Digital evaluation of axial displacement by implant-abutment connection type: An in vitro study

PURPOSE: To measure axial displacement of different implant-abutment connection types and materials during screw tightening at the recommended torque by using a contact scanner for two-dimensional (2D) and three-dimensional (3D) analyses. MATERIALS AND METHODS: Twenty models of missing mandibular left second premolars were 3D-printed and implant fixtures were placed at the same position by using a surgical guide. External and internal fixtures were used. Three implant-abutment internal connection (INT) types and one implant-abutment external connection (EXT) type were prepared. Two of the INT types used titanium abutment and zirconia abutment; the other INT type was a customized abutment, fabricated by using a computer-controlled milling machine. The EXT type used titanium abutment. Screws were tightened at 10 N·cm, simulating hand tightening, and then at the manufacturers' recommended torque (30 N·cm) 10 min later. Abutments and adjacent teeth were subsequently scanned with a contact scanner for 2D and 3D analyses using a 3D inspection software. RESULTS: Significant differences were observed in axial displacement according to the type of implant-abutment connection (P < .001). Vertical displacement of abutments was greater than overall displacement, and significant differences in vertical and overall displacement were observed among the four connection types (P < .05). CONCLUSION: Displacement according to connection type and material should be considered in choosing an implant abutment. When adjusting a prosthesis, tightening the screw at the manufacturers' recommended torque is advisable, rather than the level of hand tightening.

Influence of the connection design and titanium grades of the implant complex on resistance under static loading

PURPOSE: The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections. MATERIALS AND METHODS: Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student's t-test with the level of significance at P=.05. RESULTS: The group IT4S had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups IT4N and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation. CONCLUSION: A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

Effect of abutment screw length and cyclic loading on removal torque in external and internal hex implants

PURPOSE: The purpose of this study was to evaluate the effects of abutment screw length and cyclic loading on the removal torque (RTV) in external hex (EH) and internal hex (IH) implants. MATERIALS AND METHODS: Forty screw-retained single crowns were connected to external and internal hex implants. The prepared titanium abutment screws were classified into 8 groups based on the number of threads (n = 5 per group): EH 12.5, 6.5, 3.5, 2.5 and IH 6.5, 5, 3.5, 2.5 threads. The abutment screws were tightened with 20 Ncm torque twice with 10-minute intervals. After 5 minutes, the initial RTVs of the abutment screws were measured with a digital torque gauge (MGT12). A customized jig was constructed to apply a load along the implant long axis at the central fossa of the maxillary first molar. The post-loading RTVs were measured after 16,000 cycles of mechanical loading with 50 N at a 1-Hz frequency. Statistical analysis included one-way analysis of variance and paired t-tests. RESULTS: The post-loading RTVs were significantly lower than the initial RTVs in the EH 2.5 thread and IH 2.5 thread groups (P<.05). The initial RTVs exhibited no significant differences among the 8 groups, whereas the post-loading RTVs of the EH 6.5 and EH 3.5 thread groups were higher than those of the IH 3.5 thread group (P<.05). CONCLUSION: Within the limitations of this study, the external hex implants with short screw lengths were more advantageous than internal hex implants with short screw lengths in torque maintenance after cyclic loading.

Narrow-diameter implants with conical connection for restoring the posterior edentulous region / 대한악안면성형재건외과학회지

BACKGROUND: The objective of this retrospective study was to show results from platform-switched narrow-diameter implants in the posterior edentulous region, which we followed up for more than 1 year after functional loading. METHODS: Ninety-eight narrow implants were inserted into 66 patients. After healing, fixed implant-supported prostheses were delivered to the patients, and Periotest and radiographic examinations were performed. After the first year of loading, the implant outcome was again evaluated clinically and radiographically using the Periotest analysis. Crestal bone loss and Periotest values (PTVs) were used to evaluate the effect of surgery, prosthesis, implant, and a host-related factor. A general linear model was used to statistically detect variables statistically associated with crestal bone loss and Periotest value. RESULTS: We followed up on the implants over 1 to 4 years after loading; their survival rate was 100%, and pronounced differences from PTVs were noted among jaw location, bone quality, and loading period. No difference was detected in bone loss among the variables studied. Bone loss after functional loading was 0.14 ± 0.39 mm. The stability value from the Periotest was −3.29 ± 0.50. CONCLUSIONS: Within the limitations of this study, judicious use of platform-switched narrow implants with a conical connection must be considered an alternative for wide-diameter implants to restore a posterior edentulous region.

Resolução protética estética em plataforma Cone Morse / Esthetic prosthetic resolution inMorse Taper platform

Os problemas decorrentes de perdas dentárias em áreas estéticas têm sido motivo de intensa dedicação científica e empenho clínico a fim de alcançar estabilidade mecânica e estética favoráveis. O advento dos implantes dentários osseointegráveis supriu quesitos de suporte mecânico; no entanto, a remodelação óssea cervical ao redor de implantes com plataforma convencional pode comprometer significativamente a manutenção dos tecidos peri-implantares, gerando sérios agravos estéticos. Atualmente, o objetivo da instalação de implantes Cone Morse vai além de atender a uma tendência evolutiva em Implantodontia, proporcionando a manutenção das características teciduais peri-implantares e o favorecimento da confecção de próteses estéticas, direcionando todo o processo terapêutico a possibilitar perfil de emergência ideal e relacionamento natural e harmonioso com os tecidos circunjacentes. Logo, essa revisão bibliográfica tem o intuito de apresentar tais características, que conferem um alto índice de sucesso e de longevidade das peças protéticas, garantindo maior previsibilidade de manutenção das condições em reabilitações protéticas.

The issues arising from tooth loss in esthetic zones have been the subject of intense scientific dedication andclinical commitment of which purpose is to achieve favorable mechanical and esthetic stability. The adventof osseointegrated dental implants has satisfied the need for mechanical support; however, cervical boneremodeling around implants with conventional platform may significantly compromise the maintenance ofperi-implant tissues, causing serious esthetic injuries. The purpose of Morse Taper implant placement goesbeyond the current evolutionary trend in Implantology. It provides maintenance of peri-implant tissue characteristicsand facilitates esthetic prosthesis design, thus allowing an ideal emergence profile and a naturaland harmonious relationship with surrounding tissues to be achieved during the entire therapeutic process.Therefore, this literature review aims at presenting the characteristics that confer a high rate of success andlongevity to prosthetic parts, ensuring greater predictability of maintenance in prosthetic rehabilitation.

Load-bearing capacity of screw-retained CAD/CAM-produced titanium implant frameworks (I-Bridge®2) before and after cyclic mechanical loading

Implant-supported screw-retained fixed dental prostheses (FDPs) produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics. OBJECTIVE: The aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks. MATERIAL AND METHODS: Ten five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge®2-concept (I-Bridge®2, Biomain AB, Helsingborg, Sweden) and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation). One half of the specimens was tested for static load-bearing capacity without any further treatment (control), whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test). All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05). RESULTS: All the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control) to 7,592 N±901 N (test). The cyclic mechanical ...

Effects of abutment taper on the uniaxial retention force of cement retained implant restorations / Effects of abutment taper on the uniaxial retention force of cement retained implant restorations / Efeito da conicidade do pilar na resistência de união de coroas cimentadas sobre implantes

Aim: The purpose of this study was to evaluate the bond strength of metallic crowns cemented to straight and angled customizable abutments with zinc phosphate. Material and Method: Thirty-nine external hex nalogs and abutments were divided in group S: customizable straight abutment (n = 10), group A17 with 17° angled abutment (n = 10) and group A30 with 30° angled abutment (n = 10) all cemented with zinc phosphate. The metal copings were cemented onto their corresponding metal dies according manufacture guidelines. Data from the all groups were compared with a 1-way ANOVA (?=.05) and Tukey's test. SEM evaluation were performed (n = 3) aiming to investigate microscopic features of the abutment-cement-crown interfaces. Results: The mean force (SD) required to dislodge the crowns in the S, A17 and A30 groups was 357.26 (62.21) N; 251.50 (20.13) N and 276.70 (17.96) N respectively. The Tukey test (p <0.05) revealed a significant statistically differences between the groups (p =.002) and the 17° angled abutment and 30° angled abutment group were statistically similar to each other and different from the group of straight abutments. Zinc phosphate showed an inhomogeneous cement line in SEM analysis. Conclusions: Within the limitations of this study, it can be conclude that the available surface area and convergence of the abutments axial walls of the straight abutments positively influenced bond strength in metallic crowns cemented with zinc phosphate.

Mechanical analysis of conventional and small diameter conical implant abutments

PURPOSE: The aim of the present study was to evaluate if a smaller morse taper abutment has a negative effect on the fracture resistance of implant-abutment connections under oblique compressive loads compared to a conventional abutment. MATERIALS AND METHODS: Twenty morse taper conventional abutments (4.8 mm diameter) and smaller abutments (3.8 mm diameter) were tightened (20 Ncm) to their respective implants (3.5 x 11 mm) and after a 10 minute interval, implant/abutment assemblies were subjected to static compressive test, performed in a universal test machine with 1 mm/min displacement, at 45degrees inclination. The maximum deformation force was determined. Data were statistically analyzed by student t test. RESULTS: Maximum deformation force of 4.8 mm and 3.8 mm abutments was approximately 95.33 kgf and 95.25 kgf, respectively, but no fractures were noted after mechanical test. Statistical analysis demonstrated that the evaluated abutments were statistically similar (P=.230). CONCLUSION: Abutment measuring 3.8 mm in diameter (reduced) presented mechanical properties similar to 4.8 mm (conventional) abutments, enabling its clinical use as indicated.