Wednesday, December 16, 2015

Trinia CAD/CAM Discs and Blocks - An Ultralight Alternative to Metal Substructures

Trinia, a CAD/CAM fiber-reinforced composite, was first introduced in 2010 and has achieved remarkable clinical success and acceptance among dental professionals worldwide. With the growing demand for alternatives to metal substructures in dentistry, Trinia CAD/CAM blocks and discs are the new advanced solution to CAD/CAM metal-free restorations.

Trinia was designed with appropriate mechanical properties as well as proper esthetic characteristics to meet a broad range of clinical indications; resulting in a product with high flexural strength and compressive strength. This resilient and ultralight biocompatible resin material provides dentist and dental laboratories with a more efficient and cost-effective alternative to metal bars milled in titanium, or cast in semi-precious and precious metals.

Benefits include:
    Durable and resilient
    Lightweight
    Biocompatible
    Adjustable
    No firing required
    High flexural strength
    Cost-effective alternative to metal
    Unique mechanical properties with high flexural and compressive attributes

Indications of Clinical Use

TRINIA can be utilized for the following indications: copings, substructures or frameworks for permanent and transitional anterior or posterior crowns, bridgework, and substructures that can be either cemented or uncemented restorations, such as telescopic prosthetics.

Trinia CAD/CAM discs and blocks are composed of multi-directional interlacing fiberglass and resin within several layers. Trinia is available in 98mm circular discs, 89mm D-shaped discs, as well as 40mm and 55mm blocks. Following the proper milling procedures, Trinia can be milled on most leading wet and dry milling systems with extreme precision by nano-diamond burs.

Trinia is durable with a flexural strength of 393MPa, compression strength of 374MPa (Parallel) and 339MPa (Perpendicular), and resilient with biocompatible material. Trinia makes their products in the United States, so dental professionals can be assured they are made from high quality materials and adequate manufacturing. 

CAD/CAM Recommendations:
    Eclipse design for bars
    Minimum 0.7mm wall thickness
    Minimum 7.0mm2 connector
    Maximum 15mm cantilever

About Iverson Dental Labs

Iverson Dental Laboratories, a high-volume full-service dental lab, is an industry-leading provider of high-quality dental lab products and services to dental professionals nationwide. Established 1991 in Southern California by Corey Iverson, CEO, with a vision to be a reliable provider of quality dental restorations that exhibit strong mechanical properties and beautiful esthetics in the interest of patients' oral health.

With a modern and evidence-based approach, they continuously stay on the forefront of CAD/CAM technologies to increase productivity and consistency within their manufacturing processes to produce exceptional restorations.


Iverson aims to be the ultimate dental resource by offering continuing education seminars on digital workflows and on advanced implant procedures/techniques. Our purpose aligns with our clinicians, to restore oral health and confidence in every patient's smile.

Tuesday, October 6, 2015

Advantages of CAD/CAM Custom Abutments in Implant Dentistry

The use of CAD/CAM (computer-aided design/computer-aided manufacturing) technology to design and manufacture custom implant abutments is a highly predictable and reliable fabrication process; demonstrating survival rates comparable to conventionally fabricated abutments2. The latest generation of CAD/CAM techniques allows the “clinician or technician to fully customize the abutment contour to match carefully the clinical situation after tissue customization with provisional restorations”1.

Benefits of CAD/CAM Custom abutments

·         Precisely configures abutment for ideal anatomic contours1
·         Optimal design for esthetic emergence profile1
·         Highly predictable manufacturing process2
·         Availability of angulation correction1    
·         100% survival rates reported up to a 6-year period2
·         No technical complications reported up to a 6-year period2
·         Cheaper than gold cast abutments1

Over the last 10 years, dental CAD/CAM digital systems have been gaining increased use in implant dentistry because of the accurate and calculable nature of CAD/CAM technology. For instances, some studies found the fit of “CAD/CAM implant frameworks to be statistically superior to that of conventional cast frameworks”1. It also has improved productivity and efficiency of prosthetic manufacturing processes within the dental lab. Continuous improvements to CAD/CAM technology have started to challenge the technique of fabricating dental implants and abutments using conventional methods.

Implant abutments should be made from biocompatible materials with adequate mechanical properties to meet the functional, biological and esthetic demands1. Furthermore, they should “accurately and passively fit on their mating implants to prevent complications, such as screw loosening, bone loss and abutment fractures during function”1. To achieve optimal mucogingival esthetics, dental implant abutments require the appropriate emergence profile needed to support the surrounding soft tissue, especially for esthetically driven patients1.

Implant abutments can be either stock, cast custom or CAD/CAM custom abutments. The main advantage of stock abutments is their lower initial cost, but a major disadvantage is the ideal anatomic contour and emergence profile cannot be achieved. Cast custom abutments have similar tough mechanical properties to CAD/CAM custom abutments; however, the complicated fabrication process of investing, casting and finishing could be prone to manufacturing errors1. Whereas, the use of CAD/CAM technology to design and manufacture custom abutments has been clinically proven to be extremely accurate due to the predictable nature of computer-aided manufacturing2.

In a 2014 systematic review by Harvard School of Dental Medicine, researchers found CAD/CAM technology is able to provide results that are comparable to that of conventional techniques for implant survival, abutment survival, technical and biological complications2. In the study, a total of 101 patients were treated with a total of 138 CAD/CAM implant abutments with the same patient group seen at 12, 36, and 67 months. Three different major CAD/CAM systems were used to fabricate the dental implant abutments: Procera (Nobel Biocare), Straumann Cares, and Zirconzahn. Amazingly, they found the CAD/CAM abutment survival rate is 100% and no complications were reported, including screw loosening or fracturing of the abutment2.

In sum, CAD/CAM custom abutments have demonstrated survival rates comparable to conventionally fabricated abutments and have several advantages over other fabrication methods, allowing the technique to be a viable option for manufacturing custom implant abutments.  

About the Company

Since 1991, Iverson Dental laboratory has provided dentists with high quality dental lab products and excellent dental lab services to ensure dental patients are completely satisfied with their restoration outcome. Iverson dental labs strongly believes in using high quality certified materials and authentic manufacturing components to fabricate their dental prosthetics given that material quality influences longevity of the restoration. Iverson Labs values their skilled team of certified dental technicians because clinical evidence has shown adequate skills of the technician are important for the long-term success of a restoration. Iverson dental labs strive to be a great dental resource for dental professionals by offering training on digital dentistry and new dental implant techniques at their cutting edge on-site operatory and training facility.

To inquire more about CAD/CAM custom implant abutments, please visit http://www.iversondental-labs.com or call us at (800) 334-2057.

Reference:

1. Kim, E., & Shin, S. (n.d.). Influence of the implant abutment types and the dynamic loading on initial screw loosening. The Journal of Advanced Prosthodontics J Adv Prosthodont, 21-21.


2. Kapos, T., & Evans, C. (n.d.). CAD/CAM Technology for Implant Abutments, Crowns, and Superstructures. The International Journal of Oral & Maxillofacial Implants Int J Oral Maxillofac Implants, 117-136.

Monday, October 5, 2015

How Patients’ Decisions Influence Treatment Planning in Restorative Dentistry

As part of treatment planning, you as the dentist introduce options to your patients. After a relaxed conversation, a treatment plan is agreed upon between you and your dental patient. You use the best available research-based literature, clinical experience and patient opinions to guide your treatment decisions. As a dentist, you exercise substantial influence on which treatment method is chosen. Patients’ decisions can lead to less than ideal, though clinically adequate, treatment plans that give patient satisfaction over the long-term1. Patients’ decisions are most affected by their relationship with you as their dentist over factors such as time, access, and cost1. Health service providers may affect the decision-making process between you and your patient if specific treatments are favored or excluded on financial grounds. Kalsi and Hemmings recommends letters should be sent to patients explaining the “nature of all proposed options, including advantages and disadvantages, complications, success rates, biological and financial costs” and the consequences if no treatment is carried out1.

Many psychological and social determinants influence patients’ values and decision-making when choosing a treatment plan in restorative dentistry. Frequently, a component of compromise between both parties in deemed acceptable even when clinical evidence indicates an alternative treatment to be more appropriate.

The best possible treatments should be based on the best available literature; however, the majority of treatment plans are greatly impacted by patients’ desires and expectations, which may not be based on sound knowledge1. Patients’ wishes should be determined at the first treatment planning consultation to sort out whether they are realistic and possible within your own skill set, experience and knowledge1. It is widely known that no dentist should perform any treatment that could harm a patient.

Time, number of appointments, use of anesthesia or sedative agents, pain and suffering are significant aspects to your patients’ decisions when selecting a treatment plan. You need to clarify biological and financial cost-benefit analyses to the patient1. Also identify clinical factors, such as age, medical history and economics.

Patients seek dental treatment for three main reasons: comfort, aesthetics, and function. Patients are the real judge of whether their treatment is successful or not, so it is vital that they are pleased with their dental product1. Their subjective assessments of a proposed treatment do not always correspond with their acceptance of evidence-based suggestions from clinical research literature. This assessment is contingent on the value patients accredit to a treatment. Aesthetic awareness can push patients to ask for destructive, biologically invasive work in situations where appearances could easily and equally be improved with lower risks of morbidity. For example, bleaching and bonding with veneers may “improve aesthetics with the same effect as full coverage crowns, with less tooth destruction and risk of dental pulp death and pain”1.

Factors that affect patients’ decisions when deliberating treatment options:
  Availability and access to care
  Real cost per treatment option
  Perceived value for money
  Past dental history: positive or negative attitudes
  Dentist’s confidence and competence
  Patient’s confidence in dentist’s competence
  Patient’s confidence in the treatment plan
  Time and number of appointments
  Perceived impact to quality of life
  Pain and inconvenience associated with treatment1

Interestingly, patients place more emphasis on your recommendations rather than on objective, evidence-based literature1. If a dentist advocates a treatment, the patient is 2−21 times more likely to have it done1. Comparatively, Kalsi and Hemmings found the endorsements made by evidence-based literature made no difference to a patient when choosing to proceed with a treatment. Confidence in your advice establishes the foundation of a professional relationship with the patient.

The significance of the dentist-patient relationship cannot be minimized, and a positive relationship is most likely to prompt a patient consenting for treatment. Patients put a lot of value on your recommendations. At the same time, patients want to play a collaborative role with you in the decision-making process. A treatment plan that is not evidence-based or approved with the patient runs the risk of losing a patient or, at worst, medico-legal action1. However, treatment plans with an “element of compromise can be acceptable if, following full discussion with the patient, and taking into account all relevant factors, the benefits outweigh the disadvantages. This is the basis of informed consent”1.

About the Company

Since 1991, Iverson Dental laboratories have provided dentists with high quality dental lab products and excellent dental lab services to ensure dental patients are completely satisfied with their restoration outcome. Iverson dental labs strongly believes in using high quality certified materials and authentic manufacturing components to fabricate their dental prosthetics given that material quality influences longevity of the restoration. Iverson values their skilled team of certified dental technicians because clinical evidence has shown adequate skills of the technician are important for the long-term success of a restoration. Iverson labs strive to be a great dental resource for dental professionals, offering training on CAD/CAM technologies in digital dentistry and advanced dental implant techniques at their cutting edge on-site operatory and training facility.

To find more helpful resources about restorative dentistry or to inquire about our dental lab services, please visit http://www.iversondental-labs.com or call us at (800) 334-2057.



References:

1. The influence of patients' decisions on treatment planning in restorative dentistry. (2013). Dental Update, 40, 698-710.

Tuesday, September 29, 2015

What Factors Influence Patient Satisfaction in Restorative Dentistry

According to “The Dental Practice-Based Research Network” (GPBRN), five general factors that influence dental patient satisfaction include:

1.  Technical quality of care
2.  Interpersonal factors
3.  Convenience
4.  Financial issues
5.  Office environment

Patient Satisfaction can influence a “patient’s likelihood of choosing a dentist, making and keeping appointments, and complying with dentists’ recommendations[1]. Satisfaction can be considered a combination of the dissonance between the patients’ expectations and their experiences. Therefore, patient satisfaction is an important part of dental care that has the potential to impact restorative dentistry treatment outcomes [1].

Higher ratings of patient satisfaction in restorative dentistry occurs in cases with more experienced dentists because of greater proficiency, when the defective restoration is repaired rather than replaced, when restorative materials are a natural tooth color material rather than amalgam, and when the tooth is a premolar or an anterior tooth.

Effectively communicating the patient’s treatment plan and paying attention to concerns they may have are the most prominent components when patients are judging a dentist’s skill and quality of care. Whether the dentist recognizes their patient’s pain, talks over their fears, and aids in conquering their fears are very significant in terms of patient satisfaction. Patients deduce dental expertise from the dentist’s capacity to manage discomfort and provide a dental visit free from negative experiences.

It is vital to include patients in treatment decisions on medications, restorative material options and dental prosthetic procedures. Dentist’s who educate and involve their patients in treatment decisions, provide adequate time to comprehend facts and have their questions satisfactorily answered are more likely to have higher rates of satisfaction among their patients. Patients who are given more preparatory information have much better control of postoperative discomfort because their dentist effectively communicated what they should expect in terms of pain and how to control the discomfort.

Indeed, patients tend to use non-technical aspects of dental visits to appraise dentists’ technical capabilities. A dentist’s skills and quality of care are partially based on personal interactions with the dentist, the patient’s level of comfort, and post-treatment sensitivity. Steps can be taken to improve patient satisfaction by changing office policies or procedures, patient education and involvement, and/or the dentist’s interpersonal methods.

Dental practitioners should remember that human and psychological aspects of care are essential factors in determining the quality of care provided.

About the Company:

Since 1991, Iverson Dental laboratory has provided dentists with high quality dental lab products and excellent dental lab services to ensure their dental patients are completely satisfied with the restoration outcome. Iverson dental labs strive to be a great dental resource for dentists by offering training on digital dentistry and new dental implant techniques at their high-tech on-site operatory and training facility. Iverson dental labs strongly believes in using high quality certified materials and authentic manufacturing components to fabricate their dental prosthetics. Iverson Labs also strongly believes in having a knowledgeable team of certified dental technicians because clinical evidence has shown the skills of the clinician and technician are important for the long-term success of a restoration.

Reference:

1. Riley, J., Gordan, V., Rindal, D., Fellows, J., Qvist, V., Patel, S., . . . Gilbert, G. (n.d.). Components of patient satisfaction with a dental restorative visit. The Journal of the American Dental Association, 1002-1010.

Wednesday, September 23, 2015

The Importance of Finding a Dental Lab You Can Trust and Depend on for Quality Dental Lab Products and Services to Meet Patients’ High Expectations

In order to meet dental patients’ high expectations for long-lasting and highly esthetic dental restorations, its essential for dentists to find a dental laboratory they can trust and rely on for quality dental lab products to ultimately provide optimal patient care services. The long-term success of modern dental restorations depends on a number of factors that dentists must take into consideration when choosing the best dental laboratory to fabricate their patients’ dental prosthetics. Such factors include the lab’s ability to employ skilled dental lab technicians to adequately fabricate high quality dental lab products, and the lab’s ability to preserve the strength and esthetics of dental materials for restorations by executing proper lab techniques and procedures.

The success or failure of a dental restoration is also determined by how effective the dental lab’s communication methods are, prompting dentists to find a dental lab they can depend on for effective communication. Finding a dental lab that a dentist can trust to consistently deliver first-rate dental lab products and dental lab services can be taxing, but the alternative can lead to unsatisfied patients and be damaging to a dentist’s reputation.

Clinical evidence has shown the “skills of the clinician and technician are important for the long-term success of a restoration,” therefore dental laboratories must ensure their lab technicians have the skills and knowledge necessary to manufacture high quality prostheses on a consistent basis [1]. For instances, fabricating porcelain crowns and bridges is a highly sensitive technique and requires adequate skills of lab technicians because “minor laboratory faults may result in clinically unacceptable surface layers” [1]. One major fault is the formation of porosities that in turn may negatively affect the surface roughness, texture and shade of the restoration. Common reasons for the formation of porosities in dental porcelain as described by Rashid are “laboratory faults during condensation, in-appropriate powder/liquid mixing ratio and due to variations in firing time and temperature.”

The long-term clinical success of modern dental restorations greatly depends on “the physical properties of the material, the laboratory fabrication process, the laboratory fabrication technique and clinical procedures that may damage these brittle [ceramic] materials” [1]. The surface roughness and microstructure of dental materials, particularly dental ceramics, are also factors that influence the strength and long-term success of a restoration. During laboratory processessuch as powder compaction, process of forming, firing and shapingcan cause flaws in dental ceramics when the procedure is not performed correctly. Rashid explains during lab processes, flaws may become inherited in the surface and/or microstructure of dental ceramics that can compromise the strength and esthetics of a restoration. Surface roughness will “lead to a non-uniform stress distribution and concentrate locally an applied stress due to the shape differences in the surface layer… developed cracks cannot propagate randomly but occur or propagate at points with higher stress,” causing fractures at these points of high stress [1]. In other words, laboratory processes can influence the existence of micro cracks and residual stresses that affects the longevity of the material, and therefore should be executed competently with the correct dental lab procedures and techniques by capable lab techs.

Along with the ability to adequately manufacture ceramics and other dental materials with acceptable mechanical properties, the lab technician must also have the ability to recreate esthetic details that will match the patient’s natural tooth shape, texture and shade characteristics. Dr. Markus Blatz, restorative dentistry’s leading researcher at the University of Pennsylvania School of Dental Medicine, states the goal of restorative intervention is “to mimic nature as closely as possible” and the dental materials used should “depend on the patient’s needs” [6]. Recreating esthetic details that mimic the patient’s natural teeth is crucial when “subtle details in texture, anatomy, and contours keep the ceramic restoration from looking contrived and can provide the element of ‘prefect imperfection’ that natural teeth exhibit” [4]. In The Penn Dental Journal for the University of Pennylvania School of Dental Medicine, Dr. Blatz explains how he relies on the artistic skills of his dental technicians to first plan and design the substructures using CAD/CAM systems, and then build “the individual teeth by hand and applying the layers of ceramic on top of the copings and frameworks” [7]. He further adds, “Despite all technical advancements, machines are not able to recreate the intricate and subtle esthetic features of a natural tooth. That’s why [the lab technician’s] artistic expertise is so important" [7].

Restorative dentistry also requires effective communication between the dental lab and dental practice to achieve the restorative goals set by the patient and dentist. With the development of software programs and effective web applications, dental labs can now use web content management systems (WCMS) to communicate to the dental office and manage laboratory cases at a faster and more accurate rate. As stated by Alshiddi, “Laboratory case management is a teamwork that should involve good communications between not only the dentist and the dental technician, but also other staff in the dental office (e.g., dental assistant and receptionist) and dental laboratory (e.g., laboratory owner, receptionist and delivery person)” [2]. When managing a large number of dental lab cases, the lab must implement an effective content management system that will manage all of the dental cases coming from multiple forms of communication methods (e.g., hand-written lab authorization forms, telephone, email, photographs, electronic STL files, etc.). Equally important is the lab’s understanding of individual software requirements and design of the software that will essentially, if implicated correctly, improve communication and will ensure long term relationships between the dental office and dental laboratory [2].

Providing excellent dental lab services will lead to “well-designed prostheses, satisfied clinician and comfortable professional relationship between the clinician and dental technician/laboratory” [2]. The dental laboratory must provide great customer service for dentists and their dental office personnel, so all parties can work effectively together in the interest of the patient’s oral health. Collaborative technical advice on routine or complex dental cases is a very important service that dental laboratories should exceed at every time. The lab needs to have a strong management team to implement and oversee quality control processes on every dental case. They must also have an effective logistic team to ensure dental cases are fabricated and delivered in time for the patient’s scheduled appointment. Offering in-house custom shade appointments should be available for doctors and their patients, making sure the lab facility is up to professional standards in appearance and services they provide. 

As stated in General Dental Council’s (GDC) policy document Principles of dental team working, “members of the dental team will work effectively together” and members have to “communicate clearly and effectively with other team members and colleagues in the interest of patients” [3]. Given these points, choose a dental lab that employs a knowledgeable team of certified dental technicians that can consistently fabricate high quality dental lab products. Also, finding a lab that can effectively communicate with the dentist and dental office personnel is essential for the overall success of a dental practice.

About the Company

Since 1991, Iverson Dental laboratories has provided dentists with high quality dental lab products and excellent dental lab services to ensure dental patients are completely satisfied with their restorative outcome. Iverson dental labs offer training on digital dentistry and new dental implant techniques at their high-tech operatory and training facility. Iverson dental labs strongly believes in using high quality certified materials and authentic manufacturing components to fabricate their dental restorations. Iverson also strongly believes in having a dedicated, knowledgeable team of certified dental technicians because clinical evidence has shown the skills of the lab technician are critical for the long-term success of a restoration. They serve dentists from all over North America with a strong following in Pennsylvania (PA), Texas (TX), and California (CA), where they are leading the way in providing professional dental lab services and products to ultimately improve patient care in restorative dentistry.








Reference:

1. Rashid, H. (n.d.). The effect of surface roughness on ceramics used in dentistry: A review of literature. European Journal of Dentistry Eur J Dent, 571-571.

2. Alshiddi, I. Communication Between Dental Office and Dental Laboratory: From Paper-based to Web-based. Pakistan Oral & Dental Journal, Vol. 34 Issue 3, p555.

3. Berry, J., Nesbit, M., Saberi, S., & Petridis, H. (2014). Communication methods and production techniques in fixed prosthesis fabrication: A UK based survey. Part 1: Communication methods. BDJ Br Dent J.

4. Weston, J., & Haupt, E. (n.d.). Creating Aesthetic Success Through Proper Clinician and Laboratory Technical Communication. Dental Clinics of North America, 371-382.

5. Miyazaki, T., Nakamura, T., Matsumura, H., Ban, S., & Kobayashi, T. (n.d.). Current status of zirconia restoration. Journal of Prosthodontic Research, 236-261.

6. Blatz, M. (2013, January 1). Prosthetic parameters and materials for anterior implant esthetics. Lecture. https://www.for.org/en/video-insights/markus-blatz-prosthetic-parameters-and-materials-anterior-implant-esthetics?rate=KDjDad61ETC0oRsYOyMxaye7jTkb3qvyTEpMruuj9qM


7. Bonett, J. (2009). Bringing Da Vinci to Dentistry. Penn Dental Journal, 5(2), 2-5. Retrieved August 31, 2015, from http://www.dental.upenn.edu/pdf/penn-dental-journal/pdj_spring09.pdf

Wednesday, September 9, 2015

The Importance of Effective Communication Between the Dental Lab and Dentist to Ultimately Provide Better Patient Care

“Communication is the key to success in cosmetic dentistry/laboratory relations” [3]. The importance of good communication has been highlighted by a number of studies [3]. Effective communication between the dentist and the dental laboratory is critical when fabricating well-designed, high quality dental restorations to ultimately provide patients with the best dental care. The effectiveness of the communication methods used by the dental lab to collaborate with the dental office is also a major factor that determines the success or failure of dental lab products.

As reported by Berry et al., “prosthodontics is a discipline that requires a synergy between the dentist and dental technician in order to fabricate intraoral prostheses with acceptable fit, function and aesthetics.” Although restorative dentistry is first about restoring the teeth’s function and oral health of the patient, and next the esthetic appearance; the patient’s growing demand for realistic esthetics and long-lasting restorations is challenging the industry to meet these high expectations by producing dental products that exhibit both attributes. Recreating esthetic details that mimic the patient’s natural teeth is crucial when “subtle details in texture, anatomy, and contours keep the ceramic restoration from looking contrived and can provide the element of ‘prefect imperfection’ that natural teeth exhibit” [4]. Precise design parameters, shade matching, and available tooth structures should all be decided and effectively communicated by the clinician to the dental lab in order to successfully achieve a highly esthetic restoration that will match the patient’s natural tooth contours and shades [4].

The lab technician’s ability to transfer exact shade matching, along with the ability of the clinician to communicate accurate tooth shades, is a challenging aspect of communication; especially, when an increasing number of patients are demanding esthetically brilliant prostheses. Determining a precise shade (e.g., color, surface texture, shade characteristics) is first dependent on the clinician and must be effectively communicated to the lab technician in order for the lab tech to achieve exact shade matching for the final restoration. Exact shade communication is important between the technician and dentist because dental techs are remotely located and usually never see the patient [1].  In consonances with a study on color matching, Seal et al. reported, “precise color communication is integral to the development of esthetic harmony and overall restorative success.” 

The methods used by the dental lab to communicate with the dental practice are also major factors that influence the accuracy of dental lab products. With the development of software programs and effective web applications, dental labs can now use web content management systems (WCMS) to communicate to the dental office and manage laboratory cases at a faster and more accurate rate. As stated by Alshiddi, “Laboratory case management is a teamwork that should involve good communications between not only the dentist and the dental technician, but also other staff in the dental office (e.g., dental assistant and receptionist) and dental laboratory (e.g., laboratory owner, receptionist and delivery person)” [3]. When managing a large number of dental lab cases, the lab must implement an effective content management system that will manage all of the dental cases coming from multiple forms of communication methods (e.g., hand-written lab authorization forms, telephone, email, electronic STL files, etc.). Equally important is the lab’s understanding of individual software requirements and design of the software that will essentially, if implicated correctly, improve communication and will ensure long term relationships between the dental office and dental laboratory [3].

The dental laboratory must provide great customer service for dentists and their dental office personnel so all parties can work together proficiently. Providing excellent dental lab services will lead to satisfied clinicians and comfortable professional relationships between the clinician and dental technician/laboratory [3]. Collaborative technical advice on routine and complex dental cases is a very important service that dental laboratories should exceed at every time. The dental lab must have an effective logistic team to make sure dental cases are fabricated in time for the patient’s scheduled appointment, also ensuring patients are satisfied with their dental care services.

“By far my happiest [Dentists] with the happiest patients are the ones that communicate with the laboratory and view it as part of a team effort to achieve the right result for the patient,” stated one dental technician in a study on the communication methods used between the lab and dentist [1].

Along with adequate skills of the dental laboratory and clinician, good teamwork through effective communication between the dentist and dental lab leads to high quality dental restorations with excellent fit, function and esthetics. When problems arise from inaccurately fabricated prostheses, the patient will usually blame the dentist/dental office for the mishap. For this reason, its imperative dentists choose the best dental laboratory that can effectively communicate with their dental office to ensure satisfied patients every time and to ultimately provide better patient care.



About the Company:

Since 1991, Iverson Dental laboratory has provided dentists with high quality dental lab products and excellent dental lab services to ensure their dental patients are completely satisfied with the restoration outcome. Iverson dental labs strives to be a great dental resource for dentists by offering training on digital dentistry and new dental implant techniques at their high-tech operatory and training facility. Iverson dental labs strongly believes in using high quality certified materials and authentic manufacturing components to fabricate their dental restorations. Iverson also strongly believes in having a knowledgeable team of certified dental technicians because clinical evidence has shown the “skills of the clinician and technician are important for the long-term success of a restoration” [1].



Reference:

1. Berry, J., Nesbit, M., Saberi, S., & Petridis, H. (2014). Communication methods and production techniques in fixed prosthesis fabrication: A UK based survey. Part 1: Communication methods. BDJ Br Dent J.

2. Afsharzand, Z., Rashedi, B., & Petropoulos, V. (n.d.). Communication Between the Dental Laboratory Technician and Dentist: Work Authorization for Fixed Partial Dentures. J Prosthodontics Journal of Prosthodontics, 123-128.

3. Weston, J., & Haupt, E. (n.d.). Creating Aesthetic Success Through Proper Clinician and Laboratory Technical Communication. Dental Clinics of North America, 371-382.

4. Seal, M., Talukdar, P., Srivastav, V., & Pendharkar, K. (2014). Colour Matching: A Review of Conventional and Contemporary Dental Colour Matching Systems. International Journal of Oral Care and Research, 2(5), 47-53.

Tuesday, September 8, 2015

The Importance of Finding a Quality Dental Lab to Adequately Fabricate Your Dental Lab Products

Although there are thousands of dental laboratories worldwide, not all of them communicate effectively and provide their dentists with high quality dental lab products that exhibit longevity and lifelike esthetics. The long-term success of modern dental restorations depends on a number of factors that dentists must take into account to ultimately provide their patients with the best dental care services available on the market. Such factors include adequate skills of laboratory technicians, proficient dental laboratory processes, and effective communication methods between the dental lab and dentist. 

In order for a dental restoration to have a successful outcome, proper manufacturing procedures and techniques must be followed to ensure the patient’s high demand for durable and esthetically pleasing prostheses are met. According to Rashid, long-term clinical success of modern dental restorations greatly depends on “lab fabrication techniques and clinical procedures that may damage these brittle materials,” along with physical properties of the material and adequate skills of dental lab technicians. For instances, fabricating porcelain crowns and bridges is a highly sensitive technique and requires adequate skills of lab technicians because “minor laboratory faults may result in clinically unacceptable surface layers” [1]. One major fault is the formation of porosities that in turn may negatively affect the surface roughness, texture and shade of the restoration. Common reasons for the formation of porosities in dental porcelain as described by Rashid are “faults during condensation, in-appropriate powder/liquid mixing ratio and due to variations in firing tine and temperature.”

As a matter of fact, major faults have been indentified when lab technicians do not adequately finish the surface of dental ceramics. For instances, if the surface of the dental material is rough it will “abrade the opposing dentition or restoration,” and Rashid highly recommends the lab technician finish and/or polish the surface appropriately [1]. Considering recent studies on wear of antagonist enamel, Miyazaki et al. confirmed that adequate surface finish of all-ceramic restoratives resulted in least wear of antagonist enamel and suggests that the “antagonist enamel wear is significantly affected by the degree of surface finish.” For that reason, it is very important lab technicians have adequate skills and tools required to achieve an extremely smooth surface for least wear of opposing enamel.

Furthermore, the surface quality and composition of a dental restorative material determines the initial bacterial adhesion, and clinical studies have shown a rough surface will accumulate more plaque [1]. The oral cavity is “constantly contaminated by a complex diversity of microbial species that have a strong tendency to colonize surfaces” and if the “roughness were sub-gingival, the retention of the microorganisms would be more” [1]. Increased amounts of plaque on rough surfaces of ceramics and enamel is the major cause of dental caries and also a harmful influence on periodontal tissue [1].

The surface roughness and microstructure of dental materials, particularly dental ceramics, is also a factor that influences the strength of a restoration. During laboratory processessuch as powder compaction, process of forming, firing and shapingcan cause flaws in dental ceramics when the procedure is not executed correctly. According to Rashid, during lab processes flaws may become inherited in the surface and/or microstructure of dental ceramics that can compromise the strength and esthetics of a restoration. Surface roughness will “lead to a non-uniform stress distribution and concentrate locally an applied stress due to the shape differences in the surface layer… developed cracks cannot propagate randomly but occur or propagate at points with higher stress” [1]. More simply put, laboratory processes can influence the existence of micro cracks and residual stresses, and therefore should be executed competently by lab technicians.

Additionally, Rashid argues other lab processes are can be factors that influence the microstructure and thus the strength of the restoration. Specifically, damage to restorations can be “caused during grinding; pull-out caused during polishing, micro-porosity present on the subsurface and the introduction of large pores by technicians during restoration manufacture are common technical laboratory flaws “ [1]. Consequently, clinical success of a dental restoration is largely determined by the skills and knowledge of the dental lab and their technicians, along with effective communication between the dentist and dental lab to successfully collaborate on a dental case.

Accordingly, restorative dentistry requires effective communication “between the dentist and dental technician in order to fabricate intraoral prostheses with acceptable fit, function and aesthetics” [3]. As stated in General Dental Council’s (GDC) policy document Principles of dental team working, “members of the dental team will work effectively together” and members have to “communicate clearly and effectively with other team members and colleagues in the interest of patients” [3]. Collaborative technical advice on routine and complex dental cases is an important service that dental laboratories should provide. Finding a dental laboratory that can effectively communicate with their dentist is essential to the clinical success of a dental restoration. Also, time is money. Dental Labs need to have an efficient logistics team to assure dental cases are fabricated in time for the patient’s scheduled appointment.

Given these points, choose a dental lab that employs a knowledgeable team of certified dental technicians that can adequately fabricate high quality dental lab products. Also, finding a lab that can effectively communicate with the dentist on a consistent basis is essential for the overall success of a dental practice; ultimately to provide their dental patients with the best dental care services available on the market.



About the Company:

Since 1991, Iverson Dental laboratory has provided dentists with high quality dental lab products and excellent dental lab services to ensure their dental patients are completely satisfied with the restoration outcome. Iverson dental labs strives to be a great dental resource for dentists by offering training on digital dentistry and new dental implant techniques at their high-tech operatory and training facility. Iverson dental labs strongly believe in using high quality certified materials and authentic manufacturing components to fabricate their dental restorations. Iverson also strongly believes in having a knowledgeable team of certified dental technicians because clinical evidence has shown the “skills of the clinician and technician are important for the long-term success of a restoration” [1].


Reference:

1. Rashid, H. (n.d.). The effect of surface roughness on ceramics used in dentistry: A review of literature. European Journal of Dentistry Eur J Dent, 571-571.

2. Miyazaki, T., Nakamura, T., Matsumura, H., Ban, S., & Kobayashi, T. (n.d.). Current status of zirconia restoration. Journal of Prosthodontic Research, 236-261.

3. Berry, J., Nesbit, M., Saberi, S., & Petridis, H. (2014). Communication methods and production techniques in fixed prosthesis fabrication: A UK based survey. Part 1: Communication methods. BDJ Br Dent J.

Monday, August 31, 2015

Pros and Cons of IPS e.max® Lithium Disilicate Glass-Ceramics for Dental Restorations

For more than a decade, clinical trials have recorded high chipping rates in porcelain fused to zirconia (PFZ) dental restorations because of the relatively weak bond between the porcelain veneer and strong zirconia core. Porcelain fused to metal (PFM) dental restorations experience veneer chipping as well, however, clinical evidence has shown they perform better than PFZ restorations [1]. The major problem with PFM restorations is the metal substructure does not provide the most appealing esthetics. Therefore, researchers and clinicians developed monolithic all-ceramic dental restorations in an attempt to resolve these issues. One such monolithic all-ceramic dental restoration was developed by Ivoclar-Vivadent called IPS e.max® lithium disilicate.

When considering U.S. dental patient’s high demand for esthetically driven restorations, a dental professional must make informed decisions about the quality, longevity and esthetics of a dental restoration in order to have a high acceptance rate among their patients. Thus, the dental practice will be more successful by means of new and retained patients. This article will briefly analyze the pros and cons of lithium disilicate glass-ceramics.

Microstructure of Lithium Disilicate (LS2)

Dental ceramics can be classified by their microstructure (i.e., composition of glass-to-crystalline ratio) [2]. Lithium Disilicate (LS2) has a glass-based system (mainly silica) with crystalline fillers, formed by the controlled crystallisation of the glass material [2]. The crystalline filler particles are added to increase the strength of the glass-ceramic; cracks caused by stress are “arrested by the lithium disilicate crystals, providing a substantial increase in the flexural strength” [2].

Pros

One pro to lithium Disilicate glass-ceramic restorations is an observed low chipping and fracture rate [1]. Lithium disilicate has an unusual microstructure that contributes to its relatively high flexural strength of 360-400MPa. The spread of cracks is deflected, branched and blunted by lithium disilicate needle-like crystal structure – providing a substantial increase in the flexural strength [2]. In a 2015 study, Valenti evaluated the clinical performance of 110 lithium disilicate crowns over a 9-year period and found 2 crowns had core fractures and 1 crown chipped. They found the “overall survival probability was 96.1% up to 9 years, with a failure rate of 1.8%” [3].

Six other clinical studies (Richter et al. 2009; Nathanson 2008; Reich et al. 2010; Fasbinder et al. 2010; Bind 2011; Sorensen et al. 2009b) showed 97.9% of 237 IPS e.max ® lithium d­­isilicate (CAD crowns) restorations survived after a mean observation period of 4 years. The 2.1% failure rate included 0.4% irreparable chipping, 0.4% secondary caries and 1.3% fractures. Glass-ceramics exhibit lower strength relative to Porcelain fused to zirconia but higher chip fracture resistance. High chip fracture resistance is due to an elongated grain structure that inhibits crack propagation and contributes to its toughness, while it limits the strength by “promoting crack initiation within a relatively coarse microstructure” [1].

Another pro is lithium disilicate has superior esthetics compared to other ceramic materials. The monolithic structure and glass-ceramic system of lithium disilicate allows the material to take on translucent and light diffusing properties. Natural enamel has translucent qualities that transmits light rather than reflect or scatter it. The optical compatibility between the glassy matrix and the crystalline phase minimizes internal scattering of the light as it passes through the material—high translucency depends on the transmission of light through the core material [2]. Sravanthi et al. study argues that the “core translucency therefore becomes one of the primary factors in controlling aesthetics and is a critical consideration in selection of materials.” The study used a reflectance spectrophotometer (records the amount of light reflected) to compare the translucency of crowns fabricated with three different commercially available all-ceramic materials including alumina - CAD-CAM Procera, Lithium disilicate - Pressable IPS e.max Press, Zirconia - CAD-CAM Lava [4]. Out of all three ceramic materials, lithium disilicate was found to have the maximum translucency even when the coping was at a 0.8mm thickness.

Lastly, glass-ceramics can be “readily etched and silanized at the intaglio surfaces, with attendant superior bonding to a support substrate” [1]. In other words, lithium disilicate has the ability to be easily etched or milled out of a homogenous material by computer-aided-design/computer-aided-manufacturing (CAD/CAM) digital systems. This technology assures acute accuracy of the fabrication of the designed restoration. The silanization of the restoration’s surface helps increase the hydrophobicity of the glass-ceramic.  

Cons

Although lithium disilicate crown applications have a high survival and success rate, they may be “less suitable for applications where stress concentrations can be high, e.g. FDP [fixed dental prosthesis] connectors” [1]. The 360-400MPa flexural strength of lithium disilicate is relatively weak compared to the 1,000MPa flexural strength of zirconia-based restorations. For this reason, FDPs with frameworks made of glass-ceramics require “larger connector areas to meet load-bearing requirements relative to their stronger zirconia counterparts” [1]. Whereas, lithium disilicate single crowns are supported by underlying dentin that exhibits greater strength and stability then lithium disilicate multiple-unit restorations. However, a 10-year study evaluated the long-term outcome of three-unit FDPs made from monolithic lithium disilicate ceramic (IPS e.max Press, Ivoclar Vivadent) and found that the survival and success rates were similar to those of conventional metal-ceramic FDPs [7].

Next, one study analyzed the friction and wear behavior of human enamel that opposed lithium disilicate restorations and found evidence of abrasive wear behavior of the opposing enamel [5]. Lee et al. found the “enamel that opposed lithium disilicate glass ceramic exhibited cracks, plow furrows, and surface loss, which indicated abrasive wear as the prominent wear mechanism.” It’s worth noting that adequate surface finishing of dental ceramics influences wear on opposing enamel and requires competent skills of the dental laboratory to achieve an acceptable polished surface. A rough surface will abrade the opposing enamel of a restoration and “it is highly recommended that the surface is finished and polished appropriately” [6].  

To conclude, the flexural strength of previous glass-ceramic materials was relatively weak until the development of highly esthetic and strong lithium disilicate glass-ceramics. The highly specialized monolithic structure of IPS e.max ® lithium d­­isilicate by Ivoclar Vivadent can achieve great structural integrity with superior translucent esthetics compared to other all-ceramic materials. For this reason, Lithium disilicate is a viable option for dental patients who are seeking longevity and beautiful esthetics for their dental restoration.

About the Company:

Since 1991, Iverson Dental laboratory has provided dentists with high quality dental lab products to ensure their patients are completely satisfied with the restoration outcome. Iverson’s highly knowledgeable team of certified dental technicians specialize in all-ceramic restorations, dental implants, cosmetic and digital dentistry. Iverson dental labs strongly believe in using high quality certified materials and authentic manufacturing components to fabricate their dental restorations.

To inquire more about all-ceramic dental lab products, please visit http://www.iversondental-labs.com.

Reference:

1. Zhang Y, Chai H, Lee JJ, Lawn BR. Chipping resistance of graded zirconia ceramics for dental crowns. J Dent Res. 2012;91:311–5. [PMC free article] [PubMed]

2. Shenoy A, Shenoy N. Dental ceramics: An update. J Conserv Dent. 2010;13:195–203. [PMC free article] [PubMed]

3. Valenti M, Valenti A. Retrospective survival analysis of 110 lithium disilicate crowns with feather-edge marginal preparation. Int J Esthet Dent. 2015 Summer;10(2):246-57.

4. Sravanthi, Y., Ramani, Y. V., Rathod, A. M., Ram, S. M., & Turakhia, H. (2015). The Comparative Evaluation of the Translucency of Crowns Fabricated with Three Different All-Ceramic Materials: An in Vitro Study. Journal of Clinical and Diagnostic Research: JCDR, 9(2), ZC30–ZC34. doi:10.7860/JCDR/2015/12069.5559

5. Lee, A., Swain, M., He, L., & Lyons, K. (n.d.). Wear behavior of human enamel against lithium disilicate glass ceramic and type III gold. The Journal of Prosthetic Dentistry, 1399-1405.

6. Rashid, H. (n.d.). The effect of surface roughness on ceramics used in dentistry: A review of literature. European Journal of Dentistry Eur J Dent, 571-571.

 


7. Kern, M., Sasse, M., & Wolfart, S. (n.d.). Ten-year outcome of three-unit fixed dental prostheses made from monolithic lithium disilicate ceramic. The Journal of the American Dental Association, 234-240. 

Tuesday, August 4, 2015

Pros and Cons of Porcelain Fused to Zirconia (PFZ) Dental Restorations

In the last few decades, there has been an increasingly huge demand for highly esthetic dental restorations among U.S. dental patients. New developments and advances in all-ceramic dental materials have replaced metal-ceramic systems, such as porcelain-fused-to-metal (PFM) prostheses, with all-ceramic systems. Advancements in bonding techniques resulted in the development of porcelain fused to zirconia (PFZ) restorations, finding superior esthetics compared with PFM restorations.

Metal-free all-ceramic restorations offer better esthetics and biocompatibility than porcelain fused to metal (PFM) prostheses [1]. Although PFZ prostheses offer better esthetics than metal ceramic systems, dentists must evaluate the pros and cons of PFZ prostheses in order to make an informed decision on providing the best dental lab products to their patients. This article will briefly analyze the cons and pros of porcelain fused to zirconia restorations.

Microstructure of PFZ Restorations

Dental ceramics can be classified by their microstructure (i.e., amount and type of crystalline phase and glass composition)[1]. Zirconia oxide (ZrO2) has a polycrystalline solid-based composition, formed by “directly sintering crystals together without any intervening matrix to from a dense, air-free, glass-free, polycrystalline structure”[1]. Solid-sintered zirconia-oxide ceramic is widely used as a framework material for dental implants, dental crowns, fixed-partial dentures, and other dental lab products.

Conventional dental porcelain is a partially glassy material that contains high amounts of leucite crystals added to aluminum oxide. This pressed-glass ceramic undergoes “dispersion strengthening through the guided crystallization of leucite”[1]. Porcelain is widely used for veneer layering onto a zirconia core (PFZ) or a metal core (PFM).   

Cons of PFZ Restorations

To begin with, clinical research and practices have reported high occurrences of veneer chipping and fractures in all major brands of PFZ systems, especially in posterior prostheses [2]. The porcelain overlay can chip during mastication, most notably at the coping level were thickness is a factor that influences the survival and success of the restoration [3]. According to Agustin et al., porcelain veneer chipping most often occurs as an esthetic defect without affecting the survival of the restoration and is easily repaired by polishing or intraoral repair; it often goes unnoticed by the patient. For this reason, Agustin et al. five-year study reported the survival rates of zirconia-based fixed dental prostheses to be 97-99%.

Although the survival rate is favorable, clinical studies have revealed a high rate of fractures for porcelain-veneered zirconia-based restorations that affect the success of the restoration—varying between 6% and 15% over a 3- to 5-year period. The success of the restoration is dependent on whether the restoration’s esthetics is compromised or not. Agustin et al. believes the reason for the high rate of fractures is uncertain but suspects the bond between the porcelain and the zirconia substructure failed. One likely reason could be the porcelain veneer has a weak flexural strength of 90MPa, contrasted to zirconia’s high flexural strength of 900–1200 MPa [2]. Another likely reason was found in a Baldassarri et al. 2012 clinical study, “the presence of a radial tensile stress in the overlay porcelain of zirconia-ceramic prostheses… may lead to the large clinical chips and fractures of these prostheses.”

Another con to porcelain-veneered zirconia-based restorations is a reported high wear loss of antagonist enamel because porcelain consists of leucite crystal grains that act as an abrasive surface during mastication [4]. Porcelain also consists of feldspathic glass that disappears after wear, leaving large leucite grains to be exposed and act as abrasive materials on the opposing enamel [5]. In fact, Porcelain-veneered zirconia shows higher wear loss on opposing enamel than that of polished zirconia. Rashid reviewed an Odatsu et al. study that used carborundum points, silicone points and diamond polishing paste on zirconia and traditional feldpsathic porcelain to examine the materials surface roughness. They found the “feldspathic porcelain showed highest surface roughness values after finishing and polishing procedures” [7]. They concluded, “a rough surface will abrade the opposing dentition or restoration, and it is highly recommended that the adjusted surface is finished and polished appropriately” [7].

Pros of PFZ Restorations

Despite the low flexural strength of the layered porcelain for PFZ restorations, superior fracture resistance of the zirconia ceramic core is a major pro. According to Miyazaki et al., in a study assessing zirconia-based restorations found the zirconia frameworks rarely got damaged and the complications that did occur were at the veneering ceramic level. In a 10-year clinical study, Sax et al. assessed the long-term survival rate of zirconia-based posterior fixed dental prostheses with zirconia frameworks and found the “zirconia frameworks exhibited very good long-term stability” [6].

In 2012, Agustin et al. analyzed porcelain veneer behavior on zirconia ceramic cores using a scanning electron microscopy (SEM) and found 71.66% of the facture type for zirconia-core restorations were cohesive – meaning the facture only occurred at the surface level without affecting the ceramic-core interface. In another study with the same objective, Saito reported 88.8% of fracture types were cohesive. Since most of the fractures are cohesive in nature, the veneered porcelain can be easily repaired without much concern the ceramic core is fractured [7].

Finally, PFZ restorations have the ability to mask discolored underlying tooth structures because zirconia has opaque characteristics that allow the prepared tooth to be concealed. Since the zirconia core is highly opaque, a porcelain overlay is needed to improve the esthetics of the zirconia core to appear more translucent, more similar to natural teeth. The dual layers of porcelain and zirconia from PFZ restorations allow the prosthetic to hide any discoloration and/or defects from the prepared tooth, making it a top option for patients who may have these issues.

Some studies, particularly Agustin et al., have concluded the survival rate is not dependent on esthetic defects but on the functional survival of the restoration. But with an ever-growing society that demands perfection in esthetics for dental restorations, functionality is not the only characteristic desired for dental restorations by the majority. Although the 1,000 MPa zirconia substructure exhibits good long-term stability, the failure of the layering porcelain can be seen as ultimately a failure of the restoration. After much clinical research, it is safe to say the porcelain layer on PFZ restorations is not reliable for the long-term success of esthetics. Consequently, PFZ restorations are at the risk of failing as an acceptable restoration among U.S. dental patients.

Resource Box:

Iverson Dental Laboratories is a cutting edge dental lab that utilizes advances in dental technology and procedures to fabricate high quality dental lab products. Their highly knowledgeable team of certified dental technicians specialize in all-ceramic restorations, dental implants, cosmetic and digital dentistry. Iverson strongly believes in using high quality certified materials and authentic manufacturing components to fabricate all their dental restorations. They proudly make 100% of their dental lab products at their Southern California dental labs, allowing them to have one of the fastest turnaround rates in the industry.

To learn more about quality options for dental lab products, please visit http://www.iversondental-labs.com.

References:

1. Shenoy A, Shenoy N. Dental ceramics: An update. J Conserv Dent. 2010;13:195–203. [PMC free article] [PubMed]

2. Baldassarri M, Stappert CF, Wolff MS, Thompson VP, Zhang Y. Residual stresses in porcelain-veneered zirconia prostheses. Dent Mater. 2012;28:873–9. [PMC free article] [PubMed]


3. Triwatana P, Nagaviroj N, Tulapornchai C. Clinical performance and failures of  zirconia-based fixed partial dentures: a review literature. J Adv Prosthodont. 2012;4:76–83. [PMC free article] [PubMed]

4. Agustin-Panadero R, Román-Rodríguez JL, Ferreiroa A, Solá-Ruíz MF, Fons-Font A. Zirconia in fixed prosthesis. A literature review. J Clin Exp Dent. 2014;6:e66–73. [PMC free article] [PubMed]

5. Miyazaki, T., Nakamura, T., Matsumura, H., Ban, S., & Kobayashi, T. (n.d.). Current status of zirconia restoration. Journal of Prosthodontic Research, 236-261.

 

6. Sax C, Hammerle CH, Sailer I. 10-year clinical outcomes of fixed dental prostheses with zirconia frameworks. Int J Comput Dent. 2011;14:183–202. [PubMed]

 

7. Saito A, Komine F, Blatz M, Matsumura H. A comparison of bond strength of layered veneering porcelains to zirconia and metal. J Prosthet Dent. 2010;104:247–57. [PubMed]

7. Rashid, H. (n.d.). The effect of surface roughness on ceramics used in dentistry: A review of literature. European Journal of Dentistry Eur J Dent, 571-571.