The International Journal of Prosthodontics, 02/2009

The following are the three best scientific posters that were presented at the 27th International Congress of the Italian Academy of Prosthetic Dentistry held in Bologna on November 21 and 22, 2008.

Purpose: This paper describes the effects of implant-related dentistry on patient profiles and the types of fixed dental prostheses provided in clinical practice. Materials and Methods: All implant- and tooth-supported prostheses provided in a prosthodontic practice between 1984 and 2007 were tabulated. Incidence was analyzed in relation to gender, age at time of prostheses insertion, and prostheses type. Results: Tooth-supported single crowns (TSCs) and tooth-supported fixed dental prostheses (TFDPs) were involved in 97% of treatments requiring fixed dental prostheses from 1984 to 1991. From 1991 to 2007, however, a marked increase in the number of implants restored directly corresponded with a decrease in the number of TFDPs so that by 2007, implant-supported fixed dental prostheses (IFDPs) accounted for 81% of all tooth replacements. Between 1984 and 2007 the incidence of TFDPs was 61% in females and 39% in males, whereas the incidence of IFDPs was 55% in females and 45% in males. IFDPs were also involved in 35% of restorations in patients under 31 years of age and TFDPs in 19%. In the under-21 years age group, IFDPs were more common in females (9%) than males (4%), but in the 21 to 30 years age group they were more common in males (21%) than females (13%). There was a decrease in three-unit TFDPs, in TFDPs with four or more pontics and those not satisfying Ante's Law, and in teeth used that had been subjectively assessed to have an unfavorable 10-year prognosis at the time of prosthesis insertion. Conclusions: The incorporation of osseointegrated implant dentistry into a clinical practice has resulted in changes in the patient profile and type of fixed dental prostheses provided, including a decrease in the use of TFDPs; an increase in the referral of patients under 31 years of age; a decrease in three-unit, long-span, and complex TFDPs; and a decrease in tooth abutments assessed to be structurally or biologically compromised.

Purpose: Since tooth loss may be considered to affect postural control, the aim of this study was to compare body balance control among samples of edentulous and dentate community-dwelling elderly subjects. Materials and Methods: A case control study was conducted using test and control groups matched by age, gender, body fat, and muscle composition. The test group included all participants of the 2006 Kyoto Health Seminar who wore a full denture in either or both arches. The control group was blindly selected from the same population, but only included individuals who retained all of their dentition with either natural teeth or crown prostheses. The results of physical fitness examinations and stabilometer tests were compared between these two groups. Results: The test and control groups both included 12 male and 23 female subjects. Body balance ability, measured by time spent standing on one leg with eyes open (P = .013) and functional reach (P = .037), was significantly less in the test group when compared to the control, as shown by analysis done using the Mann-Whitney U test. The stabilometer examination also indicated that sway area (an accurate indicator of postural balance) and body sway (evidence of energy consumption for postural control) while standing with eyes closed were both significantly higher in the test group (P = .035 and .048, respectively; Wilcoxon signed ranks test) than the control. Conclusion: It is suggested that tooth loss is a risk factor for postural instability. This further suggests that proprioceptive sensation from the periodontal ligament receptor may play a role in body balance control.

This in vitro study investigated whether a resin-bonded dental prosthesis (RBDP) with a hyperstatic, rigid joint was preferable to an isostatic, nonrigid construction in terms of debonding and fracture strength. RBDPs replacing a missing molar with a rigid (design I) or a resilient model (design II) were compared to a commercially available system (Crownless Bridge Work) (design III, control). All groups were subjected to thermocycling (TC) and dynamic mechanical loading (ML) in a dual-axis chewing simulator (TC: 6,000 x 5°C/55°C; ML: 1,200,000 x 49 N x 1.4 Hz). None of the RBDPs of design III showed movement or fracture during the test period. Significant differences between designs I and III (P = .0049) and between designs II and III (P = .0007) were noted. Despite a tendency for lower fracture values of design I, no significant differences could be established between the test designs with a rigid or nonrigid construction. The commercially available dental prosthesis with a nonrigid joint was confirmed to resist a 5-year survival simulation.

Purpose: The aim of this study was to evaluate a new gingival retraction system relative to clinical success for fixed dental restorations under various clinical conditions. Materials and Methods: Two hundred sixty-nine abutment teeth were evaluated. The ability to displace gingiva was indirectly measured by the quality of the final impression. Preparation finish line with respect to the crest of the marginal gingiva (Level I through III) and type of preparation finish line (ie, shoulder or beveled) were recorded. The reproduction of the preparation finish line and an absence of bubbles or voids (Criteria I through III) were assesed. The results were compared with an established retraction system using one retraction cord. Results: Of the 269 impressions evaluated, 93.7% were clinically acceptable and showed complete reproduction of the preparation finish line; 17.5% showed small defects but the impressions were still rated clinically acceptable and categorized as Criteria II. Only 6.3% of the impressions were unacceptable and categorized as Criteria III. A significant influence on the quality of the impressions was found when the preparation finish line was more than 2 mm subgingivally for shoulder (P < .004) as well as beveled preparations (P < .004). Nearly twice as many impressions were rated Criteria III when using the Magic FoamCord (MFC) system compared to impressions done with the single cord retraction technique. Conclusions: In cases of epigingival and subgingival (< 2 mm) preparation margins, MFC was a less traumatic alternative method of gingival retraction. However, when there were deep subgingival margins and a beveled preparation, the material was less effective than the single cord retraction technique.

Purpose: In the last decade several studies have evaluated the clinical outcome of implants inserted into autografts and rehabilitated with fixed restorations in either oneor two-step surgical protocols. However, no study has investigated implants placed into homografts; thus, a case series analysis was performed to verify the clinical outcome of implants inserted into fresh frozen bone (FFB) and bearing fixed prosthetic restorations. Materials and Methods: Fifty-eight patients underwent iliac crest homograft transplants and 238 implants were inserted. Seventy-one double-etched, 19 sandblasted and acid-etched-1 (SLA1), 10 grit-blasted and acid-etched, 73 anodic oxidized, 39 CaPo4 ceramic-blasted, 19 SLA2, and seven additional implants of various types were used. Implant diameter and length ranged from 3 to 5 mm and from 7 to 16 mm, respectively. Implants were inserted to replace 15 incisors, 14 canines, 102 premolars, and 107 molars. A total of 111 restorations were performed. Results: No implants were lost. Cox regression analysis showed that implant type and type of edentulism directly correlated with a lower bone resorption and thus had a better clinical outcome and success rate. Conclusion: Implants bearing fixed restorations and inserted into FFB have higher survival and succes rates compared to those placed in nongrafted and grafted jaws reported in previous studies.

The aim of this study was to evaluate stress patterns at the bone-implant interface of tilted versus nontilted implant configurations in edentulous maxillae using finite element models of two tilted and one nontilted configuration. Analysis predicted the maximum absolute value of principal compressive stress near the cervical area of the distal implant for all models. The tilted configurations showed a lower absolute value of compressive stress compared with the nontilted, indicating a possible biomechanical advantage in reducing stresses at the bone-implant interface.

This study aimed to analyze the accuracy resulting from dual-arch impressions when compared to conventional impressions in complex preparations (ie, inlay and partial crown). One hundred eighty impressions were made using two different dual-arch trays; conventional trays served as the control. The accuracy of the dies obtained (Fuji-Rock EP, GC Europe) was assessed indirectly from the change of 59 transversal dimensions. Statistical analysis (t test, analysis of variance) revealed that less rigid dual-arch trays performed better than rigid ones. Though the inlay preparation was more difficult to reproduce with dual-arch trays, it can be concluded that the accuracy obtainable with nonrigid dual-arch trays is comparable to impressions taken from full-arch trays.

The aim of this article is to introduce criteria for planning treatment with a removable dental prosthesis (RDP) in a partially dentate arch, including the indications for placement of dental implants. The retention of RDPs is achieved through clasps, adhesive attachments, crowns, and fixed partial dentures with intra- or extracoronal attachments, telescopes, root caps, and/or prefabricated interradicular retainers. RDP designs vary from a removable partial denture to an overdenture prosthesis. Potential abutment teeth are selected for RDP retention according to their prognosis, their position in the arch, and the planned prosthesis design. Retainer selection mainly depends on the remaining tooth substance, the intra- and intermaxillary relationships, esthetics, and financial aspects. With dental implants as additional retainers, the supportive area for the RDP is increased, the soft tissue load is minimized, and the extension of the base of the prosthesis can be reduced to enhance a patient's comfort. For RDP planning, strategic considerations are needed to determine the appropriate prosthesis design, to select the abutment teeth, and to choose the appropriate retention element for each particular abutment.

Purpose: Saliva is a complex secretion that plays an important role in stomatognathic system activities, and its absence may lead to damaged functions such as mastication. Thus, the aim of this study was to investigate the effect of salivary flow rate on masticatory efficiency. Materials and Methods: Sixty dentate subjects were divided into three groups (n = 20) according to salivary flow rate: control (group 1), hyposalivation (group 2), and hypersalivation (group 3). All subjects from group 2 were under dermatologic treatment and taking systemic oral isotretinoin. Subjects from groups 1 and 3 were not taking any systemic medication and hypersalivation was induced in group 3 subjects by using a 6% citric acid solution. Masticatory efficiency was evaluated using an artificial test material (Optosil) and a sieving method. Masticatory efficiency was calculated as the weight percentage of the fragmented test food that passed through the 10-mesh (2-mm aperture) sieve. Data were analyzed using analysis of variance (P < .05). Results: The masticatory efficiency values (%) under normal, hypo-, and hypersalivation were 6.40 (± 4.35), 7.63 (± 5.57), and 4.73 (± 4.85), respectively. However, no statistical differences were found among groups. Conclusion: Within the experimental design of this study, it could be concluded that patients with reduced or increased salivary flow do not present alterations in masticatory efficiency.

Purpose: The aim of this study was to investigate whether wearing complete dentures during sleep can improve the apnea-hypopnea index (AHI). Materials and Methods: A total of 34 edentulous patients (16 men and 18 women, mean age: 72.5 ± 8.8 years) completed the study. Portable sleep recording was performed for two nights in patients' homes. All patients wore complete dentures one night and slept without dentures the other night. Information about medical history and denture use was obtained for all patients. The occurrence of obstructive sleep apnea syndrome (OSAS) was calculated in edentulous patients, and the effect that wearing complete dentures during sleep had on the AHI was evaluated. Results: Twenty-seven of the 34 patients suffered from OSAS with an AHI >= 5. The mean AHI in patients sleeping with dentures was lower than that of those without dentures (13.3 ± 10.0 versus 17.7 ± 14.6, P = .022). Nineteen of these 27 patients showed a decrease in AHI while eight showed an AHI increase, of whom four showed increases of more than 5 points when wearing dentures during sleep. Conclusions: Wearing complete dentures during sleep improves the AHI of most edentulous OSAS patients. In contrast, some patients suffer from AHI increases due to the use of complete dentures. Also in some patients, any significant change in AHI associated with the usage of complete dentures went unnoticed. Thus, careful attention should be given when complete dentures are recommended for edentulous OSAS patients.

This study aimed to compare the surface roughness of a novel dental porcelain following different polishing procedures. One hundred twenty Imagine Reflex porcelain disks were prepared and randomly assigned into six groups according to different treatments: Group 1: CeraMaster polishing system (CP); Group 2: CP + diamond polishing paste (DP); Group 3: Sof-Lex polishing system (SS); Group 4: SS + DP; Group 5: SiC paper polishing; Group 6: reglazing (control). After the respective treatments, surface roughness values were measured using a profilometer. Qualitative analysis was performed using scanning electron microscopy. Results demonstrated that a combination of the CeraMaster polishing system and a diamond polishing paste could produce similar superficial smoothness to that of the reglazed surface of the tested porcelain.

Purpose: The aim of this study was to evaluate surgical and prosthetic care and aftercare of maxillary overdentures supported by six endosseous implants and a milled bar mesostructure with Ceka attachments. Materials and Methods: Thirty-nine consecutive patients with an edentulous maxilla who reported problems wearing a conventional maxillary denture were treated with an overdenture supported by six endosseous implants and a milled bar mesostructure (solid bar with position Ceka attachments). Prosthetic and surgical care and aftercare were scored from the first visit until 10 years after the augmentation of the maxilla. Patient satisfaction was assessed at the end of follow-up. Results: On the basis of problems patients experienced with wearing their conventional dentures, three groups of patients were distinguished: patients with lack of retention of their conventional maxillary denture related to anatomic problems (n = 24), patients with gagging problems (n = 9), and patients not tolerating a conventional maxillary denture due to subjective problems not related to an anatomic substratum (n = 6). The need for care and aftercare was comparable between the three groups. The overall 10-year implant survival rate was 86.1%. Loss of implants occurred mostly during the first year after placement. Surgical aftercare predominately consisted of care related to the removal and replacement of implants (ie, reaugmentation, replacement of implants, and abutment connection). Prosthetic aftercare consisted mainly of routine inspections, oral hygiene care, and activation or replacement of Ceka attachments. Finally, all patients functioned well with their overdentures and remained satisfied throughout the study. Conclusion: Irrespective of the mentioned underlying reasons for not functioning with a conventional maxillary denture, an implant-retained maxillary overdenture, opposed by either an implant-retained mandibular overdenture or natural dentition, was shown to be an effective, predictable, and reliable treatment option that did not need much aftercare other than adjustments of the Ceka attachments.

Purpose: This prospective clinical trial investigated the effect of different fabrication techniques on screw-joint stability in implant-retained frameworks. Materials and Methods: Seventy-nine dental implants (39 Brånemark System and 40 Straumann) were inserted into 20 patients with an edentulous mandible. One of two fabrication techniques was randomly chosen as a definitive restoration, either a cast bar or a bar superstructure modified with the Cresco Ti Precision (CTiP) technique. The patients were divided into four groups depending on the type of implant and prosthetic superstructure: Straumann-conventional (Sc), Straumann-Cresco (SCr), Brånemarkconventional (Bc), and Brånemark-Cresco (BCr). Initial torque values and removal torque values were recorded with a custom-made digital torque controller both 1 week (T1) and 3 months (T2) after clinical function. Results: Statistical analysis revealed significant differences in absolute detorque values at T1 (P = .002) with 4.51 Ncm (SD = 3.80) for the Sc group, 10.65 Ncm (SD = 4.42) for SCr, 11.24 Ncm (SD = 4.00) for Bc, and 9.02 Ncm (SD = 3.81) for BCr. At T2 (P = .000) the median values of lost torque were 5.08 Ncm (SD = 4.05) for the Sc group, 10.51 (SD = 3.00) for SCr, 7.50 (SD = 5.86) for Bc, and 9.41 Ncm (SD = 4.54) for BCr. However, when correlation of detorque values to initial torque values was performed, no statistical differences were found between groups or time points. The percentage of lost torque at T1 (P = .849) and T2 (P = .058) was 28.60% (SD = 21.80) and 32.85% (SD = 24.65), 30.04% (SD = 12.49) and 30.80% (SD = 8.66), 32.11% (SD = 11.37) and 21.03% (SD = 16.53), and 25.33% (SD = 10.69) and 27.83% (SD = 12.57) for the Sc, SCr, Bc, and BCr groups, respectively. Conclusions: The screw-joint stability of passivated bars is not superior to cast superstructures. A general decrease of approximately 30% of initial torque values can be expected in clinical situations, independent of the implant system used.

The aim of this research was to study the impact of loading on partial dentures within the supporting soft tissue with respect to different attachment techniques. A finite element model was developed to calculate the stress and strain distribution in this tissue. The model consisted of the left half of a mandible with three remaining teeth that had suffered an atrophy in the anterior region, and a partial denture over the toothless area that was connected at the left mandibular canine using an attachment system. Resulting stress/strain distributions are presented for different load cases using a commercially available prefabricated attachment system.

Purpose: The aim of this study was to compare the masticatory performance, maximum occlusal force, and occlusal contact area of subjects with bilaterally missing molars, treated either with the shortened dental arch (SDA) concept or with distal extension removable partial dentures (RPDs), during a 1-year follow-up. Materials and Methods: This study included three groups of 10 subjects each, in which SDA and RPD groups displayed bilateral molar loss in the mandible. Subjects with complete natural dentition (CD) served as the control group. Masticatory performance was evaluated by the multiple sieve method. Standard cubes (edge length: 8 mm, 0.9 g) shaped from a high viscosity polysiloxane molding material (Zetaplus, Zhermack) were used as the test food. Maximum occlusal force (N) and occlusal contact area (mm2) were evaluated using dental prescale films. Results: No statistically significant differences regarding masticatory performance between the groups or evaluation periods were demonstrated. In the RPD group, masticatory performance with and without prostheses showed no significant differences. SDA patients showed significantly lower contact area and occlusal force than both the CD and RPD groups (P < .05). Conclusion: SDA can be an alternative to distal extension RPDs with respect to masticatory performance in subjects with bilaterally missing molars in one dental arch, despite remarkable reductions in maximum occlusal force and occlusal contact area.