Relationship between masticatory cycle morphology and unilateral crossbite in the primary dentition.

Occlusion is an important factor that affects chewing. Unilateral posterior crossbites (UPXBs) have been reported to be one of the most prevalent malocclusions in the primary dentition and patients with UPXBs show abnormal condylar motion on the crossbite side in the mediolateral direction during mastication. The aims of this study were to investigate the characteristics of common chewing cycles in the primary dentition in children with UPXBs, when chewing gum on the UPXB side and on the non-UPXB side, and to compare the average chewing pattern with a group of children with a normal buccal relationship. Twenty children in the primary dentition with a UPXB (6 boys, mean age 5.3 ± 1.2 years, and 14 girls, 4.8 ± 1.3 years of age; 9 with a left and 11 with a right UPXB) and 10 children with a normal occlusion were randomly selected. Chewing movements were recorded with the Sirognathograph computer analysing system (COSIG II). All children were asked to chew gum on both sides. The chewing patterns were averaged and analysed in two projection planes and compared using a Student's t-test with respect to the relationship between chewing pattern and occlusion. Significance was set at P ≤ 0.05. Children with a UPXB showed a difference between the chewing pattern on the UPXB and non-UPXB sides. Greater lateral deviation in the chewing cycle was observed on the working side when chewing on the non-UPXB side. The closing angle was found to be more pronounced towards the non-working side when chewing on the UPXB side and the time spent in maximal intercuspation showed reduced values when chewing on the same side. Children with a UPXB opened their mouths wider and showed greater chewing cycles in the sagittal and horizontal projection planes while chewing on the UPXB side and also in the frontal projection while chewing on both the UPXB and the non-UPXB sides in comparison with the control group, P ≤ 0.05. Children with a UPXB produced chewing cycles with a shorter rest position and more frequently in a reverse direction when chewing on the UPXB side in comparison with children with a normal occlusion and with the non-UPXB side. Based on the results of this study, early treatment is recommended to normalize the masticatory chewing cycle pattern to ensure normal growth and development of the orofacial system.

The Slovenian version of the Oral Health Impact Profile Questionnaire (OHIP-SVN): translation and psychometric properties.

The aim of the study was to develop and to test the psychometric properties of the Slovenian version (OHIP-SVN) in the new cultural context. Construct validity was tested on 430 subjects, test-retest reliability on 60 subjects, internal consistency on 460 subjects, and responsiveness on 30 patients with a treatment demand (toothache). The significant association between the OHIP summary scores and the self-reported oral health (p < 0.001) confirmed the construct validity. The test-retest reliability showed high intraclass correlation coefficients and no significant differences between the two administrations (p > 0.05). The internal consistency showed high Cronbach's alpha (0.97). The responsiveness was confirmed by the statistically significant difference between the mean OHIP score at baseline and follow-up (p < 0.001) and by a considerable effect size in the patients with a treatment demand (0.515). The OHIP-SVN, as one of the first translation into one of the Slavic family of the languages proves that this instrument is suitable for the assessment of the Oral Health Related Quality of Life in Slovenia.

Oral health related quality of life in Slovenian patients with craniomandibular disorders.

Sixty eight consecutive Slovenian patients with craniomandibular disorders (CMD) participated as the study group and another 400 adults from the regional population sample participated as the control group. The aim was to determine the impact of craniomandibular disorders to the self-perceived oral health related quality of life (OHRQoL) and to compare the OHRQoL with a control group. The mean Oral Health Impact Profile (OHIP) summary scores were computed for all patients with the same diagnosis and for the same subgroups of the axis I according to the RDC/TMD exam protocol. The mean OHIP subscores for the seven domains of the OHIP questionnaire were compared between the study and the control group. Significantly higher OHIP summary scores and all the OHIP subscores were obtained in the CMD patients in comparison with the control group (p<0.05). Furthermore, in the CMD group, patients with two related diagnoses had significantly higher impaired OHRQoL than patients with a single one. The results revealed: 1. The CMD subjects are highly associated with the reduced OHRQoL, 2. Higher number of diagnoses of the axis I according to the RDC/TMD results in the more impaired OHRQoL, 3. The higher age of the patients revealed the more impaired OHRQoL.

Psychometric properties of Croatian and Slovenian short form of oral health impact profile questionnaires.

AIM: To develop Croatian and Slovenian versions of the 14-item Oral Health Impact Profile (OHIP) Questionnaire. METHODS: The English original version of the OHIP questionnaire was translated into Croatian (OHIP-CRO14) and Slovenian (OHIP-SVN14) language by a forward-backward translation method. The psychometric properties of the OHIP-CRO14 and OHIP-SVN14 were tested. Concurrent validity was tested on 623 subjects (193 Croatian and 430 Slovenian), test-retest reliability on 115 subjects (55 Croatian and 60 Slovenian), internal consistency on 678 subjects (218 Croatian and 460 Slovenian), and responsiveness on 51 patients (21 Croatian and 30 Slovenian) in demand of treatment (toothache). RESULTS: Concurrent validity was confirmed by the association between the OHIP summary scores and self-reported oral health (correlation coefficients ranged from 0.40 to 0.60, P<0.001). Test-retest reliability showed high intraclass correlation (correlation coefficients, 0.79-0.94). Internal consistency showed high Cronbach alpha (0.77-0.91). Responsiveness was confirmed by a significant difference between the mean OHIP score at baseline and follow-up (P<0.001 for both Croatian and Slovenian patients) and high effect size in Croatian and Slovenian patients in demand of treatment (3.00 and 0.57, respectively). CONCLUSION: Psychometric properties of OHIP-CRO14 and OHIP-SVN14 render these instruments suitable for the assessment of Oral Health Related Quality of Life in Croatia and Slovenia.

Fracture resistance and reliability of new zirconia posts.

STATEMENT OF PROBLEM: The radicular portion of zirconia endodontic posts often need to be reshaped to achieve a definitive form and may be airborne-particle abraded to improve adhesion during luting. Therefore, the surface of the tetragonal zirconia ceramics may be transformed and damaged, influencing the mechanical properties of the material. PURPOSE: This study compared the fracture resistance of prefabricated zirconia posts with a new retentive post-head after different surface treatments. MATERIAL AND METHODS: Experimental zirconia posts of 2 different diameters, 1.3 mm and 1.5 mm, were produced from commercially available zirconia powder. A cylindro-conical outline form was used for the root portion of the system and a post-head with 3 retentive rings was designed. Sixty posts of each diameter were divided into 3 groups (n=20). Group 1 was ground with a coarse grit diamond bur; Group 2 was airborne-particle abraded with 110-microm fused alumina particles, and Group 3 was left as-received (controls). Posts were luted into the root-shaped artificial canals with the Clearfil adhesive system and Panavia 21 adhesive resin luting agent. The posts were loaded in a universal testing machine at an inclination of 45 degrees with the constant cross-head speed of 1 mm/min. The fracture load (N) necessary to cause post fracture was recorded, and the statistical significance of differences among groups was analyzed with 1-way ANOVA followed by the Fischer LSD test (alpha=.05). The variability was analyzed using Weibull statistics. RESULTS: Load to fracture values of all zirconia posts depended primarily on post diameter. Mean fracture loads (SD) in Newtons were 518.4 (+/-101.3), 993.6 (+/-224.1), and 622.7 (+/-110.3) for Groups 1 through 3, respectively, for thicker posts, and 385.9 (+/-110.3), 627.0 (+/-115.1), and 451.2 (+/-81.4) for Groups 1 through 3, respectively, for thinner posts. Airborne-particle-abraded posts exhibited significantly higher resistance to fracture (P<.05) than those in the other 2 groups for diameters 1.3 mm and 1.5 mm. Grinding reduced Weibull modulus compared with controls, and the values were 4.1 and 6.5 for thicker and thinner posts, respectively. CONCLUSION: Within the limitations of this study, the results suggest that grinding leads to a significant drop in load to fracture of zirconia posts, whereas airborne-particle abrasion increased the fracture load.

Gingival inflammatory response induced by chemical retraction agents in beagle dogs.

PURPOSE: The aim of this in vivo study on dogs was to investigate and compare the inflammatory potential of four different retraction agents on the gingival connective tissue. MATERIALS AND METHODS: All procedures on eight beagle dogs were performed under general anesthesia: taking oral hygiene measures, placing retraction cords medicated with four chemical agents into the gingival sulci, and taking tissue biopsies. The specimens were evaluated after a 10-minute exposure to chemical agents. The inflammatory response of the connective tissue underlying the sulcular and junctional epithelium triggered by retraction agents was assessed quantitatively. Microscopic images of tissue specimens were morphometrically analyzed using a computer-assisted morphometric method. RESULTS: The most intense inflammatory response in the connective tissue underlying the sulcular epithelium was triggered by astringent retraction agents--Racestyptine in specimens taken after 1 day and 1 week and Rastringent after 1 day (P < .05). Tetrahydrozoline-sympathomimetic vasoconstrictor (Visine) was found to have the lowest inflammatory potential. Retraction chemicals produced no significant effects on the connective tissue subjacent to the junctional epithelium. The ratio of the connective tissue area to that of the inflammatory infiltrate showed that 25% aluminum chloride (Racestyptine) was the most aggressive and tetrahydrozoline the least aggressive retraction agent used. CONCLUSION: All the retraction chemicals tested increased the infiltration with inflammatory cells in gingival connective tissue.

Electron microscopic analysis of the effects of chemical retraction agents on cultured rat keratinocytes.

STATEMENT OF PROBLEM: Chemical retraction agents used in fixed prosthodontics for temporary displacement of free gingival tissue before impression making can cause injury to the gingival tissue cells. PURPOSE: This study evaluated changes in cultured rat keratinocytes treated with 2 chemical agents used for gingival retraction. Treated cultures were compared with untreated cultures. MATERIAL AND METHODS: Keratinocytes of rat gingiva were grown in a specific medium for 10 days. After treating 1 group of specimens with 0.05% tetrahydrozoline and another group with 25% aluminum chloride, both for 10 minutes, the cultured cells were examined with scanning and transmission electron microscopy and compared with control specimens. RESULTS: Twenty-five percent aluminum chloride produced a significantly greater extent of cellular damage than 0.05% tetrahydrozoline, which caused only mild changes in the cultured cells. CONCLUSION: On the basis of the morphologic and ultrastructural changes in primary cell cultures of rat keratinocytes observed in this study, it was concluded that 25% aluminum chloride was significantly more aggressive than 0.05% tetrahydrozoline.