process in 9.8% of the cases. The mean extraction time was 3.17 ± 2.52 min. The Rhein83® method showed a success rate of 84.4%, followed by the Phibo® and conventional methods (71.1%) and the Sanhigia® method (46.7%). CONCLUSIONS: The Rhein83® drilling technique increases the removal probability of fractured abutment screws. The initial mobility of the fragment is also a significant factor in the removal success.

Graphene-Doped Polymethyl Methacrylate (PMMA) as a New Restorative Material in Implant-Prosthetics: In Vitro Analysis of Resistance to Mechanical Fatigue.

BACKGROUND AND PURPOSE: Provisional prostheses in restorations over several implants with immediate loading in completely edentulous patients increase the risk of frequent structural fractures. An analysis was performed of the resistance to fracture of prosthetic structures with cantilevers using graphene-doped polymethyl methacrylate (PMMA) resins and CAD-CAM technology. METHODS: A master model was produced with four implants measuring 4 mm in diameter and spaced 3 mm apart, over which 44 specimens representing three-unit fixed partial prostheses with a cantilever measuring 11 mm were placed. These structures were cemented over titanium abutments using dual cure resin cement. Twenty-two of the 44 units were manufactured from machined PMMA discs, and 22 were manufactured from PMMA doped with graphene oxide nanoparticles (PMMA-G). All of the samples were tested in a chewing simulator with a load of 80 N until fracture or 240,000 load applications. RESULTS: The mean number of load applications required for temporary restoration until the fracture was 155,455 in the PMMA-G group versus 51,136 in the PMMA group. CONCLUSIONS: Resistance to fracture under cyclic loading was three times greater in the PMMA-G group than in the PMMA group.

Interventions to Maintain Locator-Retained Mandibular Overdentures on Both External Hex and Internal Connection Implants: A Retrospective Study.

PURPOSE: To quantify the rate of maintenance interventions of mandibular prostheses: complete dentures and overdentures retained by two implants, with either internal hex or external hex connections. MATERIALS AND METHODS: This study analyzed patients with edentulous mandibles treated with distinct treatment protocols: a control group received complete dentures; a second group received Locator-retained overdentures supported by two external hex connection implants; and a third group received overdentures supported by internal hex connection implants. All of the maintenance interventions associated with the prosthetic treatment after delivery were recorded (starting from 2000 until the final assessment in 2012). Moreover, patient satisfaction was assessed using a 0 to 10 visual analog scale. RESULTS: The final sample was composed of 136 patients: 56 in the control group, 31 in the hex implant overdenture group, and 49 in the internal connection overdenture group followed over a period of 60 months (ranging from 3 to 144 months). Prosthetic adjustment was the most frequent intervention carried out, particularly within the control group (a mean rate of 1.1 ± 1.9 times/subject/year) in comparison with the internal connection (0.6 ± 0.8 times/subject/year) and hex implant overdenture groups (0.3 ± 0.2 times/subject/year). Relining was also frequently required, occurring on average every 4 years in the control group and every 7 years in the overdenture groups. Abutment loosening was more frequent in the hex implant overdenture group than in the internal connection overdenture group (8/31 versus 8/49), as well as abutment wear (5/31 versus 5/49). Gingival inflammation was significantly more common in the hex implant overdenture group (19/31 patients), as compared with the controls (16/56 subjects), and satisfaction was higher in patients in the two overdenture groups (mean Oral Satisfaction Scale [OSS] score of 8.1 ± 1.9 for external and 8.4 ± 1.6 for internal connections) than in the control group (5.3 ± 3.3). CONCLUSION: Locator-retained overdentures needed less than half the number of maintenance interventions when compared with the control group, and maintenance was required every 2 to 4 years.

In vitro retention capacity of two overdenture attachment systems: Locator® and Equator®.

BACKGROUND: It is necessary to know the in vitro behavior of different attachment systems to be used clinically. The evolution of retention capacity over 10 years (14,600 insertion/de-insertion cycles) was determined in vitro, evaluating two overdenture attachment systems (Locator® and OT Equator®). MATERIAL AND METHODS: The study used an implant replica compatible with the abutments of both systems. 10 Locator® and 10 OT Equator® attachments were screwed to the abutments. Nylon inserts were attached and tested, subjecting them to 14,600 insertion and de-insertion cycles (representing 10 years functional life) in axial direction. The universal test machine crosshead speed was 50 mm/min with a de-insertion range of 2 mm. RESULTS: The initial retention of Locator® was 17.02 N and of Equator® 16.36 N. After 14,600 cycles, Locator® suffered a mean loss of retention of 50.89%, while Equator® lost 69.28%. Both systems showed retention increases up to the first 1,000 cycles, which decreased thereafter up to 14.600 cycles. Statistically significant differences between the systems were found after 7,500 cycles. CONCLUSIONS: Both systems presented acceptable retention capacities after 14,600 cycles. Significant differences in retention force between the systems evolved after 7,500 cycles (5 years in vitro use). These results should be treated with caution and should be verified clinically. Key words:Denture, mandibular prosthesis implantation, attachment, dental implant-abutment connection, denture retention.

Patient-centered and clinical outcomes of mandibular overdentures retained with the locator system: A prospective observational study.

STATEMENT OF PROBLEM: Whether clinical or demographic variables affect the perception of treatment in terms of quality of life and satisfaction is unknown. PURPOSE: The purpose of this prospective study was to make an evidence-based assessment of the treatment outcomes (patient- and clinically based) of locator-retained mandibular overdentures. MATERIAL AND METHODS: This prospective observational study assessed patients with edentulism who had worn mandibular overdentures supported by 2 implants and retained by the locator system for at least 1 year of functional life (N=80). Medical histories were reviewed, and patients underwent oral examinations. Prosthetic clinical outcomes and patient well-being were registered using the Oral Health Impact Profile 20 (OHIP-20) and Oral Satisfaction Scale (OSS). RESULTS: Patient well-being scored an overall OHIP-20 score of 19.0 ±14.0 of 80 (the higher the score, the greater the impact and the worse the oral health-related quality of life); overall oral satisfaction was 8.3 ±1.7 of 10. Women suffered greater social impact (0.8 ±1.0) and disability (0.4 ±0.8) than men (0.4 ±0.7 versus 0.2 ±0.4, respectively). Impact on well-being was inversely proportional to both patient age and the age of the prosthesis (r=-0.25; P<.01). Implants had been placed on average 73.6 ±39.2 months previously, showing a survival rate of 82.5%. Most of the overdentures had been functioning for over 60 months. Relining (46.3%), readjustments (82.5%), and changes of nylon retention (1.5 ±1.8 per patient over 60 months of use) devices negatively influenced well-being. CONCLUSIONS: Mandibular overdentures produced good results with regard to quality of life and oral satisfaction, but attention should be paid to factors affecting clinical outcomes and patient well-being.

Effect of retention design of artificial teeth and implant-supported titanium CAD-CAM structures on fracture resistance.

BACKGROUND: For implant-supported hybrid prostheses, high mastication forces and reduced acrylic resin thickness over a metal substructure often cause failures arising from tooth or resin fractures. To assay fracture resistance of artificial teeth and resin in implant-supported hybrid prostheses in relation to the titanium structure and retention design supporting teeth. MATERIAL AND METHODS: 40 specimens bearing incisors were divided into four groups according to the titanium structure supporting the teeth and the type of load force applied: Group I (Control; n=10): Application of static loading to ten incisors set over a metal structure with internal retention. Group II (Control; n=10): Application of static loading to ten incisors set over a metal structure with external retention. The remaining study specimens (n=20) were subjected to 120,000 masticatory and thermal cycles in a chewing simulator. Afterwards, static loading was applied until the point of fracture using an Instron machine. Group III (Study; n=10): Application of dynamic and static loading to ten incisors set over a metal structure with internal retention. Group IV (Study; n=10): Application of dynamic and static loading to ten incisors set over a metal structure with external retention. Data obtained for the four groups was analyzed and compared, determining the type of fracture (cohesive or adhesive) using a reflected light microscope. RESULTS: Statistical analysis confirmed that there were significant differences in fracture resistance between the four groups. External retention was found to have more fracture resistance than the internal retention. CONCLUSIONS: Hybrid prostheses with titanium substructures and external retention obtained significantly better results than samples with internal retention. KEY WORDS: Chewing simulator, thermocycler, fatigue, implant-supported hybrid prosthesis, acrylic teeth, fracture, metal structure design.

Oral health-related quality of life of implant-supported overdentures versus conventional complete prostheses: Retrospective study of a cohort of edentulous patients.

BACKGROUND: This work aims to confirm if implant-supported overdentures are a good treatment option for edentulous patients and offer an improvement in quality of life compared with traditional complete prostheses (dentures). MATERIAL AND METHODS: This retrospective clinical descriptive study included three evaluation groups: validation group (n=57); control group of patients with complete removeable prostheses (n=56); study group of patients with implant-supported overdentures retained with the Locator® system (n=80). The study also validated the Oral Health Impact Profile-20 questionnaire. Individual protocols were created that included socio-demographic data, the Oral Health Impact Profile-20 (OHIP-20) questionnaire and Oral Satisfaction Scale (OSS). Descriptive and bivariate statistical analysis was carried out applying χ², Pearson, Kruskal-Wallis, and Student t tests, transferring data into SPSS-Windows® software from a Microsoft® Excel spreadsheet. RESULTS: The OHIP-20 proved to be a valid instrument and provided reliable assessment of health-related quality of life among both the Spanish general population and edentulous patients. The control and study groups proved comparable, showing socio-demographic homogeneity. For patients with overdentures retained by means of the Locator® system, these restorations had significantly lower impact on quality of life (19 vs 33), both generally and for each individual questionnaire item, and much higher satisfaction with the state of their oral cavities (8.3 vs 5.3) than patients wearing dentures; both sets of data showed a direct linear relationship, so that as the level of impact on quality of life increased, perceived oral satisfaction worsened. CONCLUSIONS: Patients rehabilitated with implant supported overdentures retained by the Locator® system, presented significantly lower levels of impact on their quality of life and significantly higher oral satisfaction than patients with conventional complete prostheses.