Impact of the superimposition methods on accuracy analyses in complete-arch digital implant investigation.

OBJECTIVES: To measure the impact of the superimposition methods on accuracy analyses in digital implant research using an ISO-recommended 3-dimensional (3D) metrology-grade inspection software. MATERIALS AND METHODS: A six-implant edentulous maxillary model was scanned using a desktop scanner (7Series; DentalWings; Montreal, Canada) and an intraoral scanner (TRIOS 4; 3Shape; Copenhagen, Denmark) to generate a reference and an experimental mesh, respectively. Thirty experimental standard tesselletion language (STL) files were superimposed onto the reference model's STL using the core features of six superimposition methods, creating the following groups: initial automated pre-alignment (GI), landmark-based alignment (G1), partial area-based alignment (G2), entire area-based alignment (G3), and double alignment combining landmark-based alignment with entire model area-based alignment (G4 ) or the scan bodies' surface (G5). The groups underwent various alignment variations, resulting in sixteen subgroups (n = 30). The alignment accuracy between experimental and reference meshes was quantified by using the root mean square (RMS) error as trueness and its fluctuation as precision. The Kruskal-Wallis test with a subsequent adjusted post-hoc Dunn's pairwise comparison test was used to analyze the data (α = 0.05). The reliability of the measurements was assessed using the intraclass correlation coefficient (ICC). RESULTS: A total of 480 superimpositions were performed. No significant differences were found in trueness and precision among the groups (p > 0.05), except for partial area-based alignment (p < 0.001). Subgroup analysis showed significant differences for partial area-based alignment considering only one scan body (p < 0.001). Initial automated alignment was as accurate as landmark-based, partial, or entire area-based alignments (p > 0.05). Double alignments did not improve alignment accuracy (p > 0.05). The entire area-based alignment of the scan bodies' surface had the least effect on accuracy analyses. CONCLUSIONS: Digital oral implant investigation remains unaffected by the superimposition method when ISO-recommended 3D metrology-grade inspection software is used. At least two scan bodies are needed when considering partial area-based alignments. CLINICAL SIGNIFICANCE: The superimposition method choice within the tested ISO-recommended 3D inspection software did not impact accuracy analyses in digital implant investigation.

Impact of the superimposition methods and the designated comparison area on accuracy analyses in dentate models.

OBJECTIVES: To measure the impact of superimposition methods and the designated comparison area on accuracy analyses of dentate models using an ISO-recommended 3-dimensional (3D) metrology-grade inspection software (Geomagic Control X; 3D Systems; Rock Hill, South Carolina; USA). MATERIALS AND METHODS: A dentate maxillary typodont scanned with a desktop scanner (E4; 3 Shape; Copenhagen; Denmark) and an intraoral scanner (Trios 4; 3 Shape; Copenhagen; Denmark) was used as reference. Eight groups were created based on the core features of each superimposition method: landmark-based alignment (G1); partial area-based alignment (G2); entire tooth area-based alignment (G3); double alignment combining landmark-based alignment with entire tooth area-based alignment (G4); double alignment combining partial area-based alignment with entire tooth area-based alignment (G5); initial automated quick pre-alignment (G6); initial automated precise pre-alignment (G7); and entire model area-based alignment (G8). Diverse variations of each alignment and two regions for accuracy analyses (teeth surface or full model surface) were tested, resulting in a total of thirty-two subgroups (n = 18). The alignment accuracy between experimental and reference meshes was quantified using root mean square (RMS) error as trueness and its repeatability as precision. The descriptive statistics, a factorial repeated measures analysis of variance (ANOVA) and a post hoc Tuckey multiple comparison tests were used to analyze the trueness, and precision (α = 0.05). RESULTS: A total of 576 superimpositions were performed. The unique partial area-based superimposition method demonstrated the least precise alignment and was the sole group to exhibit a significant difference (p<.001). Automated initial pre-alignments demonstrated similar accuracy to other superimposition methods (p>.05). Double alignments did not result in accuracy improvement (p>.05). The designated comparison area displayed differences in both trueness (p<.001) and precision (p<.001), leading to an overall discrepancy of 8 ± 4 µm between selecting the teeth surface or full model surface. CONCLUSIONS: The superimposition method choice within the tested software did not impact accuracy analyses, except when the alignment relies on a unique and reduced area, such as the palatal rugae, a single tooth, or three adjacent teeth on one side. CLINICAL SIGNIFICANCE: The superimposition method choice within the tested ISO-recommended 3D inspection software did not impact accuracy analyses.

Interim restoration using dynamic abutments to re-treat a single-implant crown with a labial angulation: A clinical report.

The cause of some peri-implant problems may be primarily attributable to the design of the prosthesis. A screw-retained interim implant may be advisable for reversibility and to avoid peri-implant cement, although screw retention may be difficult for maxillary anterior implants with a labial angulation. In the treatment described, a interim screw-retained crown was attached to a dynamic abutment with a lingual screw access hole to obtain a correctly fitting restoration.

Factors Affecting the Decision to Use Cemented or Screw-Retained Fixed Implant-Supported Prostheses: A Critical Review.

PURPOSE: This review aimed to compile and enumerate all the factors described in the literature that may affect the decision to use either cemented or screw-retained restorations and to determine the relative weights of each factor by type of retention and prosthesis. MATERIALS AND METHODS: The literature was reviewed, and the factors were classified as either determining (present in a clinical situation in which one of the retention mechanisms was clearly more suitable than the other) or conditioning (present in clinical situations in which one type of restoration was not clearly more advantageous than the other). RESULTS: Three determining factors (esthetic outcome, retention, and biologic risk) and five conditioning factors (passive fit, fracture strength, occlusal area, complications, and retrievability) were identified. CONCLUSION: Although there is not a clearly better alternative for all clinical situations, determining factors in certain scenarios can render one of the two approaches more recommendable. For esthetic reasons, when the implant angle cannot be corrected to conceal the access hole, cementation is more suitable; however, screw retention is the better option when the occlusal space is under 6 mm or margins cannot be located supra- or equigingivally. In the absence of determining factors, the decision should be based on conditioning factors, which carry different weights depending on the type of prosthesis.

Does Length, Diameter, or Bone Quality Affect Primary and Secondary Stability in Self-Tapping Dental Implants?

PURPOSE: Implant stability is a clinically valuable measurement of the strength of implant anchorage in the bone during placement and in the post-osseointegration period. This study aimed to determine 1) the effect of implant diameter and length and bone quality on measurements of primary and secondary stability (insertion torque [IT] and implant stability quotient [ISQ]), 2) the correlation between IT and primary and secondary ISQ, and 3) differences in ISQ in the post-osseointegration period (secondary stability) compared with immediate post-placement (primary) stability. PATIENTS AND METHODS: In this longitudinal clinical study, titanium self-tapping implants were inserted in edentulous patients. The implants were grouped according to 3 independent variables: length (10 and 11.5 mm), diameter (3.75 and 4.25 mm), and bone quality (Lekholm and Zarb classification) to analyze primary and secondary implant stability (outcome variables). Statistical analyses were performed using the Student t test for paired data, 1-way analysis of variance, and the Tukey procedure for multiple pairwise comparisons. RESULTS: Data were collected on 88 self-tapping implants inserted in 63 partially edentulous patients. IT and implant stability were affected by diameter (3.75-mm implants, 26.5-N/cm IT and 74.0 ISQ; 4.25-mm implants, 33.8-N/cm IT and 77.0 ISQ) and bone type (type 1 + 2, 34.86-N/cm IT and 77.4 ISQ; type 3, 27.09-N/cm IT and 75.6 ISQ; type 4, 20.63-N/cm IT and 70.5 ISQ; P < .01 for all comparisons). Secondary ISQ was affected by diameter only (77.41 for 3.75- vs 75.51 for 4.25-mm implants). IT correlated with primary ISQ (R = 0.56; P < .01), although no clear correlation with secondary stability was found. CONCLUSIONS: IT and primary ISQ in self-tapping implants differed in patients with different bone quality and implant diameter but did not differ between the 2 implant lengths compared in this study. Secondary stability was not substantially affected by any of these factors. Although IT was closely related to primary ISQ, it was unrelated to secondary ISQ. Very high primary ISQ values tended to decrease, whereas intermediate and low values tended to increase, in the transition to secondary stability.

Oral aesthetic-related quality of life of muco-supported prosthesis and implant-retained overdenture wearers assessed by a new, short, specific scale (QoLDAS-9).

OBJECTIVES: To validate a new questionnaire for evaluating the 'Oral aesthetic-related quality of life (OARQoL)' of prosthetically restored patients. 'OARQoL' assesses the impact of the self-perceived dental aesthetics on patients' well-being. METHODS: The 'Quality of Life associated with Dental Aesthetic Satisfaction (QoLDAS)' index was designed. After a pilot trial, 70 patients were distributed into two groups depending on their type of prosthetic rehabilitation: Group 1 (CD; n=34): muco-supported complete dentures, and Group 2 (IO; n=36): implant-retained overdentures. Patients answered the QoLDAS and the Oral Health Impact Profile (OHIP-20sp) questionnaires, and reported their satisfaction on a visual analogue scale (VAS). Socio-demographic and prosthesis-related factors were registered. Psychometric properties of the QoLDAS were investigated. Correlations between both indices were explored using the Spearman's rank test. Descriptive and non-parametric probes were run to evaluate the effect of the study variables on the OARQoL (α=0.05). RESULTS: The QoLDAS-9 was reliable and valid. The factor analysis confirmed the existence of three dimensions and meaningful inter-correlations among the nine finally included items. Both scales were inversely correlated. The self-reported aesthetic and functional satisfaction and the education level significantly modulated the OARQoL as measured with the QoLDAS-9. CONCLUSIONS: The QoLDAS-9 confirmed its psychometric capacity for assessing the OARQoL of CD and IO wearers. Both groups showed comparably high OARQoL. Superior education degrees lead to lower OARQoL. CLINICAL SIGNIFICANCE: The QoLDAS-9 may be recommended for anticipating the effect of prosthetic restorations on OARQoL. CD and IO are predictable treatment options for improving the aesthetic self-perception of edentulous patients.

Validation of the 'Quality of Life with Implant Prostheses (QoLIP-10)' questionnaire for wearers of cement-retained implant-supported restorations.

OBJECTIVES: To validate the 'Quality of Life with Implant-Prostheses (QoLIP-10)' questionnaire for assessing the impact of cemented implant prostheses on Oral Health-Related Quality of Life (OHRQoL). METHODS: 84 subjects wearing implant restorations were distributed as follows: Group 1 (SD-I; n=35): screwed FDPs (fixed dental prostheses) supported by 2 implants; Group 2 (SD-II; n=7): screwed FDPs supported by 3-5 implants; Group 3 (CD-I; n=36): cemented FDPs supported by 2 implants; and Group 4 (CD-II; n=6): cemented FDPs supported by 3-5 implants. The QoLIP-10 and the Oral Health Impact Profile (OHIP-14sp) scales were used. Data related to global oral satisfaction, socio-demographics, health-behaviors, and prostheses, were gathered. Reliability and validity of the QoLIP-10 were investigated. Correlations between both indices were explored with the Spearman's rank test. Descriptive and non-parametric probes were run to evaluate the effect of the study variables on the OHRQoL (α=0.05). RESULTS: The QoLIP-10 confirmed its psychometric capacity for cemented implant prosthesis wearers. Both tests were inversely correlated. The QoLIP-10 attributed the significantly worst QoL to long-span cemented prostheses. Groups were significantly discriminated by the QoLIP-10 performance dimension. The variable complaints about the mouth and the three global oral satisfaction measures significantly modulated the OHRQoL. CONCLUSIONS: Patient satisfaction depends upon the extension and the type of retention of implant FDPs. CLINICAL SIGNIFICANCE: The QoLIP-10 may help estimating the effect of cemented FDPs on patients' well-being. When compared to screwed FDPs, short cemented implant restorations lead to greater improvements in patients' self-perceived QoL.

Hydrogen peroxide whitens teeth by oxidizing the organic structure.

OBJECTIVES: The mechanism of tooth bleaching using peroxide oxidizers is not fully understood. It is unknown whether peroxide radicals make teeth whiter by deproteinizing, demineralizing, or oxidizing tooth tissues. This study was designed to define the mechanism of tooth bleaching and determine which of tooth enamel chemical components is/are affected by bleaching. METHODS: Sixty sound teeth were collected from adult patients. The teeth were divided into 6 equal groups (n=10). Groups 1, 2, 3 and 4 were treated for 4 days with one of the following solutions: deproteinizing (NaOH) that removes organic content, demineralizing (EDTA) that decalcifies the mineral content, oxidizing (H(2)O(2)) and distilled water (control). Group 5 and 6 were pre-treated with either deproteinizing or demineralizing solutions before treating them with oxidizing solutions for 4 days. Changes in enamel elemental ratios, crystallinity index and tooth shade parameters of the treated teeth were examined by means of EDS, Raman spectroscopy and shade-spectrophotometry. The data obtained was analysed with Wilcoxon Signed-Ranks Test, and the statistical significance was set at p<0.05. RESULTS: Tooth deproteinization increased the lightness by 4.8 ± 2.7°, tooth demineralization resulted in 8.5 ± 5.6° decrease in the lightness and tooth oxidization induced 19.9 ± 6.5° increase in the lightness. Oxidization of the deproteinized teeth did not influence shade parameters, but oxidation of the demineralized teeth resulted in 10.7 ± 5.8° increase in the lightness. CONCLUSION: Hydrogen peroxide does not induce significant changes in tooth enamel organic and inorganic relative contents, and it whitens teeth just by oxidizing their organic matrix. These findings are of great clinical significance since they explain the mechanism of tooth bleaching, and help understanding its limitations and disadvantages.

Influence of technique and pouring time on dimensional stability of polyvinyl siloxane and polyether impressions.

This study aimed to determine how impression technique and pouring time affect casts obtained using polyvinyl siloxane (PVS) and polyether (PE) impressions. A total of 480 impressions were taken using three techniques: single-step (SS), two-step (TS), and two-step with a spacer (TSS). Impressions were poured after 1 and 24 hours and 7 and 14 days. Significant differences (P < .01) were found between the TS technique and the SS and TSS methods as well as between PE and PVS (P < .01) in terms of the effects of pouring time. SS and TSS yielded similar dimensional results, while greater dimensional change was induced with TS. PE impressions had to be poured no later than 7 days after preparation to ensure dimensional stability.

A 10-year retrospective study of the survival rate of teeth restored with metal prefabricated posts versus cast metal posts and cores.

OBJECTIVE: The aim of this retrospective study was to compare the cumulative survival rate of teeth restored with prefabricated posts and with cobalt-chrome cast post-cores. METHODS: 112 endodontically treated teeth restored with prefabricated post and cobalt-chrome cast post-and-cores were evaluated. Teeth were considered as failures when were objective or radiologic sign of endodontic failure, post or root fracture, or when they had been extracted at the moment of the evaluation. Kaplan-Meier's method was used to reconstruct the survival curves of the restorations and to test the variable type of post-and-core restoration. RESULTS: 93 of the posts were still in function without clinical or radiographic signs of failure at the time of the examination resulting in a survival rate of 83.03% after a mean follow-up period of 10.08 years. When comparing the two techniques, prefabricated posts showed a slightly higher survival rate: 84.6% versus 82.6%.Focusing on tooth-type, maxillary premolars (n=30) had the highest failure rate (30%) and also the lowest mean lifetime, with 6-and-a-half years. Maxillary incisors (n=20) showed the highest success rate (5%) with only one case of failure. CONCLUSIONS: The results showed no significant difference between both groups after a 10-year average follow-up.

The correlation between crown-implant ratios and marginal bone resorption: a preliminary clinical study.

PURPOSE: The crown-implant ratio is defined as the physical relationship between each individual restoration's parts located both inside and outside the bone. This relationship represents the physical concept of a type I lever, which may be of biomechanical importance in implant treatment outcomes. MATERIALS AND METHODS: Specific patient data related to fixed implant prostheses were retrieved and studied in an effort to clinically and radiographically correlate crown-implant ratios. RESULTS: Recorded marginal bone resorption around implants (2.11 +/- 1.30 mm) at the end of a defined observation period did not correlate with the measured crown-implant ratio, which yielded values between 0.43 and 1.5 mm (P > .05). CONCLUSION: The mechanical determinants of implant success or failure are still not defined. It has been postulated that an increase in both crown-tooth, and comparably crown-implant, ratios would lead to a resultant increase in the magnitude of nonaxial forces transmitted to the tooth or implant. This could then lead to an increased vulnerability of either tooth or implant abutments to supporting bone loss. However, additional factors appear to impact long-term bone maintenance behavior around either type of abutment. Within the limited scope of this study, crown-implant ratios were not associated with recorded peri-implant bone loss. Int J Prosthodont 2010;23:33-37.

Electromyographic study of activity of the masseter and anterior temporalismuscles in patients with temporomandibular joint (TMJ) dysfuction: Comparison with the clinical dysfunction index

Objectives: A comparison was made between the electromyographic patterns specific to patient with temporomandibulardisorders and that of normal healthy patients. Study design: Electromyographic tests were carriedout during rest and function of the masseter muscles and anterior temporalis muscles in a homogeneous groupconsisting of 95 patients for whom such pathology and its different degree of severity had been previously studiedby means of a Helkimo Test. The electromyographic exploration results were compared to those of a controlgroup consisting of 31 healthy subjects. Results: There were significant differences among patients with a differentdegree of clinical dysfunction, as well as between these and the control group. These differences were moreimportant during maximum effort clenching and mastication. During maximum effort clenching, differences inmasseteric activity were observed between control group and group III, between groups I and II and betweengroups I and III. Meanwhile, differences in temporalis activity were significant among all groups except betweengroups I and II. The multiple comparison analysis demonstrated the existence of significant statistical differencesbetween healthy subjects and patients with severe TMD. However, the linear combination of these electromyographic(EMG) variables led us to elaborate four linear functions that classify all subjects into four well definedgroups. Once extreme cases were eliminated, our EMG classification revealed an 80% match with that of theHelkimo Test. We thus conclude that in many cases, classification using electromyographic criteria matches thatestablished by the Helkimo Test (AU)

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Electromyographic study of activity of the masseter and anterior temporalis muscles in patients with temporomandibular joint (TMJ) dysfunction: comparison with the clinical dysfunction index.

OBJECTIVES: A comparison was made between the electromyographic patterns specific to patient with temporomandibular disorders and that of normal healthy patients. STUDY DESIGN: Electromyographic tests were carried out during rest and function of the masseter muscles and anterior temporalis muscles in a homogeneous group consisting of 95 patients for whom such pathology and its different degree of severity had been previously studied by means of a Helkimo Test. The electromyographic exploration results were compared to those of a control group consisting of 31 healthy subjects. RESULTS: There were significant differences among patients with a different degree of clinical dysfunction, as well as between these and the control group. These differences were more important during maximum effort clenching and mastication. During maximum effort clenching, differences in masseteric activity were observed between control group and group III, between groups I and II and between groups I and III. Meanwhile, differences in temporalis activity were significant among all groups except between groups I and II. The multiple comparison analysis demonstrated the existence of significant statistical differences between healthy subjects and patients with severe TMD. However, the linear combination of these electromyographic (EMG) variables led us to elaborate four linear functions that classify all subjects into four well defined groups. Once extreme cases were eliminated, our EMG classification revealed an 80% match with that of the Helkimo Test. We thus conclude that in many cases, classification using electromyographic criteria matches that established by the Helkimo Test.

In vivo study of the wear of a reinforced composite used to cover implant-supported frameworks.

The goal of this study was to research the wear shown by a material (Cristobal+) offered as an alternative to ceramics in the covering of an implant-supported fixed prosthesis. Twenty-six active cusps were used in this study; the control group consisted of 12 cusps adjacent to restorations composed of Cristobal+. Five images were obtained from each sample and analyzed using computer software that creates an arch along each cusp, so each image gives the value of the radius described by that arch. If a sample showed any sign of wear, the values for the successive radii would be increasingly larger since a flattened arch would produce a larger radius. An analysis of the paired Student t test was applied. After assessing the results, a statistically significant difference in wear was noted (P < .05). Within the limitations of this study, it can be concluded that the wear of the cusps under function made with Cristobal+ reinforced composite was greater than that of the natural adjacent cusps.

Electromyographic comparisons between clenching, swallowing and chewing in jaw muscles with varying occlusal parameters

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The aim of this study is to determine the influence of Angle molar class, presence of a posterior crossbite, anterior guidance, as well as gender in the muscular activity of the masticatory system in a population of healthy dental students.Study design: Surface electromyography recordings are made for the masseter, anterior and posterior temporalis and digastric muscles; in three different tests: clenching at maximum intercuspation, swallowing and chewing.Results: The results obtained show that: men achieve a higher masseter activity at maximum effort than women.Women achieve higher values than men, for the digastric muscles in deglution. Angle class II show higher activitythan other classes for the temporalis muscle in deglution, while class III show higher activity than other classes for all muscles in maximum effort. The anterior guidance does not cause significant differences. The presence of a posterior crossbite affects the behaviour of anterior temporalis and masseter muscles.Conclusion: The results of this study show the influence of the occlusal parameters on the muscular activity of the stomatognatic system (AU)

Electromyographic comparisons between clenching, swallowing and chewing in jaw muscles with varying occlusal parameters.

UNLABELLED: The aim of this study is to determine the influence of Angle molar class, presence of a posterior crossbite, anterior guidance, as well as gender in the muscular activity of the masticatory system in a population of healthy dental students. STUDY DESIGN: Surface electromyography recordings are made for the masseter, anterior and posterior temporalis and digastric muscles; in three different tests: clenching at maximum intercuspation, swallowing and chewing. RESULTS: The results obtained show that: men achieve a higher masseter activity at maximum effort than women. Women achieve higher values than men, for the digastric muscles in deglution. Angle class II show higher activity than other classes for the temporalis muscle in deglution, while class III show higher activity than other classes for all muscles in maximum effort. The anterior guidance does not cause significant differences. The presence of a posterior crossbite affects the behaviour of anterior temporalis and masseter muscles. CONCLUSION: The results of this study show the influence of the occlusal parameters on the muscular activity of the stomatognatic system.