Is the clinical performance of internal conical connection better than internal non-conical connection for implant-supported restorations? A systematic review with meta-analysis of randomized controlled trials

Microgap Formation in Conical Implant-Abutment Connections Under Oblique Loading: Influence of Cone Angle Mismatch Through Finite Element Analysis

OBJECTIVES

This study evaluated different designs of the conical implant-abutment connection (IAC) and their resistance to microgap formation under oblique loads as specified by the ISO standard for testing dental implants. Also evaluated was the effect of deviations from the ISO specifications on the outcomes.

METHODS

Finite element analysis was conducted to compare the microgap formation and stress distribution among three conical IAC designs (A, B, and C) in two loading configurations: one compliant with ISO 14801 and one with a modified load adaptor (non-ISO). The different IAC designs varied in the taper, diameter, and cone height. The cone angle mismatch (Cam) between the implant and abutment was considered. A torque of 20 Ncm and oblique loads (up to 400 N) were simulated.

RESULTS

The stresses produced by the screw-tightening torque varied among the different IAC designs. The contact height was approximately 0.3 mm for Designs A and B, and less than 0.03 mm for Design C. Under oblique loads, Design A maintained IAC sealing without gap formation up to 400 N. With the ISO adaptor, gaps appeared in Design B at 300 N and in Design C at 90 N. The non-ISO adaptor resulted in gap formation at 160 N for Design B and at 50 N for Design C.

CONCLUSIONS

The IAC design and cone angle mismatch significantly influenced microgap formation, with some designs showing zero gaps even when the oblique load reached 400 N. The non-ISO adaptor increased gap formation in IACs B and C.

The impact of a 1 mm interimplant distance on the interproximal crestal bone height: a case report with a 10-year follow-up and literature review

BACKGROUND

Between adjacent dental implants, an interimplant distance (IID) of at least 3 mm has been recommended to avoid resorbing the interproximal crestal bone. The effect of a 2 mm IID on crestal bone loss has been investigated but the literature is scarce when it comes to an IID of 1 mm. There is a need to document such clinical situations when they occur and elucidate if such a narrow IID is deleterious or not to the interproximal crest. The present case deals with an IID of 1 mm in the premolar area where, for the first time, the fate of an interimplant crest is reported after a 10-year follow-up.

CASE PRESENTATION

A 57-year-old patient attended with 2 hopeless maxillary premolars. The mesio-distal space available for implant rehabilitation was too narrow to receive standard diameter implants and keep an inter-implant distance (IID) of 3 mm as recommended by accepted guidelines. A protocol of immediate implant placement and provisionalization involving 2 implants of Ø 3.5 mm was implemented; placement in the extraction sockets resulted in an IID of 1 mm. After 3 months of healing the final prosthesis was delivered; the patient has been followed for 10 years now. Surprisingly, the findings showed that the interimplant crest was maintained 1.40 mm coronal to the shoulder of the neck of the implants. Bone completely filled the space between the prosthetic concave abutments and the interproximal papilla was closing the embrasure. The literature reports only 2 experimental studies involving a 1 mm IID; both showed that this did not lead to the resorption of the interproximal bone.

CONCLUSIONS

Unexpectedly, the present case with an IID of 1 mm did not lead to the resorption of the interproximal bone after 10 years. It is speculated that the reason for that is due to the implants displaying an internal conical connection, the platform-switching feature, concave abutments and subcrestal placement. The fate of the interproximal crest of implants placed with an IID of 1 mm lacks scientific evidence. More studies are warranted to elucidate this question in order to propose the best implant treatment in cases displaying a limited mesio-distal space.

3D analysis of soft tissue dimensional changes after dental implant placement with butt-joint vs. conical connection: a 12-month randomized control trial

PURPOSE

to quantify the soft tissue dimensional changes after single-gap implant placement, during healing abutment and crown delivery phase for butt-joint and conical implant-abutment connection type.

METHODS

forty patients were enrolled in the study and received randomly allocated implants with butt-joint and conical implant-abutment connection type. A standard healing abutment was placed after 6 months for two weeks. The definitive screw retained full-ceramic crowns were manufactured in a digital workflow. The soft tissue profile was digitized using IOS on following stages: pre-op, immediately, two, 7 and 14 days post-op, pre-exposure, immediately after exposure, two weeks after exposure (pre-delivery), immediately after crown delivery, 6 and 12 months after delivery. The intraoral scans were matched in the metrology software (Geomagic Control X). The mean maximum and mean average differences in mm were gathered to assess the soft tissues change. Various anamnesis parameters have been taken into account.

RESULTS

the conical connection implant system exhibited more soft tissue gain and less recession, compared to the butt-joint connection type within the 12 months follow-up period. A higher loss of soft tissue was observed in the distal papilla than in the mesial one.

CONCLUSIONS

the implant-abutment connection type may influence the reaction of peri-implant soft tissue within the 12 months follow-up period.

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

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of select 2023 dental literature to briefly touch on several topics of interest to modern restorative dentistry. Each committee member brings discipline-specific expertize in their subject areas that include (in order of appearance here): prosthodontics; periodontics, alveolar bone, and peri-implant tissues; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine, oral and maxillofacial surgery, and oral radiology; and dental caries and cariology. The authors have focused their efforts on presenting information likely to influence the daily dental treatment decisions of the reader with an emphasis on current innovations, new materials and processes, emerging technology, and future trends in dentistry. With the overwhelming volume of literature published daily in dentistry and related disciplines, this review cannot be comprehensive. Instead, its purpose is to inform and update interested readers and provide valuable resource material for those willing to subsequently pursue greater detail on their own. Our intent remains to assist colleagues in navigating the tremendous volume of newly minted information produced annually. Finally, we hope readers find this work helpful in providing evidence-based care to patients seeking healthier and happier lives.

Most meta-analyses in oral health do not have conclusive and robust results

OBJECTIVES

In meta-analyses with few studies, between-study heterogeneity is poorly estimated. The Hartung and Knapp (HK) correction and the prediction intervals can account for the uncertainty in estimating heterogeneity and the range of effect sizes we may encounter in future trials, respectively. The aim of this study was to assess the reported use of the HK correction in oral health meta-analyses and to compare the published reported results and interpretation i) to those calculated using eight heterogeneity estimators and the HK adjustment ii) and to the prediction intervals (PIs).

METHODS

We sourced systematic reviews (SRs) published between 2021 and 2023 in eighteen leading specialty and general dental journals. We extracted study characteristics at the SR and meta-analysis level and re-analyzed the selected meta-analyses via the random-effects model and eight heterogeneity estimators, with and without the HK correction. For each meta-analysis, we re-calculated the overall estimate, the P-value, the 95 % confidence interval (CI) and the PI.

RESULTS

We analysed 292 meta-analyses. The median number of primary studies included in meta-analysis was 8 (interquartile range [IQR] = [5.75-15] range: 3-121). Only 3/292 meta-analyses used the HK adjustment and 12/292 reported PIs. The percentage of statistically significant results that became non-significant varied across the heterogeneity estimators (7.45 %- 16.59 %). Based on the PIs, >60 % of meta-analyses with statistically significant results are likely to change in the future and >40 % of the PIs included the opposite pooled effect.

CONCLUSIONS

The precision and statistical significance of the pooled estimates from meta-analyses with at least three studies is sensitive to the HK correction, the heterogeneity variance estimator, and the PIs.

CLINICAL SIGNIFICANCE

Uncertainty in meta-analyses estimates should be considered especially when a small number of trials is available or vary notably in their precision. Misinterpretation of the summary results can lead to ineffective interventions being applied in clinical practice.

Influence of prosthetic index structures and implant materials on stress distribution in implant restorations: a three-dimensional finite element analysis

BACKGROUND

Mechanical complications affect the stability of implant restorations and are a key concern for clinicians, especially with the frequent introduction of new implant designs featuring various structures and materials. This study evaluated the effect of different prosthetic index structure types and implant materials on the stress distribution of implant restorations using both in silico and in vitro methods.

METHODS

Four finite element analysis (FEA) models of implant restorations were created, incorporating two prosthetic index structures (cross-fit (CF) and torc-fit (TF)) and two implant materials (titanium and titanium-zirconium). A static load was applied to each group. An in vitro study using digital image correlation (DIC) with a research scenario identical to that of the FEA was conducted for validation. The primary strain, sensitivity index, and equivalent von Mises stress were used to evaluate the outcomes.

RESULTS

Changing the implant material from titanium to titanium-zirconium did not significantly affect the stress distribution or maximum stress value of other components, except for the implant itself. In the CF group, implants with a lower elastic modulus increased the stress on the screw. The TF group showed better stress distribution on the abutment and a lower stress value on the screw. The TF group demonstrated similar sensitivity for all components. DIC analysis revealed significant differences between TF-TiZr and CF-Ti in terms of the maximum (P < 0.001) and minimum principal strains (P < 0.05) on the implants and the minimum principal strains on the investment materials in both groups (P < 0.001).

CONCLUSIONS

Changes in the implant material significantly affected the maximum stress of the implant. The TF group exhibited better structural integrity and reliability.

Advanced Antimicrobial and Anti-Infective Strategies to Manage Peri-Implant Infection: A Narrative Review

Despite reductions in bacterial infection and enhanced success rate, the widespread use of systemic antibiotic prophylaxis in implant dentistry is controversial. This use has contributed to the growing problem of antimicrobial resistance, along with creating significant health and economic burdens. The basic mechanisms that cause implant infection can be targeted by new prevention and treatment methods which can also lead to the reduction of systemic antibiotic exposure and its associated adverse effects. This review aims to summarize advanced biomaterial strategies applied to implant components based on anti-pathogenic mechanisms and immune balance mechanisms. It emphasizes that modifying the dental implant surface and regulating the early immune response are promising strategies, which may further prevent or slow the development of peri-implant infection, and subsequent failure.

Conometric Connection for Implant-Supported Crowns: A Prospective Clinical Cohort Study

BACKGROUND

Traditional screw or cemented connections in dental implants present limitations, prompting the exploration of alternative methods. This study assesses the clinical outcomes of single crowns and fixed partial prostheses supported by conometric connections after one year of follow-up.

METHODS

Twenty-two patients received 70 implants, supporting 33 rehabilitations. Biological responses and prosthodontic complications were evaluated at baseline, 6 months, and 12 months.

RESULTS

All implants exhibited successful osseointegration, with no losses or peri-implant inflammation. Marginal bone levels showed minimal changes, well below pathological thresholds. The difference in marginal bone loss (MBL) was -0.27 ± 0.79 mm between T0 and T1, and -0.51 ± 0.93 mm between T0 and T2. No abutment screw loosening or crown chipping occurred. However, coupling stability loss was observed in nine cases.

CONCLUSIONS

The conometric connection demonstrated successful integration and minimal complications after one year. This alternative shows promise, particularly in simplifying handling and improving marginal adaptation. Further research with larger sample sizes and longer follow-up is warranted for comprehensive validation.

Survival and complication rates of two dental implant systems supporting fixed restorations: 10-year data of a randomized controlled clinical study

OBJECTIVES

To compare clinical, radiographic, biological and technical long-term outcomes of two types of dental implants over a period of 10 years.

MATERIALS AND METHODS

Ninety-eight implants were placed in 64 patients, randomly allocated to one of two manufacturers (AST and STM). All implants were loaded with fixed restorations. Outcome measures were assessed at implant insertion (Ti), at baseline examination (TL), at 1, 3, 5, 8 and 10 (T10) years. Data analysis included survival, bone level changes, complications and clinical measures.

RESULTS

Re-examination was performed in 43 patients (23 AST and 20 STM) at 10 years. The implant level analysis was based on 37 (AST) and 32 (STM) implants. Survival rates of 100% were obtained for both groups. The median changes of the marginal bone levels between baseline and T10 (the primary endpoint) amounted to a loss of 0.07 mm for group AST and a gain of 0.37 mm for group STM (intergroup p = 0.008). Technical complications occurred in 27.0% of the implants in group AST and in 15.6% in group STM. The prevalence of peri-implant mucositis was 29.7% (AST) and 50.1% (STM). The prevalence of peri-implantitis amounted to 0% (AST) and 6.3% (STM).

CONCLUSIONS

Irrespective of the implant system used, the survival rates after 10 years were high. Minimal bone level changes were observed, statistically significant but clinically negligible in favor of STM. Technical complications were more frequently encountered in group AST, while group STM had a higher prevalence of peri-implant mucositis.

Different Conical Angle Connection of Implant and Abutment Behavior: A Static and Dynamic Load Test and Finite Element Analysis Study

Dental implants are artificial dental roots anchoring prosthetic restorations to replace natural teeth. Dental implant systems may have different tapered conical connections. Our research focused on the mechanical examination of implant-superstructure connections. Thirty-five samples with 5 different cone angles (24°, 35°, 55°, 75°, and 90°) were tested for static and dynamic loads, carried out by a mechanical fatigue testing machine. Fixing screws were fixed with a torque of 35 Ncm before measurements. For static loading, samples were loaded with a force of 500 N in 20 s. For dynamic loading, the samples were loaded for 15,000 cycles with a force of 250 ± 150 N. In both cases, the compression resulting from load and reverse torque was examined. At the highest compression load of the static tests, a significant difference (p = 0.021) was found for each cone angle group. Following dynamic loading, significant differences (p < 0.001) for the reverse torques of the fixing screw were also shown. Static and dynamic results showed a similar trend: under the same loading conditions, changing the cone angle-which determines the relationship between the implant and the abutment-had led to significant differences in the loosening of the fixing screw. In conclusion, the greater the angle of the implant-superstructure connection, the smaller the screw loosening due to loading, which may have considerable effects on the long-term, safe operation of the dental prosthesis.