Effects of modifying implant screw access channels on the amount of extruded excess cement and retention of cement-retained implant-supported dental prostheses: A systematic review

Evaluation of the marginal adaptation and debonding strength of two types of CAD-CAM implant-supported cement-retained crowns

BACKGROUND

In-vitro data from a clinically well-known lithium disilicate ceramic reference was used to assess the expected performance of resin-based materials in implant dentistry. The purpose of the study was to compare the bond strength and marginal adaptation of nano-ceramic hybrid composite crowns cemented to stock cement-retained abutments to lithium disilicate crowns.

METHODS

Twenty abutment analogs were embedded into auto-polymerizing acrylic resin blocks. The blocks were divided into 2 groups according to the restorative crown material. The 2 groups were divided as follows: Resin nano-ceramic group and lithium disilicate group. Abutment analogs in both groups were scanned using a laboratory scanner, and the restorations were designed, manufactured, and cemented with resin cement over the corresponding group. All samples were tested for marginal adaptation and bond strength after storage for 24 hours at 37 °C in 100% humidity. Data were collected, tabulated, and statistically analysed using the appropriate tests. Normality was checked using Shapiro Wilk test and Q-Q plots. Data were normally distributed. Variables were presented using mean, 95% Confidence Interval (CI) and standard deviation in addition to median and Inter Quartile Range (IQR). Differences between groups regarding debonding forces was assessed using independent t test. Two Way ANOVA was performed to assess the effect of material and bonding on marginal gap. All tests were two tailed and p value was set at < 0.05.

RESULTS

Marginal gap and debonding force values were significantly different according to the type of material used (P < .05). Resin nano-ceramic crowns presented lower marginal gap values before (20.80 ± 8.87 μm) and after (52.11 ± 22.92 μm) bonding than lithium disilicate crowns. The debonding force value for resin nano-ceramic crowns (284.30 ± 26.44 N) was significantly higher than that for lithium disilicate crowns (253.30 ± 33.26 N). Adhesive failure mode was detected in all the specimens in both groups.

CONCLUSIONS

The type of material used for implant-supported cement-retained crowns had a statistically significant effect on marginal adaptation and bond strength. Resin nano-ceramic implant-supported cement-retained crowns had better marginal adaptation and higher bond strength than those manufactured using lithium disilicate.

Abutment margin levels and residual cement occurrence in cement-retained implant restorations: An observational study

OBJECTIVES

To evaluate the association between different vertical levels of the abutment margin and residual cement prevalence in cement-retained implant restorations with customized abutments.

METHODS

One hundred and nine single-unit cement-retained implant restorations with a screw-access channel were included. The crowns were intraorally cemented on the abutments, and excess cement was removed. The abutment-crown complex was unscrewed, and the abutment-crown complex and peri-implant tissue were photographed. Residual cement presence was recorded by dividing the abutment-crown complex and peri-implant tissue into four quadrants: mesial, distal, buccal, and lingual. The prevalence of residual cement was compared according to the height of the custom abutment margin of the corresponding quadrant. A multilevel model was used for statistical analysis (α = .05).

RESULTS

Cement remnants were discovered on 72.48% of the dental implants. When the restoration quadrants were compared, cement remnants were present on 51.38%, 39.45%, 20.18%, and 17.43% of the mesial, distal, buccal, and lingual surfaces, respectively (p < .01). Regarding the abutment margin level, cement residues were found in 60.22% and 61.4% of the 0.5 mm subgingival and ≥1 mm subgingival margin groups, respectively, which were significantly more than those in the supragingival (23.65%) and equigingival (26.59%) margin groups (p < .01). After adjustment for confounding factors, the adjusted odds ratio (with 95% confidence interval) for residual cement in the subgingival margin groups was 3.664 (1.71, 7.852) when compared to the supragingival and equigingival margin groups.

CONCLUSIONS

The risk of residual cement occurrence was 3.66-fold higher with a subgingival abutment margin than with supragingival and equigingival abutment margins.

The effect of different cleansing methods for removing temporary cement on the tensile bond force of permanently cemented implant-supported metal copings: An in vitro study

Objectives

Complete cleaning of temporary cement before permanent cementation of cement‐retained implant‐supported prosthesis (CISP) when recementing the crown is critical. This study evaluated the effect of different cleaning methods for removing traces of temporary cement on the final tensile bond force (TBF) of CISP recemented with resin cement.

Materials and Methods

Seventy computer‐aided design/computer‐aided manufacturing metal implant‐supported copings were prepared and distributed into seven groups (N = 10). Copings of six groups (60 samples) were cemented with temporary cement with eugenol and subjected to 5000 thermocycling. After debonding by a universal testing machine, the internal surfaces of the copings were cleaned using one of the six following methods: 1‐an ultrasonic water bath (UW), 2‐sandblasting, then washing with water (SW), 3‐sandblasting and an ultrasonic water bath (SUW), 4‐an ultrasonic isopropyl alcohol bath (UA), 5‐sandblasting, then washing with isopropyl alcohol (SA) or 6‐sandblasting and an ultrasonic isopropyl alcohol bath (SUA). Then the subjects were subsequently cemented by dual‐cure self‐adhesive resin cement. In the seventh group (control, N = 10), the copings were cemented by dual‐cure self‐adhesive resin cement without the temporization phase. The TBF was tested using a universal testing machine with a cross‐head speed of 1 mm/min. Two‐way analysis of variance (ANOVA) and post‐hoc Tamhane tests were used for statistical analysis at a significance level of α = .05.

Results

The maximum mean of TBF value was observed in SUA group (845 ± 203 N), and the minimum was observed in the temporary cement group (49 ± 20 N). All groups which were cleaned with isopropyl alcohol showed significantly higher TBF values compared with those cleaned with water.

Conclusions

Cleaning of the inner surface of metal copings after debonding with sandblasting and isopropyl alcohol results in the highest value of TBF by eliminating the effect of remaining eugenol and removing traces of temporary cements.

Assessment of Preload Loss after Cyclic Loading in the OT Bridge System in an “All-on-Four” Rehabilitation Model in the Absence of One and Two Prosthesis Screws

The aim of this study was to evaluate the stability of prosthetic screws after applying cyclic loadings in an “all-on-four” rehabilitation model with the OT Bridge system. The model was tested both with and without anterior screws. Four implant analogues following the “all-on-four” concept were inserted in an edentulous mandibular resin model. An OT Bridge system with a Cr–Co prosthetic framework was fabricated. Depending on the presence or absence of one or two anterior screws on the implant analogues, three groups were created, i.e., Gr.1: three tightening screws, Gr.2: two tightening screws, Control Group: four tightening screws. Each single group underwent subsequent 400,000 cyclic loads, simulating approximately a year of chewing by using a dynamometer machine. This cycle was repeated five times for each group, and preload loss values were evaluated on each prosthetic screw after each cycle. All the data obtained were analyzed by one-way ANOVA and Student’s t-test. No statistically significant differences after intragroup analysis were found. A statistically significant difference within the Gr.1 between the screws in positions 33 and 36, equal to 15.2% (p-value = 0.0176), was found. The OT Bridge seems a useful system to maintain the retention of a prosthesis during mechanical stress conditions even in the absence of one screw in an “all-on-four” rehabilitation. This could represent a good solution to solve the esthetic problem of the screw buccal access hole for fixed solutions.

Esthetic Evaluation and Acceptability of Different Hole Designs on Implant Crowns from the Perspective of Patients and Dentists in China

PURPOSE

Abutment access hole on dental implant crowns may facilitate crown retrieval and reduce cement overflow but present esthetic obstacle for patients. This study aimed to investigate the esthetic evaluation and acceptability of implant crowns with different hole designs from the perspective of patients and dentists.

MATERIALS AND METHODS

Anterior and posterior implant zirconia crowns were fabricated into three types: no hole (NH), 1 mm micro hole (MH), and 2.5 mm regular hole (RH). The NH crown was set as the control, and the anterior and posterior crowns with MH and RH were evaluated. The subjects, who were recruited randomly, were comprised of lay patients (n=60) and professional dentists (n=30). All subjects were invited to evaluate the esthetic performance of MH and RH crowns on a Visual Analog Scale (VAS), rate them from 0 to 10, state their acceptability of these crowns, and label them as acceptable and unacceptable.

RESULTS

The ANOVA analysis of the VAS esthetic evaluation showed that the size of the hole, the position of the teeth, and the professional background of the subject significantly and independently affected esthetic perception. Crowns with MH in the posterior position had higher esthetic scores and acceptability compared with crowns with RH in the anterior position, and dentists tended to show higher acceptance and better esthetic rating for crowns with holes compared with lay patients.

CONCLUSION

The hypothesis that patients and dentists hold similar esthetic evaluations or acceptability towards implant crown hole designs was rejected. Lay patients had a lower tolerance for venting holes than dentists. Crowns with 1 mm micro holes were more recommendable than crowns with regular abutment access holes from the point of view of satisfying patients' esthetic needs.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

This comprehensive review of the 2019 restorative dental literature is offered to inform busy dentists regarding remarkable publications and noteworthy progress made in the profession. Developed by the Scientific Investigation Committee of the American Academy of Restorative Dentistry, each author brings discipline-specific expertise to 1 of 8 sections of the report: (1) prosthodontics; (2) periodontics, alveolar bone, and peri-implant tissues; (3) implant dentistry; (4) dental materials and therapeutics; (5) occlusion and temporomandibular disorders; (6) sleep-related breathing disorders; (7) oral medicine and oral and maxillofacial surgery; and (8) dental caries and cariology. The report targets important information likely to influence day-to-day dental treatment decisions. Each review is not intended to stand alone but to update interested readers so that they may visit source material when greater detail is desired. As the profession moves toward evidence-based clinical decision-making, an incredible volume of potentially valuable dental literature continues to increase. It is the intention of this review and its authors to provide assistance in negotiating the extensive dental literature published in 2019. It is our hope that readers find this work useful in the clinical management of dental patients.