Crown Removal Research Articles

Coronectomy: not just for Wisdom Teeth

Coronectomy is most commonly associated with the management of impacted lower third molars where complete removal poses a high risk of inferior alveolar nerve damage. However, coronectomy may be indicated for the management of other teeth with a significant risk of morbidity. A case of a LL6 extended coronectomy is presented. The aim was to prevent inferior alveolar nerve damage, and ensure adequate crown and root removal to facilitate orthodontic alignment of the teeth. Surgery was aided by cone beam CT, and a piezo-surgical technique. CPD/Clinical Relevance: This case demonstrates the novel application of a coronectomy to manage an infra-occluded lower left first molar, facilitating orthodontic treatment, where complete removal posed a high risk of inferior alveolar nerve damage.

Six-year survival of single crowns — A massive data analysis

ObjectivesNumerous clinical trials have proven the long-term stability of metal and metal-ceramic crowns. However, data on their performance under practice conditions are rare. PurposeTo evaluate the longevity of crowns by means of massive data analyses. MethodsThe data were extracted from the data warehouse of a major German national health insurance company (BARMER, Berlin, Germany). The analysis focused on crown types with the lowest deductibles. Metal crowns and metal-ceramic crowns with ceramic veneering on the vestibular aspects of teeth 15–25 and 34–44 placed from 2012 to 2017 were included. The placement of the crowns, crown removals and tooth extractions were identified using the corresponding fee codes. Kaplan–Meier survival analyses were conducted for the outcomes “crown removal or extraction” and for “extraction”. ResultsThe cumulative six-year survival rates were 88.0 % for the outcome “crown removal or extraction” and 92.5 % for the outcome “extraction” (N = 192,868). The survival functions had slightly steepening but close to linear courses. ConclusionsThe outcome of the treatment with metal and metal-ceramic crowns was moderately inferior in comparison to clinical trials. However, treatment with metal and metal-crowns is judged to be a reliable and safe option under practice conditions. Clinical significance statementClinicians must inform patients about potential treatment outcomes. Therefore, additional knowledge about single crown outcomes under general practice settings based on large database analyses is important.

Utilization of Er:YAG Laser in Retrieving and Reusing of Lithium Disilicate and Zirconia Monolithic Crowns in Natural Teeth: An In Vitro Study

The study examined the effect of noninvasive crown retrieval/reuse process using an erbium-doped yttrium aluminum garnet laser (Er:YAG). Twenty-six extracted human teeth were prepared for a crown. The crown was milled using lithium disilicate (LD) and zirconia (Z) materials, n = 13 per group, with three for scanning electron microscopy (SEM). The crown was luted using composite resin cement and subjected to a laser retrieval process. After the retrieval process, the crown was cleaned, re-cemented and laser-retrieved two more times, without and with additional tooth reduction mimicking clinical refreshment of dentin. Retrieval time and temperature were analyzed using analysis of variance (ANOVA). Surface changes were observed through SEM. The retrieval times were 267.1 ± 130.43, 220 ± 79.09, 277.1 ± 126.44, 368.4 ± 136.14, 355 ± 159.39, and 419.2 ± 121.36 s for first, second, third LD and Z groups, respectively (p = 0.009). The maximal temperatures were 23.95.1 ± 1.89 °C, 24.86 ± 2.01 °C, 24.17 ± 1.53 °C, 22.88 ± 1.51 °C, 24.03 ± 1.74 °C, and 21.99 ± 1.32 °C for first, second, third LD and Z groups, respectively (p = 0.006). Er:YAG laser crown removal is an effective retrieval tool for all-ceramic crowns. Minimal changes to teeth and crowns were observed following laser irradiation.

Exploring the use of pulsed erbium lasers to retrieve a zirconia crown from a zirconia implant abutment.

Removal of cement-retained implant fixed restorations when needed, can be challenging. Conventional methods of crown removal are time consuming and costly for patients and practitioners. This research explored the use of two different types of pulsed erbium lasers as a non-invasive tool to retrieve cemented zirconia crowns from zirconia implant abutments. Twenty identical zirconia crowns were cemented onto 20 identical zirconia prefabricated abutments using self-adhesive resin cement. The specimens were divided into two groups for laser assisted crown removal; G1 for erbium-doped yttrium aluminum garnet laser (Er:YAG), and G2 for erbium, chromium-doped yttrium, scandium, gallium and garnet (Er,Cr:YSGG). For the G1, after the first crown removal, the specimens were re-cemented and removed again using the Er:YAG laser. Times needed to remove the crowns were recorded and analyzed using ANOVA (α = 0.05). The surfaces of the crown and the abutment were further examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses. The average times of zirconia crown removal from zirconia abutments were 5 min 20 sec and 5 min 15 sec for the Er:YAG laser of first and second experiments (G1), and 5 min 55 sec for the Er,Cr:YSGG laser experiment (G2). No statistical differences were observed among the groups. SEM and EDS examinations of the materials showed no visual surface damaging or material alteration from the two pulsed erbium lasers. Both types of pulsed erbium lasers can be viable alternatives for retrieving a zirconia crown from a zirconia implant abutment. Despite operating at different wavelengths, the Er:YAG and Er,Cr:YSGG lasers, perform similarly in removing a zirconia crown from a zirconia implant abutment with similar parameters. There are no visual and elemental composition damages as a result of irradiation with pulsed erbium lasers.

MAGNETIC MALLET – FEEL THE FUTURE

In dentistry, chisel and mallet or dental bur has been used for various procedures since decades. Magnetic mallet (MM) is a dynamic, exclusive and patented device which makes use of electromagnetic impact, which allows a high – intensity and brief impact force to obtain plastic deformation of the bone. This avoids the applied forces influencing the whole of the craniofacial complex and has lot of advantages when compared to conventional chisel and mallet or bur used for bone cutting. Use of magnetic mallet prevents benign paroxysmal vertigo syndrome and reduces patient discomfort as well. It allows operator to use the handpiece of magnetic mallet with only one hand and the impulses are applied with a control pedal. It also allows better visibility of the operating field and control of the osteotome entry direction. Magnetic mallet can be also used for removal of crowns, bridges and implant components. This article emphasizes the advantages of magnetic mallet over conventionally used chisel and mallet in dentistry for various procedures. KEY WORDS : electrical mallet, sinus elevation, dental implant, electromagnetic dental mallet.

Comparison of Success Rates of Cone Beam Computed Tomography in the Retrieval of Metal-Ceramic vs All-Ceramic Implant-Supported Restorations: An In Vitro Study.

To assess the success rates of cone beam computed tomography (CBCT) in identifying the locations and directions of abutment screw access holes (ASAHs) in metal-ceramic and all-ceramic implant restorations. Thirty-two implants were inserted into four clear acrylic casts. Metal-ceramic and all-ceramic crowns were placed on the inserted implants in two successive tasks. A maxillofacial radiologist determined the locations and angles of the ASAHs based on the CBCT images that were taken from the casts. Locations obtained from the CBCT images were carefully transferred to the crowns as access points. A prosthodontist pierced the crowns along the proposed access points and in the direction determined based on the CBCT images. Proper crown removal was considered to be the mark of success of CBCT in detecting ASAH location and direction. Fisher exact and chi-square tests were used to compare the results between the two types of restoration. Success rates of CBCT for defining ASAH location and direction were, respectively, 96.9% and 93.8% in metal-ceramic restorations and 78.1% and 59.4% in all-ceramic restorations. There were no significant differences between the two restoration types regarding the detection of location in either molar (P = .333) or premolar (P = .226) crowns. Abutment angle did not affect the success rate of CBCT in determining ASAH location or direction in metal-ceramic restorations. CBCT images define the locations and directions of ASAHs in metal-ceramic restorations more reliably than in all-ceramic restorations. In contrast to the metal-ceramic crowns, the success rate of CBCT in all-ceramic crowns is more dependent on abutment angle and crown morphology.

Effect of Repairing Endodontic Access Cavities on Survival of Single Crowns and Retainer Restorations

IntroductionThis retrospective study aimed to analyze the effect of repairing endodontic access cavities with composite on the survival of single crowns and retainer restorations of fixed or removable dental prostheses. MethodsDental records of patients attending a university dental clinic were retrospectively screened for single crowns and retainer restorations receiving endodontic treatment after crown placement. Survival (no further intervention) and failure (removal, loss or replacement of crown, replacement of access restoration, or recementation of restoration) of crowns and retainers with repaired endodontic access cavities were recorded. The mean annual failure rates were calculated, and the effect of individual-, tooth-, and restoration-related variables on survival was assessed by univariate log-rank tests and multivariate Cox regression analyses with shared frailty (P < .05). ResultsOne hundred eighty repaired crowns/retainers placed in 151 patients were included (4.5 ± 3.3 years follow-up). Survival after 2, 5, 7, and 10 years amounted to 82.7%, 71.5%, 67.3%, and 48.8% (mean annual failure rate = 9.0%, 6.5%, 5.5%, and 6.9%), respectively. Although tooth type, kind of restoration, endodontic irrigant, repair conditioning methods, and kind of composite affected survival in the univariate regression analyses, only the kind of restoration (single crown vs retainer restoration) remained significant in the multivariate Cox regression model. ConclusionsRepairing endodontic access cavities with composite increases the longevity of single crowns and retainer restorations.

MORPHOMETRY OF TRACHEIDS OF Pinus taeda L. FROM A PRUNING TEST IN NE ARGENTINA.

The northeast region of Argentina is characterized by fast-growing forest plantations, Pinus taeda among them. The objective of this study was to evaluate the influence of pruning and stand structure on the morphometric characteristics of tree tracheids. We evaluated 18 trees of 16 years old, from a silvicultural stand essay, with 1660 plants/ha as initial density, without thinning, three pruning treatments 0%, 50% and 70% removal of the green crown belong to the dominant, codominant and suppressed strata. Tree slices were taken at 1.3 m height, the conditioned samples were observed and measured with a microscope with digital camera. The data was analyzed using mixed linear models. Pruning did not have effect on the width and length of tracheids, but it affected to the cell wall thickness, which decreased with increasing pruning intensity. While the social position (stratum) had significant influences on the length of tracheids, given greater for individual in dominant stratum, followed by codominant and suppressed stratum. The cell wall width and thickness were not affected by the stratum. Regardless of the social position in the stand, the tracheid’s length showed an increasing pattern from pith to bark with the lower values near to the pith.

Antibacterial effect of chitosan nanoparticles in combination with diode laser on E.coli bacterial strain

Background /Aim: The antibacterial effect was assessed by dead/live technique by conjunction between chitosan nanoparticle and diode laser (970nm), were chitosan has an excellent biocompatibility with tissues; save to human with no side effect; excellent bioactivity effect; chelation ability, good absorptive capacity, and antimicrobial activity regarding gram-positive and gram-negative bacteria. The studies have showed chitosan mechanism action related to the films formed around the cell which prevents nutrients absorption. Other res,earch indicates that, using laser radiation in the treatment of dental hard tissue and helping in the root canal formation, the addition effects of diode laser is bacteriostatic effect on bacterial strains present in root canal. The laser radiation was transmitted through quartz optical fibers, which could introducing laser light inside root canal, around canal curvatures and irregularities more easily. Throughout this review the aim of our study is present and discuss the antimicrobial activity of chitosan nanoparticles in combination with diode laser against oral bacteria especially the E.coli and aimed for developing commercial products such as an irrigant solution for root canal. The aim of this study was to estimate the ability of 970-nm diode laser to disinfection in combination with chitosan nanoparticlesagainst negative charged E.coli bacterial strain Materials and methods: The root canals of 40 extracted single-rooted incisors teeth were prepared by rotary system. After crown removal, the roots were autoclaved. The teeth were inoculated with E. coli suspension for two weeks. The samples were divided into four groups (n=10). The samples of the first group G1 (n=10) were inoculated with bacteria only as control group, the second group G2 (n=10) were inoculated with bacteria & chitosan, the group will be divided in 2 subgroup according to the time of incubation (60 seconds, 90 seconds) (n=5). The third group G3 were inoculated with bacteria and treated with a 970-nm diode laser, the group will be divided in 2 subgroup according to the time of laser irradiation (60 seconds, and 90 seconds) (n=5). The fourth group G4 (n=10) were inoculated with bacteria &chitosan and treated with diode laser, the group will be divided in 2 subgroup according to the time of laser irradiation (60 seconds, and 90 seconds) (n=5). Bacterial samples were taken from the root canals and the cultivation. was carried out. The standard deviation of colony-forming units (CFU) for each specimen were measured to compare the reduction in CFU in each group. Results: low mean CFU/mL is recorded in Group2 (chitosan with laser) followed by Group3 (chitosan) and Group 4 (laser), respectively. The difference in CFU/mL between the three groups is statistical significant (P ≤ 0.05).Conclusion: The results of this research show that 970-nm diode laser in combination with chitosan nanoparticles could be used as a complementary disinfection device in root canal treatment and ability to increase the success rate in endodontic therapy.

Effect of temporary cement removal methods from human dentin on zirconia-dentin adhesion

This study evaluated the effect of temporary cement residue removal methods from human coronary dentin on the bond strength of adhesively-luted zirconia on dentin. Forty non-carious human molars were embedded in acrylic resin and the dentin surfaces were exposed. Temporary acrylic crowns were provisionally cemented with zinc oxide cement without eugenol and stored in distilled water (37 °C/15 days). After crown removal, the excess temporary cement was removed from dentin according to one of the following cleaning methods: (n = 8 per group): (a) air-water rinse (AW), (b) pumice paste (PP), (c) air-abrasion with aluminum oxide particles (Al2O3) (AA), (d) sodium bicarbonate spray (SB) or (e) glycine powder (CP). Forty zirconia cylinders were made and each cylinder was adhesively luted onto each tooth after adhesive resin (Scotch Bond Universal, 3 M ESPE-SBU) application using resin cement (RelyX Ultimate, 3 M ESPE) and photo-polymerized from each surface for 20 s. The bonded specimens were stored in distilled water (37 °C) for 90 days. The bonded interface was loaded under shear (1 mm/min). Data (MPa) were analyzed using 1-way ANOVA and Tukey's test (α = 0.05). Mean bond strength was significantly affected by the cleaning method (p = 0.0289). Cleaning with AA method resulted in significantly higher bond strength than with SB (p < 0.05) but similar to CP, PP and AW (p > 0.05). All cleaning methods were effective in removing temporary resin cement from dentin surfaces. Air-abrasion with aluminum oxide particles was more effective than with sodium bicarbonate spray promoting adhesion between zirconia and dentin.

In Vitro Examination of the Use of Er:YAG Laser to Retrieve Lithium Disilicate Crowns from Titanium Implant Abutments.

Removal of cement-retained implant crowns can be difficult and often requires sectioning of the prosthesis by rotary instruments. This study aimed to measure how much time is required in crown removal and the temperature changes when erbium-doped yttrium aluminum garnet (Er:YAG) laser was used to retrieve lithium disilicate crowns from titanium implant abutments luted with composite resin (CR) cement and resin-modified glass ionomer (RMGI). Forty identical lithium disilicate crowns were fabricated for prefabricated titanium abutments. CR and RMGI cements were used to lute the crowns, 20 specimens for each cement. Specimens were kept in 100% humidity for 48 hours. Er:YAG laser was then used to facilitate the crown retrieval. The retrieval time was recorded. The temperature changes at the abutment level for each type of cement were recorded during irradiation of 10 specimens for each type of cement from 1 to 10 minutes. Data were analyzed using t-test (ɑ = 0.01) and paired t-test (ɑ = 0.05). The surfaces of the crown and the abutment were further examined using scanning electron microscopy (SEM). The average times of crown removal from titanium abutments were 196.5 seconds for CR and 97.5 seconds for RMGI groups with statistical significance (p < 0.001). The temperatures measured from 1 to 10 minutes of irradiation ranged from 18° to 20.8° for CR and 18° to 23° for RMGI at the abutment surface, and 22.1° to 24.6° for CR and 22° to 24.8° for RMGI at the crown surface. No statistical differences were observed between temperature changes at the abutment or the crown for each cement (p = 0.63); however, there was a statistically significant difference between the temperatures at the abutment and crown for both cements (p < 0.001). SEM examination showed no visible damage caused by treatment with Er:YAG laser. It is faster to remove lithium disilicate crowns from titanium implant abutments when luted with RMGI compared to CR cement. The temperature rise was higher in the crown compared to the abutment. The type of cement had no effects on temperature changes. Heat generated from Er:YAG irradiation does not appear to be high enough to have any adverse effect on implant osseointegration.

Coronectomy of partially erupted lower third molars

Background: Coronectomy is an intentional removal of tooth crown leaving the roots intact in their position. It is especially indicated to prevent nerve damage due to close relation between roots and mandibular canal. Most coronectomy studies refer to deeply impacted lower third molars with few including partially erupted ones. No series with only partially erupted third molars is available.

The Effects of Music Listening During Extraction of the Impacted Mandibular Third Molar on the Autonomic Nervous System and Psychological State

Pain, anxiety, and nervousness related to dental procedures can cause acute changes in the autonomic nervous system. Music is widely accepted as a relaxation method during dental treatment; however, its effects during dental treatment are unclear. The authors explored the effects of listening to music during extraction of the impacted mandibular third molar on the autonomic nervous system and the psychological state and hypothesized that listening to music would suppress sympathetic nervous activity and decrease anxiety. In this prospective study, 40 patients scheduled for extraction of an impacted mandibular third molar were randomized into 2 groups: extraction without music (control group) and extraction while listening to music (music group). Heart rate variability was recorded during the experiment, and Modified Dental Anxiety Scale and State-Trait Anxiety Inventory (STAI) scores were recorded before and after the procedure. Descriptive and bivariate statistics were computed and the P value was set at .05. An increased low-to-high frequency ratio was observed in the control group during incision and flap reflection, bone removal, and separation of the tooth crown; the ratio was significantly decreased in the music group during these time points (P<.05). Compared with the control group, the music group had a significantly greater decrease in postoperative STAI State Anxiety scores from preoperative levels (P<.05). This study suggested that listening to music while undergoing extraction of the impacted mandibular third molar suppresses activity of the sympathetic nerves during incision, flap reflection, bone removal, and separation of the tooth crown and relieves anxiety after treatment. Future studies will focus on the mechanisms involved and methods to prevent the onset of systemic incidents.

Laser Aided Ceramic Restoration Removal: A Comprehensive Review.

Introduction: All-ceramic restorations are being widely used due to its various advantages. However, they have restricted durability and may have to be removed. The conventional procedure for removal is grinding the restoration with rotary instruments which are considered time-consuming and inconvenient. A newer advantageous method is the application of lasers for debonding ceramics from the tooth surface. The objective of this study is to provide a comprehensive literature review on laser-aided ceramic restorations debonding. Methods: We searched PubMed and Google Scholar databases. Seven articles from 2011 to 2018 were identified. Studies were assessed for the efficacy of laser application and the amount of pulpal temperature rise. Results: Studies selected were categorized according to variables including shear bond strength, debonding time and intrapulpal temperature. Oztoprak and Iseri investigated that erbium-doped yttrium, aluminum, and garnet (Er:YAG) laser application reduced shear bond strength of ceramic laminate veneers. The time of debonding took an average of 190 seconds in Rechmann's study and 106 seconds in Morford's study. One of the main issues while using the laser is thermal irritation of the pulp. A 5.5°C temperature increase may cause pulpal damage according to Zach and Cohen. Philips et al and Rechmann et al reported no intrapulpal harm due to temperature increase. Additionally, Phillips et al demonstrated that the laser setting affects both the debonding time and the temperature alterations and that a laser adjustment of 2.5 W/25 Hz would be the best safest group. Conclusion: Removal of ceramic crowns and veneers from tooth surfaces can be successfully done by Er:YAG laser application in a less time-consuming procedure and without any harm to the underlying dentin. However, a temperature rise in the pulp may occur which could be overcome by adequate air water cooling.

Implant Digital Impression in the Esthetic Area.

The aim of this report is to describe two standardized protocols for digital impression when implant support rehabilitation is used in the esthetic area. The two techniques were used to transfer all provisional crown parameters to definitive restorations in different clinical scenarios. In the direct technique, an impression (STL1) is made of the provisional restorations attached to the implants, with surrounding gingival tissue. The second scan (STL2) captures the sulcular aspect of the peri-implant soft tissue immediately after removal of the provisional restoration. The last impression (STL3) of the complete arch is made with a standardized scanbody attached to the implant to capture the 3D location of the implant. The direct technique is indicated when the peri-implant soft tissues are stable upon removal of the provisional restoration. The indirect technique is used when the gingival tissue collapses rapidly after the removal of the provisional crown. The impressions of the provisional restoration and the position of the implant are similar to those obtained with the direct technique, and the shape of the peri-implant tissue is extrapolated from the negative shape obtained from making the digital impression when the provisional restoration is taken out of the mouth. Finally, in both techniques the 3 scans are superimposed to obtain a file, which contains the details of the peri-implant soft tissue. The direct and indirect digital techniques allowed realization of a predictable definitive restoration in the esthetic zone in different clinical scenarios, reducing the duration of clinical procedures.

Coronectomies: assessment and treatment planning

Coronectomy procedures are widely carried out in secondary care, involving the removal of the dental crown, while retaining the roots in situ. This paper defines and explains the rationale behind coronectomy. It also seeks to review the indications for referral of wisdom teeth, and how to identify high-risk wisdom teeth radiographically using two- and three-dimensional imaging. Using this information, this article aims to provide the practitioner with information on short- and long-term management of high-risk wisdom teeth and discusses coronectomy versus extraction. It also discusses the complications of coronectomy and the importance of adequate consent.

Centering ability and canal transportation of curved root canals after using different nickel–titanium preparation systems

Purpose To evaluate centering ability and canal transportation in curved root canals after using different nickel–titanium (Ni-Ti) preparation systems including two rotary systems [Revo-S and Twisted File (TF)] and hand Ni-Ti-Flex K-files using cone-beam computed tomography. Materials and methods Seventy-five extracted human premolars with similar range of canal curvature (25–35°) were used, after crown removal and working length determination, samples were randomly divided into three groups (n = 25) according to the type of instruments used. Group I (Revo-S), group II (TF) and group III (Ni-Ti-Flex). Preinstrumentation and postinstrumentation cone-beam computed tomography images were recorded at several root canal levels (3, 5, 7, 9, and 11 mm) from the apex under the same circumstances, superimposed and then the centering ability and canal transportation were calculated using specific equations. Results Revo-S system produced less mean value of canal transportation and more centering ability than TF and Ni-Ti-Flex systems. In addition, the middle canal level (7 mm) recorded the least mean value of transportation with the highest centering ability for all used instruments. Conclusion Preparation of curved root canal using rotary systems produced less change in original canal path compared with the hand Ni-Ti files.

Rehabilitation of compromised permanent incisors with anatomically adjustable fiber post

Purpose To evaluate clinically and radiographically the rehabilitated compromised upper permanent central incisors with the everStick post. Patients and methods Thirty-six children patients aged from 10 to 16 years were divided into three equal groups (12 patients each). Group I, flared root canals of the patients were rehabilitated with the everStick post. Group II, flared root canals were rehabilitated with EasyPost/composite, and group III (control), unflared root canals were rehabilitated with EasyPost/core. The clinical parameters included the reinforced tooth, mucosa, temporary crown, and reinforcing system. The radiographical parameters were the periapical status, periodontal ligament condition, root fracture or resorption, and changes at the interfaces of the reinforcing system. All patients were followed up clinically and radiographically at 3, 6, 12 and 18 months. Results Both everStick and control group showed 100% clinical success, while EasyPost/composite group showed debonding of the reinforcing system in one patient with a clinical success rate of 91.7%, and the difference was not statistically significant (P > 0.05). Radiographic assessment showed no evidence of root fracture or external root resorption and no periodontal or periapical pathology that require crown removal for clinical interference. The radiographic findings showed 100% success rate for all studied groups. Conclusion The use of direct anatomical everStick posts in the rehabilitation of flared canals functioned well for 18 months with favorable clinical, radiographical, and aesthetic results.

Evaluation of retentive strength of four luting cements with stainless steel crowns in primary molars: An in vitro study

Stainless steel crown (SSC) is the most reliable restoration for primary teeth with extensive caries. Retention is of great importance for a successful restoration and is provided by various factors such as luting cements. The aim of this study was to evaluate the retentive strength of SSC cemented with four different luting cements. In this in vitro study, A total of 55 extracted primary first molars were selected. Following crown selection and cementation (one with no cement and four groups cemented with resin, glass ionomer, zinc phosphate, and polycarboxylate), all the specimens were incubated and thermocycled in 5°C-55°C. Retentive properties of SSCs were tested with a mechanical test machine. First dislodgement of each specimen and full crown removal were recorded. One-way ANOVA test followed by least significant difference test and Kruskal-Wallis test was used for retentive strength comparison at the level of significance of P < 0.05. The results of the study showed that the specimens cemented with zinc phosphate exhibited higher retentive strength as compared to glass ionomer and polycarboxylate (P < 0.001 and P = 0.023, respectively). Zinc phosphate cement showed the most promising results; thus, it can be preferably used for cementation of the teeth with no grossly broken down crowns.

Laser-assisted removal of all ceramic fixed dental prostheses: A comprehensive review.

The aim of this comprehensive review was to assess the effectiveness of erbium lasers in the removal of all ceramic fixed dental prostheses (FDPs). Indexed databases were searched without language or time restriction up to and including December 2017 using different combinations of the following keywords: "lasers"; "phototherapy"; "crowns"; "prostheses and implants"; "inlays"; "ceramics"; "dental porcelain"; "zirconium"; "removal"; "debonding"; "fixed dental prostheses"; "veneers"; "laminates"; and "fixed bridge." All levels of available evidence including experimental studies, case reports and case series were included. Six clinical studies reporting a total of 13 cases and 6 experimental studies were included. Results from all studies showed that erbium lasers are effective reducing the shear bond strengths of all ceramic FDPs, in terms of easy removal of the restorations with none or minimal damage to teeth or ceramic surfaces. Laser-assisted removal of all ceramic FDPs is a promising treatment protocol. Further well-designed controlled clinical trials and longitudinal prospective studies are needed to determine the precise laser parameters and duration of irradiation that could be used for removal of ceramic restorations with varying thicknesses. Benefits of lasers over mechanical instrumentation for crown removal encompass efficient restoration retrievability without restoration or teeth surfaces damages; and relatively easier and time effective procedure with no prerequisite for anesthetic agents. It is however imperative for clinicians to be well-trained and exhibit adequate knowledge regarding recommended power settings and laser-safety parameters with reference to interactions between light and different tissues and ceramics.