Porcelain crowns

Patients compare Zirconia against Cercon, or Lava against Nacera, the way they would compare two phones. But most crowns that fail early do not fail because the wrong ceramic was chosen — they fail because the margin, the join between crown and prepared tooth, is not tight.

An acceptable margin has a gap under 100 micrometres, a clear shoulder or chamfer so the lab has room to build ceramic, and sits level with the gum or no more than 0.5mm into the gingival sulcus. Once the gap exceeds 200 micrometres the luting cement dissolves over time, bacteria get underneath, and the tooth inside decays again — while from the outside the crown still looks perfectly white and intact.

That is why the try-in appointment is never dropped to shorten a schedule, and why we take a bitewing X-ray after cementation: the film shows an open margin clearly, which both the naked eye and a dental probe can miss.

A tooth with a living pulp is still nourished. Its dentine keeps its moisture and its elasticity, so it handles chewing forces well. A root-treated tooth has lost that supply: the dentine dries and grows brittle year by year, and the risk of a vertical root fracture climbs with it — and a vertical root fracture almost always ends in extraction.

So the rule at Dental Việt Nam is to keep the pulp wherever possible. Root canal treatment is only indicated on specific evidence: decay reaching the pulp chamber, a pulp test showing irreversible inflammation, or a lesion visible at the root apex. Taking the nerve out "so it will not be sensitive" or "to make preparation easier" is a wrong indication, and it takes decades off that tooth.

Where a tooth genuinely needs root treatment and has lost a lot of structure, the core is rebuilt with a fibre post and composite before preparation, rather than preparing straight into what little tooth is left.

Crowning 8 to 16 teeth at once means rebuilding the entire biting surface of the front of the mouth. If the closed-bite height ends up a few tenths of a millimetre higher or lower than where it physiologically sat, the chewing muscles and the jaw joint have to compensate.

The consequence does not show up in the chair. It arrives weeks to months later: jaw muscles aching on waking, clicking on opening, a dull ache at the temples, or one crown that keeps chipping at the same spot.

Articulating paper only shows where the contacts are. Occlusal force analysis also shows which contact lands first, what percentage of the load it takes, and how many milliseconds apart the two sides meet — that is enough data to adjust from, rather than grinding by feel and asking the patient whether it seems better.