The International Journal of Prosthodontics, 01/2015

Purpose: Excess cement left in the peri-implant sulcus after the placement of prosthetic restorations risks inflammation in the peri-implant tissue. While many current studies deal with the question of how to avoid undetected excess cement, relatively little is known about the clinical consequences of this complication. This study analyzed the clinical findings associated with excess cement. Further, the influence of the sojourn time of undetected excess cement in the peri-implant pocket on clinical findings was investigated. Materials and Methods: Within the scope of a retrospective clinical follow-up, the suprastructures that were originally cemented with a methacrylate cement were revised in 93 patients (171 implants). The patients were split into two groups according to the time between placement of the prosthetic restoration and revision. Group 1 (G1) had treatment revisions within 2 years of restoration placement (71 patients with 126 implants); in group 2 (G2), treatment revisions were conducted at a later time (22 patients with 45 implants). For the purpose of statistical analysis, both groups were further analyzed based on the presence/absence of excess cement at the time of revision. Results: By definition, the average time to revision in G1 was shorter than in G2 (0.71 years versus 4.07 years). There was no significant difference in the frequency of excess cement at revision between G1 (59.5%) and G2 (62.2%). The clinical findings around the implants in G1 were significantly less severe than in G2 (bleeding on probing: G1 without excess cement-17.6%, G1 with excess cement-80%, G2 without excess cement-94.1%, G2 with excess cement-100%; suppuration: G1 without excess-0%, G1 with excess cement-21.3%, G2 without excess cement-23.3%, G2 with excess cement-89.3%). After removing the excess cement, cleaning and disinfecting the implant abutment and restoration, and using a different cement, significantly fewer signs of inflammation were found at further follow-up in both groups. Conclusions: Within the limitations of this retrospective observational study, excess cement was present in a high number of cement-retained implant restorations. Signs of inflammation were present in a large proportion of implants at short- to medium-term follow-up. At the time of restoration revisions, the clinical observation of previously undetected excess cement was associated with increased prevalence of inflammation. Removal of excess cement significantly reduced the signs of inflammation.

This study evaluates the influence of interimplant distance (ID) on patient satisfaction and quality of life (QOL) of 55 patients who received mandibular overdentures supported by two implants. IDs were measured over the residual ridge crest and linearly on all of the patients' mandibular casts. The crestal detours of all patients were determined by subtracting these two values from each other. Higher IDs were associated with better QOL scores (P < .05), whereas higher crestal detour values were associated with better general comfort, chewing, ease of hygiene maintenance, esthetics, pain, and QOL scores (P < .05).

Purpose: The purpose of this study was to analyze the removal of implant-supported crowns retained by three different cements using an air-accelerated crown remover and to evaluate the patients' response to the procedure. Materials and Methods: This controlled clinical trial was conducted with 21 patients (10 women, 11 men; mean age: 51 ± 10.2 years) who had received a total of 74 implants (all placed in the posterior zone of the mandible). Four months after implant surgery, the crowns were cemented on standard titanium abutments of different heights. Three different cements (two temporary: Harvard TEMP and Improv; and one definitive: Durelon) were used and randomly assigned to the patients. Eight months later, one blinded investigator removed all crowns. The number of activations of the instrument (CORONAflex, KaVo) required for crown removal was recorded. The patients completed a questionnaire retrospectively to determine the impact of the procedure and to gauge their subjective perception. A linear regression model and descriptive statistics were used for data analysis. Results: All crowns could be retrieved without any technical complications or damage. Both abutment height (P = .019) and cement type (P = .004) had a significant effect on the number of activations, but the type of cement was more important. An increased total number of activations had no or only a weak correlation to the patients' perception of concussion, noise, pain, and unwillingness to use the device. Conclusions: Cemented implant crowns can be removed, and the application of an air-accelerated device is a practicable method. A type of cement with appropriate retention force has to be selected. The impact on the patients' subjective perception should be taken into account.

This study aimed to evaluate the correspondence of intraoral digitization (ID) with extraoral digitization (ED) after impression taking. One-stage putty-andwash impressions and ID were carried out in a randomized order for 10 subjects. The impressions were used to make casts, which were then subjected to ED. ID datasets were aligned to create computer-aided design reference models. Deviations between ID and ED were calculated. The mean positive and negative deviations were 37.7 and -48.4 μm, respectively, for one quadrant. The results showed that the ID system is well suited for the acquisition of single-tooth restorations and is of limited suitability for the acquisition of small multipleunit restorations.

Epidermolysis bullosa (EB) is a rare skin disorder characterized by blister formation in response to minor trauma and accompanied by extracutaneous manifestations. The use of endosseous implants to support fixed prostheses for the rehabilitation of patients with recessive dystrophic EB might provide a considerably better clinical treatment outcome than traditional prosthodontic interventions. This case history report describes the clinical management of such an afflicted patient. Implants were placed immediately following teeth extractions and subsequently loaded with fixed full-arch prostheses. This treatment option is proposed for patients with recessive dystrophic EB to preclude mucosal irritation associated with wearing removable prostheses.

Purpose: This in vitro study evaluated the adhesive strength of a technique to lute implant cylinders to metal frameworks in implant-supported prostheses and ensure a good passive fit. Materials and Methods: Different height samples were tested: In group 1, implant cylinders were 5 mm long; in group 2, they were 10 mm long. A universal testing machine (Instron) was used to perform pullout tests. Results: The luting technique provided enough adhesive strength for clinical use with greater adhesive strength in group 2 (mean pull-out strength: 2.85 kN in group 1 versus 3.79 kN in group 2). Conclusions: The luting technique provides enough adhesive strength for clinical use. Moreover, specimens with a larger surface for adhesion demonstrated higher adhesive strength compared with shorter specimens.

Purpose: This study investigated the effect of implant design and bone quality on insertion torque (IT), implant stability quotient (ISQ), and insertion energy (IE) by monitoring the continuous change in IT and ISQ while implants were inserted in artificial bone blocks that simulate bone of poor or poor-to-medium quality. Materials and Methods: Polyurethane foam blocks (Sawbones) of 0.16 g/cm3 and 0.32 g/cm3 were respectively used to simulate low density and low- to medium-density cancellous bone. In addition, some test blocks were laminated with a 1-mm 0.80 g/cm3 polyurethane layer to simulate cancellous bone with a thin cortical layer. Four different implants (Nobel Biocare Mk III-3.75, Mk III-4.0, Mk IV-4.0, and NobelActive-4.3) were placed into the different test blocks in accordance with the manufacturer's instructions. The IT and ISQ were recorded at every 0.5-mm of inserted length during implant insertion, and IE was calculated from the torque curve. The peak IT (PIT), final IT (FIT), IE, and final ISQ values were statistically analyzed. Results: All implants showed increasing ISQ values when the implant was inserted more deeply. In contrast to the ISQ, implants with different designs showed dissimilar IT curve patterns during the insertion. All implants showed a significant increase in the PIT, FIT, IE, and ISQ when the test-block density increased or when the 1-mm laminated layer was present. Tapered implants showed FIT or PIT values of more than 40 Ncm for all of the laminated test blocks and for the nonlaminated test blocks of low to medium density. Parallel-wall implants did not exhibit PIT or FIT values of more than 40 Ncm for all of the test blocks. NobelActive-4.3 showed a significantly higher FIT, but a significantly lower IE, than Mk IV-4.0. Conclusions: While the existence of cortical bone or implant designs significantly affects the dynamic IT profiles during implant insertion, it does not affect the ISQ to a similar extent. Certain implant designs are more suitable than others if high IT is required in bone of poor quality. The manner in which IT, IE, and ISQ represent the implant primary stability requires further study.

Technical difficulties in the construction of hard palate obturators following oncologic surgery are due to the recording limitations of the entire defect area, plus prosthesis base instability during recording of maxillomandibular relationships. This article describes a time-saving technique that ensures stable and precise recording bases. A light-polymerizing acrylic resin layer is used for making the first impression of the defect, while simultaneously obtaining an acrylic resin impression tray and base for recording maxillomandibular relationships. Adhesive paper copies are used for the arrangement of the anterior teeth.

Purpose: Titanium dental implants have a high success rate; however, there are instances when a modified surface may be desirable. The aim of this article was to systematically review the different types of implant coatings that have been studied clinically, in vivo and in vitro, and the coating techniques being implemented. Materials and Methods: The literature was searched electronically and manually through The Cochrane Library, Medline, and PubMed databases to identify articles studying dental implant surfaces and coating techniques. The database search strategy revealed 320 articles, of which 52 articles were considered eligible-40 in relation to implant coatings and 12 to the coating technique. An additional 30 articles were retrieved by hand search. Results: Several materials were identified as possible candidates for dental implant coatings; these include carbon, bisphosphonates, bone stimulating factors, bioactive glass and bioactive ceramics, fluoride, hydroxyapatite (HA) and calcium phosphate, and titanium/titanium nitride. HA coatings still remain the most biocompatible coatings even though the more innovative bioglass suggests promising results. The most common coating techniques are plasma spraying and hydrocoating. More recent techniques such as the nanoscale technology are also discussed. Conclusions: Several implant coatings have been proposed, and some appear to give better clinical results and improved properties than others. Clinical trials are still required to provide compelling evidence-based results for their longterm successful outcomes.

In this study, the influence of restoration type, symmetry, and color on the perception of dental appearance was evaluated. An esthetic questionnaire was completed by 29 patients before and after esthetic rehabilitation. In addition, 94 dentists from four countries (Germany, the United Kingdom [UK], China, and Switzerland) evaluated the influence of the above factors using before-and-after rehabilitation pictures. The most invasive treatment was recommended by Chinese dentists, while German, Swiss, and UK dentists recommended comparable treatment options. As for restorative symmetry, restoration type, and color, significant differences could be found among and within the dentists of the four countries (P ≤ .05).

Purpose: The purpose of this study was to evaluate, in situ, the initial adhesion of microorganisms to as well as the surface roughness and chemical composition of ProBase Hot (Ivoclar Vivadent), a hard acrylic resin, and Vertex Soft (Vertex-Dental), an acrylic-based soft liner, used in removable dental prostheses. Materials and Methods: Equal sized disks of ProBase Hot and Vertex Soft were prepared and polished according to the recommended procedures for clinical use. Two disks of each material were mounted in individual oral splints and exposed for 4 hours to the oral cavities of 15 participants. The microbial adhesion to each material's surface was measured with the pour plate technique using rich and selective growth media. Statistical analysis was performed using the Student t test. Scanning electron microscopy and chemical composition analyses obtained through electron probe radiographic microanalysis of sample disks also were performed. Results: In comparison to ProBase Hot, Vertex Soft presented higher microbial adhesion, namely regarding total aerobes, anaerobes, streptococci, and mutans streptococci (P < .05). Also, Vertex Soft presented higher surface roughness. Differences in the chemical composition of the two materials also were found. Conclusions: The Vertex Soft liner has been found to be more susceptible to microbial adhesion than the acrylic resin ProBase Hot, probably due to its greater surface roughness. The application of Vertex Soft liner to a hard denture base may lead to a higher risk of oral and systemic infections for patients, highlighting a greater need for plaque control, especially for more susceptible individuals.

Purpose: The influence of hormonal fluctuations on pain and mastication was evaluated in patients with painful temporomandibular disorder (TMD) symptoms. Materials and Methods: Fifty women were assigned to menstrual cycle and oral contraceptive groups (n = 25). Their TMD was diagnosed by Research Diagnostic Criteria for Temporomandibular Disorders. Pain levels, maximum oclusal force (MOF), and masticatory performance (MP) were measured in all menstrual cycle phases. Results: A lower pain level was observed in the ovulatory phase when compared to menstrual and luteal phases (P = .02). No differences were found regarding MOF (P = .20) or MP (P = .94). Conclusions: Hormonal fluctuations intensify pain in women with symptomatic TMD without impairing mastication.

Fracture strength and accelerated fatigue reliability of two zirconia abutment systems were tested. Thirty-six implants with a Morse taper (MT; n = 18) or cone (C; n = 18) design were restored with metallic crowns. Loads were applied as single load to failure (SLF) or mouth-motion cycles using a step-stress accelerated life testing (SALT) method. SLF mean values were 690 ± 430 N and 209 ± 25 for MT and C groups, respectively. In terms of the SALT results, 8 specimens survived (50,000 cycles) and 7 failed (maximum load 400 N) in the MT group; whereas for the C group all abutments failed before the maximum number of cycles. Failure mode was fracture of the Y-TZP abutments for both groups. Higher reliability for a mission of 50,000 cycles at 175 N for MT versus C designs was determined, and significant differences in fracture modes were observed.

Purpose: To evaluate differences in masticatory muscle function during chewing of model foods designed to differ in fracture strength between dentate subjects (n = 5, ages 59 to 68 years) versus patients treated with a maxillary conventional complete denture opposing natural dentition or one of the following types of mandibular complete dentures: conventional, implant-supported overdenture, implant-supported fixed denture (n = 20, ages 45 to 83 years). The authors hypothesized that denture wearers would differ in duration of chewing, frequency of chewing, and masticatory muscle activity while preparing a bolus for swallowing. Materials and Methods: Surface electromyography was recorded bilaterally from the masseter, anterior temporalis, and anterior digastric. Masticatory muscle activity was evaluated using scaled values of the area under the electromyographic curve, while subjects chewed agar-based model foods with different fracture strengths. Chewing duration and frequency also were calculated from electromyographic recordings. Mixed model analysis of variance with "subject" as a random factor was used during statistical analysis. Logarithmic transformation was required to achieve normalization of residuals for the duration of chewing and the relative masticatory muscles activity, but not for the chewing frequency. Results: Relative masticatory muscle activity was 2.57 times higher for the denture wearers than for the dentate subjects during chewing of model foods (P < .0001). The reduction in masticatory muscle activity from the 1st to the 10th chewing cycle was proportionally less in magnitude and occurred more gradually for denture wearers compared to dentate subjects. While chewing sequence duration increased with food fracture strength, it did not differ significantly in treatment versus dentate groups. Chewing cycle frequency did not differ between groups or with food fracture strength. Conclusions: The observed increases in relative masticatory muscle activity for denture wearers compared to the dentate subjects during oral food processing likely reflect supplemental mechanical efforts to accommodate the use of dentures for preparing a bolus for swallowing.