The use of Bite Registration is a necessity and viewed as a simple procedure by most however if not done properly is a waste of time and money for both clinician and laboratory.
How do you decide which material to use? Is your choice driven by cost, accuracy or prescribed restoration?
BITE REGISTRATION MATERIAL CHOICE
There are a number of material choices for taking a bite registration including wax or high durometer polyvinyl siloxane materials such as Blu Mousse -Generic Pentron, Memoreg -Heraues Kulzer and Quick Bite -Clinicians Choice to name a few. There is a place for both but when should they be used and what factors should be considered when making your decision?
Making the decision regarding which Bite Registration material is a simple one and is based on the impression materials that accompany it to the lab.
ALGINATE OPPOSING ALGINATE
Most commonly used for study models, diagnostic models, esthetic wax ups, orthodontic records or appliances and Bruxism or TMJ splints require a wax bite material. Ideally it should be a Type III baseplate wax due to its ability to withstand higher temperatures without deformation or a specific bite registration wax made from beeswax or a combination of paraffin and ceresin. These materials could still deform under higher temperatures especially during transport but are ideal for these procedures mainly due to their lack of flow and detail. The use of a PVS like material for alginate produced models is contraindicated due to the inability of the highly detailed occlusal registration to fit the lack of detail produced from an alginate. If a PVS bite registration is your material of choice, make sure a lateral bite registration is taken with the patient closed in centric. (Fig 1a, 1b) PVS / POLYETHER OPPOSING PVS / POLYETHER
These impression materials used for the majority of crown and bridge / implant procedures produce highly detailed, highly accurate impressions and require a bite registration that can produce the same, hence the need for a high durometer PVS bite registration material.
DUAL ARCH IMPRESSIONS
Although dual arch impressions / trays offer the ability to simultaneously take a working model, opposing model and bite registration, a separate PVS bite registration should be taken as well. It has been proven that a bite registration provided by dual arch impressions provides superior maximum intercuspal relationships over full arch models, if done correctly!1,2 However, how sure are you that the patient has closed passively into centric? If the impression material reaches its gel phase as the patient closes it could cause a lateral shift of the mandible or prevent the patient from closing completely thus an inaccurate bite. An additional consideration, when a patient has been anesthetized the chance of closing into centric is greatly reduced even if guided into position by the clinician unless a PVS guide or shim (Fig 2) is utilized to ensure complete closure into a centric occlusal position4.
PVS OPPOSING ALGINATE
Alginate materials should NOT be used to oppose a PVS or PE impression material due to the lack of occlusal detail and the inability of a highly accurate PVS bite material (Fig 3a) to adapt to them5. These inaccuracies prevent proper articulation (Fig 3b) and lead to heavy occlusal contacts of the definitive restoration. In order to obtain an accurate bite registration the opposing models should be impressed in either a PVS material or an alginate substitute such as Alginot -Kerr, Status Blue -Zenith/DMG, Silgimix -Sultan Chemists or the first 2nd generation intra oral duplicating material CounterFIT -Clinicians Choice. These materials offer the flow characteristics and detail similar to that of a PVS material at a cost comparable to alginate. In addition, the alginate substitutes are dimensionally stable allowing multiple pours without the ripping, tearing or the dehydration associated with hydrocolloid impression materials.
When choosing an alginate substitute keep in mind that although they are lower cost PVS materials they still are PVS materials which as with your C&B impression materials prefer a dry field. Stay away from materials that contain scents or flavours as they stimulate salivary activity.
THE BEST BITE REGISTRATION TECHNIQUE
The most common practice for acquiring a bite registration is to express the bite registration material onto the occlusal surface of mandibular posterior teeth and have the patient close. Is this the best technique? There are a couple of significant factors that would indicate no.
1. If taking a bite registration for full arch impressions the bite material must be expressed onto both quadrants and due to the fast set time of these materials it may reach its gel phase prior to the patient completely closing. This can result in a lateral shift of the mandible or prevent the patient from closing entirely.
2. How can you be sure the patient has closed completely into centric?
The most common purpose for taking a bite registration is to record the patients bite in passive centric occlusion. The only way to be SURE you have achieved this is by taking the registration with the patient passively closed3. Inject the registration material into the preparation site (Fig 4) , delivering a thick buccal bead while injecting up along the buccal surface of occlusion (Fig 5,6). Apply light pressure to the cheek until the material is set (Fig 7). This creates a rigid buccal wall and the occlusal detail around the preparation site delivering the BEST and most accurate passive, centric occlusion bite registration.
In extremely conservative crown preparations such as for full gold restorations it may difficult to express these materials through the standard green mixing tips designed for thicker viscosity materials into such a small space. However Quick Bite from Clinicians Choice has been developed with the same resin technology adopted for their impression materials which allows it to be delivered through the larger gauge yellow mixing tips with the intra oral delivery tip for the smaller and hard to reach areas. An added benefit to the resin filled chemistry is that it is not as brittle as other bite registration materials allowing cutting and carving without crumbling.
In order to ensure that all laboratory procedures are done correctly and accurately, simple tools such as bite registration should be sent with every case. The proper materials used with the right procedure / technique will aid in the prevention of common headaches such as heavy occlusal contacts and ensure restorations are fabricated with proper cuspid rise and group function.
Gregg Tousignant, CDT graduated Dental Technology from George Brown College in 1992, Certified Dental Technician since 1994 from the National Board for Certification in the USA. He has worked for 12 years as a dental technician, was certified as an instructor for Heraeus Kulzer where he provided a number of hands-on programmes for indirect composites and denture injection systems. Gregg currently provides lectures and hands-on courses for both the General / Cosmetic dentist as well as dental and hygiene schools across Canada. Course topics include Tooth Whitening, Impressioning, Temporization, Direct Veneer Colour Change including the invisible Class IV restoration and the Sensitivity Free Direct Posterior Composite. He has also been published in Oral Health and the Journal of the Toronto Academy of Cosmetic Dentistry. Gregg is currently serving as Technical Support Manager for Clinical Research Dental where he provides technical support and hands-
on courses consistent with the Company’s philosophy, Teaching Better Dentistry.
REFERENCES
1. Merle H. Parker, MS, DDS, Steven M. Cameron, DDS, James C. Hughbanks, DMD, David E. Reid, DDS, Comparison of Occlusal Contacts in Maximum Intercuspation for two impression techniques, US Army Activity, Fort Gordon, Nov 2005
2. Michael DiTolla, DDS, Achieving Accurate Bite Registrations, Dental Economics, June 2006
3. Ronald E. Goldstein, DDS, A Precise Bite Registration Technique, Inside Dentistry, July /August, 2008
4. GJ Kaplowitz, Trouble shooting dual arch impressions, JADA 1996 127: 234-240
5. Boksman, DDS, Tousignant, CDT, Alginate Substitues Rational For Their Use, Dentistry Today, April, 2009 page 48
———
Although dual arch impressions / trays offer the ability to simultaneously take a working model, opposing model and bite registration, a separate PVS bite registration should be taken as well
———
In extremely conservative crown preparations such as for full gold restorations it may difficult to express these materials through the standard green mixing tips designed for thicker viscosity materials into such a small space
———
In order to ensure that all laboratory procedures are done correctly and accurately, simple tools such as bite registration should be sent with every case
