Clinical Success of Screw-retained Dental Implants: A Systematic Review.

OBJECTIVE: The objective of the research was to review the literature on clinical evaluation and success of screw-retained dental implants by assessing the marginal bone loss (MBL). METHODS: Online electronic databases such as PubMed/MEDLINE, Google Scholar, and Cochrane Library were searched using appropriate keywords for the last 20 years, dated from January 1, 2000, till August 1, 2021, with a restriction on language. Additional sources like major journals, unpublished studies, conference proceedings, and cross-references were explored. Information curated for data extraction included methodology, population, type of implants used, and duration of follow-up. RESULTS: The PubMed/MEDLINE, Google Scholar, Cochrane Library, and additional sources identified a huge number, out of which 637 search results were screened, out of which 322 were duplicates. The remaining 315 unique studies were screened for the titles and abstracts, and 23 articles were selected for full-text screening. A total of six articles that matched the eligibility criteria were processed for qualitative analysis. CONCLUSION: Despite the uncertain retrievability of screw-retained implant-supported fixed restorations, this treatment option in fixed implant prosthodontics is a reliable and effective choice, especially for implant-supported long-span fixed partial dentures (FPDs), full-arch FPDs, and cantilever FPDs.

Peri-implant mucosal response to implant-supported overdentures: A systematic review and meta-analysis.

OBJECTIVES: To systematically review and evaluate the effects of different types of attachments, implant numbers and loading protocols on the peri-implant mucosa of implant-supported overdentures (ISODs). BACKGROUND: The impact of peri-implant tissue health on the ISOD treatment outcome is unclear, and current evidence is inadequate on this aspect. MATERIALS AND METHODS: A systematic literature search for randomised controlled trials or prospective studies was conducted in indexed databases from 1995 to April 2020. The focused question was as follows: How does the peri-implant mucosa respond to implant-supported or implant-tissue-supported complete overdentures based on different types of attachments, implant numbers, and loading protocols, in terms of clinical outcomes achieved [plaque index (PI), gingival index (GI), probing pocket depth (PD) and bleeding index (BI)]? A random- or fixed-effects model was applied to measure the significance of standardised mean differences (SMD) of PD between the groups. RESULTS: Seventeen studies met the eligibility criteria. The SMD for PD between splinted/bar and unsplinted/stud attachments was 0.10 mm (95% CI: -0.27 to 0.47; P = .60) and between 2- and 4-implant groups was 0.15 mm (95% CI: -0.16 to 0.45; P = .34), which were not statistically significant. Significant difference (P = .003) was observed between immediate/early loading and delayed loading (SMD = 0.46 mm [95% CI: 0.16 to 0.75]). CONCLUSIONS: Probing depth for the immediate loaded implants was significantly higher than for the delayed loading group. No attachment type, implant number or loading protocol seemed to have a clear advantage over the other, in terms of other peri-implant mucosal outcome measures.

Retrospective evaluation of marginal bone loss around implants in a mandibular locator-retained denture using panoramic radiographic images and finite element analysis: A pilot study.

BACKGROUND: The follow-up of the peri-implant marginal bone loss is the most important criterion for the determination of implant success. PURPOSE: The purpose of this study is to measure marginal bone loss using panoramic radiographic images (PRI) of patients treated using a mandibular, two implant-supported, locator-retained denture and to evaluate the compatibility of these findings with those of the finite element analysis (FEA). MATERIALS AND METHODS: The PRI of patients who had a mandibular, two implant-supported, locator-retained denture were assessed, and the mesial and distal marginal bone loss of both right- and left-sided implants was measured. Mandibular and maxillary models, which have the features of bilateral balanced occlusion, were created. The surfaces of the generated models were converted in a computer-aided design model that could be transferred to the FEA software, and the forces were defined on contacts formed in maximum intercuspation, lateral, and protrusive movement position for bilateral balanced occlusion. RESULTS: The bone loss in the mesial and distal regions at the right- and left-sided implants was not statistically significant. Higher stresses were formed on the vestibular side under protrusive movement, on the lingual side under maximum intercuspation, on the distolingual side under left unilateral biting, and on the mesiolingual side under right unilateral biting in the FEA. CONCLUSION: According to FEA, peri-implant bone resorption may be higher in the buccal and palatal regions, implying that panoramic radiographs can be misleading in understanding the amount of peri-implant bone resorption.

Implant-prosthetic rehabilitation after radiation treatment in head and neck cancer patients: a case-series report of outcome.

BACKGROUND: Slovenia has a high burden of head and neck cancer. Patients are mostly treated with surgery followed by radiation therapy. Advanced surgical and prosthodontic techniques have expanded the rehabilitation options. The aim of the study was to review the outcome of implant-prosthetic treatment after radiation therapy. PATIENTS AND METHODS: Twenty irradiated head and neck cancer patients who received a removable implant-supported denture at the University Medical Centre Ljubljana were included in the study. Kaplan-Meier survival analysis, Cox proportional hazard models and logistic regression were used to assess the implant survival and success rate. RESULTS: Twenty patients had 100 implants inserted. The estimated implant survival rate was 96% after 1 year and 87% after 5 years. Failures were mostly observed before loading (91.2%). Implants inserted in the transplanted bone were significantly more likely to fail. Out of 89 implants supporting the dentures, 79 implants (88.7%) were successful, meaning that they were functionally loaded and exhibited no pain, radiolucency or progressive bone loss. Prosthetic treatment was significantly less successful in older patients. The attachment system and the number of implants did not have a statistically significant influence on the success rate. CONCLUSIONS: Implant-supported dentures have been shown to be a reliable treatment modality after head and neck cancer surgery and radiation therapy. Possible early failures should be communicated with the patients.

Long-term success of dental implant-supported dentures in postirradiated patients treated for neoplasms of the maxillofacial skeleton: a retrospective study.

OBJECTIVES: The reconstruction of oral function in irradiated patients with craniofacial tumors is a significant challenge. The aim of this study was to detect long-term success of dental implant-supported dentures in postirradiated patients treated for neoplasms of the maxillofacial skeleton. MATERIALS AND METHODS: From 2004 to 2011, 36 irradiated patients underwent oral function reconstruction using implant-supported prostheses. Bone augmentation was completed using vascularized bone grafts in 22 patients. Fourteen patients were treated by hyperbaric oxygen therapy (HBO). A total of 198 dental implants were used in jaw rehabilitation. After loading, implant success rates, biological and prosthetic complications, patient satisfaction, and psychological changes were recorded. RESULTS: Bone augmentation of the jaw was successful and vascularized grafts provided an additional vascular supply in compromised irradiated tissue. Rehabilitation was successful in all of the patients after loading. Thirty-eight dental implants failed, and 35 implants were removed. The success rate of the implants was 93.6 % for 10 years after loading. It was not a significant difference in implant success rate between the HBO group and the other groups. The prosthodontic maintenance results and complication rates showed that patients required intervention 0.19 times per year. All patients were satisfied with the oral restoration results. CONCLUSION: The restoration of oral function in radiotherapy patients with tumor resection using implant-supported prostheses is a viable treatment option. CLINICAL RELEVANCE: Either alone or in combination with HBO, dental implant-supported prostheses can be used an effective therapeutic approach for irradiated patients with oral function reconstruction.

Assessment of the stress transmitted to dental implants connected to screw-retained bars using different casting techniques.

Passive fit of the prosthetic superstructure is important to avoid complications; however, evaluation of passive fit is not possible using conventional procedures. Thus, the aim of this study was to check and locate mechanical stress in bar restorations fabricated using two casting techniques. Fifteen patients received four implants in the interforaminal region of the mandible, and a bar was fabricated using either the cast-on abutment or lost-wax casting technique. The fit accuracy was checked according to the Sheffield's test criteria. Measurements were recorded on the master model with a gap-free, passive fit using foil strain gauges both before and after tightening the prosthetic screws. Data acquisition and processing was analyzed with computer software and submitted to statistical analysis (ANOVA). The greatest axial distortion was at position 42 with the cast-on abutment technique, with a mean distortion of 450 µm/m. The lowest axial distortion occurred at position 44 with the lost-wax casting technique, with a mean distortion of 100 µm/m. The minimal differences between the means of axial distortion do not indicate any significant differences between the techniques (P = 0.2076). Analysis of the sensor axial distortion in relation to the implant position produced a significant difference (P < 0.0001). Significantly higher measurements were recorded in the axial distortion analysis of the distal sensors of implants at the 34 and 44 regions than on the mesial positions at the 32 and 42 regions (P = 0.0481). The measuring technique recorded axial distortion in the implant-supported superstructures. Distortions were present at both casting techniques, with no significant difference between the sides.

Influência na retenção de coroas cimentadas sobre implantes com e sem orifício ao parafuso / Retention influence of crowns cemented on implants with and without screw access

Introdução: na Implantodontia, o mecanismo de retenção da restauração ao intermediário pode ser cimentado ou parafusado. Os cimentados apresentam difícil reversibilidade, entretanto, o uso de um orifício de acesso ao parafuso permitiria tal reversibilidade, aliando o baixo custo dos componentes à reversibilidade das próteses aparafusadas. Objetivo: o objetivo desse trabalho é avaliar a resistência à tração de próteses sobre implantes cimentadas, possuindo ou não acesso ao parafuso do intermediário. Métodos: foram confeccionados 16 corpos de prova (análogos de implantes regulares, intermediários “Tiprep” (Bionnovation, São Paulo/SP) e 16 coroas totais metálicas, sendo que 8 eram coroas convencionais para controle (G1) e outras 8 coroas foram construídas com um orifício de acesso ao parafuso, transpassando o metal, sendo o grupo experimental (G2). As coroas foram cimentadas com RelyX U100 (3M ESPE) e os espécimes do G2 tiveram a abertura de acesso ao canal restaurado com resina composta fotopolimerizável Filtek Supreme XT (3M ESPE). Os espécimes foram submetidos a teste de tração em máquina de ensaio universal 24 horas após a cimentação. Resultados: o G1 apresentou média de 191,075N; o G2 161,280N. Aplicado o teste não-paramétrico de Kolmogorov-Smirnov, a variável dependente seguiu a distribuição normal (p=0,923) e, com o teste t de Student, verificou-se não existir diferença estatisticamente significativa (p=0,353) entre os grupos. Foi considerado o nível de significância de 5%, p=0,05. Conclusões: com base nas análises, pode-se afirmar que o orifício de acesso ao parafuso não compromete ou diminui a retenção das coroas.

Introduction: In Implantology, the retention mechanism of the restoration to the intermediate can be cemented or screwed. The cemented one present difficult reversibility, however, the use of an access hole to the screw would allow such reversibility, combining the low cost of the components to the reversibility of the screwed prosthesis. Objective: The aim of this study is to evaluate the shear bond strength of prostheses on cemented implants, having or not access to the intermediate screw. Methods: Sixteen specimens were prepared (similar to regular implants, "Tiprep" intermediates (Bionnovation, São Paulo/ SP) and 16 metal crowns, of which 8 were for conventional crowns control (G1) and another 8 crowns were made with an access hole to the screw, trespassing the metal, being the experimental group (G2).The crowns were cemented with RelyX U100 (3M ESPE) and the specimens from the G2 had the opening of the channel restored with light cured composite resin Filtek Supreme XT (3M ESPE). Specimens were subjected to tensile test in a universal testing machine 24 hours after cementation. Results: G1 showed average of 191.075 N; G2 showed 161.280 N. Applied the nonparametric Kolmogorov-Smirnov test, the dependent variable followed normal distribution (p = 0.923) and, with the Student t-test, there was no difference statistically significant (p = 0.353) between groups. It was considered the level of significance of 5%, p = 0.05. Conclusions: Based on the analysis, it can be stated that the access hole to the screw does not compromise or decrease the retention of crowns.

A oclusão nas próteses totais implantossuportadas mediatas e imediatas / Occlusion in mediate and immediate implant-supported dentures

A reabilitação de indivíduos totalmente desdentados, desde os primordios conceitos e fundamentos da reabilitação oclusal, tem sido um grande desafio para os profissionais da Odontologia. Porém, essa filosofia tornou-se otimizada pelas próteses totais fixas implantossuportadas, denominadas próteses protocolo, representando uma modalidade clinicamente previsível no âmbito da Odontologia moderna. Contudo, esse protocolo terapêutico tradicional requer um tempo de cicatrização óssea e consequente reabilitação prolongados, o que fundamentou a proposta do carregamento imediato dos implantes, que apresenta como vantagem principal a reabilitação funcional e estética dos pacientes em um período significativamente diminuto. O propósito do presente artigo é discutir, baseado na literatura contemporânea, os fundamentos biomecânicos e funcionais de oclusão aplicados às próteses do tipo protocolo com carregamento mediato e imediato, proporcionando evidências clínicas que visem à longevidade das reabilitações orais envolvidas nessa modalidade terapêutica. Pré-requisitos como: boa qualidade óssea, excelente estabilidade primária, adequado número de implantes, esplintagem rígida e, principalmente, o controle e o domínio dos fundamentos biomecânicos da oclusão estática e dinâmica são imprescindíveis para a previsibilidade e longevidade desses tratamentos.

Rehabilitation of edentulous patients has been a challenge for professionals since the primary concepts and fundaments of occlusal rehabilitation. However, this philosophy has been improved by implant-supported fixed dentures that represent a predictable clinical modality on modern dentistry. Nevertheless, considering that the traditional protocol requires a long period for bone healing and definitive rehabilitation, immediate loading of implants has been advantageous for functional and esthetic rehabilitation of patients in a reduced period. The aim of this study is to discuss the biomechanical and functional fundaments of occlusion for implant-supported fixed dentures with mediate and immediate loading to provide clinical evidences for longevity of this treat ment modality based on the current literature. According to this, some prerequisites as proper bone quality, excellent primary stability, sufficient number of implants, rigid splinting, and control and mastering of biomechanical fundamentals of static and dynamic occlusion are mandatory for treatment predictability and longevity.

Influence of prosthetic screw material on joint stability in passive and non-passive implant-supported dentures.

OBJECTIVES: This study evaluated the influence of prosthetic screw material on joint stability in implantsupported dentures at two levels of fit. METHODS: Ten mandibular implant-supported dentures were fabricated. Twenty cast models were fabricated using these dentures. Four groups (n=10) were tested, according to the vertical fit of the dentures [passive and non-passive] and prosthetic screw materials [titanium (Ti) or gold (Au) alloy]. The one-screw test was performed to quantify the vertical misfits using an optic microscope. The loosening torque for the prosthetic screws was measured 24 hours after the tightening torque (10 Ncm) using a digital torque meter. Data were analyzed by two-way ANOVA and Tukey's test (alpha=0.05). RESULTS: Overall, dentures with passive fit and Ti screws resulted in significantly higher loosening torque of the prosthetic screws (p<0.05). No significant interaction was found between fit level and screw material (p=0.199). The prosthetic screw material and fit of implant-supported dentures have an influence on screw joint stability. Ti screws presented higher joint stability than Au screws and minimum of misfit should be found clinically to improve the mechanical behavior of the screw joint.

Prosthetic laboratory influence on the vertical misfit at the implant/UCLA abutment interface

An inadequate fit at the abutment/implant interface can generate mechanical and biological problems. The laboratorial stages could induce misfit in such interface when the castable UCLA abutment type is used. The purpose of this study was to comparatively evaluate the performance of three prosthetic laboratories (Labs A, B and C) by vertical fit analysis of castable UCLA abutments on the casting and soldering stages of the same prosthesis. Four fixed prostheses were built by each laboratory using castable UCLA abutments. The evaluation was made by scanning electron microscopy under 500x magnification in the mesial and distal regions of each element of the prosthesis, totalizing 24 measurements per laboratory. The results were analyzed statistically by Kruskal-Wallis test (p<0.05). In the casting process, the values presented by the laboratories differed significantly to each other (p=0.004). After soldering, the values presented by the laboratories showed no significant difference (p=0.948). It may be concluded that the fit values obtained in the casting stage of UCLA abutments can be influenced when processed by different laboratories, and that conventional soldering itself increased the degree of framework misfit, regardless of which laboratory made it.

Um ajuste inadequado na interface pilar/implante pode gerar problemas mecânicos e biológicos. Etapas laboratoriais podem induzir a um desajuste em tal interface quando pilares do tipo UCLA calcináveis são utilizados. Este estudo propôs-se a avaliar comparativamente o desempenho de três laboratórios de prótese dentária (Labs A, B e C) pela análise do ajuste vertical de pilares UCLA calcináveis durante o processo de fundição e solda de uma mesma prótese. Quatro próteses fixas foram confeccionadas por cada laboratório utilizando pilares do tipo UCLA calcinável. A avaliação foi feita em microscopia eletrônica de varredura sob aumento de 500 x nas faces mesial e distal de cada elemento da prótese, totalizando 24 medidas por laboratório. Os resultados foram analisados estatisticamente pelo teste de Kruskal-Wallis (p<0,05). Na fundição, os valores apresentados pelos laboratórios diferiram estatisticamente (p=0,004). Após a análise da solda, os valores não apresentaram diferença significante entre os laboratórios (p=0,948). Pode-se concluir que os valores de ajuste obtidos no estágio de fundição de pilares UCLA, podem ser influenciados quando processados por diferentes laboratórios e que o processo de solda convencional, por si só, aumenta o grau de desajuste da infra-estrutura, independente do laboratório que a realizou.