DOCTOR EDUCATION · OCCLUSION CONNECTIONS
Why Do My Crowns Keep Breaking?
If your porcelain keeps fracturing, your bonding keeps failing, or you are adjusting the same crown for the third time — the problem is usually not the lab, the material, or the patient.
The pattern most dentists recognize
You prep well. Your margins are clean. Your lab is good. The case seats beautifully and the patient leaves happy.
Then:
- The porcelain chips at three months.
- The patient returns saying it “feels high” after you already adjusted it twice.
- The opposing tooth develops a wear facet that was not there before.
- The patient starts reporting soreness they never had.
- You replace the crown, and eighteen months later the replacement fails the same way.
When this happens once, it is a case. When it happens across your practice, it is a pattern — and patterns come from method, not luck.
Ceramic restorations continue to break under abnormal occlusal loads — buccal abractions on cuspid and fracture of incisal edges persist after adjustments.
It is that the restoration was built to a bite position the patient’s muscles do not accept. The tooth is being asked to absorb a load it was never positioned to receive.
It is a dentist application problem of not knowing the key principles, steps and method of what to look for and how adjust the bite properly.
That is a measurable problem. It is not a matter of opinion or philosophy.
Why stronger materials do not solve it
The instinct is to reach for a tougher material. Move from feldspathic to lithium disilicate. From lithium disilicate to zirconia. Each step buys time.
But a material change treats the fracture as a strength problem. If the restoration is loaded off-axis, or loaded at a position the musculature is actively fighting, greater strength simply relocates the failure. The crown survives and the opposing tooth wears. The ceramic crown breaks. Or the root fractures. Or the surrounding bone resorbs and the implant fails.
The force did not go away. It went somewhere else.
What articulating paper is actually telling you
Articulating paper marks where teeth touch. It does not tell you:
- how hard each contact is loaded
- in what sequence contacts arrive
- whether the muscles are relaxed or bracing when they arrive
- whether the jaw position you registered is one the patient can physiologically sustain
A mark is a mark. Two contacts can leave identical marks while one carries several times the load of the other.
Occlusal intensity, by contrast, is measurable once the physiologic mandibular closing path has been determined. Surface EMG records muscle activity during a functional clench in microvolts — sensitive to the 5.5 µV level — which allows an occlusal contact to be identified at the 10 to 20 micron level.
Electromyographic (EMG) Recording Before and After Functional Clench
Unbalanced bite versus balanced GNM bite. The muscle twitch after an unbalanced clench is the CNS reporting that the position was not accepted.
Before and after: proprioceptive CNS signaling. Using the first tooth contact and Scan 12’s EMG high low chart muscle activity and rest responses are recorded before and after occlusal adjustment following GNM protocols. The response immediately surrounding a functional clench reveals the quality of that activity — unrested before occlusal balancing, calm after physiologic balancing.
Left and right anterior temporalis and left and right masseter EMGs monitored at a gain of 10 µV using Myotronics K7 Scan 12, showing first-tooth-contact EMG responses. EMG Occlusal Timing and First Tooth Contact — Scan 12 →
The sensor is not as precise as its reputation
Digital occlusal recording systems work at a coarser scale than their reputation suggests. The sensor itself is 100 µm thick — squarely inside the 8–200 µm range of articulating paper. And in published in-vitro testing, its force readings did not hold up: for an applied force of 10 N, individual sensing elements returned digital levels spanning roughly 25 to 55 — meaning a single raw reading of 50 could represent anywhere from 10 to 22 N. Representative error reached 9.2%, maximum error 22.5%. The systems proved highly valid for measuring timing; for absolute or relative force, agreement was poor.
Source: Cerna, Ferreira, Zaror, Navarro & Sandaval, in-vitro evaluation, Cranio: Journal of Craniomandibular and Sleep Practice, 2015. Read the full study review →
And there is a problem no amount of sensor precision can fix: the wafer changes the bite it is measuring. Anything placed between the teeth makes the mandible react and compensate. The width of the wafer forces the mouth open around it; as the orbicularis oris, buccinators, and lip musculature accommodate it, the mandible naturally posteriorizes — altering the very occlusal relationship being recorded. The wafer accurately records high spots at whatever position the mandible was compensated into. That is not the same as recording the correct position.
The Effect of Thickness of Wafer of Digital Occlusal Scanners →
Even and balanced is not the same as correct
Centric holds. The marks are even. Neither one tells you the position is right.
And here is the trap in “adjust until the marks look even”: just because all the occlusal articulating marks — or digital wafer recordings — look even and balanced does not mean the mandible is closing in the correct position. Evenness describes how the load is distributed among the teeth. It says nothing about whether the position the mandible closed to is one the musculature accepts. A perfectly balanced bite in the wrong position is still the wrong bite — it is simply wrong evenly.
There is a deeper problem than sensitivity: the typical dentist is working from a two-dimensional recording understanding of what is actually a six-dimensional event — anteroposterior, vertical, lateral, pitch, yaw, and roll. And the contacts most workflows study are voluntary ones: the patient closing with strained, braced musculature. When involuntary closure is produced with low-frequency dental TENS, the mandibular closing torquing contacts reveal themselves — the very contacts that load restorations off-axis, and the ones a voluntary clench routinely hides.
This is the distinction that decides which teeth you adjust. A habitual, voluntary closing path and a physiologic, involuntary TENS closing path are not the same path — so the prematurities each one reveals appear in different locations. A dentist adjusting to marks produced by tight, straining muscles is adjusting real contacts at the wrong position. The marks are accurate. The position they were made in is not.
Why Articulating Paper Does Not Reflect Functional Occlusion →
The position you built to
Most restorative failure of this kind traces back to a single decision made early and rarely revisited: where the jaw was when the bite was registered.
If that position came from a retruded record, a habitual closure the patient had already adapted to, or a maximum-intercuspation the patient reached by bracing, then everything built afterward inherits it. The crown is not failing. The crown is reporting.
A patient can accommodate a wrong position for years — until you place something rigid and unyielding into it. Ceramic does not accommodate. It fractures.
The Lost Vertical Dimension Patient — What Actually Went Wrong →
How you find out instead of guessing
Rather than inferring jaw position from anatomy or from a record taken under bracing, you measure what the muscles are actually doing.
- Electromyography (EMG) shows whether the closing muscles are at rest or working — before, during, and after you take the record.
- Computerized mandibular scanning (jaw tracking) shows the path the mandible actually travels, its velocity, and whether the closure repeats.
- Low-frequency TENS relaxes the musculature so the position you register is a physiologic one rather than a learned one.
- Electrosonography (ESG) records joint sounds — an objective reading of whether the position is being reached through a compromised structure. If the joint is announcing itself during function, that is information you want before you prepare a single tooth, not after.
At Occlusion Connections these measurements are taken with the Myotronics K7, and the scans are read complete, top to bottom — not sampled for the one number that supports a conclusion already reached.
The point is not the instrument. The point is that jaw position becomes an observation rather than an assumption.
Left K7 jaw tracking recording measures physiologic mandibular position relative to habitual CO/MIP. Using Myotronics K7 Kinesiograph jaw tracker a pathologic posterior mandibular closure path is identified with low frequency dental TENS. Voluntary mandibular closure is not coincident with the physiologic closing path. Right K7 jaw track recording shows the voluntary closure is coincident with the involuntary mandibular closure — physiologic, unstrained, after GNM occlusion.
Muscles and the central nervous system cannot be relaxed or in a state of neutrality when the involuntary mandibular closing path is not coincident with the voluntary closing path. Where there is a mismatch of closing path forces that is when teeth wear, crowns break, bone loss occurs and implants fail.
Kinesiograph — It’s from the Greek kinesis (movement) + graph (to record) — literally a movement recorder. Myotronics’ device is the Mandibular Kinesiograph (MKG), the jaw-tracking lineage that became K7. So the stem is kinesio-graph.
What changes in your restorative work
Dentists who begin measuring rather than inferring typically report the same shifts:
- Fewer post-cementation adjustments, because the position was correct before the case was fabricated.
- Fewer remakes.
- Full-mouth cases that hold, because the vertical and the trajectory were established before preparation rather than negotiated afterward.
- Patients who stop reporting muscle symptoms you previously had no framework to explain.
- Predictability that survives being applied to the next case, and the one after that.
None of that requires abandoning the restorative dentistry you already do well. It changes what you establish before you begin.
This is not a philosophy question
Dentists are often told they must pick a camp — centric relation, neuromuscular, one school against another. That framing has cost the profession a great deal of time.
The question worth asking is narrower and answerable: can you show, with objective measurement, that the position you restored to is one the patient’s musculature accepts and can sustain?
If yes, the philosophy label does not matter. If no, no label will save the case.
Where to go from here
If the pattern in this article is familiar, the next step is to see the measurement performed and interpreted on real patients rather than read about it.
- Why Your Dental Occlusion Doesn’t Hold — Even When Everything Looks Right
- The Trained Pattern — Why Good Dentists Miss What K7 Would Show Them
- Doctor Education — the full library of OC clinical articles
GNM Masterclass Training
Occlusion Connections teaches the measurement protocol, the interpretation, and the restorative sequencing that follows from it.
The entry point is Level 1 — the foundational course where the measurement protocol is taught from the beginning. Levels 2 through 4B build on it in sequence.
COURSES ARE AGD PACE APPROVED
Updated: August 4, 2026
Written by Clayton A. Chan, D.D.S. — Founder and Director, Occlusion Connections | Las Vegas, Nevada
Occlusion Connections — The Center for Gneuromuscular Dentistry and Orthopedic Advancement
6170 W. Desert Inn Rd., Las Vegas, NV 89146