A survey of removable partial denture casts and major connector designs found in commercial laboratories, Athens, Greece.

PURPOSE: This survey was conducted to study the prevalence of partial edentulism, the type of removable partial denture (RPD) support, the type of major connectors, and the frequency of their use in relation to the partial edentulism classes encountered, concerning patients in Athens, Greece. MATERIALS AND METHODS: The material comprised 628 final casts for RPDs. Each cast was photographed in a way that would allow the number of existing teeth, the classification of partial edentulism, the RPD support, and the particular parts of the metal framework to be identified. Data collected were analyzed statistically using prevalence tables and the χ(2) test. RESULTS: Two hundred seventy six (43.9%) casts were for the maxilla and 352 (56.1%) for the mandible. The most frequently encountered group was Kennedy class I for both arches, while class IV was the classification least encountered (p < 0.001). Of all RPDs constructed, 96.8% had a metal framework (tooth-borne and tooth/tissue-borne), while 3.2% of the RPDs were frameless (tissue-borne, acrylic dentures). The U-shaped palatal connector (horseshoe) in the maxilla and the lingual bar in the mandible were the most frequently used for all partial edentulism classes, at 55.2% and 95%, respectively. CONCLUSIONS: Analysis of the casts revealed that the type of major connectors selected does not comply with the indications for their applications, considering the lack of dental history and clinical examination. This notes the need for further training dentists and dental technicians in aspects of RPD framework design.

Temperature rise during intraoral polymerization of self-cured hard denture base liners.

The aim of this in-vivo study was to evaluate the temperature rise during polymerization of five chairside self-cured hard denture base reliners. For the same patient, 30 identical baseplates, exposing a space on their tissue surface to accommodate the lining material, were made of a light-cured denture base material. A hole was drilled in the center of this area to enable the thermocouple wire of the temperature measuring device to have direct access to the palatal surface of the baseplate. Six baseplates were used for each of the five lining materials tested. Temperature recordings were made every 15 seconds. Data were analyzed using single factor analysis of variance (ANOVA) and the Scheffe's post-hoc analysis for multiple comparisons. The mean maximum temperature values ranged from 40.2 degrees C to 45.7 degrees C being statistically different among the materials (P<0.001). The maximum peak temperature was 53 degrees C and the lowest 39 degrees C. Also the difference between the time each material reached the peak of temperature was statistically significant (P<0.0001). A temperature range of 5.5 degrees C was demonstrated among materials, with the highest polymerization temperatures recorded for Flexacryl Hard and the lowest for Rebase and GC Reline hard. Ufi-gel hard showed the fastest polymerization cycle and was the first to reach the maximum temperature. The available chairside hard liners must be chosen with care considering the thermal effect on the oral mucosa and the discomfort of patient.

The prevalence of temporomandibular disorders among two different denture-wearing populations.

AIM: The aim of this clinicostatistical study was to profile the complete denture wearers of two different populations, to determine any possible relationship between the prevalence of temporomandibular disorders (TMDs) and factors involved in complete denture wearing and to compare this prevalence between the groups. MATERIALS AND METHODS: Denture wearers who attended the clinics of the Dental School and Hospital, University of Bristol, U.K. (group A) and the Dental School, University of Athens, Greece (group B), were examined. An approximately equal number of patients; 115 for group A and 136 for group B, were selected. The examination included: (a) a history record with reference to sex, age, years of complete denture experience, sets of dentures used, age of the current dentures, time period of every day denture wearing, any difficulties on opening the mouth, and/or pain at the temporomandibular joint (TMJ) region and (b) a craniomandibular clinical examination in relation to midline deviation, pain and sounds from the joints, pain in the related muscles and inspection of the vertical dimension of occlusion. Data collected were analyzed using the chi-square test. RESULTS: Denture wearers of group A were older, presented with greater experience in complete denture wearing, used more sets of dentures, most wore dentures exhibiting decreased vertical dimension of occlusion and wore their dentures only in the day time. The TMDs prevalence was not statistically significantly different between A and B groups (34.8% and 41.2% respectively). In group B the TMDs prevalence was greater in females. There was a decreasing TMDs prevalence with increasing age. Neither of the groups showed significant TMDs prevalence in relation to the denture experience, the number of dentures used, the age of the present denture nor the vertical dimension of occlusion. Group B showed a decreasing TMDs prevalence in relation to continuous denture wearing. CONCLUSIONS: This clinicostatistical study showed that two different population groups of complete denture wearers who presented with different profiles have similar prevalence of TMDs.

A long term study on residual monomer release from denture materials.

The aim of this long term study was to investigate the release of residual monomer from different denture materials, throughout a 38 months time period after curing and storage in water Specimens made of four denture base resins (three heat polymerizing, one auto polymerizing) and one hard liner were subjected to residual monomer determination using gas liquid chromatography. The residual monomer estimation carried out on three occasions: one week, 12 months and 38 months after curing. The data obtained were analyzed using two-way Anova followed by Scheffe's test for post hoc multiple comparisons at alpha=0.05. Heat polymerized denture base acrylic resins showed less residual monomer than auto polymerized ones (p<0.001) and released no statistically significant amounts of monomer (p>0.05), during the 38 months storage time period. Auto polymerized denture materials, which had higher residual monomer content, released statistically significant amounts of monomer (p<0.001) during the first twelve months storage, but not during the last twenty six months period (p>0.05). Heat polymerized denture base acrylic resins released insignificant amounts of residual monomer during the storage period, whereas both the auto polymerized denture base resin and the hard liner released significant amounts of residual monomer during the initial storage time period but insignificant ones during the remainder of the storage period.

A Survey of Removable Partial Denture (RPD) Retentive Elements in Relation to the Type of Edentulism and Abutment Teeth Found in Commercial Laboratories, Athens, Greece.

OBJECTIVE: The aim of this survey was to record removable partial denture (RPD) retentive elements and abutment teeth in partially edentulous patients, identified in commercial laboratories in Athens, Greece. MATERIAL AND METHODS: 628 master casts with the corresponding cast metal frameworks used in the construction of RPDs were evaluated. Casts were photographed to identify the number and position of existing teeth, the partial edentulism class and the retentive elements. Prevalence tables and the x(2) test were used for the statistical analysis of the collected data (α=.05). RESULTS: There were 276 maxillary (43.9%) and 352 (56.1%) mandibular casts. Maxillary edentulism entailed almost a total absence of right third molars in 96.7% and left third molars 96.0% of casts, with lower rates for the first and second molars. Edentulism in the posterior mandible presented a similar pattern. The most profound findings concerning retentive elements were: 91.9% of the retainers used were clasps and the remaining 8.1% were attachments. Of the clasps used, 48.9% were of the Roach Τ type, a finding more common in Kennedy Class I as compared to other Kennedy Classes (p<0.01). The circumferential clasps accounted for 19.3% of the total clasps used, and it was less frequently presented (8.8%) in Kennedy I Classes (p<0.01). CONCLUSIONS: Roach clasps were used in the majority of cases whereas RPI clasps and attachments were rarely used.

The Effect of Repeated Microwaving Disinfection on the Dimensional Stability of Acrylic Dentures.

OBJECTIVE: The aim of this study was to evaluate the effect of repeated microwave disinfections on the dimensional stability of acrylic dentures. MATERIALS AND METHODS: Three groups of dentures made of a heat polymerized acrylic resin were tested. I: dentures kept in water (control group). II: dentures microwaved daily while being immersed into water (wet disinfection). III: dentures microwaved daily without being immersed into water (dry disinfection).Measurements were taken across three reference points, on two occasions: after curing and immersion in water for 24 hours, and one week later.Data obtained were analyzed using one-way analysis of variance (ANOVA) and Scheffe's multiple range test. RESULTS: The results showed that the microwave disinfection provokes dimensional changes of the same pattern (shrinkage). The dentures which underwent wet disinfection exhibited the greatest shrinkage (p<0.05). CONCLUSIONS: Disinfection using microwave energy may cause dimensional changes (shrinkage) of complete dentures.The microwave "dry disinfection" method can be safely applied in everyday practice since the dimensional changes which occurred seem to be of no clinical significance.

A modified method for rebasing implant-retained overdentures.

There is a constant need for rebasing implant-retained overdentures because of the inevitable continuous absorption of the underlying residual ridge, which results in a lack of proper occlusion and possible rotation of the denture around the retentive components. This step-by-step article describes all of the clinical and laboratory procedures needed for rebasing a mandibular implant overdenture retained with a bar on two implants, securing an accurate fit. This procedure can be applied successfully for rebasing overdentures with different superstructures (ball attachments or magnets), and for replacing worn or damaged retentive components and matrices.

Comparison of denture stomatitis prevalence in 2 population groups.

PURPOSE: The aim of this cross-sectional study was to profile complete denture wearers in 2 different unmatched and nonrandomized population groups and compare any possible relationships between the prevalence of denture stomatitis and other factors involved in wearing complete dentures. MATERIALS AND METHODS: Denture wearers who attended the clinics of the Dental School and Hospital, University of Bristol, United Kingdom (group A), and the Dental School, University of Athens, Greece (group B), were examined. The examination included a record of gender, age, years wearing a complete denture, number of dentures used, duration of current denture's usage, daily time period of denture wearing, and clinical examination of the maxillary denture-bearing mucosa. Data were analyzed using the chi-square test. RESULTS: Denture wearers of group A were older, more experienced in wearing complete dentures, and had used more sets of dentures. The majority of patients used dentures exhibiting decreased vertical dimension of occlusion and wore their dentures only in the daytime. Denture stomatitis prevalence was statistically significantly different between groups A and B (27% and 39.7%, respectively). In both groups, the denture stomatitis prevalence was greater in women. There was no statistically significant difference between the groups regarding the age of denture wearers, the number of dentures used, or the vertical dimension of occlusion. In group B, the denture stomatitis prevalence was significantly related to the years of denture-wearing experience and the current denture's usage. In both groups, continuous denture wearing was highly related to denture stomatitis prevalence. CONCLUSIONS: This cross-sectional study showed that 2 different population groups of denture wearers presented different complete denture wearing habits and denture stomatitis prevalence. Comparisons indicate that proper denture wearing habits decrease the prevalence of denture stomatitis.

A clinical 5-year longitudinal study on the dimensional changes of complete maxillary dentures.

PURPOSE: Acrylic resin complete dentures exhibit dimensional changes mainly because of processing shrinkage and expansion because of water uptake. The aim of this 5-year clinical study was to determine the dimensional changes occurring during construction and in service in maxillary complete dentures made of two types of acrylic resin. MATERIALS AND METHODS: Complete dentures were constructed for 17 edentulous patients. Nine patients received dentures made of conventional heat-cured acrylic resin, and eight patients received dentures made of rapid heat-cured acrylic resin. Measurements were taken across three reference points (second molars bilaterally and central incisors) on six occasions: at the flasking stage, at the denture insertion appointment, and after 1 week, 1 month, 3 months, and 5 years of use. The data obtained were analyzed using one-factor repeated-measures ANOVA, one-way ANOVA, and Duncan's multiple comparisons test. RESULTS: The two types of dentures showed the same pattern of dimensional changes. A shrinkage of up to 0.27% was estimated at the insertion stage. During the first 3 months of use, a decrease of the initial dimensional change was observed. After a 3-month period, a gradual compensation for the initial shrinkage started to take place. At the end of the study period (5 years), an expansion of up to 0.35% was measured. CONCLUSION: Maxillary complete dentures made of either conventional or rapid heat-cured acrylic resin exhibited dimensional changes that were considered clinically acceptable.

Evaluation of porosity in microwave-processed acrylic resin using a photographic method.

STATEMENT OF PROBLEM: The effect of microwave polymerization on the porosity of denture base resin has not been fully determined. PURPOSE: This study investigated the effect of microwave energy on the porosity of 2 heat-activated denture base resins. MATERIAL AND METHODS: Two heat-activated denture base resins, one conventional (Paladon 65) and one designed for microwave polymerization (Acron MC), were used to prepare 50 test specimens. Five groups of 10 specimens each were established: Group A (Paladon 65, water bath); Group B(1) (Paladon 65, short microwave cycle); Group B(2) (Paladon 65, long microwave cycle); Group C(1) (Acron MC, short microwave cycle); and Group C(2) (Acron MC, long microwave cycle). Half of the specimens in each group were 3 mm thick, the other half 6 mm thick. After being polymerized, specimens were cut so that 3 cross-sectional areas were formed (S(1), S(2), and S(3)). These surfaces were polished and photographed under a microscope at x100 magnification. On the developed photographs, the area of each pore was measured with a digital planimeter, and the total area of pores per surface was calculated in percentage form. The total number of pores on each surface and the topographical distribution of the pores also were recorded. A 3-factor repeated-measures analysis of variance was used to compare porosity data, and a 1-way analysis of variance was performed to determine possible interactions between groups based on material and specimen thickness (P<.05). The effect of surface area on porosity data was analyzed with the use of contrasts. RESULTS: Group A specimens exhibited no pores. In the thicker specimens of Groups B(1) and B(2), giant pores (area as great as 3.69 mm(2)) and small, gaseous pores of almost uniform shape and size were found. In Groups C(1) and C(2), only the smaller pores were found; these were not clinically significant. Of the observed surfaces, 75.3% were free of pores and 24.7% contained at least one pore. In a selected group of pore-bearing surfaces, the majority (81%) had pores located near the center. The thicker specimens in Group B exhibited the greatest amount of porosity (P<.0001); Group C specimens exhibited the least porosity. Repeated-measures analysis of variance showed that polymerization cycle had no effect on porosity (P=.19). The 3 other factors (material, specimen thickness, and surface) and all possible interactions among them were significant (P<.05). Among the surfaces, S(1) and S(2) exhibited the highest total mean value of porosity (0.71% and 0.74%, respectively) and S(3) the lowest (0.025%). S(3) showed a different pattern of porosity than S(1) and S(2). CONCLUSION: Within the limitations of this in vitro study, minor porosity was identified in thin and more severe porosity in thicker areas of conventional resin specimens that underwent microwave polymerization. The resin designed specifically for microwave polymerization exhibited no clinically significant porosity.