Does increasing vertical dimension of occlusion in centric relation affect muscular activity? An electromyographic study.

OBJECTIVE: In many esthetic treatments, clinicians may consider the option to modify the maxillo mandibular position. A raise of the vertical dimension of occlusion (VDO) may help restore esthetics, increase the space for dental materials, and reduce the invasiveness of dental procedures. Traditionally, VDO increases are done by using the centric relation (CR) position. Despite a long history of use, the neuromuscular effects of different maxillo mandibular relations are not fully studied. The aim of this study was to investigate the effect of alterations of maxillo-mandibular relation from maximal intercuspal position (MIP) to a raised VDO CR position on jaw-elevator muscle activity. MATERIALS AND METHODS: Fifteen healthy individuals were asked to carry out maximal voluntary clenching (MVC) in MIP and in CR on individual splints. Electromyographic (EMG) activity of the masseter and anterior temporalis muscles was assessed in µV as the root mean square of the amplitude. Specific indexes and ratios were also computed. Data analyzed in MIP and CR were compared by paired student's t-tests. RESULTS: MVC levels were not negatively affected by a VDO increase in CR position. On the contrary masseter muscles showed a statistically significant increase (p < 0.005). No significant effect on the anterior temporalis was observed. CONCLUSION: These results suggest that no immediate negative effect on maximum voluntary clenching was induced by a VDO increase in CR position. A slight increase observed in EMG clenching levels could be explained by the increase in VDO when clenching on the splint. CLINICAL IMPLICATIONS: The results of this study support the use of CR position as a pragmatic reference position due to the absence of relevant or negative changes in neuromuscular function.

Centric relation-A biological perspective of a technical concept.

BACKGROUND: Few terms and concepts have been so extensively debated in dentistry as the words 'centric relation' (CR). Debates involve its biological, diagnostic and therapeutic usefulness. METHODS: A review of the literature on the current concepts on CR as a diagnostic or therapeutic aid in dentistry was provided. Clinical trials assessing the superiority of one CR recording method over the others to identify patients with temporomandibular disorders (diagnostic use) or to manage patients with prosthodontic or orthodontic needs (therapeutic use) were tentatively included. RESULTS: Due to the absence of literature addressing either of the above targets, a comprehensive overview was provided. The diagnostic use of CR as a reference position to identify the correct position of the temporomandibular joint condyle within the glenoid fossa is not supported and lacks anatomical support. From a therapeutic standpoint, the use of CR can be pragmatically useful in prosthodontics as a maxillo-mandibular reference position when occlusal re-organization is warranted and/or when the position of maximum intercuspation is no longer available. CONCLUSIONS: The derived occlusal goals from a diagnostic misuse of CR are generally the result of circular reasoning, that is a technique is based on the recording of a certain condylar position that is believed to be 'ideal' and the treatment is considered successful when such position is shown by the specific instrument that was manufactured for that purpose. The term 'Centric Relation' might be replaced with the term 'Maxillo-Mandibular Utility Position'.

A patient presentation: Planning and executing a difficult case in a full digital workflow.

OBJECTIVE: In patients requiring extensive tooth replacement, including a change of VDO and/or a new orientation of the occlusal plane, a fully digital workflow still tends to be considered too much complex to be planned and performed. This clinical report describes a full mouth rehabilitation performed with a full digital approach. CLINICAL CONSIDERATIONS: In a 50-year-old man with several missing teeth in the upper and lower arch, extensive decay on multiple teeth, severe attrition of the anterior teeth, treatment of the upper and lower arches was performed with dental implants, crowns and veneers. All prosthodontic therapy was realized with full monolithic ceramic materials (zirconia and lithium disilicate). The combination of digital information and monolithic materials enabled the clinician, the dental laboratory technician and the patient, to communicate effectively during treatment planning and to use the combination of digital workflow and monolithic materials to simplify the steps of treatment of a difficult case. CONCLUSIONS: The combination of full digital workflow with full monolithic restorations in a full mouth rehabilitation allows a simplification of every clinical and lab step in a typically complex treatment.

The Relationships Between Tooth-Supported Fixed Dental Prostheses and Restorations and the Periodontium.

PURPOSE: To search the literature and to critically evaluate the findings on the periodontal outcomes of restorations and tooth-supported fixed prostheses. MATERIALS AND METHODS: PubMed was searched according to a systematic methodology, previously reported, but updated to include a larger database. Filters applied were: Case reports, clinical trial, review, guideline, randomized controlled trial, meta-analysis, systematic reviews, and English. A narrative review was then synthesized to discuss periodontal outcomes related to restorations and tooth-supported fixed prostheses. Relevant data was organized into four sections: Direct restorations, indirect restorations, biologic width or supracrestal tissue attachment and tooth preparation/finish line design. RESULTS: While increased gingival index, bleeding on probing, probing depth and clinical attachment loss have been associated with subgingival restorations, intracrevicular margins do not cause periodontal diseases. Inflammation and bone loss occur, for both direct and indirect restorations, only with large overhangs. Different restorative materials are associated with different clinical responses when placed in the gingival sulcus or within the epithelial and connective tissue attachments. When the connective tissue attachment is removed, histological changes occur causing its apical shift and subsequent re-establishment. Gingival displacement during impression procedures can cause gingival recession. Emergence profile can have a range of values, not associated with periodontal diseases. Periodontal response appears to be clinically not different when compared among different finish line designs. CONCLUSIONS: Contemporary procedures and materials used for the placement and fabrication of tooth-supported restorations and fixed prostheses are compatible with periodontal health when adequate patient education and motivation in self-performed oral hygiene are present. Periodontal diagnostic criteria should be thoroughly reviewed before fixed restorative treatments are planned and executed.

Metal-free materials for fixed prosthodontic restorations.

BACKGROUND: Fixed prosthodontic treatment (crowns, fixed dental prostheses (FDPs), complete arch prostheses) involves the use of several different materials to replace missing tooth structure. Traditionally full metal or metal frameworks veneered with ceramic (metal-ceramic (MC)) have been used. In recent years several different metal-free systems have become available to clinicians and patients. In general, metal-free restorations should allow practitioners to better reproduce natural tooth colour, avoiding shortcomings of MC restorations. The comparative in service clinical performance of fixed prosthodontic treatments of different materials is unclear. OBJECTIVES: To assess the effects of metal-free materials for prosthodontic restorations compared to metal-ceramic or other conventional all-metal materials. SEARCH METHODS: Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (searched 3 May 2017), Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 4) in the Cochrane Library (searched 3 May 2017), MEDLINE Ovid (1946 to 3 May 2017), and Embase Ovid (1980 to 3 May 2017). The US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials (searched 3 May 2017). No restrictions were placed on the language or date of publication when searching the electronic databases. SELECTION CRITERIA: Randomised controlled trials (RCTs) in which the clinical performance of metal-free fixed prosthodontic restorations was compared with metal-ceramic (MC) or other conventional restorations in adult patients requiring prosthodontic treatment. RCTs in which the clinical performance of different kinds of metal-free systems were compared among themselves were also considered. DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane. Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted independently and in duplicate. Trial authors were contacted for missing information. Available results for the outcomes of interest of the systematic review of the studies included were tabulated as they could not be included in a formal meta-analysis. MAIN RESULTS: Nine trials involving a total of 448 participants were included. We judged two trials to be at unclear risk of bias and seven to be at high risk of bias. The majority of items of risk of bias were evaluated to be at unclear or high risk level in more than 50% of the included trials. Each trial except two was addressing a different type of intervention. All evidence was rated as being of very low quality due to problems with risk of bias and imprecision of results, the latter being due to very small sample sizes, low event rates, 95% confidence intervals including the possibility of benefit for both the test and control groups, or combinations of these problems. This means that we are very uncertain about all of the results presented in this review.One trial compared metal-free single crowns (full contour zirconia) to cast gold single crowns in 224 participants and found insufficient evidence of a difference in failure rate after one year, but after five years there was some evidence of a benefit for the gold crowns. There was insufficient evidence of a difference for crown complications at either time of assessment.One trial compared three-unit metal-free FDPs (lithium disilicate) to three-unit metal-ceramic FDPs in 37 participants. There was insufficient evidence of a difference in bridge failure at one and six years, but some evidence of a benefit for the lithium disilicate group in terms of bridge complications at six years. One trial compared zirconia-ceramic FDPs to metal-ceramic FDPs in 34 participants but found insufficient evidence of a difference in bridge failures (i.e. no failures in either treatment group), bridge complications or patients' aesthetic evaluation at any time of assessment up to three years.One trial compared metal-free cantilevered FDPs to metal-ceramic cantilevered FDPs in 21 participants. There was insufficient evidence of a difference for any primary outcome: bridge failures (i.e. no failures in either treatment group), bridge complications, or patients' aesthetic evaluation at any time of assessment up to three years.One trial compared metal-free implant-supported screw retained single crowns (zirconia veneered with feldspathic ceramic) to metal-ceramic implant-supported screw-retained single crowns in 20 participants. There was insufficient evidence of a difference for any primary outcome: crown failures (i.e. no failures in either treatment group), crown complications, or satisfaction/aesthetic evaluation at any time of assessment up to two years.Two trials compared metal-free implant abutments (zirconia) to metal implant abutments both supporting single crowns in 50 participants. There was insufficient evidence of a difference in abutment failure at one year.One trial compared metal-free implant-supported FDPs made of two different types of zirconia ceramic in 18 participants. There was insufficient evidence of a difference in failures at any time of assessment up to 10 years (i.e. no failures in either treatment group). There was some evidence of a benefit for the zirconia-toughened alumina group in terms of complications (chipping).One trial compared metal-free tooth-supported FDPs made with two different veneering techniques (pressed versus layered) in 40 participants. There was insufficient evidence of a difference for failures (i.e. no failures in either treatment group) or complications at any time of assessment up to three years. AUTHORS' CONCLUSIONS: There is insufficient evidence to support or refute the effectiveness of metal-free materials for fixed prosthodontic treatment over metal-ceramic or other type of standard restorations. The overall quality of existing evidence was very low, therefore great caution should be exercised when generalising the results of the included trials. Until more evidence becomes available clinicians should continue to base decisions on which material to use for fixed prosthodontic treatment on their own clinical experience, whilst taking into consideration the individual circumstances and preferences of their patients. There is urgent need of properly designed RCTs.

Prosthodontic planning in patients with temporomandibular disorders and/or bruxism: A systematic review.

STATEMENT OF PROBLEM: The presence of temporomandibular disorders (TMDs) and/or bruxism signs and symptoms may present multifaceted concerns for the prosthodontist. PURPOSE: The purpose of this systematic review was to evaluate the relationship between prosthetic rehabilitation and TMDs and bruxism. MATERIAL AND METHODS: Three research questions were identified based on different clinical scenarios. Should prosthodontics be used to treat TMD and/or bruxism? Can prosthodontics cause TMDs and/or bruxism? How can prosthodontics be performed (for prosthetic reasons) in patients with TMDs and/or bruxism? A systematic search in the PubMed database was performed to identify all randomized clinical trials (RCTs) comparing the effectiveness of prosthodontics with that of other treatments in the management of TMDs and/or bruxism (question 1); clinical trials reporting the onset of TMDs and/or bruxism after the execution of prosthetic treatments in healthy individuals (question 2); and RCTs comparing the effectiveness of different prosthodontics strategies in the management of the prosthetic needs in patients with TMDs and/or bruxism (question 3). RESULTS: No clinical trials of the reviewed topics were found, and a comprehensive review relying on the best available evidence was provided. Bruxism is not linearly related to TMDs, and both of these conditions are multifaceted. Based on the diminished causal role of dental occlusion, prosthetic rehabilitation cannot be recommended as a treatment for the 2 conditions. In theory, they may increase the demand for adaptation beyond the stomatognathic system's tolerability. No evidence-based guidelines were available for the best strategy for managing prosthetic needs in patients with TMDs and/or bruxism. CONCLUSIONS: This systematic review of publications revealed an absence of RCTs on the various topics concerning the relationship between TMD and bruxism and prosthodontics. Based on the best available evidence, prosthetic changes in dental occlusion are not yet acceptable as strategies for solving TMD symptoms or helping an individual stop bruxism. Clinicians should take care when performing irreversible occlusal changes in healthy individuals and in patients with TMD and/or bruxism.

Is bruxism a risk factor for dental implants? A systematic review of the literature.

PURPOSE: To systematically review the literature on the role of bruxism as a risk factor for the different complications on dental implant-supported rehabilitations. MATERIAL AND METHODS: A systematic search in the National Library of Medicine's Medline Database was performed to identify all peer-reviewed papers in the English literature assessing the role of bruxism, as diagnosed with any other diagnostic approach (i.e., clinical assessment, questionnaires, interviews, polysomnography, and electromyography), as a risk factor for biological (i.e., implant failure, implant mobility, and marginal bone loss) or mechanical (i.e., complications or failures of either prefabricated components or laboratory-fabricated suprastructures) complications on dental implant-supported rehabilitations. The selected articles were reviewed according to a structured summary of the articles in relation to four main issues, viz., "P" - patients/problem/population, "I" - intervention, "C" - comparison, and "O" - outcome. RESULTS: A total of 21 papers were included in the review and split into those assessing biological complications (n = 14) and those reporting mechanical complications (n = 7). In general, the specificity of the literature for bruxism diagnosis and for the study of the bruxism's effects on dental implants was low. From a biological viewpoint, bruxism was not related with implant failures in six papers, while results from the remaining eight studies did not allow drawing conclusions. As for mechanical complications, four of the seven studies yielded a positive relationship with bruxism. CONCLUSIONS: Bruxism is unlikely to be a risk factor for biological complications around dental implants, while there are some suggestions that it may be a risk factor for mechanical complications.

Malpositioned osseointegrated implants relocated with segmental osteotomies: a retrospective analysis of a multicenter case series with a 1- to 15-year follow-up.

PURPOSE: This multicenter case series evaluates retrospectively the clinical outcomes of malpositioned implants surgically relocated in a more convenient position by segmental osteotomies. MATERIALS AND METHODS: Authors who published, on indexed journals or books, works about malpositioned implant correction by segmental osteotomies were contacted. Five centers, out of 11 selected, accepted to participate in this study. The dental records of patients who underwent implant relocation procedures were reviewed. Implant survival rates were analyzed and a blinded assessor examined clinical photos and periapical radiographs to evaluate esthetic outcome (pink esthetic score [PES]) and changes of marginal bone level over time. Patients were requested to fill a verbal rating scale form about discomfort, compliance, and satisfaction related to the procedure. RESULTS: Fifteen malpositioned implants relocated by segmental osteotomies were followed for a period ranging from 1 to 15 years (mean 6.0 ± 3.9 years). The overall implant survival rate from baseline to the last follow-up visit was 100%. The mean marginal bone loss was 0.36 mm at the 12-month follow-up visit and no relevant further changes were observed at the following examinations. Significant esthetic improvement was recorded at 1-year examination with PES evaluation (p < .0001). Patients' feedback described this procedure as not excessively invasive and uncomfortable, reporting a high final satisfaction rate. CONCLUSIONS: The present study suggests that implant relocation with segmental osteotomies could be an effective alternative method to correct the position of unrestorable malpositioned implants in a single-stage surgery.

Restoration of immediately loaded implants in a minimal number of appointments: a retrospective study of clinical effectiveness.

PURPOSE: The purpose of this study was to assess the clinical effectiveness of an experimental technique versus the conventional method for the fabrication of implant-supported fixed complete dentures. MATERIALS AND METHODS: Between January 2005 and June 2010, edentulous patients who had received rehabilitation by means of nonsegmented fixed implant-supported complete dentures were identified from the pool of individuals treated at Eastman Institute for Oral Health, University of Rochester. Data collection consisted of a chart review and recording of treatment variables in a customized database. Variables of interest included number of implants per patient, time of implant placement, number of appointments required to complete prosthesis fabrication, type of appointments, manufacturing process used for creation of the framework, and fit of the framework. The number of appointments for conventional and experimental protocols was evaluated for statistical significance using two-way analysis of variance. Presence or absence of clinically acceptable prosthesis fit with the two techniques was evaluated using the Fisher exact test and exact logistic regression analysis. RESULTS: Forty-two patients (48 arches) were included. When the experimental technique was used, prosthesis fabrication and delivery required an average of 4 appointments, whereas the conventional technique required an average of 7.8 appointments to deliver the definitive prosthesis. The prostheses fabricated with the experimental technique showed clinically passive fit on the implants in 17 of 18 arches. The frameworks fabricated with the conventional technique achieved clinically passive fit in 18 of 30 arches. CONCLUSIONS: The experimental technique significantly reduced the number of appointments required to fabricate a nonsegmented fixed implant-supported prosthesis. Moreover, this experimental technique provided clinically acceptable fit of the prosthesis in a significantly greater number of cases compared to a conventional implant elastomeric impression technique.

A retrospective analysis of 102 zirconia single crowns with knife-edge margins.

STATEMENT OF PROBLEM: Clinical reports of feldspathic porcelain veneered-zirconia crowns placed on teeth with knife-edge marginal finish lines have recently been presented but with data available for only a limited number of crowns in the anterior maxilla. PURPOSE: This retrospective study evaluated the clinical success and survival of feldspathic porcelain veneered-zirconia crowns fabricated with knife-edge margins in a private practice. MATERIAL AND METHODS: One hundred and two teeth (51 anterior, 51 posterior) were prepared with knife-edge margins and restored with feldspathic porcelain veneered-zirconia crowns. The modified California Dental Association (CDA) criteria were used to clinically evaluate subjects recalled between May and December 2010. Data were analyzed with descriptive statistics. RESULTS: The mean follow-up time was 20.9 months (SD, 13.6; range, 10-72). One tooth had to be extracted because of an endodontic problem not related with the restoration, 2 crowns had minor chipping of the veneering porcelain, while no crowns exhibited fracture of the zirconia core. CONCLUSIONS: In this retrospective evaluation, feldspathic porcelain veneered-zirconia crowns with knife-edge margins provided clinical performance similar to that reported with other margin designs.

Perception of the maxillary incisor position with respect to the protrusion of nose and chin.

OBJECTIVES: The aim of this work was to evaluate whether the protrusion of nose and chin influence the perception of the ideal tooth anterior limit line. The orthodontic, or combined orthodontic-surgical diagnosis, and the following treatment plan are in close correlation with a patient's requirements for aesthetic facial balance. This requires consideration of the position of the maxillary incisors which is often modified by treatment; it is obvious how important it is to clarify which are the facial features which determine the aesthetically ideal anteroposterior position of the incisors. MATERIALS AND METHODS: Photographs of a female and a male patients' smiling profiles, carried out in natural head position (NHP), were modified progressively with respect to the protrusion of nose and chin. The altered images (17 images for each subject) were viewed and analysed by a panel made up of 19 resident orthodontists and 12 orthodontists who had more than 10 years experience. RESULTS AND CONCLUSIONS: The hypothesis that the perception of the tooth anterior limit line is not influenced by the protrusion of nose and chin was statistically confirmed. The judgement of the tooth anterior limit line was independent of the protrusion of the nose and chin. We were not able to pinpoint a correlation between the entity of the protrusion or retraction of nose and chin and the changes of the ideal position of the maxillary incisor.

Plasmacytoma of the mandible associated with a dental implant failure: a clinical report.

The case report of a patient is presented who had been suffering from a plasmacytoma of the spine several years back, and who had developed a new plasmacytoma of the mandible, 3 years subsequent to the insertion of a dental implant. This second solitary lesion occurred 15 years after the first one, and without signs of conversion to multiple myeloma. Research in animal models has shown multinucleated giant cells, belonging to the monocyte-macrophage lineage, persisting between the titanium surface and the lymphohemopoietic compartment, at least 1.5 years after implant insertion. Factors that increase the proliferative activity of precursor B cells, for example a protracted macrophage activation, are likely to increase the risk of B cell oncogenesis. A possible role of the titanium surface in an increase of precursor B cell proliferative activity, thus facilitating a new localization, was evaluated.

Multidisciplinary treatment of agenesis in the anterior and posterior areas: a long term retrospective analysis.

Twenty-two implants inserted in the anterior area in 15 patients, and 24 implants inserted in the posterior area in 9 patients, for a total of 46 implants in orthodontic patients suffering from single or multiple agenesis, were analyzed retrospectively. The average time of follow-up, subsequent to the prosthetic insertion was 60.3 months. The average time from actual diagnosis of agenesis to the completion of therapy was 76.2 months. There were no implant failures, although 17.4% experienced prosthetic complications. Analysis of the sample identified 5 critical issues that are frequently underestimated at the time of determining the therapeutic strategy. 1. Timely comprehensive management of the patient; 2. management of the biological interface (surgery and hygiene maintenance); 3. prosthetic problems; 4. long term effects of bone remodeling; 5. alternative therapy.

Bonded provisional restorations for esthetic soft tissue support in single-implant treatment.

During the early phases of single-implant treatment, clinician needs and patient expectations can be challenging. This article describes a technique for making a simple bonded provisional restoration. In addition to minimizing patient discomfort without increasing laboratory costs, the technique enables soft tissue preservation through all treatment phases, from tooth loss to implant loading.