Bleaching of nonvital teeth: a clinically relevant literature review

Today, the bleaching of nonvital, discolored teeth is a low-risk routine treatment for improving esthetics. This review article focuses on the etiology of tooth discolorations, different treatment techniques, and risks of bleaching procedures. Some tooth discolorations in endodontically treated teeth are caused by dental treatments. The three most popular techniques for nonvital tooth bleaching are the walking bleach technique, inside/outside bleaching, and in-office bleaching. The walking bleach technique is a relatively reliable, fairly simple technique for dentists and patients. Inside/outside bleaching can be used additionally when internal and external bleaching must be combined. Inoffice bleaching seems to be a short-term solution, the effects of which can largely be attributed to dehydration of the teeth. There are still some open questions concerning the bleaching agents. Improved safety seems desirable with regard to adding thiourea as a scavenger of radicals or newer materials such as sodium percarbonate. The thermocatalytic technique, insufficient cervical sealing, and high concentrations of bleaching agents should be avoided, as this can increase the risk of cervical root resorptions. Patients should be informed about the low predictability of bleaching success and the risk of recurrent discoloration. The risk of cervical root resorption should be discussed with the patient. There is a strong correlation between root resorption and dental trauma.

Hand and ultrasonic instrumentation for orthograde root canal treatment of permanent teeth

Root canal treatment is a frequently performed dental procedure and is carried out on teeth in which irreversible pulpitis has led to necrosis of the dental pulp. Removal of the necrotic tissue remnants and cleaning and shaping of the root canal are important phases of root canal treatment. Treatment options include the use of hand and rotary instruments and methods using ultrasonic or sonic equipment. OBJECTIVES: The objectives of this systematic review of randomized controlled trials were to determine the relative clinical effectiveness of hand instrumentation versus ultrasonic instrumentation alone or in conjunction with hand instrumentation for orthograde root canal treatment of permanent teeth. MATERIAL AND METHODS: The search strategy retrieved 226 references from the Cochrane Oral Health Group Trials Register (7), the Cochrane Central Register of Controlled Trials (CENTRAL) (12), MEDLINE (192), EMBASE (8) and LILACS (7). No language restriction was applied. The last electronic search was conducted on December 13th, 2007. Screening of eligible studies was conducted in duplicate and independently. RESULTS: Results were to be expressed as fixed-effect or random-effects models using mean differences for continuous outcomes and risk ratios for dichotomous outcomes with 95% confidence intervals. Heterogeneity was to be investigated including both clinical and methodological factors. No eligible randomized controlled trials were identified. CONCLUSIONS: This review illustrates the current lack of published or ongoing randomized controlled trials and the unavailability of high-level evidence based on clinically relevant outcomes referring to the effectiveness of ultrasonic instrumentation used alone or as an adjunct to hand instrumentation for orthograde root canal treatment. In the absence of reliable research-based evidence, clinicians should base their decisions on clinical experience, individual circumstances and in conjunction with patients' preferences where appropriate. Future randomized controlled trials might focus more closely on evaluating the effectiveness of combinations of these interventions with an emphasis on not only clinically relevant, but also patient-centered outcomes.

Formation of caries-like lesions in vitro on the root surfaces of human teeth in solutions simulating plaque fluid

Lesion formation on root surfaces of human posterior teeth was studied in acetate/lactate buffers with a background electrolyte composition based on plaque fluid analyses. Lesion depth after 28 days at 37 degrees C was measured in relation to: the presence or absence of cementum; the concentration of undissociated buffer; the presence or absence of magnesium ions at plaque fluid concentration. Each factor was evaluated at several values of -log(ion activity product for hydroxyapatite): pI(HA). Solutions were formulated to minimize variation in pH, which varied by < or =0.03 for a given comparison (individual pI(HA)) and by 0.42-0.82 over the range of pI(HA) within experiments. Lesions on surfaces from which cementum had been ground were significantly deeper than on intact surfaces, but this is considered to be due to subsurface mechanical damage and not to a solubility difference. Neither the concentration of undissociated buffer nor the presence of magnesium ions significantly affected lesion depth. Lesion depth was strongly influenced by the correlated variations in pI(HA) and pH. At pI(HA) 54 and 55, only extremely shallow lesions formed. From pI(HA) 56, lesion depth increased with increasing pI(HA). The results confirm that the solubility of the mineral of root tissues is higher than that of hydroxyapatite, but indicate that it is probably lower than suggested by Hoppenbrouwers et al. [Arch Oral Biol 1987;32:319-322]. For calcium concentrations of 3-12 mM, the critical pH for root tissue mineral was calculated as 5.22-5.66 assuming solubility equivalent to pI(HA) 54 and 5.08-5.51 assuming pI(HA) 55.

Complication and failure rates in patients treated for chronic periodontitis and restored with single crowns on teeth and/or implants

Objectives: To assess the biological and technical complication rates of single crowns on vital teeth (SC-V), endodontically treated teeth without post and core (SC-E), with a cast post and core (SC-PC) and on implants (SC-I). Material and methods: From 392 patients with chronic periodontitis treated and documented by graduate students during the period from 1978 to 2002, 199 were reexamined during 2005 for this retrospective cohort study, and 64 of these patients were treated with SCs. Statistical analysis included Kaplan–Meier survival functions and event rates per 100 years of object-time. Poisson regression was used to compare the four groups of crowns with respect to the incidence rate ratio of failures, and failures and complications combined over 10 years and the entire observation period. Results: Forty-one (64%) female and 23 (36%) male patients participated in the reexamination. At the time of seating the crowns, the mean patient age was 46.8 (range 24–66.3) years. One hundred and sixty-eight single unit crowns were incorporated. Their mean follow-up time was 11.8 (range 0.8–26.4) years. During the time of observation, 22 biological and 11 technical complications occurred; 19 SC were lost. The chance for SC-V (56) to remain free of any failure or complication was 89.3% (95% confidence interval [CI] 76.1–95.4) after 10 years, 85.8% (95% CI 66–94.5) for SC-E (34), 75.9% for SC-PC (39), (95% CI 58.8–86.7) and 66.2% (95% CI 45.1–80.7) for SC-I (39). Over 10 years, 95% of SC-I remained free of failure and demonstrated a cumulative incidence of failure or complication of 34%. Compared with SC-E, SC-I were 3.5 times more likely to yield failures or complications and SC-PC failed 1.7 times more frequently than did SC-E. SC-V had the lowest rate of failures or complications over the 10 years. Conclusions: While SCs on vital teeth have the best prognosis, those on endodontically treated teeth have a slightly poorer prognosis over 10 years. Crowns on teeth with post and cores and implant-supported SCs displayed the highest incidence of failures and complications.

Teeth restored using fiber-reinforced posts: in vitro fracture tests and finite element analysis

In dentistry the restoration of decayed teeth is challenging and makes great demands on both the dentist and the materials. Hence, fiber-reinforced posts have been introduced. The effects of different variables on the ultimate load on teeth restored using fiber-reinforced posts is controversial, maybe because the results are mostly based on non-standardized in vitro tests and, therefore, give inhomogeneous results. This study combines the advantages of in vitro tests and finite element analysis (FEA) to clarify the effects of ferrule height, post length and cementation technique used for restoration. Sixty-four single rooted premolars were decoronated (ferrule height 1 or 2 mm), endodontically treated and restored using fiber posts (length 2 or 7 mm), composite fillings and metal crowns (resin bonded or cemented). After thermocycling and chewing simulation the samples were loaded until fracture, recording first damage events. Using UNIANOVA to analyze recorded fracture loads, ferrule height and cementation technique were found to be significant, i.e. increased ferrule height and resin bonding of the crown resulted in higher fracture loads. Post length had no significant effect. All conventionally cemented crowns with a 1-mm ferrule height failed during artificial ageing, in contrast to resin-bonded crowns (75% survival rate). FEA confirmed these results and provided information about stress and force distribution within the restoration. Based on the findings of in vitro tests and computations we concluded that crowns, especially those with a small ferrule height, should be resin bonded. Finally, centrally positioned fiber-reinforced posts did not contribute to load transfer as long as the bond between the tooth and composite core was intact.

Investigating interocclusal perception in tactile teeth sensibility using symmetric and asymmetric analysis

The purpose of this clinical trial was to determine the active tactile sensibility of natural teeth and to obtain a statistical analysis method fitting a psychometric function through the observed data points. On 68 complete dentulous test persons (34 males, 34 females, mean age 45.9 ± 16.1 years), one pair of healthy natural teeth each was tested: n = 24 anterior teeth and n = 44 posterior teeth. The computer-assisted, randomized measurement was done by having the subjects bite on thin copper foils of different thickness (5-200 µm) inserted between the teeth. The threshold of active tactile sensibility was defined by the 50% value of correct answers. Additionally, the gradient of the sensibility curve and the support area (90-10% value) as a description of the shape of the sensibility curve were calculated. For modeling the sensibility curve, symmetric and asymmetric functions were used. The mean sensibility threshold was 14.2 ± 12.1 µm. The older the subject, the higher the tactile threshold (r = 0.42, p = 0.0006). The support area was 41.8 ± 43.3 µm. The higher the 50% threshold, the smaller the gradient of the curve and the larger the support area. The curves showing the active tactile sensibility of natural teeth demonstrate a tendency towards asymmetry, so that the active tactile sensibility of natural teeth can mathematically best be described by using the asymmetric Weibull function.

Permanent teeth with horizontal root fractures after dental trauma. A retrospective study

The purpose of the present retrospective study was to evaluate the post-traumatic healing of the pulp and periodontium of 32 permanent teeth with horizontal root fractures. Twenty-nine patients, 8-48 years old, who presented at our department with a root fracture between January 2001 and April 2007, participated in the study. Root-fractured teeth with a loosened or dislocated coronal fragment were repositioned and splinted for 14-49 days (average: 34 days). In cases of severe dislocation of the coronal fragment, prophylactic endodontic treatment was performed. Follow-up examinations were conducted routinely after 1,2,3,6, and 12 months. For this study, follow-up took place for up to 7 years post trauma. Of 32 root-fractured teeth, 29 (91%) survived. 10 teeth (31%) exhibited pulpal healing; 13 teeth (41%) were prophylactically endodontically treated within 2 weeks of injury. At the fracture line, interposition of calcified tissue was evident in 6 teeth (19%), and interposition of granulation tissue was observed in 8 teeth (25%). The prognosis of the root-fractured teeth was good, and one-third of the teeth with root fractures possessed a vital pulp at the final examination.

Immunohistochemical localization of osteoclastogenic cell mediators in feline tooth resorption and healthy teeth

Tooth resorption is among the most common and most challenging problems in feline dentistry It is a progressive disease eventually leading to tooth loss and often root replacement. The etiology of moth resorption remains obscure and to date no effective therapeutic approach is known. The present study is aimed at assessing the reliability of radiographic imaging and addressing the possible involvement of receptor activator of NF kappa B (RANK), its ligand (RANKL), and osteoprotegerin (OPG) in the process of tooth resorption. Teeth from 8 cats were investigated by means of radiographs and paraffin sections followed by immunolabeling. Six cats were diagnosed with tooth resorption based on histopathologic and radiographic findings. Samples were classified according to a four-stage diagnostic system. Radiologic assessment of tooth resorption correlated very strongly with histopathologic findings. Tooth resorption was accompanied by a strong staining with all three antibodies used, especially with anti-RANK and anti-RANKL antibodies. The presence of OPG and RANKL at the resorption site is indicative of repair attempts by fibroblasts and stromal cells. These findings should be extended by further investigations in order to elucidate the pathophysiologic processes underlying tooth resorption that might lead to prophylactic and/or therapeutic measures. J Vet Dent 27(2); 75 - 83, 2010

Do mucositis lesions around implants differ from gingivitis lesions around teeth?

The purpose of this review was to compare peri-implant mucositis and gingivitis with respect to the pathogenesis aspects.

Micromorphology and adhesive performance of Er:YAG laser-treated dentin of primary teeth

This study evaluated (1) the micromorphology by scanning electron microscopy (SEM) and (2) the adhesive performance by microtensile bond strength (μTBS) of diamond bur-treated dentin compared to Er:YAG laser-treated dentin of human primary teeth. (1) For qualitative SEM evaluation, dentin of 18 second primary molars (n = 3/method) was treated with either diamond bur as a control (group 1a: 40 μm diamond bur only (clinical situation); group 1b: grinding + 40 μm diamond bur) or with Er:YAG laser (group 2a (clinical situation, manufacturer's settings): 200 mJ/25 Hz (5 W) + 100 mJ/35 Hz (3.5 W) laser only; group 2b (experimental setting "high"): grinding + 400 mJ/20 Hz (8 W); group 2c (manufacturer's setting "finishing"): grinding + 100 mJ/35 Hz (3.5 W); group 2d (experimental setting "low"): grinding + 50 mJ/35 Hz (1.75 W)). (2) For evaluation of adhesive performance, 64 second primary molars were divided into four groups and treated as described for group 1b and groups 2b/c/d (n = 16/method), and μTBS of Clearfil SE/Clearfil Majesty Esthetic to dentin was measured. The SEM micrographs were qualitatively analyzed. The μTBS values were compared with a Kruskal-Wallis test. The significance level was set at α = 0.05. SEM micrographs showed the typical micromorphologies with a smear layer for the diamond bur groups and open dentin tubules for all laser-treated groups. However, in group 2d, the laser beam had insufficiently irradiated the dentin area, rendering the underlying ground surface partly visible. There were no statistically significant differences between μTBS values of the four groups (p = 0.394). This suggests that Er:YAG laser treatment of dentin of primary molars provides bond strengths similar to those obtained following diamond bur treatment.

Irrigants for non-surgical root canal treatment in mature permanent teeth

Root canal treatment is carried out on teeth in which irreversible pulpitis has led to necrosis of the dental pulp. As a treatment option it is an alternative to dental extraction. Mechanical preparation and irrigation with antiseptic or antibacterial solutions destroys bacteria and cleans the infected root canal. Irrigants should be effective in deactivating bacteria in the entire root canal space without causing any adverse tissue reactions. Sodium hypochlorite (NaOCl) and chlorhexidine are commonly used but there is uncertainty as to which solution, concentration or combination is the most effective.

Single crowns versus conventional fillings for the restoration of root filled teeth

Endodontic treatment, involves removal of the dental pulp and its replacement by a root canal filling. Restoration of root filled teeth can be challenging due to structural differences between vital and non-vital root filled teeth. Direct restoration involves placement of a restorative material e.g. amalgam or composite directly into the tooth. Indirect restorations consist of cast metal or ceramic (porcelain) crowns. The choice of restoration depends on the amount of remaining tooth which may influence long term survival and cost. The comparative in service clinical performance of crowns or conventional fillings used to restore root filled teeth is unclear.

Tactile sensibility of single-tooth implants and natural teeth under local anesthesia of the natural antagonistic teeth

The term osseoperception describes the capability of developing a subtle tactile sensibility over dental implants. The present clinical study aims at clarifying the question of how far tactile sensibility is to be attributed to the periodontium of the natural opposing tooth of the implant.

Tenascin-C and matrix metalloproteinase-9 levels in crevicular fluid of teeth and implants

The role of and interaction between bacterial infection and biomechanical impact in the development of peri-implant inflammatory processes is not clear.