The Interaction of Two Widely Used Endodontic Irrigants, Chlorhexidine and Sodium Hypochlorite, and Its Impact on the Disinfection Protocol during Root Canal Treatment.

In recent years, sodium hypochlorite and chlorhexidine digluconate have been the gold standard of irrigation solutions utilized within the disinfection protocol during root canal treatments. Nowadays, it is known that, during chemical disinfection of the root canal, consecutive application of sodium hypochlorite and chlorhexidine digluconate leads to the formation of an orange-brown precipitate. This precipitate is described as being chemically similar to para-chloroaniline, which is suspected to have cytotoxic and carcinogenic effects. Concerns also exist regarding its influence on the leakage of root canal fillings, coronal restorations, and tooth discoloration. The purpose of this article is to review the literature on the interaction of sodium hypochlorite and chlorhexidine digluconate on the tooth and its surrounding tissues, and to discuss the effect of the precipitate formed during root canal treatment. We further address options to avoid the formation of the precipitate and describe alternative irrigation solutions that should not interact with sodium hypochlorite or chlorhexidine digluconate.

Influence of Ascorbic Acid as a Growth and Differentiation Factor on Dental Stem Cells Used in Regenerative Endodontic Therapies.

BACKGROUND: Vitamin C is one of the major extracellular nonenzymatic antioxidants involved in the biosynthesis of collagen. It promotes the growth of fibroblasts, wound healing processes, and enhances the survival and differentiation of osteoblasts. The potential effects of ascorbic acid on human dental pulp cells (DPC) and the cells of the apical papilla (CAP) used in actual regenerative endodontic procedures remain largely unknown. In this study, we investigated the possible employment of ascorbic acid in the differentiation and regenerative therapies of DPC and CAP. METHODS: Nine extracted human wisdom teeth were selected for this study. Subpopulations of stem cells within DPC and CAP were sorted with the mesenchymal stem cell marker STRO-1, followed by treatments with different concentrations (0 mM, 0.1 mM, 0.5 mM, and 1.0 mM) of ascorbic acid (AA), RT-PCR, and Western blot analysis. RESULTS: FACS analysis revealed the presence of cell subpopulations characterized by a strong expression of mesenchymal stem cell marker STRO-1 and dental stem cell markers CD105, CD44, CD146, CD90, and CD29. Treatment of the cells with defined amounts of AA revealed a markedly increased expression of proliferation marker Ki-67, especially in the concentration range between 0.1 mM and 0.5 mM. Further investigations demonstrated that treatment with AA led to significantly increased expression of common stem cell markers OCT4, Nanog, and Sox2. The most potent proliferative and expressional effects of AA were observed in the concentration of 0.1 mM. CONCLUSIONS: AA might be a novel and potent growth promoter of human dental cells. Increasing the properties of human dental pulp cells and the cells of the apical papilla using AA could be a useful factor for further clinical developments of regenerative endodontic procedures.

Efficacy of 8% arginine on dentin hypersensitivity: A multicenter clinical trial in 273 patients over 24 weeks.

OBJECTIVES: To assess the efficacy of 8% arginine containing prophylaxis products over 24 weeks in subjects with dentin hypersensitivity (DH). METHODS: 297 patients with established DH (Schiff score 2, 3) in three European study centers were randomly assigned to either 8% arginine and calcium carbonate in-office prophylaxis paste and the respective toothpaste (test group) or fluoride-free prophylaxis paste and sodium monoflourophosphate toothpaste as a negative control group. Air blast (Schiff Score) and tactile (Visual Analog Scale) sensitivity scores were assessed at baseline (BL_0), after single application of the prophylaxis paste (BL_1) and after 4, 8, and 24 weeks of continuous at-home use of the toothpaste. RESULTS: 273 subjects completed the study. Test and control group presented statistically significant percentage reductions (t-test, p < 0.05) in Schiff Score at BL_1 and at 24 weeks relative to BL_0 (difference in %; test group: -23.6, -44.9, control group: -8.8, -32.7). The pooled Schiff Score for the two evaluated teeth yielded a significantly greater alleviation of DH in the test group than in the control group at all evaluation appointments (Ancova, p < 0.05; difference in %: 15.3, 7.4, 10.6, 17.2). CONCLUSIONS: A significant relief of DH was demonstrated after application of the 8% arginine prophylaxis products over 24 weeks compared to a negative control. CLINICAL SIGNIFICANCE: Whilst DH is influencing patients' eating, drinking and tooth brushing habits as well as social life interactions it is important that clinicians are able to offer evidence based immediate and long-lasting treatment methods in order to manage their patients' discomfort.

[Risk Factors for Postoperative Delirium after Cardiac Surgery]. / Risikofaktoren des postoperativen Deliriums in der Herzchirurgie.

Background Delirium is a common psychiatric disorder after cardiac surgery and predisposes patients to increased mortality and morbidity. Its prevention requires knowledge of the risk factors involved. Objective What are preoperative risk factors for postoperative delirium after cardiac surgery? Methods Prospective longitudinal study of 241 elective cardiac surgical patients with preoperative assessment of potential risk factors and delirium assessment twice daily over five postoperative days. Results 13 % of the patients experienced delirium. Reduced cognitive performance (OR: 3.80; 95 % CI: 1.66 - 8.66), higher comorbidity (OR: 1.36; 95 % CI: 1.07 - 1.7) and higher age (OR: 1.08; 95 % CI: 1.02 - 1.13) increased the risk of delirium. Conclusion Delirium after cardiac surgery is common. It occurs in particular in patients with low cognitive performance, higher comorbidity and higher age.

Push-out bond strength of RealSeal SE and AH Plus after using different irrigation solutions.

INTRODUCTION: The aim of this investigation was to evaluate the influence of different endodontic irrigants (sodium hypochlorite [NaOCl], chlorhexidine [CHX], and EDTA) on the push-out bond strength of the obturation materials RealSeal SE (SybronEndo, Orange, CA) and AH Plus (Dentsply International Inc, York, PA). METHODS: Two hundred human root canals were prepared and divided into 2 groups according to the filling material (RealSeal SE vs AH Plus). Each group was subdivided into 5 groups according to the irrigation protocol (0.9% saline [control], 3% NaOCl, 3% NaOCl with saline, 17% EDTA, and 2% CHX). After obturation, roots were sliced into 1-mm discs for push-out assessment. Compressive loading was performed using an universal testing machine at a speed of 0.5 mm/min. Two-way analysis of variance and the Kruskal-Wallis test were performed for pair-wise comparisons to assess the differences between the experimental groups. RESULTS: AH Plus exhibited a significantly higher bond strength than RealSeal SE (mean = 2.53 and 1.53 MPa, respectively; P < .05), except with saline alone (P > .05). Within the AH Plus groups, no significant differences existed between the irrigants and saline alone (P > .05). The bond strength of RealSeal SE with saline alone or with NaOCl and saline did not differ from that of AH Plus with saline alone (P > .05). However, the push-out bond strength of RealSeal SE decreased by approximately half (P < .05 compared with RealSeal SE with saline alone) after rinsing with NaOCl alone, EDTA, or CHX. CONCLUSIONS: The bond strength of RealSeal SE is highly influenced by the irrigant used.

Expression of the IGF-1, IGFBP-3 and IGF-1 receptors in dental pulp stem cells and impacted third molars.

IGF-1 regulates the metabolism of hard dental tissue through binding to the IGF-1 receptor on target cells. Furthermore, IGF-binding-protein-3 promotes the accessibility of IGF-1. The aim of this study was to investigate the expression of IGF-1, IGFBP-3 and IGF-1R in STRO-1-positive dental pulp stem cells (DPSCs) and fully impacted wisdom teeth in relation to tooth development. Third molars were surgically removed from 60 patients and classified into two groups: teeth showing ongoing development (group 1) and teeth that had completed root shaping (group 2). The transcript and protein levels of IGF-1, IGFBP-3 and IGF-1R were investigated using RT-PCR and immunohistochemistry. The expression of the same proteins was also analyzed in DPSCs. The teeth from group 1 showed significantly stronger expression of IGF-1 and IGF-1R. The major sources of all of the proteins investigated immunohistochemically in sections of wisdom teeth were odontoblasts, cementoblasts and cell colonies in the pulpal mesenchyme. These colonies were identified as stem cells in view of their positivity for STRO-1, and the cells were subsequently sorted by flow cytometry. These DPSCs demonstrated high levels of pluripotency markers and IGF-1 and IGF-1R. We conclude that members of the IGF-1 family are involved in the late stage of tooth development and the process of pulpal differentiation.

The influence of parotid gland sparing on radiation damages of dental hard tissues.

OBJECTIVE: The aim of the present study was to evaluate whether radiation damage on dental hard tissue depends on the mean irradiation dose the spared parotid gland is subjected to or on stimulated whole salivary flow rate. MATERIAL AND METHODS: Between June 2002 and October 2008, 70 patients with neck and cancer curatively irradiated were included in this study. All patients underwent dental treatment referring to the guidelines and recommendations of the German Society of Dental, Oral and Craniomandibular Sciences prior, during, and after radiotherapy (RT). During the follow-up period of 24 months, damages on dental hard tissues were classified according to the RTOG/EORTC guidelines. The mean doses (D(mean)) during spared parotid gland RT were determined. Stimulated whole saliva secretion flow rates (SFR) were measured before RT and 1, 6, 12, 24 months after RT. RESULTS: Thirty patients showed no carious lesions (group A), 18 patients developed sporadic carious lesions (group B), and 22 patients developed general carious lesions (group C). Group A patients received a D mean of 21.2 ± 11.04 Gy. Group B patients received a D(mean) of 26.5 ± 11.59 Gy and group C patients received a D(mean) of 33.9 ± 9.93 Gy, respectively. The D(mean) of group A was significantly lower than the D(mean) of group C (p < 0.001). Additionally, the mean SFR 6 months after RT of group A was significantly higher than the mean SFR of group C (p < 0.01). CONCLUSIONS: Irradiation damage on dental hard tissue correlates with increased mean irradiation doses as well as decreased salivary flow rates. CLINICAL RELEVANCE: Parotid gland sparing resulting in a dose below 20 Gy reduces radiation damage on dental hard tissues, and therefore, the dose may act as a predictor for the damage to be expected.

How valid and applicable are current diagnostic criteria and assessment methods for dentin hypersensitivity? An overview.

OBJECTIVES: Although dentin hypersensitivity is a common clinical condition and is generally reported by the patient after experiencing a sharp, short pain caused by one of several different external stimuli, it is often inadequately understood. The purpose of this paper is to discuss different available diagnostic approaches and assessment methods used in order to suggest a basis to diagnose, monitor, and measure these challenging painful conditions related to dentin hypersensitivity in daily practice and scientific projects properly. MATERIAL AND METHODS: A PubMed literature search strategy including the following MeSH terms were used as follows: "dentin sensitivity"[MeSH Terms] OR "dentin"[All Fields] AND "sensitivity"[All Fields] OR "dentin sensitivity"[All Fields] OR "dentin"[All Fields] AND "hypersensitivity"[All Fields] OR "dentin hypersensitivity"[All Fields] AND "diagnosis"[Subheading] OR "diagnosis"[All Fields] OR "diagnosis"[MeSH Terms] AND "assessment"[All Fields] AND ("methods"[Subheading] OR "methods"[All Fields] OR "methods"[MeSH Terms]. Furthermore, alternative terms such as "validity," "reliability," "root," "cervical," "diagnostic criteria," and "hypersensitivities" were additionally evaluated. RESULTS: The literature search, also including the alternative terms and journals, revealed only a small number of specific papers related to valid diagnosis, diagnostic criteria, and assessment methods of dentin hypersensitivity. Outcomes from these publications showed that the response to different stimuli varies substantially from one person to another and is, due to individual factors, often difficult to assess correctly. Furthermore, the cause of the reported pain can vary, and the patient's description of the history, symptoms, and discomfort might be different from one to another, not allowing a reliable and valid diagnosis. CONCLUSIONS: The dental practitioner, using a variety of diagnostic and measurement techniques each day, will often have difficulties in differentiating dentin hypersensitivity from other painful conditions and in evaluating the success of a conducted therapy in a reliable way. CLINICAL RELEVANCE: Correct diagnosis of dentin hypersensitivity including a patient's history screening and a brief clinical examination in combination with the identification of etiologic and predisposing factors, particularly dietary and oral hygiene habits associated with erosion and abrasion, is essential. The relevant differential diagnosis should be considered to exclude all other dental conditions with similar pain symptoms.

A prospective, randomized clinical trial of a two-step self-etching vs two-step etch-and-rinse adhesive and SEM margin analysis: four-year results.

PURPOSE: The aim of this blinded, randomized, prospective long-term study was to evaluate the clinical performance of the two-step self-etching adhesive AdheSE (AS, Ivoclar Vivadent) compared to the etch-and-rinse adhesive system Excite (EX, Ivoclar Vivadent) in combination with the hybrid resin composite Tetric Ceram HB (Ivoclar Vivadent) for Class I and II restorations. MATERIALS AND METHODS: In accordance with a split mouth design, 50 patients received 100 restorations in premolars and molars. The restorations were assigned at random to the self-etching (AS) or the etch-and-rinse (EX) group. Each restoration was scored according to the modified Ryge criteria at baseline and after 6, 12, 24 and 48 months. Epoxy resin replicas of 60 restorations were made at each observation period for an additional SEM analysis of the occlusal margins. RESULTS: After 4 years, 60 of 100 restorations could be evaluated. The cumulative survival rate for group EX was 100% and for group AS 96.7%. One restoration in group AS had failed due to marginal gap formation. For the criterion marginal adaption in group AS, significantly more bravo ratings (30%) were observed after 4 years compared to group EX (6.7%) (p < 0.05; Mann-Whitney U-test). The results of the SEM margin analysis revealed no significant differences between groups AS and EX (Mann-Whitney U-test; p > 0.05). CONCLUSION: Both adhesive systems performed satisfactorily over the four-year observation period. A significant deterioration over time was found for the criterion marginal adaption in AdheSE.

A prospective, double-blind, randomized clinical trial of a one-step, self-etch adhesive with and without an intermediary layer of a flowable composite: a 2-year evaluation.

OBJECTIVE: The aim of this prospective, double-blind, randomized long-term study was to evaluate the clinical performance of the self-etch adhesive AdheSE One in combination with the nanohybrid composite resin Tetric Evo Ceram for Class 1 and 2 restorations. The improvement of the clinical performance with the additional use of a flowable composite resin for cavity lining was tested. METHOD AND MATERIALS: In accordance with a split-mouth design, 50 patients received 100 restorations in premolars and molars. One restoration of each patient was chosen at random to be restored with an intermediary layer of a flowable composite resin. Each restoration was scored according to the modified Ryge criteria at baseline and after 6, 12, and 24 months. RESULTS: After 24 months (recall rate 88%), the results of the Ryge evaluation for groups without (group T) and with application (group TF) of Tetric Flow were as follows: marginal adaptation, Alpha 40/40 and Bravo 3/4; marginal discoloration, Alpha 39/41 and Bravo 4/3; and filling integrity, Alpha 42/42 and Bravo 1/2. All restored teeth remained vital. The parameters hypersensitivity, recurrent caries, surface, color match, and proximal contact were scored Alpha for all teeth. Between groups, no statistically significant differences could be detected (Mann-Whitney U test, P > .05). CONCLUSION: In consideration of the short observation period, the clinical use of AdheSE One in stress-bearing posterior cavities reached acceptable clinical results with a 1.1% cumulative failure rate after 2 years. The use of a flowable composite resin did not show an improved clinical performance.

Parotid gland-recovery after radiotherapy in the head and neck region--36 months follow-up of a prospective clinical study.

BACKGROUND: The aim of the present study was to evaluate the recovery potential of the parotid glands after using either 3D-conformal-radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) by sparing one single parotid gland. METHODS: Between 06/2002 and 10/2008, 117 patients with head and neck cancer were included in this prospective, non-randomised clinical study. All patients were treated with curative intent. Salivary gland function was assessed by measuring stimulated salivary flow at the beginning, during and at the end of radiotherapy as well as 1, 6, 12, 24, and 36 months after treatment. Measurements were converted to flow rates and normalized relative to rates before treatment. Mean doses (D(mean)) were calculated from dose-volume histograms based on computed tomographies of the parotid glands. RESULTS: Patients were grouped according to the D(mean) of the spared parotid gland having the lowest radiation exposure: Group I - D(mean) < 26 Gy (n = 36), group II - D(mean) 26-40 Gy (n = 45), and group III - D(mean) > 40 Gy (n = 36). 15/117 (13%) patients received IMRT. By using IMRT as compared to 3D-CRT the D(mean) of the spared parotid gland could be significantly reduced (D(mean) IMRT vs. 3D-CRT: 21.7 vs. 34.4 Gy, p < 0.001). The relative salivary flow rates (RFSR) as a function of the mean parotid dose after 24 and 36 months was in group I 66% and 74%, in group II 56% and 49%, and in group III 31% and 24%, respectively. Multiple linear regression analyses revealed that the parotid gland dose and the tumor site were the independent determinants 12 and 36 months after the end of RT. Patients of group I and II parotid gland function did recover at 12, 24, and 36 months after the end of RT. CONCLUSIONS: If a D(mean) < 26 Gy for at least one parotid gland can be achieved then this is sufficient to reach complete recovery of pre-RT salivary flow rates. The radiation volume which depends on tumor site did significantly impact on the D(mean) of the parotids, and thus on the saliva flow and recovery of parotid gland.

Closing the gap between oral hygiene and minimally invasive dentistry: a review on the resin infiltration technique of incipient (proximal) enamel lesions.

Dental caries on (proximal) tooth surfaces is still a problem in many industrialized countries. The objectives of this review were to present the scientific basis and the principles of the resin infiltration concept, to discuss the inherent clinical applications, and to describe how these backgrounds can be integrated into the concept of minimal intervention dentistry. Data were identified by searches of the Cochrane Registers, Medline, and Scopus. Articles published in English and German through December 2008 were selected, and most up-to-date or relevant references were chosen. Cross-referencing of significant articles identified additionally relevant articles written in other languages and those of historical value. A total of 23 in vitro studies (focusing on penetration depths or demineralization prevention) were found, and 3 clinical studies (involving 122 subjects) could be retrieved; these studies were not comparable. With an increased understanding of the caries process, it is now recognized that demineralized but noncavitated enamel lesions can be arrested or remineralized in many situations. The clinical research evidence on the resin infiltration technique currently is of moderate extent to reach any decisive conclusions; however, based on available laboratory and clinical studies, it seems convincing that resin infiltration of enamel lesions should reduce (or even stop) the progress of white spot lesions. Combining this ultraconservative restorative approach (which is considered microinvasive) with a substantial caries remineralization program may provide therapeutic benefits and significantly reduce both long-term restorative needs and costs, thus complementing the concept of minimal intervention dentistry.

The influence of application of different desensitisers on root dentine demineralisation in situ.

AIM: To evaluate the influence of three desensitisers on root caries demineralisation in situ. METHODS: The root surfaces of 36 freshly extracted human molars were used to prepare root dentine specimens. These specimens were distributed among the following groups: A: Admira Protect, V: VivaSens, H: Hyposen, C: control group, untreated. Two dentine specimens of each group were inserted into two buccal aspects of intraoral mandibular appliances. The appliances were worn by nine persons for five weeks, day and night. One side was brushed daily with a toothpaste. On the other side, plaque was allowed to grow. Individual oral hygiene techniques were performed without any fluorides. After the in situ period, two slabs were ground. The depth of the demineralised areas was determined using a polarised light microscope. RESULTS: ANOVA revealed significant differences between brushed and non-brushed specimens. Lesion depths in the brushed group were significantly decreased (p < 0.05, Tukey's test). CONCLUSIONS: Within the limitations of an in situ study it can be concluded that the demineralisation of the root surface can be hampered by application of desensitisers under different oral hygiene conditions. The application of clinical proven desensitising agents might have a caries-protective effect on exposed root surfaces.

Maxillary molars with morphologic variations of the palatal root canals: a report of four cases.

INTRODUCTION: The purpose of this article was to show the importance of the knowledge of the anatomy of root canals. Unusual root and root canal morphologies associated with both buccal roots of upper molars have been recorded in several studies in the literature. However, scientific information focusing on variations of the palatal root is rare. METHODS: In this report, four cases are presented involving the root canal treatment of maxillary first and second molars with unusual morphologic configurations of the palatal root canals. RESULTS: During root canal treatment, type IV and V configurations as defined by Vertucci of the palatal canals of two first and two second maxillary molars were identified. After mechanical instrumentation, the canals were obturated. Radiologic and clinical re-evaluation showed no signs of inflammation. CONCLUSIONS: This report describes and discusses the possibility of different root and canal variations of the maxillary molars from a clinical point of view. Anatomic variations can occur in any tooth, and palatal roots of maxillary first and second molars are no exception. Therefore, careful examination of radiographs and internal anatomy of teeth is essential.

Effect of Cisplatin on parotid gland function in concomitant radiochemotherapy.

PURPOSE: To determine the influence of concomitant radiochemotherapy with cisplatin on parotid gland tissue complication probability. METHODS AND MATERIALS: Patients treated with either radiotherapy (n = 61) or concomitant radiochemotherapy with cisplatin (n = 36) for head-and-neck cancer were prospectively evaluated. The dose and volume distributions of the parotid glands were noted in dose-volume histograms. Stimulated salivary flow rates were measured before, during the 2(nd) and 6(th) weeks and at 4 weeks and 6 months after the treatment. The data were fit using the normal tissue complication probability model of Lyman. Complication was defined as a reduction of the salivary flow rate to less than 25% of the pretreatment flow rate. RESULTS: The normal tissue complication probability model parameter TD(50) (the dose leading to a complication probability of 50%) was found to be 32.2 Gy at 4 weeks and 32.1 Gy at 6 months for concomitant radiochemotherapy and 41.1 Gy at 4 weeks and 39.6 Gy at 6 months for radiotherapy. The tolerated dose for concomitant radiochemotherapy was at least 7 to 8 Gy lower than for radiotherapy alone at TD(50). CONCLUSIONS: In this study, the concomitant radiochemotherapy tended to cause a higher probability of parotid gland tissue damage. Advanced radiotherapy planning approaches such as intensity-modulated radiotherapy may be particularly important for parotid sparing in radiochemotherapy because of cisplatin-related increased radiosensitivity of glands.

The influence of different irradiation doses and desensitizer application on demineralization of human dentin.

The aim of the present study was to evaluate the effect of different irradiation doses after desensitizer application on the onset of initial demineralization of human dentin in situ. The root surfaces of 45 freshly extracted caries-free human molars were cleaned, thereby removing the cementum. From each tooth two root dentin specimens were prepared. The specimens were distributed among the following experimental groups: 0, 0.5, 1, 2 and 5Gy. The irradiation dose was fractionally applied (0.5Gy/day). One dentin specimen of each group was inserted into both buccal aspects of nine intraoral mandibular appliances. On one side the specimens were additionally coated with the desensitizer Hyposen (H). On the other side, the specimens were left untreated (C). The appliances were worn by nine persons for five weeks day and night. During meals, the appliance was stored in 10% sucrose solution. After the in situ period, slabs (150microm) were ground and studied using a polarized light microscope. Concerning radiation dose, significant differences were observed between the control and 5Gy group (p<0.05, Tukey s test). Pairwise comparison showed that lesion depths in groups treated with Hyposen were significantly decreased. Within the limitations of this study it can be concluded that higher radiation doses seem to increase the caries susceptibility of dentin. The additional application of a desensitizer hampers the demineralization and might have a caries-protective effect on exposed irradiated root surfaces.

Parotid-gland-sparing 3D conformal radiotherapy in patients with bilateral radiotherapy of the head and neck region--results in clinical practice.

The aim was to improve the prediction rate of hyposalivation after using a modern 3D-conformal-radiotherapy-technique (3D-CRT) by sparing of the contralateral parotid gland. Between June 2002 and October 2006, 107 patients (90 male, 17 female, average age: 58 years) with squamous cell carcinoma of the head and neck were included in a prospective, non-randomized study. All patients were treated using 3D-CRT. Parotid function was assessed by measuring stimulated salivary flow before, during and at the end of radiotherapy, as well as 1, 6 and 12 months after radiotherapy. Measurements were converted to flow rates and normalized relative to that before treatment. Mean doses (D(mean)) were calculated from dose-volume histograms (DVHs) based on computed tomographies (CTs) for the left and right parotid gland separately. Patients were grouped according to the D(mean) of the lowest irradiated parotid gland. Group I included all patients who received a D(mean)<26Gy (n=23), group II D(mean) 26-40Gy (n=38) and group III D(mean)>40Gy (n=46). By the time of 6 months after irradiation, salivary flow rates decreased continuously during the therapy. In group I the flow rate decreased to 59%, in group II to 40% and in group III to 14%, p<0.05. One year after irradiation a recovery effect could be measured in all groups. A sufficient saliva flow rate can be proven if one parotid gland is spared with a D(mean) dose <26Gy. Approximately, one quarter of the participants showed a significant improvement.

Fracture strength of different soldered and welded orthodontic joining configurations with and without filling material.

The aim of this study was to compare the mechanical strength of different joints made by conventional brazing, TIG and laser welding with and without filling material. Five standardized joining configurations of orthodontic wire in spring hard quality were used: round, cross, 3 mm length, 9 mm length and 7 mm to orthodontic band. The joints were made by five different methods: brazing, tungsten inert gas (TIG) and laser welding with and without filling material. For the original orthodontic wire and for each kind of joint configuration or connecting method 10 specimens were carefully produced, totalizing 240. The fracture strengths were measured with a universal testing machine (Zwick 005). Data were analyzed by ANOVA (p=0.05) and Bonferroni post hoc test (p=0.05). In all cases, brazing joints were ruptured on a low level of fracture strength (186-407 N). Significant differences between brazing and TIG or laser welding (p<0.05, Bonferroni post hoc test) were found in each joint configuration. The highest fracture strength means were observed for laser welding with filling material and 3 mm joint length (998 N). Using filling materials, there was a clear tendency to higher mean values of fracture strength in TIG and laser welding. However, statistically significant differences were found only in the 9-mm long joints (p<0.05, Bonferroni post hoc test). In conclusion, the fracture strength of welded joints was positively influenced by the additional use of filling material. TIG welding was comparable to laser welding except for the impossibility of joining orthodontic wire with orthodontic band.